Engineering Commons^™

Nondestructive Evaluation Of Additively Manufactured Parts Using Resonant Inspection And Frequency Domain-Based Correlation Criteria, Gita Deonarain

Dissertations, Master's Theses and Master's Reports

Additive manufacturing (AM) enables the production of highly customized and geometrically complex components; however, these parts remain susceptible to a wide range of defect types and severities. The combination of complex geometries and distributed defects presents a significant challenge for post-process nondestructive evaluation (NDE). Conventional inspection techniques, such as computed tomography and ultrasonic testing, are often limited by geometry, material, accessibility, and cost, while in situ monitoring is not yet sufficiently mature to replace post-process inspection.

This dissertation establishes the Frequency Domain Assurance Criterion (FDAC) as a quantitative, vibration-based framework for defect detection in AM components. FDAC captures spatial–spectral correlations …

A Study In The Advanced Manufacturing Of Full Solids Oxide Fuel Cells (Sofcs) Via Aerosol Deposition (Ad) Methods With Macro- And Microstructural Defect Characterization, Davis A. Warmuth

Graduate Theses, Dissertations, and Problem Reports (ETD)

The goal of this work is to 3D print a full SOFC layer-by-layer using aerosol deposition (AD) at a resolution of 5 μm. To achieve this goal, several studies were undertaken to develop and optimize an AD system to use ceramic inks. A 130 kHz AD system was developed with 4 material pumps to allow for depositions of individual compositions of the in-situ mixture of multiple solutions to allow for the fabrication of functional gradients in three dimensions. This system was then programmed to deposit air electrode layers containing different material ratios and porous microstructures, comparing their electrochemical performance to …

The Efficacy Of Hybrid Manufacturing For High Stress Automotive Components, Logan Trimmer

Harrisburg University Other Works

The goal of this research was to establish the viability of using hybrid manufacturing for automotive applications. By verifying that high-stress components can be created, it can be assumed that any other lower stress part could be made to match the strength requirements. A limiting factor of adoption for hybrid manufacturing is how new the technology is. Studies on time and cost were performed allowing for comparisons with traditional manufacturing technologies (casting, forging, milling) used in automotive applications. This research utilized a Haas Automation UMC750 5-axis CNC mill with a Meltio laser wire direct energy deposition attachment. Fusion 360 was …

Influence Of Build Plate Location On Tensile Properties And Residual Stresses In Lpbf-Fabricated Stainless Steel 316 Components, Yareli Zelaya Pavón

Honors Program Theses and Research Projects

Additive manufacturing (AM), particularly Laser Powder Bed Fusion (LPBF), enables rapid production of complex metal components with minimal waste. Stainless Steel 316 (SS316) is widely used in engineering applications due to its corrosion resistance and mechanical reliability. This study investigates the influence of build plate location on tensile properties and residual stresses in LPBF-fabricated SS316. Twelve tensile specimens and nine unsupported bridge structures were fabricated at different build plate positions using a “machine model.” Tensile testing provided stress-strain data to evaluate peak stress, elastic modulus, and strain at break, while bridge curvature measurements quantified residual stress through warping. Results indicate …

Fabrication And Evaluation Of Large Alumina Crucibles By Vat Photopolymerization Additive Manufacturing For High-Temperature Actinide Chemistry, R. Joey Griffiths, Christy Santoyo, Jean-Baptise Forien, Bradley Childs, Andrew J. Swift, Andrew Cho, Alexander Wilson-Heid, George Ankrah, Devin Rappleye, Aiden A. Martin, Jason Jeffries, Kiel Holliday

Faculty Publications

Additive manufacturing (AM) offers opportunities to advance the design and function of ceramic tooling in high temperature actinide pyrochemistry. In technical ceramics such as alumina, conventional forming techniques often restrict design flexibility and can limit experimental progress. In this study, we investigate the use of vat photopolymerization (VP) with commercial resins to fabricate large-scale alumina crucibles, reaching dimensions up to 125 mm, which is significantly larger than typically reported for dense VP ceramics. Notably, these additively manufactured components are produced using consumer-grade hardware, which limits process control, but offers significant upside in scalability and accessibility. Using microscopy and X-ray computed …

Upcycling Commodity Polymers To Advanced Materials For Energy And Environmental Sustainability, Anthony Griffin-Espinoza

Dissertations

Synthetic polymers play an essential role in nearly every aspect of our lives. Extending beyond single-use packaging, polymeric material design has progressed to attain tailorable architectures granting exceptional performance across advanced applications, including carbon-fiber reinforced polymer composites for aerospace, conductive materials for soft electronics, and drug carriers for biomedicine. While highly promising, intricately designed polymers needed to achieve excellent performance often have limited processability, complex synthetic methods, and expensive precursors. Furthermore, due to a lack of recyclability, commodity polymer waste streams result in both environmental impacts and a substantial loss of economic value. This dissertation focuses on developing robust strategies …

A Precipitation-Hardened High-Entropy Alloy With Excellent Mechanical Properties Additively Manufactured By In-Situ Alloying, Matthew Luebbe, Shahryar Mooraj, Jonathan Poplawsky, Hans Pommerenke, Wen Chen, Haiming Wen

Materials Science and Engineering Faculty Research & Creative Works

Studies on precipitation-hardened high-entropy alloys (PHEAs) have demonstrated high strength, good ductility, and thermal stability, making them excellent candidates for high-temperature structural applications such as nuclear reactors. However, many complex parts for those applications would need to be produced via additive manufacturing (AM), whose rapid cooling rates and multiple heating cycles could change the microstructure of the chosen alloys and accordingly their mechanical properties. A PHEA, (Fe0.3Ni0.3Mn0.3Cr0.1)88Ti4Al8, which was developed and produced via conventional manufacturing in our previous work with high strength but low ductility, was chosen to test the effects of AM on the microstructure and mechanical properties. Scanning …

Bending Fatigue In Additively Manufactured Metals: A Review Of Current Research And Future Directions, Md Bahar Uddin, Sriram Praneeth Isanaka, Frank Liou

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Metal additive manufacturing (MAM), also referred to as 3D printing, has proven remarkable in the fabrication of complex metal components in multiple sectors. However, the assessment of this revolutionary process through bending fatigue is frequently impeded due to concerns about mechanical and physical conditions of the printed components. The unique layer-by-layer production process results in varied microstructures, anisotropy, and intrinsic defects that considerably differ from traditionally manufactured wrought metals. This review article aims to integrate and evaluate historical and contemporary research on the bending fatigue of additively manufactured materials. More specifically, the impact of process parameters, build orientation, surface conditions, …

Hybrid Multi-Layer Sandwich Beams Using 3d Printing Technology With Energy Absorption Features, Hour Ali Alhefeiti

Thesis/ Dissertation Defenses

This study explores the use of additive manufacturing (AM) technology to create sandwich composite structures, focusing on the manufacturing process, testing, and anticipated impact. The rising cost of manufacturing prototypes using conventional methods has led to the exploration of 3D printing as a viable alternative. The research problem addresses the challenges in manufacturing sandwich composites and the need for automation across the civil, mechanical, aerospace, and aviation industries. The study aims to investigate 3D-printed sandwich composite structures and compare experimental, finite-element analysis, and theoretical results. The proposed methodology includes preparing a CAD model with five different core infill patterns (Cross …

Experimental Investigation Of 3d Printed Tpu Triboelectric Composites For Biomechanical Energy Conversion In Knee Implants, Osama Abdalla, Milad Azami, Amir Ameli, Emre Salman, Milutin Stanacevic, Ryan Willing, Shahrzad Towfighian

Mechanical Engineering Faculty Scholarship

Although total knee replacements have an insignificant impact on patients’ mobility and quality of life, real-time performance monitoring remains a challenge. Monitoring the load over time can improve surgery outcomes and early detection of mechanical imbalances. Triboelectric nanogenerators (TENGs) present a promising approach as a self-powered sensor for load monitoring in TKR. A TENG was fabricated with dielectric layers consisting of Kapton tape and 3D-printed thermoplastic polyurethane (TPU) matrix incorporating CNT and BTO fillers, separated by an air gap and sandwiched between two copper electrodes. The sensor performance was optimized by varying the concentrations of BTO and CNT to study …

Manufacturing Of Origami-Inspired Mechanisms Via Sheet Lamination, Tyler R. Stevens

Theses and Dissertations

Origami-inspired mechanisms combine compact, lightweight, reconfig- urable devices, yet despite decades of growth in origami theory, industrial uptake remains limited. As a result, origami predominately appears as prototypes or in low-volume, bespoke applications. Manufacturing (which has received little development) remains the chief bottleneck: most origami fabrication routes are still under-explored, labor-intensive, and fundamentally unsuited to scale. This dissertation addresses that barrier by establishing a process-centric framework for origami manufacturing and demonstrates fabrication workflows capable of transitioning designs from prototypes to production. A survey of more than 180 publications on origami manufacturing approaches yields a manufacturing-oriented taxonomy that links each surrogate …

Recent Advancement In Conformal Cooling Channels: A Review On Design, Simulation And Future Trends, Soroush Masoudi, Barun K. Das, Muhammad Aamir, Majid Tolouei-Rad

Research outputs 2022 to 2026

The cooling phase of a moulded part plays a crucial role in the injection moulding (IM) process, accounting for 50 to 80 % of total cycle time, and significantly impacting the quality of moulded parts. During the last decade, the advancement of different additive manufacturing (AM) processes, especially metal 3D printing, has facilitated the production of mould parts, such as cores and cavities, with complex-shaped internal conformal cooling channels (CCCs). These innovative cooling systems exhibit significant potential to replace traditional straight-drilled cooling design, as they offer more efficient and uniform cooling performance by facilitating more effective heat transfer, considerably enhancing …

Tensile Performance Sensitivity To Variations Of Standard 17-4 Ph Heat Treatments On Lpbf-Produced Material, Ben Brown, Cory Read, Joseph Newkirk, Frank Liou

Materials Science and Engineering Faculty Research & Creative Works

Standard heat treatments for metals of a particular composition are typically designed with the assumption of a conventional starting microstructure, such as that produced by casting or wrought processing. When applied to metals fabricated by Laser Powder Bed Fusion (LPBF) metal additive manufacturing (AM), these heat treatments can produce inconsistent performance due to the unique as-built microstructures. This study investigates how modifications to standard heat treatments for 17-4 PH steel influence the microstructure and mechanical properties of LPBF-fabricated material. Specimens were produced and subjected to varying solutionizing and homogenizing treatments followed by standard aging treatments. Microstructures were characterized using optical …

Warpage-Resistant, Under-Extrusion-Free, High-Surface-Quality Additive Manufacturing Process For Polyethylene-Based Composite Radiation Shielding Material, Duo Xu, Volodymyr Korolovych, You Lyu, Jacqueline Aslarus, Domingo R. Flores-Hernandez, Simo Pajovic, William T. Heller, Lembit Sihver, Svetlana V. Boriskina

Informatics and Engineering Systems Faculty Publications

Polyethylene (PE) is one of the best shielding materials for primary space radiation due to its high hydrogen content. For effective secondary neutron shielding, boron-rich fillers are incorporated to enhance performance. The semicrystalline nature and high thermal expansion coefficient of PE impede its adoption for in situ additive manufacture in space via the fused deposition modeling (FDM) 3D printing. We developed an optimized PE blend to mitigate the effects of under-extrusion and warpage. Guided by studies on extrusion and warpage, we developed an optimal set of printing parameters for the proposed PE blend. The optimum PE blend─both in its pure …

Comparison Of Peening Effect Between Additive Manufacutred And Drawing Titanium Alloy, Hitoshi Soyama

15th International Conference on Shot Peening

Although additively manufactured (AM) metals are attractive materials, their remarkable weak fatigue properties are an obstacle to their practical application. Thus, post-processing to improve their fatigue properties is required. In the present study, powder bed fusion using laser sintering titanium alloy, i.e., PBF-LS/Ti6Al4V was treated by shot peening (SP), submerged laser peening (SLP), cavitation peening (CP), and fine particle bombarding (FPB), then the fatigue properties were investigated by a torsional fatigue test, comparing with drawing Ti6Al4V. It was revealed that the fatigue strength at 10⁷ was 446 ± 5 MPa for PBF-LS/Ti6Al4V treated by FPB+CP, 359 ± 9 MPa …

Improvement Of The Fatigue Behaviour Of Additive Manufatured Scalmalloy By Using Surface Improvement Processes, Francisco José Boby Alcaide, Irene Eras, José Manuel De Los Santos, Alejandro Munoz Castro, Antonio Perinan Butrón, Jorge Sogorb

15th International Conference on Shot Peening

The use of light metals such as Aluminum alloys has experienced a remarkable increase for the additive manufacturing (AM) industry, especially in aerospace.

AM Scalmalloy®. (an Al-Mg-Sc alloy) shows outstanding behavior with much higher mechanical performance with respect to other alloys for powder bed fusion laser-based (PBF-LB) process like AlSi10Mg or AlSi7Mg. Recent studies have mainly focused on static loading, with minor attention to cyclic loading despite its vital importance in many applications.

In this work, the fatigue performance of PBF-LB Scalmalloy was investigated considering the effects of surface treatments to identify the set of optimal post-processes. Shot peening with …

The Effect Of Surface Treatment On The Fatigue Strength Of Sus316l Additive Manufactured Products, Hitoshi Nishijima, Yuji Kobayashi, Toshiya Tsuji, Kiyotaka Masaki

15th International Conference on Shot Peening

Rotating bending fatigue tests were conducted to investigate the effect of shot peening and barrel finishing on fatigue properties of SUS316L made by laser PBF which was one of additive manufacturing processes. Surface roughness, residual stress, and fatigue strength were investigated for each specimen. As a result, the fatigue strength of the barrel finished specimens was almost same or better than that of the shot peened specimens. Barrel finished specimens increased 4.1 times higher fatigue strength than as-built specimens. The surface roughness of the specimens after barrel finishing was reduced by up to 96% compared to the as-built specimens. On …

Sustainable Additive Manufacturing Of Polymer Composites: A Review, Wan Sharuzi Wan Harun, Faiz Ahmad, Farhana Mohd Foudzi, Fujio Tsumori, Arun Kumar Thirugnanasambandam, Mohammed Saber

The Nexus of Sustainability and Energy Technology Journal

Additive Manufacturing (AM) of polymer composites has matured from a prototyping tool into a viable process for functional components. This review critically assesses this progress, focusing on the intersection of performance, sustainability, and industrial readiness. Advancements in AM processes now accommodate diverse reinforcements, from nanoscale fillers to continuous fibres, yielding parts with exceptional mechanical properties. Concurrently, a sustainability strategy has emerged, prioritising bio-based and recycled feedstocks, enhanced process energy efficiency through novel out-of-oven curing, and circular economy principles. However, widespread industrial adoption is hindered by persistent challenges. These include managing fibre-matrix interfacial integrity, the inherent anisotropy of printed parts, complex …

Data Compression In Additive Manufacturing: Recent Progress And Opportunities, Dongmin Ethan Kang, Wenmeng Tian

Publications

A crucial aspect of quality control for Additive Manufacturing (AM) processes is the acquisition of diverse data from the entire lifecycle of the product. AM data has grown significantly in terms of diversity and volumes, resulting in diverse data formats of increasing volumes, including time series, images, and point clouds. Large quantities of these data are essential for effective in-situ process monitoring and ex-situ non-destructive evaluation. However, this will result in large manufacturing and inspection datasets that are difficult to manage for users, which will delay the broader adoption of AM for mission critical applications. This motivates the urgent need …

Digital Twins, Ai, And Cybersecurity In Additive Manufacturing: A Comprehensive Review Of Current Trends And Challenges, Md Sazol Ahmmed, Laraib Khan, Muhammad Arif Mahmood, Frank Liou

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The development of Industry 4.0 has accelerated the adoption of sophisticated technologies, including Digital Twins (DTs), Artificial Intelligence (AI), and cybersecurity, within Additive Manufacturing (AM). Enabling real-time monitoring, process optimization, predictive maintenance, and secure data management can redefine conventional manufacturing paradigms. Although their individual importance is increasing, a consistent understanding of how these technologies interact and collectively improve AM procedures is lacking. Focusing on the integration of digital twins (DTs), modular AI, and cybersecurity in AM, this review presents a comprehensive analysis of over 137 research publications from Scopus, Web of Science, Google Scholar, and ResearchGate. The publications are categorized …

Impact Of Print Speed And Nozzle Temperature On Tensile Strength Of 3d Printed Abs For Permanent Magnet Turbine Systems, Wirawan Wirawan, Hilmi Iman Firmansyah, Satworo Adiwidodo, Mohammad Sukri Mustapa

Journal of Mechanical Engineering Science and Technology (JMEST)

Operational parameters must be integrated into turbine systems' main components, which are determined by turbine systems' functional requirements. The need for producing component designs more effectively raises the possibility of using additive manufacturing. The study focuses on the optimization of the mechanical properties of the principal components of magnetic turbines manufactured with 3D printers using Acrylonitrile Butadiene Styrene (ABS), by changing the temperature and speed of the nozzle. The approach consisted of modeling a standard test piece in CAD software and producing ABS-based test pieces using a 3D printer with print speeds of 50, 70, 90, and 110 mm/s and …

Distinctive Transpassivation Behavior And Characteristics Of Passive Films Of Laser Powder Bed Fusion Produced And Annealed Ti–6al–4v In Hank's Solution, Yi Fan Zhang, Liang Yu Chen, Ze Xin Wang, Hong Yu Yang, Maksym Bobrov, Dobuvyy Oleksandr, Yong Liu, Lai Chang Zhang

Research outputs 2022 to 2026

Passivated Ti alloys typically demonstrate enhanced corrosion resistance due to the formation of passive films. Intriguingly, in comparison to the annealed Ti–6Al–4V, laser powder bed fusion (LPBF) produced Ti–6Al–4V exhibits significantly attenuated transpassivation behavior in Hank's solution. This work investigated the electrochemical responses of both samples before and after the transpassivation region to illustrate the underlying mechanism for the phenomenon. In the passivation region, both samples displayed analogous passivation behavior, with the annealed and LPBF-produced Ti–6Al–4V having the current densities of 6.64 × 10⁻⁶ and 8.14 × 10⁻⁶ A cm⁻² at 1 V, respectively. Between 1.5 V …

3d Printed Cnt/Tpu Triboelectric Nanogenerator For Load Monitoring Of Total Knee Replacement, Osama Abdalla, Mahmood Chahari, Milad Azami, Amir Ameli, Emre Salman, Milutin Stanacevic, Ryan Willing, Shahrzad Towfighian

Mechanical Engineering Faculty Scholarship

This study presents the development and characterization of a novel triboelectric nanogenerator (TENG) designed as a self-powered sensor for load monitoring in total knee replacement (TKR) implants. The triboelectric layers comprise a 3D-printed thermoplastic polyurethane (TPU) matrix with carbon nanotube (CNT) nanoparticles and kapton tape, sandwiched between two copper electrodes. To optimize sensor performance, the proposed CNT/TPU TENG sensor is fabricated with varying CNT concentrations and thicknesses, enabling a comprehensive analysis of how material composition and structural parameters influence energy harvesting efficiency. The 1% CNT/TPU composite demonstrates the highest power output among the tested samples. The solid CNT/TPU-based TENG generated …

Surface Resistivity Correlation To Nano-Defects In Laser Powder Bed Fused Molybdenum (Mo)-Silicon Carbide (Sic) Alloys, Andrew Mason, Larry W. Burggraf, Ryan A. Kemnitz, Nate Ellsworth

Faculty Publications

The integration of Silicon Carbide (SiC) nanoparticles into Laser Powder Bed Fusion (LB-PBF) Molybdenum (Mo) printing represents a significant advancement in refractory metal additive manufacturing. Our investigation examined how varying SiC nanoparticle sizes affect the microstructural and electrical properties of LB-PBF-printed molybdenum components while maintaining a 0.01 mass fraction of Mo. At an Linear Energy Densities (LED) of 1.8 J/mm, the addition of 80 nm SiC particles achieved a 46% reduction in porosity, while sheet resistance decreased by 6% at LED of 2.0 J/mm with 80 nm SiC particles. These performance improvements stem from several mechanisms: SiC particles serve as …

Additive Manufacturing Of Zinc-Based Biomaterials: Fabrication, Performance And Property Evaluation, S. Bandekian, M. Zolfaghari Baghbaderani, J. Drelich, S. Sharif, A.F. Ismail, H. R. Bakhsheshi-Rad

Michigan Tech Publications

The use of zinc and its alloys in additive manufacturing has become an important focus in interventional medical field. This is because zinc as an implant is naturally degradable, has solid mechanical characteristics, and is biocompatible. Biodegradable Zn-based metals made with additive manufacturing offer significant advantages in creating personalized medical implants. This review aims to provide an overview of different types of additive manufacturing methods and processes that can be used in the fabrication of Zn-based medical implants. It offers a comprehensive understanding of additive-manufactured Zn-based alloys for interventional surgeries. The study also summarizes the relationships between degradation properties, mechanical …

Mixed-Mode Fracture Analysis Of Additively Manufactured Periodic Orthotropic Functionally Graded Microcellular Materials, Behnam Shahbazian

Theses and Dissertations

The quest for safety, efficiency, and innovation in aerospace engineering demands a relentless focus on understanding how materials and structures behave under extreme and complicated loading conditions. Among the many challenges faced by engineers in this field, predicting and preventing structural failure stands out as both a fundamental necessity and a complex problem. Fracture mechanics, the science of how materials fail under stress, is a cornerstone of this effort. Whether it is the fuselage of an aircraft enduring cyclic loading or the lightweight components of a spacecraft resisting impact, the ability to accurately predict fracture behavior directly influences the reliability …

Advancing Additive Manufacturing For Extreme Environments Through Simulated Microgravity Printing, Laura Nayeli Molina

Open Access Theses & Dissertations

Additive Manufacturing (AM) holds significant potential for space exploration by enabling on-demand fabrication of components, reducing payload costs, and enhancing mission adaptability. However, microgravity introduces challenges in thermal regulation, material deposition, and structural integrity. This research explores the feasibility of submerged AM using neutral buoyancy in silicone oil to simulate microgravity conditions on Earth. A 3D printer was modified for submerged operation, with samples printed under three conditions: no oil (ambient air), submerged in oil, and simulated microgravity at varying temperatures. Mechanical tests, fracture surface analysis, and density measurements were performed to evaluate tensile strength, surface adhesion, and dimensional stability. …

Open Accessarticle Crystal Plasticity Modeling Of Dislocation Density Evolution In Cellular Dislocation Structures, Md Mahabubur Rohoman, Caizhi Zhou

Faculty Publications

The complex thermal cycles during the solidification process in metal additive manufacturing (AM) lead to the formation of high-density dislocation networks, organizing into submicron-scale cellular structures. These ultrafine structures are recognized as crucial for enhancing the mechanical properties of AM metals. In this study, we investigate the evolution of dislocation density within these cellular structures under plastic deformation and its impact on mechanical response using dislocation density-based crystal plasticity finite element (CPFE) modeling. The model incorporates the evolution of both statistically stored dislocation (SSD) and geometrically necessary dislocation (GND). Our simulations reveal that the yield and flow stresses of dislocation …

Revolutionizing Medical Implant Fabrication: Advances In Additive Manufacturing Of Biomedical Metals, Yuhua Li, Deyu Jiang, Rui Zhu, Chengliang Yang, Liqiang Wang, Lai Chang Zhang

Research outputs 2022 to 2026

Additive manufacturing has emerged as a transformative technology for producing biomedical metals and implants, offering the potential to revolutionize patient care and treatment outcomes. This article reviews the recent advances in additive manufacturing (AM) of biomedical metal implants, especially load-bearing biomedical alloys, biodegradable alloys, novel metals, and 4D printing, whose properties are systematically assessed to facilitate material selection for specific medical applications. The applications of the most cutting-edge artificial intelligence in AM and surface functional modification are also presented. This article also explores the application of AM in various medical specialties, such as orthopedics, dentistry, cardiology, and neurosurgery, demonstrating its …

Impact Of Delayed Artificial Aging On Tensile Properties And Microstructural Evolution Of Directed Energy Deposited Scalmalloy®, Rachel Boillat-Newport, Sriram Praneeth Isanaka, Frank Liou

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Scalmalloy® is a novel alloy designed to work with the unique processing inherent in additive manufacturing (AM). This alloy is post-processed using a single artificial aging treatment rather than a multistep heat treatment, as often noted in traditional manufacturing processes. Much of the literature details the impact of direct aging treatments around the temperature and time recommended by the manufacturer, 325 °C for 4 h; however, few studies have explored the impact of delayed artificial aging on the resulting mechanical and microstructural behavior. This study explored this missing link and determined the impact that the time between the fabrication of …