Upload
mohammad-tawfik
View
1.932
Download
1
Tags:
Embed Size (px)
DESCRIPTION
Citation preview
3- POINT BENDING
Cairo University Faculty Of EngineeringAerospace Engineering Department
Class : 1st Year
Submitted To : Prof. / Mohammed Tawfik
Contents
Defining the Problem Proposed solutions Final design Execution Testing Practical problems
Defining the problem:
Finding a suitable device which is capable of measuring the deflection in any thin beam due to the applied bending moment. To do this we realized we must apply a perpendicular force to the beam while it is held by two supports.
We thought about many solutions
but some of them were impractical and others were too expensive to implement. Some of those thoughts is presented in the following lines.
Proposed solutions:
Trying to build a computerized model
Its idea was to apply the force by using hydraulic press and measure it by using an electronic sensor connected to a computer. In addition of measuring the deflection in the beam by an electronic micrometer also connected to the computer. Then graphing the relation between the applied moment and deflection, but we found it very complicated and needs more experience.
We tried to simplify our concept and achieve a simple design by fixing the supports in the base and applying the load by attaching it to a movable hook sliding on the rod. Further more, measuring the deflection using spring micrometer. But we found that in this design we cant measure the deflection in the point which we apply the load on. Moreover, the tips of the supports were u-shaped so, the reaction acts on a circular surface not in a certain point.
Simple Design
We improved our design to over come those problems by using a knife -edge tips and changing the way we apply the load as shown in figure
Final design
Testing
We have used this device to make different experiments:
Applying fixed load at the center of the rod and measuring the deflection at different points.
Applying fixed load at different positions and measuring the deflection.
Measuring the modulus of elasticity of an unknown material.
0 5 10 15 20 25 30
-3.5
-3
-2.5
-2
-1.5
-1
-0.5
0
Position of measuring point
Applying fixed load on the center of aluminum rod
Defl
ecti
on i
n m
m
0 5 10 15 20 25 30
-1.2
-1
-0.8
-0.6
-0.4
-0.2
0
Applying fixed load in different positions on yellow cupper rod Position of measuring point
Defl
ecti
on
in
mm
0 5 10 15 20 25
-0.3
-0.25
-0.2
-0.15
-0.1
-0.05
0
Measuring point position
Deflecti
on i
n m
mApplying fixed load in n0n – Centric positions on
yellow cupper rod
0 2 4 6 8 10 12 14 16 18 20
-0.25
-0.2
-0.15
-0.1
-0.05
0
Measuring point position
Deflecti
on i
n m
m
Y
X
P
L/2 L/2
Used Relations
Practical Problems o Adjusting the orientation of the cylindrical
supports’ knife perpendicular to the edge of the rod .
o The tips of the cylindrical supports weren’t accurate enough .
o The cylindrical supports slide hardly in the slot .
Prepared by :Abdelrahman Hussien MahmoudAhmed Fathy El-ShazlyAhmed Fawzy El-Araby Ahmed M. Zaki Alaa Mohammed AbdullahAmr Mahmoud Lotfy Cindrella Mohamed OkashaRadwa Magdy Abdelmohsen Marco Mounir Abdallah Mohamed Samy El-Alfy
THANK YOU
Questions ?