Katherine Piper

Katherine Piper

3rd Year PhD Student in Computational Mechanics

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A list of all the posts and pages found on the site. For you robots out there, there is an XML version available for digesting as well.

Pages

Posts

portfolio

publications

Ductile fracture in functionally graded materials: Insight into crack behavior within the gradient interface

Published in in arXiv: materials science, 2024

Despite advances in manufacturing making metal functionally graded materials (FGMs) more common, numerical methods for predicting fracture in ductile functionally graded materials remain limited. In this work we study the crack propagation in ductile FGMs, specifically focusing on crack propagation within the gradient region of an FGM. We investigate the direct effects of plasticity, and the exact correlations between accumulated plastic strain and crack growth patterns in an FGM. Through this, we determine key differences in crack growth patterns between well-studied brittle FGMs, and more recently developed ductile FGMs. We provide substantial insight on the influence of both the angle of incidence and the width of the gradient, and expose potential pathways for engineering crack-arresting behavior in ductile FGMs

Recommended citation: Piper, Katherine, and Vinamra Agrawal. "Ductile fracture in functionally graded materials: Insight into crack behavior within the gradient interface." arXiv preprint arXiv:2411.18642 (2024).
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An Alternative Design Space for High-Power Wick-Type Evaporators for Electronics Cooling

Published in Status Pending in arXiv: materials science, 2026

High power spacecraft have long relied on Loop Heat Pipes (LHPs) for passive thermal management. Performance of LHPs and other evaporative cooling systems has historically been governed by a porosity/ permeability tradeoff, which both limits performance and constrains manufacturing approaches. In this work, we unify prior models of wetting, meniscus formation, and capillary evaporation, to demonstrate these surface phenomena act as independent, separately tunable parameters governing evaporator performance, decoupled from bulk porosity and permeability. This independence enables large-pore wicks with reduced risk of clogging and a wider range of lower-cost manufacturing methods, including additive manufacturing. In a direct comparison between evaporators with identical bulk wick properties, our optimized approach provides a 42% performance improvement in conductance while maintaining the cost savings of additive manufacturing and the flight-proven long term reliability of LHPs. These results establish a pathway for additively manufactured, high-performance, low-cost passive evaporators, addressing manufacturing constraints that have limited LHP deployment in terrestrial applications such as electronics thermal management and waste heat recovery.

Recommended citation: Piper, Katherine, and Scott N Roberts. "An Alternative Design Space for High-Power Wick-Type Evaporators for Electronics Cooling." (2026).
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talks

Fracture in Ductile Functionally Graded Materials.

Published:

Functionally graded materials promise idealized properties including controlled thermal expansion ratios, more efficient cooling paths, and optimized structural properties. However, unknown metal phases formed within the gradient region when manufacturing FGMs have a wide range of properties which limit the accuracy of numerical methods. Existing studies on fracture in gradient materials avoid metals due to these complex phase transformations within the gradient region. In this study, we use experimental techniques to aid in developing an accurate phase field simulation of fracture mechanics in a gradient alloy between C300 and Invar36. We have developed a methodology for measuring mechanical properties within a gradient alloy and implementing these properties into a state-of-the-art phase field model for fracture. Additionally, we identify critical compositions and metal phases which would lead to variance in fracture propagation.

(Upcoming) Constructing Surrogate Models with Constraints for Additive Manufacturing.

Published:

Machine learning models for additive manufacturing often result in unreliable predictions which violate physical or manufacturing constraints and require significant post-hoc correction. In this talk, we present an alternate approach to machine learning to strictly enforce constraints while avoiding pitfalls of traditional neural-network-based methods. We develop Newton-type methods for engineering scale problems, addressing the need for reliable constrained optimization in additive manufacturing. By discretizing the optimization statement as a quadratic program and solving a second-order KKT system via interior point (barrier) methods, we enforce constraints by construction rather than through penalization. Our methods are structure-preserving, enforcing any underlying governing laws, geometric constraints, or other application-dependent requirements. We demonstrate this approach on a range of test problems and identify further applications for these methods to find reliable, constraint-satisfying predictions in additive manufacturing

(Upcoming) Multiscale Architectured Wick Geometries in Additively Manufactured Loop Heat Pipes

Published:

Recent advances in additive manufacturing have enabled high-volume, low-cost production of multiscale architectured porous wicks for loop heat pipes. Wicks developed through additive manufacturing, however, have low permeability, limiting thermal performance. We develop a physics-informed design approach for additively manufactured loop heat pipe wicks, aiming to maximize the rate of surface evaporation, compensating for other shortcomings in the additive manufacturing process. Using our multiscale architectured porous wicks, we find a 50% improvement in thermal performance over other state-of-the-art designs. Additionally, we demonstrate a 2-week design-manufacturing-test lead time and less than 3% performance variation across several manufactured samples. In addition to our design methodology and process, we present the motivation for low-cost manufacturing of loop heat pipes and future avenues for development in multiscale porous architectured materials.

teaching

Teaching experience 1

Undergraduate course, University 1, Department, 2014

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Teaching experience 2

Workshop, University 1, Department, 2015

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