ME 115: Dynamics of Materials Manuel Leija Christian Reyes

to Vehicle Vehicle Collision To further understand collisions and the effects in different cases, three dimensional kinematic and dynamic force analysis is essential.

Three Car Collision: 2D Assume two cars colliding perpendicular to each other, find the resulting forces and momentum after collision. How would it affect another on-coming vehicle if hit?

Three Car Collision: 2D Solving the previous problems would seem easy for anyone, but in reality, there are a lot more factors to be considered.

Solidworks Model of Truck

Solidworks Model of Car

Vehicle Data Working Model: Truck=2900 lb and 45 mph, Car1=2200 lb and 25 mph, Car2=2200 lb and 25 mph, Coefficient of Restitution =1 Nastran (unrealistic): Same as Working Model Nastran (realistic): Same as Working Model but with a coefficient of friction=.5 between the road and the tires

Working Model Simulation

Working Model: 2D

Equations: 2D Car A: x = xo + v*t Solved for time to collide with Truck using xo = 0 and x = 50 ft, and constant velocity vA = 25 mph (440 in/s) Car B: (x – xo)B = vB*tA = (vB/vA)(x – xo)A Solved distance that would cause collision using Car A as reference with xoB = 0 at vB = 45 mph (792 in/s)

Other General Equations: 2D Kinematics of Rigid Bodies Position Analysis, Translation, Rotation Kinetics of Rigid Bodies General Plane Motion Momentum and Impulse Conservation of Energy

Nastran 4D Three dimensional kinematic and dynamic analysis made easy. Similar scenario with only two vehicles. Two different situations: Unrealistic (frictionless surface) Realistic (with friction)

Unrealistic (No Friction)

Linear Momentum Data

Right Before Impact

Bam!!

Realistic (with Friction)

Realistic (with Friction)

Before Impact (with Friction)

Immediately After Impact

Basic Drop Test

Maximum Contact Force (at h=2ft)

Learning Experience How to use modeling programs to simulate real life situations. Use analytical techniques from class for solving problems. Despite what most car manufacturers say, truth be told, do not roll your car!!!!  It’s not just the car itself that damages the vehicle, it’s all translated energy also. It’s all about impulse and momentum!!