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# Cd chap 2 - static loading

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### Cd chap 2 - static loading

1. 1. CHAPTER 2 : STATIC LOADING
2. 2. 2.1 STRESS DISTRIBUTION IN BASIC MACHINE COMPONENTS 1. Rod  Critical point (in general): Any point  Critical point (specifically): At stress cncentrated points
3. 3. 2.1 STRESS DISTRIBUTION IN BASIC MACHINE COMPONENTS  Stress at stress concentrated points
4. 4. 2.1 STRESS DISTRIBUTION IN BASIC MACHINE COMPONENTS  Shear stress in a ‘rod’ (pin, bolt and rivet)  Shear stress (ave) = P/A
5. 5. 2.1 STRESS DISTRIBUTION IN BASIC MACHINE COMPONENTS  Bearing stress in a ‘rod’ (pin, bolt and rivet)
6. 6. 2.1 STRESS DISTRIBUTION IN BASIC MACHINE COMPONENTS 2. Beam a. Normal stress b. Transverse shear stress c. Deflection
7. 7. 2.1 STRESS DISTRIBUTION IN BASIC MACHINE COMPONENTS  Normal stress:  Along beam direction  Maximum at the top or at the bottom x My I   
8. 8. 2.1 STRESS DISTRIBUTION IN BASIC MACHINE COMPONENTS (for rectangular beam) • Shear Stress
9. 9. 2.1 STRESS DISTRIBUTION IN BASIC MACHINE COMPONENTS
10. 10. 2.1 STRESS DISTRIBUTION IN BASIC MACHINE COMPONENTS  Critical points:  In beams actually, we design for normal stress and shear stress separately. x x xy
11. 11. 2.1 STRESS DISTRIBUTION IN BASIC MACHINE COMPONENTS  Deflection  Assuming linear in material and geometry, P1 x y w dx  2 2 dx yd EIM 
12. 12. 2.1 STRESS DISTRIBUTION IN BASIC MACHINE COMPONENTS  Design of beams  Prismatic design:  Design for normal stress Sreqd = Required section modulus For long beam.  Design for shear stress For short beam with concentrated load Especially for wood beam  Fully stressed beam design
13. 13. 2.1 STRESS DISTRIBUTION IN BASIC MACHINE COMPONENTS T L    GJ TL  J T  3. Shaft
14. 14. 2.1 STRESS DISTRIBUTION IN BASIC MACHINE COMPONENTS 4. Thin Cylinder
15. 15. 2.1 STRESS DISTRIBUTION IN BASIC MACHINE COMPONENTS 5. Thick Cylinder P2 P1 R2 R1
16. 16. 2.1 STRESS DISTRIBUTION IN BASIC MACHINE COMPONENTS  Critical Points:  Inner points: r = R1  Highest maximum shear stress r H R
17. 17. 2.2 MATERIAL PROPERTIES  Basic material properties:  Physical: Density  Mechanical:  Young’s modulus  Shear modulus  Yield strength  UTS  Elongation at break  Reduction of area  Poisson’s ratio  Toughness: modulus of toughness, modulus of resilience  Hardness (Brinnel, Rockwell, Vickers)  Impact strength (Izod, Charpy)  Test:  Tensile test  Hardness test  Impact test
18. 18. 2.2 MATERIAL PROPERTIES  Tensile test
19. 19. 2.2 MATERIAL PROPERTIES  Standard codes 1. Society of Automotive Engineers (SAE) 2. British Standards (BS) 3. European standards – (EN) 4. ASTM (UNS) 5. Japanese Industrial Standards (JIS) 6. Germany steel grades (DIN) 7. China steel grades (GB)
20. 20. 2.2 MATERIAL PROPERTIES  Determine the alloy content, properties, applications and its code number. 1. Cast Iron 2. Carbon Steel & Alloys 3. Stainless Steel & Alloys 4. Aluminum & Alloys 5. Magnesium & Alloys 6. Copper &Alloys 7. Titanium & Alloys 8. Zircanium & Alloys 9. Nickel & Alloys 10. Zinc & Alloys
21. 21. 2.3 FAILURE THEORY  To develop FS of the design  Static failure theory  Tresca’s theory  von Misses’s theory
22. 22. 2.3 FAILURE THEORY 1 1.25 - 1.5 for exceptionally reliable materials used under controllable conditions and subjected to loads and stresses that can be determined with certainty - used almost invariably where low weight is a particularly important consideration 2 1.5 - 2 for well-known materials under reasonably constant environmental conditions, subjected to loads and stresses that can be determined readily. 3 2 - 2.5 for average materials operated in ordinary environments and subjected to loads and stresses that can be determined. 4 2.5 - 3 for less tried materials or for brittle materials under average conditions of environment, load and stress. 5 3-4 for untried materials used under average conditions of environment, load and stress. 6 3-4 should also be used with better-known materials that are to be used in uncertain environments or subject to uncertain stresses. 7 Repeated loads : the factors established in items 1 to 6 are acceptable but must be applied to the endurance limit (ie. a fatigue strength ) rather than to the yield strength of the material. 8 Impact forces : the factors given in items 3 to 6 are acceptable, but an impact factor (the above dynamic magnification factor ) should be included. 9 Brittle materials : where the ultimate strength is used as the theoretical maximum, the factors presented in items 1 to 6 should be approximately doubled. 10 Where higher factors might appear desirable, a more thorough analysis of the problem should be undertaken before deciding on their use. based on yield strength - according to Juvinall & Marshek op cit.