Resistance Behavior Research Articles

Performance and durability of additively and subtractively manufactured resin-based onlay restorations after thermomechanical aging.

To evaluate the effect of material type on dimensional stability, occlusal surface wear, fracture resistance, and failure behavior of resin-based onlay restorations. A mandibular right first molar typodont was prepared and digitized using an intraoral scanner to virtually design an onlay restoration with the minimum occlusal thickness of 1.5mm. Resin-based onlay restorations (n = 15 per group) were fabricated either additively from 2 different resins indicated either for definitive or interim use or subtractively with a composite resin. After cementing onlays to corresponding dies, each of them was digitized before and after thermomechanical aging (B-STL and A-STL), and then subjected to load-to-failure test to evaluate fracture resistance. The B-STL and A-STL of each onlay were also compared to assess the dimensional stability and occlusal surface wear. One-way analysis of variance and Tukey honestly significant difference tests were used to evaluate dimensional stability, occlusal surface wear, and fracture resistance. The chi-square test was used to evaluate the Weibull modulus and characteristic strength among the groups (α = 0.05). Material type affected investigated outcomes (p<0.001). The additively manufactured resin indicated for definitive use led to the highest external surface deviations and the additively manufactured resin indicated for interim use led to the highest mesiodistal width deviations (p≤0.033). The onlays fabricated from the additively manufactured resin indicated for definitive use had the highest occlusal surface wear, while those in composite resin had the lowest (p≤0.006). The composite resin onlays had the highest fracture resistance values and reliability (p≤0.035). Tested subtractively manufactured composite resin had the lowest occlusal surface wear with the highest fracture resistance and reliability. Additively manufactured resins had lower dimensional stability, while tested resin for additively manufactured definitive restorations had the highest occlusal surface wear.

Comparative Study of Corrosion Resistance in Heat-Treated Bainitic and Pearlitic Steels in Sodium Chloride Solution under Room and Elevated Temperatures

The development of multiphase bainitic/martensitic steel aims to enhance the mechanical properties and corrosion resistance compared to traditional pearlitic steel. However, the impact of elevated temperatures on the corrosion resistance behavior of these materials cannot be overlooked. This study investigates the corrosion resistance behavior of multiphase bainitic/martensitic steel and pearlitic steel at varying temperatures. Electrochemical tests using Electrochemical Impedance Spectroscopy (EIS) and Linear Polarization (LP) in a 3.5 wt.% NaCl solution demonstrate a consistent trend: acicular bainitic steel exhibits superior corrosion resistance compared to granular bainitic steel and pearlitic steel at both room temperature and elevated temperatures. Further characterization using Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD) reveals that the formation of oxide layers significantly contributes to the enhanced corrosion resistance observed in these materials.

Mechanical Behavior and Innovative Applications of Fiber-Reinforced Cementitious Composite and Fiber-Reinforced Polymer in Infrastructures

Fiber-reinforced cementitious composite (FRCC) and fiber-reinforced polymer (FRP) have been widely applied in infrastructures. Their mechanical behavior and innovative applications are examined in this article. Firstly, the mechanical behaviors of FRCC and the corresponding improving methods are elaborated. The bond behavior of the FRP–concrete interface, which has a significant effect on the strengthening effect of FRP, is reviewed. A proposed method to enhance the bond behavior is also introduced. In addition, the effectiveness of FRP is demonstrated in terms of improving the load-bearing capacity, stiffness, crack resistance, fatigue resistance, and other behaviors of existing structures. Furthermore, the feasibility of fibers or FRPs in new constructions is also validated. Finally, the future prospects of the research and applications of FRCC and FRP are discussed.

Study on Collision Dynamics Similarity of Thickness Distortion Model of Train Five-Hole Thin-Walled Structure

Full-scale train collision tests are rarely carried out because of high cost, but small-scale model tests have good economy and repeatability, providing a new research method for train crashworthiness design. The metal thin-walled tube is a commonly used energy-absorbing structure for trains. Its collision characteristics directly affect the impact resistance and collision behavior evolution process of trains. This paper studies the collision dynamics similarity of the small-scale model of a five-hole thin-walled energy-absorbing structure at the end of a high-speed train. Firstly, the dynamic mechanical behavior and governing equations of high-speed train collision were analyzed, and the applicable similarity criterion was derived by similarity transformation to develop a similarity scale model. According to the simulation, the energy absorption, peak force and other key responses of the full-scale prototype collision were analyzed. Then, the applicability of the thickness distortion scale model of the five-hole energy-absorbing structure in the high-speed train was proved by equation analysis and error analysis. The impact dynamic responses of the complete similarity model and the distortion similarity model were discussed. A correction program with collision deceleration as the dependent variable was proposed for the distortion similarity model, and the fitting relationship between the distortion factor and the correction factor was obtained. The results calculated by the proposed method prove that the peak force-deformation-energy absorption error of the thickness distortion similarity model in predicting the dynamic responses of the prototype collision is less than 8%, which means the thickness distortion scale model has good accuracy in the prediction of full-scale prototype collision dynamics responses.

Effects of discrete fibre reinforcements on the wear resistance behaviour of polyamide-based spur gears

Abstract In many situations, the polymer gears are the perfect replacement for traditional metal gears. Compared to metal gears, the polymer gears will generate more heat at the gear tooth contact surface and more wear loss. Hence, this study aims to decrease the wear loss and increase the load-carrying capacity of the polymer gears. To achieve this, the reinforcement materials were added to the base polymer gear material. In this study, Nylon-66 was chosen as the polymer matrix material and an isolated glass fibre and steel grid were used as the reinforcement materials. Three different types of polymer spur gears such as Polyamide Gear (Nylon-66), Reinforced Polyamide Gear (Nylon-66+Glass Fibre), and Hybrid Glass Fiber Steel Grid Gear (Nylon-66+Glass Fibre+Steel Grid) named PG, RPG and HGFSGG were fabricated using injection moulding machine and each type of gears were compared for wear loss and specific wear rate under the similar testing conditions. The wear test was performed in the Forschungsstelle fur Zahnrader und Getriebebau (FZG) test rig at 1500 rpm with an applied load of 20 N for 12.5 hours continuously. From the test results, it was identified that HGFSGG polymer spur gears have exhibited a lower surface temperature and better wear properties compared to the other two types of spur gears. From the Scanning Electron Microscope (SEM) analysis, it was noticed that the PG spur gear exhibited deep and uniform wear at the gear tooth surface. In contrast, RPG spur gear exhibited glass fibre distortion and abrasive-type wear. The SEM micrograph of HGFSGG spur gear reveals the presence of very few surface flaws in the gear tooth surface.

Shear Elastic Buckling and Resistant Behavior of Single-Side-Stiffened Steel Corrugated Shear Walls

Stiffened steel corrugated shear walls (SSCSWs) have achieved extensive applications in building structures and serve as efficient lateral force-resisting members. Single-side-stiffened steel corrugated shear walls (SS-SCSWs) are more flexible in terms of their structural configuration compared to conventional SSCSWs because this novel structural member effectively reduces wall thickness and simplifies the construction process. In this paper, numerical analyses were carried out to investigate the shear elastic buckling and resistant behavior of SS-SCSWs. A formula for the equivalent flexural stiffness of single-side stiffeners was given based on theoretical analysis. The elastic buckling and elastoplastic analyses of SS-SCSWs were carried out by finite element (FE) models to determine the value of the equivalent flexural stiffness coefficient. Meanwhile, the elastic and elastoplastic transition stiffness ratios of single-side stiffeners were proposed to predict the minimum stiffness required for the stiffener to provide sufficient constraint. The accuracy of the above formulas was verified by calculating the shear elastic buckling loads, the ultimate shear resistance, and the out-of-plane displacements of the SS-SCSWs. Furthermore, parametric analyses were performed to reveal the influences of the aspect ratio and plate thickness on shear resistance capacity. The equivalent flexural stiffness coefficients in both the elastic and elastoplastic analyses were determined to be 0.45 and 0.7, respectively, through curve fitting. The results indicated that the theory of BS-SCSWs could accurately predict the shear elastic and elastoplastic behavior of SS-SCSWs after modifying its expression for flexural stiffness. Consequently, the modified theoretical formulas were demonstrated to be suitable for SS-SCSWs in practical designs.

Research on the Effect of Microstructure Modulation on the Corrosion Resistance Behaviour of L-PBF Alloy 718

The micro-structures and corrosion behavior of laser powder bed fusion (L-PBF) alloy 718 (power 140 W, speed 800 mm s−1) after various heat treatments (650 °C, 940 °C, and 1020 °C) were investigated by electrochemical analysis. The result shows that as-received samples, the most prone to pitting corrosion is melt-pool boundary (MPB). The heat treatment at 940 °C demonstrates the best corrosion resistance due to the precipitation of a considerable number of needle-like and short rod-like δ phases. This indirectly reduces the dislocation density and defect density of the passivate film, resulting in improved stability and corrosion resistance.

Influence of flake graphite coated MgO particles on thermal shock resistance and fracture behaviour of MgO-C refractories based on Brazilian splitting test with digital image correlation method and acoustic emission technique

Influence of flake graphite coated MgO particles on thermal shock resistance and fracture behaviour of MgO-C refractories based on Brazilian splitting test with digital image correlation method and acoustic emission technique

High temperature oxidation resistance behavior of Ti3SiC2/Cu composites under migration of Ti and Cu atomic

The oxidation behavior and oxidation mechanism of Ti3SiC2/Cu composites were investigated using constant temperature oxidation method. The Ti3SiC2/Cu composites were prepared at different sintering temperatures. Results showed that the relationship between the oxidation reaction rate of Ti3SiC2/Cu composites in air at 700°C∼900°C and the oxidation temperature was in accordance with the parabolic law of oxidation kinetics. The oxidation weight gain and oxide layer thickness of Ti3SiC2/Cu composites at 700 °C and 800 °C were insignificant, with oxidation reaction rates of 3.0692×10-9 kg2m-4h-1 and 6.9856×10-9 kg2m-4h-1, respectively, and the oxidation rate of Ti3SiC2/Cu composites at 900 °C was enhanced to 1.00907×10-8 kg2m-4h-1. Ti3SiC2/Cu composites oxidized at 900°C formed a protective oxide layer, which was mainly a multilayer structure composed of different kinds of oxides: the outer layer was mainly composed of TiO2; the intermediate layer mainly consisted of CuO; the inner layer mainly made up of TiO2 and SiO2.

Influence of PPS on the structural, mechanical, thermal, thermo-mechanical, and flame resistance behavior of Na-ionomer/polyphenylene sulphide blend

The morphology, mechanical, thermal, thermo-mechanical, and flammability properties of Na-ionomer/PPS blends were investigated. FESEM study revealed a transition from a homogeneous structure in pure Na-ionomer to a biphasic sea-island morphology at 20% PPS and a co-continuous micro-fibrous structure at 30% PPS and above. Both tensile and flexural modulus were improved substantially at higher PPS loadings (above 30 wt%). Thermogravimetric analysis and differential scanning calorimetry showed that increasing PPS content improved the thermal stability and altered the crystallization behavior of the blends, with maximum thermal stability observed at 50% PPS. Dynamic mechanical analysis demonstrates increased stiffness and elastic properties in the blends as PPS content was increased, particularly at higher temperatures. Additionally, flame resistance was improved with PPS concentration due to the formation of a protective char layer. These findings suggest that Na-ionomer/PPS blends with higher PPS content are suitable for high-performance applications requiring enhanced mechanical, thermal, thermo-mechanical, and flame-resistant properties.

Women’s Strategies to Cope with Harassment in Za’atari Camp and the Role of Humanitarian Reporting Mechanisms

Abstract The refugee experience is frequently marred by pervasive gender-based violence, particularly harassment, in refugee camps. Women, disproportionately affected due to entrenched gender biases, often suffer in silence due to societal stigma. In Za’atari Camp in Jordan, women face various forms of sexual and gender-based violence (SGBV), notably verbal harassment, exacerbating their plight amidst a culture of victim-blaming. While humanitarian efforts have made strides, challenges persist in reporting and adopting sensitive response mechanisms. This study aims to evaluate gaps in protection plans, response procedures, and reporting at Za’atari Camp, analysing coping mechanisms and resistance behaviours of women facing harassment. With 409 survey responses, findings reveal enduring verbal harassment and reporting barriers fuelled by fear of repercussions and survivor blaming. Addressing these challenges is crucial for the effective implementation of humanitarian policies and standard operating procedures, necessitating collective action to create a supportive environment for all women in the camp.

Effects of current density on the corrosion resistance of micro-arc oxidation coatings on Ti6Al4V welded joints

The effects of different current densities in micro-arc oxidation (MAO) on the microstructure and corrosion resistance of electron beam welded Ti6Al4V alloy joints are investigated by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD). The electrochemical corrosion behavior is studied in a 3.5% NaCl solution by polarization and electrochemical impedance spectroscopy (EIS). The thickness of the BM-MAO coating (base metal region) increases gradually with current densities and reaches a maximum at 16 A/dm2. In comparison, the thickness of the WZ-MAO coating (welded zone) increases initially and reaches a maximum at 12 A/dm2 before decreasing gradually. When the current density is 10–14 A/dm2, the WZ-MAO coating is thicker than the BM-MAO coating. However, the thickness of the WZ-MAO coating is smaller at 16 A/dm2. The BM-MAO and WZ-MAO coatings show decreased porosity with increasing current densities, and the porosity of the latter is lower. Dynamic potential polarization tests reveal a significant reduction in the self-corrosion current density at the BM area and welded joint (WJ), by an order and two orders of magnitude, respectively, after the application of MAO coatings with different current densities. The BM-MAO and WJ-MAO coatings deposited at a current density of 12 A/dm2 exhibit optimal corrosion resistance. The corrosion resistance of BM-MAO coating is better than that of WJ-MAO at different current densities according to the equivalent resistance and dielectric behavior.

Resistant starch formation and behavior changes of non-pigmented rice starches by repeated autoclaving

Resistant starch formation and behavior changes of non-pigmented rice starches by repeated autoclaving

Enhanced ablation resistance and mechanical behavior of spark plasma sintered ZrB2-SiC composites with TiC addition

The study evaluated the ablation resistance and mechanical behavior of spark plasma sintered ZrB2-25 vol% SiC-TiC (5–15 vol%) composites. The addition of TiC improved ablation resistance by promoting the formation of ZrO2.TiO2 and TiO2 phases on the oxidized composites. The ZrB2-25 vol% SiC-15 vol% TiC composite exhibited the lowest mass ablation rate of 0.11 mg/s and maximum fracture toughness of 5.8±0.29 MPa.m0.5. After ablation, SiC particle pull-out, crack deflection and crack bridging were identified as the primary toughening mechanisms. The maximum microhardness of 23.01±1.18 GPa and compressive strength of 1688.2±75.5 MPa were obtained for the ZrB2-25 vol% SiC-10 vol% TiC composite, which correspond to 92.86 % and 94.31 % of their respective maximum values prior to ablation. Furthermore, nanoindentation studies revealed significant improvements in both elastic modulus and nanohardness with the addition of TiC due to reduction in porosity and refinement in SiC grain size. After ablation, the elastic modulus and nanohardness reduced. However, the ZrB2-25 vol% SiC-10 vol% TiC composite retained a maximum elastic modulus of 433.61 GPa and nano-hardness of 21.88 GPa. The oxidation behavior of ZrB2-SiC composites containing TiC was analyzed at 1500°C for 6 hours in air. The TiC-containing composite exhibited lower mass gain, lower parabolic oxidation rate constant and a thin oxide layer compared to the ZrB2-SiC composites.

Preparation and characterization of modified CNC/waterborne polyurethane composite film

To improve the water resistance and mechanical performance of waterborne polyurethane, modified cellulose nanocrystal (CNC) as a kind of environmentally friendly material was added into the solution of waterborne polyurethane by the in-situ polymerization and mechanical blending way, and two different modified CNC/waterborne polyurethane composite films were prepared. The results show that due to the addition of modified CNC, the composite film prepared by in-situ polymerization way showed much better behavior in both water resistance and mechanical properties than that made by the mechanical blending method. When the content of modified CNC was 5% in the composite, the water resistance of the composite film increased by 34.6%. At the same time, the tensile property of the composite film was improved when using in-situ polymerization to fabricate the film, and the value of maximum tensile stress rose by 143.9%.

Characteristics of Urinary Tract Infections in Patients with Diabetes from Timișoara, Romania: Prevalence, Etiology, and Antimicrobial Resistance of Uropathogens.

Background and Objectives: Diabetic patients are more likely to develop infections compared to the general population, especially urinary tract infections (UTIs). The aim of this study was to assess the prevalence of UTIs in a population of patients with diabetes (DM) from Romania, to identify the most common uropathogens and their antimicrobial resistance (AMR) patterns, as well as to determine the correlations between resistance behavior and particularities of patients with UTIs according to DM type. Materials and Methods: The hospital records of 1282 type 1 (T1D) and type 2 DM (T2D) adult inpatients who were ordered urine cultures during hospitalization were reviewed, and all 241 patients who presented a positive urine culture were included in the present study analysis. Results: The prevalence of UTIs in diabetic patients was 18.8% and higher in patients with T2D vs. T1D. Patients with UTIs and T2D had a significantly older age, longer duration of DM, higher waist circumference and body mass index, lower levels of estimated glomerular filtration rate, and more frequent chronic complications of DM than patients with T1D. E. coli was the most frequently isolated uropathogen (56.4%), with a significantly higher incidence for T2D, followed by K. pneumoniae (12.9%) and Enterococcus spp. (9.5%). Although the acquired resistance phenotypes were more frequently isolated in T2D patients (over 90% of the multidrug-resistant and extended-spectrum beta-lactamase-producing isolates, respectively, and 75% of the total carbapenem-resistant organisms), no statistically significant correlation was found regarding the distribution of AMR patterns in the two types of DM. Conclusions: The present study brings new data regarding the prevalence of UTIs in diabetic patients from Western Romania. By identifying the spectrum of uropathogens and their AMR pattern, this paper may contribute to improving UTI management in diabetic patients, thus reducing antibiotic overuse and preventing recurrent UTIs.

The Impact of Non‐Monolithic Semiconductor Capacitance on Organic Electrochemical Transistors Performance and Design

AbstractThe existing device models for organic electrochemical transistors (OECTs) fail to provide any device design guidelines for optimized performance parameters such as transconductance that are pivotal for the applications OECTs in sensing. Moreover, the current models are based on the questionable assumption of a homogenous organic semiconductor layer, and all predict a linear behavior of the resistance with the OECT channel length. Consequently, the experimentally observed nonlinear resistance behavior in OECTs has been overlooked thus far. Here, an OECT device model is developed that accurately describes the nonlinear behavior of the OECT channel resistance and offers the first guidelines for maximizing transconductance. The model is inherently nonlinear and the nonlinearity stem from the non‐monolithic capacitance of the organic semiconductor layer. Moreover, the model provides a consistent and reliable estimations for the contact resistance in OECTs. The success of the model in accurately describing and providing predictions of the OECT operation by relating the device's geometrical parameters with electrochemical parameters of the semiconductor layer paves the way toward unlocking OECT potentials in diverse applications, from biosensing to neuromorphic computing and flexible electronics.

Fire resistance behaviour of non-load bearing LSF walls with restrained thermal elongation

In this research study, based on suitable and rational thermal and sequentially coupled structural FE (finite element) analyses, the fire resistance behaviour and FRLs (fire resistance levels) of non-load bearing LSF (light gauge steel framed) walls with restrained thermal elongation were deeply analysed. The FE analysis results confirmed that CFS (cold-formed steel) channel studs of the mentioned walls collapsed prematurely due to additional compression loads caused by the effects of fire and the thermal elongation restraints at stud ends, which led to the reduced FRLs of these walls. Besides, the wall height and the clearance between the stud ends and rigid floors were shown as having significant effects on the FRLs of non-load bearing LSF walls with restrained thermal elongation. In contrast, the effects of the thickness and depth of CFS channel studs and cavity insulation were inconsiderable. Finally, a simplified and reliable design equation and some recommendations were proposed for some types of non-load bearing fire-rated LSF walls commonly used in Australia. This paper presents details of this study, including its analyses, outcomes, and proposals.

Research Progress on the Relationship Between Microstructure and Properties of AISI 321 Stainless Steel

AISI 321 stainless steel is widely used in chemical pipelines and nuclear power, prompting research on its high-temperature performance and corrosion resistance. This review focuses on the effects of alloy elements, second-phase particle formation, and heat treatment processes on the microstructure and properties of AISI 321 stainless steel. Fine tuning of alloying elements can affect the mode and effect of dynamic recrystallization, altering the high-temperature flow deformation of AISI 321 stainless steel. In order to achieve phase equilibrium, the relationship between corrosion resistance and high-temperature creep behavior and high-temperature mechanical behavior in the presence of second-phase particles was also analyzed. This review outlines the basic heat treatment procedures for improving material properties, providing a new perspective for solution treatment and improving corrosion resistance. In addition, the latest research progress on other factors affecting the high-temperature performance of AISI 321, such as coatings, was briefly introduced.

The Influence of In-Mould Annealing and Accelerated Ageing on the Properties of Impact-Modified Poly(Lactic Acid)/Biochar Composites.

In the last few decades, a large number of natural additives have been analysed in connection with the improvement of the properties of poly(lactic acid) (PLA) bioplastic materials. This article comprehensively analyses the applicability of a highly stable and progressive multifunctional additive produced from renewable resources-biochar. The effect of biochar on the structural development and various thermo-mechanical properties was evaluated as a function of the biochar size and volume, addition of an impact modifier and in-mould annealing during injection moulding. In addition, the effect of accelerated ageing on the change in properties was also analysed. The evaluated results showed a significant influence of the particle size and biochar content on the properties of PLA biocomposites. However, the crucial aspect was the production process with a higher mould temperature and longer production time. Consequently, the effect of additives with adjusted processing worked synergistically on the performance of the resulting biocomposites. The accelerated ageing process did not induce any significant changes in the mechanical, impact and heat resistance behaviour of neat PLA. On the other hand, significant effects on the behaviour of the modified PLA biocomposites were observed. Impact-modified PLA achieved a toughness of 28 kJ/m2, an increase of 61% compared to neat PLA. Similar observations were made when submicron biochar was incorporated into the PLA matrix (a 22% increase with PLA/5B1). These increases were even more pronounced when injected into a 100 °C mould. Due to the synergistic effect, excellent impact toughness results of 95 kJ/m2 (a 428% increase) were achieved with PLA/IM/5B1. Moreover, these results persisted even after accelerated ageing.