Finite Element Analysis And Optimum Of Tungsten Carbide Anvil On Multi-anvil High Pressure Devices

High-pressure physics has been revolutionized since Bridgman established the principle of massive support and the principle of lateral support, which made it possible to reach pressure over 5 GPa. It leads to the synthesis of some superhard materials such as diamond and cubic boron nitride under high pressure and high temperature (HPHT). The physical properties of many materials have been studied under HPHT as well. The high-pressured research must use the high-pressure apparatus; the progress of the high-pressured science is depending on the development of the pressure technique.The high pressure apparatus in China is mainly cubic high pressure apparatus (CHPA), which is the most effective apparatus used in industry to synthesize diamond and CBN. CHPA is a type of"multi-anvil apparatus."At present, many high-pressure measurements and synthesis are performed with a cubic high-pressure apparatus. Its tungsten carbide (WC) anvils are the main consumption part, whose lifetime affects the cost of the operation of a CHPA.At present, the numerical value of stress and its distribution on the anvil can not be measured directly in experiments under high pressure. A finite element analysis can solve the problem in high-pressure research. A finite element analysis can produce an enormous amount of numerical data. The key to interpreting these date is finding a small subset of the number date that can be used to determine if one experimental configuration is better than another. In order to gain a better understanding of the design parameters, it seems worthwhile to closely examine the stress distribution in the WC anvil with the various dimensions of WC anvils using finite element stress analysis methods.Since the first attempt by Mao and Bell, it is now common practice to use a beveled anvil face on single-crystal diamond anvil in order to reduce the high–stress concentration near the corner and achieve a more concentrated load in the center sample chamber, but researcher does not do this work on the anvil used in multi-anvil apparatus. In order to gain optimal dimensions of WC anvils that can gain a higher chamber pressure and long lifetime than traditional WC anvils, we simulated the numerical value of stress and the distribution rule of the various beveled anvils by computer-aided design (CAD) and finite-element calculations. The analysis results show that the proper angle of the bevel is between 41.5°to 43.5°, and the proper length of the bevel is 13.5 mm. These results have been approved in many of high pressure experiments in CHPA. So, the finite model of high pressure anvil is successful computed model.In the fields of physics, geophysics, and geochemistry the quest for knowledge and understanding of the behavior of matter under the conditions found within our earth and other planets has called high pressure apparatus of ever larger volume high-pressure cell capability. Multi-anvil devices that employ WC anvils can accommodate much larger sample volumes than the other high pressure apparatus. In order to extend the lifetime of an anvil made of tungsten carbide used in a large volume cubic high-pressure apparatus, we analyzed the properties of an anvil with different magnitude of interference matching the steel supporting ring under high pressure using finite element method. It is found that the peak value and distribution of Von Mises stress does not change obviously when the magnitude of interference is smaller than 0.3 mm. When the magnitude of interference reaches 0.3 mm, the peak value of Von Mises stress and its distribution changes substantially, due to which the performance of the anvil can be significantly affected. Thus, the magnitude of interference ought to be between 0.1 mm and 0.25 mm. The simulated results have been approved in many high pressure experiments in CHPA.We can design of the WC anvil with reason dimension base on the 3rd theory of strength. However, the exact shear strengthστof WC anvil is not known, it is very difficult to determine the dependence of shear strength on an anvil. Knowing the shear strengthστof cemented tungsten carbide would greatly help design of the safely WC anvil with reason dimension base on the 3rd strength theory. Therefore, study of the strength of cemented tungsten carbide - the anvil's material- is of significant interest. Ruoff reported the yield strength of 3% cobalt cemented tungsten carbide in [Ruoff, J. Appl. Phys, 50, 582 (1979)], but the shear strength is not know until now. Base on the theoretical analysis, we performed finite element simulations of multi-anvil apparatus experiment to determined the shear strength for 3﹪cobalt cemented tungsten carbide. The shear strength is 2.635 GPa, which has been verified by high pressure synthesis experiment. This would greatly help design of the safely WC anvil with reason dimension base on the 3rd theory of strength. The method can be applied to study the mechanical response of different material variants under high pressure conditions. From above simulation analysis results, we think that the finite element analysis can solve the problem in design WC anvil. This method can reduces the design cost, and extend lifetime of a WC anvil used in CHPA. We suggest that the finite element method should be applied in the design of the ultrahigh equipment. A finite element analysis can solve the problem in high-pressure research.