| We developed a new dynamic measurement system therein was especially designed by assembling a scanning laser extensometer, a frequency response analyzer for detecting the amplitude and phase lag of strain in response to a sinusoidal time-varying stress and a standard servo-hydraulic mechanical testing machine equipped with an infrared lamp heater. We developed a $quot;non-contacting$quot; extensometric technique based on a potable scanning laser caliper. This opto-electronic instrument, as such, did not suffice for our needs because a displacement signal corresponding to 1㎛ was comparable to a scatter band of noise. To improve the signal-to-noise ratio to a desired level, a dual-channel programmable active filter, together with a set of optical filters, was employed. As a result of this and some other technical improvements requisite for the intended measuring a low frequency cyclic micro deformation response of, say, 3㎛ in displacement amplitude within an accuracy of ±0.1㎛ was established. Anelastic behavior of a polycrystalline aluminum has been examined through the measurements of the dynamic Young`s modulus and internal friction over a temperature range from 25 to 400℃ at frequencies of 0.05 and 0.1㎐. One broad peak of internal friction is observed over the ranges 240 to 260℃, together with marked decreases in the experimental data. It is concluded that the peak phenomenon is due to grain-boundary relaxation. |
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