Buckling Of Thin-walled Columns Research Articles

Predicting the crashworthiness of vehicle structures made by lightweight design materials and innovative joining methods

Abstract New materials (high strength steel, aluminium) and new joining methods (spot weld-bonding, clinching, toxing, riveting) are increasingly important in body engineering due to the demands of weight and cost reduction in the automotive industry. At the same time manufacturers and customers demands on passive safety are growing. Thin-walled columns are basic components in the concept and design of automotive body structures. Their crashworthiness behaviour is of fundamental importance in the safety design of the whole vehicle because their plastic collapse is the mechanism that is used to dissipate the kinetic energy of the vehicle in an accident. The mechanism of plastic collapse should be reliable and its evolution during the crash regular so that the desired quantity of absorbed energy, a low load uniformity and the required level of deformation load can be achieved without increasing danger for the vehicle passengers. To predict the characteristic values of automotive front structures energy absorption, e.g. weight specific energy absorption, load uniformity and structural effectiveness, the buckling of thin-walled columns, representing body front side members, were investigated in an experimental study. Geometries used for front side members like closed-hat, double-U and octagonal columns made by conventional steel, high-strength steel and light alloys were joined with different joining methods e.g. spot-welding, press-joining and structural adhesive. The design parameters of the specimen (t/a-ratio, flange width, joining width, material thickness, etc.) were varied in a wide range. Axial and non-axial quasi-static tests and even dynamic tests with different collision speeds were carried out. The results of this experimental based study are useful in the advanced crashworthiness design phase of automotive body structures. A software tool for body engineers, named ‘PRE-CRASH’, will be available soon to predict crashworthiness of the design. Due to that, design time and experimental work during prototype testing can be reduced in near future.

Compression Tests of Long Welded I‐section Columns

The results of compression tests of long, welded I-section columns composed of slender plates of high tensile steel are described. Tests of concentrically loaded specimens are compared with a finite strip nonlinear analysis model for predicting the elastic interaction of local and overall buckling of thin-walled columns. Tests of concentrically and eccentrically loaded specimens are compared with a finite strip nonlinear analysis model for predicting the elastic interaction of local and overall buckling of thin-walled columns. Tests of concentrically and eccentrically loaded specimens are compared with the proposed AISC Load and cross sections. The column strengths are also compared with those of compact columns of equivalent weight to demonstrate the economies available for columns with slender cross sections.

Torsional-flexural buckling of locally buckled columns

An investigation dealing with the interaction of local and overall buckling of thin-walled columns is described. Due to weakening effects of local buckling, overall buckling (flexural, torsional, or torsionalflexural) takes place at a lower load than the column would carry in the absence of local buckling. A solution scheme based on the finite element method is presented. The stiffness matrices presented by Barsoum and Gallagher are used in this study. The concept of effective width is used to account for the post-buckling strength of the locally buckled component plates. The post-buckling behavior and the use of effective width concept introduce nonlinearity into the problem. An interative solution procedure is employed in the solution scheme. A computer program has been prepared for the IBM 370/165 computer. The effects of local buckling on the column buckling strength are examined. Torsional—flexural buckling behavior of columns in the post-local-buckling range is discussed. Interaction of buckling modes is also discussed. Results on typical doubly and singly symmetric columns are presented.