What is Vehicle Dynamics, Tires Flashcards
What is Vehicle Dynamics?
How a vehicle behaves during motion
-> How does a vehicle respond to a certain driver input
-> Analysis whether that response is safe and comfortable
What are the two approaches to Vehicle Dynamics, Explain them
Empirical -> trial an error
Analytical –> use of mathematical models that follow the laws of physics to predict the response of a car
Draw a flowchart concerning vehicle dynamics
what are the 3 areas of vehicle dynamics?
Longitudinal Dynamics -> how does the vehicle respond under acceleration, breaking and how stable is the car in a straight line
Lateral Dynamics –> How does the vehicle respond while turning
Vertical Dynamics –> How does the car respond vertically
What materials exist in tires?
Antioxidants, Antiozoneants, Curing Systems
Filler (Carbon & Black Silica)
Natural Rubber
Textiles
Synthetic Polymers
Steel
What do Antioxidants, Antiozoneants, Curing Systems do for the tire?
Antioxidants –> Prevents thermal degradation of the natural rubber from oxygen
Antiozoneants –> Prevents thermal degradation of the natural rubber from oxygen
Curing Systmes –> Helps to vulcanise the rubber (Harden it)
What do Fillers do for the tire
Fillers improve wear resistance and traction
Silica decreases the rolling resistance
What do textiles do for the tire
Reinforce the tire
provides dimentional stability
What is dimensional stability
a materials ability to maintain its original dimensions and shape
how is steel implemented into the tire, what does it do for the tire
steel embedded in tire belts
-> provides more stability and stiffness to the tread
-> improves wear performance and road handling
What does natural rubber do for the tire
visoelastic material
Tear and fatigue (crack) resistance
Deformation and mechanical resistance
Impermeable substance
What do synthetic polymers do for the tire
Decreases rolling resistance and wear
Increases Traction
What’s the Notion for an Elastic Material, Friction and a Damper/dashpot
What is the notation for a metal
what is the notation for a kelvin model of a visoelastimer
what is the notation for the maxwell model of a visoelastomer
Explain the Maxwell Model
A Model that predicts the deformation of a visoelastomer
Assumes simultaneous elastic deformation and dashpot activation
Focus’ on creep behaviour, doesn’t take relaxation into account
Explain the Kelvin Model
A Model that predicts the deformation of a visoelastomer
Assumes time dependant elastic deformation and dashpot activation
Uses Maxwell and Voigt models (Creep and relaxation)
More realistic for predicting visoelastomer deformation
What is creep
gradual and permanent deformation over time
what is relaxation
observed decrease in stress when a material is stretched to a constant strain
Draw and explain a stress-strain graph for elastic deformation
Loading and unloading lines remain identical untill the yield strength is supassed
Draw and explain a stress-strain graph for visoelastic deformation.
Explain the Hysterisis Loss
Different loading and unloading lines
The gap between the loading and unloading lines is called the Hysterisis Loss
Explain the Hysterisis Loss
Constant loading and unloading of tire treads cause small permanent deformation over time
Loss in performance
Loss is compensated by the vehicles engine, - less fuel efficient
Draw and explain the distribution of stresses of a stationary tire
Symmetric distribution of forces on the contact patch
Contact pressure = inflation pressure
what is contact pressure and inflation pressure
Contact pressure -> reaction force between the car and the ground
inflation pressure –> pressure caused by the air in the tire
Draw and explain the distribution of stresses on a tire rotating anticlockwise
Distribution shifts to the left
At the same strain, the loading curve has a higher stress then the unloading
The LHS tire is loading , RHS is unloading
More stress on the LHS
Draw a picture to aid with your explanation of rolling resistance
At the centre of the tire a pair of equal an opposite forces , cause a couple and a moment against the motion of the tire.
This moment produces a force against the motion of the car called Rolling resistance
-> produced due to a property of elastic or visoelastic materials
what is the equation of Rolling Resistance
