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Fatigue modeling for wrought magnesium structures with various fatigue parameters and the concept of highly strained volume
Continuum Mechanics and Thermodynamics ( IF 2.6 ) Pub Date : 2020-04-22 , DOI: 10.1007/s00161-020-00884-2
A. Nischler , J. Denk , O. Huber

Mechanical fatigue tests of unnotched, notched, and bending twin-roll cast AZ31B magnesium alloy specimens are performed in which strain fields are analyzed with digital image correlation. Clearly, delimited macroscopic bands of twinned grains (BTGs) in which the compressive strain is significantly higher compared to the adjacent regions are observed. Conventional fatigue parameters, e.g., the strain amplitude, exhibited higher values within the BTGs. This findings are confirmed by the fact that for all investigated specimens the initial macroscopic cracks are observed within the BTGs. Consequently, for the presented concept of highly strained volume, fatigue parameters are determined from the highly strained regions with high strain amplitudes. This paper focuses on the application of the effective strain amplitude fatigue parameter decomposed in an elastic and plastic portion, the Smith-Watson-Topper fatigue parameter and energy-based fatigue parameters within the concept of highly strained volume. An extended stress–strain hysteresis model is presented to compute stress–strain hystereses for arbitrary load ratios, required to determine the mentioned fatigue parameters. The application and evaluation of five different fatigue parameters within the concept of highly strained volume demonstrates the accurate description of the fatigue life until failure.



中文翻译:

具有各种疲劳参数的变形镁结构的疲劳建模和高应变体积的概念

对未开槽,开槽和弯曲的双辊铸造AZ31B镁合金试样进行了机械疲劳测试,并通过数字图像相关分析了应变场。显然,观察到孪晶晶粒(BTG)的有限宏观带,其中的压缩应变比相邻区域高得多。传统的疲劳参数(例如,应变幅度)在BTG中显示出较高的值。对于所有研究的样品,在BTG内都观察到了最初的宏观裂纹,这一事实证实了这一发现。因此,对于提出的高应变体积的概念,从具有高应变幅度的高应变区域确定疲劳参数。本文重点研究在弹性和塑性部分中分解的有效应变振幅疲劳参数,Smith-Watson-Topper疲劳参数和基于能量的疲劳参数在高应变体积概念中的应用。提出了扩展的应力-应变滞后模型,以计算确定上述疲劳参数所需的任意载荷比的应力-应变滞后。在高应变体积概念内对五个不同疲劳参数的应用和评估证明了疲劳寿命直至失效的准确描述。提出了扩展的应力-应变滞后模型,以计算确定上述疲劳参数所需的任意载荷比的应力-应变滞后。在高应变体积概念内对五个不同疲劳参数的应用和评估证明了疲劳寿命直至失效的准确描述。提出了扩展的应力-应变滞后模型,以计算确定上述疲劳参数所需的任意载荷比的应力-应变滞后。在高应变体积概念内对五个不同疲劳参数的应用和评估证明了疲劳寿命直至失效的准确描述。

更新日期:2020-04-23
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