The necking and fracture behavior of ductile metals is a crucial aspect of understanding material deformation and failure. Ductility refers to a material's ability to undergo significant plastic deformation before rupturing. Necking and fracture are two key stages in the deformation and failure process of ductile metals.

1. Necking & Fracture Behaviour of Ductile Metals
Mr. MANICKAVASAHAM G, B.E., M.E., (Ph.D.)
Assistant Professor,
Department of Mechanical Engineering,
Mookambigai College of Engineering,
Pudukkottai-622502, Tamil Nadu, India.
Email:mv8128351@gmail.com
Dr. R.Narayanasamy, B.E., M.Tech., M.Engg., Ph.D., (D.Sc.)
Retired Professor (HAG),
Department of Production Engineering,
National Institute of Technology,
Tiruchirappalli-620015, Tamil Nadu, India.
Email: narayan19355@gmail.com

2. Engineering Stress – Engineering Strain Curve for Ductile Metal
 Beyond yield stress, plastic deformation takes place.
 Beyond ultimate strength, necking starts.
 Beyond ultimate strength stress decreases with
increasing amount of strain.

3. Contd.
1. Voids are nucleated.
2. Void growth takes place.
3. Void becomes bigger.
4. One void join with another void.
5. Fracture

4. Void Coalescence During Necking

5. Sequence of Operation which Takes Place During Necking
 Voids are nucleated around the second phase particles.
 Void growth takes place.
 One void may join with another void.
 Finally load carrying ability of the metal is lost.
 Then fracture takes place.
Fracture Under Tensile Load

6. Fracture Under Shear Stress
Sequence of Operation which Takes Place During Necking
 Voids are nucleated around the second phase particles.
 Void growth takes place.
 One void may join with another void.
 Finally load carrying ability of the metal is lost.
 Then fracture takes place.

7. Void Growth

8. Effect of Average (or) Mean (or) Hydrostatic Stress on Fracture Strain

9. Contd.
Effect of Hydrostatic stress
 Under tensile hydrostatic stress, cracks will be opened.
 Under compressive hydrostatic stress, cracks will be closed.
Hydrostatic Stress Under Tension Hydrostatic Stress Under Compression

10. Fractrography SEM Image of Fractured IF Steel
Ligament Thickness (Space
between two consecutive
Dimples)
Void
Typical Ductile Fracture
Dimple

11. Void
Dimple
Fractrography SEM Image of Fractured IF Steel
Typical Ductile Fracture

12. SEM Image of HSLA Steel
Ligament
Thickness
Dimple
Void

13. References:
Authors of Technical articles and Scopus Journals are
Acknowledged.

14. Thank You