Mechanical Impact And Thermal Shock Resistance Of Graded Composite Ceramic Tools Materials

The cutting tools was continuously subjected to alternating thermal shock and mechanical impact in high-speed intermittent turning or high-speed milling.Thermal stresses and mechanical stresses worked simultaneously, making it easy to produce fatigue crack in cuting parts. The thermal shock and mechanical impact resistance of ceramic tools materials was one of the important factors that determined the tools life. The graded composite ceramic tools could effectively ease the thermal shock and mechanical impact as well as improve the tools life in high-speed intermittent cutting process.The mechanical impact finite element model was established using the finite element software ABAQUS. The mechanical impact resistance of functionally graded ceramic tools materials and homogeneous ceramic tools materials was investigated. The results showed that fracture energy of functionally graded ceramic tools materials was higher in comparison with homogeneous ceramic tools materials. That’s because residual compressive stress which eliminated part of external stress, was formed on the surface of the sample during the preparation of functionally graded ceramic tools materials.The stress waves propagation in one-dimensional model in graded composite ceramic tools materials was investigated. Functionally graded materials (FGMs) have great potential as energy absorbing devices. It has been observed that FGMs attenuate and delay the peak stresses considerably as compared to composites with sharp interfaces. The stress time histories are highly sensitive to the type of grading and base materials properties.The thermal shock finite element model was established using the finite element software ABAQUS. The thermal shock resistance of functionally graded ceramic tools materials and homogeneous ceramic tools materials was investigated by analyzing transient temperature field and transient thermal stress field. Comparing with adverse functionally graded materials, positive functionally graded materials have a greater ability to resist thermal shock. Comparing with homogeneous materials, positive functionally graded materials have a greater ability to resist thermal shock. The influence of graded layers and layer-thickness ratio on thermal shock resistance were also analyzed.The thermal shock and thermal fatigue resistance of graded composite ceramic materials and homogeneous ceramic tools materials were investigated. The results showed that the graded ceramics exhibited higher thermal shock and thermal fatigue resistance. The influence of graded layers and layer-thickness ratio on thermal resistance were also analyzed.As for the maching of Inconel718, cutting force, chip patterns, wear behaviors and failure mechanisms of functionally graded ceramic tools were investigated. The main failure mechanism was breakage due to mechanical stress when speed is low, while The main failure mechanism was abrasive wear and adhesie wear when speed was high. Comparing with homogeneous materials ceramic tools, the graded composite ceramic tool had stronger ability to withstand thermal shock and mechanical impact. Then the simulation model above had been verifide.We should choose positive functionally graded materials. Elastic modulus, thermal expansion coefficient should increase outside to the inside, while the thermal conductivity decreases from outside to inside. We should adopt three or five graded structure. We should adopt the thickness ratio e=0.2.