Papers by Keyword: Fatigue Failures

Abstract: The problem of the foundation design of the reciprocation compressor with four cylinders is investigated. Some useful terms are retained, which include possible vibration modes, fatigue failures, environmental demands etc. The selection foundations are typical and commonly used in many industry plants. Cross references have been made to other parts of the paper at each design step in order to illustrate the utilization of previously derived formulae.

Abstract:
Destructive accident sometimes takes place though the equivalent stress is rather low in the viewpoint of strength of materials. The propagation of fatigue cracks under multi-axial stress state and cycling load gives the reason. Fatigue fracture has been considered as one of the most commonly encountered industrial problems that lead to the damage of components in engineering products. In general, the machine structure is always under stress concentration or stress cycles. Moreover, the structure material is usually under two axes or multi-axial stresses instead of uniaxial stress state. It is important, therefore, to clarify the propagation behavior and the fatigue failure problem of the crack under the multi-axial stresses and cycling load from the safety reliability and accident prevention measure. In this study, a biaxial fatigue experimental device was developed which can carry out a wide range of fatigue tests under biaxial stresses. The developed experimental device was identified with a biaxial fatigue experiments including static uniaxial and biaxial tensile test by using the aluminum alloy flat plate as specimens. The propagation behavior of fatigue crack for center notched cruciform specimen in the equal biaxial fatigue test was verified.

Abstract: Large welded structures, including ships and offshore structures, are normally in operation under cyclic fatigue loadings. These structures include many geometric as well as material discontinuities due to weld joints, and the fatigue strength at these hot spots is very important for the structural performance. In the past, various Non-Destructive Evaluation (NDE) techniques have been developed to detect fatigue cracks and to estimate their location and size. However, an important limitation of most of the existing NDE methods is that they are off-line; the normal operation of the structure has to be interrupted and the device often has to be disassembled. In this study, a new impedance-based structural health monitoring system employing piezoceramic transducers is developed with a special interest in applying the technique for welded structural members in ship and offshore structures. In particular, the impedance-based structural health monitoring technique that employs the coupling effect of piezoceramic (PZT) materials and structures is investigated.