Theory Of Elastic Failures (1).pdf

Theory of Elastic Failures

1. GOVERNMENT POLYTECHNIC MUNGER
( Dept. Of Science & Technology Govt. Of Bihar )
CONTENT
DESIGN
OF MACHINE ELEMENTS
JULY 2023 SESSION 2020-23

2. MECHANICAL ENGINEERING
Diploma In Engineering

3. THEORY
OF ELASTIC FAILURES

4. GUIDENCE
BY
ABHINAV SIR
Dept. Of Mech Engineering
GPM
Kharagpur

5. PREPARED
BY
SUMAN SAURAV
MECHANICAL ENGINEERING
62/M/20
SESSION
2020-23
SEMESTER
JYOTI KUMARI
MECHANICAL ENGINEERING
38/M/20
SESSION
2020-23
SEMESTER
BIKKI KUMAR
MECHANICAL ENGINEERING
14/M/20
SESSION
2020-23
SEMESTER
ROHIT RAJ
MECHANICAL ENGINEERING
23/M/20
SESSION
2020-23
SEMESTER
MANISH KUMAR
MECHANICAL ENGINEERING
29/M/20
SESSION
2020-23
SEMESTER
GAURAV KUMAR
MECHANICAL ENGINEERING
15/M/20
SESSION
2020-23
SEMESTER
AMARDEEP KUMAR
MECHANICAL ENGINEERING
55/M/20
SESSION
2020-23
SEMESTER

7. The meaning failure of the machine is the
non-ability of the component or a machine to
perform its function as per requirement.
Failure of a machine or any mechanical
components does not mean a total
breakdown or not operating. It can operate
but not as per our requirements
FAILURE OF MACHINE
BEHAVIOUR OF MATERIAL
The analysis of failure of material help to
know the actual reason of their failure
Some examples of such components are as follows :
I.C. engine crankshaft
Bolted and welded joints are used under eccentric
loading.
A shaft which is used in power transmission
• Ceiling fan rod
Failure of material with plastic deformations
will be either direct seperation of particles
from each other (brittle fracture) or slipping
of particles (ductile fracture or yielding)

8. A. The limiting strength for ductile materials
is yield point stress Ductile materials usually
fail by yielding i.e. permanent deformation
occurs in the materials.
B.The limiting strength for brittle materials
is ultimate stress point. Brittle materials
usually fail by fracture
FAILURE OF MACHINE BEHAVIOUR OF MATERIAL
If the material is subjected to single type of stress
(axial, bending or torsional), then it is easy to
predict, when the failure is likely to occur
If material is subjected to complex stress( Bi- axial
& Tri- axial ) system, then it is not easy to predict
the failure. In order to do this, the Theories of
failure are used.

9. Since failure of material is complex phenomenon,
no single theory is perfect in all conditions hence
there are several theory for predicting failure on
basis of different criterias.
FAILURE OF MACHINE
1. Maximum Principal Stress Theory ( M.P.S.T
or
" Rankine Theory "
⇓
⇒ Best For Brittle Material
2. Maximum Shear Stress Theory
or
" Guest/ Tresca's Theory "
⇓
⇒ Best For Ductile Material
3. Maximum Principal Strain Theory
or
" St. Venant's Theory "
4. Maximum Strain Energy Theory
or
" Haigh's Theory"

5. Maximum Shear Stress Theory
or
" Von- Mises Theory "
⇓
⇒ Best For Ductile Material

10. MAXIMUM PRINCIPAL STRESS THEORY
Henri Edouard Tresca, born on 12 October 1814, was a French
mechanical engineer. He discovered the Tresca yield criterion, also
called maximum shear stress theory, which is one of the two main failure
criteria used today for ductile materials along with von Mises yield
criterion. He became anhonorary member of the American Society of
Mechanical Engineers ASME) in 1882. He is called the ‘father of
plasticity’
1

11. MAXIMUM SHEAR STRESS THEORY
Henri Edouard Tresca, born on 12 October 1814, was a French
mechanical engineer. He discovered the Tresca yield criterion, also
called maximum shear stress theory, which is one of the two main failure
criteria used today for ductile materials along with von Mises yield
criterion. He became anhonorary member of the American Society of
Mechanical Engineers ASME) in 1882. He is called the ‘father of
plasticity’
2

12. MAXIMUM PRINCIPAL STRAIN THEORY
Henri Edouard Tresca, born on 12 October 1814, was a French
mechanical engineer. He discovered the Tresca yield criterion, also
called maximum shear stress theory, which is one of the two main failure
criteria used today for ductile materials along with von Mises yield
criterion. He became anhonorary member of the American Society of
Mechanical Engineers ASME) in 1882. He is called the ‘father of
plasticity’
3

13. MAXIMUM SHEAR STRESS THEORY
Henri Edouard Tresca, born on 12 October 1814, was a French
mechanical engineer. He discovered the Tresca yield criterion, also
called maximum shear stress theory, which is one of the two main failure
criteria used today for ductile materials along with von Mises yield
criterion. He became anhonorary member of the American Society of
Mechanical Engineers ASME) in 1882. He is called the ‘father of
plasticity’
4

14. MAXIMUM SHEAR STRESS THEORY
Henri Edouard Tresca, born on 12 October 1814, was a French mechanical
engineer. He discovered the Tresca yield criterion, also called maximum shear
stress theory, which is one of the two main failure criteria used today for ductile
materials along with von Mises yield criterion. He became anhonorary member of
the American Society of Mechanical Engineers ASME) in 1882. He is called the
‘father of plasticity’
5

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