Contact force measurement using acoustic emission analysis and system identification methods

Acoustic emission (AE) signals were used to investigate the contact force o ccurring at the head/disk interface of a computer hard drive. The AE sensor was calibrated directly using the "ball drop method" and indirectly using system identification. For the indirect calibration, a high bandwidth laser Doppler vibrometer (LDV) was used. The transfer function was established f rom the harmonic response derived at different vibration modes and frequenc ies. A finite element method based transient response simulation of impact was used to estimate the velocity and stress response of the slider. In our experiments, contact forces were found to be in the range of 5-25 mN for n ano sliders and 2-10 mN for pico sliders. (C) 2000 Elsevier Science Ltd. Al l rights reserved.