Industrial Welding Research Articles

3320 Feature-based Off-line Teaching System for Industrial Welding Robots to Assist Teaching Program Generation

The teaching operation requires huge amount of time and effort to prepare teaching programs. An objective of this study is to simplify the teaching operation for welding robots. The "welding feature" concept is utilized to develop a feature-based off-line teaching system. The old teaching programs generated in the past are distinguished by the "welding feature". When a new teaching program is generated, the most suitable teaching program is retrieved by the "welding feature" from the old teaching programs. Several suitable teaching programs are combined and modified to complete a new teaching program for new welding operation.

Manganese effects in the liver following subacute or subchronic manganese chloride exposure in rats

Manganese (Mn) toxicity is most often found in mining and welding industry workers. Accumulation of manganese in the brain can result in a syndrome similar to that of Parkinson’s disease. Observations on former Mn-alloy workers suggested that residual effects could last for years after exposure. The objective of this study was to assess effects of Mn in the liver of rats following subacute or subchronic exposure and after recovery. Male Sprague–Dawley rats were exposed to manganese chloride (MnCl 2) for 30 days, 90 days, or for 90 days followed by a 30-day post-exposure recovery period. Results showed that MnCl 2 exposure resulted in liver injury in rats and the extent of injury correlated positively with exposure time. The effect in mitochondria was stronger than in the membrane or nucleus. Most of the changes in these biomarkers recovered when manganese exposure ceased.

Corrosion of the heat‐affected zone of stainless steel weldments

PurposeThe purpose of this paper is to investigate the corrosion of the heat‐affected zone (HAZ) and weld zone of austenitic stainless steels that have been welded using two different processes. The corrosion behavior is evaluated in synthetic seawater using the electrochemical polarization technique.Design/methodology/approachWelded and unwelded UNS S30403 specimens were welded by flux core arc, and gas tungsten arc welding (GTAW) techniques. The test equipment consisted of an electrochemical three‐electrode cell using synthetic seawater as the corrosive medium. The scan rate was 10 mV/s and the potential range was −500‐500 mV vs saturated calomel electrode. The pH for the synthetic seawater was around seven. The electrochemical tests were performed after 1, 2, 3, and, 11 weeks. The metal surface was characterized by examination using an inverted microscope and scanning electron microscopy.FindingsThe polarization measurements of the flux core arc welding‐HAZ showed a high corrosion susceptibility, while GTAW‐HAZ presented good corrosion performance.Practical implicationsWith the application and correct interpretation of this electrochemical technique, designers, welding engineers, and manufactures can access important information and take correct decisions regarding welding processes to meet corrosion resistance requirements.Originality/valueThe methodology and approach of interpreting the polarization plots used in this research can be applied to study other welding techniques and different welded metals in specific corrosive media, which will be of value to the welding industry.

Research on the Motion Model of Flying Plate in Explosive Welding

Constant variably acceleration motion model of flying plate is proposed and the model formula about the relationship between speed of flying plate and clearance is put forward, which provides theorotical basis for choosing optimum clearance by collision speed of different metallic materials in explosive welding industry production. High pressure impulse X radial photograph experiment was carried out, the photos of the flying stances of flying plate in different clearances were obtained and the corresponding flying speeds of flying plate were calculated. Curve fitting of the experiment data through constant variably acceleration motion model was carried out. The results show that constant variably acceleration motion model accords well with the experiment data，and the maximum speed of flying plate calculated through constant acceleration model is in good agreement with the values through theoretical calculation. Therefore, it is concluded that the motion of flying plate in the main follows the constant variably acceleration motion.

Post-Weld Quality Inspection for CO<sub>2</sub> Laser Tailored Blank Welding with Vision Sensor

The traditional method for post-weld quality inspection is visual testing by people. Major limitations of this method are the subjectivity of judgments and time required to perform the inspection. With the increasing use of laser welding in the automotive industry, the manufacturers are struggling with the challenge to automate the quality inspection process. This paper discussed the automatic post-weld quality inspection technology by computer vision sensing for mono-thickness tailored blanks of CO2 laser welding. A visual sensor was developed for acquiring the original image of the weld seam. The sensor consists of a PC based vision camera and a stripe-type laser diode. An image processing algorithm was presented to detect the geometrical defects of the weld seam. Some experiments are carried out and some applications are given.

Automatic Detection of Porosity and Slag Inclusion in Boilers using Statistical Pattern Recognition Techniques

automatic weld inspection system can be used for training weld quality inspectors and for weld quality assessment in the welding industry. The system is aimed at increasing inspection speed, accuracy and at the same time reducing subjectivity associated with the manual interpretation of the weld radiographs. The system detects the weld defects, classifies it, and displays the output with greater accuracy compared to the previously existing methods. It implements fuzzy logic that helps in the automatic recognition of weld defects efficiently.

Applications and case studies of laser hybrid welding in the automotive industry

In joining technology, the high welding speed on the one and the good gap bridging ability on the other hand play a significant part. It is no doubt that the laser beam welding and the GMA welding have been established in the welding technology for very long, and that both processes allow a wide field of application in the joining technology. New possibilities and synergetic effects, however, are based on the combination of both processes. The laser radiation causes a very narrow thermally affected zone with a high ratio between welding depth and seam width. In the case of the laser welding process, the gap bridging ability is very low due to the small focus diameter, however very high welding speeds can be achieved. The GMA or Tandem welding process features a significantly lower energy density has a larger focused spot on the material surface and is characterised by its good gap bridging ability.

Taguchi Analysis of the Effect of Process Parameters in Friction Stir Welding

The task of obtaining suitable welding parameters for the friction stir welding process is often a difficult one, due to the lack of published data and the fact that the exact mechanism by which the process operates has not yet been fully determined. Therefore, suitable welding parameters often need to be obtained by using extensive, time consuming and expensive experimental methods. The work detailed in this paper pertains to the use of the Taguchi method as a mean to reduce the disadvantages of these experimental methods, more specifically, their cost. The Taguchi method accomplishes this task by substantially reducing the number of welding trials that are needed to obtain suitable welding parameters. This reduction leads to the parameters being obtained more rapidly and at a substantially smaller cost. In this paper a procedure for applying the Taguchi method to the friction stir welding process is presented as well as its application to the welding of a specific component. The method was applied to the welding of 4mm thick AA5083-H111 plates in a butt joint configuration, which constitutes one of the most common industrial welding scenarios. The purpose of the experimental tests was to maximize the welding speed whilst ensuring an acceptable welding quality. The quality of the welds was determined through visual inspection and tensile and bending tests. The application of the Taguchi method allowed, with a relatively small number of experimental welds, to provide some insight into the manner by which the parameters should be altered in order to optimize the process.

Eye protection practices and symptoms among welders in the Limpopo Province of South Africa+

Welding is associated with several ocular and systemic hazards especially where adequate protective measures are not taken. The purpose of this project was to study the eye protection practices and symptoms among welders in the Capricorn District of Limpopo Province, South Africa. Questionnaires designed to investigate eye protection practices and symptoms experienced were completed byone hundred and fifty (150) welders. The types of welding done were shielded metal arc (84%), oxyacetylene gas (4%) and silver brazing (12%). The number of years spent in the welding industry ranged from one to 10 years with a mean of 5 ± 3.1 years and the number of hours of welding per day ranged from one to 10 hours with a mean of 6 ± 2.1 hours. A large percentage of the welders (89%) reported wearing protective devices when welding and the most common protective devices used by the welders were: helmets (57%), goggles(22%), and face shields (15%). Six percent used inefficient protective devices such as sunglasses. Sixty one percent reported occasional exposure to welding flashes when not wearing any eye protection. Welding-related eye symptoms reported included foreign body sensation (18%), persistent after-images (31%), and watery eyes (50%). Al-though the majority of the welders wore protective devices while welding, a few did not always use such devices while others used sunglasses for protection. Moreover, many of the welders were occasionally, and only a few were always, exposed to welding flashes when protective devices were not used. Therefore, we concluded that eye protectionpractices amongst the welders appeared to be inadequate to avoid hazards associated with welding. It is recommended that an eye protection educational campaign for welders should form part of the SouthAfrican Government’s workplace safety program.

Gene expression profiling in the lung tissue of cynomolgus monkeys in response to repeated exposure to welding fumes

Many in the welding industry suffer from bronchitis, lung function changes, metal fume fever, and diseases related to respiratory damage. These phenomena are associated with welding fumes; however, the mechanism behind these findings remains to be elucidated. In this study, the lungs of cynomolgus monkeys were exposed to MMA-SS welding fumes for 229 days and allowed to recover for 153 days. After the exposure and recovery period, gene expression profiles were investigated using the Affymetrix GeneChip® Human U133 plus 2.0. In total, it was confirmed that 1,116 genes were up-or down-regulated (over 2-fold changes, P < 0.01) for the T1 (31.4 ± 2.8 mg/m3) and T2 (62.5 ± 2.7 mg/m3) dose groups. Differentially expressed genes in the exposure and recovery groups were analyzed, based on hierarchical clustering, and were imported into Ingenuity Pathways Analysis to analyze the biological and toxicological functions. Functional analysis identified genes involved in immunological disease in both groups. Additionally, differentially expressed genes in common between monkeys and rats following welding fume exposure were compared using microarray data, and the gene expression of selected genes was verified by real-time PCR. Genes such as CHI3L1, RARRES1, and CTSB were up-regulated and genes such as CYP26B1, ID4, and NRGN were down-regulated in both monkeys and rats following welding fume exposure. This is the first comprehensive gene expression profiling conducted for welding fume exposure in monkeys, and these expressed genes are expected to be useful in helping to understand transcriptional changes in monkey lungs after welding fume exposure.Electronic supplementary materialThe online version of this article (doi:10.1007/s00204-009-0486-z) contains supplementary material, which is available to authorized users.

Path Planning and System Simulation for an Industrial Spot Welding Robot Based on SimMechanics

A robot used for industrial spot welding is a 4-DOF serial mechanism, it can be applied to some special industries. There are multi via points known in path, each joint value can be accurately solved by the inverse kinematics. The quintic polynomial interpolation was adopted between each two adjacent desired via points, the continuous trajectory is formed in accordance with the time course. The simulation model is developed using SimMechnics, the movement parameters and path are obtained by simulating, the simulation results indicate that the motional parameters and path can be accurately and effectively obtained for robot analysis and design.

Addressing conflict in strategic literature reviews: disclosure is not enough

The success of the tobacco industry’s multi-decade campaign to delay regulation by manufacturing uncertainty about the studies linking cigarette smoking to lung cancer and other diseases is well documented.1 2...

An online real time ultrasonic NDT system for the quality control of spot welding in the automotive industry

Resistance spot welding is the main joining technique used for the fabrication of body-in-white structures in the automotive industry. The quality of the welds depends on the profile of the spot welding electrode cap. The increased use of zinc coated steel in the industry increases wear rate of the caps, making quality control more difficult. This paper presents a novel online real time ultrasonic NDE system for resistance spot welding which evaluates every weld as it is formed. SEM results are presented to show the alloying of the electrode caps.

An online real time ultrasonic NDT system for the quality control of spot welding in the automotive industry

Resistance spot welding is the main joining technique used for the fabrication of body-in-white structures in the automotive industry. The quality of the welds depends on the profile of the spot welding electrode cap. The increased use of zinc coated steel in the industry increases wear rate of the caps, making quality control more difficult. This paper presents a novel online real time ultrasonic NDE system for resistance spot welding which evaluates every weld as it is formed. SEM results are presented to show the alloying of the electrode caps.

Experimental and computer simulation results of the spot welding process using SORPAS software

The highly competitive nature of the automotive industry drives demand for improvements and increased precision engineering in resistance spot welding. Currently there are about 4300 weld points on the average steel vehicle. Current industrial monitoring systems check the quality of the nugget after processing 15 cars, once every two weeks. The nuggets are examined off line using a destructive process, which takes approximately 10 days to complete causing a long delay in the production process. This paper presents a simulation of the spot welding growth curves, along with a comparison to growth curves performed on an industrial spot welding machine. The correlation of experimental results shows that SORPAS simulations can be used as an off line measurement to reduce factory energy usage. The first section in your paper

CURRENT CAPABILITIES OF THE THERMO-MECHANICAL MODELLING OF WELDING PROCESSES

Some fundamental principles and advanced applications of thermo-mechanical modelling techniques used for industrial welding processes are described. The paper covers a range of modelling procedures comprising welding simulation and residual stress analysis of multi-pass, thick-walled ferritic steel pipes; welding simulation and distortion analysis of nickel-based superalloy thin plates; and inertia friction welding of dual alloy drive shafts. A number of pertinent mechanical and metallurgical concepts are discussed, including material behaviour models and material properties, microstructural evolution, solid state phase transformation and post-weld heat treatment. The paper emphasises the general methodologies of thermal modelling procedures and their role in the holistic process of the life assessment and design improvement of power plant piping systems and aeroengine casings and shaft components, operating under high temperature creep and fatigue service conditions.

Heat Transfer Prediction of In-Service Welding in a Forced Flow of Fluid

An algorithm for heat transfer prediction of in-service welding operations in a forced flow of fluid is presented. The algorithm presented is derived from Rosenthal’s 3D heat flow equation and boundary layer approximations. This was possible by the introduction of an apparent thermal conductivity kPL, which is a function of the boundary layer’s heat transfer coefficient αf and the base material’s thickness δ. This implies that a weld cooling time ΔtT1/T2 in a forced flow of fluid can now be calculated by an ordinary engineering calculator and thus enabling suitable welding parameters to be determined. The magnitude of kPL(αf,δ) was established by regression analysis of results from a parametric finite element analysis series of a total number of 112 numerical simulations. Furthermore, the result of the regression analysis was validated and verified by a welding experiment series accomplished on an in-house designed and constructed in-service welding rig. The principle design of the welding rig as well as its instrumentation, a PC based Data Acquisition system, is described. In addition, a method to measure the weld metals cooling time ΔtT1/T2 by means of thermocouple elements is described. Finally, the algorithm presented in this study proved feasible for industrial in-service welding operations of fine-grained Carbon and Carbon–Manganese steels with a maximum Carbon Equivalent (IIW) (CE) of 0.32.

Validity and Reliability of an Occupational Exposure Questionnaire for Parkinsonism in Welders

This study assessed the validity and test-retest reliability of a medical and occupational history questionnaire for workers performing welding in the shipyard industry. This self-report questionnaire was developed for an epidemiologic study of the risk of parkinsonism in welders. Validity participants recruited from three similar shipyards were asked to give consent for access to personnel files and complete the questionnaire. Responses on the questionnaire were compared with information extracted from personnel records. Reliability participants were recruited from the same shipyards and were asked to complete the questionnaire at two different times approximately 4 weeks apart. Percent agreement, kappa, intraclass correlation coefficient (ICC), and sensitivity and specificity were used as measures of validity and/or reliability. Personnel files were obtained for 101 of 143 participants (70%) in the validity study, and 56 of the 95 (58.9%) participants in the reliability study completed the retest of the questionnaire. Validity scores for items extracted from personnel files were high. Percent agreement for employment dates and job titles ranged from 83–100%, while ICC for start and stop dates ranged from 0.93–0.99. Sensitivity and specificity for current job title ranged from 0.5–1.0. Reliability scores for demographic, medical and health behavior items were mainly moderate or high, but ranged from 0.19 to 1.0. Most recent job/title items such as title, types of welding performed, and material used showed substantial to perfect agreement. Certain determinants of exposure such as days and hours per week exposed to welding fumes demonstrated mainly moderate agreement (κ= 0.42–0.47, percent agreement 63–77%); however, mean days and hours reported did not differ between test and retest. The results of this study suggest that participants' self-report for job title and dates employed are valid compared with employer records. While kappa scores were low for some medical conditions and for caffeine consumption, high kappa scores for job title, dates worked, types of welding, and materials welded suggest participants generated reproducible answers important for occupational exposure assessment.

Principal Component Imagery for the Quality Monitoring of Dynamic Laser Welding Processes

A popular technique to monitor laser welding processes is to record laser-induced plasma radiation with a highspeed camera. The recorded sequences are analyzed using pattern recognition systems. Since the raw data are too high dimensional to allow for an efficient learning, dimension reduction is necessary. The most common technique for dimension reduction in laser welding applications is to use geometric information of segmented objects. In contrast, we propose to adapt ideas from face recognition and to employ appearance-based features to describe the relevant characteristics of the recorded images. The classification performance of geometric and appearance-based features is compared on a representative data set from an industrial laser welding application. Hidden Markov models are used to capture the temporal dependences and to perform the classification of unlabeled sequences into an error-free and an erroneous class. We demonstrate that a classification system based on appearance-based features can outperform geometric features.

Experimental and theoretical investigations to the effects of zinc coatings and splash on electrode cap wear

The zinc used in coated steels causes alloying of spot welding electrode tips. This leads to tip deformation which causes substandard welds to be produced. The presence of expulsion during a weld is also an indication of poor welds and is another factor of reduced electrode life. A series of spot welds have been carried out on sheets of uncoated and sheets of galvanised steel using an industrial spot welding machine using the same welding parameters. The electrode force was varied in the experiments to show how force settings have an effect on electrode cap life. Peel tests were performed on the welds to measure weld nugget diameters and the results were plotted to generate weld growth curves and weldability lobes. SEM results and Vickers micro-hardness tests are also presented which show the alloying effects of zinc on the electrode caps. SORPAS ® has been used to simulate weld growth curves and to predict when splash will occur.