About

Todd Palmer is a Professor of Engineering Science and Mechanics and of Materials Science and Engineering at Penn State University, where he also serves as the Director of the Center for Innovative Sintered Products. His research interests encompass high energy density processing and joining of structural and advanced materials, with a focus on additive manufacturing of metals, including laser and electron beam techniques. He investigates process-structure-property relationships in additive manufacturing, as well as the application of these techniques to repair and refurbishment of parts. Palmer's work involves the characterization of phase transformations using synchrotron-based in situ x-ray diffraction techniques, and he is actively involved in the development of diagnostics for electron beam welding. His research lies at the intersection of materials processing, microstructural characterization, and materials performance, emphasizing advanced fabrication technologies such as high energy density welding, additive manufacturing, and particulate materials processing in metallic systems. Palmer has contributed significantly to the field through over 100 publications and holds four patents related to electron beam diagnostics. He collaborates with standards organizations and works closely with industry, government, and academia to advance high energy density beam processing, welding, and additive manufacturing technologies.

Research topics

• Metallurgy
• Materials science
• Composite material
• Thermodynamics
• Geology
• Chemistry
• Mechanics
• Chemical engineering

Selected publications

• Interplay of Variance Reduction and Population Control in Monte Carlo Neutron Transport

  ArXiv.org · 2025-09-26

  preprintOpen access

  Monte Carlo methods are widely used for neutron transport simulations at least partly because of the accuracy they bring to the modeling of these problems. However, the computational burden associated with the slow convergence rate of Monte Carlo poses a significant challenge to running large-scale simulations. The continued improvement in high-performance computing capabilities has put exascale time-dependent Monte Carlo neutron transport simulations within reach. Variance reduction techniques have become an essential component to the efficiency of steady-state simulations, and population control techniques are an integral part of time-dependent simulations, but combining them can create algorithmic conflicts. This study investigates the performance of steady-state variance reduction techniques when extended to time-dependent problems and examines how variance reduction and population control techniques combine to impact the effectiveness of time-dependent simulations. Simulations were conducted using various combinations of these techniques across multiple test problems to assess their performance. While this study does not examine all possible variance reduction and population control combinations, the findings emphasize the importance of carefully selecting algorithms to simulate large-scale time-dependent problems effectively. Notably, using weight windows with weight-based combing for population control can significantly hinder simulation performance, whereas pairing weight windows with uniform combing can provide the efficiencies necessary for successfully computing the results of massive problems. Further performance gains were observed when steady-state weight windows were replaced with time-dependent versions.

  PublisherOA PDFDOI

• Monte Carlo uncertainty quantification and sensitivity analysis for the C5G7 benchmark

  2025-04-01

  reportOpen access
  PublisherOA PDFDOI

• Metals are key to the global economy — but three challenges threaten supply chains

  Nature · 2025-10-13

  article
  PublisherDOI

• Modelling of Nitrogen Dissolution during the GTA Welding of Iron and Steels

  2025-01-06

  book-chapter1st authorCorresponding

  Nitrogen dissolution during the arc welding of steels is a long-standing issue in the welding research community. Unfortunately, the complexity of the arc welding process has made it impossible to accurately predict these nitrogen concentrations using conventional thermodynamics. An attempt to fundamentally understand this complex process is pursued here using mathematical modelling techniques. In this model, plasma phase calculations are combined with those for nitrogen absorption on the surface and those for convection and diffusion of nitrogen in the weld pool to determine the resulting nitrogen distribution in the weldment. This methodology, unlike previous models, is based solely on fundamental principles and can take into account the effects of changes in welding parameters on the resulting nitrogen concentration. A superior correlation is thus observed between the nitrogen concentrations observed in controlled GTA welding experiments and those calculated by this model.

  PublisherDOI

• Interplay of Variance Reduction and Population Control in Monte Carlo Neutron Transport

  Nuclear Science and Engineering · 2025-10-14

  article
  PublisherDOI

• Improvements in MC/DC Domain Decomposition Functionality

  2025-01-01

  article
  PublisherDOI

• Contributions of sub-surface intergranular phases on fatigue crack initiation in additively manufactured austenitic stainless steel

  Journal of Materials Science · 2025-08-18

  articleOpen accessSenior author

  Abstract Fatigue failures in additively manufactured 316L austenitic stainless steel produced using laser powder bed fusion processes are often attributed to the presence of process-related defects or surface roughness. To better investigate the role of surface roughness on fatigue properties, internal pores were mitigated using hot isostatic pressing, and strain-controlled fatigue testing was performed with the surface in the as-deposited condition. In the absence of internal defects, crack initiation was expected to occur at the surface, which displayed arithmetic mean surface roughness ( Sa ) values between 10 and 40 µm as the build angle decreased from a vertical (90°) to a 45° orientation. Even though a decrease in average fatigue life with this increase in surface roughness was observed, there was no evidence of fatal cracks initiating from as-deposited surface asperities. Instead, widespread brittle intergranular fracture occurred within fine-grained sub-surface regions in the contour passes along the specimen perimeter that were populated by sub-micrometer-sized Cr 2 N particles and nanometer-sized α-tridymite oxides that decorated the austenite grain boundaries. The width of these brittle fracture regions increased by 100 µm as the build angle changed from 90° to 45°. At the same time, the fraction of decorated grain boundaries (30–45%) and precipitate length (up to 10 µm) within these wider contour regions increased, driving the observed decreases in the fatigue life. Graphical abstract

  PublisherOA PDFDOI

• Collision Cutoffs in Gamma Transport for Predicting Teller Light

  Transactions of the American Nuclear Society · 2025-01-01

  article
  PublisherDOI

• Developing statistical tools to analyze historical stress-controlled fatigue data in additively manufactured austenitic stainless steel

  Materials Science and Engineering A · 2024-04-28 · 1 citations

  articleOpen accessSenior authorCorresponding
  PublisherOA PDFDOI

• Impact of Solidification Segregation on the Thermal Stability of Oxides and Nitrides in Additively Manufactured 316L Austenitic Stainless Steel

  Proceedings of the ... ASM Heat Treating Society Conference · 2024-09-24

  articleSenior author

  Abstract The increasing demand for accurate fatigue modeling of powder metallurgy components in automotive, aerospace, and medical industries necessitates improved knowledge of composition-microstructure interactions. Variations in feedstock composition and thermomechanical history can produce unique microstructures whose impact on fatigue performance has not been adequately quantified. When characterizing additively manufactured 316L that is within nominal standard chemistry limits, oxide and nitride species were observed preferentially in the specimen contour region. Thermodynamic simulations provide evidence of segregation of the low manganese and high nitrogen composition driving this precipitation of these phases. When present in the specimen, they promoted brittle fracture mechanisms during fatigue.

  PublisherDOI

Frequent coauthors

• J. W. Elmer

  Lawrence Livermore National Laboratory

  57 shared

• T. DebRoy

  Pennsylvania State University

  45 shared

• S. S. Babu

  Oak Ridge National Laboratory

  17 shared

• E. D. Specht

  Oak Ridge National Laboratory

  15 shared

• Jayme Keist

  Pennsylvania State University

  13 shared

• J. J. Blecher

  3D Systems (United States)

  11 shared

• J.S. Zuback

  10 shared

• Wei Zhang

  10 shared

Education

• Ph.D., Materials Science and Engineering

  Pennsylvania State University

Awards & honors

• Past Chair, American Welding Society C7B Sub-Committee on El…
• Vice Chair, American Welding Society D20 Committee on Additi…
• Chair, Fellows Committee, American Welding Society
• Chair, Awards Committee, American Welding Society