振動試験機を用いた溶接鋼管の疲労特性評価

抄録

It usually takes a lot of time to evaluate fatigue characteristics of welded steel pipes by fatigue testing machine commonly used. The purpose of this study is to obtain them in a short time by using a vibration testing machine. Steel pipe specimens with a joint welded by Fiber laser or TIG welding were prepared. They were fixed on a vibration testing machine in cantilever form. The force applied to a specimen by vibration testing machine is inertial force produced by specimen vibration, and then the problem is to extend the force up to testing force which is available for fatigue. To resolve it, an additional mass was attached at the tip of the specimen, and the excitation frequency was chosen at a value around the primary bending mode using the resonance curve. The vibration tests were conducted, and the relationships between acceleration amplitudes of excitation and numbers of cycles to failure were investigated. The relationships were converted into S-N curves by using relations between acceleration amplitudes and stress amplitudes. The S-N curves had a good correlation with the test results got by a regular fatigue testing machine. It was concluded that differences in fatigue characteristics of welding methods used in pipes could be evaluated in a short time.