Drop Hammer Test Machine Research Articles

Multidisciplinary optimization of collapsible cylindrical energy absorbers under axial impact load

In this article, the multi-objective optimization of cylindrical aluminum tubes under axial impact load is presented. The specific absorbed energy and the maximum crushing force are considered as objective functions. The geometric dimensions of tubes including diameter, length and thickness are chosen as design variables. D/t and L/D ratios are constricted in the range of which collapsing of tubes occurs in concertina or diamond mode. The Non-dominated Sorting Genetic Algorithm-II is applied to obtain the Pareto optimal solutions. A back-propagation neural network is constructed as the surrogate model to formulate the mapping between the design variables and the objective functions. The finite element software ABAQUS/Explicit is used to generate the training and test sets for the artificial neural networks. To validate the results of finite element model, several impact tests are carried out using drop hammer testing machine.

Experimental Research on the Low Velocity Impact Damage of CCF300/QY8911 Composite Laminates

A group of low-velocity impact tests on CCF300/QY8911 composite laminates were implemented by the low-velocity drop hammer test machine. The dent depth and the internal damage pattern with corresponding impact energy were studied, the internal delamination damage state of laminates after impact were observed through thermal layer exposing tests, and the mechanism of low-velocity impact delamination damage were discussed. The results indicated that there existed a significant inflection point in the curve of impact energy verse dent depth of CCF300/QY8911 composite material, which was also the transition point of different damage patterns. When the impact energy was smaller than the inflection energy, the damage pattern consisted mainly of matrix flaws and delamination damages, but when the impact exceeded the inflection energy, delamination damage hardly expanded while the expansion of damage was mainly fiber break.

An investigation on low-velocity impact response of elastomeric & crushable foams

Abstract The mechanical behavior of elastomeric foam, in particular, Ethylene Propylene Diene Methyle (EPDM) and crushable foams, in particular, Expanded Poly-Propylene (EPP) and Poly Urthane Rigid (PUR), under low-velocity impact are studied experimentally and numerically. At first, these foams were loaded under quasi-static loading in compression. In order to study the dependence of their behavior on strain rate, the loadings were performed in two rates, 3 mm/min and 100 mm/min. The low-velocity impact tests were applied using a drop hammer testing machine. The drop heights of projectile in all tests were 0.5 and 1 m. The thickness effect of specimens on absorption of energy and parameters such as, contact force and displacement of specimens are discussed. Then, the dynamic factors of force and energy for three types of foam are investigated. Since, EPP showed an insensitive property to the thickness of specimen in the impact tests, it is possible to define dynamic factors for different thickness of this type of foam. Finally, all test results are compared with numerical results through implementation of ABAQUS finite element package. Good agreements between numerical results and experimental data show the capability of numerical modeling to fulfill the experimental investigation.

金属焼結体の高速圧縮変形挙動

A dynamic compression test was carried out on sintered Cu and Fe compacts to clarify their deformation behaviour using a drop-hammer testing machine. The results obtained were as follows:1) At the high strain rate of about 3×102/sec, the sintered Fe compacts showed sharp pseudo-yield points, but pre-strained specimens did not show such pseudo-yield behaviour.2) For the first impact of Cu compacts, the dynamic load increased gradually with increasing time, but in the subsequent dynamic tests, the load increased abruptly and then became constant.3) The dynamically-deformed sintered Fe showed upper and lower yield points. On the contrary, the specimens statically deformed showed only single yield point.

高速静荷重下における岩石の力学的性質 (第1報)

Mechanical behaviors of rocks under the dynamic loading are investigated in this paper. Here, the dynamic loading means not impact loading, but high-speed loading.In the case of dynamic loding test using a drop-hammer, the shock waves should be eliminated perfectly. Under such condition, the rock specimens are definitely subjected only to an elastic pressure. From the above consideration, a new drop-hammer testing machine was designed. It consists of an anvil, a drop-hammer and a cylindrical dynamometer. The anvil is weighed about 800kg and mounted on four dampers. The drop-hammer is weighed about 40kg, having a damper in its body. On the other hand, the dynamometer is equipped with eight resistance-type wire strain gages. From the tests the following results were obtained, using cementmortar, sandstone, or marble specimens.(1) The compressive strength of rocks increases with the loading-rate ; namely, the ratio of the dynamic compressive strength to the static one is about 1.5 for cementmortar, about 1. 6 for sandstone, and about 1.9 for marble. In these cases, the average loading-rates of the dynamic loading tests are about 3.0-12×105kg·cm-2. sec-1.(2) The values of the secant modulus of elasticity increases with the loading-rate; namely, the ratio of the dynamic modulus of elasticity to the static modulus of elasticity is about 3. 2 for cementmortar and sandstone, about 1. 6 for marble.(3) The values of the strain of rock specimens measured at failure decrease as the loading-rate increases.

1打撃破砕試験による岩石の裂砕溝について

1打撃破砕試験による岩石の裂砕溝について