Thick Metal Plate Research Articles

Local energy adjustment mechanism in a novel laser-enhanced plasma arc heat source

This study aims to enhance the localized energy of the plasma arc to meet the requirement of thick metal plate welding. To achieve this, a novel hybrid heat source by coaxial arranging the laser and plasma arc was proposed, named laser-enhanced plasma arc (LPA). This special torch combines the two kind sources by a tubular tungsten electrode which the laser passes through, use laser to heat localized plasma arc to modify the energy distribution. The three-dimensional temperature field was measured to clarify the effect of laser on plasma arc energy distribution and the absorption characteristics of laser by plasma arc. The numerical simulation model was established to reveal the influence mechanism. Results show that there is a high laser absorption region in the plasma arc, and it exists obvious effects of plasma arc pressure and temperature on laser absorption rate. The location and size of the high laser absorption region change as the welding parameters because the temperature and pressure of plasma arc change. The results also substantiate that the hybrid source energy can be adjusted locally to increase the effective flame length of the plasma arc by changing the laser energy and plasma arc parameters, which is beneficial for thick metal plate welding.

A novel method for the welding of tailor-welded blanks with different thicknesses based on the diode laser source

Due to weld defects occurred in the traditional laser welding of tailor-welded blanks with different thicknesses, a novel processing method is proposed in this paper. In this method, thin and thick metal plates are obliquely cut and then butt jointed to form an eave-like structure. When a laser beam irradiates on the marginal area of the thick plate, the molten metal flows into the gap and welds two plates together. Using this method, stainless steel tailor-welded blanks with a plate thickness combination of 2.0 mm and 1.0 mm are successfully welded by a diode laser source, and welded samples are free from cracks and pores. This method supplies a concise and quick processing way for the processing of tailor-welded blanks in industry.

Differential readings of capacitance-based controls of attitude and displacements at the micro/nano scale

Four-quadrant plane capacitive sensors with electrodes made by thick metal plates were used in a novel configuration of a bridge-based circuit for measurement of both displacement and small angles over two axes. Their design, fabrication and testing by means of a specifically designed differential set-up is presented and discussed in terms of the measurement model, considerations of signal recovery, linearity, resolution, and noise. Numerical calculations of the capacitors, including corrective terms for fringe effects and tilt between electrodes in a differential configuration, are developed to simulate the overall measuring system. Tests of the model were then performed and validated by means of a comparison with the results of displacement and small angle rotation runs traced by an interferometer and an autocollimator. Sensitivities of approximately 0.11 V µm−1 with a 1 × 10−3 relative standard deviation, and of 0.13 V mrad−1 with a 3 × 10−3 relative standard deviation, were determined, with displacements of up to ±50 µm and yaw rotations of up to ±10 mrad.

Modeling and Analysis of Cyber–Physical System Based on Object-Oriente Generalized Stochastic Petri Net

Cyber–physical system (CPS) is a complex system that contains multiple components working cooperatively. According to its characteristics, we propose an object-oriented generalized stochastic Petri net (OGSPN), in which the CPS is abstracted into several types of objects and its logical structure and working process is visually described. Moreover, we model and measure the time consumed by each activity in CPS for quantitative analysis. To simplify the process of performance analysis on this model, in this article we propose a compression algorithm to convert OGSPN into a generalized stochastic Petri net (GSPN). Considering the uncertainty in CPS, we use a fuzzy mathematics based method to process the compressed model of GSPN for improving the accuracy of the performance analysis. We apply our method to a real-world thick metal plate production line in a manufacturing company, and the availability of our method is verified by extensive experiments.

Anticipating heat accumulation in laser oxygen cutting of thick metal plates

Excessive heating of the metal sheet during laser oxygen cutting can cause quality deterioration and even lead to cut loss and possible machine idle time, especially for cutting of thick plates, where the cutting speed is slower. There are at least three different strategies to handle quality deterioration by heat accumulation in flame laser cutting of thick plates: to optimize the process parameters for preheated zones, to generate tool paths that avoid such regions, or to use active cooling to remove the excessive heat. For any of these strategies to work, it is crucial to correctly identify when and where heat accumulations occur. This can be done by real-time temperature measurements, by simulating heat propagation on the metal plate, or by defining empirical criteria based on experimental data. This paper takes a close look at these methods of heat accumulation detection, their advantages and disadvantages, and how they can be integrated into different approaches to tackle unwanted heat accumulations in laser cutting. Furthermore, three case studies are provided, one for each above-mentioned method, where the detection of quality degradation due to heat accumulation is demonstrated with a series of experiments. For all case studies, at least one action is proposed to improve the cut quality. All experiments were conducted for 15 mm mild steel plates using a 4 kW industrial fiber laser cutting machine.

Experimental and numerical investigations on the energy-absorption of a bending-straightening structure

This paper introduces an energy-absorption structure which dissipates energy utilising the ‘bending-straightening’ process and the friction of a thin metal plate. Three repeated tensile tests were carried out to investigate the force and energy characteristics of the structure. Different loading methods and loading rates of the simulation were studied and the numerical model was verified. Furthermore, the effects of the metal plate thickness, width, the central distance of the structure and the friction coefficient on the energy-absorption of the absorber were studied systematically. The results show that the structure is of good test reproducibility and the loading process is steady. The stable tensile force (STF) and the dissipated energy increase with the rising of the structural parameters significantly. With some of the engineering improvements, the absorber can be implemented in the seat anti-impact structure and this work can provide guidelines for the design and analysis for engineering applications.

2D visualization and optimization of EMAT signal for small defect detection in thick plates

The paper focus on a new combined experimental methodology and signal processing for an EMAT based on a Halbach magnet system in order to increase smaller defect detection in thick metallic plates. The visualization of the EMAT signal using a novel dynamic C-scan procedure is based on a continuous movement of the transducer above plate and an off-line signal processing that is enhanced and optimized for detection of small defects (5%) located on the opposite side of metallic plates (50 mm). The feasibility and performance of the acquisition signal method, and several signal processing algorithms are validated using experimental measurements. The results present an optimized two-dimensional visualization technique for EMAT signal, which can be used for continuous surface scans of plates for detection of smaller defects that self-calibrate as the scan is conducted.

Gap Detection Using Convolutional Neural Network and Adaptive Control in Robotic Plasma Welding

Welding is an essential technology for joining metal plates. In general, gas metal arc welding (GMAW) generates a large amount of fumes in the welding of thick metal plates. In contrast, the butt joining of thick metal plates can be achieved using plasma arc welding (PAW) with a lower amount of fumes. Further, the improvement of the welding environment is critical in welding. In particular, if there are gaps between the base metals, the welding conditions are adjusted based on the gap. A visual sensor, such as a complementary metal-oxide-semiconductor (CMOS) camera, is useful for observing the welding situation. In this study, such a camera was attached to a plasma torch. During welding, we obtained weld pool images using the camera and detected the gaps by processing the images. As the arc light is very intense, it is difficult to obtain a clear image of the weld pool in PAW. In conventional welding, a constant current is used; however, pulsed welding current is used herein to obtain a clear image. The frequency of the current is 20 Hz, which indicates that the interval time is 50 ms. Moreover, the welding current was reduced to 30 A to minimize the effect of the intense arc light while the shutter of the CMOS camera was opened. The exposure time of the CMOS camera is 1 ms. Furthermore, gaps can be detected through image processing. It is necessary to identify the base metals with or without a gap. It was observed that the gap is darker than the solid area of the base metal. Moreover, a gap can be detected through the binarization method. The center area is not dark in the image of the weld pool without the gap. As the image of the weld pool is uneven without a gap, the binarization method can provide a detection result with some errors. Hence, it is challenging to identify whether there is a gap. A convolutional neural network (CNN) is useful for analyzing images. Thus, we applied a CNN to the weld pool image. If the gap is identified using the CNN, the binarization method is used to obtain the gap width. Hence, in PAW, welding conditions are adjusted based on the gap.

A study of heat transfer through the heavy plate thickness under multi-slit jet impingement

The influence of cooling models and moving velocity on the temperature variation and cooling rate through the thickness of a metal plate is experimentally investigated. In this investigation, the cooling process is divided into four stages: a starting stage (I), a rapid cooling stage (II), a slow cooling stage (III) and a stopping stage (IV). Based on the curves, cooling rate, temperature difference, the heat transfer coefficient and center temperature curves are discussed. The results indicate that the cooling model and moving velocity influence the heat transfer on the surface, and affects the cooling rate through the thickness by changing the temperature difference. When the flow rates of nozzles 1, 2 and 3 are set to be V1, V2 and V3 respectively, the highest heat transfer is observed when V1 > V2 > V3. Under this cooling model, the maximum temperature difference occurs at the time of transition from the rapid cooling stage (II) to the slow cooling stage (III). In the slow cooling stage (III), increased moving velocity improves the synchronization of the heat transfer and decreases the maximum heat flux. As well, the speed of motion affects the internal heat conduction and cooling rate by affecting surface heat transfer.

A data framework for environmental assessment of metal arc welding processes and welded structures during the design phase

Welding is a widely used technology that allows the joining of thick metal plates for the development of large structures (e.g. piping, tanks, vessels). Many industries are intensively using welding for manufacturing and assembly activities. Sustainability assessment of welded structures is currently performed with misleading information in terms of data heterogeneity (nature) and quality (source). The data required to carry out a robust environmental analysis are spread among different documents and become available only when the project is finalized. This paper aims to define a data framework for a life cycle inventory of metal arc welding processes to preventively assess the environmental performances of different processes for comparison and decision-making analysis. The framework is presented as innovative solutions for life cycle inventory that provide (i) a common data structure (model), (ii) necessary data (input/output), and (iii) physical allocation/placement of data (project design documents). This study was performed in accordance with the international standard organization ISO 14040/14044 by using an attributional life cycle assessment (aLCA). Two structures (an oil and gas riser and a ship hull) were investigated considering the same functional unit: the manufacturing, use, and disposal of a welded structure able to guarantee the engineering requirements (according to a specific standard) in terms of strain, stress, and corrosion allowance over the expected lifetime of 20 years. In both cases, the share of welding process in respect to an overall product/structure life cycle impact assessment is strictly dependant on the project design choice and can be negligible for high-corrosion-resistance materials (e.g., Inconel alloy). On the other hand, the use of traditional metals (e.g., carbon steel) allows a large decrease of the environmental load, and the influence of the welding process becomes significant in a life cycle perspective.

Comparative life cycle assessment of metal arc welding technologies by using engineering design documentation

The paper aims to analyze and compare the environmental performances of metal arc welding technologies: gas metal arc welding (GMAW), shielded metal arc welding (SMAW), gas tungsten arc welding (GTAW), submerged arc welding (SAW), and flux-cored arc welding (FCAW). Welding is considered one of the most energy-intensive processes in manufacturing. This study was performed in accordance with the international standard ISO 14040/14044 by using attributional life cycle assessment (aLCA). The functional unit is defined as the “the development of 1 metre of welding seam (qualified by ASME section IX requirements) to join 25 millimetres thick of metal plates made in carbon steel material and considering a V-bevel configuration.” Different configurations of base/filler materials and standardized bevel geometries have been analyzed as welding scenarios. The inventory considers all inputs (e.g., electric energy and filler material) and outputs (e.g., fume emissions and slags) involved in each welding process. A framework for data collection starting from available project documentation is presented as an innovative solution for the inventory phase. The impact assessment includes the human health, resources (midpoints/endpoint), and ecosystems (endpoint) categories from the ReCiPe (H) and cumulative energy demand (CED) methods. This study reveals a notable dominance in terms of the environmental burdens of GTAW and SMAW processes, as they present higher impacts in most of the impact categories. SMAW is the most energy-consuming process, and this aspect is reflected in the environmental performance. Conversely, GMAW presents the least environmental load, accounting for less than one third compared with GTAW in terms of the CED indicator and performing very well in terms of the ReCiPe endpoint indicator. Via analysis of different scenarios, the main outcomes are the following: (i) the use of V bevels significantly increases the environmental load when the metal plate thickness increases and (ii) the use of specific materials such as Inconel alloy exacerbates the environmental concerns associated with welding processes. The use of project documentation allows robust analysis of welding activity. Sensitivity analysis shows how the range of values for specific parameters (e.g., volts and amps) affects each technology in a different manner. Indeed, those ranges have a limited impact on the result accuracy (up to 20%) for more automatized welding processes (e.g., GMAW, SAW, and FCAW), in which only a small number of parameters are set by the operator, and the operator skills are less influential on the quality of the weld.

Determination of the Magnetic Permeability, Electrical Conductivity, and Thickness of Ferrite Metallic Plates Using a Multifrequency Electromagnetic Sensing System

In this paper, an inverse method was developed which can, in principle, reconstruct arbitrary permeability, conductivity, thickness, and lift-off with a multi-frequency electromagnetic sensor from inductance spectroscopic measurements. The system fives the error of "Bad character(s) in field Abstract" for no reason. Please refer to manuscript for the full abstract.

Numerical investigation of sand-basalt heat storage system for beam-down solar concentrators

This study aims to investigate the performance of a novel combined receiver storage system (RSS) for beam down solar concentrator. The proposed system consists of large sand volume located at the ground underneath the secondary reflector of the beam-down tower. The top of the storage volume is covered by an absorber system which contains a thick black painted metal plate. The absorber plate absorbs the reflected solar flux and converts it to heat. The heat energy is then transferred to the storage media using metal rods. The performance of the thermal storage material of different mixing ratios of sand and basalt are investigated. The unsteady governing equations for the system are solved using a finite element heat transfer model. The model is validated and used to predict the temperature distribution inside the storage media of different conducting rods configurations. The utilization factor of the storage media for various cases is calculated and documented. The results showed that the utilization factor is in the range 0.53–0.73 depending on the conductive rods configuration and the sand – basalt mixture ratio.

A three-stage model for the perforation of finite metallic plates by long rods at high velocities

Abstract A three-stage theoretical model is presented herein to predict the perforation of a thick metallic plate struck normally by a long rod at high velocities. The model is suggested on the basis of the assumption that the perforation of a thick metallic plate by a long rod can be divided into three stages: (1) initial penetration; (2) plug formation and (3) plug slipping and separation. Various analytical equations are derived which can be employed to predict the ballistic limit, residual velocity and residual length of the long rod. It is demonstrated that the present model predictions are in good agreement with available experimental results for the perforation of finite steel targets struck normally by steel as well as tungsten alloy long rods at high velocities. It is also demonstrated that the dynamic maximum shear stress of a plate material has strong effect on plug formation and plug thickness which, in turn, exerts considerable influence on the residual velocities and lengths of a long rod at impact velocities just above the ballistic limit.

Experiments on formation mechanism of root humping in high-power laser autogenous welding of thick plates with stainless steels

Deep penetration laser welding is an efficient and effective way to produce the heavy section structure. Deep penetration can be achieved by high-power autogenous laser welding; however, it poses a significant challenge in obtaining good quality of welds, which are free of imperfects such as root hump, under-fill, and collapse. It is partially attributed to a lacking of understanding on the formation of imperfects. In this paper, we looked into the formation mechanism of root humping experimentally. The laser autogenous welding were implemented using a 10 kW fiber laser on thick stainless steel plates. A high-speed imaging system was applied to observe the metallic vapor and molten pool flow during the welding process. The formation mechanism of root humping with different focal positions were analyzed and discussed. The results showed that the most important welding parameter was the focal position; it had a strong effect on the formation of root hump; it affected the penetration mode of laser keyhole welding. The root hump had a large volume and were generated periodically when a positive defocus was applied. When a negative defocus was applied, the root hump had a small volume and with no obvious periodicity. On the other hand, the welding speed could be optimized to suppress root hump only when a negative defocus was applied. Finally, applying a bottom shielding gases played a positive role in reducing root hump. The results from our study provides the evidences to develop the strategies to suppress root hump during high-power laser autogenous welding on thick metal plates.

Response of Ti microstructure in mechanical and laser forming processes

Microstructural deformation mechanisms present during three different forming processes in commercially pure Ti were analysed. Room temperature mechanical forming, laser beam forming and a combination of these two processes were applied to thick metal plates in order to achieve the same final shape. An electron backscatter diffraction technique was used to study the plate microstructure before and after applying the forming processes. Substantial differences among the main deformation mechanisms were clearly detected. In pure mechanical forming at room temperature, mechanical twinning predominates in both compression and tensile areas. A dislocation slip mechanism inside the compression and tensile area is characteristic of the pure laser forming process. Forming processes which subsequently combine the laser and mechanical approaches result in a combination of twinning and dislocation mechanisms. The Schmid factor at an individual grain level, the local temperature and the strain rate are factors that determine which deformation mechanism will prevail at the microscopic level. The final microstructures obtained after the different forming processes were applied are discussed from the point of view of their influence on the performance of the resulting formed product. The observations suggest that phase transformation in Ti is an additional microstructural factor that has to be considered during laser forming.

Experimental investigation of cutting performance for different material compositions of Cr/Ni-steel with 1 μm laser radiation

Best edge quality for thick metal plates is one of the current main challenges to create a unique selling proposition for laser cutting machines. Various approaches have been used to optimize the cutting performance of different materials. The reported results show in general that when a new material batch is loaded to the laser cutting machine, even of the same material type, diverse results are obtained. These differences have been attributed to fluctuations in the chemical composition of the used alloys. This letter analyses the influence of five different material compositions of Cr/Ni-steel (X5CrNi18-10/1.4301/SUS304/stainless steel) and compares achievable qualities and process windows using a solid state fusion cutting system. A larger process window is observed by increasing sulfur content of the material in this study.

Fracture behavior of wood-steel dowel joints under quasi-static loading

This study analyses a common L-shape configuration formed by wood members and a thick metal plate, duly fastened with steel dowels. Four connecting arrangements were experimentally tested, considering different values of space between dowels and distance to the boundary edge, which allowed measuring the initial stiffness and moment-carrying capacity. A three-dimensional finite element model, including a trapezoidal bilinear cohesive law, was developed to reproduce mixed-mode loading through cohesive zone modelling. Very satisfactory agreements between numerical predictions and experimental results were registered, regarding the full-extension of the load-displacement curves and damage profiles of the joints. In light of these, the model was applied in a larger range of possible combinations of distances to get global trends of the initial stiffness and moment-carrying capacity of these joints.

Method for Rapid Impact Localization for Subsea Structures

In the subsea engineering, protective structures made from thick metallic plates are often used to house and protect fragile equipment against potential damage due to impact by debris. The ability to quickly localize impacts on the protective structure will help mitigate damage to equipment and lower the likelihood of system failure. This paper presents an innovative in-situ impact localization system with a sparse array of lead zirconate titanate (PZT) sensors. The impact localization method uses linear regression, which is adaptive to expected environmental changes, such as immersion in water. Furthermore, the proposed impact localization system is not sensitive to the amplitude of the detected signal, which enables the system to bypass the interference introduced by signal saturation/clipping and be robust against sensor degradation. Results from an impact experiment on an aluminum plate verified the predictive accuracy of the linear regression models, as well as the accuracy and precision of impact localization.

Bi-eddy current sensor based automated scanning system for thickness measurement of thick metallic plates

Generally, the thickness of thick metallic plates is measured by exploitation of some physical phenomenon outside of eddy currents which are naturally limited for thin plates with respect to the skin effect. Indeed, it is the capacitive or ultrasound sensors which are the commonly used for thick plates. This paper proposes an alternative for thickness evaluation of thick metallic plates using eddy currents. The measurement system consists mainly of two eddy current sensors, an impedance analyzer LCR-meter and a personnel computer equipped with the Labview software. The plate we want to measure its thick thickness is placed between the two sensors. The proposed measurement procedure is based on lift-offs evaluation of a bi-eddy current sensor. The system has been verified and validated with success using several thick aluminum plates. The realized experimental setup can be used for online thickness measurement in some industrial applications.