各向异性铝合金板材本构关系及其有限元模拟

为了减轻自身重量,采用铝合金板材和冲压成形工艺制造高速列车车体已经成为现代化铁路车辆的发展方向.但是,铝合金板材的力学性能是各向异性的,其冲压成形过程复杂,变形规律不易把握.采用Barlat三参数屈服准则获得了各向异性铝合金板材的应力应变关系曲线,并通过有限元模拟和拉伸实验进行了对比验证,结果表明采用Barlat三参数屈服准则获得的各向异性铝合金板材的应力应变关系曲线可应用于各向异性铝合金板材的有限元分析,并初步对各向异性铝合金板材的冲压成形过程进行了非线性接触有限元模拟,获得了比较理想的有限元分析结果,这对改进高速列车车体加工工艺、缩短冲压模具调试周期、降低生产成本具有积极的意义.     

本构方程对6016铝合金板材成形极限影响分析

通过单向拉伸试验和半球形刚模胀形试验分别得到了6016铝合金板材的室温应力应变曲线和成形极限图(FLD),拟合应力应变曲线获得了Hollomon,Power和Voce本构方程.应用DYNAFORM软件进行了刚模胀形试验的有限元模拟,分析了三种本构方程对6016铝合金成形极限的影响.模拟结果和试验结果对比表明:本构方程的选择对铝合金板材成形极限有显著的影响,相比Power与Hollomon,采用Voce本构方程进行模拟能够更精确地预测铝合金板材的成形极限.     

基于PamStamp的高强钢板热成形工艺研究

以汽车U形梁零件为例,以22MnB5高强钢板的力学及热物理性能的实验数据为基础,建立了有限元分析模型,并运用PamStamp软件进行了热冲压成形以及成形后的淬火冷却的全部过程的模拟分析,根据模拟结果进行了物理试验验证,结果表明模拟结果与试验结果一致。     

前挤压工件和模具的温度分布有限元分析

在高精密冷成形加工中,工件和模具的温度变化直接影响工件的成形精度.通过对前挤压加工过程机械热力偶合有限元模拟,对材料的流动、由于塑性变形和接触面之间的摩擦所产生的热量、工件和模具中的热传导、工件与模具之间的热交换、在成形期间和其后冷却过程中工件和模具中温度的分布等进行了分析;对工件和模具的机械和热力学性能和诸如冲头的速度、摩擦系数等加工条件对温度在工件和模具中的分布的影响进行了研究.有限元模拟的结果表明,在成形加工中由于热膨胀和冷却的影响,工件和模具中温度的变化将影响工件的成形精度.工件的性能对热的产生和温度分布有决定性的影响;加工条件的变化会影响温度的高低和分布.     

铁路罐车封头冲压成形研究

为保证某型铁路罐车封头冷冲压成形质量,设计了具有圆形拉延筋、矩形拉延筋和不设置拉延筋3种结构形式的拉延模具型面;使用有限元方法,对3种模具结构形式下封头的冲压成形过程进行模拟分析,对比了封头起皱趋势、 成形回弹和料厚变化等模拟结果,并根据仿真结果选择合理的模具结构形式进行了试验.研究结果表明:采用矩形拉延筋进行封头冲压成形,能更有效的避免封头出现起皱、鼓包等成形缺陷,而且成形后回弹量较小;矩形拉延筋模具冲压试验所得封头无成形缺陷,测得封头最小料厚为9.6 mm,最大料厚为10.5 mm,与模拟结果基本一致;采用矩形拉延筋模具进行该型封头冷冲压成形是有效的.      

涡轮叶片锻造成形过程的计算机模拟

用塑性有限元方法对涡轮叶片的锻造成形过程进行了计算机模拟，得到叶片变形的应力应变状态和模具受力情况，得到与实际生产相符的结果。     

船体外板冷弯成形回弹数值模拟关键技术研究

如何精确的预测出回弹量在船体外板冷弯成形中是一个非常关键的因素,有限元数值模拟技术的引入,为推动回弹问题的解决提供了有利的工具.文章基于船体外板多点成形技术冷压成形的回弹数值模拟的数学模型的建立问题,重点介绍了本构模型、单元类型、数值计算方法的选择及接触与摩擦的处理等,为后续的回弹模拟研究奠定了基础.     

基于ANSYS的天圆地方接口有限元分析

为了验证除湿设备天圆地方接口结构布置的合理性,基于ANSYS有限元分析软件建立有限元模型,对接口模型进行应力和变形分析,结果表明结构布置满足安全生产需要。为了节约成本,结合模拟结果对接口的平面框架结构提出优化方案,通过ANSYS有限元分析对优化方案进行计算。结果表明:优化方案在改善受力状况的同时,节省了材料用量,达到了节约成本的目的。     

前挤压工件和模具的温度分布有限元分析

在高精密冷成形加工中，工件和模具的温度变化直接影响工件的成形精度，通过对前挤压加工过程机械热力偶合有限元模拟，对材料的流动，由于塑料变形和接触面之间的摩擦所产生的热量，工件和模具中的热传导，工件与模具之间的热交换，在成形期间和其后冷却过程工件和模具中温度的分布等进行了分析，对工件和模具的机械和热力学性能和诸如冲头的速度，摩擦系数等加工条件对温度在工件和模具中的分布的影响进行了研究，有限元模型的结果表明，在成形加工中由于热膨胀和冷却的影响，工件和模具中温度的变化将影响工件的成形精度，工件的性能对热的产生和温度分布有决定性的影响，加工条件的变化会影响温度的高低和分布。     

基于RBF神经网络模型的板料成形变压边力优化

为了解决变压边力优化过程中RBF(radial basis function )神经网络隐层节点训练难的问题,利用人工智能算法的优越性,建立了基于人工免疫算法的RBF神经网络,并将其用于非线性函数的逼近中.结合分块压边圈与改变压边力控制技术,通过Dynaform软件进行数值模拟获得成形数据,建立了变压边力与成形质量之间的RBF神经网络近似模型.利用人工免疫智能算法对该近似模型进行优化,获得最优压边力参数.将该方法应用于S形梁冲压成形中,与优化前的结果进行比较,采用优化后最优变压边力可以抑制起皱,最大起皱量减少了89.53%.      

Compliant assembly modeling and deformation analysis considering macro residual stress in engineering component

Based on the manufacturing history chain, a component's macro residual stress is introduced to the subsequent assembly model. In the simulated method, the simulation cost is saved via mapping the bulk stress profile directly to the component compared to our previous study. It thus facilitates the finite element analysis(FEA) which takes the component location in blank and the thickness of blank as two influence parameters. The methodology is proved to be feasible by the validation experiment designed for a typical assembly structure from the aerospace industry. The results show that the bulk stress originating from material preparation affects the downstream large-scale assembly deformation. The investigation of this research helps systematically to improve compliant assembly precision.     

Galling failure analysis in sheet metal forming process

Galling is a known failure mechanism in sheet metal forming operations,and it can lead to fracture of the products and jamming of the tool. The temperature field and normal contact pressure distributions of the tool and the blank were studied with a finite element analysis model under the action of different blank holder force and frictional coefficient. A series of forming tests of the high strength steel were conducted to validate the finite element model. The characteristics of galling failure,the damage...     

Sensitivity Analysis of Effect Related with Material Process and Assembly Variations to Loads Deformation and Stress on HSS Stamping Die

During stamping process, the material properties, process design parameters and production environments inevitably have variation and noisy factors, which possibly affect the sheet metal formability and the deformation of the die structure.After gaining a success in applying sheet metal forming numerical simulation analysis to get the forming loads during stamping process, a methodology of die structure analysis based on sheet metal forming simulation was proposed and validated by experiments.Based on these results, the effect related with initial blank thickness, blank holder force, blank positioning error and die alignment error variations to a DP600 hyperbolic bottomed cup drawing die's forming loads(especially unbalanced loads), and deformation and stress was studied numerically.The influence level of these variations to the die's forming loads, deformation and stress was disclosed.The findings can guide die design, die tryout and process control for high-strength steel(HSS) stamping with increased forming load and decreased sheet metal formability.     

Finite Element Optimization of Vee-ring Factor in Fine-blanking Process

The vee-ring is one of the most characteristic features of the fine-blanking process which is derived from the conventional blanking. With the vee-ring, a counter plate and some other working parameters, a component with a precise geometry and smoothly blanked surface can be produced without any major secondary operations. However, these working parameters are always empirically determined or determined by trial-and-error method, which is time-consuming and expensive. In this study, a numerical simulation method was used to analyze the effect of vee-ring factors on product quality, such as distance between vee-ring and punch, vee-ring height and blank holder force, so as to obtain as high clean cut ratio as possible. During the simulation, the model was assumed as axisymmetric one and the workpiece was considered as rigid plastic material, meanwhile the tools were defined as rigid bodies so as to shorten the computational time. A damage model taking into account the influence of hydrostatic stress was used to simulate material fracture in fine-blanking. The result obtained from the simulation indicated that with the help of vee-ring, the metal material near the shear band does not flow with the punch penetration and high compressive stress in the shear band is generated. Consequently, higher clean cut ratio can be obtained with a vee-ring model than the one obtained with a plane blank holder model. Furthermore, the longer the distance between vee-ring and punch is, the higher the height of roll-over becomes.     

Application of Decision Tree Algorithm in Stamping Process

Introduction Learning is the main symbol of human intelli-gence and the basic means to acquire the knowl-edge. Machine learning can extract the rules hid-den in data through analyzing the relations amongobjects, which is also computational theory to in-vestigate learning. Nowadays, various methodsare adopted in machine learning field, such as deci-sion tree, Bayesian classification, neural network,genetic algorithm and rough set[1]. Many machinelearning methods have been used as the convenien…     

Discrete Element Simulation of Asphalt Mastics Based on Burgers Model

Introduction With the rapid development of highway construc-tions, the performances of asphalt mixtures haveattracted considerable attention. Asphalt mastic is themost important component that affects the perform-ances of asphalt mixtures, and lots of res…     

板材成形模拟中模具曲面的描述和光顺

为解决在有限元中曲线、曲面的描述和光顺问题，提出一种适合有限元模拟的模具曲面修正方法．采用基于点的曲面表达方式描述模具曲面，利用原始型值点与修正后的型值点之间的误差描述光顺，并利用ABAQUS软件建立了相应的计算机模拟系统．模拟结果表明，该系统适用于采用有限元模拟模具曲面修正．     

制动盘试验模态与数值模态的分析与研究

基于有限元法得到制动盘的固有频率和振型,同时运用试验模态技术对制动盘进行模态试验,得到了模态参数,将试验模态与仿真计算的结果进行比较,从而验证了有限元分析结果的可靠性。     

机车车辆车体结构动应力计算方法

为了提高机车车辆的疲劳寿命,优化其结构设计,提出了基于多系统仿真模型和有限元方法的动应力混合计算方法,计算了机车车辆车体结构的动应力。建立以车体为核心的机车多体系统仿真模型,并进行动力学分析,获得关键位置的载荷时间历程。通过有限元准静态应力法,计算了车体结构的准静态应力影响因子。通过载荷时间历程和对应单位载荷作用下的应力影响因子的相互相乘叠加求和计算,获得车体结构在随机动载作用下的应力历程,对实际线路车体结构动应力测试结果和刚性车体与柔性车体的仿真结果进行了对比。对比结果表明:其误差分别是2.462%和7.258%,说明此计算方法计算精度高。     

预应力混凝土梁非线性分析单元模型

为了能够准确有效地分析混凝土梁中预应力钢筋的力学性能,模拟结构中存在的普通钢筋、预应力直线钢筋和预应力曲线钢筋,提出了一种预应力混凝土梁非线性分析的单元模型。应用有限元理论,采用全拉格朗日列式的三维杆单元模拟预应力钢筋;采用实体退化组合壳单元模拟结构;应用钢筋单元和混凝土单元之间的位移场关系形成钢筋对混凝土单元的贡献,将预应力钢筋对结构的作用直接反映在单元模型内部。预应力混凝土T梁的破坏过程模拟结果表明梁的跨中挠度计算结果和试验实测数据吻合,单元模型有效地反映了预应力束的力学性能。