A new technique for the measurement of residual stresses is presented. The technique is based on strain measurements following thermal stress relaxation. The heat input is supplied by a low power infrared laser and the strain is measured with speckle pattern correlation interferometry. This paper presents a comprehensive overview of the technique and an example of how it has been applied in a practical situation.
Metal-matrix composites may offer better damping properties than unreinforced alloys. Because damping properties (and metalmatrix composites) are becoming important in airframe design, the damping capabilities of a number of aluminum-matrix composites were measured over a wide range of frequencies at low strain amplitudes, using a new laser vibrometer technique. Silicon carbide and alumina reinforcements resulted in a material with damping properties similar to that of unreinforced aluminum 6061-T6, but unidirectional and planar-random graphite continuous-fiber reinforcements increased the damping by 5 and 14 times, respectively. The increased damping of the continuous fiber composites is attributed to the absence of interfacial reaction resultingfrom the highpressure infiltration method used for their manufacture.42
A tracer gas is injected into a single subchannel of a large air flow model of a reactor rod bundle. Axial variations in the tracer flux are determined by sampling at two downstream positions in both the injection subchannel and those adjacent to it. This information, with measured subchannel area changes, is used to calculate crossflows and the turbulent eddy diffusion coefficient. The latter number agrees with the results of other investigators in regular pipe flows. Also determined are distributional factors which would be required for modeling the transport equations, for this particular scalar distribution, with a typical lumped parameter computer code.
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