Experimental Modal Analysis of a First Stage Blade in ALSTOM Gas Turbine

Failures of turbine blades are one of the most critical problems in power generating industry. Among the different failure mechanisms, resonant vibration of blades has a major role and therefore is the subject of many recent research works. Therefore, in this paper, modal analysis of a first stage blade in ALSTOM gas turbine is investigated and natural frequencies and vibration modes of blade are found in various conditions. For this purpose, a cloud-point model of a gas turbine blade has been created using 3D Laser Digitizer. Then the numerical calculation by finite element method using ANSYS software based on experimental test conditions is utilized and Experimental natural frequencies have been obtained. The results show acceptable agreement between the experimental and FEM results.

Laser Digitizer/Stereo Vision Methods for Simultaneous Measurement/Analysis of Sheet Metal Forming Strain/Geometry

Conventionally, strain has been measured using scribed, etched, or printed grids together with a ruler and dividers or a graduated, transparent Mylar® overlay. Touch trigger probe equipped Coordinate Measuring Machines (CMMs) are used to measure geometry. More recently, stereo computer vision has been proposed, but, because accuracy quickly diminishes with camera distance to the part, application has been limited to small test samples. On CMMs, laser digitizers are growing in use. To date, however, accurate, simultaneous measurement / analysis of both strain and geometry has not been reported. This paper presents two new CMM based research methods that address this. The laser digitizer method uses a circle grid, and the stereo computer vision approach uses a square grid. Parallel computing is used to accelerate computer processing time. A dual thickness tailor welded steel test dome, an aluminum test dome, and a wrinkled double layer truck part illustrate practical application.