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What are the steps involved in general design procedure? Explain.

1. Recognition of need. First of all, make a complete statement of the problem, indicating the need, aim or purpose for which the machine is to be designed. 2. Synthesis (Mechanisms). Select the possible mechanism or group of mechanisms which will give the desired motion. 3. Analysis of forces. Find the forces acting on each member of the machine and the energy transmitted by each member. 4. Material selection. Select the material best suited for each member of the machine. 5. Design of elements (Size and Stresses).

State any four disadvantages of rolling bearings as compared to journal bearings

Disadvantages of rolling bearing as compared to Journal Bearing: 1) Initial cost is very high 2) Noisy in normal operation. 3) Shock capacity is less. 4) Finite life due to failure by fatigue. 5) Dirt & metal chips can enter the bearing & may lead it to failure. 6) Occupies greater diametral space compared to journal bearing.

Square thread

Square threads

Square threads are the most commonly used thread form for the power screws. Following table gives you various thread forms and comparisons.




Screw Form

Characteristic

Application

State any four advantages and disadvantages of welded joints over riveted joints.

1. The welded structures are usually lighter than riveted structures. This is due to the reason, that in welding, gussets or other connecting components are not used. 2. The welded joints provide maximum efficiency (may be 100%) which is not possible in case of riveted joints. 3. Alterations and additions can be easily made in the existing structures. 4. As the welded structure is smooth in appearance, therefore it looks pleasing. 5. In welded connections, the tension members are not weakened as in the case of riveted joints. 6. A welded joint has a great strength.

State any four applications of spring.

1) To cushion, absorb or control energy to external load : Car springs, Railway buffers 2) To store Energy : Watches Toys 3) To Measure forces : Spring Balances, Gauges ,Engines 4) To provide clamping force in Jigs & fixtures. 5) To apply forces as in brakes, clutches & spring loaded valve.

Define Endurance limit and draw typical S-N curve for steel.

Endurance Limit: It is defined as maximum value of the completely reversed bending stress which a polished standard specimen can withstand without failure, for infinite number of cycles (usually 107 cycles).It is known as endurance or fatigue limit (ϭe).

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