How do you design an engine that can go 100,000 miles between oil changes? How do you make soles for sneakers that help an athlete to stop fast, change, direction, and accelerate? Can we apply the "stickiness" of a gecko's feet to create adhesives that can be used around the house?
Surface finish affects how components function, look, and wear, in applications from engines to footwear to hip joints. There's a common perception in industry that surface texture is a number that you read from a gauge—some target value to be achieved. But the reality is much more interesting and complex.
Dr. Donald Cohen, one of the country's foremost experts in surface roughness, has been leading classes in surface roughness, friction, and tribology for over twenty years. Dr. Cohen's classes focus on surface texture analysis and how surface texture relates to functions such as wear, fit, and friction. The training is designed for scientists, engineers, technicians and students working in the fields of automotive, medical devices, aerospace, materials, polymers, and others.
The ten modules of this class focus on the following topics (these ten modules are also available individually on udemy):
1. Introduction to surface texture and measurement
• Why is surface texture important?
• Instruments for measuring surface roughness and texture
• Correlation between measurement instruments
This module is available for free, as an introduction to the class and to surface texture in general.
2. Filtering of surface texture measurements
• How spatial wavelengths/frequencies make up surface texture
• Roughness vs waviness vs form
• Setting cutoff wavelengths
• Specifying texture per the ISO 1302 and ASME 14.36 standards
Much of the following course material builds on this module, so we recommend it as a starting point.
3. Surface texture parameters
• Introduction to common 2D and 3D surface texture parameters
• Amplitude (height) parameters
• Spatial parameters
• Hybrid parameters
• Functional parameters
• The best parameters for various applications and functions.
4. Wear
• Wear mechanisms and how they progressively modify a surface and alter its functionality
• Surface texture parameters for quantifying wear
• The relationships between wear and material properties.
5. Dry Friction
• The mechanisms of friction in non-lubricated systems
• Measuring friction and parameters for quantifying friction
• How surface texture relates to friction
• The "area of real contact"
• Plastic and elastic deformation.
6. Lubricated Friction
• The mechanisms of lubricated friction and how it is quantified
• Lubricants and lubricant properties (viscosity)
• The effects of surface texture in lubricated systems
• The hydrodynamic, elastohydrodynamic, mixed and boundary regimes
• How friction differs in each of these regime.
7. Rolling friction
• The mechanisms of dry, rolling friction
• Definitions and difference between tractive rolling, tractive friction, and rolling friction
• The reasons why rolling friction is so much lower than sliding friction
• The relationship between surface texture, lubrication, and rolling friction.
8. Surface Energy, Wetting and Surface Roughness
• The relationship between surface energy and surface wetting
• The dynamics that determine how a liquid will react on a surface
• The role of surface texture on whether a liquid will wet a surface
• Hydrophilic and hydrophobic surfaces
• Surface modifications to achieve a desired wettability.
9. Seals, Sealing, and Surface Finish
• Types of sealing systems and materials
• Impact of surface roughness and waviness
• Surface texture parameters for sealing applications
• Virtual gaskets (aka "morphological filters")
• The Bearing Ratio (or Material Ratio) curve and its application to seals.
10. Coatings: Surface Roughness from Substrate to Topcoat
• How the surface texture of the substrate and each level of a coating system affects final appearance
• Instruments for measuring paint appearance
• Specifications for controlling spatial wavelength bands on substrates and coating layers.
Each of these modules is also available independently on udemy. Note that you save 20% by purchasing this full course.
This class may be for you if you:
• work in manufacturing, quality, or design engineering
• want to learn how surface texture affects performance
• need to solve problems related to surface texture in your work or research
• are a student exploring any of these areas.
