A Novel Method to Predict the Low-Cycle Fatigue Life
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TECHNICAL ARTICLE—PEER-REVIEWED
A Novel Method to Predict the Low-Cycle Fatigue Life Lihong Huang . Huan Sheng Lai . Kang Lin Liu
Submitted: 10 August 2018 Ó ASM International 2018
Abstract Since fatigue failure commonly occurs in mechanical equipment, the prediction of the fatigue life is important to ensure safety in the running cycle of production. In this paper, a method is proposed to predict the low-cycle fatigue life. The accuracy of the proposed method is compared to the strain energy criterion and Coffin–Manson/Basquin equation with three different materials. The results indicate that accuracy of the proposed method is similar to the strain energy criterion and Coffin–Manson/Basquin equation in predicting the lowcycle fatigue life.
DW DWp DWS DWt Dee =2 Dep =2 Det =2 Dr=2 r0f
Keywords Fatigue life prediction Low-cycle fatigue Strain energy criterion Coffin–Manson/Basquin equation
Introduction
List of Symbols b Fatigue strength exponent C Material constant E Young’s modulus K0 Cyclic strain hardening coefficient n0 Cyclic strain hardening exponent Nf Number of fatigue failure cycles m Material constant R2 Determination coefficient of a fitted curve Re Strain ratio
L. Huang H. S. Lai (&) K. L. Liu School of Chemical Engineering, Fuzhou University, Fuzhou 350116, Fujian, China e-mail: [email protected] K. L. Liu e-mail: [email protected] L. Huang Fuzhou University Zhicheng College, Fuzhou 350002, China
Strain energy density Plastic strain energy density Complementary energy density parameter Total strain energy density Elastic strain amplitude Plastic strain amplitude Total strain amplitude Stress amplitude Fatigue strength coefficient
Fatigue failure is one of the most normal failure modes for engineering structures under fatigue loads. Commonly, if the number of fatigue failure cycles is larger than 104, it is defined as high-cycle fatigue; otherwise, it is low-cycle fatigue. For low-cycle fatigue, the stress level is larger than the yield stress, which causes plastic deformation to occur. Hence, the fatigue life is normally described using the strain amplitude. The corresponding fatigue life estimation method is Basquin equation which uses the elastic strain amplitude to characterize the fatigue life [1]. The plastic strain amplitude has also been used to characterize the fatigue life in Coffin–Manson equation [2, 3]. The total strain amplitude prediction method is generated by the sum of Basquin equation and Coffin–Manson equation. Alternatively, the strain energy criterion is another method to predict the fatigue life for the low-cycle fatigue [4, 5]. Unlike the method of Coffin–Manson/Basquin equation, the strain energy criterion can be used in the tension– compression loading condition and in the multiaxial loading conditions [6–9]. Thus, more attention has recently been paid to the strain energy criterion to predict the
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J Fail. Anal. and Preven.
fatigue life for the low-cycle fatigue under complex loading conditions [10–14]. The method based on the critical plane concep
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