Dijital Fotogrametri Tabanlı Başlangıç Kusurlarının Gemi Tipi Desteklenmiş Levhaların NLFEM ile Nihai Mukavemet Analizlerinde Kullanılabilirliğinin İncelenmesi

Abstract

Bu çalışmada, başlangıç sehimlerinin gemi tipi desteklenmiş panel yapılarının nihai mukavemet değerleri üzerindeki etkileri, başlangıç sehim formlarının nasıl elde edildiği açısından ele alınmış ve analiz edilmiştir. Gemilerdeki desteklenmiş paneller, operasyonel ömürleri boyunca karmaşık yükleme koşullarına maruz kalmakta ve yapısal bütünlüklerinin korunmasını kaçınılmaz hale getirmektedir. Mukavemetlerinin ve göçme modlarının doğru bir şekilde tahmin edilmesi, çeşitli kusurların davranışları üzerindeki etkilerinin kapsamlı bir şekilde anlaşılmasını gerektirir. Bu çalışmada, başlangıç kusurlarının iki temel kaynağı ele alınmıştır. Bunlar, doğrusal öz değer burkulma analizi sonuçları ve dijital fotogrametri tabanlı ölçümler sonucunda ortaya çıkan burkulma modu şekilleridir. Üretim sürecinden kaynaklanan burkulma modu şekilleri, doğrusal statik yapısal analiz kullanılarak elde edilmiştir. Öte yandan, fiziksel yapının yüksek çözünürlüklü görüntülerini analiz ederek kusurları yakalamak ve ölçmek için dijital fotogrametri kullanılmıştır. Sayısal hesaplamalar, bu iki tür başlangıç kusurunun doğrusal olmayan sonlu elemanlar yöntemi (NLFEM) analizlerine dahil edilmesiyle gerçekleştirilmiştir. Burkulma modu kusurları geometrik düzensizlikler olarak uygulanırken, fotogrametri tabanlı kusurlar ideal geometriden istatistiksel olarak temsili sapmalar olarak elde edilmiştir. Desteklenmiş panelin yapısal davranışı, boyuna tek eksenli basınç yüklemesi altında analiz edilmiştir. Ansys 2019R2 versiyonundan itibaren artık kullanılmayan Türk Loydu'nun S.P 01/19 teknik genelgesinde verilen prosedür yerine yeni bir NLFEM proje şeması kullanılmıştır. Önerilen bu yöntemin geçerliliği, Ansys 2022R2 versiyonunda, burkulma modu başlangıç kusurlarını dikkate alan iki doğrulama çalışması ile kanıtlanmıştır. Daha sonra, Trabzon'daki bir tersanede imal edilen modelden dijital fotogrametri yöntemi ile Photomodeler V. 2023.3.0.238 programında oluşturulan desteklenmiş panel yapısı için bir uygulama çalışması yapılmıştır. NLFEM analizi, hem öz değer burkulma analizinden sonra elde edilen başlangıç sehimleri modeli ile hem de kaynak montaj işlemlerinden sonra doğal olarak yapısal bozulmalara uğramış model için gerçekleştirilmiştir. Karşılaştırmalı nihai mukavemet sonuçları oldukça tutarlı belirlenmiş ve bu da dijital fotogrametrik modelleme yönteminin gemi yapı elemanlarının mukavemet analizinde kullanılabileceğini göstermiştir.

Keywords

• Gemi mukavemeti
• başlangıç kusurları
• nihai mukavemet
• NLFEM
• Dijital Fotogrametri
• desteklenmiş levha

Evaluation of the Applicability of Digital Photogrammetry-Based Initial Imperfections on NLFEM Ultimate Strength Analysis of Ship- Type Stiffened Plates

Abstract

In this study, the effects of initial imperfections on the ultimate strength values of ship-type stiffened plate structures are discussed and analysed from the point of view of how the initial imperfection forms are obtained. Ship stiffened panels are subjected to complex loading conditions during their operational lifespan. Accurate prediction of their strength and failure modes necessitates a thorough understanding of the effects of various imperfections on their behavior. Two primary sources of initial imperfections are considered: the buckling mode shapes resulting from linear eigenvalue buckling analysis and measurements based on digital photogrammetry. Buckling mode shapes, arising from the manufacturing process are extracted using linear static structural analysis. Digital photogrammetry is employed to capture and quantify imperfections by analysing high-resolution images of the physical structure. Numerical investigation is conducted by incorporating these two types of initial imperfections into non-linear finite element method (NLFEM) calculations. The buckling mode imperfections are applied as geometric perturbations, while the photogrammetry-based imperfections are incorporated as statistically representative deviations from the ideal geometry. Stiffened panel's structural response is analysed under longitudinal uniaxial compression. A new NLFEM project schematic has been utilized instead of the procedure outlined in the technical circular S.P 01/19 by Türk Loydu, which has been discontinued after ANSYS® Workbench™V.2019R2. This is proven by two validation case studies in ANSYS® Workbench™2022R2 version for considering buckling mode initial imperfections. A case study is then conducted using a 3D model of a stiffened plate panel, which is fabricated in a shipyard located in Trabzon, created by Photomodeler V. 2023.3.0.238 employing the digital photogrammetry method.NLFEM analysis is carried out for both initially deflected model after eigenvalue buckling analysis and naturally deflected model after welding operations. The comparative ultimate strength results are quite consistent, and this shows that the digital photogrammetric modelling method can be used in the analysis of ship structural elements.

Keywords

• Ship strength
• stiffened plate
• initial imperfection
• ultimate strength
• NLFEM
• Digital Photogrammetry

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