Key Engineering Materials Vols. 326-328

Abstract: The fluidic muscle cylinder consists of an air bellows tube, flanges and lock nuts. Its features are softness of material and motion, simplicity of structure, low production cost and high power efficiency. Recently, unlike the pneumatic cylinder, the fluidic muscle cylinder without air leakage, stick slip, friction or seals was developed as a new concept actuator. It has characteristics such as light weight, low price, high response, durable design, long life, high power and high contraction. In this study, we carried out finite element modeling and analysis on the main design variables such as contraction ratio and force, and diameter increment of the fluidic muscle cylinder. On the basis of finite element analysis, the prototype fluidic muscle cylinder was fabricated and tested. Finally, we compared the test results with the finite element analysis.

Abstract: In order to develop more elaborate and speedy system for large objects than existing selective laser sintering (SLS), this study applies a new selective dual-laser sintering process. It contains a 3-axis dynamic focusing scanner system for scanning large area instead of the existing fθ lens. As sintering parameters, the sintering temperature, the laser beam power and the layer thickness have a great influence on sintering of the polymer and metal powder. This paper will address the development of a solid freeform fabrication (SFF) system employing the dual laser system. Experiments were performed to evaluate the effect of a scanning path and to fabricate the large-sized object.

Abstract: The tensile property of PC/ABS was investigated with an optical image analysis method in the paper. With the consideration of polymer micro mechanism, a three-stage phenomenon based model is used to describe the true stress-strain curves. The regression constants obtained with the method could be described with definite physical meanings. It is shown that two lateral contractions are not identical at the later necking stages. The fracture strain could be used as a criterion to describe uniaxial tensile fracture.

Abstract: In this paper, a novel nano-moiré grating fabrication technique was proposed for nanometer deformation measurement. The grating fabrication process was performed with the aid of Atomic Force Microscope (AFM) on the basis of micro-fabrication technique. On the analysis of some correlative factors of influencing grating line quality, some important experimental parameters were optimized. In this study, some parallel and cross nano-gratings with frequencies of from 10000lines/mm to 20000lines/mm were fabricated. The successful experimental results demonstrate that the nano-grating fabrication technique is feasible and also indicated that these nano-gratings with nano-moiré method can be applied to deformation measurement, which offers a nanometer sensitivity and spatial resolution.

Abstract: Recently, many research works were concentrated on how to improve the accuracy of displacement fields in digital image correlation (DIC). However, the original displacement fields calculated at discrete locations using DIC are unavoidably contaminated by noises. If the strain fields are directly computed by differentiating the original displacement fields, the noises will be amplified even at a higher level and the resulting strain fields are untrustworthy. To acquire reliably estimation of strain fields, in this paper, Savitaky-Golay (SG) filters are introduced to obtain smoothed displacement fields and reasonable strain estimation. The principle of two-dimensional SG filters is described in detail first. Then images of uniaxial tensile and three-point bending experiments were used to verify the proposed approach. The resulting smoothed displacement fields and strain fields clearly show that the proposed method is simple and effective.

Abstract: Digital image correlation (DIC) is a whole-field and non-contact strain measuring method. It could provide deformation information of a specimen by processing two digital images that are captured before and after the deformation. In this work, a hybrid genetic algorithm, in which a simulated annealing mutation process and adaptive mechanisms are added to the real-parameter genetic algorithm, is used to search the corresponding subset after deformation. To invest the accuracy and reliability of this method, some key parameters are considered. The results indicate that the out-of-plane shift should be included, and a subset with 30x30 pixels should be recommended. The population size of 500, 100 generations, and 60 iterations are good enough. As for the searching strategy, it is recommended that the design variables are divided into three groups, each time only one group is under search, and they takes terms consecutively.

Abstract: A kind of dynamic tracking system for conducting high accuracy measurement of transparent liquid concentration is designed by means of line matrix CCD receiving fringes in accordance with the relations between liquid concentration and refractive index as well as the relations among refractive index, interference light wavelength of optical fiber F-P interferometer and grade orders. The detecting system can recognize or detect 0.01% of concentration variations via measuring a group of alcohol.

Abstract: Based on the principle of moiré techniques, a new method combined with Electric Addressing SLM technique was proposed. The specimen grating is modulated by the SLM system, and its the frequency can be changed with aid of a 4f Fourier system. The moiré is generated by the overlapped specimen grating and a reference grating in the Fourier system. Typical test is conducted with a polyurethane beam. The successful results verify the feasibility of the method, and show its good potential of further application to the in-plane deformation measurement.

Abstract: 3DP(three dimensional printing) technology is one of SFF(solid freeform fabrication) technologies which have recently come into a spotlight due to its adaptability to various applications. This technology has a great advantage in terms of short fabrication time for a prototype at a low cost, especially when it comes with multi-nozzle inkjet printing technology. However, it has also a disadvantage since it requires additional curing time, after jetting a binder material, and post-processing time in order to increase the mechanical strength of a product. In this study, a novel 3DP process is proposed to overcome slow solidification and elaborate post-process by adopting photo curing method into the conventional 3DP process. Mechanical properties, such as tensile and bending strengths, of specimens fabricated with the proposed 3DP process were measured and compared with those fabricated with the conventional 3DP process. As a result, it is found that mechanical strengths of specimens from the proposed novel 3DP process show three times higher than those from the conventional 3DP process. Besides, the overall fabrication time with the proposed novel 3DP process is about two times faster than that with the conventional 3DP process, because it does not need additional curing and post-processing time.

Abstract: In this study, the digital image correlation method(with Newton-Raphson iteration method) is used to measure the in-plane deformation of poly-crystal aluminum. When the specimen is exerted a tensile load, the strain distribution of the specimen surface will be inhomogeneous. The micro-deformation of the poly-crystal aluminum is studied under a SEM(scanning electron microscope), a series of images of the micro crystal are captured during the loading process. By using digital image correlation to analyze the images, the displacement and strain of a micro-crystal are obtained, which provide important data for further analysis of the inhomogeneous properties of the poly-crystal aluminum.