In this paper the expressions are derived for estimating bending wave intensity and its components at arbitrary frequency in one-dimensional structures such as beams. There is a critical frequency fo above which there...In this paper the expressions are derived for estimating bending wave intensity and its components at arbitrary frequency in one-dimensional structures such as beams. There is a critical frequency fo above which there are two bending waves with different wave numbers propagating along a structure and the estimates of bending wave intensity and its components become quite complicated, and it may not be possible to measure bending wave intensity using the existing intensity techniques. The expressions are also derived for calculating approximate estimate error resulting from using the existing intensity theory. To verify the theoretical results, a series of measurements was carried out on a masonry column under laboratoryconditions.展开更多
Quasi-longitudinal waves are one type of structural waves, which are important at high frequencies. This paper studies the estimate theory and measurement technique of quasi-longitudinal waves, analyzes the bias error...Quasi-longitudinal waves are one type of structural waves, which are important at high frequencies. This paper studies the estimate theory and measurement technique of quasi-longitudinal waves, analyzes the bias error due to the effect of bending waves. In a two-dimensional quasi-longitudinal wave held, the intensity vector is the sum of the effective intensity vector and the intensity variation vector. Its axial component is proportional to two imaginary parts of cross spectral densities and in the measurement, it is measured by a pair of two-transducer arrays. In a one-dimensional quasi-longitudinal wave field, the intensity variation is zero, the intensity is proportional to only one imaginary part of a cross spectral density and it can be measured using a two-transducer array. If bending and quasi-longitudinal waves coexist and the contribution from bending waves cannot be eliminated or reduced to a certain extent, the measured quasi-longitudinal wave intensity will contain a large error. The results measured on the three-beam structure show that quasi-longitudinal wave intensity can be accurately measured using the intensity technique when bending waves are negligible in comparison with quasi-longitudinal waves.展开更多
文摘In this paper the expressions are derived for estimating bending wave intensity and its components at arbitrary frequency in one-dimensional structures such as beams. There is a critical frequency fo above which there are two bending waves with different wave numbers propagating along a structure and the estimates of bending wave intensity and its components become quite complicated, and it may not be possible to measure bending wave intensity using the existing intensity techniques. The expressions are also derived for calculating approximate estimate error resulting from using the existing intensity theory. To verify the theoretical results, a series of measurements was carried out on a masonry column under laboratoryconditions.
文摘Quasi-longitudinal waves are one type of structural waves, which are important at high frequencies. This paper studies the estimate theory and measurement technique of quasi-longitudinal waves, analyzes the bias error due to the effect of bending waves. In a two-dimensional quasi-longitudinal wave held, the intensity vector is the sum of the effective intensity vector and the intensity variation vector. Its axial component is proportional to two imaginary parts of cross spectral densities and in the measurement, it is measured by a pair of two-transducer arrays. In a one-dimensional quasi-longitudinal wave field, the intensity variation is zero, the intensity is proportional to only one imaginary part of a cross spectral density and it can be measured using a two-transducer array. If bending and quasi-longitudinal waves coexist and the contribution from bending waves cannot be eliminated or reduced to a certain extent, the measured quasi-longitudinal wave intensity will contain a large error. The results measured on the three-beam structure show that quasi-longitudinal wave intensity can be accurately measured using the intensity technique when bending waves are negligible in comparison with quasi-longitudinal waves.
