The influence of residual stresses on welded joints and other inhomogeneous materials with cracks

Abstract

Residual stresses in many structural components are often produced during the fabrication or bonding processes, due to the cooling from elevated temperatures. Examples for such behavior are: welded and soldered joints, composites, functionally graded materials, coatings, etc. The residual stresses in these materials affect the stress and strain fields in the vicinity of the crack tip, thus making the crack driving force to become different compared to a material without residual stresses. In this paper, the influence of residual stresses is analyzed using FEM software ABAQUS and post processing routine based on the method of configurationally forces. A previous application of this method has included investigations on the influence of mechanical in homogeneities (Young's modulus, yield stress, hardening coefficient) in welded joints of high-strength low-alloyed steels (HSLA). However, these analyses did not include the effect of in homogeneity in thermal properties (coefficient of thermal expansion). The main goal of this paper is to find out the effect of thermally induced residual stresses on the crack driving force in biomaterials and to use the obtained data to improve the integrity and work safety of welded and other inhomogeneous structures.

Zaostali naponi u mnogim konstrukcijama nastaju tokom hlađenja u procesu proizvodnje ili spajanja materijala. Primeri su: zavareni i zalemljeni spojevi, kompoziti, materijali sa izraženom anizotropijom, prevlake i dr. Zaostali naponi u slučaju ovakvih materijala utiču na polje napona i deformacija u okolini vrha prsline i dovode do promene vrednosti sile rasta prsline u odnosu na materijal bez zaostalih napona. U ovom radu, uticaj zaostalih napona je analiziran metodom konačnih elemenata, primenom programskog paketa ABAQUS, uz korišćenje postprocesorskog programa razvijenog primenom metode konfiguracionih sila. Ovaj pristup je ranije primenjen na ispitivanje uticaja nehomogenosti mehaničkih osobina (modula elastičnosti, granice tečenja, koeficijenta deformacionog ojačavanja) na spojeve niskolegiranih čelika povišene čvrstoće, ali bez uzimanja u obzir nehomogenosti koeficijenta termičkog širenja materijala. Cilj ovog rada je analiza uticaja termički unetih zaostalih napona na silu rasta prsline u bimaterijalnim spojevima i korišćenje dobijenih rezultata za obezbeđenje integriteta i sigurnog rada zavarenih konstrukcija i struktura sastavljenih od više materijala.