Energy Absorbtion Research Articles

Effect of bonding strength on the energy absorption of Al foam-filled cylindrical tube

Effect of bonding strength on the energy absorption of Al foam-filled cylindrical tube

Shock And Impact Energy Absorbtion AndControl By Active Material Based Systems

Perfection of energy absorbtion means is the current trend in oscillation and shock suppression systems development. Active materials, which are able to convert mechanical energy into another kind and dissipate it, are promising in the field. Their employment for oscillation suppression is elaborated well enough, but their application for the shock and impact process control remains a challenge. The present paper discusses applications of active materials for shock and impact energy absorbtion and its control. Possibilities of employing piezoelectric materials for the development of systems in which the shock and impact characteristics become controllable are considered. One possibility is to control friction between contact elements of the system links which makes it possible to control the structure of the impact system. Shock energy conversion into electric energy in piezomaterial and its dissipation is another possibility, including the possibility of damping parameters alteration. Composite structures containing piezomaterial and electro rheological materials allow us to develop adaptive energy absorbing systems with extended possibilities to regulate process parameters within a wide range. Such systems are adjustable and need no external energy sources. Systems based on active material can be successfully used in various shock suppression applications. Sports engineering can be mentioned as one of the most challenging areas.

Evaluation of First Peak Stress in Axial Collapse of Circular Cylindrical Shell

In this paper, the elastoplastic nonlinear behavior of circular tubes subjected to statical axial compression is studied by using finite element method. In order to estimate the performance of compressive energy absorbtion for circular tubes, the effects of material and geometrical properties on first peak compressive stress o are investigated. From this study, it is found that the peak stressσ1 can be expressed as σ1/E≅f (t/R, (∂σ/∂e) σ=σ1/E), regardless of the stress-strain formulations. Here, t is the thickness, R is the radius of a tube, E is Young's modulus and (∂σ/∂e) σ=σ1 is the stress gradient at σ=σ1. Based on this fact, one can estimate the stress σ1 for the power law hardening material from the results of al for the material with the strain-hardening portion of stress-strain curve being a straight line.

Energy absorbtion and mean crushing load of thin-walled grooved tubes under axial compression

In the present study, crashworthiness characteristics of thin-walled steel tubes containing annular grooves are studied. For this purpose, the grooves are introduced in the tube to force the plastic deformation to occur at predetermined intervals along the tube. The aims are controlling the buckling mode and predicting energy absorption capacity of the tubes. To do so, circumferential grooves are cut alternately inside and outside of the tubes at predetermined intervals. Quasi-static axial crushing tests are performed and the load-displacement curves are studied. Theoretical formulations are presented for predicting the energy absorption and mean crushing load. It is found a good agreement between the theoretical results and experimental findings. The results indicate that the load-displacement curve and energy absorbed by the axial crushing of tubes could be controlled by the introduction of grooves with different distances. Also, grooves can stabilize the deformation behavior and thus, the proposed method could be a good candidate as a controllable energy absorption element.

The calculation of dynamic JR-curves from the finite element analysis of a Charpy test using a rate-dependent damage model

A two-dimensional analysis of the Charpy V-notch specimen subjected to impact loading, according to the standard DIN EN 10045-1, is carried out, using a transient explicit dynamic finite element program. An elastic-viscoplastic, temperature dependent, constitutive relation for a porous plastic solid based on the Gurson damage model is developed. Ductile fracture of the matrix material will be described by the nucleation and subsequent growth of voids to coalescence. An updated Lagrange–Jaumann formulation is employed accounting for large strain and rotation. The discretization is based on four-node plane strain solid elements with one Gauss point. The equations of motion are integrated numerically by an explicit integration algorithm utilising a lumped mass matrix. The predictions of the numerical analysis in terms of force deflection response, crack resistance behaviour and deformation energy absorbtion are compared with results from Charpy tests which were carried out according to the low-blow technique.

Effect of lifelong nicotine inhalation on bone mass and mechanical properties in female rat femurs.

As tobacco smoking has been identified as a risk factor in the development of osteoporosis, possible deleterious effects of nicotine inhalation on bone mineral density (BMD) and mechanical properties of the femur in female rats were studied. Female Sprague Dawley rats were exposed to nicotine vapour 20 hours a day 5 days a week for 2 years. The nicotine concentration in the inhaled air was kept at a level, giving a plasma nicotine concentration exceeding that of heavy smokers. Throughout the study, the nicotine-exposed rats weighed approximately 10% less than the control rats. At the end of the study the rats were anesthesized and blood was collected by heart puncture for determination of nicotine in plasma. Both femurs were resected and scanned by dual X-ray absorptiometry (DXA). There was no difference in BMD between control rats (n = 7) and nicotine-exposed rats (n = 23) (mean 0.216 +/- 0.021 g/cm(2) and 0. 210 +/- 0.014 g/cm(2), respectively (P = 0.19)). The left femur was used for mechanical testing of the shaft and the neck. No significant difference could be demonstrated in ultimate bending moment, ultimate energy absorbtion, stiffness, or deflection between the two groups. In conclusion, no negative effects of nicotine inhalation on the femurs of female rats were found.

Rayleighons

In the present paper, the idea is advanced that super-deep penetration of some microparticles into various metal targets observed by hypervelocity impact represents the self-propagation of a specific internal solitary wave forming a cavity with the projectile moving inside without drag. This solitary wave is named the rayleighon because it propagates with the Rayleigh speed. The cavity of a rayleighon is shown to be free of tractions. Rayleighon energy is proven to be conserved because there is no absorbtion or emission of energy (as distinct from cracks and dislocations absorbing or emanating energy). A family of rayleighons that have been computed are provided in this paper.

Aerosols in optoacoustics: Formulation of the problem

The author formulates an optoacoustic theory of aerosol by using a simple two-fluid model. A theoretical description of acoustic signal generation in a gas by radiant energy absorbtion in a fine dispersed condensed matter is presented. Velocity, thermal relaxations and thermal conductivity are taken into account. Special cases of a new set of equations for temperature and pressure are discussed and their relevance to the preceding works of other authors is shown.

Recrystallization-etch approach to study the plastic energy absorbtion at crack initiation and extension of pressure-vessel steel A533B-1

To evaluate the elastic-plastic fracture toughness parameter of nuclear pressure-vessel steel A533B-1, a newly developed technique (the recrystallization-etch technique) for plastic strain measurement was applied to different sizes of compact tension specimens with a crack length/specimen width of 0.6–0.5 that were tested to generate resistance curves for stable crack extensions. By means of the recrystallization-etch technique, the plastic energy dissipation or work done within an intense strain region at the crack tip during crack initiation and extension was measured experimentally. Furthermore, the thickness effects on this crack tip energy dissipation rate were examined in comparison with other fracture-parameter J integrals. Thickness effects on critical energy dissipation and energy dissipation rate during crack extension were obtained and the energy dissipation rate dWp/da in the mid-section shows a constant value irrespective of specimen geometry and size, which can be used as a fracture parameter or crack resistance property.

Calculation of the Temperature in a Conductive Track of an Arc on the Surface of a Magnet-Blast Chute

The space and time temperature distribution is analyzed for a conductive track of a high current arc that was burned in the insulating channel of a magnet-blast chute. The thermal conditions in absence of boiling and ablation were considered by a combination of the methods of continuous and instantaneous energy sources, when the energy consumption for the phase transition is assumed to be uniform. The purpose of such analysis was a study of possibilities for using the additional energy absorbtion capacity of chutes by increasing the permissible temperature of their walls up to the boiling point.

The response of compact bone in tension at various strain rates

The paper examines the behavior of anisotropic compact bone in tension at a range of strain rates. Specimens of fresh bovine bone were loaded at strain rates between. 001 and 200 sec−1. This bone was shown to exhibit considerable plasticity throughout the range, except when tested in a direction normal to the long axis. The modulus of elasticity, breaking stress and breaking strain were found to vary with strain rate. There is a maximum energy absorbtion capability at a strain rate of .1 sec−1.

Absorption of light in the reflecting skin of a collisionless plasma

It is shown that the reflecting layer of a collisionless plasma behaves as a resistive system if there is a point where the plasma frequency is twice the frequency of the reflected light; the absorbtion of energy as well as the lifetime of the layer are calculated.