Evaluation of a thermomechanical model for prediction of residual stress during laser powder bed fusion of Ti-6Al-4V

Ganeriwala, Rishi; Strantza, Maria; King, Wayne E.; Clausen, B.; Phan, Thien Q.; Levine, Lyle E.; Brown, Donald W.; Hodge, Neil E.

doi:10.1016/j.addma.2019.03.034

Cited by 100 publications

(51 citation statements)

References 28 publications

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“…The predicted and measured residual stress are highly compressive along both scan direction and build direction since during the cooling cycle the heat-affected zone begins to cool down and the shrinkage of material in this zone tend to occur, but the shrinkage is restrained by the plastic strain formed during the heating stage, thus, the compressive stress state builds up in the solidified part. Moreover, the predicted and measured residual stress along the build direction showed higher value compare to that along the scan direction, this is due to the fact that the heat transfer mechanism varies in different directions and would result in different temperature gradient and cooling rates [40]. , and scan pattern of unconnected zigzag.…”

Section: Resultsmentioning

confidence: 96%

Analytical Modeling of Residual Stress in Laser Powder Bed Fusion

Mirkoohi¹,

Ning²,

Liang³

2020

Preprint

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Rapid and accurate prediction of residual stress in metal additive manufacturing processes is of great importance to guarantee the quality of the fabricated part to be used in a mission-critical application in the aerospace and automotive industries. Experimentation and numerical modeling are valuable tools for measuring and predicting the residual stress; however, to-date conducting experimentation and numerical modeling is expensive and time-consuming. Thus, herein, a physics-based thermomechanical analytical model is proposed to predict the residual stress of the additively manufactured part rapidly and accurately. A moving point heat source approach is used to predict the temperature field by considering the effects of scan strategies, heat loss, and energy needed for solid-state phase transformation. Due to the high temperature gradient in this process, part experiences a high amount of thermal stress following solidification which may exceed the yield strength of the material. The thermal stress is obtained using Green’s function of stresses due to the point body load. The Johnson-Cook flow stress model is used to predict the yield surface of the part under repeated heating and cooling. As a result of the cyclic heating and cooling and the fact that the material is yielded, the residual stress build-up is predicted based on incremental plasticity and kinematic hardening behavior of the metal according to the property of volume invariance in plastic deformation in coupling with the equilibrium and compatibility conditions. The computational methodology is realized with the laser powder fusion of maraging steel 350 as a material of example. The validation of the predictive models has been presented in terms of the comparison of predicted and measured scan-direction and build-direction residual stress distributions along depth of build under various process parameter combinations. Moreover, for the first time, the Jonson-Cook parameters of maraging steel 350 are predicted using analytical modeling of machining forces and non-linear optimization techniques.

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Section: Resultsmentioning

confidence: 96%

Analytical Modeling of Residual Stress in Laser Powder Bed Fusion

Mirkoohi¹,

Ning²,

Liang³

2020

Preprint

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“…The predicted and measured residual stresses are highly tensile along both scan direction and build direction since, during the cooling cycle, the heat-affected zone begins to cool down and the shrinkage of material in this zone tends to occur; thus, the tensile stress state builds up in the heated zone. Moreover, the predicted and measured residual stress along the build direction showed higher values compared to that along the scan direction, which is due to the fact that the heat transfer mechanism varies in different directions and would result in different temperature gradient and cooling rates [38]. The variation in temperature gradient and cooling rate resulting from different heat transfer mechanisms would impact the microstructural evolution and material properties, which then impact the residual stress.…”

Section: Resultsmentioning

confidence: 97%

“…Temperature dependent material properties of IN718 (temperature is in • C)[37][38][39][40][41].Density g/cm 3ρ = 8.19 − 39.2 × 10 −2 T 25 < T ≤ 1170 ρ = 7.40 − 88.0 × 10 −2 (T − 1200) T > 1170 Thermal Conductivity W/m • C k = 39.73 − 24.0 × 10 −3 T + 2 × 10 −3 T −2 25 < T < 1170 k = 29.6 T > 1170 Specific Heat J/kg • C C p = 420.24 + 0.026T − 4 × 10 −6 T 2 25 < T ≤ 1170 C p = 650 T > 1170 Thermal Expansion 1/ • C α = −9 × 10 −13 T 2 − 7.7 × 10 −9 T + 1.1 × 10 −5 25 < T ≤ 1100 α = 1.8 × 10 −5 T > 1100Elastic Modulus GPa E = 5.2 × 10 −5 T 2 − 0.088T + 1.6 × 10 2 25 < T ≤ 798 E = 3.1 × 10 −5 T 2 − 0.23T + 2.9 × 10 2 798 < T < 2500Yield Strength MPa…”

mentioning

confidence: 99%

Analytical Modeling of Residual Stress in Laser Powder Bed Fusion Considering Part’s Boundary Condition

Mirkoohi

Tran

et al. 2020

Crystals

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Rapid and accurate prediction of residual stress in metal additive manufacturing processes is of great importance to guarantee the quality of the fabricated part to be used in a mission-critical application in the aerospace, automotive, and medical industries. Experimentations and numerical modeling of residual stress however are valuable but expensive and time-consuming. Thus, a fully coupled thermomechanical analytical model is proposed to predict residual stress of the additively manufactured parts rapidly and accurately. A moving point heat source approach is used to predict the temperature field by considering the effects of scan strategies, heat loss at part’s boundaries, and energy needed for solid-state phase transformation. Due to the high-temperature gradient in this process, the part experiences a high amount of thermal stress which may exceed the yield strength of the material. The thermal stress is obtained using Green’s function of stresses due to the point body load. The Johnson–Cook flow stress model is used to predict the yield surface of the part under repeated heating and cooling. As a result of the cyclic heating and cooling and the fact that the material is yielded, the residual stress build-up is precited using incremental plasticity and kinematic hardening behavior of the metal according to the property of volume invariance in plastic deformation in coupling with the equilibrium and compatibility conditions. Experimental measurement of residual stress was conducted using X-ray diffraction on the fabricated IN718 built via laser powder bed fusion to validate the proposed model.

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“…The second kind of approach used to solve the full-scale model is the thermo-mechanical simulation of the entire part but using a layer agglomeration strategy to speed up the calculation. Each macro layer (or block), when activated is either heated at one time [158,159] or scanned by a heat source with fictious parameters in order to reach the full penetration of the block itself [160,161]. A 'multiscale approach' is also adopted in literature [147,162] where the equivalent body heat flux is first derived from a micro-scale laser-scanning model and input to a meso-scale model for the simulation of the in-plane stress and finally into the full-scale model to obtained the final residual stress state.…”

Section: Full-scale Modelsmentioning

confidence: 99%

Understanding powder bed fusion additive manufacturing phenomena via numerical simulation

Ferro

Berto

Romanin

2020

Frattura Ed Integrità Strutturale

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The increasing interest in additively manufactured metallic parts from industry has issued a formidable challenge to the academic and scientific world that is asked to design new alloys, optimize process parameters and geometry as well as guarantee the reliability of a new generation of loadbearing components. Unfortunately, understanding the interaction between different phenomena associated to metal-additive manufacturing processes is a very difficult task. In this scenario, numerical modelling emerges as a valid technique to face problems related to the influence of process parameters on metallurgical and mechanical properties of additively manufactured components. This contribution is aimed at summarizing the most important outcomes about metal-additive manufacturing process obtained via numerical simulation with particular reference to powder bed fusion techniques. The fundamentals of additive manufacturing numerical simulation will be also explained in detail. Thermal, metallurgical as well as mechanical aspects are covered.

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Evaluation of a thermomechanical model for prediction of residual stress during laser powder bed fusion of Ti-6Al-4V

Cited by 100 publications

References 28 publications

Analytical Modeling of Residual Stress in Laser Powder Bed Fusion

Analytical Modeling of Residual Stress in Laser Powder Bed Fusion

Analytical Modeling of Residual Stress in Laser Powder Bed Fusion Considering Part’s Boundary Condition

Understanding powder bed fusion additive manufacturing phenomena via numerical simulation

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