MODEL DESCRIPTION
Vehicle Crash tests are complex and expensive activities to engage in. They are usually done to check the safety of a vehicle and the safety of occupants in the vehicle by analyzing the deformation of the bumper or the rear end of the vehicle. These tests can be very hazardous as the engineers and living participants are exposed to injuries. Therefore, to save money and prevent danger to human life, it is advisable to model these situations as accurately as possible.
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The models used in this paper are based on vehicle-to-vehicle collisions (VTV), vehicle-to-barrier collisions (VTB) as well as occupant-vehicle reaction modeling.
The Kelvin Model
The Kelvin model shows a mass, or two masses, attached to each other by a spring of constant k and a damper of constant c (representing an underdamped motion).
When analysing car crashes, it is important to understand the dynamics of crashes and why the model talked about in the project fits the real-world problem. The automotive chassis of a car is the skeletal frame on which mechanical parts such as engines, tires, axle assemblies, brakes, and so on are bolted. The chassis is the backbone of any automobile and so needs to have significant properties. They are usually made from steel and aluminum alloys. This is because steel is easy to find and can be easily machined. A chassis being the support for any automobile, has to be rigid to absorb vibrations from the engine and the energy from collisions. It must be lightweight so to prevent large fuel consumption. The absorptivity of energy during collisions is the basis of this project. If cars were designed to quickly stop from high speed after a head-on collision, occupants would not survive car crashes since human beings and most mammals are soft-brained. It is, therefore, important that collisions are damped.
The above image shows a car chassis.
Assumptions
1. Motion of the vehicle is assumed to occur in one degree of motion in the horizontal direction.
2. Motion of occupant is assumed to occur in the horizontal direction.
3. Human participants are assumed or represented as point particles.
4. Front end of the vehicle undergoes plastic or elastic deformation.
5. Models of crashes are underdamped systems, and so velocity and energy are lost.
6. The system is assumed to have no friction.
7. The spring obeys Hooke’s law throughout the spring’s range of motion.
8. The spring and damper are massless.
9. The mass before and after collision is the same.