FEM Analysis of Spring-backs in Age Forming of Aluminum Alloy Plates

The age forming technology, characterized by huge spring-backs, has been developed to manufacture large integral wing-skin panel parts, which necessitates devising a method of predicting spring-backs. A 7B04-T7451 aluminum alloy creep test in tension is accomplished at 155 ℃, and the creep curves are obtained. The material constants of the mechanism-based creep constitutive equations are determined through experiments. The age forming process and the spring-backs of 7B04 aluminum alloy plates are analyzed using the commercial finite element software ABAQUS. The effects of plate thickness and forming time on spring-backs are researched. The spring-backs decrease with the increase of plate thickness and forming time. The test results verify the reliability of the finite element method （FEM） analysis.

Spring-back deformation in tube bending

The spring-back of a bending metal tube was studied through extensive experiments and finite element method （FEM） analysis. An approximate equation for the spring-back angle of bending was deduced. It is noted that the mechanical properties of the material （in a tubular form） are quite different from those found in the standard tensile tests （when the materials are in bar forms）. This is one of the major reasons that result in the discrepancies in the outcomes of experimental study, FEM calculations, and spring-back analysis. It is therefore of crucial importance to study the mechanical properties of the materials in their tubular forms. The experiments and FEM simulations prove that the spring-back angle is significantly affected by the mechanical properties of the materials. The angle decreases accordingly with plastic modulus, but changes inversely with the hardening index and elastic modulus The spring-back angle is also affected by the conditions of tube deformation： it increases accordingly with the relative bending radius but changes inversely with the relative wall thickness. In addition, the spring-back angle increases nonlinearly with the bending angle.

Research on spring-back behavior of high strength steel sheets

To investigate the spring-back behavior of dual-phase （DP） steel, V-shape spring-back experiments with different bending angles, relative bending radii and blank holding forces were carried out in this paper. It is concluded that with the increase of V-shape angle or blank holding force, the spring-back of DP steel sheets decreases; while raising fiIlet radius of punch, which has the most apparent effects on spring-back, advances spring-back angle. Among DP590, DP780 and DP980, higher strength yields more notable spring-back due to larger elastic deformation. The difference of spring-back among these materials is relevant with the microstructure and mechanical properties. The total elastic deformation approximately equals the ratio of the strength corresponding to the applied load to the modulus of elasticity.

板厚对T2紫铜板U形弯曲回弹的影响

采用U形弯曲模对T2紫铜板进行弯曲试验,测量卸载后的弯曲角回弹量,结果表明:在板厚0.15-2.0mm的范围内随着板厚的增加,试样的弯曲角回弹量逐渐减小。为了精确描述弯曲角回弹量与板厚之间的关系,分别用最小二乘法拟合与拉格朗日插值获得两者之间的函数关系式,接着用一组弯曲角回弹量的测量值去验证两种方法的计算精度,验证结果表明:最小二乘法拟合得到的函数关系式的计算值具有更小的均方根误差,可以用来预测T2紫铜板的弯曲角回弹量,对于分析T2紫铜板的弯曲变形以及合理制定弯曲工艺具有一定的指导意义。

深基坑卸载回弹参数研究及隆起量计算

着重对回弹量影响最密切而求值比较模糊的若干参数，进行较准确的描述性定义和取值方法的研究，归纳出概念清晰、计算结果相对准确且方便工程应用的计算方法．

AP1000主管道冷段弯管回弹量的理论计算

为满足AP1000主管道冷段弯管所要求的尺寸精度,根据316LN超低碳控氮奥氏体不锈钢的材料特性,结合AP1000主管道冷段弯管的尺寸参数,通过塑性弯曲理论计算确定冷段弯管纯弯曲时的弯曲力矩、回弹角和半径回弹补偿量,为AP1000主管道冷段弯管成型模具设计提供参考。

U型钢弯曲回弹试验及回弹规律数值分析

通过对25U型钢弯曲回弹前后实际曲率半径与型材弯曲理论公式数值计算结果的对比、分析,结果表明:25U型钢在弯曲半径大于1 000 mm时,随着弯曲半径的减小,所对应回弹量增大,回弹前的弯曲半径与型材弯曲理论公式数值计算结果之间存在很大的误差;当弯曲半径小于1 000 mm时,随着弯曲半径的减小,所对应回弹量变化不大,并且与型材弯曲理论公式数值计算结果之间的误差较小。实际应用中以1 000～2 500 mm曲率半径为主,因此需在这一范围内对型材弯曲理论公式进行修正,修正后的型材弯曲理论公式数值计算结果与实验值相吻合,可以用于计算25U型钢加工设备的控制量,指导实际生产。

C5210磷青铜薄板微弯曲回弹的尺寸效应

采用RG-2000型微机控制电子万能试验机,通过微弯曲试验,研究了C5210磷青铜薄板的厚度、晶粒尺寸以及弯曲半径等相关尺寸对其微弯曲回弹的影响。结果表明:C5210磷青铜薄板的厚度、晶粒尺寸和弯曲半径等对其回弹均有显著的影响,具有明显的尺寸效应;薄板的厚度越大,回弹量越小,厚度对回弹量的影响非常显著;薄板的晶粒尺寸越大,回弹量越小,当晶粒尺寸大于40μm时,回弹量呈缓慢减小趋势;回弹量随着弯曲半径的增大而增大,而且薄板的厚度越小,增大的趋势越明显。

Quantitative Prediction of Reduction in Large Pipe Setting Round Process

The control manner during the process to ensure the quality of pipe products mainly relies on the operator’s experience, so it is very necessary to study the setting round process and obtain its spring-back law. The setting round process is shaping an oval section pipe into circular section, so it is difficult to provide a quantificational analysis for its spring-back process because of the curvature inequality of pipe section neutral layer. However, the spring-back law of the circle-oval process can be easily predicted. The experimental method is firstly used to establish the equivalent effect between the setting round process and the circle-oval process. The setting round process can be converted into the circle-oval process. There are two difficulties in the theoretical analysis for the circle-oval process: elastic-plastic bending problem of curved beam; statically indeterminate problem. A quantitative analytic method for the circle-oval process is presented on the basis of combination of the spring-back law of plane curved beam with the element dividing idea in finite element method. The ovality after unloading versus the relative reduction is plotted with analytical and experimental results respectively, which shows a fair agreement. Finally, the method of quantitative prediction of reduction for large pipe setting round is given based on the equivalent effect and the analytical results. Five pipes, which are needed to be set round, are used to carry out experiment so as to verify this method. The results of verification experiment indicates that, in the experimental range, the residual ovality are all under 0.35% after the once only setting round with the theoretical prediction reductions. It is much less than the 1% requirement of pipe standard. Applying the established theoretical analysis is able to correct the pipe ovality with sufficient accuracy, which provides theoretical direction to plant use.

Numerical simulation for sheet metal forming process of 16Mn blade of large concrete-mixer truck

A finite element analysis method was used to simulate the stamping process of the blade of a large concrete-mixer truck. The updated Lagrange method and the elasto-plastic constitutive equation were adopted to solve the large strain and displacement deformation of the blade. A modified Coulomb friction model was used to solve the sliding contact between the blade and the dies. The von Mises stress distribution in the blade, the spatial displacement variation and the spring-back of the typical node were investigated in the simulation. The von Mises stress in the blade where the spring-back occurs is lowered from 463.0MPa to 150.0MPa before and after the spring-back. A typical node in the blade has a 3.33mm spring-back in Z direction. The results of the (experiments) agree well with the simulation. The analysis results are valuable for designing optimal tool dies.

NUMERICAL STUDY ON FLANGING AND SPRINGBACK OF STAMPED THICK METAL PLATE

A quasi-three-dimensional shell element model, which can beeffectively used to simulate the flanging and spring-backdeformation, is introduced into the independently developed CAEsoftware, KMAS, In this model, a double surface contact algorithm,which allows the gap between punch and die to change, and a spring-back treatment scheme based on finite element meshing are described.And then the flanging and spring-back deformations of the retractor'skickstand of a railcar made of stamped thick metal plate arenumerically simulated. The simulation results of flanging deformationare compared with those of international commercial software,PAM-STAMP, and experimental ones. Finally, a predicting scheme ofspring-back quantily for this problem is given.

容器管座冷装技术研究

通过对管座冷装过程中收缩、回弹等阶段的变化趋势研究,总结出管座安装时轴向尺寸控制的方法以及工艺保障措施。

A Numerical Approach on Reduction of Young’s Modulus During Deformation of Sheet Metals

The paper investigates the elastic behavior of the metal after unloading. For this purpose the strip of metal with tensile gauge length was simulated with high and low strength material. Further the channel forming was modeled for combination of materials to predict the spring-back and compared the results. It is observed that the Young’s modulus (E-value) decreases with the increase in plastic strain. The strength of the material has no effect on the decrease in the E-value after unloading during tension test. However in channel forming the E-value after unloading depends on the starting E-value, spring-back angle and maximum strain achieved in the channel. The proposed mathematical equations to determine the E-value after unloading from the tension test and channel forming test gives very good prediction with each other. It is also found that the lowest spring-back occurred in the channel with the composite Hard-Soft material.

引线头成形工艺及模具设计

分析了引线头零件的工艺性和成形难点,确定了合理的工艺方案,介绍了按此方案设计的2套折弯模的结构和工作过程。结果表明,2套模具结构新颖、工作可靠,在生产中取得了良好的经济效益。

不锈钢螺旋板的成形工艺及模具设计

介绍了螺旋形板类零件成形模具的设计方法及工作原理,通过对不锈钢螺旋板的成形工艺及设计方案进行分析、比较,阐述了采用试验螺旋导程回弹量参数设计模具的合理性及采用成形模进行成形的合理性,对类似产品的模具设计具有一定的参考价值。

Tensile and Spring-Back Behavior of DP600 Advanced High Strength Steel at Warm Temperatures

In recent years, the use of advanced high strength steels in automotive industry has been increased remarkably. Among advanced high strength steels, dual phase （DP） steels have gained a great attention owing to a combination of high strength and good formability. However, high strength usually increases the spring-back behavior of the material, which creates problems for the parts during the assembly. Thus, the uniaxial tensile deformation and spring-back behaviors of DP600 advanced high strength steel were investigated in rolling （0°）, diagonal （45°） , and transverse （90°） directions in the temperature range from room temperature （RT） to 300 ℃. All tests were performed at a deformation speed of 25 mm/min. A V-shaped die （60°） was used for the spring-back measurements. The results indicated that the formability and spring-back of the material were decreased with increasing the temperatures. The material showed complex behaviors in different directions and at different temperatures.

Improved knowledge-based neural network(KBNN)model for predicting spring-back angles in metal sheet bending

We develop an efficiently improved knowledge-based neural network(KBNN)associated with optimization algorithms and finite element analysis(FEA)to accurately predict spring-back angles in metal sheet bending.The well-known V and U prevalent processes of bending are considered.The KBNN predictive results are based on the empirical model and artificial neural network(ANN)modeling.The empirical model is constructed from the FEA results using response surface method,while the multilayer perceptron is employed to create the ANN.The trained KBNN can accurately model the relation-ship between the spring-back angles and process parameters.The obtained results are validated against other existing methods showing a high accuracy.