Additive Manufacturing for Energy Applications III: Modeling and Non-destructiveTesting in Additive Manufacturing
Sponsored by: TMS Structural Materials Division, TMS: Additive Manufacturing Committee, TMS: Nuclear Materials Committee
Program Organizers: Isabella Van Rooyen, Pacific Northwest National Laboratory; Indrajit Charit, University of Idaho; Subhashish Meher, Idaho National Laboratory; Michael Kirka, Oak Ridge National Laboratory; Kumar Sridharan, University of Wisconsin-Madison; Xiaoyuan Lou, Purdue University
Tuesday 2:00 PM
March 16, 2021
Room: RM 1
Location: TMS2021 Virtual
Session Chair: Xiaoyuan Lou, Auburn University
2:00 PM Invited
Porosity in Metal Additive Manufacturing: X-ray Tomography Insights: Anton du Plessis1; 1Research Group 3D Innovation, Stellenbosch University
Porosity in metal additive manufacturing is a concern and occurs widely in many different forms and in different distinctive 3D distributions. In this regard, X-ray tomography is well suited to quantify pore morphologies, 3D distributions, and holistically quantify this porosity. It can be used to forensically analyse the mechanism behind the porosity formation and hence can be used to optimize the process parameters. Insights from X-ray tomography may extend to a better understanding of the porosity formation, as well as the effect of porosity on mechanical properties through “time-lapse” non-destructive imaging of pores in mechanical tests. In this talk I will demonstrate a variety of examples where X-ray tomography provides insights as those described above. Finally, the challenges and limitations will be discussed particularly with regards to sample size, material, limits on X-ray penetration, image quality and post-processing of X-ray tomography data.
2:20 PM
Effects of Void Configuration on the Overall Thermal and Mechanical Behavior of Porous Materials: A Numerical Modeling Approach: Yu-lin Shen1; Mohammad Abdo2; Binh Pham2; Isabella Van Rooyen2; 1University of New Mexico; 2Idaho National Laboratory
Additively manufactured materials typically contain lack-of-fusion porosity and other defects. The techniques may also be used in conjunction with nuclear fuel system design to fabricate variable or functionally graded porous structures. Understanding how the pore configuration affects the overall material properties calls for detailed numerical modeling analyses. In this study a finite element based micromechanical approach is undertaken, with attention devoted to various shapes (aspect ratios), sizes, and periodic spatial distributions of the existing voids. Starting with one pore per unit cell, we gradually increase the level of complexity of the geometric model. With uniform spherical pores, the effective thermal response is found to be insensitive to the spatial distribution of the voids. The elastic property, however, can be significantly affected. When the aspect ratio of the pores deviates from unity, anisotropy becomes important and the underlying geometry plays an increasing role in dictating the overall thermal and mechanical behavior.
2:40 PM
Experimental and Numerical Investigation of Single Clads Generated by Directed Energy Deposition Additive Manufacturing Processes: Luis Nuñez; John Shelton1; Kyu Cho1; 1Northern Illinois University
Directed energy deposition (DED) is a highly complex phenomenon that involves large thermal gradients that are present during laser melting and solidification of both the substrate and filler material. Understanding how the processing parameters effect thermal gradients and clad geometry and development is key to the efficiency, and control of the DED process. In this investigation, clad tracks were fabricated using an OPTOMEC 850M LENS machine located at Norther Illinois University. Empirical relationships were developed that relate the linear mass density, the ratio of the scan speed and powder feed rate, and dilution at various power levels. Additionally, a cross-sectional 2D numerical model of a single clad was developed in order to better understand the melt pool dynamics that play a role in clad generation. This model was used to investigate linear mass density and its effect on thermal gradients, clad geometry and dilution and their relation to microstructure.
3:00 PM
Multi-scale Multi-fidelity Metamodeling for Advanced Materials: Mohammad Abdo1; Yu-Lin Shen2; Cam Pham1; Isabella Von Rooyen1; 1Idaho National Laboratory; 2University of New Mexico
Machine learning has proven indispensable for predicting effective material properties, and other modeling aspects of heterogeneous materials such as composites, multi-layered structures, or functionally graded additively manufactured materials. This work proposes utilization of a multiscale technique that bridges the gap between different scales of modeling and experimental sparse measurements based on sensitivity studies. The goal is to construct a metamodel that can predict bulk properties by lumping the information learnt from the different scales as well as the experimental data into a single model. This model should no longer need to utilize either of these various scale simulators, yet still resolves a vast range of physical behaviors extracted from the training process and reveals the propagated uncertainties. This can guide nuclear fuel and reactor components design, help to understand the effect of porosity and geometric distribution of pores, interface modeling on the overall effective material properties such as thermal conductivity.
3:20 PM
Detection of Defects in Additively Manufactured Metals Using Thermal Tomography: Alexander Heifetz1; Dmitry Shribak1; Zoe Fisher1; William Cleary2; 1Argonne National Laboratory; 2Westinghouse Electric Company
Quality control of additively manufactured (AM) metallic structures is essential prior to deployment of these structures in a nuclear reactor. We investigate the limits of detection of sub-surface porosity defects in AM stainless steel 316L and Inconel 718 alloys using thermal tomography nondestructive evaluation method. Thermal tomography reconstructs spatial thermal effusivity of the structure from time-dependent surface temperature measurements of flash thermography. Our studies are based on computer simulations of heat transfer through solids using COMSOL software suit. Using the model of layered media, in which defect in a solid is represented with a layer of un-sintered metallic powder with appropriate thermophysical parameters, we obtain depth profile of thermal effusivity for the structure. Computer simulations indicate that at 1mm depth, layers of 50µm thickness are detectable in SS316L. Corrections to layered media model to account for diffusion of heat around the defect solid boundary, and experimental validations are currently investigated.
3:40 PM
Real Time Non-destructive Evaluation during 3D Manufacturing of Metal Parts: Araz Yacoubian1; 1LER Technologies, Inc.
Additive manufacturing, such as laser sintering or melting of additive layers can produce parts rapidly at small volume and in a factory setting. To make the parts having nuclear quality and yet low cost, a real-time non-destructive evaluation (NDE) technique is required to detect defects while they are being manufactured. The NDE technique utilizes a multimodal optical sensor unit that is incorporated in a direct metal laser sintering machine to capture defects in real-time. The sensor data can be used to identify defects as they occur such that immediate corrective action by the machine can be taken. It also provides parameters that enable the prediction if the part is of nuclear quality. Test results of additive manufactured parts will be presented and the predicted results are compared to actual flaws.
4:00 PM
Combining Modelling and Microstructural Studies in Explaining the Laser Parameter Effect on Superalloy Cracking during Selective Laser Melting: Marcus Lam1; 1Monash University
High-strength Ni-based superalloys such as IN738LC is known to be difficult for Selective Laser Melting (SLM) due to their high crack susceptibility. Although previous parametric studies on IN738LC and similar alloys indicated the SLM laser parameter as an important factor, the underlying mechanisms are not clear. In this presentation, we are reporting a research on the laser parameter effects utilizing a high-fidelity SLM model incorporating computational fluid dynamic (CFD), finite element analysis (FEA) and the calculation of phase diagram (CALPHAD). Some of the SLM physics involved in the CFD model are phase transformation, boiling, molten liquid flow etc. The thermal field from CFD was processed by FEA to investigate the thermal stress effect. The defects and microstructure were also studied to compare with the models. The result indicates that the laser parameter effect on cracking is originated from interrelated factors such as solidification conditions, thermal stress, and grain structure.
4:20 PM Cancelled
Simulation of Part Printability in Electron Beam Melting Additive Manufacturing: Yousub Lee1; Patxi Fernandez-Zelaia1; Srdjan Simunovic1; Mike Kirka1; 1Oak Ridge National Laboratory
Electron beam melting is an additive manufacturing process used to print metallic components with complex geometries for aerospace applications. A preheating characteristic enables this technology to avoid large accumulation of residual stress during printing. However, cracking mechanisms particularly in Ni-based superalloys are associated with not only residual stress but also with microstructure (i.e., solidification morphology, transient evolution of Ƴ’). In this study, we investigate the effect of scan strategies on 1) thermal history and microstructure (e.g., Ƴ and Ƴ’), 2) stress development, and 3) cracking susceptibility of Ni-based superalloys during printing. The transient evolution of Ƴ’ is predicted based on thermal cycle and thermodynamic phase diagram in finite element method. Also, thermo-mechanical simulation is utilized to track transient stress evolution.
4:40 PM
Defect Analysis in Selectively Laser Melted Parts via Surface Topography Characterization: Qingyang Lu1; Matteo Seita1; 1Nanyang Technological University
Lack-of-fusion or keyhole porosity defects are often difficult to eliminate completely from parts produced via selective laser melting because of the process intrinsic variability. In situ monitoring provides a valuable solution to infer the occurrence of such defects, in principle. In practice, however, the acquired signals do not provide first-hand information about the nature and location of such defects. We devise a new in situ monitoring technique that relies on the acquisition of optical images of both recoated powder layers and consolidated surfaces. Using specialized numerical image analysis, we produce a topographic map of each layer and use it to detect surface irregularities. By correlating the location of these features with porosities found in the builds via computed tomography, we propose a robust methodology for defect detection. Our technique offers the possibility of detecting defects in real time, shortening the time required for quality assurance of parts.