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Flashcards in Chapter 6 Deck (11):
1

What is:

  • Tensile Deformation
  • Compressive Deformation
  • Elastic Deformation
  • Plastic Deformation
  • Elastic Limit

Tensile Deformation: Changes shape under tension.

Compressive Deformation: Changes shape under compression.

Elastic Deformation: Goes back to its original shape.

Plastic Deformation: Permanent change in shape.

Elastic Limit: Stretched beyond the elastic limit, causes plastic deformation.

2

What is the equation for HOOKE'S LAW?

F = kx

k is the spring constant

k = F ÷ x 

^^^^^^^^

Gradient of a Force vs Extension graph.

3

State HOOKE'S LAW.

The extension of a spring is directly proportional to the force applied.

This is true as long as the elastic limit of the spring has not been exceeded.

4

What is this?

Q image thumb

A hysteresis loop.

5

What DOES NOT obey HOOKE'S LAW?

Rubber bands do not obey Hooke's Law.

6

What is the equation for STRESS and what are its UNITS?

σ = F ÷ a

Units : Nm² or Pa

7

What is the equation for STRAIN and what are its UNITS?

Σ = Extention ÷ Original Length

Σ = x ÷ L

Strain has no units, it is a ratio or a percentage.

8

State what each point on the graph represents.

Q image thumb

P : Limit of proportionality - Hooke’s Law no longer obeys at this point.

E  : Elastic limit.

Y1 & Y2: The yield point - The wire is about to give

UTS (Ultimate Tensile Strength) : Stress at its limit - About to break - The wire begins to thin out.

9

What is the equation for THE YOUNG MODULUS and what are its UNITS?

 

σ ÷ Σ

Stress ÷ Strain

Units: Pa or Nm²

10

How do you calculate the GRADIENT on a STRESS vs STRAIN GRAPH?

σ ÷ Σ

The Young Modulus is the gradient, which relates to te stiffness of the material.

11

What is the equation for ELASTIC POTENTIAL ENERGY?

½Fx

For a spring that obeys Hooke's Law: 

F = ½kx²