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Materials > Mechanical properties > Flashcards

Mechanical properties Flashcards

1
Q

It is necessary to know the characteristics of materials for design purposes so that … will not be excessive and … will not occur.

A

deformation, fracture

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2
Q

Factors considered when testing a material:

A

nature of applied load and its magnitude, environment

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3
Q

When a force is applied to a material, it will change its shape and size, this is called…

A

deformation

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4
Q

A tensile load produces an…

A compressive load produces a …

A

elongation, contraction

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5
Q

… of a material depends on its ability to sustain a load without undue deformation or failure. This is determined experimentally using the … test.

A

Strength, tension

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6
Q

… machines are designed to read the load required to maintain specimen streching

A

Tensile

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7
Q

Shapes of the cross-sections of specimens for testing are usually … and …

A

Circular , rectangular

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8
Q

… configuration was chosen so that during testing, deformation is confined to the narrow centre region and reduce likelihood of fractures at the end.

A

Dogbone

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9
Q

Output of a tensile test is recorded as … vs …

A

load, elongation

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10
Q

Load and deformation characteristics depend on specimen …

A

size

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11
Q

Engineering stress is obtained by…. Expressed with formula…

A

Dividing applied load F by Specimen’s original cross-sectional area A0, N/m^2=Pa

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12
Q

Strain is obtained by….

It has no units.

A

Dividing the change in the specimens gauge length by original gauge length.

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13
Q

Stress-strain diagram is … of the specimen geometry

A

independent

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14
Q

For yielding, there is a slight increase in … above … limit which will cause material to deform permanently. Hence plastic deformation occurs.

A

stress, elastic

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15
Q

After yielding, an increase in load is supported by the specimen until it reaches the ultimate tensile stress. What is this stage called?

A

Strain hardening

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16
Q

At ultimate stress, cross-sectional area begins to decrease in a localised region of the specimen. The specimen breaks at the fracture stress, what is this stage called?

A

Necking

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17
Q

Linear relationship between stress and strain within elastic region is defined by …

A

Hookes law

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18
Q

When can E / Modulus of elasticity / Young’s modulus be used?

A

Only if material has linear-elastic behaviour

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19
Q

Young’s modulus is a … property

A

material

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20
Q

1 GPa = … Pa

… MPa

A

10^9

10^3

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21
Q

The modulii of elasticity are smaller for …

A

polymers (0.2 and 5 Gpa)

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22
Q

Deformation in which stress and strain are proportional is called …

A

elastic deformation

23
Q

Young’s modulus is a measure of … , or a material’s resistance to elastic deformation.

A

stiffness

24
Q

The … the modulus, the stiffer the material, or the … the elastic strain that results from the application of a given stress.

A

greater, smaller

25
Q

There are some materials for which the elastic portion of the stress-strain curve is not linear, hence not possible to determine the modulus of elasticity. Such as…

A

gray cast iron, concrete, and many polymers

26
Q

Elastic means …

A

reversible

27
Q

On the atomic scale, macroscopic elastic strain is manifested as small changes in the … spacing and the stretching of … bonds

A

both interatomic

28
Q

Magnitude of modulus of elasticity is a measure of the … to … of adjacent atoms, that is, the interatomic bonding forces.

A

resistance, seperation

29
Q

Differences in E values among metals, ceramics, and polymers are a direct consequence of … that exist for the three material types.

A

different types of atomic bonding

30
Q

When deformation exceeds the elastic region , … deformation occurs

A

plastic

31
Q

Transition from elastic to plastic is gradual for most metals, some curvature results at the onset of plastic deformation, which … more rapidly with rising stress.

A

increases

32
Q

Plastic deformation is accomplished by means of …; motion of dislocations.

A

slip

33
Q

For metals, point of yielding may be determined as the initial departure from linearity of the stress-strain curve, called the…

A

proportional limit

34
Q

Proportional limit is difficult to measure, by convention, a straight line is constructed parallel to the elastic portion of the stress strain curve at some specified strain offset, usually 0.002, the stress corresponding to the intersection of this line is the …

A

yield strength

35
Q

When a material is loaded into the plastic region and then unloaded, … …. is recovered.

A

elastic strain

36
Q

When a material is loaded into the plastic region and then unloaded, … … remains and material is subjected to a … …

A

plastic strain, permanent set

37
Q

When a material is loaded into the plastic region and then unloaded, if load is re-applied, there will be a higher … … because of strain hardening but less ductility.

A

yield stress

38
Q

Maximum stress on the the stress-strain curve is … …

A

Tensile strength

39
Q

A measure of the degree of plastic deformation that has been sustained at fracture is…

A

ductility

40
Q

Ductility can be measured by percent … and percent …

A

elongation, reduction in area

41
Q

A material that experiences very little or no plastic deformation upon fracture is termed …, they are considered to be those having a fracture strain less than 5%

A

brittle

42
Q

Ceramic materials are … brittle than metals.

A

more

43
Q

What is the mechanism of deformation of crystalline?

A

dislocation motion

44
Q

what is the mechanism of deformation in highly ionic compounds?

A

slip systems and resistance to motion of ions of like charge past one another.

45
Q

… is the capacity of a material to absorb energy when it is deformed elastically and upon unloading have this energy recovered

A

resilience

46
Q

… is the strain energy per unit volume required to stress a material from an unloaded state up to the point of yielding.

A

Modulus of resilience. Ur

47
Q

… is indicative of a materials ability to absorb energy up to fracture.

A

Toughness

48
Q

… represents entire area under stress-strain curve.

A

Toughness

49
Q

… materials must display both strength and ductility

A

Tough

50
Q

A … body both elongates and contracts laterally under an axial tensile load

A

deformable

51
Q

Measure of a material’s resistance to localised plastic deformation is …

A

Hardness

52
Q

For hardness, the … the material, the larger and deeper is the indentation, and the lower is the hardness index number.

A

softer

53
Q

Large hardness refers that the material is:

A

resistant to plastic deformation, resistance to cracking in compression, has good wear properties.

54
Q

Both … and … are indicators of a metal’s resistance to plastic deformation.

A

tensile strength, hardness

Materials (2 decks)

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