大型组合挤压筒蠕变-疲劳累积损伤机理及设计准则研究

Heavy metal extrusion presses are widely used for producing fixed-section products for application in the aero-space, automotive, railbound vehicle, energy, weaponry industries. Withstanding at 450 to 550℃ and 500 to 700MPa in the extrusion process, the container is one of key components of the extrusion press. However, the existed design method hasn’t considered creep-fatigue interactions, and therefore, the containers perform short lifetime and low reliability. To improve the lifetime and reliability, this research proposal is aimed to provide a creep-fatigue design procedure for the compound container. Firstly, the stress-strain behaviors of the compound container duiring shrink-fit process and extrusion processes are predicted with consideration of the Chaboche visoplastic constitutive model, as well as the thermo stress. Secondly, a fully coupled thermo-mechanical model with respected to the cumulative damage theory for creep-fatigue interaction is proposed to investigate the failure mechanisms of the container. Finally, the lifetime model is given as well as the creep-fatigue design criteria. In this research, the degradation mechanism of the extrusion container within the lifetime will be explored. Also, a new design approach respected to the creep-fatigue interaction is proposed for improving the serve-life and reliability of the compound containers. Therefore, this research has significant impacts on design theory of extrusion containers.

万吨级挤压成套装备是航空航天、交通、能源、武器装备等领域的重要基础制造装备，作为挤压过程中容纳锭坯的挤压筒是其关键部件之一，承受了交变的高温（450～550℃）高压（500～700MPa）。针对目前挤压筒因静强度失效准则进行设计，而导致服役寿命短、可靠性差的问题，本研究将首先根据材料粘弹性本构方程，分析具有多层预应力结构的组合挤压筒包辛格效应，揭示服役过程中应力/应变演变规律，探明因温度变化引起的热应力波动；进而，引入材料累积损伤模型，研究蠕变—疲劳交互作用下各层筒的应力松弛行为和失效机理；最终，建立挤压筒的服役寿命预测模型和蠕变—疲劳失效设计准则。通过本项目研究可阐明复杂服役条件下挤压筒性能退化基本规律，提出基于蠕变—疲劳失效准则，为大型挤压筒服役寿命和可靠性提升奠定重要理论基础。

大型挤压筒是铝挤压生产不可或缺的工具，在挤压生产过程中承受了极端的高温高压。本项目针对目前挤压筒因按静强度失效准则进行设计，而导致服役寿命短、可靠性差的问题，开展了系列研究，基本达到了预期目标，取得了如下成果：1）推导了多层组合式挤压筒弹性设计理论模型、弹塑性设计理论模型，提出了疲劳/蠕变线性累加应力演化模型和寿命预测的理论模型；2）初步建立了热作模具钢疲劳-蠕变交互作用下的粘塑形统一理论模型和参数提取方法，开展了热作模具钢H13的系列高温疲劳实验；3）获得铝合金挤压筒过程的材料流动特性及微观组织演化模型，并在此基础上进行了挤压过程数值模拟，获取挤压筒的热-力边界条件；4）培养博士生1名，硕士生3名；5）已发表国际期刊论文2篇（SCI、EI收录各1篇），参加学术会议1次，申请发明专利1项。特别说明：本课题研究内容获得2015年度青年基金的继续支持，目前初步开展的挤压筒热-力边界条件和热作模具的粘塑形统一理论模型等研究，将有利于进一步全面研究挤压筒疲劳蠕变设计理论。