Quantitative characterization of carbon/carbon composites matrix texture based on image analysis using polarized light microscope

A quantitative characteristic method was proposed for characterizing the matrix texture of carbon/carbon(C/C) composites, which determined the mechanical and physical properties of C/C composites. Based on the cloud theory that was commonly used for uncertain reasoning and the transformation between quantitative and qualitative characterization, so the relationship between the extinction angle and texture types was built by the cloud models for describing the texture of microstructure, moreover, linguistic controllers were established to analyze the matrix texture in accordance with the features of the polarized light microscope (PLM) image. On this basis, the extinction angle could be calculated from the PLM image of the C/C composites. In contrast to the results of measurement, the errors between calculative values and measured values were maintained 1–2° in basically. Meanwhile, the PLM image of C/C composites was segmented by the component, in particular, the matrix with mixed textures was further segmented by the difference of texture. It means that the quantitative characterization of C/C composites matrix based on single PLM image has been realized. Microsc. Res. Tech. 78:908–917, 2015. © 2015 Wiley Periodicals, Inc.     

The use of polarized light microscopy in examining the structure of carbon fibres*

The structure of carbon fibres has been examined using the optical microscope. Three types of fibre structure have been identified which differ in the orientation of the graphite crystallites within the transverse plane, the type of precursor can be identified by the shape of the carbonized fibre. The particular type of structure is determined by the process conditions which the fibre has undergone. Subsequent heat treatment merely enhances the crystallite alignment of the structure without altering the direction of preferred orientation.     

Demonstration of high lateral resolution in laser confocal microscopy using annular and radially polarized light

The authors present the experimental result of improved lateral resolution in laser confocal microscopy (LCM) by using annular and radially polarized light as the input illumination of an existing LCM. The authors examined the lateral resolution of the LCM by imaging a single fluorescent bead and measuring the lateral width of the single bead profile appearing in the optical image. Compared to no aperture and linearly polarized light, the central peak of the single bead profile narrowed by ∼40%, being as small as 122 nm in full width at half maximum using 405 nm laser excitation in a reflection imaging. In addition, the authors showed that radial polarization helps to preserve the circular shape of the single bead profile whereas linearly polarized light tends to induce an elongation along the polarization direction. Microsc. Res. Tech., 2009. © 2009 Wiley-Liss, Inc.     

The effect of detector size on the signal-to-noise ratio in confocal polarized light microscopy

We introduce a signal-to-noise ratio in an attempt to suggest an optimum pinhole size for confocal polarized light microscopes. We find that pinhole sizes which are typically 60% greater than those used in nonpolarized light confocal microscopy are appropriate.     

Straigtness measurement using a heterodyne moiré method

Optical heterodyne interferometry is a new interference technique, allowing quick and accurate measurements of dimension. A similar technique can determine the fringe phase of the moiré method as intensity is modulated by movement of the reference grating. The phase difference between certain points in the moiré pattern is detected automatically.The interference fringes generated by laser are used to measure straightness. Small displacement of fringes is detected with the heterodyne moiré method. Generally, beam flutter caused by air disturbance becomes a serious problem in systems using long beam paths, though it can be reduced by controlling the air flow.     

Numerical analysis of projection welding on auto-body sheet metal using a coupled finite element method

A comprehensive finite element method employing a subroutine to link up submodules of commercial code ANSYS is proposed to perform analysis of projection welding in quantitative detail. In order to solve the complexity due to dynamic changes in heat and electrical current flow paths, as well as temperature-dependent material properties, information about contact interfaces and the geometry of the projection areas have been taken into account. By updating parameter information among these submodules in an incremental manner, a truly thermal-electrical-mechanical coupled numerical analysis is realized for projection welding simulation. A case study of an automotive door assembly welding process is carried out and a series of experiments is conducted to confirm the validity of the newly developed method. The agreement between the experimental and numerical results is satisfactory, indicating that the incrementally coupled finite element method may be suitable for projection welding research. Finally, future work to extend this method in optimizing projection welding process design is also presented.     

Practical considerations in the use of polarized light microscopy in the analysis of the collagen network in articular cartilage

Polarized light microscopy is a traditional method for visualizing the collagen network architecture of articular cartilage. Articular cartilage repair and tissue engineering studies have raised new demands for techniques capable of quantitative characterization of the scar and repair tissues, including properties of the collagen network. Modern polarized light microscopy can be used to measure collagen fibril orientation, parallelism, and birefringence. New commercial instruments are computer controlled and the measurements are easy to perform. However, often the interpretation of results causes difficulties, even errors, because the theoretical aspects of the technique are demanding. The aim of this study was to describe the instrumentation and properties of a modern polarized light microscope, to point out some sources of error in the interpretation of the results, and to recall the theoretical background of the polarized light microscopy.     

动态线偏振光散射纳米颗粒粒度测量法的研究与分析

多重散射是传统动态光散射法测量纳米颗粒溶液浓度上限受到限制的主要原因。为此文中提出了动态线偏振光散射纳米颗粒粒度测量法,通过改变颗粒入射光和散射光的偏振状态,降低颗粒间多重散射的影响。现利用Mie散射理论分析了入射光与散射光偏振状态之间的关系,并通过实验方法探知偏振光在散射介质中的传输特性,揭示了在动态光散射中使用垂直偏振光作为入射光的实验依据。最后对动态线偏振光散射颗粒测量法和传统光子相关光谱测量法进行了实验及分析,通过两种方法的比较,验证了上述理论的正确性。     

Rapid surface reconstruction from a point cloud using the least-squares projection

A new approach for the rapid and robust surface reconstruction from a point cloud is presented based on the distance field and the least-squares projection (LSP) algorithm. This novel approach works directly on the point cloud without any explicit or implicit surface reconstruction procedure. First, a coarse base polygonal model was created directly from the distance field for the given point cloud through the iso-surface extraction. After acquiring a rough base polygonal model, we obtain a quality polygonal model through the iterative refinement and least-squares projection which projects current working polygonal model onto the point cloud in a least-squares sense. The main contribution of this work is the robust and fast surface reconstruction from randomly scattered 3D points only without any further information. We demonstrate the validity and efficiency of this new approach through a number of application examples.     

The application of Bayesian spectral analysis to optical sectioning using structured light imaging

We describe significant improvements to a well‐established method of obtaining optical sectioning in a conventional wide‐field microscope. This method relies on the projection of a single‐frequency grid pattern onto an object followed by mathematical manipulation of three images taken with the grid in different phases. Here, we present the use of Bayesian Spectral Analysis to determine accurate estimates of the phase of the grid pattern, permitting rapid and precise calibration of grid location. In common with previous algorithms, multiple images are combined to produce both an optical section and a wide‐field image. We describe innovations such as the use of non‐uniform phase or least‐squares solutions involving more than three images, in conjunction with direct phase estimates obtained using Bayesian Spectral Analysis, to yield images substantially free of artefacts. Auxiliary results, such as a method for determining the tilt of the grid, are also presented.     

The optimum projection angle of fringe projection for ball grid array inspection based on reflectance analysis

A solder bump is regarded as a specular-dominant shiny component that distorts the height profile and causes poor repeatability during the bump height measurement. In this paper, we analyze the relationship between the projection angle and other factors based on the general reflectance mechanism of the specular surface. An optimum projection angle exists, such that can produce the best repeatability of the bump height measurement; therefore, we propose a convenient experimental system with a circular motion guide that can evaluate the optimum projection angle experimentally. The experimental results show that best repeatability is obtained with the optimum projection angle. The proposed method to find the optimum projection angle in this paper can therefore be applied to the many cases of measurement for ball grid array samples having specular-dominant shiny component.     

The polarized AB plot for the frequency‐domain analysis and representation of fluorophore rotation and resonance energy homotransfer

The graphical representation of single‐frequency phase‐modulation fluorescence lifetime imaging data, referred to as the AB plot, is extended to take into account measurements of the polarized components of the fluorescence. For a hindered rotator model (characterized with a single excited‐state lifetime, a single rotational correlation time and limiting initial and final anisotropies) the rotational correlation time and the excited lifetime can be determined from the AB plot of any two of the following emission components: parallel, perpendicular, total emission or combinations thereof. A strategy for resolving the component hindered rotations and lifetimes for mixtures of two hindered rotators from measurements of the total, parallel and perpendicular components of the emission is developed. The analysis does not require prior knowledge of the initial limiting anisotropy or of the steady‐state anisotropy or of the excited state lifetime. Plots in polarized AB space derived for heterogeneous systems are constructed to aid interpretation of frequency‐domain dynamic depolarization imaging microscopy experiments. These plots can be used to distinguish spatially dependent rotational correlation time heterogeneity from heterogeneity in limiting anisotropies. The effects of noise and aperture depolarization are discussed. It is anticipated that the polarized AB plot will provide a useful adjunct to existing methods for visualizing and analysing dynamic polarization phenomena arising from molecular dynamics and homo‐energy transfer in single‐frequency microscopy applications.     

Boundary element numerical analysis of elastic indentation of a sphere into a bi-layer material

The initial part of load/penetration plot in depth sensing spherical indentation (nano-indentation) is analysed. The results of a numerical study using a specifically developed simulation tool based on the boundary element method are presented.They reveal that the usual linear relationship between the indentation depth and the square of the contact radius for homogeneous materials is also valid in the case of a bi-layer material.It is also shown that the elastic response of the bi-layer material is specific of the coating alone only if the indentation depth, h, is less than 2% of the coating thickness, t.For higher indentation depths (10%>h/t>1%), the macro-elastic response of the composite is seen to saturate with an overall elastic response still containing a contribution of roughly 10% of the coating modulus.The hypothesis of indentation limit h/t<10% of bi-layer material insuring coating-specific response for penetration hardness (Bückle's rule) is roughly two orders of magnitude high when applied by default to the corresponding coating-specific elastic response.     

Characterisation of lubricants on ball bearings by FT‐IR using an integrating sphere

Fourier transform‐infrared reflectance microspectroscopy has been used extensively for the examination of coatings on non‐planar surfaces such as ball bearings. While this technique offers considerable advantages, practical application has many drawbacks, some of which are easily overcome by the use of integrating sphere technology. This paper described the use of an integrating sphere for the quantification of thin layers of lubricant on the surface of ball bearings and the parameters that require optimisation in order to obtain reliable data. Several applications of the technique were discussed including determination of lubricant load on 12.7mm steel ball bearings and the examination of degraded lubricant on post‐mortem specimens. Copyright © 2007 John Wiley & Sons, Ltd.     

Statistical analysis of a method for monitoring fibre outside diameter using dual beam of edge diode light

Results of studies of the metrological feasibilities of an optical method of filament diameter measuring are presented. The analysis is based on statistical approximation of the experimental results. Systematic and random contributions to the total measurement error are estimated, and are equal to −0.15 μm and +0.15 μm, respectively, in the acceptable range of fibre lateral displacement equal to about 1 mm. Resolution of the method is about 0.05 μm.     

The analysis for light elements of hard gold electrodeposits

Examinations of gold-cobalt electrodeposits by Auger spectroscopy and prompt radiation analysis are reported. Auger analyses indicate low C, N and O levels after surface erosion by Ar⁺ sputtering. Nuclear (d, p) reactions indicate levels of C, N comparable with reported values. A sputtering artefact is thought to account for the difference. The results are consistent with suggestions in the literature that inclusions dispersed in the bulk of the electrodeposit contain complex potassium cobalt cyanide.