MIT2_72s09_lec10

MIT2_72s09_lec10 - MIT OpenCourseWare http://ocw.mit.edu...

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Unformatted text preview: MIT OpenCourseWare http://ocw.mit.edu 2.72 Elements of Mechanical Design Spring 2009 For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms . 2.72 Elements of Mechanical Design Lecture 10: Bolted joints 2 Martin Culpepper, All rights reserved olted joint +s and s ood: Low cost? Able to be disassembled Strong Compatible with almost any material ad: Takes up a lot of space Micro-slip/hysteresis/damping problems Difficult to model and control Can require long fabrication and assembly time 3 Martin Culpepper, All rights reserved olted joints: Their purpose olted joints = connectors, impact many parts: Stiffness Vibration Damping Stability Load capacity olted joints are semi-permanent! Max benefit obtained when it is highly preloaded, i.e. near the yield point Threads can plastically deform/work harden Some elements of bolted joints are not reusable olted joints are used to create assemblies that resist: (i) Tensile loads (ii) Moments (iii) Shear loads olts are NOT meant to resist (i) (iii) Components 5 Martin Culpepper, All rights reserved natomy of a bolted joint Grip t Tensile stress area d Major diameter area t Threaded length in grip d Unthreaded length in grip Major diameter (unthreaded) l t w t w H Bolt L T L t 1 t 2 H Nut l t l d A t A d 6 Martin Culpepper, All rights reserved Things to consider with the clamped member: 1. Stone or lap the surface (increase stiffness) 2. Remove burs (increase joint stiffness) 3. Be sure flange surfaces are flat so bolt does not bend oint components: Clamped member 7 Martin Culpepper, All rights reserved Rolled Threads Cut Threads Head Shank Steel is most common olted joint components: Bolt NEVER in shear or bending Stress concentrations at the root of the teeth Fatigue crack propagation!...
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This note was uploaded on 02/24/2012 for the course MECHANICAL 2.72 taught by Professor Martinculpepper during the Spring '09 term at MIT.

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MIT2_72s09_lec10 - MIT OpenCourseWare http://ocw.mit.edu...

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