Elasticity

Plastic Deformation

Deformation is basically strain which means a change in the size and shape of an object. It takes place due to a change in temperature or an applied force. The different forms of deformation may happen depending on the size, material and the force applied. Thus, on the basis of these factors, we classify it into elastic deformation and plastic deformation. Firstly, elastic deformation is reversible and it disappears after we remove the applied forces. For instance, stretching of a rubber band. However, this article will focus on plastic deformation.

plastic deformation

                                                                                                                                           Plastic Deformation

Introduction to Plastic Deformation

Plastic deformation is the process in which the object changes its size or shape in a way that is not reversible because of the applied force. Even after the applied force removes, the shape remains the same. For instance, the bending of steel rocks.

We can notice plastic deformation in many objects like plastics, metals, soils, rocks and concrete. The mechanisms causing plastic deformation vary widely. Plasticity in metals is a result of dislocations.

On the other hand, in brittle materials like concrete, rock and bone, it arises due to the slippage of micro cracks. There are two prominent mechanisms of plastic deformation in metals which we know as Slip and Twinning.

Slip and Twinning

We refer to slip as the prominent mechanism of deformation of metals. It involves the sliding of blocks of crystal over one another along different crystallographic planes which we call slip planes.

In twinning, the portion of crystals takes up an orientation associated with the orientation of the rest of the untwined lattice in a symmetrical and defined way. Through the image below, you can get a depiction of slip and twinning deformation in a face-centred cubic crystal.

plastic deformation

We use pressure and heat to shape objects into the preferred form. The speed of stress causes rapid material changes. Moreover, at times it may not able to conform to the structural changes resulting in the breaking of the material.

When we use plastic deformation in the manufacture of goods, we carry it out under controlled heat and pressure. This allows the material to adjust to the structural changes and incrementally bend until the desired shape is achieved.

For instance, hard thermo-setting plastics, crystals and ceramics have negligible plastic deformation changes.

Difference between Slip and Twinning

Through the table given below, we can take a look at the difference between slip and twinning:

Slip

Twinning

It takes place in distinct multiples of atomic spacing. The movement of atoms is lesser in atomic spacing.
The orientation of the crystal above and below the slip plane remains the same after deformation as earlier. Orientation difference happens across the twin plane.
It occurs in several milliseconds. Occurs in a few microseconds.
It happens over a wide plane. It involves every atomic plane.
Slip lines are present in even or odd numbers. Twin lines arise in pair.
Slip takes place when shearing stress on the slip plane in the slip direction strikes a threshold value which we refer to as the critical resolved shear stress. No critical resolved shear stress for twinning.

FAQ on Plastic Deformation

Question 1: What is plastic deformation?

Answer 1: Plastic deformation is the process in which the object changes its size or shape in a way that is not reversible because of the applied force. Further, even after the applied force removes, the shape remains the same. For instance, the bending of steel rocks. We can notice plastic deformation in many objects like plastics, metals, soils, rocks and concrete.

Question 2: State two differences between slip and twinning.

Answer 2: First of all, slip occurs in discrete multiples of atomic spacing. On the other hand, in twinning, the movement of atoms is lesser in atomic spacing. Further, slip occurs in several milliseconds whereas twinning takes place in a few microseconds.

Question 3: What causes plastic deformation?

Answer 3: Plastic deformation is the permanent distortion that happens when a material is subjected to tensile, compressive, bending or torsion stresses that surpass its yield strength and as a result forces it to elongate, compress, buckle, bend, or twist.

Question 4: Is plastic deformation reversible?

Answer 4: Plastic deformation is the ability of a solid material to endure permanent deformation which is a non-reversible change of shape in response to applied forces.

Share with friends

Customize your course in 30 seconds

Which class are you in?
5th
6th
7th
8th
9th
10th
11th
12th
Get ready for all-new Live Classes!
Now learn Live with India's best teachers. Join courses with the best schedule and enjoy fun and interactive classes.
tutor
tutor
Ashhar Firdausi
IIT Roorkee
Biology
tutor
tutor
Dr. Nazma Shaik
VTU
Chemistry
tutor
tutor
Gaurav Tiwari
APJAKTU
Physics
Get Started

Browse

Elasticity

Leave a Reply

avatar
  Subscribe  
Notify of

Browse

Elasticity

Download the App

Watch lectures, practise questions and take tests on the go.

Customize your course in 30 seconds

Which class are you in?
No thanks.