Structural modification with additional degrees of freedom in large systems

Canbaloğlu, Güvenç
In the design and development stages of mechanical structures, it is important to predict the dynamic characteristics of modified structures. Since time and cost are critical in design and development stage, structural modification methods predicting the dynamic responses of modified structures from those of the original structure and modification properties are very important, especially for large systems. In this thesis structural modification methods are investigated and an effective structural modification method for modifications with additional degrees of freedom is adapted to structures with distributed modifications and the performance of the method is investigated. A software program is developed in order to apply the structural modification method with additional degrees of freedom. In the software, the dynamic response of the modified structure is predicted by using the modal analysis results of ANSYS for the original structure and dynamic stiffness matrix of the modifying structure. In order to validate the approach used and the program developed, the dynamic analysis results obtained for modified structures by ANSYS are compared with those obtained by using the software. In order to investigate the performance of the structural modification method in real applications, the method is applied to a scaled aircraft model, and the results are compared with experimental results. In order to demonstrate the importance of using the structural modification method with additional degrees of freedom for distributed modification, lumped and distributed models are used for a distributed modification and results are compared. It is concluded in this study that using structural modification methods with additional degrees of freedom for a distributed modification increases the accuracy of the results, and it is observed that the method adapted is efficient for local modifications.


Structural Optimization Using ANSYS
Panayırcı, H. Murat; Oral, Süha; Department of Mechanical Engineering (2006)
This study describes the process of performing structural optimization using ANSYS. In the first part, the general concepts in optimization and optimization algorithms for different type of optimization problems are covered. Also finite element method is introduced briefly in this part. In the second part, important definitions in structural optimization are mentioned. Then the optimization methods available in ANSYS are explained with their theories. Necessary steps to perform optimization with ANSYS are d...
Mechanical properties identification of viscoelastic / hyperelastic materials based on experimental data
Tabakcı, Alican; Konukseven, Erhan İlhan; Erkmen, Aydan Müşerref; Department of Mechanical Engineering (2010)
Mechanical simulation of viscoelastic materials and assigning a viscoelastic material to the modeled parts in the simulations are difficult task. For the simulations, material model should be well chosen and material coefficients of the chosen models should be known. In order to obtain accurate simulations, hyperelastic characteristics of the viscoelastic materials should be investigated and hyperelastic model should be incorporated in the solutions. Material models and material model’s coefficients are cho...
Analysis of thin walled open section tapered beams using hybrid stress finite element method
Akman, Mehmet Nazım; Oral, Süha; Department of Mechanical Engineering (2008)
In this thesis, hybrid stress finite element is formulated for the analysis of the isotropic, thin walled, open section beams with variable cross sections. The beam element has two nodes each having seven degrees of freedom. Assumption of stress field is sufficient to determine the element stiffness matrix. Axial, flexural and torsional effects are taken into account in the analysis. The methodology can be applied both to the tapered and the uniform beams. Throughout this study, firstly element cross-sectio...
Fabrication of high density alumina ceramics from nanopowders through colloidal processing.
Kayacı, Hüseyin Utkucan; Çınar, Simge; Department of Metallurgical and Materials Engineering (2020)
Utilizing nanopowders in production of fully dense materials with fine grain structures is highly advantageous, particularly where high mechanical properties are desired. Besides, recently developed techniques, such as 3D-printing of ceramics, may require high solids content suspensions. Despite the advantages of slurry based processing of oxide ceramics, production of nano-structured high density bodies is still a challenge. The main limitation in colloidal processing of nanopowders is their unexpectedly h...
Finite element structural model updating by using experimental frequency response functions
Öztürk, Murat; Özgüven, Hasan Nevzat; Department of Mechanical Engineering (2009)
Initial forms of analytical models created to simulate real engineering structures may generally yield dynamic response predictions different than those obtained from experimental tests. Since testing a real structure under every possible excitation is not practical, it is essential to transform the initial mathematical model to a model which reflects the characteristics of the actual structure in a better way. By using structural model updating techniques, the initial mathematical model is adjusted so that...
Citation Formats
G. Canbaloğlu, “Structural modification with additional degrees of freedom in large systems,” M.S. - Master of Science, Middle East Technical University, 2009.