Computer Aided Engineering Design

INTRODUCTION 19

Table 1.2 Coefficients and Exponents for Eq. 1.16

ASTM# Material Range of d Exponentb Coefficient A Correlation
(mm) (MPa) Factor

A227 Cold drawn 0.5-16 – 0.1822 1753.3 0.998
A228 Music wire 0.3-6 – 0.1625 2153.5 0.9997
A229 Oil tempered 0.5-16 – 0.1833 1831.2 0.999

Step 8: The four types of end conditions for the coil, as shown in Figure 1.5, are

Plain-Ends ⇒ Na = Nt (total number of coils)

Plain-Ground-ends ⇒ Na = Nt – 1

Figure 1.5 End conditions for a helical compression spring

A229

A227

A228

(A) Plain end (B) Plain and ground end (C) Square end

SI (mm)

0.10

0.12

0.16

0.20

0.25

0.30

0.35

0.40

0.45

0.50

0.55

0.60

0.65

0.70

0.80

0.90

1.00

1.10

1.20

1.40

1.60

1.80

2.00

2.20

2.50

2.80

3.00

3.50

4.00

4.50

5.00

5.50

6.00

6.50

7.00

8.00

9.00

10.0

11.0

12.0

13.0

14.0

15.0

16.0

Table 1.1(b) Preferred wire diameters