curved surfaces

The isogeometric method was introduced to bridge the gap between computer-aided design (CAD) and analysis. This method offers advantages such as precise geometric modeling, suitable refinement methods, easy access to higher-order functions, and higher computational accuracy. The aim of this research is to provide an efficient method for applying the distributed loads on curved surfaces in isogeometric analysis. One of the main challenges in this method is how to apply boundary conditions on complex geometries. In curved models, some control points may not lie on the geometry, leading to ambiguity in the distribution of loads on these points. This study uses NURBS functions, which are standard non-interpolatory functions in CAD systems, to approximate the solution space and describe the geometry. Additionally, to leverage the capabilities of CAD tools, the process of importing geometries created in Rhino into isogeometric analysis using Bézier extraction is explained. The results confirm the accuracy and efficiency of the proposed method.

Improving the mechanical properties of the 3D printed parts by a 3D printer based on fused filament fabrication by continuous fibers (carbon, glass, and aramid) has been the focus of many researchers. Due to the nature of additive manufacturing processes that produce the parts layer by layer, in most of the research, continuous fibers are layered on a 2D surface. Robots with high degrees of freedom have been used in cases where fibers are placed on curved surfaces. In this research, a method for deposition of the continuous glass fibers on a curved surface is presented. This method is implemented on a simple and cheap 3D printer. The presented method is based on modifying the G-code, creating a rotating axis for the nozzle, and applying and using computer-aided design and manufacturing techniques. Finally, by 3D scanning of the printed sample and comparing it with the 3D model, the amount of deviation and tolerance of the surface form is determined. The obtained experimental results indicate the effectiveness of the presented method for the deposition of continuous fibers on curved surfaces. With the presented system, continuous fibers are deposited on a curved surface that consists of paths with different degrees of curvature, by simultaneous impregnation of fiber and polymer. Comparing the scanned sample with the printed sample shows that the maximum deviation is 0.1 mm. This error is acceptable due to the nature of shrinkage and distortion of thermoplastic polymer materials in forming processes according to the DIN 16901 standard.

Digital shearography is an optical, full-field and non-destructive method that can be used in identification of the defects by using image processing techniques. In this method, the surface displacement gradients are directly extracted from the fringe patterns, which requires processing of the phase information in the fringe images obtained in the experimental tests. One of the most important parameters of the shearography is the shear distance, playing an important role in the detection of the defects and quantitative measurements. Any mistake in the selection of the appropriate value for this parameter, makes it difficult to identify the right defect size. This parameter needs to be corrected because the changing in the shear size on the curved surfaces severely reduces the accuracy of the estimating of the defect size. In this paper, a method for estimating the size of the defects in curved surfaces by processing the shearography images is introduced. Geometric analysis is used to calculate the size of the accurate shear distance along the curvature, which can be used to improve the results of the defect estimation. Improvement of the defect size estimation for defects of 10, 16 and 20 mm has been measured as 15, 9.6 and 15%, respectively. It concluded that the proposed method can be used for better estimation of the defect size in the curved surfaces.