Thermal expansion of cementite and thermoelastic stresses in white cast iron
Thermal expansion of cementite and thermoelastic stresses in white cast iron
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DOI：
10.1016/0921-5093(94)09616-5
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发表时间：
1995
期刊：
影响因子：
6.4
通讯作者：
S. Hartmann;H. Ruppersberg
中科院分区：
文献类型：
--
作者：
S. Hartmann;H. Ruppersberg
用X射线衍射法高精度地测定了纯渗碳体在30~320℃温度范围内的三个微观微分热膨胀系数，并用这些数据计算了含有不同形状和取向的渗碳体夹杂物的白口铸铁的平均三轴热弹应力。测定了30~300℃温度范围内白口铸铁中铁素体相(211)晶面间距的取向分布。然而，根据传统X射线应力分析的形式对这些数据进行评估，结果是完全错误的，因为这种形式是基于这样的假设，即在被X射线穿透的薄表面层中只存在平行于表面的双向平均应力。结果表明，实际观察到的是试件内部的三轴平均相比应力，由于渗碳体板的择优取向，这些应力是复杂的。垂直于辐照表面的平均相特定应力分量σ330仅在表面以下亚微米范围内降为零。由于平衡条件，它在外表面恰好为零。
With X-ray diffraction the three microscopic differential thermal expansion coefficients of pure cementite were determined with high precision in the temperature range 30–320 °C. These data were used to calculate the average three-axial thermoelastic stresses in white cast iron with differently shaped and oriented cementite inclusions. Between 30 and 300 °C the orientation distribution of the (211) interplanar spacing of the ferrite phase in white cast iron was determined. An evaluation of these data according to the formalism of conventional X-ray stress analysis, however, yields completely wrong results because this formalism is based on the assumption that only biaxial average stresses parallel to the surface exist in the thin surface layer which is penetrated by the X-rays. It is demonstrated that what were observed in reality were the three-axial average phase-specific stresses from the interior of the specimen, which are complicated because of the preferred orientation of the cementite plates. The average phase-specific stress component σ33perpendicular to the irradiated surface drops to zero only in a sub-micrometre range below the surface. Because of the equilibrium conditions it is exactly zero at the external surface.