FATIGUE LIFE OF ADDITIVE TITANIUM ALLOY UNDER STRESS CONCENTRATION CONDITIONS

Abstract

The paper presents a numerical and experimental study of the cyclic durability of titanium alloy VT6 obtained using modern additive printing technology. In particular, the additive method of cold metal transfer during wire-arc surfacing was used. After printing, the deposited workpiece was subjected to a temperature annealing procedure to relieve residual stresses. Samples with double-sided fillets were cut out using electrical discharge cutting in three different directions relative to the direction of plate growth. Using a stereo microscope, the surface roughness after electrical discharge cutting was measured. To study the effect of stress concentration on mechanical behavior under low-cycle fatigue, cyclic tests were carried out using the equipment of the Center for Experimental Mechanics of Perm National Research Polytechnic University. For vertical, horizontal and diagonal orientations of the samples, the dependences of cyclic durability on the amplitude of the applied stresses were constructed. It is shown that the direction of the cut does not significantly affect the characteristics of resistance to low-cycle fatigue of the additive titanium alloy VT6 in the presence of stress concentration. Based on numerical modeling, a comparison was made between the results of cyclic tests and the results obtained on samples with a one-sided chamfer. It was demonstrated that the quality of the sample surface treatment at high values of normal stresses does not significantly affect the cyclic durability. With a decrease in the stress amplitude, a greater durability was obtained on polished samples.