Side protective beams:
As noted earlier, to enhance occupant safety and reduce the injuries and also absorb more energy during side impacts, nowadays, inside the car door, hollow tubes and also profiles with open sections and various forms of cross-section are embedded which are useful and very efficient in order to meet these requirements.
In this part, we are looking for the best profiles for the thin-walled side protective beams of cars’ doors so that fulfill some criteria mentioned as follow:
- The rate of energy absorption: To determine the amount of this energy, the force- deformation diagram is applied. The area under the graph represents the amount of energy absorbed by the side ...view middle of the document...
This profile is shown in Figure 6b.
The third closed profile is bumper profile derived from the paper . Figure 7 shows this profile.
Here are three different types of the models can be used as a side protective beam profile which are widely used in this field. In these three profiles, the variables are the length and width dimensions of the profile. It will be examined, whether having a larger impact surface is more effective to absorb impact energy or a longer dimension in the impact direction. Figures 8a, 8b, and 8c show these three profiles.
_ Geometrical dimension:
The length of side protective profile and its section length are 947 mm and 194 mm, respectively. Also, the thickness of shell element is 2.3 mm. Figure 9 shows section dimensions of 2s profile.
Also in the paper , it is mentioned that for a cylindrical body shape, the diameter and length of the profile are 200 mm and 150 mm, respectively.
_ Element dimension
For a side protective tube, the length of each element is 10 mm. Moreover, the element length of rigid body is 20 mm. Belytschko-Tsay (shell) is considered as element type, as well.
_ Material Model:
Mild steel is selected as the material of the side protective tube. Also, for the cylindrical rigid body, Young modulus is 210 Gpa, Poisson coefficient is 0.3 and its density is 4250 kg/m3. Therefore, mass of the rigid body would be 20 kg. To solve this simulation, Cowper Symond’s method is applied (coefficients are 40 and 5). Also in formulating the material, Mat_ piecewise _linear_plasticity model is used.
Other coefficients in this simulation are the same as the validation simulation, although it is noteworthy that initial velocity is 13.889 m/s based on the paper .
In this part, simulation results are presented as diagrams. It should be noted, however, in this graph, Energy – Displacement curves, are cyclic curves suggesting continues touch in return stage. As a result, to determine the area under the curve is considered as far as the rigid body is going forward.
• In comparing profiles numbers 8, 9 and 10, it can be concluded that the less width of the side protective profile and the larger dimension in impact direction, the less displacement. It should be asserted that the influence of this factor on displacement is significant.
• In comparing profiles numbers 1, 2, 3, and 4 it can be concluded that the less number of dents and bumps, the less displacement. Of course, as long as cross-section area is fixed. The impact of this factor on the rate of displacement is noticeable.
• In comparing profiles numbers 5 and 6 and also numbers 1 and 4 it can be concluded that perpendicular angles and sharp corners don’t have remarkable effect on the rate of the displacement.
By means of comparing the amount of absorbed energy:
• In comparing profiles numbers 8, 9, and 10 it can be concluded that the larger dimension along the impact direction, the more absorbed energy. But this difference is negligible...