Transcript Material Choices and Beam Bending

Engineering H191 - Drafting / CAD
Material Joining and Beam Bending
Lab 5
Autumn Quarter
Gateway Engineering Education Coalition
Lab 5
P. 1
Engineering H191 - Drafting / CAD
Beam Deflection
• Every object acts as a spring – it will deflect when
a force is applied
• Extent of deflection depends on force applied,
material properties and object shape
Autumn Quarter
Gateway Engineering Education Coalition
Lab 5
P. 2
Engineering H191 - Drafting / CAD
Differences in Deflection
Although the beams have the same cross-sectional
area, the moments of inertia are different
Because the moments of inertia are different, the
beams deflect different amounts
Autumn Quarter
Gateway Engineering Education Coalition
Lab 5
P. 3
Engineering H191 - Drafting / CAD
Moments of Inertia
• A larger moment of inertia means that the beam
will be more resistant to deflection
I = Area Moments of Inertia (depends on object shape)
bi
h
b
I
1 3
bh
12
Autumn Quarter
ho
hi
I  Io  Ii
bo
Gateway Engineering Education Coalition
Lab 5
P. 4
Engineering H191 - Drafting / CAD
Stress and Strain: Simple Definitions
Strain:


P
Stress:  
A
l
(lb/inch2)
L
(original length)
P (applied force)
A
(cross-sectional area)

(deflection from original length)
Autumn Quarter
Gateway Engineering Education Coalition
Lab 5
P. 5
Engineering H191 - Drafting / CAD
Stress and Strain: Simple Definitions
Strain:


P
Stress:  
A
l
(lb/inch2)
Stress vs. Strain Curves:
Linear Portion (Hooke’s Law):
  E
Young’s Modulus
(slope of curve or
material stiffness)
Autumn Quarter
Gateway Engineering Education Coalition
Lab 5
P. 6
Engineering H191 - Drafting / CAD
Cantilever Beam Bending Equation
• In this lab, you will measure the deflection d for
various loads P. Using this information and other
measurements, calculate Young’s modulus E for
each beam.
y
x

s
P
L
Autumn Quarter
Gateway Engineering Education Coalition
Ps2
3L  s 
 
6 EI
Lab 5
P. 7
Engineering H191 - Drafting / CAD
Material Joining
• A separate demonstration will be given on the
welding procedure
• The final product will form a ‘T’ shape
Autumn Quarter
Gateway Engineering Education Coalition
Lab 5
P. 8
Engineering H191 - Drafting / CAD
Things to Consider:
• How will joining the beams through welding affect
the overall stiffness?
• Is there any advantage to choosing a more
flexible material such as aluminum over a stiffer
material such as steel?
• Hypothetically, if you were to design a 9x9” robot
spring quarter, which materials do you feel would
be most suited for use?
• Which shapes would form a stiffer chassis?
Autumn Quarter
Gateway Engineering Education Coalition
Lab 5
P. 9
Engineering H191 - Drafting / CAD
Questions ?
Autumn Quarter
Gateway Engineering Education Coalition
Lab 5
P. 10