M. Leary

• BSc., BMech.Eng.(hons). PhD
• Professor (Associate) at RMIT University

Heat-treated aluminium thin-walled tubes combine efficient energy absorptive properties with low weight, making them common engineering structures for impact mitigation. Recently, the integration of foam cores within these structures further increases their energy absorption capabilities, however, these foams are stochastic leading to unpredictable...

Feedstock powder characteristics affect the quality of metal parts manufactured by laser-based powder bed fusion of metals (PBF-LB/M). However, identifying the decisive powder characteristics remains challenging due to the complexity of the PBF-LB/M process and lack of in-situ, process-relevant data. This study assesses four gas-atomised (GA) virgi...

Metallic lattices have emerged as a class of lightweight, strong, and multifunctional materials with growing applications. However, their specific strengths (strength-to-density ratios) often fall significantly short of those of their bulk metal counterparts. Thin-plate lattices (TPLs), featuring submillimeter-thick metal plates, present a promisin...

Powder bed fusion (PBF) is an important additive manufacturing (AM) technology that is widely implemented to rapidly fabricate high-precision metallic, polymeric, ceramic, and composite components. The build time for PBF-based manufacture, however, remains extensive. To address this issue, recently high-speed sintering PBF processes, such as HP’s M...

The growing demand for lightweight, high-performance engineering materials continues to drive material innovation. Mechanical metamaterials are cellular materials, which usually consist of interconnected networks of struts, plates, and/or shells, organized into repeating unit cells. Titanium alloy (Ti-6Al-4V) solid-strut lattices are the most commo...

Additive manufacturing (AM) enables the fabrication of complex lattice structures that are infeasible with traditional manufacturing processes. These structures are typically implemented with constant cross-sectional strut elements; this strategy is expedient but leads to sub-optimal structural efficiency. Numerical continuum models allow robust me...

Purpose This study aims to comprehensively investigate the electron beam powder bed fusion (EB-PBF) process for copper, offering validated estimations of melt pool temperature and morphology through numerical and analytical approaches. This work also assesses how process parameters influence the temperature fluctuations and the morphological change...

Laser metal deposition (LMD) provides an emerging opportunity for the economic fabrication of high-value components at low production volume. Despite the technical and commercial opportunities associated with LMD, there exist potential failure-modes that differ from those typical of traditional manufacture; concurrently, LMD is typically applied to...

Introduction: Bone tumors, characterized by diverse locations and shapes, often necessitate surgical excision followed by custom implant placement to facilitate targeted bone reconstruction. Leveraging additive manufacturing, patient-specific implants can be precisely tailored with complex geometries and desired stiffness, enhancing their suitabili...

Additive manufacturing (AM) enables patient-specific lattice-based implants with porosity engineered to encourage bone ingrowth and to mimic bone’s mechanical stiffness. The strength of the bone-implant interface can be measured through a destructive ‘push-out’ testing. The aim of this study is to explore the effect of implant-bone stiffness ratio...

Hollow-strut lattices (HSLs) with submillimetre-diameter hollow channels are emerging lightweight multifunctional metamaterials. High-strength aluminium alloys are highly attractive as hollow-strut materials due to their low density, cost efficiency, and corrosion resistance. However, their laser powder bed fusion (LPBF) is more challenging than co...

For the first time in the literature, this study validates the absorption phenomena in Multi-Jet Fusion (MJF) printed polypropylene (PP) structures through Laser Flash (LFA) and Corrected Porosity (CP) methods. The influence of process parameters such as build height and build orientation was investigated on tensile properties, crystallinity, poros...

Introduction: Stress shielding is a common complication following endoprosthetic reconstruction surgery. The resulting periprosthetic osteopenia often manifests as catastrophic fractures and can significantly limit future treatment options. It has been long known that bone plates with lower elastic moduli are key to reducing the risk of stress shie...

This chapter provides useful methods by which 3D print designs can be generated from 3D medical images (including CT and MRI), 3D optical surface scans (including photogrammetry and structured light scanning), and computer-aided design software. Guidance is provided regarding CT scanning methods, anatomical contour delineation and segmentation meth...

Flora and fauna have evolved to distribute their structural mass efficiently in response to their environment. Inspired by this structural efficiency, functionally graded lattices (FGL) are an emerging subset of non-uniform lattices that employ density gradients for a function-driven mechanical response. These gradients are controlled by stepwise o...

Inspired by the cross-sectional optimization of civil engineering, hollow-strut metal lattices are an emerging new class of cellular materials that can be used for a variety of applications. The recent introduction of laser powder bed fusion (LPBF) additive manufacturing (AM) processes to the hollowstrut metal lattice space has facilitated their fa...

A generative design methodology is presented that solves for minimum volume and compliance space-frame systems, with consideration of stress and buckling constraints. The solution space is explored using formal topology optimisation routines. A parameterisation method converts voxelised topology optimisation solutions into skeletonised connectivity...

Purpose This paper aims to present a methodology for the detection and categorisation of metal powder particles that are partially attached to additively manufactured lattice structures. It proposes a software algorithm to process micro computed tomography (µCT) image data, thereby providing a systematic and formal basis for the design and certific...

3D printing has become widely used to rapidly prototype and manufacture novel or bespoke objects or replacement components in a wide range of marine industries, engineering, and research. 3D-printed objects are subject to marine biofouling, impacting their operation and longevity. Application of antifouling paints or coatings adds costly and time-c...

Additive manufactured (AM) components are increasingly being applied to fatigue-limited applications and are often safety–critical, necessitating confidence in the predicted fatigue response. The fatigue failure mode is highly sensitive to variations in loading, materials and geometry; therefore, published AM fatigue data must be accompanied by rob...

Additive manufacturing (AM) technologies such as laser-based powder bed fusion (LB-PBF) facilitate the fabrication of complex lattice structures. However, these structures consistently display dimensional variation between the idealised and as-manufactured specimens. This research proposes a method to characterise the impact of common LB-PBF powder...

Purpose: Bone tumours must be surgically excised in one piece with a margin of healthy tissue. The unique nature of each bone tumour case is well suited to the use of patient-specific implants, with additive manufacturing allowing production of highly complex geometries. This work represents the first assessment of the combination of surgical robo...

The design freedom offered by additive manufacturing (AM) enables the fabrication of components with internal surfaces that are challenging to access post-manufacture. This is of concern, as the surface condition can markedly deteriorate fatigue performance. Additionally, the adaptation of surface finishing methods for AM components with topologica...

Surface roughness is traditionally evaluated with contact profilometry; however, these methods are not compatible with complex additive manufactured lattice structures due to limited physical access. For these scenarios, computed tomography (CT) is often used to provide qualitative insight into surface roughness but does not directly yield roughnes...

Purpose Planning for bone tumor resection surgery is a technically demanding and time-consuming task, reliant on manual positioning of planar cuts in a virtual space. More elaborate cutting approaches may be possible through the use of surgical robots or patient-specific instruments; however, methods for preparing such a resection plan must be deve...

Laser directed energy deposition (L-DED) is an additive technology that offers a rapid solution for repairing mining components made of High Chromium White Iron (HCWI) on site. However, the refined carbide morphology from the rapid cooling in L-DED is detrimental to the wear resistance of the repairs. In this study, two types of powder (Ti powder a...

The purpose of this research is to develop a hybrid experimental and computational model to estimate the absorption of the laser for Laser-Based Powder Bed Fusion (LB-PBF) of IN718. The research also aims to find an underlying knowledge on the effect of absorption ratio on meltpool morphology. This model helps to improve the accuracy of the predict...

Additive manufacturing (AM) technologies such as laser-based powder bed fusion (LB-PBF) facilitate the fabrication of complex lattice structures. However, these structures consistently display dimensional variation between the idealised and as-manufactured specimens. This research proposes a method to characterise the impact of common LB-PBF powder...

The purpose of this work is to identify the principle of electron beam powder bed fusion (EB-PBF) and the performance of this AM method in the processing of copper components. This review details the experimentally reported properties, including microstructural, mechanical and physical properties of pure copper made by EB-PBF. The technical challen...

In the current work, sandwich structure (Ti-6Al-4V)-Ni-(Ti-6Al-4V) is printed by Laser Engineered Net Shaping (LENS). This sandwich structure allows the general repair of broken parts with dissimilar materials. The chief objective of this research is to propose a new method to produce a sandwich structure comprising Ti-6Al-4V and Nickel by DED, whi...

Sea chests are arguably the most problematic vessel niche areas with respect to managing and preventing marine biofouling. This is partly due to the design and location of these structures, as well as the difficulty in managing them with conventional antifouling technologies. Antifouling coatings are typically designed for use on flat exposed hull...

Triply periodic minimal surfaces (TPMS) present a starting point for designing infinitely many novel cellular solids, creating the need for a structured approach to their design and evaluation. In this study the design space is formalised using a set of input parameters and evaluation metrics to provide a structured and reproducible approach to des...

One problematic task in the laser-based powder bed fusion (LB-PBF) process is the estimation of meltpool depth, which is a function of the process parameters and thermophysical properties of the materials. In this research, the effective factors that drive the meltpool depth such as optical penetration depth, angle of incidence, the ratio of laser...

Purpose This paper reviews the synergy of Industry 4.0 and additive manufacturing (AM) and discusses the integration of data-driven manufacturing systems and product service systems as a key component of the Industry 4.0 revolution. This paper aims to highlight the potential effects of Industry 4.0 on AM via tools such as digitalisation, data trans...

The Programmatic Lattice Generator (PLG) is a software tool for generating lattice structures through the repetition of strut based lattice unit cells. The code has an extended library of unit cell topologies and additional functionality. It provides information on connectivity, length, orientation and printability of each strut element. The code h...

Additive Manufacturing (AM) technologies such as Laser-Based Powder Bed Fusion (LB-PBF) enables fabrication of complex lattice structures. However, LB-PBF processes inherently induce dimensional variation between idealised and as-manufactured specimens. This research proposes and implements a method to characterise the structurally relevant geometr...

Hollow-walled lattices are a recent optimization upon the conventional dense-walled lattice design. These novel microstructures can achieve extremely low densities while exhibiting robust technical properties including high ductility, strength, and stiffness. However, the current fabrication process for these structures is ineffective, requiring mu...

Generative design refers to the automated design of components through the use of computer-aided engineering (CAE) tools. This is an enabling technology which allows reduced lead times in component design, particularly for custom and unique parts; improved certification of components; efficient exploration of the design space; and results in optimi...

Additive manufacturing (AM) refers to a collection of manufacturing methods involving the incremental addition of material to build a part directly in its final or near-final geometry, usually in a layer-by-layer process. Metal AM in particular has seen great industrial adoption and maturation. This technology enables increased freedom of design in...

Purpose To design and manufacture a customized thoracic phantom slab utilizing the 3D printing process, also known as additive manufacturing, consisting of different tissue density materials. Here, we demonstrate the 3D‐printed phantom's clinical feasibility for imaging and dosimetric verification of volumetric modulated arc radiotherapy (VMAT) pla...

A porcupine’s quill is an extraordinary natural armor capable of withstanding high compression load. By unravelling the unique properties of the porcupine quill design, the bioinspired structures can be applied in engineering applications. The present work investigates both the mechanical and chemical properties of a porcupine quill. An axial compr...

The Voronoi design was utilized for a biodegradable patient-specific bone scaffold with macro pores (> 4 mm) for the surgical treatment of a critical-sized bone defect. We have focused on the relationship between scaffold design and mechanical properties. Through a combination of experiments and simulations and have presented morphological and mech...

Titanium alloys such as Ti-6Al-4V offer a potential lightweight alternative to traditional armour steels for ballistic protection due to their reduced density of approximately 60% that of steel and tensile properties better than rolled homogenous armour steel. The manufacture of metallic armour often requires substantial thermomechanical processing...

Additive manufacturing (AM) techniques such as selective laser melting (SLM) enable the fabrication of complex metallic lattice structures. By tuning geometric and topological parameters, these structures can be manufactured to exhibit a range of useful properties, including excellent strength-to-weight ratios and energy absorption capabilities. Wh...

Prediction of meltpool features in Laser-Based Powder Bed Fusion (LB-PBF) is a complex non-linear multiple phase dynamic problem. In this investigation, numerical simulations and analytical models are offered to predict meltpool temperature and to provide a methodology to estimate melt track quality. By determining the meltpool temperature, differe...

Hollow-walled lattices are novel cellular materials with lower densities than conventional dense-walled lattices. However, their manufacturability by laser powder bed fusion (LPBF) is not yet established. This study investigates the LPBF manufacturability of Ti-6Al-4V hollow-walled struts with respect to strut outer diameter, wall thickness (contro...

Laser-based powder bed fusion is a thermal metal additive manufacturing process suitable for the fabrication of complex structures. Laser-based powder bed fusion induces large localized thermal gradients and cooling rates, which can produce significant variation in mechanical properties by affecting the underlying microstructure and porosity. This...

In this work, the influence of a compliant hyperelastic polymeric phase infiltrated inside stiff auxetic lattices is studied through experimental and numerical approaches. Samples were fabricated using material jeting technology (MJT). The design principle mimics examples of biological materials wich combine stiff and compliant materials to attain...

Titanium alloys are attractive lightweight alternatives to steels for armour applications. However, their ballistic performance remains much less understood than their conventional mechanical performance. This research correlates the microstructural features of the Ti6Al4V alloy manufactured by laser powder bed fusion (LPBF) in as-built and post-he...

— Planning for bone tumor resection surgery is a technically demanding and time-consuming task, reliant on manual positioning of cutting planes (CPs). This work describes an automated approach for generating bone tumor resection plans, where the volume of healthy bone collaterally resected with the tumor is minimized through optimized placement of...

Removing a volume of tissue as a single mass can be a complicated operation, and in many cases it would be advantageous to be able to remove more complex geometries and preserve nearby critical regions. In this paper, we present a novel robot with 2 degrees of freedom, designed for cutting around a parametric torus-shaped volume. The kinematics of...

Metal additive manufacturing involves manufacturing techniques that add material to produce metallic components, typically layer by layer. The substantial growth in this technology is partly driven by its opportunity for commercial and performance benefits in the aerospace industry. The fundamental opportunities for metal additive manufacturing in...

Additive Manufacturing (AM) technologies such as Laser-Based Powder Bed Fusion (LB-PBF) enables the manufacturing of high efficiency lattice structures. However, the LB-PBF processes inherently generate local geometric effects. The practical implications of these geometric effects on structural performance is of critical importance to effective AM...

The rapid growth of additive manufacturing (AM) technologies has enabled the emergence of geometrically sophisticated materials or structures with tailored and/or enhanced mechanical responses. In addition to dense-walled lattice structures, innovation within the past decade has identified that hollow-walled lattice topologies exhibit the multiface...

This research aims to identify how meltpool temperature is determined by process parameters in Laser-Based Powder Bed Fusion (LB-PBF) and the effect of meltpool temperature and heat treatment temperature on microstructure and tensile properties. The study illustrates how crystallographic features in 316L stainless steel were developed in response t...

Laser Powder Bed Fusion (L-PBF) is an additive manufacturing (AM) technology which has enabled the fabrication of highly complex structures and components. A major challenge in producing these high complexity structures is predicting where defects are likely to occur, and how severe those defects will be. In this study build geometry is linked to m...

Existing material extrusion 3D printing methods of bone-equivalent phantoms for Computed Tomography (CT) imaging in Radiotherapy is limited by the geometrical inaccuracies and the achievable density ranges. The interlace deposition method proposed in this research facilitates the production of densities within the range of polylactic-acid (PLA) and...

Purpose Fused deposition modelling (FDM) is increasingly being explored as a commercial fabrication method due to its ability to produce net or near-net shape parts directly from a computer-aided design model. Other benefits of technology compared to conventional manufacturing include lower cost for short runs, reduced product lead times and rapid...

Nature offers inspirational solutions which are beyond our expectations. Plants and animals are made of well-architectured structures and materials to protect themselves against harsh environments and enemies, same goes to porcupines. Under emergency condition, porcupine protects itself by jabbing the quills into the skin of the assailant. The long...

Laser Powder Bed Fusion (L-PBF) technology is increasingly important for the fabrication of innovative engineering systems, including functionally integrated systems, bespoke medical implants, and high-value optimized structures. Increasingly, these engineered systems are well understood from a technical perspective; however, a remaining challenge...

Laser powder bed fusion technology is technically and economically mature and provides an opportunity for commercially significant engineering outcomes. These commercial outcomes are predicated on a robust understanding of the design tools and methodologies enabled by laser powder bed fusion (L-PBF). This chapter synthesizes commercial best-practic...

When reporting surface quality, the roughest surface is a reference for the measurements. In LPBF due to recoil pressure and scan movement, asymmetric surface is shaped, and surface roughness has different values in different measurement orientations. In this research, the influence of the laser powder bed fusion (LPBF) process parameters on surfac...

Additive Manufacturing (AM) enables the fabrication of lattice structures with optimal mechanical, fluid, and thermal properties. However, during the AM fabrication process, defects are produced in the strut and node elements which comprise the lattice structure. This leads to discrepancies between the AM fabricated lattice and its idealised Comput...

Poor surface finish is a primary challenge to the commercial implementation of Additive Manufacturing (AM). To solve this problem, various Material Removal Rate (MRR) processes have been proposed. However, current methods provide sub-optimal outcomes for the complex geometry enabled by AM. Abrasive Centrifugal Barrel Finishing (ACBF) and Wet Abrasi...

This review investigates the available metallic powder bed additive manufacturing technologies with respect to their basic principles and capabilities in terms of developing orthopedic implants. Detailed descriptions of commonly used metallic alloys employed for orthopedic applications are also presented. The relationship between implant surface pr...

Additive Manufacturing (AM), commonly referred to as 3D printing, offers the ability to not only fabricate geometrically complex lattice structures but parts in which lattice topologies in-fill volumes bounded by complex surface geometries. However, current AM processes produce defects on the strut and node elements which make up the lattice struct...

Material jetting technology is gaining popularity due to its distinctive capability to produce multi-material parts by UV curing in a single process. A unique composite behavior with improved mechanical properties can be achieved due to the ability to spatially vary the composition of hard and soft photopolymer. This characteristic is exceptionally...

Fe-Cr-C near-eutectic alloys are commonly used in wear resistant parts in mining applications, due to their excellent erosion and abrasion wear resistance. Laser metal deposition is an additive technology that presents opportunities for manufacturing mining components, as well as repairing worn areas of wear resistant parts. However, Fe-Cr-C hypoeu...

The abrasive wear behaviour of laser metal deposited Fe-28Cr-2.7C alloy with subsequent heat treatments has been investigated. Two heat treatments were applied: (HT1) 1200°C for 4 hrs then air cooled to room temperature, followed by 960°C for 4 hrs then air cooled, and (HT2) 960°C for 4 hrs then air cooled. The abrasive wear resistance of the HT1 c...

The gyroid has been identified as a cellular topology suitable for engineering applications, particularly in its solid-network form, for biomedical applications. Its solid-surface form has received less attention but offers additional benefits of a continuous surface that partitions space and provides large surface area for heat transfer or cell at...

Metal additive manufacturing (MAM) enables the fabrication of structures with complexity and resolution that cannot be achieved by traditional manufacturing techniques, including lattice structures. However, MAM processes inherently induce local manufacturing defects, resulting in variation between the idealised and as-manufactured geometry and pot...

Additive manufactured (AM) cellular structures have received much research attention due to their specific strength and energy absorption capabilities, and a range of geometric, material and processing parameters has been found to affect their manufacturability and mechanical performance. To investigate the effects of wall thickness and cell size o...

Lattice structures fabricated via Additive Manufacturing (AM) offer improved performance over traditional manufacturing methods, however, predicting their mechanical behaviour both accurately and with acceptable computational efficiency remains a challenge. AM associated defects combined with multiple high aspect-ratio strut elements require fine 3...

The Additive Manufacturing (AM) process plays an important role in enabling cross-disciplinary research in engineering and personalised medicine. Commercially available clinical tools currently utilised in radiotherapy are typically based on traditional manufacturing processes, often leading to non-conformal geometries, time-consuming manufacturing...

Anthropomorphic radiotherapy phantoms require tissue-equivalent materials to achieve Hounsfield Units (HU) that are comparable to those of human tissue. Traditional manufacturing methods are limited by their high-cost and incompatibility with patient-specific customisation. Additive Manufacture (AM) provides a significant opportunity to enable manu...

Grade 23 Ti-6Al-4V additively manufactured by selective electron beam melting (SEBM) has found important clinical applications as bone implants since 2007. In general, an as-built rough surface is desirable for bone ingrowth, but at the expense of fatigue performance. This study assesses the relative influence of the surface condition and internal...

Purpose Metal additive manufacturing is an inherently thermal process, with intense localised heating and for sparse lattice structures, often rapid uneven cooling. Thermal effects influence manufactured geometry through residual stresses and may also result in non-isotropic material properties. This paper aims to increase understanding of the evol...

Additive manufacture (AM) enables the fabrication of highly efficient lattice structures. However, the mathematical efficiency of characterising AM lattice geometry can be poor, potentially restricting the commercial application of AM lattice structures. This research quantifies the effect of the polygon order used to characterise the geometric res...

The field of robotic surgery has progressed from small teams of researchers repurposing industrial robots, to a competitive and highly innovative subsection of the medical device industry. Surgical robots allow surgeons to perform tasks with greater ease, accuracy, or safety, and fall under one of four levels of autonomy; active, semi-active, passi...

The extreme customisation and rapid prototyping capabilities of the 3D printing process allows the manufacture of low-cost and patient-specific radiotherapy phantoms for quality assurance purposes. However, the associated printing techniques and materials are experimentally limited and are yet to be quantified in terms of manufacturability and repr...