【作者】 赵亮；

【导师】 李明哲；

【作者基本信息】 吉林大学 ， 材料加工工程， 2018， 博士

【摘要】 随着高压物理、地球科学和高压化学的发展,以及对超硬材料需求的不断增长,人们对超高压设备的要求也在不断提高。超高压模具在生产实践中是产生超高压力的核心部件,除了需要有承受超高压力的能力外,还需要有足够大的合成空间以满足使用要求。超高压模具大型化是现代高压设备发展的重要趋势,大型化的高压模具不但能够提高单次的合成产量,最重要的是可以提升合成产品的品质。然而,在目前的技术条件下,高压模具大型化过程中面临的最主要的问题是较大尺寸硬质合金的生产加工难度较高,成本较大,而且质量不能得到保证,这些因素限制了模具大型化的发展进程。为了降低高压模具硬质合金压缸的制造难度、提高模具承压能力,同时降低模具大型化难度,设计了剖分式超高压模具。该模具在充分考虑大质量支承和侧向支承原理的基础上结合了传统的厚壁圆筒容器的结构特点,是一种新型的超高压模具。该模具主要包含三个部分:内部离散的硬质合金压缸、中间的高强钢离散块和外部的高强钢支撑环。该结构可以有效的消除压缸周向应力,降低压缸应力水平,使模具的极限承压能力得到较大程度提高。最重要的是降低了零件尺寸,易于扩大腔体容积,降低模具使用成本。本文通过有限元分析方法对剖分式高压模具进行一系列的研究和优化,对比内壁为弧面和平面两种类型腔体的应力状态,对不同离散程度的压缸进行了应力分析,比较支撑环离散条件下的应力特点,对具有离散化压缸和离散化支撑环的高压模具优化,为剖分式超高压模具的设计、加工和应用提供理论依据和参考。本文主要研究内容和结论如下:1.剖分式超高压模具设计和结构分析剖分式高压模具是应用大质量和侧向支承原理同时结合厚壁圆筒的结构特点设计而成,是一种实现超高压模具大型化的新思路。压缸内壁有两种形式,一种是弧面内壁,与年轮式压缸相比,降低了压缸应力水平;另外一种是平面内壁,与前两种相比能够进一步消除压缸应力。剖分式超高压模具是一种全新的超高压模具结构,对其进行了相关的力学分析,推导出工作载荷传递特点,对相关参数的计算和相关设计原则进行介绍,为超高压模具的设计提供理论指导。2.剖分式超高压模具有限元模型建立根据所涉及高压模具的结构特点,应用有限元分析软件Ansys/Workbench对其进行有限元的模型建立。对建立模型中的单元格类型、边界条件、材料参数模型和接触以及摩擦条件等进行探讨。应用静态隐式算法对年轮式模具和弧面剖分式高压模具在预紧状态和施加载荷状态下的应力分布情况进行分析,年轮式模具压缸内壁都会产生很高的应力,周向应力是导致年轮式压缸破坏的主要因素,而弧面型剖分式模具应力水平较低。为进一步降低离散化压缸的应力水平,将弧面压缸优化为平面式压缸。通过比较分析表明,剖分式压缸对支撑环的应力影响很小。3.剖分式结构压缸的应力分析对比年轮式压缸和剖分式压缸在施加载荷条件下的应力分布情况。数值模拟结果表明,弧面型剖分式离散化压缸应力远远小于年轮式压缸,弧面剖分式的压缸能够有效地降低压缸所受等效应力、最大切应力和周向应力。将弧面压缸优化为平面式压缸后进一步降低了压缸应力水平,使压缸在支撑环预紧作用和内部工作载荷的作用下处于类似静水压力环境,降低了压缸所受切应力。硬质合金剖分块在支撑环的预紧作用下相互挤压,并且产生摩擦作用,增强了侧向支撑效果,使剖分式压缸的承压能力得到增强。模拟结果表明,三种模具的极限承压能力分别为5.1GPa、5.9GPa和7.6GPa。模具极限承压能力测试结果表明,年轮式压缸、弧面型剖分式压缸和平面型剖分式压缸在破坏时所对应液压油的压力分别为7.5MPa、9.4MPa和12.4MPa。4.压缸离散化对模具应力的影响在模具大型化中可以根据模具的具体尺寸来决定压缸的剖分块数,对于平面型剖分式模具随着离散程度的增加压缸应力逐渐升高,同时讨论预紧力对压缸应力的影响。对不同离散程度的压缸的极限承压能力进行预测,最后模拟结果通过实验进行验证。在选取剖分块数时,应该结合具体的模具尺寸和生产应用情况,当模具尺寸较小时剖分块数不易过多,而当压缸的尺寸较大时,为降低硬质合金的加工制造难度宜选用离散程度大的压缸。选取合适的离散化程度的压缸对高压模具的设计和生产应用具有重大意义。5.支撑环离散对模具的影响将高强钢支撑环同样进行离散化,可以使模具大型化难度更低。数值模拟结果表明,在支撑环离散程度较低时,应力变化很小,通过比较分析后可以发现,支撑环的离散程度不易过大。讨论了不同摩擦系数时,支撑环的应力变化,在制作支撑环零件时,应该综合考虑加工制造成本使零件表面粗糙度降低。为限制内部离散部分的径向位移,提出了将模具端面由平面变为斜面的方法。将支撑环离散化易于实现模具大腔体。6.剖分式超高压模具的优化为使剖分式高压模具的应力分布更加合理,应用目标参数优化设计的方法对模具进行最优尺寸计算。分析了压缸高径比、高度比、压缸外径以及压缸锥角和端面角度对结构受力的影响,得到在一定条件下的各个参数最佳值,为剖分式超高压模具的设计提供参考。更多还原

【Abstract】 With the development of high pressure physics,geophysics,high pressure chemistry and the increasing demand for super-hard materials,the demand for high pressure equipment is also increasing.The ultra-high pressure die is the core component to produce ultra-high pressure in production practice.In addition to the ability to withstand ultra-high pressure,it is also necessary to ensure that the synthetic space is sufficiently large to meet the requirements of use.The main trend of the development of modern high pressure equipment is the large-scale high pressure die.The large high pressure die can not only improve the sample volume,but also improve the quality of the synthetic product.However,under the current technological conditions,the most important problem in the process of large scale high-pressure die is the difficulty in the production and processing of large cemented carbide part.The processing cost of large size parts is larger,and the quality could not be guaranteed,which limits the process of the large size of the die.In order to reduce the manufacturing difficulty of high pressure die cemented carbide cylinder,and reduce the difficulty of large scale of pressure die,a split type ultra-high pressure die is designed.This kind of die is a new type of ultra-high pressure die,which takes full consideration of the principle of massive support and lateral support,at the same time combines the characteristics of the thick wall cylinder.The structure mainly consists of three parts: the internal discrete hard alloy pressure cylinder,the middle high strength steel discrete block and the external high strength steel supporting rings.This type structure can effectively eliminate the circumferential stress of the cylinder,lower the cylinder stress level,and the ultimate bearing capacity of the die has been improved.The most important thing is to reduce the size of the parts,and it is easy to expand the volume of the cavity,and reduce the large-scale difficulty of the high pressure die.In this paper,a series of research and optimization of the split-type high pressure die is carried out by the finite element method.The stress states of the two types of cavity with the cambered and the plane surface inner wall are compared,and the stress of the pressure cylinder with different degrees of dispersion is analyzed.The stress characteristics of different discrete degrees of supporting ring are analyzed,and the high pressure die with discrete cylinder and discrete supporting ring are optimized,which provides a theoretical basis and reference for the design,manufacturing and application of the split type ultra-high pressure die.The main contents and conclusions of this paper are as follows:1.Design and structural analysis of split ultra-high pressure die.The split type high pressure die is designed to apply the principle of massive support and lateral support at the same time combined with the structure characteristics of the thick wall cylinder.It is a new idea to realize the large size of ultra-high pressure die.There are two forms inside the inner wall of the cylinder,one is the inner wall of the cambered surface and the stress level of the cylinder is greatly reduced compared with the belt-type cylinder,the other is the plane surface,which further reduces the stress level.The split type ultra-high pressure die is a new type of die structure.The related mechanical analysis is carried out,the characteristics of pressure transfer are derived,the calculation of the related parameters and the related design principles are introduced.2.The establishment of finite element model of split-type ultra-high pressure dieAccording to the structure characteristics of the high pressure die,the finite element analysis software Ansys/Workbench is used to establish the finite element model.The cell type,boundary condition,material parameter model and contact-friction condition in the model are discussed.The static implicit algorithm is used to analyze the stress distribution of the belt-type die and cambered surface split high pressure die under the pre-tightening state and the loading state.The inner wall of the cylinder of the belt-type die produces great stress.Circumferential stress is the main factor leading to the failure of the cylinder of belt-type die.However,the split cylinder with a cambered surface is low.In order to further reduce the stress level of the discrete cylinder,the cambered surface cylinder is optimized to a plane type cylinder.Through comparison and analysis,it is shown that the stress of the supporting ring has little influence on the cylinder of the split type die.3.Stress analysis of split-type cylinderThe stress distributions of the belt-type cylinder and split-type cylinder under the same loading condition are compared.The results of numerical simulation show that the stress of dissecting discrete cylinder with cambered surface is much smaller than that of the belt-type cylinder,and the split cylinder can efficiently eliminate the equivalent,maximum shear and circumferential stresses of the cylinder.Optimizing the cambered surface to plane surface can further eliminate the stress level of the cylinder,and under the action of pre-tightening of the supporting ring and internal loading on the inner wall,the cylinder is in a similar hydrostatic pressure environment,which greatly reduces the shear stress of the cylinder.The cemented carbide divided block squeezes another under the pre-tightening action of the supporting ring,and produces frictional effect,which enhances the effect of the lateral support,and improves the bearing capacity of the split cylinder.The simulation results show that the ultimate bearing capacities of the three kinds of dies are 5.0,5.9 and 7.6GPa,respectively.The ultimate bearing capacity tests results show that hydraulic oil pressures reach 7.5MPa,9.4MPa and 12.4MPa when the belt-type cylinder,split cylinder with cambered surface and split cylinder with plane surface breakup,respectively.4.The influence of cylinder discretization on the stress of the dieThe split number of the cylinder can be determined by the specific dimensions of the pressure die.The stress of the cylinder with plane surface increases gradually with the increase of the discrete degree,and at the same time the influence pre-tightening stress on the stress of cylinder is discussed.The ultimate bearing capacity of split cylinders with different degrees of dispersion is predicted.Finally,the simulation results are verified by the experiment.It is necessary to take full consideration of the pressure die’s size and application when determining the divided number of cylinder.It is not fit to divide the cylinder too much when high pressure die with a small size.When the size of the cylinder is larger,it is appropriate to choose a large discrete cylinder to reduce the difficulty of the hard alloy processing and manufacturing.It is of great significance for the design and production of the high pressure die to select the suitable pressure cylinder with the degree of discretization.5.The influence of supporting ring dispersion on high pressure dieThe supporting ring of high strength steel is also discretized,which can make the mold larger and easier.The results of numerical simulation show that the stress change is very small when the dispersion degree supporting ring is relatively low.After comparison and analysis,it is found that the discrete degree of the supporting ring is not suitable for large.The stress changes of the supporting ring are discussed under different coefficient of friction.When making supporting ring parts,the manufacturing cost should be considered to reduce the surface roughness of the parts.In order to restrict the radial displacement of the discrete part,a method of transforming the die face from the plane to the inclined plane is put forward,which can effectively reduce the displacement of the discrete part.It is easy to realize the large cavity of the die by discretization of the supporting ring6.Optimization of the split type ultra-high pressure dieIn order to make the stress distribution of the split-type high pressure die more reasonable,the optimum design method of the target parameters is used to calculate the optimum size of the die.The influence of the height to diameter ratio,the height ratio,the outer diameter of the cylinder and the angle of the cylinder as well as the end angle of the pressure die on the stress of the structure are analyzed.The optimum value of each parameter under certain conditions is obtained,which provides a reference for the design of a split type ultra-high pressure die.更多还原