Entity

Time filter

Source Type

Scotts Valley, CA, United States

Ganeriwala S.N.,SpectraQuest Inc. | Kanakasabai V.,SpectraQuest Inc. | Richardson M.,Vibrant Technology Inc
Conference Proceedings of the Society for Experimental Mechanics Series | Year: 2011

On-line surveillance of the structural integrity of wind turbines is a critical need in this currently fast growing industry. The structural integrity of the turbine blades themselves is critical to the continued operation of a wind turbine. It is well known that the resonant or modal properties of a mechanical structure are directly influenced by its physical properties. Hence, any change in the physical properties of a structure should cause a change in its modal parameters. One question is always apparent though; "Do structural faults cause significant changes in a structure's modal parameters?" In this paper, we present test results from a wind turbine blade with different cracks induced in it. Each result shows that some of the modes of the blade are significantly affected by a crack, and that the modal parameters change more significantly with a more severe crack. Changes in modal frequency, damping, and mode shape are considered. Using changes in modal parameters to indicate physical damage to turbine blades should be implemented in the online continuous monitoring of wind turbines. In such a system, differences between monitored modal parameters and their base-line values could be compared to both absolute and percentage difference warning levels. Comparing changes between operating and baseline modal parameters with warning levels will indicate when the blades of a wind turbine have undergone physical damage. Source


Zhuge J.,Crystal Instruments | Richardson M.,Vibrant Technology Inc
Sound and Vibration | Year: 2010

The four generations of digital vibration control systems (VCS) that are categorized as standalone, PC-based, PC-tethered, and fully networked developed by US companies are discussed. One of the earliest digital VCS (HP5427) was developed by Hewlett Packard and another company, General Radio Company, produced Gen-Rad GR2500 series standalone control system, which was the most successful controller sold during the 1980. The first second generation VCS, DP540, was developed by Data Physics, which had an impressive and flexible graphical user interface. The DP540 used multiple ISA plug-in DSP cards for inputting control signals to the PC and outputting the drive signal. Dactron Incorporation worked for the development of the next generation VCS and designed Dactron LASER series, in which PC was not used in the control loop, but only as a peripheral of the VCS. The fourth generation VCS, Spider-81, is developed by Crystal Instruments in the year 2010, which integrates the IEEE 1588 time synchronization technology into its design. Source


Ganeriwala S.N.,SpectraQuest Inc. | Yang J.,SpectraQuest Inc. | Richardson M.,Vibrant Technology Inc
Sound and Vibration | Year: 2011

The structural integrity of blades is critical to the continued operation of a wind turbine. Resonant or modal properties of a mechanical structure are directly influenced by its physical properties. So any change in the physical properties of a structure should cause a change in its modal parameters. In this article, we present test results from a wind turbine blade with different induced cracks. Each result shows that some of the modes of the blade are significantly affected by a crack and that the modal parameters change more significantly with a more severe crack. Source


Formenti D.L.,Blackhawk Technology Company | Ottman D.,Hillerich and Bradsby Co. | Richardson M.H.,Vibrant Technology Inc
Conference Proceedings of the Society for Experimental Mechanics Series | Year: 2011

In this paper, we demonstrate a new approach to evaluating the dynamic behavior of baseball bats. Using this approach we can compare the ball striking one spot on a bat versus another, and also compare the performance of one bat design versus another. We can quantity a ball striking the "sweet spot" on a bat versus the "sting" felt at the handle when the ball strikes the wrong spot. This new approach uses IRFs (Impulse Response Functions), which simulate the impact of a ball striking a bat. The IRFs are synthesized using an experimentally derived modal model of the bat. The modal data is obtained by a standard roving impact test of the bat. Two different quantitative measures are used for comparing IRFs. One measure is called the SCC (Shape Correlation Coefficient). It is a numerical measure of the co-linearity of two deflection shapes. It is the same as the FRAC (Frequency Response Assurance Criterion) calculation, but we apply it to the time domain IRFs as well as frequency domain FRFs. The second numerical measure is called the SPD (Shape Percent Difference). The SPD is a numerical measure of the difference between two deflection shapes. It not only indicates when two shapes are different, but quantifies the magnitude of their difference. The IRFs of several different baseball bats are compared using both the SCC and SPD calculations over all time samples. These measures show graphically how similar or different the impulse responses of different bats are. ©2010 Society for Experimental Mechanics Inc. Source


Schwarz B.,Vibrant Technology Inc | Richardson M.,Vibrant Technology Inc
Conference Proceedings of the Society for Experimental Mechanics Series | Year: 2014

Damping forces are typically ignored during the Finite Element Analysis (FEA) of mechanical structures. In most real structures, it can be assumed that there are several damping mechanisms at work, but they may be difficult to identify, and even more difficult to model. Since both mass & stiffness matrices are available during an FEA, a common method of modeling viscous damping is with a proportional damping matrix. That is, the viscous damping matrix is assumed to be a linear combination of the mass & stiffness matrices. Therefore, in order to model viscous damping with a proportional damping matrix, the two constants of proportionality must be determined. In this paper, a least-squared-error relationship between experimental modal frequency & damping and the proportional damping constants of proportionality is developed. An example is included in which experimental modal parameters are used to calculate the constants of proportionality. The modal parameters of an FEA model with proportional damping are then compared with the original experimental modal parameters. © The Society for Experimental Mechanics 2014. Source

Discover hidden collaborations