Biomechanics Exam 2
Face stress acts on
1st subscript in stress refers to
Direction of stress
2nd subscript indicates
ductile
A ___________ material is one that exhibits a large plastic deformation prior to failure.
Linearly elastic
A ________________ material is one for which the stress and strain are linearly proportional with the modulus of elasticity being the constant of proportionality
Rigid
A ________________ material is one that cannot be deformed even under very large loads
Linearly elastic-linearly plastic
A _________________ material has two different regions with two different slopes in which stresses and strains are linearly proportional
Brittle
A _________________ material is one that shows a sudden failure (rupture) without undergoing a considerable plastic deformation
Rigid-perfectly plastic
A ___________________ material does not exhibit any elastic behavior, and once a critical stress is reached, it will deform continuously and permanently until failure
Ductile
A ___________________ material is one that exhibits a large plastic deformation prior to failure
Axial, or normal force
A direction that is normal *(PERPENDICULAR)* to the cut section
more
A high modulus material would take on (more/less) load or stress compared to bone
Elastic Limit
A material that has been subjected to stress levels beyond the ______________ will not resume to its original shape upon unloading
material function
A mathematical equation that relates stresses to strains is called a ___________.
Toughness
A measure of the capacity of a material to sustain permanent deformation
Strain
A measure of the degree or intensity of deformation
Tensile force
A pulling action trying to elongate a part
Compressive force
A pushing action trying to shorten a part
Linearly elastic-perfectly plastic
After a linear elastic response a __________________ material is on that deforms continuously at a constant stress level
Linearly elastic material
An elastic material whose stress-strain diagram is a straight line is called
Move in the direction of the applied force
An object subjected to an external force will?
Elastic
Area in the _____________ region represents energy stored in the material
Compressive stresses
Compressive stresses that are associated with compressive loading is called?
incompressible
Constant density but also no volume change
The ability of a material to resume to its original *(STRESS FREE)* size and shape upon removed of applied loads.
Define Elasticity
The ability to undergo shape change
Define deformability
Constituitive Relations/Equations
Equations are meant to reflect a relationship between cause and effect (Pertubations - Response)
two
For a linear isotropic material how many material properties are needed to define it?
Curve implies varying slope and nonlinear behavior,
For a stress-strain diagram of a material in the elastic region the straight line up to the proportionality limit followed by a curve. The curve implies what?
Elastic *Young's Modulus*
For linearly elastic materials, stress is linearly proportional to strain and the constant of proportionality is called the________________ of the material.
offset method
For some materials, it may not be easy to distinguish the yield point. The yield strength of such materials may be determined by the __________.
Materials are weaker in shear than in axial loading
How does a material behave under cyclic loading
Isotropic
If the mechanical properties of a material are independent of direction or orientation, then the material is called _____________.
Bending moment
Indicate the extent of bending action to which the cut part is subjected
Axial, or Normal force
Is a measure of the pushing or pulling action of the externally applied forces in a direction *perpendicular* to the cross section
harder
Larger radius (easier/harder) to twist
harder
Larger shear modulus G, (easier/harder to twist)
nonlinear plastic
Materials for which the stress-strain curve in the elastic region is not a straight line are known as_____________________materials.
Nonlinear elastic materials
Materials for which the stress-strain curve in the elastic region is not a straight line are known as
Shear forces
Measures of resistance to the sliding action of one cut section over the other
Tensile stresses
Normal stresses that are associated with tensile loading are called
ultimate strength
On the stress-strain diagram, the highest stress level corresponds to the _____________ of the material.
Elastic limit
On the stress-strain diagram, the stress corresponding to the ______________ is the highest stress that can be applied to the material without causing permanent deformation.
Permanent deformation
Plasticity implies
Isotropic
Properties are NOT the same in any direction at a point
Homogeneus
Properties are the same from point to point
Stress concentration
Stress concentrated around a hold is known as
Increased
Stress level equal to its ultimate strength will experience an (increased/decreased) rate of deformation
Principle planes, 45 degrees
Structures in pure torsion will often fail along one of the _____________________ spiral fraction approximately ______________
Line of action
Subscripts indicate
higher
The *higher* the elastic modulus the *stiffer* the material and the (higher/lower) the resistance to deformation
Shear
The ________________ stress is comparable to the intensity of the frictional force over the surface area upon which it is applied
J, Polar moment of intertia
The __________________________ reflects how much material there is to resist
Resilience
The ability of a material to store or absorb energy without permanent deformation is called the ___________ of the material.
resilliance
The ability to store or absorb energy without permanent deformation is called
Hooke's Law
The analogy between elastic materials and springs is known as ______________.
Hysteresis loop
The area enclosed by the ______________ signifies the total strain energy dissipated as heat while loading and unloading a material.
elastic strain
The area under the stress-strain diagram in the elastic region corresponds to the _____________ energy stored in the material while deforming the material.
moment, shear forces (V)
The bending load generates normal stress due to _____________ and shear stresses due to _________________
Elastic (Young's Modulus)
The distinguishing factor in linearly elastic materials is their _____________.
stiffness
The elastic modulus of a material is a relative measure of the ________ of one material with respect to another.
Area under the curve
The energy required to cause deformation is located where in a stress-strain curve?
Elastic limit
The greatest stress that can be applied to the material without causing any permanent deformation within the material
Stiffer
The higher the elastic modulus the _______________ the material
Ultimate strengh
The highest stress point on a curve is called the
Stress
The intensity of the internal force over the cut section (force per unit area)
Average stress
The intensity of the stress distribution over the area is not uniform
Stress
The internal resistance of a material to deformation due to externally applied forces is called
Tougher
The larger the area under the stress-strain diagram the (tougher/weaker) the material
<0.1%
The linear region for metals is?
weaker
The lower the elastic modulus the ________________ the material
Shear stress
The measure of the internal forces acting *PARALLEL* or *TANGENT* to the plane of cut
Twisting torque
The measure of twisting action of the externally applied forces along an axis normal to the plane of the cut section
uniaxial or simple tension test
The mechanical response of materials under tensile loading is analyzed by
Deform
The object will ______________ if its motion is constrained in the direction of the applied force
Elastic strain energy
The release of this energy brings the body back to its original shape upon unloading
Failure point
The stress at which rupture occurs is called the
Strain hardening
The technique of changing the yield point of a material by loading the material beyond its yield point is called _____________.
strain hardening, increases
The technique of changing the yield point of a material is called _______________________ which ______________ the yield strength of the material
shear stress, slope
Torsional strength is max ___________________ Torsional stiffness is ___________________
Toughness
Total area under the stress-strain curve indicates
True
True or False: (Mohr's Circle) If the unit normal points in the positive direction and the direction of the stress if positive the stress is considered a positive stress
True
True or False: Nonlinear elastic materials may have a linear elastic region in their stress-strain diagram at low stress levels
True
True or False: Shear stress and normal stress are independent
False
True or False: The Higher the shear modulus the less rigid the material is
True
True or False: The larger the cross-sectional area the more difficult it is to deform
True
True or False: The length of a specimen under compression decreases, and both Δl and ϵ become negative
True
True or False: The longer the specimen the larger the deformation in tension
True
True or False: When a body is subjected to tension, its length increases and both Δl and ϵ are positive
Strain
Unit deformation of a material as a result of an applied load is called
Translational/Rotational, Action/Reaction
What are two types of motion for deformable bodies?
Magnitude, Direction, and duration of the applied forces, material properties, and environmental conditions
What does the shape change in body mechanics depend on?
Plastic deformation
When materials are loaded beyond their elastic limits they undergo _______________
Plastic strain
___________ energy is dissipated as heat while deforming the material.
Plasticity
________________ implies permanent (unrecoverable) deformations.
Elasticity
________________ is defined as the ability of a material to resume its original (stress-free) size and shape upon removal of applied loads.
Shear modulus
_________________ is the constant of proportionality between shear stress and shear strain for linearly elastic materials.
Shear stress, normal stress
____________________ is a measure of the intensity of internal forces acting parallel or tangent ot a plane of cut while __________________ are associated with the inensity of internal forces that are perpendicular to the plane of cut
indicates the sections normal
first subscript indicates
Elastic modulus
is equal to the slope of the stress-strain diagram in the elastic region
Direction the force is acting in
second subscript indicates