Laboratory tests offer significant insight into the factors that contribute to the performance of the material. One main advantage is that a laboratory test offers highly controlled conditions, which helps isolate individual features and ignore distracting variables.
Key Points to Remember
The main points to remember before performing any abrasion test are:
- Understand why one is performing the test and what needs to be done with the data
- Confirm that the end point is understood and defined. For visual comparisons, it is better to have an agreed upon rating chart between the deemed parties of what actually is acceptable.
- Reduce operator error by offering effective training for lab personnel
- Clear ambiguity in the test method
The Abrasion Test
Wear is a response that results from the conditions to which the complete system is exposed. The test conditions such as such as the nature of the abradant, variable action of the abradant over the specimen area, the specimen tension, pressure between the abradant and the specimen and the dimensional changes in the specimen impact the abrasion in the specimen.
For a laboratory abrasion test, it is important to accept the fact that it will not be possible to precisely identify all the influences that create the wear condition. The parameters that must be adhered to while conducting tests needs to be specified by most standardized test methods. In case one is not following an established test, careful consideration needs to be given to the following influences:
- Contact geometry
- Length of exposure
- Interacting material surfaces
- Normal force
- Sliding speed
- Environmental conditions
- Material composition and hardness
Example of Recreating Wear
In order to demonstrate how complicated it is to recreate wear, the following example is considered, which is presented by Adam Varley of Vartest Laboratories.
A person’s body weight presses down the fabric when a person sits on an upholstered chair and the cushioning fabric pushes up against the upholstery fabric, compressing it, and the body of the user provides a force that drives the fabric they are wearing across the surface of the upholstery fabric causing abrasion to occur. Tension or shear forces at the same time are placed on the fabric as it pulls against its support.
There needs to be an enormous variation with body shapes and sizes that need to be considered. Also different fabrics need to be considered. Most textile technologists agree that wear on textiles includes all interacting factors that may cause a fabric to fail; rubbing, flexing, snagging, stretching, twisting, and exposure to chemicals, sunlight, heating, etc.
Factors specific to the fibers such as fiber content, fiber mechanical properties, fiber shape and dimension, yarn structure, yarn twist, yarn size, yarn ply, and the type, kind and amount of finishing materials added to the fibers or yarns, fabric construction, thickness, thread count and weave type.
Certain helpful hints to be followed include:
- The fact whether or not a specific type of abrasion test correlates with end-use performance depends not only on a similarity of abrading mechanisms, but also on the extent to which that mechanism is maintained during the course of the abrasion test.
- Abrasion resistance is a combination of .fundamental properties of the specimen such as elasticity, hardness, strength (both cohesive, tensile, and shear strength, toughness and especially in the case of wear resistance, thickness.
- The wear mechanism is based on the topography of the counterface abradant. It is preferable in most cases to use an abrasive only once, unless it can be refreshed.
- Different types of wear can occur in combination or on different areas of the same component.
- Particles that are responsible for erosion or abrasion are between 1 µm and 500 µm in size.
- Materials may not exhibit the same relative order of resistance to abrasion when tested by different methods.
- Test methods that lack critical procedural information could introduce problems with reproducibility.
- When multilayered systems are evaluated the substrate plays a key role. While evaluating results of tests on a range of substrate materials use caution.
- Loading systems and humidity have an impact on test system dynamics.
- One should not assume that wear rate is a linear function of time or the number of contact cycles it is very much based on the type of wear, materials and the contact conditions.
- One must make sure that steady-state conditions are achieved. Certain materials may require a run-in period.
- Extrapolate results only with great caution.
- Do not use loads that exceed the ultimate strength of a material or speeds that can cause a thermal condition on the test specimen.
This information has been sourced, reviewed and adapted from materials provided by Taber Industries.
For more information on this source, please visit Taber Industries.