drsa inreach
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Internal Stresses in Aluminum Engines. Data. DRSA Inreach. Measuring Residual Stresses. Introduction of research project Solidification of casting alloys Stresses and strains Crystal lattices Diffraction Neutrons Experimental design Data Analysis of data. - PowerPoint PPT PresentationTRANSCRIPT
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DRSA Inreach
Internal Stresses in Aluminum Engines
Data
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Introduction of research project Solidification of casting alloys Stresses and strains Crystal lattices Diffraction Neutrons Experimental design Data Analysis of data
Measuring Residual Stresses
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FCC Aluminum Diffraction Pattern
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Experimental Geometry
Detectors
Engine Head
Beam Aperture
Transmitted Neutron Beam
Scattered Neutrons
Monochromator
Sampling Volume
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Experimental Geometry
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Count scattered neutrons as a function of scattering angle for the Al (311)
For a neutron wavelength of 0.154906 nm the Al (311) peak is at 2θ of about 79 degrees
Plot counts against angle to map out the peak
Diffraction Peaks
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Peaks
77 77.5 78 78.5 79 79.5 80 80.50
500
1000
1500
2000
2500
Aluminum (311)
Scattering Angle (degrees)
Neu
tron
Cou
nts
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Goal is to measure strains and ultimately stresses Strain is measured relative to unstressed sample Therefore, repeat all measurements on
unstressed samples◦Made by cutting up the engine and re-measuring the
samples removed from the engine◦Removing the samples from engine relieves stresses
Reference Peak Positions
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Bragg’s Law has a Direction
IncidentBeam Scattered
Beam
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Look at three directions around the valve ports
Stress Components
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Stress Components
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Stress Components
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In 1-D, law was σ=Eε, where:◦ σ is stress,◦ E is Young’s Modulus and◦ ε is strain
More complicated in 3-D:
Where:◦ σ R,A,H is the Radial, Axial or Hoop stress (pick one) ◦ ε R,A,H is the Radial, Axial or Hoop Strain (pick one)◦ ν is Poisson’s Ratio
Hook’s Law in 3-D
),,,, (
211 HARHARHARE
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Al (311) Scattering Angle
Depth (mm) Radial Axial Hoop
0 78.7291° 78.8203° 78.7864°
6 78.7701° 78.7942° 78.7632°
12 78.6396° 78.7036° 78.6999°
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From the peak angles, calculate the “d” spacings From the “d” spacings, calculate the strains using:◦Strain ε = (d-d0)/d0 , for Al (311) do = 0.122082 nm
From Young’s Modulus (E) and Poisson’s ratio (ν), calculate components of stress using:
Al E=68.9 GPa, ν=0.33 For R,A,H pick one component each time and
recalculate
Data Analysis
),,,, (
211 HARHARHARE
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Next week: Analysis of Data
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Poisson’s Ratio
Isotropic MaterialStrain in x-direction is εx = ΔL/LStrain in transverse (y and z) direction is εT = ΔL’/LPoisson’s Ratio is ν = - εT/εx