Influence of Specimen Fabrication
For specimen dimensions below 1 mm, maximized precision of specimen preparation is a basic requirement. This includes high accuracy of specimen dimensions, avoidance of burrs or notches, and a surface without grooves or excessive roughness.
Any change in the tested material caused by the fabrication method - such as cold work or overheating - must be avoided.
The JTE publication discusses the influence of different fabrication methods. Electrical discharge machining can lead to a recast or white layer, a heat-affected zone, micro cracks or residual stresses near the surface. Mechanical machining can influence the surface through cutting stresses, striations and machining heat.
A grinding process causes low influence on the material during shaping. Circular grinding provides high geometrical accuracy, and water cooling can reduce machining heat to a minimum level. An additional polishing process can be applied if needed.