Design a helical spring which will fit inside a tube of inside diameter of 25 mm and provide a load of 400 n at a spring height of 65 mm and 240 n at a spring height of 72 mm. your answer should include specifications of (a) the actual spring constant obtained; (b) the required wire diameter, (c) the spring coil diameter; (d) the number of active coils, and (e) the free length of the spring. your design must take into account the following design assumptions: • the ends are squared and ground • the spring will be manufactured from astm a228 cold-drawn steel a clash allowance of 10% should be used • modulus of rigidity of steel is g= 79 gpa the spring is manufactured without presetting.

A3-mm-thick panel of aluminum alloy (k 177 w/m-k, c 875 j/kg-k and ? = 2770 kg/m) is finished on both sides with an epoxy coating that must be cured at or above t,-150°c for at least 5 min. the production line for the curing operation involves two steps: (1) heating in a large oven with air at ts,0-175°c and a convection coefficient of h, 40 w/m2. k, and (2) cooling in a large chamber with air at 25°c and a con- vection coefficient of he 10 w/m2.k. the heating portion of the process is conducted over a time interval te which exceeds the ime required to reach 150°c by 5 min (h = r + 300 s). the coating has an emissivity of ? = 0.8, and the temperatures of the oven and chamber walls are 175 and 25°c, respectively. if the panel is placed in the oven at an initial temperature of 25°c and removed from the chamber at a safe-to-touch tempera ture of 37°c, what is the total elapsed time for the two-step curing operation?