Elastic deformation is reversible, and the deformation disappears after the applied forces are removed. A typical example is the stretching of a spring. Plastic deformation is a process in which the body, due to exerted force, varies its shape or size in a manner that is not at all reversible. It is experienced by many things, including metals, plastics, rocks, concrete, and wood. This type of deformation is always irreversible, and it continues even after the removal of the exerted force. The bending of metal rods is a good example. There are many analytical explanations of plasticity. One of the main descriptions is deformation theory. Here, the Cauchy stress tensor is a direct function of the strain tensor (of order d-1 in d dimensions). Even though this explanation is correct when a small section of the matter is put through increasing loading (like strain loading), this description does not account for irreversibility.
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Plastic Deformation Questions and Answers
1) What is meant by elastic deformation?
Elastic deformation is reversible, and the deformation dies out after the applied forces are removed. A typical instance is the stretching of a spring.
2) What is meant by plastic deformation?
Plastic deformation is a process in which the body, due to exerted force, varies its shape or size in a manner that is not at all reversible. It is experienced by many things, including metals, plastics, rocks, concrete, and wood. This type of deformation is always irreversible, and it continues even after the removal of the exerted force. The bending of metal rods is a good example.
3) What are the two significant mechanisms of plastic deformation in metals?
In metals, plasticity is a result of dislocations, while in brittle substances such as rock, bone, and concrete, plasticity exists due to microcrack slippage. The two significant mechanisms of plastic deformation in metals are twinning and slip.
4) What is meant by slip?
Slip is one of the significant mechanisms of deformation in metals. Slip happens when a crystal body is stressed in tension beyond its elastic threshold. It stretches slightly, and a step appears on the surface, showing the displacement of one section of the crystal.
5) What is meant by twinning?
In twinning, the section of crystals imbibes an orientation connected to the orientation of the remaining untwined lattice in a definite and symmetrical way.
6) Give one difference between slip and twinning.
Slip happens in discrete multiples of atomic spacing. In twinning, the motion of atoms is less than in atomic spacing.
7) Give a brief about plasticity in metals.
In a pure metal’s crystal, plasticity is predominantly caused by two ways of deformation in the crystal lattice: twinning and slip. Twinning is a type of plastic deformation which happens along two planes because of a set of forces exerted on the metal piece. Slip is a deformation which displaces the atoms through numerous interatomic distances corresponding to their starting positions. The majority of metals display more plasticity when they are hot than when they are cold.
Lead displays ample plasticity at normal temperatures. On the other hand, cast iron does have enough plasticity for some forging activities, even when it is hot. This attribute is of importance in forming, extruding and shaping actions on metals. The majority of metals are turned into plastic bodies by heating, so they can be shaped when hot.
8) What is deformation theory?
There are many analytical explanations of plasticity. One of the main descriptions is deformation theory. Here, the Cauchy stress tensor is a direct function of the strain tensor (of order d-1 in d dimensions). Even though this explanation is correct when a small section of the matter is put through increasing loading (like strain loading), this description does not account for irreversibility.
9) Give a brief account of plastic deformation in soils and sand.
In particular, clays and soils show a significant level of inelasticity under some load. The reasons for plasticity in sand and soils can be complicated and are heavily dependent on water content, microstructure, and chemical composition. Plasticity property in soils is produced predominantly by the adjacent grains’ rearrangement of clusters.
10) Give a brief about plasticity in amorphous materials.
In the case of amorphous substances, the occurrence of “dislocations” is not at all applicable since the whole substance does not have long-range order. Such objects can still go through plastic deformation. As amorphous substances (for example, polymers) are sufficiently ordered, these materials possess a large amount of wasted space or free volume. Stretching these bodies in tension cracks up these sections and generates hazy appearances on these materials. This appearance is the culmination of crazing as fibrils are created within the bodies in sections of heavy hydrostatic stress. The substance may change from an ordered look to a “crazy” orientation of stretch marks and strain.
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Practice Questions
1) What is meant by stress?
2) What is the relationship between plasticity and stress?
3) What is the main difference between elasticity and plasticity?
4) What are the applications of plastic deformation?
5) What is the relationship between slip and twinning?
6) What is the principle behind the working of spring?
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