2001 Volume 2001 Issue 190 Pages 141-150
This paper describes a measuring device using piezoelectric material, which was developed to monitor features of the stress history of a structural member. The device counts the number of cycles of the fluctuating stress by the level crossing count method and the rain flow method. Microcomputers are used in this device to perform operations of those counting methods. The device can also display the operation results and the stress level of the monitored structural member with the liquid crystal display (LCD).
In order to see the performance of the test manufacture of the measuring device, experiments were carried out using a fatigue testing machine. The strain detector using piezoelectric polymer film was bonded onto a smooth specimen and multiple repeated stresses were applied to that specimen. As the result, the stress history measuring device can operate under a stress range from -110 MPa to 110 MPa, and a frequency over 1 Hz. Then, the device using the level crossing count method and the rain flow method can count accurately the number of cycles of the fluctuating stress.
