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Fatigue Failure Criteria
Published in Ansel C. Ugural, Youngjin Chung, Errol A. Ugural, Mechanical Engineering Design, 2020
Ansel C. Ugural, Youngjin Chung, Errol A. Ugural
In the rotating-beam test, the machine applies a pure bending moment to the highly polished, so-called “mirror finish” specimen of a circular cross-section (Figure 7.4b). As the specimen rotates at a point on its outer surface, the bending stress varies continuously from maximum tension to maximum compression. This fully or completely reversed bending stress can be represented on the stress S-cycles N axes by the curves of Figure 7.4c. It is obvious that the highest level of stress is at the center, where the smallest diameter is about 0.3 in. The large radius of curvature avoids stress concentration. Various standard types of fatigue specimens are used, including those for axial, torsion, and bending stresses described in the ASTM manual on fatigue testing.
Failure and Design
Published in Zainul Huda, Metallurgy for Physicists and Engineers, 2020
In fatigue testing, a cylindrical test piece is subjected to alternating stress cycles with a mean stress of zero; the results so obtained are plotted in the form of an S-N curve (stress versus cycles to failure curve). The S-N curve is plotted with the stress amplitude (S) on the vertical axis and the logarithm of “N” on the horizontal axis (see Figure 10.8).
Fatigue Failure Criteria
Published in Ansel C. Ugural, Youngjin Chung, Errol A. Ugural, MECHANICAL DESIGN of Machine Components, 2018
Ansel C. Ugural, Youngjin Chung, Errol A. Ugural
In the rotating-beam test, the machine applies a pure bending moment to the highly polished, so-called mirror finish, specimen of circular cross section (Figure 7.4b). As the specimen rotates at a point on its outer surface, the bending stress varies continuously from maximum tension to maximum compression. This fully or completely reversed bending stress can be represented on the stress S-cycles N axes by the curves of Figure 7.4c. It is obvious that the highest level of stress is at the center, where the smallest diameter is about 7.5 mm. The large radius of curvature avoids stress concentration. Various standard types of fatigue specimens are used, including those for axial, torsion, and bending stresses described in the ASTM manual on fatigue testing.
Assessment of remaining fatigue life based on temperature-evolution measurements
Published in Nondestructive Testing and Evaluation, 2022
Atsushi Akai, Yuka Kojima, Yasumoto Sato
Figure 5 schematises the experimental setup for measuring the temperature increase in the material during torsional fatigue testing. The specimen was subjected to a fully reverse cyclic torsional loading at 50 Hz using a 10-kgf-m Schenk-type fatigue testing machine (Mori Testing Machine Co., Ltd., SE-10, Japan). The drive side of the Schenk-type fatigue testing machine consists of an electric motor, an eccentric device and a crank mechanism. The rotational movement of the eccentric device with respect to the electric motor is converted to cyclic torsional loading via the crank mechanism and then transmitted to the specimen. Changing the eccentricity of the eccentric device during testing using the controller allows the torsional angle to be tuned to produce a specified shear strain amplitude. The Schenk-type fatigue testing machine can mechanically apply cyclic torsional loading to specimens at a relatively high frequency.
Study on flexural strength, modulus, and fatigue cracking of cementitiously stabilised materials
Published in Road Materials and Pavement Design, 2018
Tirupan Mandal, Tuncer B. Edil, James M. Tinjum
Fatigue damage leads to a reduction in modulus of the CSL, thus affecting pavement response (Yeo, Vuong, & Alderson, 2002). Several researchers (Casmer, 2011; González, Jameson, de Carteret, & Yeo, 2013; Li & Dong, 2011; Litwinowicz & Brandon, 1994; Midgley & Yeo, 2008; Otte, 1978; Pretorius, 1970; Raad, 1981; Sobhan & Mashnad, 2003; Wang, Zhang, Xu, & Jian, 2011) have studied the fatigue behaviour of cement-stabilised soils. According to AASHTO T321 (2014), the fatigue life (N) is defined as the total number of load repetitions that causes a 50% decrease in initial stiffness or modulus. The objective of a fatigue test is to determine the fatigue life and/or the initiation of failure (Weibull, 1961). Flexural fatigue testing is typically used for determining fatigue characteristics of bound material that undergoes repetitive bending in transportation infrastructure, such as concrete and asphalt, and can be considered for cement-stabilised materials. Fatigue and resilient response of material in the pavement structure are important aspects for determining required maintenance frequency and the life cycle of bound layers (Huang, 2004).
Evaluation of mode II fatigue disbonding using Central Cut Plies specimen and distributed strain sensing technology
Published in The Journal of Adhesion, 2019
Fabricio N. Ribeiro, Marcias Martinez, Calvin Rans
The main objective of this work is to perform a critical evaluation of the Central Cut Plies specimen as a potential candidate for mode II fatigue testing of bonded composite structures. For this evaluation, two main aspects were focused on: (i) assessing the suitability of different measurement techniques for observing disbond growth and (ii) evaluating the influence of specimen geometry and materials on the fatigue testing capabilities. These main aspects are investigated using a combination of experimental, numerical and analytical techniques.