Papers by Keyword: Impact Experiment

Abstract: Stress wave propagation effect and failure characteristics were studied by one-stage light-gas gun induced-plate impact experiment technology on limestone. The results show that dispersion effect and attenuation character are existed in impacting rock; failure division properties are analyzed by splitting cut observation, the results show that the failure specimen can be divided by three different failure divisions which are head failure zone, middle tension-compression failure zone and tail fracture failure zone. On this basis, impact-damaged process of rock is numerically simulated to analyze impact-damaged mechanism of limestone specimens.

Abstract: An impact experiment of cantilever-type piezoelectric generator is founded in order to record and analyze the first crest of output waveform. For the first crest, the analysis results show that the impact velocity, the peak voltage and the electric energy have positive correlation. The impact velocity has little influence to electricity. With the impact amplitude raised, the peak voltage, the electricity and the electric energy will rise, however, the rate of rising will descend.

Abstract: Build the model of motocross-style helmet with a dual - density and series-parallel EPS buffer layer and trial-produce helmet samples. Establish the impact experiment of the helmet model and obtain the values of HIC and Peak ACC based on the testing regulations of ECE R22.05. According to the analysis of the test results, the influence law of different EPS material densities to cushioning effect of the helmet was analyzed specifically. Experimental results show that the minimum values of HIC and Peak ACC can be obtained when the density of EPS is designed to be 0.06g/cm³; a dual - density and series - parallel EPS buffer layer has higher than 76 % of the energy absorption efficiency, and this buffer structure well reduces the values of HIC and Peak ACC, and provides effective protection for the head.

Abstract: This paper introduces the impact experiment and an engineering application of the new composited wall which composed of calcium silicate composited board. Clearly defines the impact resistance of the wall in different connection as interior walls and exterior walls through observing the wall’s changes in the number of 5 times or even up to 50 times impact (10 times of the national standard). It can be known from the experiment that long wall has large vibration but good integrity. The window wall may fracture easily and is not able to meet the minimum standard requirements of impact resistance when the width is small. It needs to take reinforce measures.

Abstract: CFRP composite material, which is reinforced with carbon fiber, features superior heat and corrosion resistance, and these benefits enables the gradual applications on aerospace industries and sports-entertainment business. However, guarantee on superior strength and rigidity on harsh condition, such as hot moisture environment and collision load is extremely difficult. Therefore, in study moisture absorption test was conducted until complete moisture absorption in test specimen using hygrothermal heat chamber to evaluate strength degradation in CFRP composite under hygrothermal environment. As a result, the effect of moisture absorption and impact loads of approximately 50% reduction in strength are shown.

Abstract: Thin-walled cylindrical shells are widely used in many industrial sectors as light structural elements. Determination of their buckling strength under various types of loading conditions is a crucial work for engineering design. Due to the needs of research of crashworthiness, dynamic buckling of cylindrical shells subjected to the strong axial impact becomes a frontier issue in recent years. The axial impact is a very complex dynamic process because of the coupling of multiple effects. In this paper, the buckling mechanism of cylindrical shells subjected to axial impact and the influences of boundary conditions, and energy absorption properties have been investigated by experiments.

Abstract: Impact experiment of a set of steel/RC composite beams was conducted. To consider the influence of local impact residual deformation, transient response was investigated using elastic-plastic contact law. Experiments show that the main failure mode is related to the value of potential energy of impacter and energy dissipation capacity of sand cushion. Each theoretical analysis result is slightly less than its corresponding experimental value. Experimental values and elastic-plastic contact analysis results present that the maximum displacement and the maximum steel strain on the lower layer at midspan increase with the thickness of sand cushion and the height of impacter.

Abstract: The method for prescribing the site of the first buckling lobe in the axial impact of the tubular structure is proposed. The inertia force induced by the solid mass attached to the tube during the impact is exploited to trigger the first buckling lobe. When the tube with the solid mass undergoes a large acceleration, the inertia force of the solid mass is expected to bend on the tube wall. In the experiment, the rectangular solid mass was attached to the aluminum alloy square tube. The tube fixed to the drop-hammer was impacted against the stationary rigid plate at the velocity of 5 or 7.7 m/s. For the case of the tube without the solid mass, the site of the first buckling lobe varied and the slight wavy plastic deformation remained further than the buckling lobes. On the other hand, when the tube with the solid mass was impacted, the onset of the first buckling lobe was observed at the portion where the solid mass was attached and the wavy deformation stated above was suppressed. The corresponding computation was also conducted using the dynamic explicit finite element method. The result showed a good agreement with the experimental one.

Abstract: Various polygonal tubes were compressed in the axial direction under quasi-static and dynamic loading conditions. The effect of the polygonal shape and the wall thickness on the crush behavior is investigated, in which the cyclic buckling takes place. The numbers of polygonal edges were 3, 4, 5, 6 and 7 in the experiment. A circular tube was also tested for comparison. The tubes were machined from aluminum alloy A5056 bar. Crush strength is estimated as an index of the energy absorption capacity of the tube. It increases with increasing the number of polygonal edges of the tube, although it almost saturates when the number of polygonal edges is more than 6. For the wider variety of polygonal tubes than that in the experiment, numerical simulation is performed using the dynamic explicit finite element code DYNA3D. The computed crush behavior well agrees with the corresponding experimental one, however, the difference in collapse mode arises due to the slight imperfections in experiment. The deformation pattern becomes more irregular for the thinner-walled tube. Further, it is presumed that the large hardening exponent in the plastic property of the material could prevent the buckling switching from the symmetric mode to asymmetric one in the crushing of circular tube.

Abstract: Stress-strain curves of some kinds of materials at high strain-rate conditions were able to be determined by a drop weight experiment system which has only to measure the force-time relation using a load-cell but not to measure directly the deformation or deformation-rate of specimen. To evaluate the strain-rate or the strain of the specimen it had been necessary to measure the motion, i.e. the velocity or the displacement of tup and anvil so far. In this new method the velocity and the displacement of the tup and the anvil which contacted the both end surfaces of specimen were calculated using a personal computer on the basis of the equations of motion for the tup and the anvil, respectively. The differential equations, in which the measured dynamic-force versus time characteristics were contained, were integrated by Runge-Kutta method using the personal computer. In the differential equation of motion of the anvil, a spring coefficient K for the rubber cushion beneath the anvil is used. For the first approximation of the coefficient K is assumed to be the value determined by the oscillation method of cantilever beam. The spring coefficient K with high accuracy is determined when the computed strain of the specimen on the basis of the method described above is almost equal to the measured strain of it by using a micrometer caliper after the dynamic compression. The coefficient K with the higher accuracy can be obtained the incremental compression experiment using some kinds of hard stop ring in the prescribed height.