功平衡法薄板件装配偏差传递机理研究

金属薄板零件广泛应用于汽车车身等产品中,由于影响系数法在薄板件的装配过程中不能精确分析零件偏差和装配偏差之间的关系,提出一种基于功平衡法的柔性薄板零件装配偏差分析模型。应用两个厚度不同的悬臂梁研究零件在焊接过程中的偏差变化,经分析可知焊接过程中焊枪做功相同,以此为基础建立零件偏差和装配偏差之间的基于功平衡法敏感系数矩阵。最后应用Z型薄板零件阐述了装配偏差分析过程,结果表明功平衡装配偏差分析模型的精确性。     

运用随机有限元法与正交试验的车身焊装定位点稳健设计

基于随机有限元法与正交试验设计,提出一种车身薄板件焊装夹具定位点稳健设计方法。研究车身件焊接装配过程,通过随机有限元方法,建立焊装夹具误差与零件定位偏差的关系,有效模拟出车身零件因焊装夹具产生的法向定位偏差。以夹具定位点位置为设计参数,夹具定位误差为噪声参数,设计正交试验,分析不同定位方案下零件的定位精度,确定最佳定位方案。该方法在一前围侧板的焊装案例上得以验证。     

基于曲面配准的柔性件装配偏差分析

传统柔性件装配偏差分析模型未考虑实际装配过程中装配体下架对装配偏差的影响。利用总体刚度矩阵构建装配偏差力学模型,通过曲面配准技术模拟装配夹具完全释放后的装配体形态,进而求解装配体的装配偏差,并通过飞机壁板件模型进行仿真实验,验证"装配夹具完全释放"对于装配体装配偏差分析的必要性。     

车身柔性薄板件搭边焊接接头的回弹偏差模型

当前汽车车身薄板件点焊回弹模型采用薄板端部的点接触模型,未考虑实际点焊工艺中设置的搭边量,因此不适用于实际装配质量分析。通过对柔性薄板定位装配过程的研究及实际点焊生产工艺的分析,建立了面接触搭边悬臂梁结构,并在对焊接接头受力分析的基础上提出了一种考虑搭边量的点焊回弹偏差数学模型,后与无搭边回弹偏差模型作参数敏感性对比分析。最后,通过分析矩形薄板件实例的装配偏差,表明了该偏差分析模型的有效性。     

多工位装配过程夹具系统公差和维护综合优化设计

提出一种面向二维多工位装配过程、综合考虑装配夹具系统全寿命周期成本、产品零件孔制造成本和产品质量损失成本的公差和维护综合优化方法。分析多工位装配尺寸偏差传递关系,建立多工位装配过程产品质量损失模型。然后根据4-2-1夹具定位原则,构建考虑夹具磨损过程损失的夹具定位销副偏差统计数字特征模型。继而发展了以夹具系统全寿命周期成本、零件孔制造成本和和产品质量损失成本为装配总成本最小化的定位销公差、零件孔公差与更换周期优化模型。以汽车侧围装配过程为例,分别研究定位销公差、零件孔公差、定位销更换周期、配合间隙、平均磨损率和磨损率方差对装配总成本的影响,并优化设计定位销公差、零件孔公差和定位销更换周期。所提出的综合优化设计方法比采用定位销等公差设计、零件孔等公差设计、定位销与零件孔等公差设计和定周期更换设计的装配总成本分别减少了16.25%、11.31%、39.93%和13.54%。该方法为产品装配夹具系统高质量低成本设计提供了一种新的途径。     

车身柔性虚拟装配偏差模拟分析

在轿车样车试制阶段,为了减少车身尺寸功能评估周期和降低评估成本,引入了车身的虚拟装配.针对功能评估中虚拟装配关键技术,包括装配过程夹具偏差、焊接处理及多工位装配等提出解决方案,实现了在考虑制造偏差、夹具偏差、连接偏差和多工位装配基础上的车身虚拟装配.通过案例论证了提出的虚拟装配方法的可行性.结果表明,该模型的准确度较高,适用于柔性薄板零件的装配偏差分析.     

飞机机身壁板件装配偏差分析建模

飞机机身主要由多块壁板件构成,其装配质量直接影响飞机整体性能。装配偏差模型是保证装配质量的理论工具,但对壁板件装配偏差建模的研究还不够完善。针对某型飞机壁板件串并联装配的工艺特点,考虑零件制造偏差和夹具定位偏差,利用确定性分析法分析零件刚性定位偏差,结合影响系数法及超元刚度理论进行柔性偏差分析,建立单工位下飞机壁板件串并联装配偏差模型,并分别进行偏差模型计算和装配变形仿真,通过两者结果对比验证了本偏差模型的有效性。     

基于ABAQUS的柔性薄板装配过程仿真

针对柔性薄板零件装配过程中的受力变形与接触现象,运用ABAQUS有限元软件,提出了一种柔性件装配过程仿真分析的新方法。首先通过重启动分析、数据传递技术和自由度耦合功能,模拟柔性件的实际装配过程,构建其装配过程仿真模型,该模型充分考虑了零件之间的接触及摩擦现象;然后在搭建的柔性件装配试验平台上进行柔性薄板装配过程实验,通过仿真与实验所得装配偏差数据的对比分析,验证了仿真方法的正确性。     

柔性件装配偏差的有限元分析

利用有限元法对两个刚性小、形状不同且易变形的柔性件进行装配偏差分析。采用"6-2-1"定位方式对柔性件进行定位,通过影响系数法对柔性件装配偏差进行建模,分析在焊接装配中产生的偏差。结合有限元软件Workbench和MATLAB进行仿真计算,与CATIA TAA分析结果进行对比。研究结果表明:薄板A中测量点偏差的分析结果与CATIA TAA仿真结果存在偏差,而薄板B中测量值与CATIA TAA仿真结果基本相同,验证了分析结果的有效性,为产品分析提供了方便。最后,研究了焊接点个数对柔性件装配偏差的影响,得出柔性件装配偏差随着焊接点个数的增加呈先减小、后增加的趋势。     

多工位薄板装配偏差流传递的状态空间模型

借鉴控制理论中的状态空间方法,研究多工位薄板装配过程中偏差流传递、变换和累积关系的状态空间模型.以零件偏差为状态矢量,夹具偏差为控制矢量,研究夹具偏差和零件偏差之间的对应关系以及零件在工位间转换过程中的重定位偏差,建立多工位装配过程偏差流传递的状态方程;以零件测量偏差为输出矢量,建立表征测点位置和数量的输出方程.最后通过实际零件的装配过程说明该模型的应用方法.     

Principle and Simulation of Fixture Configuration Design for Sheet Metal Assembly with Laser Welding, Part 1: Finite-Element Modelling and a Prediction and Correction Method

The quality of the stamping process has a direct effect on laser welded sheet metal assembly. The fixture plays an important role in the satisfactory metal fit-up that laser welding requires. The traditional "3-2-1" locating scheme will no longer suffice for the deformable laser sheet metal assembly process. Because of the often poor stamping quality, a complex die fixture has to be employed to meet the metal fit-up requirements. The die fixture corresponds to an "infinite-2-1" locating scheme where the tooling cost is very high and yet lacks flexibility. This limits the application of laser welding. In this paper, a new locating scheme with both total locating and direct locating for welds is proposed. A total locating scheme is used to locate the overall assembly, and a direct locating scheme is used to locate the weld location, which is critical for ensuring correct metal fit-up. A finite-element model and a prediction and correction method for the direct locator configuration are developed in this paper. A case study is used to show that the proposed method is effective for sheet metal assembly for laser welding.     

Simultaneous optimization of fixture and joint positions for non-rigid sheet metal assembly

This paper presents an optimization methodology for non-rigid sheet metal assembly variation by considering part variation, fixture variation, fixture layout, and joint positions, as well as the assembly spring back. The proposed algorithm integrates the finite element analysis (FEA) with a powerful global optimization algorithm, called the mode-pursuing sampling (MPS) method to simultaneously search for the optimal fixture and joint positions in order to minimize the assembly variation. An example application study is presented to demonstrate the optimization procedure and its effectiveness.     

Weld Pattern Design for Sheet Metal Laser Welding Considering Fixturing Quality

In sheet metal assembly by laser welding, metal fit-up is an important specification for achieving welding quality. The fixture plays an important role in satisfying the intimate metal fit-up that laser weld requires. The fixturing quality for sheet metal laser welding is directly related to the assembly weld patterns used (weld location, weld length, etc.). The design of assembly weld patterns is a critical phase in the fixture design cycle. Traditionally, the determination of the weld pattern is based on the designer’s experience. Because of this it is quite easy to cause unexpected deviations from the assembly weld quality requirements. In this study, a new computer-aided design approach for the assembly weld pattern is developed, where the sources of variation in the weld areas of the parts are considered in detail. Using this approach, the weld location and the weld length obtained are much more reasonable and cost-justified. A simple example and a case study show that the approach presented for assembly weld pattern design can reasonably meet the fixturing quality requirements.     

车身多工位装配系统可靠性评估与维护策略研究

针对车身多工位装配系统夹具的衰退过程,提出了夹具元件磨损、来料零件偏差以及定位元件配合公差等多因素集成影响下的车身装配系统可靠性评估方法。在给定车身波动阈值条件下,提出了基于可靠性模型的多工位夹具部件的动态维护策略。通过一个四工位薄板件装配案例对所提方法进行了应用验证,为夹具系统维护与车身尺寸质量控制提供了理论指导。     

薄板件焊装仿真零件定位偏差的计算方法

使用数字化匹配技术,可有效缩短新车型的开发周期、降低成本和提高车身装配质量,核心是有限元仿真模型的精度。仿真模型中定位偏差的计算是否正确,直接影响模型的分析精度,夹具偏差和零件偏差是主要影响因素,二者共同决定零件定位偏差。通过对夹具与零件偏差的相互作用分析,给出了零件定位偏差的计算方法,并利用Abaqus软件进行了焊装验证。结果表明,所述定位偏差的计算方法是正确、有效的,为进一步利用仿真分析模型进行公差分析预测,实现设计制造的并行开发提供了必要条件。     

FLEXIBLE ASSEMBLY FIXTURING LAYOUT MODELING AND OPTIMIZATION BASED ON GENETIC ALGORITHM

There are many welding fixture layout design problems of flexible parts in body-in-white assembly process, which directly cause body assemble variation. The fixture layout design quality is mainly influenced by the position and quantity of fixture locators and clamps. A general analysis model of flexible assembles deformation caused by fixture is set up based on "N-2-1" locating principle, in which the locator and clamper are treated as the same fixture layout elements. An analysis model for the flexible part deformation in fixturing is set up in order to obtain the optimization object function and constraints accordingly. The final fixture element layout could be obtained through global optimal research by using improved genetic algorithm, which effectively decreases fixture elements layout influence on flexible assembles deformation.     

A parametric study of sheet metal joints for dimensional integrity

The characteristics of joints between parts are one of the most critical issues in variation simulation analysis. This paper presents a parametric study of the dimensional variation characteristics of butt joints and slip joints. These two basic joints encompass the whole domain of joints used in sheet metal assemblies for structural extension. A geometrical model was proposed for predicting the assembly variation in order to take into consideration the possibility of part deformation and tool variation. Butt joints act like rigid bodies in the normal direction. For slip joints, the sensitivity coefficient in the slip direction is a function of tooling variations. The variation from individual part and tooling can be eliminated or substantially reduced if the product structure and assembly process is properly designed. A simple four-part assembly example shows the structure and assembly process. This result provides improved understanding of sheet metal assembly processes and provides a new idea for adaptive product and process design.     

A parametric study of sheet metal joints for dimensional integrity

The characteristics of joints between parts are one of the most critical issues in variation simulation analysis. This paper presents a parametric study of the dimensional variation characteristics of butt joints and slip joints. These two basic joints encompass the whole domain of joints used in sheet metal assemblies for structural extension. A geometrical model was proposed for predicting the assembly variation in order to take into consideration the possibility of part deformation and tool variation. Butt joints act like rigid bodies in the normal direction. For slip joints, the sensitivity coefficient in the slip direction is a function of tooling variations. The variation from individual part and tooling can be eliminated or substantially reduced if the product structure and assembly process is properly designed. A simple four-part assembly example shows the structure and assembly process. This result provides improved understanding of sheet metal assembly processes and provides a new idea for adaptive product and process design.     

Application of Bayesian networks for diagnostics in the assembly process by considering small measurement data sets

The ability of variation source diagnosis in the auto body assembly process plays an essential role in the success of the manufacturing enterprises. However, it is more challenging to identify the process faults associated with the compliant sheet metal parts based on small measurement data sets. A new Bayesian networks (BN) modeling approach under the condition of small data sets is proposed. The main causal links are identified based on mapping of the variation sensitivity matrix. The interaction effects are detected according to the conditional mutual information tests. After the network structure is determined, the Bayesian approach is used to obtain the conditional probability tables by incorporating prior probability distributions. The evaluation of diagnostic performance concerning evidence number and log-odds noise levels is also presented. A real bracket assembly case was used to illustrate the whole procedures for fixture fault diagnosis. The examined test cases demonstrate the proposed BN approach is practical and effective, even when incomplete evidences are observed and a medium-level noise is present.     

轿车车体装配尺寸偏差控制技术

基于偏差流理论,针对夹具的优化设计及鲁棒设计、柔性件装配偏差分析与综合、制造过程在线测量、故障诊断和偏差在线补偿,从设计和制造并行角度对车体偏差控制进行了系统综述,论述了面向设计和面向制造的偏差控制的辩证统一关系。结合所提出的偏差流库和偏差流检测站的概念,给出了偏差流控制的系统模型,丰富了偏差流理论。