Modeling on the Moving Induction Heating Used in Weld-Based Additive Manufacturing

This paper numerically investigates the application induction heating in weld-based additive manufacturing to reduce residual stresses. To avoid time-consuming transient electromagnetic calculation, the induction heat is assumed to be constant in the arc coordinate. Thermo-electromagnetic coupling analysis is performed only at a typical time to obtain the representative distribution of induction heat, which is then transferred to the thermal analysis of multilayer deposition as a secondary heat source. Furthermore, the effects of real-time induction preheating and postheating on residual stress state are analyzed in comparative simulations. The results show that both induction preheating and postheating lead to more homogeneous heat input and lower residual stresses compared with the case without induction heating.Mechanical Engineerin

Validation of the Mechanical Behavior of an Aeronautical Fixing Turret Produced by a Design for Additive Manufacturing (DfAM)

The design of parts in such critical sectors as the manufacturing of aeronautical parts is awaiting a paradigm shift due to the introduction of additive manufacturing technologies. The manufacture of parts designed by means of the design-oriented additive manufacturing methodology (DfAM) has acquired great relevance in recent years. One of the major gaps in the application of these technologies is the lack of studies on the mechanical behavior of parts manufactured using this methodology. This paper focuses on the manufacture of a turret for the clamping of parts for the aeronautical industry. The design of the lightened turret by means of geometry optimization, the manufacture of the turret in polylactic acid (PLA) and 5XXX series aluminum alloy by means of Wire Arc Additive Manufacturing (WAAM) technology and the analysis by means of finite element analysis (FEA) with its validation by means of a tensile test are presented. The behavior of the part manufactured with both materials is compared. The conclusion allows to establish which are the limitations of the part manufactured in PLA for its orientation to the final application, whose advantages are its lower weight and cost. This paper is novel as it presents a holistic view that covers the process in an integrated way from the design and manufacture to the behaviour of the component in useThis project has received funding from the ELKARTEK program of the Basque Government (Project VIRTUA3D, under Contract nº KK-2022/00025) and HAZITEK (Project ADDHOC, under Contract nº ZL-2022/00665)

Literature Review on Thermomechanical Modelling and Analysis of Residual Stress Effects in Wire Arc Additive Manufacturing

The wire arc additive manufacturing (WAAM) process is a 3D metal-printing technique that builds components by depositing beads of molten metal wire pool in a layer-by-layer style. Even though manufactured parts commonly suffer from defects, the search to minimize defects in the product is a continuing process, for instance, using modeling techniques. In areas where thermal energy is involved, thermomechanical modeling is one of the methods used to determine the input thermal load and its effect on the products. In the WAAM fabrication process, the thermal load is the most significant cause of residual stress due to the extension and shrinkage of the molten pool. This review article explores the thermomechanical effect and stress existing in WAAM-fabricated parts due to the thermal cycles and other parameters in the process. It focuses on thermomechanical modeling and analysis of residual stress, which has interdependence with the thermal cycle, mechanical response, and residual stress in the process during printing. This review also explores some methods for measuring and minimizing the residual stress during and after the printing process. Residual stress and distortion associated with many input and process parameters that are in complement to thermal cycles in the process are discussed. This review study concludes that the thermal dependency of material characterization and process integration for WAAM to produce structurally sound and defect-free parts remain central issues for future research.publishedVersio

Residual Stresses Analysis of 3D Printed Plate By using Wire Arc Additive Manufacturing -WAAM-

Additive manufacturing represents a relatively newly developed technology with many rapidly changing innovations . One of the most important processes in additive manufacturing is 3D printing. For a couple of decades, polymers have dominated the materials used in 3D printing. In the last few years, 3D printing of metals has had a high impact on interest in this technology. One 3D printing process that uses metals is Wire Arc Additive Manufacturing (WAAM). This technique has some technical obstacles that may detract from its use in commercial applications. One of the crucial issues concerns the control of residual stresses and related distortions. The evolution of residual stresses can theoretically be simulated by using computational software for the WAAM process, in a manner similar to welding process modeling, using nonlinear finite element codes such as ABAQUS, ANSYS, SYSWELD, etc. This study focuses on using SYSWELD to model the WAAM process.In this thesis, the key reference problem is the simulation of the WAAM process for a vertical 3D printed plate. This “reference” problem was chosen because =WAAM printed plates have been fabricated at Lehigh University and thus, comparisons can easily be made between simulations and experimental measurements. The simulated WAAM parts examined in the study compare two types of steel alloys: 1) austenitic stainless-steel grade 316L and, 2) Low carbon steel S355J2G3. The residual stress components of particular interest were determined to be: 1) Longitudinal stresses across the width of the plate and, 2) the maximum principle stress. The distortion of the WAAM plate after the metal deposition processes are complete illustrate the difficulty in maintaining dimensional tolerances. The simulation process predicts higher residual stresses and lower distortion for the low carbon steel alloy, when compared with the austenitic stainless steel

Parametric Study of Residual Stresses in Wire and Arc Additive Manufactured Parts

Wire and Arc Additive Manufacturing (WAAM) is a cost-effective additive manufacturing process due to its capability to fabricate large metal parts with high deposition rate and low equipment cost. Although this method is gaining popularity in manufacturing industry, more research is needed to understand process parameters’ effects on residual stress (RS) distribution and part distortion. As such, a 3D thermo-elastic-plastic transient model was established in ABAQUS and employed to investigate the effect of process parameters such as the torch speed, the deposition power and the interlayer dwell time on RS distribution and distortion in WAAM part. The numerical model utilized a comprehensive three-dimensional transient heat transfer model to calculate the temperature distribution and gradient in WAAM process for various process parameters. The heat source was reproduced by a user subroutine DFLUX in ABAQUS. The calculated temperature was exported into mechanical model to predict residual stress and distortion. Variation of microstructural morphology in WAAM components is also critical as it can influence RS in the part. Therefore, the USDFLD user subroutine was utilized to incorporate mechanical property change due to microstructure variation in the mechanical analysis. Both thermal and mechanical models were validated with the experimental data. A 30-layer high wall was built using a GMA-WAAM process with a collaboration with students at Clarkson University. The WAAM setup utilized a gas metal arc welding process for deposition of hot 718 Inconel electrode on a A36 steel substrate. Temperature histories, which is necessary for validating the thermal model, were collected at five locations on the substrate. Lattice spacing for strain calculation was measured by neutron diffraction technique on ex-situ basis, at Oak Ridge National Laboratory. The numerical results showed process parameters can induce significant impact on RS and distortion in the WAAM part. As such, these parameters should be optimized to produce WAAM parts with low RS

Design study for wire and arc additive manufacture

Additive Manufacture (AM) is a technique whereby freeform structures are produced by building up material in a layer by layer fashion. Among the different AM processes, Wire and Arc Additive Manufacture (WAAM) has the ability to manufacture large custom-made metal workpiece with high efficiency. A design study has been performed to explore the process capabilities of fabricating complicated geometries using WAAM. Features such as enclosed structures, crossing structures, and balanced building structures have been investigated in this study. Finite Element (FE) models are employed to take the thermo-mechanical performance into account. Robot tool path design has been performed to transfer the WAAM component designs into real components efficiently. This paper covers these essential design steps from a technical as well as practical point of view

Fatigue strengthening of damaged steel members using wire arc additive manufacturing

In this study, a directed energy deposition (DED) process called wire arc additive manufacturing (WAAM) is employed for the fatigue strengthening of damaged steel members. Three steel specimens with central cracks were tested under a high-cycle fatigue loading (HCF) regime: (1) the reference specimen; (2) the WAAM-repaired specimen with an as-deposited profile, and (3) the WAAM-repaired specimen machined to reduce stress concentration factors (SCF). The corresponding finite element (FE) simulation of the WAAM process was calibrated using static experimental results, which revealed the main mechanism. The process was found to introduce compressive residual stresses at the crack tip owing to the thermal contraction of the repair. The FE results also revealed that stress concentration exists at the root of the as-deposited WAAM; this stress concentration can be mitigated by machining the WAAM to a pyramid-like shape. The fractography analysis indicated that the cracks were initiated at the WAAM-steel interface, and microscopic observations revealed that the microcracks were arrested by the porosities in the melted interface. The results of this pioneering study suggest that WAAM repair is a promising technique for combating fatigue damage in steel structures

Criticality of porosity defects on the fatigue performance of wire + arc additive manufactured titanium alloy

This study was aimed at investigating the effect of internal porosity on the fatigue strength of wire + arc additive manufactured titanium alloy (WAAM Ti-6Al-4V). Unlike similar titanium alloys built by the powder bed fusion processes, WAAM Ti-6Al-4V seldom contains gas pores. However, feedstock may get contaminated that may cause pores of considerable size in the built materials. Two types of specimens were tested: (1) control group without porosity referred to as reference specimens; (2) designed porosity group using contaminated wires to build the specimen gauge section, referred to as porosity specimens. Test results have shown that static strength of the two groups was comparable, but the elongation in porosity group was reduced by 60% and its fatigue strength was 33% lower than the control group. The stress intensity factor range of the crack initiating pore calculated by Murakami’s approach has provided good correlation with the fatigue life. The kink point on the data fitting curve corresponds well with the threshold value of the stress intensity factor range found in the literature. For predicting the fatigue limit, a modified Kitagawa-Takahashi diagram was proposed consisting of three regions depending on porosity size. Critical pore diameter was found to be about 100 µm

Designing a WAAM based manufacturing system for defence applications

Current developments in “Wire+Arc Additive Manufacturing” (WAAM) have demonstrated the suitability of the technology for rapid, delocalized and flexible manufacturing. Providing a defence platform with the ability of on-board WAAM capability, would give the platform unique advantages such as improved availability of its systems and ability to recover its capability after being subject to shock. This paper aims to investigate WAAM technology and define a WAAM based manufacturing system for In-platform applications