Overlay Type Research Articles

Wear Performance Evaluation of Polymer Overlays on Engine Bearings.

Modern engine bearing materials encounter the challenge of functioning under conditions of mixed lubrication, low viscosity oils, downsizing, start-stop engines, potentially leading to metal-to-metal contact and, subsequently, premature bearing failure. In this work, two types of polymer overlays were applied to the bearing surface to compensate for extreme conditions, such as excessive loads and mixed lubrication. Two different polymer overlays, created through a curing process on a conventional engine bearing surface with an approximate thickness of 13 µm, were investigated for their friction and wear resistances under a 30 N load using a pin-on-disc setup. The results indicate that the newly developed polymer overlay (NDP, PAI-based coating) surface has a coefficient of friction (COF) of 0.155 and a wear volume loss of 0.010 cm3. In contrast, the currently used polymer overlay (CPO) in this field shows higher values with a COF of 0.378 and a wear volume loss of 0.024 cm3, which is significantly greater than that of the NDP. It was found that, in addition to accurately selecting the ratios of solid lubricants, polymer resins, and wear-resistant hard particle additives (metal powders, metal oxides, carbides, etc.) within the polymer coating, the effective presence of a transfer film providing low friction on the counter surface also played a crucial role.

Evaluation for long-term skid resistance of ultra-thin asphalt overlay based on texture characteristics

To evaluate the durability of ultra-thin asphalt overlays in terms of skid resistance accurately, the long-term degradation trends in texture characteristics need to be carried out comprehensively. In this paper, three types of ultra-thin asphalt overlays with different gradations were selected. The long-term abrasion test was conducted, with friction coefficient and texture characteristics tested in each abrasion cycle. Additionally, the stress state changes at the interface of the tire and mixtures were also obtained. Finally, the reliability of texture characteristics was validated based on the correlation between different indicators. The results show that the friction coefficient and texture characteristic show a two-stage decay pattern during the abrasion process, with a significant decrease in stress between 0.75 and 2.5 MPa at the interface of tire and mixtures. The surface mean texture depth (SMTD), root-mean-square deviation of surface (Sq), peak density of surface (Spd), and spatial fluctuations of texture (Δα) were correlated with British pendulum number (BPN) strongly, and the Sq and Δα were recommended as reliable evaluation parameters for the long-term skid resistance of ultra-thin asphalt overlays. This study provides theoretical guidance for the optimal design and field monitoring of ultra-thin asphalt overlays from the perspective of surface texture characteristics.

Thermal contraction coordination behavior between unbound aggregate layer and asphalt mixture overlay based on the finite difference and discrete element coupling method

AbstractThe constraint action of the unbound aggregate layer underneath plays an important role in affecting the temperature strains in the top asphalt layer. The focus of the present paper is to investigate the interactive thermal contraction mechanisms between the asphalt mixture and granular base layers to offer a new perspective in promoting the understanding of the thermal cracking disease. In this paper, both experiments and simulations were conducted for the thermal contraction tests. A novel numerical modeling of virtual composite structures was proposed using wall‐zone coupling operation based on the finite difference and discrete element coupling method. The experimental composite structures containing three types of asphalt mixture overlays and five types of unbound aggregate base layers were developed for verification. The thermal contraction and restraint mechanism were revealed from both macro and microscopic scales. The proposed numerical modeling shows a 94% high accuracy. The particle displacement vector and contact force chain could explain the thermal contraction behavior of composite structures. Smaller particle motion displacement or stronger contact force chain result in a higher restraint strain of the asphalt overlay. The thermal contraction behavior can be coordinated through the compaction and loosening of unbound aggregates. The material parameters and cooling temperature differences in the asphalt overlay have slight effects on the constraint action of a base layer, while the gradation and mechanical parameters of the unbound aggregate layer show significant impaction. The parameters, cohesion C and friction angle φ, show a quadratic function with the restraint coefficient. This work has significant guidance on the selection of pavement structure and materials to improve the thermal cracking problem and lay the basis for the mechanical theoretical calculation to predict thermal cracking.

Fracture load and failure mode of semi-direct resin composite occlusal veneers: Influence of design and mechanical cycling

AimsTo evaluate the influence of the type of preparation and mechanical cycling on the fracture load and failure mode of semi-direct posterior resin composite restorations. MethodsIn total, 70 healthy third molars were used; 10 belonging to the control group (C - unprepared teeth) and 60 teeth prepared and restored with nanoparticle resin composite, divided into 3 groups (n = 20): O - exclusively occlusal preparation (Table Top); OV - occlusal preparation with buccal extension (Veneerlay); OVP - Occlusal preparation with chamfer on the proximal and buccal-lingual/palatal surfaces (Overlay). The preparations were performed with diamond burs with a thickness of 1 mm. The restorations were made with nanoparticulate resin composite (Filtek Z350 XT) and subsequently received additional polymerization (thermoprocessing). Cementation was performed with the use of universal adhesive system (Single Bond Universal) on dental substrate and dual resin cement (RelyX ARC). Half of the teeth in each group (n = 10) were submitted to mechanical cycling, simulating 6 months of clinical service (5 × 105 fatigue cycles), under dynamic loading of 130 N, at a frequency of 2Hz. Fracture load tests were performed in a universal testing machine with a 200 kgf load cell. Failure mode was classified using scores. Generalized linear models and Fisher Exact tests were applied to the data (significance level of 5%). ResultsThere were no significant differences between the types of preparation (p = 0.9435), or relative to cycling (p = 0.3764). The Fisher Exact Test showed a significant association between the groups and the type of failure (p = 0.0006), with preparations O (with cycling) and OVP (with and without cycling) exhibiting most failures with restoration fractures without involvement of the dental remnant. ConclusionsSemi-direct restorations showed resistance to fracture load similar to that of healthy teeth and were capable of withstanding functional masticatory loads. The type of preparation influenced the failure mode of teeth. The Table Top and Overlay types of preparations were those had fewer catastrophic failures, suggesting that since they are more conservative preparations, they made it possible for the tooth to receive a new restorative procedure in the future in cases of failures.

Analysis of Air Pollution Distribution in West Pasaman Regency Effects of Palm Oil Mills

The purpose of this research was to identify sources of pollution and analyze the level of pollution for the parameters of TSP (Dust), particulates, NO2, and SO2 and to map their distribution. The research was conducted at 9 (nine) palm oil mills spread throughout West Pasaman Regency. The data used are primary and secondary data. The primary data includes particulates, TSP, SO2, and NO2 gases. Secondary data consists of test results data at the Environmental Service in 2017, morphological data, and factory location maps. Data processing methods include statistical analysis of Shapiro Wilk. Then proceed with descriptive analysis to determine the characteristics of the range of minimum and maximum values of air pollution distribution. Spatial analysis of the overlay type was carried out using a GIS application. Particulate, TSP, NO2 and SO2 test results at each location have met the required air quality standards. mapping the distribution of air pollutants for the parameters TSP (Dust), NO2 and SO2 with the direction of their spread according to the wind direction. Comparison with the latest regulations, namely PP Number 22 of 2021 Appendix VII, shows that the test results are still below the set quality standards. With the test values obtained and the meteorological factors in each company, it shows that there is no significant effect of pollutant content from sources of pollution on the environment around the palm oil mills.

A Review Study on the Performance of Flexible Pavements

Pavements are significant resources of expressway infrastructure. The nation has seen colossal expansion in the vehicle population and expanded hub stacking design during the last decade, leaving its street network overemphasized and prompting untimely disappointment. The kind of weakening present in the asphalt ought to be considered for deciding if it has a useful or underlying inadequacy, so that suitable overlay type and configuration can be created. The structural properties of asphalt are redirection and it is completed by Benkelman Beam & deflectometer test. The evaluation of street conditions is needed to distinguish the explanations behind disintegration before any restoration work is completed. The fundamental boundaries including in the appraisal of street conditions are avoidance and unpleasantness estimation which decided utilizing different test, for example, FWD, Benkelman shaft test, profilometer, and slide obstruction test. This appraisal additionally helps in focusing on the upkeep works as indicated by the necessity. A few procedures are utilized to evaluate the road conditions and contrast and standard standards. In this concentrate on a stretch of road is break down for similar where techniques utilized are visual strategy, Benkelman beam test and slide opposition test. The structural and useful assessment are dissected and created by different specialists. The paper presents an itemized audit of different asphalt exhibitions on primary and utilitarian assessment of adaptable asphalt to inspect the job of components identified with asphalt materials, surface deflection, ecological conditions, sort of traffic and volume of traffic, and to distinguish the constraints and holes in the current information on such examinations.

Adhesive Property and Road Performance Evaluation of Asphalt Overlay Pavement with Geotextile Interlayer

Geosynthetic interlayer systems are effective techniques to control reflective cracking and have better waterproof performance in damaged asphalt pavements. The interlayer bonding performance is critical to its function. This research investigated the interfacial adhesive property and road performance of asphalt overlay with geotextile interlayer. First, shear damage energy characteristics of geotextile interlayer have been investigated by varying tack coat types (SBS-modified asphalt, virgin asphalt, and emulsified asphalt), application rates (0.3 kg/m2–1.2 kg/m2), spraying times (1–2), upper mixture paving temperature (140°C–180°C), service temperature (5°C–45°C), and soaking time (0 h–96 h). In addition, bending fatigue tests, rutting tests, and semicircular bending tests were carried out to evaluate the comprehensive road performance of the asphalt overlay. The results showed that the interface adhesive property of asphalt overlay with geotextile interlayer using SBS-modified asphalt is best when the application rate is 0.8 kg/m2. The higher paving temperature is beneficial for the geotextile interlayer adhesion performance when the SBS-modified asphalt is sprayed at one time, while the paving temperature has almost no effect when the SBS-modified asphalt is sprayed at two times. The geotextile interlayer adhesion performance is less affected by temperature and more affected by water immersion. Compared with the common asphalt overlay types, the asphalt overlay with geotextile interlayer using SBS-modified asphalt shows better overall performance.

Exploring Engineering Students’ Perception on using Augmented Reality to Improve Learning Performance in the Context of COVID-19 Pandemic

The study evaluates the energy engineering students’ perception and insights concerning the use and usefulness of AR technology in online engineering education during COVID-19 pandemic. The assessment is based on the following criteria: usefulness, suitability, advantages for different activities, types of overlays. Results show an increased interest for AR applications in all types of teaching activities, and its usefulness for a better understanding of studied topics. Among the most important advantages of using AR are considered closer connection to practice, speeding and deepening learning. Overall, these results indicate an improved user perception of AR from acceptance to high interest.

Evaluating the Performance of Concrete Overlays in Missouri

The Missouri Department of Transportation (MoDOT) has used concrete overlays as a pavement rehabilitation method since at least the 1930s, with over 40 projects constructed in the last two decades alone. However, there has not been an integral effort to comprehensively evaluate the performance of those projects in relation to design parameters, as-built construction quality, traffic levels, or distress progression. The objective of this study was to undertake a critical analysis of concrete overlays in Missouri as a first step to recommend improvements to MoDOT’s overlay selection, design, and construction practices. MoDOT uses three types of concrete overlays: unbonded overlays (UBOL), big block overlays (BBOL), and bonded overlays (BOL). It was found that UBOL projects exhibited the lowest international roughness index values among all types of overlays. The most predominant distress for UBOL was longitudinal cracking, which appeared more often at the center of the slab or in the right wheelpath. Cracking in the right wheelpath was particularly evident on projects that used a slab width greater than 12 ft and asphalt shoulders. Although BBOL and BOL projects did not deviate from the standard slab size, the rightmost panels tended to exhibit more distress, which might also point to weak support around the mainline-shoulder area. Recommendations for future projects include revising the design thickness procedures to be site-specific, revising the thickness quality control practices, and the continued use of geotextiles as interlayers for projects that require a bond breaker.

Node formation mechanisms in acoustofluidic capillary bridges

Using acoustofluidic channels formed by capillary bridges two models are developed to describe nodes formed by leaky and by evanescent waves. The liquid channel held between a microscope slide (waveguide) and a strip of polystyrene film (fluid guide) avoids solid-sidewall interactions. With this simplification, our experimental and numerical study showed that waves emitted from a single plane surface, interfere and form the nodes without any resonance in the fluid. Both models pay particular attention to tensor elements normal to the solid–liquid interfaces they find that; initially nodes form in the solid and the node pattern is replicated by waves emitted into the fluid from antinodes in the stress. At fluids depths near half an acoustic wavelength, most nodes are formed by leaky waves. In the glass, water-loading reduces node–node separation and forms an overlay type waveguide which aligns the nodes predominantly along the channel. One new practical insight is that node separation can be controlled by water depth. At 0.2 mm water depths (which are smaller than a ¼ wavelength) nodes form from evanescent waves. Here a suspension of yeast cells formed a pattern of small dot-like clumps of cells on the surface of the polystyrene film. We found the same pattern in sound intensity normal, and close, to the water-polystyrene interface. The capillary bridge channel developed for this study is simple, low-cost, and could be developed for filtration, separation, or patterning of biological species in rapid immuno-sensing applications.

Rehabilitation and Repair of Concrete Overlays

Concrete overlays are a growing solution in the United States for pavement rehabilitation and preservation. Many different overlay types and designs can be used based on existing conditions and to achieve a variety of design goals. Recent performance studies have indicated that concrete overlays are capable of providing an extended service life of 35 years or more. However, the intended design life of an overlay may be shorter, and in some cases, overlays experience early distresses and failures. Because many agencies are new to concrete overlays, there is a growing need to identify best practices for rehabilitation and repair of these pavements. This paper presents a survey of typical shortand long-term distresses that have been observed on US concrete overlay projects. Common failure modes vary based on overlay type and design details, and distresses frequently depend on local materials and climate conditions. Best practices and case studies for rehabilitation and repair of concrete overlays are identified, offering options both for extension of concrete overlay service life as well as rehabilitation or reconstruction with a new pavement surface.

Quantifying In Situ Tack Coat Performance Using the TackBond Tester for Quality Control

In light of the various quality assurance (QA) issues pertaining to tack coats that occur during construction, there is a need for a means of verifying interlayer bond quality in situ. Despite the immense use of tack coat as a constituent in paving, there are no construction specifications with provisions for the quantification of tack coat bond quality in laboratory or field settings. In this study, a construction QA process for tack coat bond performance was proposed. A novel field tack coat bond strength test device, TackBond, was developed and used for this purpose. The performance of engineered (new tack coat technologies that are tracking less) and conventional tack coats was also evaluated in the laboratory and the field using the developed TackBond test system. The TackBond device was improved in this study by adding features that render it more practical, portable, accurate, and better suited for a variety of pavement surface conditions. Engineered tack coat performance was compared with that of tack coats used conventionally on both milled and overlay surface types. The suitability of the TackBond Test device for capturing the true response of each tack coat was first evaluated by comparing results from TackBond laboratory tests with monotonic direct shear tests (DST) on laboratory-produced samples. Strong correlations between the two test types were achieved. Results of field and laboratory TackBond tests showed that the in situ QA control process developed in this study could be effectively used to improve the in situ tack coat bond performance.

Beds, overlays and mattresses for preventing and treating pressure ulcers: an overview of Cochrane Reviews and network meta-analysis.

Beds, overlays and mattresses for preventing and treating pressure ulcers: an overview of Cochrane Reviews and network meta-analysis.

Comparison of Fracture Resistance for Chairside CAD/CAM Lithium Disilicate Crowns and Overlays with Different Designs.

To determine the fracture resistance of chairside computer-aided design and computer-assisted manufacturing (CAD/CAM) lithium disilicate full coverage crowns and two different designs of overlay restorations for premolars. CAD/CAM lithium disilicate (IPS e.max CAD for CEREC/HT A1 C14, Ivoclar Vivadent) restorations (15 specimens/group) with 1.5 mm occlusal thickness and 1.0 mm chamfer were designed and fabricated with a chairside CAD/CAM system (CEREC, Dentsply Sirona). The restorations were prepared in three different designs: (1) full coverage crowns, (2) overlays with the margin located 2 mm above the gingiva, and (3) overlays with the margin located 4 mm above the gingiva. Restorations were cemented using conventional resin luting cement (Multilink, Ivoclar Vivadent) with primer system (Monobond Plus, Ivoclar Vivadent) to resin printed dies, load cycled (2,000,000 load cycles at 1 Hz with 275 N force), and then finally loaded with a steel indenter until failure. Scanning electron microscopy observations of fractured surfaces were also conducted. Group results were analyzed with one-way analysis of variance, and the medians were evaluated independently with Kruskal-Wallis. The fracture force of CAD/CAM lithium disilicate restorations was significantly different (p < 0.001) depending on the design of the restoration. Full coverage crowns showed significantly higher force to fracture (1018.8 N) than both types of overlays (p = 0.002 for overlay 2.0 mm and p < 0.001 for overlay 4.0 mm above gingiva). Among the two overlays, the restoration with the margin located 2 mm above the gingiva showed significantly higher fracture force (813.8 N) than the overlay with margin at 4 mm above the gingiva (436.1 N; p < 0.001). The fracture appearance of the crowns was much more complex than that of the overlay restorations. Full coverage chairside CAD/CAM lithium disilicate premolar crown showed higher fracture resistance than overlay restorations. Overlays with the margin located 2 mm above the margin demonstrated higher resistance than those with the margin located 4 mm above the gingiva.

Color-Coded Map Overlay Augmentation for Unmanned Vehicle Sensor Management

Four color-coded overlays that augment a tactical map were evaluated as candidates for multi-unmanned vehicle (UV) sensor management by a single operator. Each overlay provided six levels of temporal information to indicate how long ago each map location had been viewed by a UV. Twelve participants completed 140 trials, each trial posing a question to be answered by retrieving spatial-temporal information from static map overlays. The accuracy of the participants’ answers significantly differed as a function of overlay type. Suggestions for overlay design and future research methodology are provided.

Static overlays for pressure ulcer prevention: a hospital-based health technology assessment

At Odense University Hospital (OUH) alternating-air mattresses (AAM) are used in the prevention of pressure ulcers (PU); however, static overlays might be more effective and have lower costs. To investigate the properties and consequences of using static overlays for prevention of PU at OUH, a hospital-based health technology assessment (HTA) was conducted. Two types of static overlays were tested in an observational study and compared with AAM for patients with a medium-high risk of PU in geriatric and orthopaedic wards at OUH. Incidence of PU was investigated 7 months before (n=720) and 6 months after implementation (n=837). Staff attitudes were examined in a questionnaire survey (n=55) and focus group interviews (n=13). Patients who had tried one of the overlays and the AAM were interviewed (n=12). No statistical difference in PU incidence was found before and after the implementation of overlays (2.5% before, 2.7% after, P=0.874, n=1557) and no patients lying on overlays developed PU (n=123). Staff had mixed attitudes, but the majority preferred having overlays as an option for their patients. Interviewed patients preferred overlays due to less noise and improved mobility. Both types of overlay are effective in PU prevention. However, overlays introduce challenges for staff and clear guidelines for the selection of support surfaces are needed. Overall, it is recommended that static overlays are considered as an alternative to AAM for PU prevention.

Bond strength and chloride resistance of epoxy and concrete overlays on bridge decks

ABSTRACT The deteriorating condition of infrastructure, combined with fiscal limitations experienced by many agencies, necessitates increased service life of bridges. Maintenance and preservation methods such as overlays and sealers have been known to protect bridge decks from deterioration, while also extending a bridge’s service life. It is important to understand the characteristics of various overlay types to make informed maintenance decisions, thus assessing and comparing the performance of thin epoxy overlays and low slump dense concrete (LSDC) overlays is desirable. To evaluate the performance of these two overlay types, the chloride resistance and long-term bond strength of the overlays were assessed. Three bridges were chosen to install each overlay type, with corresponding field and laboratory evaluations performed. The above tests results indicated that the initial bond strength of both overlays is good, but that the thin epoxy overlays showed decreased performance after 300 F/T cycles. The bond performance of the LSDC remain unchanged for the duration of the freeze–thaw testing, indicating superior long-term performance. As expected, the epoxy overlay performed much better than the LSDC overlay with respect to chloride resistance. These performance metrics are important to keep in mind when selecting maintenance and rehabilitation methods for bridges.

Long-term performance evaluation of Iowa concrete overlays

ABSTRACT The use of concrete overlays has long been recognised as a cost-effective pavement maintenance and rehabilitation strategy. However, the long-term performance of various types of concrete overlays has not been fully investigated since there has not been enough performance data available to conduct such an evaluation. Concrete overlays have been regularly constructed on Iowa roadways since the late 1970s and many older projects are still in use. Performance-related data for in-service concrete overlays have been acquired from the available resources to evaluate long-term performance of concrete overlays in Iowa. The information collected includes Pavement Condition Index (PCI), International Roughness Index (IRI), overlay type, construction year, overlay thickness, joint spacing, traffic, and other construction and design-related data. Based on an evaluation of PCI and IRI changes during service life, it is observed that concrete overlays can provide at least 20 years of service life. In terms of PCI ratings, 89% of concrete overlays investigated have PCI values greater than 60% as of the time of the analysis. Similarly, 93% of concrete overlays have IRI values lower than 2.7 m/km (170 in/mile). The effects of overlays type and design features on long-term performance of Iowa concrete overlays are also discussed.

Nondestructive Corrosion Evaluation of Reinforced Concrete Bridge Decks with Overlays: An Experimental Study

Abstract Concrete corrosion induced by deicing agents can decrease the durability of concrete bridge decks by causing cross-sectional loss of reinforcement, concrete delamination, and spalling owing to the expansion of corroded reinforcement. The installation of overlays can extend the service life of the deteriorated decks. However, overlays present challenges in the evaluation of the corrosion condition of the underlying decks. This laboratory study employed three nondestructive testing (NDT) methods to assess the effects of seven types of overlays on corrosion evaluation for concrete bridge decks. The NDT methods were electrical resistivity (ER), ground-penetrating radar (GPR), and half-cell potential (HCP). The ER method could not evaluate the corrosive environment in the concrete decks through the overlays. The GPR method could detect the corrosive environment through four of the seven overlays. The HCP method could detect the decrease of electrical potential over the actively corroded reinforcement for all seven specimens; however, only two of the seven specimens could be identified as having active corrosion per ASTM C876-15, Standard Test Method for Corrosion Potentials of Uncoated Reinforcing Steel in Concrete. Overlay debonding did not affect GPR and HCP testing results in this study.

Post-treatment of arc-welded aluminum alloy joints by laser shock peening

The possibility to improve aluminum alloy welded joints with laser shock penning was demonstrated. It was shown that microhardness of peened area in heat affected zone is higher than one without post-treatment. Also in this area the residual tensile stresses turns into residual compressive stresses. Laser peening process is proposed to carry out using low-energy lasers. In this case were analysed different types of ablative overlays.