Monitoring of the outer diameter of long items using the optical diffraction method

AbstractOptical measurements have been made on the water lenses which form under pressure at grain boundaries in polycrystalline ice. Monochromatic light from a point source is focused by the lenses but, because the lenses are microscopic in size, the image is blurred by diffraction. The diffraction pattern observed under a microscope has been compared with the computed diffraction pattern to deduce the angle 2θat the rim of each lens. This is the dihedral angle for water at a grain boundary in ice, and gives the ratio of the grain-boundary energy to that of an ice-water interface. The most sensitive measurements are those made on the rings of the virtual diffraction pattern formed on the object side of the lens. They giveθ= 12.5 ± 0.5° for the grain boundary under observation, which is 26% lower than the previous value forθfound by ignoring diffraction.

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Residual Stresses in Steel and Zirconium Weldments

Journal of Pressure Vessel Technology ◽

10.1115/1.2842274 ◽

1997 ◽

Vol 119 (2) ◽

pp. 137-141 ◽

Cited By ~ 15

Author(s):

J. H. Root ◽

C. E. Coleman ◽

J. W. Bowden ◽

M. Hayashi

Keyword(s):

Residual Stress ◽

Electron Beam ◽

Neutron Diffraction ◽

Residual Stresses ◽

Prolonged Exposure ◽

Electron Beam Welding ◽

Three Dimensional ◽

Diffraction Method ◽

Outer Diameter ◽

Stress Relieving

Three-dimensional scans of residual stress within intact weldments provide insight into the consequences of various welding techniques and stress-relieving procedures. The neutron diffraction method for nondestructive evaluation of residual stresses has been applied to a circumferential weld in a ferritic steel pipe of outer diameter 114 mm and thickness 8.6 mm. The maximum tensile stresses, 250 MPa in the hoop direction, are found at mid-thickness of the fusion zone. The residual stresses approach zero within 20 mm from the weld center. The residual stresses caused by welding zirconium alloy components are partially to blame for failures due to delayed hydride cracking. Neutron diffraction measurements in a GTA-welded Zr-2.5Nb plate have shown that heat treatment at 530°C for 1 h reduces the longitudinal residual strain by 60 percent. Neutron diffraction has also been used to scan the residual stresses near circumferential electron beam welds in irradiated and unirradiated Zr-2.5Nb pressure tubes. The residual stresses due to electron beam welding appear to be lower than 130 MPa, even in the as-welded state. No significant changes occur in the residual stress pattern of the electron-beam welded tube, during a prolonged exposure to thermal neutrons and the temperatures typical of an operating nuclear reactor.

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Resting myosin cross-bridge configuration in frog muscle thick filaments.

The Journal of Cell Biology ◽

10.1083/jcb.102.2.610 ◽

1986 ◽

Vol 102 (2) ◽

pp. 610-618 ◽

Cited By ~ 32

Author(s):

M Cantino ◽

J Squire

Keyword(s):

Myosin Head ◽

Freeze Fracture ◽

Optical Diffraction ◽

Outer Diameter ◽

X Ray ◽

Cross Bridge ◽

Thick Filaments ◽

Myosin Filaments ◽

Cross Bridges ◽

The Right

Clear images of myosin filaments have been seen in shadowed freeze-fracture replicas of single fibers of relaxed frog semitendinosus muscles rapidly frozen using a dual propane jet freezing device. These images have been analyzed by optical diffraction and computer averaging and have been modelled to reveal details of the myosin head configuration on the right-handed, three-stranded helix of cross-bridges. Both the characteristic 430-A and 140-150-A repeats of the myosin cross-bridge array could be seen. The measured filament backbone diameter was 140-160 A, and the outer diameter of the cross-bridge array was 300 A. Evidence is presented that suggests that the observed images are consistent with a model in which both of the heads of one myosin molecule tilt in the same direction at an angle of approximately 50-70 degrees to the normal to the filament long axis and are slewed so that they lie alongside each other and their radially projected density lies along the three right-handed helical tracks. Any perturbation of the myosin heads away from their ideal lattice sites needed to account for x-ray reflections not predicted for a perfect helix must be essentially along the three helical tracks of cross-bridges. Little trace of the presence of non-myosin proteins could be seen.

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