Pan Michaleris's research while affiliated with York College of PA and other places

Publications (32)

Article
Thermal management is a critical issue for Selective Laser Sintering (SLS) of polymers, as the thermal history within the powder bed has a significant impact on the produced part quality. Numerical simulations can calculate the thermal history of a build, as well as residual stress, distortion, lack of fusion, and powder aging effects. Model parame...
Article
Laser powder bed fusion (L-PBF) additive manufacturing (AM) is one type of metal-based AM process that is capable of producing high-value complex components with a fine geometric resolution. As melt-pool characteristics such as melt-pool size and dimensions are highly correlated with porosity and defects in the fabricated parts, it is crucial to pr...
Article
One of the challenges for process control of laser powder bed fusion additive manufacturing lies in thermal control. Excessively low laser power may lead to incomplete melting, while too high laser power can lead to keyholing, increasing the porosity of parts. Considering a thermal finite-element model from our prior work, a secant-based iterative...
Article
Control of laser power to improve part quality is critical for fabrication of complex components via Laser Powder Bed Fusion (LPBF) additive manufacturing (AM) processes. If the laser power is too low, it will result in a small melt pool and lack of fusion; on the other hand, if the laser power is too high, it will result in keyhole and material ev...
Article
Thermo-mechanical finite element modeling of additive manufacturing processes, such as Directed Energy Deposition and Laser Powder Bed Fusion, has been widely applied for the prediction and mitigation of part distortion. However, as the size of modeled geometries gets larger, the number of nodes and elements required in the finite element mesh incr...
Article
Numerical simulation has been posited as a key tool to reduce the unwanted distortion which occurs during laser powder bed fusion additive manufacturing, yet the scale and speed of the process makes traditional moving source modeling impractical. In this work a part-scale model is validated for the distortion modeling of laser powder bed fusion man...
Article
Thermal modeling of additive manufacturing processes such as Laser Powder Bed Fusion is able to calculate a thermal history of a build. This simulated thermal history can in turn be used as an input to further simulate temperature related characteristics such as residual stress, distortion, microstructure, lack of fusion porosity, and hot spots. In...
Article
This paper presents an analytical computation of temperature field evolved in a directed energy deposition process, using single-bead walls as illustrating examples. Essentially, the temperature field evolution during the deposition of a wall is computed by super-position of the temperature field generated by the laser source depositing the current...
Conference Paper
In modeling and simulating thermo-mechanical behavior in a directed energy deposition process, it often needs to compute the temperature field evolved in the deposition process since thermal history in the deposition process would affect part geometry as well as microstructure, material properties, residual stress, and distortion of the final part....
Article
Full-text available
The effect of substrate surface preheating on part distortion in laser cladding is investigated through the experimental results of laser deposited Ti-6Al-4V. In situ temperature and distortion measurements were used to monitor the behavior of the substrates before, during, and after deposition. The resulting trends were analyzed, and it was determ...
Chapter
This chapter introduces the topic of additive manufacturing simulation. The motivation for modeling AM processes and mitigating build failure without costly iterative experiments is detailed. A short survey of modeling literature for welding, directed energy deposition, and powder bed fusion processes is made. A list of the primary challenges in th...
Chapter
This chapter outlines the methodology to numerically solve the equations which describe the thermal and mechanical equations for AM processes. This discussion follows that used by the Netfabb Simulation tool which was used to complete the FE validation studies in the rest of the book. However, the modeling approach is general, and may be applied to...
Article
There is a need for the development of lumped-parameter models that can be used for real-time control design and optimization for laser-based additive manufacturing (AM) processes. Our prior work developed a physics-based multivariable model for melt-pool geometry and temperature dynamics in a single-bead deposition for a directed energy deposition...
Article
A three-dimensional finite element model is developed to allow for the prediction of temperature, residual stress, and distortion in multi-layer Laser Powder-Bed Fusion builds. Undesirable residual stress and distortion caused by thermal gradients are a common source of failure in AM builds. A non-linear thermoelastoplastic model is combined with a...
Article
In situ experimental measurements of the laser powder bed fusion build process are completed with the goal gaining insight into the evolution of distortion in the powder bed fusion build process. Utilizing a novel enclosed instrumented system, five experimental builds are performed. Experimental builds compare materials: Ti-6Al-4V and Inconel® 718,...
Article
Experimental measurements are a critical component of model development, as they are needed to validate the accuracy of the model predictions. Currently, there is a deficiency in the availability of experimental data for laser powder bed fusion made parts. Here, two experimental builds of cylindrical geometry, one using a rotating scan pattern and...
Article
There has been continuing effort in developing analytical, numerical, and empirical models of laser-based additive manufacturing (AM) processes in the literature. However, advanced physics-based models that can be directly used for feedback control design, i.e., control-oriented models, are severely lacking. In this paper, we develop a physics-base...
Article
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 transformati...
Article
Due to the repeated thermal cycling that occurs with the processing of each subsequent layer, the microstructure of additively manufactured parts undergoes complex changes throughout the deposition process. Understanding and modeling this evolution poses a greater challenge than for single-cycle heat treatments. Following the work of Kelly and Char...
Article
The accurate modeling of thermal gradients and distortion generated by directed energy deposition additive manufacturing requires a thorough understanding of the underlying physical processes. One area that has the potential to significantly affect the accuracy of thermomechanical simulations is the complex forced convection created by the inert ga...
Article
Distortion mitigation techniques for large parts constructed by additive manufacturing processes are investigated. Unwanted distortion accumulated during deposition is a common problem encountered in additive manufacturing processes. The proposed strategies include depositing equal material on each side of a substrate to balance the bending moment...
Article
A method to analyze and visualize thermal metrics extracted from coaxial thermal images collected during a 3D directed energy deposition is developed as a non-destructive means to assess thermally-driven material characteristics and part quality. Standard practice for part qualification in additive manufacturing is through costly post-process non-d...
Article
In situ measurements of the accumulation of distortion during additive manufacturing (AM) of titanium and nickel base alloys are made as a function of changes in dwell time between the deposition of individual layers. The inclusion of dwell times between individual layers to allow for additional cooling during the deposition process is a common tec...
Article
A finite element modeling strategy is developed to allow for the prediction of distortion accumulation in additive manufacturing (AM) large parts (on the order of meters). A 3D thermoelastoplastic analysis is performed using a hybrid quiet inactive element activation strategy combined with adaptive coarsening. At the beginning for the simulation, b...
Article
Full-text available
In this paper, we advocate for a more harmonized approach to model development for additive manufacturing (AM) processes, through classification and metamodeling that will support AM process model composability, reusability, and integration. We review several types of AM process models and use the direct metal powder bed fusion AM process to provid...
Article
The ability to simulate the thermal, mechanical, and material response in additive manufacturing offers tremendous utility for gaining a deeper understanding of the process, while also having significant practical application. The approach and progress in establishing an integrated computational system for simulating additive manufacturing of metal...
Chapter
Full-text available
Large scale computing is a well-known research area since it is heavily desired by many science and engineering disciplines to simulate complex and sophisticated problems. However, due to the unprecedented amount of data and computations involved, it also poses challenges for current available numerical algorithms and computer hardware.
Article
As parallel and distributed computing gradually becomes the computing standard for large scale problems, the domain decomposition method (DD) has received growing attention since it provides a natural basis for splitting a large problem into many small problems, which can be submitted to individual computing nodes and processed in a parallel fashio...

Citations

... Nevertheless, the authors acknowledge the inevitable modeling errors associated with FEA-based models including NET-FABB SIMULATION, and future work will include validating the proposed modeling methodologies using experimental data. Preliminary results of this paper were presented at the ASME Dynamic Systems and Control Conference [28]. This paper has added new results and an entirely new section on exploration of additional process parameters and input-feature space (Sec. ...
... As a transformative modeling technique, there is an explosive application of PIML across various fields in the last few years [159]. However, PIML in AM is still at its infancy, with only a handful of relevant research efforts on PIMI [164][165][166][167] and PIMT [165,168,169]. Physics-informed ML is anticipated to play a revolutionary role in future data-driven AM modeling, by eliminating its dependence on intensive AM data yet without sacrifice of modeling accuracy. ...
... However, this global optimization approach required hundreds of iterative simulations. Instead of optimizing the laser power profile globally, Irwin et al. [30] used the secant method to iteratively find the optimal laser power in each time step to control the melt pool volume in PBF. It was reported that the controlled simulation took about 2.3 times longer than the regular simulation needed in the test case of a 2-track, 5 mm length geometry. ...
... There are few works on the analytical modeling of multi-track deposition. Li et al., (2018Li et al., ( , 2017 presented an analytical computation of the temperature field in thin-walled samples. A transient solution to a point heat source in a semi-infinite body is used together with a pair of positive and negative heat inputs to compute the temperature field including the effect of heat accumulation. ...
... In another study by Asadi et al. [27], a Gaussian process-based model predictive controller for controlling the melt pool cross-sectional area in PBF was developed and tested in the FEM simulation. While these studies provided the simulation results, Wang et al. [28] used a closed-loop simulation as a feedforward controller to generate the laser power profile and implemented the designed laser power profile in actual PBF experiments. The closed-loop simulation was based on a lumped-parameter melt pool model and a designed nonlinear inverse-dynamics controller for controlling the melt pool cross-sectional area. ...
... Equations 1-11 represent the thermomechanical model that enables prediction of RS during the PBF-LB process. As discussed earlier, a set of experimentally determined temperature-dependent material properties, including Young's modulus, k, , c v , and for IN625, adopted from [6,44,46,52] are tabulated into the model. Denlinger et al. [44], who used the same thermo-elastic-plastic modeling approach, compared the predicted distortion with that measured using a differential variable reluctance transducer. ...
... The finite element (FE) method is a widely used approach for predicting thermal-induced deformation in LPBF. Gouge et al. [25][26][27], Luo and Zhao [28], DebRoy et al. [29], Bandyopadhyay and Traxel [14], Wei et al. [16], and Schoinochoritis et al. [30] have recently published comprehensive review articles on thermomechanical modeling in AM. Based on various computational strategies, the available thermomechanical models to predict thermal-induced deformation in AM are categorized as shown in Fig. 3, and described herewith. ...
... For both models, some common conditions are employed. Convective and radiative heat losses are incorporated for all surfaces exposed to the external environment, having a temperature of 25 • C. The convection coefficients are adjusted to the part geometry following the procedures described by Chao et al. [32] to account for the conduction between the solid build material and the surrounding powder bed. ...
... PBF-LB processing is complex, with a range of parameters in uence the microstructural properties of the printed alloy parts. Examples of these are energy density [12], scanning parameters [13], powder bed temperature [14], build height [7] [15] and build orientation [9]. Moreover, processing parameters must be optimised to avoid the formation of porosity and cracks, which have been reported by Leuders et al. [16], to greatly in uence the properties of the fabricated components. ...
... 3) and experimental validation (Sect. 4) studies following procedures recommended in the literature [25]. In the verification studies (Sect. ...