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Screw Jack Optimization

The document describes formulating an optimization problem to minimize the weight of a power screw subjected to an axial load F. The design variables are the pitch p, major diameter d, nut height h, and screw length s. The constraints are that the screw must be self-locking, shear stress must not exceed the material yield strength, bearing stress must not exceed the material yield strength, and the critical buckling load must be less than the applied load F.

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Esmael Adem
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289 views3 pages

Screw Jack Optimization

The document describes formulating an optimization problem to minimize the weight of a power screw subjected to an axial load F. The design variables are the pitch p, major diameter d, nut height h, and screw length s. The constraints are that the screw must be self-locking, shear stress must not exceed the material yield strength, bearing stress must not exceed the material yield strength, and the critical buckling load must be less than the applied load F.

Uploaded by

Esmael Adem
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as DOCX, PDF, TXT or read online on Scribd
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Formulate the problem of minimum weight design of a power screw subjected to an axial load, F, using the pitch (p),

major
diameter (d), nut height(h), and screw length (s) as design variables. Consider the following constraints in the
formulation:
1. The screw should be self-locking.
2. The shear stress in the screw should not exceed the yield strength of the material in shear. Assume the shear strength in shear
(according to distortion energy theory), to be 0.577σy, where σy is the yield strength of the material.
3. The bearing stress in the threads should not exceed the yield strength of the material,σy.
4. The critical buckling load of the screw should be less than the applied load, F.

Formulate the optimization problem of minimum weight design of a power screw subjected to an axial load, F, using the pitch
(p), major diameter (d), nut height(h), and screw length (s) as design variables. Consider the following constraints in the
formulation:
1. The screw should be self-locking.
2. The shear stress in the screw should not exceed the yield strength of the material in shear. Assume the shear strength in shear
(according to distortion energy theory), to be 0.577σy, where σy is the yield strength of the material.
3. The bearing stress in the threads should not exceed the yield strength of the material,σy.
4. The critical buckling load of the screw should be less than the applied load, F.

4.3.7 Example 14: Design of Screw Jack


The screw jack as shown in Fig. 4.8 is to be designed such that the weight of the
screw is minimum [36]. The constraints imposed on the design are: design of
screw jack should be self locking; torsional shear stress induced in the screw

should not increase the torsional shear strength of screw material; shear stress in
the threads of screw and nut should not increase the torsional shear strength of
screw and nut material, respectively; bearing pressure should not exceed the
bearing strength and the buckling strength of the screw should be more than
the load lifted by the screw jack. Design variables are the outer diameter of the
screw (d), height of nut (h) and length of screw (l). Design vector can be defined

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