Papers by Keyword: Impact Response

Abstract: In the present paper, a mathematical model has been constructed in order to describe the impact response of a linear Kirchhoff-Love plate made of viscoelastic auxetic material possessing fractional viscosity. Auxetic’s Poisson’s ratio is a time-dependent value changing from negative to positive magnitudes with time. In the case of a linear plate, the solution out of the contact domain is found through the Green function, and within the contact zone via the modified Hertz contact theory. Integral equations for the contact force and local indentation have been obtained.

Abstract: The aim of this paper is to propose the impact failure analysis of reinforced concrete beam using tensile softening technique based on the damage mechanics. In general, tensile crack is the most dominant factor for concrete and it is not appropriate to evaluate their effect by theory of plasticity. Thus mechanical failure of concrete is considered by not only conventional plastic theory but also damage mechanics. In the analysis to calculate the plastic deformation, Drucker-Prager yield surface model is employed, on the other hand Von-Mises yield surface model is applied for the reinforcing bar. Besides, mechanical influence of tensile crack in the concrete is also considered as the decrease of effective cross-section area using anisotropic damage variable. Several impact tests of RC beam are reviewed and their impact response are simulated by proposed analysis method. As a result, it is confirmed that proposed method can simulate impact response of RC beam and it could predict precise failure condition such as the distribution of concrete crack using anisotropic damage model.

Abstract: Impact response of contact lenses is measured using the Levitation Mass Method (LMM). In the LMM, a small mass collides with contact lenses and the impact force is measured with high accuracy as the inertial force of the moving part. A pneumatic linear bearing is used to achieve linear motion with sufficiently small friction acting on the moving part. Hysteresis loop and consumed energy as mechanical characteristics of contact lenses are also calculated.

Abstract: In the present paper, the problem on normal low-velocity impact of a solid upon an isotropic spherical shell is studied without considering the changes in the geometrical dimensions of the contact domain. At the moment of impact, shock waves (surfaces of strong discontinuity) are generated in the target, which then propagate along the shell during the process of impact. Behind the wave fronts up to the boundary of the contact domain, the solution is constructed with the help of the theory of discontinuities and one-term ray expansions. The ray method is used outside the contact spot, but the Laplace transform method is applied within the contact region. It is assumed that the viscoelastic features of the shell are exhibited only in the contact domain, while the remaining part retains its elastic properties. In this case, the contact spot is assumed to be a plane disk with constant radius, and the viscoelastic features of the shell are described by the fractional derivative standard linear solid model. In the case under consideration, the governing differential equations are solved analytically by the Laplace transform technique. As a result, the exact solution of the contact force is determined as a function of time.

Abstract: In this study, we conducted water hammer experiments in the tube which was periodically supported by various numbers of clamps, named periodic structure, initiated by a projectile impact. The parts of the polycarbonate (PC) tube supported by 1-7 steel clamps make the tube stiffer and heavier than the original PC tube and are expected to cause a filtering effect of the frontal frequency components in the water hammer. According to our experimental observations, we confirmed that higher frequency components more than 1 kHz in the wave front were attenuated and the peak strains in circumferential direction of the tube were decreased 20% from the original PC tube. Moreover, we conducted numerical simulations of the water hammer wave similar to the experimental setup. Numerical results also revealed that frontal peak is attenuated 22% through periodic structure.

Abstract: To study the impact response characteristics of multilayer structure, cantilever-type electrothermal actuators based on MEMS, a composite cantilever-beam model consisting of two layers of materials, SiO₂ and Al, is built. By using the engineer mechanics theory, the von mise stress under the impacts in the fuze system can be obtained. Meanwhile, the Finite Element Method (FEM) simulation is made to get the deformation displacement of the fixed end and the von mises stress distribution of the model. Besides, the natural frequency response is studied. The results present the actuators response characteristics of impacts in the fuze system.

Abstract: is present project investigated the impact penetration response of woven jute fiber reinforced composites subjected to wide range of low impact velocities. Hand layout woven jute fibers are thermally compressed to ensure no internal defects formed in the composites. Six layers of woven jutes are stacked together using different fiber orientations [0/q/0]_s. Low impact velocities are used ranging between 5 – 20 m/s. Force-time, force-displacement and energy-time curves are obtained automatically during the impact tests. The results are then discussed with considering the composite fragmentations and failure mechanisms. It is found that 0⁰ composite orientations capable to absorb sufficiently impact energy for 5 m/s but not for velocity greater than 10 m/s. When fiber orientations used between 15 – 45⁰, the composite impact resistance increased indicating two significant peak forces. These peak forces represent different type of failure mechanisms occurred during the striker progresses.

Abstract: The effect of low velocity impact response on the thin laminated composite cylindrical shell with different stacking sequences was investigated. Finite element simulation using ABAQUS software was the base of the study during the analysis. The framework was to study the stress and displacement in radial and circumferential directions through finite element simulation. For simplicity, an arbitrarily picked circumferential path at where the impactor impacts the shell surface was selected. The graphs plotted based on stress and displacement variables Vs radial and circumferential directions did not show the significant changes for laminations with different stacking sequences. In addition, The 90 degree along circumferential and radial directions was found to be the critical point.

Abstract: Based on the ANSYS/LS-DYNA software, the analysis for the 40m span geodesic spherical domes under impact load is carried out. By changing the mass of impact object, impact velocity and impact location, the parametric analyses on the dynamic response of the structures under the impact loading are carried out. The three failure modes of the spherical domes are summed up: local dent of structure and global collapse of structure, Punch failure of structure. Then the characteristics of the dynamic response of the structure with different failure mode, such as the impact course, impact load, speed of nodes, displacement of nodes, and stress of bars, are investigated. It is further improvement of failure mode for single-layer reticulated dome under impact.

Abstract: Thin-walled tubes are generally used as impact energy absorber in various application due to their ease of fabrication and installation, high energy absorption capacity and long stroke. However, the main drawback of plain tube is the high initial peak force. A concentric plunger in the form of tapered block is proposed to overcome this shortcoming while at the same time, improving the impact performance. Static and dynamic axial crushing were performed to determine the initial peak force (IPF), crush force efficiency (CFE) and specific energy absorption (SEA) for the concentric plunger with various taper angles. It was found that the concentric plunger affected the tube impact response. Comparison with plain circular tube was carried out and it was found that the concentric plunger improved the impact response of the tube especially in term of initial peak force.