Machine Design_slide 2

Machine - Week1,Lecture2 Material Strength and Stiffness P = A0 l l0 = l0 Hookes Law strain = E Material Strength and Stiffness Stress-strain

Info iconThis preview shows pages 1–10. Sign up to view the full content.

View Full Document Right Arrow Icon
ENGR 3220 – Machine Design ENGR 3220 – Machine Design Week 1, Lecture 2 Week 1, Lecture 2
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Material Strength and Stiffness ε σ E l l l A P = - = = 0 0 0 strain Hooke’s Law
Background image of page 2
Material Strength and Stiffness Stress-strain diagram obtained from the standard tensile test (a) Ductile material; (b) brittle material. pl marks the proportional limit; el, the elastic limit; y, the offset- yield strength as defined by offset strain a; u, the maximum or ultimate strength; and f, the fracture strength.
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Material Strength and Stiffness Tension specimen after necking The diagrams shown in slide 2 are called engineering stress-strain diagrams because these strain and stresses are not true values. These calculations are based on the original area before the load is applied. In reality, as the load is applied and the area is reduced, the actual stress is larger than the engineering values.
Background image of page 4
Material Strength and Stiffness True stress-strain diagram plotted in Cartesian coordinates 0 ln 0 l l l dl l l = = ε
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Shear and Torsion Strength J Tr l Gr = = θ τ 0 max Where θ is in radians, r is the radius of the specimen G is called shear modulus, l 0 the gauge length, T is applied torque, J is the polar second moment of area of the cross section
Background image of page 6
Strength and Cold Work Cold working is the process of plastic straining below the re-crystallization temperature in the plastic region of the stress-strain diagram.
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Hardness kpsi H S or MPa H S B u B u 5 . 12 23 . 0 86 58 . 1 - = - = Rockwell Hardness (H R ) Brinell Hardness (H B ) The resistance of a material to penetration by a pointed tool is called hardness. For cast iron = Mpa H kpsi H S B B u 41 . 3 495 . 0 For steels
Background image of page 8
Impact Properties The strain rate increases, as it is under impact conditions, the strength increases. Actually when strain rates are very high, the yield strength seems to approach the ultimate strength. But since the elongation has little change, that means the ductility remains the same.
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 10
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 04/16/2011 for the course ENGR 3220 taught by Professor Turro during the Spring '11 term at UOIT.

Page1 / 25

Machine - Week1,Lecture2 Material Strength and Stiffness P = A0 l l0 = l0 Hookes Law strain = E Material Strength and Stiffness Stress-strain

This preview shows document pages 1 - 10. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online