Crack initiation in VHCF regime on forged titanium alloy under tensile and torsion loading modes

Abstract

This paper is focused on the VHCF behavior of aeronautical titanium alloy under tensile and torsion fatigue loadings. Tensile tests were carried out with two different stress ratios: R = À1 and R = 0.1. Both surface and subsurface crack initiations were observed. In the case of subsurface crack initiation several fatigue life controlling mechanisms of crack initiation were found under fully-reversed loading conditions: initiation from (1) strong defects; (2) 'macro-zone' borders; (3) quasi-smooth facets and (4) smooth facets. Tests with stress ratio R = 0.1, have shown that initiation from the borders of 'macro-zones' becomes the dominant crack initiation mechanism in presence of positive mean stress. Like for the tensile results, surface and subsurface crack initiations were observed under ultrasonic torsion in spite of the maximum shear stress location on the specimen surface. But the real reason for the subsurface crack initiation under torsion was not found.

VHCF response of as‐built SLM AlSi10Mg specimens with large loaded volume

“…10 However, there are still very few results on the VHCF behavior of SLM parts, 11,12 even if the number of machinery components that may sustain VHCF is rapidly increasing in the last years (see, e.g., the numerous applications where high frequency vibrations are present). [13][14][15][16][17][18][19] For these reasons, the experimental assessment of the VHCF response of AM parts is currently of utmost interest between researchers and industries working in the AM field and would permit a proper and safe design of AM components subject to fatigue loads for very high number of cycles.…”

Determination of the Critical Plane and Assessment of Fatigue Durability Under Various Cyclic Loading Regimes

“…В настоящее время установлено, что относительно небольшие циклические напряже-ния (меньшие классического предела усталости материала), действующие с высокой час-тотой (порядка 1 кГц и выше), могут приводить к разрушению конструкций [21][22][23][24][25]. Вы-сокочастотное нагружение приводит к значительным наработкам (N ~ 10 В последние годы разработаны и реализованы методики СВМУ испытаний [25-27] для весьма ограниченного набора циклических нагружений, в первую очередь для ревер-сивного и пульсирующего растяжения-сжатия [26, 27], а также кручения образцов [28][29][30].…”

Effect of forging process on high cycle and very high cycle fatigue properties of TC4 titanium alloy under three‐point bending

“…The deformation degree and deformation rate also affect the α phase and β phase ratio, shape, size, and distribution 25,26 . In 2016, Nikitin et al 27 studied the very high cycle fatigue crack initiation mechanism of forging treated VT3‐1 titanium alloy under tensile ( R = 1, R = 0.1) and torsional fatigue loading. It was found that crack initiation could be observed on the surface and subsurface under both loading modes.…”