Papers by Keyword: Optical Method

Abstract: This paper presents a modification of the optical marker method for fluid particle trajectories analysis. Known optical visualization methods involving the addition of uniform indicator particles, require special methods of illuminating a single section of the liquid. Other of the disadvantages of this method is also the need to record suitably quick sequence of images, as well as problems in obtaining information about the three-dimensional motion of particles. The proposed modification involves the use of a set of markers, each of which is uniquely identified. The paper presents the results of laboratory tests carried out using the suggested markers.

Abstract: Analyzing applications involving industrial robots, these can generally be classified into two categories. In the first category, the robot is used to position an object or a tool in its working space. In the second category, the robot is used for programmed and continuous movement of an object in the working space. These two categories of use of industrial robots determine two families of characteristics considered fundamental for the assessment of performance robots: pose characteristics and tracking path characteristics. The pose characteristics are generally expressed by the pose accuracy and pose repeatability (positioning and orientation). From this category is “distance accuracy”, whose analysis is the subject of this paper. The authors present a method for measuring and evaluating of this characteristic, through 3D triangulation with two digital theodolits. The experimental researches were made for a welding robot type Cloos-Romat. The presented case study validates the results of the experimental research, the method and the used algorithm.

Abstract: The thermal tunable behavior of polyethylene inverse opal photonic crystals was investigated and the mechanism of this behavior was illustrated. Based on these researches, a method of determination of melting point was established. This principle of such method is that at the temperature of above the melting point, the molecular chain of the materials started to move and caused the destruction of the ordered nanostructure of the inverse opal. This destruction could be real-time monitored by the reflectance spectra. In addition, this process could also be observed by naked eyes because the structure color of the materials was also changed. Thus, the melting point of the materials could be detected by our method without using complex and expensive analyzer.

Abstract: There is a high risk of insulation system dielectric instability when partial discharge (PD) occurs. Therefore, measurement and monitoring of PD is an important preventive tool to safeguard high-voltage equipment from wanton damage. PD can be detected using optical method to increase the detection threshold and to improve the performance of on-line measurement of PD in noise environment. The PD emitted energy as acoustic emission. We can use this emitted energy to detect PD signal. The best method to detect PD in power transformer is by using acoustic emission. Optical sensor has some advantages such as; high sensitivity, more accuracy small size. Furthermore, in on-site measurements and laboratory experiments, it isoptical methodthat gives very moderate signal attenuations. This paper reviews the available PD detection methods (involving high voltage equipment) such as; acoustic detection and optical detection. The advantages and disadvantages of each method have been explored and compared. The review suggests that optical detection techniques provide many advantages from the consideration of accuracy and suitability for the applications when compared to other techniques.

Abstract: Glass transition temperature is an important thermal property for polymer materials. When its temperature exceeds this temperature, the exhibiting characters dramatically changes. Although the experimental techniques suited to this temperature measurement are well-established, the full-field optical measurement method has not been employed to characterize this property. Therefore, this paper aims to measure the glass transition temperature using optical method.

Abstract: The aim of this work is to identify parameters driving constitutive equations of materials with displacement field measurements carried out by image stereo-correlation during an unidirectional tensile test. We evaluate two identification techniques. The first one is the virtual fields method which consists in writing the principle of virtual work with particular virtual fields. It is generally used in the case of linear elasticity and it requires a perfect knowledge of the model in terms of boundary condition since the virtual fields used must be kinematically admissible. This method allows to determine parameters by a direct and fast calculation, without iterations. The second method is the finite element model updating method. It consists in finding constitutive parameters that achieve the best match between finite element analysis quantities and their experimental counterparts. This method is more adaptable than the virtual field method but it needs to spend more calculation time.

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.