Fracture evaluation of square transversal section specimens subjected by torsional cyclic loads
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MRS Advances © 2019 Materials Research Society DOI: 10.1557/adv.2019.449
Fracture evaluation of square transversal section specimens subjected by torsional cyclic loads Pavel Almaguer-Zaldivar1, Patricia Zambrano-Robledo2 and José Martínez-Grave-de-Peralta3 1
Universidad de Holguín. Avenida XX Aniversario s/n. Piedra Blanca, Holguín, Cuba, CP 80700
2
Universidad Autónoma de Nuevo León, Avenida Manuel L. Barragán, No. 4904, Monterrey, México, CP 64290
3
Universidad de Holguín. Avenida XX Aniversario s/n. Piedra Blanca, Holguín, Cuba, CP 80700
ABSTRACT
In this work, the evaluation of the growth of cracks in specimens of square cross section requested by symmetrical cyclic torsion moments was performed. The specimens were manufactured from AISI 1015. A pre-crack was machined on one side to induce the crack growth. The crack length with the increase in the number of cycles was measured by means of penetrating liquids method. By means of the Finite Element Method, the stress – strain state of the specimens was simulated. The displacements in the crack tip were determined to apply the technique of the Crack Tip Opening Displacements to calculate the Stress Intensity Factor. The calculated Stress Intensity Factor was related to the dimensions of the specimen and the size of the crack to propose an equation for the shape function.
INTRODUCTION Different models of fatigue crack growth were presented in 1. A brief review of the existing methods to determine the Stress Intensity Factor (SIF) was made in 2. In 3 the calculation of the SIF in plates under uniform load was studied. The experimental results of the crack propagation trajectory in high-strength steel specimens were presented in 4. The fatigue crack growth for austenitic stainless steels were evaluated experimentally and numerically in 5. In another investigation 6, the experimental and numerical analysis of fatigue crack growth in pressure vessels were performed. In the reviewed literature, it is observed that the largest number of studies to evaluate the SIF is
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performed for failure modes I [7-11] or II [8, 10-11. In 12, an experimental and numerical study of the influence of the deviating drill on the crack propagation for mixed modes I y II was carried out. The studies in mode III are scarce 5, 10-11. When modes of fracture are combined, modes II and III can be neglected. 11 In these investigations, FEM has been used to evaluate SIF. The objective of this paper is to present an equation to evaluate the shape function in specimens of square cross section requested by symmetric cyclic torsion. A pre-crack on one side of the cross section was machined to the specimens to induce failure. By combining the experimental results and the FEM analysis the desired function was obtained. EXPERIMENT Rectangula
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