Theoretical and experimental comparison of point mobility measurement methods
Author
Shabalin, Dmytro
Term
4. term
Education
Publication year
2013
Pages
64
Abstract
This thesis investigates the strengths and weaknesses of point mobility measurement methods by comparing a new approach based on localized acoustic excitation with the conventional “shaker via stinger” technique. The work covers the theoretical basis for two-channel FFT analysis, fundamentals of acoustics, beam vibration analysis using Bernoulli–Euler theory, and FEM-based modal and harmonic (mode superposition) analysis. A robust acoustic excitation device, denoted adaptor m#3, is developed with an emphasis on usability and stability; it integrates two transducers in a single stiff enclosure to improve robustness. The adaptor m#3 method is validated on a cantilever beam by comparing results with both analytical solutions and measurements from the shaker method, showing general agreement and indicating that adaptor m#3 is more robust with satisfactory accuracy. The method is then applied to the vibration analysis of a compressor housing shell and compared with FEM simulations. Findings suggest that simplified numerical models can yield inaccurate results at certain excitation points, whereas measurement-based results are more precise and reliable. Overall, adaptor m#3 is concluded to be a practical and robust prototype for measuring dynamic properties of mechanical systems, with potential for further development to enhance accuracy.
Dette speciale undersøger styrker og svagheder ved metoder til måling af punktmobilitet og sammenligner en ny metode baseret på lokaliseret akustisk eksitation med den konventionelle “shaker via stinger”. Arbejdet omfatter teoretisk grundlag for tokanals FFT-analyse, grundlæggende akustik, vibrationsanalyse af bjælker med Bernoulli–Euler-teori samt FEM-baseret modal- og harmonisk (modesuperpositions-)analyse. En robust akustisk eksitationsenhed, kaldet adaptor m#3, udvikles med fokus på brugervenlighed og stabilitet; den integrerer to transducere i én stiv kapsling for bedre robusthed. Metoden med adaptor m#3 valideres på en udkraget bjælke ved at sammenligne resultater med både analytiske løsninger og målinger fra “shaker via stinger”, hvor der generelt ses god overensstemmelse, og adaptor m#3 fremstår mere robust med tilfredsstillende nøjagtighed. Den nye metode anvendes derefter til vibrationsanalyse af en skalstruktur fra et kompressorhus og sammenholdes med FEM-simuleringer. Resultaterne indikerer, at forenklede numeriske modeller for visse eksitationspunkter kan give misvisende resultater, mens målinger giver mere præcise og pålidelige data. Samlet konkluderes det, at adaptor m#3 er en brugbar og robust prototype til måling af dynamiske egenskaber i mekaniske systemer, som kan videreudvikles for øget præcision.
[This apstract has been generated with the help of AI directly from the project full text]