Evaluation of plastic strain work and multiaxial fatigue life in CuZn37 alloy by means of thermography method and energy-based approaches of Ellyin and Garud
Evaluation of plastic strain work and multiaxial fatigue life in CuZn37 alloy by means of thermography method and energy-based approaches of Ellyin and Garud
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DOI：
10.1111/ffe.12854
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发表时间：
2018-06
影响因子：
3.7
通讯作者：
D. Skibicki;A. Lipski;Ł. Pejkowski
中科院分区：
文献类型：
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作者：
D. Skibicki;A. Lipski;Ł. Pejkowski
在多轴载荷的情况下，使用不同的模型来预测疲劳寿命。通常，它们分为 3 个子组：基于应力的高循环状态、基于应变的低循环状态和基于能量的模型，这些模型被认为是最通用且适用于高循环和低循环状态的模型。基于能量的模型的应用需要了解塑性应变期间耗散的能量以及弹性应变能。该能量的计算又需要指定应力和应变张量分量。然而，确定真实物体中作用的应力是一项复杂的任务。本文试图回答热成像是否能够确定低周单轴和多轴疲劳试验（包括非比例载荷）中的塑性应变能的问题。第二个问题是是否可以使用这种方法来预测疲劳寿命。为此，在 CuZn37 黄铜上进行疲劳测试期间，使用热成像相机记录了温度变化的历史。在此基础上，接下来计算疲劳载荷循环中消耗的塑性应变能密度值。将这些值与根据力和扭矩测量确定的磁滞回线计算的值以及用双轴引伸计测量的应变进行比较。通过应用 2 个模型，应变能密度进一步用于预测疲劳寿命：基于能量的 Ellyin 模型和基于应变的模型，其中能量用作非比例因子。将预测的疲劳寿命与实验的疲劳寿命进行比较。结果可以说是非常令人满意的。
In the case of multiaxial loading, different models are used for prediction of fatigue life. Usually, they are divided into 3 subgroups: stress‐based for high‐cycle regime, strain‐based for low‐cycle regime, and energy‐based models, which are considered to be the most universal and applicable for both high‐cycle and low‐cycle regimes. The application of energy‐based models requires knowledge of the energy dissipated during the plastic strain, as well as the elastic strain energy. Calculation of this energy in turn requires specification of stress and strain tensor components. Determination of the stresses acting in real objects is a complicated task, however. In this paper, an attempt was made to answer the question of whether thermography enables the determination of plastic strain energy in low‐cycle uniaxial and multiaxial fatigue tests, including non‐proportional loadings. The second question was whether it is possible to use this methodology for fatigue life prediction. For this purpose, a history of temperature changes was recorded during fatigue tests conducted on CuZn37 brass, using a thermographic camera. On this basis, the values of plastic strain energy density, dissipated in the fatigue loading cycle, were calculated next. These values were compared with the values calculated from the hysteresis loops, determined from force and torque measurements, together with strains measured with a biaxial extensometer. The strain energy density was further used for prediction of fatigue life with the application of 2 models: the energy‐based model of Ellyin and a strain‐based model, where the energy was used as a non‐proportionality factor. The predicted fatigue lives were compared with experimental ones. The results can be considered as very satisfactory.