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首页> 外文期刊>Metallurgical and Materials Transactions A >Cold-Cracking Assessment in AA7050 Billets during Direct-Chill Casting by Thermomechanical Simulation of Residual Thermal Stresses and Application of Fracture Mechanics
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Cold-Cracking Assessment in AA7050 Billets during Direct-Chill Casting by Thermomechanical Simulation of Residual Thermal Stresses and Application of Fracture Mechanics

机译：残余热应力的热力模拟和断裂力学的应用在冷铸AA7050钢坯中的冷裂评估

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摘要

Thermally induced strains and stresses developed during direct-chill (DC) semicontinuous casting of high strength aluminum alloys can result in formation of micro-cracks in different locations of the billet. Rapid propagation of such micro-cracks in tensile thermal stress fields can lead to catastrophic failure of ingots in the solid state called cold cracking. Numerical models can simulate the thermomechanical behavior of an ingot during casting and after solidification and reveal the critical cooling conditions that result in catastrophic failure, provided that the constitutive parameters of the material represent genuine as-cast properties. Application of fracture mechanics, on the other hand, can help to derive the critical crack length leading to failure. In the present research work, the state of residual thermal stresses was determined in an AA7050 billet during DC casting by means of ALSIM5. Simulation results showed that in the steady-state conditions, large compressive stresses form near the surface of the billet in the circumferential direction, whereas in the center, the stresses are tensile in all directions. Magnitudes of von Mises effective stresses, the largest component of principal stresses and the fracture mechanics concepts, were then applied to investigate the crack susceptibility of the billet.
机译：在高强度铝合金直接冷（DC）半连续铸造过程中产生的热应变和应力会导致在坯料的不同位置形成微裂纹。这种微裂纹在拉伸热应力场中的快速传播会导致固态锭的灾难性破坏，这种现象称为冷裂纹。数值模型可以模拟铸锭在铸造过程中和凝固后的热机械行为，并揭示出导致灾难性破坏的关键冷却条件，前提是该材料的本构参数代表真正的铸态性能。另一方面，断裂力学的应用可以帮助推导导致断裂的临界裂纹长度。在当前的研究工作中，借助ALSIM5确定了DC铸造过程中AA7050钢坯中的残余热应力状态。仿真结果表明，在稳态条件下，在坯料表面沿圆周方向会形成较大的压缩应力，而在中心处，应力会在所有方向上拉伸。然后，使用冯·米塞斯有效应力的大小，主应力的最大组成部分和断裂力学概念来研究钢坯的裂纹敏感性。

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  • 来源
    《Metallurgical and Materials Transactions A》 |2009年第13期|3304-3313|共10页
  • 作者

    M. Lalpoor; D.G. Eskin; L. Katgerman;

  • 作者单位

    Materials Innovation Institute 2628 CD Delft The Netherlands;

    Materials Innovation Institute 2628 CD Delft The Netherlands;

    Department of Materials Science and Engineering Delft University of Technology Delft 2628 CD The Netherlands;

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