Double-sided incremental forming (DSIF) gaining importance in shaping 3D sheet metal components without relying on geometric-specific tooling. The challenge persists in forming high-work hardening aerospace aluminium alloys (AA2xxx) with better properties (tensile and fatigue) along with accuracy. The amount of spring-back for the AA2xxx is more especially when deformation is carried out using a tempered sheet compared to an annealed one. In contrast, the strength of an annealed sheet will be less compared to a tempered one. In the present work, an experimental work is carried out to study the effect of heat treatment (solution treatment-quenching-aging) on the tensile and fatigue properties of components formed using annealed sheets, along with the dimensional deviations that occur during heat treatment compared to the DSIF formed part. Various geometries (pyramid, cone, free-form) are formed using annealed (AA2024-O) sheets followed by heat treatment (HT, to attain AA2024-T62). Results show that the fatigue life of specimens extracted from DSIF components before HT is significantly lower than that of the as-received material. This reduction is due to decreased uniform elongation. However, after heat treatment, the fatigue life of specimens extracted from DSIF components increased compared to the as-received material before HT. This improvement is attributed to the precipitation of fine second-phase particles. These particles impede dislocation motion, enhancing fatigue life under given strain amplitudes. For the geometries formed in present work, the maximum dimensional deviations from intended geometry before heat treatment ranged from-0.43 mm to-0.59 mm, (where the negative values indicate under forming). After heat treatment of components, measurements were carried out again, and it is observed that an increase in dimensional deviations (i.e., varied from-0.52 mm to-0.64 mm) with difference in magnitude less than 150 mu m compared to initially formed DSIF part. This indicates that the warpage due to rapid quenching is minimal. (c) 2025 The Authors. Published by ELSEVIER Ltd. This is an open access article under the CC BY-NC-ND license

Hybrid manufacturing is the combination of two or more different processes to overcome their individual limitations and take advantage of their combined strengths to produce components more efficiently and eco-friendly than existing processes. Double-sided incremental forming (DSIF) and metal additive manufacturing (MAM) using direct energy deposition are the most flexible processes that do not require geometry-specific tooling to produce customized and complex metal parts. However, there is no absolute geometrical freedom, and each process and machine has certain limitations (MAM process has gravity and torch accessibility constraints due to lower surface inclinations and intricate shapes, respectively). Hence, the main objective of the present work is to demonstrate the feasibility thereof from the judicious hybridization of DSIF and MAM processes ( termed as HyDAM, Hybrid Deformation aided Additive Manufacturing) in terms of product complexity by exploiting the geometrical freedom offered from both processes. Non-planar substrates are formed using DSIF and deposition is carried out using wire-based direct energy deposition (W-DED). In the present work, two complex geometries which are difficult to fabricate by conventional AM process due to torch accessibility and gravity constraints are considered to demonstrate their feasibility through proposed hybrid process. An appropriate build orientation of the component is chosen, and the corresponding substrate is formed using DSIF. The material deposited on the formed substrate with a suitable deposition path. The feasibility of proposed HyDAM is successfully demonstrated by fabricating complex components using a three-axis machine during deposition. Future work includes the automatic feature recognition for HyDAM, role of process parameters on bead asymmetry, path planning, exploring complex geometries (for example: deposition of non-planar cellular/perforated structures), performing thermo-mechanical analysis, and achieving the good accuracy.

Stretch forming with reconfigurable tooling is a flexible manufacturing process that has the potential to produce complex and customized components. A cushion (hyperelastic material) is placed between reconfigurable pinheads and sheet metal to reduce the height of dimples on formed components. Conformability between the cushion and pinhead interface is important in enhancing the accuracy of components. Among various existing cushion types, the component-specific cushion designed in earlier work improved the conformability and accuracy of components. However, considering gaps between neighboring pins after adjusting them to desired height based on component and pinhead surfaces in cushion design can further significantly enhance its effectiveness and is yet to be addressed. In the present work, an analytical model is developed by considering gaps between neighboring pins at every location to determine the conformability through a measure of global shape error (i.e., maximum geometrical deviation) for obtaining a range of base radius of scooped-out patch that further enhances accuracy. To demonstrate the effectiveness of the proposed methodology, finite element analysis of multipoint-stretch forming is performed to form a spherical shape using component-specific cushions designed with and without considering gaps between neighboring pins. Results clearly indicate that the base radius of scooped-out patch between 0.85 and 0.95 times the pinhead radius significantly improved the conformability. The accuracy and surface quality of the component formed using a component-specific cushion designed by considering gaps between neighboring pins enhanced significantly (68

Multi-point stretch forming (MPSF) is a flexible manufacturing technology that uses reconfigurable tools to produce a variety of three-dimensional sheet metal components. An elastic cushion is placed between the surfaces of reconfigurable tool and the sheet metal to reduce the possibility of dimple formation. It is well known that elastic cushion deformation behavior significantly affects the accuracy and surface quality of components. In the present work, a component-specific elastic cushion is designed to achieve better conformability between the pin heads and cushion (by scooping out the material from the flat cushion selectively). An analytical model is developed to determine the volume of material to be scooped out and its location based on pin head and component geometries. To demonstrate the effectiveness of the developed methodology, finite element analysis (FEA) is performed to form double curvature (spherical) component with a cushion of constant thickness and a component-specific cushion with different pin matrix sizes. Results indicate that the deformation is more uniform with significant improvement in shape accuracy of the component formed with a component-specific cushion.

Electric pulse aided deformation is gaining importance in plastic deformation processes because of its ability to form difficult-to-form materials like Ti-6Al-4V at much lower temperatures than hot/superplastic forming processes. Applying electric pulses with suitable parameters during plastic deformation reduces the flow stress near instantaneously (stress-drop) due to thermal (expansion and softening) and electro-plastic effects. To quantify the electro-plastic effect, one needs to predict thermal effects accurately. In the present work, electrically assisted uniaxial tensile tests on Ti-6Al-4V are carried out both in elastic and plastic regions. Flow stress reduction due to thermal effects are predicted using finite element analysis. Comparison of predicted thermal effects with that of experimentally measured in elastic region revealed that they are in excellent agreement, as it is well known that thermal expansion only plays a role in the elastic region. In the plastic region, a considerable difference between measured (thermal and athermal) and predicted (only thermal effects) stress-drop values is observed, and this difference is due to the electro-plastic effect. The effect of different process parameters on electro-plastic effect is studied, and the same is quantified.

Energy consumption is an important metric used to evaluate the sustainability potential of manufacturing processes. Due to the low volume and mass customization potential, additive manufacturing (AM) processes have experienced exponential growth in recent years, resulting in heightened ecological consciousness surrounding energy usage. Gaining insight into the energy-intensive sub-systems and sub-processes and identifying strategies for their minimization enables manufacturers to save on energy costs and also aids in reducing their carbon footprint. This study delves into the energy consumption characteristics of the powder bed fusion (PBF) process, particularly selective laser melting (SLM). Through experimental investigation, we investigate how certain factors impact energy usage, namely capacity utilization, layer thickness, and part orientation. We present a novel formulation for estimating primary and total energy consumption in PBF processes, offering a comprehensive energy consumption model. Our results demonstrate significant energy savings with increased capacity utilization—up to a 32.68% reduction in total energy consumption (TEC) per part. Layer thickness variations show the lowest TEC at 25 μm, which can be attributed to the SLM machine's reduced operational time and energy usage of auxiliary components. Furthermore, altering part orientation for the given case study yielded a 50% reduction in TEC, highlighting orientation as a critical factor in energy efficiency. Our formulation, benchmarked against experimental data and specific energy consumption (SEC) values from the literature, effectively captures these parameters' influence on energy usage. The insights from this research advance our understanding of energy dynamics in SLM processes and pave the way for more energy-efficient practices in AM.

Electric pulse aided deformation (EPAD) processes are gaining importance as they have potential to deform difficult-to-form materials at lower temperatures due to electro-plastic (EP) effect. To exploit the use of electric aid in metal forming processes, tool design needs special attention to minimize the joule heating (depends on electric current path) and maximize the electro-plastic effect (if any). In the present work, a custom-designed V-bending experimental setup is fabricated in such a way that current can be passed either throughout the specimen or only through the deformation zone. Effect of electric current path on force drop and springback is studied by carrying out experiments (involves thermal plus EP effect if any) and fully coupled electro-thermo-mechanical finite element analysis (thermal effects only). Results indicate that significantly higher force drop, and springback reduction are observed when current is passed through the deformation zone compared to throughout the specimen. In addition, contribution of EP effect to springback reduction is more when current is passed through the deformation zone at the end of deformation (i.e., before punch retraction).

Double-sided incremental forming (DSIF) process is gaining industrial importance as it has the capability to form complex 3D sheet metal components without using component-specific tooling. It is necessary to form the components in an energy-efficient way without compromising on quality. Almost all the earlier attempts on the energy analysis of single point incremental forming (which is less preferable as it results in poor accuracy, formed components of opening size less than 200 mm × 200 mm) focused on the energy consumption (predicted using either measured forming forces or power) under various process parameters and different machine tools. Energy necessary for free traverse of tools in predefined path is much higher compared to that required to plastically deform the sheet. Energy/power required for free traverse of tool is the significant contributor to the total energy when the tools have to move against the gravity (as in the case of scaled-up machines). Therefore, strategies to reduce energy consumption to move the tools need to be developed, and the present work is an attempt towards the same. In the present work, a mechanics-based model is developed to predict power and energy consumption (i.e., during free movement of tools and to deform sheet) during forming of any arbitrary geometry considering the chosen DSIF machine configuration. Predicted variation in power with forming time for various geometries is compared with measured ones, and they are in excellent agreement. Analysis is carried out to select the process parameters such that energy required to plastically deform the sheet is reasonably less with good surface quality. The effect of component orientation on energy consumption is emphasized. Finally, a process planning strategy is proposed (that includes selecting process parameters and using them to estimate deflection compensations for enhancing accuracy, choosing component orientation, tool type, support force) to form the components with improved surface quality and accuracy in an energy-efficient way. Results indicate that the energy consumption is reduced in the range of 10 to 50

Components fabricated in metal additive manufacturing, including wire arc additive manufacturing, undergo complex thermal cycles, resulting in residual stresses and thermal distortions. The present work investigates the effect of applying in-situ electric pulses to the component after the deposition of every layer to reduce residual stresses. The experimental results revealed that electropulsing resulted in dislocation rearrangement/annihilation, thereby decreasing dislocation density. A significant reduction in the fraction of low angle grain boundaries was observed for electropulse-treated samples, indicating a decrease in residual stress. Further, X-ray diffraction results also confirm a reduction in residual stress (24.0–29.4% reduction compared to untreated samples). The method can effectively be used to address specific regions selectively in addition to in-situ reduction of residual stresses in deposited components.Abbreviations: EBSD: electron backscattered diffraction; EPT: electropulsing treatment; EWF: electron wind force; GND: geometrically necessary dislocations; KAM: Kernel average misorientation; LAGBs: low angle grain boundaries; WAAM: wire arc additive manufacturing; XRD: X-ray diffraction

Electric pulse aided deformation is gaining importance because of its potential to deform difficult-to-form materials (high strength steels, magnesium, and titanium alloys) at very low temperatures compared to hot/superplastic forming due to the electro-plastic effect. In the present work, electrically assisted draw-bending experiments on Ti-6Al-4V alloy are carried out to study the effect of electric pulse parameters (current density, energy density, frequency) on deformation energy and retained height of components. A custom-designed experimental setup is fabricated where there is a provision to pass the current only in the deformation zone to minimize the overall joule heating. Results indicate that deformation energy decreased, and retained height increased with increased energy density due to increased temperature rise. It is observed that force-drop and retained height increased with an increase in current density at constant energy density (temperature rise nearly the same), which is attributed to the electro-plastic effect. No significant change in the hardness values is observed with and without electric aid.

Wire-based direct energy deposition (W-DED) tech-niques in metal additive manufacturing allow part -fabrication at higher deposition rates and lower costs. Given the lack of any support mechanism, these pro-cesses face challenges in fabricating overhanging fea-tures. The inherent overhang capability of weld -beads and higher-order kinematics can help real-ize certain complex geometries. However, signifi-cant challenges like non-uniform slicing, constrained deposition-torch accessibility, etc., limit the efficacy of these approaches. The present work describes a deformation-aided deposition process designed to overcome some of these limitations and to manufac-ture complex metallic components. It is based on a se-quential combination of deposition and bending pro-cesses: a shape fabricated through W-DED deposition is bent to form the required shape. The cycle of deposi-tion and bending is repeated until the final desired ge-ometry is realized. The anisotropic and deterministic behaviors of the deposited components are analyzed in terms of springback and the punch force. Finally, the benefit of current hybrid process is demonstrated through a few illustrative geometries.

Electric pulse aided deformation (EPAD) of metals reduces the flow stress due to both thermal (expansion as well as softening) and electro-plastic (EP) effects. To quantify the electro-plastic effect during pulse application, close prediction of stress-drop due to thermal effects is very important. Testing machine relaxes due to sudden drop in stress at the instant of pulse application and this aspect must be considered in deformation analysis of the predictive methodology to accurately estimate the stress-drop. Coupled electro-thermo-mechanical finite element analysis by incorporating the testing machine stiffness is carried out during the present work to estimate the stress-drop due to thermal effects and validated. Results indicate that the testing machine stiffness significantly influences the stress-drop. In addition, experimental and numerical studies carried out during the present work explain the role of relative rate of deformation and thermal expansion during pulse application to quantify the EP effect. In the present work, cold-rolled and annealed automotive (CMn 440) steel is used and there is a reasonable EP effect.

Multi-point stretch forming (MPSF) is one of the flexible manufacturing processes that uses the reconfigurable tools to produce the three-dimensional sheet metal components. An elastic cushion is placed between the tools and sheet surfaces to avoid direct contact and reduce the dimples as well as wrinkles. The cushion is also known to play an important role as it directly affects the component surface characteristics (accuracy and quality) and thickness strain distribution. An attempt made to apply stretching on the cushion resulted in enhancement of accuracy. In the present work, an analytical methodology is proposed to predict the initial thickness of cushion and stretching load necessary to apply on the cushion. FEA of MPSF of the spherical geometry is carried out with and without application of stretching load on the cushion. Results indicate that effective stress and strain distributions are more uniform when the stretching is applied to cushion thickness in certain range. Proposed methodology can be effectively used to determine initial cushion thickness before stretch and stretch load necessary to achieve chosen final cushion thickness to enhance the accuracy of sheet metal components formed using MPSF.

Double-sided incremental forming (DSIF) is capable of forming complex three-dimensional components without using component-specific tooling. Forming the components with favourable residual stresses, mechanical properties, and accuracy is still one of the challenging tasks. It is known that the support tool contact condition in DSIF changes the magnitude of residual stresses, thereby allowing the possibility to alter the spring-back and mechanical properties by controlling the support force. In the present work, finite element analysis (FEA) and experimental work are carried out to study the effect of support force (varied from 0 to 500 N) on residual stresses, sheet thinning, and accuracy. A custom-designed tool is used to apply specified force within an acceptable range. In addition, tensile and strain-controlled fatigue tests are also carried out to study the effect of the support force. Results indicate that forming forces predicted using FEA are in good agreement with measured forces. Residual stress measurements and predictions at selected locations indicate that through-thickness residual stress gradients are minimum at a nominal support force (150 N), and improvement in fatigue life is also achieved at the same supporting force.

Application of electric pulses during plastic deformation of a metal results in reduction of flow stress. This reduction can be due to both thermal and athermal effects. Increase in the mobility of dislocations due to electron wind is known as electroplastic effect. Almost all the studies on electric pulse aided tensile tests, current is applied through the entire specimen and it contributes to higher joule heating. In this work, electric pulse aided tensile tests are carried out on modified specimens with a provision to apply the electric current through centre portion of gauge length of specimen to reduce the overall joule heating. Finite element simulations are carried out to validate the specimen geometry in terms of stress strain behaviour. Results of single pulse experiments show that there is a significant effect of current carrying length on instantaneous stress drop (increased from 70 MPa to 122.5 MPa when length increased from 30 to 60 mm). Multiple pulse experimental results revealed that specimen with high current carrying length experienced a higher temperature because of accumulation of heat. Comparison of stress drops with electric pulse aid with that of corresponding temperatures with only thermal aid shows that electric pulse caused higher stress drop.

Dent resistance is one of the main requirements of the automotive exterior panel. Researchers use different methods like experimentation, analytical predictions and numerical methods to evaluate the sheet’s dent performance. This work focused primarily on assessing the dent performance of high strength Interstitial free steel of 0.7mm thickness. Laboratory specimens are tested at the different pre-strain levels by forming the sheet to different depths. A semi-empirical relation is developed in the present work to estimate the optimum strain levels to be achieved in the forming for better dent performance. This relation can be used primarily for the performance comparison of the different steel grades as numerical analysis and experimentation needs more resources and time 

Decisions made in the development stage of a new products will affect the whole lifecycle of the product. Manufacturing costs, product performance, maintainability and customer satisfaction in the use phase are parameters the engineers need to consider. In a sustainability perspective can durability and a potential long lifetime with less breakdowns be regarded as positive. Additionally, in a circular economy perspective the potentials for easy disassembly, recyclability and remanufacturing or reuse at the end of life are important. The selection of precision levels and tolerance limits on geometry and material properties in the design phase of mechanical components are decisive for these aspects. While tolerance selections traditionally focused most on meeting customer requirements and interchangeability of parts for assembly, the product development engineers are now facing several "Design for X"—challenges where tolerance selections and distributions are one of the key issues. This paper describes a Closed Loop Tolerance Engineering (CLTE) model describing information flow for tolerance engineering throughout the product lifecycle. The model includes feed forward and feedback of data and information between functional requirements description, tolerance synthesis and analysis, manufacturing process capabilities, measured product performance and end-of-life considerations.

Double Sided Incremental Forming (DSIF) is gaining importance over Single Point Incremental Forming (SPIF) due to its ability to form complex geometries and the capability to obtain better accuracies. In the present work, residual stresses are measured in pyramidal components formed using SPIF, DSIF using X-ray diffraction technique. Residual stress development mechanism during SPIF and DSIF is studied using Finite Element Analysis (FEA). Stress development along circumferential and meridional directions are explained using bending and unbending of sheet material taking place around forming tool. It is observed that the residual stresses are compressive on the outer surface and tensile on the inner surface of sheet in both circumferential and meridional directions. In DSIF, supporting tool restricts the unbending of sheet causing the residual stresses to be less compressive on the outer surface and less tensile on the inner surface compared to SPIF. It is also observed that with an increase in tool diameter, spring back increased, hence, meridional residual stress on the outer surface became more compressive and circumferential residual stress on the inner surface became more tensile. Residual stresses in ISF are compared with FEA predictions of conventional stamping process.

Double sided incremental forming (DSIF) has potential to form complex three-dimensional sheet metal components without using component specific tooling. Forming tool deflection and sheet spring-back are significant factors contributing to the geometrical inaccuracy of DSIF components. Numerical prediction and experimental measurement of sheet spring-back is time consuming. In addition, available analytical methods to predict and compensate sheet spring-back uses theory of small deflections by neglecting the membrane effects. With increase in sheet deflection beyond its thickness, membrane forces experienced by the middle plane of sheet due to stretching significantly resists the applied transverse load. In the present work, combination of small deflection and membrane theories are used to predict and compensate sheet deflections, so that a single methodology can be used for small as well as large components. Proposed methodology is validated using experimental and numerical predictions and they are in very good agreement. Two geometries (axisymmetric, free form components) with different component openings are formed to validate the proposed predictive methodology. Results indicate there is significant improvement (maximum error is less than 800 mu m) in accuracy of components formed using compensated tool paths developed using proposed model. In addition, support tool maintained contact with component throughout forming (maximum force on the support tool is less than 60 N).