Strain Gage Ramifications on Mistuning in As-Manufactured Models and Experimental Testing

Blade-mounted strain gages are vital during rig and engine development to ensure safe engine operation. However, they also enable a change in dynamics of integrally bladed rotors (IBRs). State-of-the-art IBR dynamic response predictions are accomplished using as-manufactured models (AMMs) generated via optical topography measurements and mesh morphing. Two AMM finite element models (FEMs) are created of a 20-bladed IBR. One FEM has no strain gages present, where the second FEM includes strain gages on six blades. Traditionally, strain gages and lead wires are treated as the same material property as the IBR itself. It will be shown that the inclusion of strain gages in AMM's using this method changes the IBR's predicted mistuning. An alternative AMM approach is developed that changes the material properties of the finite elements attributed to the strain gages. The predicted mistuning for each AMM is accomplished using the fundamental mistuning model identification (FMM ID), where the predicted mistuning will be compared to both traveling wave excitation (TWE) experiments and a rotating, single stage compressor rig. Findings show mistuning predictions of the nonstrain gaged AMM compare far better to the experiments compared to the inclusion of the strain gages in the AMM. Additionally, altering material properties of the strain gages in the AMM improve mistuning prediction compared to treating the strain gages as the parent IBR material. Therefore, AMM should be acquired using clean, nonstrain gaged rotors or the material properties of strain gaged elements need to be altered to more accurately model the component.

Analisis of posture in school-age children according to optical topography

Purpose of study: the study of posture in school children in three planes according to computer optical topography. Patients and methods. A screening examination of 1835 children was performed using computer optical topography of the back, the average age was 11.2±1.7 years, girls 930 (50.6%), boys 905 (49.3%). Results and conclusion. The study showed that computer optical topography is a highly effective method for screening diagnostics of posture disorders in school children, posture disorders are a common condition, according to the topographic classification of posture disorders, occur in 69.46% of school age children.