VIDYA VIKAS INSTITUTE OF ENGINEERING & TECHNOLOGY, MYSURU-570028 DEPARTMENT OF MECHANICAL ENGINEERING Question bank on Leaf Springs (Module 2-part 4) DESIGN OF MACHINE ELEMENTS-II 17ME64 6th semester VTU CBCS scheme 1. A truck spring has 10 leaves and is supported at a span of 100 cm with a central band of 80 mm width. A load of 6 kN is applied at the center of spring whose permissible stress is 300 N/mm2. The spring has a ratio of total depth to width of about 2.5. Determine the width, thickness, deflection of leaves. 2. A semi-elliptical spring has an overall length of 1.1 m and sustains a load of 70 kN at its centre. The spring has 3 extra full length leaves and 13 graduated leaves with central band of 100 mm width. All the leaves are to be stressed equally without exceeding 420 N/mm2 when fully loaded. The total depth of spring is twice the width. If E is 2.1x105 N/mm2 determine: Thickness and width of leaves. Nip to be provided for pre-stressing. The load exerted on clipping bolts after spring is assembled. 3. A locomotive spring has an overall length of 1.5m and sustains a load of 85 kN at its centre. The spring has 3 full length leaves and 15 graduated leaves with a central band of 120 mm width. All the leaves are to be stressed to 300 N/mm2 when fully loaded. The ratio of spring depth to width is3. Take E= 2.1x105 N/mm2. Determine: Thickness and width of leaves. The initial space to be provided between the full length leaves and graduated leaves before band load is applied. The load exerted on the band after the spring is assembled. 4. A locomotive spring has an overall length of 1m and is to carry a central load of 12 kN and is to deflect not more than 75 mm. The spring has 10 leaves two of which are full length leaves and have been pre stressed so that all leaves have the same stress after the full load is applied. The maximum stress in the leaves is not to exceed 380 MN/m2. Determine: (i) Thickness and width of leaves. (ii) The initial space to be provided between the full length leaves and graduated leaves before band load is applied. (iii)The load exerted on the band after the spring is assembled . 5. The leaf spring supports a load of 40kN on a span of 120 cm. the maximum width of the leaf is 16 cm. If the safe permissible tensile stress and the young’s modulus for the spring are 500 and 2.1x105 N/mm2 respectively, design the leaf spring and evaluate the maximum deflection. 6. A load of 25 kN is supported by a leaf spring consisting of 10 graduated leaves. The span is 0.8 metres and the material is chrome vanadium steel having a permissible stress of 600 MPa. Young’s modulus is 2.1x105 MPa. Design the spring if the deflection is limited to 80 mm. 1 of 2 N S SRIRAM VIDYA VIKAS INSTITUTE OF ENGINEERING & TECHNOLOGY, MYSURU-570028 DEPARTMENT OF MECHANICAL ENGINEERING Question bank on Leaf Springs (Module 2-part 4) DESIGN OF MACHINE ELEMENTS-II 17ME64 6th semester VTU CBCS scheme 7. A semi elliptical automobile leaf spring of 1.2 m span carries a load of 700 N. It has 10 leaves of which two are running to full length. The width of each leaf is 50 mm. Determine suitable thicknesses of the leaves to keep deflection under load to 70 mm. Also determine the stress in the spring. 8. A plate spring, simply supported at the ends has a span of 800 mm. it is of varying width and constant thickness. For a maximum deflection of 25 mm for a central load of 3 kN, determine the required thickness and width. E= 2.1x105 N/mm2 and permissible stress is 380 MN/m2. 9. A 100 mm outside diameter coil spring having 10 active coils of 12.5 mm dia wire is in contact with a 750 mm long cantilever spring having 6 graduated leaves of 100 width and 6.5 mm thickness as shown in fig. 1 below. Determine what force if gradually applied to the top of the coil spring causes the cantilever spring to deflect by 25 mm? What will be the maximum shear stress in the coil spring? 10. A semi elliptical leaf spring has an effective length of 1.5 meters. The spring seat, midway between shackles carries a helical spring upon which is imposed an impact equivalent of 1000 Nm of energy. The laminated spring is composed of 10 graduated leaves and two extra full-length leaves, each 6.5 mm thick and 50 mm wide. The coil spring is composed of 6 effective turns of 50 mm wire. The mean coil diameter is100 mm. Calculate the maximum stress induced in each spring. Refer fig. 2 11. A cantilever beam of uniform strength made of C 50 steel and 10 mm thick, is to absorb an impact of 200 N-m with a deflection of 50 m. Determine the length of the spring and maximum width. Use a factor of safety as 3. If this beam is to be made into a leaf spring, what will be the breadth and number of leaves? Design a leaf spring for a truck to the following specifications: Maximum load on the springs 140 kN Number of springs 4 Material for spring Chromium Vanadium steel Permissible tensile stress 600 N/mm2 Maximum number of leaves 10 Span of spring 1000 mm Permissible deflection 80 mm Young’s modulus of spring 2x105 N/mm2. 2 of 2 N S SRIRAM
