Mechanical Engineering Answers

Two concentric spheres of diameters d1 = 0.8 m and d2 = 1.2 m, have surface temperatures T1 = 450 K and T2 = 300 K 

respectively. If the surface emissivities are 0.5 and 0.05 respectively, determine the net radiation heat exchange between 

the two spheres.

If the intensity of radiation emitted by a surface covered with lamp black (α = 0.96) in the normal direction is 1.85 x 103

W/m2

Sr. Calculate the temperature of the surface if it follows Lambert’s Cosine Law

An air refrigerator works between the pressure limit of 1 bar and 5 bar

A pump has an overall efficiency of 88% and volumetric efficiency of 92% while consuming 8HP. Determine the mechanical efficiency and the horsepower loss due to friction.

3. A 150X 100 X 15 mm mild steel angle is to be welded to a mild steel plate by fillet

weld along the edge of 150mm leg. A tensile load of 200kN acts through the gravity

axis of the angle. Determine weld lengths if the centre of gravity is at distance of

50mm from end B as shown in the figure below. The allowable shear stress in weld

material is 73N/mm2�

A plate 100 mm wide, 200 mm long, and 12 mm thick is loaded in tension in the direction of the length. The plate contains an edge crack with the crack length of 16 mm. The material is steel with KIC = 80 MPa√m, and Sy = 950 MPa. Determine the maximum possibleload that can be applied before the plate (a) yields, and (b) has uncontrollable crack growth.

A thick-walled cylinder of 450 mm outside diameter and 340 mm inside diameter, made of BS 535 A99 steel alloy, is subjected to an internal pressure of P. The maximum depth of radial crack in longitudinal direction on the outer surface of this cylinder is 22 mm. If the factor of safety against fracture failure of this cylinder is 3.1, what maximum safe internal pressure (P) can be applied to the cylinder?

The plate with a circular hole in the following figure is subjected to a tensile stress of σ0 at the boundaries AB and CD. The plate is made of steel 4340 material with Sy = 1515 MPa, if b = 200 mm, a = 50 mm, and the plate thickness, t = 20 mm, determine the maximum value of σ0 that can be safety applied considering a safety factor of 1.5. 

Perform another analysis to calculate the maximum value of σ0 assuming two edge cracks of 2 mm each at points E and F of the hole, in directions perpendicular to the loading direction. What is the percentage of reduction of the allowable stress (σ0) if cracks are present?

A cylinder contains pressurized gas at 500 MPa and has the outer and inner diameters of 600 mm and 450 mm respectively. Determine the maximum permissible radial crack dimension on the outer surface of the cylinder in order to avoid further propagation of crack based on safety factor of 2.0. The cylinder material is BS 816 M40 of yield strength 1515 MPa.

A rectangular plate of length 2h = 20 mm, width 2b = 50 mm and thickness 5 mm, containing a central crack of length 2a, is subjected to a uniform tensile stress of 40 MPa in the direction of its length as shown in the figure. Determine the maximum permissible crack dimension to avoid its further propagation choosing a factor of safety of 1.6. The plate material is BS 816M40.