Using FEM-DEM coupling method to study three-body friction behavior

Engineering for profit from waste. Proceedings of the Institution of Mechanical Engineers

This article simulates the Taylor-Couette shear model by using the discrete element method to study mechanical properties and force chain changes in the granular flow in friction pair clearance. The mechanical properties and force chain structures of a granular system can be studied by changing the granular friction coefficient, granule size, fractional area, inner rotational speed, and other causes. Shear, normal, and unbalanced forces increase with increasing friction coefficient. A higher friction coefficient corresponds to a higher average contact forces. When the surface of the inner ring is rougher, the normal and unbalanced forces are smaller and the shear force is higher. This condition greatly influences the internal force chain structure of the granular media.

Force Chain Evolution and Force Characteristics of Shearing Granular Media in Taylor-Couette Geometry by DEM

Per- and poly-fluoroalkyl substance remediation from soil and sorbents: A review of adsorption behaviour and ultrasonic treatment.

The service life of a diesel fuel injector is highly affected by the tribological properties of the fuel. This study aims to investigate the friction and wear behaviors of emulsified bio-oil (EBO), which is a very promising alternative fuel for engines. Sliding wear tests were performed with a ball-on-disk tribometer using a GCr15 steel ball and a flat specimen as a counterpart. In these tests, the total sliding distance was 500 m, the load ranged from 10 to 20 N, and the oscillation frequency ranged from 30 to 50 Hz. Experimental results showed that EBO had better tribological properties than diesel oil and crude bio-oil. Contact load and oscillation frequency significantly influenced friction coefficient, wear volume, and wear damage pattern. The friction coefficient decreased with an increase in load and increased with an increase in oscillation frequency. Furthermore, the wear volume slightly increased with an increase in load or oscillation frequency. The damage mechanism is attributed to adhesive wear under low load and to abrasive wear under high load. The transition in the wear mechanism is related to the adsorption of the molecules in the EBO, the microstructural contact surface, and the mechanical actions.

Comparison and Analysis of the Influence of Test Conditions on the Tribological Properties of Emulsified Bio-Oil

Granular lubrication is a promising extreme environment lubrication candidate. Lubricated by granular media, the startup dynamic process of a plain journal is significant to the mechanical performance, which is not well investigated yet. A research model focusing on the startup process of a granular flow lubrication bearing is constructed by the discrete element method. The granules filled in slim gaps extrude and collide with each other, which transfers the force to the shaft and causes instability to the shaft movement. During the movement from rest to stable running position, repeated position mutations of the shaft were found to occur. The variations in axis resistance torque and average unbalanced force are indistinctive, whereas those in average contact force, coordination number, and slip ratio are apparent. In this process, the force interacts within the inner granular assembly, which results in the formation of a force chain network. The breakage and reconstruction of this network can be used to ...

DEM Simulation on the Startup Dynamic Process of a Plain Journal Bearing Lubricated by Granular Media

The invention discloses an end face friction and abrasion tester which mainly comprises a transmission device and a pressure loading device, wherein the transmission device comprises a servo motor vertically arranged above an upper box body; an output shaft of the servo motor vertically penetrates into the upper box body and a lower box body which are fixed on optical shafts; a coupler in the upper box body and the lower box body is connected with the motor shaft and a main shaft; one end, which extends out of the lower box body, of the main shaft is provided with an upper test piece; the pressure loading device comprises a base, a first support, a second support and the optical axis, and the first support, the second support and the optical axis are arranged on the base; a transmission shaft is arranged in the two supports; the transmission shaft, bevel gears, a screw rod, a screw rod nut and a spring form the pressure loading system. The friction force and the temperature are measured by setting a pressure load, adjusting a rotating speed of the motor and selecting the type of the test piece. The end face friction and abrasion tester is simple in structure, visible, easy to operate, convenient to maintain and low in cost.

End face friction and abrasion tester

The utility model discloses an end face frictional abrasion tester which mainly comprises a transmission device and a pressure loading device, wherein the transmission device comprises a servo motor vertically arranged above an upper box body; an output shaft of the servo motor vertically penetrates into the upper box body and a lower box body which are fixed on an optical shaft; a coupler in the upper box body and the lower box body are connected with a motor shaft and a main shaft; an upper test piece is arranged at one end, which extends out of the lower box body, of the main shaft; the pressure loading device comprises a base, a first support and a second support which are arranged on the base, and the optical shaft; a transmission shaft is arranged in the two supports; the transmission shaft, a bevel gear, a screw rod, a screw rod nut and a spring form the pressure loading device. The friction and the temperature are measured by setting a pressure load, adjusting the rotating speed of the motor and selecting the type of the test piece. The end face frictional abrasion tester is simple in structure, intuitive, easy to operate, convenient to maintain and low in cost.

End face frictional abrasion tester

In order to study the dilatancy phenomenon of confined granular assembly under shearing in parallel interface, a parallel-panel shear model is constructed by discrete element method (DEM) in this paper. While the relative motion happens between the upper and lower panels, the panel and particles displacement are monitored. The expansion of upper plate and the change of particles force chain are shown. The results show that: the internal particle system keeps repeating the dilatancy and compression process, and the relationship between shear dilatancy phenomenon and force chain structure is close.

Wei Gu

Papers

Force Chain Evolution and Force Characteristics of Shearing Granular Media in Taylor-Couette Geometry by DEM

DEM Simulation on the Startup Dynamic Process of a Plain Journal Bearing Lubricated by Granular Media

End face friction and abrasion tester

End face frictional abrasion tester

DEM Simulation on Dilatancy Phenomenon of Confined Granular Assembly under Shearing in Parallel Interface