Metrology-6-Surface Texture Flashcards
What can careful finishing of components improve?
- Fatigue resistance
- Bearing properties
- Interchangeability
- Wear resistance
These can lead to longer operational life
What are engineering components often subject to?
Repeated reversals of stress which causes fatigue
Where are failures due to fatigue always initiated or started?
At a sharp corner or defect, such as the root of a surface irregularity.
such fatigue failures can arise due to surface defects even on non-working surfaces of the component.
What would not make a good bearing?
A perfect surface with no irregularities and therefore perfectly smooth.
What would a perfect surface allow?
Metal-to-metal contact and would not maintain a lubrication film. This would cause surface bonding, very similar to two slip gauges
being wrung together.
What is done to traditional bearings surfaces?
Scraping providing
large contact areas with valleys which helped to
maintain the lubrication film.This form of finishing is expensive and other methods
are used such as including low friction materials in the
bearing surfaces.
What is the rate of wear dependent on?
The surface area of a material contact.The larger the area of contact, the lower the load per unit area, and
hence the lower the rate of wear.
How long have surface texture assessments been practiced for?
The last 150 years
When didsurface measurement instrumentation become common place?
After 1945,
What did early engineers rely on for surface texture quantification?
Visual/ tactile comparative measurements
Sets of roughness standards have been developed for every machining method and obtainable value known.
how due you increase roughness?
Reducing the spacing of the high points
What aspects do most surfaces exhibit?
Roughness: The irregularities in the surface arising from the inherent action of the cutting process.
Waviness: The irregularities caused mainly due to machine vibration and deflections under cutting force.
Errors of form: The departure from the geometrical shape
What are the primary and secondary quantifiers of surface texture?
Primary: roughness
secondary: waviness
What is the most common design of surface texture measuring?
A mechanical stylus is used to trace the surface, providing a signal which is electronically magnified.
What do the skid and stylus of a surface texture instrument provide?
Skid provides a measurement datum
Stylus provides accurate texture assessments
