Chapter6c

Chapter6c - Chapter Outline Introduction To understand and...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
1 1 MSE 2090: Introduction to Materials Science Chapter 6, Mechanical Properties Mechanical Properties of Metals How do metals respond to external loads? ± Stress and Strain ¾ Tension ¾ Compression ¾ Shear ¾ Torsion ± Elastic deformation ± Plastic Deformation ¾ Yield Strength ¾ Tensile Strength ¾ Ductility ¾ Toughness ¾ Hardness Chapter Outline Optional reading (not tested): details of the different types of hardness tests, variability of material properties (starting from the middle of page 174) 2 MSE 2090: Introduction to Materials Science Chapter 6, Mechanical Properties To understand and describe how materials deform (elongate, compress, twist) or break as a function of applied load, time, temperature, and other conditions we need first to discuss standard test methods and standard language for mechanical properties of materials. Introduction Stress, σ (MPa) Strain, ε (mm / mm) 3 MSE 2090: Introduction to Materials Science Chapter 6, Mechanical Properties Types of Loading Tensile Compressive Shear Torsion 4 MSE 2090: Introduction to Materials Science Chapter 6, Mechanical Properties Concepts of Stress and Strain (tension and compression) To compare specimens of different sizes, the load is calculated per unit area. Engineering stress: σ = F / A o F is load applied perpendicular to speciment cross- section; A 0 is cross-sectional area (perpendicular to the force) before application of the load. Engineering strain: ε = Δ l / l o ( × 100 %) Δ l is change in length, l o is the original length. These definitions of stress and strain allow one to compare test results for specimens of different cross- sectional area A 0 and of different length l 0 . Stress and strain are positive for tensile loads, negative for compressive loads
Background image of page 1

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

View Full DocumentRight Arrow Icon
2 5 MSE 2090: Introduction to Materials Science Chapter 6, Mechanical Properties Concepts of Stress and Strain (shear and torsion) Shear stress: τ = F / A o F is load applied parallel to the upper and lower faces each of which has an area A 0 . Shear strain: γ = tg θ ( × 100 %) θ is strain angle Torsion is variation of pure shear. The shear stress in this case is a function of applied torque T, shear strain is related to the angle of twist, φ . Shear Torsion θ F Ao 6 MSE 2090: Introduction to Materials Science Chapter 6, Mechanical Properties Stress-Strain Behavior Elastic Plastic Stress Strain Elastic deformation Reversible : when the stress is removed, the material returns to the dimensions it had before the loading. Usually strains are small (except for the case of some plastics, e.g. rubber). Plastic deformation Irreversible : when the stress is removed, the material does not return to its original dimensions. 7
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 12/08/2011 for the course MSE 2090 taught by Professor Leoindzhiglei during the Fall '10 term at UVA.

Page1 / 7

Chapter6c - Chapter Outline Introduction To understand and...

This preview shows document pages 1 - 3. Sign up to view the full document.

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