The present paper evaluates the Thermoelastic and Second Harmonic signals acquired on a fatigue cycling Single Edge Notched Tension sample made of stainless steel AISI 304L. Three load ratios are in particular investigated: R=-1, 0, 0.1. The thermoelastic signal is used to evaluate the Stress Intensity Factor via two approaches: the Stanley-Chan linear interpolation method, and the over-deterministic least square fitting method using a Williams’ series expansion stress function. Some outputs of the present investigation include: the evaluation of an iterative procedure to localize the crack tip position from thermoelastic maps; an evaluation of the influence of the number of terms retained in the William’s solution (up to 20), in relation with the extent of the least-square fitting data input area, on the values of Stress Intensity Factor and T-stress; some insights on the influence of negative R-ratios and crack-closure. The present study also proposes an original interpretation of the Second Harmonic signal observed on the wake of the crack, which enables also the possibility to use this parameter to reveal the presence and extent of crack-closure.

Investigation of the crack tip stress field in a stainless steel SENT specimen by means of Thermoelastic Stress Analysis

M. Ricotta;G. Meneghetti
2019

Abstract

The present paper evaluates the Thermoelastic and Second Harmonic signals acquired on a fatigue cycling Single Edge Notched Tension sample made of stainless steel AISI 304L. Three load ratios are in particular investigated: R=-1, 0, 0.1. The thermoelastic signal is used to evaluate the Stress Intensity Factor via two approaches: the Stanley-Chan linear interpolation method, and the over-deterministic least square fitting method using a Williams’ series expansion stress function. Some outputs of the present investigation include: the evaluation of an iterative procedure to localize the crack tip position from thermoelastic maps; an evaluation of the influence of the number of terms retained in the William’s solution (up to 20), in relation with the extent of the least-square fitting data input area, on the values of Stress Intensity Factor and T-stress; some insights on the influence of negative R-ratios and crack-closure. The present study also proposes an original interpretation of the Second Harmonic signal observed on the wake of the crack, which enables also the possibility to use this parameter to reveal the presence and extent of crack-closure.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11577/3300317
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