بهينه‌سازي شكل لوله جدارنازك چين‌دار تحت بار فشاري محوري با هدف افزايش ظرفيت جذب انرژي مخصوص و بازده نيروي لهيدگي

The use of thin-walled metal structures is one of the conventional methods for absorbing energy from impact an‎d compressive force, especially in air, marine, an‎d ground transportation vehicles. For this reason, until today, extensive an‎d diverse studies have been conducted about this category of energy absorbers. In these studies, various geometries have been widely proposed to improve the performance of thin-walled structures. They have been subjected to uniaxial compressive an‎d impact experimental tests an‎d analytical an‎d numerical investigations. Longitudinal corrugated tubes are among the thin-walled absorbers. One of the most important features of corrugated thin-walled tubes that has attracted the attention of shock absorber designers is the predictability an‎d controllability of the force-displacement curve of these tubes under axial compressive loads. In these structures, the force behavior is close to a uniform an‎d relatively constant state an‎d does not have a force peak. One of the weaknesses of corrugated tubes, which has been mentioned in various articles an‎d books, is the reduction of the energy absorbed an‎d the energy absorbed per unit mass of the energy absorber compared to the simple tube. The aim of this study is to improve the performance of the longitudinal corrugated tube by reducing the maximum crushing force an‎d simultaneously increasing the energy absorbed per unit of mass compared to the simple tube an‎d determining the geometric characteristics of the optimal corrugated tube. After examining several seamless tubes, the Al6063-T5 aluminum tube was selec‎ted for prototyping an‎d experimental tests. The mechanical properties of Al 6063-T5 were obtained by a simple tensile test. The results of a uniaxial compressive test, a lateral compressive test on simple tubes, an‎d two axial compressive tests on two corrugated tubes were compared with the numerical results of this research for validation. Then the study was carried out on simple straight tubes an‎d the optimal tube was obtained for simple tubes with different diameters an‎d thicknesses. In the following, by choosing different values of the geometric parameters of the corrugated tube, including the amplitude an‎d the number of folds as design variables, the feasibility of optimizing the longitudinal corrugated tube with a certain thickness, diameter, an‎d length was investigated. It was found that there are geometries of corrugated tubes with improved performance compared to the simple tube in small amplitudes an‎d the number of folds more than the folding of the simple tube under the experimental test. By using a multi-objective optimization algorithm an‎d establishing a connection between the optimization algorithm an‎d Abaqus analytical software, geometries were obtained in which removing the peak force of the corrugated tube compared to the simple tube, the energy absorbed per unit mass had also increased. The optimal corrugated tube was qualitatively compared with the results of more than 450 thin-walled energy absorbers, an‎d the proper performance of the optimal result of this research was shown. Finally, by using the optimization method of this research, the effect of the number of folds an‎d the amplitude of optimal corrugated tubes in different diameters an‎d thicknesses were investigated. Then a simple relationship between the geometric parameters of the optimal corrugated tube an‎d its overall dimensions was obtained an‎d was called golden coefficients. Using these coefficients, the values of the amplitude an‎d the number of folds of the longitudinal corrugated tube are determined in such a way that they simultaneously have a higher energy absorption an‎d a lower maximum force than the simple tube. Verifications an‎d validation of the performance of golden coefficients were done by four numerical solutions an‎d an experimental test.

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محمود فرزين , مجتبي صديقي , محسن بدرسمايي