A coupled cellular automata-finite element (CAFE) model has been developed to simulate the phenomenon of dynamic recrystallization (DRX) during the laser shock peening (LSP) process on the titanium alloy, Ti6Al4V. Although microstructure changes resulting from DRX during LSP treatment have been observed and studied experimentally, there is no work to-date on a model that is capable of simulating LSP while also capturing the potential effects of microstructure evolution due to DRX. Creating an LSP model that couples DRX during the high intensity shock wave propagation is a major challenge considering the very high-strain rates and nanosecond-scale time duration, as well as the requirement to repeatedly update the grain boundary locations and the localized mechanical properties of grains during the simulation. This paper introduces the first modeling framework for simulating microstructural evolution due to DRX during the LSP treatment process. The framework includes predictions of both continuous DRX (cDRX) and discontinuous DRX (dDRX), as well as the influence of the predicted microstructure evolution on the resulting stress-strain fields arising from LSP treatment. For an experimentally determined initial microstructure and specific LSP process parameters, the final state of residual stress predicted by this CAFE model shows substantially increased local variation in the compressive stress field as compared to the case when DRX is not considered. This variation is particularly evident in the vicinity of the part surface where most of the DRX is observed and predicted to occur. In addition, based on the process conditions for the specific LSP treatment considered, cDRX is predicted to be the dominant mechanism of microstructural evolution. This is because the overall temperature increase that occurs during LSP, arising due to plastic deformation alone when an ablative surface coating is included, is found to be insufficient to induce dDRX-based nucleation in the Ti6Al4V alloy. (c) 2025 Bailey et al. Published by ELSEVIER Ltd. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0)

Residual stress (RS) significantly impacts the mechanical performance of components. Measurement of RS often provides incomplete data in terms of components of stress and spatial density. Employing such fields in finite element simulations results in significant modification of the field to achieve equilibrium and compatibility among strains. To overcome this, an iterative stress reconstruction algorithm (ISRA) is developed to estimate 3D RS fields that satisfy equilibrium, are stress component-wise complete, and represent the characterized data sampled. An Al 7075-T651 plate and an additively manufactured (AM) A36 steel wall are considered for RS reconstruction using measurement data from the literature. A maximum variation of similar to 2.5 MPa in the Al plate, and similar to 10 MPa in the steel wall are observed between the reconstructed and measured stresses. Furthermore, unknown stress components emerge and reach significant magnitudes (upto similar to 2.3 MPa in the Al plate and similar to 45 MPa in the AM wall) during ISRA. Indeed, it is found that minor errors in measurement or data processing are eliminated through the physical requirements during ISRA. Employing a reconstructed RS field is hence not just more accurate given its compatibility, but it additionally corrects for minor errors in measurement. Furthermore, it is found that spatially dense measurement data result in convergence with fewer iterations. Finally, although ISRA yields a nonunique solution dependent on boundary conditions, measurement errors, fitting errors, and mesh density, it accommodates for uncertainties and inaccuracies in measurement, as opposed to failing to reach a physically realistic converged solution.

The objective of the generation expansion master plan is to determine the necessary capacity and types of power plants for accommodating future load growth. The current software utilized for guiding generation planning primarily relies on the load duration curve (LDC) paradigm, which overlooks the chronological order of events. Additionally, the optimization process does not consider the environmental costs associated with power plants, as these costs are calculated separately once the optimal plan is finalized. This research study focuses on incorporating wind power plant modeling into generation planning models based on the LDC approach. Furthermore, the article emphasizes the integration of environmental costs into the optimization process, enabling researchers and policymakers to make more informed decisions regarding the growth of electricity and energy resources. The paper employs the widely used and reputable Wien Automatic System Planning (WASP) Package, version WASP-IV planning tool to identify the most optimal capacity expansion plans for Oman’s Main Interconnected Network (MIS) as a specific case study. In this tool, the load is represented using the LDC approach, while the built-in optimization feature does not account for environmental costs. To overcome this limitation, environmental costs are added to fuel costs so that they become part of the optimization function. The results show that when the opportunity cost of gas and environmental costs are considered in the optimization process, a significant number of wind generators are selected. To guarantee that non-dispatchable renewable technologies are fairly considered by decision-makers, the study suggests including opportunity costs as input data in generation planning models.

Dimensional tolerances for high-speed-machined aluminum products continue to tighten due to the demand for automated assembly of complex monolithic parts in aerospace and other industries. Understanding the contribution of inherent residual stress in wrought Al 7050-T7451 plate, common in aircraft manufacture, to distortion of high-aspect-ratio machined parts is critical but remains problematic due to the alloy's low residual stress magnitude over large geometries. Prior investigations into residual stress effects on machined part distortion suffer inadequate characterizations of the wrought material stress field, either because of low fidelity due to "slitting" methods, confounding effects in machined-layer removal methods, or small sample size when using neutron diffraction (ND). In this work, inherent residual stress is measured via ND at 860 locations in a 90.5 mm thick Al 7050-T7451 plate having dimensions 399 mm in the rolling direction and 335 mm in the transverse direction. Unlike prior studies, the ND residual stress is reconstructed using an iterative algorithm to ensure fully compatible, equilibrated 3D field prior to examining its effect on distortion. The findings from simulations and experiments show that inherent residual stress alone could distort a high-aspect-ratio part beyond aerospace industry requirements, that slitting measurements may not sufficiently characterize residual stress for predicted distortion, and that parts machined from different plate thickness locations could exhibit reversed distortion patterns. Thus, research into distortion prediction that considers machining should carefully characterize and reconstruct inherent residual stress so that the coupled machining effects are accurately modeled.

Introduced is a three-dimensional, physics-based mathematical model capable of efficiently predicting self-excited chatter vibration phenomena in the cold rolling of metal strip and sheet. The described nonlinear chatter model combines the 3D mill structural dynamics behavior with the elastic-plastic rolling process dynamics to predict conditions of instability in a single-stand 4-high mill that can lead to both third-octave and fifth-octave chatter. Formulation of the 3D chatter model is achieved by coupling the dynamic simplified-mixed finite element method with a nonlinear roll-bite process dynamics model to capture self-exciting feedback interactions. In contrast to prior approaches to model chatter in the cold rolling of flat metals, the presented method abandons several simplifying assumptions, including 1D or 2D linear lumped parameter analyses, vertical symmetry of the upper and lower halves of the roll-stack, and continuous contact between the rolls and strip. The model is demonstrated for a single-stand 4-high rolling mill considering the detrimental third-octave self-excited chatter condition. Detailed stability analyses that show time histories of the 3D mill behaviors are presented, respectively, for stable, marginally stable, and unstable rolling speeds, and for changes in the lower housing stiffness to reflect more realistic, asymmetric rolling mill conditions.

Powder-based directed energy deposition is one of the major additive manufacturing processes for producing and repairing large-size and high-value metallic components. Due to the rough surface finish and low dimensional accuracy, DED products require post-build machining. Accordingly, the effects of post-machining on build properties is an emerging and important field of research. To date, most of the reported machining cases have been performed after the entire build's completion, even though interlayer machining may be applied due to design modification or to achieve improved deposition control on localized regions of high curvature. Therefore, in this work, for the first time, the influence of interlayer machining on the processing–structure–properties relationships in powder-based directed energy deposition of stainless steel 316L is investigated. Four types of single-track builds are manufactured on stainless steel 316L substrates: single-layer, double-layer, machined single-layer, and double-layer with interlayer machining. The effects of interlayer machining on the microstructure and residual stress before and after the second layer's deposition are studied via metallographic imaging and neutron diffraction. In single-layer samples, due to induced plastic strains and heat generated during the machining operation, the microstructure reveals dynamic recrystallization, exhibited by smaller, more equiaxed grains. In the double-layer samples, interlayer machining leads to considerable variation in the microstructure, with grains oriented almost parallel to the scan direction. The interlayer machining also results in greater tensile residual stresses near the interface between the two deposited layers. Findings of this work reveal that interlayer machining has significant effects that should be considered in the design and control of processing–structure–properties–performance relationships in directed energy deposition.

Additive manufacturing (AM) is known to generate large magnitudes of residual stresses (RS) within builds due to steep and localized thermal gradients. In the current state of commercial AM technology, manufacturers generally perform heat treatments in effort to reduce the generated RS and its detrimental effects on part distortion and in-service failure. Computational models that effectively simulate the deposition process can provide valuable insights to improve RS distributions. Accordingly, it is common to employ Computational fluid dynamics (CFD) models or finite element (FE) models. While CFD can predict geometric and thermal-fluid behavior, it cannot predict the structural response (e.g., stress–strain) behavior. On the other hand, an FE model can predict mechanical behavior, but it lacks the ability to predict geometric and fluid behavior. Thus, an effectively integrated thermofluidic–thermomechanical modeling framework that exploits the benefits of both techniques while avoiding their respective limitations can offer valuable predictive capability for AM processes. In contrast to previously published efforts, the work herein describes a one-way coupled CFD-FEA framework that abandons major simplifying assumptions, such as geometric steady-state conditions, the absence of material plasticity, and the lack of detailed RS evolution/accumulation during deposition, as well as insufficient validation of results. The presented framework is demonstrated for a directed energy deposition (DED) process, and experiments are performed to validate the predicted geometry and RS profile. Both single- and double-layer stainless steel 316L builds are considered. Geometric data is acquired via 3D optical surface scans and X-ray micro-computed tomography, and residual stress is measured using neutron diffraction (ND). Comparisons between the simulations and measurements reveal that the described CFD-FEA framework is effective in capturing the coupled thermomechanical and thermofluidic behaviors of the DED process. The methodology presented is extensible to other metal AM processes, including power bed fusion and wire-feed-based AM.

Wire arc additive manufacturing (WAAM) has received increasing use in 3D printing because of its high deposition rates suitable for components with large and complex geometries. However, the lower forming accuracy of WAAM than other metal additive manufacturing methods has imposed limitations on manufacturing components with high precision. To resolve this issue, we herein implemented the hybrid manufacturing (HM) technique, which integrated WAAM and subtractive manufacturing (via a milling process), to attain high forming accuracy while taking advantage of both WAAM and the milling process. We describe in this paper the design of a robot-based HM platform in which the WAAM and CNC milling are integrated using two robotic arms: one for WAAM and the other for milling immediately following WAAM. The HM was demonstrated with a thin-walled aluminum 5356 component, which was inspected by X-ray micro-computed tomography (μCT) for porosity visualization. The temperature and cutting forces in the component under milling were acquired for analysis. The surface roughness of the aluminum component was measured to assess the surface quality. In addition, tensile specimens were cut from the components using wire electrical discharge machining (WEDM) for mechanical testing. Both machining quality and mechanical properties were found satisfactory; thus the robot-based HM platform was shown to be suitable for manufacturing high-quality aluminum parts.

Introduced is a new physics-based three-dimensional (3D) mathematical model capable of efficiently predicting time histories of the nonlinear structural dynamics in cold rolling mills used to manufacture metal strips and sheets. The described model allows for the prediction of transient strip thickness profiles, contact force distributions, and roll-stack deformations due to dynamic disturbances. Formulation of the new 3D model is achieved through a combination of the highly efficient simplified-mixed finite element method with a Newmark-beta direct time integration approach to solve the system of differential equations that governs the motion of the roll-stack. In contrast to prior approaches to predict structural dynamics in cold rolling, the presented method abandons several simplifying assumptions and restrictions, including 1D or 2D linear lumped parameter analyses, vertical symmetry, continuous and constant contact between the rolls and strip, as well as the inability to model cluster-type mill configurations and accommodate typical profile/flatness control mechanisms used in industry. Following spatial and temporal convergence studies of the undamped step response, and validation of the damped step response, the new model is demonstrated for a 4-high mill equipped with both work-roll bending and work-roll crown, a 6-high mill with continuously variable crown (CVC) intermediate rolls, and finally a complex 20-high cluster mill. Solution times on a single computing processor for the damped 4-high and 20-high case studies are just 0.37 s and 3.38 s per time-step, respectively.

This work investigates the coupling of inherent residual stress (IRS) and machining-induced residual stress (MIRS) on the final-state of residual stress (FRS) and distortion when high-speed machining (HSM) high aspectratio aluminum components. Motivation for this work stems from the simplifications in related numerical investigations that give rise to two limitations: First, the mapping of incompatible, incomplete, and/or spatially scarce IRS profiles generates unrealistic distortions and incorrect stress fields during static equilibration. Second, the simulation of machining via element deletion, inactive elements approach, or Boolean subtraction (removal) of material either ignores thermal and MIRS effects, or implements them based on simplified analytical/empirical models. Such practices therefore prevent a thorough understanding of how IRS and MIRS are coupled. Accordingly, two wrought aluminum 7050 blocks having different IRS profiles (based on stress relief) are considered in this work. An iterative stress reconstruction algorithm is implemented to numerically model a spatially-complete and fully-compatible IRS field in each aluminum block using limited data from slitting measurements documented in the literature. A 2D orthogonal cutting model is used to validate the material and damage models employed, as well as to elucidate the influences of IRS and MIRS on FRS. A 3D end milling model, which adopts the validated material and damage definitions, is then applied with different tool paths to reveal the coupled effects of IRS and MIRS on the distortion when HSM a C-channel featuring high aspect-ratio walls. The results reveal that the interaction between IRS and MIRS is nonlinear in nature, thus contrasting assumptions allowing for their superposition, as are widely reported and adopted in the literature. The results also show that the nonlinear coupling between IRS and MIRS varies according to both the component and location of stress within the machined part. Moreover, the findings reveal that the final part distortion is significantly influenced by the nonlinear coupling, as well as the specific machine tool path implemented.

As functionally gradient materials (FGMs) reveal innovative mechanical properties, they have aroused huge interest in multiple industry areas. In this study, a hybrid manufacturing (HM) technique that combines a directed energy deposition (DED)-type additive manufacturing (AM) fabrication process with milling-type machining is investigated. In the DED process examined, Inconel 718 (IN718) and stainless steel 316L (SS316L) metal powders were blown into the molten pool at different and varying respective flow rates to achieve specific composition ratios for different printed layers so that a smooth gradient transition from SS316L to IN718 was achieved. Due to the attendant generation of rough surfaces common to such FGMs, partition milling was employed after fabrication, and the cutting temperatures and forces were simultaneously recorded considering the significant anisotropy in mechanical properties. The surface roughness of each FGM gradient section and tool wear mechanism were also measured after machining. Through analysis of the experimental results, the machining mechanism was revealed, which provides new insights into the machinability of SS316L/IN718 FGMs.

Plasma-enhanced chemical vapor deposition (PECVD) provides a low-temperature, highly-efficient, and catalyst-free route to fabricate graphene materials by virtue of the unique properties of plasma. In this paper, we conduct reactive molecular dynamics simulations to theoretically study the detailed growth process of graphene by PECVD at the atomic scale. Hydrocarbon radicals with different carbon/hydrogen (C/H) ratios are employed as dissociated precursors in the plasma environment during the growth process. The simulation results show that hydrogen content in the precursors significantly affects the growth behavior and properties of graphene (e.g., the quality of obtained graphene, which is indicated by the number of hexagonal carbon rings formed in the graphene sheets). Moreover, increasing the content of hydrogen in the precursors is shown to reduce the growth rate of carbon clusters, and prevent the formation of curved carbon structures during the growth process. The findings provide a detailed understanding of the fundamental mechanisms regarding the effects of hydrogen on the growth of graphene in a PECVD process.

High-fidelity flatness defects in cold-rolled strip and sheet, arising from highly localized thickness strain variations, present an ongoing challenge to the metal industry. A primary cause of such defects, based on rolling practice, but for which the effects have not been rigorously investigated, is the transfer of localized work-roll diameter deviations due to roll grinding error. This study addresses high-fidelity work-roll diameter deviation transfer in the cold rolling of stainless steel, aluminum, and copper. Parametric studies are performed on a 4-high mill to examine the influences of roll diameter, reduction, strip width, and material on the transfer of high-fidelity work roll diameter deviations. Studies are conducted using an efficient 3D roll-stack model that predicts strip thickness profile deviations via the simplified-mixed finite element method. Reduction deviations on the outgoing strip, which correlate to strip flatness/shape defects, are quantified and analyzed to understand the transfer characteristics of work-roll grinding deviations relative to perfectly ground (smooth) work rolls. The results reveal that high-fidelity transfer depends not only on roll grinding deviation amplitudes and mill loading, but also on the specific locations of deviations along the roll face length due to 3D bulk roll-stack deformations as well as effective stiffness ratio between the work roll and the strip. Concluding the study is a novel approach to identify customized work roll grinding profiles tailored specifically to eliminate pre-existing high-fidelity strip flatness defect patterns, wherein “corrective” high-fidelity roll diameter profiles account for the predicted 3D mill deflections, contact force distributions, and coupled micro-/macro-scale deformation mechanics.

Presented is an investigation into laser impact welding (LIW) wherein experimentally measured surface profiles of the flyer and target foils are incorporated to study their effects on the transient physical phenomena that occur during this rapid, collision-based joining process. During LIW, thermal response, plastic strains, and shear stresses evolve over a sub-microsecond timescale, which necessitates the use of computational modeling to predict the influence that surface roughness has on the material response and resulting joint morphology. White light interferometry is used to experimentally characterize the surface profiles of an aluminum 1100 flyer foil and a stainless steel 304 target foil. The profiles are mapped to material volumes within a plane strain, thermomechanical simulation employing an Eulerian framework. A spatially and temporally varying laser-induced plasma pressure is applied to the flyer foil, and the resulting transient phenomena are analyzed at timeframes ranging from initial contact through complete weld formation. To reveal effects of the rough foil surfaces, results from the same computational model using smooth foil surfaces are also obtained. When the rough surface profiles are included, it is found that significant differences in the thermal response and plastic strains are observed, and these differences are hypothesized to arise from the effects of discontinuous surface contact along the collision path. The incorporation of rough surface asperities also reveals two distinct regions prior to the weld initiation point; the first where elastic rebound occurs at a negligible collision angle, leaving interfacial voids, and the second where superficial shear deformation flattens the surfaces without mutual ablation and jetting. The work represents the first study in which measured surface profiles of the flyer and target foils are incorporated into a computational model of laser impact welding.

Transient thermomechanical phenomena such as extreme plastic strains and temperature spikes that occur during laser impact welding are impractical to experimentally observe given the sub-microsecond duration of the joining process. Thus, computational models are necessary to study in-situ behavior along the weld interface. While researchers have utilized computational models for such investigations, this work elucidates the specific influence of microstructure-level modeling that captures the associated inhomogeneity/anisotropic effects at smaller scales. An aluminum 1100-H19 flyer and a stainless steel 304-O target foil are modeled using an Eulerian framework to simulate cases with and without microstructure consideration during laser impact welding of dissimilar metallic foils. When considering microstructure modeling, variations in flow stress reveal intermittently elevated temperatures along the weld interface due to concentrations of shock pressure at relatively small grains; however, they are not found to be a significant source of instability initiating or influencing the joint formation. Grain refinement and material hardening are suggested within a 10 mu m-thick zone of the flyer near the weld interface, while severe plastic deformation in the target indicates possible martensitic phase transformation. Grain boundary sliding driven by variations in yield surfaces among individual grains gives rise to relatively higher collision velocity. Consequently, higher plastic strain rates along with greater amounts of plastic heat dissipation at the interface result in increased material jetting at higher temperatures. Alternating transient shear stresses are predicted in each model, though the inhomogeneous model predicts the brief appearance of a concentrated shear zone in the rebound region which is not seen in the homogeneous model. This work illuminates correlations between microstructure and transient phenomena during laser impact welding of dissimilar metallic foils, thus demonstrating a numerical modeling approach extensible to numerous other impact welding processes that complete within a very short time span.

A hybrid metal-additive manufacturing (AM) process that combines laser-based powder bed fusion (PBF-LB) with interlayer burnishing is investigated using a comprehensive modeling framework to provide new insights into how the inhomogeneous microstructure and residual stress from the laser powder bed fusion process affect the induced residual stress field that evolves during interlayer burnishing. Researchers have recently studied changes in microstructure resulting from similar hybrid metal-additive processes, however, it was only hypothesized that the resulting microstructure has some influence on the induced residual stress. In addition, researchers have numerically investigated the influence of burnishing/rolling process parameters on induced stress but neglected the effects of microstructure, thereby making homogeneous, isotropic assumptions. Such practice inhibits the prediction of microstructure-driven anisotropy that can exist in the inhomogeneous fused layer. This paper parametrically examines the influence of microstructure modeling, inherent residual stress mapping, and environment temperature on the induced residual stress during the hybrid metal-additive process. The demonstrated modeling framework incorporates inherent residual stresses that emerge from the laser powder bed fusion process, as well as the predicted microstructure, in a subsequent burnishing simulation to elucidate their individual and combined influences on the burnishing-induced residual stress. Findings reveal that modeling an inhomogeneous PBF-LB microstructure introduces an anisotropic distribution of plastic strain and residual stress along the burnished surface; a periodicity in planar stress components along the treated surface coincides with the PBF-LB scan lines. Effects of inherent residual stress on the burnishing-induced residual stress is less significant, but nonetheless observable. Elevated temperatures not only reduce the magnitude of compressive residual stress induced but also result in less variation of residual stress component magnitudes predicted along scan lines and hatch spaces. The presented framework offers new insights into the decoupled influences of microstructure and PBF-LB residual stress on burnishing-induced stresses that are not distinguishable via experimental techniques. However, trends in averaged residual stress through the depth of the specimen, as well as surface hardness magnitudes after burnishing show good agreements, respectively, with X-ray diffraction and microindentation measurements documented in the literature.

Described is a hybrid metal additive manufacturing (AM) method that integrates in situ laser shock peen (LSP) forming with laser powder bed fusion (PBF) to mitigate vertical distortions during part builds. LSP has recently been proposed to reduce tensile residual stresses during selective laser melting (SLM). The effects of LSP on part distortion, however, have not been rigorously examined. It is proposed here that SLM can be integrated with in situ LSP forming to reduce distortion of the upper surface of parts during or after printing. To study the distortion correction capability, a 2-stage computational framework is created, which includes physics-based models of the SLM process and LSP treatment. Stage 1 includes thermomechanical SLM simulation to predict surface geometry and is applied to model four 50-μm layers of a 316L part having a 4 mm × 4 mm footprint. Stage 2 of the framework includes an elastic-plastic thermomechanical shock-wave simulation to predict LSP surface treatment forming effects. Surface distortion is examined for varying laser spot size, overlap, and part temperatures from 300 to 500 K, using a nanosecond-pulsed infrared laser. For the 316L SLM sample, the upper surface is predicted to have $\sim $ 9-μm vertical distortion on the 200-μm 4-layer build. With a 2-μm allowable distortion, only 44.13% of the surface initially conforms. After one LSP forming treatment at 300 K, conformance improves to 84.75%. After a third LSP forming, with 50% laser power-density increase, surface conformance increases to 91%, demonstrating potential of the hybrid AM-LSP process in reducing finish-machining.

This work represents the first investigation into the influence of residual stress (RS) from powder-based metal additive manufacturing (AM) on the post-process machining-induced stress and distortion for thin-walled components. Machined part distortion and surface residual stress pose major challenges in several industries, including for aerospace applications involving monolithic structures. However, the influence of initial RS in the bulk material on high-speed machining-induced stress and distortion is still not well understood. This is particularly true for more recent hybrid (additive and subtractive) manufactured components in which significant tensile and compressive RS develops from the rapid thermal cycles during the AM build. It is hypothesized in this work that, even for a simple thin-walled structure, the initial RS in the AM bulk material significantly influences the RS and distortion induced by high-speed machining. It is further hypothesized that the degree of influence of the initial RS on machining-induced RS and distortion varies significantly according to the specific tool path, even for the same net material removal. To test these hypotheses, a numerical modeling approach is presented considering a thin-walled directed energy deposition (DED) structure subjected to high-speed end-milling. A compatible RS field for the DED build is established using an iterative reconstruction algorithm based on limited neutron diffraction measurements, and the full reconstructed RS field is then imposed as an initial state in the end-milling simulation that follows. To assess the influence of the initial DED RS on the machining-induced stress and distortion, as well as to examine how this influence varies with machining strategy, two different tool paths are considered for the same net material removal, both with and without considering RS inherent to the DED build. The findings reveal significant influence of the DED RS on the high-speed machining-induced distortion and RS, and further, this influence is seen to vary greatly with the machining strategy. Normalized root-mean-square differences (NRMSD) of up to 25% and 29%, respectively, are observed in the machining-induced RS for the two different tool paths when DED inherent RS is considered. Likewise, maximum NRMSD of up to 44% and 40% are revealed in the post-machining distortion for the two respective machining strategies when DED RS is included. In addition, variations observed in the stress triaxiality computed during machining suggests that inclusion of the DED RS influences the localized response of the material near the tool-workpiece interface. The technical approach demonstrated can be extended beyond hybrid manufacturing to generate important scientific insights regarding distortion and machining-induced stress for conventionally manufactured monolithic components in the aerospace and other performance-critical industries.

In this work, laser shock peening (or simply laser peening) is investigated for the first time as a post welding treatment for dissimilar foils joined via the fully-mechanical, high-velocity laser impact welding technique. Single and double laser peening shots were applied to laser-impact-welded foils using three different metallic material combinations. Subsequent lap shear testing showed that single-shot laser peening increased the average weld strength by 12% to 25%, depending on the flyer and target material combination. In contrast, with double-shot laser peening, the average weld strength decreased regardless of the flyer and target materials involved. Scanning electron microscope images revealed wavy weld interfaces and increased interlocking between the foils for the single-shot laser peening treatments as compared to the initial “flat” weld interface geometry, thereby leading to greater flyer/target weld strength. In the double-shot laser peening treatments, however, separations and melting were observed along the weld interface due to rebounding and excessive plastic heat dissipation of the foils. The findings of this study reveal the first insights and effects regarding the application of laser shock peening as a post-welding treatment beyond conventional fusion-based welding to high-velocity impact welding methods.

Despite the proliferation of cellular fused filament fabrication (FFF) polymer components for a variety of industrial applications, few studies have investigated their fluid-structure interaction (FSI) behavior during loading, particularly under dynamic impact conditions. Furthermore, the extent to which residual stresses from the FFF build process affect the dynamic load bearing characteristics has not been addressed. In this work, simulations and experiments are conducted for cylindrical nylon specimens fabricated with two different internal closed-cell cavity structures to assess the influence of the entrapped fluid and the FFF residual stresses on the state of stress during high strain-rate impact. The demonstrated 2-stage computational approach includes a thermomechanical model of the FFF build to calculate residual stress and distortion, which forms the initial state for a subsequently executed dynamic impact model using smoothed particle hydrodynamics (SPH) to capture the effects of air within the internal cavities. Dynamic displacement boundary conditions for the FSI simulations are identified using digital image correlation (DIC), obtained from impact experiments on the FFF specimens performed using split Hopkinson pressure bar (SHPB) tests. Findings reveal that FFF residual stresses significantly influence the stress-strain response during dynamic impact, even at strain rates of 500-600 s(-1). In addition, while the influences of both FFF residual stress and FSI vary with internal cellular structure, the study reveals that their coupled effects must be considered to accurately characterize the impact behavior. Validity of the 2-stage numerical approach, as well as significance of FFF residual stress and the influence of FSI, are justified by comparing numerical predictions with experimental measurements, and observing root-mean-square stress errors within 12.77% and 11.87%, and peak stress errors within 1.93% and 1.34% for the two specimens.