Evaluations of instrumentation for measuring biodynamic responses of the hand-arm system.
Welcome-DE; Dong-RG; McDowell-TW; Wu-JZ
10th International Conference on Hand-Arm-Vibration, June 2004, Las Vegas, Nevada. 2004 Jun; :94-96
Introduction: The biodynamic response (BR) of human hand-arm system is one of the important foundations for the future standardization on the measurement and risk assessment of hand-transmitted vibration (Griffin, 1994). It is also useful for the design of improved vibrating tools and the development of anti-vibration devices. There are considerable differences among the previously reported datasets of the biodynamic response. The large variations could have resulted from many different sources or factors. Those factors may be broadly classified into two categories: (1) natural factors and (2) instrumentation problems. While the natural factors can be either controlled during the experiment or considered as fixed or random variables in the study design, the systematic errors caused by the instrumentation problems could lead to misleading results and improper conclusions. Therefore, the specific aims of this study are to develop a systematical methodology for the calibration and evaluation of instrumentation, and to comprehensively examine a measurement system equipped with a new instrumented handle developed at the National Institute for Occupational Safety and Health (NIOSH). Results: The instrumented handle displays excellent linear behavior. The force measurement is independent to the force load position along the handle. The original handle-fixture system has a fundamental resonant frequency of 1.452 Hz. and a secondary resonant frequency of 2.536 Hz. With the fingers positioned on the measuring cap. the resonant frequencies of the handle-fixture system were only marginally reduced (approximately 50 Hz). The measuring cap did not display obvious bending (distribution difference < 3%) up to 1,500 Hz. The hand coupling had no significant effect (<5%) on the vibration distribution below 2.000 Hz. The measured dynamic mass as shown in Figure 2. The 1 D system responses on the handle were also reliably detected with the handle. The shear and bending loads have little effect on the handle behaviors. With an improved fixture design. the fundamental resonant frequency becomes 1.924 Hz. which further improved the handle behaviors. Discussion and Conclusion: This study addressed the fundamental instrumentation issues that have not been systematically reported and summarized. The information, methods. and results presented in this paper can be used to help establish a generally acceptable methodology for the further measurement and investigation of the BR. This study demonstrated that the proposed methods for instrumentation calibration and evaluation can help identify and correct the potential system problems, improve the design of the handle-fixture structures, avoid major measurement errors, debug data errors, and assure the accuracy of the experimental data. Therefore. the methodology can be directly used to help collect reliable and consistent data to improve the current ISO 10068 (1998), and to establish a trustable database of human hand-arm system biodynamic responses for both research purposes and practical applications. The NIOSH handle is acceptable for the BR measurement up to at least 1.500 Hz.
Vibration; Vibration-exposure; Vibration-disease; Extremities; Measurement-equipment; Analytical-instruments; Analytical-processes; Models
10th International Conference on Hand-Arm-Vibration, June 2004, Las Vegas, Nevada