STUDY AND COMPARISON OF FATIGUE AND CRACK PROPAGATION IN WELOMETAL PRODUCED BY SOME M.M. A.W. BASIC AND RUTILE ELECTRODES

Abstract

All the engineering components are subjected to cyclic loading under service conditions, and it has been estimated that 90% of the failures which occure in Engineering components can be attributed to fatigue. Hence for safe working condition it is necessary to know the fatigue behaviour of the components and materials. The objective of this dissertation is to study the fatigue behaviour of weld metal of rutile and basic electrodes from three different manufacturers and to compare them. Secondly and main purpose of selecting these electrodes is to study the influence cf strength and toughness on the fatigue properties. For the later purpose two electrodes having same ultimate strength but difkerent toughness are selected. In addition to above, fatigue crack pro-pagation in these electrode weld metal is to be studied, also their fracture toughness (R curve) is to be correlated with existing standards for steels and their conventional toughness. The investigation is carried out on specimens prepared from the welds produced by the electrodes to be tested. V and U notches are provided on the specimens and SN curves for pulsating bending load are plotted for both type of notches with failure criteria of crack initiation. The specimens o± the two electrodes (basic and rutile) having same tensile strength are further used to study crack propagation and compare fracture toughnesso After investigation it has been concluded that fatigue strength of the rutile electrodes seems to be ultimate strength governed whereas in the basic electrodes it is toughness governed. For same ultimate strength the basic electrode has better endurance limit but the rutile electrode is superior with respect to resistanc, against cyclic crack propagation. Considering all safety relevant parameter one basic electrode can be identified which has optimum static and cyclic strength, as well as toughness properties