DETERMINING THE COEFFICIENT OF FRICTION OF WOOD-BASED MATERALS FOR FURNITURE PANELS IN THE ASPECT OF MODELLING THEIR SHREDDING PROCESS

In order to improve the power selection of the drive unit for the shredding machines,theauthors determine the values of friction coefficients used in the cutting force models. These values consider the friction between steel and such wood-based materials as chipboard, MDF and OSB. The tests concern laminated and non-laminated external surfaces and surfaces subjected to cutting processes. The value of the coefficient of friction for the tested materials is in the range: for the static coefficient of friction 0.77-0.33, and for the kinetic coefficient of friction 0.68-0.25. The highest values of the static and kinematic coefficient of friction were recorded for MDF (non-laminated external surface) and they were equal respectively: 0.77 and 0.68. In turn, thesmallest values of the discussed coefficients were recorded for chipboard (laminated external wood-base surface), which were at the level of 0.33 and 0.25, resp.

Performance of Ground Anchored Walls Subjected to Dynamic and Pseudo-Static Loading

This study investigates the response of pre-stressed anchored excavation walls under dynamic and pseudo-static loadings. A finite difference numerical model was developed using FLAC2D, and the results were successfully validated against full-scale experimental data. Analyses were performed on 10, and 20-m-height stabilized excavated slopes with 60° to 90° of inclination angle with the horizon to represent an applicable variety of wall geometries. In dynamic analysis, the statically stabilized models were subjected to 0.2 to 0.6g of the dynamic peak acceleration to evaluate the effect of ground acceleration on their performance. Furthermore, pseudo-static analyses were performed on the statically stabilized models with pseudo-static coefficients ranging from 0.06 to 0.22. The results revealed that ground anchored slopes generally showed acceptable performances under dynamic loading, while higher axial forces were induced to ground anchors in higher and steeper models. Furthermore, comparing the results of dynamic and pseudo-static analyses showed a good agreement between the two methods' predictions in the mobilized axial force along the ground anchors. Pseudo-static coefficients were then proposed to replicate dynamic results, considering the slope geometry and dynamic load peak acceleration. The results revealed that higher and steeper stabilized slopes required higher values of pseudo-static coefficients to match the dynamic predictions successfully. The results indicate that pseudo-static coefficient tend to increase with the increase in dynamic load peak acceleration in any given model. Doi: 10.28991/cej-2021-03091703 Full Text: PDF

Moisture – Influenced friction properties of ackee apple (Blighia sapida) seeds

The friction properties of ackee apple (Blighia sapida) seeds at an 11.9, 17, 22, 27, and 32% (w.b.) seed moisture were determined, which are vital for designing their processing techniques and equipment to replace the present manual methods. The ackee apple grows in many West African countries, especially Nigeria. The ackee seeds were harvested at Lanlate, Oyo State, Nigeria, where ackee trees are predominant. Standard experimental methods were adopted to determine the properties. The data were analysed using an ANOVA and the least significant difference (LSD) at P ≤ 0.05. As the moisture increased, the static coefficient of friction on glass (27.6–36.40), aluminium (27.0–30.2), polyvinyl chloride (PVC; 27.9–32.8) surfaces and normal stress at 200 g (8.73–8.93 g×cm–2), 300 g (11.65–11.79 g×cm^–2) and 400 g (14.37–14.65) loads increased significantly and linearly. The shear stress linearly decreased at a 200 g load (1.62–1.25 g×cm^–2), but was non-significant at the 300 and 400 g loads. The coefficient of internal friction linearly decreased (0.744–0.588) implying that the wet seeds flow more easily than the dry ones, which should be considered in designing conveyors. The relationships between the ackee seeds' moisture and friction properties were expressed with regression models. Data for designing the handling techniques and machines for the ackee seeds were obtained.

Effect of the angle of the laid-up filaments on the surfaces on the coefficient of static friction between parts manufactured by extrusion-based 3D printing

Three-dimensional printers, particularly the extrusion-based ones, are driving a global academic, industrial, and social revolution. The accessibility of the technology has allowed a number of enthusiasts and scientists to dedicate efforts to improve the technical properties of the parts produced. However, there is little literature on the measurement of the coefficient of friction, especially the static one, between a pair of printed parts. In this sense, an investigation was carried out in two stages, in which at first the static coefficient of friction was measured, through a simple apparatus based on the concept of the inclined plane, varying the angle of the filaments laid up on the surfaces of the two parts in contact. The parameter was analyzed at three levels—0°, 45°, and 90°—in components manufactured in poly(lactic acid) and poly(ethylene glycol terephthalate). In the second part of the research, a case study was carried out to test and validate the effects of the best and worst friction conditions on the behavior of the insertion force of snap-fit connections. The results obtained show a significant influence of the filament angle in the interaction between two printed parts. Combinations of contact with different angles decrease the static coefficient of friction, while faces with equal angles tend to increase the magnitude of the response, especially if the arrangement of the filaments allows a fit of the surfaces opposite to sliding. The static coefficient of friction of poly(lactic acid) varied from 0.12 to 0.38, while the static coefficient of friction of poly(ethylene glycol terephthalate) varied from 0.13 to 0.21. The responses of the inclined plane test allowed to predict the behavior of the insertion force and plan the design of quick fittings.

Testing the Validity of Greenwood and Tripp’s Sum Surface Assumption for Elastic-Plastic Contact

The complexity of modeling friction between rough surfaces has prompted many researchers to use Greenwood and Tripp’s sum surface assumption to simplify the analysis. This assumption approximates the contact between two rough surfaces as contact between their equivalent sum surface and a rigid plane. In this work, we develop detailed finite element models to test the sum surface assumption for surfaces with Gaussian and exponential autocorrelation functions. We consider surfaces with differing surface roughness and correlation length values. For each case, we conduct simulations of two rough surfaces interacting in compression followed by shear, and a corresponding equivalent surface model based on the sum surface assumption. Multiple realizations of each parameter combination are simulated to obtain a statistical picture of the responses. We find that (a) the sum surface assumption consistently under-predicts the static coefficient of friction and (b) the equivalent surface model is less accurate for surfaces with differing correlation length-to-surface roughness ratios.

EFFECTS OF MOISTURE CONTENT ON SOME ENGINEERING PROPERTIES OF ARECANUT (ARECA CATECHU L.) FRUIT WHICH ARE RELEVANT TO THE DESIGN OF PROCESSING EQUIPMENT

The physical and mechanical properties of fresh arecanut fruit have not been comprehensively and thoroughly investigated scientifically yet. This made the researchers and engineers not to be precise in designing the fresh arecanut handling machine. Thus, the present study was aimed to investigate some engineering properties of arecanut fruit in three moisture viz. 67.66%, w.b. (underripe stages), 64.86%, w.b. (ripe stages), and 33.90%, w.b. (overripe stages). In general, the results of the study show that the geometric and arithmetic mean diameter, surface area, bulk and true density, porosity, angle of repose, compression force and static coefficient of friction at different surfaces (stainless steel, plywood, and glass) of arecanut fruit were found to increase 2.16%, 2.70%, 4.26%, 0.02%, 42.16%, 42.41%, 9.97%, 17.04%, 20.30%, and 22.04% respectively at decrease of moisture content from 67.66%, w.b. to 33.90%, w.b. However, sphericity, aspect ratio, thousand fruit mass, and bulk density of the arecanut fruit were found to decrease 2.31%, 3.31%, 34.54%, and, 50.24%, respectively at a decrease of moisture content from 67.66% (w.b.) to 33.90% (w.b.). Some engineering properties of arecanut fruit indicate something slightly different from the arecanut kernels so that this data can help the researcher or engineer to design the fresh arecanut fruit handling machine more precisely.

EFFECTS OF MOISTURE CONTENT ON SOME ENGINEERING PROPERTIES OF ARECANUT (ARECA CATECHU L.) FRUIT WHICH ARE RELEVANT TO THE DESIGN OF PROCESSING EQUIPMENT

The physical and mechanical properties of fresh arecanut fruit have not been comprehensively and thoroughly investigated scientifically yet. This made the researchers and engineers not to be precise in designing the fresh arecanut handling machine. Thus, the present study was aimed to investigate some engineering properties of arecanut fruit in three moisture viz. 67.66%, w.b. (underripe stages), 64.86%, w.b. (ripe stages), and 33.90%, w.b. (overripe stages). In general, the results of the study show that the geometric and arithmetic mean diameter, surface area, bulk and true density, porosity, angle of repose, compression force and static coefficient of friction at different surfaces (stainless steel, plywood, and glass) of arecanut fruit were found to increase 2.16%, 2.70%, 4.26%, 0.02%, 42.16%, 42.41%, 9.97%, 17.04%, 20.30%, and 22.04% respectively at decrease of moisture content from 67.66%, w.b. to 33.90%, w.b. However, sphericity, aspect ratio, thousand fruit mass, and bulk density of the arecanut fruit were found to decrease 2.31%, 3.31%, 34.54%, and, 50.24%, respectively at a decrease of moisture content from 67.66% (w.b.) to 33.90% (w.b.). Some engineering properties of arecanut fruit indicate something slightly different from the arecanut kernels so that this data can help the researcher or engineer to design the fresh arecanut fruit handling machine more precisely.