压头损伤和残余应力对三点弯曲疲劳试验装置测试精度的影响研究
首发时间:2016-05-18
摘要:材料中的残余应力是影响材料疲劳性能的重要因素。本文对影响新型弯曲疲劳疲劳测试装置精度的因素进行了一定研究,主要针对影响三点弯曲疲劳性能的四种压头损伤(即压头不同磨损程度)和不同测试材料的残余应力的相关影响因素进行了有限元计算。计算结果表明相同的疲劳循环荷载作用下,压头磨损越严重,试样加载点的弯曲挠度越小,对弯曲疲劳疲劳测试装置测试精度的影响就越大。在疲劳循环载荷加载初期,试样中存在残余应力对其弯曲挠度-时间曲线几乎是没有影响的,而在疲劳循环载荷加载中后期时,残余应力对弯曲挠度-时间曲线影响较为显著,且残余应力越大,对试样弯曲挠度-时间曲线的影响越明显。相比拉伸残余应力,压缩残余应力对此装置测定镍基高温合金K403的疲劳性能影响更为显著。
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Effect of indenter damage and residual stress on the test accuracy of three-point bending fatigue test device
Abstract:Residual stress within material is the key factor that affects fatigue characteristic of material. Residual stress and indenter damage can lead to low test accuracy when three-point bending fatigue test device is employed to test fatigue characteristic of material. Finite element analysis has been conducted to clarify the effect of indenter damage and residual stress on test accuracy of fatigue characteristic of material in this work. The numerical results show that the larger indenter damage results in the smaller bending deflection at the loading point when the specimens are subjected to the same fatigue load, which leads to the low test accuracy of device. In the initial stage of the test, there is little effect of residual tensile and compressive stresses on the deflection - time curve. However, as stress cycle proceeds, the effect of the residual stresses on deflection - time becomes obvious. Furthermore, the greater residual stress leads to the larger deflection. Accordingly, the test accuracy is reduced. In comparison with the effect of tensile stress, the effect of compressive stress on test accuracy of fatigue characteristic of Nickel-based superalloy K403 is more significant.
Keywords: Three-point bending fatigue Test accuracy Indenter damage Residual stress
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压头损伤和残余应力对三点弯曲疲劳试验装置测试精度的影响研究
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