金属板料激光冲击成形中的冲击动力学问题研究初探

介绍激光冲击成形机理,分析激光冲击波产生原因,初步探讨了金属板料冲击成形中的力学效应及板料塑性变形情况.     

金属板料激光无模成形技术研究的现状

金属板料激光无模成形是一种先进柔性制造技术,它包括激光热应力成形、激光冲击成形二种方法,本文分别介绍它们研究的现状、机理、特点,同时也指出其存在的问题。     

金属板料成型的三维弹塑性大变形有限元模拟

根据非线性连续介质力学的基本原理推导板料成型分析的三维弹塑性大变形全量拉格朗日法的有限元列式，首次给出其矩阵表达式的显式，并对圆板半球形凸膜胀形进行了模拟，模拟与实际结果吻合较好。     

金属板料激光无模成形技术研究的现状

金属板料激光无模成形是一种先进柔性制造技术,它包括激光热应力成形、激光冲击成形二种方法,本文分别介绍它们研究的现状、机理、特点,同时也指出其存在的问题.     

金属板料的几种无模成形技术的研究现状

介绍了用于板料塑性成形加工的喷丸成形、数字化渐进成形、无模多点成形、激光热应力成形和激光站压成形等几种无模成形技术的国内外研究现状、基本原理和特点，并就关键技术、存在问题及今后的发展趋势作了简要分析。     

激光冲击对金属板料裂纹的影响模型

研究了含有裂纹的金属板料在激光冲击波载荷作用下裂纹尖端应力强度因子和裂纹扩展速度的变化,利用断裂力学理论,对激光冲击加载下裂尖参数计算模型进行优化,采用应力强度因子叠加法,将外加载荷引起的应力强度因子和激光冲击后残留的残余压应力引起的应力强度因子叠加,推导出下裂纹尖端应力场强度因子表达式,由此可精确计算出金属板料的裂纹萌生寿命和裂纹扩展速度,实验验证了航空钛合金Ti6Al4V激光冲击后残余应力对裂纹扩展速度的影响,从而建立了激光冲击作用对板料裂纹扩展的影响的理论模型。     

钛合金板料激光冲击变形的数值模拟和实验

实验研究了激光能量和不同的冲击路径、冲击次数对TA2钛合金板料变形的影响，并用ABAQUS软件进行了有限元模拟。结果表明：随着激光能量的增加，板料的变形量增大；板料几何尺寸和厚度越大，板料越难变形；冲击次序不同，板的变形量也不同，板的变形以沿板的长度方向且对称冲击为最大。通过数值模拟可优化激光冲击的相关参数，预测板料变形。     

激光冲击效果的影响因素及其发展趋势

简单介绍了激光冲击加工技术产生的背景、发展概况，详细分析了激光冲击加工的基本原理和主要影响因素，并对其激光的功率密度，约束层表面的涂层及涂层材料重要影响因素进行了分析研究，介绍了激光冲击工艺应用于实际加工，以改善材料的疲劳强度，耐磨性及抗裂性能等特性，最后对激光冲击加工的发展现状及未来研究趋势做了探讨。     

金属板料无模成型制造集成系统的研究与应用示范

由吉林大学开发的无模成形集成系统以多点成形技术为核心，利用计算机控制一系列规则排列的冲头点阵，通过调整冲头高度形成所需的成形曲面，代替模具实现金属板壳类件的无模、快速、数字化成形。     

Analysis and experiment on deformation of sheet metal by laser shock wave

The mechanism of laser shock deformation and the reason for the production of the shockwave are introduced. An evaluation formula of the detonation wave pressure in the system of laser, energy transferring-medium and sheet metal is built according to the theory of detonation wave and blasting gas-dynamics. The minimal energy of the laser pulse is evaluated on the basis of the formula of the laser shock pressure and evaluation of dynamic yielding strength. The experiment is also validated. The result shows that the quantity of sheet metal deforming is nonlinearly increased with laser energy, i.e., pressure of the laser shock wave. Under a laser-induced ultra-high pressure and high strain rate, structural steels and composite materials undergo plastic deformation. __________ Translated from Journal of Nanjing University of Aeronautics and Astronautic, 2005(S1) (in Chinese)     

汽车覆盖件冲压成形仿真研究进展

汽车覆盖件冲压成形仿真技术的发展,突破了原有汽车冲压件模具及工艺设计的设计方法,对保证工件质量、减少材料消耗、缩短产品开发周期、降低制造成本具有重要意义.概述了目前汽车覆盖件冲压成形仿真所涉及到的热点领域,如摩擦与接触、回弹分析、模具系统和工艺参数、材料屈服模型和板料形状设计,讨论了这些领域的研究进展和进一步研究的发展方向.     

Improvement of formability for the incremental sheet metal forming process

In order to obtain competitiveness in the field of industrial manufacture, a reduction in the development period for the small batch manufacture of products is required. In order to meet these requirements, an incremental sheet metal forming process has been developed. In this process, a small local region of a sheet blank deforms incrementally by moving a hemispherical head tool over an arbitrary surface. In this work, an incremental sheet metal forming process controlled three dimensionally by a computer has been accomplished. It has been shown by the experiments that a sheet blank is mainly subject to shear-dominant deformation. Therefore, the final thickness strain can be predicted. The uniformity of thickness throughout the deformed region is one of the key factors to improve the formability in the sheet metal forming processes. Using the predicted thickness strain distribution, the intermediate geometry is decided in the manner that a shear deformation is restrained in the highly shear-deformed region and vice versa. This double-pass forming method is found to be very effective so that the thickness strain distribution of a final shape can be made more uniform.     

薄板类零件加工变形的解决方法

薄板类零件在现代产品中的应用非常广泛,针对使用传统的加工工艺、加工设备加工薄板类零件,易造成零件变形的情况。先从薄板类零件变形的类型和原因着手分析,进而从加工工艺、加工技术条件、加工刀具、装夹方法几个方面研究薄板类零件加工变形的解决方法,从而达到减小加工变形的目的。     

激光冲击软模大面积微弯曲成形方法

为了实现金属箔板大面积微弯曲成形,本文结合激光冲击微弯曲成形技术与软模成形技术的优点,提出了激光冲击软模大面积微弯曲成形方法。 该方法是在脉冲激光冲击波压力下,将软模作为柔性冲头作用于金属箔板来实现工件成形的。实验中使用了Innolas Gmbit公司生产的Spitlight 2000 THG脉冲激光器,将250 μm厚的聚氨酯橡胶薄膜作为软模,采用德国LPKF-ProtoMat-C60型雕刻机在印刷电路板上加工出深度为120 μm的U型多槽模具,实现了在厚度为30 μm的铜箔板上一次性对3个U型凹槽冲击成形。用KEYENCE VHX-1000C超景深三维显微系统进行工件观测,结果显示工件上的微成形槽具有良好的轮廓质量。以ANSYS/LS-DYNA为平台,使用有限元建模（FEM）方法对微弯曲过程进行了数值模拟。实验和模拟结果均表明,加载软模的工件与模具的U型凹槽特征在形状上更加接近,成形工件更加均匀,而且具有较好的表面质量,其最大平均成形深度可达110 μm,大于激光直接冲击成形的最大深度（88 μm）,说明使用软模提高了充型能力。     

A general forming limit criterion for sheet metal forming

The forming limit of sheet metal is defined to be the state at which a localized thinning of the sheet initiates during forming, ultimately leading to a split in the sheet. The forming limit is conventionally described as a curve in a plot of major strain vs. minor strain. This curve was originally proposed to characterize the general forming limit of sheet metal, but it has been subsequently observed that this criterion is valid only for the case of proportional loading. Nevertheless, due to the convenience of measuring strain and the lack of a better criterion, the strain- based forming limit curve continues to play a primary role in judging forming severity. In this paper it is shown that the forming limit for both proportional loading and non-proportional loading can be explained from a single criterion which is based on the state of stress rather than the state of strain. This proposed criteria is validated using data from several non-proportional loading paths previously reported in the literature for both aluminum and steel alloys. In addition to significantly improving the gauging of forming severity, the new stress-based criterion is as easy to use as the strain-based criterion in the validation of die designs by the finite element method. However, it presents a challenge to the experimentalist and the stamping plant because the state of stress cannot be directly measured. This paper will also discuss several methods to deal with this challenge so that the more general measure of forming severity, as determined by the state of stress, can be determined in the stamping plant.     

Finite element simulations of sheet metal forming under complex strain paths

Fracture is a common defect in sheet metal forming and it is essentially caused by tensile instability. This paper analyzes some experiments and theories for building forming limit diagrams of sheet metal and points out the advantages and disadvantages of current experiments and theories. According to this, a method that integrates the finite element simulation and experiment was used to research the forming limit diagrams of the sheet metal under complex strain paths. Taking the rear hanger that undergoes twice stamping as an example, the strain paths of the dangerous point of the rear hanger is investigated. Finally, the forming method of the rear hanger is confirmed. Results indicate that finite element method (FEM) can achieve the complex strain paths and different strain paths will have great impacts on the result of the sheet metal forming. __________ Translated from Journal of Jiangsu University (Natural Science Edition), 2005, 26(4): 289–293 [译自: 江苏大学学报 (自然科学版)]     

薄钢板激光焊接实验研究

通过对汽车用冷轧薄钢板的激光拼焊的实验研究表明,虽然激光焊接接头的塑性有所下降,但其焊接强度与母材相近,且其焊接影响区小,对汽车覆盖件和地板等零件的焊接具有较好的效果。     

Lubricant test methods for sheet metal forming

Sheet metal forming of tribologically difficult materials such as stainless steel, Al-alloys and Ti-alloys or forming in tribologically difficult operations like ironing, punching or deep drawing of thick plate requires often use of environmentally hazardous lubricants such as chlorinated paraffin oils in order to avoid galling. The present paper describes a systematic research in the development of new, environmentally harmless lubricants focusing on the lubricant testing aspects. A system of laboratory tests has been developed to study the lubricant performance under the very varied conditions appearing in different sheet forming operations such as stretch forming, deep drawing, ironing and punching. The laboratory tests have been especially designed to model the conditions in industrial production. Application of the tests for evaluating new lubricants before introducing them in production has proven successful and has in a number of examples assisted the substitution of environmentally hazardous lubricants by more friendly ones in industrial production.     

单点激光冲击精确成形的控制方法研究

根据单次冲击304不锈钢矩形薄板得到的激光能量与变形量的关系图,利用最小二乘法进行曲线拟合得到曲线的近似表达式.根据激光冲击成形的原理、特点,建立了激光冲击成形控制系统.冲击过程中,利用控制激光能量得到相应变形量进行多次冲击,并加入实时反馈控制,最终实现板料的单点精确成形.