عنوان البحث(Papers / Research Title)
Detection of Crack in a Simple Unswept Wing Using Free Vibration Analysis
الناشر \ المحرر \ الكاتب (Author / Editor / Publisher)
نورس حيدر مصطفى أل سيد حيدر
Citation Information
نورس,حيدر,مصطفى,أل,سيد,حيدر ,Detection of Crack in a Simple Unswept Wing Using Free Vibration Analysis , Time 5/5/2011 3:50:44 PM : كلية الهندسة
وصف الابستركت (Abstract)
البحث منشور في المجلة العراقية للهندسة الميكانيكية و هندسة المواد
الوصف الكامل (Full Abstract)
Detection of Crack in a Simple Unswept Wing Using Free Vibration AnalysisHatem. H. Obeid, Nawras Haidar Mostafa, Salwan Obeed Waheed, and Sattar Hantosh College of EngineeringBabylon University, Iraq, 2008
Abstract:
The present research is concerned with an investigation of the vibration characteristics of a cracked wing structure. Finite element method has been used to formulate the free vibration analysis. Ansys v9.0 program was used as a mathematical tool in implementation the analysis and extract the results. Effect of several parameters such as (effect of crack ratio, crack location, and crack inclination angle) on the natural frequencies and mode shapes were studied. The results indicate that the natural frequencies are affected in the presence of a crack; but it doesn’t give an indication to the crack location. While, using mode shape is a powerful tool to detect the crack and its magnitude along the wing’s length. The crack inclination angle is investigated to show its effect on the crack identification where relatively little error may appear if crack angle wasn’t normal to the wing axis. Also the presence of the crack may cause to transform and exchange the modes between each other depending on the crack location and its magnitude.
Introduction:
Vibration monitoring has great potential for machine condition monitoring. One form of damage that can lead to catastrophic failure if undetected is fatigue cracking of the structural elements. A crack in an elastic structural element introduces considerable local flexibility due to the strain energy concentration in the vicinity of the crack tip under load. Long ago, this effect was recognized and the idea of an equivalent spring, a local compliance, was used to quantify in a macroscopic way the relation between the applied load and the strain concentration around the tip of the crack (Chondros, 1998)
One-dimensional beam or box-beam models are widely used as the analytical approach to investigate the primary aeroelastic phenomena during the initial design of an aircraft wing. The most important variables that affect the aerodynamic forces as well as the wing’s dynamics are the flexural deflection along the wingspan and the twisting of camber about a spanwise axis. The problem of the understanding of the dynamics of a structure is largely depends on the way of various damages undertaken. Since damage (e.g., crack, corrosion, creep) in a structure usually changes the mass, stiffness and/or damping distribution of the structure either locally or globally, vibration characteristics of the structure may be changed so that evaluation of vibration responses may be used to detect the damage. The importance and summary on previous research can be found in several survey papers, for instance the one by Doebling et al. (1998).
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