Tire Performance : Tread wear and vibration of tire

Wear is an indication of the life service of the tire. At each point with in the tire footprint, there is a normal contact force and a set of tanget force. When the resultant in-plane force exceeds the friction resistances associated with the normal force at a given point, the point slips and abrasion energy is generated.

We will consider the factors that affect tire wear. More even pressure distributions reduce the number of low pressure point and minimize the likelihood of slippage. High lateral forces associated with sharp cornering increase the likelihood of slipage and thus accelerate the tread wear. Tread wear is also dependent on the road texture, tread material properties and the temperature (High temperature High tread wear). Life service of tire or tread life is defined as the travel distance at which the nonskid depth reaches a specified value. Thus, all things being equal, the nonskid should be maximized to maximize tread life. For industrial tire, life service  or tread life is defined as the working time at which the nonskid depth reaches a specified value. However, too deep a nonskid can lead to unstable tread block elements, which may result in uneven wear and poor handling performance. Driver should buy the depth gauge for measure the tire wear of his tire. A key feature of tread wear performance is the evenness of wear. Uneven wear generate noise and ride disturbances and causes additional premature wear of isolated spot on the tread surface. Tire swiching inside/outside wheel position is reduce uneven wear. In industrial tire uneven wear generate radial crack on side wall.

Tire vibration charateristics of a tire design can be computed by finite element analysis(FEA), yielding the natural frequencies and associated mode shapes in the radial, lateral, and circumferential directions. The mode shapes and natural frequencies can also be measured by rolling the tire on  drums or flat tracks and measuring the tire response. To prevent resonace, the tire's  first natural frequencies should be different from the vehicle' s naural frequencies.

Rubber to metal bonding

Rubber to metal bonding is used in wide industrial such as shaft seals, gaskets, engine mount ,rubber rolling, bridge bearings etc. Elastermer selection is important in rubber product that present above. In this content we will present principal and performance of rubber to metal bonding detail as below. 

Principal of bonding agents

• Applied like tackfree paints or varnishes to bond elastomers on rigid substrates under vulcanization conditions.
• Advantage , Simultaneous molding and bond formation process between elastermer and substrate.

Requirement of bonding agents

• Bond strength such as initial bonding . type of elastomer and vulcanization system.
• Application such as application method, film formation and drying condition.
• Storage such as shelf lift at variable temperature, freeze-thaw-stability and heat resistance.
• Processing such as vulcanization method, prebreaking, method fouling and short curing cycles.
• Resistance such as boiling water, salt spray climate, glycol and heat etc.

Product of rubber to metal bonding.

There are two type as standard product and special product. Standard products has three products as primer, covercement and one coat bonding agent. Special products has two product as waterbased bonding agents and electrostatic sprayable bonding agents.

Bonding performance.

Bonding performance influence  from rubber selection , hardness of cured rubber , carbon black concentration and type of carbon black, anioxidant or antiozonants type, curative, compound cure, plasticizer concentration and type.

Adhesive selection.

• Which elastomer stock?
• Durometer of the cured rubber compound.?
• Cure speed?
• Rigid substrate selection?
• Special pre-bake and or sweep requirements.
• How will adhesive be applied to the metal?

Instruction of rubber to metal bonding

Figure 1 Instruction of rubber to metal bonding

How to apply rubber to metal bonding.

• Brush coating used in small scale ; usually applied undiluted.
• Spray coating : used in large scale ; using jig for complex and specified area shape.
• Dip coating : used in large scale ; avoiding tears and fatty edges from dip tank.
• Roller coating : used in large flat sheets or roller components ; low product waste , uniformity film thickness.

Figure 2 example of rubber to metal bonding*

Ref. from http://www.butserrubber.com/products/

Hysteresis effect in race car tire and street car tire.

Tires are made from rubber, which is a viscoelastic material the loading and unloading stiffness curve are not exactly the same thus which make a loop with the unloading curve below the loading. The area within the loop is the amount of dissipated energy during loading and unloading. We are called hysteresis loop or damping properties .As a tire rotates under the weight and carry load of a vehicle, it experiences repeated cycles of deformation and recovery and it dissipates energy loss as heat. The amount of dissipated energy depends on the mechanical characteristics of the tire. Hysteresis energy loss in rubber decreases as temperature increases. The hysteresis effect causes a loaded rubber not to rebound fully after load removal.
Consider a high hysteresis race car tire rolling over road irregularities. The deformation tire recovers slowly and therefore, it cannot push the footprint tail on the road as hard as the footprint head. The difference in tail and head pressure causes a resistance force, which is called rolling resistance. Race car have high hysteresis tire to increases friction and limited traction that improve stability during running match. Street car such as passenger car  truck tire and solid tire have a low hysteresis tire to reduce the rolling resistance and low operating temperature that improve fuel consumption.  Hysteresis level of tire inversely effect the stopping distance such as a high hysteresis tire make the stopping shorter however it wear rapidly and has a shorter life time but do not affect with race car .