Chapter 9 - Mechanics of Biological Material Flashcards
(17 cards)
What is tensile stress? Example?
Axial or normal stress from “pulling apart” force
*ACL, stretching, muscle contraction
What is shear stress? Example?
Twisting the knee
compressive stress? Example?
Axial stress from “pushing or squashing” load
*deforms by shortening
*Jumping, squatting
τ= A/F , what does this formula mean?
shear stress is the internal resistance of a material (like muscle, and tendon)
Larger the force, the more shear stress
larger the area, the less shear stress (because the force is spread out more)
T=F×r , what does this formula mean?
The larger the force or the longer the moment arm, the greater the torque
Torque is what causes bending or rotation of a structure or limb
How does object with greater depth changes bending loads?
objects with greater depth (more cross-sectional area, further from axis) withstand greater bending loads because of the moment arm
- A cross-sectional area farther from axis mean longer moment r
How does bone resist bending better?
has more mass or structure farther from the neutral axis, resist bending better becuase it creates greater torque resistance
What is strain?
Deformation of a material in response to an applied stress.
Strain(ε)= ΔL (change in length)/ L0 (orignial length)
What is linear strain?
refers to the change in length. The feformation occurs along the direction the the applied force
What is shear strain
refers when forces are applied parallel to a surface, causing one layer of a material to slide or deform
What is elastic behavior and plastic behavior?
elastic behavior: returns to original shape
Plastic Behavior: Permanent defromation after a certain load
In a stress and strain curve, what does a steeper slope and less steep slope mean?
Stiff material - steeper slope
Pliant material - less steep slope
what is the difference between isotropic and anisotropic?
Refers how materials respond to external forces or changes in different directions
Isotropic: material have same mechanical properties in all direction
Anisotropic: material have different mechanical properties in every direction
What is hyaline?
Articular cartilage on ends of the bone
What is fibrous cartilage?
Connective tissue: menisci of knee
What is elastic carilage?
flexible, ears, nose
What is creep and stress relaxation?
effect when load is applied over time or deformation over time
