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Non-Uniform Thermal Behavior and Shell Growth within Mould for Wide and Thick Slab Continuous Casting

STEEL RESEARCH INTERNATIONAL 2012年第12期83卷 1203-1213页

作者： Tang, Ling Yao, Man Wang, Xudong Zhang, Xiaobing Dalian Univ Technol Sch Mat Sci & Engn Dalian 116024 Liaoning Provin Peoples R China Jiangsu Shagang Grp Chief Engn Off Zhangjiagang 21562 Jiangsu Peoples R China

This work mainly presented two aspects, inverse problem model technique that allowed detailed description of heat transfer behaviors in the mould from simulations of coupled measured temperature. Additionally, shell growth rate defined for discussing irregular shell growth was presented for wide and thick continuous casting slab. As a result, the inverse problem model provided good agreement on prediction of mould temperatures. Furthermore, the model's transient approach could show the non-uniform characteristics of heat flux and shell thickness. The non-uniformity of heat transfer was significantly prominent on outside radius face more than that of inside radius face, and the non-uniformity of shell thickness distribution on narrow face is smaller than that of wide face. It was also able to analyze behavior of initial solidified shell within the mould through the shell growth rate. Shell growth rate reached the maximum in the region of 100200 mm below meniscus, as well as local heat flux. Effect of casting speed on the non-uniformity of heat transfer and shell growth rate was also discussed. Although complex in nature, these models likely became part of optimization and control of continuous casting process.

关键词： continuous casting heat transfer shell growth non-uniformity inverse algorithm

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Quantitative microwave-induced thermoacoustic tomography

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MEDICAL PHYSICS 2010年第7期37卷 3752-3759页

作者： Yao, Lei Guo, Gaofeng Jiang, Huabei Univ Florida Dept Biomed Engn Gainesville FL 32611 USA

Purpose: Microwave-induced thermoacoustic tomography (MI-TAT) is an imaging modality that exploits dielectric contrast while producing images with high ultrasound resolution. Existing reconstruction algorithms for MI-TAT are qualitative and can image only the distribution of the absorbed microwave energy or power loss density. Here the authors describe a method for quantitative MI-TAT and obtain the distribution of dielectric property which directly correlates with tissue structural and functional information. Methods: The authors implement the quantitative MI-TAT method based on the finite-element (FE) solution to the Helmholtz equation for electromagnetic field coupled with the thermoacoustic wave equation. Regularization techniques are also used in the FE-based reconstruction algorithm. Results: Simulation results are obtained under various practical scenarios including different noise levels, different contrast levels between the heterogeneity and background region, and multiple targets with various sizes and shapes. Conclusions: The quantitative MI-TAT method described can provide accurate recovery of conductivity distribution in heterogeneous media and is insensitive to noise effect. (C) 2010 American Association of Physicists in Medicine. [DOI: 10.1118/1.3456926]

关键词： thermoacoustic tomography microwave imaging inverse algorithm finite-element method

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Magnetic Flux Leakage Signal Inversion Based on Improved Efficient Population Utilization Strategy for Particle Swarm Optimization

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RUSSIAN JOURNAL OF NONDESTRUCTIVE TESTING 2017年第12期53卷 862-873页

作者： Han, Wenhua Wu, Zhengyang Zhou, Mengchu Hou, Edwin Su, Xiaoyan Wang, Ping Tian, Guiyun Shanghai Univ Elect Power Coll Automat Engn Shanghai 200090 Peoples R China New Jersey Inst Technol Dept Elect & Comp Engn Newark NJ 07102 USA Nanjing Univ Aeronaut & Astronaut Coll Automat Engn Nanjing 210016 Peoples R China Newcastle Univ Sch Elect & Elect Engn Newcastle Upon Tyne NE1 7RU Tyne & Wear England

In this paper, an improved efficient population utilization strategy for particle swarm optimization (IEPUS-PSO) for high dimension problem is proposed to estimate defect profile from magnetic flux leakage (MFL) signals. In the IEPUS-PSO, a mutation probability is proposed to distinguish local version and global version in particle change model and a self-adapted mutation operator, which is used to update the particles' positions randomly, is introduced into EPUS-PSO. The IEPUS-PSO- based inversing technique is used to estimate the defect profiles. The estimated defect profiles of simulation signals demonstrate that the inversing technique based on the IEPUS-PSO outperforms the one based on EPUS-PSO. The results estimated from real MFL signals by the IEPUS-PSO-based inversing technique indicate that the algorithm is capable of decreasing the computation time. The results show that the IEPUS-PSO-based inversing technique could improve the reconstruction precision by two orders of magnitude for the MFL simulation signals, and for the real MFL signals, the computation time is reduced by about 30% nearly under the same reconstruction precision.

关键词： inverse algorithm profile estimation magnetic flux leakage signal inversion

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Image Reconstruction of a Charge Coupled Device Based Optical Tomographic Instrumentation System for Particle Sizing

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SENSORS 2010年第10期10卷 9512-9528页

作者： Idroas, Mariani Rahim, Ruzairi Abdul Green, Robert Garnet Ibrahim, Muhammad Nasir Rahiman, Mohd Hafiz Fazalul Univ Teknol Malaysia Fac Chem & Nat Resources Engn Utm Skudai 81310 Johor Malaysia Univ Teknol Malaysia Fac Elect Engn Utm Skudai 81310 Johor Malaysia Sheffield Hallam Univ Sch Engn Sheffield S1 1WB S Yorkshire England Univ Malaysia Perlis Sch Mechatron Engn Arau 02600 Perlis Malaysia

This research investigates the use of charge coupled device (abbreviated as CCD) linear image sensors in an optical tomographic instrumentation system used for sizing particles. The measurement system, consisting of four CCD linear image sensors are configured around an octagonal shaped flow pipe for a four projections system is explained. The four linear image sensors provide 2,048 pixel imaging with a pixel size of 14 micron x 14 micron, hence constituting a high-resolution system. Image reconstruction for a four-projection optical tomography system is also discussed, where a simple optical model is used to relate attenuation due to variations in optical density, [R], within the measurement section. Expressed in matrix form this represents the forward problem in tomography [S] [R] = [M]. In practice, measurements [M] are used to estimate the optical density distribution by solving the inverse problem [R] = [S](-1) [M]. Direct inversion of the sensitivity matrix, [S], is not possible and two approximations are considered and compared-the transpose and the pseudo inverse sensitivity matrices.

关键词： bubbles velocity optical tomography inverse algorithm

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Detection and quantification of damage in bridges using a hybrid algorithm with spatial filters under environmental and operational variability

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STRUCTURES 2021年 32卷 617-631页

作者： Lakshmi, K. CSIR Struct Engn Res Ctr CSIR Campus Chennai 600113 Tamil Nadu India

It is essential to isolate the environmental effects on the structure from the incipient damage during structural health monitoring, failing which, may mislead the diagnostic process in a way, either, by giving false positive alarms or masking the existing real damage. The modal filter is popularly used to handle environmental variability, while detecting the current state of the structure, during structural health monitoring. However, this technique is a qualitative one and it cannot identify the spatial location and the extent of the damage. In this paper, the modal filter is combined with an inverse algorithm to localize and quantify the extent of damage, while handling environmental variability. The inverse damage detection problem is formulated as a constrained optimization problem and solved using a Multi cluster hybrid adaptive differential search algorithm (MCHADSA). A new damage index is proposed, to detect the exact time instant of damage, alleviating the effecting confounding factors like environmental and operational variability (EoV) and measurement noise. Numerical experiments are conducted to evaluate the performance of the proposed inverse damage diagnostic MCHADS algorithm and the results are presented in this paper. A beam girder is taken as the first example followed by a more realistic example of a live bridge across river Amaravati near Dharapuram, Tamil Nadu, India. The studies presented in this paper indicate that the proposed Modal filter-based hybrid inverse algorithm is effective in localizing as well as quantifying the damage. The effect of modeling errors is also investigated in the proposed algorithm.

关键词： Structural health monitoring Damage detection Environmental variability Modal filter inverse algorithm Meta-heuristic algorithms Constrained optimization technique Differential search

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Forecast of tsunamis from the Japan-Kuril-Kamchatka source region

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NATURAL HAZARDS 2006年第3期38卷 411-435页

作者： Yamazaki, Y Wei, Y Cheung, KF Curtis, GD Univ Hawaii Manoa Dept Ocean & Resources Engn Honolulu HI 96822 USA

This paper describes an investigation of the subfault distribution along the Japan-Kuril-Kamchatka subduction zone for the implementation of a far-field tsunami forecast algorithm. Analyses of seismic data from 1900 to 2000 define the subduction zone, which in turn is divided into 222 subfaults based on the fault characteristics. For unit slip of the subfaults, a linear long-wave model generates a database of mareograms at water-level stations along the subduction zone and at warning points in the North Pacific. When a tsunami occurs, an inverse algorithm determines the slip distribution from near-source water-level records and predicts the waveforms at the warning points using the pre-computed mareograms. A jackknife resampling scheme uses combinations of input water-level records to provide a series of waveform predictions for the computation of the confidence-interval bounds. The inverse algorithm is applied to hindcast two major tsunamis generated from the Japan-Kuril-Kamchatka source and the computed tsunami heights show good agreement with recorded water-level data.

关键词： earthquakes fault inverse algorithm long-wave model subduction tsunamis tsunami forecast tsunami warning

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Tomographic reconstruction of damage images in hollow cylinders using Lamb waves

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ULTRASONICS 2014年第7期54卷 2015-2023页

作者： Hu, Bin Hu, Ning Li, Leilei Li, Weiguo Tang, Shan Li, Yuan Peng, Xianghe Homma, Atsushi Liu, Yaolu Wu, Liangke Ning, Huiming Chongqing Univ Sci & Technol Coll Met & Mat Engn Chongqing 401331 Peoples R China Chongqing Univ Coll Aerosp Engn Chongqing 400044 Peoples R China Chiba Univ Dept Mech Engn Inage Ku Chiba 2638522 Japan Tohoku Univ Dept Nanomech Aoba Ku Sendai Miyagi 9808579 Japan

Lamb wave tomography (LWT) is a potential and efficient technique for non-destructive tomographic reconstruction of damage images in structural components or materials. A two-stage inverse algorithm proposed by the authors for quickly reconstructing the damage images was applied to hollow cylinders. An aluminum hollow cylinder with an internal surface pit and a Carbon Fiber Reinforced Plastic (CFRP) laminated hollow cylinder with an artificial internal surface damage were used to validate the proposed method. The results show that the present method is capable of successfully reconstructing the images of the above damages in a larger inspection area with much less experimental data compared to some conventional ultrasonic tomography techniques. (C) 2014 Elsevier B.V. All rights reserved.

关键词： Lamb wave tomography inverse algorithm Damage image Attenuation

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Characterization of the interface heat transfer coefficient during non-isothermal bulk forming of Ti-6Al-4 V alloy

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PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART B-JOURNAL OF ENGINEERING MANUFACTURE 2011年第B9期225卷 1703-1712页

作者： Yeom, J-T Park, N-K Shin, T-J Hwang, S. M. Hong, S. S. Shim, I. O. Lee, Y. H. Lee, C. S. Korea Inst Mat Sci Special Alloys Res Grp Chang Won 641831 South Korea Pohang Univ Sci & Technol Dept Mech Engn Pohang South Korea Agcy Def Dev Taejon 300600 South Korea POSCO Tech Res Labs Wire Rod Res Grp Pohang South Korea Pohang Univ Sci & Technol Dept Mat Sci & Engn Pohang South Korea

An investigation on the interface heat transfer coefficient during bulk forming of glass-coated Ti-6Al-4 V was carried out. Heat transfer experiments were conducted where two dies were heated to various temperatures and Ti-6Al-4 V cylindrical specimen heated to 970 degrees C was upset tested. Temperature changes of the lower die consisting of AISI H13 were recorded in relation to the process variables such as reduction ratio, lubrication condition, and initial die temperature. The temperature change data were analysed to determine the interface heat transfer coefficients between lubricated die and glass-coated workpiece by using the plotting approach on calibration curves derived from analytical method and the inverse algorithm coupled to finite element (FE) analysis. The former was to determine the initial guessing values for applying the inverse algorithm. The validation of final coefficients determined by the inverse algorithm was made by comparison between the upsetting process and the FE analysis results.

关键词： interface heat transfer coefficient Ti-6Al-4 V one-dimensional conduction model inverse algorithm FE analysis

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inverse solution to heat transfer coefficient during heat assembly of aluminum alloy drill pipes

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ADVANCES IN MECHANICAL ENGINEERING 2017年第7期9卷

作者： Sun, Youhong Wang, Xiaofeng Liu, Baochang Ding, Dali Meng, Qingnan Jilin Univ Construct Engn Coll West St Democracy Changchun 130026 Jilin Peoples R China Minist Land & Resources Key Lab Drilling & Exploitat Technol Complex Cond Changchun Jilin Peoples R China Jilin Univ State Key Lab Superhard Mat Changchun Jilin Peoples R China Jilin Univ Sch Math Changchun Jilin Peoples R China

With the rapid development of oil and gas industry, as well as geological exploration industry, the requirements on properties of aluminum alloy drill pipes are increasing. During heat assembly of aluminum alloy drill pipes, the cooling process inside the pipes has a direct impact on the connection performance of pipes. Thus, study of the convective heat transfer coefficient between the cooling water and the internal wall of aluminum alloy pipes is important. Conventional algorithms cannot easily solve the problem of determining the heat transfer coefficient at the complex structure of aluminum alloy drill pipes. Therefore, this article conducts a heat assembly experiment between aluminum alloy drill pipes and steel joints to obtain adequate, accurate temperature data. Based on these experimental data and an inverse heat conduction model, the heat transfer coefficients during the heat assembly process are determined by a finite element program and the differential evolution algorithm. The correlation curve between the cooling water flowrate and the convective heat transfer coefficient obtained in this article is important in the accurate prediction of heat transfer capacity and temperature field distribution during heat assembly at different cooling water flowrates. The analysis results show that the heat transfer coefficients are nonlinear functions of cooling water flowrates. The temperature is highest at location A(1) and gradually declines backward along the axis of the drill pipe. The heat transfer coefficient gradually declines backward along the axis of the drill pipe. The increasing flowrate of cooling water will cause the convective heat transfer coefficient along the axis of the drill pipe to escalate irregularly.

关键词： Heat transfer coefficient inverse algorithm aluminum alloy drill pipe steel joint heat assembly

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inverse heat flux problem in quenching

American Society of Mechanical Engineers, Heat Transfer Divi...

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American Society of Mechanical Engineers, Heat Transfer Division, (Publication) HTD 2000年 366卷 271-278页

作者： Alam, M. Khairul Kuriger, Rex J. Zhong, Rong Department of Mechanical Engineering 251 Stocker Center Ohio University Athens OH 45701 United States

The quenching process is an important heat treatment method used to improve material properties. However, the heat transfer during quenching is particularly difficult to analyze and predict. To collect temperature data, quench probes have been used in controlled quenching experiments. The process of determination of the heat flux at the surface from the measured temperature data is the inverse Heat Conduction Problem (IHCP), which is extremely sensitive to measurement errors. This paper reports on an experimental and theoretical study of quenching which is carried out to determine the surface heat flux history during a quenching process by an IHCP algorithm. The inverse heat conduction algorithm is applied to experimental data from a quenching experiment The surface heat flux is then calculated, and the theoretical curve is compared with experimental results.

关键词： inverse algorithm Optimization Quenching

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