In response to an ageing global population,the primary hip and knee arthroplasty rate continues to increase.Although an effective treatment,up to 25%patients may require revision arthroplasty during their lifetime,com...In response to an ageing global population,the primary hip and knee arthroplasty rate continues to increase.Although an effective treatment,up to 25%patients may require revision arthroplasty during their lifetime,commonly due to periprosthetic loosening.Revision procedures are associated with significantly increased healthcare costs;therefore,timely and accurate diagnostics are critical for clinicians and patients.Loosening,which may be septic or aseptic,remains a challenge and requires thorough clinical examination and multimodal imaging evaluation.Plain radiographs remain an essential diagnostic tool but advanced imaging modalities such as computed tomography,magnetic resonance imaging and nuclear medicine are playing an increasingly important role.This comprehensive review,through outlining the available radiological modalities,their respective strengths and weaknesses and the pertinent imaging findings,may help radiologists and orthopaedic surgeons make more informed decisions in the management of periprosthetic loosening.展开更多
Transmission towers,serving as the support structure of transmission lines,are significant for the functional-ity of an electric transmission system.Bolt joint loosening is one of the critical factors that can affect ...Transmission towers,serving as the support structure of transmission lines,are significant for the functional-ity of an electric transmission system.Bolt joint loosening is one of the critical factors that can affect the safety and stability of transmission towers.In this study,the effects of bolt joint loosening on the dynamic characteristics of a 220-kV angle steel transmission tower are the main topic of concern.First,the mechanical properties of typical joints subjected to different degrees of bolt loosening are studied by finite solid-element simulation,based on which a finite hybrid-element modeling method is developed for a tower structure suffering varying loose degrees in the joints.Taking a 220-kV angle steel transmission tower as the object,the influence of the position and degree of loosening on the tower’s natural frequencies and mode shapes are simulated and discussed.The results demonstrate that the main-member splice joint and the main diagonal-horizontal member gusset plate joint account for the dominant impact on the dynamic characteristics of the tower.In addition,the dominant joint shifts from the main-member splice joint to the main diagonal-horizontal member gusset plate joint as the considered modal order increases.In the case of double joints loosening simultaneously,the loosening of nondomi-nant joints has nonnegligible effects on the tower as well.展开更多
BACKGROUND Aseptic acetabular loosening can result from various factors that can be categorized into groups:patient-related,surgeon-related and implant-related.We present a case of a 63-year-old patient who at first u...BACKGROUND Aseptic acetabular loosening can result from various factors that can be categorized into groups:patient-related,surgeon-related and implant-related.We present a case of a 63-year-old patient who at first underwent a total hip arthro-plasty(THA)using a metal-on-metal bearing due to hip arthrosis.Follow-up visits revealed no complications after the procedure.Two years after the THA,acetabular component loosening occurred due to subsequent trauma of the opposite hip,necessitating a revision THA using a ceramic-on-ceramic bearing.CASE SUMMARY We aim to illustrate a rare case where the primary reason for undergoing THA revision was not only incomplete bone graft incorporation but also improper limb load distribution.Following the revision arthroplasty,a 9-year follow-up visit revealed improvements in all evaluation measures on questionnaire compared to the state before surgery:Harris Hip Score(before surgery:15;after surgery:95),Western Ontario and McMaster Universities Arthritis Index(before surgery:96;after surgery:0),and Visual Analogue Scale(before surgery:10;after surgery:1).CONCLUSION Opposite-hip trauma caused a weight transfer to the limb after a THA procedure.This process led to a stress shielding effect,resulting in acetabular component loosening.展开更多
The analysis of plastic loosening zone of tunnels with cold condition,high in situ stress,and weak stratum is the key scientific problem of tunnel construction in cold areas.Based on the unified strength theory and co...The analysis of plastic loosening zone of tunnels with cold condition,high in situ stress,and weak stratum is the key scientific problem of tunnel construction in cold areas.Based on the unified strength theory and considering the coupling effect of high in situ stress and low-temperature field,the analytical model of the plastic loosening zone of tunnel surrounding rocks was proposed,and the influence laws of physical parameters(initial ground stress,freezing temperature,excavation radius,and intermediate principal stress)was explored.The results illustrate that:(1)with the coupling of low temperature and stress fields,the in-situ stress has a more significant effect on the radius of the plastic loosening zone of the tunnel surrounding rocks,showing a nonlinear correlation.When the in situ stress is small,the influence of the temperature field on the radius of the plastic loosening zone is more obvious.(2)The radius of the plastic loosening zone of the tunnel surrounding rocks increases synchronously with the excavation radius and gradually decreases with the increase of the intermediate principal stress.(3)The greater the temperature difference in the low-temperature field,the tunnel stability has a more significant response to the intermediate principal stress and is positively correlated with the coefficient of the intermediate principal stress.(4)In the actual project,the proposed model can well describe the mechanical behavior and deformation characteristics of tunnel surrounding rocks in low-temperature environment,showing applicability.The research results are expected to provide a theoretical basis for the study of tunnel stability in cold areas.展开更多
Threaded fasteners naturally tend to loosen under vibration,impact,or alternating thermal load.Various anti-loosening methods or strategies are widely applied for preventing loosening,including a few anti-loosening de...Threaded fasteners naturally tend to loosen under vibration,impact,or alternating thermal load.Various anti-loosening methods or strategies are widely applied for preventing loosening,including a few anti-loosening designs and anti-loosening structures.In this review,a variety of influencing factors that improved the anti-loosening ability and helped guide the anti-loosening designs of threaded fasteners are summarized.Second,the anti-loosening structures are classified into two categories,that is,conventional and new-style anti-loosening structures.The former refers to widely used structures in engineering applications,while the latter refers to novel structures not available in the markets.The research on the evaluation and comparison of various conventional anti-loosening structures in terms of preventing loosening is summarized in detail and the newstyle anti-loosening structures from five different aspects are also surveyed based on different structural characteristics.In the future,the effects of combined factors on loosening should be considered to achieve optimal anti-loosening designs.More quantitative research on the mathematical relationship between the anti-loosening performance of conventional structures and structural parameters must be conducted.Furthermore,novel structures with excellent abilities to prevent loosening are needed,and issues of difficulties in installation and disassembly,low strength at thread,large deformation,and temperature dependence also need to be addressed.展开更多
[Objective] This study was conducted to explore the effects of deep loos- ening on soil structure and the activity of maize root system, to provide a theoreti- cal basis for the efficient and rational use of water res...[Objective] This study was conducted to explore the effects of deep loos- ening on soil structure and the activity of maize root system, to provide a theoreti- cal basis for the efficient and rational use of water resources. [Method] Three differ- ent loosening treatments for maize in ridges were performed in field trials as fol- lows： conventional ridge tillage, loosening the cm in spring （deep loosening in spring）, and depth of 30 cm in autumn （deep loosening in soils between rows to a depth of 30 oosening the soils between rows to a autumn）. Then the soil properties and the development of root system were measured to evaluate the effects of different loosening methods. [Result] Soil compactness was significantly reduced after deep loosening in spring, There were significant differences in soil compactness in 0-20 cm depth and soil bulk density in 0-40 cm depth between deep loosening in spring and deep loosening in autumn, deep loosening in spring and conventional ridge tillage. The soil water holding capacity was also significantly different between the two deep loosening treatments and conventional ridge tillage. Moreover, the root ac- tive absorption area of maize of deep loosening in spring was higher than that of conventionai ridge tillage. [Conclusion] Deep loosening can reduce soil compactness, bulk density, and improve soil water holding capacity, soil water content and the root activity of maize. Deep loosening in spring is better in soil improvement be- cause spring is closer to the growth period of crops than autumn. So, deep loosen- ing is conducive to the improvement of soil compactness and structure.展开更多
AIM To assess serum levels of RANK-ligand(RANKL) and osteoprotegerin(OPG) as biomarkers for periprosthetic joint infection(PJI) and compare their accuracy with standard tests.METHODS One hundred and twenty patients pr...AIM To assess serum levels of RANK-ligand(RANKL) and osteoprotegerin(OPG) as biomarkers for periprosthetic joint infection(PJI) and compare their accuracy with standard tests.METHODS One hundred and twenty patients presenting with a painful total knee or hip arthroplasty with indication for surgical revision were included in this prospective clinical trial. Based on standard diagnostics(joint aspirate, microbiological, and histological samples) and Musculoskeletal Infection Society consensus classification,patients were categorized into PJI, aseptic loosening,and control groups. Implant loosening was assessed radiographically and intraoperatively. Preoperative serum samples were collected and analyzed for RANKL, OPG, calcium, phosphate, alkaline phosphatase(AP), and the bone-specific subform of AP(b AP). Statistical analysis was carried out, testing for significant differences between the three groups and between stable and loose implants. RESULTS All three groups were identical in regards to age, gender, and joint distribution. No statistically significant differences in the serum concentration of RANKL(P = 0.16) and OPG(P = 0.45) were found between aseptic loosening and PJI, with a trend towards lower RANKL concentrations and higher OPG concentrations in the PJI group. The RANKL/OPG ratio was significant for the comparison between PJI and non-PJI(P = 0.005). A ratio > 60 ruled out PJI in all cases(specificity: 100%, 95%CI: 89, 11% to 100.0%) but only 30% of non-PJI patients crossed this threshold. The positive predictive value remained poor at any cut-off. In the differentiation between stable and loose implants, none of the parameters measured(calcium, phosphate, AP, and b AP) showed a significant difference, and only AP and b AP measurements showed a tendency towards higher values in the loosened group(with P = 0.09 for AP and P = 0.19 for b AP). CONCLUSION Lower RANKL and higher OPG concentrations could be detected in PJI, without statistical significance.展开更多
Existing research on the competitive failure relationship,failure mechanism,and influencing factors of bolt loosening and fatigue under different preloads is insufficient.This study analyzes the competitive failure re...Existing research on the competitive failure relationship,failure mechanism,and influencing factors of bolt loosening and fatigue under different preloads is insufficient.This study analyzes the competitive failure relationship between bolt loosening and fatigue under composite excitation through competitive failure tests of bolt loosening and fatigue under different preloads.The results indicated that the failure mode of the bolt is only related to the load ratio(R)and is unrelated to the initial preload and excitation amplitude,which only determine the failure life of the bolt.The small axial loads of composite excitation can restrain bolt failure,and the significant degree of this restraining effect is differ-ent for different preloads.Subsequently,a fracture analysis of the bolt was performed to verify the competitive failure relationship of the bolt from a microscopic perspective,and the competitive failure mechanism of the bolt was deter-mined.Based on the findings,we propose a calculation equation for the optimal preload of 8.8 grade high-strength bolts that can serve as a reference for engineering applications.展开更多
BACKGROUND The majority of published data report the results of biomechanical tests of various design pedicle screw performance.The clinical relevance and relative contribution of screw design to instrumentation stabi...BACKGROUND The majority of published data report the results of biomechanical tests of various design pedicle screw performance.The clinical relevance and relative contribution of screw design to instrumentation stability have been insufficiently studied.AIM To estimate the contribution of screw design to rate of pedicle screw loosening in patients with degenerative diseases of the lumbar spine.METHODS This study is a prospective evaluation of 175 patients with degenerative diseases and instability of the lumbar spine segments.Participants underwent spinal instrumentation employing pedicle screws with posterior only or transforaminal interbody fusion.Follow-up was for 18 mo.Patients with signs of pedicle screw loosening on computed tomography were registered;logistic regression analysis was used to identify the factors that influenced the rate of loosening.RESULTS Parameters included in the analysis were screw geometry,type of thread,external and internal screw diameter and helical pitch,bone density in Hounsfield units,number of levels fused,instrumentation without anterior support,laminectomy,and unilateral and bilateral total facet joint resection.The rate of screw loosening decreased with the increment in outer diameter,decrease in core diameter and helical pitch.The rate of screw loosening correlated positively with the number of fused levels and decreasing bone density.Bilateral facet joint removal significantly favored pedicle screw loosening.The influence of other factors was insignificant.CONCLUSION Screw parameters had a significant impact on the loosening rate along with bone quality characteristics,the number of levels fused and the extensiveness of decompression.The significance of the influence of screw parameters was comparable to those of patient-and surgery-related factors.Pedicle screw loosening was influenced by helical pitch,inner and outer diameter,but screw geometry and thread type were insignificant factors.展开更多
Bolted connections are commonly used in aerospace structures.Once the bolts on the aircraft are damaged or loose,the consequence will be disastrous.Therefore,monitoring bolt loosening is especially required.However,pe...Bolted connections are commonly used in aerospace structures.Once the bolts on the aircraft are damaged or loose,the consequence will be disastrous.Therefore,monitoring bolt loosening is especially required.However,periodic manual inspection costs much money and time.And it is very difficult to achieve multi-point monitoring for many bolted structures in an aircraft.Therefore,a low-cost,reliable detection method based on wireless sensor networks is presented.The reed switch is selected as a sensor for bolt loosening monitor.The chip PT2262 and PT2272are chosen as hardware codec chip for multi-point placement.A wireless transmitter and receiver circuit is designed on 315 MHz frequency.The codec chip and the wireless transmission are triggered by the reed switches.Bolt loosening is detected by the receiving terminal and indicated by light and sound alarms.The wireless transmitter and the receiver circuit are tested and the monitoring system is verified by experiments.The results show that bolt loosening can be effectively detected within 300 m.The developed sensor network is expected to solve multi-point bolt detection problems and provide a low-cost and reliable monitoring technology.展开更多
In low rectal cancer surgery,the section of rectum destal to the lower tumor maigin is relaxed and lengthened after fully isolation of the organ. This would facilitate the adoption of anus saving operation.Before and ...In low rectal cancer surgery,the section of rectum destal to the lower tumor maigin is relaxed and lengthened after fully isolation of the organ. This would facilitate the adoption of anus saving operation.Before and after fully isolation of the rectum in low ratal cancer surgery, the distance between the lower tumor margin and the anorectal line was measured by the same rectuscope introduced through the anus.The two results were compared .The average lengthening was less than 1 cm if the lower tumor marginanorectal line distance was 5 cm.It was 1─2 cm if the lower tumor margin-anorectal distance was 6 cm.It was more than 2 cm if the distance was 7─9 cm.The loosening and lengthening of the rectal canal was related to the presence of lymphnode metastasis and the skill of the operator.The lengthening was also influenced by the body build of the patient,involvement of the rectal circumference and the Dukes stage. Modified Park's operation,trans abdominosacral resection with anastormosis of rectum,and anterior resection on transpubic approach are indicated for those in whom the lower tumor margin-anorectal line distance was 5 cm The rectectomy-anastomosis in the abdominal cavity(Dixon's operation)is indicated for those in whom the lower tumor margin-anorectal line was 6 cm.If manual anastomosis is difficult,stapling device may be used. The anus saving resection is easy if the distance was 7─9 cm.展开更多
BACKGROUND Spinal metallosis is a rare complication following spinal instrumentation whereby an inflammatory response to the metal implants results in the development of granulomatous tissue.CASE SUMMARY We describe t...BACKGROUND Spinal metallosis is a rare complication following spinal instrumentation whereby an inflammatory response to the metal implants results in the development of granulomatous tissue.CASE SUMMARY We describe the case of a 78-year-old woman who had recurrence of back pain 5 years after lumbar spine posterior decompression and instrumented fusion.Lumbar spine radiographs showed hardware loosening and magnetic resonance imaging showed adjacent segment disease.Revision surgery revealed evidence of metallosis intraoperatively.CONCLUSION Spinal metallosis can present several years after instrumentation.Radiography and computed tomography may demonstrate hardware loosening secondary to metallosis.Blood metal concentrations associated with spinal metallosis have yet to be established.Hence,metallosis is still an intraoperative and histopathological diagnosis.The presence of metallosis after spinal instrumentation likely indicates a more complex underlying problem:Pseudarthrosis,failure to address sagittal balance,infection,and cross-threading of set screws.Hence,identifying metallosis is important,but initiating treatment promptly for symptomatic implant loosening is of greater paramount.展开更多
Objective To observe IL-1B,IL-6 and TNF-a level change of the joint fluid in the experimental knee joint degeneration and the effect of the local loosening therapy.Methods Thirty rabbits were divided into 3 groups at ...Objective To observe IL-1B,IL-6 and TNF-a level change of the joint fluid in the experimental knee joint degeneration and the effect of the local loosening therapy.Methods Thirty rabbits were divided into 3 groups at random:ten in the normal contrast group,ten in the blank model group and ten in the loosening therapy group to observe the IL-1B,IL-6 and TNF-a change of the joint fluid before and after the treatment in each group.Result IL-1B,IL-6 and TNF-a level in the blank model group was obviously higher than that in the normal group.(P<0.05).IL-1B,IL-6 and TNF-a level in the treatment group was obviously lower than that in the normal group.(P<0.05).Conclusions 1)IL-1B,IL-6 and TNF-a level of the joint fluid in the blank model group was obviously higher than that in the normal group.2)Loosening soft tissues of the knees can improve IL-1B,IL-6 and TNF-a level of the joint fluid.展开更多
The consideration of unsaturated conditions is infrequently addressed in current Terzaghi’s soil arching research.A modified analytical method for calculation of unsaturated loosening earth pressure above shallow tra...The consideration of unsaturated conditions is infrequently addressed in current Terzaghi’s soil arching research.A modified analytical method for calculation of unsaturated loosening earth pressure above shallow trapdoor is proposed in this paper.By assuming the existence of a vertical slip surface above the trapdoor,the stress state of the soil in the loosening area are delineated in the extended Mohr–Coulomb circle.To account for the non-uniform distribution of vertical stress at arbitrary points along the horizontal differential soil trip,a virtual rotation circle trajectory of major principal stress is employed.Subsequently,the average vertical stress acting on the soil trip is determined through integral approach.Taking into account the influence of matric suction on soil weight and apparent cohesion,the differential equation governing the soil trip is solved analytically for cases of uniform matric suction distribution and alternatively using the finite difference method for scenarios involving non-uniform matric suction distribution.The proposed method’s validity is confirmed through comparison with published results.The parameter analysis indicates that the loosening earth pressure initially decreases and subsequently increases with the increase of the soil saturation.With the rise of groundwater level,the normalized effective loosening earth pressure shows a decreasing trend.展开更多
Loosening of threaded fasteners is a key failure mode,which is mainly caused by the slippage and friction behaviors on the thread and bearing surfaces,and will affect the integrity and reliability of products.Numerous...Loosening of threaded fasteners is a key failure mode,which is mainly caused by the slippage and friction behaviors on the thread and bearing surfaces,and will affect the integrity and reliability of products.Numerous scholars have conducted research on the loosening of threaded fasteners;however,comprehensive reviews on the loosening of threaded fasteners have been scarce.In this review article,we define loosening as a loss of preload and divide it into non-rotational and rotational loosening.The causes and mechanisms of non-rotational and rotational loosening are summarised.Some essential topics regarding loosening under transverse vibration have also attracted significant attention and have been investigated widely,including the loosening curve,critical condition of loosening,and influencing factors of loosening.The research carried out on these three topics is also summarised in this review.It is believed that our work will not only help new researchers quickly understand the state-of-the-art research on loosening,but also increase the knowledge of engineers on this critical subject.In the future,it is important to conduct more quantitative research on local slippage accumulation,and the relationship between local slippage accumulation and rotational loosening,which will have the potential to comprehensively unravel the loosening mechanism,and effectively guide the anti-loosening design of threaded fasteners.展开更多
This study investigates the vibration characteristics of bolted-flange-joined conical-cylindrical shells(BFJCCSs)through both theoretical analysis and experimental testing.The proposed model incorporates the pressure ...This study investigates the vibration characteristics of bolted-flange-joined conical-cylindrical shells(BFJCCSs)through both theoretical analysis and experimental testing.The proposed model incorporates the pressure distribution within the bolted joint and accounts for the flange effect.The energy expressions for the conical and cylindrical shells are derived from Donnell's shell theory,while those for the flanges are obtained from the Euler-Bernoulli beam theory.The Lagrange equation is used to derive the dynamic equation,and the experimental studies on the BFJCCS are conducted to validate the accuracy of the model.Subsequently,the comprehensive effects of bolt loosening and bolt number on the frequency parameters are analyzed.Additionally,the effects of the flange dimensions and cone angle on the vibration behavior of the BFJCCS are discussed.In particular,the dynamic differences between the welded conical-cylindrical shell(WCCS)and BFJCCS are investigated.It is found that compared with the WCCS,the fundamental frequency of the BFJCCS is reduced by 7.6%,and the corresponding modal damping ratio is reduced by 21.0%.However,the high-order frequencies of the BFJCCS are higher than those of the WCCS,accompanied by a higher modal damping ratio.Compared with the bolt loosening degree,the bolt number has a more significant effect on frequencies.As the bolt number decreases,the impact of the bolt loosening degree diminishes gradually.展开更多
BACKGROUND Pedicle screw fixation is frequently used to treat unstable thoracolumbar injuries;however,the rate of instrumentation failure remains considerable.The primary contributing factor leading to instrumentation...BACKGROUND Pedicle screw fixation is frequently used to treat unstable thoracolumbar injuries;however,the rate of instrumentation failure remains considerable.The primary contributing factor leading to instrumentation failure is poor bone quality.On the other hand,some evidence suggests that surgical tactics can influence long-term instrumentation stability.AIM To assess factors that influence the stability of spinal instrumentation in patients with thoracolumbar injuries.METHODS This study is a non-randomized single center ambispective evaluation of 204 consecutive patients(117 men;87 women)with unstable thoracolumbar injuries.All patients underwent either stand-alone or combined with anterior column reconstruction instrumentation.In cases with spinal cord and nerve root injuries,either posterior or anterior decompression were performed.Patients with pedicle screw loosening were identified via computed tomography imaging.Out of those,cases with clinically significant instrumentation failure were registered.RESULTS The rate of pedicle screw loosening detected by computed tomography was inversely correlated with bone radiodensity figures and an increased association with the number of instrumented levels,residual kyphotic deformity,laminectomy,and lumbosacral fixation.Intermediate screws and anterior reconstruction were associated with a clinically relevant decreased risk of pedicle screw loosening development.Either complete or partial posterior fusion within instrumented levels was capable of decreasing instrumentation failure risk,while extensive decompression with laminectomy and at least one-level total facetectomy were associated with an increased risk of instrumentation failure.Anterior decompression does not have a negative impact on instrumentation stability.CONCLUSION Intermediate screws,anterior reconstruction and posterior tension band preservation are associated with decreased rates of instrumentation instability development.Posterior fusion is beneficial in terms of instrumentation failure prevention.展开更多
BACKGROUND Total knee arthroplasty(TKA)is a widely used treatment for advanced knee osteoarthritis;however,the incidence of failures requiring revision surgery is increasing.Identifying the causes of TKA failure and a...BACKGROUND Total knee arthroplasty(TKA)is a widely used treatment for advanced knee osteoarthritis;however,the incidence of failures requiring revision surgery is increasing.Identifying the causes of TKA failure and assessing the outcomes of revision procedures are essential for improving patient care.We hypothesized that infection and aseptic loosening are the primary causes of TKA failure and that revision TKA(rTKA)significantly enhances functional outcomes.AIM To examine the primary causes of TKA failure and evaluate the functional outcomes following rTKA.METHODS This descriptive study was conducted at the Department of Orthopedic Surgery,Civil Hospital,Bahawalpur,from April to September 2024.A total of 118 patients undergoing rTKA for failed primary TKA were included.Data on demographics,causes of failure,and surgical details were collected.Functional outcomes were evaluated using the Knee Society Score and Visual Analog Scale before and six months after surgery.Statistical analysis was performed using SPSS version 25.0,with statistical significance set at P<0.05.RESULTS The leading causes of TKA failure were infection(45.8%),aseptic loosening(44.1%),and periprosthetic fractures(10.2%).The rTKA significantly improved knee function,with the mean Knee Society Score increasing from 39.43±6.18 to 78.91±6.17(P<0.001).Pain levels decreased substantially,with the mean Visual Analog Scale scores reducing from 7.99±1.37 to 1.42±1.17(P<0.001).No significant differences in outcomes were observed between single-stage and two-stage revision procedures.CONCLUSION Infection and aseptic loosening are the predominant causes of TKA failure.The rTKA effectively enhances knee function and alleviates pain,offering significant benefits to patients.展开更多
This paper investigates the self-loosening of threaded fasteners subjected to dynamic shear load. Three kinds of typical coatings, PTFE, MoS_2, and TiN applied to bolts and nuts, are tested in this investigation. The ...This paper investigates the self-loosening of threaded fasteners subjected to dynamic shear load. Three kinds of typical coatings, PTFE, MoS_2, and TiN applied to bolts and nuts, are tested in this investigation. The study experimentally examines the loosening mechanisms of fasteners and assesses the anti-loosening performance of the three tested coatings based on their tightening characteristics, loosening curves, and the damage of thread surface. Additionally, the anti-loosening performance of the three coatings is compared under different load forms. The results indicate that the PTFE and MoS_2 coatings have significant anti-loosening effect, whereas the anti-loosening performance of Ti N coating is not satisfactory. It is also found that an appropriate increase of the initial tightening torque can significantly improve the anti-loosening effect. In addition, the microscopic analyses of PTFE and MoS2 coating reveal that a reduced initial tightening torque leads to fretting wear on the thread contact surfaces of fasteners, thereby aggravating the damage.展开更多
In this study,a refined numerical model for segmental lining of a shield tunnel,which contains detailed models of reinforcement and connecting bolts,is established using finite element software.The model is first vali...In this study,a refined numerical model for segmental lining of a shield tunnel,which contains detailed models of reinforcement and connecting bolts,is established using finite element software.The model is first validated by the results from a full-scale model test.Then,based on the load-structure method,this numerical model is adopted to investigate the internal force distribution and the transverse deformation characteristics of the shield tunnel when it is subject to local soil loosening.The influence of loosening position,loosening range,and loosening extent on the mechanical response is extensively studied through comprehensive numerical analyses.The results show that the main influence of local soil loosening on the ring is to disturb the force balance and change the constraint conditions,thus changing the deformation pattern and force state.After the loosening occurs,the bending moment of the ring in the loosening range increases and the axial force decreases.The vertical convergence of the ring is the largest and the equivalent stiffness of the ring is the smallest when the local soil loosened at the haunch and the loosening range a is 90°.The vertical convergence of the ring increases with increasing of the loosening extent,and the equivalent stiffness decreases linearly with increasing of the loosening extent.The results can enhance our understanding of mechanical behaviors of segmental lining associated soil loosening,and will show a possible way for detecting soil loosening based on the measured deformation and internal forces.展开更多
文摘In response to an ageing global population,the primary hip and knee arthroplasty rate continues to increase.Although an effective treatment,up to 25%patients may require revision arthroplasty during their lifetime,commonly due to periprosthetic loosening.Revision procedures are associated with significantly increased healthcare costs;therefore,timely and accurate diagnostics are critical for clinicians and patients.Loosening,which may be septic or aseptic,remains a challenge and requires thorough clinical examination and multimodal imaging evaluation.Plain radiographs remain an essential diagnostic tool but advanced imaging modalities such as computed tomography,magnetic resonance imaging and nuclear medicine are playing an increasingly important role.This comprehensive review,through outlining the available radiological modalities,their respective strengths and weaknesses and the pertinent imaging findings,may help radiologists and orthopaedic surgeons make more informed decisions in the management of periprosthetic loosening.
基金The Youth Foundation Project of Jiangsu Province(No.BK20230337)the Natural Science Research of Jiangsu Higher Education Institutions of China(No.22KJB560004)the National Natu-ral Science Foundation of China(No.52278523)。
文摘Transmission towers,serving as the support structure of transmission lines,are significant for the functional-ity of an electric transmission system.Bolt joint loosening is one of the critical factors that can affect the safety and stability of transmission towers.In this study,the effects of bolt joint loosening on the dynamic characteristics of a 220-kV angle steel transmission tower are the main topic of concern.First,the mechanical properties of typical joints subjected to different degrees of bolt loosening are studied by finite solid-element simulation,based on which a finite hybrid-element modeling method is developed for a tower structure suffering varying loose degrees in the joints.Taking a 220-kV angle steel transmission tower as the object,the influence of the position and degree of loosening on the tower’s natural frequencies and mode shapes are simulated and discussed.The results demonstrate that the main-member splice joint and the main diagonal-horizontal member gusset plate joint account for the dominant impact on the dynamic characteristics of the tower.In addition,the dominant joint shifts from the main-member splice joint to the main diagonal-horizontal member gusset plate joint as the considered modal order increases.In the case of double joints loosening simultaneously,the loosening of nondomi-nant joints has nonnegligible effects on the tower as well.
文摘BACKGROUND Aseptic acetabular loosening can result from various factors that can be categorized into groups:patient-related,surgeon-related and implant-related.We present a case of a 63-year-old patient who at first underwent a total hip arthro-plasty(THA)using a metal-on-metal bearing due to hip arthrosis.Follow-up visits revealed no complications after the procedure.Two years after the THA,acetabular component loosening occurred due to subsequent trauma of the opposite hip,necessitating a revision THA using a ceramic-on-ceramic bearing.CASE SUMMARY We aim to illustrate a rare case where the primary reason for undergoing THA revision was not only incomplete bone graft incorporation but also improper limb load distribution.Following the revision arthroplasty,a 9-year follow-up visit revealed improvements in all evaluation measures on questionnaire compared to the state before surgery:Harris Hip Score(before surgery:15;after surgery:95),Western Ontario and McMaster Universities Arthritis Index(before surgery:96;after surgery:0),and Visual Analogue Scale(before surgery:10;after surgery:1).CONCLUSION Opposite-hip trauma caused a weight transfer to the limb after a THA procedure.This process led to a stress shielding effect,resulting in acetabular component loosening.
基金Postdoctoral Fellowship Program of CPSF,Grant/Award Number:GZC20240167Chengdu University of Technology Postgraduate Innovative Cultivation Program,Grant/Award Number:CDUT2022BJCX007Huzhou Key Laboratory Fund,Grant/Award Number:HGB23E002。
文摘The analysis of plastic loosening zone of tunnels with cold condition,high in situ stress,and weak stratum is the key scientific problem of tunnel construction in cold areas.Based on the unified strength theory and considering the coupling effect of high in situ stress and low-temperature field,the analytical model of the plastic loosening zone of tunnel surrounding rocks was proposed,and the influence laws of physical parameters(initial ground stress,freezing temperature,excavation radius,and intermediate principal stress)was explored.The results illustrate that:(1)with the coupling of low temperature and stress fields,the in-situ stress has a more significant effect on the radius of the plastic loosening zone of the tunnel surrounding rocks,showing a nonlinear correlation.When the in situ stress is small,the influence of the temperature field on the radius of the plastic loosening zone is more obvious.(2)The radius of the plastic loosening zone of the tunnel surrounding rocks increases synchronously with the excavation radius and gradually decreases with the increase of the intermediate principal stress.(3)The greater the temperature difference in the low-temperature field,the tunnel stability has a more significant response to the intermediate principal stress and is positively correlated with the coefficient of the intermediate principal stress.(4)In the actual project,the proposed model can well describe the mechanical behavior and deformation characteristics of tunnel surrounding rocks in low-temperature environment,showing applicability.The research results are expected to provide a theoretical basis for the study of tunnel stability in cold areas.
基金supported by the National Natural Science Foundation of China(No.51675050 and 51935003)。
文摘Threaded fasteners naturally tend to loosen under vibration,impact,or alternating thermal load.Various anti-loosening methods or strategies are widely applied for preventing loosening,including a few anti-loosening designs and anti-loosening structures.In this review,a variety of influencing factors that improved the anti-loosening ability and helped guide the anti-loosening designs of threaded fasteners are summarized.Second,the anti-loosening structures are classified into two categories,that is,conventional and new-style anti-loosening structures.The former refers to widely used structures in engineering applications,while the latter refers to novel structures not available in the markets.The research on the evaluation and comparison of various conventional anti-loosening structures in terms of preventing loosening is summarized in detail and the newstyle anti-loosening structures from five different aspects are also surveyed based on different structural characteristics.In the future,the effects of combined factors on loosening should be considered to achieve optimal anti-loosening designs.More quantitative research on the mathematical relationship between the anti-loosening performance of conventional structures and structural parameters must be conducted.Furthermore,novel structures with excellent abilities to prevent loosening are needed,and issues of difficulties in installation and disassembly,low strength at thread,large deformation,and temperature dependence also need to be addressed.
基金Supported by National Maize Industry Technology System(CARS-02-38)Science and Technology Development Project of Jilin Province(LFGC14308)Special Fund for Scientific Research in the Public Interest(201303125-03)
文摘[Objective] This study was conducted to explore the effects of deep loos- ening on soil structure and the activity of maize root system, to provide a theoreti- cal basis for the efficient and rational use of water resources. [Method] Three differ- ent loosening treatments for maize in ridges were performed in field trials as fol- lows： conventional ridge tillage, loosening the cm in spring （deep loosening in spring）, and depth of 30 cm in autumn （deep loosening in soils between rows to a depth of 30 oosening the soils between rows to a autumn）. Then the soil properties and the development of root system were measured to evaluate the effects of different loosening methods. [Result] Soil compactness was significantly reduced after deep loosening in spring, There were significant differences in soil compactness in 0-20 cm depth and soil bulk density in 0-40 cm depth between deep loosening in spring and deep loosening in autumn, deep loosening in spring and conventional ridge tillage. The soil water holding capacity was also significantly different between the two deep loosening treatments and conventional ridge tillage. Moreover, the root ac- tive absorption area of maize of deep loosening in spring was higher than that of conventionai ridge tillage. [Conclusion] Deep loosening can reduce soil compactness, bulk density, and improve soil water holding capacity, soil water content and the root activity of maize. Deep loosening in spring is better in soil improvement be- cause spring is closer to the growth period of crops than autumn. So, deep loosen- ing is conducive to the improvement of soil compactness and structure.
基金Supported by The"Deutsche Arthrose-Hilfe e.V.",No.P192-A362-2009-12
文摘AIM To assess serum levels of RANK-ligand(RANKL) and osteoprotegerin(OPG) as biomarkers for periprosthetic joint infection(PJI) and compare their accuracy with standard tests.METHODS One hundred and twenty patients presenting with a painful total knee or hip arthroplasty with indication for surgical revision were included in this prospective clinical trial. Based on standard diagnostics(joint aspirate, microbiological, and histological samples) and Musculoskeletal Infection Society consensus classification,patients were categorized into PJI, aseptic loosening,and control groups. Implant loosening was assessed radiographically and intraoperatively. Preoperative serum samples were collected and analyzed for RANKL, OPG, calcium, phosphate, alkaline phosphatase(AP), and the bone-specific subform of AP(b AP). Statistical analysis was carried out, testing for significant differences between the three groups and between stable and loose implants. RESULTS All three groups were identical in regards to age, gender, and joint distribution. No statistically significant differences in the serum concentration of RANKL(P = 0.16) and OPG(P = 0.45) were found between aseptic loosening and PJI, with a trend towards lower RANKL concentrations and higher OPG concentrations in the PJI group. The RANKL/OPG ratio was significant for the comparison between PJI and non-PJI(P = 0.005). A ratio > 60 ruled out PJI in all cases(specificity: 100%, 95%CI: 89, 11% to 100.0%) but only 30% of non-PJI patients crossed this threshold. The positive predictive value remained poor at any cut-off. In the differentiation between stable and loose implants, none of the parameters measured(calcium, phosphate, AP, and b AP) showed a significant difference, and only AP and b AP measurements showed a tendency towards higher values in the loosened group(with P = 0.09 for AP and P = 0.19 for b AP). CONCLUSION Lower RANKL and higher OPG concentrations could be detected in PJI, without statistical significance.
基金Supported by National Natural Science Foundation of China(Grant No.51675446)Independent Subject of State Key Laboratory of Traction Power(Grant No.2019TPL-T13).
文摘Existing research on the competitive failure relationship,failure mechanism,and influencing factors of bolt loosening and fatigue under different preloads is insufficient.This study analyzes the competitive failure relationship between bolt loosening and fatigue under composite excitation through competitive failure tests of bolt loosening and fatigue under different preloads.The results indicated that the failure mode of the bolt is only related to the load ratio(R)and is unrelated to the initial preload and excitation amplitude,which only determine the failure life of the bolt.The small axial loads of composite excitation can restrain bolt failure,and the significant degree of this restraining effect is differ-ent for different preloads.Subsequently,a fracture analysis of the bolt was performed to verify the competitive failure relationship of the bolt from a microscopic perspective,and the competitive failure mechanism of the bolt was deter-mined.Based on the findings,we propose a calculation equation for the optimal preload of 8.8 grade high-strength bolts that can serve as a reference for engineering applications.
文摘BACKGROUND The majority of published data report the results of biomechanical tests of various design pedicle screw performance.The clinical relevance and relative contribution of screw design to instrumentation stability have been insufficiently studied.AIM To estimate the contribution of screw design to rate of pedicle screw loosening in patients with degenerative diseases of the lumbar spine.METHODS This study is a prospective evaluation of 175 patients with degenerative diseases and instability of the lumbar spine segments.Participants underwent spinal instrumentation employing pedicle screws with posterior only or transforaminal interbody fusion.Follow-up was for 18 mo.Patients with signs of pedicle screw loosening on computed tomography were registered;logistic regression analysis was used to identify the factors that influenced the rate of loosening.RESULTS Parameters included in the analysis were screw geometry,type of thread,external and internal screw diameter and helical pitch,bone density in Hounsfield units,number of levels fused,instrumentation without anterior support,laminectomy,and unilateral and bilateral total facet joint resection.The rate of screw loosening decreased with the increment in outer diameter,decrease in core diameter and helical pitch.The rate of screw loosening correlated positively with the number of fused levels and decreasing bone density.Bilateral facet joint removal significantly favored pedicle screw loosening.The influence of other factors was insignificant.CONCLUSION Screw parameters had a significant impact on the loosening rate along with bone quality characteristics,the number of levels fused and the extensiveness of decompression.The significance of the influence of screw parameters was comparable to those of patient-and surgery-related factors.Pedicle screw loosening was influenced by helical pitch,inner and outer diameter,but screw geometry and thread type were insignificant factors.
基金supported by the National Natural Science Foundation of China (Nos.51105209,61401211, 51175267)the China Postdoctoral Science Foundation (Nos.2012M511760, 2013T60540)+3 种基金the Specialized Research Fund for the Doctoral Program of Higher Education (No.20113219120005)the Jiangsu Province Science and Technology Support Program (No.BE2012034)the Ministry of Science & Technology of Zhengzhou (No. 131PPTGG425)the Zijin Intelligent Program of Nanjing University of Science and Technology (No. 2013ZJ0203)
文摘Bolted connections are commonly used in aerospace structures.Once the bolts on the aircraft are damaged or loose,the consequence will be disastrous.Therefore,monitoring bolt loosening is especially required.However,periodic manual inspection costs much money and time.And it is very difficult to achieve multi-point monitoring for many bolted structures in an aircraft.Therefore,a low-cost,reliable detection method based on wireless sensor networks is presented.The reed switch is selected as a sensor for bolt loosening monitor.The chip PT2262 and PT2272are chosen as hardware codec chip for multi-point placement.A wireless transmitter and receiver circuit is designed on 315 MHz frequency.The codec chip and the wireless transmission are triggered by the reed switches.Bolt loosening is detected by the receiving terminal and indicated by light and sound alarms.The wireless transmitter and the receiver circuit are tested and the monitoring system is verified by experiments.The results show that bolt loosening can be effectively detected within 300 m.The developed sensor network is expected to solve multi-point bolt detection problems and provide a low-cost and reliable monitoring technology.
文摘In low rectal cancer surgery,the section of rectum destal to the lower tumor maigin is relaxed and lengthened after fully isolation of the organ. This would facilitate the adoption of anus saving operation.Before and after fully isolation of the rectum in low ratal cancer surgery, the distance between the lower tumor margin and the anorectal line was measured by the same rectuscope introduced through the anus.The two results were compared .The average lengthening was less than 1 cm if the lower tumor marginanorectal line distance was 5 cm.It was 1─2 cm if the lower tumor margin-anorectal distance was 6 cm.It was more than 2 cm if the distance was 7─9 cm.The loosening and lengthening of the rectal canal was related to the presence of lymphnode metastasis and the skill of the operator.The lengthening was also influenced by the body build of the patient,involvement of the rectal circumference and the Dukes stage. Modified Park's operation,trans abdominosacral resection with anastormosis of rectum,and anterior resection on transpubic approach are indicated for those in whom the lower tumor margin-anorectal line distance was 5 cm The rectectomy-anastomosis in the abdominal cavity(Dixon's operation)is indicated for those in whom the lower tumor margin-anorectal line was 6 cm.If manual anastomosis is difficult,stapling device may be used. The anus saving resection is easy if the distance was 7─9 cm.
文摘BACKGROUND Spinal metallosis is a rare complication following spinal instrumentation whereby an inflammatory response to the metal implants results in the development of granulomatous tissue.CASE SUMMARY We describe the case of a 78-year-old woman who had recurrence of back pain 5 years after lumbar spine posterior decompression and instrumented fusion.Lumbar spine radiographs showed hardware loosening and magnetic resonance imaging showed adjacent segment disease.Revision surgery revealed evidence of metallosis intraoperatively.CONCLUSION Spinal metallosis can present several years after instrumentation.Radiography and computed tomography may demonstrate hardware loosening secondary to metallosis.Blood metal concentrations associated with spinal metallosis have yet to be established.Hence,metallosis is still an intraoperative and histopathological diagnosis.The presence of metallosis after spinal instrumentation likely indicates a more complex underlying problem:Pseudarthrosis,failure to address sagittal balance,infection,and cross-threading of set screws.Hence,identifying metallosis is important,but initiating treatment promptly for symptomatic implant loosening is of greater paramount.
基金Project(99JJy2081)supported by the Natural Science Foundation of Hunan Province
文摘Objective To observe IL-1B,IL-6 and TNF-a level change of the joint fluid in the experimental knee joint degeneration and the effect of the local loosening therapy.Methods Thirty rabbits were divided into 3 groups at random:ten in the normal contrast group,ten in the blank model group and ten in the loosening therapy group to observe the IL-1B,IL-6 and TNF-a change of the joint fluid before and after the treatment in each group.Result IL-1B,IL-6 and TNF-a level in the blank model group was obviously higher than that in the normal group.(P<0.05).IL-1B,IL-6 and TNF-a level in the treatment group was obviously lower than that in the normal group.(P<0.05).Conclusions 1)IL-1B,IL-6 and TNF-a level of the joint fluid in the blank model group was obviously higher than that in the normal group.2)Loosening soft tissues of the knees can improve IL-1B,IL-6 and TNF-a level of the joint fluid.
基金supported by the National Natural Science Foundation of China(Grant No.41874067)the Innovative Funds Plan of Henan University of Technology(No.2022ZKCJ07)the Commonweal Technology Project of Jinhua City(No.2023-4-037).
文摘The consideration of unsaturated conditions is infrequently addressed in current Terzaghi’s soil arching research.A modified analytical method for calculation of unsaturated loosening earth pressure above shallow trapdoor is proposed in this paper.By assuming the existence of a vertical slip surface above the trapdoor,the stress state of the soil in the loosening area are delineated in the extended Mohr–Coulomb circle.To account for the non-uniform distribution of vertical stress at arbitrary points along the horizontal differential soil trip,a virtual rotation circle trajectory of major principal stress is employed.Subsequently,the average vertical stress acting on the soil trip is determined through integral approach.Taking into account the influence of matric suction on soil weight and apparent cohesion,the differential equation governing the soil trip is solved analytically for cases of uniform matric suction distribution and alternatively using the finite difference method for scenarios involving non-uniform matric suction distribution.The proposed method’s validity is confirmed through comparison with published results.The parameter analysis indicates that the loosening earth pressure initially decreases and subsequently increases with the increase of the soil saturation.With the rise of groundwater level,the normalized effective loosening earth pressure shows a decreasing trend.
基金The authors are grateful for support by the National Natural Science Foundation of China(Nos.51935003 and 51675050)the National Defense Fundamental Research Foundation of China(No.JCKY2016204B201)。
文摘Loosening of threaded fasteners is a key failure mode,which is mainly caused by the slippage and friction behaviors on the thread and bearing surfaces,and will affect the integrity and reliability of products.Numerous scholars have conducted research on the loosening of threaded fasteners;however,comprehensive reviews on the loosening of threaded fasteners have been scarce.In this review article,we define loosening as a loss of preload and divide it into non-rotational and rotational loosening.The causes and mechanisms of non-rotational and rotational loosening are summarised.Some essential topics regarding loosening under transverse vibration have also attracted significant attention and have been investigated widely,including the loosening curve,critical condition of loosening,and influencing factors of loosening.The research carried out on these three topics is also summarised in this review.It is believed that our work will not only help new researchers quickly understand the state-of-the-art research on loosening,but also increase the knowledge of engineers on this critical subject.In the future,it is important to conduct more quantitative research on local slippage accumulation,and the relationship between local slippage accumulation and rotational loosening,which will have the potential to comprehensively unravel the loosening mechanism,and effectively guide the anti-loosening design of threaded fasteners.
基金supported by the National Natural Science Foundation of China(No.12272088)the Out-standing Youth Science Foundation of Liaoning Province of China(No.2024JH3/50100013)。
文摘This study investigates the vibration characteristics of bolted-flange-joined conical-cylindrical shells(BFJCCSs)through both theoretical analysis and experimental testing.The proposed model incorporates the pressure distribution within the bolted joint and accounts for the flange effect.The energy expressions for the conical and cylindrical shells are derived from Donnell's shell theory,while those for the flanges are obtained from the Euler-Bernoulli beam theory.The Lagrange equation is used to derive the dynamic equation,and the experimental studies on the BFJCCS are conducted to validate the accuracy of the model.Subsequently,the comprehensive effects of bolt loosening and bolt number on the frequency parameters are analyzed.Additionally,the effects of the flange dimensions and cone angle on the vibration behavior of the BFJCCS are discussed.In particular,the dynamic differences between the welded conical-cylindrical shell(WCCS)and BFJCCS are investigated.It is found that compared with the WCCS,the fundamental frequency of the BFJCCS is reduced by 7.6%,and the corresponding modal damping ratio is reduced by 21.0%.However,the high-order frequencies of the BFJCCS are higher than those of the WCCS,accompanied by a higher modal damping ratio.Compared with the bolt loosening degree,the bolt number has a more significant effect on frequencies.As the bolt number decreases,the impact of the bolt loosening degree diminishes gradually.
基金Supported by AI For Spinal Surgery Planning and Results Assessment Project under the“Priority 2030”Academic Leadership Initiative,No.6.18-01/240724-15.
文摘BACKGROUND Pedicle screw fixation is frequently used to treat unstable thoracolumbar injuries;however,the rate of instrumentation failure remains considerable.The primary contributing factor leading to instrumentation failure is poor bone quality.On the other hand,some evidence suggests that surgical tactics can influence long-term instrumentation stability.AIM To assess factors that influence the stability of spinal instrumentation in patients with thoracolumbar injuries.METHODS This study is a non-randomized single center ambispective evaluation of 204 consecutive patients(117 men;87 women)with unstable thoracolumbar injuries.All patients underwent either stand-alone or combined with anterior column reconstruction instrumentation.In cases with spinal cord and nerve root injuries,either posterior or anterior decompression were performed.Patients with pedicle screw loosening were identified via computed tomography imaging.Out of those,cases with clinically significant instrumentation failure were registered.RESULTS The rate of pedicle screw loosening detected by computed tomography was inversely correlated with bone radiodensity figures and an increased association with the number of instrumented levels,residual kyphotic deformity,laminectomy,and lumbosacral fixation.Intermediate screws and anterior reconstruction were associated with a clinically relevant decreased risk of pedicle screw loosening development.Either complete or partial posterior fusion within instrumented levels was capable of decreasing instrumentation failure risk,while extensive decompression with laminectomy and at least one-level total facetectomy were associated with an increased risk of instrumentation failure.Anterior decompression does not have a negative impact on instrumentation stability.CONCLUSION Intermediate screws,anterior reconstruction and posterior tension band preservation are associated with decreased rates of instrumentation instability development.Posterior fusion is beneficial in terms of instrumentation failure prevention.
文摘BACKGROUND Total knee arthroplasty(TKA)is a widely used treatment for advanced knee osteoarthritis;however,the incidence of failures requiring revision surgery is increasing.Identifying the causes of TKA failure and assessing the outcomes of revision procedures are essential for improving patient care.We hypothesized that infection and aseptic loosening are the primary causes of TKA failure and that revision TKA(rTKA)significantly enhances functional outcomes.AIM To examine the primary causes of TKA failure and evaluate the functional outcomes following rTKA.METHODS This descriptive study was conducted at the Department of Orthopedic Surgery,Civil Hospital,Bahawalpur,from April to September 2024.A total of 118 patients undergoing rTKA for failed primary TKA were included.Data on demographics,causes of failure,and surgical details were collected.Functional outcomes were evaluated using the Knee Society Score and Visual Analog Scale before and six months after surgery.Statistical analysis was performed using SPSS version 25.0,with statistical significance set at P<0.05.RESULTS The leading causes of TKA failure were infection(45.8%),aseptic loosening(44.1%),and periprosthetic fractures(10.2%).The rTKA significantly improved knee function,with the mean Knee Society Score increasing from 39.43±6.18 to 78.91±6.17(P<0.001).Pain levels decreased substantially,with the mean Visual Analog Scale scores reducing from 7.99±1.37 to 1.42±1.17(P<0.001).No significant differences in outcomes were observed between single-stage and two-stage revision procedures.CONCLUSION Infection and aseptic loosening are the predominant causes of TKA failure.The rTKA effectively enhances knee function and alleviates pain,offering significant benefits to patients.
基金the financial support provided by the National Science Funds for Distinguished Young Scholars(No.51025519)the Changjiang Scholarships and Innovation Team Development Plan(No.IRT1178)the Self-Topic Fund of Traction Power State Key Laboratory(No.2016TPL-Z03)
文摘This paper investigates the self-loosening of threaded fasteners subjected to dynamic shear load. Three kinds of typical coatings, PTFE, MoS_2, and TiN applied to bolts and nuts, are tested in this investigation. The study experimentally examines the loosening mechanisms of fasteners and assesses the anti-loosening performance of the three tested coatings based on their tightening characteristics, loosening curves, and the damage of thread surface. Additionally, the anti-loosening performance of the three coatings is compared under different load forms. The results indicate that the PTFE and MoS_2 coatings have significant anti-loosening effect, whereas the anti-loosening performance of Ti N coating is not satisfactory. It is also found that an appropriate increase of the initial tightening torque can significantly improve the anti-loosening effect. In addition, the microscopic analyses of PTFE and MoS2 coating reveal that a reduced initial tightening torque leads to fretting wear on the thread contact surfaces of fasteners, thereby aggravating the damage.
基金the financial support provided by National Key R&D Program of China under Grant No.2018YFB2100901the National Natural Science Foundation of China under Grant Nos.51938008,52090081and China Academy of Railway Sciences Fund Project under Grand No.2019YJ181.
文摘In this study,a refined numerical model for segmental lining of a shield tunnel,which contains detailed models of reinforcement and connecting bolts,is established using finite element software.The model is first validated by the results from a full-scale model test.Then,based on the load-structure method,this numerical model is adopted to investigate the internal force distribution and the transverse deformation characteristics of the shield tunnel when it is subject to local soil loosening.The influence of loosening position,loosening range,and loosening extent on the mechanical response is extensively studied through comprehensive numerical analyses.The results show that the main influence of local soil loosening on the ring is to disturb the force balance and change the constraint conditions,thus changing the deformation pattern and force state.After the loosening occurs,the bending moment of the ring in the loosening range increases and the axial force decreases.The vertical convergence of the ring is the largest and the equivalent stiffness of the ring is the smallest when the local soil loosened at the haunch and the loosening range a is 90°.The vertical convergence of the ring increases with increasing of the loosening extent,and the equivalent stiffness decreases linearly with increasing of the loosening extent.The results can enhance our understanding of mechanical behaviors of segmental lining associated soil loosening,and will show a possible way for detecting soil loosening based on the measured deformation and internal forces.
