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.

Geometrical properties of underutilized cereal varieties of Himalayan origin for the development of future processing equipments.

This paper presents the database of physical and engineering characteristics of grains and flours of five underutilized cereal varieties viz sorghum, buck wheat, pearl millet, proso millet and barley of Himalayan origin. The results revealed a significant difference in width, length and breadth of these cereals. The sphericity value of cereal grains showed significant difference (p≤0.05) in the range 97.42 to 137.25.84% which was found to be highest for sorghum grain while as aspect ratio was found highest for proso millet grain. The static coefficient of friction samples was found maximum on corrugated board for the flour and grain. The hausner ratio and compressibility index indicated poor flowability of the sorghum flour. The bulk density, tapped density and porosity values of cereal grains varied significantly for cereal grains as well as flours. ATR-FTIR (attenuated total reflectance-Fourier transform infrared spectroscopy) confirmed the different types of linkages present in the flour samples found within the absorption bands of 3500-993 cm-1.

Geometrical properties of underutilized cereal varieties of Himalayan origin for the development of future processing equipments.

This paper presents the database of physical and engineering characteristics of grains and flours of five underutilized cereal varieties viz sorghum, buck wheat, pearl millet, proso millet and barley of Himalayan origin. The results revealed a significant difference in width, length and breadth of these cereals. The sphericity value of cereal grains showed significant difference (p≤0.05) in the range 97.42 to 137.25.84% which was found to be highest for sorghum grain while as aspect ratio was found highest for proso millet grain. The static coefficient of friction samples was found maximum on corrugated board for the flour and grain. The hausner ratio and compressibility index indicated poor flowability of the sorghum flour. The bulk density, tapped density and porosity values of cereal grains varied significantly for cereal grains as well as flours. ATR-FTIR (attenuated total reflectance-Fourier transform infrared spectroscopy) confirmed the different types of linkages present in the flour samples found within the absorption bands of 3500-993 cm-1.

Wax-oil lubricants to reduce the shear between skin and PPE

Prolonged use of tight-fitting PPE, e.g., by COVID-19 healthcare workers leads to skin injuries. An important contributor is the shear exerted on the skin due to static friction at the skin-PPE interface. This study aims to develop an optimised wax-oil lubricant that reduces the friction, or shear, in the skin-PPE contact for up to four hours. Lubricants with different wax-oil combinations were prepared using beeswax, paraffin wax, olive oil, and mineral oil. In-vivo friction measurements involving seven participants were conducted by sliding a polydimethylsiloxane ball against the volar forearms to simulate the skin-PPE interface. The maximum static coefficient of friction was measured immediately and four hours after lubricant application. It was found that the coefficient of friction of wax-oil lubricants is mainly governed by the ratio of wax to oil and the thermal stability and morphology of the wax. To maintain long-term lubricity, it is crucial to consider the absorption of oil into the PPE material. The best performing lubricant is a mixture of 20 wt% beeswax, 40 wt% olive oil, and 40 wt% mineral oil, which compared to unlubricated skin, provides 87% (P = 0.0006) and 59% (P = 0.0015) reduction in instantaneous and 4-h coefficient of friction, respectively.

Wax-Oil Lubricants to Reduce the Shear Between Skin and PPE

Prolonged use of tight-fitting PPE, e.g., by COVID-19 healthcare workers leads to skin injuries. An important contributor is the shear exerted on the skin due to static friction at the skin-PPE interface. This study aims to develop an optimised wax-oil lubricant that reduces the friction, or shear, in the skin-PPE contact for up to four hours. Lubricants with different wax-oil combinations were prepared using beeswax, paraffin wax, olive oil, and mineral oil. In-vivo friction measurements involving seven participants were conducted by sliding a polydimethylsiloxane ball against the volar forearms to simulate the skin-PPE interface. The maximum static coefficient of friction was measured immediately and four hours after lubricant application. It was found that the coefficient of friction of wax-oil lubricants is mainly governed by the ratio of wax to oil and the thermal stability and morphology of the wax. To maintain long-term lubricity, it is crucial to consider the absorption of oil into the PPE material. The best performing lubricant is a mixture of 20 wt% beeswax, 40 wt% olive oil, and 40 wt% mineral oil, which compared to unlubricated skin, provides 87% (P = 0.0006) and 59% (P = 0.0015) reduction in instantaneous and 4-hour coefficient of friction, respectively.

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.

Specific Problems in Measurement of Coefficient of Friction Using Variable Incidence Tribometer

The subject of this paper is the solution to specific problems in the measurement of the coefficient of the sliding friction of material pairs using a variable incidence tribometer. The aim of this work was to solve the questions of the measurement of the static coefficient of friction using a variable incidence tribometer from the perspective of metrology. In particular, we intended to research the expression of the credibility of this measurement and the possibility of increasing the credibility of the measurement. Another problem that needs to be solved is the method of carrying out the measurement, which has an impact on its achieved uncertainty. Sliding friction is a phenomenon that depends on many material properties such as contact area roughness, moisture, lubricants, temperature, and relative motion velocity. If environmental conditions are defined, the main input parameter is the relative motion velocity. For this input quantity, friction force becomes a symmetrical problem, and it is only necessary to explore this phenomenon for positive values of velocities. Symmetry in this area simplifies the research of this science topic.