ABSTRACT Mechanical components and structures wear out as a result of friction between surfaces in relative motion. Residual stresses play an important role for the tribological performance of components since compressive residual stresses yield positive effects on wear resistance. However, the real effect of residual stresses on the tribological performance of surfaces is not entirely clear. The objective of this work is to evaluate the residual stress behavior during a pin-on-disk wear test of quenched and tempered AISI 4340 disk specimens against a counter-body of steel AISI E 52100. Tests were performed in shot peened and non-shot peened specimens in six steps and residual stresses were evaluated after each one by X-ray diffraction technique using sin2y method. The results shown that wear rate of the shot peened specimens was approximately fifty percent lower. Shot peening induced compressive residual stresses contributed to this effect even though they were modified during the pin-on-disk test.

Resumo O conhecimento das tensões residuais geradas nos processos de soldagem apresenta especial importância no desempenho das estruturas e componentes soldados, pois durante a vida em serviço eles estarão sujeitos a diferentes níveis de carregamentos, que associados aos campos de tensões residuais pré-existentes podem levar à ruptura inesperada. Neste contexto, o presente trabalho tem como objetivo estudar o nível das tensões residuais geradas em juntas soldadas, pelo processo arame tubular (FCAW - Flux Cored Arc Welding), de aço ASTM A 131 Grau A, usadas na construção naval, por difração de raios-X, usando a técnica do sen2ψ. Foi realizado um estudo comparativo das mudanças nos campos de tensões quando adotadas restrições para manter a geometria de projeto da junta, bem como uma análise numérica computacional pelo método de elementos finitos, com os resultados obtidos pelo método experimental. A maioria dos resultados das tensões residuais mostrou que houve similaridade qualitativa, na sua natureza, entre o modelo e os experimentos nas regiões da zona termicamente afetada e do metal de solda. As análises de microdureza Vickers e a caracterização microestrutural por microscopia óptica das juntas soldadas complementaram o presente estudo.

Abstract The knowledge of the residual stresses generated on the welding processes implies special relevancy in welded structures and components, because during his service life they will be working at several loading conditions that associated to the pre-existing residual stresses fields they can lead to a catastrophic failure. In this context, the present work has the purpose to study the residual stresses field generated in joints welded by the FCAW (Flux Cored Arc Welding) process, of ASTM A 131 grade A steel, used in ship construction, by X-ray diffraction, using the sin2ψ technique. It was realized a comparative study of the changes in the stress fields when adopted restrictions in order to maintain the design of the joint, as such a numerical computational analysis by the finite element method, with the results of the experimental analysis. The majority of residual stresses results had demonstrated qualitative similarity in their nature between the model and the experimental work in the heat affected region and welded zone. The Vickers microhardness analysis and microstructural characterization by optical microscopy had complemented the present work.