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All questions of Theories of Failure for Mechanical Engineering Exam
The principal stresses at a point in a critical - section of a machine component are σ1 = 60 MPa, σ2 = 5 MPa and σ3 = – 40 MPa. For the material of the component, the tensile yield strength is σy = 200 MPa. According to the maximum shear stress theory, the factor of safety is- a)1.67
- b)3.6
- c)4
- d)2
Correct answer is option 'D'. Can you explain this answer?
The principal stresses at a point in a critical - section of a machine component are σ1 = 60 MPa, σ2 = 5 MPa and σ3 = – 40 MPa. For the material of the component, the tensile yield strength is σy = 200 MPa. According to the maximum shear stress theory, the factor of safety is
a)
1.67
b)
3.6
c)
4
d)
2
 | Pallabi Tiwari answered |
According to principal stress theory, which option represents the correct relation between yield strength in shear (YSS) and the yield strength in tension (YST)?- a)YSS=0.5YST
- b)YSS=0.577YST
- c)YST=0.5YSS
- d)YST=0.577YSS
Correct answer is option 'A'. Can you explain this answer?
According to principal stress theory, which option represents the correct relation between yield strength in shear (YSS) and the yield strength in tension (YST)?
a)
YSS=0.5YST
b)
YSS=0.577YST
c)
YST=0.5YSS
d)
YST=0.577YSS
 | Ashutosh Sharma answered |
Explanation: Shear diagonal is at 45’ and by equation of shear stress theory, the required relation is obtained.
Pitting occurs on _____ of the component. - a)Surface
- b)Inner body
- c)Inside or on surface
Correct answer is option 'A'. Can you explain this answer?
Pitting occurs on _____ of the component.
a)
Surface
b)
Inner body
c)
Inside or on surface
| | Amrita Chauhan answered |
Explanation: Pitting is a process in which small holes occur on a surface of component.
All the theories of failure, will give nearly the same result when- a)when one of the principal stresses at a point is large in comparison to the other
- b)when shear stresses act
- c)when both the principal stresses are numerically equal
- d)For all situations of stress
Correct answer is option 'A'. Can you explain this answer?
All the theories of failure, will give nearly the same result when
a)
when one of the principal stresses at a point is large in comparison to the other
b)
when shear stresses act
c)
when both the principal stresses are numerically equal
d)
For all situations of stress
| | Shraddha Datta answered |
When one of the principal stresses at a point is large in comparison to the other, the situation resembles uniaxial tension test. Therefore all theories give nearly the same results.
In a 2D stress system, the two principal stress are p1 = 180 N/mm2 (tensile) and p2 (compressive). For the materials, yield stress in simple tension and compression is 240 N/mm2 and Poisson’s ratio is 0.25. According to maximum normal strain theory for what value of p2 shall yielding commence?- a)240 N/mm2
- b)180 N/mm2
- c)195 N/mm2
- d)200 N/mm2
Correct answer is option 'C'. Can you explain this answer?
In a 2D stress system, the two principal stress are p1 = 180 N/mm2 (tensile) and p2 (compressive). For the materials, yield stress in simple tension and compression is 240 N/mm2 and Poisson’s ratio is 0.25. According to maximum normal strain theory for what value of p2 shall yielding commence?
a)
240 N/mm2
b)
180 N/mm2
c)
195 N/mm2
d)
200 N/mm2
| | Sankar Dasgupta answered |
Yielding may occur either in tension or compression.
For yielding in tension,
According to normal strain theory,
For yielding in compression,
For yielding in tension,
According to normal strain theory,
For yielding in compression,
Permissible bending moment in a circular shaft under pure bending is M, according to maximum principal stress theory of failure. According to maximum shear theory of failure, the permissible bending moment in the shaft is- a)M/2
- b)M
- c)
- d)2 M
Correct answer is option 'B'. Can you explain this answer?
Permissible bending moment in a circular shaft under pure bending is M, according to maximum principal stress theory of failure. According to maximum shear theory of failure, the permissible bending moment in the shaft is
a)
M/2
b)
M
c)
d)
2 M
 | Hiral Sharma answered |
According to maximum principal stress theory,
σ1 = σy
According to maximum shear stress theory,
Under pure bending,
Therefore, in both the cases, permissible bending moment is M,
σ1 = σy
According to maximum shear stress theory,
Under pure bending,
Therefore, in both the cases, permissible bending moment is M,
Buckling is elastic instability which leads to sudden large lateral deflection.- a)True
- b)False
Correct answer is option 'A'. Can you explain this answer?
Buckling is elastic instability which leads to sudden large lateral deflection.
a)
True
b)
False
 | Athul Das answered |
Buckling is a phenomenon that occurs in structural elements when they are subjected to compressive loads. It is an elastic instability that leads to sudden large lateral deflection. When a structural member, such as a column or a beam, is subjected to a compressive load, it experiences a tendency to buckle or buckle out of its original shape. This is due to the fact that the compressive load causes the member to deform, and if the load is large enough, the member will no longer be able to support the load and it will buckle.
Buckling can occur in various types of structures, including columns, beams, plates, shells, and even thin-walled structures like pipes and tubes. The critical load at which buckling occurs is known as the buckling load or the critical buckling load. It is the maximum load that the structure can support without buckling.
Buckling can be classified into different modes, depending on the geometry and boundary conditions of the structure. Some common buckling modes include:
1. Euler Buckling: This is the most basic form of buckling and occurs when a long, slender column is subjected to an axial compressive load. The buckling mode is characterized by a uniform deflection of the column along its length.
2. Lateral-Torsional Buckling: This type of buckling occurs in beams that are subjected to combined bending and axial compressive loads. It is characterized by a combination of lateral deflection and twisting of the beam.
3. Local Buckling: Local buckling occurs in thin-walled structures, such as plates and shells, where certain regions of the structure undergo buckling while the rest of the structure remains unaffected.
Buckling is a critical design consideration in many engineering applications. It is important to understand the buckling behavior of structural elements in order to ensure their stability and safety. Designers and engineers use various methods and techniques, such as the Euler buckling equation, finite element analysis, and experimental testing, to predict and prevent buckling in structures.
In conclusion, buckling is an elastic instability that occurs when a structural element is subjected to compressive loads. It leads to sudden large lateral deflection and can occur in various types of structures. Understanding and predicting buckling behavior is crucial for the safe and efficient design of structural elements.
Buckling can occur in various types of structures, including columns, beams, plates, shells, and even thin-walled structures like pipes and tubes. The critical load at which buckling occurs is known as the buckling load or the critical buckling load. It is the maximum load that the structure can support without buckling.
Buckling can be classified into different modes, depending on the geometry and boundary conditions of the structure. Some common buckling modes include:
1. Euler Buckling: This is the most basic form of buckling and occurs when a long, slender column is subjected to an axial compressive load. The buckling mode is characterized by a uniform deflection of the column along its length.
2. Lateral-Torsional Buckling: This type of buckling occurs in beams that are subjected to combined bending and axial compressive loads. It is characterized by a combination of lateral deflection and twisting of the beam.
3. Local Buckling: Local buckling occurs in thin-walled structures, such as plates and shells, where certain regions of the structure undergo buckling while the rest of the structure remains unaffected.
Buckling is a critical design consideration in many engineering applications. It is important to understand the buckling behavior of structural elements in order to ensure their stability and safety. Designers and engineers use various methods and techniques, such as the Euler buckling equation, finite element analysis, and experimental testing, to predict and prevent buckling in structures.
In conclusion, buckling is an elastic instability that occurs when a structural element is subjected to compressive loads. It leads to sudden large lateral deflection and can occur in various types of structures. Understanding and predicting buckling behavior is crucial for the safe and efficient design of structural elements.
In a structural member, there are perpendicular tensile stresses of 100 N/mm2 and 50 N/mm2. What is the equivalent stress in simple tension, according to the maximum principal strain theory? (Poisson’s ratio = 0.25)- a)Zero
- b)87.5 N/mm2
- c)50 N/mm2
- d)100 N/mm2
Correct answer is option 'B'. Can you explain this answer?
In a structural member, there are perpendicular tensile stresses of 100 N/mm2 and 50 N/mm2. What is the equivalent stress in simple tension, according to the maximum principal strain theory? (Poisson’s ratio = 0.25)
a)
Zero
b)
87.5 N/mm2
c)
50 N/mm2
d)
100 N/mm2
| | Alok Iyer answered |
Equivalent stress
= σ1 - μσ2
= 100 - 0.25 x 50 = 87.5 N/mm2
= σ1 - μσ2
= 100 - 0.25 x 50 = 87.5 N/mm2
A mechanical component may fail as a result of which of the following- a)elastic deflection
- b)general yielding
- c)fracture
- d)each of the mentioned
Correct answer is option 'D'. Can you explain this answer?
A mechanical component may fail as a result of which of the following
a)
elastic deflection
b)
general yielding
c)
fracture
d)
each of the mentioned
 | Isha Nambiar answered |
Explanation: Failing simply means unable to perform its function satisfactorily.
Type of load affects factor of safety.- a)True
- b)False
Correct answer is option 'A'. Can you explain this answer?
Type of load affects factor of safety.
a)
True
b)
False
 | Ishaan Malik answered |
Explanation: Dynamic load has higher factor of safety as compared to static loading.
If there are residual stresses in the material, than lower factor of safety is used.- a)True
- b)False
Correct answer is option 'B'. Can you explain this answer?
If there are residual stresses in the material, than lower factor of safety is used.
a)
True
b)
False
 | Divya Banerjee answered |
Explanation: Residual stress increases the chance of failure.
A shaft subjected to pure torsion is to be designed which of the following theories gives the largest diameter of shaft?- a)Maximum principal stress
- b)Maximum shear stress theory
- c)Strain energy theory
- d)All the above theories give same diameter
Correct answer is option 'B'. Can you explain this answer?
A shaft subjected to pure torsion is to be designed which of the following theories gives the largest diameter of shaft?
a)
Maximum principal stress
b)
Maximum shear stress theory
c)
Strain energy theory
d)
All the above theories give same diameter
| | Kirti Sharma answered |
It is clear from the relation T/J = (Shear Stress)/ (Radial Distance) that a shaft subjected to pure torsion is to be designed for maximum shear stress theory.
For cast iron components, which of the following strength are considered to be the failure criterion?- a)Ultimate tensile strength
- b)Yield Strength
- c)Endurance limit
- d)None of the mentioned
Correct answer is option 'A'. Can you explain this answer?
For cast iron components, which of the following strength are considered to be the failure criterion?
a)
Ultimate tensile strength
b)
Yield Strength
c)
Endurance limit
d)
None of the mentioned
| | Akshat Mehta answered |
Explanation: Ultimate tensile strength is the highest stress a component can undergo before failingand hence is used as a criterion.
For ductile material the suitable theory of failure is- a)maximum principal stress theory
- b)maximum shear stress theory
- c)both (a) and (b)
- d)None of these
Correct answer is option 'B'. Can you explain this answer?
For ductile material the suitable theory of failure is
a)
maximum principal stress theory
b)
maximum shear stress theory
c)
both (a) and (b)
d)
None of these
| | Partho Jain answered |
For ductile material the most suitable theory is maximum shear stress theory.
Other theories for ductile material, Maximum Strain Energy Theory and Maximum Shear Stress Theory (Most Conservative Theory)
For brittle material the most suitable theory is Maximum Principal Stress Theory.
Other theories for brittle material, Maximum Principal Stress Theory.
Other theories for ductile material, Maximum Strain Energy Theory and Maximum Shear Stress Theory (Most Conservative Theory)
For brittle material the most suitable theory is Maximum Principal Stress Theory.
Other theories for brittle material, Maximum Principal Stress Theory.
The critical buckling load depends upon which of the following parameters?- a)Yield strength
- b)Modulus of elasticity
- c)Radius of gyration
- d)Each of the mentioned
Correct answer is option 'D'. Can you explain this answer?
The critical buckling load depends upon which of the following parameters?
a)
Yield strength
b)
Modulus of elasticity
c)
Radius of gyration
d)
Each of the mentioned
| | Shruti Bose answered |
Explanation: It depends on moment of inertia(which further depends on radius of gyration), elasticity and yield strength.
A certain steel has proportionality limit of 300 N/mm2 in simple tension. It is subjected to principal stress of 120 N/mm2 (tensile), 60 N/mm2 (tensile) and 30 N/mm2 (compressive). The factor of safety according to maximum shear stress theory is- a)1.50
- b)1.75
- c)1.80
- d)2.00
Correct answer is option 'D'. Can you explain this answer?
A certain steel has proportionality limit of 300 N/mm2 in simple tension. It is subjected to principal stress of 120 N/mm2 (tensile), 60 N/mm2 (tensile) and 30 N/mm2 (compressive). The factor of safety according to maximum shear stress theory is
a)
1.50
b)
1.75
c)
1.80
d)
2.00
| | Priyanka Shah answered |
Proportionality limit shear stress
Maximum shear stress
Maximum shear stress
Which of the following theories of failure is most appropriate for a brittle material?- a)Maximum principal strain theory
- b)Maximum principal stress theory
- c)Maximum shear stress theory
- d)Maximum strain energy theory
Correct answer is option 'B'. Can you explain this answer?
Which of the following theories of failure is most appropriate for a brittle material?
a)
Maximum principal strain theory
b)
Maximum principal stress theory
c)
Maximum shear stress theory
d)
Maximum strain energy theory
| | Arshiya Roy answered |
Maximum principal stress theory (Rankine theory) is suitable for brittle materials.
For components made of ductile materials like steel, subjected to static loading which of the following strength is used as a failure of criterion?- a)Yield strength
- b)Ultimate strength
- c)Endurance limit
- d)None of the mentioned
Correct answer is option 'A'. Can you explain this answer?
For components made of ductile materials like steel, subjected to static loading which of the following strength is used as a failure of criterion?
a)
Yield strength
b)
Ultimate strength
c)
Endurance limit
d)
None of the mentioned
 | Anirban Khanna answered |
In elastic material there is considerable plastic deformation at yielding point.
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