Lecture 3 Flashcards
Types of Forces and Their Applied Loads:
Tensile, Tension, or Distractive Force:
Action: Elongates fibers in a material.
Compressive Force:
Action: Pushes together fibers of a material.
Shear Force:
Action: Intensity of a force parallel to the surface on which it acts.
Torque:
Action: A pair of two equal and opposite parallel forces moving in opposite directions on an object separated by a distance.
Importance Forces and Their Applied Loads:Describes the relationship between force, deformation, and time.
Understanding these forces helps comprehend how structures in the musculoskeletal system adapt to gravity and other loads.
Provides insights into how viscoelastic materials deform and adapt over time.
Relevant to understanding the behavior of ligaments, muscles and tendons, cartilage, joints, and bones.
Rheology:
Describes the relationship between force, deformation, and time.
Rheology Properties and function
They govern how materials deform under mechanical load.
Key properties: Elasticity, Plasticity, Viscoelasticity, Strength.
What is elasticity in materials?
Elasticity refers to the property of a material to return to its original state after the deforming force/strain has been applied and removed.
This means the material can deform within a certain range until it enters the plastic range.
What is strength in materials?
Strength is the ability of a material to withstand an applied load without failure or plastic deformation. It is often defined in terms of the tensile stress required to break the material under a single load.
Define plasticity in materials.
Plasticity is the property of a material to permanently deform when it is loaded beyond its elastic range. It means the material can permanently deform within a certain range until it reaches failure, and unloading within this range always results in permanent deformation.
What is stress, and how is it measured?
Stress refers to the force per unit area of a structure, measuring the intensity of the force. When a structure is loaded with forces, stresses are created throughout the body. There are two types of stresses: normal stress and shear stress. Normal stress can be compressive or tensile, depending on whether the force is perpendicular to the surface (compressive) or stretching the material (tensile). Shear stress occurs when the force is parallel to the cross-sectional area.
Define strain and its types.
Strain represents the degree of deformation, indicating the change in length or angle in a material subjected to a load. There are two types of strain: normal strain and shear strain. Normal strain involves a change in the length of a material and can be either tensile (stretching) or compressive (shortening), such as in a bar of rubber. Shear strain refers to a change in the angle of a material.
What is a stress-strain curve?
A stress-strain curve is a plot of stress (usually on the y-axis) versus strain (usually on the x-axis). It illustrates the mechanical relationship between the load applied to the tissue or structure (stress) and the resulting deformation (strain) over time.
This curve depicts how a material deforms in response to force and applied load.
Which structures of the spine are of primary concern in terms of stress and strain?
The structures of the spine that are most concerning in terms of stress and strain include the ligaments, muscles and tendons, cartilage, joints, and bones.
These structures are subject to various forces and loads, and understanding their stress and strain characteristics is crucial for assessing spinal health and function.
Modulus of Elasticity:
The modulus of elasticity is a measure of the stiffness of a material.
How is Modulus of Elasticity defined on the stress/strain curve?
as the ratio of stress to strain within the elastic or linear region of the stress-strain curve.
What does the Modulus of Elasticity slope of the stress-strain curve represent?
The slope of the curve represents stiffness. A steeper slope indicates a higher modulus of elasticity, meaning the material is stiffer and requires a higher stress to induce a given amount of strain. Conversely, a less steep slope indicates a more flexible material that deforms more readily under a given stress.
Why is the Modulus of Elasticity slope important?
determines the amount of stress a material can withstand over time. A steeper slope indicates a stiffer material but with less ability to deform, leading to quicker ultimate failure. An example of this might be a metal rod.
