To eliminate the defects during piston skirt isothermal forming process,simulations under different process parameters such as the deformation temperature and friction factor were analyzed with the rigid-plastic FEA.D...To eliminate the defects during piston skirt isothermal forming process,simulations under different process parameters such as the deformation temperature and friction factor were analyzed with the rigid-plastic FEA.Deformation pattern,metal flow and influence of process parameters were concluded.The prediction load value with a relative error of 4.98% is more accurate to the testing one than that from the empirical formula whose relative error is up to 50.8%.Finally,based on the simulation results,an improved process at 300 ℃ and 0.005-0.05 s-1 was verified without any defects by the physical try-out.展开更多
Many disadvantages exist in the traditional die design method which belongs to serial pattern. It is well known that heat treatment is highly important to the dies. A new idea of concurrent design for heat treatment p...Many disadvantages exist in the traditional die design method which belongs to serial pattern. It is well known that heat treatment is highly important to the dies. A new idea of concurrent design for heat treatment process of die and mould was developed in order to overcome the existent shortcomings of heat treatment process. Heat treatment CAD/CAE was integrated with concurrent circumstance and the relevant model was built. These investigations can remarkably improve efficiency, reduce cost and ensure quality of R and D for products.展开更多
A generalized mathematical model is developed to predict the changes of temperature, rolling pressure, strain,strain rate, and austenite grain size for plate hot rolling and cooling processes. The model is established...A generalized mathematical model is developed to predict the changes of temperature, rolling pressure, strain,strain rate, and austenite grain size for plate hot rolling and cooling processes. The model is established mainly by incorporating analytical and numerical method for differential equations under complicated boundary conditions. An industrial rolling and cooling process of plate is simulated by the model, in which the thickness of steel Q235B plate is rolled from initial 200 mm to final 12 mm by 13-passes in a two-high mill. The calculated results are in good agreement with measured data. Different from FEM simulation, the model takes very short time in calculation and makes the influence of rolling passes on precision to be very slight.展开更多
Two layer BP neural network was designed for the semi solid apparent viscosity simulation. The apparent viscosity simulations of Sn 15%Pb alloy and Al 4.5%Cu 1.5%Mg alloy stirred slurries were carried out. The trained...Two layer BP neural network was designed for the semi solid apparent viscosity simulation. The apparent viscosity simulations of Sn 15%Pb alloy and Al 4.5%Cu 1.5%Mg alloy stirred slurries were carried out. The trained BP neural network forecast the curve of the apparent viscosity versus solid volume fraction of Sn 15%Pb alloy, under the condition of shear rate, =150 s -1 , and cooling rate of G =0.33 ℃/min. The simulation results are well agreement with the experimental values given in references. The fitted mathematical formula of Sn 15%Pb alloy apparent viscosity, under the condition of the cooling rate of G =0.33 ℃/min, was obtained by optimization method. The results show that the precision of apparent viscosity simulation value by neural network is much better than that of its calculation value by fitted mathematical formula.展开更多
A plastic deformation zone near a screw dislocation is treated as an equivalent transformation inclusion by means of the Eshelby inclusion theory. A closed form solution for determining the interaction between a screw...A plastic deformation zone near a screw dislocation is treated as an equivalent transformation inclusion by means of the Eshelby inclusion theory. A closed form solution for determining the interaction between a screw dislocation and a plastically deformed zone of an arbitrary shape is obtained by using the solution between a dislocation and an equivalent transformation inclusion.展开更多
The uniform experiment design is an effective way of optimizing technology scheme for refining the grain size during multistage deformation. In this paper, it is adopted to evaluate the effect of each technology param...The uniform experiment design is an effective way of optimizing technology scheme for refining the grain size during multistage deformation. In this paper, it is adopted to evaluate the effect of each technology parameter on final grain size of AISI H13 hot work tool steel during multistage deformation. It has been verified that the technology scheme for refining the final grain size can be determined rapidly and efficiently with the aid of the uniform design. The results show that the deformation parameters and the intermission time after deformation of the first stage affect the final grain size remarkably. For AISI H13 hot work tool steel, the final grain size can be refined notably when deformation parameters for the first stage are set as follows: a deformation temperature range of 1?025 1?085 ℃; a true strain of above 0.26 and the interpass time between the first and the second stage of deformation less than 10 s.展开更多
A meshfree method based on reproducing kernel approximation and point collocation is presented for analysis of metal ring compression. The point collocation method is a true meshfree method without the employment of a...A meshfree method based on reproducing kernel approximation and point collocation is presented for analysis of metal ring compression. The point collocation method is a true meshfree method without the employment of a background mesh. It is shown that, in a point collocation approach, the remesh problem because of the mesh distortion in FEM （finite element method） and the low efficiency in Galerkin-based meshfree method are avoided. The corrected kernel functions are introduced to the stabilization of free-surface boundary conditions. The solution of symmetric ring compression problem is compared with a conventional finite element solution, and reasonable results have been obtained.展开更多
In this paper one-point quadrature'assumed strain'mixed element formulation based on the Hu-Washizu variational principle is presented.Special care is taken to avoid hourglass modes and volumetric locking as w...In this paper one-point quadrature'assumed strain'mixed element formulation based on the Hu-Washizu variational principle is presented.Special care is taken to avoid hourglass modes and volumetric locking as well as shear locking.The assumed strain fields are constructed so that those portions of the fields which lead to volumetric and shear locking phenomena are eliminated by projection,while the implementation of the proposed URI scheme is straightforward to suppress hour- glass modes.In order to treat geometric nonlinearities simply and efficiently,a corotational coordinate system is used.Several numerical examples are given to demonstrate the performance of the suggested formulation,including nonlinear static/dynamic mechanical problems.展开更多
The biomechanical relationship between the articular cartilage defect and knee osteoarthritis (OA) has not been clearly defined. This study presents a 3D knee finite element model (FEM) to determine the effect of cart...The biomechanical relationship between the articular cartilage defect and knee osteoarthritis (OA) has not been clearly defined. This study presents a 3D knee finite element model (FEM) to determine the effect of cartilage defects on the stress distribution around the defect rim. The complete knee FEM, which includes bones, articular cartilages, menisci and ligaments, is developed from computed tomography and magnetic resonance images. This FEM then is validated and used to simulate femoral cartilage defects. Based on the obtained results, it is confirmed that the 3D knee FEM is reconstructed with high-fidelity level and can faithfully predict the knee contact behavior. Cartilage defects drastically affect the stress distribution on articular cartilages. When the defect size was smaller than 1.00cm2, the stress elevation and redistribution were found undistinguishable. However, significant stress elevation and redistribution were detected due to the large defect sizes ( 1.00cm2). This alteration of stress distribution has important implications relating to the progression of cartilage defect to OA in the human knee joint.展开更多
For a more accurate forming calculation and numerical simulation of hydraulic turbine blade, ex- perimental studies on the flow stress of stainless steel 0Crl3Ni5Mo were carried out upon Gleeble-1500 thermal simulator...For a more accurate forming calculation and numerical simulation of hydraulic turbine blade, ex- perimental studies on the flow stress of stainless steel 0Crl3Ni5Mo were carried out upon Gleeble-1500 thermal simulator under different deformation conditions. The results then were analyzed and the effects of all influencing factors were summarized consequently. New mathematic models were conceived. Utilizing the software Matlab, regression coefficients were calculated by the least square method. The model has an eminent capability of curve-fitting performance with impact structure whose correlation coefficient is up to 0.908 0 and the cosine coefficient is 0.995 8. All mathematic models and process parameters can be used in engineering calculations or computer simulations.展开更多
文摘To eliminate the defects during piston skirt isothermal forming process,simulations under different process parameters such as the deformation temperature and friction factor were analyzed with the rigid-plastic FEA.Deformation pattern,metal flow and influence of process parameters were concluded.The prediction load value with a relative error of 4.98% is more accurate to the testing one than that from the empirical formula whose relative error is up to 50.8%.Finally,based on the simulation results,an improved process at 300 ℃ and 0.005-0.05 s-1 was verified without any defects by the physical try-out.
基金ItemSponsored by National Natural Science Foundation of China (50075053) Science and Technology Foundation ofShanghai Higher Education (03 HZ01)
文摘Many disadvantages exist in the traditional die design method which belongs to serial pattern. It is well known that heat treatment is highly important to the dies. A new idea of concurrent design for heat treatment process of die and mould was developed in order to overcome the existent shortcomings of heat treatment process. Heat treatment CAD/CAE was integrated with concurrent circumstance and the relevant model was built. These investigations can remarkably improve efficiency, reduce cost and ensure quality of R and D for products.
文摘A generalized mathematical model is developed to predict the changes of temperature, rolling pressure, strain,strain rate, and austenite grain size for plate hot rolling and cooling processes. The model is established mainly by incorporating analytical and numerical method for differential equations under complicated boundary conditions. An industrial rolling and cooling process of plate is simulated by the model, in which the thickness of steel Q235B plate is rolled from initial 200 mm to final 12 mm by 13-passes in a two-high mill. The calculated results are in good agreement with measured data. Different from FEM simulation, the model takes very short time in calculation and makes the influence of rolling passes on precision to be very slight.
文摘Two layer BP neural network was designed for the semi solid apparent viscosity simulation. The apparent viscosity simulations of Sn 15%Pb alloy and Al 4.5%Cu 1.5%Mg alloy stirred slurries were carried out. The trained BP neural network forecast the curve of the apparent viscosity versus solid volume fraction of Sn 15%Pb alloy, under the condition of shear rate, =150 s -1 , and cooling rate of G =0.33 ℃/min. The simulation results are well agreement with the experimental values given in references. The fitted mathematical formula of Sn 15%Pb alloy apparent viscosity, under the condition of the cooling rate of G =0.33 ℃/min, was obtained by optimization method. The results show that the precision of apparent viscosity simulation value by neural network is much better than that of its calculation value by fitted mathematical formula.
基金Project supported by the National Basic Research Program of China (No.2004CB619303)the National Science Foundation of China (No.10572088).
文摘A plastic deformation zone near a screw dislocation is treated as an equivalent transformation inclusion by means of the Eshelby inclusion theory. A closed form solution for determining the interaction between a screw dislocation and a plastically deformed zone of an arbitrary shape is obtained by using the solution between a dislocation and an equivalent transformation inclusion.
基金TheNationalNaturalScienceFoundationofChina (No .5 0 0 75 0 5 3)
文摘The uniform experiment design is an effective way of optimizing technology scheme for refining the grain size during multistage deformation. In this paper, it is adopted to evaluate the effect of each technology parameter on final grain size of AISI H13 hot work tool steel during multistage deformation. It has been verified that the technology scheme for refining the final grain size can be determined rapidly and efficiently with the aid of the uniform design. The results show that the deformation parameters and the intermission time after deformation of the first stage affect the final grain size remarkably. For AISI H13 hot work tool steel, the final grain size can be refined notably when deformation parameters for the first stage are set as follows: a deformation temperature range of 1?025 1?085 ℃; a true strain of above 0.26 and the interpass time between the first and the second stage of deformation less than 10 s.
基金the National Natural Science Foundation of China （No. 50275059）.
文摘A meshfree method based on reproducing kernel approximation and point collocation is presented for analysis of metal ring compression. The point collocation method is a true meshfree method without the employment of a background mesh. It is shown that, in a point collocation approach, the remesh problem because of the mesh distortion in FEM （finite element method） and the low efficiency in Galerkin-based meshfree method are avoided. The corrected kernel functions are introduced to the stabilization of free-surface boundary conditions. The solution of symmetric ring compression problem is compared with a conventional finite element solution, and reasonable results have been obtained.
文摘In this paper one-point quadrature'assumed strain'mixed element formulation based on the Hu-Washizu variational principle is presented.Special care is taken to avoid hourglass modes and volumetric locking as well as shear locking.The assumed strain fields are constructed so that those portions of the fields which lead to volumetric and shear locking phenomena are eliminated by projection,while the implementation of the proposed URI scheme is straightforward to suppress hour- glass modes.In order to treat geometric nonlinearities simply and efficiently,a corotational coordinate system is used.Several numerical examples are given to demonstrate the performance of the suggested formulation,including nonlinear static/dynamic mechanical problems.
基金the National Natural Science Foundation of China (No. 81071235)the Medicine and Engineering Interdisciplinary Fund of Shanghai Jiaotong University (No. YG2010MS26)
文摘The biomechanical relationship between the articular cartilage defect and knee osteoarthritis (OA) has not been clearly defined. This study presents a 3D knee finite element model (FEM) to determine the effect of cartilage defects on the stress distribution around the defect rim. The complete knee FEM, which includes bones, articular cartilages, menisci and ligaments, is developed from computed tomography and magnetic resonance images. This FEM then is validated and used to simulate femoral cartilage defects. Based on the obtained results, it is confirmed that the 3D knee FEM is reconstructed with high-fidelity level and can faithfully predict the knee contact behavior. Cartilage defects drastically affect the stress distribution on articular cartilages. When the defect size was smaller than 1.00cm2, the stress elevation and redistribution were found undistinguishable. However, significant stress elevation and redistribution were detected due to the large defect sizes ( 1.00cm2). This alteration of stress distribution has important implications relating to the progression of cartilage defect to OA in the human knee joint.
基金the National Natural Science Foundation of China (No. 56675133)the National Basic Research Program (973) of China (No. 2006CB705401)
文摘For a more accurate forming calculation and numerical simulation of hydraulic turbine blade, ex- perimental studies on the flow stress of stainless steel 0Crl3Ni5Mo were carried out upon Gleeble-1500 thermal simulator under different deformation conditions. The results then were analyzed and the effects of all influencing factors were summarized consequently. New mathematic models were conceived. Utilizing the software Matlab, regression coefficients were calculated by the least square method. The model has an eminent capability of curve-fitting performance with impact structure whose correlation coefficient is up to 0.908 0 and the cosine coefficient is 0.995 8. All mathematic models and process parameters can be used in engineering calculations or computer simulations.
