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