Prediction of Surface Roughness During Dry Sliding Wear

Due to the relatively low strength and poor wear resistance of unalloyed titanium and its good mechanical properties, corrosion resistance, and biocompatibility. Ti6Al4V has been extensively used in various type of application including aerospace, biomedical and offshore industries. The goal of this research is to enhance the surface properties of the high strength alloys are examine such as Ti6Al4V pin sliding against Al2O3disc, due to the various surfaces roughness parameters. The COF and the wear rate were found to be lower at higher applied load due to higher frictional heating leading to thermal oxidation and thereby formation of several mm thick tribo-layers on the worn surfaces. Characterization of the tribological sample was performed using a scanning electron microscope (SEM) equipped with energy dispersive X-ray analysis (EDAX) to ensure that the wear pattern and debris morphologies of the Ti6Al4V and alumina disks were distinct, suggesting a surface roughness value determined by 3D profilometer at various load and sliding speed of 0.01ms-1.

Operational reliability of suspended facade structures with variable thickness of the cladding layer

The article presents the results of laboratory tests of experimental samples for mechanical safety, aimed at obtaining data pertaining to the performance of protective and decorative brick facade structures on metal substructures. The designs of the samples are atypical, with a different arrangement of bricks in the face layer and with ledges evenly distributed over the surface of the sample. Based on the test results, structure behavior under load, the absolute values of the displacement of the cladding layer, and the values of the bond strength between bricks and mortar were established. During the tests, the displacement of the protective and decorative structure in the direction of the applied load and the values of the forces, corresponding to the strength limit, were recorded.The article addresses the issue of the lack of rules for the design and testing of suspended facade systems made of bricks on metal substructures in the regulatory and technical documentation of the Russian Federation.

The tribological performance of W-DLC in solid–liquid lubrication system addivated with Cu nanoparticles

Judicious selection of additives having chemical and physical compatibility with the DLC films may help improving the triboligical properties and durability life of DLC-oil composite lubrication systems. In this study, Cu nanoparticles were added to PAO6 base oil to compose a solid-liquid composite lubrication system with W-DLC film. The effects of nanoparticle concentration, test temperature and applied load on tribological performance were systematically studied by a ball-on-disk friction test system. The tribological results illustrated that Cu nanoparticles could lower the coefficient of friction (COF) and dramatically reduce the wear rates of W-DLC films. The optimal tribological behavior was achieved for the 0.1 wt.% concentration under 30 ℃ and the applied load of 100 N. The test temperature and applied load were vital influencing factors of the solid–liquid lubrication system. The bearing effect and soft colloidal abrasive film of spherical Cu nanoparticle contributed to the excellent tribological performance of the composite lubrication system under mild test conditions, meanwhile, the local delamination of W-DLC film and oxidation were the main causes of the friction failure under harsh test conditions. With test temperature and applied loads increase the degree of graphitization of the W-DLC film increased. In conclusion, there are several pivotal factors affecting the tribological performance of solid–liquid lubrication systems, including the number of nanoparticles between rubbing contact area, graphitization of the worn W-DLC films, tribofilms on the worn ball specimens and oxidation formed in friction test, and the dominant factor is determined by the testing condition.

Survivability of Suddenly Loaded Arrays of Micropillars

When a multicomponent system is suddenly loaded, its capability of bearing the load depends not only on the strength of components but also on how a load released by a failed component is distributed among the remaining intact ones. Specifically, we consider an array of pillars which are located on a flat substrate and subjected to an impulsive and compressive load. Immediately after the loading, the pillars whose strengths are below the load magnitude crash. Then, loads released by these crashed pillars are transferred to and assimilated by the intact ones according to a load-sharing rule which reflects the mechanical properties of the pillars and the substrate. A sequence of bursts involving crashes and load transfers either destroys all the pillars or drives the array to a stable configuration when a smaller number of pillars sustain the applied load. By employing a fibre bundle model framework, we numerically study how the array integrity depends on sudden loading amplitudes, randomly distributed pillar strength thresholds and varying ranges of load transfer. Based on the simulation, we estimate the survivability of arrays of pillars defined as the probability of sustaining the applied load despite numerous damaged pillars. It is found that the resulting survival functions are accurately fitted by the family of complementary cumulative skew-normal distributions.

Load-Settlement Response of A Footing Over Buried Conduit in A Sloping Terrain: A Numerical Experiment-Based Artificial Intelligent Approach

Settlement estimation of a footing located over a buried conduit in a sloping terrain is a challenging task for practicing civil/geotechnical engineers. In the recent past, the advent of machine learning technology has made many traditional approaches antiquated. This paper investigates the viability, development, implementation, and comprehensive comparison of five artificial intelligence-based machine learning models, namely, multi-layer perceptron (MLP), Gaussian processes regression (GPR), lazy K-Star (LKS), decision table (DT), and random forest (RF) to estimate the settlement of footing located over a buried conduit within a soil slope. The pertaining dataset of 3600 observations was obtained by conducting large-scale numerical simulations via the finite element modelling framework. After executing the feature selection technique that is correlation-based subset selection, the applied load, total unit weight of soil, constrained modulus of soil, slope angle ratio, hoop stiffness of conduit, bending stiffness of conduit, burial depth of conduit, and crest distance of footing were utilized as the influence parameters for estimating and forecasting the settlement. The predictive strength and accuracy of all models mentioned supra were evaluated using several well-established statistical indices such as Pearson’s correlation coefficient (r), root mean square error (RMSE), Nash-Sutcliffe efficiency (NSE), scatter index (SI), and relative percentage difference (RPD). The results showed that among all the models employed in this study, the multi-layer perceptron model has shown better results with r, RMSE, NSE, SI, and RPD values of (0.977, 0.298, 0.937, 0.31, and 4.31) and (0.974, 0.323, 0.928, 0.44 and 3.75) for training and testing dataset, respectively. The sensitivity analysis revealed that all the selected parameters play an important role in determining the output value. However, the applied load, constrained modulus, unit weight, slope angle ratio, hoop stiffness have the highest strength with the relative importance of 18.4%, 16.3% and 15.3%, 13.8%, 11.4%, respectively. Finally, the model was translated into a functional relationship for easy implementation and can prove useful for practitioners and researchers in predicting the settlement of a footing located over a buried conduit in a sloping terrain.

Roof deformation and collapse of stamps with isolated grooves: a contact mechanics approach

This paper has revisited the roof deformation and collapse of stamps with isolated grooves based on a contact mechanics approach, with emphasis on establishing the non-adhesive and adhesive contact solutions for surfaces containing a shallow rectangular groove with the effects of applied load and interfacial adhesion taken into account. By solving singular integral equations and using the energy release rate approach, closed-form solutions are derived analytically for the deformed groove shapes, interfacial stress distributions and equilibrium relations between load and contact size, which reduce to the previously proposed solutions without adhesion or without applied load. Finite element analysis is performed to validate the non-adhesion solutions, while experiment results of stamp collapse reported in the literature are adopted to examine the adhesion solutions. By introducing the Johnson parameter a to represent a competition between surface energy and elastic strain energy of the groove, four kinds of contact behaviors of the groove roof can be characterized appropriately: non-adhesion, weak adhesion, intermediate adhesion and strong adhesion. Hysteresis loop and energy loss due to distinct load/unloading paths are revealed in the cases of intermediate and strong adhesion. We also provided the critical applied pressure to achieve roof collapse and the corresponding equilibrium contact size for full range of a.