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. 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 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 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 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? What is transferred through the collision and through which dynamic principles allows this transfer to occur?

Vehicle Information Truck Data: Truck Data: Weight = 2900 lb Weight = 2900 lb Velocity = 45 mph (792 in/s) Velocity = 45 mph (792 in/s) Coefficient of Restitution =0 (perfectly plastic) Coefficient of Restitution =0 (perfectly plastic) Car Data: Car Data: Weight = 2200 lb Weight = 2200 lb Velocity = 25 mph (440 in/s) Velocity = 25 mph (440 in/s) Coefficient of Restitution = 0 (perfectly plastic) Coefficient of Restitution = 0 (perfectly plastic)

Solidworks Model of Truck

Solidworks Model of Car

Working Model Simulation

Working Model: 2D

Equations: 2D Truck: x = x o + v*t Truck: x = x o + v*t Solved for time to collide with Truck using x o = 0 and x = 50 ft, and constant velocity v A = 25 mph (440 in/s) Solved for time to collide with Truck using x o = 0 and x = 50 ft, and constant velocity v A = 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 Truck can start anywhere from 990 to 1350 ft. in the y-direction of it’s starting point to ensure a collision Car: (x – x o ) B = v B* t A = (v B /v A )(x – x o ) A Car: (x – x o ) B = v B* t A = (v B /v A )(x – x o ) A Solved distance that would cause collision using Car A as reference with x oB = 0 at v B = 45 mph (792 in/s) Solved distance that would cause collision using Car A as reference with x oB = 0 at v B = 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 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 Kinematics of Rigid Bodies Position Analysis, Translation, Rotation Position Analysis, Translation, Rotation Kinetics of Rigid Bodies Kinetics of Rigid Bodies General Plane Motion General Plane Motion Momentum and Impulse Momentum and Impulse Conservation of Energy Conservation of Energy

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

Unrealistic (No Friction)

Linear Momentum Data

Right Before Impact

Bam!!

Realistic (with Friction)

Before Impact (With Friction)

Immediately After Impact

Basic Drop Test (Height = 2ft)

Maximum Contact Force (at h=2ft)

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