Stub Acme Screw Analysis

External Parameters

≔ID 16 Cylinder inner diameter≔CP 3000 Cylinder pressure

≔F =⋅⋅⎛⎜⎝――ID

2

⎞⎟⎠

2

CP 301.593 Maximum Cylinder Force

≔d 18.43 Cylinder diameter at thread root

Thread Parameters

≔tpi 2 Threads per inch≔h 0.16 Total thread height≔tc 0.2112 Thread crest thickness≔b +⎛⎝tc⎞⎠ ⋅⋅2 h tan ((14.5 )) Thread root thickness

≔n 1 Threads analyzed≔l ⋅⋅n d Total thread length≔P =⋅0.38 F 114.605 Load analyzed

*Shigley's (pg. 419)

Bending Stress

≔M =⋅P⎛⎜⎝―h

2

⎞⎟⎠

9.168 ⋅ Moment at thread root

≔c ―b

2Height from neutral axis

≔I ――⋅l b

3

12Second moment of area

≔σb =――⋅M c

I21.99

Factor of Safety

≔SYFlange 54500

Scot 52 / 1026≔SYCylinder 60000

A-36 Steel

≔FOSb =――――SYFlange

σb

2.478

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Transeverse Shear Stress

≔V =P 114.605 Shear Force

≔A ⋅l b Area of thread root crossection

≔τtsmax =――3 V

2 A20.201

≔SSYFlange ⋅0.577 SYFlange

*Shigley's (pg. 225)

≔FOSts =――――SSYFlange

τtsmax

1.557

Axial Shear Stress (Stripping)

Since the Flange is the weaker material, shearing will occur at the root of the Flange thread (Line A).

Cylinder Flange≔he −h 0.010 Engaged height

≔be +⎛⎝tc⎞⎠ ⋅⋅2 he tan ((14.5 ))

Thread thickness at base of engagement.

≔AS ⋅be l Shear area

≔τas =――P

AS

13.708

≔FOSas =――――SSYFlange

τas

2.294

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References

Shigley's Mechanical Engineering Design 9th Edition (Budynas, Nisbett)

Mechanics of Materials 5th Edition (Beer, Johnston, DeWolf, Mazurek)

Static Screw Stresses PDF (Cagatay Basdogan, Ph. D.) (Koc University)

Screw Thread Design PDF (Fastenal Engineering & Design Support)

Machinery's Handbook 28th Edition (Oberg, Jones, Horton, Ryffel)

Created with PTC Mathcad Express. See www.mathcad.com for more information.