Quantifying Time Dependent Viscoelastic Deformation during Coordinate Metrology Audits
Unmanaged viscoelastic creep under metrology clamping fixtures consumes up to forty percent of engineering tolerances, requiring documented dwell periods.
Contact Stress
Meaning
Mechanical resistance developed at the interface of two solid bodies under compressive load represents a fundamental structural metric. When force is applied across a localized surface area, contact stress arises and can generate internal shear stress beneath the boundary. Engineers analyze these localized forces to prevent premature subsurface cracking or spallation in gears and rolling-element bearings.
This assessment differs from bulk stress measurements since it concentrates exclusively on the immediate boundary region where the two bodies touch.
Interfacial Pressure
Distribution of surface forces varies depending on the geometry and elastic modulus of the mating components. Under a non-conforming scenario, hertzian contact stress governs the distribution, creating an elliptical pressure profile. Rigid substrates generate high peak pressures that demand careful lubrication to avoid metal-on-metal contact.
Repetitive Wear
Repetitive applications of contact stress induce micro-cracks that initiate below the surface and propagate outward. Surface forces exceeding the fatigue limit of the material accelerate this mechanical degradation. Surface texturing and surface hardening treatments can mitigate this type of damage.
Calculation Method
Mathematical models and finite element analysis determine the pressure profile across the contact zone. Calculating contact stress requires knowing the Poisson ratio, the applied load, and the radii of curvature of the contacting bodies. Accurate calculations help in sizing mechanical components to ensure operational reliability.