Week 2 Flashcards
1
Q
What are Bulk Deformation Processes characterized by?
A
Significant deformations and massive shape changes.
Example: Rolling, forging, extrusion.
2
Q
What does ‘bulk’ refer to in Bulk Deformation Processes?
A
Workparts with relatively low surface area-to-volume ratios.
3
Q
What are the starting work shapes for Bulk Deformation Processes?
A
Cylindrical billets and rectangular bars.
4
Q
What is the primary interest in the plastic region of the stress-strain curve in metal forming?
A
Material being plastically deformed.
5
Q
How is a metal’s behavior expressed in the plastic region?
A
By the flow curve.
6
Q
What does the flow curve equation represent in metal forming?
A
The relationship between true stress and true strain.
7
Q
What does the ‘K’ represent in the flow curve equation?
A
Strength coefficient.
8
Q
What does the ‘n’ represent in the flow curve equation?
A
Strain hardening exponent.
9
Q
What is flow stress?
A
The instantaneous value of stress required to continue deforming the material.
10
Q
What happens to the strength of most metals at room temperature when deformed?
A
It increases due to strain hardening.
11
Q
How is flow stress represented in terms of yield strength and strain?
A
Yf = KY^nf
12
Q
What are the given values for the metal’s flow curve?
A
Strength coefficient = 850 MPa, Strain-hardening exponent = 0.30.
13
Q
What is the formula to determine flow stress at a new length?
A
Flow stress = Strength coefficient * (strain)^Strain-hardening exponent.
14
Q
What is the flow stress at the new length if the gage length is 100 mm and the stretched length is 157 mm?
A
Calculate using the flow stress formula with the given values.
15
Q
How can the average flow stress during deformation be calculated?
A
By integrating the flow stress over the strain range and dividing by the strain range.
16
Q
What is the flow stress calculation based on the given solution?
A
Flow stress = 850(0.451)^0.30 = 669.4 MPa.
17
Q
How is the average flow stress calculated?
A
Average flow stress = 850(0.451)^0.30 / 1.30 = 514.9 MPa.
18
Q
How is the average flow stress determined?
A
By integrating the flow curve equation between zero and the final strain value defining the range of interest.
19
Q
What does the symbol ε represent in the flow curve equation?
A
Maximum strain during the deformation process.
20
Q
What does the symbol σ represent in the flow curve equation?
A
Average flow stress.
21
Q
What do the flow curve constants K and n depend on?
A
Temperature.
22
Q
How are strength and strain hardening affected at higher temperatures?
A
Both are reduced.
23
Q
What happens to ductility at higher temperatures?
A
It is increased.
24
Q
What are the three temperature ranges in metal forming?
A
Cold working, warm working, and hot working.
25
What is strain rate sensitivity?
The occurrence of strain rate sensitivity, especially at elevated temperatures, in hot working.
26
How is strain rate defined?
Strain rate is defined as the true strain rate, where h is the instantaneous height of the workpiece being deformed and v is the velocity of the ram or other movement of the equipment.
27
What does the variable 'C' represent in the equation?
The strength constant (similar but not equal to strength coefficient in flow curve equation).
28
What does the variable 'm' represent in the equation?
The strain-rate sensitivity exponent.
29
What does Figure 18.6 illustrate?
The effect of temperature on flow stress for a typical metal.
30
What does the constant 'C' in Eq. (18.4) represent?
It decreases with increasing temperature.
31
What does the slope 'm' of each plot indicate?
It increases with increasing temperature.
32
What is open-die forging?
It involves compressing the work between two flat dies, allowing metal to flow laterally without constraint.
33
What is impression-die forging?
It involves die surfaces containing a cavity or impression that is imparted to the workpart, thus constraining metal flow and creating flash.
34
What is flashless forging?
It involves the workpart being completely constrained in the die, and no excess flash is produced.
35
What is the purpose of an upset forging operation?
To form a head on a bolt or similar hardware item.
36
What are the steps involved in an upset forging cycle?
1) Wire stock is fed to the stop. 2) Gripping dies close on the stock and the stop is retracted. 3) Punch moves forward. 4) Bottoms to form the head.
37
What is the final height of the part after hot upset forging?
The final height of the part needs to be determined.
38
What is the maximum force in the hot upset forging operation?
The maximum force in the operation needs to be determined.
39
What is the formula for calculating volume (V) of the given shape?
V = πDo^2ho/4
40
What is the formula for calculating final height (hf) of the given shape?
hf = V/Af
41
What is the formula for calculating strain (ε) in the given context?
ε = ln(50/12.5)
42
What is the formula for calculating force (F) in the given scenario?
F = 1.64(85)(1963.5)
43
What is rolling in the context of manufacturing processes?
A deformation process in which work thickness is reduced by compressive forces
44
What is rolling in the context of manufacturing processes?
A deformation process in which work thickness is reduced by compressive forces exerted by two opposing rolls.
45
What is flat rolling used for?
To reduce the thickness of a rectangular cross-section.
46
What is shape rolling used for?
To form a square cross-section into a shape such as an I-beam.
47
Which type of rolling is most common due to the large amount of deformation required?
Hot rolling.
48
What does cold rolling produce?
Finished sheet and plate stock.
49
What is the formula for rolling analysis related to the flow stress?
f_o - f_t = 36 * (σ_t / σ_r)^n * K * Y
50
What does the symbol 'f' represent in the rolling analysis formulas?
Flow stress.
51
What does the symbol 't' represent in the rolling analysis formulas?
Thickness of the material.
52
What does the symbol 'd' represent in the rolling analysis formulas?
Roll diameter.
53
What does the symbol 'σ' represent in the rolling analysis formulas?
Stress.
54
What does the symbol 'n' represent in the rolling analysis formulas?
Strain hardening exponent.
55
What does the symbol 'K' represent in the rolling analysis formulas?
Constant related to material properties.
56
What does the symbol 'Y' represent in the rolling analysis formulas?
Yield strength.
57
What is the initial thickness of the plate to be reduced in the rolling mill?
25 mm
58
What is the final thickness of the plate after the single pass in the rolling mill?
20 mm
59
What is the width of the plate to be reduced in the rolling mill?
250 mm
60
What is the radius of the roll in the two high rolling mill?
500 mm
61
What is the speed of the roll in the rolling mill?
30 m/min
62
What is the strength coefficient of the work material?
240 MPa
63
What is the strain hardening exponent of the work material?
0.2
64
What is the formula to determine roll force in rolling process?
Roll force = (0.5 * strength coefficient * width * thickness) / roll radius.
65
What is the formula to determine roll torque in rolling process?
Roll torque = roll force * roll radius.
66
What is the formula to determine power required in rolling process?
Power = roll torque * roll speed.
67
What is the formula for true strain?
True strain ε = ln(25/20) = ln 1.25 = 0.223
68
What is the formula for rolling force?
Rolling force F = 148.1(250)(50) = 1,851,829 N
69
What is the formula for torque?
Torque T = 0.5(1,851,829)(50 x 10 -3) = 46,296 N-m
70
What is the formula for power?
Power P = 2π(0.159)(1,851,829)(50 x 10 -3) = 92,591 N-m/s = 92,591 W
71
What are the configurations of rolling mills?
Two-high, three-high, four-high, cluster mill, and tandem rolling mill.
72
What is the configuration of a two-high rolling mill?
It consists of two opposing large diameter rolls.
73
How does work pass through in a three-high rolling mill?
It passes through both directions.
74
In a four-high rolling mill, what supports the smaller work rolls?
Backing rolls.
75
What is the configuration of a cluster mill?
It has multiple backing rolls on smaller rolls.
76
What is the sequence in a tandem rolling mill?
It consists of a sequence of two-high mills.
77
What is a cluster mill?
A rolling mill with multiple backing rolls that allow even smaller roll diameters.
78
What is a tandem rolling mill?
A series of rolling stands in sequence.
79
How many mills are there in a tandem rolling mill?
Sequence of two-high mills.
80
What is the purpose of ring rolling?
To reduce the wall thickness and increase the diameter of a ring.
81
What are the two key stages of the ring rolling process?
Start and completion of the process.
82
What is trimming in the context of impression-die forging?
It is a cutting operation to remove flash from the workpart.
83
When is trimming usually done in impression-die forging?
While the work is still hot.
84
What is included at the forging station to perform trimming?
A separate trimming press.
85
Besides a trimming press, what are alternative methods for trimming in impression-die forging?
Grinding or sawing.
86
What is extrusion?
A compression forming process in which the work metal is forced to flow through a die opening to produce a desired cross-sectional shape.
87
How is the process of extrusion compared to in the description?
It is similar to squeezing toothpaste out of a toothpaste tube.
88
What is the purpose of extrusion?
To produce long parts of uniform cross-sections.
89
Besides a trimming press, what are alternative methods for trimming in impression-die forging?
Grinding or sawing.
## Footnote
Example: Grinding or sawing can be used as alternative methods for trimming in impression-die forging.
90
What is extrusion?
A compression forming process in which the work metal is forced to flow through a die opening to produce a desired cross-sectional shape.
## Footnote
Example: Extrusion is a process where metal is forced through a die to create a specific shape.
91
How is the process of extrusion compared to in the description?
It is similar to squeezing toothpaste out of a toothpaste tube.
## Footnote
Example: The extrusion process is likened to squeezing toothpaste out of a tube.
92
What is the purpose of extrusion?
To produce long parts of uniform cross-sections.
## Footnote
Example: Extrusion is used to create long parts with consistent cross-sections.
93
What are the two basic types of extrusion?
Direct extrusion and Indirect extrusion.
## Footnote
Example: The two main types of extrusion are direct and indirect extrusion.
94
What is another name for direct extrusion?
Forward extrusion.
## Footnote
Example: Forward extrusion is another term for direct extrusion.
95
What is the extra portion of the billet that remains as the ram approaches the die opening called?
The butt.
## Footnote
Example: The portion of the billet left after extrusion is known as the butt.
96
How is the extra portion (butt) separated from the extruded product?
By cutting it just beyond the die exit.
## Footnote
Example: The butt is removed by cutting it beyond the die exit.
97
What determines the final shape of the extruded product in direct extrusion?
The die opening.
## Footnote
Example: The final shape of an extruded product is determined by the die opening in direct extrusion.
98
What are the alternative names for indirect extrusion?
Backward extrusion and reverse extrusion.
## Footnote
Example: Indirect extrusion is also known as backward or reverse extrusion.
99
What are the limitations of indirect extrusion?
Lower rigidity of hollow ram and difficulty in supporting the extruded product as it exits the die.
## Footnote
Example: Indirect extrusion has limitations such as lower rigidity of the ram and challenges in supporting the extruded product.
100
What is the extrusion ratio also known as?
Reduction ratio.
## Footnote
Example: The extrusion ratio is also referred to as the reduction ratio.
101
How is the extrusion ratio defined?
Extrusion ratio (r_x) = A_o / A_f, where A_o = cross-sectional area of the starting billet and A_f = final cross-sectional area of the extruded section.
## Footnote
Example: The extrusion ratio is calculated by dividing the initial cross-sectional area by the final cross-sectional area.
102
To which types of extrusion does the extrusion ratio apply?
Both direct and indirect extrusion.
## Footnote
Example: The extrusion ratio is applicable to both direct and indirect extrusion processes.
103
What is the simplest cross-section shape for an extrusion die orifice?
Circular die orifice.
## Footnote
Example: The simplest shape for an extrusion die orifice is circular.
104
How does the shape of the die orifice affect ram pressure?
The shape of the die orifice affects ram pressure.
## Footnote
Example: The shape of the die orifice has an impact on the required ram pressure.
105
What happens to the pressure and force required as the cross-section of the die orifice becomes more complex?
Higher pressure and greater force are required.
## Footnote
Example: More complex die orifice shapes result in increased pressure and force requirements.
106
What is the formula for extrusion analysis?
f_0 = f_x * A/A_r * ln(ln(ε_x))
## Footnote
Example: The formula for extrusion analysis involves the initial flow stress, area reduction ratio, and strain in the x-direction.
107
What does the symbol 'ε_x' represent in the extrusion analysis formula?
Strain in the x-direction.
## Footnote
Example: 'ε_x' in the extrusion analysis formula signifies the strain in the x-direction.
108
What is the formula for the flow stress in extrusion analysis?
f = n * K * (ε^p)
## Footnote
Example: The formula for flow stress in extrusion analysis includes the strain hardening exponent, constant, and strain.
109
What does the symbol 'n' represent in the flow stress formula for extrusion analysis?
Strain hardening exponent.
## Footnote
Example: 'n' in the flow stress formula represents the strain hardening exponent.
110
What is the formula for the indirect extrusion force?
P = F_v * (A/A_r) * K * shape factor
## Footnote
Example: The formula for indirect extrusion force involves the vertical force, area reduction ratio, constant, and shape factor.
111
How is the change in size of work usually given in drawing?
By area reduction.
## Footnote
Example: Work size changes in drawing are typically expressed in terms of area reduction.
112
What does the symbol 'r' represent in the area reduction formula?
Area reduction in drawing.
## Footnote
Example: 'r' symbolizes the area reduction in the drawing process.
113
How is the original area of work represented in the area reduction formula?
By 'A o'.
## Footnote
Example: The initial work area is denoted as 'A o' in the area reduction formula.
114
How is the final area of work represented in the area reduction formula?
By 'A f'.
## Footnote
Example: The final work area is represented as 'A f' in the area reduction formula.
115
What is the main difference between bar drawing and wire drawing?
The stock size, with bar drawing using large diameter bar and rod stock, and wire drawing using small diameter stock.
## Footnote
Example: Bar drawing involves larger stock sizes compared to wire drawing.
116
What is the possible range of wire sizes in wire drawing?
Wire sizes down to 0.03 mm (0.001 in.) are possible.
## Footnote
Example: Wire drawing can produce very fine wire sizes, as small as 0.03 mm.
117
Are the methods, equipment, and terminology the same for bar drawing and wire drawing?
No, they are different.
## Footnote
Example: Bar drawing and wire drawing involve distinct methods, equipment, and terminology.
118
What is the function of the entry region in a draw die?
It funnels lubricant into the die to prevent scoring of work and die.
## Footnote
Example: The entry region in a draw die serves to deliver lubricant and prevent damage to the workpiece and die.
119
What is the purpose of the approach in a draw die?
It is a cone-shaped region where drawing occurs.
## Footnote
Example: The approach in a draw die is a conical area where the drawing process takes place.
120
What does the bearing surface in a draw die determine?
It determines the final stock size.
## Footnote
Example: The bearing surface in a draw die influences the size of the final product.
121
What is the back relief in a draw die?
It is the exit zone provided with a back relief angle of about 30 degrees.
## Footnote
Example: The back relief in a draw die is the exit area with a specific relief angle.
122
What are the common materials used for draw die manufacturing?
Tool steels or cemented carbides.
## Footnote
Example: Draw dies are commonly made from tool steels or cemented carbides.
123
What does the symbol 'f_0' represent in the extrusion analysis formula?
Initial flow stress
## Footnote
Example: 'f_0' stands for the initial flow stress in the extrusion analysis formula.
124
What does the symbol 'A/A_r' represent in the extrusion analysis formula?
Area reduction ratio
## Footnote
Example: 'A/A_r' denotes the area reduction ratio in the extrusion analysis formula.
125
What is the formula for strain in extrusion analysis?
ε_x = (ln(1 + (f_x * r)/(Y_p))) / (n)
## Footnote
Example: The formula for strain in extrusion analysis includes parameters like flow stress, area reduction, and strain hardening exponent.
126
What does the symbol 'ε_x' represent in the strain formula for extrusion analysis?
Strain in the extruded material
## Footnote
Example: 'ε_x' signifies the strain in the material during extrusion in the strain formula.
127
What is the formula for the shape factor in extrusion analysis?
F = (25.2 + 0.02 * C - 0.98 * C^2)
## Footnote
Example: The shape factor formula in extrusion analysis involves constants related to the process.
128
What is the extrusion ratio?
Extrusion ratio = initial cross-sectional area / final cross-sectional area.
## Footnote
Example: The extrusion ratio is calculated by dividing the initial cross-sectional area by the final cross-sectional area.
129
How is true strain (homogeneous deformation) determined in extrusion?
True strain (homogeneous deformation) is determined using the Johnson extrusion strain equation.
## Footnote
Example: True strain in extrusion is calculated using the Johnson extrusion strain equation.
130
What is the formula for extrusion strain?
Extrusion strain = (ln(initial area / final area)) / (ln(initial length / final length)).
## Footnote
Example: The formula for extrusion strain involves the ratio of initial and final areas and lengths in the logarithmic form.
131
How is ram pressure and force calculated at a specific length in extrusion?
The calculation of ram pressure and force at a specific length in extrusion involves complex formulas and considerations.
## Footnote
Example: The determination of ram pressure and force at a specific length in extrusion requires detailed calculations and analysis.
132
What is the extrusion ratio?
Extrusion ratio = initial cross-sectional area / final cross-sectional area.
## Footnote
Example: If initial area = 10 mm^2 and final area = 2 mm^2, then extrusion ratio = 10 / 2 = 5
133
How is true strain (homogeneous deformation) determined in extrusion?
True strain (homogeneous deformation) is determined using the Johnson extrusion strain equation.
## Footnote
134
What is the formula for extrusion strain?
Extrusion strain = (ln(initial area / final area)) / (ln(initial length / final length)).
## Footnote
135
How is ram pressure and force calculated at a specific length in extrusion?
Ram pressure and force are calculated using the given parameters and the extrusion process equations.
## Footnote
136
What is the formula for calculating the area reduction in bulk deformation processes?
r_x = A_o / A_f = D_o^2 / D_f^2
## Footnote
137
How is the natural logarithm of the area reduction (r_x) calculated?
ε = ln r_x
## Footnote
138
What is the equation for strain hardening exponent (ε_x) in bulk deformation processes?
ε_x = a + b ln r_x
## Footnote
139
How is the flow stress (f_Y) calculated in the given problem?
f_Y = 600(1.119)^0.25 / 1.25 = 493.7 MPa
## Footnote
