L2(L5 Makeup);C3 Flashcards
What are the five types of load bearing tissues?
Bone Ligaments Tendons Cartilage Muscles
These load bearing tissues adapt _____ and _____ to their loading environment
Positively, Negatively
What is the definition of a load?
Externally applied forces and torques
There are six different mechanical loading modes, name them
- Tension
- Compression
- Shear
- Torsion
- Bending
- Combined
What is deformation?
When loaded, musculoskeletal tissues change shape
The slope of a load deformation curve represents what?
Stiffness
What is the formula for slope in a deformation curve?
K=change in load/ change in deformation
What is compliance?
The inverse of stiffness (1/K)
As an increased slope, stiffness _______
Increases
True or false, stress and strain are a measure.
False, they are converted and normalized.
What is mechanical stress?
When muscles develop internal resistance to loading.
What is the formula for mechanical stress?
(Sigma)σ=Force/Area
What is the difference between stress and pressure?
Stress is internal measure of force/cross sectional area
Pressure is external measure of force/surface area
Stress is a ________ load
Normalized
What does normalization mean?
Normalization is a way of allowing comparison of materials. You divide load by cross sections area.
Stress is the ______ force over a large ________ _______
Same, cross-sectional area
What is mechanical strain?
This is another way of measuring change in shape of material (or object) that is caused by loading.
What’s the difference between deformation and strain?
Deformation is measured in absolute terms (m)
Strain is measured in relative terms (%)
What is the formula for strain?
ε=(dimensions change/unloaded dimension)x100
Strain, like stress, is __________
Normalized
For the linear portion of stress and strain, slope represents the _______ ________
Elastic modulus (E)
What do we convert deformation to?
Stress and strain curves
What is Hookes law? Wha does it determine?
σ =E x ε
This determines stress and strain are linearly related
σ =E x ε is similar to what equation?
Y=mx
Recap! What are the formulas for stress, and strain?
Stress= force (load) divided by cross sections area
Strain= deformation (change in band) divided by unloaded change multiply by 100
Load deformation curves characterize ________
Stress strain curves characterize ________
Structural properties
Material properties
What is visoelasticity?
This is fluid in the muscles that change the way it shapes. It response to loading dependent on the rate of which tissues are loaded.
MSK tissues exhibit a combination of ______ and _______ behaviour
Elastic, viscous
What is elasticity?
When loading is removed, original shape is restored and no energy is lost.
What are the four properties of viso-elasticity?
Strain rate dependency
Stress relaxation
Creep
Hysteresis
Describe strain rate dependency, what does viso elastic material depend on? What is this a function of?
the rate at which the material is being deformed will dictate how much force is produced. Viso-elastic material will depend on the speed and load. This is a function of stress and strain
What is stress relaxation? What is this a function of?
This is also known as constant strain. This is a function of stress and time. Stress relaxation is when you take a tissue and hold it at constant strain. The resistance will decrease over time. Fluid distributes itself until it has a steady state. Stress will overall decrease.
What is creep? What is it a function of?
This is also known as constant stress. This is a function strain and time. When you apply constant stress, strain keeps going until fluid distributes itself.
What is hysteresis? What is it a function of?
This is when the loading cycle differs from unloading cycle. This is a function fo stress and strain. Energy is lost on its way back up due to viso elastic proprieties
Explain the following terms:
Compression Tension Shear Stress Torsion Combined Deformation
Compression- pressing or squeezing force directly axially through a body
Tension- pulling or stretching force directly through a body
Shear- force directly parallel to body
Stress- force/area distributed of force over body
Torsion- Load producing twisting of a body around longitudinal axis
Combined- more than 1 action
Deformation- change in shape
