Rapid evaluation of fatigue limit on thermographic data analysis

Abstract

Based on infrared thermography, the graphic methods such as Luong's method and Risitano's method are proved to be rapid and efficient for fatigue limit determination comparing to conventional methods. However, the determination procedure involves visual inspection so contains man-made uncertainties, which restricts their usage. In the present paper, we propose three new treatment methods in terms of relation curve between experimental temperature response (or dissipated energy) and the applied stress amplitude so as to determine the fatigue limit with uniqueness. Those three methods were all evaluated by applying to the experimental data from literature and the error of results were discussed and analyzed. In addition, numerical experiments were carried out to investigate the influence of loading stepped length and random error on each new treatment method.

Comparison of Experimental Thermal Methods for the Fatigue Limit Evaluation of a Stainless Steel

“…Moreover, regarding the use of the W and/or the Q parameters, the definition of a standardized and non-subjective procedure is beyond the scope of the paper. A possible way to overcome this weakness, reducing the uncertainty of the fatigue limit evaluation, is to adopt the iteration procedures proposed in [6,39].…”

A new model for fatigue life prediction based on infrared thermography and degradation process for CFRP composite laminates

“…(1) Parameters ρ, C, k are material constants and independent of the internal states. (2) Thermoelastic sources the only causes small fluctuations of temperature but does not contribute to mean temperature rising [39]. (3) Internal coupling source between internal variables and temperature, s ic , can be neglected [43].…”

“…where a 1 , b 1 , a 2 , and b 2 denote four empirical constants determined according to two straight lines in Fig. 1(b) [39]. σ fl is the value of maximum applied loading stress corresponding to fatigue limit [37].…”

“…(1) Determine fatigue limit In this step, the improved thermographic method three in [39] was applied here to determine the fatigue limit (Fig. 6).…”

“…In the present paper, a new fatigue life prediction model for composites materials is proposed by combining IRT data and damage accumulation process. Firstly, the improved thermographic method proposed recently [39] is used here to obtain fatigue limit rapidly. Then, a curve fitting method is used to estimate the value of the stiffness threshold under the load corresponding to the fatigue limit.…”