Prediction of Residual Life Assesment Using Thermography and Crack Growth Analysis

Abstract

The most important characteristics for service safety of complex metal structures are those describing crack initiation and growth caused by static or dynamic, variable loading. Crack initiation and growth is subject of numerous investigations by different methods. The paper shows the possibility of applying infrared thermography to the problems of fracture mechanics. The main aim of testing was to qualitative relate the temperature changes of the spacemen measured by infrared thermography with the evaluation of fatigue cracks in steel specimen. Based on the distribution of temperature on the surface of the sample, during the action of force, the spread of plastic zones and crack tip are determined. The increase of temperature produced by the plastic deformation at the crack tip has been measured by infrared camera Thermal CAM SC640, FLIR Systems. SE(B) specimens were tested in three-point bending (TPB), following the procedures of ASTM E1820, on electrical mechanical testing machine with crack tip opening displacement (CTOD) control, at room temperature. Numerical simulation of stress distribution on the same model under same condition is presented, too. The results showed that thermography is a method suitable for monitoring and prediction of crack initiation and growth, as well as critical stress in elastic and elastic-plastic deformations. Fatigue crack growth behaviour of cracked TPB specimen made of S355 J2 G3 steel using Paris relation is considered.