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Y.B. Shao¹, S.P. Chiew², Y. Chen¹, S.T. Lie²
Structural Longevity, Vol.3, No.3, pp. 171-189, 2010, DOI:10.3970/sl.2010.003.171
Abstract For a square tubular T-joint under axial loading, failure occurs easily along the weld toe because high stress concentration exists in this region. This phenomenon can be used to explain why brittle fracture is dominant when the joint is subjected to cyclic loading, such as faigue loading or earthquake loading. To improve the seismic resistance of a square tubular joint, collar plate can be used to reinforce the joint connection. However, the aseismic behaviour of the collarplate reinoforced tubular joint must be assessed because only the increase of the load carrying capacity can not guarantee the capacity of energy dissipation… More >

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N. Kawagoishi¹, A. Ohkubo², S. Yoshimi³, K. Yamane⁴, K. Morino⁵
Structural Longevity, Vol.3, No.3, pp. 191-199, 2010, DOI:10.3970/sl.2010.003.191
Abstract Rotating bending fatigue tests were carried out using a radical nitrided nickel base superalloy, Alloy 718, at 500 ℃, to investigate the effect of radical nitriding on the initiation and propagation behavior of a fatigue crack at elevated temperature. The nitriding was conducted at 500 ℃ for 12h which was relatively low temperature compared with other nitriding technologies. Compound layer was formed on the specimen surface with the thickness of about 4µm. Hardness of the base alloy was hardly affected by nitriding. When stress levels were high, a crack initiated from the specimen surface in the aged alloy, and the… More >

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T. Nagano¹, M. Moriyama^2,3, N. Kawagoishi⁴, Y. Kobayashi⁴
Structural Longevity, Vol.3, No.3, pp. 201-211, 2010, DOI:10.3970/sl.2010.003.201
Abstract In the present study, rotating bending fatigue tests up to 108 cycles were carried out to investigate the effects of hardness of base steel and shot and reverted austenite, γ, on the fatigue strength and the fracture mechanism in wide range of fatigue life of shot peened 3.5GPa-grade maraging steel. By shot peening, hardening and compressive residual stress were yielded in the surface layer of specimen, causing increase in fatigue strength in the wide region of fatigue life. The S — N curves showed duplex S — N properties because of the transition of fracture origin from the specimen surface… More >

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Younho Cho¹, Weibin Li¹, Bin Yang¹
Structural Longevity, Vol.3, No.3, pp. 213-219, 2010, DOI:10.3970/sl.2010.003.213
Abstract This paper aims at an experimental method for detecting thermal-damages in a tube-like structure using acoustic nonlinear parameter of ultrasonic guided waves. The material nonlinearity of aluminum pipe specimens, which have been subjected to different heat-loading cycles, is measured to characterize the microdamages. Flexible Polyvinylidene Fluoride (PVDF) comb transducers are used to generate and receive the fundamental and second harmonic waves. The amplitude of the second harmonic wave is extracted from the Fast Fourier Transform (FFT) spectrum of a received signal. The measured relative nonlinear parameter increases monotonically as a function of the propagation distance, and the relative nonlinear parameter… More >

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Hitesh Kapoor¹, James L. Blackshire², Som R. Soni³
Structural Longevity, Vol.3, No.3, pp. 221-238, 2010, DOI:10.3970/sl.2010.003.221
Abstract Damage detection in constrained geometry structures like z-pinned, co-cured composite pi-joints is established using pitch-catch ultrasound and scanning laser vibrometry measurements. Ultrasonic pitch-catch measurements consisted of a network of PZT (Lead Zirconate Titanate) sensors placed on the specimen and sensing Lamb waves at each sensor location, where measurements were taken at symmetric top and bottom sensor locations for healthy and damaged pijoint specimens. Results showed the presence of fatigue-induced bend damage of the joint as a reduced peak-to-peak amplitude response across the joint. Scanning laser vibrometry measurements were used to study the propagation of Lamb waves within the narrow, constrained… More >

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