Browsing by Author "Gornyakov, Valeriy"

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    Computationally efficient models of high pressure rolling for wire arc additively manufactured components
    (MDPI, 2021-01-04) Gornyakov, Valeriy; Sun, Yongle; Ding, Jialuo; Williams, Stewart
    High pressure multi-layer rolling is an effective method to reduce residual stress and distortion in metallic components built by wire arc additive manufacturing (WAAM). However, the mechanisms of the reduction in residual stress and distortion during multi-layer rolling are not well understood. Conventional finite element models for rolling are highly inefficient, hindering the simulation of multi-layer rolling for large WAAM components. This study aims to identify the most suitable modelling technique for finite element analysis of large WAAM component rolling. Four efficient rolling models were developed, and their efficiency and accuracy were compared with reference to a conventional large-scale rolling model (i.e., control model) for a WAAM built wall. A short-length transient model with fewer elements than the control model was developed to reduce computational time. Accurate predictions of stress and strain and a reduction in computational time by 96.5% were achieved using the short-length model when an implicit method for numerical solution was employed, while similar efficiency but less accurate prediction was obtained when an explicit solution method was adopted. A Eulerian steady-state model was also developed, which was slightly less efficient (95.91% reduction in computational time) but was much less accurate due to unrealistic representation of rolling process. The applicability of a 2D rolling model was also examined and it was found that the 2D model is highly efficient (99.52% time reduction) but less predictive due to the 2D simplification. This study also shows that the rigid roller adopted in the models is beneficial for improving efficiency without sacrificing accuracy
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    Data supporting: 'Modelling and optimising hybrid process of wire arc additive manufacturing and high-pressure rolling'
    (Cranfield University, 2022-10-04 10:54) Gornyakov, Valeriy; Sun, Yongle; Ding, Jialuo; Williams, Stewart
    Figure 7 Predicted distortion of the WAAM part after deactivation of clamps . Figure 8 Longitudinal RS distributions along the vertical path in the symmetry plane for the full-length mechanical models after clamps deactivation, compared to experimental measurements [5]. The flat roller (a) and slotted roller (b) were used in the rolling simulations, and the full-length model was based on the solution mapped from the steady-state region of the reduced-length WAAM + IL rolling model Figure 10 Concurrent evolution of temperature and longitudinal stress (a), as well as the longitudinal PS (b), in the layer 6 during WAAM deposition of layers 6-8 in conjunction with IL rolling using the flat roller. The data were collected at the top of layer 6 in the inspection plane and the rolling phases are highlighted in the yellow shaded areas. Figure 11 Concurrent evolution of temperature and longitudinal stress (a), as well as longitudinal PS (b), in the layer 6 during WAAM deposition of layers 9-11 in conjunction with IL rolling using the flat roller. The data were collected at the top of layer 6 in the inspection plane and the rolling phases are highlighted in the yellow shaded areas. Figure 12 Concurrent evolution of temperature and longitudinal stress (a), as well as longitudinal PS (b), in the layer 6 during WAAM deposition of layers 12-14 in conjunction with IL rolling using the flat roller. The data were collected at the top of layer 6 in the inspection plane and the rolling phases are highlighted in the yellow shaded areas. Figure 13 Concurrent evolution of the longitudinal PS and stress in the layer 9 during WAAM deposition of layers 9-16 in conjunction with IL rolling using the slotted roller. The data were collected at the top of layer 9 in the inspection plane (the slotted roller started rolling on layer 6) and the rolling phases are highlighted in the yellow shaded areas. Figure 18 Evolution of longitudinal PS in the layer 6 during WAAM deposition and stacked 4L rolling with flat roller. The rolling phases are highlighted in the yellow shaded areas.
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    Dataset for Computationally Efficient Models of High Pressure Rolling for Wire Arc Additively Manufactured Components
    (Cranfield University, 2021-01-04 13:51) Gornyakov, Valeriy; Sun, Yongle; Ding, Jialuo; Williams, Stewart
    1. Dataset for Figure 5: Equivalent plastic strain obtained along centreline on the top of the WAAM wall.2. Dataset for Figure 6: Reaction forces obtained at the rotation point of the rollers (note that only half of the WAAM component was considered in the models).3. Dataset for Figure 13: Longitudinal PS distributions on inspection planes.4. Dataset for Figure 14: Longitudinal RS distributions on inspection planes.
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    Dataset for Efficient determination and evaluation of steady-state thermal-mechanical variables generated by wire arc additive manufacturing and high pressure rolling
    (Cranfield University, 2021-11-04 09:14) Gornyakov, Valeriy; Sun, Yongle; Ding, Jialuo; Williams, Stewart
    1. Dataset for Figure 5: Temperature histories predicted by the short thermal WAAM model at the thermocouple locations: (a) TP1, (b) TP2, (c) TP3 and (d) TP4. The experimental measurements by Ding [34] are also included for comparison.2. Dataset for Figure 11: Longitudinal RS distributions along the Z-direction (through wall height, see Figure 10b for the path of the line plots) in the mapped long mechanical model before and after clamps removal for the WAAM component. The experimental measurements by Ding et al. [34] and Colegrove et al. [5] are also included, which were conducted using neutron diffraction after clamps removal.3. Dataset for Figure 12: Verification of out-of-plane distortion predicted by the mapped long mechanical model after clamps removal. Note that the experimental measurement by Ding [34] using a 3D laser scanner was based on a four-layer deposited wall, and the WAAM model was adapted accordingly.
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    Dataset for Understanding and designing post-build rolling for mitigation of residual stress and distortion in wire arc additively manufactured components
    (Cranfield University, 2022-01-10 08:55) Gornyakov, Valeriy; Ding, Jialuo; Sun, Yongle; Williams, Stewart
    Dataset for Figure 9 Influence of friction coefficient on longitudinal PS in the WAAM built component after rolling: a) flat roller, b) profiled roller, and c) slotted roller (F = 50 kN). Dataset for Figure 10 Vertical penetration of slotted roller for different friction coefficients (F = 50 kN). Dataset for Figure 11 Influence of friction coefficient on longitudinal RS distributions in the WAAM built component after rolling with a) flat roller, b) profiled roller and c) slotted roller (F = 50 kN). Dataset for Figure 13 Influence of rolling load on longitudinal PS in the WAAM component after rolling: a) flat roller, b) profiled roller, and c) slotted roller (µ = 0.1). Dataset for Figure 15 Influence of rolling load on the longitudinal RS in the WAAM component after rolling: a) flat roller, b) profiled roller, and c) slotted roller (µ = 0.1). Dataset for Figure 16 Influence of roller design on mitigation of the compressive longitudinal PS caused by WAAM deposition. The rolling loads are a) 25 kN, b) 50 kN and c) 75 kN (µ = 0.1). Dataset for Figure 17 Influence of roller design on mitigation of the tensile longitudinal RS caused by WAAM deposition. The rolling loads are a) 25 kN, b) 50 kN, and c) 75 kN (µ = 0.1). Dataset for Figure 19 Influence of the post-build rolling using the flat roller on the WAAM deposition RS obtained by the long mechanical model before and after clamps removal (F = 50 kN and µ = 0.1). Dataset for Figure 20 Comparison of vertical distortion in as-built and post-build rolled full-length WAAM component after removal of clamps (flat roller, F = 50 kN and µ = 0.1). Dataset for Figure 21 Comparison of vertical distortion in long WAAM components after post-build rolling with flat, profiled and slotted rollers at rolling loads of a) 25 kN, b) 50 kN, and c) 75 kN (µ = 0.1). Dataset for Figure 22 Comparison in a) PS and b) RS predictions between flat roller models with and without consideration of the WAAM deposition before rolling simulation (µ = 0.5).
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    Efficient determination and evaluation of steady-state thermal-mechanical variables generated by wire arc additive manufacturing and high pressure rolling
    (IOP, 2021-11-02) Gornyakov, Valeriy; Sun, Yongle; Ding, Jialuo; Williams, Stewart
    Wire arc additive manufacturing (WAAM) of large component is susceptible to residual stress (RS) and distortion, which are detrimental and need to be mitigated through high pressure rolling or other methods. In this study, an efficient modelling approach is developed to simulate both WAAM and rolling, and this approach can also be applied to other manufacturing processes to determine steady-state variables. For a clamped wall component, the computationally efficient reduced-size WAAM and rolling models (i.e. short models) can obtain steady-state solutions equivalent to those obtained by conventional full-size models. In the short models, the undesirable effect of reducing the length of the modelled component is counteracted by imposing additional longitudinal constraint as proper to specific processes. The steady-state solution obtained by the short model in clamped condition is then mapped to a long model for analysis of RS and distortion after removal of clamps. The WAAM model predictions of temperature, RS and distortion are in good agreement with experimental measurements. For the steady-state region in the WAAM deposited wall, compressive longitudinal plastic strain (PS) is approximately uniformly formed, and the influential factors and implications of the PS are analysed. The high pressure rolling on the wall after WAAM deposition introduces tensile PS that compensates for the compressive PS induced by the WAAM deposition, thereby mitigating the tensile RS in the clamped wall and alleviating the bending distortion after the removal of clamps. This study demonstrates an efficient approach for modelling large-scale manufacturing and provides insights into the steady-state strains and stresses generated by WAAM and rolling.
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    ItemOpen Access
    Efficient modelling and evaluation of rolling for mitigation of residual stress and distortion in wire arc additive manufacturing.
    (Cranfield University, 2021-08) Gornyakov, Valeriy; Ding, Jialuo; Sun, Yongle
    Wire and Arc Additive Manufacturing (WAAM) is a promising technology for manufacturing large-scale parts with low costs and short lead time. One of the main challenges in applying WAAM in industry is the effective control of residual stress and distortion. It has been found that high-pressure inter-layer rolling can effectively mitigate the residual stress and distortion of WAAM components. However, the mechanism behind the mitigation efficacy is of a complex nature and has not been well understood. Finite element analysis (FEA) has proven to be a reliable and accurate method for simulating the thermo-mechanical process. The FEA simulation of large-scale inter-layer rolling is challenging due to the high computational cost and complicated coupling between WAAM and rolling. This research is based on efficient models for simulating WAAM deposition and rolling processes, and their combination for large-scale structures. The efficient modelling method is developed using a reduced-size model to determine the steady-state solution, and then mapping the solution to a full-size structure for further analysis. This method is successfully applied to study the evolution of residual stress and plastic strain during the post-build and inter-layer rolling of WAAM deposited walls. The numerical predictions are verified with experimental results. Cyclic formation of tensile residual stress occurs during the WAAM deposition, whereas inter-layer rolling counteracts the development of the residual stress. The effectiveness of roller designs is studied for reducing residual stress of the WAAM process. Compared with a flat roller, a slotted roller can induce greater longitudinal plastic strains and more effectively reduce the tensile residual stress in the WAAM wall. Removal of the clamps only results in a slight redistribution of residual stress in the post-build and inter-layer rolled WAAM components, since the rolling mitigates most of the tensile residual stresses caused by WAAM. To enhance the manufacturing efficiency, stacked-layers rolling can replace inter- layer rolling for RS and distortion mitigation in tall WAAM parts. Influences of main process parameters, such as rolling load and roller-to-component friction, on mitigation of RS and distortion are also studied. Finally, based on the understanding gained through the simulations, recommendation of an optimal rolling strategy is made for future industrial application.
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    ItemOpen Access
    Modelling and optimising hybrid process of wire arc additive manufacturing and high-pressure rolling
    (Elsevier, 2022-09-22) Gornyakov, Valeriy; Sun, Yongle; Ding, Jialuo; Williams, Stewart
    Hybrid process of wire arc additive manufacturing (WAAM) and high-pressure rolling can build large-scale components with low detrimental residual stress (RS) and distortion. We developed an efficient coupled process model for a steel wall to simulate the interaction between WAAM deposition and rolling. The predicted RS distributions and wall dimensions agree well with experimental results. Cyclic variation of longitudinal tensile RS occurs during WAAM deposition and inter-layer rolling in clamped condition. The influence depth of deposition and rolling is characterised by the number of the underlying layers that are plastically deformed after each process cycle. For the inter-layer rolling with a flat roller, the rolling has smaller influence depth than the deposition; consequently, the rolling does not eliminate but rather contains the regeneration of WAAM tensile RS after thermal cycles. Rolling with a slotted roller introduces more tensile plastic strain and thereby more effectively reduces WAAM tensile RS and unclamping distortion. Compared to the inter-layer rolling, stacked-four-layer rolling has larger influence depth and hence achieves similar RS mitigation efficacy with fewer rolling operations, while post-build rolling has lower efficacy due to insufficient penetration. Therefore, stacked-layers rolling with slotted roller is recommended for an optimal hybrid process of WAAM and rolling.
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    ItemOpen Access
    Understanding and designing post-build rolling for mitigation of residual stress and distortion in wire arc additively manufactured components
    (Elsevier, 2021-12-21) Gornyakov, Valeriy; Ding, Jialuo; Sun, Yongle; Williams, Stewart
    Post-build rolling can mitigate residual stress (RS) and distortion in large-scale components built by wire arc additive manufacturing (WAAM). In this study, based on numerical simulations that considered both WAAM deposition and vertical rolling, the mechanisms of rolling-enabled mitigation of RS and distortion in a WAAM-built steel wall are elucidated. The influences of process configuration and condition, such as roller design (flat, profiled and slotted rollers), rolling load (25–75 kN) and roller-to-wall friction coefficient (0–0.8) on the distributions of plastic strain (PS) and RS were investigated. It is found that the slotted roller is most effective to introduce tensile PS for counteracting the compressive PS generated by the WAAM deposition, thereby reducing the tensile RS in the clamped condition and the final distortion after removal of clamps. Higher rolling load increases the rolling-induced tensile PS, which leads to more extensive mitigation of the WAAM-generated tensile RS. The simulations also demonstrate that the friction coefficient significantly affects the PS and RS when the slotted roller is employed. However, the efficacy of the flat/profiled roller is insensitive to friction coefficient. This study could underpin the development of an optimal post-build rolling process for efficient mitigation of RS and distortion in WAAM components.