Heavy-duty freight railway axles are no less important than those of passenger trains,owing to the potentially catastrophic results caused by the derailment of trains carrying hazardous substances.Intrinsic and extrin...Heavy-duty freight railway axles are no less important than those of passenger trains,owing to the potentially catastrophic results caused by the derailment of trains carrying hazardous substances.Intrinsic and extrinsic imperfections challenge classical design theories built based on the safe life concept,and damage tolerance assessment becomes vital for the safety and reliability of long-term serviced railway axles,as pits and scratches are common defects for heavy-duty railway axles.In this work,four-point rotating bending fatigue tests of AAR-CM railway axle steel specimens with semicircular and circumferential groove notches are conducted.The fatigue limit of the semicircular notched specimens was evaluated based on fracture mechanics theory,in which non-conservative results are obtained by the El Haddad model and the S–N curves of circumferential groove notched specimens are correlated by the theory of critical distance(TCD).展开更多
NiTi alloy lattice structures are crucial for reusable energy absorption due to their shape memory effects.However,existing NiTi alloy lattice structures always suffer from localized deformation bands during loading,c...NiTi alloy lattice structures are crucial for reusable energy absorption due to their shape memory effects.However,existing NiTi alloy lattice structures always suffer from localized deformation bands during loading,causing local strains to exceed the recoverable strain limit of the alloy and significantly reducing their reusable energy-absorbing capacity.In this study,we developed a NiTi alloy helical lattice structure(HLS)to effectively prevent localized deformation bands.This is attributed to its struts distributing stress and strain uniformly through torsional deformation,thereby alleviating local stress concentrations and suppressing the formation of localized deformation bands.Additionally,its unit cells provide mutual support and reinforcement during deformation,effectively preventing the progression of localized deformation bands.The NiTi alloy HLS exhibits superior reusable energy absorption compared to previously reported reusable energy-absorbing materials/structures and enhanced damage tolerance under large compression strain.This study provides valuable insights for the development of high-performance reusable NiTi alloy energy-absorbing lattice structures.展开更多
The discipline of damage tolerance assessment has experienced significant advancements due to the emergence of smart materials and self-repairable structures.This review offers a comprehensive look into both tradition...The discipline of damage tolerance assessment has experienced significant advancements due to the emergence of smart materials and self-repairable structures.This review offers a comprehensive look into both traditional and innovative methodologies employed in damage tolerance assessment.After a detailed exploration of damage tolerance concepts and their historical progression,the review juxtaposes the proven techniques of damage assessment with the cutting-edge innovations brought about by smart materials and self-repairable structures.The subsequent sections delve into the synergistic integration of smart materials with self-repairable structures,marking a pivotal stride in damage tolerance by establishing an autonomous system for immediate damage identification and self-repair.This holistic approach broadens the applicability of these technologies across diverse sectors yet brings forth unique challenges demanding further innovation and research.Additionally,the review examines future prospects that combine advanced manufacturing processes with data-centric methodologies,amplifying the capabilities of these‘intelligent’structures.The review culminates by highlighting the transformative potential of this union between smart materials and self-repairable structures,promoting a sustainable and efficient engineering paradigm.展开更多
Soft robotics focuses on addressing the locomotion problem in unstructured environments and the manipulation problem of non-cooperative objects,which inevitably leads to soft robots encountering multiple uncertainties...Soft robotics focuses on addressing the locomotion problem in unstructured environments and the manipulation problem of non-cooperative objects,which inevitably leads to soft robots encountering multiple uncertainties and damages.Therefore,improving the robustness of soft robots in hostile environmental conditions has always been a challenge.Existing methods usually improve this robustness through damage isolation,material elasticity,and self-healing mechanisms.In contrast to existing methods,this paper proposes a method to improve the robustness of an untethered soft-swallowing robot based on the physical properties of fluids,such as the high specific heat capacity of water,the viscosity of soft glue,and the shear thickening of non-Newtonian fluids.Based on this method,we developed a soft-swallowing robot with enhanced heat resistance,damage tolerance,and impact mitigation capability by only replacing its fluid working medium.Experiments show that the developed soft-swallowing robot can withstand high temperatures above 600°C,maintain high performance even after enduring hundreds of damages,and protect grasped object from more than 90%of external impacts.This principle extends beyond the three fluids used in this study.Other fluids,such as magnetic fluid,can increase adhesion to metal materials,whereas oily fluids can reduce frictional resistance between soft structures.Additionally,other solid materials with elasticity and compliance can serve as alternative working mediums for the soft-swallowing robot.This work contributes an effective method for fluid-dependent soft robotic systems to resist the damage from uncertain factors in harsh environments.展开更多
In addition to well-defined DNA repair pathways, all living organisms have evolved mechanisms to avoid cell death caused by replication fork collapse at a site where replication is blocked due to disruptive covalent m...In addition to well-defined DNA repair pathways, all living organisms have evolved mechanisms to avoid cell death caused by replication fork collapse at a site where replication is blocked due to disruptive covalent modifications of DNA. The term DNA damage tolerance （DDT） has been employed loosely to include a collection of mechanisms by which cells survive replication-blocking lesions with or without associated genomic instability. Recent genetic analyses indicate that DDT in eukaryotes, from yeast to human, consists of two parallel pathways with one being error-free and another highly mutagenic. Interestingly, in budding yeast, these two pathways are mediated by sequential modifications of the proliferating cell nuclear antigen （PCNA） by two ubiquitination complexes Rad6-Rad18 and Mms2-Ubc13-Rad5. Damage-induced monoubiquitination of PCNA by Rad6-Rad18 promotes translesion synthesis （TLS） with increased mutagenesis, while subsequent polyubiquitination of PCNA at the same K164 residue by Mms2-Ubc13-Rad5 promotes error-free lesion bypass. Data obtained from recent studies suggest that the above mechanisms are conserved in higher eukaryotes. In particular, mammals contain multiple specialized TLS polymerases. Defects in one of the TLS polymerases have been linked to genomic instability and cancer.展开更多
According to the rules of UIC515-3,the service loads of the axles are defined,which include some different loads cases as follows:the static loads;the impact loads resulted from running through the rail joints and une...According to the rules of UIC515-3,the service loads of the axles are defined,which include some different loads cases as follows:the static loads;the impact loads resulted from running through the rail joints and unevenness rails;the loads through curves and from braking.Through the calculating and analysis,the stress distribution of the hollow axles is obtained for 200 km/h high speed motor trains used in China.At the same time,the fatigue crack growth of hollow axles is studied,and the initial surface cracks of 2 mm depth caused by hard objects strike or the other causes are discussed.On the basis of the linear elastic fracture mechanics theory,the stress intensity factor of the crack of the geometry transition outside the wheel seat is also studied.Associated with fatigue crack propagation equation and the corresponding crack propagation threshold,the crack propagation characteristics under different shapes are calculated.Then the running distances are educed with different shapes propagating to the critical length,and the estimation of the residual lives about hollow axles which are the reference values of examine and repair limit of the hollow axle is given.展开更多
Impact damage tolerance is provided in intensity design on composites. The compression intensity of impacted composites requires more than 60% of its original intensity. The influence of impact on compressive intensit...Impact damage tolerance is provided in intensity design on composites. The compression intensity of impacted composites requires more than 60% of its original intensity. The influence of impact on compressive intensity and electrical resistance of carbon fabric/epoxy-matrix composites was studied in this paper. The experimental results shows that impact can cause damage in composites, degenerate compressive intensity, and increase resistance. The electrical resistance change rate was used as an evaluation indicator of impact damage tolerance of composites. Impact damage, which results from the applying process of composites, can be identified in time by electrical resistance measurement. So, the safety performance of composites can also be improved.展开更多
In this paper an experimental study on damage tolerance behaviour of composite panels with softening strips is carried out. A prediction method of residual strength of panels with softening strips is proposed. The com...In this paper an experimental study on damage tolerance behaviour of composite panels with softening strips is carried out. A prediction method of residual strength of panels with softening strips is proposed. The comparison between estimated and experimental results shows that the prediction method can be applied to design. In this paper the failure mechanisms are described.展开更多
The main purpose of this paper is providing a reference for further research. According to the papers and reports on structural durability and probabilistic damage tolerance, the present paper summarized the pro- gres...The main purpose of this paper is providing a reference for further research. According to the papers and reports on structural durability and probabilistic damage tolerance, the present paper summarized the pro- gress of the theoretical considerations and engineering application. Several models used in structural durability and probabilistic damage tolerance are reviewed. The characteristics and problems of these methods are ana- lyzed. A new kind of combined analysis model on structural durability and damage tolerance are also introduced. New progress of analysis theory and numerical methods on structural reliability are discussed, such as the re- sponse surface method and numerical method combining neural networks and Monte Carlo simulation. The analy- sis shows that these methods can improve computational efficiency significantly and maintain high computational accuracy. Finally, some prospects of the key research directions are discussed.展开更多
Anomaly distribution is an essential input for the probabilistic damage tolerance assessment,which is required by the airworthiness certification criteria Federal Aviation Regulation(FAR)33.70.The default anomaly dist...Anomaly distribution is an essential input for the probabilistic damage tolerance assessment,which is required by the airworthiness certification criteria Federal Aviation Regulation(FAR)33.70.The default anomaly distribution of hole features has been established and published in airworthiness advisory circular 33.70-2 based on historical anomaly data collected from cracked or ruptured parts recorded in laboratory analysis reports of the special industries before 2005.However,for other industries,this default anomaly distribution fails to reflect the machining level of these industries.Besides,insufficient historical maintenance anomaly data makes the mathematical model of the default distribution inapplicable,and few models can deal with the production data.Therefore,this paper proposes a model for achieving the anomaly distribution of hole features induced by machine or maintenance process,including collecting anomaly data,deriving the exceedance number by the probability of detection(POD),conducting the curve fitting process,and calibrating and modifying the anomaly distribution.The anomaly distribution and the probability of failure(POF)are dependent on defect numbers as well as confidence levels.To recommend the number of collected data and the correction factor for the POFs with different sample numbers and confidence levels,the sensitivity analysis is conducted by quantifying the influence of the anomaly distributions of different anomaly numbers on the POFs.Results show that when the anomaly number is 25,the differences between the POFs are less than 32.9%,and a 1.329 correction factor zP is supposed to modify the POF.When the anomaly number is larger than 50,a 1.2 correction factor zP is supposed to obtain the most conservative risk value with a 95%confidence level.展开更多
Overview of the DNA damage response(DDR)in tumor cells.DDR is a highly coordinated signaling network that repairs DNA damage caused by intrinsic cellular processes and extrinsic insults,thereby preventing genome insta...Overview of the DNA damage response(DDR)in tumor cells.DDR is a highly coordinated signaling network that repairs DNA damage caused by intrinsic cellular processes and extrinsic insults,thereby preventing genome instability.Depending on the type of damage,distinct DNA damage repair and DNA damage tolerance(DDT)pathways are involved and coordinately regulated.展开更多
Fabricating damage tolerant porous ceramics with efficient energy absorption and impact-resistant capability has been a challenge because of the brittle nature of ceramic materials.In nature,mineralized tissues or org...Fabricating damage tolerant porous ceramics with efficient energy absorption and impact-resistant capability has been a challenge because of the brittle nature of ceramic materials.In nature,mineralized tissues or organisms such as cuttlebones and diatoms have evolved with hierarchical porous structures to overcome this difficulty.A bioinspired design of ceramic lattice structure with pores at multiple length scales,ranging from few nanometers to hundreds of micrometers,is proposed in the present work.These ceramic lattices with hierarchical porous structures were successfully fabricated via 3D cryogenic printing.Under quasi-static compressions,the printed ceramic lattices showed unprecedented long plateau strain(∼60%)and a specific energy absorption of∼10 kJ·kg^(−1) with a porosity of∼90%.The resulting energy absorption capability was comparable with most composites and metals,thus overcoming the brittle nature of traditional porous ceramics.This was attributed to the delayed destruction of the lattice structure,as well as the gradual collapse of pores at multiple length scales.Similar trends have also been observed under split Hopkinson pressure bar(SHPB)tests,indicating excellent energy absorption under high strain-rate impacts.The proposed 3D printing technique that produces hierarchical pores was also demonstrated to apply to other functional materials,such as silicon carbide,barium titanate,hydroxyapatite,and even titanium alloy,thus opening up new possibilities for fabricating bioinspired hierarchical porous structures.展开更多
Probabilistic damage tolerance is a critical method to understand and communicate risk and safety.This paper reviews recent research on the probabilistic damage tolerance design for life-limited parts.The vision of th...Probabilistic damage tolerance is a critical method to understand and communicate risk and safety.This paper reviews recent research on the probabilistic damage tolerance design for life-limited parts.The vision of the probabilistic damage tolerance assessment is provided.Five core parts of the probabilistic damage tolerance method are introduced separately,including the anomaly distribution,stress processing and zone definition,fatigue and fracture calculation method,probability of failure(POF)calculation method,and the combination with residual stress induced by the manufacturing process.The above currently-available risk assessment methods provide practical tools for failure risk predictions and are applied by the airworthiness regulations.However,new problems are exposed with the development of the aeroengines.The time-consuming anomaly distribution derivation process restricts the development of the anomaly distribution,especially for the developing aviation industries with little empirical data.Additionally,the strong transient characteristic is prominent because of the significant temperature differences during the take-off and climbing periods.The complex loads then challenge the fatigue and fracture calculation model.Besides,high computational efficiency is required because various variables are considered to calculate the POF.Therefore,new technologies for the probabilistic damage tolerance assessment are provided,including the efficient anomaly distribution acquisition method based on small samples,the zone definition method considering transient process,and stress intensity factor(SIF)solutions under arbitrary stress distributions combined with the machine learning method.Then,an efficient numerical integration method for calculating failure risk based on the probability density evolution theory is proposed.Meanwhile,the influence of the manufacturing process on residual stress and the failure risk of the rotors is explored.The development of the probabilistic damage tolerance method can meet the requirement of the published airworthiness regulation Federal Aviation Regulation(FAR)33.70 and guide the modification or amendment of new regulations to ensure the safety of the high-energy rotors.展开更多
To study the conservative life of the artificial mechanical heart valve holder,CATIA software was used for modeling,and ABAQUS finite element analysis was used to analyze the stress of the valve holder in the complex ...To study the conservative life of the artificial mechanical heart valve holder,CATIA software was used for modeling,and ABAQUS finite element analysis was used to analyze the stress of the valve holder in the complex environment of the human body and the residual thermal stress during production and processing.The damage tolerance method based on fracture mechanics analyzes the maximum initial crack size that the heart valve holder can tolerate under the premise that the structural safety life is longer than the life of the implanted patient.The results show that the maximum initial crack size is only tens of microns;the traditional S/N life analysis can only obtain non-conservative life,and the damage tolerance method is the basic requirement for analyzing the life and quality control of artificial mechanical heart valves.展开更多
To ensure the structural integrity of life-limiting component of aeroengines,Probabilistic Damage Tolerance(PDT)assessment is applied to evaluate the failure risk as required by airworthiness regulations and military ...To ensure the structural integrity of life-limiting component of aeroengines,Probabilistic Damage Tolerance(PDT)assessment is applied to evaluate the failure risk as required by airworthiness regulations and military standards.The PDT method holds the view that there exist defects such as machining scratches and service cracks in the tenon-groove structures of aeroengine disks.However,it is challenging to conduct PDT assessment due to the scarcity of effective Probability of Detection(POD)model and anomaly distribution model.Through a series of Nondestructive Testing(NDT)experiments,the POD model of real cracks in tenon-groove structures is constructed for the first time by employing the Transfer Function Method(TFM).A novel anomaly distribution model is derived through the utilization of the POD model,instead of using the infeasible field data accumulation method.Subsequently,a framework for calculating the Probability of Failure(POF)of the tenon-groove structures is established,and the aforementioned two models exert a significant influence on the results of POF.展开更多
In practical engineering applications,composite laminates frequently encounter complex multiple low-velocity impact events.The damage coupling caused by the different Angles Between Impact Positions(ABIP)is a key fact...In practical engineering applications,composite laminates frequently encounter complex multiple low-velocity impact events.The damage coupling caused by the different Angles Between Impact Positions(ABIP)is a key factor in reducing the load-bearing capacity of the laminates.It is worth noting that in real impact events,the delamination damage information of laminates is easier to capture directly.Therefore,it is crucial to predict the damage tolerance of laminates by analyzing their delamination damage images.This paper adopts an integrated finite element model to present an in-depth study on the damage characteristics and Compression-After-Impact(CAI)strength of carbon/glass hybrid laminates subjected to multiple low-velocity impacts at different ABIP.By leveraging the recognition capabilities of Convolutional Neural Networks(CNN)and taking into account the impact of noise,it aims to establish the implicit mapping relationship between delamination damage images and impact parameters,as well as CAI strength.This approach facilitates the inverse inversion of impact parameters for multiple low-velocity impacts of laminates under different ABIP,as well as effective prediction of CAI strength.展开更多
This paper proposed a new method for quantitative assessment of visual detectability of damage based on logistic regression,using the Probability of Detection(POD)as a criterion.Experiments were performed to establish...This paper proposed a new method for quantitative assessment of visual detectability of damage based on logistic regression,using the Probability of Detection(POD)as a criterion.Experiments were performed to establish the massive hit/miss data of visual inspection.Authoritative investigations verified the reliability of the data.The prediction function concluded comprises more than one flaw size parameters,including the depth and diameter of the dents.The results show that the depth and diameter of the dents are pivotal for the evaluation of detectability;the type of detection,the detection distance,and the qualifications of personnel are critical external factors to be considered.This function,with an accuracy rate of nearly 85%,is capable of predicting the visual detection probability of impact damage under various detection environments,which will provide a reference for the damage tolerance design of composite materials and field maintenance in the NonDestructive Testing(NDT)field.展开更多
To address the issue that B_(4)C ceramics are difficult to be wetted by aluminum metals in the composites,TiB_(2)was introduced via an in-situ reaction between TiH_(2)and B_(4)C to regulate their wettability and inter...To address the issue that B_(4)C ceramics are difficult to be wetted by aluminum metals in the composites,TiB_(2)was introduced via an in-situ reaction between TiH_(2)and B_(4)C to regulate their wettability and interfacial bonding.By pressure infiltration of the molten alloy into the freeze-cast porous ceramic skeleton,the 2024Al/B_(4)C-TiB_(2)composites with a laminate-reticular hierarchical structure were produced.Compared with 2024Al/B_(4)C composite,adding initial TiH_(2)improved the flexural strength and valid fracture toughness from(484±27)to(665±30)MPa and(19.3±1.5)to(32.7±1.8)MPa·m^(1/2),respectively.This exceptional damage resistance ability was derived from multiple extrinsic toughening mechanisms including uncracked-ligament bridging,crack branching,crack propagation and crack blunting,and more importantly,the fracture model transition from single to multiple crack propagation.This strategy opens a pathway for improving the wettability and interfacial bonding of Al/B_(4)C composites,and thus produces nacre-inspired materials with optimized damage tolerance.展开更多
In order to facilitate the determination of the calendar life of mechanical parts,the author summarized his relevant research papers that had studied for many years as eight distinct topics:(A).The principle and metho...In order to facilitate the determination of the calendar life of mechanical parts,the author summarized his relevant research papers that had studied for many years as eight distinct topics:(A).The principle and method for compiling the equal-damage temperature and humidity spectrum;(B).The principle for preparing the high concentration medium solution;(C).The principle and method for determining the metal calendar life;(D).The principle and method for determining the protective coating calendar life;(E).The principle and method for determining the total calendar life;(F).The principle of the reliability processing;(G).The principle and method for determining the corrosion damage tolerance;(H).The principle and matching design method to ensure that the total fatigue life and the total calendar life of the mechanical part were safe simultaneously.The above contents established a complete set of theoretical systems and methods for determining the calendar life.展开更多
Fatigue crack growth is a critical phenomenon in engineering structures,accounting for a significant percentage of structural failures across various industries.Accurate prediction of crack initiation,propagation path...Fatigue crack growth is a critical phenomenon in engineering structures,accounting for a significant percentage of structural failures across various industries.Accurate prediction of crack initiation,propagation paths,and fatigue life is essential for ensuring structural integrity and optimizing maintenance schedules.This paper presents a comprehensive finite element approach for simulating two-dimensional fatigue crack growth under linear elastic conditionswith adaptivemesh generation.The source code for the programwas developed in Fortran 95 and compiled with Visual Fortran.To achieve high-fidelity simulations,the methodology integrates several key features:it employs an automatic,adaptive meshing technique that selectively refines the element density near the crack front and areas of significant stress concentration.Specialized singular elements are used at the crack tip to ensure precise stress field representation.The direction of crack advancement is predicted using the maximum tangential stress criterion,while stress intensity factors are determined through either the displacement extrapolation technique or the J-integral method.The simulation models crack growth as a series of linear increments,with solution stability maintained by a consistent transfer algorithm and a crack relaxation method.The framework’s effectiveness is demonstrated across various geometries and loading scenarios.Through rigorous validation against both experimental data and established numerical benchmarks,the approach is proven to accurately forecast crack trajectories and fatigue life.Furthermore,the detailed description of the program’s architecture offers a foundational blueprint,serving as a valuable guide for researchers aiming to develop their specialized software for fracture mechanics analysis.展开更多
基金Supported by National Natural Science Foundation of China(Grant No.12232004)Guangdong Provincial Basic and Applied Basic Research Foundation(Grant No.2022A1515140111)+1 种基金Anhui Provincial Science and Technology Projects(Grant No.JB24075)Sichuan Provincial Science and Technology Program(Grant Nos.2024NSFSC2020,2023YFG0234)。
文摘Heavy-duty freight railway axles are no less important than those of passenger trains,owing to the potentially catastrophic results caused by the derailment of trains carrying hazardous substances.Intrinsic and extrinsic imperfections challenge classical design theories built based on the safe life concept,and damage tolerance assessment becomes vital for the safety and reliability of long-term serviced railway axles,as pits and scratches are common defects for heavy-duty railway axles.In this work,four-point rotating bending fatigue tests of AAR-CM railway axle steel specimens with semicircular and circumferential groove notches are conducted.The fatigue limit of the semicircular notched specimens was evaluated based on fracture mechanics theory,in which non-conservative results are obtained by the El Haddad model and the S–N curves of circumferential groove notched specimens are correlated by the theory of critical distance(TCD).
基金financially supported by the National Key R&D Program of China(No.2022YFB4600500)the National Safety Academic Fund(Nos.U2130201 and U2330105).
文摘NiTi alloy lattice structures are crucial for reusable energy absorption due to their shape memory effects.However,existing NiTi alloy lattice structures always suffer from localized deformation bands during loading,causing local strains to exceed the recoverable strain limit of the alloy and significantly reducing their reusable energy-absorbing capacity.In this study,we developed a NiTi alloy helical lattice structure(HLS)to effectively prevent localized deformation bands.This is attributed to its struts distributing stress and strain uniformly through torsional deformation,thereby alleviating local stress concentrations and suppressing the formation of localized deformation bands.Additionally,its unit cells provide mutual support and reinforcement during deformation,effectively preventing the progression of localized deformation bands.The NiTi alloy HLS exhibits superior reusable energy absorption compared to previously reported reusable energy-absorbing materials/structures and enhanced damage tolerance under large compression strain.This study provides valuable insights for the development of high-performance reusable NiTi alloy energy-absorbing lattice structures.
文摘The discipline of damage tolerance assessment has experienced significant advancements due to the emergence of smart materials and self-repairable structures.This review offers a comprehensive look into both traditional and innovative methodologies employed in damage tolerance assessment.After a detailed exploration of damage tolerance concepts and their historical progression,the review juxtaposes the proven techniques of damage assessment with the cutting-edge innovations brought about by smart materials and self-repairable structures.The subsequent sections delve into the synergistic integration of smart materials with self-repairable structures,marking a pivotal stride in damage tolerance by establishing an autonomous system for immediate damage identification and self-repair.This holistic approach broadens the applicability of these technologies across diverse sectors yet brings forth unique challenges demanding further innovation and research.Additionally,the review examines future prospects that combine advanced manufacturing processes with data-centric methodologies,amplifying the capabilities of these‘intelligent’structures.The review culminates by highlighting the transformative potential of this union between smart materials and self-repairable structures,promoting a sustainable and efficient engineering paradigm.
基金Supported by Ningbo Municipal Natural Science Foundation of China(Grant No.2022J134)Zhejiang Provincial Natural Science Foundation of China(Grant No.LQ24E050001)+1 种基金Ningbo Municipal Science and Technology Innovation Ecological Cultivation Project of"Science and Technology Innovation Yongjiang 2035"of China(Grant No.2024Z066)National Natural Science Foundation of China(Grant No.51975505)。
文摘Soft robotics focuses on addressing the locomotion problem in unstructured environments and the manipulation problem of non-cooperative objects,which inevitably leads to soft robots encountering multiple uncertainties and damages.Therefore,improving the robustness of soft robots in hostile environmental conditions has always been a challenge.Existing methods usually improve this robustness through damage isolation,material elasticity,and self-healing mechanisms.In contrast to existing methods,this paper proposes a method to improve the robustness of an untethered soft-swallowing robot based on the physical properties of fluids,such as the high specific heat capacity of water,the viscosity of soft glue,and the shear thickening of non-Newtonian fluids.Based on this method,we developed a soft-swallowing robot with enhanced heat resistance,damage tolerance,and impact mitigation capability by only replacing its fluid working medium.Experiments show that the developed soft-swallowing robot can withstand high temperatures above 600°C,maintain high performance even after enduring hundreds of damages,and protect grasped object from more than 90%of external impacts.This principle extends beyond the three fluids used in this study.Other fluids,such as magnetic fluid,can increase adhesion to metal materials,whereas oily fluids can reduce frictional resistance between soft structures.Additionally,other solid materials with elasticity and compliance can serve as alternative working mediums for the soft-swallowing robot.This work contributes an effective method for fluid-dependent soft robotic systems to resist the damage from uncertain factors in harsh environments.
基金Acknowledgments The authors wish to thank Landon Pastushok, Michelle Hanna and other members from the Xiao laboratory for helpful discussion. This work was supported by the Canadian Institutes of Health Research operating grants MOP-38104 and MOP-53240 to W Xiao, and the National Natural Science Foundation of China（Grant no. 30560132） to F Xu.
文摘In addition to well-defined DNA repair pathways, all living organisms have evolved mechanisms to avoid cell death caused by replication fork collapse at a site where replication is blocked due to disruptive covalent modifications of DNA. The term DNA damage tolerance （DDT） has been employed loosely to include a collection of mechanisms by which cells survive replication-blocking lesions with or without associated genomic instability. Recent genetic analyses indicate that DDT in eukaryotes, from yeast to human, consists of two parallel pathways with one being error-free and another highly mutagenic. Interestingly, in budding yeast, these two pathways are mediated by sequential modifications of the proliferating cell nuclear antigen （PCNA） by two ubiquitination complexes Rad6-Rad18 and Mms2-Ubc13-Rad5. Damage-induced monoubiquitination of PCNA by Rad6-Rad18 promotes translesion synthesis （TLS） with increased mutagenesis, while subsequent polyubiquitination of PCNA at the same K164 residue by Mms2-Ubc13-Rad5 promotes error-free lesion bypass. Data obtained from recent studies suggest that the above mechanisms are conserved in higher eukaryotes. In particular, mammals contain multiple specialized TLS polymerases. Defects in one of the TLS polymerases have been linked to genomic instability and cancer.
基金National Basic Research and Development Program of China(973 Program,No.2007CB714705).
文摘According to the rules of UIC515-3,the service loads of the axles are defined,which include some different loads cases as follows:the static loads;the impact loads resulted from running through the rail joints and unevenness rails;the loads through curves and from braking.Through the calculating and analysis,the stress distribution of the hollow axles is obtained for 200 km/h high speed motor trains used in China.At the same time,the fatigue crack growth of hollow axles is studied,and the initial surface cracks of 2 mm depth caused by hard objects strike or the other causes are discussed.On the basis of the linear elastic fracture mechanics theory,the stress intensity factor of the crack of the geometry transition outside the wheel seat is also studied.Associated with fatigue crack propagation equation and the corresponding crack propagation threshold,the crack propagation characteristics under different shapes are calculated.Then the running distances are educed with different shapes propagating to the critical length,and the estimation of the residual lives about hollow axles which are the reference values of examine and repair limit of the hollow axle is given.
基金Funded by Key Laboratory of Nondestructive Testing (Nanchang Hangkong University)Ministry of Education, China(No. ZD200829001)Department of Education of Jiangxi Province, China(No. GJJ10531)
文摘Impact damage tolerance is provided in intensity design on composites. The compression intensity of impacted composites requires more than 60% of its original intensity. The influence of impact on compressive intensity and electrical resistance of carbon fabric/epoxy-matrix composites was studied in this paper. The experimental results shows that impact can cause damage in composites, degenerate compressive intensity, and increase resistance. The electrical resistance change rate was used as an evaluation indicator of impact damage tolerance of composites. Impact damage, which results from the applying process of composites, can be identified in time by electrical resistance measurement. So, the safety performance of composites can also be improved.
文摘In this paper an experimental study on damage tolerance behaviour of composite panels with softening strips is carried out. A prediction method of residual strength of panels with softening strips is proposed. The comparison between estimated and experimental results shows that the prediction method can be applied to design. In this paper the failure mechanisms are described.
文摘The main purpose of this paper is providing a reference for further research. According to the papers and reports on structural durability and probabilistic damage tolerance, the present paper summarized the pro- gress of the theoretical considerations and engineering application. Several models used in structural durability and probabilistic damage tolerance are reviewed. The characteristics and problems of these methods are ana- lyzed. A new kind of combined analysis model on structural durability and damage tolerance are also introduced. New progress of analysis theory and numerical methods on structural reliability are discussed, such as the re- sponse surface method and numerical method combining neural networks and Monte Carlo simulation. The analy- sis shows that these methods can improve computational efficiency significantly and maintain high computational accuracy. Finally, some prospects of the key research directions are discussed.
基金funded by the National Natural Science Foundation of China,grant number U2233213The work was supported by the Innovation Team of Complex System Safety and Airworthiness of Aero Engine from the Co-Innovation Center for Advanced Aero-engine of ChinaIn addition,the authors wish to thank the financial support of the Tianmushan Laboratory(Laboratory of Aviation in Zhejiang Province),Hangzhou,China.
文摘Anomaly distribution is an essential input for the probabilistic damage tolerance assessment,which is required by the airworthiness certification criteria Federal Aviation Regulation(FAR)33.70.The default anomaly distribution of hole features has been established and published in airworthiness advisory circular 33.70-2 based on historical anomaly data collected from cracked or ruptured parts recorded in laboratory analysis reports of the special industries before 2005.However,for other industries,this default anomaly distribution fails to reflect the machining level of these industries.Besides,insufficient historical maintenance anomaly data makes the mathematical model of the default distribution inapplicable,and few models can deal with the production data.Therefore,this paper proposes a model for achieving the anomaly distribution of hole features induced by machine or maintenance process,including collecting anomaly data,deriving the exceedance number by the probability of detection(POD),conducting the curve fitting process,and calibrating and modifying the anomaly distribution.The anomaly distribution and the probability of failure(POF)are dependent on defect numbers as well as confidence levels.To recommend the number of collected data and the correction factor for the POFs with different sample numbers and confidence levels,the sensitivity analysis is conducted by quantifying the influence of the anomaly distributions of different anomaly numbers on the POFs.Results show that when the anomaly number is 25,the differences between the POFs are less than 32.9%,and a 1.329 correction factor zP is supposed to modify the POF.When the anomaly number is larger than 50,a 1.2 correction factor zP is supposed to obtain the most conservative risk value with a 95%confidence level.
基金the National Natural Science Foundation of China(Grant No.82330090 and Grant No.82341006 to C.G.)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA0460403 to C.G.)the Natural Science Foundation of Shanxi Province(Grant No.202203021211155 to X.M.).
文摘Overview of the DNA damage response(DDR)in tumor cells.DDR is a highly coordinated signaling network that repairs DNA damage caused by intrinsic cellular processes and extrinsic insults,thereby preventing genome instability.Depending on the type of damage,distinct DNA damage repair and DNA damage tolerance(DDT)pathways are involved and coordinately regulated.
基金supported by the National Natural Science Foundation of China(Grant No.52305359)the startup funding from the Huazhong University of Science and Technology,the Opening fund of the State Key Laboratory of Nonlinear Mechanics and Natural Science Foundation of Hubei Province(No.2023AFB141)。
文摘Fabricating damage tolerant porous ceramics with efficient energy absorption and impact-resistant capability has been a challenge because of the brittle nature of ceramic materials.In nature,mineralized tissues or organisms such as cuttlebones and diatoms have evolved with hierarchical porous structures to overcome this difficulty.A bioinspired design of ceramic lattice structure with pores at multiple length scales,ranging from few nanometers to hundreds of micrometers,is proposed in the present work.These ceramic lattices with hierarchical porous structures were successfully fabricated via 3D cryogenic printing.Under quasi-static compressions,the printed ceramic lattices showed unprecedented long plateau strain(∼60%)and a specific energy absorption of∼10 kJ·kg^(−1) with a porosity of∼90%.The resulting energy absorption capability was comparable with most composites and metals,thus overcoming the brittle nature of traditional porous ceramics.This was attributed to the delayed destruction of the lattice structure,as well as the gradual collapse of pores at multiple length scales.Similar trends have also been observed under split Hopkinson pressure bar(SHPB)tests,indicating excellent energy absorption under high strain-rate impacts.The proposed 3D printing technique that produces hierarchical pores was also demonstrated to apply to other functional materials,such as silicon carbide,barium titanate,hydroxyapatite,and even titanium alloy,thus opening up new possibilities for fabricating bioinspired hierarchical porous structures.
基金the National Natural Science Foundation of China,grant number U2233213.
文摘Probabilistic damage tolerance is a critical method to understand and communicate risk and safety.This paper reviews recent research on the probabilistic damage tolerance design for life-limited parts.The vision of the probabilistic damage tolerance assessment is provided.Five core parts of the probabilistic damage tolerance method are introduced separately,including the anomaly distribution,stress processing and zone definition,fatigue and fracture calculation method,probability of failure(POF)calculation method,and the combination with residual stress induced by the manufacturing process.The above currently-available risk assessment methods provide practical tools for failure risk predictions and are applied by the airworthiness regulations.However,new problems are exposed with the development of the aeroengines.The time-consuming anomaly distribution derivation process restricts the development of the anomaly distribution,especially for the developing aviation industries with little empirical data.Additionally,the strong transient characteristic is prominent because of the significant temperature differences during the take-off and climbing periods.The complex loads then challenge the fatigue and fracture calculation model.Besides,high computational efficiency is required because various variables are considered to calculate the POF.Therefore,new technologies for the probabilistic damage tolerance assessment are provided,including the efficient anomaly distribution acquisition method based on small samples,the zone definition method considering transient process,and stress intensity factor(SIF)solutions under arbitrary stress distributions combined with the machine learning method.Then,an efficient numerical integration method for calculating failure risk based on the probability density evolution theory is proposed.Meanwhile,the influence of the manufacturing process on residual stress and the failure risk of the rotors is explored.The development of the probabilistic damage tolerance method can meet the requirement of the published airworthiness regulation Federal Aviation Regulation(FAR)33.70 and guide the modification or amendment of new regulations to ensure the safety of the high-energy rotors.
文摘To study the conservative life of the artificial mechanical heart valve holder,CATIA software was used for modeling,and ABAQUS finite element analysis was used to analyze the stress of the valve holder in the complex environment of the human body and the residual thermal stress during production and processing.The damage tolerance method based on fracture mechanics analyzes the maximum initial crack size that the heart valve holder can tolerate under the premise that the structural safety life is longer than the life of the implanted patient.The results show that the maximum initial crack size is only tens of microns;the traditional S/N life analysis can only obtain non-conservative life,and the damage tolerance method is the basic requirement for analyzing the life and quality control of artificial mechanical heart valves.
基金supported by the National Major Science and Technology Project,China(No.J2019-Ⅳ-0007-0075)the Fundamental Research Funds for the Central Universities,China(No.JKF-20240036)。
文摘To ensure the structural integrity of life-limiting component of aeroengines,Probabilistic Damage Tolerance(PDT)assessment is applied to evaluate the failure risk as required by airworthiness regulations and military standards.The PDT method holds the view that there exist defects such as machining scratches and service cracks in the tenon-groove structures of aeroengine disks.However,it is challenging to conduct PDT assessment due to the scarcity of effective Probability of Detection(POD)model and anomaly distribution model.Through a series of Nondestructive Testing(NDT)experiments,the POD model of real cracks in tenon-groove structures is constructed for the first time by employing the Transfer Function Method(TFM).A novel anomaly distribution model is derived through the utilization of the POD model,instead of using the infeasible field data accumulation method.Subsequently,a framework for calculating the Probability of Failure(POF)of the tenon-groove structures is established,and the aforementioned two models exert a significant influence on the results of POF.
基金supported by the National Natural Science Foundation of China(Nos.12372068 and 12202066)。
文摘In practical engineering applications,composite laminates frequently encounter complex multiple low-velocity impact events.The damage coupling caused by the different Angles Between Impact Positions(ABIP)is a key factor in reducing the load-bearing capacity of the laminates.It is worth noting that in real impact events,the delamination damage information of laminates is easier to capture directly.Therefore,it is crucial to predict the damage tolerance of laminates by analyzing their delamination damage images.This paper adopts an integrated finite element model to present an in-depth study on the damage characteristics and Compression-After-Impact(CAI)strength of carbon/glass hybrid laminates subjected to multiple low-velocity impacts at different ABIP.By leveraging the recognition capabilities of Convolutional Neural Networks(CNN)and taking into account the impact of noise,it aims to establish the implicit mapping relationship between delamination damage images and impact parameters,as well as CAI strength.This approach facilitates the inverse inversion of impact parameters for multiple low-velocity impacts of laminates under different ABIP,as well as effective prediction of CAI strength.
基金supported by COMAC Beijing Aeronautical Science&Technology Research Institute。
文摘This paper proposed a new method for quantitative assessment of visual detectability of damage based on logistic regression,using the Probability of Detection(POD)as a criterion.Experiments were performed to establish the massive hit/miss data of visual inspection.Authoritative investigations verified the reliability of the data.The prediction function concluded comprises more than one flaw size parameters,including the depth and diameter of the dents.The results show that the depth and diameter of the dents are pivotal for the evaluation of detectability;the type of detection,the detection distance,and the qualifications of personnel are critical external factors to be considered.This function,with an accuracy rate of nearly 85%,is capable of predicting the visual detection probability of impact damage under various detection environments,which will provide a reference for the damage tolerance design of composite materials and field maintenance in the NonDestructive Testing(NDT)field.
基金financially supported by the National Natural Science Foundation of China(Nos.51502053,52072091,51621091)Heilongjiang Touyan Team,China。
文摘To address the issue that B_(4)C ceramics are difficult to be wetted by aluminum metals in the composites,TiB_(2)was introduced via an in-situ reaction between TiH_(2)and B_(4)C to regulate their wettability and interfacial bonding.By pressure infiltration of the molten alloy into the freeze-cast porous ceramic skeleton,the 2024Al/B_(4)C-TiB_(2)composites with a laminate-reticular hierarchical structure were produced.Compared with 2024Al/B_(4)C composite,adding initial TiH_(2)improved the flexural strength and valid fracture toughness from(484±27)to(665±30)MPa and(19.3±1.5)to(32.7±1.8)MPa·m^(1/2),respectively.This exceptional damage resistance ability was derived from multiple extrinsic toughening mechanisms including uncracked-ligament bridging,crack branching,crack propagation and crack blunting,and more importantly,the fracture model transition from single to multiple crack propagation.This strategy opens a pathway for improving the wettability and interfacial bonding of Al/B_(4)C composites,and thus produces nacre-inspired materials with optimized damage tolerance.
文摘In order to facilitate the determination of the calendar life of mechanical parts,the author summarized his relevant research papers that had studied for many years as eight distinct topics:(A).The principle and method for compiling the equal-damage temperature and humidity spectrum;(B).The principle for preparing the high concentration medium solution;(C).The principle and method for determining the metal calendar life;(D).The principle and method for determining the protective coating calendar life;(E).The principle and method for determining the total calendar life;(F).The principle of the reliability processing;(G).The principle and method for determining the corrosion damage tolerance;(H).The principle and matching design method to ensure that the total fatigue life and the total calendar life of the mechanical part were safe simultaneously.The above contents established a complete set of theoretical systems and methods for determining the calendar life.
基金funding of the Deanship of Graduate Studies and Scientific Research,Jazan University,Saudi Arabia,through Project number:JU-20250230-DGSSR-RP-2025.
文摘Fatigue crack growth is a critical phenomenon in engineering structures,accounting for a significant percentage of structural failures across various industries.Accurate prediction of crack initiation,propagation paths,and fatigue life is essential for ensuring structural integrity and optimizing maintenance schedules.This paper presents a comprehensive finite element approach for simulating two-dimensional fatigue crack growth under linear elastic conditionswith adaptivemesh generation.The source code for the programwas developed in Fortran 95 and compiled with Visual Fortran.To achieve high-fidelity simulations,the methodology integrates several key features:it employs an automatic,adaptive meshing technique that selectively refines the element density near the crack front and areas of significant stress concentration.Specialized singular elements are used at the crack tip to ensure precise stress field representation.The direction of crack advancement is predicted using the maximum tangential stress criterion,while stress intensity factors are determined through either the displacement extrapolation technique or the J-integral method.The simulation models crack growth as a series of linear increments,with solution stability maintained by a consistent transfer algorithm and a crack relaxation method.The framework’s effectiveness is demonstrated across various geometries and loading scenarios.Through rigorous validation against both experimental data and established numerical benchmarks,the approach is proven to accurately forecast crack trajectories and fatigue life.Furthermore,the detailed description of the program’s architecture offers a foundational blueprint,serving as a valuable guide for researchers aiming to develop their specialized software for fracture mechanics analysis.
