Friction, lubrication, wear and contact mechanics.
MODULE OVERVIEW
Tribology in practical engineering work.
Tribology studies friction, lubrication and wear at contacting surfaces. A friction estimate needs the material pair, surface state, speed, load, lubricant and environment; one coefficient rarely describes all conditions.
CORE PRINCIPLES
What to establish first
Friction force is commonly approximated from normal load and an empirical coefficient.
Lubrication regime changes with speed, viscosity, load and roughness.
Wear depends on contact pressure, sliding distance and contamination.
DESIGN CONCEPTS
Terms worth checking
Coefficient of friction
Lubrication regime
Wear rate
Common applications: Bushings · Slides and guides · Seals and brake interfaces
KEY RELATIONSHIP
Coulomb friction estimate
F_f = μN
μ — friction coefficient
N — normal force, N
F_f — friction force, N
μ is condition-specific and should come from representative test or supplier data.
Use the relationship with compatible units, then review the result against the stated design conditions.
WORKED EXAMPLE
Known values → substitution → interpretation
Known values
μ = 0.15; N = 2,000 N
Method
F_f = 0.15 × 2,000
Interpretation
The initial friction estimate is 300 N; lubrication state can change it substantially.
KEY DESIGN CHECKS
Confirm the conditions behind the number
Define the governing load case, duty cycle and required design life before using a simplified relation.
Use compatible units and material data for the actual condition, temperature and manufacturing state.
Compare the result with strength, stiffness, fatigue, safety, serviceability and applicable-code requirements.
COMMON ENGINEERING MISTAKES
Keep the model within its scope
Applying coulomb friction estimate outside the assumptions shown on this page.
Using a nominal condition while a peak, alternating, transient or environmental case governs the design.
Treating a calculated value as a final component selection without checking interfaces, tolerances and the current governing standard.
AVAILABLE CALCULATORS
Select a calculator
Engineering guide resources
This source-aware module explains the governing relationship, design checks and practical application. Use the related resource below or continue to the calculator library for an interactive calculation.
ReferenceB. J. Hamrock, S. R. Schmid and B. O. Jacobson, Fundamentals of Fluid Film Lubrication.ScopeRelationships are presented for the assumptions stated on this page and linked tool.Design reviewCheck material condition, loads, environment and the applicable current code.SafetyResults are educational/preliminary and do not certify safety or compliance.
