12 research outputs found
Fluid-Structure Interaction Analysis of a Cropped Delta Wing
No full textAbstractThe fluid-structure interaction behaviour of a cropped delta wing is investigated using a computational fluid dynamics (CFD) based aeroelastic solver in time domain. Here, an N-S based finite volume solver is coupled with a finite element based linear and nonlinear structural solvers to study the nonlinear aeroelastic characteristics of the delta wing over a range of dynamic pressures. The amplitude and frequency obtained from the present coupled solver at various dynamic pressures are compared with the available experimental and computational results
Dynamic aeroelastic subsonic discrete gust response analysis of lifting surfaces in time domain using Newark's method.
No full textThe Dynamic gust response analysis of lifting surfaces of aerospace structures requires attention to two main factors, namely, the character of the gust and the aeroelastic effects. In the present work,the Dynamic aeroelastic response of subsonic airplane in discrete gusts is determined using Newmark's direct integration method.The adopted time domain method is a departure from the usual modal analysis and the frequency domain approach.The aerodynamic strip theory is assumed,but compressibility and aspect ratio corrections may be included,if desired.The method has been validated by performing discrete gust response analysis of an airfoil model of the elastic wing flying through sharp-edged gust.The unsteady aerodynamic forces on the wing are calculated from the theory of two-dimensional thin airfoils in non-uniform motion.The theory takes proper account of 'unsteadiness' by using the kussner's and Wagner's unsteady lift functions for calculating the aerodynamic forces.The pitching motion and tail effects are neglected.For validating the present work,the responses obtained from Newmark's method is compared with those reported in literature using Laplace method.It is found that the results are in close agreement with reported in the literature
A study on the fatigue crack growth behaviour of GTM718 nickel based super alloy under cold-TURBISTAN spectrum loads
No full textIn this study, the fatigue crack growth (FCG) behavior of GTM718 nickel base super alloy subjected to cold-TURBISTAN spectrum load sequence was determined by three different methods i.e., (i) Experimental, (ii) Analytical prediction using cycle-by-cycle method and, (iii) Prediction by finite element analysis (FEA). In the experimental method, a standard compact tension (CT) specimen was prepared and pre-cracked to produce a sharp fatigue crack at the notch root. Then, the specimen was subjected to spectrum load blocks repeatedly and crack growth was measured as a function of applied number of flights. Two such tests were carried out in a servo-hydraulic universal test machine with triangular waveform and at an average frequency of 2 Hz. In the second analytical method, the individual load cycles in cold-TURBISTAN spectrum block were separated through rain flow cycle counting method. For each of this counted cycle, the crack extension was determined using crack growth law which was based on two-parameter crack driving force, ΔK*. An in-house MATLAB code was written and used to determine the FCG behavior by cycle-by-cycle method. In the third FEA method, a global model of CT specimen of GTM718 was created in HYPERMESH and a local model with a pre-crack was created in FRANC3D. The FCG behavior under spectrum load was determined using FRANC3D in conjunction with MSC NASTRAN. Two different types of ‘FCG law - stress ratio effect’ combinations were employed i e., Paris’-Walker (P-W) and Bi-linear-Walker (B-W). The required constants for these laws were derived from the available experimental data of the material. It was observed that the predicted FCG behavior by analytical and FEA methods, although conservative, were fairly good when compared to experimental results
Investigación sobre la debilidad por fatiga de los nodos de vigas transversales antes y después del refuerzo del puente de acero en celosía
Get PDFIn this research, fatigue tests on full-size specimens are conducted for a steel cross-beam joint before and after reinforcement. Combined with a three-dimensional (3D) numerical simulation, the 3D stress parameters, and their redistribution rules study anew with a web crack and new crack initiation locations and fatigue weakness details are predicted. The research results include the following: 1) The empirical formula parameter m of the Z-axis stress for the new crack tip is approximately 0.05. 2) The fatigue performance of the web’s new crack tips is significantly improved by bolting reinforced steel plates, the stress range is reduced by 60%-98.78%, and the original crack stops growing in size. The health monitoring system can choose the predicted weak details as valid monitoring points so that the fatigue damage can be intelligently perceived after the reinforcement of steel bridges.En este estudio, la prueba de fatiga de una muestra a gran escala antes y después del refuerzo se llevó a cabo en la junta de viga transversal de un puente de acero. Combinado con la simulación numérica 3D, se estudiaron los parámetros de tensión 3D y las leyes de redistribución de las redes agrietadas, y se predijeron nuevas ubicaciones de grietas y detalles débiles por fatiga. Los resultados muestran que el refuerzo de la placa de acero atornillada puede mejorar la resistencia a la fatiga de la viga, y la amplitud de tensión de la punta de grieta de la placa de banda se puede reducir en más del 60%. Los puntos de monitoreo y medición se pueden establecer en los detalles débiles de la predicción, de modo que el daño por fatiga en el funcionamiento del puente de acero en la etapa posterior del refuerzo se encuentre en un estado de percepción inteligente.
