LECTURE+7+COE-3001-A

Ab m mellogeorgia tech aerospace 14 rs example

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Unformatted text preview: d supports (bolt won’t extend so washers are rigid supports to the sleeve) Case #2 : SLEEVE AND BOLT MADE OF SAME MATERIAL ²་  This then implies ↵ b = ↵ = ↵ and Eb = Es = E s ²་  InspecOon of 2- 19, 2- 20, 2- 21 confirms no forces, no stresses, and that = ↵( )T L (free expansion of the enOre assembly) 1/17/13 M. Mello/Georgia Tech Aerospace 16 MISFITS AND PRESTRAINS IN STATICALLY INDETERMINATE STRUCTRUES ²་ BOLTS 1/17/13 thread pitch (p) (distance traveled = np (2- 22) for n revoluOons of the nut) D Thread Size (common) 6- 32 8- 32 10- 24 1/4"- 20 5/16"- 18 3/8"- 16 7/16"- 14 1/2"- 13 M. Mello/Georgia Tech Aerospace 17 MISFITS AND PRESTRAINS IN STATICALLY INDETERMINATE STRUCTRUES •  TURNBUCKLES = 2np (2- 23) thread pitch (p) right hand thread Thread Size (small list of common sizes) 5/32"- 32 Diameter = 5/32” 3/16"- 24 32 threads per inch 3/16"- 32 7/32"- 24 1/4"- 20 1/4"- 28 5/16"- 18 1/17/13 (screws drawn closer together by this amount for for n revoluOons of the buckle) le| hand thread M. Mello/Georgia Tech Aerospace 18 EXAMPLE 2- 9: COPPER TUBE BETWEEN RIGID END PLATES COMPRESSED BY TURNBUCKLE GIVEN: ²་  ASSEMBLY IS INITIALLY SNUG FIT ²་  TIGHTENING OF THE TURNBUCKLES PRODUCES A PRE- STRESSED CONDITON WHEREBY CABLES ARE IN TENSION AND TUBE IS IN COMPRESSION STATICALLY INDETERMINATE ASSEMBLY WITYH A COPPER TUBE IN COMPRESSION AND TWO STEEL CABLES IN TENSION PROBLEM STATEMENT: ²་  Determine forces (Pc) and (Ps) in the Cu tube and steel cables when turnbuckles Oghtened by n turns ²་  Determine the shortening (δ) of the Copper tube 1/17/13 M. Mello/Georgia Tech Aerospace 19 EXAMPLE 2- 9: (cont.) SOLUTION : ①  Apply some basic mechanical intuiOon before analysis ²་  AS TURNBUCKLE IS ROTATED BY n FULL TURNS, THE STEEL CABLES WOULD MOVE CLOSER TO EACH OTHER BY 2np IF THE CABLES WERE UNCONTSTRAINED. ²་  THE STEEL CABLES ARE CONSTRAINED AND WILL THUS EXPERIENCE TENSION ²་  TENSION WILL ACT TO ELONGATE THE STREEL CABLES (AND THUS PARTIALLY OFFSET THE INTENDED DISPLACEMENT INDUCED BY EACH ROTATION OF THE TURNBUCKLES) ²་  THE COPPER TUBE WILL EXPERIENCE COMPRESSION ²་  TIGHTENING OF THE TURNBUCKLES PRODUCES A...
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