A series of single track clads of Inconel 625 alloy were fabricated by laser solid forming.To achieve the high dimensional accuracy and excellent mechanical properties,the effect of processing parameters on the geomet...A series of single track clads of Inconel 625 alloy were fabricated by laser solid forming.To achieve the high dimensional accuracy and excellent mechanical properties,the effect of processing parameters on the geometry,the formation of Laves phase and the residual stress was investigated.The results show that laser power and scanning speed had a dramatical influence on the width and height of single-track clads.According to the columnar to equiaxed transition curve of Inconel 625,the grain morphology can be predicted during the LSF process.With the increasing laser power and the decreasing scanning speed,the segregation degree of Si,Nb,Mo,the volume fraction and size of Laves phase increased.Vickers indentation was used to demonstrate that optimizing processing parameter can achieve the minimum residual tensile stress.展开更多
Objective：To model the stress transfer at the interface of the cemented prosthesis and femur, an axisymmetric model of the interfacial stress transfer was established. Methods ： Assuming that the prosthesis, the cem...Objective：To model the stress transfer at the interface of the cemented prosthesis and femur, an axisymmetric model of the interfacial stress transfer was established. Methods ： Assuming that the prosthesis, the cement and the femur were concentric cylinders with linear elastic and isotropic properties, distributions of the axial stresses in the prosthesis, the cement and the femur as well as the interfacial shear stresses at the prosthesis/cement interface and the cement/femur interface in the axial direction were obtained from the established axisymmetric stress transfer model. Results ： Interfacial failure was the main form for the prosthesis/cement/femur structure under external loads. Considering the residual thermal stresses, it was more likely to produce the mixed failure form than the pure shear failure form. Since the cement had a relatively high thermal expansion coefficient, the thermal effect accelerated the interface failure and thus aggravated the stress shielding effect. Due to a relatively high thermal residual temperature difference, the interfacial debonding and femur failure was more likely to occur for the cobalt-chromium alloy prosthesis material than the Ti-6A1-4V alloy prosthesis material. Conclusion： Assuming that the prosthesis, the cement and the femur are concentric cylinders with linear elastic and isotropic properties, distributions of the axial stresses in the prosthesis, the cement and the femur as well as the interfacial shear stresses at the prosthesis/cement interface and the cement/femur interface in the axial direction was obtained using the basic equations of axisymmetric elastic mechanics when the prosthesis bears the compressive stresses. Interface failure is the main failure form for the prosthesis/cement/femur structure under external loads. The thermal effects accelerate the failure of the prosthesis/cement interface and the cement/femur interface and the relaxation of the prosthesis, and then aggravates the stress shielding effect of the femur. Also, the thermal effects decrease the efficiencies of the interfacial stress transfer to some extent since it alleviates the failure of the interface and the femur, which was confirmed by the clinical results.展开更多
The method for measuring the strain of an object using an optical fiber and a frequency modulation(FM) coupled cavity semiconductor laser is proposed.This method uses the coherent FM heterodyne principle of the Michel...The method for measuring the strain of an object using an optical fiber and a frequency modulation(FM) coupled cavity semiconductor laser is proposed.This method uses the coherent FM heterodyne principle of the Michelson interferometer and can avoid the π/2 nonreciprocal phase bias and phase shifting problem existing in general fiber optic interferential sensors, the maximum detection range is limited by the coherent length of the semiconductor laser and its relative factor.展开更多
Bone remodeling is performed under the joint action of osteoblasts and osteoclasts. Since the effect of osteoclasts has been gradually recognized on bone and joint diseases, targeted researches toward osteoclasts have...Bone remodeling is performed under the joint action of osteoblasts and osteoclasts. Since the effect of osteoclasts has been gradually recognized on bone and joint diseases, targeted researches toward osteoclasts have become a hot research field. This article reviews the relevant medical literature concerning the possible effects of the fluid shear stress (FSS) on the osteoclastogenesis chiefly from the aspects of RANKL-RANK-OPG system, the macrophage colony-stimulating factor (M-CSF), and calcitonin receptor (CTR). On the basis of the changes of the expression of osteoclastic activities, it is suggested that FSS is a potent, important regulator of bone metabolism.展开更多
基金Project(2018YFB1105804)supported by the National Key R&D Program of ChinaProject(2020-TS-06)supported by the Research Fund of the State Key Laboratory of Solidification Processing(NPU),China。
文摘A series of single track clads of Inconel 625 alloy were fabricated by laser solid forming.To achieve the high dimensional accuracy and excellent mechanical properties,the effect of processing parameters on the geometry,the formation of Laves phase and the residual stress was investigated.The results show that laser power and scanning speed had a dramatical influence on the width and height of single-track clads.According to the columnar to equiaxed transition curve of Inconel 625,the grain morphology can be predicted during the LSF process.With the increasing laser power and the decreasing scanning speed,the segregation degree of Si,Nb,Mo,the volume fraction and size of Laves phase increased.Vickers indentation was used to demonstrate that optimizing processing parameter can achieve the minimum residual tensile stress.
文摘Objective：To model the stress transfer at the interface of the cemented prosthesis and femur, an axisymmetric model of the interfacial stress transfer was established. Methods ： Assuming that the prosthesis, the cement and the femur were concentric cylinders with linear elastic and isotropic properties, distributions of the axial stresses in the prosthesis, the cement and the femur as well as the interfacial shear stresses at the prosthesis/cement interface and the cement/femur interface in the axial direction were obtained from the established axisymmetric stress transfer model. Results ： Interfacial failure was the main form for the prosthesis/cement/femur structure under external loads. Considering the residual thermal stresses, it was more likely to produce the mixed failure form than the pure shear failure form. Since the cement had a relatively high thermal expansion coefficient, the thermal effect accelerated the interface failure and thus aggravated the stress shielding effect. Due to a relatively high thermal residual temperature difference, the interfacial debonding and femur failure was more likely to occur for the cobalt-chromium alloy prosthesis material than the Ti-6A1-4V alloy prosthesis material. Conclusion： Assuming that the prosthesis, the cement and the femur are concentric cylinders with linear elastic and isotropic properties, distributions of the axial stresses in the prosthesis, the cement and the femur as well as the interfacial shear stresses at the prosthesis/cement interface and the cement/femur interface in the axial direction was obtained using the basic equations of axisymmetric elastic mechanics when the prosthesis bears the compressive stresses. Interface failure is the main failure form for the prosthesis/cement/femur structure under external loads. The thermal effects accelerate the failure of the prosthesis/cement interface and the cement/femur interface and the relaxation of the prosthesis, and then aggravates the stress shielding effect of the femur. Also, the thermal effects decrease the efficiencies of the interfacial stress transfer to some extent since it alleviates the failure of the interface and the femur, which was confirmed by the clinical results.
文摘The method for measuring the strain of an object using an optical fiber and a frequency modulation(FM) coupled cavity semiconductor laser is proposed.This method uses the coherent FM heterodyne principle of the Michelson interferometer and can avoid the π/2 nonreciprocal phase bias and phase shifting problem existing in general fiber optic interferential sensors, the maximum detection range is limited by the coherent length of the semiconductor laser and its relative factor.
文摘Bone remodeling is performed under the joint action of osteoblasts and osteoclasts. Since the effect of osteoclasts has been gradually recognized on bone and joint diseases, targeted researches toward osteoclasts have become a hot research field. This article reviews the relevant medical literature concerning the possible effects of the fluid shear stress (FSS) on the osteoclastogenesis chiefly from the aspects of RANKL-RANK-OPG system, the macrophage colony-stimulating factor (M-CSF), and calcitonin receptor (CTR). On the basis of the changes of the expression of osteoclastic activities, it is suggested that FSS is a potent, important regulator of bone metabolism.
