1.
In a compression on mild steel
Correct Answer
A. Necking does not occur
Explanation
In a compression on mild steel, necking does not occur. Necking is a phenomenon that typically happens in tension, where the material starts to narrow down at a localized point before it eventually fractures. In compression, the material is subjected to forces that push it together, rather than pull it apart, which prevents the occurrence of necking.
2.
For most brittle materials generally ultimate strength in compression is much larger than the ultimate strength in tension, because
Correct Answer
A. Of flaws such as microscopic cracks or cavities
Explanation
The correct answer is that the ultimate strength in compression is generally much larger than the ultimate strength in tension because of flaws such as microscopic cracks or cavities. Brittle materials are more prone to failure in tension due to the presence of these flaws, which act as stress concentrators and reduce the material's ability to withstand tensile forces. In compression, these flaws are less likely to propagate and cause failure, resulting in a higher ultimate strength.
3.
Which of the following statement is false?
Correct Answer
A. The stress dependent part of the plastic deformation is referred to as creep, and the time dependent part which is also influenced by the temperature as slip
Explanation
The correct answer is "The stress dependent part of the plastic deformation is referred to as creep, and the time dependent part which is also influenced by the temperature as slip." This statement is false because the stress dependent part of plastic deformation is referred to as slip, and the time dependent part influenced by temperature is referred to as creep.
4.
For carbon steel, the endurance limit is approximately
Correct Answer
B. 0.5
Explanation
The endurance limit for carbon steel is approximately 0.5. This means that carbon steel can withstand cyclic loading and stress up to a certain level without experiencing fatigue failure. The endurance limit is the maximum stress that a material can endure for an infinite number of cycles without failure. In the case of carbon steel, this limit is around 0.5, indicating its ability to withstand repeated stress without breaking or wearing out.
5.
The yield stress of a twisted bar as compared to an ordinary mild steel bar is nearly
Correct Answer
A. 50% more
Explanation
The yield stress of a twisted bar is 50% more compared to an ordinary mild steel bar. This means that the twisted bar can withstand 50% more stress before it starts to deform permanently. The twisting process increases the strength and resilience of the bar, making it more resistant to bending or breaking under pressure.
6.
Which of the following is primarily responsible for toughness of steel?
Correct Answer
C. Manganese
Explanation
Manganese is primarily responsible for the toughness of steel. Manganese is added to steel as an alloying element to improve its strength, hardness, and toughness. It forms a solid solution with iron, which helps to enhance the grain structure of the steel, making it more resistant to deformation and fracture. Manganese also helps to reduce the formation of brittle phases in the steel, improving its toughness and impact resistance. Therefore, the presence of manganese in steel plays a crucial role in determining its toughness.
7.
As compared to mild steel, high carbon steel has less
Correct Answer
C. Ductility
Explanation
High carbon steel has higher hardness, ultimate strength and yield strength. But, less ductility
8.
Consider the following statements:
A: An isotropic material is always homogeneous
R: An isotropic material is one in which all the properties are the same in all the directions at every point.
Of these statements
Correct Answer
D. A is false but R is true
Explanation
An isotropic material is one in which all the properties are the same in all directions at every point. This means that the material has the same mechanical, thermal, and electromagnetic properties regardless of the direction in which they are measured. However, this does not necessarily mean that an isotropic material is always homogeneous. Homogeneous materials have the same composition and structure throughout, while isotropic materials only have the same properties in all directions. Therefore, Statement A is false because isotropic materials can be either homogeneous or non-homogeneous. Statement R is true because it accurately defines what an isotropic material is.
9.
Consider the following statements regarding tensile test diagrams for carbon steels with varying carbon contents. As the carbon content increases
1. the ultimate strength of steel decreases
2. the elongation before fracture increases
3. the ductility of the metal decreases
4. the percentage elongation of steel decreases
Of these statements
Correct Answer
A. 3 and 4 are correct
Explanation
As the carbon content increases in carbon steels, the ductility of the metal decreases. This means that the ability of the metal to deform without breaking or fracturing decreases. Additionally, the percentage elongation of the steel also decreases, indicating that the steel becomes less capable of stretching or elongating before it fractures. Therefore, statements 3 and 4 are correct.
10.
Consider the following factors:
1. Large number of loading cycles
2. Large variations in stress
3. Large stress concentrations
Those associated with fatigue failure include
Correct Answer
B. 1 and 3
Explanation
Fatigue failure occurs due to repeated loading cycles and large stress concentrations. Large variations in stress can also contribute to fatigue failure, but it is not a necessary factor. Therefore, the factors associated with fatigue failure are 1 and 3.
11.
A deviator state of stress is characterized by
Correct Answer
A. A change in volume without distortion
Explanation
A deviator state of stress is characterized by a change in volume without distortion. This means that the stress applied to a material causes a change in volume but does not cause any change in the shape or distortion of the material. This can occur, for example, when a material is subjected to hydrostatic pressure, where the stress is uniformly applied in all directions, causing a change in volume but not in shape.
12.
Which of the following methods of design would be suitable for metal structures subjected to stress reversals and impact?
1. Simple working stress design
2. Rigid plastic design
3. Semi-rigid design
4. Elastic rigid design
Select the correct answer using the codes given below:
Correct Answer
B. 1, 3 and 4
Explanation
Simple working stress design is suitable for metal structures subjected to stress reversals and impact as it considers the working stress and the material's yield strength. Semi-rigid design is also suitable as it allows for some flexibility and redistribution of stresses. Elastic rigid design is suitable as it considers the structure's elastic behavior under stress. Rigid plastic design, on the other hand, is not suitable as it assumes that the material behaves plastically and does not consider the structure's elastic behavior. Therefore, the correct answer is 1, 3, and 4.