Browsing by Author "McAndrew, Anthony"

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    2D linear friction weld modelling of a Ti-6Al-4V T-joint
    (Technological Educational Institute of Eastern Macedonia and Thrace, 2015) Lee, Lucie Alexandra; McAndrew, Anthony; Buhr, Clement; Beamish, K. A.; Colegrove, Paul A.
    Most examples of linear friction weld process models have focused on joining two identically shaped workpieces. This article reports on the development of a 2D model, using the DEFORM finite element package, to investigate the joining of a rectangular Ti-6Al-4V workpiece to a plate of the same material. The work focuses on how this geometry affects the material flow, thermal fields and interface contaminant removal. The results showed that the material flow and thermal fields were not even across the two workpieces. This resulted in more material expulsion being required to remove the interface contaminants from the weld line when compared to joining two identically shaped workpieces. The model also showed that the flash curves away from the weld due to the rectangular upstand "burrowing" into the base plate.Understanding these critical relationships between the geometry and process outputs is crucial for further industrial implementation of the LFW process.
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    3D modelling of Ti-6Al-4V linear friction welds.
    (Cranfield University, 2016-11-28 08:49) McAndrew, Anthony; Colegrove, Paul; Buhr, Clement
    Experimental data set from the article "3D modelling of Ti-6Al-4V linear friction welds"Please see the introduction tab in the excel file for further details.
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    3D modelling of Ti–6Al–4V linear friction welds
    (Taylor & Francis, 2016-12-05) McAndrew, Anthony; Colegrove, Paul A.; Buhr, Clement
    Linear friction welding (LFW) is a solid-state joining process that significantly reduces manufacturing costs when fabricating Ti–6Al–4V aircraft components. This article describes the development of a novel 3D LFW process model for joining Ti–6Al–4V. Displacement histories were taken from experiments and used as modelling inputs; herein is the novelty of the approach, which resulted in decreased computational time and memory storage requirements. In general, the models captured the experimental weld phenomena and showed that the thermo-mechanically affected zone and interface temperature are reduced when the workpieces are oscillated along the shorter of the two interface contact dimensions. Moreover, the models showed that unbonded regions occur at the corners of the weld interface, which are eliminated by increasing the burn-off.
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    A computationally efficient thermal modelling approach of the linear friction welding process
    (Elsevier, 2017-09-14) Buhr, Clement; Colegrove, Paul A.; McAndrew, Anthony
    Numerical models used to simulate LFW rely on the modelling of the oscillations to generate heat. As a consequence, simulations are time consuming, making analysis of 3D geometries difficult. To address this, a model was developed of a Ti-6Al–4 V LFW that applied the weld heat at the interface and ignored the material deformation and expulsion which was captured by sequentially removing row of elements. The model captured the experimental trends and showed that the maximum interface temperature was achieved when a burn-off rate of between 2 and 3 mm/s occurred. Moreover, the models showed that the interface temperature is reduced when a weld is produced with a higher pressure and when the workpieces are oscillated along the shorter of the two interface dimensions. This modelling approach provides a computationally efficient foundation for subsequent residual stress modelling, which is of interest to end users of the process.
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    Data underpinning "Interpass Rolling of Ti-6Al-4V Wire + Arc Additively Manufactured Features for Microstructural Refinement"
    (Cranfield University, 2018-02-19 16:44) Colegrove, Paul; McAndrew, Anthony
    Data set for grain size graphs.
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    Development of a numerical modelling approach to predict residual stresses in Ti-6Al-4V linear fraction welds.
    (2017-12) Buhr, Clement; Colegrove, Paul A.; McAndrew, Anthony
    Linear friction welding (LFW) is a solid-state joining process which has been successfully implemented to manufacture bladed-disks, chains and near-net shape components. During welding, large residual stresses are created as a consequence of a non-uniform heating of the component which can severely affect the integrity of the structure. Experimental measurement of residual stresses and temperatures on linear friction welds is difficult, so researchers have used modelling to provide a better understanding of these important characteristics. Models developed in the literature, replicate the welding process by including the oscillation of the workpieces, resulting in long computational times. Therefore, numerical models are mostly confined to 2D geometry and complex geometry cases such as keystone or bladed-disk welds are rarely considered. This thesis focuses on the development and validation of computational models capable of predicting the residual stress field developed in Ti-6Al-4V LFW without modelling the complex mechanical mixing occurring at the weld interface. Using a sequentially coupled thermo-mechanical analysis on a 3D model defined in ABAQUS, the heat was applied at the weld interface using the average heat flux post-processed from the machine data obtained during welding trials, for all the phases. The material deformation was ignored and the material expulsion is accounted for by sequentially removing rows of elements. The models were validated against thermocouples, neutron diffraction and contour method measurements. The shearing occurring at the interface while welding was found to have little effect on the final residual stress field and therefore can be omitted. The residual stress field was found to be driven by the temperature profile obtained at the end of welding, prior to cooling and by the weld interface dimensions. A low weld interface temperature, shallow thermal gradient across the weld and small weld interface dimensions should be sought to minimise the residual stress magnitude. Therefore, a low burn-off rate obtained with reduced welding frequency, amplitude and applied force should be used; however the impact of using these parameters on the microstructure and material properties may need to be considered. The modelling approach was successfully implemented on a blisk LFW and its peculiar geometry was found to have little effect on the residual stress field as the peak magnitude is driven by the overall length of the part and the thermal profile prior to cooling. Several cycles of post-weld heat treatment were also investigated for the blisk weld. The results showed that all post-weld heat treatments reduced the residual stresses, however the differences between the heat treatments on the resulting stress field was minimal. In conclusion, the thesis presents an innovative computationally efficient modelling approach capable of predicting the residual stresses within standard and complex geometry LFW.
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    Development of a numerical modelling approach to predict residual stresses in Ti-6Al-4V linear friction welds
    (2017-12) Buhr, Clement; Colegrove, Paul A.; McAndrew, Anthony
    Linear friction welding (LFW) is a solid-state joining process which has been successfully implemented to manufacture bladed-disks, chains and near-net shape components. During welding, large residual stresses are created as a consequence of a non-uniform heating of the component which can severely affect the integrity of the structure. Experimental measurement of residual stresses and temperatures on linear friction welds is difficult, so researchers have used modelling to provide a better understanding of these important characteristics. Models developed in the literature, replicate the welding process by including the oscillation of the workpieces, resulting in long computational times. Therefore, numerical models are mostly confined to 2D geometry and complex geometry cases such as keystone or bladed-disk welds are rarely considered. This thesis focuses on the development and validation of computational models capable of predicting the residual stress field developed in Ti-6Al-4V LFW without modelling the complex mechanical mixing occurring at the weld interface. Using a sequentially coupled thermo-mechanical analysis on a 3D model defined in ABAQUS, the heat was applied at the weld interface using the average heat flux post-processed from the machine data obtained during welding trials, for all the phases. The material deformation was ignored and the material expulsion is accounted for by sequentially removing rows of elements. The models were validated against thermocouples, neutron diffraction and contour method measurements. The shearing occurring at the interface while welding was found to have little effect on the final residual stress field and therefore can be omitted. The residual stress field was found to be driven by the temperature profile obtained at the end of welding, prior to cooling and by the weld interface dimensions. A low weld interface temperature, shallow thermal gradient across the weld and small weld interface dimensions should be sought to minimise the residual stress magnitude. Therefore, a low burn-off rate obtained with reduced welding frequency, amplitude and applied force should be used; however the impact of using these parameters on the microstructure and material properties may need to be considered. The modelling approach was successfully implemented on a blisk LFW and its peculiar geometry was found to have little effect on the residual stress field as the peak magnitude is driven by the overall length of the part and the thermal profile prior to cooling. Several cycles of post-weld heat treatment were also investigated for the blisk weld. The results showed that all post-weld heat treatments reduced the residual stresses, however the differences between the heat treatments on the resulting stress field was minimal. In conclusion, the thesis presents an innovative computationally efficient modelling approach capable of predicting the residual stresses within standard and complex geometry LFW.
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    Energy and force analysis of Ti-6Al-4V linear friction welds for computational modeling input and validation data
    (Springer, 2014-09-26) McAndrew, Anthony; Colegrove, Paul A.; Addison, Adrian C.; Flipo, Bertrand C. D.; Russell, Michael J.
    The linear friction welding (LFW) process is finding increasing use as a manufacturing technology for the production of titanium alloy Ti-6Al-4V aerospace components. Computational models give an insight into the process, however, there is limited experimental data that can be used for either modeling inputs or validation. To address this problem, a design of experiments approach was used to investigate the influence of the LFW process inputs on various outputs for experimental Ti-6Al-4V welds. The finite element analysis software DEFORM was also used in conjunction with the experimental findings to investigate the heating of the workpieces. Key findings showed that the average interface force and coefficient of friction during each phase of the process were insensitive to the rubbing velocity; the coefficient of friction was not coulombic and varied between 0.3 and 1.3 depending on the process conditions; and the interface of the workpieces reached a temperature of approximately approximately 1273 K (1000 °C) at the end of phase 1. This work has enabled a greater insight into the underlying process physics and will aid future modeling investigations.
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    A literature review of Ti-6Al-4V linear friction welding
    (Elsevier, 2017-10-25) McAndrew, Anthony; Colegrove, Paul A.; Buhr, Clement; Flipo, Bertrand C. D.; Vairis, Achilleas
    Linear friction welding (LFW) is a solid-state joining process that is an established technology for the fabrication of titanium alloy bladed disks (blisks) in aero-engines. Owing to the economic benefits, LFW has been identified as a technology capable of manufacturing Ti-6Al-4V aircraft structural components. However, LFW of Ti-6Al-4V has seen limited industrial implementation outside of blisk manufacture, which is partly due to the knowledge and benefits of the process being widely unknown. This article provides a review of the published works up-to-date on the subject to identify the “state-of-the-art”. First, the background, fundamentals, advantages and industrial applications of the process are described. This is followed by a description of the microstructure, mechanical properties, flash morphology, interface contaminant removal, residual stresses and energy usage of Ti-6Al-4V linear friction welds. A brief discussion on the machine tooling effects is also included. Next, the work on analytical and numerical modelling is discussed. Finally, the conclusions of the review are presented, which include practical implications for the manufacturing sector and recommendations for further research and development. The purpose of this article is to inform industry and academia of the benefits of LFW so that the process may be better exploited.
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    Modelling of the workpiece geometry effects on Ti-6Al-4V linear friction welds - open access data
    (Cranfield University, 2016-05-06 14:33) McAndrew, Anthony; Colegrove, Paul; Addison, Adrian; Flipo, Bertrand; Lee, Lucie; Russell, Michael
    Experimental data set from the article "Modelling of the workpiece geometry effects on Ti-6Al-4V linear friction welds"Please see the introduction tab in the excel file for further details.
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    Modelling of the workpiece geometry effects on Ti–6Al–4V linear friction welds
    (Elsevier, 2015-12-15) McAndrew, Anthony; Colegrove, Paul A.; Addison, Adrian C.; Flipo, Bertrand C. D.; Russell, Michael J.; Lee, Lucie Alexandra
    Linear friction welding (LFW) is a solid-state joining process that is finding increasing interest from industry for the fabrication of titanium alloy (Ti–6Al–4V) preforms. Currently, the effects of the workpiece geometry on the thermal fields, material flow and interface contaminant removal during processing are not fully understood. To address this problem, two-dimensional (2D) computational models were developed using the finite element analysis (FEA) software DEFORM and validated with experiments. A key finding was that the width of the workpieces in the direction of oscillation (in-plane width) had a much greater effect on the experimental weld outputs than the cross-sectional area. According to the validated models, a decrease of the in-plane width increased the burn-off rate whilst decreasing the interface temperature, TMAZ thickness and the burn-off required to remove the interface contaminants from the weld into the flash. Furthermore, the experimental weld interface consisted of a Widmanstätten microstructure, which became finer as the in-plane width was reduced. These findings have significant, practical benefits and may aid industrialisation of the LFW process.
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    Modelling the influence of the process inputs on the removal of surface contaminants from Ti-6Al-4V linear friction welds
    (Elsevier, 2014-11-03) McAndrew, Anthony; Colegrove, Paul A.; Addison, Adrian C.; Flipo, Bertrand C. D.; Russell, Michael J.
    The linear friction welding (LFW) process is finding increasing interest from industry for the fabrication of near-net-shape, titanium alloy Ti–6Al–4V, aerospace components. Currently, the removal of surface contaminants, such as oxides and foreign particles, from the weld interface into the flash is not fully understood. To address this problem, two-dimensional (2D) computational models were developed using the finite element analysis (FEA) software DEFORM and validated with experiments. The key findings showed that the welds made with higher applied forces required less burn-off to completely remove the surface contaminants from the interface into the flash; the interface temperature increased as the applied force was decreased or the rubbing velocity increased; and the boundary temperature between the rapid flash formation and negligible material flow was approximately 970 °C. An understanding of these phenomena is of particular interest for the industrialisation of near-net-shape titanium alloy aerospace components.
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    Realisation of multi-sensor framework for process monitoring of the wire arc additive manufacturing in producing Ti-6Al-4V parts
    (Taylor & Francis, 2018-04-30) Xu, Fangda; Dhokia, Vimal; Colegrove, Paul A.; McAndrew, Anthony; Williams, Stewart W.; Henstridge, Andrew; Newman, Stephen T.
    Wire arc additive manufacturing (WAAM) is arc welding-based additive manufacture which is providing a major opportunity for the aerospace industry to reduce buy-to-fly ratios from 20:1 with forging and machining to 5:1 with WAAM. The WAAM method can build a wide range of near net shapes from a variety of high-grade (metallic) materials at high deposition speeds without the need for costly moulds. However, current WAAM methods and technologies are unable to produce parts reliably and with consistent structural material properties and required dimensional accuracy. This is due to the complexity of the process and the lack of process control strategies. This article makes a brief review on monitoring methods that have been used in WAAM or similar processes. The authors then identify the requirements for a WAAM monitoring system based on the common attributes of the process. Finally, a novel multi-sensor framework is realised which monitors the system voltage/current, part profile and environmental oxygen level. The authors provide a new signal process technique to acquire accurate voltage and current signal without random noises thereby significantly improving the quality of WAAM manufacturing.
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    Thermal modelling of linear friction welding
    (Elsevier, 2018-06-23) Jedrasiak, P.; Shercliff, H. R.; McAndrew, Anthony; Colegrove, Paul A.
    This paper presents a finite element thermal model for linear friction welding applied to an instrumented weld in Ti6Al4V. The power at the weld interface was estimated from the measured transverse velocity and the cyclic machine load. This was compared with the power history reverse-engineered from thermocouple data. A simple analytical model captured the lateral distribution of heat input at the interface, while geometry changes and heat loss due to the expulsion of flash were included using a sequential step-wise technique, removing interface elements one layer at a time at discrete intervals. Comparison of predicted and experimental power showed a 20% discrepancy, attributed to uncertainty in the power estimate from force and displacement data, and sensitivity to the precision of locating the thermocouples. The thermal model is computationally efficient, and is sufficiently accurate for application to a new thermomechanical modelling approach, developed in a subsequent paper.