Quasi-NPR(negative Poisson’s ratio)steel is a new type of super bolt material with high strength,high ductility,and a micro-negative Poisson’s effect.This material overcomes the contrasting characteristics of the hi...Quasi-NPR(negative Poisson’s ratio)steel is a new type of super bolt material with high strength,high ductility,and a micro-negative Poisson’s effect.This material overcomes the contrasting characteristics of the high strength and high ductility of steel and it has significant energy-absorbing characteristics,which is of high value in deep rock and soil support engineering.However,research on the shear resistance of quasi-NPR steel has not been carried out.To study the shear performance of quasi-NPR steel bolted rock joints,indoor shear tests of bolted rock joints under different normal stress conditions were carried out.Q235 steel and#45 steel,two representative ordinary bolt steels,were set up as a control group for comparative tests to compare and analyze the shear strength,deformation and instability mode,shear energy absorption characteristics,and bolting contribution of different types of bolts.The results show that the jointed rock masses without bolt reinforcement undergo brittle failure under shear load,while the bolted jointed rock masses show obvious ductile failure characteristics.The shear deformation ca-pacity of quasi-NPR steel is more than 3.5 times that of Q235 steel and#45 steel.No fracture occurs in the quasi-NPR steel during large shear deformation and it can provide stable shear resistance.However,the other two types of control bolts become fractured under the same conditions.Quasi-NPR steel has significant energy-absorbing characteristics under shear load and has obvious advantages in terms of absorbing the energy released by shear deformation of jointed rock masses as compared with ordinary steel.In particular,the shear force plays a major role in resisting the shear deformation of Q235 steel and#45 steel,therefore,fracture failure occurs under small bolt deformation.However,the axial force of quasi-NPR steel can be fully exerted when resisting joint shear deformation;the steel itself does not break when large shear deformation occurs,and the supporting effect of the jointed rock mass is effectively guaranteed.展开更多
Two-order morphology of rock joints named as waviness and unevenness can be separated by morphology classification method,which plays a decisive role in the evolution of shear stress during the shear test.The joint mo...Two-order morphology of rock joints named as waviness and unevenness can be separated by morphology classification method,which plays a decisive role in the evolution of shear stress during the shear test.The joint morphology is obtained by using 3D printing and 3D laser scanning techniques and the joint model samples in two-order morphology are produced by cement mortar.Then,shear tests are performed under different normal loads.Results shows that the waviness is dominant in the total morphology during the shear test,and the shear contribution of unevenness mainly occurs in the climbing phase of shearing process.Comparing the failure modes of two-order morphology,waviness mainly embodies shear dilation characteristics and unevenness mainly shows shear wear characteristics.Based on this,a quantitative parameter is proposed to represent the ratio of the peak shear strength of the two-order morphology to that of total morphology.The functional relationship between the peak shear strength of total and two-order morphologies is determined,providing a theoretical method for further in-depth study on the shear strength of the interaction with two-order morphology of rock joints.展开更多
Periprosthetic joint infection(PJI)following total knee arthroplasty is one of the most catastrophic and costly complications that carries significant patient wellness as well as economic burdens.The road to efficient...Periprosthetic joint infection(PJI)following total knee arthroplasty is one of the most catastrophic and costly complications that carries significant patient wellness as well as economic burdens.The road to efficiently diagnosing and treating PJI is challenging,as there is still no gold standard method to reach the diagnosis as early as desired.There are also international controversies with respect to the best approach to manage PJI cases.In this review,we highlight recent advances in managing PJI following knee arthroplasty surgery and discuss in depth the two-stage revision method.展开更多
Purpose: Acromioclavicular (AC) joint dislocation is commonly treated using a clavicle hook plate (HP). However, previous reports have indicated that acromial fractures may occur after HP fixation. The purpose of this...Purpose: Acromioclavicular (AC) joint dislocation is commonly treated using a clavicle hook plate (HP). However, previous reports have indicated that acromial fractures may occur after HP fixation. The purpose of this study was to identify risk factors for acromial fractures. Methods: A retrospective study was conducted on 39 patients with AC joint dislocation who were treated using clavicle HP fixation in our hospital between 2006 and 2017. Related parameters, including Rockwood classification, hook angle, the degree of reduction, the coverage of the hook under the acromion, and the anteroposterior position of the hook under the acromion, were evaluated to identify risk factors for acromial fractures. Results: The mean age of the participants was 51.7 (range 19 - 81) years;34 were men and 5 were women. Injury occurred on the right side in 18 patients and on the left side in 21. Injuries were categorized as follows: 24 were Rockwood type III, one was type IV, and 14 were type V. Four of the 39 patients (10%) experienced acromial fractures. Statistical analyses indicated that the degree of reduction at the final follow-up was moderately correlated with the Constant score. Posterior positioning of the hook was the only identified risk factor for acromial fractures. Hook angle and the degree of reduction at the time of surgery were not significantly associated with acromial fractures. Conclusions: Postoperative shoulder function was associated with the degree of reduction at the final follow-up, suggesting that anatomical reduction is recommended for AC joint dislocation. Posterior positioning of the hook is a risk factor for acromial fractures;however, clavicle HP fixation provides a positive outcome for AC joint dislocation. Therefore, careful positioning of the hook is required for preventing acromial fractures.展开更多
On January 5,the Chinese People's Association for Friendship with Foreign Countries and the Chinese People's Institute of Foreign Affairs jointly hosted a reception commemorating the 45th anniversary of the es...On January 5,the Chinese People's Association for Friendship with Foreign Countries and the Chinese People's Institute of Foreign Affairs jointly hosted a reception commemorating the 45th anniversary of the establishment of diplomatic relationship between China and the United States in Beijing.Member of the Political Bureau of the CPC Central Committee and Foreign Minister Wang Yi attended the commemoration and delivered aspeech.David Meale,ChargédAffaires at the U.S.Embassy in China,addressed the reception.He extended on behalf of the U.S.side congratulations on the anniversary,expressing the readiness of the U.S.to implement the consensus reached by the two heads of state and promote the steady development of U.S.-China relations.More than 350 people from all walks of life of both countries attended the reception.展开更多
Objective:To explore the treatment of TOSSY type III acromioclavicular joint dislocation with clavicular hook plate combined with coracoclavicular ligament repair and its clinical effect.Methods:80 patients with TOSSY...Objective:To explore the treatment of TOSSY type III acromioclavicular joint dislocation with clavicular hook plate combined with coracoclavicular ligament repair and its clinical effect.Methods:80 patients with TOSSY type III acromioclavicular joint dislocation who were admitted to our hospital from January 2014 to January 2019 were selected.They were randomly divided into the control group(n=39,treated with clavicular hook plate)and the observation group(n=41,treated with clavicular hook plate combined with coracoclavicular ligament repair)by the random number table method.The clinical efficacy in 12 months after operation,related clinical indicators,12-month postoperative recovery and postoperative complications were compared between the two groups.Results:The excellent and good rate was 92.68%(38/41)in 12 months after operation in the observation group,which was higher than that(76.92%,30/39)in the control group(p<.05).There were no significant differences in the duration of surgery,intraoperative blood loss and HLOS between the observation group and the control group(p>.05).In 12 months after operation,abduction activity and forward flexion activity of the observation group were higher than those of the control group,and visual analogue score(VAS)was lower than that of the control group(p<.05).The incidence of complications in the observation group was slightly lower than that in the control group,but there was no statistically significant difference between the two groups(p>.05).Conclusions:For TOSSY type III acromioclavicular joint dislocation,clavicular hook plate combined with coracoclavicular ligament repair has a good clinical efficacy.It can improve shoulder joint function,alleviate shoulder pain and have fewer complications.It can provide a reference for clinical treatment of this type of acromioclavicular joint dislocation.展开更多
Several typical flexible pneumatic actuators (FPA) and different mechanical models describing their behaviors have been proposed, however, it is difficult to balance compliance and load capacity in conventional desi...Several typical flexible pneumatic actuators (FPA) and different mechanical models describing their behaviors have been proposed, however, it is difficult to balance compliance and load capacity in conventional designs, and these models still have limitations in predicting behavior of FPAs. A new flexible pneumatic bending joint (FPBJ) with special anisotropic rigidity structure is proposed. The FPBJ is developed as an improvement with regard to existing types of FPA, and its principal characteristic is derived from the special anisotropic rigidity structure. With this structure, the load capacity in the direction perpendicular to bending plane is strengthened. The structure of the new FPBJ is explained and a mathematical model is derived based on Euler-Bernoulli beam model and Hook’s law. To obtain optimum design and usage, some key structure parameters and input-output characteristics are simulated. The simulation results reveal that the relationship between the structure parameters and FPBJ’s bending angle is nonlinear. At last, according to the simulation results, the FPBJ is manufactured with optional parameters and tested. The experimental results show that the joint’s statics characteristics are reflected by the mathematical model accurately when the FPBJ is deflated. The maximum relative error between simulation and experimental results is less than 6%. However, the model still has limitations. When the joint is inflated, the maximum relative error reaches 20%. This paper proposes a new flexible pneumatic bending joint which has sufficient load capacity and compliance, and the mathematical model provides theoretical guidance for the FPBJ’s structure design.展开更多
Stress Joint (SJ) plays a key role in the Top Tensioned Riser (TTR) system for deep water engineering. A preliminary design method of tapered SJ is proposed in the paper, which could help designers obtain accurate...Stress Joint (SJ) plays a key role in the Top Tensioned Riser (TTR) system for deep water engineering. A preliminary design method of tapered SJ is proposed in the paper, which could help designers obtain accurate design data. After a further sensitive analysis is carried out, the related parameters choice and control methods are recommended in the engineering practice. By taking the extreme environment conditions into consideration, the effects of bending stress reduction and curve control are analyzed, and the 3-D FE models are established by ABQOUS for numerical evaluation to verify the correctness of design results. At last, dynamic analysis and fatigue analysis, based on actual project, are carried out with designed stress joint. The analysis results prove the feasibility and guidance of this method in the practical engineering applications.展开更多
Association of fracture of trapezium with Bennett'sfracture is very rare and makes reduction and stabilisation more difficult. We are reporting a rare case of Bennett's fracture with fracture of the trapezium ...Association of fracture of trapezium with Bennett'sfracture is very rare and makes reduction and stabilisation more difficult. We are reporting a rare case of Bennett's fracture with fracture of the trapezium and subluxation of the carpo-metacarpal joint(CMC) joint. The patient was a 47-year-old school teacher who fell from his motorbike on his outstretched right dominant hand. Radiographs and computed tomography showed fracture of the trapezium with subluxation of the CMC joint, associated with Bennett's fracture. Open reduction and internal fixation was carried out. Trapezium was reduced first and secured with a 2 mm diameter screw. Bennett's fracture was then reduced and fixed with two per-cutaneously placed Kirchner's wires. CMC was stabilised with percutaneous Kirchner's wires. Latest follow up at 12 mo showed a healed fracture with good reduction of the CMC joint. Clinically patient had no pain and normal extension, abduction and opposition of the thumb. QuickD ASH score was 3.9/100. Thus, fracture of trapezium associated with a Bennett's fracture is a rare injury and if ignored it may lead to poor results. This injury is more challenging to manage than an isolated Bennett's fracture as anatomical reduction of the trapezium with reduction of the first CMC is needed. Fracture of the trapezium should be fixed first as this will provide a stable base for reduction of the Bennett's fracture.展开更多
The most commonly used method for assessing the hydraulic erodibility of rock is Annandale's method.This method is based on a correlation between the erosive force of flowing water and the capacity of rock resista...The most commonly used method for assessing the hydraulic erodibility of rock is Annandale's method.This method is based on a correlation between the erosive force of flowing water and the capacity of rock resistance. This capacity is evaluated using Kirsten's index, which was initially developed to evaluate the excavatability of earth materials. For rocky material, this index is determined according to certain geomechanical factors related to intact rock and rock mass, such as compressive strength of intact rock, rock block size, discontinuity shear strength and relative block structure. To quantify the relative block structure, Kirsten(1982) developed a mathematical expression that accounts for the shape and orientation of the blocks relative to the direction of flow. Kirsten's initial concept for assessing the relative block structure considers that the geological formation is mainly fractured by two joint sets forming an orthogonally fractured system. An adjusted concept is proposed to determine the relative block structure when the fractured system is non-orthogonal where the angle between the planes of the two joint sets is greater or less than 90°. An analysis of the proposed relative block structure rating shows that considering a non-orthogonally fractured system has a significant effect on Kirsten's index and, as a consequence, on the assessment of the hydraulic erodibility of rock.展开更多
The objective of this work is to analyze the fatigue reliability of complex welded structures composed of multiple web-frame joints, accounting for correlation effects. A three-dimensional finite element model using t...The objective of this work is to analyze the fatigue reliability of complex welded structures composed of multiple web-frame joints, accounting for correlation effects. A three-dimensional finite element model using the 20-node solid elements is generated. A linear elastic finite element analysis was performed, hotspot stresses in a web-frame joint were analyzed and fatigue damage was quantified employing the S-N approach. The statistical descriptors of the fatigue life of a non-correlated web-frame joint containing several critical hotspots were estimated. The fatigue reliability of a web-frame joint wasmodeled as a series system of correlated components using the Ditlevsen bounds. The fatigue reliability of the entire welded structure with multiple web-frame joints, modeled as a parallel system of non-correlated web-frame joints was also calculated.展开更多
Combined bodies of rock-like material and rock are widely encountered in geotechnical engineering,such as tunnels and mines.The existing theoretical models describing the stress-strain relationship of a combined body ...Combined bodies of rock-like material and rock are widely encountered in geotechnical engineering,such as tunnels and mines.The existing theoretical models describing the stress-strain relationship of a combined body lack a binary feature.Based on effective medium theory,this paper presents the governing equation of the“elastic modulus”for combined and single bodies under triaxial compressive tests.A binary effective medium model is then established.Based on the compressive experiment of concretegranite combined bodies,the feasibility of determining the stress threshold based on crack axial strain is discussed,and the model is verified.The model is further extended to coal-rock combined bodies of more diverse types,and the variation laws of the compressive mechanical parameters are then discussed.The results show that the fitting accuracy of the model with the experimental curves of the concretegranite combined bodies and various types of coal-rock combined bodies are over 95%.The crack axial strain method can replace the crack volumetric strain method,which clarifies the physical meanings of the model parameters.The variation laws of matrix parameters and crack parameters are discussed in depth and are expected to be more widely used in geotechnical engineering.展开更多
In engineering practice, tubular X-joints have been widely used in offshore structures. The fatigue failure of tubular X-joints in offshore engineering is mainly caused by axial tensile stress. In this study, the stre...In engineering practice, tubular X-joints have been widely used in offshore structures. The fatigue failure of tubular X-joints in offshore engineering is mainly caused by axial tensile stress. In this study, the stress concentration factor distribution along the weld toe in the hot spot stress region for tubular X-joints subject to axial loads have been analyzed by use of finite element method. Through numerical analysis, it has been found that the peak stress concentration factor is located at the saddle position. Thereafter, 80 models have been analyzed, and the effect of the geometric parameters of a tubular X-joint on the stress concentration factor has been investigated. Based on the experimental values of the numerical stress concentration factor, a parametric equation to calculate the stress concentration factor of tubular X-joints has been proposed. The accuracy of this equation has been verified against the requirement of the Fatigue Guidance Review Panel, and the proposed equation is found capable of producing reasonably accurate stress concentration factor values for tubular X-joints subject to axial loads.展开更多
Very high cycle fatigue(VHCF) behaviors of bridge steel(Q345) welded joints were investigated using an ultrasonic fatigue test system at room temperature with a stress ratio R = -1. The results show that the fatig...Very high cycle fatigue(VHCF) behaviors of bridge steel(Q345) welded joints were investigated using an ultrasonic fatigue test system at room temperature with a stress ratio R = -1. The results show that the fatigue strength of welded joints is dropped by an average of 60% comparing to the base metal and the fatigue failure still occurred beyond 10~7 cycles.The fatigue fracture of welded joints in the low cycle regime generally occurred at the solder while at the heat-affected zone(HAZ) in the very high cycle regime.The fatigue fracture surface was analyzed with scanning electron microscopy(SEM),showing welding defects such as pore,micro-crack and inclusion were the main factors on decreasing the fatigue properties of welded joints.The effect of welding defects on the fatigue behaviors of welded joints was discussed in terms of experimental results and finite element simulations.展开更多
AFast quenching NdFeB permanent magnet—a high-tech product filling in the domestic gaps—has been put into mass production by the Beijing Century New Magnetics Co. Ltd. Previously, only the United States of America h...AFast quenching NdFeB permanent magnet—a high-tech product filling in the domestic gaps—has been put into mass production by the Beijing Century New Magnetics Co. Ltd. Previously, only the United States of America had patent rights for production and sale of fast quenching NdFeB Magnets, and only General Motor Company could produce such high-tech products.展开更多
基金This study has been funded by the National Natural Science Foundation of China(Grant No.41941018)and the Second Tibetan Plateau Scientific Expedition and Research Grant(Grant No.2019QZKK0708).
文摘Quasi-NPR(negative Poisson’s ratio)steel is a new type of super bolt material with high strength,high ductility,and a micro-negative Poisson’s effect.This material overcomes the contrasting characteristics of the high strength and high ductility of steel and it has significant energy-absorbing characteristics,which is of high value in deep rock and soil support engineering.However,research on the shear resistance of quasi-NPR steel has not been carried out.To study the shear performance of quasi-NPR steel bolted rock joints,indoor shear tests of bolted rock joints under different normal stress conditions were carried out.Q235 steel and#45 steel,two representative ordinary bolt steels,were set up as a control group for comparative tests to compare and analyze the shear strength,deformation and instability mode,shear energy absorption characteristics,and bolting contribution of different types of bolts.The results show that the jointed rock masses without bolt reinforcement undergo brittle failure under shear load,while the bolted jointed rock masses show obvious ductile failure characteristics.The shear deformation ca-pacity of quasi-NPR steel is more than 3.5 times that of Q235 steel and#45 steel.No fracture occurs in the quasi-NPR steel during large shear deformation and it can provide stable shear resistance.However,the other two types of control bolts become fractured under the same conditions.Quasi-NPR steel has significant energy-absorbing characteristics under shear load and has obvious advantages in terms of absorbing the energy released by shear deformation of jointed rock masses as compared with ordinary steel.In particular,the shear force plays a major role in resisting the shear deformation of Q235 steel and#45 steel,therefore,fracture failure occurs under small bolt deformation.However,the axial force of quasi-NPR steel can be fully exerted when resisting joint shear deformation;the steel itself does not break when large shear deformation occurs,and the supporting effect of the jointed rock mass is effectively guaranteed.
基金funded by National Natural Science Foundation of China(Grant Nos.42272333 and 42277147)。
文摘Two-order morphology of rock joints named as waviness and unevenness can be separated by morphology classification method,which plays a decisive role in the evolution of shear stress during the shear test.The joint morphology is obtained by using 3D printing and 3D laser scanning techniques and the joint model samples in two-order morphology are produced by cement mortar.Then,shear tests are performed under different normal loads.Results shows that the waviness is dominant in the total morphology during the shear test,and the shear contribution of unevenness mainly occurs in the climbing phase of shearing process.Comparing the failure modes of two-order morphology,waviness mainly embodies shear dilation characteristics and unevenness mainly shows shear wear characteristics.Based on this,a quantitative parameter is proposed to represent the ratio of the peak shear strength of the two-order morphology to that of total morphology.The functional relationship between the peak shear strength of total and two-order morphologies is determined,providing a theoretical method for further in-depth study on the shear strength of the interaction with two-order morphology of rock joints.
文摘Periprosthetic joint infection(PJI)following total knee arthroplasty is one of the most catastrophic and costly complications that carries significant patient wellness as well as economic burdens.The road to efficiently diagnosing and treating PJI is challenging,as there is still no gold standard method to reach the diagnosis as early as desired.There are also international controversies with respect to the best approach to manage PJI cases.In this review,we highlight recent advances in managing PJI following knee arthroplasty surgery and discuss in depth the two-stage revision method.
文摘Purpose: Acromioclavicular (AC) joint dislocation is commonly treated using a clavicle hook plate (HP). However, previous reports have indicated that acromial fractures may occur after HP fixation. The purpose of this study was to identify risk factors for acromial fractures. Methods: A retrospective study was conducted on 39 patients with AC joint dislocation who were treated using clavicle HP fixation in our hospital between 2006 and 2017. Related parameters, including Rockwood classification, hook angle, the degree of reduction, the coverage of the hook under the acromion, and the anteroposterior position of the hook under the acromion, were evaluated to identify risk factors for acromial fractures. Results: The mean age of the participants was 51.7 (range 19 - 81) years;34 were men and 5 were women. Injury occurred on the right side in 18 patients and on the left side in 21. Injuries were categorized as follows: 24 were Rockwood type III, one was type IV, and 14 were type V. Four of the 39 patients (10%) experienced acromial fractures. Statistical analyses indicated that the degree of reduction at the final follow-up was moderately correlated with the Constant score. Posterior positioning of the hook was the only identified risk factor for acromial fractures. Hook angle and the degree of reduction at the time of surgery were not significantly associated with acromial fractures. Conclusions: Postoperative shoulder function was associated with the degree of reduction at the final follow-up, suggesting that anatomical reduction is recommended for AC joint dislocation. Posterior positioning of the hook is a risk factor for acromial fractures;however, clavicle HP fixation provides a positive outcome for AC joint dislocation. Therefore, careful positioning of the hook is required for preventing acromial fractures.
文摘On January 5,the Chinese People's Association for Friendship with Foreign Countries and the Chinese People's Institute of Foreign Affairs jointly hosted a reception commemorating the 45th anniversary of the establishment of diplomatic relationship between China and the United States in Beijing.Member of the Political Bureau of the CPC Central Committee and Foreign Minister Wang Yi attended the commemoration and delivered aspeech.David Meale,ChargédAffaires at the U.S.Embassy in China,addressed the reception.He extended on behalf of the U.S.side congratulations on the anniversary,expressing the readiness of the U.S.to implement the consensus reached by the two heads of state and promote the steady development of U.S.-China relations.More than 350 people from all walks of life of both countries attended the reception.
基金Natural Science Foundation of Inner Mongolia Autonomous Region(2019MS08045).
文摘Objective:To explore the treatment of TOSSY type III acromioclavicular joint dislocation with clavicular hook plate combined with coracoclavicular ligament repair and its clinical effect.Methods:80 patients with TOSSY type III acromioclavicular joint dislocation who were admitted to our hospital from January 2014 to January 2019 were selected.They were randomly divided into the control group(n=39,treated with clavicular hook plate)and the observation group(n=41,treated with clavicular hook plate combined with coracoclavicular ligament repair)by the random number table method.The clinical efficacy in 12 months after operation,related clinical indicators,12-month postoperative recovery and postoperative complications were compared between the two groups.Results:The excellent and good rate was 92.68%(38/41)in 12 months after operation in the observation group,which was higher than that(76.92%,30/39)in the control group(p<.05).There were no significant differences in the duration of surgery,intraoperative blood loss and HLOS between the observation group and the control group(p>.05).In 12 months after operation,abduction activity and forward flexion activity of the observation group were higher than those of the control group,and visual analogue score(VAS)was lower than that of the control group(p<.05).The incidence of complications in the observation group was slightly lower than that in the control group,but there was no statistically significant difference between the two groups(p>.05).Conclusions:For TOSSY type III acromioclavicular joint dislocation,clavicular hook plate combined with coracoclavicular ligament repair has a good clinical efficacy.It can improve shoulder joint function,alleviate shoulder pain and have fewer complications.It can provide a reference for clinical treatment of this type of acromioclavicular joint dislocation.
基金Supported by National Natural Science Foundation of China (Grant No.51075363)Zhejiang Provincial Natural Science Outstanding Youth Team Foundation of China (Grant No.R1090674)+1 种基金Zhejiang Provincial Natural Science Foundation of China (Grant No.LY12E05022)Open Fund of Key Laboratory of E&M (Zhejiang University of Technology),Ministry of Education & Zhejiang Province of China (Grant No.2009EP026)
文摘Several typical flexible pneumatic actuators (FPA) and different mechanical models describing their behaviors have been proposed, however, it is difficult to balance compliance and load capacity in conventional designs, and these models still have limitations in predicting behavior of FPAs. A new flexible pneumatic bending joint (FPBJ) with special anisotropic rigidity structure is proposed. The FPBJ is developed as an improvement with regard to existing types of FPA, and its principal characteristic is derived from the special anisotropic rigidity structure. With this structure, the load capacity in the direction perpendicular to bending plane is strengthened. The structure of the new FPBJ is explained and a mathematical model is derived based on Euler-Bernoulli beam model and Hook’s law. To obtain optimum design and usage, some key structure parameters and input-output characteristics are simulated. The simulation results reveal that the relationship between the structure parameters and FPBJ’s bending angle is nonlinear. At last, according to the simulation results, the FPBJ is manufactured with optional parameters and tested. The experimental results show that the joint’s statics characteristics are reflected by the mathematical model accurately when the FPBJ is deflated. The maximum relative error between simulation and experimental results is less than 6%. However, the model still has limitations. When the joint is inflated, the maximum relative error reaches 20%. This paper proposes a new flexible pneumatic bending joint which has sufficient load capacity and compliance, and the mathematical model provides theoretical guidance for the FPBJ’s structure design.
基金supported by the National High Technology Research and Development Program of China (863 Program,Grant No. 2008AA09A105-04)
文摘Stress Joint (SJ) plays a key role in the Top Tensioned Riser (TTR) system for deep water engineering. A preliminary design method of tapered SJ is proposed in the paper, which could help designers obtain accurate design data. After a further sensitive analysis is carried out, the related parameters choice and control methods are recommended in the engineering practice. By taking the extreme environment conditions into consideration, the effects of bending stress reduction and curve control are analyzed, and the 3-D FE models are established by ABQOUS for numerical evaluation to verify the correctness of design results. At last, dynamic analysis and fatigue analysis, based on actual project, are carried out with designed stress joint. The analysis results prove the feasibility and guidance of this method in the practical engineering applications.
文摘Association of fracture of trapezium with Bennett'sfracture is very rare and makes reduction and stabilisation more difficult. We are reporting a rare case of Bennett's fracture with fracture of the trapezium and subluxation of the carpo-metacarpal joint(CMC) joint. The patient was a 47-year-old school teacher who fell from his motorbike on his outstretched right dominant hand. Radiographs and computed tomography showed fracture of the trapezium with subluxation of the CMC joint, associated with Bennett's fracture. Open reduction and internal fixation was carried out. Trapezium was reduced first and secured with a 2 mm diameter screw. Bennett's fracture was then reduced and fixed with two per-cutaneously placed Kirchner's wires. CMC was stabilised with percutaneous Kirchner's wires. Latest follow up at 12 mo showed a healed fracture with good reduction of the CMC joint. Clinically patient had no pain and normal extension, abduction and opposition of the thumb. QuickD ASH score was 3.9/100. Thus, fracture of trapezium associated with a Bennett's fracture is a rare injury and if ignored it may lead to poor results. This injury is more challenging to manage than an isolated Bennett's fracture as anatomical reduction of the trapezium with reduction of the first CMC is needed. Fracture of the trapezium should be fixed first as this will provide a stable base for reduction of the Bennett's fracture.
基金the organizations that have funded this project:the Natural Sciences and Engineering Research Council of Canada(Grant No.498020-16)Hydro-Quebec(NC-525700)Mitacs Accelerate Program(Grant Ref.IT10008)
文摘The most commonly used method for assessing the hydraulic erodibility of rock is Annandale's method.This method is based on a correlation between the erosive force of flowing water and the capacity of rock resistance. This capacity is evaluated using Kirsten's index, which was initially developed to evaluate the excavatability of earth materials. For rocky material, this index is determined according to certain geomechanical factors related to intact rock and rock mass, such as compressive strength of intact rock, rock block size, discontinuity shear strength and relative block structure. To quantify the relative block structure, Kirsten(1982) developed a mathematical expression that accounts for the shape and orientation of the blocks relative to the direction of flow. Kirsten's initial concept for assessing the relative block structure considers that the geological formation is mainly fractured by two joint sets forming an orthogonally fractured system. An adjusted concept is proposed to determine the relative block structure when the fractured system is non-orthogonal where the angle between the planes of the two joint sets is greater or less than 90°. An analysis of the proposed relative block structure rating shows that considering a non-orthogonally fractured system has a significant effect on Kirsten's index and, as a consequence, on the assessment of the hydraulic erodibility of rock.
文摘The objective of this work is to analyze the fatigue reliability of complex welded structures composed of multiple web-frame joints, accounting for correlation effects. A three-dimensional finite element model using the 20-node solid elements is generated. A linear elastic finite element analysis was performed, hotspot stresses in a web-frame joint were analyzed and fatigue damage was quantified employing the S-N approach. The statistical descriptors of the fatigue life of a non-correlated web-frame joint containing several critical hotspots were estimated. The fatigue reliability of a web-frame joint wasmodeled as a series system of correlated components using the Ditlevsen bounds. The fatigue reliability of the entire welded structure with multiple web-frame joints, modeled as a parallel system of non-correlated web-frame joints was also calculated.
基金the Major Program of National Natural Science Foundation of China(No.41941019)Shaanxi Province Innovative Talent Promotion Plan-Science and Technology Innovation Team(No.2021TD-55)Central University Natural Science Innovation Team(No.300102262402)。
文摘Combined bodies of rock-like material and rock are widely encountered in geotechnical engineering,such as tunnels and mines.The existing theoretical models describing the stress-strain relationship of a combined body lack a binary feature.Based on effective medium theory,this paper presents the governing equation of the“elastic modulus”for combined and single bodies under triaxial compressive tests.A binary effective medium model is then established.Based on the compressive experiment of concretegranite combined bodies,the feasibility of determining the stress threshold based on crack axial strain is discussed,and the model is verified.The model is further extended to coal-rock combined bodies of more diverse types,and the variation laws of the compressive mechanical parameters are then discussed.The results show that the fitting accuracy of the model with the experimental curves of the concretegranite combined bodies and various types of coal-rock combined bodies are over 95%.The crack axial strain method can replace the crack volumetric strain method,which clarifies the physical meanings of the model parameters.The variation laws of matrix parameters and crack parameters are discussed in depth and are expected to be more widely used in geotechnical engineering.
基金The research work was financially supported by the National Natural Scientice Foundation of China(Grant No.10142001)by the Shandong Provincial Natural Scientice Foundation(Grant No.Y2006F46)
文摘In engineering practice, tubular X-joints have been widely used in offshore structures. The fatigue failure of tubular X-joints in offshore engineering is mainly caused by axial tensile stress. In this study, the stress concentration factor distribution along the weld toe in the hot spot stress region for tubular X-joints subject to axial loads have been analyzed by use of finite element method. Through numerical analysis, it has been found that the peak stress concentration factor is located at the saddle position. Thereafter, 80 models have been analyzed, and the effect of the geometric parameters of a tubular X-joint on the stress concentration factor has been investigated. Based on the experimental values of the numerical stress concentration factor, a parametric equation to calculate the stress concentration factor of tubular X-joints has been proposed. The accuracy of this equation has been verified against the requirement of the Fatigue Guidance Review Panel, and the proposed equation is found capable of producing reasonably accurate stress concentration factor values for tubular X-joints subject to axial loads.
基金supported by the China National Funds for Distinguished Young Scientists(10925211)the National Natural Science Foundation of China(50878174)
文摘Very high cycle fatigue(VHCF) behaviors of bridge steel(Q345) welded joints were investigated using an ultrasonic fatigue test system at room temperature with a stress ratio R = -1. The results show that the fatigue strength of welded joints is dropped by an average of 60% comparing to the base metal and the fatigue failure still occurred beyond 10~7 cycles.The fatigue fracture of welded joints in the low cycle regime generally occurred at the solder while at the heat-affected zone(HAZ) in the very high cycle regime.The fatigue fracture surface was analyzed with scanning electron microscopy(SEM),showing welding defects such as pore,micro-crack and inclusion were the main factors on decreasing the fatigue properties of welded joints.The effect of welding defects on the fatigue behaviors of welded joints was discussed in terms of experimental results and finite element simulations.
文摘AFast quenching NdFeB permanent magnet—a high-tech product filling in the domestic gaps—has been put into mass production by the Beijing Century New Magnetics Co. Ltd. Previously, only the United States of America had patent rights for production and sale of fast quenching NdFeB Magnets, and only General Motor Company could produce such high-tech products.