Friction Piece Micrometric Cavities High Contact Pressure

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Solution Overview

Problem

Existing surface treatments and coatings fail to effectively prolong the elastohydrodynamic lubrication regime in heavily loaded friction parts, as texturizing methods are incompatible with severe contact conditions and lead to damage and pressure drop in lubricant films.

Innovation Solution

A periodic network of micrometric cavities with predefined shapes and sizes is created on the contact surface using methods like femtosecond laser pulse machining or ion beam methods, with depths less than 10 μm, to promote elastohydrodynamic lubrication, combined with a case hardening treatment for enhanced tribological performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If surface texturizing is applied to promote elastohydrodynamic lubrication, then the lubrication regime is improved, but the bearing surface area decreases causing pressure drop and surface damage

Engineering Contradiction:

Improveelastohydrodynamic lubrication regimeVSAvoidbearing surface area

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The patent applies local quality by creating micrometric cavities with specific dimensions (depth 1-10 μm, diameter 10-100 μm) at specific locations on the friction surface. These cavities are not uniformly distributed but positioned to optimize lubricant retention while maintaining sufficient bearing surface area. The local modification of surface topology allows the surface to exhibit different functional properties in different regions: smooth areas for load bearing and cavitated areas for lubricant management.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the physical parameters of the surface topology by introducing micrometric cavities with controlled depth (1-10 μm) and diameter (10-100 μm). These parameter changes are optimized based on the operating conditions (contact pressure, sliding speed, lubricant viscosity) to promote elastohydrodynamic lubrication while minimizing the reduction in bearing surface area. The cavity dimensions are specifically tuned to retain lubricant films without causing excessive pressure drop.

Inventive Principle:

Principle #35Parameter changes

2Ease of manufacture

If conventional surface treatments are used, then manufacturing simplicity is maintained, but tribological performance under high contact pressure is insufficient

Engineering Contradiction:

Improvesurface treatment simplicityVSAvoidtribological performance

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent replaces conventional mechanical surface treatment methods with laser-based processing. The laser creates the micrometric cavities through ablation of the surface layer, eliminating the need for complex mechanical texturizing equipment. This substitution maintains manufacturing simplicity while achieving superior tribological performance, as the laser can precisely control cavity dimensions and distribution without mechanical tool wear or complexity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Loss of energy

If surface texturizing is applied to reduce friction, then energy dissipation is reduced, but contact pressure tolerance decreases

Engineering Contradiction:

Improvefriction energy dissipationVSAvoidcontact pressure tolerance

Core Design Contradiction:

Loss of energyVSStress or pressure

Solution Approach 1:

The patent applies preliminary action by pre-filling the micrometric cavities with lubricant before the friction contact begins. This preliminary lubricant placement ensures that when contact occurs, the cavities immediately provide lubrication, reducing friction energy dissipation from the start. The lubricant is retained in the cavities due to their specific dimensions, creating a reservoir effect that maintains lubrication under varying contact pressures without compromising pressure tolerance.

Inventive Principle:

Principle #10Preliminary action

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The solution significantly reduces friction coefficients, increases the maximum contact pressure tolerance, and extends the service life of mechanical parts by optimizing the dimensions of the cavities to adapt to the lubrication regime, reducing wear and energy dissipation.

Implementation Method 1

promote the passage to elastohydrodynamic lubrication regime

Methodology Applied

Scientific EffectElastohydrodynamic lubrication: Lubrication

Implementation Method 2

producing a periodic network of micrometric cavities having predefined shapes and sizes... by a femtosecond laser pulse machining method

Methodology Applied

Scientific EffectLaser ablation: Laser Ablation

Data Source

PatentUS8859078B2Friction piece in a lubricated medium, working at contact pressures higher than 200 MPa

Publication Date: 2014.10.14 H E F

AI summary

Friction part in a lubricated medium working at contact pressures above 200 MPa and having a contact surface that is textured and subjected, before or after texturizing, to a case hardening treatment for a tribological function, wherein the surface is subjected to operations for producing a periodic network of micrometric cavities having predefined shapes and sizes and a period adapted to the width of the contact surface in order to promote passage to elastohydrodynamic lubrication regime.