![]() In ductile materials, plastic deformation occurs when the shear stress exceeds the shear strength before another mode of fracture can occur, with necking typically in evidence before final fracture. Numerous factors influence whether a fracture will behave in a ductile or brittle manner (Table 2). Both of these micro mechanisms primarily result in transgranular (through the grains) fracture. The cleavage mechanism occurs very suddenly via a splitting action of the planes with very little deformation involved. The shear mechanism, which occurs by sliding along specific crystallographic planes, is the basis for the macroscopic modes of elastic and plastic deformation. As a result, the two basic modes of deformation/fracture (under single loading) are shear and cleavage (Table 1). ![]() Virtually all engineering metals are polycrystalline. These will be discussed in more detail in Part 2. In combination with the other application conditions, the result is one of four primary modes of fracture: dimpled rupture (also called microvoid coalescence), cleavage, decohesive rupture and fatigue. The result is a macroscopic stress state comprised of normal stress (perpendicular to the surface) and/or shear stress (parallel to the surface). 2) may be unidirectional or multi-directional in nature and occur singularly or in combination. ![]() As heat treaters, we must also consider that residual stresses can often play an important role.Īpplied loads (Fig. ![]() The failures that result may be categorized in a broad sense as those related to fracture, wear, corrosion and dimensional change/distortion. In service, components experience different types of conditions/environments, damage mechanisms and applied loading, including tension, compression, bending, torsion and mixed modes (combinations). In simplest terms, a failure is the inability of a component part to perform its intended function (Fig. This type of information helps the heat treater create a set of do’s and don’ts that are invaluable in avoiding a repetition of the problem. ![]() Gathering all possible information about the damage event and performing a thorough failure analysis is a critical first step in the process. When a component part fails, it is only natural to ask why and then strive to determine the root cause. ![]()
0 Comments
Leave a Reply. |
Details
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |