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MCHE 3920 Final > Sheet Metal > Flashcards

Sheet Metal Flashcards

1
Q

Sheetmetal production volumes can be _______(up to ________ units)

A

High, 10^8

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2
Q

What are the two Sheetmetal production methods?

A

Bending, Matched Die Forming

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3
Q

_____________ is a sheet metal method that is simple, cheap, single curved parts, small volumes

A

Bending

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4
Q

_____________ is a sheet metal method that is complex, expensive, produces double curved parts, high volumes

A

Matched Die Forming

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5
Q

The first step in sheet metal forming is ____________________________

A

Blanking

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6
Q

In sheet metal forming, you need to exceed the materials ___________ in order to bend the metal

A

Yield Stress

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7
Q

Sheet metals will typically have some amount of ____________, but here we will assume ________ materials

A

Anisotropy, isotopic

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8
Q

What are the 4 regions on the stress strain Curve?

A

Elastic, Plastic, Necking, Unloading

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9
Q

The Yield stress is the critical point of which 2 regions?

A

Elastic and Plastic

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10
Q

The elastic region is characterized by the stress increasing _________ with strain

A

Linearly

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11
Q

The slope of the Stress Strain Curve in the elastic region is ____________________

A

Youngs Modulus

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12
Q

Interatomic bonds act like _______

A

springs

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13
Q

In the Elastic region, Upon removal of load, the material returns to original __________ and has no __________________ deformation

A

shape, permeant

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14
Q

At the _________dislocations begin to form in the __________

A

Yield Stress, Crystal Lattice

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15
Q

Yield stress can sometimes be difficult to determine from test so the ________off-set method is often used

A

0.2%

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16
Q

In the plastic region, Movement of the dislocations occur along “___________” that cause one portion of the lattice to _____relative to the other.

A

Slip Planes, slip

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17
Q

_________________ or ________________ is when slip planes begin to hinder each other and it takes more and more stress to continue to deform the material

A

Strain or work hardening

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18
Q

The ultimate strength (or Maximum _____________ is the ______________ strength a part will see before failure

A

Maximum stress, tensile strength

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19
Q

What happens after the ultimate strength as the material deforms and stress drops?

A

Necking

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20
Q

Stress is calculated using the materials __________ area, if it was calculated using ________________ area, stress would continue to increase in necking region

A

original, instantaneous

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21
Q

Calculating stress using time- varying area is called _________

A

True Stress

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22
Q

If the load is reduced or removed, the material will follow a linear ________ curve that is _________ to the elastic portion of the curve

A

Unloading, parallel

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23
Q

The point where the unloading curve ________ the strain axis is the amount of _________ deformation

A

intersects, permanent

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24
Q

The ______________ is an indication of the amount of material elongation at failure

A

Strain - Failure

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25
Q

The most, basic sheet metal forming is bending a _______ to some ________, α, with some _______, R

A

Blank, angle, radius

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26
Q

The ________________________ is the smallest radius a sheet metal bend an have

A

Minimum Bending Radius (MBR)

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27
Q

The MBR Model Assumptions are:
1. All deformations take place in a _________ defined by α and R
2. The metal deformation has the same behavior in tension as
in compression (i.e., anti-symmetric stress-strain curve)
3. The _________ (NA) does not change in length
4. The metal outside NA becomes _______, inside becomes _____
5. Metal is __________ and homogeneous

A

Zone, neutral axis, thinner, thicker, isotropic,

28
Q

As a result of the MBR assumptions, the maximum strains occur at the ________ (R+/-_____/2)

A

Surfaces, t

29
Q

The tensile strain-to-failure (εmax) will set the _____________

A

MBR

30
Q

In general, we can bend metal with a ______ radius than predicted by the model

A

Sharper

31
Q

MBR is inaccurate because there is a transition zone outside of the bend in which material _______ somewhat, meaning that some of the required deformation is ________ by this region

A

Deforms, taken up

32
Q

MBR is inaccurate because materials in bending do not experience __________, so can they can deform more than what is suggested by tensile tests. In tensile tests, _________________ is concentrated in a small volume, yet strain-to-failure is calculated using total length.

A

necking, necking deformation

33
Q

After bending the sheet metal, there will always be some amount of “___________” associated with the ___________ of the elastic strain

A

Spring back, unloading

34
Q

If we can predict the amount of spring back in a part, we can account for it by bending the part
_____________than the desired ending angle

A

more

35
Q

The amount of spring back is proportional to the ratio of __________ to ______________energy (______ + ________)

A

elastic, total, (Elastic, Plastic)

36
Q

Energy stored in the part is equal to the area under the ______________ curve

A

Stress-Strain

37
Q

It is hard to predict spring back exactly, but if it is known in a reference case, we can use the __________ to predict what it will be if we changed the thickness or the bending radius

A

Energy Ratio

38
Q

What are the three common methods for sheet metal bending covered?

A

Air bending, Bottom/V die bending, Wipe Bending

39
Q

This Sheetmetal bending method deforms part by three point loading

A

Air Bending

40
Q

This Sheetmetal bending method sandwiches the part between the die and the punch

A

Bottoming (or V-die bending)

41
Q

This Sheetmetal bending method occurs when a part is bent as a cantilever by a moving die

A

Wipe Bending

42
Q

In ______________________ sheet metal is passed relatively slowly over turning ___________ while ____________ are moved with each pass to gradually deform the part. This is good form making cylindrical and cone shapes as well as complex profiles

A

Roll bending, driving rollers, adjustable rolls,

43
Q

Roll forming has _______ tolerance control and initial investment is _______

A

Tight, high

44
Q

Roll forming is usually used with _________, but not _______, which is typically extruded

A

Steel, aluminum

45
Q

For sheet metal forming, it is often convenient to consider____________ in which each incremental change in length is divided by the instantaneous length and then summed (i.e., integrated) from the _________ to __________________

A

True strain, initial length, instantaneous length

46
Q

When metal is deformed in multiple steps, it is easier to use ___________and add the deformations after each step than it is to find the ___________strain

A

true strain, final nominal

47
Q

When tension is applied in one direction, the positive deformation (ε1) is accompanied by ___________ deformation in the other two directions.

A

negative

48
Q

Multi-axial deformations are related by ___________, ν

A

Poisson’s Ratio

49
Q

Poisson’s ratio typically falls between ______ and ______ for metals

A

.25, .35

50
Q

Recall that during plastic deformation, the crystal structure slides against each other, allowing us to assume that the _________ stays constant during ________________

A

Volume, plastic deformation

51
Q

For double-curved parts, the applied stress is _______, so uniaxial tensile test data are not sufficient to determine _________ limits

A

Biaxial, formability

52
Q

A forming limit diagram (FLD) shows ________combinations of strain in the two axes

A

Viable

53
Q

Plotted strains on a FLD are _________ Strains

A

True

54
Q

Study The FLD Curve slides

A

Study The FLD Curve slides

55
Q

Spring back in double curved parts will occur in ________directions

A

two

56
Q

What are the two types of spring back in double curved parts?

A

Out of plane, in plane

57
Q

If a part is highly double curved (e.g., hemispherical bowl) then the shape is typically _______ enough to resist spring back

A

stiff

58
Q

For shallow shapes, having some sort of _______will help the part and help prevent excessive spring back

A

flange

59
Q

What are the five methods for making double curved parts?`

A

Panel Beating, Deep Drawing, Matched Die Forming, Rubber Forming, Hydroforming

60
Q

_______________________ involves placing the part on a die or a leather sand bag and __________ it into shape with a rounded mallet and it requires a lot of time

A

Panel Beating, beating

61
Q

What Double Curved manufacturing method is this?
o Used for items like pans and cans
o Consists of a die, blank holder and a punch
o The punch draws the blank down, forming the product
o The blank is free below the punch
o Lubricant is used between the blank and the blank holder
o Too much pressure on blank or force behind the punch could rupture part

A

Deep Drawing

62
Q

Deep drawing works best if the material has a large ____________
on stress strain curve

A

plastic region

63
Q

What Double Curved manufacturing method is this?
o Similar to deep drawing, except the underside of the blank is fully supported by the lower die
o Used extensively in the automotive industry
o Can require significant upfront investment in dies and tools
o Often why different automobile brands will share body styles
o Can be done on a single line with each die doing a portion of the forming called sequential die forming

A

Matched Die Forming

64
Q

What Double Curved manufacturing method is this?
Similar to matched die forming, but lower die is a ___________ and cheaper because the lower die does not have to be matched to the upper die

A

Rubber pad

65
Q

What Double Curved manufacturing method is this?
o Instead of a punch, water under high pressure forces the sheet into the die
o Often used with tubes, where the pressure causes the to expand outward
o Expensive, but fast and can allow tight tolerances

A

Hydroforming

MCHE 3920 Final (10 decks)

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