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The sudden impact during a collision of an automobile may cost the life of passengers. Several researchers are working to design materials and structures which can absorb impact-energy before passing it to the passengers. One such solution is the crash-box-structure which is placed primarily on the frontal side, in-between the bumper and main part of an automobile. The crash-box-structure's ability to absorb energy is influenced by its deformation-properties. Both, the crash-box-structure's shape and material will decide how it affects it's deformation. The impact of various geometries and materials on the crash-box's deformation characteristics is discussed in this article. Moreover, the use of fiber-reinforced composites in the crash-box is also discussed. The surface modification may affect the impact behavior, which is also discussed in this review. © Published under licence by IOP Publishing Ltd.

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School of Mechanical Engineering

Engineering and Technology

Journal of Physics: Conference Series

A Review Thin-Wall-Tube Energy-Absorbing Structure : Crash-Box

Micro forming is a production technology of very small metal elements. This paper presents a concept of grain size regulation during LDH (Limit Dome Height) test. The proposed concept is based on an empirical formulation generated using the experimental results of SS304 and brass. An empirical model is helpful in predicting the load-stroke behavior of different metals. Particularly, results of iron, copper and nickel are demonstrated. Further the concept of control scheme is presented to predict the grain size of the material during micro forming.

Lecture Notes in Electrical Engineering

Grain Size Regulation During LDH Test

Microforming is an emerging technology to manufacture products in the light of miniaturization in several domains of industry. Plastic anisotropy is one of the material characteristics significantly affecting the micro forming process. The crystal orientation influences tensile strength, yield strength and ductility, depending on different grain sizes and principle sliding planes. The present work elaborates on the influence of the plastic anisotropic in microforming for a plane stress state condition. Yield function and constitutive equations for the anisotropic material with consideration of the crystal lattice constants and parameters of crystallography texture are proposed. The crystal orientation is considered in a subroutine VUMAT algorithm, as an internal variable based on the developed mathematical model which is implemented in Abaqus as an user material subroutine. Micro limiting dome height experimental tests for different strain paths are conducted with brass foils. The results are compared with that predicted with numerical analysis, considering critical damage and element deletions. The numerical and experimental results show a good agreement for the Alpha brass ultra-thin foils, using a set of failure criterion.

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Manufacturing Review

Effect of crystallographic texture on the forming limit in microforming of brass

Forming process in sheet metal working refers to the manufacturing of products by deforming the material in the required die cavity without being broken or local necking. Defects such as wrinkling, local necking, and cracking may occur during the process. These are the results of either reduction or increase in sheet thickness while the material is being stretched inside die cavity. Prevention of defects is important during forming and is challenging if the thicknesses of forming sheets is less than 100 microns. These sheets are applied in the manufacturing of components having two dimensions of less than millimeter size, an operation known as micro-forming. Miniaturization has attracted many fields such as medical instrumentation, mobile manufacturing, automotive, and aerospace. Appropriate strain distribution in forming ensures products with better quality. Forming limit diagram (FLD) has been invented to plot major and minor strains along with forming limit curves. In other words, FLD shows wrinkling, localized necking as well as safe zones with various strain paths, and it proves to be a basic tool for understanding rupture characteristics of the material. There are three approaches for plotting FLD such as empirical (analytical), numerical, and experimental. The research work presents experimental micro-forming investigations on an ultra-thin brass sheet of 90 microns, to plot FLD, using the limit dome height test according to ASTM E2218-02 standard. The experimental setup was designed and developed to micro-form standard specimens applying 15 mm hemispherical punch. FLD plotted with experimental and empirical approaches shows agreement on failure limit curve.

Materials and Manufacturing Processes

Micro Forming Analysis of Ultra-Thin Brass Foil

The work hardening during the forming process is generally ignored in crash analysis. This paper presents computational details of the effect of forming process on crash response of typical Sports Utility Vehicles (SUV). Forming results for front panels of a medium-sized SUV were calculated using Hyperform and LS Dyna. These were imported into the crash model and crash results compared with and without the forming effects. Time taken to generate the forming data by a variety of methods is quantified and the trade-off between time taken and accuracy is examined. LS-DYNA was used for both forming and crash simulations. The effect of thickness, work hardening and residual stresses on the crashworthiness results is measured; crash response is seen to be significantly affected when the effects of forming are included. The paper proposes a systematic method to transfer data from the forming analysis to crashworthiness analysis (both using LS-DYNA), allowing thickness, residual stress and plastic strain data selectively or in combination to be used to initialise the crash model. The relative effect of each of these forming parameters has been examined and the importance of, work hardening on the crash response of the stamping front rail has been identified. A significant change in energy absorption, peak force and stroke of the front rail was predicted, indicating a far stiffer response in the formed rail than would be expected based on the nominal material properties. Therefore, forming effects should be accounted for in vehicle crashworthiness predictions. {\textcopyright} 2011 American Institute of Physics.