جستجوی مقالات مرتبط با کلیدواژه « axial impact » در نشریات گروه « مکانیک »

In this article, the energy absorption in thin-walled corrugated pipes with and without lateral holes has been studied experimentally and numerically. In this study, these tubes have been used to absorb axial impact energy of a weight. These tubes absorb the force caused by the impact with asymmetric plastic buckling. If the force of the impacting body is greater than the minimum average buckling force, the tube will be dented and its length will decrease. The amount of pipe depression depends on the energy input to it, the geometric characteristics and the material of the pipe. In this article, it is shown that by piercing the thin-walled tube to absorb the same impact energy, the contraction length increases, and the longer the contraction length, the lower the initial force, and in other words, the possibility of control Power and damage are provided. There is a good agreement between experimental and simulation results.

In this paper¡ the behavior of cylindrical shells with uniform thickness and functionally graded thickness distributions subjected to axial quasi-static loading is investigated experimentally and subjected to axial impact is investigated experimentally and numerically. Steel cylindrical shells with uniform thickness and functionally graded thickness distributions have same inner diameter¡ length and weight. Cylindrical shells are impacted by the drop hammer apparatus and experimental axial force-time curves are obtained by using a load cell; in addition¡ impact simulations are done by Abaqus finite element software. The effect of thickness distributions on the shortening¡ energy absorption¡ buckling shape and axial force-time curve of cylindrical shells is investigated. It is found that for axial quasi-static loading¡ a change in thickness distribution of cylindrical shell is able to convert the buckling shape from mixed buckling (a combination of axisymmetric and diamond modes) to progressive buckling¡ also for axial impact loading¡ a change in thickness distribution of cylindrical shell can affect the number of complete folds. The studies also suggest that at same impact energy¡ functionally graded thickness distribution cylindrical shell compared with uniform thickness distribution cylindrical shell absorbs approximately the same energy with more shortening and transforms less mean load and peak load to under protected specimen¡ thus¡ functionally graded thickness distribution cylindrical shell is a better energy absorption specimen. It is found that there is a good agreement between the experimental and numerical results.

The effect of strain hardening modulus on axisymmetric buckling of circular cylindrical shells made of aluminum and steel materials is investigated, so the nonlinear dynamic equations of cylindrical shells with different strain hardening modulus for cylindrical shells made of aluminum material and different linear and multi-linear strain hardening modulus for cylindrical shells made of steel material are solved for three types of boundary conditions and two types of loading. It is found that under investigated conditions, changing of strain hardening modulus for cylindrical shells made of aluminum and steel materials transmit the buckling shape from plastic buckling to progressive buckling.

In this paper, the internal inversion process of metallic cylindrical shells under dynamic axial loading is investigated experimentally and numerically. Experimental tests are performed on the steel tubes in a gas gun and the required force for internal inversion is obtained using the measurement system of impact loadings. Also, numerical analysis is carried out by the finite element software ABAQUS and the accuracy of simulated models are validated with the experimental results. In this paper, all geometrical properties of the tubes and die are assumed to be constant and the effect of the projectile mass and velocity is investigated on the shortening and energy absorption of the tubes which are affected by axial impact in the internal inversion process. Therefore the projectile is shot directly to the specimen with different masses and velocities. It is observed that if the projectile mass remains constant, increasing in the impact velocity has almost no effect on the constant inversion load and just increase the tube displacement but if the impact velocity remains constant, increasing the amount of projectile mass causes increasing in the constant inversion load besides of increasing in tube displacement. Comparing the results of numerical simulations with the experimental results shows a good agreement between them.

In this paper, Abramowitc and Jones model for analyzing dynamic progressive buckling of circular tubes under axial loading have been modified. In the improved model, the dissipated energy due to shortening of tube wall and the effects of inertia of previous folding layers on new one is considered. The mean crushing force and energy absorption, which is predicted by the theoretical model, has higher accuracy than the previous theoretical model. Based on the results of this paper, it is observed that the impact velocity and the mass of striker (neglected in pervious analytical models) are important in mean crush force and absorb energy of circular tube. Also in this research, it has been observed in the experiential tests that in most of the aluminum specimens, the high impact speeds, dynamic progressive buckling and in some samples in which the speed of impact was lower, dynamic plastic buckling happened. In this paper, final reduction in axial length, energy absorption and dynamic average crushing force in specimens in which dynamic progressive buckling has been occurred, is compared and discussed. Based on the results extracted in this thesis, it has been specified that theoretical results have acceptable consistency with experimental results.