Potential Failure Mechanisms Research Articles

Off-the-shelf EBV-specific T-cell Immunotherapy for EBV-associated PTLD.

Off-the-shelf EBV-specific T-cell Immunotherapy for EBV-associated PTLD.

The Relevance of Biomechanical Analysis in Joint Replacements: A Review

Biomechanical analysis, numerical and experimental, has been extensively used for more than 3 decades to investigate the mechanical behaviour of bone and implant–bone structures in joint replacement. In this review article, a detailed overview of the state-of-the-art techniques used for the development and pre-clinical testing of orthopaedic implants has been presented, with special focus on the hip-joint and hip implants. The efficacies of biomechanical analysis in analysing failure mechanisms in joint replacement, its clinical relevance, challenges and limitations, and future directions have been highlighted. Finite element (FE) modelling and analysis have contributed immensely towards testing of clinical hypotheses and evaluation of implant designs. Over the last few decades, the size and sophistication of the FE models have increased considerably. A critical analysis of the currently available subject-specific FE modelling techniques has been presented including, development of computed tomography-scan-based FE models of bone and implant, assignment of heterogeneous bone material properties, loading and boundary conditions. The relationship between stress–strain analysis and implant failure needs careful interpretation for clinical relevance. Verification and validation of these models are essential for assessing the validity of the predicted results. The salient features of adaptive simulations including bone remodelling and tissue differentiation and its prominence in investigating potential failure mechanisms and implant design evaluations have been discussed. The key considerations for design and development of orthopaedic implants have been suggested. It is envisaged that the FE simulations would be more holistic in nature, incorporating the complexities and variabilities of the clinical problems.

Approach in improving reliability of DEMO

Reliability, Availability, Maintainability and Inspectability (RAMI) are key elements in the engineering development of the Demonstration Power Plant (DEMO) reactor. RAMI assessments play an important role during all design cycle phases by focusing on different aspects depending on the development stage. In fact, system functions, related requirements and deriving constraints are the main objective of RAMI assessment during pre-conceptual and conceptual design phases, when getting insight on the rationale of the plant. The identification of potential failure mechanisms, needs of design updates to remove such mechanisms or mitigate related consequences, become the main goal of analysis as design details increase during subsequent plant development phases. Some of the RAMI analyses performed in the 2019 for different DEMO systems and breeding blanket configurations are here presented. Results in terms of expected annual frequency of failures of components, of specific failure events and reliability/availability parameters are reported together with indications about criticality and suggestions for designers to improve reliability and availability of the systems and of the reactor. The study is based on Failure Mode and Effect Analysis (FMEA) and Reliability Block Diagram (RBD) analysis methodologies.

A modified stability analysis method of landfills dependent on gas pressure.

Excessive gas pressure (GP) in landfills is a potential triggering mechanism for slope failure, which is rarely considered in analytical models. This paper presents a modified analytical model for landfill stability dependent on GP. A two-layered GP model is established to describe the GP above and below the leachate level. The distribution of GP is then used to calculate the factor of safety (FS) using a modified wedge stability analysis method. It is found that the lack of consideration of the GP in landfill stability analysis leads to serious overestimation of the FS. In addition, the GP gas pressure within the landfill accelerates the critical interface of a multilayer liner system shifting from one to another. A new estimation criterion for FS is proposed. The proposed criterion can directly estimate the stability of the landfill by the field-tested pore pressure. Finally, the proposed method is applied to estimate the slope failure of Xiaping landfill in Shenzhen, and the results verify the proposed method.

Initial development of an RIA envelope for dispersed nuclear fuel

A reactivity insertion accident (RIA) is a design basis accident in which reactivity is rapidly injected as a result of a control rod ejection or blade drop scenario. The resultant power increase can result in fuel rod failure and subsequent release of radioactive material into the reactor’s primary system. For light water reactors, failure under RIAs is typically a result of fuel melt, pellet-cladding interaction, or rod over-pressurization. Fuel melt occurs when the fuel system is unable to transport heat out of the fuel system. Pellet-cladding interaction occurs when an aggressive fuel pellet expansion pushes on an embrittled cladding beyond its strain limit. Rod over-pressurization occurs when a fuel rod exceeds the critical heat flux and departs from nucleate boiling, causing the rod internal pressure to rapidly increase, exceeding the systems pressure, and balloon until it bursts. To prevent failure, regulators have developed safety requirements that limit the injected enthalpy based on the state of the fuel system. However, dispersed fuel could enable the removal or relaxation of regulator-imposed safety criteria. Dispersed fuel embeds fuel particles in a highly conductive metal. Dispersed particles can have a particle radius of 1 µm to greater than 100 µm. Traditional fuel systems are plagued by poor thermal conductivity, especially at higher burnups, thus reducing the ability of the fuel system to respond to an RIA. However, dispersed fuel could improve the ability of the fuel system to transport injected energy away from the fissile material and into the coolant more efficiently. Additionally, dispersing the fuel particles mitigates hard contact that typically occurs in the traditional zirconium-uranium dioxide fuel system, thus removing pellet-cladding mechanical interaction as a potential failure mechanism. This paper evaluates fuel particles dispersed in a metal matrix using the BISON fuel performance code to develop an initial failure threshold based on melt temperature of the fuel particle and/or cladding material as a function of fission density for beginning-of-life and end-of-life conditions. BISON results show that (1) reducing the size of the particles allows fission density to increase as a function of time, (2) particle-to-particle proximity must be considered to evaluate the limiting conditions, and (3) improving the fuel particle thermal conductivity improves thermal performance.

A Triboelectric Nanogenerator Consisting of Polytetrafluoroethylene (PTFE) Pellet for Self‐Powered Detection of Mechanical Faults and Inclination in Dynamic Mechanics

A reliable mechanical fixation plays a pivotal role in guaranteeing normal operation for large‐scale equipment. The detection of screw loosening or breakage as well as susceptor tilting is of significance in mechanical dynamics, especially in those with large vibration amplitude during operation. Herein, a novel triboelectric nanogenerator (TENG) is reported that consists of polytetrafluoroethylene (PTFE) pellets and a single electrode installed on the bottom of a cylinder. The basic electricity‐generating principle is the coupling of triboelectrification and electrostatic induction between the pellets and electrode. The dependence of the output voltage on the diameter/number of pellets is explored deeply, suggesting, by enlarging the diameter or increasing the number of pellets, the output voltage can be improved. By integrating the fabricated TENG on a vibration table, the capacity of self‐powered detection of screw loosening or breakage can be achieved based on TENGs, which can predict a potential mechanical failure in real time. More importantly, the TENG can be tuned to output eight‐channel data simultaneously, which enables recognizing the tiny inclining signs of equipment. This work provides a new method for the design and manufacture of intelligent sensors that can be used for failure inspection and diagnosis in future intelligent mechanics.

Slope failure mechanism assessment based on regional geological information in layered rocks

Regional geological mapping commonly records the dip and dip direction of dominant layering such as bedding and foliation but not the orientation of joints. It is common for joints to form an orthogonal pattern relative to the dominant layering. In that case, the three-dimensional possibilities can be extrapolated allowing inferences to be made about kinematically feasible structural failure mechanisms. The resulting planar sliding, wedge sliding and toppling kinematic assessment can be integrated on a stereograph. The analysis of extrapolated joint sets can be conducted in the initial desk-top stage of a site investigation. The method is demonstrated using field data from Devonian sandstones in eastern Victoria, Australia. The sandstones have joint sets and partings on axial cleavage orthogonal to bedding. The range of potential structural failure mechanisms is extrapolated from the known bedding orientation and slope face direction.

Failure analysis and revamping methods for loading threaded joints of raiseboring machine

The process of raise boring (or back reaming) has been successfully employed for vertical mine development. The technology has successfully evolved from early small borehole diameter less than 2m to large diameter greater than 8m without incident. However, in our developed raise boring machines, the threaded joints connecting reamers and drill rods suffered several fracture accidents during reaming in different geological and geotechnical conditions. Under this background, it is undoubtedly of great engineering value to explore the failure mechanisms and put forward systematic quality control and risk control measures.The fractured threaded joints were visually examined on-site, and then examined in the laboratory using fractographic and metallographic examination, mechanical testing and chemical composition analysis. Firstly, the end faces of threaded joints could not to be installed to fit the end faces of spindles due to over-specified tolerances or insufficient preload. Secondly, it was found that the manganese (Mn) contents in material samples are higher than the national standards values. Thirdly, the heat treatment of water-quenching of workpieces perhaps caused a certain degree of residual stresses. Clearly this systematic inspection suggested we should take overall improvements to eliminate the potential failure mechanisms. After check and measurement of product and process performance, the cause-and-effect relationships undoubtedly were complex and multifaceted. Therefore, the component was redesigned using revamping methods including material compositions upgrade, fitting tolerances control, optimization of heat treatment process. Moreover, a systems approach and the institution of quality management system including increasing the preload, adding anti-dropping device and executing a Plan-Do-Check-Act cycle were implemented. Through this investigation and recommendations, the device has been in operation for more than two years without any problems.

Detection of Sealant Delamination in Integrated Circuit Package Using Nondestructive Evaluation

Abstract This paper presents the development of a nondestructive evaluation method for delamination detection in integrated circuit (IC) packages. The developed method allows for quantitative detection of sealant delamination between integrated heat sink (IHS) and substrate, which is considered a potential failure mechanism in IC packages. The proposed method is expected to overcome the destructive nature of most existing techniques, while maintaining low cost of development. The reported development consists of the following processes: First, flash thermographic analysis is investigated and shown to be incapable of detecting a realistic sealant delamination. Then, ultrasonic guided waves (UGWs) are used as the chosen interrogation method due to their sensitivity to small-size damage and structural thickness variations. The complexity of the received ultrasonic signals caused by the geometric heterogeneity is resolved using a time–frequency signal processing technique. The extracted ultrasonic information, including time-of-arrival (TOA) and amplitude of wave modes received from different sensing paths under multiple excitation frequencies, is then used to construct a feature space. A multivariate Gaussian model is implemented as an information fusion and delamination detection tool, which investigates the distribution of feature space including correlations between features. Results from the developed model are compared with two existing evaluation methods, including pullout force measurement and a delamination metric. The developed method is seen to possess a similar level of accuracy with a nondestructive nature.

Modeling the stress-strain state of of a municipal solid waste landfill

Introduction. The process of municipal solid waste (further MSW) generation is inextricably linked with the life of humanity. Every day each person generates some, a small amount of garbage. As a result millions of tons of MSW are generated daily in the world which are unsuitable for further use and require disposal. There are various ways of handling MSW including their treatment, recycling and disposal. In Russian Federation the vast majority of MSW are currently located on the specially equipped facilities –– waste landfills. To date the most common waste management strategy remains their placement in a landfill. Waste landfills are arrays of stored waste and are special engineering structures designed for the safe isolation of their contents from the environment. Landfill includes gas exhaust and leachate drainage systems, liner and cover systems. The main component of this structure is waste itself. Mechanical stability of landfills should be provided at all stages of waste storage as well as after it complete filling to designed capacity and at post-closure stage. As the result of deformation of unstable waste, all landfill systems can be destroyed up to the collapse of garbage array leading to the significant environmental and other consequences. One of the most common problems leading to the various incidents at landfills is an incorrect assessment of their stability. MSW landfill is a complex multiphase system in which various interacting processes occur simultaneously. The main factor in the calculation and design of landfills is the forecast of their settlements. Studies by many authors have established that biological decomposition has a significant impact on the properties of MSW after which the waste is considered as the landfill soil with a particle size of up to 20 mm. Materials and methods. The paper presents the methodology and the results of numerical modeling of stress-strain state of the designed object “Waste Landfill”. The facility is an array of municipal solid waste of 38 meters high. Waste is stacked in the layers of 1.75 m thick. Each waste layer is covered by the loam cover of 0.25 m thick. Stress-strain state of municipal solid waste including biological creep was modelled using well-known “Soft-Soil-Creep model” (SSC-model). Results. The results of numerical simulation of stress-strain state of the waste pile at all stages of the filling and in the post-closure period are presented. An assessment of the increase in the capacity of the landfill due to the compaction and biological creep has been performed. Stability analysis of the landfill and potential failure mechanisms at different stages of filling and operation are presented. Conclusions. Numerical modeling of stress-strain state of the MSW array using the “Soft-Soil-Creep model” allows to analyze the stability of the waste pile at any stage of landfill filling and evaluate the increase in landfill capacity due to the waste settlement taking into account the mechanical creep and biocompression during layer-by-layer filling.

Seismic bearing capacity of strip footings placed near c-φ soil slopes

Seismic bearing capacity of strip footings placed near c-φ soil slopes is investigated in this work using finite element limit analysis combined with an adaptive remeshing procedure. In the analysis, the so-called pseudo-static approach is employed to quantitatively describe the seismic effects. Based on the method, the upper and lower bounds of the normalized seismic bearing capacity factor p/γB are calculated and summarized in design tables/charts for practitioner's use. Parametric studies are performed to illustrate the variation of the normalized seismic bearing capacity factor p/γB with respect to all of the problem variables defined in section 2. In addition, graphical results from upper bound analyses are also provided to display the potential failure mechanisms of the footing-slope bearing system under seismic conditions.

New insights into the potential mechanisms of spermatogenic failure in patients with idiopathic azoospermia.

Idiopathic azoospermia (IA) refers to azoospermia without a clear aetiology. Due to the unclear aetiology and pathological mechanism of IA, there is no effective treatment for IA. The development of assisted reproductive and microsperm extraction technologies has brought hope to patients with IA with fertility problems. However, there are still many patients with IA whose testes lack healthy sperm, causing infertility. Therefore, it is key to identify how testicular spermatogenic failure can be reversed to promote spermatogenesis in patients with IA to resolve fertility problems; these goals are a great challenge in reproductive medicine. The underlying genetic factors seem to be important pathological factors of IA. Understanding the role of genetic factors in the pathological mechanism of spermatogenic failure in patients with IA is of great value for future studies and treatments and is also an important reference for the reproductive health of males and their offspring. A method combining sequencing technology and bioinformatics analysis is an important means to understand the genetic pathological mechanisms. We used bioinformatics analysis to study the public human IA dataset. We found that the pathogenic mechanism of IA may be related to abnormal ciliary structure and function and disrupted RNA metabolism in spermatogenic cells. Disrupted m6A regulation of spermatogenesis may be an important pathological mechanism of IA and warrants attention. Finally, we screened for key genes and potential therapeutic drugs to determine future research directions.

Fundamentals, impedance, and performance of solid-state Li-metal microbatteries

The authors report novel results toward optimizing the electrochemical performance of high vacuum deposited lithium-based all solid-state thin film microbatteries. This study investigated hermetic encapsulation, interfacial lithium formation processes, and the role of Li-blocking and Li-nucleating layers for improved Li-metal plating on copper anodes. Photoresist was found to be an effective temporary encapsulation material, where prior to cycling, well-encapsulated Li-metal full cells yielded a total resistance reduction of nearly two orders of magnitude (282 Ω cm2) and a total capacitance increase of roughly an order of magnitude (1.35 × 10−10 F/cm2) compared with nonencapsulated Li-metal full cells. To accelerate potential failure mechanisms, high stress applied currents were used during the electrochemical formation processes. Initial cycles caused high resistance voids to form at the lithium phosphorous oxy-nitride (LiPON)/copper interface of well-encapsulated half cells. Well-encapsulated full cells, in contrast, resulted in a very low resistance composite Li-Cu anode, with a void-free LiPON interface, two orders of magnitude lower resistance (0.43 Ω cm2) and three orders of magnitude higher capacitance (6.56 × 10−8 F/cm2) compared with the half cell. Cycling performance was investigated using both Li-blocking nickel-copper and Li-nucleating gold-copper metal bilayer anodes in 100-μm diameter half cells. Nickel-copper anodes facilitated higher discharge capacity (>9 μAh/cm2) at high charge rates (>12.7 mA/cm2) due to uniform Li-metal plating on blocking electrodes. Low charge rates (<0.7 mA/cm2) displayed low discharge capacity and immediate corrosion of the cell. Gold-copper anodes displayed the opposite effect, showing sustainable cycling, minimal cell corrosion, and a discharge capacity of >6 μAh/cm2 at lower charge rates (∼0.025 mA/cm2). The work expands on fundamentals in understanding the role of the metallic anode encapsulation, interface formation, and charge storage mechanisms with respect to sustainable cell impedance for applications such as solid-state lithium metal microbatteries and microelectrochemical resistance-modulated memory devices.

Higanykorrózió jelenléte a vegyiparban

A vegyipar hazánkban és világszerte egyaránt a kiemelt fontosságú iparágak közé tartozik. Éppen ezért fontos, hogy mindig naprakészen, a legfrissebb információk alapján hozzunk döntéseket a berendezések tervezése, üzemeltetése és karbantartása során. Elengedhetetlen, hogy tisztában legyünk a lehetséges kockázatokkal és meghibásodási mechanizmusokkal. A higany által jelentett kockázatot mindenképp figyelembe kell venni, különösen a vegyiparban, ahol akár egy apró tömörtelenség is katasztrófához vezethet. A cikkben ismertetjük a higany jelentette veszélyeket a vegyiparban, illetve kísérletekkel szemléltetjük, hogy a higany milyen formában és mértékben tudja károsítani az egyes veszélynek kitett berendezések alapanyagait. Végezetül egy hőtani számítás kerül bemutatásra, amely segítségével egy közelítő érték adható meg arra, hogy egy alacsony hőmérsékleten működő hőcserélő leállítását követően a jelen lévő higany mennyi idő elteltével fog problémát jelenteni.

Vulnerability assessment of bridges subjected to extreme cyclonic events

Over the past few years, Queensland in Australia has suffered from a number of severe tropical cyclones, the most recent one being Marcia, which took place in 2015. Damage bill of Cyclone Marcia exceeded $50 million which included the cost of repairing a number of damaged road structures. Failure of road structures such as bridges isolates communities from accessing essential services and commodities. This necessitated a methodical approach to evaluate the failure of bridges to improve their resilience and provide base knowledge for developing emergency maintenance response. Although there are several methods available to evaluate the vulnerability of bridges, fault tree analysis (FTA) was selected in this study by considering its positive attributes over the other methods. FTA was used to estimate the probabilities of failure of main components (superstructure and substructure) and elements of timber and concrete bridges. Secondary data (level 1 and level 2 bridge inspection reports from Transport Main Roads in Rockhampton) before and after the Cyclone Marcia were used in conjunction with expert advice to construct fault trees for both timber and concrete bridges. Potential failure mechanisms were observed, and the degree of susceptibility of main components of timber and concrete bridges to cyclonic events was evaluated. This research was based on selected bridges under specific cyclone in one region, which is a limitation of the study. Few other case study bridges subjected to cyclonic events can be used to strengthen the understanding of the complete dynamics of the bridge failure under these extreme events.

Numerical Study on the Collapse of the Morandi Bridge

An innovative discontinuum-based micromodeling approach, the Applied Element Method, is used in this work to investigate explicitly potential failure mechanisms that might have contributed to the collapse of the Morandi Bridge in Genoa, Italy, which occurred on August 14, 2018. While, consistently with the findings presented in a previous contribution by the same authors, the initial trigger of the collapse mechanism was assumed as the release of one of the stays, this study investigates, through a sensitivity study, the impact that several parameters and epistemic uncertainties, including reduction of cables’ cross section (potentially induced by corrosion) and various possible configurations of both passive and active reinforcements in the main deck, have on the predicted failure mode. Then, to indicate the structural elements and details in which a potential presence of corrosion should be more carefully explored, the observed debris distribution is compared with its numerical counterparts.

Dobutamine stress testing in patients with Fontan circulation augmented by biomechanical modeling.

Understanding (patho)physiological phenomena and mechanisms of failure in patients with Fontan circulation—a surgically established circulation for patients born with a functionally single ventricle—remains challenging due to the complex hemodynamics and high inter-patient variations in anatomy and function. In this work, we present a biomechanical model of the heart and circulation to augment the diagnostic evaluation of Fontan patients with early-stage heart failure. The proposed framework employs a reduced-order model of heart coupled with a simplified circulation including venous return, creating a closed-loop system. We deploy this framework to augment the information from data obtained during combined cardiac catheterization and magnetic resonance exams (XMR), performed at rest and during dobutamine stress in 9 children with Fontan circulation and 2 biventricular controls. We demonstrate that our modeling framework enables patient-specific investigation of myocardial stiffness, contractility at rest, contractile reserve during stress and changes in vascular resistance. Hereby, the model allows to identify key factors underlying the pathophysiological response to stress in these patients. In addition, the rapid personalization of the model to patient data and fast simulation of cardiac cycles make our framework directly applicable in a clinical workflow. We conclude that the proposed modeling framework is a valuable addition to the current clinical diagnostic XMR exam that helps to explain patient-specific stress hemodynamics and can identify potential mechanisms of failure in patients with Fontan circulation.

Failure analysis of heat exchanger tubes of Ni-200 alloy in a titanium tetrachloride vaporizer

This paper presents a metallurgical analysis of damage occurred in heat exchanger tubes of nickel alloy (Ni-200) used for vaporizing titanium tetrachloride (TiCl4). The tubes had undergone a dual environmental condition with heating water steam inside and liquidous TiCl4 outside. Several investigations were conducted to identify the potential failure mechanism. Such investigations included visual examination and microstructural characterization via optical microscopy and scanning electron microscopy (SEM) equipped with energy dispersive X-ray analyzer (EDX). Investigations extended also to the mechanical characterization of the tube materials through hardness and tensile testing. The results of hardness and tensile tests showed that the bent tubes had sustained strain hardening, which can act as potential sites of corrosion. SEM and EDX investigations revealed that the damaged sections had corrosion product layers rich in sulfur. However, Cavitation corrosion was found to be the main corrosion form shown in the damaged tubes. It is recommended to keep TiCl4 liquid at high pressure values so that the vapor bubbles are not formed. Also, the sulfur content in the TiCl4 must be kept at very low levels.

How Can a Cutting-Edge Gallium Nitride High-Electron-Mobility Transistor Encounter Catastrophic Failure Within the Acceptable Temperature Range?

Commercial gallium nitride (GaN) high-electron-mobility transistors used for power electronics applications show superior performance compared to silicon (Si)-based transistors. Combined with an increased radiation hardening properties, they are key candidates for high-performance power systems in a harsh environment, such as space. However, for this purpose, it is key to know the potential failure mechanisms (FMs) of the devices in depth. Here, we demonstrate how the repeated thermomechanical stress in a power cycling (PC) test within specified operating conditions destroys the GaN device. Based on leakage current localization analysis, we identify an FM with a yet unknown root cause. Utilizing emission microscopy, focused ion beam cutting, and scanning electron microscope techniques, it is revealed that multilayer cracks of a GaN die are triggered by a commercial leading package structure, which shows excellent capability under frequent thermomechanical stress. Through multiphysics simulations, it is shown that the structural factors that lie behind the strong performing component properties inside the package ultimately are directly related to the failure pattern. This article is accompanied by a video demonstrating dynamic thermal distribution difference between thermography measured in a practical experiment and a multiphysics simulation result during a single PC of a PC test. This article is accompanied by a supplementary figures file demonstrating test environment, preparation process of specimens, and reverse engineering results for the simulation model.

Yield and Electrical Functionality of the Glass-Laminated Conductive Wires and Connectors

Large-area electronics is becoming an embedded part of structural elements such as automotive and architectural glasses. In this paper, the effect of glass-lamination-based fabrication process on the electrical performance and production throughput yield (TPY) of printed conductive wires and surface-mounted (SMD) connectors on polyethylene terephthalate (PET) carrier film was investigated by measuring their electrical conductivity after lamination. Based on the experiments, lamination decreases the production yield of conductive wires and connectors due to broken wires or dislocated connectors, especially if they are located close to the corners of the laminate. On the other hand, lamination was observed to improve the electrical conductivity of wires. In addition, some potential failure mechanisms are discussed.