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Showing posts from December, 2010

Closed Coiled helical springs

Springs are energy absorbing units whose function is to store energy and to restore it slowly or rapidly depending on the particular application. A spring may be defined as an elastic member whose primary function is to deflect or distort under the action of applied load; it recovers its original shape when load is released. Helical spring:  They are made of wire coiled into a helical form, the load being applied along the axis of the helix. In these type of springs the major stresses is torsional shear stress due to twisting. They are both used in tension and compression. Derivation of the Formula : I n order to derive a formula which governs the deflection and stress of closed coil helical springs, consider a closed coiled spring subjected to an axial load W. with the fallowing Assumptions: 1. The Bending and shear Force effects may be neglect 2. For the purpose of derivation of formula, the helix angle is considered to be so small that it may be neglected.

Combined effect of bending and torsion

IIf a body is subjected to Shear Force, Bending moment and Twisting moments, then the combined stress in the shaft will be calculated by using of principle of superposition. 1.Shear stress due to direct shear: The average Shear Stress due to direct shear force q = F/A Where F= Shear Force at the section A= Area of the cross section,  But the shear stress distribution in the section will get by using the equaction qd = FQ/Ib Where Q= Ay Where, A = Area between the extreme face of beam and the plane at which the shear stress is q y = Distance of the centroid of area from N.A F = Shear force at the cross-section. I = Moment of Inertia of the beam cross section about N.A. b = Width of the fiber at the plane at which shear stress is q 2.Shear stress due to Torsion: For solid or hollow shafts of uniform circular cross-section and constant wall thickness, the torsion relations are: where: R is the outer radius of the shaft. τ is the maximum

Assignment in Torsion

Assignment in Torsion: S.M.2, Unit-2 1.An aluminum shaft with a constant diameter of 50 mm is loaded by torques applied to gears attached to it as shown in Fig. Using G = 28 GPa, determine the relative angle of twist of gear D relative to gear A. 2.What is the minimum diameter of a solid steel shaft that will not twist through more than 3° in a 6-m length when subjected to a torque of 12 kN·m? What maximum shearing stress is developed? Use modulus of rigidity G = 83 GPa. (T=0.1138 d 4) 3.A solid steel shaft 5 m long is stressed at 80 MPa when twisted through 4°.  Using G = 83 GPa, compute the shaft diameter. What power can be transmitted by the shaft at 20 Hz? (P=5.19MW answer) 4.A steel propeller shaft is to transmit 4.5 MW at 3 Hz without exceeding a shearing stress of 50 MPa or twisting through more than 1° in a length of 26 diameters. Compute the proper diameter if G = 83 GPa. (diameter d = 352 mm answer) 5.Determine the maximum torque that can be applied to a hollow circ