Issue 27

L. Marsavina et alii, Frattura ed Integrità Strutturale, 27 (2014) 13-20; DOI: 10.3221/IGF-ESIS.27.02 13 Focussed on: Infrared Thermographic Analysis of Materials A review of using thermoelasticity for structural integrity assessment L. Marsavina Department Strength of Materials, Politehnica University of Timisoara,Blvd. M. Viteazu, nr.1, Timisoara 300222 Romania. msvina@mec.upt.ro R.A. Tomlinson Department of Mechanical Engineering, University of Sheffield, Mappin Street, Sheffield S1 3JD, UK. r.a.tomlinson@sheffield.ac.uk A BSTRACT . The advances in the use of thermoelastic stress analysis (TSA) for fracture mechanics assessment are reviewed. The development of techniques to determine stress intensity factor is presented followed by the application of these techniques to fatigue crack growth, crack closure and the study of mixed mode cracks. K EYWORDS . Thermoelastic Stress Analysis; Crack; Fatigue; Stress intensity factor range. I NTRODUCTION hermoelastic Stress Analysis (TSA) has been developed over last two decades to be a useful method for structural integrity assessment, Harwood and Cummins [1]. Using a sensitive infra-red detector, minute temperature changes due to the thermoelastic effect are detected from around the tip of a crack under cyclic load. The signal from the detector, S , is related to the first stress invariant by the following equation: 1 2 ( ) AS      (1) where A is a calibration constant. An expression for this first stress invariant in the region of the crack tip can be derived from stress field equations and used to determine the stress intensity factors. A typical un-calibrated thermoelastic map from a crack of 15 mm length loaded in mixed mode with  K II /  K I = 1 is shown in Fig. 1. Figure 1 : Thermoelastic data around a 15 mm crack loaded in mixed mode with applied mixed mode ratio  K II /  K I = 1. T