EFFECTS OF A BUS BODY STRUCTURE DESIGN ON ITS ABILITY TO ABSORB AND DISSIPATE IMPACT ENERGY
Ramy Helmy Kamel Bishay;
Abstract
This research is dedicated to the study of the effects of a bus body structure design on its ability to absorb and dissipate impact energy. An experimental test rig was designed and constructed to carry out the laboratory experiments, where load-deflection properties for a closed section steel tubes specimens that utilized in bus frame construction were measured. Also, circular and square cross section tubes were tested. Dents (slot or hole) were introduced to tested specimens. Results show that introducing dents to tested specimens improve impact energy absorption capability, but on the other hand specimen rigidity decreased.
A three-dimensional ANSYS finite element model was constructed to simulate the obtained experimental results. Also, simulation was conducted to validate the theoretical approach adapted in the present work, but compared to previously published experimental work. The simulation results show a good correlation with the experimental work results, which indicate that the utilized model can be used to investigate further methods to improve impact energy absorption.
Parametric study was conducted to investigate possible improvement of bus frame energy absorption capability. The effect of the cross section shape on the absorbed impact energy value was investigated. Results show that for any cross section area specimen, circular tubes absorb maximum value of impact energy, while square cross section absorbs minimum value at the same impact conditions.
For specimens with 304 mm2 cross sectional area, utilizing circular tubes instead of square tubes increases the value of energy absorbed by 21.5%, while in the case of a circular tube instead of a rectangular tube, the value of absorbed energy increased by 3.0%. Using a rectangular tube instead of a square tube increases the absorbed impact energy by 19.0%. For specimen with 384 mm2 cross section area, utilizing circular tube instead of rectangular tubes increases the absorbed impact energy by 9.0%, while in case of replacing square tubes by circular tubes, absorbed energy increased by 16.0%. Replacing square tubes with rectangular tubes increases the absorbed energy by 7.0%. In the case of 464 mm2 specimen, replacing square tubes by circular tubes increase specific absorbed energy by 21.0%, while replacing rectangular tubes with circular tubes, increases absorbed energy by 1.0%. Finally replacing a square tube with a rectangular one improves energy absorption by 20.5%.
A comparison between open and closed cross section specimens with constant cross sectional area was conducted. It was concluded that using open section in case of square tube reduces the absorbed energy by 25.6%. Closed rectangular sections were replaced by opened rectangular sections. Two cases were investigated, first case was when the open side is the minor side, while the second case was when the open sided is the major side. Results show that absorbed energy reduced by 7.0% in the first case, while energy absorbed was reduced by 25.6% in the second case respectively.
The effect of introducing fillet radius at the corners of the square and rectangular specimens was investigated. Results show that fillet radius has a significant effect on the value of absorbed energy by those specimens. For square cross section, increasing the value of fillet radius leads to enhancement in the value of the absorbed energy, while in rectangular cross section there is an optimum case for fillet radius where specimen cross section is semi-circular.
A new approach was investigated, where a transverse force is applied simultaneously to axially loaded frame member. Utilizing this method leads to a significant enhancement in the value of absorbed energy by frame. Also, it provides a control to the manner in which the frame is deformed during accident. This concept is applied to the frame members of the driver’s windows. Appling 1000 N transverse load increases the absorbed energy from 3.74 kJ to 4.55 kJ. The effect of the time lag between application of axial and transverse load was investigated. Time lag of 15 ms leads to an increase in the value of absorbed energy.
This research concluded that applying transverse load to axially loaded frame members during accident will enhance the impact energy absorption and also will control body deformation. Also an optimum CAD model for bus front section was proposed for impact energy absorption enhancement.
A three-dimensional ANSYS finite element model was constructed to simulate the obtained experimental results. Also, simulation was conducted to validate the theoretical approach adapted in the present work, but compared to previously published experimental work. The simulation results show a good correlation with the experimental work results, which indicate that the utilized model can be used to investigate further methods to improve impact energy absorption.
Parametric study was conducted to investigate possible improvement of bus frame energy absorption capability. The effect of the cross section shape on the absorbed impact energy value was investigated. Results show that for any cross section area specimen, circular tubes absorb maximum value of impact energy, while square cross section absorbs minimum value at the same impact conditions.
For specimens with 304 mm2 cross sectional area, utilizing circular tubes instead of square tubes increases the value of energy absorbed by 21.5%, while in the case of a circular tube instead of a rectangular tube, the value of absorbed energy increased by 3.0%. Using a rectangular tube instead of a square tube increases the absorbed impact energy by 19.0%. For specimen with 384 mm2 cross section area, utilizing circular tube instead of rectangular tubes increases the absorbed impact energy by 9.0%, while in case of replacing square tubes by circular tubes, absorbed energy increased by 16.0%. Replacing square tubes with rectangular tubes increases the absorbed energy by 7.0%. In the case of 464 mm2 specimen, replacing square tubes by circular tubes increase specific absorbed energy by 21.0%, while replacing rectangular tubes with circular tubes, increases absorbed energy by 1.0%. Finally replacing a square tube with a rectangular one improves energy absorption by 20.5%.
A comparison between open and closed cross section specimens with constant cross sectional area was conducted. It was concluded that using open section in case of square tube reduces the absorbed energy by 25.6%. Closed rectangular sections were replaced by opened rectangular sections. Two cases were investigated, first case was when the open side is the minor side, while the second case was when the open sided is the major side. Results show that absorbed energy reduced by 7.0% in the first case, while energy absorbed was reduced by 25.6% in the second case respectively.
The effect of introducing fillet radius at the corners of the square and rectangular specimens was investigated. Results show that fillet radius has a significant effect on the value of absorbed energy by those specimens. For square cross section, increasing the value of fillet radius leads to enhancement in the value of the absorbed energy, while in rectangular cross section there is an optimum case for fillet radius where specimen cross section is semi-circular.
A new approach was investigated, where a transverse force is applied simultaneously to axially loaded frame member. Utilizing this method leads to a significant enhancement in the value of absorbed energy by frame. Also, it provides a control to the manner in which the frame is deformed during accident. This concept is applied to the frame members of the driver’s windows. Appling 1000 N transverse load increases the absorbed energy from 3.74 kJ to 4.55 kJ. The effect of the time lag between application of axial and transverse load was investigated. Time lag of 15 ms leads to an increase in the value of absorbed energy.
This research concluded that applying transverse load to axially loaded frame members during accident will enhance the impact energy absorption and also will control body deformation. Also an optimum CAD model for bus front section was proposed for impact energy absorption enhancement.
Other data
| Title | EFFECTS OF A BUS BODY STRUCTURE DESIGN ON ITS ABILITY TO ABSORB AND DISSIPATE IMPACT ENERGY | Other Titles | تأثير تصميم بنية جسم أتوبيس على قدرته في امتصاص وتبديد طاقة التصادم | Authors | Ramy Helmy Kamel Bishay | Issue Date | 2015 |
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