新型大腔体两面顶超高压模具设计理论与实验研究

Ultrahigh pressure technology plays an important role in the fields of material synthesis and research under the extreme conditions and strongly depends on the breakthrough of high pressure experiment technology, there is an urgent need to delive the large-scale mold used for superhard material synthesis. This project for ultrahigh pressure mold is limited by massive bigness carbide processing difficulties and other issues, put forward a novel kind of structure of ultrahigh pressure die. The die structure is not only easy to implement large sample cavity volume, but also can greatly increase the cavity pressure, and it need not adopt large-scale carbide and is not limited by the space. Thus this novel ultrahigh pressure die can meet the urgent requirements of the study of structure-property, the design and synthesis of new functional materials to the large-volume and ultrahigh press environment. Multi-objective optimization of this die structure and technological parameters will be carried out adopting the finite element method and the response surface method. And combined with high pressure physics experiments, the failure mechanism and the mold cavity dimension stability influence mechanism will be revealed, the efficiency of generate pressure and pressure gradient in die cavity will be investigated by using self-made new cell structure. The scientific design scheme of ultrahigh pressure die structure will be established, it may open up a new way to design the large-scale ultrahigh pressure die.

超高压技术广泛应用于极端条件下的物质合成与研究，而超高压装置作为超高压技术的载体，在很大程度上决定着超高压技术的发展，目前用于超硬材料合成的静高压模具也迫切需要大型化。本项目针对超高压模具大型化受限于大质量硬质合金加工困难等问题，提出一种新型的大腔体两面顶超高压模具结构。该模具主要由内部的组合压缸及其固定环和外部的钢丝缠绕层构成。无需对大质量硬质合金进行加工，且不受空间限制，易于实现大体积样品腔，还能显著提升腔体压力，从而满足物质新结构与性质研究、新型功能材料的设计与合成研究对大腔体、超高压环境的迫切需求。采用有限元和响应面相结合的方法对模具结构和工艺参数进行多目标驱动优化，结合高压物理实验揭示该模具的失效机制和腔体尺寸稳定性影响机理；并用自制的新型压装结构对该模具腔体压力发生效率及压力梯度进行研究。从而建立科学的超高压模具结构设计方案，为超高压模具大型化开辟新途径。

本项目针对超高压模具大型化受限于大质量硬质合金加工困难等问题，设计一种钢丝缠绕剖分式的两面顶超高压模具结构。此新型超高压模具不但能够解决目前两面顶超高压模具大型化面临的大质量硬质合金加工困难的问题，同时还能解决腔体容积和承压能力的矛盾问题。采用有限元和响应面法对剖分式压缸结构进行了优化，结果表明：压缸数目越多，应力越小，而且采用双斜边压缸结构能够进一步降低压缸应力；而且压缸的高径比在1~2、高度比在2.4~2.8、厚度比在4.5~6.5的范围内变化时，压缸的应力较小。采用梁单元建立了钢丝缠绕超高压模具的有限元模型，研究了钢丝直径和缠绕层数对钢丝层应力分布和压缸应力及腔体容积的影响，结果表明：腔体施加工作载荷时，内层钢丝由压应力变为拉应力；钢丝直径越小，钢丝层应力越小，压缸应力也越小，但腔体容积增加多；钢丝缠绕层越多，钢丝层应力越小，腔体容积增加小；缠绕层数足够多时，钢丝层应力和腔体容积变化都较小。另外还对腔体内压力场进行了研究，结果表明剖分式压缸能够获得更高更稳定的压力场。最后根据钢丝缠绕剖分式超高压模具结构设计了相应的闭环控制的变张力缠绕装置。构建了科学的超高压模具结构设计方案，从而满足物质新结构与性质研究、新型功能材料的设计与合成研究对大腔体、超高压环境的迫切需求，为超高压模具大型化开辟了新途径。