An Effect of a Carbon-Containing Additive in the Structure of a Friction Material on Temperature of the Wet Clutch Disc

This paper consists of two parts. The first one contains a description and methodology of the composite material used as friction material in clutches. Four variants of such material, differing in the type of carbon additive (the elemental graphite, pencil graphite and foundry coke powder of various fractions) were considered. Thermal conductivity, thermal diffusivity as well as the specific heat all materials were determined experimentally. On the inertial IM-58 stand, a simulation of the braking process of the friction pair consisting of a steel disc with friction material and a counterpart in the form of a homogeneous steel disc was carried out. On this basis, averaged coefficients of friction, unchanging in the entire sliding process, were found for the four friction pairs. The experimental data obtained in the first stage were used in the second stage to develop two (2D and 3D) numerical models of the friction heating process of the friction pairs under consideration. For four variants of the friction material, a comparative spatial-temporal temperature analysis was performed using both models. It was found that a simplified axisymmetric (2D) model can be used to estimate the maximum temperature with high accuracy. The lowest maximum temperature (115.6 °C) obtained for the same total friction work was achieved on the friction surface of the material with the addition of GP-1.

Analysis of Deformation Characteristics of AZ31B Friction Heating Incremental Forming

A friction heating incremental forming (FHIF) is proposed, which does not require external heating. By means of orthogonal experimental, finite element analysis and CATIA reverse engineering methods, the forming characteristics of magnesium alloy AZ31B FHIF are studied, such as forming limit angle, dimensional accuracy, thickness distribution, equivalent stress and equivalent strain at different forming stages. The results show that: For the FHIF, the forming limit angle can be up to 76°, and the most obvious way to increase the forming limit angle is to increase the spindle speed. In the FHIF, due to the limitations of the experimental conditions, it will be different from the ideal model. The bending phenomenon first occurs in the early stage of forming, which makes the upper corner part the worst accuracy, and the lower corner part obvious defects. Compared with the theoretically stable thickness, the actual part sidewall is thinned by 11%. The simulation successfully predicts and observes the thickness change and stress-strain change trend of the entire FHIF.

The analysis of the influence of the end mills backing to their operation in mechanical treatment of wood

Долговечность концевых фрез при работе определяется несущей способностью рабочей части корпуса и износостойкостью зубьев. Под несущей способностью рабочей части понимается ее способность воспринимать возникающие нагрузки от сил резания и обеспечивать жесткость и прочность фрез. Необходимая прочность концевых фрез определяется их конструктивными параметрами и условиями работы. При фрезеровании концевыми фрезами с глубиной более одного диаметра под воздействием сил сопротивления резанию происходит отжим фрезы, усугубляющийся наличием радиального люфта шпинделя в подшипниках. При этом возникают вредные силы трения вследствие контакта задних поверхностей с обрабатываемым материалом. Возникающий от трения нагрев фрез приводит к снижению их прочности. Одним из важнейших параметров концевых фрез является затыловка задних поверхностей. Существующие способы затыловки концевых фрез не полностью удовлетворяют требованиям эффективной работы. Данный отрицательный момент связан с тем, что концевая фреза консольная система, поэтому затыловка посредством равномерного поднутрения задних поверхностей по всей длине не удовлетворяет требованиям уравнения изогнутой оси балки под действием изгибающего момента. Вредные силы трения задних поверхностей фрез об обрабатываемый материал можно устранить при затыловке путем совместного профилирования рабочей части в поперечной и продольной плоскостях. При этом прочность фрез увеличивается на 7-10, а жесткость на 3-6. На практике совместную затыловку в поперечной и продольной плоскостях можно осуществить путем изготовления корпусов с конической рабочей частью. The durability of end mills during operation is determined by the bearing capacity of the working part of the housing and the wear resistance of the teeth. The bearing capacity of the working part is understood to be its ability to absorb the arising loads from cutting forces and to provide rigidity and strength of mills. The required strength of end mills is determined by their design parameters and working conditions. When milling with end mills with a depth of more than one diameter, under the influence of resistance to cutting, the mill is pressed, which is aggravated by the presence of radial play of the spindle in the bearings. In this case, harmful frictional forces arise due to contact of the rear surfaces with the processed material. The friction heating resulting from friction leads to a decrease in their strength. One of the most important parameters of end mills is the backing of the rear surfaces. Existing methods of backing end mills do not fully satisfy the requirements of efficient operation. This negative point is because the end mill is a cantilever system, so the backing due to uniform undercutting of the rear surfaces along the entire length does not satisfy the requirements of the equation of the curved axis of the beam under the action of bending moment. The harmful friction forces of the rear surfaces of the milling cutters on the material to be processed can be eliminated when backing by jointly profiling the working part in the transverse and longitudinal planes. At the same time, the strength of the cutters increases by 7-10, and the rigidity by 3-6.In practice, joint backing in the transverse and longitudinal planes can be accomplished by manufacturing housings with a conical working part.

Evolution of Interfacial Friction Angle and Contact Area of Polymer Pellets during the Initial Stage of Ultrasonic Plasticization

Interfacial friction heating is one of the leading heat generation mechanisms during the initial stage of ultrasonic plasticization of polymer pellets, which has a significant influence on the subsequent viscoelastic heating according to our previous study. The interfacial friction angle and contact area of polymer pellets are critical boundary conditions for the analysis of interfacial frictional heating of polymer pellets. However, the duration of the interfacial friction heating is extremely short in ultrasonic plasticization, and the polymer pellets are randomly distributed in the cylindrical barrel, resulting in the characterization of the distribution of the interfacial friction angle and contact area to be a challenge. In this work, the interfacial friction angle of the polymer pellets in the partially plasticized samples of polymethyl methacrylate (PMMA), polypropylene (PP), and nylon66 (PA66) were characterized by a super-high magnification lens zoom 3D microscope. The influence of trigger pressure, plasticizing pressure, ultrasonic amplitude, and vibration time on the interfacial friction angle and the contact area of the polymer pellets were studied by a single factor experiment. The results show that the compaction degree of the plasticized samples could be enhanced by increasing the level of the process parameters. With the increasing parameter level, the proportion of interfacial friction angle in the range of 0–10° and 80–90° increased, while the proportion in the range of 30–60° decreased accordingly. The proportion of the contact area of the polymer pellets was increased up to 50% of the interfacial friction area which includes the upper, lower, and side area of the cylindrical plasticized sample.

Study on the Mechanism of Interfacial Friction Heating in Polymer Ultrasonic Plasticization Injection Molding Process

Ultrasonic Plasticization Injection Molding (UPIM) is an effective way to manufacture polymeric micro parts and has great potential for energy saving with processing polymeric materials of a small amount. To better control the UPIM process and improve the quality of micro parts, it is necessary to study the heat generation mechanism. In this paper, the interfacial friction heating process of UPIM was studied by finite element (FEM) simulation and experiment, and the temperature change in the friction interface was estimated. Then, the effects of different process parameters such as ultrasonic frequency and ultrasonic amplitude on the friction heating process were analyzed. The results showed that the rising trend of friction heating temperature was transient (finished within 1 s), and the change trend of FEM simulation was consistent with experimental results. Adjusting ultrasonic frequency and amplitude has a significant influence on the friction heating process. Increasing the ultrasonic frequency and amplitude can improve the efficiency of friction heating.

Nonlinear Dynamics of Friction Heating in Ultrasonic Welding

High temperature, short welding time, and low relative motion generate high bond quality in ultrasonic metal welding (USMW). Friction is considered to be the main heat source during USMW. Hence, a comprehensive and accurate understanding of friction heating has become particularly valuable for designing USMW processes and devices. However, stick, slip, and separation states may appear alternately in the welding zone between superimposed workpieces during USMW vibrations; hence, a strong nonlinear process is created. Furthermore, the structural dynamics and the heat transfer are highly coupled because material properties depend on temperature. In this research, we propose a fast and accurate numerical methodology to calculate the friction heating through a multiphysical approach integrating a nonlinear contact model, a nonlinear structural dynamics model, and a thermal model. The harmonic balance method and the finite element method are utilized to accelerate the simulation. Several experiments were performed with aluminum and copper workpieces under different clamping forces and vibration amplitudes to confirm the presented numerical method, resulting in a good match.