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Optics and Lasers in Engineering

Syndicate content ScienceDirect Publication: Optics and Lasers in Engineering
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Updated: 20 weeks 5 days ago

Implementation and evaluation of optical flow methods for two-dimensional deformation measurement in comparison to digital image correlation

Sun, 04/15/2018 - 06:03
Publication date: August 2018
Source:Optics and Lasers in Engineering, Volume 107

Author(s): Christoph Hartmann, Jue Wang, Daniel Opristescu, Wolfram Volk

In experimental solid mechanics optical methods allow for non-contact derivation of full-field information. In this paper, optical flow based deformation measurement routines are implemented and compared to various commonly used digital image correlation procedures. The global Horn–Schunck and the local Lucas–Kanade optical flow method are utilized and adapted for large deformation measurement. Systematic tests with synthetic images are carried out for a detailed comparison of optical flow and correlation methods for varying subset sizes, noise levels, shape functions and gray level interpolations. The synthetic test data consists of rigid translation, different sinusoidal displacements and planar rotation. Within the study, the displacement calculation and the subsequent strain calculation are discussed and analyzed separately. Furthermore, the additive effect of measurement errors, when calculating with more than two successive images is investigated. Real experimental data is processed by all implemented methods and finally compared for validation and verification purposes.





Categories: Optics news

Specific attack and security enhancement to optical image cryptosystem based on two random masks and interference

Sun, 04/15/2018 - 06:03
Publication date: August 2018
Source:Optics and Lasers in Engineering, Volume 107

Author(s): Y. Xiong, A. He, C. Quan

In this paper, we evaluate the security of an amplitude-phase retrieval attack free encryption scheme based on two random masks and interference. In the proposed cryptosystem, two phase-only masks (POMs) are generated from two random images using interference technique. The POMs are then used as encryption keys in a phase-truncated Fourier transform (PTFT) based encryption scheme. Compared to traditional PTFT-based cryptosystem, the security of the encryption scheme is improved by integrating the interference technique. Consequently, the scheme is immune to some attacks. We proposed a specific attack based on a phase retrieval algorithm with median filtering to break the cryptosystem. Numerical simulation results show that the cryptosystem is vulnerable to the proposed attack. Moreover, based on the proposed attack and the existing cryptosystem, full phase encoding technique is added to the previous cryptosystem to enhance the security.





Categories: Optics news

Advanced Fourier transform analysis method for phase retrieval from a single-shot spatial carrier fringe pattern

Sun, 04/15/2018 - 06:03
Publication date: August 2018
Source:Optics and Lasers in Engineering, Volume 107

Author(s): Zhichao Dong, Zhenyue Chen

An advanced Fourier transform analysis ( AFTA ) method is proposed in this study for phase retrieval from a single-shot spatial carrier fringe pattern ( SCFP ). It firstly extracts four phase-shifted fringe patterns ( FP ) from the SCFP with one pixel malposition, and then performs Fourier transform to each of them for their Fourier spectrums. The innovation of AFTA is making a subtraction in frequency domain directly to calculate the spectrum difference, which can generally eliminate the direct current component, thus it could mitigate the spectrum leakage problem and the edge error of traditional Fourier transform analysis ( FTA ) method significantly. After that, by making an inverse Fourier transform to the spectrum difference and a simple average operation, the phase information could be reconstructed conveniently. The time cost is approximately twice of FTA , which is still highly efficient and time-saving for dynamic or real-time measurement. AFTA is adequately validated as a promising method in fringe analysis by various simulations and comparative experiments, with emphasis of this study on its performance in terms of accuracy, noise-tolerance, carrier frequency, time cost, etc.





Categories: Optics news

Computational and experimental study on hole evolution and delamination in laser drilling of thermal barrier coated nickel superalloy

Sun, 04/15/2018 - 06:03
Publication date: August 2018
Source:Optics and Lasers in Engineering, Volume 107

Author(s): Rujia Wang, Wenqiang Duan, Kedian Wang, Xia Dong, Zhengjie Fan, Xuesong Mei, Wenjun Wang, Shuai Zhang

Computational study related to thermal stress and hole formation in laser percussion drilling of thermal barrier coated nickel alloy based on a thermal-mechanical coupled model, combined with experimental work, was conducted in this paper. The effects of laser parameters (pulse duration and laser power) and material property (elastic modulus) on delamination were discussed based on thermal stress analysis. Laser drilling with higher peak power density (>1e11W/m2) can quickly get a through-hole of 2.3 mm within 10 pulses. Stress mutation and thermal stress shock near the interfaces are responsible for the crack formation. For the case with low peak power density, solidification rate and solidification sequence between materials should also be considered. Under the same pulse duration, the thermal stress would be enhanced with increasing of laser power. With the same pulse energy, a more intense thermal stress shock in pulse cycles can be produced under a longer pulse duration. And this shock effect near the interfaces can be alleviated when laser source is far from the interfaces. Heat accumulating effect induced by stagnation phenomenon, mainly due to lower peak power, can contribute to crack extension along the interfaces. Thus, breaking through the first two layers with high drilling efficiency is an effective way to restrain/prevent the delamination and viable parameters are also determined in the paper. Furthermore, it would offer great benefits for delamination prevention that make sure the elastic modulus of TBC and BC close to each other along the thickness with a gradually approaching method in their preparations.





Categories: Optics news

Visualization of acoustic waves in air and subsequent audio recovery with a high-speed schlieren imaging system: Experimental and computational development of a schlieren microphone

Sun, 04/15/2018 - 06:03
Publication date: August 2018
Source:Optics and Lasers in Engineering, Volume 107

Author(s): Joshua S. Harvey, Hannah E. Smithson, Clive R. Siviour

We present a high-speed single-mirror double-pass coincident schlieren system and corresponding algorithms for the visualization of acoustic waves and recovery of their associated audio signals. Schlieren systems are extensively used to visualize strong shockwaves, such as those from supersonic motion or explosions. Recently, they have also been used to visualize lower amplitude non-linear acoustic phenomena, such as the weak shockwaves arising from impact events including hand claps, belt snaps, and towel cracks. Time-invariant sounds produced by loudspeakers have also been imaged, in one case leading to frequency analysis, although these have been limited to high-frequency signals at very high sound pressure levels. The research presented here shifts the focus from sound-field visualization towards audio signal recovery. A comprehensive exploration of several parameters for imaging sound sources, including frequency, wave form, and amplitude, is presented. In addition, we address for the first time the recovery of phase information, which would be essential for speech intelligibility, and the more general case of non-contact sound field reconstruction. Through image and signal processing, it is shown that audio signals can be recovered from high-speed schlieren video whose acoustic waves appear to be below the limit of visibility, and were previously deemed unrecoverable by virtue of their frequency and sound pressure level. This includes sounds at frequencies and loudnesses relevant for human hearing, producing the first ‘schlieren microphone’.





Categories: Optics news

High sensitivity strain sensors based on single-mode-fiber core-offset Mach-Zehnder interferometers

Sun, 04/15/2018 - 06:03
Publication date: August 2018
Source:Optics and Lasers in Engineering, Volume 107

Author(s): Maria Susana Avila-Garcia, Marco Bianchetti, Ronan Le Corre, Alexis Guevel, Ruth Ivonne Mata-Chavez, Juan Manuel Sierra-Hernandez, Daniel Jauregui-Vazquez, José Roberto Reyes-Ayona, Julian Moises Estudillo-Ayala, Roberto Rojas-Laguna

Mach–Zehnder interferometers make highly sensitive sensors of physical quantities based on the accumulated phase difference between two or more optical paths. In this work, the application of single-mode-fiber core-offset Mach–Zehnder interferometers as strain sensors is reported. Three in-line modal Mach–Zehnder interferometers were manufactured by splicing three pieces of single mode fiber with well-defined offset and orientation of the cores and a well-defined length of its middle section. These interferometers were characterized as strain sensors, and a maximum sensitivity of 7.46 pm/µε was obtained over the linear range 0–1754 µε. Compared to other strain sensors, the ones reported in this work achieve a high sensitivity using inexpensive single mode fiber and an easy manufacturing process.





Categories: Optics news

Fast and direct engraving of iridescent lettering on original product surface using laser interference to prevent counterfeiting

Sun, 04/15/2018 - 06:03
Publication date: August 2018
Source:Optics and Lasers in Engineering, Volume 107

Author(s): Byeong-Hak Ha, Sanghoon Ahn, Han-Sung Bae, Hee-Shin Kang, Jeng-o Kim, Jiwhan Noh

We propose the engraving of a unique interference pattern on metal with the use of high-energy 1064 nm laser pulses fired through a Fresnel biprism (FB). The grating is patterned with 500 patterns for 5 ns, and the spacing of patterns can be adjusted according to the physical value of FB. By rotating the FB, the interference pattern is machined into metal to produce an encrypted iridescent character. Encrypted letters are engraved via assigning a serial number and corporate logos to a product (on which the metal is affixed) according to the viewing angle of the interference fringe. The resulting iridescently colored letters or numbers are visible according to their viewing direction. By superimposing letters and numbers, it is possible to store complex passwords, and forgery/counterfeiting can be easily detected by merely using the naked eye and an angle meter.





Categories: Optics news

Influence of inhomogeneous refractive index fields on particle image velocimetry

Sun, 04/15/2018 - 06:03
Publication date: August 2018
Source:Optics and Lasers in Engineering, Volume 107

Author(s): Christoph Vanselow, Andreas Fischer

The influence of inhomogeneous refractive index fields on particle image velocimetry (PIV) measurements is a well known problem, which leads to an unknown measurement uncertainty in, e.g., flame flows, shock waves and super sonic flows. Previous studies give only rough estimations of the measurement error due to inhomogeneous refractive index fields, and quantitative information is only available for special conditions such as a gradient of the refractive index independent of the viewing direction. Hence, the assessment of the spatial distribution of the quantitative measurement errors inside inhomogeneous refractive index distributions especially for stereoscopic and tomographic PIV is an open question. For this purpose, the flow measurement inside a hot jet flow is considered as an example, and a general analytic description of the error of the measured particle positions inside the hot jet flow is derived, numerically evaluated and finally validated by experiments. In particular, the determination of the particle position with triangulation is investigated, which is performed in stereoscopic and tomographic PIV. As a result, the measurement error is generally larger than for standard PIV without triangulation. The theoretically predicted errors of the measured particle position are validated with experiments and here amount to 11.7 µm for standard PIV and 17.3 µm for triangulation at the same distance from the center of the flow, respectively. Note that the error estimation requires the knowledge of the refractive index field that was determined by temperature measurements in the flow. Furthermore, the error analysis shows that for triangulation the measured particle position depends on the gradient and the curvature of the refractive index field, whereas for standard PIV the measured particle position only depends on the gradient of the refractive index. For the given temperature profile with a maximum temperature of 191 °C, the resulting flow velocity error is maximally 0.8 % with standard PIV, 1.7 % for the in plane and 2.9 % for the out of plane direction with stereoscopic PIV and 1.1 % with triangulation which is performed in tomographic PIV.





Categories: Optics news

Mode matching of Continuous Scanning Laser Doppler Vibration data in the frequency domain

Sun, 04/15/2018 - 06:03
Publication date: August 2018
Source:Optics and Lasers in Engineering, Volume 107

Author(s): P. Chiariotti, M. Martarelli, P. Castellini

Applications as structural diagnostics, condition monitoring and fatigue testing are requiring the development of vibration tests characterized by reduced testing time, fine spatial resolution and high Signal to Noise Ratio (SNR). In this context, Continuous Scanning Laser Doppler Vibrometry (CSLDV) can have a great impact as a substitute of classic Discrete Scanning Laser Doppler Vibrometry (SLDV). In fact, CSLDV makes it possible to measure the target structural vibration much faster and with finer spatial resolution than SLDV, as well keeping an acceptable level of SNR. CSLDV joins together the spatial and time information, because the vibration datum obtained from the laser, which continuously scans (over time and space) the structure under test, is modulated by the Operational Deflection Shape (ODS) excited during the experiment. This results in a spectrum characterized by sideband patterns uniquely associated to the ODS excited. However, the current drawback in fully exploiting CSLDV in everyday testing is related to the necessity of being managed by an expert operator who knows how to extract meaningful information from data measured. This paper proposes a procedure which aims to automatize the information extraction process from CSLDV signals, in order to ease the utilization of CSLDV in vibration laboratories. The idea starts from a simple observation: if the mode shapes of the structure under test are known a priori, e.g. from a numerical model, an analytical formulation or previous measurements, as is the case for fatigue tests, it is possible to settle a procedure that searches for similarities between those known mode shapes (the candidate mode shapes) and ODSs that actually modulate the signal measured. This procedure can therefore be considered a pattern matching technique that is able to identify the resonance frequency related to each ODS and the mode shapes that better match with the ODSs excited. A detailed description of the algorithm is given in this paper. Moreover, the procedure is analyzed in order to discuss its sensitivity to noise, overlapping of resonance frequencies (close modes situation) and ODS complexity. The application of the approach to experimental data is also discussed.





Categories: Optics news

Hierarchical multiple-image encryption based on the cascaded interference structure and vector stochastic decomposition algorithm

Sun, 04/15/2018 - 06:03
Publication date: August 2018
Source:Optics and Lasers in Engineering, Volume 107

Author(s): Xue Zhang, Xiangfeng Meng, Yurong Wang, Xiulun Yang, Yongkai Yin, Xianye Li, Xiang Peng, Wenqi He, Guoyan Dong, Hongyi Chen

A new kind of hierarchical multiple-image encryption method based on the cascaded interference structure and vector stochastic decomposition algorithm is proposed. In this method, by using the nonequal modulus decomposition and vector stochastic decomposition algorithm, the Kth-level secret image modulated by a random phase distribution is analytically encoded into a Kth-level phase-only mask (POM) key and the (K−1)th-level complex amplitude field whose real amplitude is the (K−1)th-level secret image. Then, served as the input condition, the generated complex amplitude field is further encoded into a (K−1)th-level POM key and the (K−2)th-level complex amplitude, and so on, until the 1st-level complex amplitude field is decomposed into two POMs: one is the 1st-level key, and the other is the ciphertext. When decryption occurs, only when the high-level users simultaneously obtain all the phase keys, the correct sequential orders of phase keys, and the correct geometrical parameters, all the secret images are retrieved successfully. Both theoretical analysis and numerical simulations verify the feasibility of this method.





Categories: Optics news

Full field modal measurement with a single standard camera

Sun, 04/15/2018 - 06:03
Publication date: August 2018
Source:Optics and Lasers in Engineering, Volume 107

Author(s): Clément Jailin

The full field measurement of 8 vibration modes of a cantilever plate, up to the kHz frequency is performed using a single standard camera. The image acquisition is carried out at low rate but using fast exposure time (1/4000 s) that “freezes” a part of the motion. A deflectometry setup coupled with digital image correlation analysis allows angle fields, then deflection fields, to be measured. An out–of–plane displacement database is generated from all stored fields. This snapshot library is finally post-processed using principal component analysis techniques and adapted weights that enable space vibration fields to be extracted. A test case is performed on a reflecting cantilever steel plate. 370 deflection fields are measured allowing 8 space vibration fields to be extracted. The natural frequencies of those modes are estimated using the Rayleigh ratio. A coarse and visual comparison with a numerical simulation shows similar results for 6 of the 8 space modes.





Categories: Optics news

Interference-based multiple-image encryption using binary phase masks

Sun, 04/15/2018 - 06:03
Publication date: August 2018
Source:Optics and Lasers in Engineering, Volume 107

Author(s): Youhyun Kim, Jaehun Song, Inkyu Moon, Yeon Ho Lee

We propose a new scheme to encrypt multiple images simultaneously using two-dimensional binary phase masks. Each of the original greyscale images is first decomposed into two pure phase-only images, which corresponds to the reverse process of an optical interference. Two phase-only images have random distributions of phases in the range from 0 to 2π, and will serve as a secret image and a private key. Next, each pixel of the secret image is subdivided into four equal segments. Then, the four pixel-quadrants are separately phase encoded in accordance with the four elements of a row of a 4-order Hadamard matrix. By applying this procedure to other secret images, we obtain four phase-encoded images, which are then superimposed to yield the final encrypted image. We can successfully restore the four original images separately when the correct Hadamard matrix and the correct private key are used. We also show that the correlation coefficient (CC) is as low as 0.05 when the decryption is done by wrong Hadamard matrices and/or private keys.





Categories: Optics news

Fiber optic accelerometer based on grating inscribed over innermost-clad of multi-clad fiber

Sun, 04/15/2018 - 06:03
Publication date: August 2018
Source:Optics and Lasers in Engineering, Volume 107

Author(s): Weijia Bao, Xueguang Qiao, Qiangzhou Rong, Ruohui Wang, Zhihua Shao, Fengyi Chen

A special fiber Bragg grating (FBG) that is inscribed over the core and innermost depressed-index cladding of a short multi-clad fiber (MCLF) by femtosecond laser side-illumination technique is proposed and demonstrated for orientation-dependent measurement, experimentally. Splicing the MCLF with standard single-mode fiber (SMF) provides a cladding-mode generation mechanism via core mismatch, and then “cladding FBG” in MCLF can simultaneously generate two resonances in reflection. The cladding mode shows a significant response to fiber bending due to novel refractive-index profile of MCLF and coupling in the splicing junction. And the asymmetry “cladding FBG” configuration relatively to fiber core center enables it to perform strong orientation-dependent response to the fiber bending. These two properties are well applied to measure acceleration with high resolution of 0.02 m/s2 and orientation-dependence. The cladding and core mode also present linear wavelength-shifting with temperature variation but no intensity fluctuations. Furthermore, the accidental power perturbation or cross-sensitivity can be calibrated out by monitoring the fundamental core mode resonance.





Categories: Optics news

High-speed 3D shape measurement with structured light methods: A review

Sun, 04/15/2018 - 06:03
Publication date: July 2018
Source:Optics and Lasers in Engineering, Volume 106

Author(s): Song Zhang

High-speed 3D shape measurement (or imaging) has seen tremendous growths over the past decades, especially the past few years due to the improved speed of computing devices and reduced costs of hardware components. 3D shape measurement technologies have started penetrating more into our daily lives than ever before with the recent release of iPhone X that has an built-in 3D sensor for Face ID, along with prior commercial success of inexpensive commercial sensors (e.g., Microsoft Kinect). This paper overviews the primary state-of-the-art 3D shape measurement techniques based on structured light methods, especially those that could achieve high measurement speed and accuracy. The fundamental principles behind those technologies will be elucidated, experimental results will be presented to demonstrate capabilities and/or limitations for those popular techniques, and finally present our perspectives on those remaining challenges to be conquered to make advanced 3D shape measurement techniques ubiquitous.





Categories: Optics news

The application of moiré inversion technique in the characterization of micro-scale 3D periodic structures

Sun, 04/15/2018 - 06:03
Publication date: July 2018
Source:Optics and Lasers in Engineering, Volume 106

Author(s): Dan Wu, Huimin Xie, Dejin Huang, Kun Qin

The characterization of micro/nano periodic structures is of great importance in the micro/nano manufacturing field. Existing characterization methods based on inversion technique are mostly for planar structures. An effective method for the characterization of three-dimensional (3D) periodic structures based on inversion technique is proposed in this paper. The inversion technique is based on the stereo vision technique and the digital phase shifting method. The 3D micro/nano periodic structures were imaged and captured under the microscope from two relative camera angles. Digital reference grating were superimposed with the periodic structures as specimen gratings. Consequently, the shape and periodic structures of the specimen can be characterized by the phase shifting method. A simulation test was performed and the results indicate that the proposed method is reliable. Simultaneously, an experiment for the characterization of the periodic structure on the bulged polyimide films was carried out on an optical microscope. The method is verified effective and has potential for the characterization of various 3D periodic structures. With the aid of various high-resolution microscopes, the proposed method can be applied to characterize the 3D periodic structures from nano-scale to micro-scale.





Categories: Optics news

Deformable mirror-based optical design of dynamic local athermal longwave infrared optical systems

Sun, 04/15/2018 - 06:03
Publication date: July 2018
Source:Optics and Lasers in Engineering, Volume 106

Author(s): Benlan Shen, Jun Chang, Yajun Niu, Weilin Chen, Zhongye Ji

This paper presents a dynamic local athermalisation method for longwave infrared (LWIR) optical systems; the proposed design uses a deformable mirror and is based on active optics theory. A local athermal LWIR optical system is designed as an example. The deformable mirror is tilted by 45° near the exit pupil of the system. The thermal aberrations are corrected by the deformable mirror for the local athermal field of view (FOV) that ranges from −40 °C to 80 °C. The types of thermal aberrations are analysed. Simulated results show that the local athermal LWIR optical system can effectively detect targets in the region of interest within a large FOV and correct thermal aberrations in actual working environments in real time. The system has numerous potential applications in infrared detection and tracking, surveillance and remote sensing.





Categories: Optics news

Single-shot three-dimensional reconstruction based on structured light line pattern

Sun, 04/15/2018 - 06:03
Publication date: July 2018
Source:Optics and Lasers in Engineering, Volume 106

Author(s): ZhenZhou Wang, YongMing Yang

Reconstruction of the object by single-shot is of great importance in many applications, in which the object is moving or its shape is non-rigid and changes irregularly. In this paper, we propose a single-shot structured light 3D imaging technique that calculates the phase map from the distorted line pattern. This technique makes use of the image processing techniques to segment and cluster the projected structured light line pattern from one single captured image. The coordinates of the clustered lines are extracted to form a low-resolution phase matrix which is then transformed to full-resolution phase map by spline interpolation. The 3D shape of the object is computed from the full-resolution phase map and the 2D camera coordinates. Experimental results show that the proposed method was able to reconstruct the three-dimensional shape of the object robustly from one single image.





Categories: Optics news

A method of solving tilt illumination for multiple distance phase retrieval

Sun, 04/15/2018 - 06:03
Publication date: July 2018
Source:Optics and Lasers in Engineering, Volume 106

Author(s): Cheng Guo, Qiang Li, Jiubin Tan, Shutian Liu, Zhengjun Liu

Multiple distance phase retrieval is a technique of using a series of intensity patterns to reconstruct a complex-valued image of object. However, tilt illumination originating from the off-axis displacement of incident light significantly impairs its imaging quality. To eliminate this affection, we use cross-correlation calibration to estimate oblique angle of incident light and a Fourier-based strategy to correct tilted illumination effect. Compared to other methods, binary and biological object are both stably reconstructed in simulation and experiment. This work provides a simple but beneficial method to solve the problem of tilt illumination for lens-free multi-distance system.





Categories: Optics news

A systematic analysis for the quantitative comparison of phase retrieval methods based on alternating projections

Sun, 04/15/2018 - 06:03
Publication date: July 2018
Source:Optics and Lasers in Engineering, Volume 106

Author(s): Francisco E. Veiras, Arturo Bianchetti, Pablo Etchepareborda, Ana L. Vadnjal, Alejandro Federico

We present a numerical and experimental scheme for the systematic analysis and comparison of phase retrieval techniques based on alternating projection numerical methods. This comparison allows us to evaluate the most common and recently introduced phase retrieval methods. The proposed scheme gives a quantitative comparison that helps to elucidate the differences between them and develop proper technical implementations of phase retrieval. The comparison is made by means of a numerical and experimental scheme that allows us to evaluate phase retrieval experiments. In this work, the drawbacks of using arbitrary random initial seeds to support the phase retrieval numerical algorithms are also analyzed and discussed. Moreover, we show the convenience of using a rough object phase estimation, which is obtained by means of a simple holographic technique, as the initial seed. This seed dramatically reduces the computational load of the algorithms by decreasing the successive iterations from hundreds to less than twenty. The experimental object under study is a random phase object within a micro-channel. As a proof of concept, this micro-channel combined with a millimeter size semicircular hole, which provides a reference wave, conforms a primitive sensor. The performance of the algorithms is not only measured by the usual convergence error, but also by means of a quality index that requires a direct comparison against the generally unknown original phase object. Thus, in order to evaluate the experimental performance of the phase retrieval techniques, we implement an interferometric optical setup that allows us to compare the results obtained by both techniques. The experiment proposed is a valuable tool for quantitative experimental evaluation of phase retrieval techniques in the optical domain.





Categories: Optics news

On the formation features, microstructure and microhardness of single laser tracks formed by laser cladding of a NiCrBSi self-fluxing alloy

Sun, 04/15/2018 - 06:03
Publication date: July 2018
Source:Optics and Lasers in Engineering, Volume 106

Author(s): O.G. Devojno, E. Feldshtein, M.A. Kardapolava, N.I. Lutsko

In the present paper, the influence of laser cladding conditions on the powder flow conditions, as well as the microstructure, phases and microhardness of an Ni-based self-fluxing alloy coating are described. The optimal granulations of a self-fluxing alloy powder and the relationship between the flow of powder of various fractions and the flow rate and pressure of the transporting gas have been determined. The laser beam speed, track pitch and the distance from the nozzle to the coated surface influence the height and width of single tracks. Regularities in the formation of microstructure under different cladding conditions are defined, as well as regularity of distribution of elements over the track depth and in the transient zone. The patterns of microhardness distribution over the track depth for different cladding conditions are found. These patterns as well as the optimal laser spot pitch allowed obtaining a uniform cladding layer.





Categories: Optics news

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