The conventional forming limit diagram （FLD） is described as a plot of major strain versus minor strain. However, FLD is dependent on forming history and strain path. In the present study, a forming limit stress-bas...The conventional forming limit diagram （FLD） is described as a plot of major strain versus minor strain. However, FLD is dependent on forming history and strain path. In the present study, a forming limit stress-based diagram （FLSD） has been adopted to predict the fracture limit of aluminum alloy （AA） 5052-O1 sheet. Nakazima test is simulated by plastic constitutive formula derived from the modified Gurson-Tvergaard-Needleman （GTN） model. An in situ tensile test with scanning electron microscope （SEM） is proposed to determine the parameters in GTN model. The damage evolution is observed and recorded, and the parameters of GTN model are identified through counting void fraction at three damage stages of AA5052-O 1. According to the experimental results, the original void volume fraction, the volume fraction of potential nucleated voids, the critical void volume fraction, the void volume fraction at the final failure of material are assigned as 0.002 918, 0.024 9, 0.030 103, 0.048 54, respectively. The stress and strain are obtained at the last loading step before crack. FLSD and FLD of AA5052-O 1 are plotted. Compared with the experimental Nakazima test and uniaxial tensile test, the predicted results show a good agreement. The parameters determined by in situ tensile test can be applied to the research of the forming limit for ductile metals.展开更多
In this work, a set of GTN （Gurson-Tvergaard-Needleman） parameters of the Alloy52M dissimilar metal welded joint （DMWJ） have been calibrated, and a micromechanical analysis of in-plane constraint effects on the lo...In this work, a set of GTN （Gurson-Tvergaard-Needleman） parameters of the Alloy52M dissimilar metal welded joint （DMWJ） have been calibrated, and a micromechanical analysis of in-plane constraint effects on the local fracture behavior of two cracks, which located in the weakest regions of the DMWJ, has been investigated by the local approach based on the GTN damage model. The results show that the partition of the material and the variation of the q2 parameter make the J-resistance curves obtained by numerical simulations close to the experimental values. The numerical J-resistance curves and crack growth paths are consistent with the experiment results, which show that the GTN damage model can incorporate the in-plane constraint effect. Furthermore, after the stress, strain and damage fields at the crack tip during the crack propagation process have been calculated, and the change of the J-resistance curves, crack growth paths and fracture mechanism with in-plane constraint have been analyzed.展开更多
The influence of the MnS plastic inclusion on the accumulation of internal damage was considered, and the Gurson– Tvergaard–Needleman (GTN) model was calibrated based on the finite element inverse method and image a...The influence of the MnS plastic inclusion on the accumulation of internal damage was considered, and the Gurson– Tvergaard–Needleman (GTN) model was calibrated based on the finite element inverse method and image analysis method using ABAQUS and GTN models. The modified GTN damage model was used to simulate the initiation and propagation of cracks in an as-cast 304 stainless steel with MnS inclusions at 900 C. The simulation results agreed well with the experimental results, indicating that the model can be effectively applied to examine the high-temperature fracture behavior of MnS inclusions. The simulation and high-temperature tensile test results revealed that MnS inclusions increased the number of holes initiation and the probability of hole polymerization, reduced the crack propagation resistance, accelerated the occurrence of material fracture behavior, and were closely related to the stress state at high temperatures. When the stress triaxiality was low, the plastic strain in the metal matrix was high, and the MnS plastic inclusions accelerated the polymerization of the pores, making metal fracture failure more likely. On the other hand, when the stress triaxiality was high, the stress state in the metal matrix was biased to the tensile state, the plastic strain in the metal matrix was low, and the influence of MnS plastic inclusions on the fracture behavior was not evident.展开更多
A plate of dual phase steel was produced from low carbon steel with intercritical annealing treatment. Its optically determined surface microstructure was utilized to construct three different microstructural models. ...A plate of dual phase steel was produced from low carbon steel with intercritical annealing treatment. Its optically determined surface microstructure was utilized to construct three different microstructural models. To describe the ductile damage in the ferritic matrix, the Gurson-Tvergaard-Needleman model was used with the failure in the martensite phase being ignored. The numerical results obtained for the mechanism of void initiation and coalescence were compared with the experimental observations. The numerical results obtained from the randomly extruded 3D model showed a significantly better agreement with the experimental ones than those obtained from the 2D model or the uniformly extruded 3D model.展开更多
Worldwide, the leading cause of death is ischemic heart disease. Other than medical and surgical management, alternative therapy such as relaxing music has been identified as having an impact on reducing morbidity in ...Worldwide, the leading cause of death is ischemic heart disease. Other than medical and surgical management, alternative therapy such as relaxing music has been identified as having an impact on reducing morbidity in ischemic heart disease. Although several studies have been conducted to find out the impact of music on pain, anxiety, heart rate and stress in myocardial ischaemia, literature on the long term impact of music on severity of symptoms associated with stable angina is very sparse. Therefore, the whole purpose of this study was to determine the long term effects of Indian music on severity of symptoms in patients with stable angina. Methodology: A single blind randomized clinical trial was conducted on 60 patients of 45 to 65 years of age with stable angina. Intervention group (n = 30) listened to a music based on Indian classical system at home twice a day complementary to their regular treatment for a period of one month. Control group (n = 30) was only on their usual treatment. Both groups were assessed prior and one month after the study period for severity of symptoms based on Canadian classification of angina guidelines and their treatment. Results: Severities of symptoms (timing of the chest pain, chest pain during walking and climbing a staircase, the effect of chest pain in day to day physical activities, frequency and the number of GTN used per week and frequency of consultation a doctor for chest pain) were significantly improved in the study group (p < 0.05, p < 0.01) after intervention. However, the control group did not show any significant changes (p > 0.05). Conclusion: Systematically, regular listening of music based on Indian classical system significantly improves the severity of the stable angina symptoms. Hence music has a potential benefit in considering for use as complementary to angina treatment in reducing morbidity.展开更多
<strong>Objectives</strong>:<span> This retrospective study evaluated 1) benefits of single nucleotide polymorphism (SNP)-based chromosomal microarrays (CMAs) in the diagnosis of complete hydatidifor...<strong>Objectives</strong>:<span> This retrospective study evaluated 1) benefits of single nucleotide polymorphism (SNP)-based chromosomal microarrays (CMAs) in the diagnosis of complete hydatidiform mole (CHM) and partial HM (PHM) in products of conception (POC) and amniotic fluid (AF) specimens, and 2) frequency of whole-genome uniparental disomy (wgUPD) and triploidy in POC and AF specimens received at a US national reference laboratory.</span><span "=""> </span><b><span>Methods:</span></b><span> We reviewed consecutive 2138 POC and 3230 AF specimens and identified the cases with wgUPD and triploidy which are associated with molar pregnancy.</span><span "=""> </span><b><span>Results:</span></b><span "=""><span> Of 2138 consecutive POC specimens tested, SNP-based CMA detected wgUPD in 10 (0.47%) and triploidy in 84 (3.93%). Of the 10 wgUPD cases, 9 (90%) were confirmed as CHM. Of 3230 consecutive AF specimens, the array detected wgUPD in 1 case (0.03%) and triploidy in 11 (0.34%). </span><b><span>Conclusions:</span></b><span> SNP-based microarray allows detection of wgUPD in POC and AF specimens at a US national reference laboratory. Correctly diagnosing HM and differentiating CHM from PHM </span></span><span>are</span><span> important for clinical management. The effective SNP-based CMA detection of wgUPD in CHM may enable physicians to monitor patients at risk for gestational trophoblastic disease and neoplasm.</span><span "=""> </span><span "=""><span>Conventional chromosome analysis of POC has a high </span><span>failure rate, cannot be performed on formalin-fixed paraffin embedded samples, and cannot detect wgUPD. Further</span></span><span "=""> </span><span>multi-institutional collaborative assessmen</span><span> on accuracy, cost-effectiveness, and adequate access to SNP-based CMA, may lead this testing platform to be considered as the first-tier analysis tool for POC specimens, including those showing PHM or CHM.展开更多
基金Aeronautical Science Foundation of China （03H53048）
文摘The conventional forming limit diagram （FLD） is described as a plot of major strain versus minor strain. However, FLD is dependent on forming history and strain path. In the present study, a forming limit stress-based diagram （FLSD） has been adopted to predict the fracture limit of aluminum alloy （AA） 5052-O1 sheet. Nakazima test is simulated by plastic constitutive formula derived from the modified Gurson-Tvergaard-Needleman （GTN） model. An in situ tensile test with scanning electron microscope （SEM） is proposed to determine the parameters in GTN model. The damage evolution is observed and recorded, and the parameters of GTN model are identified through counting void fraction at three damage stages of AA5052-O 1. According to the experimental results, the original void volume fraction, the volume fraction of potential nucleated voids, the critical void volume fraction, the void volume fraction at the final failure of material are assigned as 0.002 918, 0.024 9, 0.030 103, 0.048 54, respectively. The stress and strain are obtained at the last loading step before crack. FLSD and FLD of AA5052-O 1 are plotted. Compared with the experimental Nakazima test and uniaxial tensile test, the predicted results show a good agreement. The parameters determined by in situ tensile test can be applied to the research of the forming limit for ductile metals.
基金supported by the National Natural Science Foundation of China(Grant No.51605292)the Natural Science Foundation of Shanghai(Grant No.15ZR1429000)the Youth Foundation of Shanghai(Grant No.ZZslg15013)
文摘In this work, a set of GTN （Gurson-Tvergaard-Needleman） parameters of the Alloy52M dissimilar metal welded joint （DMWJ） have been calibrated, and a micromechanical analysis of in-plane constraint effects on the local fracture behavior of two cracks, which located in the weakest regions of the DMWJ, has been investigated by the local approach based on the GTN damage model. The results show that the partition of the material and the variation of the q2 parameter make the J-resistance curves obtained by numerical simulations close to the experimental values. The numerical J-resistance curves and crack growth paths are consistent with the experiment results, which show that the GTN damage model can incorporate the in-plane constraint effect. Furthermore, after the stress, strain and damage fields at the crack tip during the crack propagation process have been calculated, and the change of the J-resistance curves, crack growth paths and fracture mechanism with in-plane constraint have been analyzed.
基金This research was supported by the National Natural Science Foundation of China (Grant Nos. 51575475 and 51675465).
文摘The influence of the MnS plastic inclusion on the accumulation of internal damage was considered, and the Gurson– Tvergaard–Needleman (GTN) model was calibrated based on the finite element inverse method and image analysis method using ABAQUS and GTN models. The modified GTN damage model was used to simulate the initiation and propagation of cracks in an as-cast 304 stainless steel with MnS inclusions at 900 C. The simulation results agreed well with the experimental results, indicating that the model can be effectively applied to examine the high-temperature fracture behavior of MnS inclusions. The simulation and high-temperature tensile test results revealed that MnS inclusions increased the number of holes initiation and the probability of hole polymerization, reduced the crack propagation resistance, accelerated the occurrence of material fracture behavior, and were closely related to the stress state at high temperatures. When the stress triaxiality was low, the plastic strain in the metal matrix was high, and the MnS plastic inclusions accelerated the polymerization of the pores, making metal fracture failure more likely. On the other hand, when the stress triaxiality was high, the stress state in the metal matrix was biased to the tensile state, the plastic strain in the metal matrix was low, and the influence of MnS plastic inclusions on the fracture behavior was not evident.
文摘A plate of dual phase steel was produced from low carbon steel with intercritical annealing treatment. Its optically determined surface microstructure was utilized to construct three different microstructural models. To describe the ductile damage in the ferritic matrix, the Gurson-Tvergaard-Needleman model was used with the failure in the martensite phase being ignored. The numerical results obtained for the mechanism of void initiation and coalescence were compared with the experimental observations. The numerical results obtained from the randomly extruded 3D model showed a significantly better agreement with the experimental ones than those obtained from the 2D model or the uniformly extruded 3D model.
文摘Worldwide, the leading cause of death is ischemic heart disease. Other than medical and surgical management, alternative therapy such as relaxing music has been identified as having an impact on reducing morbidity in ischemic heart disease. Although several studies have been conducted to find out the impact of music on pain, anxiety, heart rate and stress in myocardial ischaemia, literature on the long term impact of music on severity of symptoms associated with stable angina is very sparse. Therefore, the whole purpose of this study was to determine the long term effects of Indian music on severity of symptoms in patients with stable angina. Methodology: A single blind randomized clinical trial was conducted on 60 patients of 45 to 65 years of age with stable angina. Intervention group (n = 30) listened to a music based on Indian classical system at home twice a day complementary to their regular treatment for a period of one month. Control group (n = 30) was only on their usual treatment. Both groups were assessed prior and one month after the study period for severity of symptoms based on Canadian classification of angina guidelines and their treatment. Results: Severities of symptoms (timing of the chest pain, chest pain during walking and climbing a staircase, the effect of chest pain in day to day physical activities, frequency and the number of GTN used per week and frequency of consultation a doctor for chest pain) were significantly improved in the study group (p < 0.05, p < 0.01) after intervention. However, the control group did not show any significant changes (p > 0.05). Conclusion: Systematically, regular listening of music based on Indian classical system significantly improves the severity of the stable angina symptoms. Hence music has a potential benefit in considering for use as complementary to angina treatment in reducing morbidity.
文摘<strong>Objectives</strong>:<span> This retrospective study evaluated 1) benefits of single nucleotide polymorphism (SNP)-based chromosomal microarrays (CMAs) in the diagnosis of complete hydatidiform mole (CHM) and partial HM (PHM) in products of conception (POC) and amniotic fluid (AF) specimens, and 2) frequency of whole-genome uniparental disomy (wgUPD) and triploidy in POC and AF specimens received at a US national reference laboratory.</span><span "=""> </span><b><span>Methods:</span></b><span> We reviewed consecutive 2138 POC and 3230 AF specimens and identified the cases with wgUPD and triploidy which are associated with molar pregnancy.</span><span "=""> </span><b><span>Results:</span></b><span "=""><span> Of 2138 consecutive POC specimens tested, SNP-based CMA detected wgUPD in 10 (0.47%) and triploidy in 84 (3.93%). Of the 10 wgUPD cases, 9 (90%) were confirmed as CHM. Of 3230 consecutive AF specimens, the array detected wgUPD in 1 case (0.03%) and triploidy in 11 (0.34%). </span><b><span>Conclusions:</span></b><span> SNP-based microarray allows detection of wgUPD in POC and AF specimens at a US national reference laboratory. Correctly diagnosing HM and differentiating CHM from PHM </span></span><span>are</span><span> important for clinical management. The effective SNP-based CMA detection of wgUPD in CHM may enable physicians to monitor patients at risk for gestational trophoblastic disease and neoplasm.</span><span "=""> </span><span "=""><span>Conventional chromosome analysis of POC has a high </span><span>failure rate, cannot be performed on formalin-fixed paraffin embedded samples, and cannot detect wgUPD. Further</span></span><span "=""> </span><span>multi-institutional collaborative assessmen</span><span> on accuracy, cost-effectiveness, and adequate access to SNP-based CMA, may lead this testing platform to be considered as the first-tier analysis tool for POC specimens, including those showing PHM or CHM.
