Homework Ch 8 and 9 ME240 FALL 2022
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ME 240 Homework
Chapter 8: Failure
1. Cite one situation in which the possibility of failure is part of the design of a component or
product. (Could be anything you can think of in your life or you have seen anywhere). 2. An aircraft component is fabricated from an aluminum alloy that has a plane strain fracture
toughness of 38 MPa
√
m
. It has been determined that fracture results at a stress of 251 MPa
when the maximum (or critical) internal crack length is 2.95 mm.
a) Determine the value of Yσ
√
πa
for this same component and alloy at a stress level of 326
MPa when the maximum internal crack length is 1.48 mm.
b) Under these circumstances will the component fail?
3. Which kind of fracture is associated with the intergranular crack propagation mechanism?
4. Estimate the theoretical fracture strength (in MPa) of a brittle material if it is known that
fracture occurs by the propagation of an elliptically-shaped surface crack of length 0.25 mm
that has a tip radius of curvature of 0.004 mm when a stress of 1060 MPa is applied.
5. For a brittle material that has a specific surface energy of 0.33 J/m
2
, and flexural strength
and elastic modulus values of 88.1 MPa and 61 GPa, respectively, calculate the critical stress
(in MPa) required for the propagation of a surface crack of length 0.04 mm.
6. A plate of an alloy steel has a plane-strain fracture toughness of 50 MPa
√
m
. If it is known
that the largest surface crack is 0.5 mm long and that the value of Y is 1.1, which of the
following can be said about this plate when a tensile stress of 1200 MPa is applied?
(a) The plate will definitely not fracture.
(b) The plate will definitely fracture.
(c) It is not possible to determine whether or not the plate will fracture.
7. What is the magnitude of the maximum stress that exists at the tip of an internal crack
having a radius of curvature of 2.5×10
-4
mm (0.9843×10
-5
in.) and a crack length of 4×10
-2
mm (1.575×10
-3
in.) when a tensile stress of 100 MPa (14500 psi) is applied?
8. An aluminum oxide component must not fail when a tensile stress of 10.5 MPa is applied.
Determine the maximum allowable surface crack length if the surface energy of aluminum
oxide is 0.90 J/m
2
. The modulus of elasticity of this material is
393 GPa.
Homework of Chapter 9: Phase Diagrams 1
1. what are the three parameters that will affect the phase transformation?
2. How many phases may be in Equilibrium for binary phase diagrams and eutectic phase
diagrams, respectively.
3. What is the difference of Eutectic, Eutectoid, & Peritectic phase transformations?
4. Consider the Cu-Ni binary phase diagram (see the following figure) and answer the
questions: A copper-nickel alloy of composition 70 wt% Ni-30 wt% Cu is slowly heated from
a temperature of 1300°C.
(a) At what temperature does the first liquid phase form?
(b) What is the composition of this liquid phase?
(c) At what temperature does complete melting of the alloy occur?
(d) What is the composition of the last solid remaining prior to complete melting?
5. Consider the sugar-water phase diagram, (a) How much sugar will dissolve in 1000 g of
water at 80°C? (b) If the saturated liquid solution in part (a) is cooled to 20°C, some of the
sugar will precipitate out as a solid, because as seen in the figure, the composition of the
saturated liquid solution drops to 64 wt% sugar. How much of the solid sugar will come out
of solution upon cooling to 20°C?
2
6. For a copper-silver alloy with 71.9 wt% silver. Determine the phases and composition of
the alloy of a copper-silver alloy at 779°C. You may want to use the following phase diagram
to solve this problem.
3
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Related Questions
1. For the stress-strain curve shown below, please estimate the properties indicated.
(a) Fracture Strain
Please do your work on a separate sheet of paper,
and put your answers in the boxes on the right.
Be sure to include the proper symbol and units.
Stress Strain
70
60
50
Stress (ksi)
240
30
20
10
70
0
0.000
60
50
Stress (ksi)
40
20
10
KULL
0
0.000
0.010
0.050
0.100
Strain (in/in)
Stress Strain
0.020 0.030
Strain (in/in)
0.040
0.150
0.050
(b) Ultimate Tensile Stress
(c) Fracture Stress
(d) Proportional Limit
(e) Elastic Modulus
(1) Yield Stress
(g) Tensile Toughness
(Modulus of Toughness)
(h) Modulus of Resilience
arrow_forward
option e and f plz
arrow_forward
9) An aircraft component is made of an aluminum alloy that has a fracture toughness of 60MPavm. When a crack of 2.5mm exists in the
component, the material fractures when a stress of 440MPA is reached. If a crack of 5.5mm exists in the material, what stress would need to
be reached to cause failure?
arrow_forward
Question 1
You are working on a design team at a small orthopaedic firm. You have been asked to select a cobalt-
chrome-molybdenum (CoCr) material that will not experience plastic deformation under a specific mechanical test, as follows...
A tensile stress is applied along the long axis of a solid cylindrical rod that has a diameter of 10 mm. An applied load of some
magnitude F produces a 7x10-³ mm change in diameter (see figure below, original shape is blue, elongated shape is unshaded).
Q1G: If your design required using the new material to create a wire, what is the largest diameter that would lead to ductile
behavior while still avoiding plastic deformation when exposed to the above loading conditions?
arrow_forward
Please explain each step briefly.
arrow_forward
Question 1
You are working on a design team at a small orthopaedic firm. You have been asked to select a cobalt-
chrome-molybdenum (CoCr) material that will not experience plastic deformation under a specific mechanical test, as follows...
A tensile stress is applied along the long axis of a solid cylindrical rod that has a diameter of 10 mm. An applied load of some
magnitude F produces a 7x10³ mm change in diameter (see figure below, original shape is blue, elongated shape is unshaded).
Q1H: Provide a brief rationale based on calculations used to support your answer. That is, how would you explain the behavior of
the "new alloy" material to your design team?
Table of properties: Assume Poisson's ratio is 0.3 for all materials
Process
Elastic Modulus (GPa)
Material
CoCr F75
As cast/Annealed
210
CoCr F90
Hot forged
New alloy
Z
X
↑ F
df
O
210
110
Yield Strength (MPa)
450-517
900-1200
600
Tensile Strength (MPa)
655-890
1400-1600
700
arrow_forward
Question 1
You are working on a design team at a small orthopaedic firm. You have been asked to select a cobalt-
chrome-molybdenum (CoCr) material that will not experience plastic deformation under a specific mechanical test, as follows...
A tensile stress is applied along the long axis of a solid cylindrical rod that has a diameter of 10 mm. An applied load of some
magnitude F produces a 7x10³ mm change in diameter (see figure below, original shape is blue, elongated shape is unshaded).
Q1C-D: Using the table of material properties below, calculate the magnitude of stress (o) and applied load (F) required to produce
the 7x10-³ mm change in diameter for rods fabricated from F75 CoCr alloy (as cast) and F90 CoCr alloy (hot forged) materials.
arrow_forward
No wrong answer please , i could downvote
The piece of suture is tested for its stress relaxation properties after cutting 3 cm long sample with a diameter of 1mm. The initial force recorded after stretching 0.1 cm between grips was 5 Newtons. Assume the suture material behave as if it has one relaxation time. The gage length was 1 cm.
a. Calculate the initial stress.
b. Calculate the initial strain.
c. Calculate the modulus of elasticity of the suture if the initial stretching can be considered as linear and elastic.
d. Calculate the relaxation time if the force recorded after 10 hours is 4 Newtons.
arrow_forward
Learning Goal:
As shown, a differential element of material is distorted
after it is subjected to stresses resulting in a state of
plane strain given by = -1
-360.0 x 10-6 in/in,
Ey = 225.0 x 10-6 in/in, and
H
Yzy = 110.0 x 10-6 in/in.(Figure 1)
Figure
E dy
y
Yxy
2
& dr-
dx
BO
Part A - In-plane principal strains and their orientation
Determine the in-plane principal strains €₁ and 2 and their orientations that are associated with the differential element of material.
Express your answers to four significant figures separated by commas.
► View Available Hint(s)
€1, €2, p =
Submit
ΠΫΠΙ ΑΣΦ |
VE
Previous Answers
vec
Ĵ
he
X Incorrect; Try Again; 4 attempts remaining
Part B - Maximum in-plane shear strain and its orientation
MED
?
in/in, in/in, rad
Determine the magnitude of the maximum in-plane shear strain, in plane and its orientation relative to the differential element of materi
Express your answers to four significant figures separated by a comma.
arrow_forward
A manufacturing process that unintentionally introduces cracks to the surface of a part was used to produce load-bearing components. The design requires that the component be able to withstand a stress of 450 MPa. The component failed catastrophically in service.
You are a failure analysis engineer who must determine whether the component failed due to an overload in the service or flaws from the manufacturing process. The manufacturer claims that the components were polished to remove the cracks and inspected to ensure that no surface cracks were larger than 0.5 mm. the manufacturer believe the component failed due to operator error.
It has been independently verified that he 5 cm diameter part was subjected to a tensile load of 1 MN (106 N)
The material from which the component is made had a fracture toughness of 75 MPaÖm and ultimate tensile strength of 600 MPa. Assume external cracks for which f = 1.12.
Who is at fault for the component failure, the manufacturer or the operator?…
arrow_forward
Stuck need help!
Problem is attached. please view attachment before answering.
Really struggling with this concept.
Please show all work so I can better understand !
Thank you so much.
arrow_forward
Request:
Can you please help me with answering the following question? Thank you.
Question:
A specimen of a ceramic material having an elastic modulus of 250 GPa (36.3 x 106 psi) is pulled in tension with a stress of 750 MPa (109,000 psi). Will the specimen fail if its “most severe flaw” is an internal crack that has a length of 0.20 mm (7.87 x 10-3 in.) and a tip radius of curvature of 0.001 mm (3.94 x 10-5 in.)? Why or why not?
arrow_forward
SEE MORE QUESTIONS
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Related Questions
- 1. For the stress-strain curve shown below, please estimate the properties indicated. (a) Fracture Strain Please do your work on a separate sheet of paper, and put your answers in the boxes on the right. Be sure to include the proper symbol and units. Stress Strain 70 60 50 Stress (ksi) 240 30 20 10 70 0 0.000 60 50 Stress (ksi) 40 20 10 KULL 0 0.000 0.010 0.050 0.100 Strain (in/in) Stress Strain 0.020 0.030 Strain (in/in) 0.040 0.150 0.050 (b) Ultimate Tensile Stress (c) Fracture Stress (d) Proportional Limit (e) Elastic Modulus (1) Yield Stress (g) Tensile Toughness (Modulus of Toughness) (h) Modulus of Resiliencearrow_forwardoption e and f plzarrow_forward9) An aircraft component is made of an aluminum alloy that has a fracture toughness of 60MPavm. When a crack of 2.5mm exists in the component, the material fractures when a stress of 440MPA is reached. If a crack of 5.5mm exists in the material, what stress would need to be reached to cause failure?arrow_forward
- Question 1 You are working on a design team at a small orthopaedic firm. You have been asked to select a cobalt- chrome-molybdenum (CoCr) material that will not experience plastic deformation under a specific mechanical test, as follows... A tensile stress is applied along the long axis of a solid cylindrical rod that has a diameter of 10 mm. An applied load of some magnitude F produces a 7x10-³ mm change in diameter (see figure below, original shape is blue, elongated shape is unshaded). Q1G: If your design required using the new material to create a wire, what is the largest diameter that would lead to ductile behavior while still avoiding plastic deformation when exposed to the above loading conditions?arrow_forwardPlease explain each step briefly.arrow_forwardQuestion 1 You are working on a design team at a small orthopaedic firm. You have been asked to select a cobalt- chrome-molybdenum (CoCr) material that will not experience plastic deformation under a specific mechanical test, as follows... A tensile stress is applied along the long axis of a solid cylindrical rod that has a diameter of 10 mm. An applied load of some magnitude F produces a 7x10³ mm change in diameter (see figure below, original shape is blue, elongated shape is unshaded). Q1H: Provide a brief rationale based on calculations used to support your answer. That is, how would you explain the behavior of the "new alloy" material to your design team? Table of properties: Assume Poisson's ratio is 0.3 for all materials Process Elastic Modulus (GPa) Material CoCr F75 As cast/Annealed 210 CoCr F90 Hot forged New alloy Z X ↑ F df O 210 110 Yield Strength (MPa) 450-517 900-1200 600 Tensile Strength (MPa) 655-890 1400-1600 700arrow_forward
- Question 1 You are working on a design team at a small orthopaedic firm. You have been asked to select a cobalt- chrome-molybdenum (CoCr) material that will not experience plastic deformation under a specific mechanical test, as follows... A tensile stress is applied along the long axis of a solid cylindrical rod that has a diameter of 10 mm. An applied load of some magnitude F produces a 7x10³ mm change in diameter (see figure below, original shape is blue, elongated shape is unshaded). Q1C-D: Using the table of material properties below, calculate the magnitude of stress (o) and applied load (F) required to produce the 7x10-³ mm change in diameter for rods fabricated from F75 CoCr alloy (as cast) and F90 CoCr alloy (hot forged) materials.arrow_forwardNo wrong answer please , i could downvote The piece of suture is tested for its stress relaxation properties after cutting 3 cm long sample with a diameter of 1mm. The initial force recorded after stretching 0.1 cm between grips was 5 Newtons. Assume the suture material behave as if it has one relaxation time. The gage length was 1 cm. a. Calculate the initial stress. b. Calculate the initial strain. c. Calculate the modulus of elasticity of the suture if the initial stretching can be considered as linear and elastic. d. Calculate the relaxation time if the force recorded after 10 hours is 4 Newtons.arrow_forwardLearning Goal: As shown, a differential element of material is distorted after it is subjected to stresses resulting in a state of plane strain given by = -1 -360.0 x 10-6 in/in, Ey = 225.0 x 10-6 in/in, and H Yzy = 110.0 x 10-6 in/in.(Figure 1) Figure E dy y Yxy 2 & dr- dx BO Part A - In-plane principal strains and their orientation Determine the in-plane principal strains €₁ and 2 and their orientations that are associated with the differential element of material. Express your answers to four significant figures separated by commas. ► View Available Hint(s) €1, €2, p = Submit ΠΫΠΙ ΑΣΦ | VE Previous Answers vec Ĵ he X Incorrect; Try Again; 4 attempts remaining Part B - Maximum in-plane shear strain and its orientation MED ? in/in, in/in, rad Determine the magnitude of the maximum in-plane shear strain, in plane and its orientation relative to the differential element of materi Express your answers to four significant figures separated by a comma.arrow_forward
- A manufacturing process that unintentionally introduces cracks to the surface of a part was used to produce load-bearing components. The design requires that the component be able to withstand a stress of 450 MPa. The component failed catastrophically in service. You are a failure analysis engineer who must determine whether the component failed due to an overload in the service or flaws from the manufacturing process. The manufacturer claims that the components were polished to remove the cracks and inspected to ensure that no surface cracks were larger than 0.5 mm. the manufacturer believe the component failed due to operator error. It has been independently verified that he 5 cm diameter part was subjected to a tensile load of 1 MN (106 N) The material from which the component is made had a fracture toughness of 75 MPaÖm and ultimate tensile strength of 600 MPa. Assume external cracks for which f = 1.12. Who is at fault for the component failure, the manufacturer or the operator?…arrow_forwardStuck need help! Problem is attached. please view attachment before answering. Really struggling with this concept. Please show all work so I can better understand ! Thank you so much.arrow_forwardRequest: Can you please help me with answering the following question? Thank you. Question: A specimen of a ceramic material having an elastic modulus of 250 GPa (36.3 x 106 psi) is pulled in tension with a stress of 750 MPa (109,000 psi). Will the specimen fail if its “most severe flaw” is an internal crack that has a length of 0.20 mm (7.87 x 10-3 in.) and a tip radius of curvature of 0.001 mm (3.94 x 10-5 in.)? Why or why not?arrow_forward
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