Purpose
This study aims to propose and evaluate the progress in the basic-pixel (a strategy to generate continuous trajectories that fill out the entire surface) algorithm towards performance gain. ...The objective is also to investigate the operational efficiency and effectiveness of an enhanced version compared with conventional strategies.
Design/methodology/approach
For the first objective, the proposed methodology is to apply the improvements proposed in the basic-pixel strategy, test it on three demonstrative parts and statistically evaluate the performance using the distance trajectory criterion. For the second objective, the enhanced-pixel strategy is compared with conventional strategies in terms of trajectory distance, build time and the number of arcs starts and stops (operational efficiency) and targeting the nominal geometry of a part (operational effectiveness).
Findings
The results showed that the improvements proposed to the basic-pixel strategy could generate continuous trajectories with shorter distances and comparable building times (operational efficiency). Regarding operational effectiveness, the parts built by the enhanced-pixel strategy presented lower dimensional deviation than the other strategies studied. Therefore, the enhanced-pixel strategy appears to be a good candidate for building more complex printable parts and delivering operational efficiency and effectiveness.
Originality/value
This paper presents an evolution of the basic-pixel strategy (a space-filling strategy) with the introduction of new elements in the algorithm and proves the improvement of the strategy’s performance with this. An interesting comparison is also presented in terms of operational efficiency and effectiveness between the enhanced-pixel strategy and conventional strategies.
To overcome a shortage of flexible and low-cost solutions for wire arc additive manufacturing (WAAM) preprocessing, this work’s objective was to develop and validate an in-house computational ...programme in an open-source environment for WAAM preprocessing planning. Algorithms for reading STL (stereolithography) files and implementing rotation, slicing, trajectory planning, and machine code generation were elaborated and implemented in the Scilab environment (free and open-source). A graphical interface was developed to facilitate user interaction, with 5 options for path planning. The functionality of each work step is detailed. For validation of the software, single and multiple-layer prints, with different geometrical complexity and printing challenges, were built in a CNC table geared by the generated machine code. The validation criteria were deposition imperfection, morphological, and dimensional tolerances. The outputs showed that the parts were successfully printed. Therefore, this work demonstrates that Scilab provides the necessary resources for companies and universities to implement and/or develop algorithms for planning and generating trajectories for WAAM. Moreover, emerging ideas can be reasonably easily implemented in such software, not always possible in commercial packages.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
This work aims to propose and assess a methodology for parameterization for WAAM of thin walls based on a previously existing working envelope built for a basic material (parameter transferability). ...This work also aimed at investigating whether the working envelope approach can be used to optimize the parameterization for a target wall width in terms of arc energy (which governs microstructure and microhardness), surface finish and active deposition time. To reach the main objective, first, a reference working envelope was developed through a series of deposited walls with a plain C-Mn steel wire. Wire feed speed (WFS) and travel speed (TS) were treated as independent variables, while the geometric wall features were considered dependent variables. After validation, three combinations of WFS and TS capable of achieving the same effective wall width were deposited with a 2.25Cr-1Mo steel wire. To evaluate the parameter transferability between the two materials, the geometric features of these walls were measured and compared with the predicted values. The results showed minor deviations between the predicted and measured values. As a result, WAAM parameter selection for another material showed to be feasible after only fewer experiments (shorter time and lower resource consumption) from a working envelope previously developed. The usage of the approach to optimize parameterization was also demonstrated. For this case, lower values of WFS and TS were capable of achieving a better surface finish. However, higher WFS and TS are advantageous in terms of production time. As long as the same wall width is maintained, variations in WFS and TS do not significantly affect microstructure and microhardness.
Full text
Available for:
DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Duplex stainless steel (AID) is an alloy that, by allying both good mechanical properties and excellent corrosion resistance properties, comes increasing industrial interest every day. These ...attractions make it widely used in the most diverse industrial sectors such as pulp and paper industry, nuclear power, processing, oil and gas, among others. Its wide application in several industrial sectors constantly demands that this material is subjected to some welding process. Its high corrosion and mechanical resistance are attributed to balanced microstructure in approximately 50% ferrite and 50% austenite. In the present work, UNS S31803 AID plates were welded in a 45° bevel by conventional short-circuit MIG/MAG process, using three different weld energies, in the range of 0.5–0.8kJ/mm. The results showed that the effect of the welding energy on the ferrite volumetric fraction was very marked in the heat affected zone (HAZ) and in the weld metal this effect was not so pronounced. The mechanical properties of hardness and corrosion resistance (intergranular corrosion) were evaluated as a function of the welding energy employed. In general, both hardness and intergranular corrosion resistance were not influenced when the various welding conditions were compared. The toughness were evaluated by the crack tip opening displacement technique, compared to the base metal, and the condition 03 (19V) had the best result.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPUK, ZAGLJ, ZRSKP
The classificatory method is considered a straightforward and robust procedure for the assessment of welded joints in metallic structures. The methodology adopts a set of S–N diagrams with a ...conservative survival rate, which expresses the fatigue performance of the most employed joint configurations. In the design phase, the adoption of a structural detail correlated with a higher curve in the set conducts to high structural integrity. Nevertheless, fatigue phenomenon is essentially multifactorial and, consequently, several optimizing alternatives may be applied for life increasing. Studies focused on continuous (weldless) parts correlate fatigue performance with the material ultimate strength. Transferring this approach to welded parts, adoption of a high-strength filler metal, or any procedure intended to mitigate metallurgical inhomogeneity in the weld-affected region may propitiate fatigue life improvement. In other sense, issues related to bead geometry, notably the notch effect associated with weld toe, are also reported to have an essential influence on fatigue life of structural details. This work aims to counterbalance material and bead geometry aspects related to fatigue performance of butt joints subjected to repeated transverse loading. Two welding processes, FCAW and GMAW, as well as different filler metals and parameters, were adopted for specimens manufacturing. The ASTM-A572-Gr.50 steel was employed as a parent metal. After welding, FCAW joints presented better mechanical and metallurgical characteristics. Additionally, in order to characterize the relevance of the notch effect, half of the specimens had the original bead geometry maintained, while the others underwent a manual removal of the reinforcement. The obtained results indicate that FCAW joints present better fatigue performance in the as-welded state. However, after removing the reinforcements, both welding processes attained similar results, suggesting that the notch effect has more relevance for fatigue life than mechanical and metallurgical characteristics of the joint. Consequently, the superior performance presented by the FCAW joints in the as-welded state is assigned to the final shape of the reinforcements, which is smoother than in the GMAW case. The higher capacity of penetration and better filler metal wettability propitiated by the FCAW process is responsible for the lower notch effect.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Temperature measurement in welding constitutes relevant information for process understanding and simulation, as it can be used to validate and predict microstructure. Monitoring can be performed at ...specific points through transducers. The typical one is the thermocouple. In laser welding processes, due to the high energy concentration of the beam, the acquisition with thermocouples should be performed closer to the bead when compared to electric arc welding processes. This measurement is critical because of overheating by spatters, which can result in damage. The present work covers developing a Capacitive Discharge Welding device for thermocouple fixing and assessing possible temperature acquisition positions in keyhole laser welding. The study performed all tests with a fiber laser of 9 kW power and 3 m/min scanning speed. When placed at 2 mm from the weld centerline, the results showed a high probability of spattering due to the 71° range of incidence angle. Therefore, the thermocouple should be placed far from the weld centerline to minimize the spattering. However, it must be close enough to acquire temperatures above 727 °C. This temperature corresponds to the envisaged austenitization microstructure correlation. The study found the maximum distance at 3.5 mm based on an interpolation map, where the incidence spatters angle reduced to 59°. At a 2 mm distance from the weld centerline, the weld cross section temperatures reached more than 727 °C. However, the microstructural changes did not occur due to insufficient austenitization time. The Heat Affected Zone boundary was at 1.64 mm from the weld centerline. Therefore, to correlate microstructure with thermal cycles, it is necessary to place thermocouples at a distance below this value. However, spatter can be a problem since the range of incidence angle is about 75°. Therefore, this work recommends using more than one thermocouple for each position (redundancy) to increase valuable data.
Graphic abstract
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Additive manufacturing of metallic components has been proved useful in several industrial aspects, such as in on-demand spare parts from a virtual library, resulting in a reduction of inventory ...costs. Before going into service, components must pass through strict inspection process, attesting its integrity; thus the first stage of this inspection process consists of visual inspection, executed by qualified professionals. However, it does not allow digital data recording for future assessments; it presents limited accuracy due to the traditional gauge kits, resulting in traveling expenses for installation and hindering training of other professionals. The uncertainty relative to the presence of discontinuities in this new manufacturing process discourages future investment. Therefore, the present study proposes a low-cost inspection methodology for Wire Arc Additive Manufacturing components, based on photogrammetry techniques. This measurement process generates a 3D model using a commercial DSLR camera and an open-source processing software. The resulting photogrammetry model is compared to another one obtained using a commercial laser scanning system. The average measurement deviation between the digitized models was 0.104 mm and the accuracy of the photogrammetry system was 0.144 mm (0.104
±
0.040 mm), which is adequate for the inspection process of the 115 mm diameter part. Laser scanning is recommended whenever assessment of surface waviness is required, since the geometrical deviation is below 1.440 mm (photogrammetry limit), but above 0.400 mm (laser scanning limit). In spite of that qualitative analysis can be performed with both systems, through 2D profiles, which is useful to understand the surface behavior. Color representation is found only in the photogrammetry model. This is fundamental for visual inspection because even small discontinuities that do not present large geometrical variations can be identified on the surface. Another purpose of this study is to stimulate other researchers and engineers to use remote visual inspection through 3D models and virtual reality.
Graphical abstract
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The influence of polarity during resistance spot weld (RSW) of dissimilar lap joints on mechanical properties and failure mode is assessed in this work. A dissimilar lap joint was set using DP 600 ...dual phase steel with AISI 304 stainless steel. The experiments were performed on a medium-frequency direct current spot welding machine with proper data acquisition of voltage and welding current. Temperature evolution was also acquired by using IR camera. The mechanical properties of spot welds were evaluated by using a coach peel testing. The effect of welding current and welding time on mechanical properties was also evaluated. Correlations between polarity with the welding nugget size, failure mode, tensile strength, temperature evolution and dynamic resistance were analysed. The analysis confirmed that the polarity on dissimilar lap joints affects the behaviour of dissimilar RSWs.
Full text
Available for:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
The TIG Dressing technique has been widely used for repairing cracks in welded structures when subjected to mechanical forces that induce localized fatigue, leading to the collapse during operation. ...However, this technique has not been used for studies in structures susceptible to corrosion. In addition to changing the microstructure, it is expected that this technique increases the corrosion resistance of the edge of the weld bead which is a vulnerable region to corrosion. Moreover, the machining technique has been widely used to improve the workpieces finishing and/or structures that have been subjected to repair by welding, improving the surface roughness, increasing the corrosion resistance of these structures when subjected to aggressive environments. Thus, this work will study the effects of finishing techniques using machining and welding on the edge of the weld bead joints of 410D ferritic stainless steels, making an evaluation by mass loss in the samples which will be subjected to corrosion by immersion in NaCl containing medium. It is expected that the finishing techniques can relieve tensile stresses increasing the corrosion resistance.
Resumo Os processos de Manufatura Aditiva (MA) de Metais permitem criar peças tridimensionais através da adição progressiva de finas camadas de material. Estes processos se enquadram em duas grandes ...categorias, denominadas Fusão em Leito de Pó e Deposição por Energia Direcionada. A compreensão física dos processos de MA pode fornecer uma visão holística sobre as sensibilidades aos parâmetros de processo. Já a modelagem computacional destes processos não só pode fornecer uma visão importante dos fenômenos físicos que levam às propriedades finais do material e à qualidade do produto, mas também os meios para explorar o espaço de projeto, visando criar produtos funcionais. Esta revisão introdutória foca na MA de materiais metálicos, particularmente nas questões de modelagem física e numérica. São apresentadas considerações sobre os diversos fenômenos físicos atuantes, métodos computacionais mais empregados, técnicas para realizar a modelagem e suas respectivas validações, demonstrando os desafios e limitações atuais, assim como as perspectivas futuras da simulação computacional aplicada aos processos de MA.
Abstract Additive Manufacturing (AM) processes of metals allow creating three-dimensional parts through the progressive addition of thin layers of material. These processes fall into two major categories, called Powder Bed Fusion and Directed Energy Deposition. Physical understanding of the AM processes can provide a holistic view of the sensitivity to process parameters. Computational modeling of these processes can not only provide an important view of the physical phenomena that lead to the final properties of the material and quality of the product, but also the means to explore the design space, in order to create functional products. This introductory review focuses on the AM of metallic materials, particularly on issues of physical and numerical modeling. Considerations are presented about the various physical phenomena at work, most used computational methods, techniques to perform the modeling and their respective validations, demonstrating the current challenges and limitations, as well as the future perspectives for computer simulations applied to AM processes.
PDF
