A new approach to estimate the fatigue behavior of welded joints

M.D. CHAPETTI; L. JAUREGUIZAHAR

Rosario

Congreso; 11° Congreso Binacional de Metalurgia y Materiales - SAM-CONAMET 2011; 2011

Sociedad Argentina de Materiales - SAM

The present work is concerned with an attempt to predict the fatigue strength of welded joints by means of a fracture mechanics approach that includes the fatigue crack propagation threshold for both short and long cracks. The methodology [9], previously developed to analyze the short crack behavior in plane componentes, estimates the threshold for fatigue crack propagation as a function of crack length, ΔΚth, and the fatigue crack propagation rate as the difference between the applied driving force, ΔΚ, and ΔΚth, as follows: ()mthmKKCdNdaΔ−Δ= (4) In this expression the threshold for crack propagation is a function of crack length. This work analyses the applicability of expression (4), that allows to include the short crack behavior, to study the fatigue strength of welded joints. The influence of parameters like plate thickness, initial crack length and reinforcement angle on fatigue strength of butt-welded joints has been analyzed in previous publication, and results have shown good agreement with experimental results and trends. In this paper a brief description of an example of those previous analyses is presented [10]. Then, especific butt-joints configurations are tested and studied. In order to verify the ability of the methodology to estimate the fatigue behaviour of welded joints, a dedicated experimental methodology was implemented for the detection and monitoring of the development of surface small cracks initiated at weld toes. Good agreement was observed for the total monitored crack range, allowing the comparition of the ex-perimental results with the estimated ones.