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Mechanics of Materials > Stresses and Strains > Flashcards

Stresses and Strains Flashcards

1
Q

What is the mechanics of materials the study of?

A

The elastic behavior of materials and the stability of members.

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2
Q

When is the mechanics of materials concepts used?

A

To determine the stress and deformation of axially loaded members, connections, torsional members, thin walled pressure vessels, beams, eccentrically loaded members, and columns.

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3
Q

What is stress?

A

the force per unit area.

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4
Q

How many types of stress are there?

A

Normal stress and shear stress.

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5
Q

What is the difference between normal and shear stress?

A

In normal stress, the force is normal to the surface area and in shear stress, the force is parallel to the surface area.

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6
Q

What are the two subcategories of normal stress?

A

Tensile and compressive stress.

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7
Q

What are the sign conventions of tensile and compressive stress?

A

Tensile stresses make a part elongate in the direction of application and are considered positive. Compressive stresses make a part shrink in the direction of application and are given a negative sign.

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8
Q

What is linear strain?

A

The change in length per unit length.

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9
Q

What is shear strain?

A

Is an angular deformation resulting from shear stress.

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10
Q

What is Hooke’s Law?

A

States that the stress is proportional to the strain.

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11
Q

What is Hooke’s Law for normal stress?

A

The normal stress is equal to the product of the strain and the modulus of elasticity.

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12
Q

What is an isotropic material?

A

The properties of the material are the same in all directions.

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13
Q

What is an anisotropic material?

A

The properties of the material vary with direction.

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14
Q

What is Poisson’s ratio?

A

Is the ratio of the lateral strain to the axial strain for axially loaded members.

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15
Q

What is Hooke’s Law for a plane element in pure shear?

A

The shear stress is equal to the product of the shear strain and the shear modulus.

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16
Q

Under what conditions are the Poisson’s ratio, shear and elastic modulus related?

A

An elastic isotropic material.

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17
Q

What is strain energy?

A

Is the energy per unit volume stored in a deformed material.

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18
Q

What is the strain energy equal to?

A

It is equal to the ratio of the product of the force and the deformation to the product of the length and area.

19
Q

What is the strain energy dependent on for an axially loaded member below the proportionality limit?

A

It depends on the average force.

20
Q

What is the sign convention for the shear stress in triaxial and biaxial loading?

A

Clockwise shear stresses are positive and counter clockwise shear stresses are negative.

21
Q

What are principal stresses?

A

The maximum and minimum normal stresses.

22
Q

Where are principal stresses found?

A

The normal stresses associated with the plane where the shear stress is zero.

23
Q

What is the Mohr’s circle?

A

A circle constructed to graphically determine the principal normal and shear stresses.

24
Q

What does the maximum normal stress theory predict?

A

It uses the normal stresses to predict the failure.

25
Q

Under what conditions is the maximum normal stress theory used?

A

for brittle materials under static biaxial loading.

26
Q

When is failure expected to occur for tensile and compressive stress?

A

If the largest principle stress is greater than the ultimate strength.

27
Q

Do brittle materials have larger tensile or compressive strength?

A

Compressive strength.

28
Q

When are stress concentration factors applicable to brittle materials?

A

When the brittle materials are under static loading.

29
Q

What are the stress concentration factors?

A

Factor of safety, allowable stress, and the failure criterion.

30
Q

What does the maximum shear stress theory predict?

A

Shear stress can be used to predict yielding.

31
Q

Under what conditions is the maximum shear stress theory used?

A

Ductile materials under static loading.

32
Q

Are can normal stresses be used for the shear stress theory?

A

Yes

33
Q

According to the maximum shear stress theory. When is yielding expected to occur?

A

When the maximum shear stress exceeds the yield strength in shear.

34
Q

What is the yield strength equal to in shear for the maximum shear stress theory?

A

It is equal to half the tensile yield strength.

35
Q

What is the maximum shear stress in three dimensions?

A

The maximum of the three combined shear stresses.

36
Q

What is the distortion energy theory?

A

It is used to predict tensile are shear failure.

37
Q

Under what conditions is the distortion energy theory used?

A

It is used for steel and other ductile parts subjected to static loading.

38
Q

What is the von Mises stress?

A

It is the stress used in the left hand side of the equation for the distortion energy theory.

39
Q

Can the distortion energy theory be used for biaxial and triaxial loading?

A

Yes, the left hand of the distortion energy theory has an interchangeable equation for biaxial and triaxial conditions.

40
Q

What is the factor of safety equal to in the distortion energy theory?

A

It is equal to the tensile yield strength divided by the von Mises stress.

41
Q

If loading is pure torsion at failure then what are the stresses in the von Mises stress equal to?

A

Normal stress one is equal to normal stress two which is equal to the maximum shear stress and normal stress three is equal to zero.

42
Q

What is the When is the modified Goodman theory used?

A

A part that is subjected to a combination of static and reversed loadings.

43
Q

What is the alternating stress equal to in the modified Goodman theory?

A

Half of the range stress or half the difference between the max and minimum normal stress (the range stress).

44
Q

When is the Soderberg theory used?

A

Under variable loading.

Mechanics of Materials (4 decks)

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