Hardness Tests of Materials Definition of hardness: Hardness is a surface property. It is defined as the resistance of a material against permanent deformation of the surface in the form of scratch, cutting, indentation, or mechanical wear. Diamond is the hardest known material. In various hardness tests, the indentors are used to introduce indentation on …
In order to determine the mechanical properties of materials certain tests are carried-out. Depending on the nature of tests, these are classified as follows: Destructive Tests of Materials Generally specimens are tested on machines in the laboratory under static, dynamic or impact loadings. Most common among mechanical destructive tests are the following: Now, we shall …
The non-destructive testing (NDT) refers to a method of detecting internal flaws in engineering materials, machine components, and structures without breaking them. These tests are essential to ascertain absolute safety and reliability in engineering applications: particularly in strategic industries such as atomic energy, missiles, defense, aeronautics, space etc. The non-destructive testing techniques can be employed …
Creep in Materials The permanent deformation (strain) of a material under steady load as a function of time is called creep. A very common observation, in which length of our waist belt increases after some duration, is due to creep effect. It is thermally actuated process, and hence is influenced by temperature. It is, however, …
Definition: The behavior of materials under fluctuating and reversing loads (or stresses) is known as fatigue. This behavior is different from that under the steady load. Fatigue is, however, not a dynamic effect. The rate of loading is usually not a factor in fatigue behavior. Fatigue behavior is experienced by all materials whether metals, plastics, …
Types of Dislocation in Crystalline Solids Line imperfections are called dislocations. There are two primary types of dislocations. These are: Edge Dislocations To understand an edge dislocation, consider a perfect crystal shown in Figure 1(a). Atoms (not shown in diagram) are located on each cross-point in it. A perfect crystal is free from dislocations. Now …
Imperfections in Crystalline Solids A perfect (ideal) crystal is a perfectly ordered arrangement of atoms at the points of infinite space lattice. Any departure from this idealized arrangement makes the crystal imperfect. A perfect single crystal is rarely available. Crystalline materials have real crystals. They are of finite dimensions. They have broken bonds at the …
Crystal Structure Analysis by X Ray Diffraction Structures of solids can be determined by various techniques. Out of these techniques, X-rays and microscopic studies have helped immensely in studying crystallography of metals. Therefore these two techniques are very popular. Hence X-rays will be discussed in this article and microscopy is discussed in another one. X-RAYS …
Miller is the name of a material scientist. Indices is plural of index. Miller indices are the styles to designate the planes and directions in the unit cells and crystals. Such designations become essential for investigations of various properties in different elements. In the most general way, Miller indices are expressed by (hkl) and no …
Classification of Solids Solids, on the basis of their structures, may be classified as: Examples of such solids are as under: Metallic solids: Na, Cu, Zn; compounds such as borides, hydrides, nitrides, carbides etc. formed by transition elements. Ionic solids: NaCl, Na2SO4, MgAl204, calcite (CaCO3), magnesia (Mg0), Zincblende (or sphalerite) ZnS having FCC structure, and …