Orhan ÇAKAR, Kenan Yüce ŞANLITÜRK

Frekans tepki fonksiyonlarından transdüser kütle etkilerinin kaldırılması

Frekans Tepki Fonksiyonlarının (FTF) kalitesinin parazit ve sistematik hatalar gibi faktörlerle olumsuz yönde etkilendiği bilinmektedir. FTF’larını kullanan çeşitli analizlerin doğruluğu ve güvenilirliği de ölçülmüş verilerin kalitesine bağlıdır. Bu çalışma ölçülmüş FTF’larındaki en önemli sistematik hatalardan biri olan transdüser kütle etkisini kaldırmayı amaçlamaktadır. Bu çalışmada ölçülmüş FTF’larındaki transdüser kütle etkisinin kaldırılması için Sherman-Morrison eşitliğine dayalı olarak geliştirilen yeni bir yöntem sunulmaktadır. Burada sunulan formülasyon genel amaçlıdır ve hem sabit hem de hareketli transdüser durumlarına uygulanabilmektedir. Transdüserin gezdirildiği test durumunda yardımcı bir kütle kullanımından yararlanılmaktadır. Bununla beraber, yapının transfer FTF’nun ölçümünde yardımcı kütle kullanımına gerek duyulmaması yeni yöntemin üstün özelliklerinden biridir. Bu sayede transfer FTF’nda ilave etkiler oluşturulmamaktadır. Yöntemin uygulanabilirliği sayısal simülasyonlarla ve deneysel veriler kullanılarak incelenmiştir.

Elimination of transducer mass loading effects from frequency response functions

It is well known that the quality of measured Frequency Response Functions (FRFs) is adversely affected by many factors, most significant sources being noise and systematic errors. It is also known that the accuracy and the reliability of various analyses using the measured FRFs depend strongly on the quality of measured data. This paper aims to remove one of the major systematic errors in measured FRFs, namely the mass loading effects of transducers. This paper presents a new method based on the Sherman-Morrison identity for the elimination of mass loading effects of transducers from measured FRFs. The formulation presented here is general in the sense that it can be applied for both fixed and moving transducer cases. In the case of moving transducer type of tests, the use of dummy mass is utilized. However, one of the distinct features of the new method is that it avoids the need for the measurement of cross-FRFs of a structure with a dummy mass attached to the structure, hence avoiding further contamination of cross-FRFs. The applicability of the method is also assessed using experimental as well as simulated data.

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