Bending , objective, theory, diagram, and its calculations for more informations 00923006902338

1. Experiment # 05
Objective:
To show how to measure strain and compares the result with theory of bending.
Apparatus:
Strain gauges Trainer
Strain Gauge:
It is an electrical sensor (Transducer) that mean the strain when the load is applied its electrical
resistance changed and displacement produced is directly proportional to change in electrical
resistance.
Cantilever beam
Force
An agency which produce displacement.
F= mg

2. Stress
It is the reactional force per unit area.
T=F/A
Stress = My/I
Strain
It is the ratio of change in the length.
Young Modulus
It is the ratio between stress and strain.
Second Movement of Inertia.
Bending Movement.
Product of force and perpendicular to the distance from axial of rotations.
B.M = F*Z
Principle:
A Bending test may be performed on actual beam cross-section by using the three point loading
system. The bending fixture is supported on the platform of the hydraulic cylinder of the universal
testing machine. The loading knife edge is held in the middle crosshead. At a particular load, the
deflection at the center of the beam is determined by using a dial gauge.
Theory:
Application of a simple concentrated load at center in the case of Bending associated with shear.
Application of two concentrated loads will lead to pure bending without shear. Beams are usually
subjected to bending moment and shearing forces which vary from section to section. Bending
moment at a section in a beam is the moment that is trying to bend it and is obtained as the algebraic
sum of the moments about the section of all the forces acting on the beam either to the left or to
the right of the section.
Procedure:
1. Apply 240 VAC to strain gauge display unit switch on power of the strain display unit.
2. Connect the strain connection cable (with bending tag) to output socket of bending system.
3. Connect the bending system strain gauges to strain display as a full bridge.

3. 4. Press tare to make zero as initial reading.
5. Carefully slide hanger on beam, up to the desired position and add weight to hanger.
6. Leave the equipment to stabilize for approximately one minute then observe voltage on
single display and conceder it is initial voltage.
7. Now apply load on hanger with 1N increment and observe the final voltage.
Note: Max limit of applied load is 0.5 kg.
8. Now compare theoretical and experimental strain Values as mentioned in teacher’s Guide.
9. Gain of amplifier is 1000. If it is not so then use the zero and span adjustment knobs set it
To 1000.
Observation:
Gauge Factor:2.12
Gain of Amplifier:1000
Active Arms (N):
Young’s Modules:187.5 GPA
Sr
No
Z
(mm)
𝑽𝒊𝒏𝒊𝒕𝒊𝒂𝒍
(V)
𝑽 𝒇𝒊𝒏𝒂𝒍
(V)
b
(mm)
d
(mm)
F
(N)
M
(N-mm)
I
(𝒎𝒎 𝟒
)
Y
(mm)
𝝈 𝑬 𝒕𝒉 𝑬 𝒆𝒙𝒑
1 385 4.92 0.627 18 6 5 19.25 3.24 0.003 1.78 19 19.85
2 300 4.92 0.46 18 6 5 1.5 3.24 0.003 1.3 18 18.75
3 500 4.92 0.47 18 6 5 1.6 3.24 0.003 1.3 20 20.95