Crashworthiness Indicators Research Articles

Numeryczna analiza energochłonności cienkościennych słupów pryzmatycznych z przetłoczeniami

The paper presents results of a parametric study into energy absorption capability of thin-walled square section columns with redrawn dents, subjected to axial impact compressive load. Thin-walled aluminum tubes with four dents in the corners were under investigation. The varying parameters were the dent’s depth and distance of the dent to the base. The study was performed using Finite Element numerical code. Three crashworthiness indicators were examined: peak crushing force, crash load efficiency and stroke efficiency. The numerical results are shown in load-shortening diagrams, as well as diagrams and maps of crashworthiness indicators. It was found, that the main factor influencing a crushing mode and, subsequently, energy absorption capability, is a dent depth. The dent distance from the base is of less importance. Also a position of a dent, either at the bottom, or at the top base (the load application point) does not influence the crushing behavior significantly. For the deepest dents the relative increase of crash load efficiency (CLE) amounts 25% in comparison with the column without dents.

Energy Absorbing Effectiveness – Different Approaches

Abstract In the paper the study of different crashworthiness indicators used to evaluate energy absorbing effectiveness of thin-walled energy absorbers is presented. Several different indicators are used to assess an effectiveness of two types of absorbing structures, namely thin-walled prismatic column with flaws and thin-walled prismatic frustum (hollow or foam filled) in both cases subjected to axial compressive impact load. The indicators are calculated for different materials and different geometrical parameters. The problem of selection of the most appropriate and general indicators is discussed.

Crashworthiness optimization of combined straight-tapered tubes using genetic algorithm and neural networks

This paper was aimed to evaluate crashworthiness capability of new designed multi-cell structures with different cross-sectional shapes (i.e. square, hexagonal, octagonal, decagonal and circular) to dissipate collision energy. The multi-cell structures included outer and inner tubes connected together by four stiffening plates. Two dimensional parameters (i.e. S1 and S2) were defined to describe cross sectional configuration of the structures. Indeed, S1 and S2 were ratios of the inner tube side length to the outer tube side length at the ends of the structures. Values of both S1 and S2 were assumed as 0, 0.25, 0.5, 0.75 and 1. Longitudinal geometry of the outer tube was straight; while, both the straight or tapered geometry could be generated for the inner tube depending on the values of S1 and S2. An experimentally validated model generated in finite element code LS-DYNA was utilized to study crushing behavior of these structures under axial impact. Geometrical dimensions of these structures were optimized using ANNs (artificial neural networks) and GA (genetic algorithm) by considering three different scenarios. The optimal structures were compared together from the crashworthiness point of view by considering two conflicting crashworthiness indicators namely SEA (specific energy absorption) and PCF (peak crush force) using a decision making method called TOPSIS (technique for ordering preferences by similarity to ideal solution). Ranking of the studied cross sections was obtained as Octagonal-Circular-Decagonal-Hexagonal-Square for all the mentioned scenarios. Consequently, octagonal multi-cell structure was selected as the best cross sectional configuration among the studied cross sections. In addition, the proposed octagonal multi-cell structure was found to have higher crashworthiness capacity than conventional single-cell and simple multi-cell ones.

Crashworthiness investigation of bitubal columns reinforced with several inside ribs under axial and oblique impact loads

This paper deals with the crashworthiness capability of newly designed bitubal columns with different polygonal cross-sections (i.e. triangular, square, hexagonal, octagonal, decagonal and circular) reinforced with several inside ribs. A large number of finite element analyses were performed on these columns under axial and oblique impact loads using LS-DYNA to find the crashworthiness indicators. These columns were studied with five different size ratios (the ratios of the perimeter a of the inner tube to the perimeter b of the outer tube), namely a/ b = 0, 0.25, 0.5, 0.75 and 1. A decision-making method, which in this case is the technique for ordering preferences by similarity to the ideal solution, was then employed to select the better columns which possessed a higher energy absorption and a lower peak force. The bitubal columns with size ratios a/ b of 0.5, 0.25 and 0.75 were generally found to be the best cases. Furthermore, the multi-cell columns with the decagonal and octagonal cross-sectional shapes were selected as the best energy absorbers.

Multi-response optimization of crashworthiness parameters of bi-tubular structures

This article aims at presenting multi objective optimization of parameters that affect crashworthiness characteristics of bi-tubular structures using Taguchi method with grey relational analysis. To design the experiments, the <i>L</i>₉ orthogonal array has been used and based on that, the inner tubes have been fabricated by varying the three influence factors such as reference diameter, length difference and numbers of sides of the polygon with three levels, but all the outer cylinders have the same diameter and length 90 mm and 135 mm respectively. Then, the tailor made bi-tubular steel structures were subjected into quasi static axial compression. From the test results it is found that the crushing behaviors of bi-tubular structures with different combinations were fairly significant. The important responses (crashworthiness indicators) specific energy absorption and crush force efficiency have been evaluated from load - displacement curve. Finally optimal levels of parameters were identified using grey relational analysis, and significance of parameters was determined by analysis of variance. The optimum crashworthiness parameters are reference diameter 80 mm, length difference 0 mm and number of sides of polygon is 3, i.e., triangle within the selected nine bi-tube combinations.

Impact Behaviour of Spot-Welded Thin-Walled Frusta

Abstract In the paper the dynamic response of thin-walled, spot-welded prismatic frusta subjected to axial impact load is investigated. The parametric study into the influence of several parameters on the energy absorption capability, expressed by some crashworthiness indicators is performed, using Finite Element simulations. FE model is validated by experimental results of quasi-static and dynamic (impact) tests. Results of initial study concerning influence of spot welds are presented. Some conclusions are derived from the parametric study into the influence of frustum angle and wall thickness upon the energy absorption capability.

Crushing behavior of new designed multi-cell members subjected to axial and oblique quasi-static loads

A new design of multi-cell devices was proposed in this paper, and evaluated in terms of crashworthiness capability under quasi-static axial and oblique (9°, 18° and 27°) loading. The structures studied in the present paper were single and multi-cell members made up of two straight columns with the same shape of cross-section connected together by several ribs. They included several sectional configurations such as triangle, square, hexagon and circle with different scales (i.e. 0, 0.25, 0.5, 0.75 and 1). Finite element code LS-DYNA was used to simulate the crashworthiness behavior of the proposed members under quasi-static loads. Several crashworthiness indicators including SEA, Fmax and CFE were obtained at different crushing angles for all the columns, and a powerful decision making method known as COPRAS was then implemented to choose the best energy absorber with the criteria of having higher specific energy absorption and lower initial peak force. From the COPRAS calculations, the multi-cell members with inner tube and scale number of 0.5 were selected as the better energy absorbers, and the column with circular cross-section was also found to be the best energy absorbing device.

Crashworthiness assessment of auxetic foam-filled tube under quasi-static axial loading

This present study investigates experimentally and numerically the crush response and energy absorption performances of auxetic foam-filled square tubes under quasi-static axial loading. Three different structures: empty, conventional and auxetic foam-filled square tubes have been compared and examined with respect to the deformation modes and load–displacement curves. Standard compression tests were conducted on the tubes to evaluate the influence of auxetic foam in the energy absorption of empty tubes. Moreover, results from computer simulation have also been supplemented to further examine the abovementioned effect. It is discovered that the auxetic foam-filled square tube is superior to empty and conventional foam-filled square tubes in terms of all studied crashworthiness indicators.

Lightweight of Aluminum Alloy Bumper Based on High-Speed Crash Component Test

High-speed crashworthiness characteristics of aluminum alloy bumper were investigated both experimentally and numerically, and then lightweight deign was performed based on these studies. After the simulation results were analyzed, chose plate thickness matching as an optimization direction and got crashworthiness indicators: cross-sectional force, energy absorption, and specific energy absorption (SEA). Design of experiment (DOE) for initial 25 sampling points, which provide input data for approximation, is implemented using the optimal Latin hypercube design (OLHD) method. Polynomial response surface (PRS) models, which are used to approximate LS-DYNA simulation models, are built using the moving least square (MVS), whose all coefficients of determination are over 0.97, indicated high accuracy. The simulation results of optimal designs, which are obtained after 52 iterations of genetic algorithms (GA), show that the mass loss of 30.8%, while energy absorption increase of 4% , SEA increase of 50.3%, and crushing forces decline.

A multi-objective surrogate-based optimization of the crashworthiness of a hybrid impact absorber

This paper applies surrogate-based multi-objective optimization techniques to a crashworthiness problem in which the impact performance of a frontal crash absorber made of steel and a glass-fiber reinforced polyamide is optimized. Two well known crashworthiness indicators are considered as contrasting objective functions: the Specific Energy Absorption (SEA) and the Load Ratio (LR), whose responses are approximated by multiple types of surrogate models due to their computational cost and their noise levels. These models are quadratic and cubic polynomials, Gaussian process (kriging) and multivariate adaptive regression splines (MARS). The finite element model includes strain-rate sensitive properties, which is verified with experimental data from a drop-tower test. The thickness of the different parts, the geometry of the cross-section and the offsets of the reinforcement parts are chosen as design variables. Pareto solution is obtained after both models are verified. Results show improvements in both functions by almost 50% compared to the original design.

The effect of crashworthiness parameters on the behaviour of car-body elements

In the paper, special emphasis was put on the structural stiffness of car elements described by crashworthiness parameters. We showed how the structure parameters described by crashworthiness indicators can be calculated for various structures. The effect of crashworthiness parameters of different constructions and profiles on the relationship between the energy absorption and the maximum collision force is given. One- and multi-layer, empty and filled with different-density plastic foam elements were described. The behaviour of different elements and the effect of plastic foam density on the crashworthiness parameters were analyzed.