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The Mechanical Wear تاريخ الخبر: 13/03/2022 | المشاهدات: 580

مشاركة الخبر :

Wear is a form of surface damage that occurs as a consequence of relative motion between the surface and another surface or object, and results in the gradual removal of material from the surface. Wear may manifest itself as material displacement to the sides of grooves or material loss due to debris breakaway. There are three steps to the wear rate over time :
I. Primary or early stage, where rapid rate of change is possible.
II. Secondary or middle-age stage, where steady rate of strain is often comprised of life span at this stage.
III. Tertiary or old-age stage, or (catastrophic wear), where quick rate of strain leads to early catastrophe with increasing severity of environment conditions, such as greater temperature strain proportions, stress, and gliding velocities.
There are some types of wear as follows :
1. Adhesive wear :
It happens when two smooth bodies, whether lubricated or not, are in slipping contact. Adhesion (or bonding) happens at the interface's asperity contacts, which are sheared by slipping, resulting in the removal of a fragment from one surface and binding to the other. These fragments can later fall free from the surface where they were created and are transported back to the initial surface, or they may form loose wear particles. Adhesive wear is the most popular and difficult preventable form of wear.
2. Abrasive wear :
It happens when asperities from a rough surface or hard particles slip over a softer surface and trigger plastic deformation or fracturing of the interface. Hard asperities or hard particles trigger the plastic flow of the weaker substance in ductile fabrics of strong fracture toughness. Plastic flow can be seen on most metallic and ceramic surfaces while slipping, including on fragile ceramic materials. Metals that come into contact with asperities deform plastically even under the lightest loads.
3. Corrosive wear :
When slipping occurs in corrosive conditions, corrosive wear happens. The most corrosive medium in the air is oxygen. As a result, chemical wear in the air is often referred to as oxidative wear. The corrosion items can create a coating on the surfaces if there is no slipping. This film has the effect of delaying or even stopping corrosion. The corrosive assault persists, though, so the slipping motion wears the film down. As a result, both chemical reaction (corrosion) and abrasion are needed for chemical wear.
4. Surface fatigue wear :
It can be seen while slipping or moving along a track repeatedly. The materials may develop surface or subsurface cracks as a result of repetitive loading and unloading cycles, which will eventually result in the surface breaking up and the forming of large fragments, leaving large pits at the surface.

Lect. Dr. Marwan Abbas Madhloom