BME 214 Exam 1 Guide With
Solution
Tensile Stress - ANSWER pulling force
Compressive Stress - ANSWER pushing force
Stress (how to calculate) - ANSWER F/A
F = force
A = cross sectional area
Units N/m^2 = Pa
Strain - ANSWER deformation caused by applied stress
Epsilon = delta L / L (dimensionless)
L = original length
delta L = change in length
Stress-Strain Curve - ANSWER slope of the curve is a measure of STIFFNESS
k or E = stress/strain = sigma/epsilon
aka Elastic Modulus/Young's Modulus
, Stress-Strain Curve:
Elastic Region
Plastic Region - ANSWER Elastic Region: item will return to original shape
after deformation
Plastic Region: item changes shape permanently after deformation
Tendon Equations - ANSWER F = k (delta L)
Elastic Energy = 0.5 k (delta L)^2
Elastic Energy = 1/2 F (delta L)
k = EA/L
E = elastic modulus = stress/strain ~1.5E9 for tendon
stress = F/A
strain = delta L / L
10,000 cm^2 = 1 m^2
Safety Factor - ANSWER strength/ typical load
Energy - ANSWER energy stored/ put in when a stress is applied is
proportional to the area under the curve
Solution
Tensile Stress - ANSWER pulling force
Compressive Stress - ANSWER pushing force
Stress (how to calculate) - ANSWER F/A
F = force
A = cross sectional area
Units N/m^2 = Pa
Strain - ANSWER deformation caused by applied stress
Epsilon = delta L / L (dimensionless)
L = original length
delta L = change in length
Stress-Strain Curve - ANSWER slope of the curve is a measure of STIFFNESS
k or E = stress/strain = sigma/epsilon
aka Elastic Modulus/Young's Modulus
, Stress-Strain Curve:
Elastic Region
Plastic Region - ANSWER Elastic Region: item will return to original shape
after deformation
Plastic Region: item changes shape permanently after deformation
Tendon Equations - ANSWER F = k (delta L)
Elastic Energy = 0.5 k (delta L)^2
Elastic Energy = 1/2 F (delta L)
k = EA/L
E = elastic modulus = stress/strain ~1.5E9 for tendon
stress = F/A
strain = delta L / L
10,000 cm^2 = 1 m^2
Safety Factor - ANSWER strength/ typical load
Energy - ANSWER energy stored/ put in when a stress is applied is
proportional to the area under the curve
