Question

1) [60 pts] Helical Compression Spring A helical compression spring is wound using music wire of diameter, d, 2.64 mm. The spring has an outside diameter, OD, of 33 mm with plain ground ends and 14 coils. a) Estimate the spring rate. The spring rate is N/mm. b) What is the force needed to compress this spring to closure assuming that the spring will reach its shear strength at its solid length? The force needed to compress this spring to closure is N. c) What should be the free length to ensure that the torsional stress does not exceed the yield strength when the spring is compressed solid? What is the critical free length? Is there a possibility that the spring might buckle in service? The free length should be mm. The critical free length should be Buckling is to occur. mm.

Answer 1

. D 210 30.36 2.64 Solution Given: The diameter of the music wire (d)= 2.64mm • The outside diometer of the spring (Do) – 33 mm Plain ground ends • Total number of colls 1) = 14 • Mean spring coil diameter (0) = Do-d (0) = 33-2.64 (D) – 30.36 mer • spring index () = { c = 11.5} Torsional stiffness (G) far music wire with diameter 2.64mm is 81 Gala, From the table for Dimensional characteriytics o compression spring Number of active coils (Na) = Nt-1 (NQ) = 14-1 (Na) =13 Csolid Length (Ls)= dNf B = 2.6UX LY = 36.96 mmy To compensate curvature effect a factor is multiplied, GC+2 4 (11.5)+2 GC-3 441.5)-3 SKB = 1.116284 we need allimate Now for calculating stresses tensile of the and yield i trength strength spriting material - الم

For that we have , Sut where, A= A am 2211 MPa, mming for music 0.145 wire 2.64 mm d Sut 1920.685 MPa 2211 (2.6450otus yield strength in shear based on distorsion energy theory . 0.45 (Sut) 0.45X (1920.685) Įssy = 864.3 M8a} Ssy Ang(a)- Spring jante () :- dG & 3 Na (2.60 (81X10) k 8(11,513 X 13 R 1.3519 N/mm spring to And (b) : The force needed to compress this closure * (2.643 (864. 3) Fs & Ko D 8 X (1.44628JX (30,36) Td ssy Es = 184.27 N FS = Ans(C): - Detlection due to Load (98) :- ५४ 184,27 R 1.3519 {yo = 136.388 mm} • Free Length (Lo). ys + La 136.308 + 36.96 - ما | = 173. 268 mm

Thank you.