Serbest-Serbest Sınır Koşullarında Askı İpi Malzemesinin Modal Parametreler Üzerindeki Etkisinin Deneysel Araştırması

Abstract

Mühendislik yapılarının tasarım aşamasında, dinamik davranışlarının doğru bir şekilde belirlenmesi, uzun ömürlü ve güvenli bir kullanım için hayati öneme sahiptir. Bu amaçla yaygın olarak kullanılan yöntemlerden biri olan Deneysel Modal Analiz (DMA), yapıların doğal frekansları, sönüm oranları ve frekans yanıtı gibi temel modal parametrelerini sağlayarak dinamik davranışlarını ortaya koyar. DMA uygulamalarında yapılara, genellikle tek veya çoklu noktalardan kuvvet uygulanır ve yanıtlar çeşitli sınır koşulları altında sensörler aracılığıyla ölçülür. Bu sınır koşullarından biri olan serbest-serbest (free-free) koşulu, yapıların iplerle askıya alınarak kısıtlanmamış bir davranış sergilemesini simüle eder. Bu çalışmanın amacı, askı ipi malzemesinin bir yapının dinamik davranışları üzerindeki etkisini incelemektedir. Deneylerde iki farklı ip malzemeden - naylon ve kauçuk - oluşan dört farklı kombinasyon kullanılmıştır. Sonuçlar, farklı askı malzemeleri kullanıldığında doğal frekansların büyük ölçüde değişmediğini, ancak sönüm oranlarının belirgin şekilde etkilendiğini göstermektedir. Ayrıca, harmonik yanıt ölçümleri, askı malzemesinden kaynaklanan sönüm oranı farklarının açıkça tespit edilebildiğini doğrulamaktadır.

Keywords

• : Deneysel Modal Analiz
• Doğal Frekans
• Sönümleme oranı
• Serbest-Serbest sınır koşulu

Experimental Investigation of Suspension Cord Material Influence on Modal Parameters in Free-Free Boundary Conditions

Abstract

During the design stage of engineering structures, determining their dynamic response is essential to ensure performance and long service life. Experimental Modal Analysis (EMA) is a widely used method for this purpose, as it provides critical modal parameters (natural frequencies, damping ratios, frequency response) and reveals the dynamic behavior of structures. In the EMA, structures are typically excited at single or multiple locations, and the responses are measured using sensors under various boundary conditions. One common approach is the free-free boundary condition, which involves suspending test structures using suspension cords to simulate unconstrained behavior. This study investigates how the material of suspension cords affects the dynamic characteristics of a structure. Two cord materials—nylon and rubber—along with four different combinations of these cords were tested. Results indicate that while the natural frequencies remain unchanged (%1-%2 difference) across different suspension materials, the damping ratio is notably affected. The measured damping ratios ranged from 0.95% (nylon) to 3.45% (rubber), demonstrating the significant influence of suspension material on energy dissipation. Additionally, harmonic response measurements confirm that differences in damping ratios due to the suspension material are clearly detectable.

Keywords

• Experimental Modal Analysis
• Natural Frequency
• Damping Ratio
• Free-Free Boundary Condition

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