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

Crystals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 337 ◽  
Author(s):  
Elham Mirkoohi ◽  
Hong-Chuong Tran ◽  
Yu-Lung Lo ◽  
You-Cheng Chang ◽  
Hung-Yu Lin ◽  
...  
Keyword(s):  
Residual Stress ◽  
Thermal Stress ◽  
Kinematic Hardening ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Repeated Heating ◽  
Powder Bed ◽  
Heating And Cooling ◽  
Body Load ◽  
Point Body

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.

scholarly journals Mechanics Modeling of Residual Stress Considering Effect of Preheating in Laser Powder Bed Fusion

2021 ◽  
Vol 5 (2) ◽  
pp. 46
Author(s):  
Elham Mirkoohi ◽  
Hong-Chuong Tran ◽  
Yu-Lung Lo ◽  
You-Cheng Chang ◽  
Hung-Yu Lin ◽  
...  
Keyword(s):  
Residual Stress ◽  
Thermal Stress ◽  
Temperature Gradient ◽  
Temperature Profile ◽  
Analytical Model ◽  
Kinematic Hardening ◽  
Process Conditions ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed

This study aimed at the investigation of the effect of substrate temperature on residual stress in laser powder bed fusion using a physics-based analytical model. In this study, an analytical model is proposed to predict the residual stress through the calculation of preheating affected temperature profile and thermal stress. The effect of preheating is super-positioned with initial temperature in the modeling of temperature profile using a moving heat source approach; the resultant temperature gradient is then employed to predict the thermal stress from a point body load approach. If the thermal stress exceeds the yield strength of the material, then the residual stress under cyclic heating and cooling will be calculated based on the incremental plasticity and kinematic hardening behavior of metal. IN718 is used as a material example to pursue this investigation. To validate the predicted residual stress, experimental measurements are conducted using X-ray diffraction on IN718 samples manufactured via laser powder bed fusion under different process conditions. Results showed that preheating of the substrate could reduce the residual stress in an additively manufactured part due to the reduction in temperature gradient and resultant shrinkage stresses. However, the excessive preheating could have an opposite impact on residual stress accumulation. Moreover, the results confirm that the proposed model is a valuable tool for the prediction of residual stress, eliminating the costly experiments and time-consuming finite element simulations.

scholarly journals Mechanics Modeling of Residual Stress Considering Effect of Preheating in Laser Powder Bed Fusion

2021 ◽  
Author(s):  
Elham Mirkoohi ◽  
Hong-Chuong Tran ◽  
Yu-Lung Lo ◽  
You-Cheng Chang ◽  
Hung-Yu Lin ◽  
...  
Keyword(s):  
Residual Stress ◽  
Thermal Stress ◽  
Temperature Gradient ◽  
Temperature Profile ◽  
Analytical Model ◽  
Kinematic Hardening ◽  
Process Conditions ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed

This study aimed at the investigation of the effect of substrate preheating on residual stress in laser powder bed fusion using a physics-based analytical model. In this study, an analytical model is proposed to predict the residual stress through the calculation of preheating affected temperature profile and thermal stress. The effect of preheating is super-positioned with initial temperature in the modeling of temperature profile using a moving heat source approach; the resultant temperature gradient is then employed to predict the thermal stress from a point body load approach. If the thermal stress exceeds the yield strength of the material, then the residual stress under cyclic heating and cooling will be calculated based on the incremental plasticity and kinematic hardening behavior of metal. IN718 is used as a material example to pursue this investigation. To validate the predicted residual stress, experimental measurements are conducted using X-ray diffraction on IN718 samples manufactured via laser powder bed fusion under different process conditions. Results showed that preheating of the substrate could reduce the residual stress in an additively manufactured part due to the reduction in temperature gradient and resultant shrinkage stresses. However, the excessive preheating could have an opposite impact on residual stress accumulation. Moreover, the results confirm that the proposed model is a valuable tool for the prediction of residual stress- eliminating the costly experiments and time-consuming finite element simulations.

scholarly journals Analytical Modeling of Residual Stress in Laser Powder Bed Fusion

2020 ◽  
Author(s):  
Elham Mirkoohi ◽  
Jinqiang Ning ◽  
Steven Liang
Keyword(s):  
Residual Stress ◽  
Numerical Modeling ◽  
Thermal Stress ◽  
Maraging Steel ◽  
Analytical Modeling ◽  
Kinematic Hardening ◽  
Linear Optimization ◽  
Optimization Techniques ◽  
Repeated Heating ◽  
Heating And Cooling

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.

scholarly journals The Importance of Subsurface Residual Stress in Laser Powder Bed Fusion IN718

2021 ◽  
pp. 2100895
Author(s):  
Itziar Serrano-Munoz ◽  
Alexander Evans ◽  
Tatiana Mishurova ◽  
Maximilian Sprengel ◽  
Thilo Pirling ◽  
...  
Keyword(s):  
Residual Stress ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed

Residual Stress Measurements in a 316l Uniaxial Fatigue Sample Manufactured by Laser Powder Bed Fusion

2021 ◽  
Author(s):  
Catrin Mair Davies ◽  
Paul Sandmann ◽  
Tobias Ronneberg ◽  
Paul A Hooper ◽  
Saurabh Kabra
Keyword(s):  
Residual Stress ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
Stress Measurements

EXPLORATORY INVESTIGATION ON RESIDUAL STRESS AND DISTORTION OF 20MnCr5 CARBURIZING STEEL PROCESSED BY LASER POWDER BED FUSION

2021 ◽  
Author(s):  
Lucas Robatto ◽  
Ronnie Rego ◽  
Anderson Vicente Borille ◽  
José Maria Mascheroni ◽  
Arthur Raulino Kretzer
Keyword(s):  
Residual Stress ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
Exploratory Investigation

scholarly journals The residual stress in as-built Laser Powder Bed Fusion IN718 alloy as a consequence of the scanning strategy induced microstructure

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Itziar Serrano-Munoz ◽  
Tatiana Mishurova ◽  
Tobias Thiede ◽  
Maximilian Sprengel ◽  
Arne Kromm ◽  
...  
Keyword(s):  
Residual Stress ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Scanning Strategy ◽  
Powder Bed
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