Cushioning Optimization of Multilayer Regularly-Arranged Circular Honeycombs under In-Plane Crushing Loadings

To realize the cushioning optimization of multilayer regularly-arranged circular honeycombs under in-plane crushing loadings with high impact velocities, a finite element model is introduced to obtain the cushioning mechanical parameters. A simplified energy absorption model is used to evaluate the cushioning performance, which shows that the cushioning performance is related to dynamic plateau stress and dynamic densification strain. The impact velocity, deformation mode and configuration parameters determine them. Empirical formulas of critical velocity of deformation mode transition, dynamic densification strain and dynamic plateau stress are given from the discussion of numerical results. A feasible cushioning optimization algorithm is presented in detail.

In-Plane Crushing of Square Honeycomb Cores, Part II: Energy Absorption and Cushioning Optimization

The finite element (FE) model designed in Part I is used to obtain the cushioning mechanical parameters of square honeycomb cores (SHCs) under in-plane dynamic loadings. A simplified energy absorption model is proposed to evaluate the energy absorption performance of SHCs, which shows that the optimal energy absorption per unit volume is related to dynamic plateau stress and dynamic densification strain that are affected by configuration parameters and impact velocity. The optimal energy absorption efficiency is the reciprocal of dynamic densification strain. The dynamic plateau stress has been discussed in Part I. For SHCs, the dynamic densification strain is independent of impact velocity and determined by configuration parameters. The empirical formulas of cushioning mechanical parameters are derived from physical analysis of FE results. Based on these empirical formulas, the practical cushioning optimization algorithm is presented.

In-Plane Cushioning Optimization of Multilayer Regular Triangular Honeycombs

A finite element model is designed to obtain the mechanical parameters about cushioning property of multilayer regular triangular honeycombs under the in-plane crushing loadings with high impact velocities. A simplified energy absorption model is put forward to evaluate the energy absorption performance, which shows that the optimal energy absorption per unit volume is related to dynamic plateau stress and dynamic densification strain. Both depend on the configuration parameters of representative cell and impact velocity. From the physical analysis and discussion of the numerical results, the empirical formulas of dynamic densification strain and dynamic plateau stress are suggested in terms of configuration parameters and impact velocity. Based on these empirical formulas, a feasible cushioning optimization algorithm is put forward and presented.

Hot Dynamic Densification of Materials by Utilizing Underwater Shock Wave

Hot dynamic densification method was developed by combining self-propagating high temperature synthesis (SHS) with explosively shock powder compaction technique. This method is extremely short time processing. The main purpose in this study is to perform from synthesis to densification of TiB2-TiN system high temperature ceramic composites and TiB2-TiNi-Cu system functionally graded materials (FGMs) in one step. In TiN-TiB2 ceramic composites, they showed up to 95% of relative density. It was appeared by TEM observations that both the two phases joined tightly each other. The FGMs also were produced by the same technique. They indicated no interlayer exfoliation and no macro cracks after thermal shock tests from 973 K to room temperature. It was shown that thermoelastic property of intermetallic TiNi phase as intermediate layer between ceramics and metal layers operated effectively.

Self-Propagating High-Temperature Synthesis, Dynamic/Quasi-Static Densification, and Superplasticity of Ceramics

The microstructure evolution during high-temperature deformation at (a) high strain rates and low strains (dynamic densification, shock compression) and (b) low strain rates and high strains (quasi-static densification, superplastic regime) was studied. Off-stoichiometric titanium carbide was selected as a testing system. The results demonstrate that high-temperature deformation in a broad range of strain rates provides means for controlling the microstructure of titanium carbide. By varying deformation conditions, one can obtain materials differing in microstructure and chemical composition, in particular, with equilibrium and nonequilibrium microstructures. Accordingly, the physicochemical properties of such materials are also different.