Abstract
In many engineering structures different energy absorption systems may be used to improve crashworthiness capability of the system and to control damages that may occur in a system during an accident. Therefore, extensive research has been done on the energy-absorbing cells. In this paper, energy absorption in tapered thick walled tubes has been investigated. As a practical case, studies have been focused on the crush element of Siemens ER24PC locomotive. To investigate performance of this part at collision time, it has been modeled in Abaqus software and its collision characteristics have been evaluated. Considering that the crash element is folded at time of collision, an analytical approach has been presented for calculation of instantaneous folding force under axial load. Basis of this method is definition and analysis of main folding mechanism and calculation of average folding force. This method has been used for validation of the results of numerical solution. Since sheet thickness of the crash element is high and may be ruptured at time of collision, some damage models have been used for numerical simulations. One of the three damage models used in this paper is available in the software and coding has been done for two other damage models and desirable damage model has been specified by comparing results of numerical solution with results of laboratory test. In addition, authenticity of the desirable damage model has been studied through ECE R 66 standard. To improve crashworthiness characteristic some attempts, such as use of metal foam and creation of trigger in suitable situations to reduce maximum force resulting from collision, have been performed. Finally though different simulation optimal crush element has been introduced and its performance and efficiency have been evaluated.
Highlights
One of the ways of energy absorption during an impact is the use of energy absorbents
Simulation was done with the modified Rousselier damage model and by putting aluminum foam material with the specifications which were mentioned in the previous section inside the crash element of the Siemens locomotive
Diagram of energy absorption for the empty crash element and crash element filled with foam is shown in Figure 22 and it is found that energy absorption increases by 24% in the presence of foam while maximum force grows only by 0.2% (Figure 23)
Summary
One of the ways of energy absorption during an impact is the use of energy absorbents. Dynamic progressive buckling is one of the common energy absorption methods in thin-walled energy absorbents under impact. Wang and Lu (2002) placed thick-walled circular energy absorbents under dynamic loading and found that what destroys these absorbents is rupture of their sheet under impact. These absorbents are deformed as mushrooming after impact of these absorbents (Figure 2). The recent researches on Rousselier’s models show that this model can estimate failure mode of tensile notched bar In this Paper, three damage models i.e. Johnson–Cook, GTN and Modified Rousselier damage models have been examined for estimation of damage in testing collision of crush element of Siemens ER24PC locomotive.
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