Meaning
Localized stress fields generated between two curved surfaces in contact define the load distribution of mechanical interfaces. Calculated hertzian pressure accounts for both the geometry of the contacting bodies and their elastic moduli. This parameter is important in predicting wear in gears and snap-fit assemblies.
Contact Mechanism
Concentrated loads applied to spherical or cylindrical polymer contacts generate high compressive stresses directly beneath the contact zone. For thermoplastic parts, hertzian pressure dictates the transition from elastic behavior to permanent deformation. This threshold depends on the yield strength of the specific polymer grade.
Deformation Mode
Mechanical interaction under these localized forces produces elastic deflection that increases the contact area as the load rises. High hertzian pressure in plastic gears causes localized heating due to the low thermal conductivity of polymers. This thermal build-up accelerates material fatigue and can lead to surface pitting.
Stress Concentration
Plastic components subjected to cyclic contact loading experience maximum shear stresses below the surface rather than at the immediate boundary. When the hertzian pressure exceeds the fatigue limit of the polymer, microcracks nucleate at this subsurface point and propagate outward. This mechanism eventually causes delamination or spalling of the material.
Increasing the contact radii distributes the contact force over a larger area, thereby lowering the peak stress value to a level that the polymer matrix can sustain over the intended product lifecycle.
