Novel welding image processing method based on fractal theory

Computer vision has come into used in the fields of welding process control and automation. In order to improve precision and rapidity of welding image processing, a novel method based on fractal theory has been put forward in this paper. Compared with traditional methods, the image is preliminarily processed in the macroscopic regions then thoroughly analyzed in the microscopic regions in the new method. With which, an image is divided up to some regions according to the different fractal characters of image edge, and the fuzzy regions including image edges are detected out, then image edges are identified with Sobel operator and curved by LSM (Lease Square Method). Since the data to be processed have been decreased and the noise of image has been reduced, it has been testified through experiments that edges of weld seam or weld pool could be recognized correctly and quickly.

Analysis of defects in clean fabrication process of friction stir welding

Striving for cleaner production is a sought-after manufacturing philosophy.Friction stir welding(FSW)is a joiningtechnique with par excellence and far less invasive to the environment than even best conventional welding processes.It is energyefficient and free from consumables,affluent and radiations.It is,thus,accepted as a clean welding process that can produceacceptable quality joints.It suffers from some major challenges of defects of its own kind that subject the process open toimprovements so as to prove itself a reliable production process.This study presents a holistic characterization of defects commonlyfound in FSW joints.The finding of the present study reveals that most defects are caused by inadequate heat generation,impropermaterial movement around the pin and inadequate material consolidation behind the pin.The amount of heat generation andmaterial stirring depends on several FSW parameters which may lead to the defect formation,if not selected properly.The resultsreported in this work are derived from sound literature support and experimentation.Prescriptions are made in the form ofcharacteristics of defects such as likelihood of their location,main responsible parameters along with the recommendations forminimizing them.

Synthetically quantitative evaluation function of characteristic parameters on CO_2 arc welding process

The statistical probability and their variation regularity of the measurable characteristic parameters in the CO 2 arc welding droplet short circuiting transfer process have been studied. The statistical analysis shows that the sensitivity of each characteristic parameter with regard to the variation of the short circuiting transfer process is different. The sensitivity of 4 kinds among these characteristic parameters is more intense than that of the short circuiting transfer frequency. In order to take account of the synthetic influence of these characteristic parameters, by means of the characteristic parameters synthetic value, a quantitative evaluation function is built up to describe and evaluate the short circuiting transfer process of CO 2 arc welding in real time. The testing shows that the evaluation function can give a suitable synthetic valuation for the short circuiting transfer process with a variety of welding variables.

Keyhole Double-Sided Arc Welding Process

In the proposed method, the current/arc is guided through the keyhole so that the energy of the plasma jet is compensated while it is consumed in heating the workpiece along the keyhole. As a result, deep narrow penetration has been achieved on 12.7 mm (1/2') thick stainless steel plates using 70 A welding current.

Approximate entropy——a new statistic to quantify arc and welding process stability in short-circuiting gas metal arc welding

Based on the phase state reconstruction of welding current in short-circuiting gas metal arc welding using carbon dioxide as shielding gas, the approximate entropy of welding current as well as its standard deviation has been calculated and analysed to investigate their relation with the stability of electric arc and welding process. The extensive experimental and calculated results show that the approximate entropy of welding current is significantly and positively correlated with arc and welding process stability, whereas its standard deviation is correlated with them negatively. A larger approximate entropy and a smaller standard deviation imply a more stable arc and welding process, and vice versa. As a result, the approximate entropy of welding current promises well in assessing and quantifying the stability of electric arc and welding process in short-circuiting gas metal arc welding.

Diffusion welding process and joint's microstructure behavior of SiC_w/6061Al composite

The rules such as process parameters affecting joint properties and theevolution principle of weld's microstructure have been researched by adopting diffusion weldingprocess to connect SiC_w/6061Al composite. Experimental results show that there exists a criticaltemperature region between solid and liquid phase line of SiC_w/6061Al composite, and the regionwill shrink with the increasing of welding pressure. When diffusion welding occurred under thecritical temperature region, welding joint exhibits bad property of bonding, and the matrix and thereinforcement can't bond effectively. When diffusion welding occurred in the critical temperatureregion, the strength of welding joint changes widely with the variation of welding temperature. Whenwelding temperature varies in 10 deg C, the strength of welding joint will change obviously. Onlywhen welding temperature is higher than the critical temperature region, stable joint properties canbe obtained. Simultaneously the matrix and the reinforcement has better interfacial bonded indiffusion welding interface, and no obvious interface reaction occurred, and thus diffusion weldingof SiC_w/6061 Al composite can be successfully realized.

Experimental Investigation on the Performance of Armour Grade Q&T Steel Joints Fabricated by Flux Cored Arc Welding with Low Hydrogen Ferritic Consumables

Quenched and Tempered （Q＆T） steels are widely used in the construction of military vehicles due to its high strength to weight ratio and high hardness. These steels are prone to hydrogen induced cracking （HIC） and softening in the heat affected zone （HAZ） after welding. The use of austenitic stainless steel （ASS） consumables to weld the above steel was the only available remedy to avoid HIC because of higher solubility for hydrogen in austenitic phase. Recent studies revealed that low hydrogen ferritic （LHF） steel consumables can also be used to weld Q＆T steels, which can give very low hydrogen levels in the weld deposits and required resistance against cold cracking. Hence, in this investigation an attempt has been made to study the performance of armour grade Q＆T steel joints fabricated by flux cored arc welding with LHF steel consumables. Two different consumables namely （i） austenitic stainless steel and （ii） low hydrogen ferritic steel have been used to fabricate the joints by flux cored arc welding （FCAW） process. The joints fabricated by LHF consumable exhibited superior transverse tensile properties due to the presence of ferrite microstructure in weld metal. The joints fabricated by ASS consumable showed higher impact toughness due to the presence of austenitic phase in weld metal microstructure. The HAZ softening in coarse grain heat affected zone （CGHAZ） is less in the joints fabricated using LHF consumable due to the lower heat input involved during fabrication compared to the joints fabricated using ASS consumables.

Experimental and Simulation Studies on Cold Welding Sealing Process of Heat Pipes

Sealing quality strongly affects heat pipe performance, but few studies focus on the process of heat pipe sealing. Cold welding sealing technology based on a stamping process is applied for heat pipe sealing. The bonding mechanism of the cold welding sealing process （CWSP） is investigated and compared with the experimental results obtained from the bonding interface analysis. An orthogonal experiment is conducted to observe the effects of various parameters, including the sealing gap, sealing length, sealing diameter, and sealing velocity on bonding strength. A method with the utilization of saturated vapor pressure inside a copper tube is proposed to evaluate bonding strength. A corresponding finite element model is developed to investigate the effects of sealing gap and sealing velocity on plastic deformation during the cold welding process. Effects of various parameters on the bonding strength are determined and it is found that the sealing gap is the most critical factor and that the sealing velocity contributes the least effect. The best parameter combination （AIB3CID3, with a 0.5 mm sealing gap, 6 mm sealing length, 3.8 mm sealing diameter, and 50 mm/s sealing velocity） is derived within the experimental parameters. Plastic deformation results derived from the finite element model are consistent with those from the experiment. The instruction for the CWSP of heat pipes and the design of sealing dies of heat pipes are provided.

Research on the controller of an arc welding process based on a PID neural network

A controller based on a PID neural network （PIDNN） is proposed for an arc welding power source whose output characteristic in responding to a given value is quickly and intelligently controlled in the welding process. The new method syncretizes the PID control strategy and neural network to control the welding process intelligently, so it has the merit of PID control rules and the trait of better information disposal ability of the neural network. The results of simulation show that the controller has the properties of quick response, low overshoot, quick convergence and good stable accuracy, which meet the requirements for control of the welding process.

A Generalized Rough Set Modeling Method for Welding Process

Modeling is essential, significant and difficult for the quality and shaping control of arc welding process. A generalized rough set based modeling method was brought forward and a dynamic predictive model for pulsed gas tungsten arc welding (GTAW) was obtained by this modeling method. The results show that this modeling method can well acquire knowledge in welding and satisfy the real life application. In addition, the results of comparison between classic rough set model and back-propagation neural network model respectively are also satisfying.

Overview of stainless-steel clad-plate welding

Types of bimetal clad plate, manufacturing methods, and their fields of application were summarized. In particular,key aspects of the welding of clad-rolled stainless steel were described, including the weldability of the base and clad metals, design criteria for the transition layer, the selection of the type of welding process and consumables used, types of blanking and welding bevels, preparation and assembly prior to welding, welding procedure requirements, post-weld cleaning and heat treatment, and welding quality inspection. This paper will serve as a reference for the welding technology used in future consumer applications in related fields.

Gas metal arc welding of duplex stainless clad steel plates

The 2205 duplex stainless ＋ DH36 clad steel plate was welded by gas metal arc welding（GMAW）, and the welding performance of the clad steel plate was investigated. The results show that the adaptability of the welding procedure for the base metal of carbon steel, the transition layer, and the cladding material is excellent. The test results indicate that the phase proportion and component dilution of the GMAW-welded joints of clad steel plate can be effectively controlled to yield joints with good mechanical properties and corrosion resistance.

Statistical Analyses of the Effects of Welding Processes on Load, Extension and Hardness Properties of Welded Mild Steel Plates

Mild steel plates of thicknesses 0.5 mm,0.6 mm,0.7 mm,0.8 mm,0.9 mm and 1.0 mm were prepared as test samples.After welding with the developed welding robot and manual electric arc welding machine these test samples were subjected to Tensile Strength and Hardness tests.All data obtained including hardness,load and extension were analyzed and the data produced from electric arc welding operations,the robot welding operations and un-welded plates(control)were compared with one another.The statistical analyses of hardness,load and extension tests for developed welding robot,manual electric arc welding and un-welded(control)mild steel plates of different thicknesses were carried out.The results revealed that for hardness,the developed robot welding has the highest mean value of 115.30,standard deviation value of 14.32 and variance value of 205.06.The descriptive statistics of the load showed that the developed robot welding samples collectively have the lowest mean value of 2,536.85,standard deviation value of 704.21 and variance value of 495,911.72.The descriptive statistics of the extension in which the developed robot welding samples collectively have the lowest mean value of 1.29,standard deviation value of 0.43 and variance value of 0.18 were also determined.The result for hardness showed homogeneity of variance among hardness tests of the samples,which implies variation in the hardness test among the tests of the samples since p-value is 0.038.While the result for loads shows homogeneity of variance among loads of the samples in which the result reveals that there is no variation in the loads among the tests of the samples since p-value is 0.322.The result for extension shows homogeneity of variance among extensions of the samples in which it revealed that there is variation in the extensions among the tests of the samples since p-value is 0.011.The analysis of variance(ANOVA)test result revealed that there is a significant difference in the hardness of the samples in which developed robot welding operation gave the highest hardness compared with electric arc welding and un-welded(CONTROL)since p-value is 0.028.The ANOVA test result for load revealed that there is no significant difference in the loads of the samples since p-value is 0.51.The ANOVA test result of the extension shows that there is a significant difference in the extension of the samples in which developed robot welding operation gave the lowest extension compared with electric arc welding and un-welded(CONTROL)since p-value is 0.001.The results of hardness also showed the mean difference of 16.48 between developed robot welding and un-welded(CONTROL)samples and 7.26 between developed robot welding and electric arc welding samples.Finally,for extension the mean difference of-5.28 between developed robot welding and un-welded(CONTROL)samples and-1.22 between developed robot welding and electric arc welding samples were established.

The Mesozoic Welding Process between South and North Dabie Blocks：An Evidence from Pb Isotopes of Yanshanian Granites

The Pb isotope compositions of K-feldspar in granites is paid more and more geologists'attention,due to their importance of tracer.It is a fact that South Dabie Block(SDB)and North Dabie Block(NDB)had exited since Indosinian epoch(Wang et al.,1992;Cong et al,1994;Zhai et al.,1995;Chen et al.1995;Zhang et al,1996,Wang et al,1997).However,the welding process between SDB

Mathematical model and magnetic-control mechanism of the stability of rotating spray transfer

To realize stable rotating spray transfer in the region of high constant current is the key of realizing high deposition rate MAG welding process without helium in shielding gas and extending the welding current range of traditional MAG welding process. In this paper, the magnetic control mechanism of the rotating spray transfer is stated and mathematical model is given. Theoretic basis is established, which implements high deposition rate MAG welding process with magnetic control instead of helium in shielding gas.

Corrosion evaluation of friction stir welded lap joints of AA6061-T6 aluminum alloy

Corrosion behavior of friction stir lap welded AA6061-T6 aluminum alloy was investigated by immersion tests in sodium chloride + hydrogen peroxide solution. Electrochemical measurement by cyclic potentiodynamic polarization, scanning electron microscopy, and energy dispersive spectroscopy were employed to characterize corrosion morphology and to realize corrosion mechanism of weld regions as opposed to the parent alloy. The microstructure and shear strength of welded joint were fully investigated. The results indicate that, compared with the parent alloy, the weld regions are susceptible to intergranular and pitting attacks in the test solution during immersion time. The obtained results of lap shear testing disclose that tensile shear strength of the welds is 128 MPa which is more than 60% of the strength of parent alloy in lap shear testing. Electrochemical results show that the protection potentials of the WNZ and HAZ regions are more negative than the pitting potential. This means that the WNZ and HAZ regions do not show more tendencies to pitting corrosion. Corrosion resistance of parent alloy is higher than that for the weldments, and the lowest corrosion resistance is related to the heat affected zone. The pitting attacks originate from the edge of intermetallic particles as the cathode compared with the Al matrix due to their high self-corrosion potential. It is supposed that by increasing intermetallic particle distributed throughout the matrix of weld regions, the galvanic corrosion couples are increased, and hence decrease the corrosion resistance of weld regions.

Cold Cracking of Flux Cored Arc Welded Armour Grade High Strength Steel Weldments

In this investigation, an attempt has been made to study the influence of welding consumables on the factors that influence cold cracking of armour grade quenched and tempered （Q＆.T） steel welds. Flux cored arc welding （FCAW） process were used making welds using austenitic stainless steel （ASS） and low hydrogen ferritic steel （LHF） consumables. The diffusible hydrogen levels in the weld metal of the ASS and LHF consumables were determined by mercury method. Residual stresses were evaluated using X-ray stress analyzer and implant test was carried out to study the cold cracking of the welds. Results indicate that ASS welds offer a greater resistance to cold cracking of armour grade Q＆T steel welds.

Friction-stir welding and processing of Ti-6Al-4V titanium alloy:A review

In this work, the current understanding and development of fliction-stir welding and processing of Ti- 6Al-4V alloy are briefly reviewed. The critical issues of these processes are addressed, including welding tool materials and design, tool wea,, processing temperature, material flow, processing window and residual stresses. A particular emphasis is given to microstructural aspects and microstructure-properties relationship. Potential engineering applications are highlighted.

Friction stir based welding and processing technologies-processes,parameters,microstructures and applications:A review

Friction stir welding [FSW） has achieved remarkable success in the joining and processing of aluminium alloys and other softer structural alloys. Conventional FSW, however, has not been entirely successful in the joining, processing and manufacturing of different desired materials essential to meet the sophis- ticated green globe requirements. Through the efforts of improving the process and transferring the existing friction stir knowledge base to other advanced applications, several friction stir based daughter technologies have emerged over the timeline, A few among these technologies are well developed while others are under the process of emergence. Beginning with a broad classification of the scattered fric- tions stir based technologies into two categories, welding and processing, it appears now time to know, compile and review these to enable their rapid access for reference and academia. In this review article, the friction stir based technologies classified under the categol^J of welding are those applied for join- ing of materials while the remnant are labeled as friction stir processing （FSP） technologies. This review article presents an overview of four general aspects of both the developed and the developing friction stir based technologies, their associated process parameters, metallurgical features of their products and their feasibility and application to various materials. The lesser known and emerging technologies have been emphasized.

Comparative Study on Processing Property Between CWW CO_2 Gas Shielded Welding and SAW

Cable welding wire（CWW）CO2gas shielded welding is an innovative process arc welding with high efficiency,high quality and low consumption,in which cable wire is used as consumable electrode.CWW CO2gas shielded welding and submerged arc welding（SAW）are used for contrast studies on processing property of high strength steel A36used in ship structure.The results show that the shapes of weld seam,using CWW CO2gas shielded welding and SAW,are good and no weld defect such as air hole,flaw,slag inclusion,incomplete fusion,lack of penetration and so on are found in the weld seam.Because the rotating of arc during CWW CO2gas shielded welding process has a strong stirring effect on molten pool,the grain in the heat affected zone（HAZ）of the joints,using CWW CO2 gas shielded welding,is small.Tensile failure positions of joints by CWW CO2gas shielded welding and SAW are all in the base metal,but tensile strength of CWW CO2gas shielded welding joint is higher than that of SAW joint by an average of 2.3%.The average impact energy of HAZ,using CWW CO2gas shielded welding and SAW,is almost equal,but the average impact energy of the weld seam using CWW CO2gas shielded welding is increased by 6%,and the average impact energy of the fusion line is increased by 7%.The 180°bending tests for the joints of CWW CO2 gas shielded welding and SAW are all qualified,and the joints hardness is all less than HV 355,but hardness of CWW CO2gas shielded welding wire welding joint near the fusion line is obviously lower.It can be concluded that the properties of CWW CO2gas shielded welding are better than those of the SAW joint,and CWW CO2gas shielded welding is suitable for welding high strength steel A36used in ship structure.