The document discusses crack deformation modes and failure in materials, emphasizing various forms of cracks such as fatigue, creep, and corrosion. It explores the stages of crack initiation and propagation, along with classifications of fractures, notably ductile and brittle fractures. Additionally, it outlines three loading modes of crack deformation as introduced by Irwin: opening mode, in-plane shear, and out-of-plane shear.

1. CRACK DEFORMATION MODES
Melwin D’mello
M.E (Welding Engineering)
Department of Manufacturing Engineering,
ANNAMALAI UNIVERSITY
By,

2. CONTENTS
 Crack
 Failure
 Fracture
 Modes of crack deformation
 Liberty ships failure

3. CRACK
 A break or split in material without a complete
separation of parts.
 Generally, the term is used to describe breaks in
solid material such as metals, stone, ceramics
etc…

4. CRACK INITIATION
Physically, cracks initiate from,
 An imperfection
 An already existing crack
 A damaged (weakened) area

5. STEPS IN CRACK
 Plastic deformation
 Crack initiation
 Crack propagation
 Fracture

6. FAILURE
 Failure is the condition of not meeting a
intended objective and may be viewed as the
opposite of success.

7. REASONS FOR FAILURE ?
 Fatigue
 Creep
 Corrosion
 Wear
 And many more..

8. FRACTURE
 A fracture is the separation of an object or material
into two or more pieces under the action of stress.
 The fracture of a solid usually occurs due to the
development of certain displacement discontinuity
surfaces within the solid.

9. TYPES OF FRACTURE
 Classification is based on the ability of a material to
experience plastic deformation.
 Ductile fracture
◦ Accompanied by significant plastic deformation
 Brittle fracture
◦ Little or no plastic deformation
◦ Sudden, catastrophic

10. MODES OF CRACK
DEFORMATION
 Irwin was one of the first to study the behavior
of cracks.
 He introduced three different loading modes,
which are still used today.

11. MODES OF CRACK
DEFORMATION

12. Mode I
 Mode I denotes a symmetric opening
(opening or tension mode)

13. Mode II
 Mode II denotes an antisymmetric
separation (In-plane shear mode)

14. Mode III
 Mode III denotes an antisymmetric
separation (out-of-plane shear or tearing
mode)

15. LIBERTY SHIPS FAILURE

16. References
 A text book of “ Mechanical Metallurgy”
by Gorge E. Dieter : Third edition (Indian
edition )

17. THANK YOU