An Introduction to engineering analysis. Each team will design a tower made of balsa sticks Each...
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Transcript of An Introduction to engineering analysis. Each team will design a tower made of balsa sticks Each...
WHY STRUCTURES
FAIL
An Introduction to engineering analysis
BUILDING A TOWER
Each team will design a tower made of balsa sticks
Each team will do a structural analysis of their tower to predict where it will fail
Each tower will under go ‘destructive testing’
THE LANGUAGE OF ENGINEERS
Mass
Velocity
Force Pressure
Stress
Deformation System
Failure
Acceleration
Position
MASS
A measure of how much matter an object is made of
Does not change with environment
Metric Unit:?
English Unit:Pounds (lb or lbm)
Grams (g)
90 kg200 lbm
90 kg200 lbm
Weight: (in pounds force)200 lbf
Weight:33 lbf
POSITION
Position fully defines an object’s location in space
Metric Unit:Meters (m)
English Unit:Feet (ft)
Z
X
Y
(X, Y, Z) = (.2 m, .5 m, .6 m)
(X, Y, Z) = (.5 m, .1 m, .2 m)
(X, Y, Z) = (1 m, .3 m, .4 m)
VELOCITY
Velocity describes the rate of change of an object’s position
Metric Unit:Meters per second (m/s)
English Unit:Feet per second (ft/s)10 m/s
30 m/s
Can also be expressed as a ‘vector’(x,y) = (3 m/s, 4 m/s)
4 m/s
3 m/s
Includes both a magnitude and direction
30 m/s
Acceleration describes the rate of change of an object’s velocity
ACCELERATION
Metric Unit:m/s/s (m/s2)
English Unit:ft/s2
V = 10 m/sa = 0 m/s2
0m 10m
20m
30m
40m
50m
1 sec
0 sec
2 sec
3 sec
4 sec
5 sec
V = 10 m/sa = 2 m/s2
1 sec
2 sec
3 sec
0 sec
V = ?16 m/s
V = 10 m/s
FORCE Any influence that causes an object to
change speed, direction, or shape
Force = mass * accelerationF = m*a
Metric Unit:Newton (N)
English Unit:Pounds Force (lbf)
m = 90 kga = 9.81 m/s2
m*a = 883 N
100 kg
F = 500 N
a = 5 m/s2
PRESSURE When a force is exerted over a defined
area
Pressure = Force / AreaP = F / A
Metric Unit:Pascals (Pa)
English Unit:Pounds per square inch (PSI)
24 inches
24 inches
Force = 500 lbf
Area = 24 in x 24 in = 576 in2
P = 500 lbs / 576 in2 = .87 PSI
STRESS A measure of the internal forces acting
on a deformable structureMetric Unit:Pascals (Pa)
English Unit:Pounds per square inch (PSI)
20 m
20 m
20 m * 20 m = 400 m2
F = 883 N
Stress = P = 883 N / 400 m2 = 2.2 Pascals
F = 5000 kg * 9.81 m/s2 = 49050 N
Stress = P = 49050 N / 400 m2 = 122 Pascals
STRESS Types of stresses
Compression
Tension
Shear
DEFORMATION
Occurs when the stress in an object exceeds the yield strength of the material
Material:Purple Block
Yield Strength:1000 kPa
Deformation!
500 kPa
1200 kPa
Stressed
kPa = kilo-pascalOr 1000 pascals
SYSTEM FAILURE
Occurs when the stress in an object exceeds its ultimate strength (Compressive or Tensile)
Stressed
Deformation
System Failure!
Material:Purple Block
Yield Strength:1000 PSI
Ultimate Strength:2000 PSI
500 PSI
1200 PSI
2500 PSI
TOWER FAILURE
Next Week: Where will your tower fail?
Boom!