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Depending on the position of an atom on a surface, it can be referred to by one of several names. Figure 1 illustrates the names for the atomic positions and point defects on a surface for a simple cubic lattice. Figure 2 shows a scanning tunneling microscopy topographic image of a step edge that shows many of the features in Figure 1.
These imperfections are part of the surface and cannot be removed by cleaning. Surface quality is characterized either by the American military standard notation (eg "60-40") or by specifying RMS (root mean square) roughness (eg "0.3 nm RMS"). [1] American notation focuses on how visible surface defects are, and is a "cosmetic" specification.
A scriber is a hand tool used in metal work to mark lines on workpieces, prior to machining. The process of using a scriber is called scribing and is just part of the process of marking out . It is used instead of pencils or ink lines, because the latter are hard to see, easily erased, and imprecise due to their wide mark; scribe lines are thin ...
Variations in the electrical conductivity and magnetic permeability of the test object, and the presence of defects causes a change in eddy current and a corresponding change in phase and amplitude that can be detected by measuring the impedance changes in the coil, which is a telltale sign of the presence of defects. [5]
The end goal of this step is a clean surface where any defects present are open to the surface, dry, and free of contamination. Note that if media blasting is used, it may "work over" small discontinuities in the part, and an etching bath is recommended as a post-blasting treatment. Application of the penetrant to a part in a ventilated test ...
Fractography is the study of the fracture surfaces of materials. Fractographic methods are routinely used to determine the cause of failure in engineering structures, especially in product failure and the practice of forensic engineering or failure analysis.
Sample Ishikawa diagram shows the causes contributing to problem. The defect, or the problem to be solved, [1] is shown as the fish's head, facing to the right, with the causes extending to the left as fishbones; the ribs branch off the backbone for major causes, with sub-branches for root-causes, to as many levels as required.
Crazing is a spider web pattern of cracks penetrating the glaze. It is caused by tensile stresses greater than the glaze is able to withstand. [1] [2] Common reasons for such stresses are: a mismatch between the thermal expansions of glaze and body; from moisture expansion of the body; and in the case of glazed tiles fixed to a wall, movement of the wall or of the bonding material used to fix ...