Sheet Metal

Question 1

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

Answer 1

High, 10^8

Question 2

What are the two Sheetmetal production methods?

Answer 2

Bending, Matched Die Forming

Question 3

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

Answer 3

Bending

Question 4

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

Answer 4

Matched Die Forming

Question 5

The first step in sheet metal forming is ____________________________

Answer 5

Blanking

Question 6

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

Answer 6

Yield Stress

Question 7

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

Answer 7

Anisotropy, isotopic

Question 8

What are the 4 regions on the stress strain Curve?

Answer 8

Elastic, Plastic, Necking, Unloading

Question 9

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

Answer 9

Elastic and Plastic

Question 10

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

Answer 10

Linearly

Question 11

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

Answer 11

Youngs Modulus

Question 12

Interatomic bonds act like _______

Answer 12

springs

Question 13

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

Answer 13

shape, permeant

Question 14

At the _________dislocations begin to form in the __________

Answer 14

Yield Stress, Crystal Lattice

Question 15

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

Answer 15

0.2%

Question 16

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

Answer 16

Slip Planes, slip

Question 17

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

Answer 17

Strain or work hardening

Question 18

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

Answer 18

Maximum stress, tensile strength

Question 19

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

Answer 19

Necking

Question 20

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

Answer 20

original, instantaneous

Question 21

Calculating stress using time- varying area is called _________

Answer 21

True Stress

Question 22

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

Answer 22

Unloading, parallel

Question 23

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

Answer 23

intersects, permanent

Question 24

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

Answer 24

Strain - Failure

Question 25

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

Answer 25

Blank, angle, radius

Question 26

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

Answer 26

Minimum Bending Radius (MBR)

Question 27

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

Answer 27

Zone, neutral axis, thinner, thicker, isotropic,

Question 28

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

Answer 28

Surfaces, t

Question 29

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

Answer 29

MBR

Question 30

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

Answer 30

Sharper

Question 31

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

Answer 31

Deforms, taken up

Question 32

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.

Answer 32

necking, necking deformation

Question 33

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

Answer 33

Spring back, unloading

Question 34

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

Answer 34

more

Question 35

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

Answer 35

elastic, total, (Elastic, Plastic)

Question 36

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

Answer 36

Stress-Strain

Question 37

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

Answer 37

Energy Ratio

Question 38

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

Answer 38

Air bending, Bottom/V die bending, Wipe Bending

Question 39

This Sheetmetal bending method deforms part by three point loading

Answer 39

Air Bending

Question 40

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

Answer 40

Bottoming (or V-die bending)

Question 41

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

Answer 41

Wipe Bending

Question 42

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

Answer 42

Roll bending, driving rollers, adjustable rolls,

Question 43

Roll forming has _______ tolerance control and initial investment is _______

Answer 43

Tight, high

Question 44

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

Answer 44

Steel, aluminum

Question 45

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 __________________

Answer 45

True strain, initial length, instantaneous length

Question 46

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

Answer 46

true strain, final nominal

Question 47

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

Answer 47

negative

Question 48

Multi-axial deformations are related by ___________, ν

Answer 48

Poisson's Ratio

Question 49

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

Answer 49

.25, .35

Question 50

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

Answer 50

Volume, plastic deformation

Question 51

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

Answer 51

Biaxial, formability

Question 52

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

Answer 52

Viable

Question 53

Plotted strains on a FLD are _________ Strains

Answer 53

True

Question 54

Study The FLD Curve slides

Answer 54

Study The FLD Curve slides

Question 55

Spring back in double curved parts will occur in ________directions

Answer 55

two

Question 56

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

Answer 56

Out of plane, in plane

Question 57

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

Answer 57

stiff

Question 58

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

Answer 58

flange

Question 59

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

Answer 59

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

Question 60

_______________________ 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

Answer 60

Panel Beating, beating

Question 61

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

Answer 61

Deep Drawing

Question 62

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

Answer 62

plastic region

Question 63

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

Answer 63

Matched Die Forming

Question 64

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

Answer 64

Rubber pad

Question 65

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

Answer 65

Hydroforming