AE321_HW6

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School

University of Illinois, Urbana Champaign *

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Course

321

Subject

Mechanical Engineering

Date

Feb 20, 2024

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docx

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5

Uploaded by ChefIceSquirrel24

AE 321 – Homework 6 1. 1045 cold rolled steel: a) b) 0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0 100 200 300 400 500 600 700 800 900 Yield point Point of onset necking Failure point 1045 Steel Stress-Strain Curve Strain (mm/mm) Stress (MPa) c) Proportional limit: (0.002446, 452.056 MPa) 0.2% offset stress: 369.63 MPa (stress when strain = 0.002) Ultimate tensile strength: 809.205 MPa (maximum stress) Failure strain: 15.59% (maximum strain) d) E = σ ε Slope from (0, 0) to proportional limit (0.002446, 452.056 MPa): E = 452.056 MPa 0 0.002446 0 = 184814.391 MPa = 184.8 GPa
e) 0 0.01 0.02 0.03 0.04 -200 0 200 400 600 800 1000 1200 f(x) = 184814.39 x − 4755.46 1045 Steel unloaded after 3% straining Strain (mm/mm) Stress (MPa) 3% offset stress = 788.975 MPa Unloading curve: σ = ( ε 0.03 ) E + 788.975 σ = ( 184814.391 MPa ) ε 4755.5 MPa Final plastic strain: Unloading curve at σ = 0 0 = ( 184814.391 MPa ) ε 4755.5 MPa ε = 4755.5 184814.391 = 0.0257 = 2.57% New Yield stress = 788.975 MPa
6061-T6 aluminum alloy: a) b) 0 0.05 0.1 0.15 0.2 0 50 100 150 200 250 300 350 Yield point Point of onset necking Failure point 6061-T6 Al Stress-Strain Curve Strain (mm/mm) Stress (MPa) c) Proportional limit: (0.004749, 285.411 MPa) 0.2% offset stress: 127.760 MPa Ultimate tensile strength: 324.761MPa Failure strain: 18.25% d) E = σ ε Slope from (0, 0) to proportional limit (0.004749, 285.411 MPa): E = 285.411 MPa 0 0.004749 0 = 60099.1788 MPa = 60.1 GPa e) 3% offset stress = 185.116 MPa Unloading curve: σ = ( ε 0.03 ) E + 185.116 σ = ( 60099.1788 MPa ) ε 1617.859 MPa Final plastic strain: Unloading curve at σ = 0 0 = ( 60099.1788 MPa ) ε 1617.859 MPa ε = 1617.859 60099.1788 = 0.0269 = 2.69% New Yield stress = 185.116 MPa
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