Nathan Fonseca
Current Organizations / Institutes
The organizations/institutes from the scholar's latest article
Research Subjects
Nathan Fonseca has a total of 17 co-authors. Here are the top co-authors by number of shared publications:
- Keng Hsu
School of Manufacturing Systems and Networks, Arizona State University, Mesa, AZ 85212, USA
2 shared publications - Shams Torabnia
School of Manufacturing Systems and Networks, Arizona State University, Mesa, AZ 85212, USA
2 shared publications - Dharneedar Ravichandran
Department of Mechanical Engineering University of California Berkeley California USA
1 shared publication - Ehsan Dehghan-Niri
School of Manufacturing Systems and Networks, Arizona State University, 6075 Innovation Way W, Mesa, AZ 85212, USA
1 shared publication - Guillaume Miquelard-Garnier
Laboratoire PIMM, Arts et Métiers Institute of Technology, CNRS, CNAM, 75013 Paris, France
1 shared publication - Kenan Song
University of Georgia
1 shared publication
Latest Publications
- Open Access
- 13 November 2026
- Published by MDPI AG in Journal of Manufacturing and Materials Processing
- Vol. 10 (11) , 509
Distributionally Robust Fatigue-Constrained Topology Optimization for Additive Manufacturing Under Spatially Correlated Fatigue-Strength Uncertainty
Topology optimization is increasingly important for additive manufacturing because it enables lightweight structures with complex load paths, while process-induced variability can produce spatial heterogeneity in fatigue resistance. This study develops a distributionally robust fatigue-constrained topology optimization framework that distinguishes two sources of uncertainty: spatial variability in local fatigue strength and ambiguity in the probabilities assigned to sampled uncertainty realizations. Spatial variability is represented by a correlated fatigue-strength random field, while probability-model ambiguity is treated using a discrete Kullback–Leibler ambiguity set. The framework is evaluated using an Al 6061-T6 cantilever benchmark and transfer studies involving Ti-6Al-4V, an L-bracket geometry, and a three-dimensional benchmark. In the principal Al case, KL-DRO reduces independent out-of-sample fatigue exceedance from 17.56% to 12.88% and lowers the 95th-percentile fatigue measure from 1.999 to 1.685, with an approximately 2.2% increase in material relative to mean-risk optimization. Similar reductions are observed for the L-bracket and three-dimensional benchmarks, whereas Ti-6Al-4V and matched material studies show little or no advantage. The results therefore indicate that KL-DRO can improve out-of-sample fatigue-tail performance when fatigue risk is active and the empirical uncertainty support is sufficiently informative, but it does not universally outperform mean-risk optimization. The proposed framework provides a computational basis for incorporating spatially resolved fatigue-property uncertainty into topology optimization for additively manufactured structures.
- 13 November 2026
- Published by MDPI AG in Journal of Manufacturing and Materials Processing
- Vol. 10 (11) , 509
Open AccessDistributionally Robust Fatigue-Constrained Topology Optimization for Additive Manufacturing Under Spatially Correlated Fatigue-Strength Uncertainty
Topology optimization is increasingly important for additive manufacturing because it enables lightweight structures with complex load paths, while process-induced variability can produce spatial heterogeneity in fatigue resistance. This study develops a distributionally robust fatigue-constrained topology optimization framework that distinguishes two sources of uncertainty: spatial variability in local fatigue strength and ambiguity in the probabilities assigned to sampled uncertainty realizations. Spatial variability is represented by a correlated fatigue-strength random field, while probability-model ambiguity is treated using a discrete Kullback–Leibler ambiguity set. The framework is evaluated using an Al 6061-T6 cantilever benchmark and transfer studies involving Ti-6Al-4V, an L-bracket geometry, and a three-dimensional benchmark. In the principal Al case, KL-DRO reduces independent out-of-sample fatigue exceedance from 17.56% to 12.88% and lowers the 95th-percentile fatigue measure from 1.999 to 1.685, with an approximately 2.2% increase in material relative to mean-risk optimization. Similar reductions are observed for the L-bracket and three-dimensional benchmarks, whereas Ti-6Al-4V and matched material studies show little or no advantage. The results therefore indicate that KL-DRO can improve out-of-sample fatigue-tail performance when fatigue risk is active and the empirical uncertainty support is sufficiently informative, but it does not universally outperform mean-risk optimization. The proposed framework provides a computational basis for incorporating spatially resolved fatigue-property uncertainty into topology optimization for additively manufactured structures.
- Open Access
In–Situ Acoustic Process Monitoring of Interfacial Events in a Moving–Tool Ultrasound–Assisted Additive Manufacturing Process
Ultrasound–assisted additive manufacturing forms bonds through rapid interfacial events that are difficult to observe in situ, particularly because the deposition tool moves continuously. This study presents an energy–based acoustic framework for detecting and timing these interfacial events, demonstrated on the Resonant–Assisted Deposition (RAD) process. Rather than measuring absolute energy, the method treats the signal power of each channel as a relative indicator of acoustic energy and tracks how wave propagation is altered in structure–borne and airborne pathways, recorded by two AE sensors on the deposition head and substrate, and an airborne microphone. Because the interface acts on all pathways at once, its activity appears as a common–mode variation of the head and substrate signal powers, distinct from the opposing trade–off seen during free tool motion, and this signature locates the interfacial activities within deposition cycles. Two time–domain features segment the window: the Interfacial Slipping Duration (ISD), associated with the slip stage, and the Interfacial Consolidation Duration (ICD), the subsequent bond formation stages; together they give the interfacial–activity duration . The measured ISD is consistent with an independently reported slip stage thermal response, and the same signal–derived windows confine the time–frequency analysis to the interval where ultra–harmonic interfacial content appears. Across controlled changes in excitation frequency and substrate temperature, the features remain extractable and respond in distinguishable ways, indicating repeatability and sensitivity. The method provides a physically interpretable, fixed–sensor basis for characterizing the timing of interfacial events in a moving–tool process, intended for in–situ process monitoring.Open AccessIn–Situ Acoustic Process Monitoring of Interfacial Events in a Moving–Tool Ultrasound–Assisted Additive Manufacturing Process
Ultrasound–assisted additive manufacturing forms bonds through rapid interfacial events that are difficult to observe in situ, particularly because the deposition tool moves continuously. This study presents an energy–based acoustic framework for detecting and timing these interfacial events, demonstrated on the Resonant–Assisted Deposition (RAD) process. Rather than measuring absolute energy, the method treats the signal power of each channel as a relative indicator of acoustic energy and tracks how wave propagation is altered in structure–borne and airborne pathways, recorded by two AE sensors on the deposition head and substrate, and an airborne microphone. Because the interface acts on all pathways at once, its activity appears as a common–mode variation of the head and substrate signal powers, distinct from the opposing trade–off seen during free tool motion, and this signature locates the interfacial activities within deposition cycles. Two time–domain features segment the window: the Interfacial Slipping Duration (ISD), associated with the slip stage, and the Interfacial Consolidation Duration (ICD), the subsequent bond formation stages; together they give the interfacial–activity duration . The measured ISD is consistent with an independently reported slip stage thermal response, and the same signal–derived windows confine the time–frequency analysis to the interval where ultra–harmonic interfacial content appears. Across controlled changes in excitation frequency and substrate temperature, the features remain extractable and respond in distinguishable ways, indicating repeatability and sensitivity. The method provides a physically interpretable, fixed–sensor basis for characterizing the timing of interfacial events in a moving–tool process, intended for in–situ process monitoring. - Open Access
Crosslinked Polyethylene (XLPE) Recycling via Foams
Efficient recycling of crosslinked polyethylene has been challenging due to manufacturing difficulties caused by chemical crosslinking. This study focuses on simple processing via solid waste powder generation and particle fining for the subsequent crosslinked polyethylene inclusion and dispersion in rigid polyurethane foam. In addition, the concentration effects of crosslinked polyethylene in polyurethane were studied, showing a well-controlled foam microstructure with uniform pores, retained strength, better thermal degradation resistance, and, more importantly, increased thermal capabilities. Thus, the simple mechanical processing of crosslinked polyethylene and chemical urethane foaming showed the massive potential of recycling large amounts of crosslinked polyethylene in foams for broad applications in food packaging, house insulation, and sound reduction.
Open AccessCrosslinked Polyethylene (XLPE) Recycling via Foams
Efficient recycling of crosslinked polyethylene has been challenging due to manufacturing difficulties caused by chemical crosslinking. This study focuses on simple processing via solid waste powder generation and particle fining for the subsequent crosslinked polyethylene inclusion and dispersion in rigid polyurethane foam. In addition, the concentration effects of crosslinked polyethylene in polyurethane were studied, showing a well-controlled foam microstructure with uniform pores, retained strength, better thermal degradation resistance, and, more importantly, increased thermal capabilities. Thus, the simple mechanical processing of crosslinked polyethylene and chemical urethane foaming showed the massive potential of recycling large amounts of crosslinked polyethylene in foams for broad applications in food packaging, house insulation, and sound reduction.