Bead Area Research Articles

Optimization of pulsed GTA welding process parameters for the welding of AISI 304L stainless steel sheets

Optimization of pulsed gas tungsten arc welding (pulsed GTAW) process parameters was carried out to obtain optimum weld bead geometry with full penetration in welding of stainless steel (304L) sheets of 3 mm thickness. Autogenuous welding with square butt joint was employed. Design of experiments based on central composite rotatable design was employed for the development of a mathematical model correlating the important controllable pulsed GTAW process parameters like pulse current (Ip), pulse current duration (Tp), and welding speed (S) with weld bead parameters such as penetration, bead width (W), aspect ratio (AR), and weld bead area of the weld. The developed models were checked for adequacy based on ANOVA analysis and accuracy of prediction by conducting a confirmation test. Weld bead parameters predicted by the models were found to confirm observed values with high accuracy. Using these models, the main and interaction effects of pulsed GTAW process parameters on weld bead parameters were studied and discussed. Optimization of pulsed GTAW process parameters was carried out to obtain optimum bead geometry using the developed models. A quasi-Newton numerical optimization technique was used to solve the optimization problem and the results of the optimization are presented.

Application of Taguchi method to optimise dissimilar laser welded components

In this study CO2 Laser Beam Welding (LBW) process was successfully applied and optimised for joining a dissimilar AISI 316 stainless steel and AISI 1008 low carbon steel plates. Laser power, welding speed and defocusing distance combinations were carefully selected with the objective of producing welded joint with complete penetration, minimum fusion zone size and acceptable welding profile. Fusion zone area of dissimilar austenitic stainless steel with ferritic low carbon steel was evaluated as a function of the selected laser welding parameters. Taguchi approach was used as statistical Design of Experiment (DOE) technique for optimising the selected welding parameters in terms of minimising the fusion zone. A mathematical model was developed to describe the influence of the selected parameters on the fusion zone area and to predict its value within the limits of the variables being studied. The result indicates that the developed model can predict the welded bead area satisfactorily.

Fuzzy Regression Model to Predict the Bead Geometry in the Robotic Welding Process

Recently, there has been a rapid development in computer technology, which has in turn led to develop the fully robotic welding system using artificial intelligence (Al) technology. However, the robotic welding system has not been achieved due to difficulties of the mathematical model and sensor technologies. The possibilities of the fuzzy regression method to predict the bead geometry, such as bead width, bead height, bead penetration and bead area in the robotic GMA (gas metal arc) welding process is presented. The approach, a well-known method to deal with the problems with a high degree of fuzziness, is used to build the relationship between four process variables and the four quality characteristics, respectively. Using these models, the proper prediction of the process variables for obtaining the optimal bead geometry can be determined.

STS304L 캡슐의 펄스형 GTA 용접에서 용접변수들이 용접부 형상에 미치는 영향

The aim of this paper is to investigate the effects of welding parameters on the weld shape in seal-welding of STS304L capsule for manufacturing a radioisotope source which is widely used in nondestructive testing of metal structures using gamma ray. Pulsed gas tungsten arc (Pulsed GTA) welding is performed for thin cross sectional area of the capsule. Seven welding parameters including current waveform parameters and arc length etc. are selected as main process parameters using design of experiment. The weld shape such as bead width, penetration depth, weld area, aspect ratio and area rate is investigated to assess the effects of welding parameters. As results, the combination of pulse duty/welding speed largely affects on bead width, penetration depth, area and aspect ratio. Finally, it is concluded that the key parameters are the combination of pulse duty/welding speed, base current and arc length, and their optimal conditions are 50%/1.77mm/s, 6.4A and 1 mm.

Preparation and characterization of macroporous cellulose–tungsten carbide composite beads for expanded bed applications

The specially designed adsorbent is one of the most important bases to achieve the expanded bed adsorption (EBA) process. The prefect adsorbents tend to be of small size, large pore and high density. In the present work a new kind of macroporous cellulose beads densified by high-density tungsten carbide were prepared through the method of water-in-oil suspension thermal regeneration. The cassava starch was used as porogenic agent during the preparation. Firstly the gelatinized starch solution was added into the cellulose viscose. After the formation of cellulose beads, the composite starch could be eliminated with boiling water wash and enzymatic hydrolyzation. The sphericity of cellulose beads was not influenced by starch addition and some amount of large pores with the diameter of about 1–3 μm could be formed in the beads. Varieties of physical properties, such as wet density, water content, porosity, specific surface area and mean pore diameter of the composite beads, as the function of starch addition were investigated. The analysis of elution peaks with model proteins (packed bed mode) indicated that the mass transfer kinetic inside the macroporous beads prepared was enhanced, which might certainly benefit the chromatographic operation under high flow rate. In addition, the prepared beads showed good expansion and stability in expanded bed, and are thus suitable for expanded bed applications.

Modelling weld bead geometry using neural networks for GTAW of austenitic stainless steel

The authors analyse the importance of different weld control parameters on the weld pool geometry of gas tungsten arc welding using an online feature selection technique that suggests weld voltage and vertex–angle pair as more important than the weld voltage and torch speed pair. Using the selected features multi layer perception and radial basis function networks are developed for prediction of bead width, penetration depth, and bead area. With cross-validation the authors have extensively studied the performance of composite models (one model for all outputs) and individual models (one model for each output). The individual models are found to work better than composite models. Usually, radial basis function networks are found to work better than the multi layer perception networks. To assess the influence of weld control parameters the authors have studied the performance of both networks using different combination of inputs. Overall, the performance of the proposed models is found to be quite satisfactory.

Near Real-Time Monitoring of Bead Area Damage in Rolling Tires Using a Rotating Wheel Model and Multi-Directional Vibration Data

In current tire durability tests, technicians must stop tests periodically to inspect each tire, resulting in a time consuming, expensive, and relatively subjective process. Online tire monitoring would thus be a dramatic improvement over the current methodology. If such a system could be extended to on-line vehicle use, it could dramatically increase safety, reduce downtime, and lead to better fuel efficiency in commercial and passenger cars and trucks. A near real-time system to monitor the initiation of bead area damage in rolling tires was developed using vibration data collected from the wheel end spindle. To generate an accurate model of the forced response of the wheel end spindle, a tire on a fixed spindle was impacted with a modal punch while the tire was preloaded against a plate. The frequency response functions acquired from this system were then used to develop a rotating tire model consisting of time-delayed forcing functions applied to the tire patch at the rolling frequency; this model was used to assist in interpreting the results from the near real-time monitoring system. The near real-time continuous monitoring system has been deployed in a manufacturing test environment and utilizes frequency data from three mutually orthogonal acceleration measurements. These data are combined to create a highly sensitive composite index that identifies when the initiation of bead area damage has occurred.

Study of Design and Evaluation of Drum Assembly for High Speed Dehydration in Washing Machine

Because customers are requiring front-loaded washing machine to handle big capacity laundry and have faster rotation speed to increase drying ability, there are being a lot of studies for achievement of high speed dehydration, high-strength and lightweight of washing machine in the latest washing machine business. It is essential that strength of Drum Assembly which is composed of spin drum, shaft, flange is improved to attain that target. In term of spin drum, it is difficult to realize joint strength required at high speed operation because joint strength of mechanical press-joining method is low remarkably in comparison with welding. Also in case of shaft system, stress from bending and twisting are complexly loaded onto the shaft supporting the horizontal drum, causing problems in fracture strength and fatigue life. The results of this study show optimal joining condition for mechanical press-joining by performing lots of tensile joining strength test with various specimen under multi-change of important design factor such as seaming width, bead area and bead depth etc. and the optimal design of shafting system for big capacity, high-rotation drying through strength analysis, experiment and evaluation.

Composite indices applied to vibration data in rolling tires to detect bead area damage

The primary objective of this research was to identify an online indicator of tire bead area separation for use in tire durability testing. The dynamics of tires with asymmetric bead area damage and the transmission of vibrations to an axle housing were studied. Experimental results from online data collected on a 67-in diameter roadwheel and a 120-in diameter roadwheel are presented. Statistical measures, trends in frequency content and transient wavelet maps, and composite damage indices were all evaluated as online damage detection features. Trends in statistical measures and frequency content were both indicative of damage progression, but were also sensitive to changes in test conditions. Wavelet maps were indicative of damage progression and showed potential for locating damage circumferentially on a tire. Wavelet analysis of data from both roadwheels indicated that damage increased the amount of higher frequency content in the response signals measured at the spindle arm and axle housing. The increase in broadband content was thought to come from transient vibrations generated when the damaged bead area passed through the contact patch. Composite damage indices that combined frequency and spatial data provided very clear indicators of potential damage initiation events, even predicting the number of ruptures, by drawing out the relevant information in the signals from the ambient vibration. The most effective composite indices multiplied several data signals such that only when all data signals indicated a change would the composite indices also indicate that damage had occurred.

An experimental study on improvement of joining strength of the spin drum seaming division in washing machine

Abstract There are being a lot of studies for achievement of high speed dehydration, high-strength and lightweight of washing machine in the latest washing machine business. It is essential that press-joining strength of spin drum seaming division is improved to attain that target. Generally, we are using mechanical press joining by seaming and TIG (tungsten inert gas) welding among part joint method. Mechanical press-joining method that is mainly using for stainless steel (STS430) drum have lots of merit that consumption of energy is low more than welding and production costs cut down and generation of the corrosion is solved by removing weld zone defect and materials having different properties are enable to join without special equipment. But, it is difficult to realize joint strength required at high speed operation because joint strength of mechanical press-joining method is low remarkably in comparison with welding. Also, there are a lot of analysis difficulties and very limited research is under way due to the dynamic factor such as multistage plastic working, elastic recovery, residual stress, etc. The results of this study show optimal joining condition for mechanical press joining by performing lots of tensile joining strength test with various specimen under multi-change of important design factor such as seaming width, bead area and bead depth, etc.

Analysis of Cracks and Stresses of Welded Attachments on Full-Scale Plate Girder under Fatigue Loading

In steel structure systems such as plate girder bridges and framed structures, fatigue damage used to occur at welded areas rather than primary structural members. These damages and behaviors of the welded attachments need to be extensively investigated so that the fatigue design criterion can effectively control the fatigue damage of steel structure systems. This study utilized a full-scale plate girder on which various welding attachments were mounted. The welded attachments investigated herein included flange gussets, web gussets, vertical stiffeners, and cover plates. The fatigue cracks initiated at the longitudinal end of joint area of the weld bead and the parent metal where stress was significantly concentrated. The initiated fatigue cracks developed along the weld path and then, propagated to the parent metal in the direction perpendicular to the principal stress. The fatigue cracks developed even under a compressive stress when a significant residual stress was experienced from the welding. The fatigue strengths of the each welded attachment were evaluated and compared with the current fatigue design specifications in AASHTO [1] and JSSC [2].

Approach to jamming in an air-fluidized granular bed

Quasi-two-dimensional bidisperse amorphous systems of steel beads are fluidized by a uniform upflow of air, so that the beads roll on a horizontal plane. The short-time ballistic motion of the beads is stochastic, with non-Gaussian speed distributions and with different average kinetic energies for the two species. The approach to jamming is studied as a function of increasing bead area fraction and also as a function of decreasing air speed. The structure of the system is measured in terms of both the Voronoi tessellation and the pair distribution function. The dynamics of the system is measured in terms of both displacement statistics and the density of vibrational states. These quantities all exhibit tell-tale features as the dynamics become more constrained closer to jamming. In particular the pair distribution function and the Voronoi cell shape distribution function both develop split peaks. And the mean-squared displacement develops a plateau of subdiffusive motion separating ballistic and diffusive regimes. Though the system is driven and athermal, this behavior is remarkably reminiscent of that in dense colloidal suspensions and supercooled liquids. One possible difference is that kurtosis of the displacement distribution peaks at the beginning of the subdiffusive regime.

Textural properties of ambient pressure dried water-glass based silica aerogel beads: One day synthesis

The tedious surface modification and solvent exchange steps (∼six days) involved in the conventional ambient pressure drying of silica hydrogels (bead or bulk type) prohibit the commercial production of silica aerogels despite the low cost of water-glass precursor. The present studies were intended to reduce the processing time of the ambient pressure dried silica aerogel beads using the co-precursor method for the surface modification in the hydrogels. The textural properties of such aerogel beads have been reported and discussed. The experimental results revealed that the aerogel beads (1–2 mm in diameter) are mesoporous solids with average pore diameter ranging from 32 to 49 Å. The specific surface area and pore size distribution of the aerogel beads could be tailored over a wide range by varying the content of surface modifying agents such as trimethylchlorosilane (TMCS) and hexamethyldisilazane (HMDS) in the sol. The aerogel beads with specific surface area as high as 591 m 2/g and the corresponding cumulative pore volume of 0.5 cc/g have been synthesized in one day using the new route for the rapid surface modification in hydrogels. The aerogel beads retain their hydrophobic property up to a temperature of 773 K.

Ion-imprinted beads for molecular recognition based mercury removal from human serum

The aim of this study is to prepare ion-imprinted polymers which can be used for the selective removal of mercury ions [Hg 2+] from human serum. N-Methacryloyl-( l)-cysteine (MAC) was chosen as the complexing monomer. In the first step, Hg 2+ was complexed with MAC and the Hg 2+-imprinted poly(hydroxyethyl methacrylate- N-methacryloyl-( l)-cysteine) (MIP) beads were synthesized by suspension polymerization. After that, the template ions (i.e., Hg 2+) were removed using thiourea (0.5%, v/v) in 0.05 M HCl. The specific surface area of the MIP beads was found to be 59.04 m 2/g with a size range of 63–140 μm in diameter and the swelling ratio was 91.5%. According to the elemental analysis results, the MIP beads contained 87.0 μmol MAC/g polymer. The maximum adsorption capacity was 0.45 mg Hg 2+/g beads. The applicability of two kinetic models including pseudo-first order and pseudo-second order model was estimated on the basis of comparative analysis of the corresponding rate parameters, equilibrium capacity and correlation coefficients. Results suggest that chemisorption processes could be the rate-limiting step in the adsorption process. The relative selectivity coefficients of MIP beads for Hg 2+/Cd 2+, Hg 2+/Zn 2+ were 14.7 and 21.5 times greater than the non-imprinted (NIP) matrix, respectively. The MIP beads could be used many times without decreasing in their adsorption capacities significantly.

N-methacryloyl-( l)-histidine methyl ester carrying porous magnetic beads for metal chelate adsorption of cytochrome c

A magnetic metal-chelate adsorbent utilizing N-methacryloyl-( l)-histidine methyl ester (MAH) as a metal-chelating ligand was prepared. MAH was synthesized using methacryloyl chloride and l-histidine methyl ester. Magnetic beads with an average diameter of 50–100 μm were produced by suspension polymerization of ethylene glycol dimethacrylate (EGDMA) and MAH carried out in a dispersion medium. Specific surface area of the magnetic beads was found to be 80 m 2/g. Elemental analysis of the magnetic beads for nitrogen was estimated as 70 μmol MAH/g polymer. Magnetic beads were complexed with the Cu 2+ ions directly via MAH for the adsorption of cytochrome c from aqueous solutions. The cytochrome c adsorption on the mag-poly(EGDMA–MAH) beads was 51 mg/g. Cu 2+ complexing increased the cytochrome c adsorption significantly. The maximum cytochrome c adsorption capacity of the Cu 2+-chelated beads (carrying 68 μmol Cu 2+ per gram of polymer) was found to be 222 mg/g at pH 8.0 in phosphate buffer. Cytochrome c adsorption decreased with increasing temperature. Cytochrome c molecules could be reversibly adsorbed and desorbed ten times with the magnetic adsorbents without noticeable loss in their cytochrome c adsorption capacity. The resulting magnetic chelator beads posses excellent long term storage stability.

Reversible Immobilization of Catalase by Metal Chelate Affinity Interaction on Magnetic Beads

A magnetic metal−chelate adsorbent utilizing N-methacryloyl-(l)-cysteine methyl ester (MAC) as a metal-chelating ligand was prepared. MAC was synthesized using methacryloyl chloride and l-cysteine methyl ester dihydrochloride. Magnetic beads with an average size of 150−250 μm were obtained by suspension polymerization of 2-hydroxyethyl methacrylate (HEMA) and MAC carried out in a dispersion medium. Mag-poly(HEMA−MAC) beads were characterized by surface area measurements, swelling tests, electron spin resonance (ESR) spectroscopy, elemental analysis, and scanning electron microscopy (SEM). The specific surface area of the magnetic beads was found to be 92.6 m2/g. Elemental analysis of MAC for nitrogen was estimated as 55.4 μmol/g. Then, Fe3+ ions were chelated on the magnetic beads. The Fe3+ loading was 12.7 μmol/g of support. Fe3+-chelated magnetic beads with a swelling ratio of 62% were used in the immobilization of catalase in a batch system. This approach to the preparation of enzyme carrier has several advantages over conventional immobilization methods. An expensive, time-consuming, and critical step in the preparation of immobilized metal-affinity carriers is the coupling of a chelating ligand to the adsorption matrix. In this procedure, comonomer MAC acts as the metal-chelating ligand, and it is possible to load metal ions directly on the beads without further modification steps. The maximum catalase immobilization capacity of the mag-poly(HEMA−MAC)−Fe3+ beads was observed to be 192 mg/g at pH 5.5. The Km value for immobilized catalase [mag-poly(HEMA−MAC)−Fe3+] (32.6 mM) was higher than that for free catalase (22.8 mM). Immobilized catalase exhibits enhanced stability in reaction conditions over a wide pH range (pH 5.5−7.0) and retains an activity of 76% after 10 successive batch reactions, demonstrating the usefulness of the enzyme-loaded magnetic beads in biocatalytic applications. The optimum temperature for the immobilized preparation of mag-poly(HEMA−MAC)−Fe3+−catalase at 45 °C was 5 °C higher than that of the free enzyme at 40 °C. Storage stability was found to increase with immobilization.

Synthesis of tentacle type magnetic beads as immobilized metal chelate affinity support for cytochrome c adsorption

Magnetic poly(2-hydroxyethylmethacrylate) (mPHEMA) beads with an average diameter of 100–140 μm were produced by suspension polymerization in the presence of magnetite particles (i.e. Fe 3O 4). Specific surface area and average pore size of the magnetic beads was found to be 50 m 2/g and 819 nm, respectively. Ester groups in the mPHEMA structure were converted to imine groups by reacting with poly(ethyleneimine) (PEI) in the presence of NaH. Amino (–NH 2) content of PEI-attached mPHEMA beads was determined as 102 mg PEI/g. Then, Cu 2+ ions were chelated on the magnetic beads in the range of 20–793 μmol Cu 2+/g. Cytochrome c (cyt c) adsorption was performed on the metal chelating beads from aqueous solutions containing different amounts of cyt c at different pHs, Cu 2+ loadings and temperatures. Cyt c adsorption on the mPHEMA/PEI beads was 4.6 mg/g. Cu 2+ chelation increased the cyt c adsorption significantly (40.1 mg/g). Adsorption capacity increased with Cu 2+ loading and then reached a saturation value. Cyt c adsorption decreased with increasing temperature. Cyt c molecules could be reversibly adsorbed and eluted ten times with the magnetic adsorbents without noticeable loss in their cyt c adsorption capacity. The applicability of two kinetic models including pseudo-first order and pseudo-second order model was estimated on the basis of comparative analysis of the corresponding rate parameters, equilibrium capacity and correlation coefficients. Results suggest that chemisorption processes could be the rate-limiting step in the adsorption process. In the last part of this article, cyt c adsorption experiments were performed in a magnetically stabilized fluidized bed (MSFB) system at optimum conditions determined from the batch experiments. The adsorption capacity decreased significantly from 46.8 to 15.4 mg/g polymer with the increase of the flow-rate from 0.5 to 4.0 ml/min. The resulting magnetic chelator beads possessed excellent long-term storage stability.

Ion-Selective Imprinted Beads for Aluminum Removal from Aqueous Solutions

The aim of this study is to prepare ion-imprinted polymers that can be used for the selective removal of aluminum ions [Al3+] from aqueous solutions. N-Methacryloyl-l-glutamic acid (MAGA) was chosen as the complexing monomer. In the first step, Al3+ was complexed with MAGA and Al3+-imprinted poly(hydroxyethyl methacrylate-N-methacryloyl-l-glutamic acid) (MIP) beads were synthesized by suspension polymerization. After that, the template ions (i.e., Al3+) were removed using 0.1 M EDTA solution. The specific surface area of the MIP beads was found to be 55.6 m2/g with a size range of 63−140 μm in diameter, and the swelling ratio was 102%. According to the elemental analysis results, the MIP beads contained 640 μmol of MAGA/g of polymer. The maximum adsorption capacity was 122.9 μmol of Al3+/g of beads. The applicability of two kinetic models including pseudo-first-order and pseudo-second-order models was estimated on the basis of comparative analysis of the corresponding rate parameters, equilibrium capacity...

A Study on Fuzzy Logic Theory to Predict the Process Parameters in GMA Welding Process

Recently, there has been a rapid development in computer technology, which has in turn led to develop the automated welding system using Artificial Intelligence (AI). However, the automated welding system has not been achieved duo to difficulties of the control and sensor technologies. In this paper, the classification of the optimized bead geometry such as bead width, height, penetration and bead area in the Gas Metal Arc (GMA) welding with fuzzy logic is presented. The Fuzzy C-Means (FCM) algorithm, which is best known an unsupervised fuzzy clustering algorithm is employed here to analysis the specimen of the bead geometry. Then the quality of the GMA welding can be classified by this fuzzy clustering technique, and the optimal bead geometry can also be achieved.

Polymerisation of vinylidene fluoride in supercritical carbon dioxide: Formation of PVDF macroporous beads

Poly(vinylidene fluoride) (PVDF) macroporous beads with diameter in the range of hundreds of micrometers were produced by batch polymerisation of vinylidene fluoride (VDF) in supercritical carbon dioxide (scCO 2) using diethyl peroxydicarbonate (DEPDC) as a free radical initiator. The rate and type of stirring were found to influence strongly the morphology of polymers, and the results indicated that the shear force was the key factor. A low shear force and a suitable monomer concentration range at 6–8 mol/l were needed for the formation of PVDF macroporous beads. Scanning electron microscopy (SEM) was employed to characterize the polymer morphology, and Brunauer–Emmett–Teller (BET) method was used to analyze the surface area of the polymer macroporous beads. In addition, polydimethylsiloxane monomethylacrylate (PDMS-ma) and poly(1H,1H,2H,2H-perfluorooctyl methacrylate) (PFOMA) were found to be able to control the size of PVDF macroporous beads. We propose that the formation of PVDF macroporous beads results from the aggregation of semi-crystalline PVDF primary particles.