State of the Art of Laser Hardening and Cladding

In this paper an overview is given about laser surface modification processes, which are developed especially with the aim of hardness improvement for an enhanced fatigue and wear behaviour. The processes can be divided into such with and without filler material and in solid-state and melting processes. Actual work on shock hardening, transformation hardening, remelting, alloying and cladding is reviewed, where the main focus was on scientific work from the 21st century

Advanced Mathematics and Computational Applications in Control Systems Engineering

Control system engineering is a multidisciplinary discipline that applies automatic control theory to design systems with desired behaviors in control environments. Automatic control theory has played a vital role in the advancement of engineering and science. It has become an essential and integral part of modern industrial and manufacturing processes. Today, the requirements for control precision have increased, and real systems have become more complex. In control engineering and all other engineering disciplines, the impact of advanced mathematical and computational methods is rapidly increasing. Advanced mathematical methods are needed because real-world control systems need to comply with several conditions related to product quality and safety constraints that have to be taken into account in the problem formulation. Conversely, the increment in mathematical complexity has an impact on the computational aspects related to numerical simulation and practical implementation of the algorithms, where a balance must also be maintained between implementation costs and the performance of the control system. This book is a comprehensive set of articles reflecting recent advances in developing and applying advanced mathematics and computational applications in control system engineering

ANALYZING EFFICIENCY OF SWITCH-MODE WELDING POWER SUPPLY

esearches and studies have indicated that many of the welding quality issues are related to the weld schedule or power supply. During a weld, a certain amount of energy is lost which can be reduced to improve the efficiency of the power supply. This thesis presents a DC/DC buck converter power supply for small scale resistance spot welding (SSRSW), which can provide a testing platform for studies of different control modes, and at the end implement the results of the experiments and research done with this power supply. In this thesis, a model of the small scale resistance spot welding power supply has been implemented. The power supply uses pulse width modulation technique with MOSFETs to convert the power of a 12V battery to the weld current up to 1000A. Various measurements of voltage and current were taken at the respective terminals to calculate the energy losses. Capacitances were added with gradually increased values and again measurements were taken to calculate and analyze the energy losses in presence of the capacitances based on their numerical values. It was noted that the energy losses were reduced appreciably by this technique. So, the efficiency of the converters can be improved

Intelligent laser cladding control system design and construction.

Imperial Users onl

Index to 1981 NASA Tech Briefs, volume 6, numbers 1-4

Short announcements of new technology derived from the R&D activities of NASA are presented. These briefs emphasize information considered likely to be transferrable across industrial, regional, or disciplinary lines and are issued to encourage commercial application. This index for 1981 Tech Briefs contains abstracts and four indexes: subject, personal author, originating center, and Tech Brief Number. The following areas are covered: electronic components and circuits, electronic systems, physical sciences, materials, life sciences, mechanics, machinery, fabrication technology, and mathematics and information sciences

Fibre laser metal deposition with wire: parameters study and temperature control

This research addresses the development of a laser metal deposition process with wire feeding and melt pool temperature control. The system consists of a2 kW fibre laser, a CNC table, a wire feeder and a temperature monitoring and control system. A study of the influence of the main parameters on the process and on the deposited bead geometry was performed. The parameters analysed were: laser power, traverse speed and wire feed rate. As a result of this study, a process window was established for metal deposition of stainless steel 308LSi (wire) on stainless steel 304 (plate). The influence of the parameters on the bead geometry (height and width) was analysed applying the Design of Experiments methodology, using a full factorial design 3k. The results are presented, together with important practical considerations for laser metal deposition with wire. A closed-loop temperature control system was developed: it controls the melt pool temperature by means of modifying the laser power. The melt pool temperature was measured by a two-colour pyrometer, whereas a single-colour pyrometer was used for monitoring the workpiece (upper layer) temperature. A model of the melt pool was derived from a heat balance equation. It was then utilized for the design of the controller in the discrete domain, using the root locus method. The control algorithm was developed in LabVIEW software and executed in a computer. The control system was implemented successfully and was utilized to build single-bead walls and cylinders of stainless steel 308LSi. The study performed on the parameters and the developed temperature controller proved to be very effective tools to facilitate the transition to the deposition of titanium alloy Ti-6A1-4V, requiring only minimum adaptations. Single-bead walls and cylinders were also built in this material. Stable and smooth metal deposition was achieved for both materials. During the experiments, several strategies for the automation of wire metal deposition of multilayered structures were developed. Finally, mechanical tests were performed. The mechanical properties of the deposited materials are comparable to those in wrought (annealed) condition and to similar alloys made by laser powder deposition systems. The system developed in this work provides a means to perform stable and smooth wire metal deposition, achieving good mechanical properties. It also facilitates the transition to deposit different materials. It has a flexible structure and can be expanded or adapted to be used in other wire metal deposition systems

Feasibility of remotely manipulated welding in space. A step in the development of novel joining technologies

In order to establish permanent human presence in space technologies of constructing and repairing space stations and other space structures must be developed. Most construction jobs are performed on earth and the fabricated modules will then be delivered to space by the Space Shuttle. Only limited final assembly jobs, which are primarily mechanical fastening, will be performed on site in space. Such fabrication plans, however, limit the designs of these structures, because each module must fit inside the transport vehicle and must withstand launching stresses which are considerably high. Large-scale utilization of space necessitates more extensive construction work on site. Furthermore, continuous operations of space stations and other structures require maintenance and repairs of structural components as well as of tools and equipment on these space structures. Metal joining technologies, and especially high-quality welding, in space need developing

Applications of MATLAB in Science and Engineering

The book consists of 24 chapters illustrating a wide range of areas where MATLAB tools are applied. These areas include mathematics, physics, chemistry and chemical engineering, mechanical engineering, biological (molecular biology) and medical sciences, communication and control systems, digital signal, image and video processing, system modeling and simulation. Many interesting problems have been included throughout the book, and its contents will be beneficial for students and professionals in wide areas of interest

Quality analysis modelling for development of a process controller in resistance spot welding using neural networks techniques

Student Number : 9811923K - PhD thesis - School of Mechanical Engineering - Faculty of Engineering and the Built EnvironmentMethods are presented for obtaining models used for predicting welded sample resistance and effective weld current (RMS) for desired weld diameter (weld quality) in the resistance spot welding process. These models were used to design predictive controllers for the welding process. A suitable process model forms an important step in the development and design of process controllers for achieving good weld quality with good reproducibility. Effective current, dynamic resistance and applied electrode force are identified as important input parameters necessary to predict the output weld diameter. These input parameters are used for the process model and design of a predictive controller. A three parameter empirical model with dependent and independent variables was used for curve fitting the nonlinear halfwave dynamic resistance. The estimates of the parameters were used to develop charts for determining overall resistance of samples for any desired weld diameter. Estimating resistance for samples welded in the machines from which dataset obtained were used to plot the chart yielded accurate results. However using these charts to estimate sample resistance for new and unknown machines yielded high estimation error. To improve the prediction accuracy the same set of data generated from the model were used to train four different neural network types. These were the Generalised Feed Forward (GFF) neural network, Multilayer Perceptron (MLP) network, Radial Basis Function (RBF) and Recurrent neural network (RNN). Of the four network types trained, the MLP had the least mean square error for training and cross validation of 0.00037 and 0.00039 respectively with linear correlation coefficient in testing of 0.999 and maximum estimation error range from 0.1% to 3%. A prediction accuracy of about 97% to 99.9%. This model was selected for the design and implementation of the controller for predicting overall sample resistance. Using this predicted overall sample resistance, and applied electrode force, a second model was developed for predicting required effective weld current for any desired weld diameter. The prediction accuracy of this model was in the range of 94% to 99%. The neural network predictive controller was designed using the MLP neural network models. The controller outputs effective current for any desired weld diameter and is observed to track the desired output accurately with same prediction accuracy of the model used which was about 94% to 99%. The controller works by utilizing the neural network output embedded in Microsoft Excel as a digital link library and is able to generate outputs for given inputs on activating the process by the push of a command button