Mechanical Stress Conditions Research Articles

Increased subtalar rotational motion in patients with symptomatic ankle instability under load and stress conditions.

Differentiating subtalar and ankle instability in the clinical setting is challenging. This study aims to analyze the rotational laxity of the subtalar joint bilaterally in patients with asymptomatic and symptomatic ankle instability under simulated load and stress-induced position of the subtalar joint. A case-control study was conducted using an adjustable load device (ALD). Patients with chronic ankle instability and healthy volunteers were included. Each subject underwent a CT scan under mechanical stress and simulated weight-bearing conditions, maintaining maximum eversion and inversion hindfoot positions. The images were obtained in a single model, allowing calculations of the motion vector as well as the helical axis. The helical axis was defined by a rotation angle and a translation distance. A total of 72 feet were included in the study. Thirty-one patients with unilateral symptoms and five healthy controls were selected, defining two groups: symptomatic (n = 31) and asymptomatic (n = 41). An absolute difference of 4.6º (95%CI 2-11.1) rotation angle was found on the helical axis of the symptomatic vs. asymptomatic group (p = 0.001). No significant differences were detected in the translation distance (n.s.) between the groups. Additionally, a significant positive correlation was found between the rotation angle and translation distance through the helical axis in the asymptomatic group (r = 0.397, p = 0.027). Patients with chronic ankle instability suspected of having subtalar joint instability showed a wider subtalar range of laxity in terms of rotation about the helical axis. Furthermore, differences in kinematics between symptomatic and asymptomatic hindfeet was demonstrated when both feet were compared. III.

Corrosion of Reinforced A630-420H Steel in Direct Contact with NaCl Solution.

The deterioration of reinforced concrete structures in marine environments presents multiple problems due to the premature degradation of reinforced steel. This work aimed to study the corrosion of reinforced A630-420H steel when exposed to a 0.5 M NaCl solution. Although this carbon steel is the most widely used material for reinforced concrete structures in Chile, there is limited research on its resistance to corrosion when in contact with saline solutions. The electrochemical reactions and their roles in the corrosion rate were studied using linear sweep voltammetry, weight loss, scanning electron microscopy, and X-ray diffraction techniques. This analysis is unique as it used the superposition model based on mixed potential theory to determine the electrochemical and corrosion parameters. The outcomes of this study show that A630-420H steel has a higher corrosion rate than those of the other commercial carbon steels studied. This fact can be attributed to the competition between the cathodic oxygen reduction reaction and hydrogen evolution reaction, which also depends on the environmental conditions, exposure time, stabilization of the corrosion products layer, and presence of chloride ions. Additionally, the results under mechanical stress conditions show a brittle fracture of the corrosion product oriented longitudinally in the direction of the bend section, where the presence of pores and cracks were also observed. The corrosion products after corrosion were mainly composed of magnetite and lepidocrocite oxide phases, which is in concordance with the electrochemical results.

Comparison of multilayer and single-layer coronary plaque models on stress/strain calculations based on optical coherence tomography images.

Mechanical stress and strain conditions are closely related to atherosclerotic plaque progression and rupture and have been under intensive investigations in recent years. It is well known that arteries have a three-layer structure: intima, media and adventitia. However, in vivo image-based multilayer plaque models are not available in the current literature due to lack of multilayer image segmentation data. A multilayer segmentation and repairing technique was introduced to segment coronary plaque optical coherence tomography (OCT) image to obtain its three-layer vessel structure. A total of 200 OCT slices from 20 patients (13 male; 7 female) were used to construct multilayer and single-layer 3D thin-slice models to calculate plaque stress and strain and compare model differences. Our results indicated that the average maximum plaque stress values of 20 patients from multilayer and single-layer models were 385.13 ± 110.09kPa and 270.91 ± 95.86kPa, respectively. The relative difference was 42.2%, with single-layer stress serving as the base value. The average mean plaque stress values from multilayer and single-layer models were 129.59 ± 32.77kPa and 93.27 ± 18.20kPa, respectively, with a relative difference of 38.9%. The maximum and mean plaque strain values obtained from the multilayer models were 11.6% and 19.0% higher than those from the single-layer models. Similarly, the maximum and mean cap strains showed increases of 9.6% and 12.9% over those from the single-layer models. These findings suggest that use of multilayer models could improve plaque stress and strain calculation accuracy and may have large impact on plaque progression and vulnerability investigation and potential clinical applications. Further large-scale studies are needed to validate our findings.

Stability studies for the identification of critical process parameters for a pharmaceutical production of the Orf virus

A promising new vaccine platform is based on the Orf virus, a viral vector of the genus Parapoxvirus, which is currently being tested in phase I clinical trials. The application as a vaccine platform mandates a well-characterised, robust, and efficient production process. To identify critical process parameters in the production process affecting the virus’ infectivity, the Orf virus was subjected to forced degradation studies, including thermal, pH, chemical, and mechanical stress conditions. The tests indicated a robust virus infectivity within a pH range of 5–7.4 and in the presence of the tested buffering substances (TRIS, HEPES, PBS). The ionic strength up to 0.5 M had no influence on the Orf virus’ infectivity stability for NaCl and MgCl2, while NH4Cl destabilized significantly. Furthermore, short-term thermal stress of 2d up to 37 °C and repeated freeze-thaw cycles (20cycles) did not affect the virus’ infectivity. The addition of recombinant human serum albumin was found to reduce virus inactivation. Last, the Orf virus showed a low shear sensitivity induced by peristaltic pumps and mixing, but was sensitive to ultrasonication. The isoelectric point of the applied Orf virus genotype D1707-V was determined at pH3.5. The broad picture of the Orf virus’ infectivity stability against environmental parameters is an important contribution for the identification of critical process parameters for the production process, and supports the development of a stable pharmaceutical formulation. The work is specifically relevant for enveloped (large DNA) viruses, like the Orf virus and like most vectored vaccine approaches.

CARPEL TUNNEL SYNDROME: AN OCCUPATIONAL DISEASE

Carpal tunnel syndrome (CTS) is a common problem in certain occupations. Many etiological factors have been suggested for CTS which include repetitive, prolonged hand and intensive activities, forceful exertions, awkward or static posture, vibration, temperature extremes and localised mechanical stress. The references were taken from Grays` anatomy and B.D.Chourasiya which we are supplemented by systematic searches on Google and Pubmed with keywords, occupation incidence, carpal tunnel syndrome, repetitive activities, several specic occupations including cutting metal, dealing with meat and sh processing, slaughter house, manufacturing and construction workers, musicians, repetitive industrial work groups, frozen, food factory employees, grocery store workers, footwear factory workers, etc. In summary, this study concludes that certain occupations involving wrist activities increases the risk of carpal tunnel syndrome. It is recommended that prolonged exposure to highly repetitive action of wrist (i.e. exion and extension) movements should be avoided.

Disulfide bond reduction and exchange in C4 domain of von Willebrand factor undermines platelet binding

BackgroundThe von Willebrand factor (VWF) is a key player in regulating hemostasis through adhesion of platelets to sites of vascular injury. It is a large, multi-domain, mechano-sensitive protein that is stabilized by a net of disulfide bridges. Binding to platelet integrin is achieved by the VWF-C4 domain, which exhibits a fixed fold, even under conditions of severe mechanical stress, but only if critical internal disulfide bonds are closed. ObjectiveTo determine the oxidation state of disulfide bridges in the C4 domain of VWF and implications for VWF’s platelet binding function. MethodsWe combined classical molecular dynamics and quantum mechanical simulations, mass spectrometry, site-directed mutagenesis, and platelet binding assays. ResultsWe show that 2 disulfide bonds in the VWF-C4 domain, namely the 2 major force-bearing ones, are partially reduced in human blood. Reduction leads to pronounced conformational changes within C4 that considerably affect the accessibility of the integrin-binding motif, and thereby impair integrin-mediated platelet binding. We also reveal that reduced species in the C4 domain undergo specific thiol/disulfide exchanges with the remaining disulfide bridges, in a process in which mechanical force may increase the proximity of specific reactant cysteines, further trapping C4 in a state of low integrin-binding propensity. We identify a multitude of redox states in all 6 VWF-C domains, suggesting disulfide bond reduction and swapping to be a general theme. ConclusionsOur data suggests a mechanism in which disulfide bonds dynamically swap cysteine partners and control the interaction of VWF with integrin and potentially other partners, thereby critically influencing its hemostatic function.

Triaxial Cell for Determining Shielded Cable Transfer Impedance During Environmental Stress

Transfer impedance is a main characteristic to describe the shielding performance of shielded cables at least up to 1 GHz. Traditionally, methods, such as line-injection and triaxial cell, have been used to characterize it at ambient laboratory conditions. While the ambient laboratory conditions might represent appropriate environmental conditions for some industries, in others, such as automotive, they are only a small subset of the real conditions. Thus, there is a need to characterize the transfer impedance over different environmental conditions. In this article, the authors present and verify a new triaxial cell design that is aimed to provide reliable measurements during high thermal and mechanical stresses. First, the cell performance is compared with a commercial cell at laboratory ambient conditions. Then, measurements are performed with the new cell at highly accelerated life testing conditions. Under these high thermal and mechanical stress conditions, the cell performance is verified, and results on typical shielded cable performance under the same conditions are given.

A multi-targeting bionanomatrix coating to reduce capsular contracture development on silicone implants

BackgroundCapsular contracture is a critical complication of silicone implantation caused by fibrotic tissue formation from excessive foreign body responses. Various approaches have been applied, but targeting the mechanisms of capsule formation has not been completely solved. Myofibroblast differentiation through the transforming growth factor beta (TGF-β)/p-SMADs signaling is one of the key factors for capsular contracture development. In addition, biofilm formation on implants may result chronic inflammation promoting capsular fibrosis formation with subsequent contraction. To date, there have been no approaches targeting multi-facted mechanisms of capsular contracture development.MethodsIn this study, we developed a multi-targeting nitric oxide (NO) releasing bionanomatrix coating to reduce capsular contracture formation by targeting myofibroblast differentiation, inflammatory responses, and infections. First, we characterized the bionanomatrix coating on silicon implants by conducting rheology test, scanning electron microcsopy analysis, nanoindentation analysis, and NO release kinetics evaluation. In addition, differentiated monocyte adhesion and S. epidermidis biofilm formation on bionanomatrix coated silicone implants were evaluated in vitro. Bionanomatrix coated silicone and uncoated silicone groups were subcutaneously implanted into a mouse model for evaluation of capsular contracture development for a month. Fibrosis formation, capsule thickness, TGF-β/SMAD 2/3 signaling cascade, NO production, and inflammatory cytokine production were evaluated using histology, immunofluorescent imaging analysis, and gene and protein expression assays.ResultsThe bionanomatrix coating maintained a uniform and smooth surface on the silicone even after mechanical stress conditions. In addition, the bionanomatrix coating showed sustained NO release for at least one month and reduction of differentiated monocyte adhesion and S. epidermidis biofilm formation on the silicone implants in vitro. In in vivo implantation studies, the bionanomatrix coated groups demonstrated significant reduction of capsule thickness surrounding the implants. This result was due to a decrease of myofibroblast differentiation and fibrous extracellular matrix production through inhibition of the TGF-β/p-SMADs signaling. Also, the bionanomatrix coated groups reduced gene expression of M1 macrophage markers and promoted M2 macrophage markers which indicated the bionanomatrix could reduce inflammation but promote healing process.ConclusionsIn conclusion, the bionanomatrix coating significantly reduced capsular contracture formation and promoted healing process on silicone implants by reducing myfibroblast differentiation, fibrotic tissue formation, and inflammation.Graphical A multi-targeting nitric oxide releasing bionanomatrix coating for silicone implant can reduce capsular contracture and improve healing process. The bionanomatrix coating reduces capsule thickness, α-smooth muscle actin and collagen synthesis, and myofibroblast differentiation through inhibition of TGF-β/SMADs signaling cascades in the subcutaneous mouse models for a month.

Hindfoot motion through helical axis image-based on dynamic CT scan using an original simulated weightbearing device

BackgroundDetermining the treatment of subtalar joint (STJ) instability requires a better understanding of the biomechanical principles underlying the condition and, a proper diagnosis. This study aimed to analyze "in vivo" the range of motion of the subtalar joint (STJ) measured on two (2D) and three dimensions (3D) image-based on CT Scan using an original device that maintains a simulated weightbearing. The secondary goal was to correlate the 2D and 3D measurement. MethodsAn observational study was conducted, using an original Dynamic Simulated Weightbearing Device. Asymptomatic ankles were included. Each subject underwent a CT scan under mechanical stress and simulated weightbearing conditions, maintaining maximum eversion and inversion hindfoot positions. The images were obtained, combining both inversion and eversion positions in a single model, which allows for to calculation of the motion vector as well as the helical axis. The helical axis (rotation angle and translation distance), subtalar tilt, anterior drawer, and, subtalar and calcaneocuboid uncoverage were the determinations. ResultsForty asymptomatic ankles were included. The average range of motion of the STJ amounts to 31.5° ± 9.1° of rotation and 1.56 ± 0.8 mm of translation distance. The anterior drawer and subtalar uncoverage variables were statistically significantly related to each other (r = 0.57; P = 0.00001). However, these 2-D measured variables were not related to kinematic measures of rotation through the helical axis (3D) (p = 0.14; p = 0.19) ConclusionsThe average range of motion of the STJ amounts to 31.5° ± 9.1° of rotation and 1.56 ± 0.8 mm of translation distance. We found no significant correlation between 2D and 3D measurements. In our opinion, the rotation angle and translation distance should be considered the most accurate measurements and should be calculated on every STJ instability for comparison with the asymptomatic population Level of evidenceObservational study. Level of evidence III

Inulin-type dietary fiber stability after combined thermal, mechanical, and chemical stresses related to ultrasound processing of prebiotic apple beverage

Inulin-type fructans are promising prebiotic dietary fibers added to foods and beverages to aggregate functional properties. In this regard, this study examined the chemical and physical stability of inulin after thermal, mechanical, and chemical stress conditions provided by high-intensity ultrasound treatment. The objective was to investigate the behavior of the inulin molecular structure and its technological issues under high-energy processing to understand the feasibility of adding inulin to new products with health benefits. Temperature monitoring during high-intensity ultrasound processing was crucial because high temperatures of up to 82 ± 1 °C were reached using short processing times of up to 5.48 min. Despite the temperature rise, ultrasound specific energies of 30, 120, 210, and 300 J/g did not affect the pH, soluble solid content, total phenolic content, antioxidant activity, and sugar content of the inulin-enriched apple beverage. In addition, the ultrasound processing stresses promoted by acoustic cavitation did not modify the profile and content of the short chain inulin added to the apple juice. The specific energy of 300 J/g contributed to the physical stability of the prebiotic apple beverage because this high-energy condition inhibited inulin precipitation producing a less cloudy product. Inulin was stable to high-energy ultrasound treatment because its molecular integrity was preserved. Moreover, the nutritional and bioactive compounds of the apple beverage were stable against acoustic cavitation-induced degradation. On the other hand, inulin precipitated in the aqueous solution after cooling of samples treated up to 210 J/g clouding the apple beverage. Indeed, high-intensity ultrasound processing enhanced the technological attributes of the prebiotic beverage, preventing its clouding due to inulin precipitation. Sonication treatment increased the physical stability of the beverage because it increased the magnitude of zeta potential.

Drosophila collagens in specialised extracellular matrices.

The basement membrane (BM) constitutes a specialised form of the extracellular matrix (ECM) and plays important roles in many biological processes, such as cell migration, organ and tissue integrity, cell polarity, and the formation of metastases. In metazoans, a canonical BM is formed by only a few conserved structural core proteins: Laminin, Collagen IV, Nidogen and Perlecan. Depending on the tissue's function and mechanical load, additional matrix proteins interact with, or are incorporated into the BM, resulting in tissue-specific mechanical properties, such ashigher stiffness or elasticity, or special resistance to mechanical stress or harmful environmental conditions. Inflies, the collagen IV-like protein Pericardin forms an integral constituent of matrices around the heart and tension sensors (chordotonal organs) of the peripheral nervous system. The function and integrity of both organ systems strongly relies on the appropriate establishment of a Pericardin (Prc) matrix and the function of its adapter protein-Lonely heart (Loh). In this review, we provide anoverview of the four collagens present in flies, and willdiscuss our recent work on the formation and function of Pericardin-containing matrices, the role of the adapter protein Lonely heart and the necessity of specialised ECM molecules in tissue architecture and function.

Open-Source Culture Platform for Multi-Cell Type Study with Integrated Pneumatic Stimulation

Mechanical forces can influence the structure and development of healthy and cancerous cells and tissue microenvironments, acting on their physical shape and promoting non-genetic alterations during growth. For this reason, it is interesting to investigate the role of dynamic hydrostatic compression on such cultures, to assess the role of such stimuli on key parameters, such as cell differentiation, cell stiffness and cytoskeleton rearrangements. In this work, we present a versatile Arduino-based pneumatic system for the stimulation of a cell culture performed in a standard multi-well plate, designed to work inside a CO2 incubator. The system is capable of modifying the hydrostatic pressure inside a dedicated culture chamber following the desired pattern, and, thus, providing a mechanical hydrostatic stimulus to a cell culture growing inside it. In the present work, a human respiration-like compression pattern was used, to mimic the mechanical stress conditions inside the human lung alveoli, and make the platform compatible with the development of lung tissues and organoids.

Burst speed assessment of aero-engine turbine disk based on failure assessment diagram and global stability criterion

Aero-engine turbine disks are safety-relevant components which are operated under high thermal and mechanical stress conditions. The actual part qualification and certification procedures make use of spin-tests conducted on production-similar disks. While these tests provide, on the one hand, a reliable definition of the critical conditions for real components, on the other hand they represent a relevant cost item for engine manufacturers. The aim of this work is to present two alternative burst speed assessment methods under development based on the Failure Assessment Diagram (FAD) and a global stability criterion, respectively. In the scope of the fracture mechanics assessment, the failure modes hoop-burst and rim-peeling are investigated with semi-circular surface cracks modelled at the critical regions on the turbine disk. The comparison of the predicted critical rotational speed shows good agreement between the assessment methods.

Acceleration of bone formation by octacalcium phosphate composite in a rat tibia critical-sized defect.

BackgroundThe osteogenic capabilities and biodegradability of octacalcium phosphate (OCP) composites make them unique. Despite the excellent characteristics of OCP, their use is limited due to handling difficulties. In this study, we aimed to evaluate and compare three types of OCPs (cemented OCP (C-OCP), C-OCP with collagen (OCP/Col), and synthetic OCP (S-OCP) with alginate (OCP/Alg)) versus commercially available β-tricalcium phosphate (β-TCP) regarding their potential to accelerate bone formation in defective rat tibias.MethodsThe specimens with OCP composite were manufactured into 5 ​mm cubes and inserted into the segmental defects of rat tibias fixed with an external fixator. In addition, 3 ​mm-hole defects in rat tibias were evaluated to compare the graft material properties in different clinical situations. Serial X-ray studies were evaluated weekly and the tibias were harvested at postoperative 6 weeks or 8 weeks for radiologic evaluation. Histological and histomorphometric analyses were performed to evaluate the acceleration of bone formation.ResultsIn the critical-defect model, OCP/Alg showed bone bridges between segmentally resected bone ends that were comparable to those of β-TCP. However, differences were observed in the residual graft materials. Most β-TCP was maintained until 8 weeks postoperatively; however, OCP/Alg was more biodegradable. In addition calcification in the β-TCP occurred at the directly contacted area between graft particles and bony ingrowth was observed in the region adjacent resected surface of tibia. In contrast, no direct bony ingrowth was observed in OCP-based materials, but osteogenesis induced from resected surface of tibia was more active. In the hole-defect model, OCP/Col accelerated bone formation. β-TCP and OCP/Alg showed similar patterns with relatively higher biodegradability. In histology, among the OCP-based materials, directly contacted new bone was formed only in OCP/Alg group. The new bone formation in the periphery area of graft materials was much more active in the OCP-based materials, and the newly formed bone showed a thicker trabecular and more mature appearance than the β-TCP group.ConclusionsIn this study, OCP/Alg was equivalent to β-TCP in the acceleration of bone formation with better biodegradability appropriate for clinical situations in different circumstances. Our OCP/Col composite showed fast degradation, which makes it unsuitable for use in mechanical stress conditions in clinical orthopedic settings.The Translational Potential of this ArticleIn our research, we compared our various manufactured OCP composites to commercially available β-TCP in critical-defect rat tibia model. OCP/Col showed acceleration in hole-defect model as previous studies in dental field but in our critical-sized defect model it resorbed fast without acceleration of bony union. OCP/Alg showed matched results compared to β-TCP and relatively fast resorption so we showed market value in special clinical indication depending on treatment strategy. This is the first OCP composite study in orthopaedics with animal critical-sized tibia bone study and further study should be considered for clinical application based on this study.

Network-Based Analysis to Identify Hub Genes Involved in Spatial Root Response to Mechanical Constrains.

Previous studies report that the asymmetric response, observed along the main poplar woody bent root axis, was strongly related to both the type of mechanical forces (compression or tension) and the intensity of force displacement. Despite a large number of targets that have been proposed to trigger this asymmetry, an understanding of the comprehensive and synergistic effect of the antistress spatially related pathways is still lacking. Recent progress in the bioinformatics area has the potential to fill these gaps through the use of in silico studies, able to investigate biological functions and pathway overlaps, and to identify promising targets in plant responses. Presently, for the first time, a comprehensive network-based analysis of proteomic signatures was used to identify functions and pivotal genes involved in the coordinated signalling pathways and molecular activities that asymmetrically modulate the response of different bent poplar root sectors and sides. To accomplish this aim, 66 candidate proteins, differentially represented across the poplar bent root sides and sectors, were grouped according to their abundance profile patterns and mapped, together with their first neighbours, on a high-confidence set of interactions from STRING to compose specific cluster-related subnetworks (I–VI). Successively, all subnetworks were explored by a functional gene set enrichment analysis to identify enriched gene ontology terms. Subnetworks were then analysed to identify the genes that are strongly interconnected with other genes (hub gene) and, thus, those that have a pivotal role in the bent root asymmetric response. The analysis revealed novel information regarding the response coordination, communication, and potential signalling pathways asymmetrically activated along the main root axis, delegated mainly to Ca2+ (for new lateral root formation) and ROS (for gravitropic response and lignin accumulation) signatures. Furthermore, some of the data indicate that the concave side of the bent sector, where the mechanical forces are most intense, communicates to the other (neighbour and distant) sectors, inducing spatially related strategies to ensure water uptake and accompanying cell modification. This information could be critical for understanding how plants maintain and improve their structural integrity—whenever and wherever it is necessary—in natural mechanical stress conditions.

Memristor‐Based Security Primitives Robust to Malicious Attacks for Highly Secure Neuromorphic Systems

Internet‐of‐things (IoT) edge devices with a memristive neuromorphic system can more effectively enhance daily lives. However, cyberattacks remain critical concerns for smart IoT edge devices that process a vast body of information via networks. Herein, a highly secure neuromorphic system is reported, which can be implemented using a physically unclonable function (PUF) that exploits the high entropy achieved via the stochastic switching of a poly(1,3,5‐trivinyl‐1,3,5‐trimethyl cyclotrisiloxane) (pV3D3)‐based memristor. The excellent insulating property of pV3D3 enhances the stochasticity of the tunneling distance for randomly ruptured Cu filaments. The pV3D3 memristor‐based PUF (pV3D3‐PUF) achieves near‐ideal 50% averages for uniformity and uniqueness, excellent reliability under conditions of mechanical stress and water immersion, and reconfigurability‐bolstering security without additional hardware. Using stochastic in‐memory computing, the pV3D3‐PUF shows resilience to machine learning attacks. Furthermore, a cryptography protocol is demonstrated, which enables artificial intelligence service implementation without security issues for PUF‐integrated pV3D3 memristor‐based neuromorphic systems.

Lamellar flower inspired hierarchical alpha manganese vanadate microflowers for high-performance flexible hybrid supercapacitors

Hybrid flexible supercapacitors (HFS) offer high power density and stability making them an ideal choice for the energy storage system in wearable devices. In this work, the synthesis of lamellar flower-like alpha manganese vanadate (α-Mn 2 V 2 O 7 ) on nickel foam was proposed for efficient and highly stable HFS applications for the first time. The voltammetric characterization indicated that the capacitance contribution of α-Mn 2 V 2 O 7 is derived from the diffusion-controlled (battery-type, 89.93%) and capacitive controlled (10.07%) mechanisms in aqueous electrolyte (0.5 M KOH). The optimized α-Mn 2 V 2 O 7 electrode exhibited an impressive specific capacity of 125.6 mAhg −1 (760.3 Fg -1 ). In the HFS device configuration, the utilization of α-Mn 2 V 2 O 7 resulted in a remarkable specific capacitance of 35.7 F g −1 with energy, and a power density of 28.4 Whkg −1 and 8.5 kWkg −1 , respectively. Furthermore, the α-Mn 2 V 2 O 7 fabricated device is found to operate in a wide potential window exhibiting remarkable and stable electrochemical performance in the gel electrolyte even under mechanical stress conditions. Importantly, the α-Mn 2 V 2 O 7 HFS showed an impressive and stable performance over 5000 cycles. The superior specific capacitance performances obtained in the present study are noted to be the best results reported for vanadium-based ternary oxides so far.

Assesment of electrochemical machining-induced pitting geometry on fatigue performance of flexible pipes’ tensile armor wires

In the extraction and production of oil and gas in sea environments, multiple components and systems are used, among them, flexible dynamic pipes, responsible for the transport of fluids. Because they are exposed to mechanical stress and corrosive conditions, it is important to assess the fatigue performance of the flexible pipe's components when there are signs of corrosion on their surfaces. Especially, the steel wires that bear the mechanical load during a riser's operation, are often vulnerable components to failure derived from the combination of corrosion and oscillating loads. The present work has the objective to assess the effects of corrosion pits, characterized by their dimensions, quantities and location, in the fatigue life of flexible pipes' tension wires. To make possible the correlation of the pits' parameters with their fatigue performance, the electrical discharge machining process was used, allowing a greater control of pits' development when compared to natural corrosion. The Taguchi method was employed to reduce the total amount of parameter combinations to be tested and to ascertain the effects of each parameter in the fatigue performance. Some pits obtained by electrical discharge machining didn't have the determined dimensions, especially the narrower and deeper pits. Fatigue tests were conducted in tensile armor wire specimens to assess the number of cycles to failure at pre-defined load levels. The fatigue testing results of electrical discharge machining corroded specimens suggest a more significant effect of the pits' diameter in reducing the fatigue performance, when compared to the controlled parameters of depth, quantity, location and aspect ratio. The maximum cycles reduction was around 73%, for wider pits, located in the planar face of the specimen, and the minimum reduction, around 40%, for narrower pits, located at the edge of the specimen.

Improving the Fatigue Behaviour of PURMAL S-70 Polyurethane Paint

Oxidation is one of the main degradation mechanisms that affects most industrial components and occurs as a result of a chemical reaction by which an oxygen atom is added to the molecule of an organic substance or compound. Light, in particular the ultraviolet (UV) component, activates the process of degradation of organic materials, favouring a series of oxidation reactions that occur when the component is in contact with oxygen in the air or water (especially salt water).Given that a number of components work in variable mechanical stress conditions (vibrations caused by the technological process itself or generated by repeated starts / shutdowns of equipment), the protective coatings aim to improve the physico-chemical properties of the surfaces to reduce the degradation, as well as to improve the fatigue behaviour, knowing that the fatigue cracks are initiated from local stress concentrators caused by the surface imperfections of the components. Paper presents the experimental results on fatigue behaviour of the deposited layers, after exposure to UV radiation. In the experimental program, a 2 mm thick AlMg3 sheet (EN AW-5754) was used as substrate. The Aluminium oxide layer naturally created on the metal surface, prevents the effect of oxygen and atmospheric pollutants, but this layer is unstable in corrosive environments. Thus, for a qualitative protection, protective organic layers are used. In experiments, the polyurethane paint PURMAL S 70, RAL 9010 (PUR) and the same paint but aditivate with graphene oxide (PUR + GO) were compared. Prior to fatigue testing, the painted specimens were subjected to accelerated artificial UV-aging process with ultraviolet radiation for 72 hours. Axial fatigue tests were performed with a frequency of 40 Hz, in pulsating mode, with R = 0.053 and with decreasing loads, starting from 0.85% of the tensile strength (Rm), up to 0.5% Rm. Analysis of S‑N curves revealed that, in the field of oligocyclic fatigue there are no significant differences between the fatigue results obtained on PUR-protected specimens, compared to those protected with PUR + GO, instead in the case of polycyclic fatigue, the paint with addition of 1% graphene oxide has improved fatigue resistance.

Static mechanical properties and stress wave attenuation of metaconcrete subjected to impulsive loading

To mitigate shock wave propagation, a conventional engineered aggregate (EA) consisting of solid core coated with relatively soft material was designed to be tuned at targeted frequencies based on the local resonance mechanism. Previous studies demonstrated that metaconcrete consisting of conventional engineered aggregates (EAs) exhibited favourable attenuation performance of impulsive loading effects on structures. However, it was also found that the existence of the soft coating on conventional EA caused a reduction in the compressive strength of metaconcrete. In this study, a new type of EA by adding a relatively stiff shell outside the soft layer of the conventional EA was developed to overcome the issue of strength reduction whilst keeping its favourable wave attenuation properties. Quasi-static mechanical properties of metaconcrete consisting of conventional and newly developed EAs were examined through standard compression tests. The dynamic responses of the cylindrical metaconcrete specimens subjected to non-destructive and destructive impulsive loadings were also tested to investigate its wave attenuation capacity. The failure processes and the failure modes of metaconcrete made of different types of EAs under destructive tests were compared. It was found that adding a stiffer shell to the conventional EAs can improve the mechanical properties of metaconcrete while still keeping its good performance in mitigating stress wave propagation under both destructive and non-destructive loads.