Mahmut PEKEDİS, Hasan YILDIZ

Tabakalı kompozit bir kiriş ve levhada hasar tespitinin model tabanlı yapı sağlığı izleme teknikleriyle belirlenmesi

Bu çalışmada, model tabanlı hasar tespit tekniği algoritmaları, iç bölgelerinde delaminasyon içeren tabakalı kompozit kiriş ve levhaya uygulanmıştır. Başlangıçta, sağlıklı ve delaminasyon içeren tabakalı kompozit kiriş, deneysel olarak modal testler uygulanarak doğal frekanslar bulunmuştur. Daha sonra, sağlıklı ve hasarlı yapıya ilişkin ölçülen doğal frekanslar nümerik yöntem sonuçları ile doğrulanmıştır. Doğrulanma işlemleri tamamlandıktan sonra, sonlu elemanlar yöntemi, delaminasyon içeren tabakalı kompozit bir kiriş ve levha üzerinde uygulanıp mod şekilleri çıkartılmıştır. Mod şekillerinden eğrilik yüzeyleri çıkartılmış ve daha sonra aralıklı düzgünleştirme metodu (ADM) ile birim şekil değiştirme enerjisinde (BŞDE) kullanılarak delaminasyonun olduğu bölgeler tespit edilmiştir. Kompozit levhadaki hasar tespitleri iki farklı durum için değerlendirilmiştir. Birinci durum da, yapının başlangıçtaki sağlık durumunun biliniyor varsayımı ile tanılamalar yapılmıştır. Ancak bazen hasar tespiti yapılırken hasara uğramış yapının, hasara uğramadan önceki verileri bulunmayabilir. Bu amaçla, ikinci durumun değerlendirilmesinde hasarlı yapıya ait eğrilik modları, yüzey uydurma algoritmasıyla hasara uğramamış gibi kabul edilerek hasar tespitleri yapılmıştır. Hasar teşhisi için her iki algoritma her iki durum için değerlendirilmiştir. Elde edilen sonuçlardan, laboratuvar ortamında kompozit malzemelerden imal edilen kompozit kiriş ve levhanın iç bölgelerinde oluşan delaminasyonlar, deneysel veya nümerik yöntemlerden alınan verilerin model analiz tabanlı YSİ yaklaşımlarında kullanılmasıyla, tahribatsız bir şekilde tahmin edilebileceği kanaatine varılmıştır.

Damage diagnosis of a laminated composite beam and plate via model based structural health monitoring techniques

In this study, model based damage identification algorithms were applied for a delaminated composite beam and plate. Initially, natural frequencies of healthy and delaminated beam were measured via experimental modal analysis. Next, the natural frequencies obtained by experimental method were verified with the finite element analysis. Once the validation has been fulfilled, the next step was to apply the finite element analysis to extract the mode shapes. Then, the curvatures mode shapes were obtained from the mode shapes, and these parameters were used in the gapped smooth method (GSM) and strain energy method (SEM) to detect the location and size of the delamination. The damage diagnosis technique for composite plate was evaluated for two cases. In the first case, it was assumed that the initial health information of a structure is known. However, the information of an undamaged structure may not be available during the diagnosis process for some circumstances. Therefore, the diagnosis was conducted by evaluating the curvatures of damaged structure using surface fit techniques in order to predict the initial status for the second case. Both of the two damage detection algorithms were evaluated for these two cases. The results show that, the delamination of laminated composite beam and plate could be predicted non-destructively by employing the data obtained from experimental or numerical technique in model based SHM approach for laboratory conditions.

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