plugin-ajohnh-ME250F10-11-springsshaftscouplings

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11: Springs, shafts, and couplings October 14, 2010 esign + Manufacturing I Design + Manufacturing I University of Michigan ME250 | Fall 2010 John Hart [email protected] edu [email protected] http://www.umich.edu/~ajohnh ©2010 A.J. Hart 1
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Announcements HW2 returned (see stats on blog) Signup for DR (see guidelines) Extra lab time for sketch modeling (see Mark’s email) You may store your sketch model in the lab, but make sure it’s labeled Control system specs by next Thursday ules Rules Flipper is gravity loaded you may calculate the weight ( force, torque) Starting zone within slot see document ©2010 A.J. Hart 2
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Where are the springs? ©2010 A.J. Hart 3
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Today’s agenda Springs Basics Compression/extension rsion Torsion Constant force Leaf (cantilever) Shafts and couplings ©2010 A.J. Hart 4
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References Slocum excerpt on shafts and couplings (ctools) Shigley chapter 10, “Mechanical Springs” (ctools) Engineer’s edge feature on springs http://www.engineersedge.com/spring_menu.shtml ppliers Suppliers http://www.mcmaster.com http://www.sdp si.com http://www.wmberg.com/ http://www.smallparts.com ANY spring manufacturers MANY spring manufacturers ©2010 A.J. Hart 5
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Spring an elastic object used to store mechanical energy compression Three modes of elastic energy storage Tension/compression d i tension Bending Torsion extension What modes are used in the springs own here? torsion constant force shown here? ©2010 A.J. Hart 6 http://en.wikipedia.org/wiki/Spring_(device)
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Springs basic design parameters Free length : overall length in unloaded position Extended length : length at full rated extension (compression) Spring rate : Force per unit deflection (i.e., stiffness) Maximum load : load at full extension Hooke’s law Force [N] = stiffness [N/m] × deflection [m] : F = kx Energy [J] = 0.5 × stiffness × deflection 2 : E = 0.5kx 2 ©2010 A.J. Hart 7 Terminology: http://www.engineersedge.com/spring_terms.htm
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Compression spring Helical geometry that offers a resistance to compressive force applied axially t t i t Constant spring rate over middle 60% of range ©2010 A.J. Hart 8 http://www.ammtechspring.com/compression.html
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Compression springs – fundamentals Stiffness N D G d k 3 4 8 G : shear modulus N : number of active coils Spring index, typically 6 12 d D C ©2010 A.J. Hart 9
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Compression springs ends nd type affects number of active coils (see Shigley) End type affects number of active coils (see Shigley) ©2010 A.J. Hart 10 http://www.ammtechspring.com/compression.html
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This note was uploaded on 01/26/2011 for the course ME 250 taught by Professor Dutta during the Fall '07 term at University of Michigan.