1 / 18

ENGI 1313 Mechanics I

ENGI 1313 Mechanics I . Lecture 39: Analysis of Friction with Wedges. Lecture 39 Objective. to illustrate by example equilibrium analysis of wedges with dry friction forces. Wedge. Simple Machine Inclined plane

sunila
Download Presentation

ENGI 1313 Mechanics I

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. ENGI 1313 Mechanics I Lecture 39: Analysis of Friction with Wedges

  2. Lecture 39 Objective • to illustrate by example equilibrium analysis of wedges with dry friction forces

  3. Wedge • Simple Machine • Inclined plane • Small applied force to generate larger (orthogonal) forces for stability, lifting or moving objects

  4. Wedge (cont.) • Analysis of Force P • FBD of wedge first then object • Analyze FBD with least # of unknowns

  5. Wedge (cont.) • Block Lowered onto Wedge • If P > 0 (+) then wedge is stable • If P = 0 then wedge is self-locking • If P < 0 (-) then wedge is unstable • Small s • Large 

  6. Example 39-01 • The wedge is used to level the floor of a building. For the floor loading shown, determine the horizontal force P that must be applied to move the wedge forward. The coefficient of static friction between the wedge and the two surfaces of contact is μs = 0.25. Neglect the size and weight of the wedge and the thickness of the beam.

  7. Example 39-01 (cont.) • FBD 4 kN 4 kN 2 kN 2 kN Ax F1 N1 Ay N1 F1 P N2 F2

  8. Example 39-01 (cont.) • Beam Normal Reaction Force 4 kN 4 kN 2 kN 2 kN Ax F1 N1 Ay

  9. Example 39-01 (cont.) • Wedge Force P • Impending motion N1 F1 P  N2 F2  = 15 

  10. Example 39-01 (cont.) • Wedge Force P • Impending motion N1 F1 P  N2 F2  = 15 

  11. Example 39-02 • The wedge blocks are used to hold the specimen in a tension testing machine. Determine the design angle θ of the wedges so that the specimen will not slip regardless of the applied load. The coefficients of static friction are μA = 0.1 at A and μB = 0.6 at B. Neglect the weight of the blocks.

  12. Example 39-02 (cont.) • FBD • Test coupon • Wedge grip FB FB NB NB P FB FA NB  NA

  13. Example 39-02 (cont.) • Analysis of Test Coupon FB FB NB NB P

  14. Example 39-02 (cont.) • Analysis of Wedge Grip FB FA NB  NA

  15. Example 39-02 (cont.) • Analysis of Wedge Grip FB FA NB  NA

  16. Example 39-02 (cont.) • Analysis of Wedge Grip FB FA NB  NA

  17. Chapter 8 Problems • No Problem Set • Problem 8-1 through 8-70 applicable • Omit 8-45 and 8-61 • Answers on page 647-648

  18. References • Hibbeler (2007) • http://wps.prenhall.com/esm_hibbeler_engmech_1

More Related