Strength of material

1. SENTHUR POLYTECHNIC COLLEGE
DEPARTMENT OF AGRICULTURAL TECHNOLOGY
4020310 / STRENGTH OF MATERIALS
SEMINAR PRESENTATION
Submitted by
S.N
O
REG.NO NAME OF THE STUDENTS
1 23223659 ANISH.M
2 23223660 BAGAVATHI.T
3 23223661 GNANA CHANDRU.P
4 23223662 GOPIKA .M
5 23223663 KAVINKUMAR .A

2. Fatigue of materials

3. What is fatigue?
• It is a type of damage/failure in
materials;
Which is causedby fluctuatingor cyclic
stresses,
Under the effect of fluctuating stress a
fractured. This
point comes where the material is
level of stress is called
fatigue stress and the failure is called
fatigue failure.
The fatigue stress is much lower than
the yield stress or tensile stress.

4. • Fatigue failure is caused by initiation
and propagation of cracks and fracture
surface is perpendicular to the
direction of an applied tensile stress.
• It is brittle like in nature even in ductile
materials (fracture without prior
indication).
Ductile fracture.' the fracture caused after
plastic deformation.
without any appreciable
CBrittle Fracture: the fracture caused
plastic
deformation.

5. Cyclic stresses
• Three different stress-time modes are
possible.
• The stress can be axial (tension —
compression), bending or tor peal in nature.
n =range of stress

6. • Type (a) mode
The amplitude is symmetrical about a
mean zero stress level.
Alternating from a maximum tensile stress
to a minimum compressive stress of equal
magnitude.
It is called a reversed stress cycle.

7. Reversed stress cycle
• Type (a) mode (reversed stress cycle.)
Tensile Stress applied to a sample—Released
Compressive Stress Applied —Released. (One cycle
completes).
Example: Bending load applied to a rotating shaft. (Axles of
vehicles)

8. SPECTRUM LOADING
• Type (c) mode
The stress level vary randomly in amplitude and frequency.
Suspension wires in a railroad bridge.
Wires carry weight of bridg under static tensile load.
Additional load when a train is on bridge.