Simulation Of Cold And Hot Isostatic Pressing Of Large Size Beryllium

Beryllium has many excellent properties and is especially suitable for using as an optical material.Beryllium is widely used in many fields,which can greatly improve the performance of equipment.In the research and exploration of the traditional isostatic pressing process of beryllium in our country,the trial and error method of repeated experiments is usually used,which wastes a lot of manufacturing cost and research time.The method of numerical simulation can effectively reduce the cost of the traditional trial and error method.In addition,the method of numerical simulation can effectively predict the deformation trend of large-size beryllium material after the isostatic pressing.In this paper,according to the existing production process of large size beryllium,plasticity of the porous beryllium is described by Shima yield criterion.The cold isostatic pressing(CIP)and hot isostatic pressing(HIP)process of large size beryllium is simulated and analyzed by using the general finite element software MSC.Marc.The CIP and HIP process of large size beryllium is researched by the following work:establishing the 3D geometric model and finite element model;determining the material parameters,yield criterion,initial condition,contact condition,boundary condition,iterative method;carrying out numerical simulation calculation;comparing the simulation results with the experimental results.Then the influence of different process parameters on the properties of beryllium is analyzed.The simulation results show that:compared with the actual process,simulation errors of length,width and height deformation are about as 2.4%,2.6%,3.8%in CIP;simulation errors of length,width and height deformation are about as 0.8%,1.8%,0.05%in HIP.The relative density of beryllium in CIP and HIP is evenly distributed in most of the metal body,and it is relatively low at the edge,surface and corner.It is considered that the contact with the sheath leads to premature sintering and then the low density domain.The CIP densification is carried out gradually with the pressure loading,and the simulation error of relative density is within 0.54%.The HIP densification is mainly occurred in the second half process of the temperature and pressure rising,and the maximum relative density can reach 100%.In the process of CIP and HIP,the displacements of beryllium are distributed layer by layer,decreasing from the position close to the cladding to the central position.The equivalent stress of CIP is evenly distributed,the maximum value is 2.775 MPa,appearing near the stopper stress near the stopper.For HIP,the closer to the envelope the greater the equivalent stress is,near the edge there is a circle of high stress which can reach 424.7 MPa.Equivalent strain is evenly distributed in most domains,but changed greatly at the end face and corner of the body.The strain increasing of CIP is mainly appeared in the processes of the pressure rising,pressure holding and first half of pressure reduction,with the maximum strain as 15.79%;the strain increasing of HIP is completed in the second half processes of temperature rising and pressure rising,with the maximum strain as 15.96%.For the large-size metal beryllium,effects of process parameters,the thickness and hardness of rubber sleeve on the densification process of it in CIP,and effects of process parameters on the densification and equivalent stress of it in HIP process are also studied and analyzed in this paper.Reference suggestions are put forward for enterprises to improve the process to obtain the beryllium metal with perfect performance.