ME 115: Dynamics of Machinery

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# ME 115: Dynamics of Machinery - PowerPoint PPT Presentation

ME 115: Dynamics of Machinery. Manuel Leija Christian Reyes. Professor Granda. Please use this power point to do the grading on. This is a new revised one, the other one was an uncorrected file. Vehicle to Vehicle Collision. Vehicle collisions cause injuries and irreparable damage

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### ME 115: Dynamics of Machinery

Manuel Leija

Christian Reyes

Professor Granda
• Please use this power point to do the grading on. This is a new revised one, the other one was an uncorrected file.
Vehicle to Vehicle Collision
• Vehicle collisions cause injuries and irreparable damage
• In order to analyze the effects of the collisions so as to reduce injuries, three dimensional dynamics and computer simulation programs are necessary
Problem Statement
• If a truck runs a stop sign at a constant velocity and then suddenly collides with another car also traveling at a constant velocity, what are the effects on both vehicles
• What is transferred through the collision and through which dynamic principles allows this transfer to occur?
Vehicle Information
• Truck Data:
• Weight = 2900 lb
• Velocity = 45 mph (792 in/s)
• Coefficient of Restitution =0 (perfectly plastic)
• Car Data:
• Weight = 2200 lb
• Velocity = 25 mph (440 in/s)
• Coefficient of Restitution = 0 (perfectly plastic)
Equations: 2D
• Truck: 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)
• Truck can start anywhere from 990 to 1350 ft. in the y-direction of it’s starting point to ensure a collision
• Car: (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)
• Car can start anywhere from -33 to 170 ft. in the x-direction of it’s starting point to ensure a collision
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)
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, but the transferred energy from the striking vehicle as well.
• It’s all about the impulse and momentum principal!!