BACKGROUND The use of percutaneous transcatheter edge-to-edge repair(TEER)for mitral regurgitation(MR)has increased,including an increased application to older,frailer,and higher risk patients.CASE SUMMARY A 74 year-o...BACKGROUND The use of percutaneous transcatheter edge-to-edge repair(TEER)for mitral regurgitation(MR)has increased,including an increased application to older,frailer,and higher risk patients.CASE SUMMARY A 74 year-old woman with severe MR,a left ventricular ejection fraction of 45%,and a small circumferential pericardial effusion underwent TEER of the mitral valve.After the placement of two MitraClips,the MR was assessed as mild to moderate.Within 10-20 minutes after the completion of the case,the patient was dyspneic and hypotensive despite volume resuscitation.Point-of-care ultrasound(POCUS)showed no changes in cardiac contractility,valve function,or the pericardial space.The right heart chambers appeared small with right atrial(RA)diastolic collapse.There was no evidence of venous congestion.Further exam showed a large right pleural fluid collection.Given the clinical scenario of dyspnea,hypotension,and diastolic RA collapse,low-pressure tamponade was suspected.A thoracentesis expelled 1200 mL of blood with immediate hemodynamic improvement.The patient made an uneventful recovery.CONCLUSION The application of POCUS is crucial for detecting,diagnosing,and properly managing cardiac dysfunction and procedural complications associated with TEER.While tamponade is classically associated with a pericardial effusion and vena caval plethora,their absence does not dismiss the suspicion or diagnosis of tamponade.This case highlights the value of POCUS in assessing low-pressure tamponade caused by a large,pressurized pleural effusion.Clinical suspicion,supported by POCUS findings,was confirmed by a thoracentesis that resulted in immediate hemodynamic improvement.展开更多
The design of high-lift Low-Pressure Turbines(LPTs)causes the separation of the boundary layer on the suction side of the blade and leads to a strong secondary flow.This present study aims to minimize secondary losses...The design of high-lift Low-Pressure Turbines(LPTs)causes the separation of the boundary layer on the suction side of the blade and leads to a strong secondary flow.This present study aims to minimize secondary losses through endwall slot suction and incoming wakes in a front-loaded high-lift LPT cascade with Zweifel of 1.58 under low Reynolds number of 25000.Two slotted schemes for the boundary layer of the endwall were designed(Plan A and Plan B),and the effects of suction mass flow on secondary flow were studied.The underlying physics of the endwall boundary layer of the suction and secondary flow under unsteady wakes was discussed.The results show that slot suction at the endwall boundary layer can significantly suppress the secondary flow by removing low-momentum fluids.Plans A and B significantly reduced the secondary kinetic energy by 44.2%and 36.9%,respectively,compared with the baseline cascade at the suction mass flow ratios of 1%.With an increase in the mass flow ratio of suction,the secondary flow was gradually reduced in both Plans A and B.It is more beneficial to control the secondary flow to destroy the intersection of the pressure side and suction side of the horseshoe vortex before it develops into a passage vortex.Under unsteady wakes,the combined effects of incoming wakes and endwall boundary layer suction can further suppress the secondary flow at the suction mass flow ratios of 2%for Plan A,because the positive and negative vorticity inside upstream wakes accelerated the mixing of the main flow and secondary flow and thus increased the energy of secondary vortices.展开更多
Non-metallic inclusions and zyglo indications frequently occur in the superalloy castings produced through the traditional vacuum gravity investment casting process,particularly in components with thin-walled and comp...Non-metallic inclusions and zyglo indications frequently occur in the superalloy castings produced through the traditional vacuum gravity investment casting process,particularly in components with thin-walled and complex structural features.The vacuum-assisted low-pressure casting(VLC),a type of counter-gravity casting(CGC)method,has been developed to minimize non-metallic inclusions and zyglo indications in superalloy castings.Rectifying frames for gas turbines made from K446 alloy were produced semi-continuously using the VLC process and subsequently evaluated through tensile testing,chemical composition analysis,X-ray diffraction,and zyglo penetrant inspection.The results indicate a roughly 10%improvement in tensile strength at 800℃ compared to gravity casting.Moreover,no significant changes are observed in the chemical composition of the alloys from the beginning to the end of a casting campaign,indicating that the developed VLC process is viable for the engineering-scale production of superalloy castings.Compared to traditional vacuum gravity casting(GC)method,the application of VLC can reduce the numbers of non-metallic inclusions and Zyglo indications in the castings by over 80%.At the same time,it significantly shortens the production time by 3 to 5 days.展开更多
During the low-pressure casting of extra-large size C95800 copper alloy components,traditional linear pressurization technique leads to a rapid surge of liquid metal inlet velocity at the regions where the mold cavity...During the low-pressure casting of extra-large size C95800 copper alloy components,traditional linear pressurization technique leads to a rapid surge of liquid metal inlet velocity at the regions where the mold cavity cross-section enlarges.This rapid increasement of liquid metal inlet velocity causes serious entrapment of gas and oxide films,and results in various casting defects such as the bifilm defects.These defects detrimentally deteriorate mechanical properties of the castings.To address this issue,an innovative nonlinear pressurization strategy timely matching to the casting structure was proposed.The pressurization rate decreases at sections where the cross-section widens,but it gradually increases as the liquid metal level rises.By this way,the inlet velocity remains below a critical threshold to prevent the entrapment of gas and oxide films.Comparative analyses involving numerical simulations and casting verification illustrate that the nonlinear pressurization technique,compared to the linear pressurization,effectively diminishes both the size and number of bifilm defects.Furthermore,the nonlinear pressurization method enhances the casting yield strength by 10%,tensile strength by 14%,and elongation by 10%.Examination through scanning electron microscopy highlights that the bifilm defects arising from the linear pressurization process result in the reduction of the castings’mechanical properties.These observations underscore the efficacy of nonlinear pressurization in enhancing the quality and reliability of gigantic castings,as exemplified by a 5.4-ton extra-large sized C95800 copper alloy propeller hub with complex structures in the current study.展开更多
Pyrolysis of benzene at 30 Torr was studied from 1360 K to 1820 K in this work. Synchrotron vacuum ultraviolet photoionization mass spectrometry was employed to detect the pyroly- sis products such as radicals, isomer...Pyrolysis of benzene at 30 Torr was studied from 1360 K to 1820 K in this work. Synchrotron vacuum ultraviolet photoionization mass spectrometry was employed to detect the pyroly- sis products such as radicals, isomers and polycyclic aromatic hydrocarbons, and measure their mole fraction profiles versus temperature. A low-pressure pyrolysis model of benzene was developed and validated by the experimental results. Rate of production analysis was performed to reveal the major reaction networks in both fuel decomposition and aromatic growth processes. It is concluded that benzene is mainly decomposed via H-abstraction reaction to produce phenyl and partly decomposed via unimolecular decomposition reac- tions to produce propargyl or phenyl. The decomposition process stops at the formation of acetylene and polyyne species like diacetylene and 1,3,5-hexatriyne due to their high thermal stabilities. Besides, the aromatic growth process in the low-pressure pyrolysis of benzene is concluded to initiate from benzene and phenyl, and is controlled by the even carbon growth mechanism due to the inhibited formation of C5 and C7 species which play important roles in the odd carbon growth mechanism.展开更多
Compared with the traditional atm ospheric carburization, low-pressure carburization has the benefits of producing no surface oxidation and leaving fine, uniformly dispersed carbides in the carburized layer. However, ...Compared with the traditional atm ospheric carburization, low-pressure carburization has the benefits of producing no surface oxidation and leaving fine, uniformly dispersed carbides in the carburized layer. However, the process param eters for low-pressure carburization of 16Cr3NiWMoVNbE steel have yet to be optimized. Thus, we use the saturation-value method to optimize these parameters for aviation-gear materials. Toward this end, the m icrostructure and properties of 16Cr3NiWMoVNbE steel after different carburization processes are studied by optical microscopy, scanning electron microscopy, transm ission electron microscopy, and electron probe microanalysis. Considering the saturated austenite carbon concentration, we propose a model of carbon flux and an alloy coefficient for low -pressure carburization to reduce the carbon concentration in austenite and avoid the surface carbide network. At the early stage of carburization (30 s), the gas-solid interface has a higher concentration gradient. The averaging method is not ideal in practical applications, but the carbon flux measured by using the segm ented average m ethod is 2.5 times that measured by the overall average method, which is ideal in practical applications. The corresponding carburization tim e is reduced by 60%. By using the integral average method, the actual carburization time increases, which leads to the rapid form ation of carbide on the surface and affects the entire carburization process. Nb and Wcombine with C to form carbides, which hinders carbon diffusion and consumes carbon, resulting in a sharp decrease in the rate of C diffusion in austenite (the diffusion rate is reduced by 52% for 16Cr3NiWMoVNbE steel). By changing the diffusion coefficient model and comparing the hardness gradient of different processes, the depth of the actual layer is found to be very similar to the design depth.展开更多
AIM To evaluate the safety and feasibility of a new technology combining low-pressure pneumoperitoneum(LPP) and abdominal wall lift(AWL) in laparoscopic total mesorectal excision(TME) for rectal cancer.METHODS From No...AIM To evaluate the safety and feasibility of a new technology combining low-pressure pneumoperitoneum(LPP) and abdominal wall lift(AWL) in laparoscopic total mesorectal excision(TME) for rectal cancer.METHODS From November 2015 to July 2017,26 patients underwent laparoscopic TME for rectal cancer using LPP(6-8 mm Hg) with subcutaneous AWL in Qilu Hospital of Shandong University,Jinan,China.Clinical data regarding patients' demographics,intraoperative monitoring indices,operation-related indices andpathological outcomes were prospectively collected.RESULTS Laparoscopic TME was performed in 26 cases(14 anterior resection and 12 abdominoperineal resection) successfully,without conversion to open or laparoscopic surgery with standard-pressure pneumoperitoneum.Intraoperative monitoring showed stable heart rate,blood pressure and paw airway pressure.The mean operative time was 194.29 ± 41.27 min(range:125-270 min) and 200.41 ± 20.56 min(range:170-230 min) for anterior resection and abdominoperineal resection,respectively.The mean number of lymph nodes harvested was 16.71 ± 5.06(range:7-27).There was no positive circumferential or distal resection margin.No local recurrence was observed during a median follow-up period of 11.96 ± 5.55 mo(range:5-23 mo).CONCLUSION LPP combined with AWL is safe and feasible for laparoscopic TME.The technique can provide satisfactory exposure of the operative field and stable operative monitoring indices.展开更多
Detailed experimental measurements were conducted to study the interactions between incoming wakes and endwall secondary flow in a high-lift Low-Pressure Turbine(LPT)cascade.All of the measurements were conducted in b...Detailed experimental measurements were conducted to study the interactions between incoming wakes and endwall secondary flow in a high-lift Low-Pressure Turbine(LPT)cascade.All of the measurements were conducted in both the presence and absence of incoming wakes,and numerical analysis was performed to elucidate the flow mechanism.With increasing Reynolds number,the influence of the incoming wakes on suppressing the secondary flow gradually increased owing to the greater influence of incoming wakes on reducing the negative incidence angle at higher Reynolds numbers,leading to a lower blade loading near the leading edge and suppression of the Pressure Side(PS)leg of the horseshoe vortex.However,the effect of unsteady wakes on suppressing the profile losses gradually became weaker owing to the reduced size of the Suction Side(SS)separation bubble and increased mixing loss in the free-flow region at high Reynolds numbers.Incoming wakes clearly improved the aerodynamic performance of the low-pressure turbine cascade at low Reynolds numbers of 25,000 and 50,000.In contrast,at the high Reynolds number of 100,000,the profile loss at the midspan and mass-averaged total losses downstream of the cascade were higher in the presence of wakes than in the absence of wakes,and the unsteady wakes exerted a negative influence on the aerodynamic performance of the LPT cascade.展开更多
Low-pressure air plasma cleaning is an effective method for removing organic contaminants on large-aperture optical components in situ in the inertial confinement fusion facility.Chemical reactions play a significant ...Low-pressure air plasma cleaning is an effective method for removing organic contaminants on large-aperture optical components in situ in the inertial confinement fusion facility.Chemical reactions play a significant role in plasma cleaning,which is a complex process involving abundant bond cleavage and species generation.In this work,experiments and reactive molecular dynamics simulations were carried out to unravel the reaction mechanism between the benchmark organic contaminants of dibutyl phthalate and air plasma.The optical emission spectroscopy was used to study the overall evolution behaviors of excited molecular species and radical signals from air plasma as a reference to simulations.Detailed reaction pathways were revealed and characterized,and specific intermediate radicals and products were analyzed during experiments and simulation.The reactive species in the air plasma,such as O,HO_(2)and O_(3)radicals,played a crucial role in cleaving organic molecular structures.Together,our findings provide an atomic-level understanding of complex reaction processes of low-pressure air plasma cleaning mechanisms and are essential for its application in industrial plasma cleaning.展开更多
The influence of a key process variable on the mold filling characteristics of AZ91 Mg-alloy was studied in the low pressure EPC process.The applied flow quantity of insert gas from 1 to 5 m~3/h associated with the pr...The influence of a key process variable on the mold filling characteristics of AZ91 Mg-alloy was studied in the low pressure EPC process.The applied flow quantity of insert gas from 1 to 5 m~3/h associated with the pressurizing rate in the low pressure EPC casting process was considered for rectangle and L-shape plate casting. The experimental results show that there is an optimal flow quantity of insert gas for good mold filling characteristics in AZ91 Mg-alloy low-pressure EPC process. The optimal flow quantity of insert gas for the specimens is 3 to 4 m~3/h. Either less or higher than the optimal flow quantity of insert gas would lead to misrun defects or folds, blisters and porosity defects. The practice of hub casting confirmed that the low-pressure EPC process with an optimal processing variable exemplified as 4 m~3/h gas flow quantity was capable of producing complicated magnesium castings without misrun defects.展开更多
Alkali metal DC arc discharge has the characteristics of easy ionization,low power consumption,high plasma temperature and ionization degree,etc,which can be applied in aerospace vehicles in various ways.In this paper...Alkali metal DC arc discharge has the characteristics of easy ionization,low power consumption,high plasma temperature and ionization degree,etc,which can be applied in aerospace vehicles in various ways.In this paper,we calculate the physical property parameters of lithium vapor,one of the major alkali metals,and analyze the discharge characteristics of lithium plasma with the magnetohydrodynamic(MHD)model.The discharge effects between constant current and voltage sources are also compared.It is shown that the lithium plasma of DC arc discharge has relatively high temperature and current density.The peak temperature can reach tens of thousands of K,and the current density reaches 6 x 107 A m 2.Under the same rated power,the plasma parameters of the constant voltage source discharge are much higher than those of the constant current source discharge,which can be used as the preferred discharge mode for aerospace applications.展开更多
Pulsed-jet cleaning is recognized as the most efficient method to regenerate bag dust collectors traditionally used in industrial processes to control the emission of particulates.In this study,non-woven needle felt f...Pulsed-jet cleaning is recognized as the most efficient method to regenerate bag dust collectors traditionally used in industrial processes to control the emission of particulates.In this study,non-woven needle felt filter bags with and without a film coating material have been analyzed considering different geometries(different number N of pairs of pleated filter bag sides)in the frame of dedicated low-pressure pulsed-jet cleaning experiments.The flow structure inside the bag and the response characteristics of its wall have also been analyzed numerically through a computational fluid-dynamics/structural-dynamics(CFD-CSD)unidirectional fluid-solid coupling method.As shown by the experiments,the peak pressure(P_(0))on the wall of the filter bag with N=8 and 12 is higher,which indicates dust can be removed more effectively in these cases.The peak pressure on the wall increases first and then decreases along the direction of the bag length,while the peak pressure of the pleated filter bag with nonwoven needled felt film coating is greater than that without film coating.A comprehensive analysis of the time variation of acceleration,deformation,strain,stress and other factors,has led to the conclusion that the pleated filter bag with N=12 would be the optimal choice.展开更多
Pure Al and Al-30%Al_(2)O_(3)composite coatings are prepared on the surface of AZ31B magnesium alloy by low-pressure cold spraying.The morphology and structure of the coatings are analyzed by scanning electron microsc...Pure Al and Al-30%Al_(2)O_(3)composite coatings are prepared on the surface of AZ31B magnesium alloy by low-pressure cold spraying.The morphology and structure of the coatings are analyzed by scanning electron microscope (SEM),energy dispersive spectroscopy (EDS),and X-ray diffraction (XRD),and the effects of the addition of Al_(2)O_(3)on the microstructure of the Al-based coatings are discussed.The mechanical properties and corrosion resistance of the coatings are fully evaluated by the micro-hardness tester,electronic tensile machine,and electrochemical workstation.The results show that the coating structure is more uniform and denser,and the porosity is significantly reduced after the addition of Al_(2)O_(3).The interfaces between the coatings and the magnesium alloy substrate are distinct,and the coatings and the substrate are mechanically combined.Compared with the pure Al coating,the microhardness of the Al-Al_(2)O_(3)composite coating is increased to 61.1 HV_(0.2),and the bonding strength reaches above 53.1 MPa.The self-corrosion potential of the two coatings is higher than that of the magnesium alloy,and the self-corrosion current density is significantly lower than that of the magnesium alloy substrate.The Al-based coatings prepared by low-pressure cold spraying have high hardness,good bonding strength,and good corrosion resistance,which can be used for the repair and protection of magnesium alloy structural parts.展开更多
Effect of low-pressure carbonation （LPC） on heat inactivation of Saccharomyces cerevisiae was investigated. The cell suspension was carbonated at 1 MPa and 4℃ for 15 min and subsequently heated from 51 to 61 ℃ and...Effect of low-pressure carbonation （LPC） on heat inactivation of Saccharomyces cerevisiae was investigated. The cell suspension was carbonated at 1 MPa and 4℃ for 15 min and subsequently heated from 51 to 61 ℃ and 5 s to 5 min （heating with LPC）. As a control experiment, cell suspension was heat-treated under atmospheric pressure without LPC （heating）. The inactivation ratio of heating at 53℃ and 55℃ for l rain with LPC was approximately 1 log order higher than heating alone. Extending heating time to 5 min did not widen the difference in the inactivation ratio between heating with LPC and heating alone at both heating temperatures. At 57℃, the difference in inactivation ratio increased from 1 to 2.5 log order with extending treatment time from 5 to 15 s. The results suggested that the enhanced inactivation effect by LPC was obtained at the higher temperature with short time treatment than the lower temperature with longer time treatment. Under fluorescence microscope observation of LPC-treated cell stained with LysoSensor probe, it seemed that LPC was hardly able to acidify the cytoplasm ofS. cerevisiae. It is considered that the ability orS. cerevisiae ceils to keep their cytoplasmic pH during LPC resulted in the inferior increase in heat inactivation ratio by LPC as compared with bacteria in the previous studies.展开更多
Metal clusters RCCo_3(CO)_9(R-H,C1,Br,CH_3,Ph) were prepared in 18.8-57.3% yields from the reaction of cobalt(Ⅱ)salt and RCX_a under mild PTC conditions(latm CO,25℃).The cobalt salt was reduced to Co(CO)_4 in the pr...Metal clusters RCCo_3(CO)_9(R-H,C1,Br,CH_3,Ph) were prepared in 18.8-57.3% yields from the reaction of cobalt(Ⅱ)salt and RCX_a under mild PTC conditions(latm CO,25℃).The cobalt salt was reduced to Co(CO)_4 in the presence of Na_3S_2O_4.展开更多
Stable neutron generation with a yield of ~1.2×10^(4) neutrons per pulse was obtained during d(d,n)^(3)He reaction initiated by the high-voltage nanosecond discharge in a gap with a potential tungsten cylinder(an...Stable neutron generation with a yield of ~1.2×10^(4) neutrons per pulse was obtained during d(d,n)^(3)He reaction initiated by the high-voltage nanosecond discharge in a gap with a potential tungsten cylinder(anode)and a grounded deuterated zirconium plate(cathode)filled with deuterium at a pressure of ~10^(2) Pa.Estimated duration of the neutron pulse was ~1.5 ns.Less intensive neutron emission was registered without deuterated plate.Splashing of material of the tungsten electrode was observed during the high-voltage nanosecond discharge in the deuterium,hydrogen,helium and argon at pressures of 10^(2)-10^(4) Pa.展开更多
The propagation of the high-power microwave（HPM） with a frequency of 6 GHz in the lowpressure argon plasma was studied by the method of fluid approximation.The two-dimensional transmission model was built based on t...The propagation of the high-power microwave（HPM） with a frequency of 6 GHz in the lowpressure argon plasma was studied by the method of fluid approximation.The two-dimensional transmission model was built based on the wave equation,the electron drift-diffusion equations and the heavy species transport equations,which were solved by means of COMSOL Multiphysics software.The simulation results showed that the propagation characteristic of the HPM was closely related to the average electron density of the plasma.The attenuation of the transmitted wave increased nonlinearly with the electron density.Specifically,the growth of the attenuation slowed down as the electron density increased uniformly.In addition,the concrete transmission process of the HPM wave in the low-pressure argon plasma was given.展开更多
There are abundant natural gas resources in the marine shale gas reservoir of Middle Ordovician Wulalike Formation in the Ordos Basin,which is an important resource base for PetroChina Changqing Oilfield Company to in...There are abundant natural gas resources in the marine shale gas reservoir of Middle Ordovician Wulalike Formation in the Ordos Basin,which is an important resource base for PetroChina Changqing Oilfield Company to increase the reserves and production of oil and gas.Compared with the other shale gas reservoirs at home and aboard,however,the marine shale gas reservoir of Middle Ordovician Wulalike Formation in the Ordos Basin has a lower formation pressure coefficient and poorer reservoir physical properties and gas-bearing property,so its production increase difficulty is higher.In this paper,horizontal-well volume fracturing was studied and tested based on the earlier vertical well tests.According to the technical idea of the staged multi-cluster massive fracturing of long horizontal section,the propagation mechanisms and morphological characteristics of fractures were studied and analyzed based on the fracturing geological characteristics of the shale gas reservoir in the Ordos Basin.On this basis,a full three-dimensional fracture model was optimally established for parameter optimization.The fracturing of the test well ZP1 was carried out with 15 stages and 103 clusters.After the fracturing,a more complex fracture network was formed with a fracture complexity index of 0.4-0.6.The microseismic monitoring zone is 579 m long and 266 m wide and the fracture is 146 m high.To address the drainage difficulty after large-volume fracturing of low-pressure shale gas in the Ordos Basin,this paper carries out a gas energized fracturing test.Considering the characteristics of reservoir physical properties,gas-bearing property and segmented fractures,805 m3 liquid nitrogen was injected in stages during the fracturing of the test horizontal well.The formation pressure coefficient measured from pressure buildup data is increased from 0.7 to 0.8 to 1.88.The wellbore gaseliquid flow model was established and the parameters of long-period controlpressure drainage were optimized.The critical surface equipment was upgraded to achieve accurate measurement,safety and environmental protection.And the following research and practice results were obtained.First,based on the technological innovation and optimization,continuous gaseliquid two-phase flow is realized in the test well ZP1 and its production rate and pressure during the test are stable with the tested daily shale gas production at the wellhead of 6.42×10^(4)m^(3).Second,after fracturing,the absolute open flow of the test well reaches 26.4×10^(4)m^(3)/d,which is more than 10 times higher than the production rate of the vertical well in the same block during the test.Thus,a significant breakthrough is realized in the exploration of marine shale gas in North China.展开更多
A material removal mechanism is a prerequisite to maintaining high-quality surfaces for high-shear and low-pressure grinding using body-armor-like grinding wheels(BAGWs).However,the pressure distribution and material ...A material removal mechanism is a prerequisite to maintaining high-quality surfaces for high-shear and low-pressure grinding using body-armor-like grinding wheels(BAGWs).However,the pressure distribution and material removal efficiency for machining brittle materials using BAGWs remain unclear.This research investigated two types of elastic deformations during grinding by analyzing the contact mechanism between BAGWs and the workpiece.Additionally,the model of elastohydrodynamic pressure distribution was refined,and the material removal mechanism for machining brittle materials,incorporating the maximum undeformed chip thickness,was revealed.A material removal rate(MRR)model was established based on Hertzian contact,ductile-brittle transition,and spherical indentation theory.The theoretical model was validated through single-factor experiments utilizing a high-shear and low-pressure grinding experimental platform.At a normal grinding force of 15 N and a grinding speed of 10 m/s,the MRR could reach up to 0.276 mm3/s.The experimental results revealed that the model could accurately predict the MRR under various grinding parameters,with an average prediction error of 8.5%.展开更多
Nickel-based alloy has been widely used due to its outstanding mechanical properties.However,Nickel-based alloy is a typical difficult-to-machine material,which is a great constrain for its application in the manufact...Nickel-based alloy has been widely used due to its outstanding mechanical properties.However,Nickel-based alloy is a typical difficult-to-machine material,which is a great constrain for its application in the manufacturing field.To improve the surface quality of the ground workpiece,a new high-shear and low-pressure grinding wheel,with high ratio of tangential grinding force to normal grinding force,was fabricated for the grinding of selective laser melting(SLM)manufactured Inconel718 alloy.The principle of high-shear and low-pressure grinding process was introduced in detail,which was quite different from the conventional grinding process.The fabrication process of the new grinding wheel was illustrated.A serial of experiments with different processing parameters were carried out to investigate the grinding performance of the developed grinding wheel via analyzing surface roughness and surface morphology of the ground workpiece.The optimal processing parameters of high-shear and low-pressure grinding were obtained.The surface roughness of ground workpiece was reduced to 0.232μm from the initial value of 0.490μm under the optimal grinding conditions.It was found that the initial scratches on the ground workpiece were almost completely removed after the observations with the metalloscopy and the fieldemission scanning electron microscopy(FE-SEM).The capability of the newly developed highshear and low-pressure grinding wheel was validated.展开更多
文摘BACKGROUND The use of percutaneous transcatheter edge-to-edge repair(TEER)for mitral regurgitation(MR)has increased,including an increased application to older,frailer,and higher risk patients.CASE SUMMARY A 74 year-old woman with severe MR,a left ventricular ejection fraction of 45%,and a small circumferential pericardial effusion underwent TEER of the mitral valve.After the placement of two MitraClips,the MR was assessed as mild to moderate.Within 10-20 minutes after the completion of the case,the patient was dyspneic and hypotensive despite volume resuscitation.Point-of-care ultrasound(POCUS)showed no changes in cardiac contractility,valve function,or the pericardial space.The right heart chambers appeared small with right atrial(RA)diastolic collapse.There was no evidence of venous congestion.Further exam showed a large right pleural fluid collection.Given the clinical scenario of dyspnea,hypotension,and diastolic RA collapse,low-pressure tamponade was suspected.A thoracentesis expelled 1200 mL of blood with immediate hemodynamic improvement.The patient made an uneventful recovery.CONCLUSION The application of POCUS is crucial for detecting,diagnosing,and properly managing cardiac dysfunction and procedural complications associated with TEER.While tamponade is classically associated with a pericardial effusion and vena caval plethora,their absence does not dismiss the suspicion or diagnosis of tamponade.This case highlights the value of POCUS in assessing low-pressure tamponade caused by a large,pressurized pleural effusion.Clinical suspicion,supported by POCUS findings,was confirmed by a thoracentesis that resulted in immediate hemodynamic improvement.
基金support for this work was provided by the National Natural Science Foundation of China(No.52206060)the National Science and Technology Major Project of China(Nos.J2019-Ⅱ-0021-0042 and J2019-Ⅱ-0002-0022).
文摘The design of high-lift Low-Pressure Turbines(LPTs)causes the separation of the boundary layer on the suction side of the blade and leads to a strong secondary flow.This present study aims to minimize secondary losses through endwall slot suction and incoming wakes in a front-loaded high-lift LPT cascade with Zweifel of 1.58 under low Reynolds number of 25000.Two slotted schemes for the boundary layer of the endwall were designed(Plan A and Plan B),and the effects of suction mass flow on secondary flow were studied.The underlying physics of the endwall boundary layer of the suction and secondary flow under unsteady wakes was discussed.The results show that slot suction at the endwall boundary layer can significantly suppress the secondary flow by removing low-momentum fluids.Plans A and B significantly reduced the secondary kinetic energy by 44.2%and 36.9%,respectively,compared with the baseline cascade at the suction mass flow ratios of 1%.With an increase in the mass flow ratio of suction,the secondary flow was gradually reduced in both Plans A and B.It is more beneficial to control the secondary flow to destroy the intersection of the pressure side and suction side of the horseshoe vortex before it develops into a passage vortex.Under unsteady wakes,the combined effects of incoming wakes and endwall boundary layer suction can further suppress the secondary flow at the suction mass flow ratios of 2%for Plan A,because the positive and negative vorticity inside upstream wakes accelerated the mixing of the main flow and secondary flow and thus increased the energy of secondary vortices.
基金financially supported by the National Key Research and Development Plan Project of the Ministry of Science and Technology:Intelligent Liquid Precision Casting Technology and Application of Large Complex Thin-Wall High-End Metal Components(No.2022YFB3706800).
文摘Non-metallic inclusions and zyglo indications frequently occur in the superalloy castings produced through the traditional vacuum gravity investment casting process,particularly in components with thin-walled and complex structural features.The vacuum-assisted low-pressure casting(VLC),a type of counter-gravity casting(CGC)method,has been developed to minimize non-metallic inclusions and zyglo indications in superalloy castings.Rectifying frames for gas turbines made from K446 alloy were produced semi-continuously using the VLC process and subsequently evaluated through tensile testing,chemical composition analysis,X-ray diffraction,and zyglo penetrant inspection.The results indicate a roughly 10%improvement in tensile strength at 800℃ compared to gravity casting.Moreover,no significant changes are observed in the chemical composition of the alloys from the beginning to the end of a casting campaign,indicating that the developed VLC process is viable for the engineering-scale production of superalloy castings.Compared to traditional vacuum gravity casting(GC)method,the application of VLC can reduce the numbers of non-metallic inclusions and Zyglo indications in the castings by over 80%.At the same time,it significantly shortens the production time by 3 to 5 days.
基金supported by the National Natural Science Foundation of China(Granted Nos.51827801,52371152)the Foundation of National Key Laboratory of Precision Hot Processing of Metals(Granted No.DCQQ2790100724).
文摘During the low-pressure casting of extra-large size C95800 copper alloy components,traditional linear pressurization technique leads to a rapid surge of liquid metal inlet velocity at the regions where the mold cavity cross-section enlarges.This rapid increasement of liquid metal inlet velocity causes serious entrapment of gas and oxide films,and results in various casting defects such as the bifilm defects.These defects detrimentally deteriorate mechanical properties of the castings.To address this issue,an innovative nonlinear pressurization strategy timely matching to the casting structure was proposed.The pressurization rate decreases at sections where the cross-section widens,but it gradually increases as the liquid metal level rises.By this way,the inlet velocity remains below a critical threshold to prevent the entrapment of gas and oxide films.Comparative analyses involving numerical simulations and casting verification illustrate that the nonlinear pressurization technique,compared to the linear pressurization,effectively diminishes both the size and number of bifilm defects.Furthermore,the nonlinear pressurization method enhances the casting yield strength by 10%,tensile strength by 14%,and elongation by 10%.Examination through scanning electron microscopy highlights that the bifilm defects arising from the linear pressurization process result in the reduction of the castings’mechanical properties.These observations underscore the efficacy of nonlinear pressurization in enhancing the quality and reliability of gigantic castings,as exemplified by a 5.4-ton extra-large sized C95800 copper alloy propeller hub with complex structures in the current study.
基金This work is supported by the National Natu- ral Science Foundation of China （No.51106146 and No.51036007）, China Postdoctoral Science Foundation （No.20100480047 and No.201104326）, Chinese Univer- sities Scientific Fund （No.WK2310000010）, and Chinese Academy of Sciences.
文摘Pyrolysis of benzene at 30 Torr was studied from 1360 K to 1820 K in this work. Synchrotron vacuum ultraviolet photoionization mass spectrometry was employed to detect the pyroly- sis products such as radicals, isomers and polycyclic aromatic hydrocarbons, and measure their mole fraction profiles versus temperature. A low-pressure pyrolysis model of benzene was developed and validated by the experimental results. Rate of production analysis was performed to reveal the major reaction networks in both fuel decomposition and aromatic growth processes. It is concluded that benzene is mainly decomposed via H-abstraction reaction to produce phenyl and partly decomposed via unimolecular decomposition reac- tions to produce propargyl or phenyl. The decomposition process stops at the formation of acetylene and polyyne species like diacetylene and 1,3,5-hexatriyne due to their high thermal stabilities. Besides, the aromatic growth process in the low-pressure pyrolysis of benzene is concluded to initiate from benzene and phenyl, and is controlled by the even carbon growth mechanism due to the inhibited formation of C5 and C7 species which play important roles in the odd carbon growth mechanism.
基金financially supported by the National Key R&D Program of China (Grant No. 2016YFB0300600)the National Natural Science Foundation of China (Grant No. 51604074)
文摘Compared with the traditional atm ospheric carburization, low-pressure carburization has the benefits of producing no surface oxidation and leaving fine, uniformly dispersed carbides in the carburized layer. However, the process param eters for low-pressure carburization of 16Cr3NiWMoVNbE steel have yet to be optimized. Thus, we use the saturation-value method to optimize these parameters for aviation-gear materials. Toward this end, the m icrostructure and properties of 16Cr3NiWMoVNbE steel after different carburization processes are studied by optical microscopy, scanning electron microscopy, transm ission electron microscopy, and electron probe microanalysis. Considering the saturated austenite carbon concentration, we propose a model of carbon flux and an alloy coefficient for low -pressure carburization to reduce the carbon concentration in austenite and avoid the surface carbide network. At the early stage of carburization (30 s), the gas-solid interface has a higher concentration gradient. The averaging method is not ideal in practical applications, but the carbon flux measured by using the segm ented average m ethod is 2.5 times that measured by the overall average method, which is ideal in practical applications. The corresponding carburization tim e is reduced by 60%. By using the integral average method, the actual carburization time increases, which leads to the rapid form ation of carbide on the surface and affects the entire carburization process. Nb and Wcombine with C to form carbides, which hinders carbon diffusion and consumes carbon, resulting in a sharp decrease in the rate of C diffusion in austenite (the diffusion rate is reduced by 52% for 16Cr3NiWMoVNbE steel). By changing the diffusion coefficient model and comparing the hardness gradient of different processes, the depth of the actual layer is found to be very similar to the design depth.
基金Supported by the Special Found for Taishan Scholar Project of Shandong Province,China
文摘AIM To evaluate the safety and feasibility of a new technology combining low-pressure pneumoperitoneum(LPP) and abdominal wall lift(AWL) in laparoscopic total mesorectal excision(TME) for rectal cancer.METHODS From November 2015 to July 2017,26 patients underwent laparoscopic TME for rectal cancer using LPP(6-8 mm Hg) with subcutaneous AWL in Qilu Hospital of Shandong University,Jinan,China.Clinical data regarding patients' demographics,intraoperative monitoring indices,operation-related indices andpathological outcomes were prospectively collected.RESULTS Laparoscopic TME was performed in 26 cases(14 anterior resection and 12 abdominoperineal resection) successfully,without conversion to open or laparoscopic surgery with standard-pressure pneumoperitoneum.Intraoperative monitoring showed stable heart rate,blood pressure and paw airway pressure.The mean operative time was 194.29 ± 41.27 min(range:125-270 min) and 200.41 ± 20.56 min(range:170-230 min) for anterior resection and abdominoperineal resection,respectively.The mean number of lymph nodes harvested was 16.71 ± 5.06(range:7-27).There was no positive circumferential or distal resection margin.No local recurrence was observed during a median follow-up period of 11.96 ± 5.55 mo(range:5-23 mo).CONCLUSION LPP combined with AWL is safe and feasible for laparoscopic TME.The technique can provide satisfactory exposure of the operative field and stable operative monitoring indices.
基金provided by the National Natural Science Foundation of China(Nos.51876202 and 51836008)。
文摘Detailed experimental measurements were conducted to study the interactions between incoming wakes and endwall secondary flow in a high-lift Low-Pressure Turbine(LPT)cascade.All of the measurements were conducted in both the presence and absence of incoming wakes,and numerical analysis was performed to elucidate the flow mechanism.With increasing Reynolds number,the influence of the incoming wakes on suppressing the secondary flow gradually increased owing to the greater influence of incoming wakes on reducing the negative incidence angle at higher Reynolds numbers,leading to a lower blade loading near the leading edge and suppression of the Pressure Side(PS)leg of the horseshoe vortex.However,the effect of unsteady wakes on suppressing the profile losses gradually became weaker owing to the reduced size of the Suction Side(SS)separation bubble and increased mixing loss in the free-flow region at high Reynolds numbers.Incoming wakes clearly improved the aerodynamic performance of the low-pressure turbine cascade at low Reynolds numbers of 25,000 and 50,000.In contrast,at the high Reynolds number of 100,000,the profile loss at the midspan and mass-averaged total losses downstream of the cascade were higher in the presence of wakes than in the absence of wakes,and the unsteady wakes exerted a negative influence on the aerodynamic performance of the LPT cascade.
基金the Joint Funds of National Natural Science Foundation of China and China Academy of Engineering Physics(NSAF)(No.U2030109)National Natural Science Foundation of China(No.52075129)。
文摘Low-pressure air plasma cleaning is an effective method for removing organic contaminants on large-aperture optical components in situ in the inertial confinement fusion facility.Chemical reactions play a significant role in plasma cleaning,which is a complex process involving abundant bond cleavage and species generation.In this work,experiments and reactive molecular dynamics simulations were carried out to unravel the reaction mechanism between the benchmark organic contaminants of dibutyl phthalate and air plasma.The optical emission spectroscopy was used to study the overall evolution behaviors of excited molecular species and radical signals from air plasma as a reference to simulations.Detailed reaction pathways were revealed and characterized,and specific intermediate radicals and products were analyzed during experiments and simulation.The reactive species in the air plasma,such as O,HO_(2)and O_(3)radicals,played a crucial role in cleaving organic molecular structures.Together,our findings provide an atomic-level understanding of complex reaction processes of low-pressure air plasma cleaning mechanisms and are essential for its application in industrial plasma cleaning.
文摘The influence of a key process variable on the mold filling characteristics of AZ91 Mg-alloy was studied in the low pressure EPC process.The applied flow quantity of insert gas from 1 to 5 m~3/h associated with the pressurizing rate in the low pressure EPC casting process was considered for rectangle and L-shape plate casting. The experimental results show that there is an optimal flow quantity of insert gas for good mold filling characteristics in AZ91 Mg-alloy low-pressure EPC process. The optimal flow quantity of insert gas for the specimens is 3 to 4 m~3/h. Either less or higher than the optimal flow quantity of insert gas would lead to misrun defects or folds, blisters and porosity defects. The practice of hub casting confirmed that the low-pressure EPC process with an optimal processing variable exemplified as 4 m~3/h gas flow quantity was capable of producing complicated magnesium castings without misrun defects.
文摘Alkali metal DC arc discharge has the characteristics of easy ionization,low power consumption,high plasma temperature and ionization degree,etc,which can be applied in aerospace vehicles in various ways.In this paper,we calculate the physical property parameters of lithium vapor,one of the major alkali metals,and analyze the discharge characteristics of lithium plasma with the magnetohydrodynamic(MHD)model.The discharge effects between constant current and voltage sources are also compared.It is shown that the lithium plasma of DC arc discharge has relatively high temperature and current density.The peak temperature can reach tens of thousands of K,and the current density reaches 6 x 107 A m 2.Under the same rated power,the plasma parameters of the constant voltage source discharge are much higher than those of the constant current source discharge,which can be used as the preferred discharge mode for aerospace applications.
基金This study was financially supported by Anhui Provincial Scientific and Technological Major Project(Grant No.18030801109).
文摘Pulsed-jet cleaning is recognized as the most efficient method to regenerate bag dust collectors traditionally used in industrial processes to control the emission of particulates.In this study,non-woven needle felt filter bags with and without a film coating material have been analyzed considering different geometries(different number N of pairs of pleated filter bag sides)in the frame of dedicated low-pressure pulsed-jet cleaning experiments.The flow structure inside the bag and the response characteristics of its wall have also been analyzed numerically through a computational fluid-dynamics/structural-dynamics(CFD-CSD)unidirectional fluid-solid coupling method.As shown by the experiments,the peak pressure(P_(0))on the wall of the filter bag with N=8 and 12 is higher,which indicates dust can be removed more effectively in these cases.The peak pressure on the wall increases first and then decreases along the direction of the bag length,while the peak pressure of the pleated filter bag with nonwoven needled felt film coating is greater than that without film coating.A comprehensive analysis of the time variation of acceleration,deformation,strain,stress and other factors,has led to the conclusion that the pleated filter bag with N=12 would be the optimal choice.
文摘Pure Al and Al-30%Al_(2)O_(3)composite coatings are prepared on the surface of AZ31B magnesium alloy by low-pressure cold spraying.The morphology and structure of the coatings are analyzed by scanning electron microscope (SEM),energy dispersive spectroscopy (EDS),and X-ray diffraction (XRD),and the effects of the addition of Al_(2)O_(3)on the microstructure of the Al-based coatings are discussed.The mechanical properties and corrosion resistance of the coatings are fully evaluated by the micro-hardness tester,electronic tensile machine,and electrochemical workstation.The results show that the coating structure is more uniform and denser,and the porosity is significantly reduced after the addition of Al_(2)O_(3).The interfaces between the coatings and the magnesium alloy substrate are distinct,and the coatings and the substrate are mechanically combined.Compared with the pure Al coating,the microhardness of the Al-Al_(2)O_(3)composite coating is increased to 61.1 HV_(0.2),and the bonding strength reaches above 53.1 MPa.The self-corrosion potential of the two coatings is higher than that of the magnesium alloy,and the self-corrosion current density is significantly lower than that of the magnesium alloy substrate.The Al-based coatings prepared by low-pressure cold spraying have high hardness,good bonding strength,and good corrosion resistance,which can be used for the repair and protection of magnesium alloy structural parts.
文摘Effect of low-pressure carbonation （LPC） on heat inactivation of Saccharomyces cerevisiae was investigated. The cell suspension was carbonated at 1 MPa and 4℃ for 15 min and subsequently heated from 51 to 61 ℃ and 5 s to 5 min （heating with LPC）. As a control experiment, cell suspension was heat-treated under atmospheric pressure without LPC （heating）. The inactivation ratio of heating at 53℃ and 55℃ for l rain with LPC was approximately 1 log order higher than heating alone. Extending heating time to 5 min did not widen the difference in the inactivation ratio between heating with LPC and heating alone at both heating temperatures. At 57℃, the difference in inactivation ratio increased from 1 to 2.5 log order with extending treatment time from 5 to 15 s. The results suggested that the enhanced inactivation effect by LPC was obtained at the higher temperature with short time treatment than the lower temperature with longer time treatment. Under fluorescence microscope observation of LPC-treated cell stained with LysoSensor probe, it seemed that LPC was hardly able to acidify the cytoplasm ofS. cerevisiae. It is considered that the ability orS. cerevisiae ceils to keep their cytoplasmic pH during LPC resulted in the inferior increase in heat inactivation ratio by LPC as compared with bacteria in the previous studies.
文摘Metal clusters RCCo_3(CO)_9(R-H,C1,Br,CH_3,Ph) were prepared in 18.8-57.3% yields from the reaction of cobalt(Ⅱ)salt and RCX_a under mild PTC conditions(latm CO,25℃).The cobalt salt was reduced to Co(CO)_4 in the presence of Na_3S_2O_4.
文摘Stable neutron generation with a yield of ~1.2×10^(4) neutrons per pulse was obtained during d(d,n)^(3)He reaction initiated by the high-voltage nanosecond discharge in a gap with a potential tungsten cylinder(anode)and a grounded deuterated zirconium plate(cathode)filled with deuterium at a pressure of ~10^(2) Pa.Estimated duration of the neutron pulse was ~1.5 ns.Less intensive neutron emission was registered without deuterated plate.Splashing of material of the tungsten electrode was observed during the high-voltage nanosecond discharge in the deuterium,hydrogen,helium and argon at pressures of 10^(2)-10^(4) Pa.
基金supported by National High Technology Research and Development Program of China(Grant No.2015AA8016029A)
文摘The propagation of the high-power microwave（HPM） with a frequency of 6 GHz in the lowpressure argon plasma was studied by the method of fluid approximation.The two-dimensional transmission model was built based on the wave equation,the electron drift-diffusion equations and the heavy species transport equations,which were solved by means of COMSOL Multiphysics software.The simulation results showed that the propagation characteristic of the HPM was closely related to the average electron density of the plasma.The attenuation of the transmitted wave increased nonlinearly with the electron density.Specifically,the growth of the attenuation slowed down as the electron density increased uniformly.In addition,the concrete transmission process of the HPM wave in the low-pressure argon plasma was given.
基金Project supported by the National Major Science and Technology Project“Development Demonstration Project of Large-scale Low-permeability Lithologic-Stratigraphic Reservoirs in the Ordos Basin”(No.2016ZX05050)。
文摘There are abundant natural gas resources in the marine shale gas reservoir of Middle Ordovician Wulalike Formation in the Ordos Basin,which is an important resource base for PetroChina Changqing Oilfield Company to increase the reserves and production of oil and gas.Compared with the other shale gas reservoirs at home and aboard,however,the marine shale gas reservoir of Middle Ordovician Wulalike Formation in the Ordos Basin has a lower formation pressure coefficient and poorer reservoir physical properties and gas-bearing property,so its production increase difficulty is higher.In this paper,horizontal-well volume fracturing was studied and tested based on the earlier vertical well tests.According to the technical idea of the staged multi-cluster massive fracturing of long horizontal section,the propagation mechanisms and morphological characteristics of fractures were studied and analyzed based on the fracturing geological characteristics of the shale gas reservoir in the Ordos Basin.On this basis,a full three-dimensional fracture model was optimally established for parameter optimization.The fracturing of the test well ZP1 was carried out with 15 stages and 103 clusters.After the fracturing,a more complex fracture network was formed with a fracture complexity index of 0.4-0.6.The microseismic monitoring zone is 579 m long and 266 m wide and the fracture is 146 m high.To address the drainage difficulty after large-volume fracturing of low-pressure shale gas in the Ordos Basin,this paper carries out a gas energized fracturing test.Considering the characteristics of reservoir physical properties,gas-bearing property and segmented fractures,805 m3 liquid nitrogen was injected in stages during the fracturing of the test horizontal well.The formation pressure coefficient measured from pressure buildup data is increased from 0.7 to 0.8 to 1.88.The wellbore gaseliquid flow model was established and the parameters of long-period controlpressure drainage were optimized.The critical surface equipment was upgraded to achieve accurate measurement,safety and environmental protection.And the following research and practice results were obtained.First,based on the technological innovation and optimization,continuous gaseliquid two-phase flow is realized in the test well ZP1 and its production rate and pressure during the test are stable with the tested daily shale gas production at the wellhead of 6.42×10^(4)m^(3).Second,after fracturing,the absolute open flow of the test well reaches 26.4×10^(4)m^(3)/d,which is more than 10 times higher than the production rate of the vertical well in the same block during the test.Thus,a significant breakthrough is realized in the exploration of marine shale gas in North China.
基金supported by the National Natural Science Foundation of China(Grant No.51875329)the Natural Science Foundation of Shandong Province,China(Grant No.ZR2023ME112)+2 种基金the Taishan Scholar Special Foundation of Shandong Province,China(Grant Nos.tstp20240826 and tsqn201812064)the Key Research and Development Project of the Ningxia Hui Autonomous Region,China(Grant No.2024BEE02019)the Shandong Science and Technology Small and Medium-sized Enterprises Innovation Capacity Enhancement Project,China(Grant Nos.2022TSGC1261 and 2022TSGC1333).
文摘A material removal mechanism is a prerequisite to maintaining high-quality surfaces for high-shear and low-pressure grinding using body-armor-like grinding wheels(BAGWs).However,the pressure distribution and material removal efficiency for machining brittle materials using BAGWs remain unclear.This research investigated two types of elastic deformations during grinding by analyzing the contact mechanism between BAGWs and the workpiece.Additionally,the model of elastohydrodynamic pressure distribution was refined,and the material removal mechanism for machining brittle materials,incorporating the maximum undeformed chip thickness,was revealed.A material removal rate(MRR)model was established based on Hertzian contact,ductile-brittle transition,and spherical indentation theory.The theoretical model was validated through single-factor experiments utilizing a high-shear and low-pressure grinding experimental platform.At a normal grinding force of 15 N and a grinding speed of 10 m/s,the MRR could reach up to 0.276 mm3/s.The experimental results revealed that the model could accurately predict the MRR under various grinding parameters,with an average prediction error of 8.5%.
基金supported by the National Natural Science Foundation of China(Nos.51875329 and 51905322)China postdoctoral Science Foundation(No.2021T140420)+4 种基金Taishan Scholar Special Foundation of Shandong Province(No.tsqn201812064)Shandong Provincial Natural Science Foundation(No.ZR2017MEE050)Shandong Provincial Key Research and Development Project(No.2018GGX103008)Scientific Innovation Project for Young Scientists in Shandong Provincial Universities(No.2019KJB030)Key Research and Development Project of Zibo City(No.2019ZBXC070).
文摘Nickel-based alloy has been widely used due to its outstanding mechanical properties.However,Nickel-based alloy is a typical difficult-to-machine material,which is a great constrain for its application in the manufacturing field.To improve the surface quality of the ground workpiece,a new high-shear and low-pressure grinding wheel,with high ratio of tangential grinding force to normal grinding force,was fabricated for the grinding of selective laser melting(SLM)manufactured Inconel718 alloy.The principle of high-shear and low-pressure grinding process was introduced in detail,which was quite different from the conventional grinding process.The fabrication process of the new grinding wheel was illustrated.A serial of experiments with different processing parameters were carried out to investigate the grinding performance of the developed grinding wheel via analyzing surface roughness and surface morphology of the ground workpiece.The optimal processing parameters of high-shear and low-pressure grinding were obtained.The surface roughness of ground workpiece was reduced to 0.232μm from the initial value of 0.490μm under the optimal grinding conditions.It was found that the initial scratches on the ground workpiece were almost completely removed after the observations with the metalloscopy and the fieldemission scanning electron microscopy(FE-SEM).The capability of the newly developed highshear and low-pressure grinding wheel was validated.
