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This paper aims presents topology optimization of microfluidic channels with reverse flow.

A circular chamber with an inlet and an outlet are chosen as an initial design domain. The energy dissipation is chosen as an objective function. The incompressible Navier–Stokes equation is applied for simulating the fluidic motion in channels. An artificial friction force which is proportional to the flow velocity is substituted into the Navier–Stokes equation for controlling the design variable.

The effect of a bifurcation angle between the inlet and the outlet on a topological structure is analyzed. The flow velocity, pressure and design variable for every bifurcation angle are obtained.

This work is instructive to the design of a microfluidic system.

This study aims to investigate the influence of surface texture distribution in respect to the procedure of pavement surface wear on friction performance.

The Weierstrass–Mandelbrot (W-M) equation is used to appropriate pavement surface profile. Through this approximation, artificial rough profiles by combining fractal parameters and conventional statistical parameters for different macro-texture are created to simulate the procedure of pavement surface wear. Those artificial profiles are then imported into discrete element model to calculate the interaction forces and friction coefficient between rolling tire and road. Furthermore, wavelet theory is used to decompose the profiles into different scales and explore the correlation between the profiles of each scale and pavement friction.

The influence of tire vertical displacement (TVD) on friction coefficient is greater than fractal dimension of road surface texture. When TVD decreases, the profiles can provide higher friction, but the rolling stability of tire is poor. The optimal fractal dimension of road surface is about 1.5 when considering friction performance. The pavement friction performance improves with wavelength from 0.4 to 6.4mm and decreases with wavelength from 12.8 to 51.2mm.

Artificial fractal curves are generated and analyzed by combining W-M function with traditional parameter, which can also be used to analyze the influence of texture distribution on other pavement performance. The preliminary research provides a potential approach for the evaluation of pavement friction performance.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-11-2019-0499/

It is important to know the friction coefficient and wear loss for determination of tribological conditions at journal bearings. Tribological events that influence wear and its variations affect experimental results. The purpose of this paper is to determine friction coefficient and wear loss at CuSn10 alloy radial bearings by a new approach. In experiments, effects of bearings have been examined at dry and lubricated conditions and at different loads and velocities.

In this study, friction coefficient and wear losses of journal and bearing have been determined by a new approach with a radial journal bearing test rig and artificial neural networks (ANNs) method. The ANN typifies a learning technique that enables the hidden input‐output relationship to be mapped accurately. Bronze‐based materials have been used as bearing material. Effects of friction coefficient and wear losses have been examined at same load and velocity and at dry and lubricated conditions.

The results obtained in ANN application are close to friction test results for dry and lubricated conditions. Therefore, by using trained ANN values, the intermediate results that were not obtained in the tests can be calculated. Experimental studies will be increased and research with ANN will be continued.

By using trained ANN values, the intermediate results that were not obtained in the tests can be calculated. The training finished on 30 min whereas experimental study had continued day after day.

The purpose of this paper is to review and to provide a dipper understanding of what happens to piston rings and cylinder surfaces when manufacturing errors depicted, such as waviness and straightness. The mechanism of friction and the piston ring structural integrity, due to the surface irregularities, are analyzed either for smooth ring surface or for artificial textured, while piston ring floats into the piston groove or not.

In this work two tribological models of a piston ring- cylinder package are presented using CFD analysis. Initially, the piston ring is considered as a secured ring in the groove of piston (secured ring) while in second model, the piston ring floats into the piston groove (free ring).

Increasing the number of waves across the piston ring thickness, the structural integrity of the ring is strongly influenced. Piston ring with surface texturing reduces the mean friction force, under the consideration of cylinder straightness. The gas leaks due to existence of the ring gap, affects significantly the maximum mechanical stresses.

The novelty of this paper is the analysis of manufacturing errors, such as waviness and straightness either for smooth or for artificial textured piston ring. In particular, the piston ring structural integrity investigated while chamber gas pressure leaks through the ring gap or not. The number of the waves, their amplitude and the fluid velocity are also taken into consideration.

It was verified that the micro-texture in the front and back of the tool at the same time had a positive effect on improving the milling behavior and surface quality of the tool. The purpose of this study is to explore the rationality of simultaneous placement of micro-textures on the front and rear surfaces of ball-end milling cutters, analyze the influence of micro-texture parameters on tool milling behavior and workpiece surface quality, reveal its internal mechanism, and obtain the best micro-texture parameters by optimization.

First, the mechanism of micro-texture is studied based on the energy loss model. Second, the orthogonal experiment is designed to analyze the influence of micro-texture parameters on tool milling behavior and reveal its mechanism by combining simulation technology and cutting experiment. Finally, the parameters are optimized based on the artificial bee colony algorithm.

The results show that the simultaneous placement of micro-texture on the rake face and flank face of the tool has a positive effect on improving the milling behavior and surface quality of the tool. Taking milling force, tool wear and surface roughness as the evaluation criteria, the optimal parameter combination is obtained: the rake face micro-texture diameter is 50 µm, the distance from the micro-texture is 200 µm and the distance from the cutting edge is 110 µm; the diameter of the micro-textured flank is 40 µm, the distance from the micro-texture is 170 µm and the distance from the cutting edge is 130 µm.

Taking milling force, tool wear and surface roughness as the evaluation criteria, the optimal parameter combination is obtained: the rake face micro-texture diameter is 50 µm, the distance from the micro-texture is 200 µm and the distance from the cutting edge is 110 µm; the diameter of the micro-textured flank is 40 µm, the distance from the micro-texture is 170 µm and the distance from the cutting edge is 130 µm, which provides theoretical support for the further study of the micro-textured tool.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-01-2023-0022/

The purpose of this paper is to describe a mechanical equilibrium model of a one‐end‐fixed type rubberless artificial muscle and the feasibility of this model for control of the rubberless artificial muscle. This mechanical equilibrium model expresses the relation between inner pressure, contraction force, and contraction displacement. The model validity and usability were confirmed experimentally.

Position control of a one‐end‐fixed type rubberless artificial muscle antagonistic drive system was conducted using this mechanical equilibrium model. This model contributes to adjustment of the antagonistic force.

The derived mechanical equilibrium model shows static characteristics of the rubberless artificial muscle well. Furthermore, it experimentally confirmed the possibility of realizing position control with force adjustment of the rubberless artificial muscle antagonistic derive system. The mechanical equilibrium model is useful to control the rubberless artificial muscle.

This paper reports the realization of advanced control of the rubberless artificial muscle using the derived mechanical equilibrium model.

Streak defect and dynamic harmonic excitation (DHE) loading play important roles in machine operating conditions. The purpose of this paper was to assess the effects of streak defect and DHE loading on the tribological properties of surface-contact friction pairs, for example the differential gear end-face on the washer, via experimental investigation.

Streak defect was artificially introduced into the washer surface, which was loaded with DHE loads produced by a spring-connecting weight system. The wear scar of the washers and the monitored friction force signals were respectively scanned using scanning electron microscope (SEM) and analyzed using wavelet simulation.

The friction force curves, SEM images and discrete wavelet transform results indicate that DHE loading tends to increase friction force, to accelerate plowing damages and result in side-flow of material and plastic deformation on the surfaces of the washer. Whereas, streak oil-channel textures on washer specimen can be machined to modify the lubrication condition in the running-in stage so as to improve the tribological properties of the sliding pairs which were even subjected to DHE loading.

On the basis of this thesis research, the effect of streak defect and DHE loading on tribological performance of surface-contact sliding pairs is discussed. The results of wear form and friction state with the effect of streak defect and DHE loading facilitate to optimize the operating condition of mechanical parts.

This paper aims to propose an enhanced static model of commercial braided pneumatic artificial muscles (PAMs), which is fully analytical without the need for experimentally determined parameters.

To address the highly nonlinear issues of PAMs, the enhanced model is derived considering the irregular shapes close to their end-fittings, as well as the elastic energy stored in both their braids and rubber bladders. The hysteresis characteristics of PAMs are also explored by analyzing the friction in the crossovers of the interlacing braided strands, together with that between the strands and their surrounding bladders. The isobaric and isometric experiments of a commercial PAM are conducted to demonstrate the enhancement, and the model accuracy is evaluated and compared with some existing models in terms of root mean square errors (RMSEs). Additionally, the proposed model is simplified to facilitate the applications that entail high computational efficiency.

The proposed model agrees well with the experimental results, which indicates its viability to accurately predict the static behaviors. An overall RMSE of 5.24 N shows that the enhanced model is capable of providing higher accuracy than the existing analytical models, while keeping the modeling cost at a minimum.

The proposed model, taking account of non-cylindrical shapes, elastic energy and friction, succeeds in enhancing the static predictions of commercial PAMs. The fully analytical model may accelerate the development of novel PAM-based robots for high-precision control, while giving a deeper understanding of commercial PAMs.

Fabric-object friction force is a fundamental factor in cloth simulation. A large number of parameters influence the frictional properties of fabrics such as fabric structure, yarn structure, and inherent properties of component fibers. The purpose of this paper is to propose a novel technique for modeling fabric-object friction force in knitted fabric simulation based on the mass spring model.

In this technique, unlike other studies, distribution of friction coefficient over the fabric surface is not uniform and depends on the fabric structure. The main reason for considering non-uniform distribution is that in various segments of fabric, contact percent of fabric-object is different.

The proposed technique and common methods based on friction coefficient uniform distribution are used to simulate the frictional behavior of knitted fabrics. The results show that simulation error values for proposed technique and common methods are 2.7 and 9.4 percent as compared with the experimental result, respectively.

In the existing methods of the friction force modeling, the friction coefficient of fabric is assumed uniform. But this assumption is not correct because fabric does not have an isotropic structure. Thus in this study, the friction coefficient distribution is considered based on fabric structure to achieve more of realistic simulations.

Since the multi-component of powder metallurgy was dispersed, and each component sheared flow and tiered under the action of friction force, it was difficult to disclose the evolution characteristics of each component. Meanwhile, third body mixing with particles of each component covered on the friction surface, which further increased the difficulty of understanding evolution of each component and the corresponding third body in the friction process. To solve this problem, this paper aims to propose a mechanical assembled method which compact several component sheets in order.

Pure copper, aluminum and artificial graphite sheets with thickness 0.5, 1 and 2 mm, respectively, were assembled into a jig by mechanical compact method. The relationship between arrangement patterns of the components and its friction coefficient was studied by using fixed speed friction test machine, the speed range from 200 to 2,000 r/min and the pressure range from 0.25 to 0.64 MPa.

The testing results showed that when the distribution of same components was congregated, friction coefficient dropped from 0.6 to 0.4. While the distribution of different components was dispersed, friction coefficient dropped from 0.6 to 0.25. The friction coefficient decline was caused by performances changes of third body fluidity. The sufficiently mixed third body made third body adhesion weaker and increased third body fluidity. That provoked friction coefficient decreasing obviously at high speed. On the contrary, with the high congregation of same components, strong third body adhesion led to a rougher surface which contributed to a higher friction coefficient.

By means of the mechanical-assembled multi-layer components to reveal the influence mechanism of every component on friction properties, will provide a new test approach for tribology.