Articles de revues sur le sujet « Dimensional and geometrical precision »
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Liu, Junfeng, Yuqian Zhao, Tao Lai, Fei Li et Kexian Liu. « Identification of Geometrical Error on Multi-Axis Machine Tools Based on a Laser Tracker ». Journal of Physics : Conference Series 2185, no 1 (1 janvier 2022) : 012008. http://dx.doi.org/10.1088/1742-6596/2185/1/012008.
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Abstract The geometrical errors are affected by many factors for a multi-axis machine tool, such as materials, manufacturing, assembly, measurement, control, and environmental. The geometric error will eventually be reflected in the accuracy of the workpiece; therefore, for each part of the machine tool, the measurement of geometric error is essential. Most geometrical errors are measured separately for each axis. The single geometrical error measurement method is time-consuming. The multiple geometric error measurement methods have some limitations based on different instruments. Laser tracker based on GPS (Global Positioning System) positioning principle can measure the dimensional coordinate. Thus, the laser tracker measured geometric errors in high efficiency, high precision, wide range. This paper introduces the method of measuring the multi-axis machine geometrical error by using a laser tracker with a 1280mm×1280mm×240mm range and compares the measurement result from the traditional method. The results show the laser tracker method has high measurement accuracy, and rapid measurement and compensation of geometrical errors are achievable on a large-stroke machine tools.
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Cristofolini, Ilaria, Melania Pilla, Andrea Rao, Stefano Libardi et Alberto Molinari. « Dimensional and geometrical precision of powder metallurgy parts sintered and sinterhardened at high temperature ». International Journal of Precision Engineering and Manufacturing 14, no 10 (octobre 2013) : 1735–42. http://dx.doi.org/10.1007/s12541-013-0233-5.
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Relea, Eduard, Lukas Weiss et Konrad Wegener. « Experimental Study on the Geometrical and Dimensional Stability of Natural Stone Sorts for Precision Machinery ». Procedia CIRP 80 (2019) : 89–94. http://dx.doi.org/10.1016/j.procir.2019.01.107.
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Mühlstädt, Mike, Wolfgang Seifert, Matthias ML Arras, Stefan Maenz, Klaus D. Jandt et Jörg Bossert. « An advanced geometrical model for laminated woven fabrics using Lamé exponents with enhanced accuracy ». Journal of Composite Materials 52, no 11 (23 août 2017) : 1443–55. http://dx.doi.org/10.1177/0021998317725570.
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Three-dimensional stiffness tensors of laminated woven fabrics used in high-performance composites need precise prediction. To enhance the accuracy in three-dimensional stiffness tensor prediction, the fabric’s architecture must be precisely modeled. We tested the hypotheses that: (i) an advanced geometrical model describes the meso-level structure of different fabrics with a precision higher than established models, (ii) the deviation between predicted and experimentally determined mean fiber-volume fraction ( cf) of laminates is below 5%. Laminates of different cf and fabrics were manufactured by resin transfer molding. The laminates’ meso-level structure was determined by analyzing scanning electron microscopy images. The prediction of the laminates’ cf was improved by up to 5.1 vol% ([Formula: see text]%) compared to established models. The effect of the advanced geometrical model on the prediction of the laminate’s in-plane stiffness was shown by applying a simple mechanical model. Applying an advanced geometrical model may lead to more accurate simulations of parts for example in automotive and aircraft.
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Battey, H. S., et D. R. Cox. « High dimensional nuisance parameters : an example from parametric survival analysis ». Information Geometry 3, no 2 (9 août 2020) : 119–48. http://dx.doi.org/10.1007/s41884-020-00030-6.
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AbstractParametric statistical problems involving both large amounts of data and models with many parameters raise issues that are explicitly or implicitly differential geometric. When the number of nuisance parameters is comparable to the sample size, alternative approaches to inference on interest parameters treat the nuisance parameters either as random variables or as arbitrary constants. The two approaches are compared in the context of parametric survival analysis, with emphasis on the effects of misspecification of the random effects distribution. Notably, we derive a detailed expression for the precision of the maximum likelihood estimator of an interest parameter when the assumed random effects model is erroneous, recovering simply derived results based on the Fisher information in the correctly specified situation but otherwise illustrating complex dependence on other aspects. Methods of assessing model adequacy are given. The results are both directly applicable and illustrate general principles of inference when there is a high-dimensional nuisance parameter. Open problems with an information geometrical bearing are outlined.
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Monroy, Karla, Jordi Delgado, Lidia Sereno, Joaquim Ciurana et Nicolas J. Hendrichs. « Geometrical feature analysis of Co-Cr-Mo single tracks after selective laser melting processing ». Rapid Prototyping Journal 21, no 3 (20 avril 2015) : 287–300. http://dx.doi.org/10.1108/rpj-11-2013-0122.
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Purpose – Therefore, the purpose of this study is to understand the relationships between the processing parameters and the geometric form of the produced single tracks, in order to control dimensional quality in future experimentations. The quality of the deposited single track and layer is of prime importance in the selective laser melting (SLM) process, as it affects the product quality in terms of dimensional precision and product performance. Design/methodology/approach – In this paper, a vertical milling machining center equipped with an Ytterbium-fiber laser was used in the SLM experimentation to form single cobalt-chromium-molybdenum (CoCrMo) tracks. The different geometric features and the influence of the scanning parameters on these morphologic characteristics were studied statistically by means of ANOVA. Findings – Evidently, track height (h1) inaccuracy reduced in layer thicknesses between 100 and 200 μm. The re-melt depth (h2) was determined by the energy parameters, with laser power of 325-350 W and scanning speed (SS) of 66.6-83.3 mm/s being the most favorable parameters to obtain the required anchoring. Moreover, a contact angle of 117° was proposed as optimal, as it permitted an adequate overlapping region and a full densification, and, finally, an SS of 50 mm/s and a layer thickness of 250 were suggested for its development. Originality/value – The comprehension of the phenomena inherent to the process is related to the single track geometrical characteristics, which allow the definition of an optimal value for each factor for a further proposal of processing conditions that can finally derive a higher precision, wetting, density and mechanical properties.
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Ji, H. Z., L. Yuan et D. B. Shan. « Study on geometrical and dimensional changes in isothermal precision forging with complex shape during air cooling process ». Materials Research Innovations 15, sup1 (février 2011) : s466—s469. http://dx.doi.org/10.1179/143307511x12858957675831.
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Ueng, Shyh-Kuang, Hsin-Cheng Huang, Chieh-Shih Chou et Hsuan-Kai Huang. « Layered manufacturing for medical imaging data ». Advances in Mechanical Engineering 11, no 8 (août 2019) : 168781401987139. http://dx.doi.org/10.1177/1687814019871392.
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Layered manufacturing techniques have been successfully employed to construct scanned objects from three-dimensional medical image data sets. The printed physical models are useful tools for anatomical exploration, surgical planning, teaching, and related medical applications. Before fabricating scanned objects, we have to first build watertight geometrical representations of the target objects from medical image data sets. Many algorithms had been developed to fulfill this duty. However, some of these methods require extra efforts to resolve ambiguity problems and to fix broken surfaces. Other methods cannot generate legitimate models for layered manufacturing. To alleviate these problems, this article presents a modeling procedure to efficiently create geometrical representations of objects from computerized tomography scan and magnetic resonance imaging data sets. The proposed procedure extracts the iso-surface of the target object from the input data set at the first step. Then it converts the iso-surface into a three-dimensional image and filters this three-dimensional image using morphological operators to remove dangling parts and noises. At the next step, a distance field is computed in the three-dimensional image space to approximate the surface of the target object. Then the proposed procedure smooths the distance field to soothe sharp corners and edges of the target object. Finally, a boundary representation is built from the distance field to model the target object. Compared with conventional modeling techniques, the proposed method possesses the following advantages: (1) it reduces human efforts involved in the geometrical modeling process. (2) It can construct both solid and hollow models for the target object, and wall thickness of the hollow models is adjustable. (3) The resultant boundary representation guarantees to form a watertight solid geometry, which is printable using three-dimensional printers. (4) The proposed procedure allows users to tune the precision of the geometrical model to compromise with the available computational resources.
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FANG, CHONGHUA, QIAN LIU et XIAONAN ZHAO. « IMPROVED INTEGRATED MODEL OF ELECTROMAGNETIC SCATTERING FOR TWO DIMENSIONAL FRACTAL SEA SURFACE ». International Journal of Modern Physics B 24, no 22 (10 septembre 2010) : 4217–24. http://dx.doi.org/10.1142/s0217979210056542.
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In this paper, an improved integrated model of electromagnetic scattering for two dimensional fractal sea surface is built. Both geometrical fractal characteristic and permittivity characteristic of sea water are strictly considered, especially for the effects of salinity and temperature on the electromagnetic field scattered by sea water are added on. Finally, the calculated results from the new model are in accord with experimental results in terms of backscattering coefficient of sea water with no more than 2 dB error, which present higher precision than those traditional models. Thus, by using this model, the whole electromagnetic scattering characteristics of sea surface are obtained.
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Abeni, Andrea, Alessandro Metelli, Cristian Cappellini et Aldo Attanasio. « Experimental Optimization of Process Parameters in CuNi18Zn20 Micromachining ». Micromachines 12, no 11 (21 octobre 2021) : 1293. http://dx.doi.org/10.3390/mi12111293.
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Ultraprecision micromachining is a technology suitable to fabricate miniaturized and complicated 3-dimensional microstructures and micromechanisms. High geometrical precision and elevated surface finishing are both key requirements in several manufacturing sectors. Electronics, biomedicals, optics and watchmaking industries are some of the fields where micromachining finds applications. In the last years, the integration between product functions, the miniaturization of the features and the increasing of geometrical complexity are trends which are shared by all the cited industrial sectors. These tendencies implicate higher requirements and stricter geometrical and dimensional tolerances in machining. From this perspective, the optimization of the micromachining process parameters assumes a crucial role in order to increase the efficiency and effectiveness of the process. An interesting example is offered by the high-end horology field. The optimization of micro machining is indispensable to achieve excellent surface finishing combined with high precision. The cost-saving objective can be pursued by limiting manual post-finishing and by complying the very strict quality standards directly in micromachining. A micro-machining optimization technique is presented in this a paper. The procedure was applied to manufacturing of main-plates and bridges of a wristwatch movement. Cutting speed, feed rate and depth of cut were varied in an experimental factorial plan in order to investigate their correlation with some fundamental properties of the machined features. The dimensions, the geometry and the surface finishing of holes, pins and pockets were evaluated as results of the micromachining optimization. The identified correlations allow to manufacture a wristwatch movement in conformity with the required technical characteristics and by considering the cost and time constraints.
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Hajiahmadi, Saeed, Majid Elyasi et Mohsen Shakeri. « Evaluation of drawing force by a new dimensionless method in deep drawing process ». Proceedings of the Institution of Mechanical Engineers, Part B : Journal of Engineering Manufacture 234, no 13 (16 juin 2020) : 1604–14. http://dx.doi.org/10.1177/0954405420929770.
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In this research, geometric parameters were given in dimensionless form by the Π- Buckingham dimensional analysis method in the dimensionless group for deep drawing of a round cup. To find the best group of dimensionless parameters and the fittest dimensionless relational model, three scales of the cup are evaluated numerically by a commercial finite element software and stepwise regression modeling. After analyzing all effective geometric parameters, a fittest relational model among dimensionless parameters is found. In addition, the results of the new dimensionless model were compared with the simulation process and experimental tests. From the results, it is inferred that the geometric qualities of a large scale can be predicted with a small scale by the proposed dimensionless model. Comparing the results of the dimensionless model with experimental tests shows that the proposed dimensionless model has fine precision in the determination of geometrical parameters and drawing force estimation. Moreover, to evaluate the accuracy of the proposed dimensionless model, the predicted value of the model has been compared by the experimental results. It is shown that the dimensionless ratios of geometrical parameters can significantly affect the estimation of the drawing force by the proposed dimensionless model, but based on similarity law, because of the constant value of these dimensionless parameters in different scales, they could not be used for dimensionless analysis separately. It is also inferred that because of the effect of contact area on the coefficient of friction, which is changed by scale changing, the only dimensionless parameter that can significantly change the drawing force is the coefficient of friction. Finally, it is shown that the dimensionless geometrical parameter and the coefficient friction should be combined for dimensionless analysis.
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Toledo, D., I. Cristofolini, A. Molinari, V. Arnhold, V. Kruzhanov, P. Vervoort, M. Dougan et al. « High temperature sintering and its effect on dimensional and geometrical precision and on microstructure of low alloyed steels ». Powder Metallurgy 63, no 2 (11 février 2020) : 80–93. http://dx.doi.org/10.1080/00325899.2020.1723883.
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Zhang, Jiao, et Jianfeng Lu. « Analytical evaluation of geometric dilution of precision for three-dimensional angle-of-arrival target localization in wireless sensor networks ». International Journal of Distributed Sensor Networks 16, no 5 (mai 2020) : 155014772092047. http://dx.doi.org/10.1177/1550147720920471.
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This article focuses on the evaluation of geometric dilution of precision for three-dimensional angle-of-arrival target localization in wireless sensor networks. We calculate a general analytical expression for the geometric dilution of precision for three-dimensional angle-of-arrival target localization. Unlike the existing works in the literature, in this article, no assumptions are made regarding the observation ranges, noise variances, or the number of sensors in the derivation of the geometric dilution of precision. Necessary and sufficient conditions regarding the existence of geometric dilution of precision are also derived, which can be readily used to evaluate the observability of three-dimensional angle-of-arrival target localization in wireless sensor networks. Moreover, a concise procedure is also presented to calculate the geometric dilution of precision when it exists. Finally, several examples are used to illustrate our results, and it is shown that the performance of the proposed regular deployment configurations of angle-of-arrival sensors is better than the one with random deployment patterns.
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Cox, Daniel J., Glynn Newby, Hyung Wook Park, Steven Y. Liang, Wang-Lin Liu, Shang-Bin Hsieh et Joon Hwang. « Precision Machining with Micro-Scale Vertical Machining Center ». Journal of Advanced Computational Intelligence and Intelligent Informatics 10, no 2 (20 mars 2006) : 187–95. http://dx.doi.org/10.20965/jaciii.2006.p0187.
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Micro machining is an emerging technology with extremely large benefits and equally great challenges. The push to develop processes and tools capable of micro scale fabrication results from the widespread drive to reduce part and feature size in many industrial and commercial sectors. For many micro machining applications, the technology of mechanical solid tool machining offers attractive merits as it can create truly three-dimensional and one-of-a-kind parts of extremely high resolutions without significant limitation of part materials. For mechanical solid tool machining, the control of three-dimensional motions between machines, tools, and parts to sub-micron level of precision is a perquisite to the realization of manufacturing at such fine scales. One important factor that contributes to the machining process accuracy is the overall size of the machine tool due to the effects of thermal, static, and dynamic stabilities. This paper will assess the technological benefits of miniaturization of machine tools in the context of machine stiffness and accuracy. It also presents the design philosophy and configuration of a 4-axis miniaturized vertical machining center of positioning accuracy of 4 to 10nm and a machine volumetric envelop less than (300mm)3, which is several thousand times smaller than traditional machining centers. A series of tests are discussed for performance evaluation of the miniaturized machining center in terms of the achievable finish and part form accuracy with respect to the process parameters and part geometrical complexity in 1-D, 2-D, and 3-D cases.
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Ebrahimi, Mahmoud, Kamal Hamed Tabei, Reza Naseri et Faramarz Djavanroodi. « Effect of flow-forming parameters on surface quality, geometrical precision and mechanical properties of titanium tube ». Proceedings of the Institution of Mechanical Engineers, Part E : Journal of Process Mechanical Engineering 232, no 6 (25 octobre 2017) : 702–8. http://dx.doi.org/10.1177/0954408917738126.
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In this study, the flow-forming process for fabricating seamless thin-wall tubes is experimentally investigated on a commercially pure titanium sample. For this purpose, the influence of three processing parameters including feed rate, mandrel revolution, and thickness reduction is studied on the surface quality and geometrical accuracy of flow-formed tube. It is found that the feed rate increment results in more longitudinal displacement of the roller on the tube sample. This intern results in, more area of the material to be in contact with the roller during the tube revolution; hence, higher tube surface roughness. Also, surface finish and dimensional precision of spun tube are lessened by increment of the mandrel revolution due to the intensification of machine vibration. Additionally, increased reduction of wall thickness leads to the enlargement of diametral growth and the loss of roundness. Also, it will increase the resistance of the material flow, which results in the wave creation at the tube surface, thereby decreasing the surface quality of the spun sample.
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Ma, Hai Long, Ai Jun Tang et Qing Kui Chen. « Dynamic Models of Stability Lobes of Milling Thin-Walled Plates ». Advanced Materials Research 443-444 (janvier 2012) : 622–27. http://dx.doi.org/10.4028/www.scientific.net/amr.443-444.622.
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In the process of milling thin-walled plate, chatter is one of the major limitations on productivity and part quality even for high speed and high precision milling machines. Therefore, it is necessary to avoid chatter with a suitable choice of cutting condition. This paper studies the dynamic stability models of milling the thin-walled plate by analyzing the geometrical relationship of cutting, and derives the mathematic expressions in theory. Moreover, this paper develops a three-dimensional lobes diagram of the spindle speed, the axial depth and the radial depth. Through the three-dimensional lobes, it is possible to choose the appropriate cutting parameters according to the dynamic behavior of the chatter system.
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Ma, Hai Long, Ai Jun Tang et Qing Kui Chen. « Stability Prediction Model for Milling Process ». Advanced Materials Research 490-495 (mars 2012) : 2829–33. http://dx.doi.org/10.4028/www.scientific.net/amr.490-495.2829.
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In the process of milling thin-walled plate, chatter is one of the major limitations on productivity and part quality even for high speed and high precision milling machines. Therefore, it is necessary to avoid chatter with a suitable choice of cutting condition. This paper studies the dynamic stability models of milling the thin-walled plate by analyzing the geometrical relationship of cutting, and derives the mathematic expressions in theory. Moreover, this paper develops a three-dimensional lobes diagram of the spindle speed, the axial depth and the radial depth. Through the three-dimensional lobes, it is possible to choose the appropriate cutting parameters according to the dynamic behavior of the chatter system.
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Tan, Hai, Dadong Wang, Rongxin Li, Changming Sun, Ryan Lagerstrom, You He, Yanling Xue et Tiqiao Xiao. « A robust method for high-precision quantification of the complex three-dimensional vasculatures acquired by X-ray microtomography ». Journal of Synchrotron Radiation 23, no 5 (11 août 2016) : 1216–26. http://dx.doi.org/10.1107/s1600577516011498.
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The quantification of micro-vasculatures is important for the analysis of angiogenesis on which the detection of tumor growth or hepatic fibrosis depends. Synchrotron-based X-ray computed micro-tomography (SR-µCT) allows rapid acquisition of micro-vasculature images at micrometer-scale spatial resolution. Through skeletonization, the statistical features of the micro-vasculature can be extracted from the skeleton of the micro-vasculatures. Thinning is a widely used algorithm to produce the vascular skeleton in medical research. Existing three-dimensional thinning methods normally emphasize the preservation of topological structure rather than geometrical features in generating the skeleton of a volumetric object. This results in three problems and limits the accuracy of the quantitative results related to the geometrical structure of the vasculature. The problems include the excessively shortened length of elongated objects, eliminated branches of blood vessel tree structure, and numerous noisy spurious branches. The inaccuracy of the skeleton directly introduces errors in the quantitative analysis, especially on the parameters concerning the vascular length and the counts of vessel segments and branching points. In this paper, a robust method using a consolidated end-point constraint for thinning, which generates geometry-preserving skeletons in addition to maintaining the topology of the vasculature, is presented. The improved skeleton can be used to produce more accurate quantitative results. Experimental results from high-resolution SR-µCT images show that the end-point constraint produced by the proposed method can significantly improve the accuracy of the skeleton obtained using the existingITKthree-dimensional thinning filter. The produced skeleton has laid the groundwork for accurate quantification of the angiogenesis. This is critical for the early detection of tumors and assessing anti-angiogenesis treatments.
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Zhu, Linlin, Yuchu Dong, Zexiao Li, Xiaodong Zhang et Fengzhou Fang. « Measurement and Analysis of the Stepwise Curved Surface of Diffractive Optical Elements by a Constant Speed Confocal Probe ». Applied Sciences 9, no 11 (30 mai 2019) : 2229. http://dx.doi.org/10.3390/app9112229.
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Diffractive optical elements (DOEs) play an important role in improving imaging quality and reducing system volume. The measurement of DOE surface topography is of great significance to the evaluation of DOE quality and the optimization of its manufacturing process. However, there are still some difficulties in measuring the large curvature and the large sag of curve-based DOEs. In this paper, considering the geometrical feature information and measurement problems of curve-based DOEs, a measurement method based on a confocal measurement principle for DOE measurement is proposed. The proposed measurement data processing method is verified by a high-precision motion axis system and the stability of an ultra-precision lathe. The results show that the proposed measurement method can reconstruct and accurately evaluate the three-dimensional surface topography of DOEs.
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Zago, Marco, Nora Francesca Maria Lecis, Maurizio Vedani et Ilaria Cristofolini. « Dimensional and geometrical precision of parts produced by binder jetting process as affected by the anisotropic shrinkage on sintering ». Additive Manufacturing 43 (juillet 2021) : 102007. http://dx.doi.org/10.1016/j.addma.2021.102007.
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Budwal, Nikita, Kent Kasper, Jon Goering et Carwyn Ward. « Tooling and Infusion Design Strategies to Reduce Trade-Offs in Forming and Infusion Quality of Multi-Textile CFRPs ». Journal of Manufacturing and Materials Processing 6, no 3 (9 juin 2022) : 62. http://dx.doi.org/10.3390/jmmp6030062.
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Achieving right-first-time-manufacture (RFTM) of co-infused textile assemblies is challenging, without improving the accessibility to design knowledge of trade-offs between different tooling and infusion strategies. As demonstrated in previous work, the choice between a flexible or rigid mould material can result in trade-offs between dimensional accuracy and geometrical precision. Similarly, the choice of an infusion strategy can result in trade-offs in infusion quality and time. Building on past work, an investigation into forming variability across the length of six co-infused multi-textile components, with three different tooling inserts and two infusions set-ups, was conducted. To quantitatively assess variation, a method adapting principles of statistical process control was employed to analyse the yarn crimp measured from high-resolution cross-sectional scans of the components. The results were compared to a geometrical and dimensional analysis of the manufactured parts presented in a previous work. The analysis represents a method for capturing forming differences in textile preforms, which can be used to inform designs for the manufacture of textile CFRPs. The results were used to improve a hybrid rigid-flexible tooling design for an infused multi-textile component.
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Fu, Yue Gang, et Fan Hao Jin. « A High-Precision Binocular Measurement System ». Advanced Materials Research 823 (octobre 2013) : 402–5. http://dx.doi.org/10.4028/www.scientific.net/amr.823.402.
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The system uses three-dimensional measurement of binocular vision theory, through optical, mechanical, computer and other aspects of the technology to measure the target without contact, and up to a certain precision. In the high-voltage area, high-altitude target,and the target which is not easy to touch, there is a unique measure advantage. Binocular stereo vision is based on the principle of parallax and using imaging devices from different locations to obtain two images of the measured object and obtain three dimensional geometric of target by positional deviation between corresponding points in computer image. Binocular stereo currently used in four areas: robot navigation, micro operating system parameter detection, three-dimensional measurements and virtual reality. In addition, the system not only to measure the length of the distant object, the system can also be used to measure the width, surface area, height and tilt angle. As the tip of an optical imaging technology this system has a broad application prospects in the future.
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Badanova, Nazym, Asma Perveen et Didier Talamona. « Study of SLA Printing Parameters Affecting the Dimensional Accuracy of the Pattern and Casting in Rapid Investment Casting ». Journal of Manufacturing and Materials Processing 6, no 5 (28 septembre 2022) : 109. http://dx.doi.org/10.3390/jmmp6050109.
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Dimensional accuracy and geometric characteristics of the manufactured parts bear significant importance in product assembly. In Rapid Investment Casting, these characteristics can be affected by the printing parameters of the Additive Manufacturing method used in the pattern production process. Stereolithography is one of the important AM techniques mostly exploited in RIC due to its accuracy, smooth surface, and precision. However, the effect of SLA printing parameters on the dimensional accuracy and geometric characteristics have not been studied thoroughly. This study considers an experimental approach to study the effect of SLA printing parameters such as layer thickness, build angle, support structure density, and support touchpoint size on the dimensional accuracy and geometrical characteristics of the Castable Wax printed patterns and the Al cast parts. Taguchi’s Design of Experiment was used to define the number of experimental runs. SolidCast simulation was used to design the orientation of casting feeder to achieve directional solidification. Coordinate Measuring Machine measurements of deviations in the printed and cast parts were analyzed using the “Smaller-the-better” scheme in the two-step optimization method of Taguchi experiments. Build angle and Layer thickness were identified to be the first and the second most impactful parameters, respectively, affecting both the dimensional and geometric accuracy of Castable Wax patterns and Al cast parts, with optimal values of 0 deg and 0.25 μm, respectively. Both printed and cast parts had twice as many deviations in geometry as in dimensions. The sphere roundness and angularity were found to be the most and least accurate geometric characteristics, respectively. The dimensions in the Z direction were more accurate than in the X-Y directions, showing the smallest size deviations for height measurements and large deviations in the length, width, and diameter of the hole.
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Park, Y. B., et D. Y. Yang. « Finite element analysis for precision cold forging of helical gear using recurrent boundary conditions ». Proceedings of the Institution of Mechanical Engineers, Part B : Journal of Engineering Manufacture 212, no 3 (1 mars 1998) : 231–40. http://dx.doi.org/10.1243/0954405981515644.
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In metal forming, there are problems with recurrent geometric characteristics without explicitly prescribed boundary conditions. In such problems, so-called recurrent boundary conditions must be introduced. In this paper, as a practical application of the proposed method, the precision cold forging of a helical gear (which is industrially useful and geometrically complicated) has been simulated by a three-dimensional rigid-plastic finite element method and compared with the experiment. The application of recurrent boundary conditions to helical gear forging analysis is proved to be effective and valid. The three-dimensional deformed pattern by the finite element analysis is shown, and the forging load is compared with the experimental load. The profiles of the free surface of the workpiece show good agreement between the computation and the experiment.
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Du, Fuzhou, Ke Wen et Hao Yu. « A self-adaptive alignment strategy for large components based on dynamic compliance center ». Assembly Automation 39, no 2 (1 avril 2019) : 345–55. http://dx.doi.org/10.1108/aa-04-2018-057.
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PurposeAiming at the problems of geometric precision misalignment and unconsidered physical constraints between large components during the measurement-assisted assembly, a self-adaptive alignment strategy based on the dynamic compliance center (DCC) is proposed in this paper, using force information to guide alignment compliantly.Design/methodology/approachFirst, the self-adaptive alignment process of large components is described, and its geometrical and mechanical characteristics are analyzed based on six-dimensional force/torque (F/T). The setting method of DCC is studied and the areas of DCC are given. Second, the self-adaptive alignment platform of large components driven by the measured six-dimensional F/T is constructed. Based on this platform, the key supporting technologies, including principle of self-adaptive alignment, coordinate transfer, calculation of six-dimensional F/T and alignment process control, are illustrated.FindingsUsing the presented strategy, the position and orientation of large component is adjusted adaptively responding to measured six-dimensional F/T and the changes of contact states are consistent with the strategy. Through the setting of DCC, alignment process runs smoothly without jamming.Practical implicationsThis strategy is applied to the alignment experiment of large components muff coupling. The experimental results show that the proposed alignment strategy is correct and effective and meets the real-time requirement.Originality/valueThis paper proposed a novel way to apply force information in large component self-adaptive alignment, and the setting method of DCC was presented to make the alignment process more feasible.
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Fang, Guodong, et Jun Liang. « A review of numerical modeling of three-dimensional braided textile composites ». Journal of Composite Materials 45, no 23 (26 juillet 2011) : 2415–36. http://dx.doi.org/10.1177/0021998311401093.
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Three-dimensional (3D) braided composites with high specific energy absorption behavior and excellent fatigue performances are widely used in structures under cycle or impact load. A comprehensive literature survey is conducted to review the numerical analysis methods of 3D braided composites, including meso-geometry modeling, mesh generation techniques, and progressive damage models. When the 3D braided composites are manufactured during a process cycle, the braid yarn can move and becomes a ‘deviated or imperfect’ architecture. Elaborate meso-geometrical models which directly influence the precision of numerical results can be established by different methods. Different mesh generation techniques of different numerical methods, which manage to discretize the complex geometry models, are provided. An analysis of various models involved in the prediction of damage development and failure of 3D braided composites by using finite element method is presented. This study highlights the importance of recognizing the meso-structure for analyzing mechanical behavior of 3D braided composites.
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Saariluoma, Heikki, Aki Piiroinen, Anna Unt, Jukka Hakanen, Tuomo Rautava et Antti Salminen. « Overview of Optical Digital Measuring Challenges and Technologies in Laser Welded Components in EV Battery Module Design and Manufacturing ». Batteries 6, no 3 (16 septembre 2020) : 47. http://dx.doi.org/10.3390/batteries6030047.
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Ensuring the precision and repeatability of component assembly in the production of electric vehicle (EV) battery modules requires fast and accurate measuring methods. The durability of EV battery packs depends on the quality of welded connections, therefore exact positioning of the module components is critical for ensuring safety in exploitation. Laser welding is a non-contact process capable of welding dissimilar materials with high precision, for that reason it has become the preferred joining method in battery production. In high volume manufacturing, one of the main production challenges is reducing the time required for assessment of dimensional and geometrical accuracy prior to joining. This paper reviews the challenges of EV battery design and manufacturing and discusses commercially available scanner-based measurement systems suitable for fabrication of battery pack components. Versatility of novel metrological systems creates new opportunities for increasing the production speed, quality and safety of EV battery modules.
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Wang, Zheng Ru, Qing Ping Zhang, Cheng Wang et Gao Xiang Cai. « Parametric Design System of Precision Forging Gear Die ». Advanced Materials Research 712-715 (juin 2013) : 1153–57. http://dx.doi.org/10.4028/www.scientific.net/amr.712-715.1153.
Texte intégralRésumé :
Powerful function in three-dimensional design, SolidWorks now has found a wide range of applications in industrial design. The parametric design system of precision forging gear die in this paper is developed with VB language based on SolidWorks environment. It is described in detail that the establishment of important components of gear die in the three-dimensional model, the relation between parameters of the interface and model, and parameters drive mechanism. Input parameters in windows of VB interface, are automatically calculated the precise parameters of the gear part and geometric dimensions of the important components of the gear die. According to the input arameters, the three-dimensional model of the gear die’s assembly drawings is generated on SolidWorks environment. The parametric design system is able to shorten the time for constructing the 3D model of the precision forging gear die and improve the quality of the die design.
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Jeong, J., et I. Lee. « CLASSIFICATION OF LIDAR DATA FOR GENERATING A HIGH-PRECISION ROADWAY MAP ». ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLI-B3 (9 juin 2016) : 251–54. http://dx.doi.org/10.5194/isprs-archives-xli-b3-251-2016.
Texte intégralRésumé :
Generating of a highly precise map grows up with development of autonomous driving vehicles. The highly precise map includes a precision of centimetres level unlike an existing commercial map with the precision of meters level. It is important to understand road environments and make a decision for autonomous driving since a robust localization is one of the critical challenges for the autonomous driving car. The one of source data is from a Lidar because it provides highly dense point cloud data with three dimensional position, intensities and ranges from the sensor to target. In this paper, we focus on how to segment point cloud data from a Lidar on a vehicle and classify objects on the road for the highly precise map. In particular, we propose the combination with a feature descriptor and a classification algorithm in machine learning. Objects can be distinguish by geometrical features based on a surface normal of each point. To achieve correct classification using limited point cloud data sets, a Support Vector Machine algorithm in machine learning are used. Final step is to evaluate accuracies of obtained results by comparing them to reference data The results show sufficient accuracy and it will be utilized to generate a highly precise road map.
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Jeong, J., et I. Lee. « CLASSIFICATION OF LIDAR DATA FOR GENERATING A HIGH-PRECISION ROADWAY MAP ». ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLI-B3 (9 juin 2016) : 251–54. http://dx.doi.org/10.5194/isprsarchives-xli-b3-251-2016.
Texte intégralRésumé :
Generating of a highly precise map grows up with development of autonomous driving vehicles. The highly precise map includes a precision of centimetres level unlike an existing commercial map with the precision of meters level. It is important to understand road environments and make a decision for autonomous driving since a robust localization is one of the critical challenges for the autonomous driving car. The one of source data is from a Lidar because it provides highly dense point cloud data with three dimensional position, intensities and ranges from the sensor to target. In this paper, we focus on how to segment point cloud data from a Lidar on a vehicle and classify objects on the road for the highly precise map. In particular, we propose the combination with a feature descriptor and a classification algorithm in machine learning. Objects can be distinguish by geometrical features based on a surface normal of each point. To achieve correct classification using limited point cloud data sets, a Support Vector Machine algorithm in machine learning are used. Final step is to evaluate accuracies of obtained results by comparing them to reference data The results show sufficient accuracy and it will be utilized to generate a highly precise road map.
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Zhang, Yun Jiao, Guo Wu Wei et Jian Sheng Dai. « The Analysis of a Simplified 2R Pseudo-Rigid-Body Model with Moment Load ». Applied Mechanics and Materials 224 (novembre 2012) : 18–23. http://dx.doi.org/10.4028/www.scientific.net/amm.224.18.
Texte intégralRésumé :
Pseudo-rigid-body model (PRBM) method, which simplifies the geometrical nonlinear analysis, has become an important tool for the analysis and synthesis of compliant mechanisms. In this paper, a simplified 2R PRBM with two rigid links and two torsion springs is proposed. The characteristic radius factor and stiffness coefficients are selected as the design variables; in order to be better to simulate the tip point and tip slope, a three-dimensional objective function is formulated to optimize the new pseudo-rigid-body model. It is revealed in this paper that the precision of the tip point simulation can be improved when the coefficient of the tip slope error in the objective function is reduced.
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Gallenne, A., G. Pietrzyński, D. Graczyk, B. Pilecki, J. Storm, N. Nardetto, M. Taormina et al. « The Araucaria project : High-precision orbital parallax and masses of eclipsing binaries from infrared interferometry ». Astronomy & ; Astrophysics 632 (22 novembre 2019) : A31. http://dx.doi.org/10.1051/0004-6361/201935837.
Texte intégralRésumé :
Context. The precise determinations of stellar mass at ≲1% provide important constraints on stellar evolution models. Accurate parallax measurements can also serve as independent benchmarks for the next Gaia data release. Aims. We measured the masses and distance of binary systems with a precision level better than 1% using a fully geometrical and empirical method. Methods. We obtained the first interferometric observations for the eclipsing systems AI Phe, AL Dor, KW Hya, NN Del, ψ Cen and V4090 Sgr with the VLTI/PIONIER combiner, which we combined with radial velocity measurements to derive their three-dimensional orbit, masses, and distance. Results. We determined very precise stellar masses for all systems, ranging in precision from 0.04% to 3.3%. We combined these measurements with the stellar effective temperature and linear radius to fit stellar isochrones models and determined the age of the systems. We also derived the distance to the systems with a precision level of 0.4%. Conclusions. The comparison of theoretical models with stellar parameters shows that stellar models are still deficient in simultaneously fitting the stellar parameters (Teff, R and M) with this level of precision on individual masses. This stresses the importance of precisely measuring the stellar parameters to better calibrate stellar evolution models. The precision of our model-independent orbital parallaxes varies from 24 μas as to 70 μas and the parallaxes provide a unique opportunity to verify whether the future Gaia measurements have systematic errors.
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Vonk, N. H., N. A. M. Verschuur, R. H. J. Peerlings, M. G. D. Geers et J. P. M. Hoefnagels. « Robust and precise identification of the hygro-expansion of single fibers : a full-field fiber topography correlation approach ». Cellulose 27, no 12 (27 mai 2020) : 6777–92. http://dx.doi.org/10.1007/s10570-020-03180-z.
Texte intégralRésumé :
Abstract Over the past decades, natural fibers have become an important constituent in multiple engineering- and biomaterials. Their high specific strength, biodegradability, low-cost production, recycle-ability, vast availability and easy processing make them interesting for many applications. However, fiber swelling due to moisture uptake poses a key challenge, as it significantly affects the geometric stability and mechanical properties. To characterize the hygro-mechanical behavior of fibers in detail, a novel micromechanical characterization method is proposed which allows continuous full-field fiber surface displacement measurements during wetting and drying. A single fiber is tested under an optical height microscope inside a climate chamber wherein the relative humidity is changed to capture the fiber swelling behavior. These fiber topographies are, subsequently, analyzed with an advanced Global Digital Height Correlation methodology dedicated to extract the full three-dimensional fiber surface displacement field. The proposed method is validated on four different fibers: flat viscose, trilobal viscose, 3D-printed hydrogel and eucalyptus, each having different challenges regarding their geometrical and hygroscopic properties. It is demonstrated that the proposed method is highly robust in capturing the full-field fiber kinematics. A precision analysis shows that, for eucalyptus, at 90% relative humidity, an absolute surface strain precision in the longitudinal and transverse directions of, respectively, 1.2 × 10-4 and 7 × 10-4 is achieved, which is significantly better than existing techniques in the literature. The maximum absolute precision in both directions for the other three tested fibers is even better, demonstrating that this method is versatile for precise measurements of the hygro-expansion of a wide range of fibers. Graphic abstract
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Adamopoulos, Efstathios, Fulvio Rinaudo et Liliana Ardissono. « A Critical Comparison of 3D Digitization Techniques for Heritage Objects ». ISPRS International Journal of Geo-Information 10, no 1 (30 décembre 2020) : 10. http://dx.doi.org/10.3390/ijgi10010010.
Texte intégralRésumé :
Techniques for the three-dimensional digitization of tangible heritage are continuously updated, as regards active and passive sensors, data acquisition approaches, implemented algorithms and employed computational systems. These developments enable higher automation and processing velocities, increased accuracy, and precision for digitizing heritage assets. For large-scale applications, as for investigations on ancient remains, heritage objects, or architectural details, scanning and image-based modeling approaches have prevailed, due to reduced costs and processing durations, fast acquisition, and the reproducibility of workflows. This paper presents an updated metric comparison of common heritage digitization approaches, providing a thorough examination of sensors, capturing workflows, processing parameters involved, metric and radiometric results produced. A variety of photogrammetric software were evaluated (both commercial and open sourced), as well as photo-capturing equipment of various characteristics and prices, and scanners employing different technologies. The experimentations were performed on case studies of different geometrical and surface characteristics to thoroughly assess the implemented three-dimensional modeling pipelines.
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Schlögl, S., U. Mäder, M. Luster, M. Lassmann, P. Andermann et Chr Reiners. « Intra- and interobserver variability of thyroid volume measurements in healthy adults by 2D versus 3D ultrasound ». Nuklearmedizin 46, no 01 (2007) : 01–07. http://dx.doi.org/10.1055/s-0037-1616621.
Texte intégralRésumé :
SummaryThyroid volume measurement by ultrasonography (US) is essential in numerous clinical diagnostic and therapeutic fields. While known to be limited, the accuracy and precision of two-dimensional (2D) US thyroid volume measurement have not been thoroughly characterized. Objective: We sought to assess the intra- and interobserver variability, accuracy and precision of thyroid volume determination by conventional 2D US in healthy adults using reference volumes determined by three-dimensional (3D) US. Design, methods: In a prospective blinded trial, thyroid volumes of ten volunteers were determined repeatedly by nine experienced sonographers using conventional 2D US (ellipsoid model). The values obtained were statistically compared to the so-called true volumes determined by 3D US (multiplanar approximation), the so-called gold standard, to estimate systematic errors and relative deviations of individual observers. Results: The standard error of measurement (SEM) for one observer and successive measurements (intraobserver variability), was 14%, and for different observers and repeated measurements (interobserver variability), 17%. The minimum relative thyroid volume change significantly different at the 95% level was 39% for the same observer and 46% for different observers. Regarding accuracy, the mean value of the differences showed a significant thyroid volume overestimation (17%, p <0.01) by 2D relative to 3D US. Conclusion: 2D US is appropriate for routine thyroid volumetry. Nevertheless, the so-called human factor (random error) should be kept in mind and correction is needed for methodical bias (systematic error). Further efforts are required to improve the accuracy and precision of 2D US thyroid volumetry by optimizing the underlying geometrical modeling or by the application of 3D US.
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FOUNTAIN, G. O., D. V. KHAKHAR, I. MEZIĆ et J. M. OTTINO. « Chaotic mixing in a bounded three-dimensional flow ». Journal of Fluid Mechanics 417 (25 août 2000) : 265–301. http://dx.doi.org/10.1017/s002211200000118x.
Texte intégralRésumé :
Even though the first theoretical example of chaotic advection was a three-dimensional flow (Hénon 1966), the number of theoretical studies addressing chaos and mixing in three-dimensional flows is small. One problem is that an experimentally tractable three-dimensional system that allows detailed experimental and computational investigation had not been available. A prototypical, bounded, three-dimensional, moderate-Reynolds-number flow is presented; this system lends itself to detailed experimental observation and allows high-precision computational inspection of geometrical and dynamical effects. The flow structure, captured by means of cuts with a laser sheet (experimental Poincaré section), is visualized via continuously injected fluorescent dye streams, and reveals detailed chaotic structures and chains of high-period islands. Numerical experiments are performed and compared with particle image velocimetry (PIV) and flow visualization results. Predictions of existing theories for chaotic advection in three-dimensional volume-preserving flows are tested. The ratio of two frequencies of particle motion – the frequency of motion around the vertical axis and the frequency of recirculation in the plane containing the axis – is identified as the crucial parameter. Using this parameter, the number of islands in the chain can be predicted. The same parameter – using as a base-case the integrable motion – allows the identification of operating conditions where small perturbations lead to nearly complete mixing.
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Zhao, Wu, et Guo Ji Wang. « Analysis Geometric Precision of Workpiece and Geometric Errors Model of 5-Axis Machining Center for Processing Turbo Molecular Pump Rotor ». Advanced Materials Research 305 (juillet 2011) : 423–27. http://dx.doi.org/10.4028/www.scientific.net/amr.305.423.
Texte intégralRésumé :
The research investigates two kinds basic problems during the precision processing about turbo molecular pump rotor using 5-axis machining center. The one is to study the geometric and dimensional precision of turbo molecular pump rotor. The other one is to study the accuracy evaluative factors of 5-axis turbo molecular pump rotor machining center. For improving the processing precision to ensure the dynamic symmetry and geometric symmetry of the turbo molecular pump rotor, it focus on analyzing the allowable deviations from the turbo molecular pump rotor’s nominal geometry and dimensions specified during the design stage by defining tolerances on the part’s features using geometric dimensioning tolerancing standards and homogeneous transformation matrix. The geometric and dimensional errors deviation model of this feature can be represented by a HTM Hq. From the errors of the machine tools, using rigid body kinematics techniques and HTM, the systemic geometric volumetric error models are established for error synthesis. Volumetric accuracy model can be verified effectiveness better estimation of machine performance, by means of physical simulation and measurement.
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Elkaseer, Ahmed, Stella Schneider, Yaqi Deng et Steffen G. Scholz. « Effect of Process Parameters on the Performance of Drop-On-Demand 3D Inkjet Printing : Geometrical-Based Modeling and Experimental Validation ». Polymers 14, no 13 (23 juin 2022) : 2557. http://dx.doi.org/10.3390/polym14132557.
Texte intégralRésumé :
As additive manufacturing has evolved, 3D inkjet printing (IJP) has become a promising alternative manufacturing method able to manufacture functional multi-material parts in a single process. However, issues with part quality in terms of dimensional errors and lack of precision still restrict its industrial and commercial applications. This study aims at improving the dimensional accuracy of 3D IJP parts by developing an optimization-oriented simulation tool of droplet behavior during the drop-on-demand 3D IJP process. The simulation approach takes into consideration the effect of droplet volume, droplet center-to-center distance, coverage percentage of jetted droplets, the contact angle of the ink on the solid substrate and coalescence the performance of overlapping droplets, in addition to the number of printed layers. Following the development of the simulation tool using MATLAB, its feasibility was experimentally validated and the results showed a good agreement with a maximum deviation of 2.25%. In addition, the simulated horizontal features are compared with the results of “Inkraster” software, which also illustrates droplet behavior, however, only in 2D. For vertical features, a dial gauge indicator is used to measure the sample height, and the validation results show that the simulation tool can predicate the height of the sample with an average error of 10.89% for a large droplet diameter and 8.09% for a small diameter. The simulation results were found to be in a good agreement with the dimensions of the printed parts. The developed tool was then used to elucidate the effect of resolution of processed TIFF image and droplet diameter on the dimensional accuracy of 3D IJP parts.
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Zhang, Xi, Yuanzhi Xu, Haichao Li, Lijing Zhu, Xin Wang et Wei Li. « Flexible method for accurate calibration of large-scale vision metrology system based on virtual 3-D targets and laser tracker ». International Journal of Advanced Robotic Systems 16, no 6 (1 novembre 2019) : 172988141989351. http://dx.doi.org/10.1177/1729881419893516.
Texte intégralRésumé :
For the purpose of obtaining high-precision in stereo vision calibration, a large-size precise calibration target, which can cover more than half of the field of view is vital. However, large-scale calibration targets are very difficult to fabricate. Based on the idea of error tracing, a high-precision calibration method for vision system with large field of view by constructing a virtual 3-D calibration target with a laser tracker was proposed in this article. A virtual 3-D calibration target that covers the whole measurement space can be established flexibly and the measurement precision of the vision system can be traceable to the laser tracker. First, virtual 3-D targets by calculating rigid body transformation with unit quaternion method were constructed. Then, the high-order distortion camera model was taken into consideration. Besides, the calibration parameters were solved with Levenberg–Marquardt optimization algorithm. In the experiment, a binocular stereo vision system with the field of view of 4 × 3 × 2 m3 was built for verifying the validity and precision of the proposed calibration method. It is measured that the accuracy with the proposed method can be greatly improved comparing with traditional plane calibration method. The method can be widely used in industrial applications, such as in the field of calibrating large-scale vision-based coordinate metrology, and six-degrees of freedom pose tracking system for dimensional measurement of workpiece, as well as robotics geometrical accuracy detection and compensation.
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Bove, Alessandro, Flaviana Calignano, Manuela Galati et Luca Iuliano. « Photopolymerization of Ceramic Resins by Stereolithography Process : A Review ». Applied Sciences 12, no 7 (1 avril 2022) : 3591. http://dx.doi.org/10.3390/app12073591.
Texte intégralRésumé :
Stereolithography is known as one of the best Additive Manufacturing technologies in terms of geometrical and dimensional precision for polymeric materials. In recent years, a lot of studies have shown that the creation of ceramic resins, through a particular combination of monomeric components and ceramic powders, allows to obtain complex shape geometries thanks to the photopolymerization process. This review highlights the characteristics and properties of ceramic resins, peculiarities of the ceramic stereolithography processes, up to the relationship between the composition of the ceramic resin and the complexity of the post-processing phases. The comparison of different studies allows outlining the most common steps for the production of ceramic resins, as well as the physical and chemical compatibility of the different compounds that must be studied for the good feasibility of the process.
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Cheng, Xiang, Xian Hai Yang, Li Li et Jun Ying Liu. « Design of a Three-Axis Desktop Micro Milling Machine Tool ». Key Engineering Materials 589-590 (octobre 2013) : 735–39. http://dx.doi.org/10.4028/www.scientific.net/kem.589-590.735.
Texte intégralRésumé :
Micro milling process is more favorite than other processes for its unique advantages in ultra-precision machining of miniature components with intricate three-dimensional geometrical feature made of various materials. Aiming at micro milling applications, a three-axis desktop milling machine tool with linear motors and nano-meter linear scales has been introduced. Natural granite is used as the frame material and air-bearing cylinders are used for z-axis gravity balancing. Finite element method is applied to the design and optimization of the machine structures. The designed machine adopts linear motors and 5nm resolution linear scale using an open control architecture. The workspace is 100mm×100mm×100mm and the overall size is 610mm×650mm×630mm. Experimental evaluations show the sub-micron machining feasibility of the introduced machine.
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Hu, Yaoyuan, Bingfeng Ju et Wule Zhu. « Integrated Development of a Topology-Optimized Compliant Mechanism for Precise Positioning ». Actuators 11, no 7 (27 juin 2022) : 179. http://dx.doi.org/10.3390/act11070179.
Texte intégralRésumé :
A scheme for modelling and controlling a two-dimensional positioning system with a topology-optimized compliant mechanism is presented. The system is designed to ensure a relatively large workspace and exhibit robustness against system nonlinearities. A detailed design procedure based on topology optimization is presented, and a nonlinear description of the designed mechanism is developed as a starting point for further precise position control. The theoretical model is shown to be suitable for a considerably larger working range without losing consistency. A backstepping controller is employed to manipulate the nonlinearities in the model resulting from the geometrical and material nonlinearity of the mechanical structure. The hysteresis of the piezoelectric actuator is also taken into consideration. An experimental verification of the controller demonstrates that the proposed design approach improves the performance of compliant mechanism and satisfies the needs for precision positioning.
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Wei, Huaxian, Li Wang, Xiaodong Niu, Jian Zhang et Alessandro Simeone. « Fabrication, Experiments, and Analysis of an LBM Additive-Manufactured Flexure Parallel Mechanism ». Micromachines 9, no 11 (5 novembre 2018) : 572. http://dx.doi.org/10.3390/mi9110572.
Texte intégralRésumé :
Additive manufacturing technology has advantages for realizing complex monolithic structures, providing huge potential for developing advanced flexure mechanisms for precision manipulation. However, the characteristics of flexure hinges fabricated by laser beam melting (LBM) additive manufacturing (AM) are currently little known. In this paper, the fabrication and characterization of a flexure parallel mechanism through the LBM process are reported for the first time to demonstrate the development of this technique. The geometrical accuracy of the additive-manufactured flexure mechanism was evaluated by three-dimensional scanning. The stiffness characteristics of the flexure mechanism were investigated through finite element analysis and experimental tests. The effective hinge thickness was determined based on the parameters study of the flexure parallel mechanism. The presented results highlight the promising outlook of LBM flexure parts for developing novel nanomanipulation platforms, while additional attention is required for material properties and manufacturing errors.
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Asensio Ramos, A., et C. J. Díaz Baso. « Stokes inversion based on convolutional neural networks ». Astronomy & ; Astrophysics 626 (juin 2019) : A102. http://dx.doi.org/10.1051/0004-6361/201935628.
Texte intégralRésumé :
Context. Spectropolarimetric inversions are routinely used in the field of solar physics for the extraction of physical information from observations. The application to two-dimensional fields of view often requires the use of supercomputers with parallelized inversion codes. Even in this case, the computing time spent on the process is still very large. Aims. Our aim is to develop a new inversion code based on the application of convolutional neural networks that can quickly provide a three-dimensional cube of thermodynamical and magnetic properties from the interpreation of two-dimensional maps of Stokes profiles. Methods. We trained two different architectures of fully convolutional neural networks. To this end, we used the synthetic Stokes profiles obtained from two snapshots of three-dimensional magneto-hydrodynamic numerical simulations of different structures of the solar atmosphere. Results. We provide an extensive analysis of the new inversion technique, showing that it infers the thermodynamical and magnetic properties with a precision comparable to that of standard inversion techniques. However, it provides several key improvements: our method is around one million times faster, it returns a three-dimensional view of the physical properties of the region of interest in geometrical height, it provides quantities that cannot be obtained otherwise (pressure and Wilson depression) and the inferred properties are decontaminated from the blurring effect of instrumental point spread functions for free. The code, models, and data are all open source and available for free, to allow both evaluation and training.
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Farooq, Muhammad Umar, Saqib Anwar, M. Saravana Kumar, Abdullah AlFaify, Muhammad Asad Ali, Raman Kumar et Rodolfo Haber. « A Novel Flushing Mechanism to Minimize Roughness and Dimensional Errors during Wire Electric Discharge Machining of Complex Profiles on Inconel 718 ». Materials 15, no 20 (20 octobre 2022) : 7330. http://dx.doi.org/10.3390/ma15207330.
Texte intégralRésumé :
One of the sustainability goals in the aeronautical industry includes developing cost-effective, high-performance engine components possessing complex curved geometries with excellent dimensional precision and surface quality. In this regard, several developments in wire electric discharge machining have been reported, but the influence of flushing attributes is not thoroughly investigated and is thus studied herein. The influence of four process variables, namely servo voltage, flushing pressure, nozzle diameter, and nozzle–workpiece distance, were analyzed on Inconel 718 in relation to geometrical errors (angular and radial deviations), spark gap formation, and arithmetic roughness. In this regard, thorough statistical and microscopical analyses are employed with mono- and multi-objective process optimization. The gray relational analysis affirms the reduction in the process’s limitations, validated through confirmatory experimentation results as 0.109 mm spark gap, 0.956% angular deviation, 3.49% radial deviation, and 2.2 µm surface roughness. The novel flushing mechanism improved the spark gap by 1.92%, reducing angular and radial deviations by 8.24% and 29.11%, respectively.
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Jeon, Jin Woo, Jeong Hwan Yun, Myeong Sik Jeong, Yang Gon Kim, Hoon Jae Park, Gi Man Bae et Ji Hyun Sung. « Metal Powder Injection Molding Process for Manufacturing Adapter Component ». Key Engineering Materials 622-623 (septembre 2014) : 868–75. http://dx.doi.org/10.4028/www.scientific.net/kem.622-623.868.
Texte intégralRésumé :
Adapters are a component of the output system in the internally geared hub for a bicycle. Originally, adapter parts were produced by a machining process with low productivity and material usage rate. In this study, the metal powder injection molding (MIM) process has been applied as an alternative manufacturing method to the machining process. Microstructure analysis and mechanical property testing has been conducted in order to select the material for the adapter with changes in the nickel content. The geometrical precision of the adapter is measured by using three-dimensional scanner with various mixing ratios of the powder and the binder. The developed alternative process for the adapter results in increased productivity and material usage rate. Previously, this process was only used for small parts less than 10 mm in diameter. With this development, the MIM process may be used more widely than before.
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de Oliveira, Fabrício Borges, Maurício de Campos Porath, Vitor Camargo Nardelli, Francisco Augusto Arenhart et Gustavo Daniel Donatelli. « Characterization and Correction of Geometric Errors Induced by Thermal Drift in CT Measurements ». Key Engineering Materials 613 (mai 2014) : 327–34. http://dx.doi.org/10.4028/www.scientific.net/kem.613.327.
Texte intégralRésumé :
The occurrence of thermal drift in industrial computed tomography (CT) systems has been reported as a significant source of error on geometrical evaluations. During CT-scans, heating inside the cabinet and varying environmental conditions may affect the position of the focal spot and distort the manipulator system, leading to relative displacement of X-ray projections and distortions in the reconstructed 3D image. This paper presents an experimental investigation on influence of the thermal effects on dimensional CT measurements. A correction method based on the manipulation of the projections was developed and evaluated. The method consists in repeating the acquisition of first projection at the end of the scan and calculating the displacement vector between these projections. The remaining projections are then corrected proportionally to this displacement. The results showed a significant reduction of the roundness deviation values measured on a precision sphere after the correction.
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Chang, Yun, Jia Lee, Omar Rijal et Syed Bakar. « Efficient online handwritten Chinese character recognition system using a two-dimensional functional relationship model ». International Journal of Applied Mathematics and Computer Science 20, no 4 (1 décembre 2010) : 727–38. http://dx.doi.org/10.2478/v10006-010-0055-x.
Texte intégralRésumé :
Efficient online handwritten Chinese character recognition system using a two-dimensional functional relationship modelThis paper presents novel feature extraction and classification methods for online handwritten Chinese character recognition (HCCR). TheX-graph andY-graph transformation is proposed for deriving a feature, which shows useful properties such as invariance to different writing styles. Central to the proposed method is the idea of capturing the geometrical and topological information from the trajectory of the handwritten character using theX-graph and theY-graph. For feature size reduction, the Haar wavelet transformation was applied on the graphs. For classification, the coefficient of determination (R2p) from the two-dimensional unreplicated linear functional relationship model is proposed as a similarity measure. The proposed methods show strong discrimination power when handling problems related to size, position and slant variation, stroke shape deformation, close resemblance of characters, and non-normalization. The proposed recognition system is applied to a database with 3000 frequently used Chinese characters, yielding a high recognition rate of 97.4% with reduced processing time of 75.31%, 73.05%, 58.27% and 40.69% when compared with recognition systems using the city block distance with deviation (CBDD), the minimum distance (MD), the compound Mahalanobis function (CMF) and the modified quadratic discriminant function (MQDF), respectively. High precision rates were also achieved.
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Zago, Marco, Nora Lecis, Marco Mariani et Ilaria Cristofolini. « Analysis of the Flatness Form Error in Binder Jetting Process as Affected by the Inclination Angle ». Metals 12, no 3 (28 février 2022) : 430. http://dx.doi.org/10.3390/met12030430.
Texte intégralRésumé :
Binder jetting (BJ) has demonstrated high competitiveness among additive manufacturing processes on account of its high production rate at a low material cost. However, both the design procedure and the process for BJ have to be further developed, aiming towards the proper control of the geometrical and dimensional precision and accuracy of the final product. This paper aims to study the factors that affect the flatness form error. Five geometries were designed to obtain planes that were inclined with respect to the fabrication direction. These planes were measured by a coordinate measuring machine in both the green and sintered state, deriving the best-fitting plane and the flatness form error. The analysis of the green samples demonstrates the prevailing influence of saturation level and layer shifting on flatness form error. In the sintered parts, a dimensional change in sintering can determine shape distortion, or an increment in the surface irregularity observed in the green state. The experimental results clearly evidence the effect of both printing and sintering on the quality of the final product, which should be considered when designing parts to be produced using BJ technology.
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Batalha, A. E. F., et R. M. Araújo. « Development of removable partial dentures by using additive manufacture and casting processes ». Archives of Materials Science and Engineering 1, no 87 (1 septembre 2017) : 33–40. http://dx.doi.org/10.5604/01.3001.0010.5969.
Texte intégralRésumé :
Purpose: This work aims to present a methodology developed for dimensional analysis of removable partial dentures, following a route with a model manufactured by additive manufacture and a further casting process of a Co-Cr alloy part. Design/methodology/approach: The method for designing and manufacturing removable partial dentures (RPD) is focused on their completely virtual design. They are manufactured with resin additive manufacturing chrome-cobalt cast alloys. A 3D image correlation scanner was used for dimensional and geometrical tolerance analysis. Findings: The prostheses manufactured by CAD-CAM route are more accurate than conventional ones, but they suffer distortion during the casting process. This distortion did not interfere with the patient's well-being or with the adaptation to the prosthesis. Research limitations/implications: The technique presented herein paper allows preparing better fitting prosthesis. Providing the best comfort and masticatory power. Practical implications: Improving the precision in the manufacturing process of a removable partial denture is very important for professional dentists and their patients. Originality/value: The proposed technique and the work approach provide the prosthesis preparation with shorter ambulatory time in addition to greater comfort to the patient.