Akira Umeda

Characterization of Shock Accelerometers Using Davies Bar and strain-gages

This paper proposes a novel method for evaluating the dynamic characteristics of shock accelerometers under high acceleration levels and a wide frequency bandwidth. High accelerations of 103∼105m/s2 can be generated by the reflection of an elastic wave pulse propagating in a metal bar known as the Davies bar. The elastic wave pulse is produced by the collision of a projectile against one end of the bar, and is detected by straingages. The accelerometer to be characterized is attached to the other end of the bar. The one-dimensional theory of elastic waves enables the derivation of an input acceleration to the accelerometer from the measured strain. The dispersion of the elastic waves caused by the lateral inertia of the bar is compensated for by using a two-dimensional analytical solution. This method was validated by an experiment characterizing a piezoelectric-type accelerometer within the frequency band approximately 1 kHz∼70 kHz.

Improvement of novel NRLM method for accelerometer characterization to the range 102 m s−2

Abstract This report presents a novel method for characterizing accelerometers under medium and high accelerations ranging from 2 × 10 2 to 1 × 10 6 m s −2 . The reflection of longitudinal elastic waves in a thin circular bar is used for the excitation of a test accelerometer that is attached to the end of the bar. A newly designed laser interferometer can determine the input acceleration accurately. By improving the resolution of the interferometer, the lower acceleration limit of this method can be extended from 2000 m s −2 , the previous limit, to 200 m s −2 . The effectiveness of the method is confirmed through an experiment in which a piezoelectric-type accelerometer is characterized.

Characterization of shock accelerometers using Davies bar and laser interferometer

In this paper, we propose a novel method for evaluating the frequency response of shock accelerometers using Davies bar and interferometry. The method adopts elastic wave pulses propagating in a thin circular bar for the generation of high accelerations. The accelerometer to be examined is attached to one end of the bar and experiences high accelerations of the order of 103∼105 m/s2. A laser interferometer system is newly designed for the absolute measurement of the bar end motion. It can measure the motion of a diffuse surface specimen at a speed of 10−3 ∼100 m/s. Uncertainty of the velocity measurement is estimated to be±6×10−4 m/s, proving a high potential for use in the primary calibration of shock accelerometers. Frequency characteristics of the accelerometer are determined by comparing the accelerometers output with velocity data of the interferometry in the frequency domain. Two piezoelectric-type accelerometers are tested in the experiment, and their frequency characteristics are obtained over a wide frequency range up to several ten kilohertz. It is also shown that the results obtained using strain gages are consistent with those by this new method.