Introduction to Design of Machine Elements and Machine

Design Philosophy
http://nptel.iitm.ac.in/courses/Webcourse-contents/IIT%20Kharagpur/Machine%20design1/pdf/Module-1_Lesson-1.pdf

Product Development Approaches
http://www.nd.edu/~manufact/FME%20pdf_files/FME_Ch01.pdf



Machine Design
Ch.8 of S.B. Mathur's Mechanical Engineering (Conventional & Objective)

1. Fasteners 380 - 390
2. Keys 391-393
3. Joints 393 - 400
4. Shafts 401 - 404
5. Couplings 404 - 410
6. Riveted Joints 410 - 417
7. Welded Joints 417 - 421
8. Transmission Systems 421- 428
9. Bearings 429 - 434
10. Gears 435 - 438
11. Springs 439 - 442


1. Fasteners

Standard screw thread forms

1. BSW
2.B.A.
3. Metric
4. Square
5. Acme
6. Buttress



Types of threaded fasteners

1. Through bolts
2. Tap bolt, cap screws
3. Studs
4. Machine screws
5. Set screws

Locking devices

1.Lock nut
2. Washer

Design of bolted joints

Stresses

Initial stress

Tensile stress
Compression and shearing

External stresses

stresses due to combined load - initial and external

Power Screws

Force analysis

Design of a power screw

Design of a nut

Compound screw

Differential screw

It is necessary to determine the stresses in screw fastening due to both static and dynamic loading in order to determine their dimensions based on the strength of material being used. In order to design bolts for static loading both initial tightening and external loadings need be known.

Initial tightening load

When a nut is tightened over a screw following stresses are induced:

(a) Tensile stresses due to stretching of the bolt
(b) Torsional shear stress due to frictional resistance at the threads.
(c) Shear stress across threads
(d) Compressive or crushing stress on the threads
(e) Bending stress if the surfaces under the bolt head or nut are not perfectly normal to the bolt axis.


(a) Tensile stress

Bolts are usually designed on the basis of direct tensile stress with a large factor of safety. The initial tension in the bolt is estimated by an empirical relation P1 =284 d kN, where the nominal bolt diameter d is given in mm. The relation is used for steam tight joints. If such leakproofing is not required half of the  above estimated load may be used (142 d kN).


2. Keys 391-393
3. Joints 393 - 400
4. Shafts 401 - 404
5. Couplings 404 - 410
6. Riveted Joints 410 - 417
7. Welded Joints 417 - 421
8. Transmission Systems 421- 428
9. Bearings 429 - 434
10. Gears 435 - 438
11. Springs 439 - 442

Updated on 13 August 2020
21 July 2012