Controlled Energy Absorption Research Articles

Energy absorption control characteristics of AL thin-walled tubes under impact load

An experimental investigation was carried out to study the energy absorption characteristics of thin-walled square tubes subjected to dynamic crushing by impact loading to develop the optimum structural members. Here, the controller is introduced to improve and control the absorbed energy of thin-walled square tubes in this paper. When the controller were used, the experimental results of crushing of square tubes controlled by the controller's elements showed a good candidate for a controllable energy absorption capability in impact crushing.

A bulk silicon micromachined structure for gas microdischarge-based detection of beta-particles

This paper describes two Si micromachined structures for sensing beta-particles. The basic device (the micro-detector) includes a square silicon cathode surrounded by a concentric anode, and is formed by stacks of glass and Si wafers. Incident beta-particles ionize the gas encapsulated between the electrodes, resulting in an avalanche current pulse or ‘count’. It is shown experimentally that devices with 8 × 8 mm2 footprint can detect radiation in the proximity of sealed sources, such as 90Sr and 204Tl with 0.1–1.0 µCi strengths. The sensitivity (cpm mRad−1 h) of the micromachined device is comparable to that of commercial radiation detectors, but substantially superior when normalized to the detector volume, which is about 0.06% of the conventional detectors. An extension of the basic device, the stacked micro-detector, consists of a two-tiered arrangement of cavities separated by a thin glass intercavity attenuator that is intended to provide controlled energy absorption. Higher energy particles are detected in both cavities, while lower energy particles are detected in the first cavity and subsequently absorbed by the intercavity attenuator. This can provide initial assessment of the incident radiation without adding significant complexity to the system. Preliminary experimental validation is performed by comparing the device response to 204Tl and 90Sr.

Computational and experimental crash analysis of the road safety barrier

The paper describes the computational analysis and experimental crash tests of a new road safety barrier. The purpose of this research was to develop and evaluate a full-scale computational model of the road safety barrier for use in crash simulations and to further compare the computational results with real crash test data. The impact severity and stiffness of the new design have been evaluated with the dynamic nonlinear elasto-plastic analysis of the three-dimensional road safety barrier within the framework of the finite element method with LS-DYNA code. Comparison of computational and experimental results proved the correctness of the computational model. The tests have also shown that the new safety barrier assures controllable crash energy absorption which in turn increases the safety of vehicle occupants.

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.

Grooves effect on crashworthiness characteristics of thin-walled tubes under axial compression

Crashworthiness characteristics of thin-walled steel tubes containing annular grooves are experimentally studied. The grooves are introduced in the tube to force the plastic deformation to occur at predetermined intervals along the tube. The aims are improving the uniformity of the load–displacement behaviour and predicting energy absorption capacity of the tubes. Quasi-static axial crushing tests are performed with different groove distances. Load–displacement curves are described and energy absorption and mean post-buckling load are determined. The results show 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. The proposed method could be a good candidate as a controllable energy absorption element.

Elastic–plastic theory for initial buckling load of thin-walled grooved tubes under axial compression

The initial buckling load of a tube corresponds to the peak load in the first buckling cycle. In practice, this load is very important for crashworthiness design that gives an indication of the force required to initiate collapse and hence begin the energy absorption process. In this paper, the effects of grooves on the initial buckling load of thin-walled tubes under axial compression are investigated. The grooves are introduced in the tube to force the plastic deformation to occur at predetermined intervals along the tube. The aims are improve the uniformity of the load–displacement behaviour of axially crushed tubes, predict and control the collapse load of the tube. An analytical study based on elastic–plastic deformation is performed on the axial crushing of the thin-walled grooved tubes with alternately inside and outside annular grooves pattern on tube’s surface. The initial buckling load is predicted theoretically and compared with experimental findings. There is a good agreement between them. The results show that grooves can stabilise the deformation and the proposed method could be a good candidate as a controllable energy absorption element.

Experimental Study On Thin-walled Grooved Tubes As An Energy Absorption Device

Axial crushing behavior and crashworthiness characteristics of thin-walled steel tubes containing annular grooves are experimentally studied. The grooves determine the position of the folds and control the buckling mode of deformation. The aims are improving the uniformity of the load-displacement behavior and predicting energy absorption capacity of the tubes. Grooves are cut circumferentially and alternately inside and outside the tubes at predetermined intervals. Quasi-static axial crushing tests are performed with different groove distances. Photographs are taken during axial buckling and the specimens after crushing are sectioned axially to carry out the measurements. The deformation modes and load-displacement curves are described and energy absorption and mean post-buckling load are determined. In almost all the specimens the convolutions are achieved by folding in an axisyrnmetric concertina mode about circumferential grooves. The results show that the load-displacement curves and the energy absorbed by the axial crushing of the tubes could be controlled by changing the distances between the grooves. It is also found that grooves can stabilize the deformation and thus grooved tubes are good candidates for controllable energy absorption element.

EVALUATION OF A PAVEMENT FOR HEAT CONTROL OF ROAD SURFACE TEMPERATURE

Asphalt concrete pavement can easily absorb solar radiation heat because it is generally black in color and in summer, pavement surface temperature increases easily. In the urban region, development of a pavement that is able to control the rise of road surface temperature is expected as the city environment measure including heat island phenomenon, and also as a measure to improve heat environment in the pedestrian sidewalk space. In this research, the efficiency of the pavement to control the increase of pavement surface temperature was evaluated by taking measurements in periods with different daylight times and amount of rainfall on water supplied permeable pavement and solar radiation reflective pavement, which can control energy absorption of solar radiation.

An Experimental Investigation On The AxialCrush Of A Stainless Steel Box Component

Axial crush can provide controlled and reliable energy absorption for components requiring structural crashworthiness. An experimental investigation using thin-walled, commercial 304 stainless steel box components examined the effect of alloy composition and microstructure on quasi-static (room temperature) axial crush response. The experimental program consisted of two phases. The objective of the first phase was to develop experimental methods that would generate reproducible axial crush response for a given material. End constraints (removable, grooved caps) and collapse initiators (shallow groove patterns on specimen sidewalls) were used to ensure a specific crush mode and collapse location. A progressive axial crush study was performed in which nine specimens were compressed to record a deformation sequence during a fold formation cycle. Good agreement was obtained for crush characteristic values. The percent difference (average value basis) was less than 3% for maximum loads, 6% for minimum loads, and 3% for energy absorption. In the second phase, the same experimental methodology was used to investigate the effect of alloy composition and microstructure. A higher concentration of carbon and smaller grains resulted in an 18% increase in energy absorption in a secondary fold cycle. Overall, results showed that if an axial crush component's structural engineering response is controlled, material behavior can be isolated and then, alloy composition and microstructure can be modified to enhance energy absorption performance. Structures under Shock & Impact VI, C.A. Brebbia & N. Jones (Editors) © 2000 WIT Press, www.witpress.com, ISBN 1-85312-820-1

Behaviour of axially crushed corrugated tubes

The energy absorption characteristics of corrugated tubes are experimentally studied. The corrugations are introduced in the tube to force the plastic deformation to occur at predetermined intervals along the tube generator. The aims are to improve the uniformity of the load—displacement behaviour of axially crushed tubes, predict and control the mode of collapse in each corrugation in order to optimize the energy absorption capacity of the tube. Effect of heat treatment and foam filling of these tubes are also considered. Metal tubes are mostly used throughout this study, however, PVC tubes are also considered for comparison purposes. The experimental results of crushing of the corrugated tubes make these tubes a good candidate for a controllable energy absorption element.

Development of Crashworthiness for Railway Vehicle Structures

British Rail Research has been progressing the development of crashworthiness in rail vehicles over a number of years. Initial work entailed the development of a structural design philosophy which advocated progressive and controlled energy absorption in accidents, the investigation of theoretical methods for analysing large plastic deformations and the static crush testing of vehicle ends. In parallel, a programme of work was set up within the International Union of Railways which resulted in an instrumented collision between vehicles whose cabs had been designed to absorb energy in a predictable way. The lessons gained from these developments are being applied to the investigation of particular accidents and to the production of improved specifications for future BR vehicles.

Post-Instability Behavior of Solids

The necessity of model reformulation in elasticity results from the failure of hyperbolicity of the governing equations of motion for classical models. The reformulation is based upon the introduction of additional kinematical microstructures in the form of multivalued displacement and velocity field (or fractal functions) which arc generated by the mechanism of the instability. The small scale motions describing this microstructure interact with the original large scale motion and restore the hyperbolicity of new governing equations of motion. The applications of the reformulated models to the problem of vibrational control and impact energy absorption are discussed.