Failure analysis of railway draw-hook coupler was carried out.The nondestructive testing method was undertaken on some failed couplers in service to designate critical areas of a coupler.Draw-Hook coupler is used to c...Failure analysis of railway draw-hook coupler was carried out.The nondestructive testing method was undertaken on some failed couplers in service to designate critical areas of a coupler.Draw-Hook coupler is used to connect with the same hook coupler or automatic coupler.The influence of each connection types on the coupler strength in this study was discussed.A numerical stress analysis using FEM was performed,and many approaches including critical plane approach were carried out on fatigue life prediction of coupler under different conditions.The results of the proposed fatigue criterion and fatigue life predictions,as well as static numerical analysis,are validated with experimental results.展开更多
The main task of fracture mechanics of rock masses is the study on the propagating mechanism of fractures in rock masses , which can be efficiently conducted by discontinuty displacement (DD) numerical evaluation . Fi...The main task of fracture mechanics of rock masses is the study on the propagating mechanism of fractures in rock masses , which can be efficiently conducted by discontinuty displacement (DD) numerical evaluation . Firstly ,the element stress and displacement are analysed and the principle and steps of the numerical calculation of stress intensity factor and fracture extension force are introduced .The numerical results of parallel and echelon fracture systems ,which are compared with real field fractures .are presented. Finally . a simple engineering application example is presented .展开更多
The discovery of deep bedrock gas reservoirs in Altun forelands in the Qaidam Basin has expanded a newfield of natural gas exploration and development in China.Since then,it has always been believed that the storage s...The discovery of deep bedrock gas reservoirs in Altun forelands in the Qaidam Basin has expanded a newfield of natural gas exploration and development in China.Since then,it has always been believed that the storage space of this kind of gas reservoirs is composed of well-developed dual media of matrix pores and fractures,but the practices of such gas reservoir development began to be in contradiction with this cognition.In order to achieve a better understanding of the storage space and the main controlling factors of reservoir formation in this bedrock gas reservoir,it is necessary to investigate the dissolved increased pores characteristics and the forced fractures characteristics in the bedrock gas reservoir.Then,based on the data such as cores and cast thin sections in the bedrock intervals in the Dongping 1 and Jiantan 1 blocks,the main storage space types of deep bedrock gas reservoirs in Altun forelands were analyzed,then the main controlling factors of favorable target reservoirs in these blocks were put forward,and in combination with the regional geological background,the geological understandings of favorable target reservoirs and potential reserves were deepened in this study area.The following research results were achieved.(1)The lithology of the bedrock gas reservoirs in this area consists of calc-alkaline igneous rocks and gneiss suite regional metamorphic rocks.Matrix pores are not developed,and their development degree is mainly controlled by faults.Main effective storage spaces and permeable channels are structural fractures and dissolution fractures.(2)The main controlling factors of target reservoir formation include lithology,tectonic effect,weathering,intrusive dikes,and on the whole the rule of ternary-control is followed,namely prevalent lithologyedominant stressesehydrocarbon accumulations in the structural higher parts.(3)The potential zones of reservoir formation include the following 5 types:tectonically stress concentrated tensionetorsional zones,contact zones between lithologic interfaces of intrusive body,weathering zones of compressing uplift,slope sediment zones near circumscribed erosion area,para-conformity or unconformity interface.展开更多
Natural layered rocks subjected to layerparallel extension typically develop an array of opening- mode fractures with a remarkably regular spacing. This spacing often scales with layer thickness, and it decreases as e...Natural layered rocks subjected to layerparallel extension typically develop an array of opening- mode fractures with a remarkably regular spacing. This spacing often scales with layer thickness, and it decreases as extension increases until fracture saturation is reached. To increase the understanding of how these opening-mode fractures form in layered rocks, a series of 2D numerical simulations are performed to investigate the infilling process of fractures subjected to different driving forces. Numerical results illustrate that any one of the following could be considered as a driving force behind the propagation of infilling fractures： thermal effect, internal fluid pressure, direct extension loading, or pure compressive loading. Fracture spacing initially decreases with loading process, and at a certain ratio of fracture spacing to layer thickness, no new fractures nucleate （saturated）. Both an increase in the opening of the infilled fractures and interface delamination are observed as mechanisms that accommodate additional strain. Interface debonding stops the transition of stress from the neighboring layers to the embedded central layer, which may preclude further infilling of new fractures. Whatever the driving force is, a large overburden stress and a large elastic contrast between the stiff and soft layers （referred to as a central or fractured layer and the top and bottom layers） are key factors favoring the development of tensile stress around the infilled fractures in the models. Fracture spacing is expected to decrease with increasing overburden stress. Numerical results highlight the fracturing process developed in heterogeneous and layered sedimentary rocks which provides supplementary information on the stress distribution and failure-induced stress redistribution., It also shows, in detail, the propagation of the fracture zone and the interaction of the fractures, which are impossible to observe in field and are difficult to consider with static stress analysis approaches.展开更多
Pelvic fracture is among the most complicated fractures in traumatic orthopedics,with high mortality and morbidity rates.The main difficulty associated with the reduction surgery is significant muscle resistance.It th...Pelvic fracture is among the most complicated fractures in traumatic orthopedics,with high mortality and morbidity rates.The main difficulty associated with the reduction surgery is significant muscle resistance.It then becomes necessary to decrease the reduction force against this strong muscle resistance,for improving surgical safety.Here,we propose a novel traction method for decreasing the reduction force during pelvic reduction,and investigate the performance of the elastic traction method on decreasing the reduction force using experimental tests and simulation-based analyses.From the experimental results,the reduction force decreased by 59.2%when 10 kg of elastic traction was applied.We also establish a musculoskeletal model of the pelvic fracture reduction,for analyzing the muscle resistance and the optimal traction force applied in reduction surgeries.The elastic traction method can counteract the muscle resistance increase in the non-traction direction owing to its flexibility.We conclude that the optimal traction force applied should be in the 10–15 kg range,and recommend adopting a dynamic traction strategy rather than continuous traction in clinical settings.Elastic traction is very promising for various surgeries that require traction,including pelvic reduction.It significantly reduces force,which can significantly reduce the physical exertion of the operating surgeon,the possibility of additional injuries to the operated patient,and promotes robot-assisted reduction surgeries.展开更多
文摘Failure analysis of railway draw-hook coupler was carried out.The nondestructive testing method was undertaken on some failed couplers in service to designate critical areas of a coupler.Draw-Hook coupler is used to connect with the same hook coupler or automatic coupler.The influence of each connection types on the coupler strength in this study was discussed.A numerical stress analysis using FEM was performed,and many approaches including critical plane approach were carried out on fatigue life prediction of coupler under different conditions.The results of the proposed fatigue criterion and fatigue life predictions,as well as static numerical analysis,are validated with experimental results.
基金The research is supported by the National Nature Science Foundation of China
文摘The main task of fracture mechanics of rock masses is the study on the propagating mechanism of fractures in rock masses , which can be efficiently conducted by discontinuty displacement (DD) numerical evaluation . Firstly ,the element stress and displacement are analysed and the principle and steps of the numerical calculation of stress intensity factor and fracture extension force are introduced .The numerical results of parallel and echelon fracture systems ,which are compared with real field fractures .are presented. Finally . a simple engineering application example is presented .
基金supported by the Major S&T Special Project of PetroChim Company Limited"Research and application of key exploration and development technologies for constructing highland oilgas fields in the Qaidam Basin"(No.2016-E-01).
文摘The discovery of deep bedrock gas reservoirs in Altun forelands in the Qaidam Basin has expanded a newfield of natural gas exploration and development in China.Since then,it has always been believed that the storage space of this kind of gas reservoirs is composed of well-developed dual media of matrix pores and fractures,but the practices of such gas reservoir development began to be in contradiction with this cognition.In order to achieve a better understanding of the storage space and the main controlling factors of reservoir formation in this bedrock gas reservoir,it is necessary to investigate the dissolved increased pores characteristics and the forced fractures characteristics in the bedrock gas reservoir.Then,based on the data such as cores and cast thin sections in the bedrock intervals in the Dongping 1 and Jiantan 1 blocks,the main storage space types of deep bedrock gas reservoirs in Altun forelands were analyzed,then the main controlling factors of favorable target reservoirs in these blocks were put forward,and in combination with the regional geological background,the geological understandings of favorable target reservoirs and potential reserves were deepened in this study area.The following research results were achieved.(1)The lithology of the bedrock gas reservoirs in this area consists of calc-alkaline igneous rocks and gneiss suite regional metamorphic rocks.Matrix pores are not developed,and their development degree is mainly controlled by faults.Main effective storage spaces and permeable channels are structural fractures and dissolution fractures.(2)The main controlling factors of target reservoir formation include lithology,tectonic effect,weathering,intrusive dikes,and on the whole the rule of ternary-control is followed,namely prevalent lithologyedominant stressesehydrocarbon accumulations in the structural higher parts.(3)The potential zones of reservoir formation include the following 5 types:tectonically stress concentrated tensionetorsional zones,contact zones between lithologic interfaces of intrusive body,weathering zones of compressing uplift,slope sediment zones near circumscribed erosion area,para-conformity or unconformity interface.
基金Acknowledgements The study presented in this study was jointly supported by grants from PetroChina Innovation Foundation （Grant No. 2013D-5006-0211）, National Basic Research Programme of China （Grant No. 2011CB013503） and the National Natural Science Foundation of China （Grant No. 51279024）. The authors are grateful for their support.
文摘Natural layered rocks subjected to layerparallel extension typically develop an array of opening- mode fractures with a remarkably regular spacing. This spacing often scales with layer thickness, and it decreases as extension increases until fracture saturation is reached. To increase the understanding of how these opening-mode fractures form in layered rocks, a series of 2D numerical simulations are performed to investigate the infilling process of fractures subjected to different driving forces. Numerical results illustrate that any one of the following could be considered as a driving force behind the propagation of infilling fractures： thermal effect, internal fluid pressure, direct extension loading, or pure compressive loading. Fracture spacing initially decreases with loading process, and at a certain ratio of fracture spacing to layer thickness, no new fractures nucleate （saturated）. Both an increase in the opening of the infilled fractures and interface delamination are observed as mechanisms that accommodate additional strain. Interface debonding stops the transition of stress from the neighboring layers to the embedded central layer, which may preclude further infilling of new fractures. Whatever the driving force is, a large overburden stress and a large elastic contrast between the stiff and soft layers （referred to as a central or fractured layer and the top and bottom layers） are key factors favoring the development of tensile stress around the infilled fractures in the models. Fracture spacing is expected to decrease with increasing overburden stress. Numerical results highlight the fracturing process developed in heterogeneous and layered sedimentary rocks which provides supplementary information on the stress distribution and failure-induced stress redistribution., It also shows, in detail, the propagation of the fracture zone and the interaction of the fractures, which are impossible to observe in field and are difficult to consider with static stress analysis approaches.
基金This work was supported by Key research and development plan of the Ministry of science and technology of China[2019YFC0118002]National Natural Science Foundation(NSFC)Grant of China[61871019]+1 种基金Beijing science and technology project[Z18110001918024]Natural Science Foundation of Beijing[19L2011].
文摘Pelvic fracture is among the most complicated fractures in traumatic orthopedics,with high mortality and morbidity rates.The main difficulty associated with the reduction surgery is significant muscle resistance.It then becomes necessary to decrease the reduction force against this strong muscle resistance,for improving surgical safety.Here,we propose a novel traction method for decreasing the reduction force during pelvic reduction,and investigate the performance of the elastic traction method on decreasing the reduction force using experimental tests and simulation-based analyses.From the experimental results,the reduction force decreased by 59.2%when 10 kg of elastic traction was applied.We also establish a musculoskeletal model of the pelvic fracture reduction,for analyzing the muscle resistance and the optimal traction force applied in reduction surgeries.The elastic traction method can counteract the muscle resistance increase in the non-traction direction owing to its flexibility.We conclude that the optimal traction force applied should be in the 10–15 kg range,and recommend adopting a dynamic traction strategy rather than continuous traction in clinical settings.Elastic traction is very promising for various surgeries that require traction,including pelvic reduction.It significantly reduces force,which can significantly reduce the physical exertion of the operating surgeon,the possibility of additional injuries to the operated patient,and promotes robot-assisted reduction surgeries.
