Papers by Keyword: Irregular Loading

Abstract: Joining aluminium alloys with the use of welding techniques often impairs their strength properties and in some cases it is very difficult or even impossible. An alternative method for joining this type of material is friction welding including FSW welding. The airplane aluminium alloy 2024-T3 is an example of material that can be welded using this method. Heat emitted during the process, which contributes to the material plasticisation in the zones of welding, causes significant changes in the material structure, thus affecting the joint properties. Fatigue life calculations of this type of joint can be performed according to different approaches. One of them is a local approach which requires knowledge of local strains or stresses within the notch zone. This paper is a presentation of exemplary results of experimental and numerical tests of strain in the zone of notch that occur in a joint under time variable loading.

Abstract: The determination of damping constitutes an essential part of the cyclic characterization of soils. While because of the damping of soils is nonlinear, ie., strain-dependent, the definition of shear strain amplitude under irregular loading process construct the key point of the damping based cyclic models. This paper introduces a new damping-based model (DBM) for nonlinear soil behavior simulation and discusses on the effect of shear strain amplitude definition on model behavior. Both qualitative and quantitative analysis re-sults show that the reversed hysteresis loading curve is significantly influenced by the pre-supposed loading amplitude and generally large pre-proposed shear strain amplitude will lead to low reversed loading trajectory. Analytical comparison among several definitions indicates that defining the maximum reversal point of history as the loading amplitude performs the best.

Abstract: A series of low-cycle fatigue experiments of axial-torsional loading of variable amplitudes were performed on the tubular specimens of 304 stainless steel. Two models of multiaxial low-cycle fatigue life, KBM and FS method, are evaluated based on the fatigue life data of 304 stainless steel. Rainflow cycle counting and the Liner Damage Rule are used to calculate fatigue damage. It was shown that the part prediction results are nonconservative for the two models. The life prediction is done again based on the weight function critical plane method for the two models. The prediction results are better by using the weight function critical plane method than the previous results for KBM model. But the prediction results are improved little for FS model in spite of the weight function critical plane method being used.