# lecture6 - Chapter Chapter 6 Mechanical Properties 1...

This preview shows pages 1–15. Sign up to view the full content.

Chapter Chapter 6 Mechanical Properties 1

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

View Full Document
echanical Properties SUES TO ADDRESS Mechanical Properties ISSUES TO ADDRESS. .. Stress and strain : What are they and why are they used instead of load and deformation? Elastic behavior: When loads are small, how much deformation occurs? What materials deform least? Plastic behavior: At what point does permanent deformation occur? What materials are most resistant to permanent deformation? Toughness and ductility : What are they and how do we measure them?
Elastic Deformation 1. Initial 2. Small load 3. Unload bonds stretch tt d return to initial F F Linear- astic Elastic means reversible ! elastic Nonlinear- elastic d

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

View Full Document
Plastic Deformation (Metals) 1. Initial 2. Small load 3. Unload nes bonds planes still sheared stretch & planes shear astic + plastic d plastic F d elastic + plastic Plastic means permanent ! linear astic linear astic F d elastic elastic d plastic
Engineering Stres Engineering Stress Shear stress, : F t F Tensile stress, : F t Area, A F s Area, A F t F F s = F s F t F N lb tress has units: A o original area = t A o 2 f 2 m or in = Stress has units: N/m 2 or lb f /in 2 J/m 3 before loading

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

View Full Document
Common States of Stress Simple tension: cable A o = cross sectional area (when unloaded) F F o = F A M F s Torsion (a form of shear): drive shaft Ski lift (photo courtesy P.M. Anderson) = F s A A o A c Note: t = M / A c R here. o M 2 R
Other Common Stress States (1 Other Common Stress States (1) Simple compression: A o (photo courtesy P.M. Anderson) Canyon Bridge, Los Alamos, NM o = F A Note: compressive structure member ( < 0 here). (photo courtesy P.M. Anderson) Balanced Rock, Arches National Park

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

View Full Document
Other Common Stress States (2 Other Common Stress States (2) Bi-axial tension: Hydrostatic compression: Pressurized tank (photo courtesy Fish under water 0 (photo courtesy P.M. Anderson) P.M. Anderson) 0 > 0 < 0 h r > 0
Engineering Strain Tensile strain: Lateral strain: d /2 e= d L o - d e L = L w o L o w o Shear strain: d L /2 x = = n Strain is always 90º - y x / y tan y dimensionless. 90º

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

View Full Document
Stress Stress-Strain Testing Strain Testing • Typical tensile test machine • Typical tensile specimen Adapted specimen extensometer Callister 8 th Ed. gauge length g Adapted from Callister (Ref:H.W. Hayden, W.G. Moffatt, and J. Wulff, The Structure and Properties of Materials , Vol. III, Mechanical Behavior , p. 2, John Wiley and Sons, New York, 1965.)
Linear Elastic Properties Modulus of Elasticity, E : (also known as Young's modulus) Hooke's Law : = E e s E F Linear- e elastic F simple tension st test

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

View Full Document
Poisson's ratio, Poisson's ratio, : e L e - e =- L e Units: E : [GPa] or [psi] imensionless metals : ~ 0.33 ceramics : ~ 0.25 polymers : ~ 0.40 : dimensionless
Mechanical Properties Slope of stress strain plot (which is proportional to the elastic modulus) depends on bond strength of metal (or any material…) Adapted from Callister, 8 th Ed.

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

View Full Document
Temperature Dependence of Young’s odulus Modulus Structure-Property elation: Relation: 1 E µ m T T<T
This is the end of the preview. Sign up to access the rest of the document.
• Fall '10
• Akdogan
• Tensile strength, courtesy P.M. Anderson, photo courtesy P.M., Callister 8th Ed, Elastic Elastic Deformation

{[ snackBarMessage ]}

### Page1 / 41

lecture6 - Chapter Chapter 6 Mechanical Properties 1...

This preview shows document pages 1 - 15. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online