“…Some works have tried to maximize the energy absorption characteristics with the implementation of friction mechanisms implicit in the interface of contact between the walls of concentric tubes, obtaining favorable results in regards to the efficiency of the force of displacement (Salehghaffari and Tajdari, 2010); (Shakeri and Salehghaffari, 2007). Another option is to modify the entire rigidity of the structure through the use of imperfections or discontinuities on the walls of the profile such as dented initiators (Lee and Hahn, 1999), dented corners (Alavi and Fallah, 2012), longitudinal grooves (Zhang and Huh, 2009), patterned windows (Song and Chen, 2013) and circular discontinuities in the sides of the tube (Arnold and Altenhoft, 2004). In all the scenarios the modifications tend to decrease the value of the peak load ; however, the deformations induced by centrally located circular hole discontinuities has demonstrated better results.…”
This article details the experimental and numerical results on the energy absorption performance of square tubular profile with circular discontinuities drilled at lengthwise in the structure. A straight profile pattern was utilized to compare the absorption of energy between the ones with discontinuities under quasi-static loads. The collapse mode and energy absorption conditions were modified by circular holes. The holes were drilled symmetrically in two walls and located in three different positions along of profile length. The results showed a better performance on energy absorption for the circular discontinuities located in middle height. With respect to a profile without holes, a maximum increase of 7% in energy absorption capacity was obtained experimentally. Also, the numerical simulation confirmed that the implementation of circular discontinuities can reduce the peak load (P max ) by 10%. A present analysis has been conducted to compare numerical results obtained by means of the finite element method with the experimental data captured by using the testing machine. Finally the discrete model of the tube with and without geometrical discontinuities presents very good agreements with the experimental results.
“…Some works have tried to maximize the energy absorption characteristics with the implementation of friction mechanisms implicit in the interface of contact between the walls of concentric tubes, obtaining favorable results in regards to the efficiency of the force of displacement (Salehghaffari and Tajdari, 2010); (Shakeri and Salehghaffari, 2007). Another option is to modify the entire rigidity of the structure through the use of imperfections or discontinuities on the walls of the profile such as dented initiators (Lee and Hahn, 1999), dented corners (Alavi and Fallah, 2012), longitudinal grooves (Zhang and Huh, 2009), patterned windows (Song and Chen, 2013) and circular discontinuities in the sides of the tube (Arnold and Altenhoft, 2004). In all the scenarios the modifications tend to decrease the value of the peak load ; however, the deformations induced by centrally located circular hole discontinuities has demonstrated better results.…”
This article details the experimental and numerical results on the energy absorption performance of square tubular profile with circular discontinuities drilled at lengthwise in the structure. A straight profile pattern was utilized to compare the absorption of energy between the ones with discontinuities under quasi-static loads. The collapse mode and energy absorption conditions were modified by circular holes. The holes were drilled symmetrically in two walls and located in three different positions along of profile length. The results showed a better performance on energy absorption for the circular discontinuities located in middle height. With respect to a profile without holes, a maximum increase of 7% in energy absorption capacity was obtained experimentally. Also, the numerical simulation confirmed that the implementation of circular discontinuities can reduce the peak load (P max ) by 10%. A present analysis has been conducted to compare numerical results obtained by means of the finite element method with the experimental data captured by using the testing machine. Finally the discrete model of the tube with and without geometrical discontinuities presents very good agreements with the experimental results.
“…The choice of location for the output ports is user-and problem-dependent, but a reasonable location would be half the wavelength of deformation (during the axial crushing of a uniformly thick tube) away from the free end. The wavelength of deformation is the distance between two successive folds [15]. It indicates the average length of the tube consumed in one fold during progressive buckling.…”
Section: Progressive Buckling In the Presence Of An Imperfectionmentioning
confidence: 99%
“…Collapse initiators, also known as triggers, stress concentrators, or imperfections, can be used to initiate a specific axial collapse mode, stabilize the collapse process, and reduce the peak force during the axial crush [11,12,13]. Researchers have proposed ways of introducing buckle initiators or surface patterns to enhance energy absorption and buckling behavior by introducing various crush zones in the structure in the form of chamfering [14], dents [15], multi-corners [16], multi-cells [17,18], diamond notches and holes [19], triggering dents, circumferential grooves and stiffeners [20]. The use of col-lapse initiators has been demonstrated to reduce sensitivity to geometric and material imperfections, reduce peak crushing force, and increase energy absorption density; however, its effectiveness largely depends on the direction of the load and the general shape of the component.…”
This work introduces a design method for the progressive collapse of thinwalled tubular components under axial and oblique impacts. The proposed design method follows the principles of topometry optimization for compliant mechanism design in which the output port location and direction determine the folding (collapse) mode. In this work, the output ports are located near the impact end with a direction that is perpendicular to the component's longitudinal axis. The topometry optimization is achieved with the use of hybrid cellular automata for thin-wall structures. The result is a complex enforced buckle zone design that acts as a triggering mechanism to (a) initiate a specific collapse mode from the impact end, (b) stabilize the collapse process, and (c) reduce the peak force. The enforced buckle zone in the end portion of the tube also helps to avoid or delay the onset of global bending during an oblique impact with load angles higher than a critical value, which otherwise adversely affects the structure's capacity for load-carrying and energy absorption. The proposed design method has the potential to dramatically improve thin-walled component crashworthiness.Keywords: Thin-walled square tubes, progressive buckling, compliant mechanisms, topometry design, structural optimization, hybrid cellular automata * Corresponding Author Preprint submitted to Thin-Walled Structures June 20, 2015 This is the author's manuscript of the article published in final edited form as: Bandi, P., Detwiler, D., Schmiedeler, J. P., & Tovar, A. (2015). Design of progressively folding thin-walled tubular components using compliant mechanism synthesis. Thin-Walled Structures, 95, 208-220. http://dx
“…The authors are grateful to the Portuguese Foundation for Science and Technology (FCT) who financially supported this work, through the project PTDC/EMEPME/65009/2006 2012; 15 (2)…”
This study presents an approach for the improvement of crashworthiness properties of aluminium tubular structures using initiators introduced through localized heating. The main objective of this approach is to improve the ability to absorb impact energy in a progressive and controlled manner by a local modification of material properties. Through a localized heating in areas previously chosen for initiation, associated with the softening of the aluminium alloy the deformation can be introduced precisely, forcing the tubular structure to deform in a mode of high energy absorption and reducing the maximum load in a controlled manner. This study presents the properties for an aluminium alloy 6061-T5 modified by thermal treatment by the use of a laser beam. Experimental results are presented of quasi-static and impact tests of tubular structures using the proposed approach. This concept appears as possible and effective in the experimental work presented.
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