Full Penetration Research Articles

Parameterized multipoint-line analytical modeling of a mobile heat source for thermal field prediction in laser beam welding

The thermal effects of the “keyhole” full penetration welding mode, which is characteristic of high-power CO2 laser, are simulated introducing a multipoint-line thermal source model based on heat conduction, parameterized by the distribution of the laser beam power, and the setting of the source system layout, and to be fitted on experimentally detected cross sections of the heat-affected or fusion zones of the weld. The proposed model allows to express the thermal field according to the moving reference system fixed on the overall heat source, and to analyze the temperature profiles that develop in some detection points fixed on the workpiece, as time varies during the welding process. By this way, it can be useful in evaluating the thermal effects that result from the variation of the main welding parameters (beam power, welding speed, plate thickness), with the aim of simplifying the selection of the optimal process conditions. As an application, reference is made to a cross section of a joint between plates of AISI 304 L austenitic steel. The fitting procedure allows to set the power distribution and layout parameters of the most suitable source combination (obtained by superposition of a line and two point sources). The value of the absorption coefficient also is assumed as fitting variable, so to overcome the complex problem of evaluating the beam power actually absorbed by the material on keyhole mode welding. Finally, the fitted model is applied to carry out a detailed thermal field analysis in the welded plates.

Determination of heat source model for simulating full penetration laser welding of 316 LN stainless steel by computational fluid dynamics

The selection of appropriate heat source model is vital in predicting the temperature distribution and visualizing the dynamic fluid flow behaviour during Laser keyhole welding of Type 316 LN stainless steel. Three-dimensional (3D) numerical models were designed utilizing ANSYS Fluent by employing different heat source models. Different heat source models considered include volumetric heat sources namely Goldak double ellipsoidal, 3D conical, a coalition of 3D conical and cylindrical heat source, 3D volumetric Gaussian and Rotary Gaussian. The simulation was carried out by solving the fundamental conservation equations of mass, momentum and energy. The predicted weld bead profile by different heat sources were compared with the actual weld bead obtained from the laser welding experiment on 0.0055 m thick 316 LN stainless steel (SS) plates. It was found that simulation results of the conical-cylindrical combined (CCC) model exhibited good agreement with actual weld bead dimensions and thermal data obtained during the experiment. Therefore, the conical-cylindrical heat source model is recommended for CFD simulation of full penetration laser welding of 316 LN stainless steel for studying the effect of variation of laser power and surface active element on the weld pool development.

Competition and Monopoly In Digital Economy Ecology

The global industrial structure and trade patterns have changed significantly with the full penetration of digital information technology into social and economic life. The digital economy has become a core driving force for global economic growth, and the development of the digital economy has gradually become the consensus of all economies in the world. The article breaks through the traditional perspective to understand the digital economy. It proposes that economic factors drive the digital world's development, digital knowledge and information are the critical production factors of the digital economy, and the digital economy wealth is concentrated in a few platform companies' hands. In the digital economy era, the business ecology is experiencing innovative destruction, the real economy and retail industry are suffering heavy losses, while the information industry and digital platforms are ushering in explosive growth. Based on natural ecology principles, the article deconstructs and analyzes the digital business ecology, and proposes business development strategies such as maintaining the diversification of business forms, promoting digital empowering the real economy, the digital transformation of the real economy and digital industrialization. The article discusses platform monopoly and competition, including platform characteristics analysis, economic causes, anti-monopoly investigation cases, and the relationship between monopoly, innovation, and competition. The authorities must not ignore behaviours that harm market competition due to competition's dynamic nature and develop digital economy tolerantly and prudently, maintaining the economic ecology's diversity and balance.

Improving mechanical strength on welded joints by using optimisation technique

The welding process is an important component in many industrial operations. Welding input parameters play a very significant role in determining the quality of a weld joint. The joint quality can be defined in terms of properties such as weld-bead geometry, mechanical properties, and distortion. Generally, all welding processes are used with the aim of obtaining a welded joint with the desired weld-bead parameters, excellent mechanical properties with minimum distortion. So that in this paper presents find the suitable input parameter in welded joints and then find the full penetration of the material. By using on design of experiment (DOE), genetic algorithm and computational network are widely used to develop a mathematical relationship between the welding process input parameters and the output variables of the weld joint in order to determine the welding input parameters that lead to the desired weld quality of the welded material.

Experimental and numerical investigation of hybrid laser arc welding process and the influence of welding sequence on the manufacture of stiffened flat panels

Hybrid laser arc welding (HLAW) has gained growing attention from both industry and academic laboratories for its high efficiency and weld quality. The objective of the present paper is to develop a nonlinear finite element method for predicting the weld-induced deflection and residual stress of semi-industrial scale stiffened panel, using a novel heat source model. The novel hybrid heat source consists of a Goldak's double-ellipsoid mathematical model representing the arc source, combined with a truncated cone Gaussian mathematical model to simulate the laser source. For this purpose, three-dimensional coupled thermo-elastic-plastic finite element model has been developed with ABAQUS using an additional numerical subroutine of DFLUX written in the Fortran programming language to simulate the volumetric heat flux distributions of the HLAW process. The finite element method (FEM) is verified by comparison with experimental measurements of T-joint small-scale naval EH36 steel specimens, welded in horizontal position with full penetration using hybrid laser-arc welding process (HLAW). A good agreement is observed between the numerical results and the experimental measurements, confirming that the model developed in the present paper can be used effectively to predict the deformation behaviour of the stiffened plate structures during shipbuilding. The effect of changing welding sequence on the semi-industrial scale stiffened panel has been also studied. It is concluded that the welding sequence plays an important role in the deformation of the structures. A change of direction in the middle section, in combination with alternation of the welding paths between two consecutive reinforcements welding, leads to a significant decrease of distortion.

Flexural behavior of a novel high-strength RCFST column-to-column connection

Brittle fracture is one of the principal disincentives to limit the use of ultrahigh-strength steels in tall buildings. This paper proposes a novel column-to-column connection without full penetration welding in reinforced concrete-filled steel tubular composite columns. The paper describes an experimental investigation into the flexural behavior of the proposed RCFST column-to-column connection, in which the steel was manufactured using ultrahigh-strength steel grades H-SA700 and USD 685. Four specimens with varying configurations of reinforcing steel bars (separated type or gathered type) and column shapes (square or circular) were tested under four-point bending to evaluate the failure modes, flexural capacity, and deformation capacity. The results show that the gathered type of configuration of reinforcing steel bars can effectively improve the flexural capacities while having a negligible effect on the strain distribution of steel tubes or steel bars. Besides, the column type was found to significantly influence the strain distribution of the steel tube. The design formulae show accuracy and reliability and could be applied to assess the yield and ultimate strength of the proposed new connections.

Mechanism study of thermal fluid flow and weld root hump suppression in full penetration laser welding of Al alloy with alternating magnetic field support

In this work, the influence mechanism of alternating magnetic field on the thermal fluid flow and weld root hump suppression in full penetration laser welding of aluminum alloy was studied. A novel three dimensional transient numerical model was developed, in which a multiple reflection laser beam model, a varied metallic vapor force model and an electromagnetic model including Lorentz force and Joule heat were considered. The experimental results indicated that when the effective magnetic flux density was 57 mT and its alternating frequency was 400 Hz, a sound weld bead for 10 mm plate could be obtained. The numerical analysis showed that the periodically varied electromagnetic force exerted an upward support to the weld pool, making its geometry and flow pattern stable. The keyhole collapse at upper and middle region was enhanced and the higher laser absorption was attributed to the decreased occurrence frequency of through-keyhole. The weld root sagging formation was instantaneous, while its suppression was a persistent process. The effect of weld root hump suppression depended on the dynamic competition among the electromagnetic force and the forces that promote the weld root sagging generation in the welding process.

Diffusion Along Dislocations Mitigates Self-Limiting Na Diffusion in Crystalline Sn.

The diffusion of carrier ions in alloying anodes often develops compressive stresses in front of the propagating interface, suppressing the carrier-ion diffusion and limiting their full penetration into alloying anodes during battery cycles. This phenomenon, termed "self-limiting diffusion (SLD)", reduces the rate performance of batteries and hinders the full usage of anode materials. However, SLD is mitigated in some systems where tensile residual stresses develop at the interface, causing them to manifest significantly improved rate performance and energy capacity. Here, a comparative study of LiSi and NaSn systems to elucidate how the differing diffusion kinetics displayed by the two systems can influence SLD behaviors and the rate performance of batteries is performed. Experiments show that the Na diffusion into soft Sn crystals induces tensile stresses near the interface, promoting the nucleation of high-density dislocations. Thus-formed dislocations facilitate Na diffusion at ultrafast rates by providing pathways for dislocation pipe diffusion and alleviate SLD, making crystalline Sn suitable for fast-charging anode material. The outcomes of this study, while filling the knowledge gaps on the reasons for SLD, offer some guidelines for the appropriate choice of potential anode materials with superior rate performance and energy capacity suitable for future applications.

Investigation of the Material Point Method in the simulation of Cone Penetration Tests in dry sand

Cone penetration tests (CPTs) are widely used in geotechnical engineering for soil characterization and parameter determination. Throughout the years, experimental data have been used to determine correlations between CPT data and soil properties, such as stiffness or strength. Recent progress in advance numerical methods allows the simulation of the full CPT penetration by overcoming the limitations related to extreme deformations. The use of these numerical techniques provides new prospective to the soil characterization and determination of soil parameters, especially for the settings where limited (or no) experimental data is available and existing correlations are not accurate, or absent. This paper presents a numerical framework based on the Material Point Method (MPM) to simulate CPT in dry sand. First, it is proven that the calculation scheme is stable and accurate. Then, the model results are validated against chamber test data in terms of both cone resistance and displacement field during the penetration. Finally, some considerations about the formulation of the constitutive models of soils are presented, specifically oriented for CPT applications.

Simulation Study on Weld Formation in Full Penetration Laser + MIG Hybrid Welding of Copper Alloy.

Considering the coupling of a droplet, keyhole, and molten pool, a three-dimensional transient model for the full penetration laser + metal inert gas (MIG) hybrid welding of thin copper alloy plate was established, which is able to simulate the temperature and velocity fields, keyhole behavior, and generation of the welding defect. Based on the experimental and simulation results, the weld formation mechanism for the hybrid butt welding of a 2 mm-thick copper alloy plate was comparatively studied in terms of the fluid dynamic feature of the melt pool. For single laser welding, the dynamic behavior of liquid metal near the rear keyhole wall is complex, and the keyhole has a relatively drastic fluctuation. An obvious spattering phenomenon occurs at the workpiece backside. Meanwhile, the underfill (or undercut) defect is formed at both the top and bottom surfaces of the final weld bead, and the recoil pressure is identified as the main factor. In hybrid welding, a downward fluid flow is strengthened on the rear keyhole wall, and the stability of the keyhole root is enhanced greatly. There are large and small clockwise vortexes emerging in the upper and lower parts of the molten pool, respectively. A relatively stable metal bulge can be produced at the weld pool backside. The formation defects are suppressed effectively, increasing the reliability of full penetration butt welding of the thin copper alloy plate.

Fatigue analysis of cruciform welded joint with weld penetration defects

For the fabrication of steel structures such as steel bridges, offshore structure etc, welding is nowadays considered as an efficient metal joining process. The type of fillet welded cruciform joint are widely used in construction of long spanned bridges with improved design and increased weld quality. However, the presence of geometrical discontinuities and metallurgical nonuniformities lead to crack initiations from different positions which are difficult to detect. Moreover, when these structures are subjected to repeated loading these cracks start propagating in different directions and lead to fatigue failure of welded structures. Also, the presence of locked in stresses and other factors affect the fatigue life and fatigue crack initiation. In the present work, the cruciform fillet welded joint with full and incomplete penetration were analyzed for both load types i.e load carrying and non-load carrying by using 3D fatigue FEM analysis. The experimental study of non-load carrying cruciform joint was also carried out. The effect of incomplete penetration depth, welding deformation, residual stresses and stress magnitude on fatigue crack initiation and fatigue life of fillet welded cruciform joints was investigated. Also, the S-N curves plotted for comparing with the results of hotspot stress and experiments. The results of 3D fatigue FEM analysis were compared with S-N curves recommended by IIW and DNV GL.

The Effect of an External Magnetic Field on the Aspect Ratio and Heat Input of Gas-Metal-Arc-Welded AZ31B Alloy Weld Joints Using a Response Surface Methodology.

This study attempted to analyze and optimize the effect of an external magnetic field (EMF) on the aspect ratio and heat input for AZ31B weld joints that were welded using the gas metal arc welding (GMAW) process. The response surface methodology (RSM) was adopted for the critical analysis, and subsequently, mathematical models were developed based on the experimental results. It was observed that the EMF and its interaction with the wire feed rate significantly affected the aspect ratio and heat input, respectively. At 119 G (magnetic field), 700 mm/min (welding speed), 5.8 m/min feed rate, and 11.5 L/min (gas flow rate), the aspect ratio was 2.26, and the corresponding heat input factor (HIf) was 0.8 with almost full weld penetration.

Power Control during Remote Laser Welding Using a Convolutional Neural Network.

The increase in complex workpieces with changing geometries demands advanced control algorithms in order to achieve stable welding regimes. Usually, many experiments are required to identify and confirm the correct welding parameters. We present a method for controlling laser power in a remote laser welding system with a convolutional neural network (CNN) via a PID controller, based on optical triangulation feedback. AISI 304 metal sheets with a cumulative thickness of 1.5 mm were used. A total accuracy of 94% was achieved for CNN models on the test datasets. The rise time of the controller to achieve full penetration was less than 1.0 s from the start of welding. The Gradient-weighted Class Activation Mapping (Grad-CAM) method was used to further understand the decision making of the model. It was determined that the CNN focuses mainly on the area of the interaction zone and can act accordingly if this interaction zone changes in size. Based on additional testing, we proposed improvements to increase overall controller performance and response time by implementing a feed-forward approach at the beginning of welding.

High-velocity impact response of fiber metal laminates: Experimental investigation of projectile's deformability

The aim of this research is to investigate the influence of projectile's deformability on ballistic impact response of fiber metal laminates. High-velocity impact experiments have been carried out via a light gas gun setup using rigid, semi-rigid and deformable projectiles with the same diameter, nose shape and mass. Fiber metal laminates have been made of two identical aluminum facing plates and different number of glass/epoxy composite plies in the middle. Several local and global mechanisms for kinetic energy absorption of projectiles have been detailed and ballistic limit velocity, as well as specific perforating energy for all cases have been determined. The results indicated that by increasing the deformability of the projectile, the amount of local and global wasting energy mechanisms for dissipating the velocity of projectiles have been increased. Furthermore, the interaction between non-rigid projectiles and fiber metal laminate targets as well as permanent deformation of non-rigid projectiles, had important effects on preventing the projectile penetration. By increasing the deformability of projectiles and/or increasing the number of composite plies, permanent deformation of facing plates, fiber breakage, crushing as well as delamination and debonding have been increased and local damage modes in facing plates changed from petalling to plugging. Besides, rigid projectiles possessed less specific perforating energy compared with deformable projectiles and required minimum initial velocity for full penetration.

Temperature Gradients at the Solidification Front of Deep Hybrid Laser Welds

Abstract Grain refinement and the avoidance of columnar solidification is a great challenge in the deep penetration laser welds of thick-section steels. Further knowledge about the heat distribution and the temperature gradients in laser welds is vital for future attempts on the grain refinement of such welds. In this study, a comparative investigation was carried out for full and partial penetration hybrid laser welding of structural steel. The transient temperature distribution and temperature gradients were calculated for the experiments using a simplified three-dimensional finite element analysis. A comparative analysis was presented to investigate the influence of penetration mode on the temperature gradient in the liquid at different weld depths. The results of the numerical analysis suggested that, for given welding process parameters, full penetration welds have lower temperature gradients at the solidification front, meaning that they potentially have a higher chance of grain refinement, compared with partial penetration welds.

Experimental investigation on a pulsed TIG welding of Inconel 625

This paper discusses the joining of Inconel 625 plates using A (Activated flux) pulsed TIG welding process. Inconel 625 plates of thickness of 3 mm was welded in butt joint configuration. A pulsed TIG welding was done on plates of INCONEL 625 using three different fluxes namely Al2O3, TiO2 and V205. The quality of the weld was analyzed by measuring the bead geometry (D.O.P. & B.W.) and ultimate tensile strength. A comparison is made between each fluxes effect on the bead geometry and ultimate tensile strength values. Full penetration was not achieved in any of the welding trials. V205 flux resulted in maximum penetration. Depth of penetration was increased by a 0.3 mm when V205 was used as flux material. Maximum tensile strength was obtained when Al203 was used as flux material. Tensile test was increased by 12% when Al203 was used as flux material.

Probabilistic modelling of nanobiomaterial release from medical applications into the environment

Nanobiomaterials (NBMs) are currently being tested in numerous biomedical applications, and their use is expected to grow rapidly in the near future. Many different types of nanomaterials are employed for a wide variety of different applications. Silver nanoparticles (nano-Ag) have been investigated for their antibacterial, antifungal, and osteoinductive properties to be used in catheters, wound healing, dental applications, and bone healing. Polymeric nanoparticles such as poly(lactic-co-glycolic acid) (PLGA) are mainly studied for their ability to deliver cancer drugs as the body metabolizes them into simple compounds. However, most of these applications are still in the development stage and unavailable on the market, meaning that information on possible consumption, material flows, and concentrations in the environment is lacking. We thus modeled a realistic scenario involving several nano-Ag and PLGA applications which are already in use or likely to reach the market soon. We assumed their full market penetration in Europe in order to explore the prospective flows of NBMs and their environmental concentrations. The potential flows of three application-specific composite materials were also examined for one precise application each: Fe3O4PEG-PLGA used in drug delivery, MgHA-collagen used for bone tissue engineering, and PLLA-Ag applied in wound healing. Mean annual consumption in Europe, considering all realistic and probable applications of the respective NBMs, was estimated to be 5,650 kg of nano-Ag and 48,000 kg of PLGA. Mean annual consumption of the three application-specific materials under the full market penetration scenario was estimated to be 4,000 kg of Fe3O4PEG-PLGA, 58 kg of MgHA-collagen, and 24,300 kg of PLLA-Ag. A probabilistic material-flow model was used to quantify flows of the NBMs studied from production, through use, and on to end-of-life in the environment. The highest possible worst-case predicted environmental concentration (wc-PEC) were found to occur in sewage sludge, with 0.2 µg/kg of nano-Ag, 400 µg/kg of PLGA, 33 µg/kg of Fe3O4PEG-PLGA, 0.007 µg/kg of MgHA-collagen, and 2.9 µg/kg of PLLA-Ag. PLGA exhibited the highest concentration in all environmental compartments except natural and urban soil, where nano-Ag showed the highest concentration. The results showed that the distribution of NBMs into different environmental and technical compartments is strongly dependent on their type of application.

Effect of Welding Speed on Electron Beam Welding Thermal Efficiency

The results of thermal efficiency evaluation during electron beam welding of alloys with different thermophysical properties in the range of welding speeds from 20 m/h to 120 m/h are presented. It was shown that the thermal efficiency increased in accordance with the rising welding speed. Also, the thermal efficiency greatly depends on the thermal conductivity: the lower the thermal conductivity, the higher the thermal efficiency. Thus, with an increase in welding speed from 20 m/h to 120 m/h, the thermal efficiency grew steadily for all three considered types of alloys: values for a titanium alloy 5 V went up from 54% to 67%, while for the steel 40Kh13 values rose from 46% to 63% and the most significant increment related to duralumin D16, the thermal efficiency for this alloy increased from 18% to 40%. The equation which established the ratio between the thermal efficiency, welding speed and thermal conductivity for electron beam welding with full penetration was derived.

Lifecycle cost assessment of high strength carbon and stainless steel girder bridges

This paper addresses the lifecycle cost assessment of a steel girder bridge considering the material costs and maintenance activities along the bridge's lifecycle. A reference highway bridge case study is chosen. It was initially designed using carbon steel S355. Two more steel grades are included in the comparison: high strength carbon steel S460 and duplex stainless steel EN 1.4162. For each design option, fatigue appears to be the driving design criterion for the following critical welded details: transversal stiffeners, cope holes and full penetration butt welds in the flanges. In addition to ultimate limit state verifications, specific attention is therefore given to fatigue through the use of different verification methods: the well-known nominal stress method and the hot spot stress method. It is concluded that the net present value of the lifecycle cost of the stainless steel option is attractive compared to painted the carbon steel options.

R&D achievements for vacuum vessel towards CFETR construction

The next generation of magnetic confinement fusion experimental facility, the China Fusion Engineering Test Reactor (CFETR), is currently undergoing physical and engineering design. The essential technology research and development projects related to CFETR manufacture are in progress. As one of the demo projects for CFETR R&D, a 1/8 full-scaled vacuum vessel (VV), which aims to solve the key technologies of forming, welding, measurement, assembly, etc in the future manufacturing process of VV, was initiated in 2015 by Institute of Plasma Physics Chinese Academy of Science (ASIPP). The fabrication of two full-scaled 22.5° toroidal sectors, which are composed of two 11.25° sectors, was successfully completed in June 2019. In the manufacturing process of the VV mockup, the progress has been made in the following six aspects: engineering design and safety evaluation of the VV mockup, the high-precision forming of the hyperbolic shell, the welding deformation control of 50 mm thick full penetration structure, the nondestructive testing of the complex welds by full volume covering, the establishment of high-precision 3D measurement fiducial network and the high-precision assembly of the VV parts. This article describes the progress and achievements of the above six aspects for the CFETR VV.