This paper studies optimal shape design of pressure vessel head subject to internal uniform pressure.The optimization aims at minimizing its maximum stress while the volume of the vessel head remains no less than the ...This paper studies optimal shape design of pressure vessel head subject to internal uniform pressure.The optimization aims at minimizing its maximum stress while the volume of the vessel head remains no less than the standard ellipsoidal head.Super-ellipse curve is selected to describe the middle surface shape of the vessel head because it represents a large family of curves with only two or three parameters and makes the design and manufacture easy.The performance of different elements and element sizes of FEM modeling is carefully studied in view of computational cost,accuracy and noises of von Mises stress.The response surface of the maximum stress vs.shape design parameters is approximated by a Kriging surrogate model with EI criterion for sampling adding,based on the parameter optimization which is carried out to search the optimal shape.Finally,it is shown by numerical comparison that the super-ellipsoidal head is better than the standard ellipsoidal head and the other vessel heads in the literature.展开更多
The head of nuclear pressure vessel is a key component to guarantee the safety of nuclear power plant, so it is necessary to improve its mechanical properties during manufacturing. In the practical production,due to t...The head of nuclear pressure vessel is a key component to guarantee the safety of nuclear power plant, so it is necessary to improve its mechanical properties during manufacturing. In the practical production,due to the huge size of the ingots from which the head is manufactured, coarse grains and voids are common defects existing in the material. Furthermore, cracks may appear in the forming process. It is highly demanded that the forming process must be properly designed with suitable parameters to compact the voids, to refine and homogenize the grains and to avoid cracks. Therefore, the research on the evolution of internal voids, grain size and cracks is very important to determine the forming process of huge components. SA508-3 steel is the material to manufacture the head of pressure vessel in the nuclear island. In the previous studies, we have separately built models to evaluate the evolution of internal voids, grain size and cracks during the hot forming process for SA508-3 steel. This study integrates the models for multi-scale simulation of the forging process of the head of nuclear pressure vessel in order to control the quality of the forgings. Through the software development, the models are integrated with a commercial finite element code DEFORM. Then, the extended forging and final forging processes of the head are investigated, and some appropriate deformation parameters are recommended.展开更多
股骨头缺血性坏死(Avascular necrosis of femoral head,ANFH)是骨科常见疾病,有较高的致残率,迄今尚无较为理想的治疗方法。因此,明确股骨头内动静脉的解剖学特点尤为重要。目前关于股骨头的血管研究,仅见通过MicroCT灌注扫描[1]、超...股骨头缺血性坏死(Avascular necrosis of femoral head,ANFH)是骨科常见疾病,有较高的致残率,迄今尚无较为理想的治疗方法。因此,明确股骨头内动静脉的解剖学特点尤为重要。目前关于股骨头的血管研究,仅见通过MicroCT灌注扫描[1]、超选择性数字减影血管造影[2](DSA)、增强MRI[3]等间接手段显示股骨头内动脉,尚无直接的股骨头内动静脉三维立体构筑显示报道。本研究通过显微灌注环氧树脂联合碱腐蚀酸脱钙法制作猪股骨头内动静脉共显示铸型标本,以期为股骨头内血管研究及ANFH等髋部疾病病因、治疗方式的进一步探索提供参考。展开更多
基金Sponsored by the National Natural Science Foundation of China(Grant No.9121620111128205)+1 种基金the National Program on Key Basic Research Project(Grant No.2011CB610304)the Fundamental Research Funds for the Central Universities(Grant No.DUT 11 ZD(G)04)
文摘This paper studies optimal shape design of pressure vessel head subject to internal uniform pressure.The optimization aims at minimizing its maximum stress while the volume of the vessel head remains no less than the standard ellipsoidal head.Super-ellipse curve is selected to describe the middle surface shape of the vessel head because it represents a large family of curves with only two or three parameters and makes the design and manufacture easy.The performance of different elements and element sizes of FEM modeling is carefully studied in view of computational cost,accuracy and noises of von Mises stress.The response surface of the maximum stress vs.shape design parameters is approximated by a Kriging surrogate model with EI criterion for sampling adding,based on the parameter optimization which is carried out to search the optimal shape.Finally,it is shown by numerical comparison that the super-ellipsoidal head is better than the standard ellipsoidal head and the other vessel heads in the literature.
基金the National Science and Technology Major Project of China(No.2012ZX04012-011)the National Natural Science Foundation of China(No.51675335)
文摘The head of nuclear pressure vessel is a key component to guarantee the safety of nuclear power plant, so it is necessary to improve its mechanical properties during manufacturing. In the practical production,due to the huge size of the ingots from which the head is manufactured, coarse grains and voids are common defects existing in the material. Furthermore, cracks may appear in the forming process. It is highly demanded that the forming process must be properly designed with suitable parameters to compact the voids, to refine and homogenize the grains and to avoid cracks. Therefore, the research on the evolution of internal voids, grain size and cracks is very important to determine the forming process of huge components. SA508-3 steel is the material to manufacture the head of pressure vessel in the nuclear island. In the previous studies, we have separately built models to evaluate the evolution of internal voids, grain size and cracks during the hot forming process for SA508-3 steel. This study integrates the models for multi-scale simulation of the forging process of the head of nuclear pressure vessel in order to control the quality of the forgings. Through the software development, the models are integrated with a commercial finite element code DEFORM. Then, the extended forging and final forging processes of the head are investigated, and some appropriate deformation parameters are recommended.
文摘股骨头缺血性坏死(Avascular necrosis of femoral head,ANFH)是骨科常见疾病,有较高的致残率,迄今尚无较为理想的治疗方法。因此,明确股骨头内动静脉的解剖学特点尤为重要。目前关于股骨头的血管研究,仅见通过MicroCT灌注扫描[1]、超选择性数字减影血管造影[2](DSA)、增强MRI[3]等间接手段显示股骨头内动脉,尚无直接的股骨头内动静脉三维立体构筑显示报道。本研究通过显微灌注环氧树脂联合碱腐蚀酸脱钙法制作猪股骨头内动静脉共显示铸型标本,以期为股骨头内血管研究及ANFH等髋部疾病病因、治疗方式的进一步探索提供参考。
