Be-e Mechanical System Design MCQ Test April-20

Autofrettage is a process of pre-stressing the cylinder to develop residual compressive stress at the inner surface. This is done by subjecting the cylinder to high internal pressure, causing the material to yield and expand. Once the pressure is released, the material contracts, resulting in compressive stresses at the inner surface. This process helps to increase the fatigue life and strength of the cylinder, making it more resistant to failure under high pressure or cyclic loading conditions.

In thin cylinders, the longitudinal stress is half of the circumferential stress. This is because in a thin cylinder, the material experiences more deformation in the circumferential direction compared to the longitudinal direction. As a result, the stress in the circumferential direction is greater than the stress in the longitudinal direction. Therefore, the longitudinal stress is equal to half of the circumferential stress.

Adequate design refers to a design that meets the main functional requirements. This means that the design is able to perform the intended functions effectively and efficiently. The other options, such as cost, concept, and dimensional, may also be important considerations in design, but the most crucial aspect is ensuring that the design functions properly.

The condition for the connecting rod to be equally strong in the plane of motion (XX) and a plane perpendicular to the plane of motion (YY) is that the moment of inertia about the XX axis (Ixx) should be four times the moment of inertia about the YY axis (Iyy). This means that the connecting rod is stronger in resisting rotational motion about the XX axis compared to the YY axis.

Energy Storing Capacity is a functional requirement parameter because it specifies the ability of a system or device to store and hold energy. This parameter is important in various industries, such as renewable energy systems, batteries, and power storage devices. It determines the amount of energy that can be stored and used when needed, which is essential for the proper functioning and efficiency of these systems. Therefore, Energy Storing Capacity is a valid functional requirement parameter.

The ratio of length of stroke to cylinder bore (l/D) is usually 1.5. This means that the length of the stroke is 1.5 times the diameter of the cylinder bore. This ratio is commonly used in the design and construction of internal combustion engines, as it helps to optimize the engine's performance and efficiency. A longer stroke can increase the engine's torque output, while a larger bore diameter can improve the engine's power output. Therefore, a ratio of 1.5 is often considered a good balance between torque and power for most engine applications.

The correct answer is drop forging process. Drop forging is a manufacturing process in which a metal billet is heated and then shaped into the desired form by applying compressive forces with the help of a hammer or a press. This process is commonly used for manufacturing automotive crankshafts as it helps in producing strong and durable components with excellent mechanical properties. The drop forging process ensures that the crankshaft has the necessary strength and resistance to withstand the high stresses and loads experienced during engine operation.

There can be several adequate designs for a component, meaning that there are multiple options that meet the minimum requirements. However, there is only one optimum design, which is the best possible design that maximizes performance, efficiency, or any other desired criteria. While there may be multiple acceptable designs, there is only one design that is considered the most optimal.

The bolts for the cap of the big end of the connecting rod are subjected to only inertia force. This means that the force acting on the bolts is due to the acceleration and deceleration of the connecting rod as it moves back and forth. The gas force refers to the pressure exerted by the combustion gases in the cylinder, but this force is not directly acting on the bolts. Side thrust refers to the force exerted on the bolts in a sideways direction, but again, this force is not present in this scenario. Therefore, only the inertia force is relevant in this case.

A cylinder is considered as a thin cylinder when the ratio of the inner diameter to the wall thickness is more than 15. This means that the inner diameter of the cylinder is significantly larger than the thickness of its walls. When this ratio is greater than 15, the cylinder can be considered thin because it has a relatively small wall thickness compared to its size.

The correct answer is hemispherical head. The end-closure for a tall vertical pressure vessel is typically a hemispherical head because it provides the most efficient distribution of stress and pressure. The hemispherical shape allows for uniform distribution of pressure and minimizes the stress concentration at the junction between the head and the cylindrical shell of the vessel. This design also provides good structural integrity and is commonly used in pressure vessels to ensure safety and reliability.

The torispherical head is the correct end-closure for tankers of milk, petrol, or diesel. This type of head is a combination of a toroidal shape and a spherical shape, which allows for a more efficient distribution of stress and pressure. The torispherical head provides a smooth transition between the cylindrical section of the tanker and the closure, reducing the likelihood of stress concentration and potential failure. This design is commonly used in pressure vessels and tanks for its superior strength and structural integrity.

The correct answer is "any one of the above." This means that Class 3 pressure vessels are to be designed according to the 'Code for unfired vessel IS-2825' when any of the following conditions are met: the operating pressure is less than 17.5 kgf/cm2, the operating temperature is more than 00C and less than 2500C, or the thickness of the shell is less than 16 mm.

The correct answer is "Limited" because the question states that the parameters are specified within a range or limit. This means that there are specific values or conditions that the parameters must fall within, rather than being completely unrestricted or unspecified.

The correct answer is "Cost Per Kg." This option refers to the cost of the material per kilogram. It is a material parameter that is commonly used to compare the cost-effectiveness of different materials. By considering the cost per kilogram, manufacturers can make informed decisions about which material to use in their products, taking into account both performance and cost considerations.

The correct answer is "Desirable effects Parameters" because optimization aims to maximize the desired effects or outcomes of a system or process. By focusing on the desirable effects parameters, one can identify and implement strategies to enhance or maximize the positive aspects of the system while minimizing or mitigating any negative or undesirable effects. This approach helps to improve performance, efficiency, and overall effectiveness of the system or process being optimized.

An optimum design refers to the best or most suitable design among all the feasible options. In this context, the term "conceptual" implies that the design is based on conceptual ideas or principles rather than being purely practical or functional. It suggests that the design is innovative, creative, and focuses on the overall concept or vision rather than just meeting basic requirements. Therefore, "conceptual" is the most appropriate choice for describing an optimum design.

Option 2, "maximum shear stress =0.5(yield strength)/Factor of Safety," is the best primary design equation for designing a shaft for minimum weight. This equation considers the maximum shear stress that the shaft can withstand, which is determined by dividing the yield strength of the material by a factor of safety. By using this equation, engineers can optimize the design of the shaft to minimize its weight while ensuring it can handle the maximum expected stress. Option 1 and "None of these" are not specific design equations, and therefore, not suitable for designing a shaft for minimum weight.

Option 1 is the best secondary design equation to design the shaft to optimize cost because it is not provided in the question what Option 1 is, but it is implied that it is the most suitable option for optimizing cost. The other options are not mentioned, so it is not clear if they are relevant to cost optimization or not. Therefore, Option 1 is the correct answer.

The term "optimum design" refers to the most efficient and effective design solution for a particular problem or situation. In this context, "inclusive" means that the optimum design includes all necessary components or factors, leaving nothing out. This suggests that an optimum design should be comprehensive and consider all relevant aspects, ensuring that it is well-rounded and complete. Therefore, the answer "inclusive" is the most suitable choice as it aligns with the idea of an optimum design being thorough and all-encompassing.

A cylinder is considered as a thick cylinder when the ratio of inner diameter to the wall thickness is less than 15. This means that the inner diameter of the cylinder is significantly larger than the thickness of its walls. A ratio less than 15 indicates that the walls of the cylinder are relatively thick compared to the size of the inner diameter.

The design of the piston head is based on strength and heat transfer considerations. This means that the piston head needs to be strong enough to withstand the forces and pressures exerted on it during operation. Additionally, it needs to efficiently transfer heat away from the combustion chamber to prevent overheating. Both of these factors are important in ensuring the proper functioning and longevity of the piston head.

The correct answer is double-welded butt joint with full penetration. This is because a double-welded butt joint with full penetration provides the highest level of strength and integrity compared to the other options. The full penetration ensures that the weld joint is completely fused, resulting in a stronger bond between the materials. Additionally, the double weld adds an extra layer of reinforcement, further increasing the joint efficiency.

The design of the piston head is based on strength and heat transfer considerations. This means that the design takes into account the need for the piston head to be strong enough to withstand the forces and pressures it will experience during operation, while also allowing for efficient heat transfer between the piston head and the surrounding components. This ensures that the piston head can effectively perform its function without compromising its structural integrity or causing excessive heat buildup.

The thickness of a cylinder is calculated based on the circumferential hoop stress. This is because the hoop stress is the stress that acts circumferentially around the cylinder, and it is the primary stress that determines the required thickness to prevent failure or deformation. The other options, such as radial stress, residual stress, and whipping stress, may also play a role in the overall stress analysis of a cylinder, but they are not specifically used to calculate the thickness of the cylinder.

In thick cylinders, the axial stress across the thickness of the cylinder remains uniform throughout. This means that the stress is the same at every point along the thickness of the cylinder, regardless of the distance from the inner or outer surface. This is because the thickness of the cylinder is significant enough to distribute the stress evenly, resulting in a uniform stress distribution.

When designing pressure vessels according to the Code for unfired vessel IS-2825, the design pressure is typically taken as 1.05 times the maximum operating pressure. This is done to provide a safety factor and ensure that the vessel can withstand any potential fluctuations or variations in the operating pressure. Taking a design pressure slightly higher than the maximum operating pressure helps to account for any uncertainties or unforeseen circumstances that may arise during the vessel's operation.

The function of the piston skirt is to provide a bearing surface for side thrust. The skirt helps to maintain proper alignment of the piston within the cylinder and prevents it from rocking or tilting during operation. It also helps to distribute the side forces generated by the reciprocating motion of the piston, reducing wear and friction on the cylinder walls. By providing a smooth and stable surface, the piston skirt ensures efficient and reliable performance of the engine.

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The connecting rod is made of medium carbon steel because it needs to be strong and durable to withstand the high forces and stresses that occur during engine operation. Medium carbon steel has a good balance of strength and toughness, making it suitable for this application. Aluminium is not typically used for connecting rods as it is not as strong as steel. Cast iron is too brittle for this application, and babbits are used as a lining material for bearings, not for the connecting rod itself.