Dingxin Leng

Impulse absorption by horizontal magnetic granular chain

The granular medium is known as a protecting material for shock mitigation. We study the impulse absorption of an alignment of magnetic spheres placed horizontally under a non-uniform magnetic field. The phenomenon of the wave dispersion is presented. This system can absorb 85% ∼ 95% (88% ∼ 98%) of the incident peak force (energy) under the applied magnetic field strength in 0.1 T ∼ 1.0 T. The shock attenuation capacities are enhanced by the increment of field strength. With an intelligent control system, it is conceivable that the magnetic granular chain may offer possibilities in developing adaptive shock protectors.

Dislocation Evaluation of Fe Twist Grain Boundary Based on Molecular Dynamics

The grain boundary and dislocation motion characteristics on the atomic scale are significant for the study of material failure mechanisms. In the present work, by theoretical analysis and numerical simulation, the most stable phase of Fe crystal under given conditions is confirmed. Distribution of dislocation potential under different torsion angles is studied for BCC-Fe (001) twist grain boundary. The dislocation motion in Fe (001), Fe (110) and Fe (111) twist grain boundary under tension, compression and shear loading are also investigated.

Shock attenuation mechanisms of magnetorheological elastomers absorbers: A theoretical analysis

To predict the dynamic response of shock absorbers based on magnetorheological elastomers and investigate the contributions of various possible energy dissipation mechanisms, a modified four-parameter model of magnetorheological elastomers was proposed, which includes the viscoelastic characteristics of rubber matrix, the variable stiffness and damping property, and the interfacial bond conditions of magnetorheological elastomers under the applied magnetic field. The constitutive equations of magnetorheological elastomers were derived and all parameters were identified based on a published literature. It is theoretically demonstrated that the maximum response force under an impulse input could be attenuated approximately 30% when the magnetic field with 0.57 T is applied. Using the proposed theoretical model, it is shown that the energy dissipation mechanisms mainly come from the interfacial friction between particles and matrix, and the increment on stiffness and dynamic viscosity of the rubber matrix provides reverse contributions to the shock mitigation, while the interfacial bond stiffness has little influence on the response force amplitude. Hence, when magnetorheological elastomers are utilized in shock absorbers, it is suggested to take advantage of the interfacial friction energy.

Investigation on Field-Response Performance of Magnetic-Sensitive Rubber by Impact Experiments With Adjustable Magnetic Fields

A magnetic-sensitive rubber (MSR) can change its stiffness and damping characteristics with variant magnetic intensity. Hence, it is possible to use it in dissipating the impact energy adaptively. Although the relationships between elastic modulus, damping ratio and magnetic intensity have been investigated extensively by static tensile, compression or shear experiments as well as vibration tests, few literatures have shown the effectiveness of MSRs on energy dissipating during impact. In this present paper, a group of magnetic-sensitive specimens, composed by ferromagnetic particles with various volume fraction, particle dimensions at millimeter-scale or micrometer-scale, particle arrangement in chain-like or uniform distributions, and rubber matrix with three different types were manufactured. Then, a series of impact experiments aimed to test the capability of MSRs in mitigating shock was conducted by a self-developed drop hammer device with adjustable homogeneous magnetic field. The influences of the above factors on the acceleration responses were investigated. To explain the mechanism, the mathematical model of the impact process was established, and based on it; the acceleration response was obtained by MATLB software. The numerical solutions are validated by comparing with the corresponding test results. It is found that the volume fraction of particles and magnetic intensity has the obvious influences on the dynamic acceleration response, while the arrangement of macro-particle in matrix affects less. Micro-particles can change the characteristics of matrix more significantly than the macro-particles.Copyright

An Equivalent Method for Optimised Design of Nested Tube Energy Absorber Under Space Constraints

This paper investigates the relationship of energy absorption between individual tube and nested tubes system in order to provide an equivalent design method for engineers. Firstly, both analytical and numerical methods were presented to analyze single tube under lateral point-loading compression, and the influences of material model and tube dimensions on energy absorption was studied. Secondly, an energy absorption system consisted of nested tubes was equivalently modeled by the combination of single tube in parallels or/and in series, and the resultant deformation and energy absorption were derived analytically by the present method. Several typical examples were verified numerically. It also discussed the relationship between structural effectiveness and solidity ratio for tube system and its components. Finally, a nested tubes system was optimized based on the requirements of installation space, crush distance and energy absorption capability.Copyright