Towards Predictive Control of Extrusion Weld Seams: An Integrated Approach
Towards Predictive Control of Extrusion Weld Seams: An Integrated Approach
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DOI：
10.4028/www.scientific.net/kem.424.9
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发表时间：
2009-12
期刊：
影响因子：
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通讯作者：
A. D. den Bakker;R. Werkhoven;W. Sillekens;L. Katgerman
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文献类型：
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作者：
A. D. den Bakker;R. Werkhoven;W. Sillekens;L. Katgerman
纵向焊缝是用分流模生产的中空挤压件的固有特征。纵向焊缝的形成是一个固体连接过程，由挤出模具中的局部条件控制。作为挤出横截面内的最弱区域，期望实现这些焊缝的足够特性。在我们的研究中，焊缝完整性指标的概念，作为一种手段，量化粘接效率的介绍。该指标的值取决于多个因素：模具焊接室内的材料流动、作用于焊接平面的足够压力水平以及最终金属微观结构的演变。焊接条件的优化导致焊缝完整性指标的更高值，从而改善焊缝性能。本文提出的研究的目的是评估这一概念的可行性。在实验室规模的实验中，通过直接热挤压工艺将AA6060和AA6082铝合金坯料成形为带材。通过利用分流模，形成中心纵向焊缝。研究了焊接室的不同几何形状和工艺条件对焊缝质量的影响。通过机械测试对这些焊缝进行表征，重点关注焊缝区域在塑性不稳定性发生后适应塑性变形的能力，以及微观结构分析，以深入了解粘合性能。该表征的结果为焊缝指示器的估计提供了基础。通过计算机模拟，计算出与焊缝形成有关的特定工艺条件，并与实验结果相关联。实验结果清楚地表明，焊缝形成是由上述因素的组合控制的。通过有限元模拟验证，这些条件的不充分满足是导致焊缝质量较差的原因，与焊缝完整性指标的低值相关。通过进一步阐述的概念，在这项工作中，焊缝完整性指标的发展，未来的目标是通过有限元模拟预测焊缝性能。
Longitudinal weld seams are an intrinsic feature in hollow extrusions produced with porthole dies. The formation of longitudinal weld seams is a solid bonding process, controlled by the local conditions in the extrusion die. Being the weakest areas within the extrusion cross section, it is desirable to achieve adequate properties of these weld seams. In our research, the concept of a weld seam integrity indicator as a means of quantifying bonding efficiency is introduced. The value of this indicator depends on a number of factors: the material flow within the die weld chambers, an adequate pressure level acting on the weld planes and finally the evolution of the metal microstructure. Optimisation of the welding conditions leads to a higher value of the weld seam integrity indicator and thus to improved weld seam properties. The objective of the research presented in this paper is to assess the feasibility of this concept. In lab-scale experiments, AA6060 and AA6082 aluminium alloy billets were formed into strips by means of the direct hot extrusion process. By utilising porthole dies a central longitudinal weld seam is formed. The effect of different geometries of the weld chamber and the processing conditions on the quality of the weld seam are investigated. Characterisation of these weld seams through mechanical testing, focusing on the ability of the weld seam area to accommodate plastic deformation following the onset of plastic instability, and microstructural analysis provides insight into bonding performance. The outcome of this characterisation provides a basis for an estimation of the weld seam indicator. Through computer modelling, the particular process conditions related to weld seam formation are calculated and correlated with the experimental results. The experimental results clearly demonstrate that weld seam formation is controlled by a combination of factors as described above. Inadequate fulfilment of these conditions, verified by the FE-simulations, is the cause of inferior weld seams, associated with low values of the weld seam integrity indicator. Through further elaboration of the concepts presented in this work, the weld seam integrity indicator is to be developed, with the future aim of predicting the weld seam performance through finite element simulations.