Structural analysis	Time series analysis

Using PV-WAVE visual data analysis (VDA) software from Visual Numerics with data acquisition equipment and workstations from Hewlett-Packard^®, AAR engineers collect as much as 30 gigabytes of data from one metal fatigue experiment. After hundreds of railcar-mounted sensors collect the data, they are converted into a custom binary format and stored on huge data servers for future analysis. The value of this work depends on the quality of the data. At the high data-collection rates used in these studies, it's not uncommon to miss critical data samples. And because different instruments represent experimental values differently, the data must be scaled and normalized into a common range so values can be compared. This process of scaling data, converting them into engineering units and interpolating missing values is the linchpin of a successful experiment.

After the data are collected, checked and stored, postanalysis begins. Much postanalysis work involves time-series analysis like frequency domain and vibration analysis. PV-WAVE provides a variety of powerful functions for time-series analysis in single or multiple dimensions, including fast Fourier transformations, filtering, power-spectrum estimation and related functions like curve-fitting and interpolation. The AAR engineers also use statistic functions like averages, covariance, correlation and regression analysis to assess the test results, comparing design parameters with railroad safety standards. And because most research requires some custom analysis, PV-WAVE gives engineers the flexibility to build custom functions.

Advanced computer graphics are another key part of the postanalysis process because they help engineers make research discoveries that might otherwise have been missed. For most of the research, AAR engineers use interactive 2D plots and contours. For example, plots showing stress versus time or color contours showing stress distribution over a region can easily be produced in PV-WAVE, even for very large data sets. To help make even faster discoveries, however, AAR engineers rely on PV-WAVE's more advanced graphics.

Rich Higgins, data systems manager at the AAR research facility, says, "Until we had PV-WAVE, we weren't able to use 3D graphics and images effectively. We couldn't do more than 2D graphics. PV-WAVE is so fast and flexible that we're beginning to see the benefits of more advanced graphics."

After the analysis and graphics are completed, professional hard-copy output must be produced and integrated into publications so results can be shared. As Higgins explains, "Our end product is a final report detailing the test results. The data and results must be presented in a meaningful way so our customers can benefit from our discoveries."

Visual data analysis with PV-WAVE helps AAR engineers make more discoveries faster because of the power that integrated graphics and analysis bring to the desktop. And, thanks to PV-WAVE's easy-to-use menu and icon interface, users don't have to be computer scientists. This lets researchers spend more time on research and less time learning how to use the software. For AAR engineers, PV-WAVE is a cost-effective solution to a wide variety of postanalysis needs. These benefits translate into productivity -- more quality work done in less time and results that can easily be shared with colleagues. "With PV-WAVE, we spend less time reducing our data and more time interpreting results. We can do in minutes what used to take days," Higgins concluded.