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DRSA Inreach

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.

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DRSA Inreach

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  1. Internal Stresses in Aluminum Engines Data DRSA Inreach

  2. Measuring Residual Stresses • Introduction of research project • Solidification of casting alloys • Stresses and strains • Crystal lattices • Diffraction • Neutrons • Experimental design • Data • Analysis of data

  3. FCC Aluminum Diffraction Pattern

  4. Experimental Geometry Transmitted Neutron Beam Sampling Volume Beam Aperture Engine Head Monochromator Scattered Neutrons Detectors

  5. Experimental Geometry

  6. Diffraction Peaks • 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

  7. Peaks

  8. Reference Peak Positions • 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

  9. Bragg’s Law has a Direction Incident Beam Scattered Beam

  10. Stress Components • Look at three directions around the valve ports

  11. Stress Components

  12. Stress Components

  13. Hook’s Law in 3-D • 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: • σR,A,H is the Radial, Axial or Hoop stress (pick one) • εR,A,H is the Radial, Axial or Hoop Strain (pick one) • ν is Poisson’s Ratio

  14. Al (311) Scattering Angle

  15. Data Analysis • 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

  16. Next week: Analysis of Data

  17. Poisson’s Ratio Isotropic Material Strain in x-direction is εx = ΔL/L Strain in transverse (y and z) direction is εT = ΔL’/L Poisson’s Ratio is ν = - εT/εx

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