ANISOTROPIC-VISCOPLASTIC CHARACTERISTIC OF DOUBLE-HAT CRASH BOX CONSIDERING THE AXIAL IMPACT

• Main Author: Aziz, Ali
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/62553
• Institution: Institut Teknologi Bandung

Nowadays, vehicle safety has become an essential vehicle design objective. There are many components in vehicles designed for vehicle safety, one of them is a crash box structure. During a vehicle crash accident, the crash box structure will deform and absorb the collision's kinetic energy and reduce the risk of injuries and fatalities. Therefore, it has become a must for manufacturing companies to design vehicle energy absorption structures more accurately to improve vehicle safety. Most of the numerical simulations in design process use isotropic material assumptions. It assumes mechanical properties are identical in all directions. The isotropic assumption is more practical and easier to use when compared to anisotropic. However, many materials do not comply with this assumption, mainly from the rolling, drawing, and extrusion manufacturing. In anisotropic material, the mechanical properties might vary depending on direction. Such that it is important to use a proper numerical simulation model. The objective of this work is to observe the influence of anisotropy and viscoplasticity on double-hat crash boxes through experimental testing and numerical simulation. The predicted crashworthiness parameters from simulations using the isotropic and anisotropic models will be compared to experimental data. The isotropic model uses the von Mises yield function while the anisotropic model used refers to Afdhal’s (2021) research. The anisotropy model combines the Hill 48 yield criterion, isotropic hardening, and Cowper-Symonds viscoplasticity. The anisotropy effect of the material was observed by varying the cutting direction of the specimen. There are three cutting directions, namely parallel, diagonal, and transverse to the rolling direction. Meanwhile, the viscoplastic effect was observed using two types of loading cases, quasi-static and dynamic. In a quasi-static loading case, the specimen is tested with 2 mm/min stroke speed. While in dynamic case the specimen is crashed with 4.09 m/s . After performing numerical simulations and experiments, the results show that the anisotropy has a significant effect on the crashworthiness parameters of the structure. The material orientation that has a higher tensile strength will produce a stronger crash box and vice versa. The effect of anisotropy is quite significant on the Pmean and SEA parameters up to 6.72%, and more significant for the Pmax parameter up to 18.22%. The viscoplasticity has a significant effect in the dynamic loading case. The structure strengthens up to 30.11% when it is subjected to a 4.09 m/s impact load. The anisotropy model used can capture anisotropic and viscoplastic characteristics well. Therefore, the anisotropy model used produces more accurate results than the isotropic model.