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首页> 外文期刊>ISIJ international >Effect of Grain Size on the Fatigue Crack Growth in Steels at Temperatures 295 and 77 K
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Effect of Grain Size on the Fatigue Crack Growth in Steels at Temperatures 295 and 77 K

机译：晶粒尺寸对295和77 K温度下钢疲劳裂纹扩展的影响

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摘要

Fatigue crack growth (FCG) and threshold stress intensity in low carbon and HSLA steels with remarkably different ferrite grain sizes (d_f) at room temperature and temperature of liquid nitrogen were investigated. The FCG rates were found to decrease with decreasing temperature for all investigated microstructural states and the influence of temperature decrease was the most significant in coarse grain microstructures. The threshold values of the stress intensity factor, (ΔK_(th)), below which cracks do not propagate, decreased by between 29.1 % (d_f = 2.7μm) and 49.3% (d_f = 88.4μm) when specimens were tested at the cryogenic temperature. A general relationship between the FCG rate, the effects of grain boundary blocking on the plastic zone size and/or the crack-tip opening displacement and the effect of changing temperature, is discussed. Furthermore, the concept of a functional relation between tensile and fatigue data at cryogenic temperatures was also investigated. It was shown that the ratio of ΔK_(th) at 77 K to ΔK_(th) at 295 K is proportional to the second root of the ratio of the tensile strength values at these temperatures i.e. ΔK_(th 77 k)/ΔK_(th 295k)≈(σ_(u 77 k)/σ_(u295 k))~(1/2).
机译：研究了在室温和液氮温度下，铁素体晶粒尺寸（d_f）明显不同的低碳和HSLA钢的疲劳裂纹扩展（FCG）和阈值应力强度。对于所有研究的微观结构状态，FCG速率均随温度降低而降低，并且温度降低的影响在粗晶粒微观结构中最为明显。当在低温条件下测试样品时，应力强度因子的阈值（ΔK_（th））低于此阈值，裂纹不扩散，降低了29.1％（d_f =2.7μm）和49.3％（d_f =88.4μm）之间温度。讨论了FCG速率，晶界阻塞对塑性区尺寸和/或裂纹尖端开口位移的影响与温度变化的影响之间的一般关系。此外，还研究了低温下拉伸和疲劳数据之间的函数关系的概念。结果表明，在77 K时的ΔK_（th）与在295 K时的ΔK_（th）之比与这些温度下抗拉强度值之比的第二根成正比，即ΔK_（th 77 k）/ΔK_（th 295k）≈（σ_（u 77 k）/σ_（u295 k））〜（1/2）。

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