Jinbiao Fan

Quasi-Static Calibration Method of a High-g Accelerometer

To solve the problem of resonance during quasi-static calibration of high-g accelerometers, we deduce the relationship between the minimum excitation pulse width and the resonant frequency of the calibrated accelerometer according to the second-order mathematical model of the accelerometer, and improve the quasi-static calibration theory. We establish a quasi-static calibration testing system, which uses a gas gun to generate high-g acceleration signals, and apply a laser interferometer to reproduce the impact acceleration. These signals are used to drive the calibrated accelerometer. By comparing the excitation acceleration signal and the output responses of the calibrated accelerometer to the excitation signals, the impact sensitivity of the calibrated accelerometer is obtained. As indicated by the calibration test results, this calibration system produces excitation acceleration signals with a pulse width of less than 1000 μs, and realize the quasi-static calibration of high-g accelerometers with a resonant frequency above 20 kHz when the calibration error was 3%.

Triaxial Acceleration Measurement for Oblique Penetration Into Concrete Target

To obtain accurate data of the motion parameters of a rigid projectile during the oblique penetration event, a triaxial acceleration measurement device (TAMD) was developed, and a method for the calibration of a high-g accelerometer was presented by using a Hopkinson bar and a grating laser Doppler interferometer. The buffer structure was designed, and the cushioning capacity of it was studied to improve the survivability of the multichannel data recorder. A set of penetration experiments with concrete targets that had average compressive strengths of 35 and 45 MPa was conducted to characterize the response of monolithic concrete targets to projectile impact. The 96-mm-diameter 630-mm-long ogive-nose projectiles were machined from 35CrMnSiA steel and designed to contain a TAMD in the tail of the cavity. The projectiles were launched by a 100-mm-diameter smooth-bore powder gun to striking velocities between 300 and 600 m/s, and impacted the concrete target at an oblique angle of 0°-30°. The acceleration during the launch and the triaxial deceleration during the penetration were successfully recorded by the TAMD. The measured penetration data and deceleration-time data were analyzed.

Implantation Dynamic Testing and Calibration Techniques

Implantation dynamic testing (or new concept dynamic testing) is the information acquisition science within severe conditions. A definition of implantation dynamic testing is presented. The implantation dynamic testing refers to a real-time live measurement of dynamic parameters of a moving object with the main part of the testing systems located within the object being tested or in the same practical environment. A set of mathematical expressions (i.e. the conditional functions) for dynamic testing is described. The main characteristics, the main substances studied and the areas of application are presented. Since the performance of testing systems in implantation dynamic testing are strongly affected by the environment forces, general calibration methods are virtually not applicable. This paper presents three layers of calibration techniques: calibrations in simulated application environments, calibrations of environment factors, and tracing calibrations of dynamic parameters (also called quasi-sigma calibration). The last one is useful in many applications.

Shock Calibration of the High-g Triaxial Accelerometer

This paper describes the calibration of high-g triaxial piezoresistive accelerometer for studies of normal and oblique penetrations into concrete targets. In order to determine the dynamic sensitivity, shock calibration tests were performed using a Hopkinson bar at up to 80,000 g acceleration level and the laser-grating interferometer techniques. Comparisons with the conventional calibration methods places an importance on the transverse sensitivities, influence on the acceleration measurement is impossible to disregard. The experiment of projectile penetration of hard targets was performed. The result showed that the testing signal is more accurate than emulation signal. Agreement between theory and experiment is exhibited for the projectile residual velocity and penetration depths.

Triaxial Acceleration Measurement for Oblique Penetration of a Rigid Projectile into Concrete Target

In order to obtain accurate data of motion parameters of a rigid projectile during the oblique penetration event, a triaxial acceleration measurement device (TAMD) was developed and a unique calibration method was developed by using a pneumatic gun and two sets of grating laser Doppler interferometers. A set of penetration experiments into concrete targets with average compressive strengths of 35 and 45 MPa were conducted. The 96-mm-diameter, 630-mm-long, ogive-nose projectiles were machined from 35CrMnSiA steel and designed to contain a TAMD in the tail of the cavity. The projectiles were launched by a 100-mm-diameter, smooth-bore powder gun to striking velocities between 300 and 500 m/s and impacted the concrete target at an oblique angle of 0 to 30 degrees. The acceleration during the launch and the triaxial deceleration during the penetration were recorded successfully by the TAMD. When the oblique angle changed slightly with time, the single and double integrations of axial deceleration versus time revealed accurate concurrence with the measured striking velocity and the penetration depth, respectively.

Restraining zero drift in an ultrahigh-g impact environment

To restrain the zero drift of a piezoelectric accelerometer and the zero drift from a charge amplifier (CA) in an ultrahigh-g impact environment, a reformative design approach for an on-board ultrahigh-g deceleration–time measurement system is presented. First, a simplified zero-drift model of the on-board ultrahigh-g deceleration–time measurement system is built. Secondly, possible reasons for zero drifts in the ultrahigh-g impact environment are discussed. Then, a universal reformative CA and subsequent circuits are designed for restraining the zero drift. Finally, an air cannon is used to simulate the ultrahigh-g impact environment and a modified Michelson-type laser interferometer is set as a primary standard source to calibrate the reformative on-board measurement system. Comparisons between the measured curve and the reference curve verify that the zero drift is less than 3% of the peak value and deceleration–time data describe the real penetration process accurately. All differences in curves are not due to the proposed design and can be characterized by errors or uncertainties. Experimental results prove that the proposed design approach can restrain the zero drift effectively in the ultrahigh-g impact environment.