Q6 [15] A compressive spring is used to support a vibrating bed. The stiffness of the spring is 3 kN/m. The static force on the spring due to gravitational effect is 30 N. During operation, the spring will experience dynamic loading. For enhanced stability, each compressive spring is supported by a steel rod of 6 mm in diameter. You are retained to design the compressive spring with the help of the following preliminary decisions: - Material: music wire. - - - Wire diameter: 2.0 mm Number of active coil 6 Both ends squared and ground Peened to improve fatigue strength Factor of safety 1.2. Determine -the coil mean diameter D -the spring index C - whether there is interference between the spring and the supporting rod the maximum amplitude of fluctuating force so that the spring will have infinite life in accordance with the Zimmerli-Goodman fatigue failure criterion. Table 10-5 Mechanical Properties of Some Spring Wires Elastic Limit, Percent of Sut Diameter d, Material Tension Torsion in mm Mpsi GPa Mpsi GPa Music wire A228 65-75 45-60 3 28.0 193 11.6 80.0