Chapter 7 - Mechanical properties

Chapter 7 - Mechanical properties - Chapter 7 Mechanical...

Info icon This preview shows pages 1–18. Sign up to view the full content.

View Full Document Right Arrow Icon
1 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? Chapter 7: Mechanical Properties
Image of page 1

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

View Full Document Right Arrow Icon
2 Elastic means reversible ! Elastic Deformation 2. Small load F δ bonds stretch 1. Initial 3. Unload return to initial F δ Linear- elastic Non-Linear- elastic
Image of page 2
3 Plastic means permanent ! Plastic Deformation (Metals) F δ linear elastic linear elastic δ plastic 1. Initial 2. Small load 3. Unload planes still sheared F δ elastic + plastic bonds stretch & planes shear δ plastic
Image of page 3

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

View Full Document Right Arrow Icon
c07f04 c07f04
Image of page 4
5 Stress has units: N/m 2 or lb f /in 2 Engineering Stress Shear stress, τ : Area, A F t F t F s F F F s τ = F s A o Tensile stress, σ : original area before loading σ = F t A o 2 f 2 m N or in lb = Area, A F t F t
Image of page 5

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

View Full Document Right Arrow Icon
6 Simple tension: cable Common States of Stress o σ = F A σ σ Ski lift (photo courtesy P.M. Anderson) A o = cross sectional area (when unloaded) F F
Image of page 6
7 (photo courtesy P.M. Anderson) (photo courtesy P.M. Anderson) Canyon Bridge, Los Alamos, NM o σ = F A Simple compression: Note: compressive structure member ( σ < 0 here). A o Balanced Rock, Arches National Park
Image of page 7

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

View Full Document Right Arrow Icon
8 Tensile strain: Lateral strain: Strain is always dimensionless. Engineering Strain Shear strain: θ 90º 90º - θ y x θ γ = x / y = tan ε = δ L o Adapted from Fig. 7.1 (a) and (c), Callister & Rethwisch 3e. δ /2 L o w o - δ ε L = L w o δ L /2
Image of page 8
c07prob c07prob
Image of page 9

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

View Full Document Right Arrow Icon
10 Stress-Strain Testing • Typical tensile test machine Adapted from Fig. 7.3, Callister & Rethwisch 3e. (Fig. 7.3 is taken from 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.) specimen extensometer • Typical tensile specimen Adapted from Fig. 7.2, Callister & Rethwisch 3e. gauge length
Image of page 10
c07f02 c07f02 Mechanical test bar
Image of page 11

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

View Full Document Right Arrow Icon
12 Linear Elastic Properties Modulus of Elasticity, E : (also known as Young's modulus) Hooke's Law : σ = E ε σ Linear- elastic E ε F F simple tension test
Image of page 12
c07f05 c07f05
Image of page 13

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

View Full Document Right Arrow Icon
14 Mechanical Properties Slope of stress strain plot (which is proportional to the elastic modulus) depends on bond strength of metal Adapted from Fig. 7.7, Callister & Rethwisch 3e.
Image of page 14
c07f08 c07f08 Q: Modulus of elasticity decreases as temperature increases…Why? A: At higher temps atoms are less strongly bonded
Image of page 15

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

View Full Document Right Arrow Icon
c07f20 c07f20
Image of page 16
17 Metals Alloys Graphite Ceramics Semicond Polymers Composites /fibers E (GPa) Based on data in Table B.2, Callister & Rethwisch 3e.
Image of page 17

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

View Full Document Right Arrow Icon
Image of page 18
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern