Fundamental Mechanisms
External Parameters
Testing
Fuel Consumption
Design & Tradeoffs
100
Define rolling resistance! & what are the units?
The energy dissipated by a tire per unit distance traveled
Units = [J/m] or [N]
100
How does an increase in ambient temperature affect RR?
Increase in T leads to a decrease in capability of the compounds to dissipate energy, so RR decreases (1 degree --> 0.6% change in RR)
100
Name the stabilized test method and transient test method used to measure RR in a machine test?
Stabilized: ISO 28580
Transient: SAE J2452
100
What tire component is the largest contributor to RR?
The tread/undertread
100
In sculpture design, what are the 2 main mechanisms which compete with each other?
Bending and compression
200
Crr = ____ /_____ ?
Rolling resistance (Frr) divided by load (Z)
200
Decrease Pressure, then RR: Increases or Decreases?
RR increases,
because an under-inflated tire is over-deflected and dissipates more energy
200
The skim test is a ___ method to measure RR.
Torque, force, or electrical power
Force
200
RR contributes what % to the total fuel energy for ICEs vs. Electric vehicles
5% for ICEs
16% for electric vehicles
200
RR and Traction tradeoff is due to what? Explain the tradeoff
Due to visco-elastic properties of materials- the frequencies of material's deformation are different.
300
Describe the 3 basic energy loss mechanisms of a rolling tire?
1. Flattening/ bending (of tire to form contact patch)
2. Shearing of rubber
3. Sliding of tread blocks on the ground
300
RR ______'s as macro surface increases in roughness
RR ______'s as curvature of ground increases
INCREASES (for both)
300
Provide 3 differences between ISO 28580 and SAE J2452 tests
300
Name at least 3 design factors that can be optimized between tire and vehicle to reduce energy consumption
Any of : CRR, Gear ratio, aero drag, mass of tire/wheel, static alignment setttings
300
Does RR increase or decrease with increasing mileage? WHY?
DECREASES, because reduced hysteretic rubber volume and stiffer tread blocks
400
Fill in the blanks:
Energy dissipation depends on rigidity and loss of materials; which behavior is a function of _____, _____, and _____.
Temperature, Frequency, and Strain
400
Why do you consume energy when you apply a load to a tread block?
Because any change in strain of rubber (via compression, extrusion, or shear) will produce hysteresis energy loss
400
How do you reduce measurement uncertainty due to manufacturing uncertainty?
Increase sample size
400
*FREEBEE* Spell Adams Last Name
Tuiletufuga
400
How do BAZ pattern and cured ANT both impact RR?
They both can impact footprint shape.
Rounder footprint shape leads to more transversal bending. And more BAZ turns increases hysteretic material.
500
What is RR primarily due to?
Viscoelastic heat dissipation in the rubber
(Energy dissipation due to tire deformation in the contact patch)
500
Fully explain impact of rolling time on RR
Initially, at low rolling times RR decreases rapidly and non-linearly. But after a significant time RR reaches steady state. This is because it takes a significant time for the tire to heat up and reach steady state operating temp (and RR level)
500
Which is the the greatest and why: manufacturing uncertainty OR machine uncertainty?
Manufacturing uncertainty is significantly larger due to function of design and process, and bc its not well correlated to weight
500
Name the empirical linear formula derived that predicts differences in fuel consumption. AND what does the sensitivity coeff. depend on?
Alpha depends on fuel energy density and effective energy efficiency
500
In what 2 ways can mixed chutes impact RR?
Mass increases with mixed chute, which increases RR. Higher hysteretic material properties of mixed chute will increase RR