Effect of stress relaxation on distortion in additive manufacturing process modeling

Abstract A method for modeling the effect of stress relaxation at high temperatures during laser direct energy deposition processes is experimentally validated for Ti-6Al-4V samples subject to different inter-layer dwell times. The predicted mechanical responses are compared to those of Inconel ® 625 samples, which experience no allotropic phase transformation, deposited under identical process conditions. The thermal response of workpieces in additive manufacturing is known to be strongly dependent on dwell time. In this work the dwell times used vary from 0 to 40 s. Based on past research on ferretic steels and the additive manufacturing of titanium alloys it is assumed that the effect of transformation strain in Ti-6Al-4V acts to oppose all other strain components, effectively eliminating all residual stress at temperatures above 690 °C. The model predicts that Inconel ® 625 exhibits increasing distortion with decreasing dwell times but that Ti-6Al-4V displays the opposite behavior, with distortion dramatically decreasing with lowering dwell time. These predictions are accurate when compared with experimental in situ and post-process measurements.

[1]  Rémy Glardon,et al.  3D FE simulation for temperature evolution in the selective laser sintering process , 2004 .

[2]  Radovan Kovacevic,et al.  Numerical Modeling of Heat Distribution in the Electron Beam Melting® of Ti-6Al-4V , 2013 .

[3]  Lin Li,et al.  Finite element modelling of substrate thermal distortion in direct laser additive manufacture of an aero-engine component , 2013 .

[4]  Lars-Erik Lindgren,et al.  Modelling of metal deposition , 2011 .

[5]  A. M. Deus,et al.  Rapid tooling by laser powder deposition : Process simulation using finite element analysis , 2005 .

[6]  H. Bhadeshia,et al.  Transformation Temperatures and Welding Residual Stresses in Ferritic Steels , 2007 .

[7]  Pan Michaleris,et al.  Finite element modeling discretization requirements for the laser forming process , 2004 .

[8]  Cristina H. Amon,et al.  Residual stress-induced warping in direct metal solid freeform fabrication , 2002 .

[9]  P. Michaleris,et al.  Residual stress and distortion modeling of electron beam direct manufacturing Ti-6Al-4V , 2015 .

[10]  Alberto Cardona,et al.  Computational modelling of shaped metal deposition , 2011 .

[11]  Pan Michaleris,et al.  Minimization of welding distortion and buckling : modelling and implementation , 2011 .

[12]  Miguel Cervera,et al.  Finite element modeling of multi-pass welding and shaped metal deposition processes , 2010 .

[13]  R. Fabbro,et al.  Analytical and numerical modelling of the direct metal deposition laser process , 2008 .

[14]  Ninggang Shen,et al.  THERMAL MODELING OF ELECTRON BEAM ADDITIVE MANUFACTURING PROCESS - POWDER SINTERING EFFECTS , 2012 .

[15]  E. Collings,et al.  Materials Properties Handbook: Titanium Alloys , 1994 .

[16]  Philip J. Withers,et al.  Welding residual stresses in ferritic power plant steels , 2007 .

[17]  J. Mei,et al.  Influence of position and laser power on thermal history and microstructure of direct laser fabricated Ti–6Al–4V samples , 2005 .

[18]  Wenyi Yan,et al.  Experimental investigation and 3D finite element prediction of the heat affected zone during laser assisted machining of Ti6Al4V alloy , 2010 .

[19]  T. Clyne,et al.  Residual Stress Generation during Laser Cladding of Steel with a Particulate Metal Matrix Composite , 2006 .

[20]  P. Withers,et al.  Measured residual stress distributions for low and high heat input single weld beads deposited on to SA508 steel , 2009 .

[21]  Pan Michaleris,et al.  Effect of inter-layer dwell time on distortion and residual stress in additive manufacturing of titanium and nickel alloys , 2015 .

[22]  S. Babu,et al.  In situ observations of lattice expansion and transformation rates of α and β phases in Ti–6Al–4V , 2005 .

[23]  H. Bhadeshia,et al.  Characterizing Phase Transformations and Their Effects on Ferritic Weld Residual Stresses with X-Rays and Neutrons , 2008 .

[24]  J. Goldak,et al.  A new finite element model for welding heat sources , 1984 .

[25]  Mohammad Pervez Mughal,et al.  Three-Dimensional Finite-Element Modelling of Deformation in Weld-Based Rapid Prototyping , 2006 .

[26]  Steven E. Benzley,et al.  A Comparison of All Hexagonal and All Tetrahedral Finite Element Meshes for Elastic and Elasto-plastic Analysis , 2011 .

[27]  J. Beuth,et al.  Control of Residual Thermal Stresses in Shape Deposition Manufacturing , 1995 .

[28]  P. Michaleris.  Modeling metal deposition in heat transfer analyses of additive manufacturing processes , 2014 .