DEVELOPMENT AND EVALUATION OF CALIBRATION PROCEDURE FOR A FORCE-MOMENT BALANCE USING DESIGN OF EXPERIMENTS

Abstract

TO MEASURE THE AERODYNAMIC AND HYDRODYNAMIC FORCES AND MOMENTS ACTING ON SCALED MODELS IN WATER AND WIND TUNNEL TESTS, MULTI-COMPONENT STRAIN GAUGE FORCE AND MOMENT BALANCE ARE USUALLY USED. THEIR PERFORMANCE AND ACCURACY LARGELY DEPENDS ON THE RIG AND CALIBRATION METHOD, INCLUDING THE LOAD TABLE (DESIGN MATRIX) AND ANALYSIS OF EXPERIMENTAL DATA. IN THIS ARTICLE, FOR THE CALIBRATION OF A SIX-COMPONENT BALANCE, A CALIBRATION PROCEDURE USING THE BOX-BEHNKEN DESIGN (BBD) OF EXPERIMENTS WAS DEVELOPED. IN THE SUGGESTED DESIGN MATRIX, IN ADDITION TO ALL POSSIBLE COMBINATIONS OF THE TWO-COMPONENT LOAD OF THE SIX COMPONENT LOAD (TEST VECTORS WITH TWO ACTIVE FACTORS), THE PURE LOADS (TEST VECTORS WITH ONE ACTIVE FACTOR) ARE ALSO USED. THE IMPLEMENTATION OF THE DESIGN MATRIX WAS DONE USING A CALIBRATION RIG, WHICH HAS THE ABILITY TO PERFORM FORMAL EXPERIMENTAL DESIGN TECHNIQUES COMPLETELY. THE OBTAINED EXPERIMENTAL DATA WERE FITTED WITH SECOND-ORDER EQUATIONS USING REGRESSION ANALYSIS. THE STATISTICAL SIGNIFICANCE OF INDEPENDENT VARIABLES AND INTERACTIONS WAS TESTED USING THE ANALYSIS OF VARIANCE (ANOVA) WITH 95% CONFIDENCE (α = 0.05). THE RESULTS OF RESIDUALS INDICATE THAT THE SUGGESTED MODEL SUFFICIENTLY PREDICTS THE RESPONSES AS A FUNCTION OF INPUT FACTORS. THE COMPARISON BETWEEN THE MODIFIED BOX-BEHNKEN DESIGN (MBBD) AND BBD CALIBRATIONS INDICATES THAT THE MBBD METHOD ESTIMATES THE DATA MORE ACCURATE. THE RESULTS SHOW THAT THE MBBD METHOD IS THE MOST APPROPRIATE METHOD COMPARED TO THE EXISTING METHODS FOR CALIBRATING BALANCE IN THIS PAPER.