Fundamental Principles: Part I

Question 1

Who said “Selection of the correct material for a given design depends partially on understanding the elementary principles of mechanics and materials, concepts of forces, deformation and failure of structures under load, improvement in mechanical properties by heat treatment or other means, and design of structures”

Answer 1

Thomas Lunsford

Question 2

Vertical pylons experience a force ______ _________

Answer 2

Directly downward

Question 3

_______ _________ experience a torque at the foot plate near the proximal end of the ankle joint

Answer 3

Foot orthoses

Question 4

Equation for torque

Answer 4

T= F x L

Question 5

Equation for stress

Answer 5

Stress = F (force) / Ao (initial cross-sectional area)

Question 6

Equation for strain

Answer 6

Strain - Delta L (change in length) / Lo (initial length)

Question 7

The “o” in Ao and Lo stand for?

Answer 7

Initial

Question 8

_______ and _______ represent normalized quantities of force and deformation

Answer 8

Stress and strain

Question 9

What are the four primary types of stress?

Answer 9

Compression, tension, shear, and bending

Question 10

Type of stress that pushes together

Answer 10

Compression

Question 11

Type of stress that pulls apart

Answer 11

Tension

Question 12

Type of stress that makes a scissoring action

Answer 12

Shear

Question 13

Type of stress that makes a flexing action

Answer 13

Bending

Question 14

If area of ________ surface increases, shear stress decreases

Answer 14

Bonded

Question 15

In bending, ________ on top and ________ on bottoms

Answer 15

Compression, tension

Question 16

What are the two forms of shear stress?

Answer 16

Deformation by shear force and by torsion.

Question 17

Why is it important for O/P practice to have a basic understanding of material science?

Answer 17

Practitioners use their materials knowledge to design solutions and fabrication procedures to create devices that support a patients goals

Question 18

The loading scenario from force and torque is

Answer 18

Stress

Question 19

The materials behavior resulting from stress

Answer 19

Strain

Question 20

a ______ ________ relationship usually occurs between stress and strain

Answer 20

Positive linear

Question 21

How low stress, stress and strain are _________ proportional

Answer 21

Directly

Question 22

Materials stiffness or resistance to plastic deformation

Answer 22

Modulus of elasticity

Question 23

Hookes law equation

Answer 23

Stress = strain x constant (young’s modulus)

Question 24

A material that requires relatively large amounts of stress to produce small amounts of strain

Answer 24

High stiffness

Question 25

A material that requires relatively small amounts of stress to produce large amounts of strain

Answer 25

Low stiffness

Question 26

True or False: the modulus of elasticity is NOT effected by temperature

Answer 26

False

Question 27

As temp increases, stiffness ______

Answer 27

Decreases

Question 28

Elastic elongation and strain are produced _________ to applied tensile force

Answer 28

Parallel

Question 29

Deformation nor recovered from release of stress (this is permanent)

Answer 29

Plastic deformation

Question 30

Beyond the ________ range, plastic deformation will take place

Answer 30

Elastic

Question 31

On a stress strain graph, what is the proportional limit?

Answer 31

It marks the limit where a material cannot return to its original shape

Question 32

Most common tensile strength test

Answer 32

Uniaxial tensile testing

Question 33

Test used to calculate stress and strain

Answer 33

Uniaxial tensile testing

Question 34

Max that a material can handle before failure

Answer 34

Tensile stress

Question 35

The ability of a material to resist forces

Answer 35

Strength

Question 36

Defined as force per unit of the cross-sectional area of material

Answer 36

Stress

Question 37

The geometric lines that compose a prismatic beam in flexural stress

Answer 37

Fiber

Question 38

The point at which the material begins to maintain a deformation change

Answer 38

Yield stress

Question 39

Stress at which a material ruptures

Answer 39

Ultimate stress

Question 40

If a material lengthens or shortens in response to stress, it is said to experience

Answer 40

Strain

Question 41

The region where the slope is a straight line is called the

Answer 41

Elastic region

Question 42

Defined as the point of application of the result of a uniformly distributed force acting on the area

Answer 42

Centroid of an area