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Formability of tailor-welded blanks for rate-dependent materials.

机译：用于速率相关材料的拼焊板的可成型性。

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摘要

The primary objective of the thesis is to carry out a prediction analysis on the formability of tailor-welded blanks (TWBs) for rate-dependent materials. This includes (i) the development of a modified vertex theory for the forming limit prediction of rate-dependent sheet metals, and (ii) the establishment of a systematic approach for analyzing the formability of TWBs taking fully into account their structural behaviors and weldment effects.;The study was motivated by the apparent discrepancies between the measured forming limit diagrams (FLDs) of rate-dependent sheet metals (e.g., AKDQ steel) and those predicted values using the conventional vertex theory. Therefore, in this thesis, a modification to the vertex theory is proposed to extend the capability of forming limit prediction to the rate-dependent metals. A novel form of quasi-linear stress-strain relation based on the power-hardening rule is analytically derived to model the constitutive behavior of rate-dependent materials. The stress-strain relation of rate-dependent material is then coupled into the vertex theory to deduce the critical conditions for localized necking (i.e., forming limits) of sheet metals. Forming limit test was performed to measure the FLD of AKDQ sheets. The measured FLD was compared to the prediction based on the modified theory and good agreement was observed.;Due to the structural nature of TWB, the general formability measures, such as FLD, are not simply applicable to analyzing the formability of TWB. Therefore, the thesis proposes a formability analysis of TWBs by considering the effects of their structure design and weldment properties. An experimental measurement system was established to acquire the distinctive material properties and rate-dependent mechanical data of weldment. The experimental data were then implemented into the forming simulations of TWB. The geometrical design of TWB, including weldment, were modeled and defined carefully. The newly modified vertex theory was employed to deduce the forming limits of each material region in TWB so as to identify the critical status and location of localized necking and failure of TWB. The simulation results were verified with the experimental results using both AKDQ and Al-TWBs for the case studies of rate-dependent and rate-independent materials analysis respectively.
机译：本文的主要目的是对速率相关材料的拼焊板（TWB）的可成形性进行预测分析。这包括（i）开发用于预测速率相关钣金的成形极限的改进的顶点理论，以及（ii）建立一种系统方法来分析TWB的可成形性，同时充分考虑其结构特性和焊接效果这项研究是受速率依赖的钣金（例如AKDQ钢）的测得成形极限图（FLD）与使用常规顶点理论的预测值之间的明显差异所激发的。因此，在本文中，提出了对顶点理论的改进，以将形成极限预测的能力扩展到速率相关金属。通过分析，推导了一种新的形式的基于功率硬化规则的准线性应力-应变关系，以对速率依赖材料的本构行为进行建模。然后将速率相关材料的应力-应变关系耦合到顶点理论中，以推断出钣金局部缩颈（即成形极限）的临界条件。进行成形极限测试以测量AKDQ板材的FLD。将测量的FLD与基于改进理论的预测进行比较，并观察到良好的一致性。；由于TWB的结构性质，一般可成形性度量（例如FLD）不能简单地用于分析TWB的可成形性。因此，本论文考虑结构设计和焊件性能的影响，提出了TWB的可成形性分析。建立了一个实验测量系统，以获取独特的材料性能和焊件速率相关的机械数据。然后将实验数据实施到TWB的成型仿真中。对TWB的几何设计（包括焊件）进行了仔细建模和定义。利用新近改进的顶点理论推导了TWB中每个材料区域的成形极限，从而确定了TWB局部缩颈的关键状态和位置。使用AKDQ和Al-TWB分别通过实验结果验证了仿真结果，分别用于速率依赖和速率独立材料分析的案例研究。

著录项

  • 作者

    Cheng, Chi Ho.;

  • 作者单位

    Hong Kong Polytechnic University (Hong Kong).;

  • 授予单位 Hong Kong Polytechnic University (Hong Kong).;
  • 学科 Engineering Mechanical.
  • 学位 Ph.D.
  • 年度 2010
  • 页码 429 p.
  • 总页数 429
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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