Mechanical and microstructural investigations of the biaxial Bauschinger effect in sheet metals

金属板材中双轴鲍辛格效应的机械和微观结构研究

• 批准号: 318682861
• 负责人: Professor Dr.-Ing. Martin Franz-Xaver Wagner
• 金额: --
• 依托单位: Lehrstuhl für Technische Mechanik (LTM)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2016
• 资助国家: 德国
• 起止时间: 2015-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/318682861?language=en
• 关键词: Mechanical; microstructural; investigations; biaxial; Bauschinger

The well-known Bauschinger effect refers to changes of the yield stress associated with load reversal. Numerous studies have been reported on the Bauschinger effect under uniaxial loading and on the corresponding microstructural mechanisms. However, similar effects can be expected to occur under multi-axial loading conditions, particularly during deformation of sheet metals, where such effects may well be highly relevant for forming technology. In this research project, biaxial in-plane deformation of sheet metals with a load reversal from biaxial tension to biaxial compression is studied for the first time with a focus on biaxial Bauschinger effects. Special new experimental setups were developed at Technische Universität Chemnitz, allowing for uniaxial tension and compression testing, on the one hand, and for biaxial compression-compression testing, of sheet materials, on the other hand. These new mechanical testing methods will now be used to tackle the interesting materials science challenge of documenting biaxial Bauschinger effects, and to identify their microstructural origins. As model sheet materials, technologically pure aluminum (EN-AW 1050) and DC06 steel will be used. In detailed mechanical investigations, cruciform samples will be deformed (in collaboration with partners in Erlangen) systematically to different biaxial tensile strain levels, and then smaller samples will be cut from these samples and subjected to biaxial compressive loading. Complementary Finite Element simulations will be used to analyze the corresponding stress and strain states, with a special focus on the effect of textures in the sheet materials on anisotropic material behavior. Moreover, the simulations will allow for a separate consideration of strength differential effects. Special attention in this project will be paid to the identification and quantification of the microstructural mechanisms (most importantly, the formation and annihilation of dislocation cells) that strongly affect the biaxial Bauschinger effects during the various deformation stages, by extensively using electron microscopy (SEM, EBSD, STEM, TEM, transmission Kikuchi diffraction) and X-ray diffraction methods. Furthermore, the generation and evolution of residual stresses during the loading history will be considered in detail and related to microstructural observations using X-ray diffraction. Both ex situ measurements of samples after different amounts of deformation (prior to and after the load reversal), and in situ measurements during biaxial deformation will be performed, the latter in collaboration with colleagues from Villigen, Switzerland, at the dedicated POLDI setup for neutron diffraction.

众所周知的鲍辛格效应是指屈服应力随载荷反转而发生的变化。关于单轴载荷下的包辛格效应及其微观结构机制的研究已经有大量报道。然而，在多轴载荷条件下也可能出现类似的影响，特别是在金属板变形过程中，这种影响可能与成形技术高度相关。在本研究项目中，首次研究了从双轴拉伸到双轴压缩载荷逆转时金属板的双轴面内变形，重点研究了双轴鲍辛格效应。在Technische Universität Chemnitz开发了特殊的新实验装置，一方面可以进行单轴拉伸和压缩测试，另一方面可以进行板材的双轴压缩-压缩测试。这些新的机械测试方法现在将用于解决记录双轴包辛格效应的有趣材料科学挑战，并确定其微观结构起源。作为模型板材料，技术上纯铝（EN-AW 1050）和DC06钢将被使用。在详细的力学研究中，十字形样品将（与Erlangen的合作伙伴合作）系统地变形到不同的双轴拉伸应变水平，然后从这些样品中切割出较小的样品并进行双轴压缩加载。互补有限元模拟将用于分析相应的应力和应变状态，特别关注板材中纹理对材料各向异性行为的影响。此外，模拟将允许单独考虑强度差异效应。本项目将通过广泛使用电子显微镜（SEM， EBSD， STEM， TEM，透射菊池衍射）和x射线衍射方法，特别关注在各个变形阶段强烈影响双轴包辛格效应的微观结构机制（最重要的是位错细胞的形成和湮灭）的鉴定和量化。此外，在加载过程中残余应力的产生和演变将被详细考虑，并与使用x射线衍射的微观结构观察有关。将进行不同变形量（载荷反转前后）后样品的非原位测量，以及双轴变形期间的原位测量，后者将与来自瑞士Villigen的同事合作，在专用的POLDI装置上进行中子衍射。