Abstract: In the paper, experimental analysis of dynamic plastic behaviour of different structural materials at high and very high strain rates up to 105 s-1 in various modes at lowered, room and elevated temperatures, is presented. The paper describes laboratory set ups for testing material specimens, based on various modifications of the Hopkinson bar technique. The paper focuses the attention on experimental tests and their interpretation. The results reported here will be useful for the designers working on the dynamic behaviour of building and mechanical protective structures made of different materials such as steels, aluminium alloys, ceramic and sand bricks, mortars, woods (pine, birch and aspen), ceramics and concrete fireproof and soils (sand, clay and sandy soil clay).
Abstract: In order to clarify the relationship between the mechanical properties of synthetic quartz and the electromagnetic phenomena during its fracture, a series of uniaxial compression tests were carried out at quasi-static and dynamic rates. Not only the stress-strain curves but also the output of ferrite-core antenna located close to the specimens were measured in a shield box made of permalloy plates. Since the synthetic quartz has three characteristic axes, i.e. optical axis, electric axis and machine axis, the effect of loading direction on the mechanical properties and electromagnetic phenomena of quarts was also examined. The dynamic compressive strength was greater than those in static tests and there is strain-rate dependence in their strength of synthetic quartz. It was also found that there are not any remarkable differences due to the loading direction with respect to the intensity of electromagnetic waves measured in the dynamic compression tests, i.e. the electromagnetic phenomenon does not depend on the loading direction.
Abstract: Wood-plastic composites (WPCs) which consist of wood flour and plastics have been widely used as architectural materials for a long time. However, the impact resistance is not always high and basic mechanical properties at high strain rate are not fully understood. In order to clarify the tensile behavior at high strain rates, split Hokinson pressure bar method was used for WPCs consisting of polypropylene. The effects of mixing ratio on the maximum stress and elongation at break were examined at high strain rates.
Abstract: The influence of the shell material (copper and silicon carbide) on the detonation process in cylindrical high explosive charge is experimentally and numerically investigated. We observed the significant differences of wave pictures in the detonation products and in the shells, which were due to differences in the sound velocities in the shells and rapid destruction of the ceramic shell under explosion loading. The specific features of a wave picture at the interface HE/ceramics due to desensitization of explosive under loading by an advanced wave in the shell were detected. Those features lead to decreasing of detonation pressure, blurring of the detonation front, and to increasing of mass velocity behind detonation front that is typical for under-compressed detonation. On the symmetry axis of HE charge in the ceramic shell behind the detonation front the long zone with practically constant pressure was observed. We have identified the mechanism of transmission of disturbances from the periphery to the symmetry axis of the HE charge. The source of the emergence of this zone is identified as transverse waves propagating directly behind the detonation front from the periphery to the symmetry axis of the HE charge.
Abstract: Skin laceration injury caused by a penetration of small curvature edge frequently occurs in a domestic accident. An assessment method for this injury is necessary in order to develop a safer manufactured product. To assess the risk of skin laceration injury in a penetration accident, a skin simulant made from silicone rubber was proposed. However, mechanical responses of this skin simulant under dynamic penetration loading have not yet been investigated. In this study, a drop weight penetration test device was developed in order to simulate penetration accidents under impact velocities of over 1 m/s. The device was then used for investigating the dynamic responses of skin simulant against several blades with different tip curvature radii. Load, penetration depth, impulse and energy at rupture were then determined from the test results. Load and penetration depth at rupture increased with the increase of tip curvature radius of the blades. Furthermore, the drop weight test result showed larger response compared to the quasi-static test result which might be caused by the viscous effect and the polymer characteristics such as cross-linking of the skin simulant.
Abstract: Bioplastics have attracted attention over the years from a perspective of environmental protection. Recently, attention is focused on bioplastics derived from inedible objects. Polyhydroxyalkanoates (PHAs) are known as a microbial origin plastic and expected to deal effectively with the food security issue. In this study, in order to use PHA for industrial and machinery parts and products, polycaprolactone (PCL) was blended with a PHA-based pellet to improve ductility and tensile strength. The effects of additives on tensile strength and elongation at break, dynamic tensile tests of the polymer blends were examined using split Hopkinson bar (SHPB) method at high strain rates.
Abstract: The work presents results of the experimental study of dynamic compression of various modifications of bitumen: bitumen 40/60, polymer-bitumen binder and rubber bitumen. The tests were carried out using the Kolsky method. The tests were conducted for the sample temperature of-15 and 20 °C. It is shown that polymer modifier and rubber additives have a significant influence on the carrying capacity of the bitumen samples at slow loading, but they do not provide significant advantages in the dynamic tests. Strain rate dependence of maximum compressive stress was obtained for the bitumens. It is shown that this dependence can be predicted by the incubation time criterion. The values of the quasi-static and dynamic strength, characterizing the carrying capacity of bitumen at slow and fast loading, are defined.
Abstract: Long rod has strong ability of penetrating into targets with high velocity because of the big ratio of L/D. In the process of the penetration, the resistance of target is so big that the deformation of the head of the projectile is severe. There are many factors influence the process, which make it difficult to get analytic solutions. In this paper, we propose a simplified calculation method which considering engineering strain of the head of projectile. And the rigid-plastic model was used to describe the constitutive model of projectiles. The relationship between the engineering strain of the mushroom area and velocity was analyzed, which is exponential. Then, combined with cavity expansion theory, the calculation results about the DOP are in good agreements with the experimental results. At last, there are numerical simulations about the relative experiments, and the results obtained from numerical simulations show the deformation of the projectile and the depth of the penetration, which are in good agreement with the theoretical calculation and experiments.
Abstract: Ballistic performance has been studied by impacting a long rod projectile into a bulk glass material and a layered specimen. The shock wave interaction on the material boundaries showed that it greatly influences the fracture configuration of glass material. A high speed photographic technique was applied in the experiment to observe the shock wave interaction and damage evolution in the bulk material. Transparent BK7 glass was used as the main material to observe the dynamic fracture phenomena. The depth of penetration (DOP) was measured to assess the ballistic efficiency of the bulk specimen compared with specimens that consisted of selected inter-layer materials, specifically rubber and a steel plate. The obtained results show that the use of a lower impedance material as an inter-layer is effective to enhance the ballistic performance while reducing the shock amplitude and delaying the wave propagation. These findings are in good agreement with the results of a numerical analysis using AUTODYN.