Chapter 5, Problem 97CP

A spring package with two springs and an external force, 200N. The short spring has a loin of 35 mm. Constantly looking for spring for short spring so that total compression is 35 mm (d). Known values: Long spring:                        Short spring:C=3.98 N/mm                    Lo=65mmLo=87.4mmF=c·fTotal compression is same for both spring.                             200 = (3.98(c1) × 35) + (c₂ × 35) 200 = 139.3 + 35c₂ 200 - 139.3 = 35c₂ 60.7 = 35c₂ c₂ = 60.7/35 Short spring (c₂) = 1.73 N/mm According to my study book, the correct answer is 4.82N/mm What is wrong with the calculating?

What is the reason for this composition?

Homework: ANOVA Table for followed design B AB Dr -1 -1 1 (15.18,12) 1 -1 -1 (45.48.51) -1 1 -1 (25,28,19) 1 1 (75.75,81)

20. [Ans. 9; 71.8 mm] A semi-elliptical laminated spring is made of 50 mm wide and 3 mm thick plates. The length between the supports is 650 mm and the width of the band is 60 mm. The spring has two full length leaves and five graduated leaves. If the spring carries a central load of 1600 N, find: 1. Maximum stress in full length and graduated leaves for an initial condition of no stress in the leaves. 2. The maximum stress if the initial stress is provided to cause equal stress when loaded. [Ans. 590 MPa ; 390 MPa ; 450 MPa ; 54 mm] 3. The deflection in parts (1) and (2).

Q6/ A helical square section spring is set inside another, the outer spring having a free length of 35 mm greater than the inner spring. The dimensions of each spring are as follows: Mean diameter (mm) Side of square section (mm) Active turns Outer Inner Spring Spring 120 70 8 7 20 15 Determine the (1) Maximum deflection of the two springs and (2) Equivalent spring rate of the two springs after sufficient load has been applied to deflect the outer spring 60 mm. Use G = 83 GN/m².

Q2/ The bumper springs of a railway carriage are to be made of rectangular section wire. The ratio of the longer side of the wire to its shorter side is 1.5, and the ratio of mean diameter of spring to the longer side of wire is nearly equal to 6. Three such springs are required to bring to rest a carriage weighing 25 kN moving with a velocity of 75 m/min with a maximum deflection of 200 mm. Determine the sides of the rectangular section of the wire and the mean diameter of coils when the shorter side is parallel to the axis of the spring. The allowable shear stress is not to exceed 300 MPa and G = 84 kN/mm². Q6/ A belical

11. A load of 2 kN is dropped axially on a close coiled helical spring, from a height of 250 mm. The spring has 20 effective turns, and it is made of 25 mm diameter wire. The spring index is 8. Find the maximum shear stress induced in the spring and the amount of compression produced. The modulus of rigidity for the material of the spring wire is 84 kN/mm². [Ans. 287 MPa; 290 mm]

What is the reason for this composition?

Homework: ANOVA Table for followed design B AB Dr -1 -1 1 (15.18,12) 1 -1 -1 (45.48.51) -1 1 -1 (25,28,19) 1 1 (75.75,81)