Significant Material Degradation Research Articles

Nano Material Innovation in Enhancing Corrosion Resistance of Offshore Structures

Offshore structures are constantly exposed to the corrosive marine environment, causing significant material degradation and potentially jeopardizing structural integrity. This research explores recent innovations in nanomaterial technology to improve the corrosion resistance of offshore structures. The main focus is given to the development of nano-composite coatings incorporating metal oxide nanoparticles and carbon nanotubes. An electrophoretic deposition method was used to apply the coatings on steel substrates, followed by characterization using scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). Results showed a significant improvement in corrosion resistance, with the nano-composite coatings exhibiting a reduction in corrosion rate of up to 85% compared to conventional coatings. In addition, these coatings exhibited superior adhesion and abrasion resistance in simulated extreme marine conditions. These findings highlight the great potential of nanomaterials in extending the service life and improving the reliability of offshore structures, with important implications for the oil and gas and offshore renewable energy industries.

Loss parameter identification of a welded ring core lamination of NO‐electrical steel

AbstractLamination packaging processes such as welding lead to a significant material degradation of non‐oriented (NO) electrical steel sheets. Increase in iron loss and decrease in permeability are the results of the deterioration. For an efficient modeling of a drive train, the accurate parameterization of the iron loss is of upmost importance. For this reason, the iron loss model is expanded to include the influences of welding procedure. Its influence can be classified into changes in the grain size diameter and residual stresses . In this study, a locally varying iron loss model for the simulation of effects of weld‐packaging on the electromagnetic properties of non‐oriented (NO) electrical steel sheets is presented. Packaging technologies such as interlocking, welding, clinching and gluing are typically utilized for the manufacturing of electric steel stacks of electric machines. Understanding the micro‐structural changes due to the macro‐structural degradation accruing to weld‐packaging helps in the accurate understanding of its influence on the performance and achievable range of the electric vehicle. Five (5) electric steel probes are annealed for the modeling of the local varying iron loss model at five different temperatures and electromagnetically measured to determine its magnetization and loss values. This will help in determining the grain size dependency of the different loss parameters. The annealed probes are measured under mechanical stresses showing also the residual stress dependency.

Experimental investigation on structural degradation and dynamic characterization of a cycle-pedestrian bridge

In the last century in Italy and, in particular, in Padua, the cycle-pedestrian bridges represented a connective system of the city that assumed a historical and strategic importance. Indeed, the city owes a significant part of its vitality to this type of works. However, some of these constructions are affected by significant material degradation phenomena and by structural issues related to the dynamic interaction between pedestrians and structure (a.k.a. “lock-in” effect). This paper will explore the case of a historic cycle-pedestrian bridge illustrating the construction methods, the realization phases and the maintenance works carried out. The adopted identification techniques are then illustrated with reference to the operational modal analysis (OMA) and the experimental investigations carried out in the static and dynamic field. The tests were conducted with particular reference to the possibilities of improving the dynamic behaviour of the bridge in terms of frequencies on the horizontal plane. The experimental results before and after the introduction of some constraints to the horizontal displacement are then illustrated, as well as the results of a series of non-destructive tests on some significant points of the structural elements. The work closes by examining possible future structural solutions and related monitoring systems.

Research on 18th-Century Building Structures in Terms of Static Scheme Changes.

The evaluation of the technical condition of historic buildings that have operated for several hundred years is a complicated issue. Even buildings that are in very poor condition must be checked and assessed in terms of their further repair, strengthening, or compliance with conditions that allow the facility to be safely operated. Most 18th-century buildings have not survived to this day retaining their original arrangements and structural elements. Renovations and repair work in the past were often carried out using materials of uncertain quality, with repair work of different qualities and without detailed analysis or methodology, based only on the experience of the former builders. In historic structures, the character of the work of individual structural elements has often changed due to significant material degradation, the poor quality of repair work, or the loss of adequate support. When load transfers change, internal forces are redistributed, and, as a result, the static scheme changes. This article presents an overview of identified defects affecting the change in static schemes in historical building structures built in the 18th century, using the example of a historic building with a large number of aforementioned defects. The process of assessing the technical condition of the facility is presented, in which non-destructive testing (NDT) methods were used. Detailed computational analyses were carried out for the wooden roof truss structure, which had partially lost its support.

Role of Copper Migration in Nanoscale Ageing of Supported CuO/Al2O3 in Redox Conditions: A Combined Multiscale X‐ray and Electron Microscopy Study

AbstractChemical Looping Combustion is a promising midterm solution to mitigate CO2 emission, by carrying out indirect fuel combustion and allowing inherent separation of CO2. During the CLC process, an oxygen carrying material is subjected to successive oxidation‐reduction reactions at high temperature which induce significant material degradation. CuO/Al2O3 based materials have been widely considered as promising oxygen carriers (OC). However, the oxygen carrier ageing mechanisms (active phase migration and interactions with the support, phase transitions) are not well understood. Herein, an in‐depth overview of the material evolution is achieved by employing a multi‐scale characterization approach. At the μm‐scale, copper migration within the alumina support has been observed using Scanning Transmission X‐ray Microscopy (STXM) and Scanning Electron Microscopy (SEM). The spatial distribution of the Cu−Al species provides information on copper mobility and the different phases interactions. A comprehensive mechanism is proposed concerning the redox behaviour of the CuO/Al2O3 system, relating the diffusion of the Cu‐species, the active phase‐support interactions, and the role of copper in the Al2O3 support phase transition to the temperature and the number of redox cycles. Understanding the ageing process of CuO/Al2O3 materials paves a way to design more stable oxygen‐carriers.

Moisture-induced changes in the mechanical behavior of 3D printed polymers

Commonly used 3D printing polymers, such as nylon and polylactic acid (PLA), can experience significant material degradation when exposed to moisture and high temperatures for extended periods. Understanding the extent of their degradation is critical to their long term use and can also inform end-of-life strategies, such as recycling or recovery. Specimens of nylon, carbon fiber-reinforced nylon composite, and PLA, three popular 3D printing materials, were 3D printed and immersed in deionized water at 21 °C and 70 °C to evaluate the effect of moisture and temperature on their mechanical and chemical properties. Water absorption rates were much higher at elevated temperatures and, at both temperatures investigated, the nylon-based materials absorbed up to 10 times more water than PLA. A direct relationship between moisture absorption and reduction in flexural properties was observed for the nylon-based specimens, with the flexural modulus of nylon decreasing by as much as 60% after 7 days of immersion. PLA, however, displayed negligible mechanical property degradation after immersion at 21 °C, but showed substantial physical degradation after being immersed in water at 70 °C for 7 days. Analogous changes in chemical structure and crystallinity were observed via Fourier transform infrared spectroscopy and differential scanning calorimetry.

Deep semi-supervised learning of dynamics for anomaly detection in laser powder bed fusion

Highly complex data streams from in-situ additive manufacturing (AM) monitoring systems are becoming increasingly prevalent, yet finding physically actionable patterns remains a key challenge. Recent AM literature utilising machine learning methods tend to make predictions about flaws or porosity without considering the dynamical nature of the process. This leads to increases in false detections as useful information about the signal is lost. This study takes a different approach and investigates learning a physical model of the laser powder bed fusion process dynamics. In addition, deep representation learning enables this to be achieved directly from high speed videos. This representation is combined with a predictive state space model which is learned in a semi-supervised manner, requiring only the optimal laser parameter to be characterised. The model, referred to as FlawNet, was exploited to measure offsets between predicted and observed states resulting in a highly robust metric, known as the dynamic signature. This feature also correlated strongly with a global material quality metric, namely porosity. The model achieved state-of-the-art results with a receiver operating characteristic (ROC) area under curve (AUC) of 0.999 when differentiating between optimal and unstable laser parameters. Furthermore, there was a demonstrated potential to detect changes in ultra-dense, 0.1% porosity, materials with an ROC AUC of 0.944, suggesting an ability to detect anomalous events prior to the onset of significant material degradation. The method has merit for the purposes of detecting out of process distributions, while maintaining data efficiency. Subsequently, the generality of the methodology would suggest the solution is applicable to different laser processing systems and can potentially be adapted to a number of different sensing modalities.

Fractional stress-dilatancy equation based on critical state lines with arbitrary form

The original state-dependent fractional stress-dilatancy (FSD) equation for soils is developed based on the critical state lines (CSLs) with linear form. However, experimental evidences showed that the CSLs of soil in the p ′ –q and e–p ′ planes could be both nonlinear as well due to significant material degradation. This note aims to propose a unified FSD equation for soils with arbitrary types of CSLs. Detailed derivations are provided. To validate the proposed FSD equation, a series of triaxial test results of ballast and rockfill are simulated.

Improved Performance of Bacterial Nanocellulose Conduits by the Introduction of Silk Fibroin Nanoparticles and Heparin for Small-Caliber Vascular Graft Applications.

Bacterial nanocellulose (BNC) is a promising material for small-caliber artificial blood vessels, although promoting its anticoagulant properties with more rapid endothelialization would improve long-term patency. Silk fibroin nanoparticles (SFNP) were introduced into the luminal wall surface of BNC conduits both with and without heparin (Hep) through pressurization followed by fixation. Hep was introduced in two ways: (1) embedded within SF nanoparticles to form SF-HepNPs for construction of the BNC-SF-HepNP conduit and (2) chemically grafted onto BNC and BNC-SFNP to form BNC-Hep and BNC-SFNP-Hep conduits. Fourier transform infrared spectroscopy confirmed the formation of SF-HepNPs, although they did not incorporate into the fibrillar network due to their large size. Hep was successfully grafted onto BNC and BNC-SFNP, verified by toluidine blue staining. The hemocompatibility and cytocompatibility of the five samples (BNC, BNC-SFNP, BNC-SF-HepNP, BNC-Hep, and BNC-SFNP-Hep conduits) were compared in vitro. The heparinized BNC-Hep and BNC-SFNP-Hep conduits improved the anticoagulant properties, and BNC-SFNP-Hep promoted human umbilical vein endothelial cell proliferation but also controlled excessive human arterial smooth muscle cell proliferation, assisting rapid endothelialization and improving lumen patency. No significant inflammatory reaction or material degradation was observed after subcutaneous implantation for 4 weeks. Autogenous tissues were observed around the conduits, and cells infiltrated into the edges of all samples, the BNC-SFNP conduit causing the deepest infiltration, providing an appropriate microenvironment for angiogenesis when used in small-caliber blood vessel applications. Few inflammatory cells were found around the BNC-Hep and BNC-SFNP-Hep conduits. Thus, the anticoagulant properties of the BNC-SFNP-Hep conduit and its stimulation of endothelialization suggest that it has great potential in clinical applications as a small-caliber artificial blood vessel.

Fabric Response to COVID-19 Ozone Sterilization

Limited availablilty of personal protective equipment (PPE) during the current COVID-19 pandemic has led to frequent unsafe reuse of personal protective clothing by healthcare workers and the public The application of ozone gas to sterilize PPEs for reuse has been proposed However, the potential damage inflicted on the fabrics has not been reported in the scientific literature A study was conducted to investigate the changes in fabric elasticity that may be associated with a two-hour exposure to ozone gas at a concentration of 17 ppm No significant material degradation was found The results suggest that use of ozone gas to sterilize PPEs for reuse against COVID-19 virus can be effective Copyright © 2020 Textile Bioengineering and Informatics Society

Impact of Steel Properties on the Corrosion of Expandable Rock Bolts

The selection of ground support for underground excavations typically focuses on matching a system to the anticipated ground conditions. In this context, the emphasis on materials selection involves picking a rock bolt type that meets a set of predefined capacity and deformation properties to manage the applied loads. Exposure of ground support to corrosive environments in underground hard rock mines can result in significant material degradation and loss of mechanical performance. This can have significant repercussions on the structural integrity of excavations in rock and potential falls of ground that may endanger the safety of workers and equipment. Consequently, there is a need to ensure that the selected rock bolt provides sufficient resistance to corrosion for the working life of the excavation. Current design practice is limited in selecting rock bolt types perceived as more resistant to corrosion, e.g., grouted versus friction rock stabilizer bolts. This investigation suggests, however, that there are significant variations in corrosion susceptibility of rock bolts that may otherwise display similar mechanical behavior. This has significant implications for mines operating in very corrosive environments.

Stress corrosion of Ni-based superalloys

The development of gas turbines to increase fuel efficiency is resulting in progressively higher operating temperatures in the under platform regions of the blades. These regions have traditionally been considered low risk areas. However, higher metal temperatures combined with stresses and the deposition of contaminants from the cooling air system may result in complex degradation mechanisms. Static stress corrosion testing has been conducted on C-ring specimens at a range of stresses in a hot corrosion environment. Cracks were observed in C-rings after exposure times greater than 100 h. Scanning electron microscopy (SEM) systems were used to image cracks and characterise deposits to improve understanding of the mechanism. Finite element analysis (FEA) has been used to model the stress intensity under test conditions. CMSX-4 specimens subject to static stresses combined with hot corrosion demonstrated significant material degradation (crack initiation and propagation) suggesting a combined stress corrosion mechanism resulting in cracking.

Investigating mechanical degradation due to fire exposure of aluminum alloy 5083 using crystal plasticity finite element method

Fire exposure causes significant mechanical property degradation of metallic materials. This paper investigates the influence of fire exposure on mechanical response of AA5083 through in situ neutron diffraction tensile tests and crystal plasticity finite element simulations. The Mechanical Threshold Stress (MTS) model is utilized, with a focus on the lattice strain response under tensile loading before and after exposure. A rigorous material parameter calibration procedure is proposed for this MTS model directly based on yield stress, plastic flow, hardening and rate dependency as a function of temperature, requiring only the macroscopic stress–strain curve. Material parameters of virgin material and fire-exposed material with full recrystallization are calibrated separately using this procedure. To initiate the investigation of mechanical degradation caused by fire exposure, a fire-exposed specimen with partial recrystallization is simulated by assigning material parameters and texture of recrystallized grains to selected grains in the virgin material according to the recrystallization fraction. Experimentally measured stress–strain curves and lattice strain evolution are employed to validate the simulations. For the first time, the local mechanical response of AA5083 is compared between in situ testing and finite element simulations, and the discrepancies of lattice strain evolution between virgin and fire-exposed material are discussed. Finally, the influence of fire-exposure on stress and lattice strain distribution is investigated to provide insight into mechanical property degradation.

Inhibitor or promoter: Insights on the corrosion evolution in a graphene protected surface

Corrosion is a fundamental electrochemical problem that results in significant material degradation and failure and affects the performance of many engineering components. Additionally, corrosion associated material losses often produce contamination of surrounding media. Discovery of two-dimensional (2D) materials has opened a venue for multiple attempts in designing atomically thin anticorrosive coatings for prevention and control of corrosion propagation in metals. It was shown that graphene, for example, when uniformly coating a metal surface can inhibit corrosion-initiated degradation of copper and nickel. Here we demonstrate that graphene plays an important role in oxidation-based corrosion processes. Non-uniform graphene coverage has an enormous effect on corrosion protection and may lead even to acceleration of corrosion. We demonstrate that when immersed in sodium chloride solution the exposed edges of graphene become the centers for iron oxidation and propagation. Beneficially, high mechanical stability of graphene substantially eliminates metal losses and leads to only oxidation-based mass increase. Our extensive characterization analysis indicates the reason for this is high concentrations of trapped chlorine atoms on the edge of detached from the surface graphene flake. Chlorine increases metal dissolution and results in significant oxidation sites along the graphene edge line.

Direct evaluation of influence of electron damage on the subcell performance in triple-junction solar cells using photoluminescence decays

Tandem solar cells are suited for space applications due to their high performance, but also have to be designed in such a way to minimize influence of degradation by the high energy particle flux in space. The analysis of the subcell performance is crucial to understand the device physics and achieve optimized designs of tandem solar cells. Here, the radiation-induced damage of inverted grown InGaP/GaAs/InGaAs triple-junction solar cells for various electron fluences are characterized using conventional current-voltage (I–V) measurements and time-resolved photoluminescence (PL). The conversion efficiencies of the entire device before and after damage are measured with I–V curves and compared with the efficiencies predicted from the time-resolved method. Using the time-resolved data the change in the carrier dynamics in the subcells can be discussed. Our optical method allows to predict the absolute electrical conversion efficiency of the device with an accuracy of better than 5%. While both InGaP and GaAs subcells suffered from significant material degradation, the performance loss of the total device can be completely ascribed to the damage in the GaAs subcell. This points out the importance of high internal electric fields at the operating point.

Long-term biological performance of injectable and degradable calcium phosphate cement

Enhancing degradation of poorly degrading injectable calcium phosphate (CaP) cements (CPCs) can be achieved by adding poly(lactic-co-glycolic acid) (PLGA) microparticles, generating porosity after polymer degradation. CPC-PLGA has proven to be biodegradable, although its long-term biological performance is still unknown. Optimization of injectability could be achieved via addition of carboxymethyl cellulose (CMC). Here, we evaluated the long-term in vivo performance of CPC-PLGA with or without the lubricant CMC in comparison to the devitalized bovine bone mineral (DBBM) predicate device Bio-Oss®. Rabbit femoral bone defects were injected with a CPC-formulation or filled with Bio-Oss® granules. Samples were retrieved at 6 and 26 weeks. Material degradation for Bio-Oss® was marginal, starting with 57% material remnants at implantation, 49% at 6 weeks, and 35% at 26 weeks, respectively. In contrast, CPC-PLGA and CPC-PLGA-CMC showed significant material degradation, starting with 100% material remnants at implantation, 56 and 78% at 6 weeks, and 8 and 21% at 26 weeks. Bone formation showed to be rapid for Bio-Oss®, with 24% at 6 weeks, and a similar value (27%) at 26 weeks. Both CPC-PLGA and CPC-PLGA-CMC showed a continuous temporal increase in bone formation, with 13 and 6% at 6 weeks, and 44 and 32% at 26 weeks. This study showed that CPC-PLGA induces favorable bone responses with >90% degradation and >40% new bone formation after an implantation period of 26 weeks.

The effects of acid erosion and remineralization on enamel and three different dental materials: FT-Raman spectroscopy and scanning electron microscopy analysis.

FT-Raman spectroscopy and scanning electron microscopy (SEM) were employed to test the hypothesis that the beverage consumption or mouthwash utilization would change the chemistry of dental materials and enamel inorganic content. Bovine enamel samples (n = 36) each received two cavity preparations (n = 72), each pair filled with one of three dental materials (R: nanofilled composite resin, GIC: glass-ionomer cement, RMGIC: resin-modified GIC). Furthermore, they were treated with three different solutions (S: artificial saliva, E: erosion/Pepsi Twist or EM: erosion + mouthwash/Colgate Plax). Reduction of carbonate content of enamel was greater in RE than RS (P < 0.01). Increment of carbonate was greater in GICEM than in GICE and GICS (P < 0.01; P < 0.001). Significant material degradation was found in RE, REM, GICE, and GICEM than in RS and GICS (P < 0.01; P < 0.001). SEM showed clear enamel demineralization after erosion. Material degradation was greater after E and EM than S. GIC and RMGIC materials had a positive effect against acid erosion in the adjacent enamel after remineralization with mouthwash. The beverage and mouthwash utilization would change R and GIC chemical properties. A professional should periodically monitor the glass-ionomer and resin restorations, as they degrade over time under erosive challenges and mouthwash utilization. Microsc. Res. Tech., 2016. © 2016 Wiley Periodicals, Inc. Microsc. Res. Tech. 79:646-656, 2016. © 2016 Wiley Periodicals, Inc.

Uniform polymer particles formulated with ultraviolet protective materials for the protection of UV sensitive molecules

Ultraviolet radiation can cause significant degradation of skin, pharmaceuticals, and other materials. Previous work has shown that encapsulation of ultraviolet sensitive molecules or proximity to protective molecules can provide protection from photo-oxidation. This study explores the protective capacity of uniform polymeric particles containing both ultraviolet sensitive materials (beta-carotene) and ultraviolet protective materials (ultraviolet absorbers oxybenzone, avobenzone, and octyl-4-methoxycinnamate and the antioxidant vitamin E). Oxybenzone and avobenzone provided the most protection when used singly and provided the best protection overall when paired with vitamin E, preserving over 80% of the beta-carotene after 60 min of exposure. Ultraviolet absorber combinations did not show a synergistic effect due to photosensitization.

Photodegradation and photostabilization of polymers, especially polystyrene: review.

Exposure to ultraviolet (UV) radiation may cause the significant degradation of many materials. UV radiation causes photooxidative degradation which results in breaking of the polymer chains, produces free radical and reduces the molecular weight, causing deterioration of mechanical properties and leading to useless materials, after an unpredictable time. Polystyrene (PS), one of the most important material in the modern plastic industry, has been used all over the world, due to its excellent physical properties and low-cost. When polystyrene is subjected to UV irradiation in the presence of air, it undergoes a rapid yellowing and a gradual embrittlement. The mechanism of PS photolysis in the solid state (film) depends on the mobility of free radicals in the polymer matrix and their bimolecular recombination. Free hydrogen radicals diffuse very easily through the polymer matrix and combine in pairs or abstract hydrogen atoms from polymer molecule. Phenyl radical has limited mobility. They may abstract hydrogen from the near surrounding or combine with a polymer radical or with hydrogen radicals. Almost all synthetic polymers require stabilization against adverse environmental effects. It is necessary to find a means to reduce or prevent damage induced by environmental components such as heat, light or oxygen. The photostabilization of polymers may be achieved in many ways. The following stabilizing systems have been developed, which depend on the action of stabilizer: (1) light screeners, (2) UV absorbers, (3) excited-state quenchers, (4) peroxide decomposers, and (5) free radical scavengers; of these, it is generally believed that excited-state quenchers, peroxide decomposers, and free radical scavengers are the most effective. Research into degradation and ageing of polymers is extremely intensive and new materials are being synthesized with a pre-programmed lifetime. New stabilizers are becoming commercially available although their modes of action are sometimes not thoroughly elucidated. They target the many possible ways of polymer degradation: thermolysis, thermooxidation, photolysis, photooxidation, radiolysis etc. With the goal to increase lifetime of a particular polymeric material, two aspects of degradation are of particular importance: Storage conditions, and Addition of appropriate stabilizers. A profound knowledge of degradation mechanisms is needed to achieve the goal.Electronic supplementary materialThe online version of this article (doi:10.1186/2193-1801-2-398) contains supplementary material, which is available to authorized users.

Evaluation of the use of bioethanol fuelled buses based on ambient air pollution screening and on-road measurements

Mitigation measures to reduce greenhouse gas emissions may have adverse effects on urban air quality and human exposure to harmful pollutants. The use of bioethanol fuelled vehicles is increasing worldwide and may create new undesired pollution effects. Different measurement campaigns were performed in a pilot study to contribute to the understanding of the consequences associated with the use of bioethanol blended fuel (E95) on a series of pollutants. Ambient screening measurements of NO2, O3, acetic acid, formaldehyde and acetaldehyde were performed at different urban locations, exposed and not exposed to the circulation of bioethanol buses. In addition, volatile organic compounds were measured at the exhaust pipe of a bioethanol fuelled bus, both under idling conditions (carbonyls; DNPH cartridge) and under on-road driving conditions applying online monitoring (PTR-TOF). Higher ambient acetaldehyde values were measured at locations exposed to bioethanol fuelled buses than at locations not exposed, and very high acetaldehyde and acetic acid values were measured from the exhaust pipe during driving conditions (acetaldehyde>150ppm; acetic acid≈20–30ppm) and modelled at close distance to the bioethanol bus. Human exposure to high concentration of acetaldehyde is expected, and it may involve a significantly increased chance in developing cancer. The high concentration of acetic acid will involve odour annoyance and significant material degradation or corrosion.