 Introduction of research project  Solidification of casting alloys  Stresses and strains  Crystal lattices  Diffraction  Neutrons  Experimental design  Data  Analysis of data

Detectors Engine Head Beam Aperture Transmitted Neutron Beam Scattered Neutrons Monochromator Sampling Volume

 Count scattered neutrons as a function of scattering angle for the Al (311)  For a neutron wavelength of nm the Al (311) peak is at 2θ of about 79 degrees  Plot counts against angle to map out the peak

 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

Incident Beam Scattered Beam

 Look at three directions around the valve ports

 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

Depth (mm)RadialAxialHoop ° ° ° ° ° ° ° ° °

 From the peak angles, calculate the “d” spacings  From the “d” spacings, calculate the strains using: ◦ Strain ε = (d-d 0 )/d 0, for Al (311) d o = 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

Isotropic Material Strain in x-direction is ε x = ΔL/L Strain in transverse (y and z) direction is ε T = ΔL’/L Poisson’s Ratio is ν = - ε T /ε x