Taking CPU time cost and analysis accuracy into account, dynamic explicit finite ele- ment method is adopted to optimize the forming process of autobody panels that often have large sizes and complex geometry. In this...Taking CPU time cost and analysis accuracy into account, dynamic explicit finite ele- ment method is adopted to optimize the forming process of autobody panels that often have large sizes and complex geometry. In this paper, for the sake of illustrating in detail how dynamic explicit finite element method is applied to the numerical simulation of the autobody panel forming process,an example of optimization of stamping process pain meters of an inner door panel is presented. Using dynamic explicit finite element code Ls-DYNA3D, the inner door panel has been optimized by adapting pa- rameters such as the initial blank geometry and position, blank-holder forces and the location of drawbeads, and satisfied results are obtained.展开更多
Finite element method(FEM) was used to simulate the forming process of shotpeening the wing skin panel. Experiment of shotpeeing the wing skin panel was carried out. The results show that equivalent deformation in sho...Finite element method(FEM) was used to simulate the forming process of shotpeening the wing skin panel. Experiment of shotpeeing the wing skin panel was carried out. The results show that equivalent deformation in shotpeening process can be obtained using the elongation and bending result caused by thermal stress that is induced by applying temperature load on the surface of the part. Deformation of the part in the shotpeeing process can be analyzed using this method. The parameters and their relationships are identified.展开更多
The local buckling of stiffened panels is one of possible failure modes and concerned by engineers in the preliminary design of lightweight structures. In practice,a simplified model,i.e.,a rectangular plate with elas...The local buckling of stiffened panels is one of possible failure modes and concerned by engineers in the preliminary design of lightweight structures. In practice,a simplified model,i.e.,a rectangular plate with elastically restrained along its unloaded edges,is established and the Ritz method is usually employed for solutions. To use the Ritz method,however,the loaded edges of the plate are usually assumed to be simply supported. An empirical correction factor has to be used to account for clamped loaded edges. Here,a simple and efficient method,called the quadrature element method(QEM),is presented for obtaining accurate buckling behavior of rectangular plates with any combinations of boundary conditions, including the elastically restrained conditions. Different from the conventional high order finite element method(FEM),non-uniformly distributed nodes are used,and thus the method can achieve an exponential rate of convergence. Formulations are worked out in detail. A computer program is developed. Improvement of solution accuracy can be easily achieved by changing the number of element nodes in the computer program. Several numerical examples are given. Results are compared with either existing solutions or finite element data for verifications. It is shown that high solution accuracy is achieved. In addition,the proposed method and developed computer program can allow quick analysis of local buckling of stiffened panels and thus is suitable for optimization routines in the preliminary design stage.展开更多
For the structural-acoustic radiation optimization problem under external loading,acoustic radiation power was considered to be an objective function in the optimization method. The finite element method(FEM) and boun...For the structural-acoustic radiation optimization problem under external loading,acoustic radiation power was considered to be an objective function in the optimization method. The finite element method(FEM) and boundary element method(BEM) were adopted in numerical calculations,and structural response and the acoustic response were assumed to be de-coupled in the analysis. A genetic algorithm was used as the strategy in optimization. In order to build the relational expression of the pressure objective function and the power objective function,the enveloping surface model was used to evaluate pressure in the acoustic domain. By taking the stiffened panel structural-acoustic optimization problem as an example,the acoustic power and field pressure after optimized was compared. Optimization results prove that this method is reasonable and effective.展开更多
Slip and deformation of concrete sandwich panels under uniformly distributed loads is concerned. The effect of slip on the deformation of concrete sandwich panels are studied,and the analytical expressions of slip and...Slip and deformation of concrete sandwich panels under uniformly distributed loads is concerned. The effect of slip on the deformation of concrete sandwich panels are studied,and the analytical expressions of slip and deformation for concrete sandwich panels is obtained. These formulae can describe the slip distribution and account for its effect on deformation. In order to restrict the bound of formula, the formula of crack moment is obtained. The results of theoretical calculation are compared with those of tests and finite element methods. The comparison shows that the results of theoretical calculation are in accord with those of tests and finite element methods. So the theoretical calculation can be used to calculate slip and deformation of concrete sandwich panels in practical projects.展开更多
The forming of sheet metal in a desired and attractive shape is a process that requires an understanding of materials, mechanics and manufacturing principles. Manufacturing a consistent sheet metal component is challe...The forming of sheet metal in a desired and attractive shape is a process that requires an understanding of materials, mechanics and manufacturing principles. Manufacturing a consistent sheet metal component is challenging due to the nonlinear interactions of various material and process parameters. One of the major issues in the manufacturing of inconsistent?sheet metal?parts is springback. Springback is the elastic strain recovery in the material after the tooling is removed and the final shape of the product depends on the springback amount formed. In this study according to the result of simulation the inverted compensation method is adopted to optimize die surface design. Similarly, to predict and compensate the springback error this study presented an analytical approach of forming process in a stepwise modification of the automobile roof panel. Moreover, based on?Dynaform?and?finite element analysis of sheet metal stamping simulation the sprinback in automobile roof panel is predicted and compensated.?In addition, this study examines the significant requirements of the sheet metal forming precision of automobile body and the simulation of forming, stamping and springback of automobile roof panel is carried out, and the result of simulation also is analyzed.展开更多
Most researches on the static performance of stiffened panel joined by friction stir welding(FSW) mainly focus on the compression stability rather than shear stability. To evaluate the potential of FSW as a replacem...Most researches on the static performance of stiffened panel joined by friction stir welding(FSW) mainly focus on the compression stability rather than shear stability. To evaluate the potential of FSW as a replacement for traditional rivet fastening for stiffened panel assembly in aviation application, finite element method(FEM) is applied to compare compression and shear stability performances of FSW stiffened panels with stability performances of riveted stiffened panels. FEMs of 2024-T3 aluminum alloy FSW and riveted stiffened panels are developed and nonlinear static analysis method is applied to obtain buckling pattern, buckling load and load carrying capability of each panel model. The accuracy of each FEM of FSW stiffened panel is evaluated by stability experiment of FSW stiffened panel specimens with identical geometry and boundary condition and the accuracy of each FEM of riveted stiffened panel is evaluated by semi-empirical calculation formulas. It is found that FEMs without considering weld-induced initial imperfections notably overestimate the static strengths of FSW stiffened panels. FEM results show that, buckling patterns of both FSW and riveted compression stiffened panels represent local buckling of plate between stiffeners. The initial buckling waves of FSW stiffened panel emerge uniformly in each plate between stiffeners while those of riveted panel mainly emerge in the mid-plate. Buckling patterns of both FSW and riveted shear stiffened panels represent local buckling of plate close to the loading corner. FEM results indicate that, shear buckling of FSW stiffened panel is less sensitive to the initial imperfections than compression buckling. Load carrying capability of FSW stiffened panel is less sensitive to the initial imperfections than initial buckling. It can be concluded that buckling loads of FSW panels are a bit lower than those of riveted panels whereas carrying capabilities of FSW panels are almost equivalent to those of riveted panels with identical geometries. Finite element method for simulating static performances of FSW and riveted stiffened panels is proposed and evaluated and some beneficial conclusions are obtained, which offer useful references for analysis and application of FSW to replace rivet fastening in aviation stiffened panel assembly.展开更多
A comparison research about the implicit and explicit solutions of sheet forming simulation was presented. On the platform of Autoform and Ls dyna3D, a dynamic forming simulation of a sideframe, of Santana 2000 was do...A comparison research about the implicit and explicit solutions of sheet forming simulation was presented. On the platform of Autoform and Ls dyna3D, a dynamic forming simulation of a sideframe, of Santana 2000 was done, and the engineering strain, the thickness distribution and the FLD between the two softwares were compared. It indicates that their results coincide with each other very much and the areas of the wrinkle and failure are the same roughly. Further, the characteristics of the two softwares in geometric model and preprocessing of the finite element were discussed and the questions which need attention provided.展开更多
The present paper reviews the vibro-acoustic modelling of extruded aluminium train floor structures including the state-of-the-art of its industrial applications, as well as the most recent developments on mid-frequen...The present paper reviews the vibro-acoustic modelling of extruded aluminium train floor structures including the state-of-the-art of its industrial applications, as well as the most recent developments on mid-frequency mod- elling techniques in general. With the common purpose to predict mid-frequency vibro-acoustic responses of stiffened panel structures to an acceptable accuracy at a reasonable computational cost, relevant techniques are mainly based on one of the following three types of mid-frequency vibro- acoustic modelling principles: (1) enhanced deterministic methods, (2) enhanced statistical methods, and (3) hybrid deterministic/statistical methods. It is shown that, although recent developments have led to a significant step forward in industrial applicability, mature and adequate prediction tech- niques, however, are still very much required for solving sound transmission through, and radiation from, extruded aluminium panels used on high-speed trains. Due to their great potentials for predicting mid-frequency vibro-acoustics of stiffened panel structures, two of recently developed mid-frequency modelling approaches, i.e. the so-called hybrid finite element-statistical energy analysis (FE-SEA) and hybrid wave-based method- statistical energy analysis (WBM-SEA), are then recapitulated.展开更多
“结构-隔热”一体化复合墙板(SIW墙板)是一种新型粮食平房仓墙体构件,由内、外叶混凝土墙和保温板通过连接件组成。为研究粮食侧压力作用下SIW墙板力学性能的可靠性及随机参数的灵敏度,建立了有限元分析模型,以内叶墙挠度和混凝土强度...“结构-隔热”一体化复合墙板(SIW墙板)是一种新型粮食平房仓墙体构件,由内、外叶混凝土墙和保温板通过连接件组成。为研究粮食侧压力作用下SIW墙板力学性能的可靠性及随机参数的灵敏度,建立了有限元分析模型,以内叶墙挠度和混凝土强度不同控制条件的功能函数为失效准则,采用蒙特卡洛拉丁超立方抽样方法,对影响SIW墙板承载力的随机输入参数按分布类型开展了100000次抽样及计算,分析了SIW墙板的可靠性,量化了随机参数的灵敏度。研究结果表明:有限元模拟结果与试验结果相差不足5%,功能函数失效概率分别为P f1=5.02×10^(-2)、P f 2=3.30×10^(-4),建立的有限元模型是有效的,对比规范其可靠度均在安全范围之内,应主要考虑影响混凝土强度失效较大的参数;粮食重力密度、混凝土弹性模量和保温板弹性模量的变化对SIW墙板混凝土强度可靠性的影响较大。研究成果为SIW墙板结构设计及优化提供了参考依据。展开更多
文摘Taking CPU time cost and analysis accuracy into account, dynamic explicit finite ele- ment method is adopted to optimize the forming process of autobody panels that often have large sizes and complex geometry. In this paper, for the sake of illustrating in detail how dynamic explicit finite element method is applied to the numerical simulation of the autobody panel forming process,an example of optimization of stamping process pain meters of an inner door panel is presented. Using dynamic explicit finite element code Ls-DYNA3D, the inner door panel has been optimized by adapting pa- rameters such as the initial blank geometry and position, blank-holder forces and the location of drawbeads, and satisfied results are obtained.
文摘Finite element method(FEM) was used to simulate the forming process of shotpeening the wing skin panel. Experiment of shotpeeing the wing skin panel was carried out. The results show that equivalent deformation in shotpeening process can be obtained using the elongation and bending result caused by thermal stress that is induced by applying temperature load on the surface of the part. Deformation of the part in the shotpeeing process can be analyzed using this method. The parameters and their relationships are identified.
基金partially supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘The local buckling of stiffened panels is one of possible failure modes and concerned by engineers in the preliminary design of lightweight structures. In practice,a simplified model,i.e.,a rectangular plate with elastically restrained along its unloaded edges,is established and the Ritz method is usually employed for solutions. To use the Ritz method,however,the loaded edges of the plate are usually assumed to be simply supported. An empirical correction factor has to be used to account for clamped loaded edges. Here,a simple and efficient method,called the quadrature element method(QEM),is presented for obtaining accurate buckling behavior of rectangular plates with any combinations of boundary conditions, including the elastically restrained conditions. Different from the conventional high order finite element method(FEM),non-uniformly distributed nodes are used,and thus the method can achieve an exponential rate of convergence. Formulations are worked out in detail. A computer program is developed. Improvement of solution accuracy can be easily achieved by changing the number of element nodes in the computer program. Several numerical examples are given. Results are compared with either existing solutions or finite element data for verifications. It is shown that high solution accuracy is achieved. In addition,the proposed method and developed computer program can allow quick analysis of local buckling of stiffened panels and thus is suitable for optimization routines in the preliminary design stage.
文摘For the structural-acoustic radiation optimization problem under external loading,acoustic radiation power was considered to be an objective function in the optimization method. The finite element method(FEM) and boundary element method(BEM) were adopted in numerical calculations,and structural response and the acoustic response were assumed to be de-coupled in the analysis. A genetic algorithm was used as the strategy in optimization. In order to build the relational expression of the pressure objective function and the power objective function,the enveloping surface model was used to evaluate pressure in the acoustic domain. By taking the stiffened panel structural-acoustic optimization problem as an example,the acoustic power and field pressure after optimized was compared. Optimization results prove that this method is reasonable and effective.
基金Supported by Natural Science Foundation of Tianjin (No.06YFJMJC05800)
文摘Slip and deformation of concrete sandwich panels under uniformly distributed loads is concerned. The effect of slip on the deformation of concrete sandwich panels are studied,and the analytical expressions of slip and deformation for concrete sandwich panels is obtained. These formulae can describe the slip distribution and account for its effect on deformation. In order to restrict the bound of formula, the formula of crack moment is obtained. The results of theoretical calculation are compared with those of tests and finite element methods. The comparison shows that the results of theoretical calculation are in accord with those of tests and finite element methods. So the theoretical calculation can be used to calculate slip and deformation of concrete sandwich panels in practical projects.
文摘The forming of sheet metal in a desired and attractive shape is a process that requires an understanding of materials, mechanics and manufacturing principles. Manufacturing a consistent sheet metal component is challenging due to the nonlinear interactions of various material and process parameters. One of the major issues in the manufacturing of inconsistent?sheet metal?parts is springback. Springback is the elastic strain recovery in the material after the tooling is removed and the final shape of the product depends on the springback amount formed. In this study according to the result of simulation the inverted compensation method is adopted to optimize die surface design. Similarly, to predict and compensate the springback error this study presented an analytical approach of forming process in a stepwise modification of the automobile roof panel. Moreover, based on?Dynaform?and?finite element analysis of sheet metal stamping simulation the sprinback in automobile roof panel is predicted and compensated.?In addition, this study examines the significant requirements of the sheet metal forming precision of automobile body and the simulation of forming, stamping and springback of automobile roof panel is carried out, and the result of simulation also is analyzed.
文摘Most researches on the static performance of stiffened panel joined by friction stir welding(FSW) mainly focus on the compression stability rather than shear stability. To evaluate the potential of FSW as a replacement for traditional rivet fastening for stiffened panel assembly in aviation application, finite element method(FEM) is applied to compare compression and shear stability performances of FSW stiffened panels with stability performances of riveted stiffened panels. FEMs of 2024-T3 aluminum alloy FSW and riveted stiffened panels are developed and nonlinear static analysis method is applied to obtain buckling pattern, buckling load and load carrying capability of each panel model. The accuracy of each FEM of FSW stiffened panel is evaluated by stability experiment of FSW stiffened panel specimens with identical geometry and boundary condition and the accuracy of each FEM of riveted stiffened panel is evaluated by semi-empirical calculation formulas. It is found that FEMs without considering weld-induced initial imperfections notably overestimate the static strengths of FSW stiffened panels. FEM results show that, buckling patterns of both FSW and riveted compression stiffened panels represent local buckling of plate between stiffeners. The initial buckling waves of FSW stiffened panel emerge uniformly in each plate between stiffeners while those of riveted panel mainly emerge in the mid-plate. Buckling patterns of both FSW and riveted shear stiffened panels represent local buckling of plate close to the loading corner. FEM results indicate that, shear buckling of FSW stiffened panel is less sensitive to the initial imperfections than compression buckling. Load carrying capability of FSW stiffened panel is less sensitive to the initial imperfections than initial buckling. It can be concluded that buckling loads of FSW panels are a bit lower than those of riveted panels whereas carrying capabilities of FSW panels are almost equivalent to those of riveted panels with identical geometries. Finite element method for simulating static performances of FSW and riveted stiffened panels is proposed and evaluated and some beneficial conclusions are obtained, which offer useful references for analysis and application of FSW to replace rivet fastening in aviation stiffened panel assembly.
文摘A comparison research about the implicit and explicit solutions of sheet forming simulation was presented. On the platform of Autoform and Ls dyna3D, a dynamic forming simulation of a sideframe, of Santana 2000 was done, and the engineering strain, the thickness distribution and the FLD between the two softwares were compared. It indicates that their results coincide with each other very much and the areas of the wrinkle and failure are the same roughly. Further, the characteristics of the two softwares in geometric model and preprocessing of the finite element were discussed and the questions which need attention provided.
基金sponsored by the NationalNatural foundation of China(Grant Nos.U1434201 and 51175300)
文摘The present paper reviews the vibro-acoustic modelling of extruded aluminium train floor structures including the state-of-the-art of its industrial applications, as well as the most recent developments on mid-frequency mod- elling techniques in general. With the common purpose to predict mid-frequency vibro-acoustic responses of stiffened panel structures to an acceptable accuracy at a reasonable computational cost, relevant techniques are mainly based on one of the following three types of mid-frequency vibro- acoustic modelling principles: (1) enhanced deterministic methods, (2) enhanced statistical methods, and (3) hybrid deterministic/statistical methods. It is shown that, although recent developments have led to a significant step forward in industrial applicability, mature and adequate prediction tech- niques, however, are still very much required for solving sound transmission through, and radiation from, extruded aluminium panels used on high-speed trains. Due to their great potentials for predicting mid-frequency vibro-acoustics of stiffened panel structures, two of recently developed mid-frequency modelling approaches, i.e. the so-called hybrid finite element-statistical energy analysis (FE-SEA) and hybrid wave-based method- statistical energy analysis (WBM-SEA), are then recapitulated.
文摘“结构-隔热”一体化复合墙板(SIW墙板)是一种新型粮食平房仓墙体构件,由内、外叶混凝土墙和保温板通过连接件组成。为研究粮食侧压力作用下SIW墙板力学性能的可靠性及随机参数的灵敏度,建立了有限元分析模型,以内叶墙挠度和混凝土强度不同控制条件的功能函数为失效准则,采用蒙特卡洛拉丁超立方抽样方法,对影响SIW墙板承载力的随机输入参数按分布类型开展了100000次抽样及计算,分析了SIW墙板的可靠性,量化了随机参数的灵敏度。研究结果表明:有限元模拟结果与试验结果相差不足5%,功能函数失效概率分别为P f1=5.02×10^(-2)、P f 2=3.30×10^(-4),建立的有限元模型是有效的,对比规范其可靠度均在安全范围之内,应主要考虑影响混凝土强度失效较大的参数;粮食重力密度、混凝土弹性模量和保温板弹性模量的变化对SIW墙板混凝土强度可靠性的影响较大。研究成果为SIW墙板结构设计及优化提供了参考依据。