纯钼薄板温变形行为及本构建模研究

Deformation behavior and constitutive modeling of thin pure molybdenum sheet at room to medium temperatures

摘要:

纯钼薄板在航天领域中有很好的应用前景，而准确表征纯钼板在温热条件下的力学性能是明确钼构件成形性的必要条件。因此，本文基于在不同温度(20-500℃)和应变速率（5×10-4-1×10-2s-1）条件下进行的拉伸试验，对纯钼薄板的流动应力行为、厚向异性和断裂行为进行了研究。结果表明，纯钼薄板的变形抗力对温度敏感，同时，厚向异性指数r随温度变化较小。应变硬化指数从室温到300℃呈显著增大趋势，之后随着温度升高而趋于稳定。随着温度升高，纯钼薄板的断裂延伸率先升高后略减小。裂纹产生于晶界，随后晶粒沿着晶间裂纹的分离导致断口分层现象的产生。建立了修正的Johnson-Cook纯钼薄板本构模型，模型平均误差低于5%。

Abstract:

Thin molybdenum sheet is a promising material for aerospace applications. Quantifying the mechanical behavior of the molybdenum sheet at elevated temperatures is important to understand the formability of the molybdenum component. To this end, tensile tests were carried out at different temperatures (20-500℃) and strain rates(5×10-4-1×10-2s-1). The rheological, normal anisotropic and fracture behaviors during tension were analyzed. The results show that the deformation resistance of thin pure molybdenum sheet is sensitive to temperature while the r-value (Lankford parameter) varies little within the test temperature range. When the temperature is below 300℃, the strain hardening exponent increases with increasing temperature, and it tends to be stable when the temperature is above 300℃. With the increase of temperature, the elongation to fracture of pure molybdenum sheet increases and then decreases slightly. The crack is generated at the grain boundary, and the separation of crystal grains along grain boundaries causes delamination of fractures. A modified Johnson-Cook model was established to characterize the constitutive behavior of the molybdenum sheet, of which the mean error is less than 5%.