재료의 기계적 거동(Mechanical Behavior of Materials)

Lecture 2 – Overview of Mechanical Behavior

(1-dimensional definition of stress and strain)

Heung Nam HanProfessor

Department of Materials Science & Engineering

College of Engineering

Seoul National University

Seoul 151-744, Korea

Tel : +82-2-880-9240

Fax : +82-2-885-9647

email : hnhan@snu.ac.kr

Office hours : Tuesday, Thursday 15:30~17:00

Homepage : http://mmmpdl.snu.ac.kr

2016-03-08

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Tensile Test

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Tensile Test Specimen

A standard tensile specimen with circular cross section

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Engineering Stress and Strain

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Engineering Stress-Strain Curve

Initial area

Extension/initial length

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True Stress and Strain

* Incompressibility

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Engineering Strain

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Stress-Strain Curves

dσ/dε

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Strain Hardening and Necking

ε<εu ε>εu

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Holloman Equation

where σ is the true stress, ε is

true strain, K is strength

coefficient, and n is the

strain-hardening exponent.

n=εu

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UYP, LYP and serration

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Strain rate sensitivity & Temperature effect