Signal Improvement for Underwater LIBS

We employed a collinear long-short double-pulse laser induced breakdown spectroscopy (LS-DP-LIBS) to detect the underwater metal samples. The emission spectra, time-resolved signal, plasma images and sound characteristics of plasma shockwaves are experimentally investigated in this work. The results show that the underwater signal of Al, Cu and Fe spectral lines are significantly improved by collinear LS-DP-LIBS with inter-pulse delay of 35 us. The mechanism of the signal improvement is considered to be the pre irradiation effect of the long pulse laser beam. In the collinear LS-DP-LIBS method, the long pulse first generates a cavitation bubble in water and provides a gaseous environment. Then the short pulse generates the plasma from the sample surface. The present experiments show that the collinear LS-DP-LIBS method offers a significant signal improvement in underwater measurement of metal samples. This new method has great potential in deep-sea exploration using LIBS

Improved Analysis of Manganese in Steel Samples Using Collinear Long–Short Double Pulse Laser-Induced Breakdown Spectroscopy (LIBS)

A long-short double pulse laser-induced breakdown spectroscopy (long-short DP-LIBS) method was employed to improve the performance of LIBS for the measurement of manganese in steel samples. The long pulse was generated by a Nd:YAG laser which was operated at free runing (FR) mode. To investigate the detection ability without sample preparation, the steel washers were tested using SP-LIBS and long-short DP-LIBS, respectively. The measurement results show that the long-short DP-LIBS method was able to record clear spectra from the rusty steel washers. The steel washers were also measured after the polishing process. The measurement results show that the signal intensity was enhanced by long-short DP-LIBS. Through the observation with scanning electron microscope (SEM) on the laser craters, the results suggest that the improvement of detection ability can be attributed to the pre-radiation effect of long-pulse laser beam. Next, the analytical performance for quantitative measurement of manganese was evaluated by employing ten standard steel samples. The results show that the linearty fit (R2) of calibration curve is 0.988 for long-short DP-LIBS, whereas, R2 is only 0.810 for SP-LIBS under the same measurement conditions. The five times repeated measurement results show that the average Relative Standard Deviation (RSD) of the tested samples is 29.3% for SP-LIBS and is 10.5% for long-short DP-LIBS. The prediction results also show that the average Relative Error of Prediction (REP) is 94.9% for SP-LIBS and it 4.9% for long-short DP-LIBS. The experimental results in current work demonstrate that long-short DP-LIBS is promising for the on line measurement of steel in the steelmaking plant

EVALUATION OF 3D MEASUREMENT USING CT-TDLAS

In order to satisfy the requirements of high quality and optimal material manufacturing process, it is important to control the environment of the manufacturing process. Depending on these processes, it is possible to improve the quality of the product by adjusting various gases. With the advent of the TDLAS (Tunable laser absorption spectroscopy) technique, the temperature and concentration of the gases can be measured simultaneously. Among them, CT-TDLAS (Computed tomography-tunable diode laser absorption spectroscopy) is the most important technique for measuring the distributions of temperature and concentration across the 2-dimensional planes. In this study, suggest a 3-dimensional measurement to consider the irregular flow of supplying gases. Used the SMART (simultaneous multiplicative algebraic reconstruction technique) algorithm among the CT algorithms. Phantom data sets have been generated by the using Gaussian distribution method. It can be shown expected temperature and concentration distributions. The HITRAN database in which the thermo-dynamical properties and the light spectra of H2O are listed were used for the numerical test. The relative average temperature error ratio in the results obtained by the SMART algorithm was about 3.2% for temperature. The maximum error was 86.8K

Study on tightly coupled LiDAR-Inertial SLAM for open pit coal mine environment

With the rapid development of artificial intelligence and unmanned and other related disciplines, the intelligence and unmanned of coal mining equipment has become a new trend. The application of intelligent equipment will greatly improve the productivity of coal mine operations as well as personnel safety. In this environment, the existing LIDAR-based Simultaneous localization and mapping (SLAM) solution is prone to positioning drift and large mapping errors. To address these problems, a tightly coupled SLAM algorithm based on LiDAR (Light Detection and Ranging) and IMU (Inertial Measurement Unit) is proposed, which uses both LiDAR and IMU sensors as data inputs.The front-end uses an iterative extended Kalman filter to fuse the pre-processed LiDAR feature points with the IMU data and uses backward propagation to correct the radar motion distortion, the back-end uses the LiDAR relative positional factor to use the LiDAR inter-frame alignment results as a constraint factor together with the loopback factor to complete the global factor map optimization. The robustness and accuracy of the algorithm are verified using open source dataset and open pit coal mine field dataset. The experimental results show that the accuracy of the proposed algorithm is consistent with the current LiDAR SLAM algorithm in the urban structured environment, while the proposed algorithm improves the localization accuracy by 46.00% and 23.15% with higher robustness than the FAST-LIO2 and LIO-SAM tightly coupled algorithms for the open pit coal mine field environment of more than 2000 meters long, respectively

Feasibility Investigation for Online Elemental Monitoring of Iron and Steel Manufacturing Processes using Laser-Induced Breakdown Spectroscopy

The metallurgical industries are very important for social development. In order to improve the metallurgical techniques and quality of products, the real-time analysis and monitoring of iron and steel manufacturing processes are very significant. Laser-induced breakdown spectroscopy (LIBS) has been studied and applied for the contents measurement of iron and steel. In this paper, the remote open-path LIBS measurement was studied under different sample temperature, lens to target distance (LTD), sample angle conditions to clarify its online measurement features. The 3D profile measurement system of parallel laser beam fringes projection was also developed to measure the sample profile at different sample temperature. The measurement results demonstrated the robustness of remote open-path LIBS system and 3D profile measurement system. However, the correction is necessary to enhance the detection ability of LIBS online measurement. In order to improve the precision and accuracy of real-time elemental measurement, an innovative co-axial laser beam measurement system combining LIBS and 3D profile techniques is proposed to automatically adjust the focus unit and measure the sample components. The further study of this promising method will be developed for online application of iron and steel manufacturing processes

Quantitative Elemental Analysis Using Long-Short Double-Pulse Laser Induced Breakdown Spectroscopy

鉄鋼プロセス，ボイラなどの様々な産業プロセスにおいて，物質の元素組成をリアルタイムで計測可能な技術が求められている．鉄鋼プロセスでは，鉄鉱石，コークス，石灰石などを原料として，鋼板などを製造する過程で各プロセス中の成分組成を計測することが求められ，溶融金属の組成などをリアルタイム制御することなどが重要となる．しかし，現在まで，これらの産業プロセスで元素組成をリアルタイムで計測可能な技術や装置は実用化されていない．レーザーを用いた非接触，リアルタイム計測方法として，レーザー誘起ブレークダウン分光法(Laser Induced Breakdown Spectroscopy，LIBS)がある．本研究では，LIBSを用いた元素組成の定量計測を目的に，ロング・ショートダブルパルスLIBSの開発を行った．本手法を鋼材中のマンガン及び炭素計測に適用し，計測の安定性，定量性に優れた特性を有することを実証した．The understanding of the controlling factors is becoming more important to improve the efficiency of industrial systems including steel-making processes, boilers and so on. Laser diagnostics such as laser-induced breakdown spectroscopy (LIBS) makes it possible to monitor these parameters due to their fast response, high sensitivity, and non-contact features. In this study, a new collinear long and short double pulse LIBS method was developed to improve the detection ability and the measurement accuracy by the control of the plasma cooling process using the long pulse-width laser radiation. The plasma generated by the short pulse-width laser is stabilized and maintained at high temperature during the plasma cooling process by long pulse-width laser radiation. The method was demonstrated to have better measurement stability and quantitative measurement characteristics for Manganese and Carbon measurement in the steel samples compared to the normal single pulse LIBS method

CURRENT DENSITY EFFECTS ON PLASMA EMISSION DURING PLASMA ELECTROLYTIC OXIDATION (PEO) ON AZ91D-MAGNESIUM ALLOY

The effect of bipolar pulse mode current ratio on plasma behavior was investigated in PEO on AZ91D Mg-Alloy. Two cases of current ratio including 1.20 and 0.88 were applied to the sample. Plasma emission behavior was studied using plasma images and plasma emission measured by photodetector and Intensified Charged-Couple Device (ICCD) camera. The current ratio of greater than 1 shows the continuous increase and then stabilization in emission intensity with a gradual increase in voltage throughout the PEO process. In contrast, the current ratio of less than 1, a sudden drop in plasma emission intensity with voltage was found after 786s. Therefore, PEO process can be divided into two regimes, arc regime and soft regime, before and after voltage drop respectively. Results of measured spectra show that a soft regime does not have atomic or ionic excitation during PEO process. It is demonstrated that the growth of porous layer during PEO can be controlled, which is benefit for the protective oxide coating of sample

Sulfur Detection in Coke by Laser-Induced Breakdown Spectroscopy

Accurate determination of sulfur (S) content in coke is of great significance to improve the quality of iron and steel. In this study, the sulfur in coke standard samples was detected in argon (Ar) atmosphere using laser-induced breakdown spectroscopy (LIBS), and S I 182.034 nm was chosen as the analytical line. The experimental results showed that it was advantageous to detect S in the early stage of plasma generation. Compared with tablet samples, the spectral intensities of binder samples on the copper foil tape were greater and the signal-to-noise ratio (SNR) was also greater. As for reduplicate experiments, the coefficient of variation (CV) of spectral intensities of binder samples was 10.58% and that of tablet samples was 88.54%. The plasma signal induced by binder samples was stronger and more stable. The internal standard method and support vector machine regression (SVR) were used to quantitatively analyze the sulfur content in binder samples, and SVR showed more accurate prediction accuracy. R2 of SVR with electron density and self-absorption correction was 0.965, root mean square error of prediction (RMSEP) was 0.18 wt.% and the limit of detection (LOD) was 0.026%. This result proved the applicability of binder for sulfur measurement in coke using LIBS

Sample Temperature Effect on Steel Measurement Using SP-LIBS and Collinear Long-short DP-LIBS

Laser induced breakdown spectroscopy (LIBS) has been investigated as a potential multi-element quantitative analysis tool for the quality control of on-line steel production. This research investigated influence of sample temperature on steel sample measurement using collinear long-short dual-pulse LIBS (long-short DP-LIBS) and single-pulse LIBS (SP-LIBS). The standard steel sample has been uniformly heated in a muffle furnace from 20°C to 700°C. The experimental results show that sample temperature has significantly effect on measurement result using SP-LIBS. However, long-short DP-LIBS can effectively reduce the sample temperature effect on measurement result. The detection characteristics of long-short DP-LIBS and SP-LIBS were compared using the intensity ratio of I Mn 404.136 nm/I Fe 400.524 nm and I Fe 402.187 nm/I Fe 400.524 nm under different delay time and different sample temperature conditions. The signal intensity and plasma temperature can be maintained higher and more stable for a period of time and at different sample temperature by long-short DP-LIBS with smaller error bar compared with that of SP-LIBS, which indicated long-short DP-LIBS has better measurement repeatability than SP-LIBS. The plasma temperature correction method was applied to compare the detection features of long-short DP-LIBS and SP-LIBS. The signal stability of long-short DP-LIBS measurement was improved significantly at different sample temperature with plasma temperature correction. These results demonstrated that the effect of sample temperature can be reduced using long-short DP-LIBS method to improve the on-line detection capability for steel measurement in complex environment