Materiels Flashcards

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1
Q

Define what a bulk property is

A

mechanical properties that arise from the atoms or molecules acting together after bonding

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2
Q

Give the equation for density

A

Density = Mass / Volume

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3
Q

Define Hookes Law

A

The force needed to stretch a spring is directly proportional to it’s extension from its natural length giving rise to Force = Spring Constant x Extension

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4
Q

In a Force - Extension graph what happens when the constant gradient suddenly slopes downward

A

The spring has reached the limit of proportionality

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5
Q

What happens to a spring after it passes the limit of proportionality

A
  • The spring elastically deforms causing hookes law to no longer apply as force is no longer directly proportional to extension and less force is able to cause larger extensions
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6
Q

When does a spring reach its elastic limit

A

At the point of elastic deformation, the limit of proportionality of the string

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7
Q

What happens when a spring reaches its elastic limit

A

The spring will begin to behave and deform plastically, so the shape changes cannot be reversed

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8
Q

Define Plastic deformation

A

Where an object deforms to the point that it will not return back to its original shape

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9
Q

When 2 springs are connected in parallel how do you calculate their combined spring constant

A

K(Total) = K(1) + K(2)

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10
Q

When 2 springs are connected in series how do you calculate their combined spring constant

A

1/K(Total) = 1/K(1) + 1/K(2)

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11
Q

Describe the equation for work done on springs

A

Work done = 1/2 x Force x extension

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12
Q

Define what a tensile force is

A

A pulling force on an object

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13
Q

In a Force-Extension graph what does the area under the loading curve equal?

A

Work done

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14
Q

Why on the Force-extension graph for loading and unloading rubber different

A

As it deforms and energy is also wasted in the thermal store

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15
Q

Give the equation for stress

A

Stress = Force / Cross Sectional Area

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16
Q

Give the equation for Strain

A

Strain = Extension / Original Length

17
Q

Give the equation for Youngs Modulus

A

Youngs Modulus = Stress / Strain = (Force x Length) / (Area x Extension)

18
Q

Define Youngs Modulus

A

The measure of stiffness of a material and ability to withstand a force without an extension

19
Q

In order, list the stages of change on a Stress-Strain Graph

A
  • P - Limit of proportionality where stress is no longer directly proportional to strain
  • E - The material becomes elastically deformed
  • Y1 - Yeild point 1 where the material weakens temporarily
  • Y2 - Yeild point 2 where a small increase in stress causes a larger increase in strain as the wire undergoes plastic flow
  • UTS - Ultimate Tensile Stress - Maximum tensile stress that can be reached
  • B - Breaking point where the wire looses its strength, extends, becomes narrower at its weakest point and finally fractures