Papers by Keyword: Strain Amplitude

Abstract: Vibration systems require the damping materials operating at high service temperature. In this paper, damping performance of HT100, M2052 and S316L at 350K were evaluated by applying different frequencies, strain amplitudes and heating rates. It is found that the internal friction dependence of frequency of HT100, M2052 and S316L all show a characteristic of Check function, and the resonance frequency has a negative linear correlation with the material physical parameters. The strain amplitude as well as heating rate has no obvious effect on the resonance frequencies of the materials, but significantly enhance the internal friction of the interface damping alloys such as M2052 and HT100, but small on single-phase alloys such as S316L. The internal friction mechanism for HT100 and M2052 are of static hysteresis at 350K, and HT100 and M2052 are applicable candidates for working at temperatures around 350K from the viewpoint of vibration reduction.

Abstract: The effects of strain amplitude variation on the functional properties of a superelastic NiTi wire were investigated in terms of critical stress to induce martensite, accumulated residual strain, dissipated energy, lower plateau stress, and stress at maximum strain. Wire specimens were subjected to training by pseudoelastic cycling, being mechanically strained up to strain amplitudes of 4, 6, 8, 10, 12 and 14%. A total of 20 cycles were performed at each condition at room temperature and strain rate of 10^-3s^-1. In order to assess if the wires were able to maintain stable their functional properties after training, samples subjected to cycling at 8 and 14% strain amplitudes were aged at room temperature and retested. The results showed that the functional properties tend to stabilize faster when the alloy is subjected to lower strain amplitudes. It was observed that part of the functional properties was recovered if aged at room temperature.

Abstract: Vibration and noise are the dangers for equipment, human health and environment. Developing of a new Mg matrix composite with high damping performance and high strength rate has been acknowledged as an important approach for the reduction of vibrations and prevention of noise. In this paper, xHA/Mg-3Zn-0.5Zr (x=0.5wt.%, 1wt.%, 1.5wt.%) composites were prepared by vacuum induction melting and hot extruding. The microstructure and damping performance were observed and measured using an optical microscope and a dynamic thermomechanical analysis apparatus (DMA), respectively. The influence of HA and environmental factors (temperature, frequency and strain amplitude) on the damping performance of HA/Mg-3Zn-0.5Zr composites were studied. The results showed that the damping performance of HA/Mg-3Zn-0.5Zr composites increased with increasing HA content and strain amplitude. The damping mechanism was in line with the G-L theory and interface damping theory. The damping values were strongly amplified at 150-300°C. The plot of damping versus temperature showed a peak for the Mg-3Zn-0.5Zr-1HA composite at 235°C. The low frequency damping values of xHA/Mg-3Zn-0.5Zr were higher than the high frequency damping values. It is suggested that the change of damping by a variety of external factors is due to the presence of different dominant damping mechanism at different conditions. Furthermore, it was found that at increased HA content, the grain size of HA/Mg-3Zn-0.5Zr composites decreased and the tensile strength and elongation of HA/Mg-3Zn-0.5Zr composites improved. This work will be beneficial for the study of Mg based joint implant materials with high vibration damping performance.

Abstract: The uniaxial and multiaxial non-proportional cyclic experiments of 16Mn steel under strain-control were carried out using MTS809 machine and Teststar control system. Cyclic softening was observed for 16Mn steel under strain-control cyclic loading. The restraining effects of mean strain, strain amplitude, non-proportional loading path and their histories to subsequent cyclic softening were revealed, and some useful conclusions for establishing constitutive model of non-proportional cyclic were obtained.

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: The uniaxial and multiaxial non-proportional cyclic experiments of 16Mn steel under strain-control were carried out using MTS809 machine and Teststar control system. Cyclic softening was observed for 16Mn steel under strain-control cyclic loading. The restraining effects of mean strain, strain amplitude, non-proportional loading path and their histories to subsequent cyclic softening were revealed, and some useful conclusions for establishing constitutive model of non-proportional cyclic were obtained

Abstract: Through tensile tests of shape memory alloy(SMA) wires, bars and plates, this paper analyzes hysteretic energy-dissipating capacities of these smart SMA materials in cyclic loading conditions. According to the test results, this article demonstrates the influence on energy dissipating capacity of SMA wires, bars and plates by different strain amplitudes, loading frequencies, cyclic numbers and pre-strains, then obtains change rules of hysteretic energy-dissipation. The test results show that the SMA wires is better than the other two SMA bars and plates, the SMA wires, bars and plates had better to be training before civil engineering application.

Abstract: An investigation on low frequency strain amplitude dependence damping characteristic of as-cast high damping Mg-based alloys continuously extending to microplastic strain was carried out. Two-stage damping behavior via strain amplitude was particularly reported. The first is the strain amplitude strongly dependent part due to breakaway loss and the second is the strain amplitude weakly dependent part due to microplastic deformation loss, which is also frequency dependent. The damping mechanism is discussed in detail.