車架之實驗模態分析實務與振動模態特性探討

Practical Approach of Experimental Modal Analysis on the Frame Structure and its Vibration Characteristics Study

王栢村 ； 陳昱成 ； 陳勇全

《中華民國振動與噪音工程學會論文集》 2010 (2010/06) Pp. 123-128

https://doi.org/10.30028/CSSVANNUAL.201006.0123

摘要

車架之強度與安全性為車輛設計主要考慮因素之一，而車架振動特性也為有興趣之設計重要參考資訊。本文應用實驗模態分析(experimental modal analysis, EMA)技術於一多功能車輛(utility vehicle, UV)車架以探討其振動特性，藉由EMA可求得結構模態參數，包括：自然頻率、模態振型及模態阻尼比。本文介紹針對此UV車架之EMA實務方法步驟，包括：驅動器及感測器選擇、量測點規劃、EMA預測試方法、量測之頻率響應函數(frequency response function, FRF)檢視、曲線嵌合或稱模態參數擷取、以及EMA測試結果評估等，分別探討EMA規劃、實驗與量測數據後處理之實務技巧，也針對典型EMA實驗結果，包括FRF、操作變形振型(operational deflection shape, ODS)、及模態參數，就UV車架結構之振動特性做探討，實驗所得之模態參數除了可以作為確認分析模型之模型驗證外，也是結構設計變更之重要參考依據，本文完整呈現針對UV車架三維結構進行EMA之詳細探討。

關鍵字

實驗模態分析 ； 頻率響應函數 ； 模態參數 ； 多功能車輛 ； 車架結構

並列摘要

One of major concerns about the vehicle frame structure is strength and safety, and its vibration characteristics are also of interest. This work applies the experimental modal analysis (EMA) to the utility vehicle (UV) frame structure to study its vibration characteristics. The modal parameters, i.e. natural frequencies, mode shapes and modal damping ratios, can be obtained by EMA. This work presents the procedure of EMA, in particular applied to the UV frame structure, including the selection of actuator and sensor for measurement, the measurement grid point layout, the pretest for EMA, the evaluation on measured frequency response functions (FRFs), curve fitting process or so called modal parameter extraction, and, finally, the test results evaluation. The practical concerns of EMA in planning and measurement as well as post processing on the measured data are discussed. The typical results of EMA experiments, including FRFs, ODS, modal parameters are shown to reveal the UV frame structural vibration characteristics. The obtained experimental modal parameters can be used not only for structural model verification to validate the analytical model but also the important information for structural design modification. This work presents the practical approach of EMA, in particular for the three-dimensional UV frame structure.

並列關鍵字

experimental modal analysis ； frequency response function ； utility vehicle ； frame structure