BACKGROUND Subchondral fatigue fracture of the femoral head(SFFFH)mainly occurs in young military recruits and might be confused with osteonecrosis of the femoral head.However,less research focuses on the risk factor ...BACKGROUND Subchondral fatigue fracture of the femoral head(SFFFH)mainly occurs in young military recruits and might be confused with osteonecrosis of the femoral head.However,less research focuses on the risk factor for SFFFH.AIM To evaluate the intrinsic risk factors for SFFFH in young military recruits.METHODS X-ray and magnetic resonance imaging data were used for analysis.Acetabular anteversion of the superior acetabulum,acetabular anteversion of the center of the acetabulum(AVcen),anterior acetabular sector angle(AASA),posterior acetabular sector angle,superior acetabular sector angle,neck-shaft angle(NSA),inferior iliac angle(IIA),and ischiopubic angle were calculated.Then,logistic regression,receiver operating characteristic curve analysis,and independent samples t-test were performed to identify the risk factors for SFFFH.RESULTS Based on the results of logistic regression,age[odds ratio(OR):1.33;95%confidence interval(95%CI):1.12-1.65;P=0.0031]and treatment timing(OR:0.86;95%CI:0.75-0.96;P=0.015)could be considered as the indicators for SFFFH.AVcen(P=0.0334),AASA(P=0.0002),NSA(P=0.0007),and IIA(P=0.0316)were considered to have statistical significance.Further,AVcen(OR:1.41;95%CI:1.04-1.95)and AASA(OR:1.44;95%CI:1.21-1.77),especially AASA(area under curve:66.6%),should be paid much more attention due to the higher OR than other indicators.CONCLUSION We have for the first time unveiled that AASA and age could be key risk factors for SFFFH,which further verifies that deficient anterior coverage of the acetabulum might be the main cause of SFFFH.展开更多
The fatigue crack behavior of U75V rail under different quenching rates was studied using SEM and CLSM.The results show that the pearlite interlayer spacing and fatigue crack growth rate decrease,and the deflection pa...The fatigue crack behavior of U75V rail under different quenching rates was studied using SEM and CLSM.The results show that the pearlite interlayer spacing and fatigue crack growth rate decrease,and the deflection path of cracks and the number of branching cracks of U75V rail increases with an increase of cooling rate.The tearing edge of unstable region transites from pearlite lamellae to dimple.The fatigue crack growth path is closely related to the orientation of lamellae in pearlite microstructure.There are three modes direction of fatigue crack growth path and pearlite lamellar,which are parallel,vertical and 45°angle,and most of the branch cracks occur at an angle of 45°between the lamellar direction and the crack direction.More specifically,the deflection paths of cracks and branching crack have a relaxation effect on the stress intensity at the crack tip,which restrains the fatigue crack growth rate.展开更多
BACKGROUND Stress fractures of the femoral neck are not common in clinical practice,and simultaneous stress fractures of the femoral neck and proximal femur of the unilateral femur are even more rare.We introduce a ca...BACKGROUND Stress fractures of the femoral neck are not common in clinical practice,and simultaneous stress fractures of the femoral neck and proximal femur of the unilateral femur are even more rare.We introduce a case of this type of fracture that was treated in our department,analyze the causes,and review similar stress fractures reported in the literature to provide references for the diagnosis and treatment of such conditions.CASE SUMMARY A 62-year-old female,with a free medical history,was admitted to the hospital mainly due to pain in the right hip and worsening pain in the right thigh.The patient had no obvious history of trauma.X-ray and computed tomography showed fracture of the femoral neck and proximal femur.The patient had undergone surgery 1 year prior to address a fracture of the left proximal femur that had occurred in a traffic accident.Our first consideration was stress fracture of the femoral neck;however,simultaneous stress fractures of the femoral neck and proximal femur of the unilateral femur were seen.The femoral neck stress fracture was a tension fracture,with obvious displacement and varus deformity of the hip.Considering that the patient was an elderly female,we performed total hip arthroplasty.Follow-up X-rays showed that the stress fracture of the proximal femur had mostly healed after 3 mo.CONCLUSION Muscle fatigue and hip varus deformity provide an anatomical basis for the occurrence of femoral neck stress fractures.展开更多
In the present study, an aero pneumatic fatigue testing machine for complete dentures was designed, fabricated, and tested for the evaluation of the fatigue life of reinforced complete upper denture (CUD). On completi...In the present study, an aero pneumatic fatigue testing machine for complete dentures was designed, fabricated, and tested for the evaluation of the fatigue life of reinforced complete upper denture (CUD). On completion and testing, it was observed that the machine has the potential of generating reliable number of cyclic data. The machine’s performance was evaluated using test specimens of identical CUDs that were machined in conformity with standard procedures. The fatigue machine compressed the lower dental arch over the upper denture-specimen in centric occlusion, in the same way that the two masticatory muscles pull the lower jaw over the upper jaw during chewing. The incorporation of glass fibres into the CUD using a sandwich technique quadruples the lifespan of the denture (<em>P</em> = 0.004). The low standard deviation, along with the low coefficient of variation (CV) of the group of unreinforced dentures shows the repeatability of the results and the reliability of the machine. The high standard deviation and coefficient of variation of reinforced dentures was expected, since a high variation of results is usually recorded in fibre reinforcement cases. This research confirmed the view that the crack during denture fracture initiates in the anterior palatal area and propagates to the posterior.展开更多
For the first time,an allowable defect analysis of the bowl body of XZZ 1200-G Centrifuge was made by using fatigue fracture mechanics method;and,again for the first time,the design fatigue curve of the dangerous sect...For the first time,an allowable defect analysis of the bowl body of XZZ 1200-G Centrifuge was made by using fatigue fracture mechanics method;and,again for the first time,the design fatigue curve of the dangerous section of the bowl body was given out、which may form the basis for the design and use of the centrifuge.展开更多
Guillotine machines are used to cut bulk quantities of paper,often thousands at a time.More the number of papers to be cut at once,more load is required to cut.This machine undergoes a frequent failure of one of its h...Guillotine machines are used to cut bulk quantities of paper,often thousands at a time.More the number of papers to be cut at once,more load is required to cut.This machine undergoes a frequent failure of one of its hinges,which prevents the operation of the machine.A combination of torsional forces and bending mo-ments are acting on the hinge when operating.Torsional stresses induced due to the friction between the con-tacting surfaces of the crank rod and the hinge.The bending moment induced due to the alternating motion and the load acted upon the cutting mechanism.The crank transforms the rotational movement into a translational motion of the blade,which results in the formation of a cyclic load in the form of a sinusoidal with a mean value not equal to zero.This leads to fail the hinge in the mode of fatigue.Naked eye observations of the fracture surface reviled a clear failure initiation point and striation marks of crack propagation and a sudden fracture re-gion which evident a fatigue failure due to cyclic loading.To redesign the failed hinged to avoid such failure,it is essential to,(i)define and evaluate the stresses developed by the combined loading condition(ii)understand the nature of the cyclic stress induced.The force acting on the hinge was calculated by the law of conservation of momentum created by the blades'inertia and its'supportive structure.It was understood that the mean stress value of the cyclic load is not equal to zero,the modified Goodman diagram is used.Computational simulations are conducted using Finite Element Analysis(FEA)on the ANSYS fatigue tool.By applying the fatigue analysis theories and conducting FEA for stress analysis,the reason for the failure is revealed and then necessary pre-cautions could be taken to prevent such failures in the future.展开更多
The realization of an ideal combination of mechanical and fatigue properties is prerequisites for practical application of titanium(Ti)microalloyed steel in automotive field.The fatigue behavior of four Ti microalloye...The realization of an ideal combination of mechanical and fatigue properties is prerequisites for practical application of titanium(Ti)microalloyed steel in automotive field.The fatigue behavior of four Ti microalloyed high-strength beam steels with different Ti contents was systematically studied.The results show that the content of microalloying element Ti has a significant effect on the fatigue properties,especially in the steel with a high Ti content.For the experimental Ti microalloyed steel,inclusion-induced crack initiation is the main fatigue failure mode.Different from general fatigue fracture mechanism in Ti-contained steel,no TiN,which is the most detrimental to fatigue behavior,was found in fatigue crack initiation area.However,the large-sized TiN and oxide complex inclusion with a core-shell structure is the dominant cause of fatigue fracture.Because of the intense-localized deformation at the interface between complex inclusion and matrix,the angular TiN in the outer shell has a serious deteriorating effect on the fatigue properties,which is consistent with the result of the Kernel average misorientation map.Besides,the modification effect of a small amount of MnS on large-sized inclusion is not obvious and has little effect on the fatigue behavior.For more practical guidance,the critical inclusion sizes of the experimental steels were also investigated by experimental extrapolation method.With the increasing tensile strength,the inclusion sensitivity of the experimental steels increases,leading to the small critical inclusion size.展开更多
The microstructure of 2624-T39 aluminum alloy was analyzed by means of metallographic(OM), scanning electron microscope(SEM) and transmission electron microscope(TEM). The effects of different microstructure character...The microstructure of 2624-T39 aluminum alloy was analyzed by means of metallographic(OM), scanning electron microscope(SEM) and transmission electron microscope(TEM). The effects of different microstructure characteristics on the tensile properties and fatigue crack growth rate of 2624-T39 aluminum alloy were studied.Results showed that the grain size of the alloy was a typical fiber structure along the rolling direction, and the main second phase was the A_(l2)CuMg phase. The grain size of the alloy had an obvious influence on the fatigue crack growth rate, and the alloy showed a lower fatigue crack growth rate due to the larger grain size. The crack initiation zone on the fracture surface of alloys with lower fatigue crack growth rate was relatively rough, the crack propagation zone had obvious fatigue striations, and the transient fracture zone had a large number of smaller dimples.展开更多
文摘BACKGROUND Subchondral fatigue fracture of the femoral head(SFFFH)mainly occurs in young military recruits and might be confused with osteonecrosis of the femoral head.However,less research focuses on the risk factor for SFFFH.AIM To evaluate the intrinsic risk factors for SFFFH in young military recruits.METHODS X-ray and magnetic resonance imaging data were used for analysis.Acetabular anteversion of the superior acetabulum,acetabular anteversion of the center of the acetabulum(AVcen),anterior acetabular sector angle(AASA),posterior acetabular sector angle,superior acetabular sector angle,neck-shaft angle(NSA),inferior iliac angle(IIA),and ischiopubic angle were calculated.Then,logistic regression,receiver operating characteristic curve analysis,and independent samples t-test were performed to identify the risk factors for SFFFH.RESULTS Based on the results of logistic regression,age[odds ratio(OR):1.33;95%confidence interval(95%CI):1.12-1.65;P=0.0031]and treatment timing(OR:0.86;95%CI:0.75-0.96;P=0.015)could be considered as the indicators for SFFFH.AVcen(P=0.0334),AASA(P=0.0002),NSA(P=0.0007),and IIA(P=0.0316)were considered to have statistical significance.Further,AVcen(OR:1.41;95%CI:1.04-1.95)and AASA(OR:1.44;95%CI:1.21-1.77),especially AASA(area under curve:66.6%),should be paid much more attention due to the higher OR than other indicators.CONCLUSION We have for the first time unveiled that AASA and age could be key risk factors for SFFFH,which further verifies that deficient anterior coverage of the acetabulum might be the main cause of SFFFH.
基金Inner Mongolia Science and Technology Major Project(No.ZDZX2018024)Natural Science Foundation of Inner Mongolia(No.2019LH05016)+1 种基金Research Program of Science at Universities of Inner Mongolia Autonomous Region of China(No.NJZY20089)Innovation Fund of Inner Mongolia University of Science and Technology(No.2019QDL-B06)。
文摘The fatigue crack behavior of U75V rail under different quenching rates was studied using SEM and CLSM.The results show that the pearlite interlayer spacing and fatigue crack growth rate decrease,and the deflection path of cracks and the number of branching cracks of U75V rail increases with an increase of cooling rate.The tearing edge of unstable region transites from pearlite lamellae to dimple.The fatigue crack growth path is closely related to the orientation of lamellae in pearlite microstructure.There are three modes direction of fatigue crack growth path and pearlite lamellar,which are parallel,vertical and 45°angle,and most of the branch cracks occur at an angle of 45°between the lamellar direction and the crack direction.More specifically,the deflection paths of cracks and branching crack have a relaxation effect on the stress intensity at the crack tip,which restrains the fatigue crack growth rate.
基金Supported by Suzhou Gusu Health Talent Program Training Program,No.GSWS2020121。
文摘BACKGROUND Stress fractures of the femoral neck are not common in clinical practice,and simultaneous stress fractures of the femoral neck and proximal femur of the unilateral femur are even more rare.We introduce a case of this type of fracture that was treated in our department,analyze the causes,and review similar stress fractures reported in the literature to provide references for the diagnosis and treatment of such conditions.CASE SUMMARY A 62-year-old female,with a free medical history,was admitted to the hospital mainly due to pain in the right hip and worsening pain in the right thigh.The patient had no obvious history of trauma.X-ray and computed tomography showed fracture of the femoral neck and proximal femur.The patient had undergone surgery 1 year prior to address a fracture of the left proximal femur that had occurred in a traffic accident.Our first consideration was stress fracture of the femoral neck;however,simultaneous stress fractures of the femoral neck and proximal femur of the unilateral femur were seen.The femoral neck stress fracture was a tension fracture,with obvious displacement and varus deformity of the hip.Considering that the patient was an elderly female,we performed total hip arthroplasty.Follow-up X-rays showed that the stress fracture of the proximal femur had mostly healed after 3 mo.CONCLUSION Muscle fatigue and hip varus deformity provide an anatomical basis for the occurrence of femoral neck stress fractures.
文摘In the present study, an aero pneumatic fatigue testing machine for complete dentures was designed, fabricated, and tested for the evaluation of the fatigue life of reinforced complete upper denture (CUD). On completion and testing, it was observed that the machine has the potential of generating reliable number of cyclic data. The machine’s performance was evaluated using test specimens of identical CUDs that were machined in conformity with standard procedures. The fatigue machine compressed the lower dental arch over the upper denture-specimen in centric occlusion, in the same way that the two masticatory muscles pull the lower jaw over the upper jaw during chewing. The incorporation of glass fibres into the CUD using a sandwich technique quadruples the lifespan of the denture (<em>P</em> = 0.004). The low standard deviation, along with the low coefficient of variation (CV) of the group of unreinforced dentures shows the repeatability of the results and the reliability of the machine. The high standard deviation and coefficient of variation of reinforced dentures was expected, since a high variation of results is usually recorded in fibre reinforcement cases. This research confirmed the view that the crack during denture fracture initiates in the anterior palatal area and propagates to the posterior.
文摘For the first time,an allowable defect analysis of the bowl body of XZZ 1200-G Centrifuge was made by using fatigue fracture mechanics method;and,again for the first time,the design fatigue curve of the dangerous section of the bowl body was given out、which may form the basis for the design and use of the centrifuge.
文摘Guillotine machines are used to cut bulk quantities of paper,often thousands at a time.More the number of papers to be cut at once,more load is required to cut.This machine undergoes a frequent failure of one of its hinges,which prevents the operation of the machine.A combination of torsional forces and bending mo-ments are acting on the hinge when operating.Torsional stresses induced due to the friction between the con-tacting surfaces of the crank rod and the hinge.The bending moment induced due to the alternating motion and the load acted upon the cutting mechanism.The crank transforms the rotational movement into a translational motion of the blade,which results in the formation of a cyclic load in the form of a sinusoidal with a mean value not equal to zero.This leads to fail the hinge in the mode of fatigue.Naked eye observations of the fracture surface reviled a clear failure initiation point and striation marks of crack propagation and a sudden fracture re-gion which evident a fatigue failure due to cyclic loading.To redesign the failed hinged to avoid such failure,it is essential to,(i)define and evaluate the stresses developed by the combined loading condition(ii)understand the nature of the cyclic stress induced.The force acting on the hinge was calculated by the law of conservation of momentum created by the blades'inertia and its'supportive structure.It was understood that the mean stress value of the cyclic load is not equal to zero,the modified Goodman diagram is used.Computational simulations are conducted using Finite Element Analysis(FEA)on the ANSYS fatigue tool.By applying the fatigue analysis theories and conducting FEA for stress analysis,the reason for the failure is revealed and then necessary pre-cautions could be taken to prevent such failures in the future.
基金supported by the National Natural Science Foundation of China(No.52104369)the China Postdoctoral Science Foundation(No.2021M700374).
文摘The realization of an ideal combination of mechanical and fatigue properties is prerequisites for practical application of titanium(Ti)microalloyed steel in automotive field.The fatigue behavior of four Ti microalloyed high-strength beam steels with different Ti contents was systematically studied.The results show that the content of microalloying element Ti has a significant effect on the fatigue properties,especially in the steel with a high Ti content.For the experimental Ti microalloyed steel,inclusion-induced crack initiation is the main fatigue failure mode.Different from general fatigue fracture mechanism in Ti-contained steel,no TiN,which is the most detrimental to fatigue behavior,was found in fatigue crack initiation area.However,the large-sized TiN and oxide complex inclusion with a core-shell structure is the dominant cause of fatigue fracture.Because of the intense-localized deformation at the interface between complex inclusion and matrix,the angular TiN in the outer shell has a serious deteriorating effect on the fatigue properties,which is consistent with the result of the Kernel average misorientation map.Besides,the modification effect of a small amount of MnS on large-sized inclusion is not obvious and has little effect on the fatigue behavior.For more practical guidance,the critical inclusion sizes of the experimental steels were also investigated by experimental extrapolation method.With the increasing tensile strength,the inclusion sensitivity of the experimental steels increases,leading to the small critical inclusion size.
基金financially supported by the National Key R&D Program of China(No.2016YFB0300800)。
文摘The microstructure of 2624-T39 aluminum alloy was analyzed by means of metallographic(OM), scanning electron microscope(SEM) and transmission electron microscope(TEM). The effects of different microstructure characteristics on the tensile properties and fatigue crack growth rate of 2624-T39 aluminum alloy were studied.Results showed that the grain size of the alloy was a typical fiber structure along the rolling direction, and the main second phase was the A_(l2)CuMg phase. The grain size of the alloy had an obvious influence on the fatigue crack growth rate, and the alloy showed a lower fatigue crack growth rate due to the larger grain size. The crack initiation zone on the fracture surface of alloys with lower fatigue crack growth rate was relatively rough, the crack propagation zone had obvious fatigue striations, and the transient fracture zone had a large number of smaller dimples.
