Identification of relevant wavelet functions for multiscale characterization of manufactured surfaces using a genetically optimized neural network

Multiscale surface characterization is a powerful tool that is used for process monitoring, surface quality control, and manufacturing optimization by establishing a link between process variables and functional performances. The multiscale decomposition approach using continuous and discrete wavelets is widely applied to take into account scales dependency. However, the optimal choice of the analysis wavelet function and the number of decomposition level is still a big issue. In this article, the artificial neural network theory was combined with the wavelet concept and was optimized based on the genetic algorithm to identify the relevant wavelet function for multiscale characterization of abraded surface topographies. Then, an extensive wavelet function library was developed and the proposed algorithm was applied to topographic data obtained from various abrasive finishing processes. The results show the pertinence of this approach to select the relevant wavelet, and a universal relevant wavelet function for abraded surface characterization was determined

Mutual influence of cross hatch angle and superficial roughness of honed surfaces on friction in ring-pack tribo-system

The cylinder bore surface texture, widely produced by the honing technique, is an essential factor for a good engine performance (friction, oil consumption, running-in, wear etc.). This explains the improvement and development of various new honing techniques. These different honing processes generate surfaces with various texture features characteristics (roughness, valleys depth, cross hatch angle, etc.). This paper addresses a comparison of ring-pack friction for cylinder surfaces produced by plateau honing and helical slide honing. It takes in consideration the mutual effect of superficial plateau roughness amplitude and honing angle. A numerical model is developed to predict friction within the cylinder ring-pack system in mixed lubrication regime. The results show the effectiveness of helical slide honed surface texture in comparison to plateau honed bore surface

Running-in wear modeling of honed surface for combustion engine cylinder liners

The texture change during running-in alters the performance and efficiency of a tribo-mechanical system. During mass production of cylinder liners, a final finishing stage known as ‘‘plateau honing’’ is commonly added to reduce the running-in wear process of the liner surface. The majority of researchers think that this operation improves the engine efficiency and decreases oil consumption. It was believed that there are close links between the surface topography of honed cylinders change and their wear resistance during running-in. However, these interactions have not yet been established. Some running-in wear models were developed in the open literature to predict topographical surface changes without considering the running-in conditions. The present paper thus investigates the various aspects of the wear modeling that caused running- in problems in honed surfaces and its implications on ring-pack friction performance. To illustrate this, plateau honing experiments under different conditions were first carried out on an instrumented vertical honing machine. The plateau honing experiments characterize the surface modifications during running-in wear of cast-iron engine bores using advanced characterization method. Based on the experimental evidence, a running-in wear model was developed. Finally, a numerical extension of the developed model was applied to solve the Reynolds equation by taking into account the real surface topographies of the engine bore. This enables us to predict realistic friction performance within the cylinder ring-pack tribosystem

Experimental study of coated tools effects in dry cutting of natural fiber reinforced plastics

This work aims to investigate the tribological effects of coated tools on the surface finish of natural fiber reinforced plastics (NFRPs) during profile milling process with particular emphasis on the natural fiber cutting mechanisms and tool wear. Both up-milling and down-milling configurations were considered. The cutting experiments were carried out on unidirectional flax fibers reinforced polypropylene resin (UDF/PP) using three different cutting tools. Uncoated tungsten carbide, titanium diboride (TiB2) coated and diamond coated were used to conduct profile milling tests. Tribological cutting contacts were evaluated by measuring the specific cutting energy. Surface state was acquired by a scanning electronic microscope (SEM) and an optical microscope (OM). Surface topography was measured using a 2D Surfascan stylus profilometer. Machined NFRP surface finish was characterized using standard and multiscale analysis based on wavelets transform. Results show that the cutting edge radius made by tool coating has a significant effect on surface finish. Natural fiber shearing is more efficient once the removed chip thickness exceeds the cutting edge radius value. Moreover, it had been demonstrated that the pertinent scales for surface finish analysis are between 50 μm and 1 mm which correspond to the multiscale fiber reinforcement structure. Furthermore, and unlike the uncoated tool, TiB2 and diamond coatings allow a good wear resistance of the cutting tools against the tribological solicitations of flax composite machining

On the multiscale tribological signatures of the tool helix angle in profile milling of woven flax fiber composites

The present study is focused on tribological and multiscale analysis for the machined surfaces of bi-directional flax fibers reinforced polypropylene composites. This is to track the multiscale effect of the helix angle of the cutting tool, related to its kinematic, on the cutting mechanisms. The results show that the helix angle has significant effect on the tribological performances which affect the tribo-contact interaction between the flax fibers and the cutting edge. The fibers orientation in the woven reinforcement has significant effect on the surface quality. The multiscale analysis reveals the pertinent scales that activate the helix angle effect

Energy efficiency optimization of engine by frictional reduction of functional surfaces of cylinder ring-pack system

International audienceFriction reduction, lower oil consumption, and limitation of greenhouse gases emissions are the chief objectives of the automotive industry in order to improve the environmental efficiency of vehicle engines.In this paper, a strategy for ring-pack friction reduction through cylinder liner finish optimization based on coupling instrumented honing experiments and numerical prediction of elastohydrodynamic friction is proposed.The results show that honed surfaces produced by fine abrasion by honing stones yield the optimal elastohydrodynamic friction. They also demonstrate the limitations of ISO 13565 standard roughness parameters in giving a complete description of the functional performances of cylinder surface finishes

Wear study of structured coated belts in advanced abrasive belt finishing

Advanced belt finishing process is remarkably simple and inexpensive. The principle of operation is simple: pressure-locked shoes platens circumferentially press an abrasive coated belt on a rotating workpiece. This abrasive machining process reduces significantly surface irregularities subsequently improving geometrical quality and increasing wear resistance and fatigue life. It is therefore extensively used in automotive industry to superfinish crankshaft journals. However, the major industrial issue about this manufacturing process is its efficiency and robustness. One of the most promising ways to solve this issue is to control the distribution and morphology of the abrasive grits. Recently a new generation of abrasive belts coated with structured and shaped agglomerate grits has been commercially available. These structured coated belts with mastered cutting edge orientations promise to be more efficient as they have a better wear resistance compared to the traditional coated abrasive belt. Therefore, this work aims to discuss these assumptions and to establish the link between three structured coated belts, the surface finishes and the physical mechanisms which govern their wear performances. In particular a parametric study, based on the cycle time and the rotation speed, is lead in order to analyze the potential of each structure in terms of surface roughness improvement, wear resistance and consumed energy. The experimental results have demonstrated that, depending on the abrasive structure considered and for a same number of revolutions, modifying the cycle time or the rotation speed can lead to different surface finishes and belt's wear

On the multiscale tribological signatures of the tool helix angle in profile milling of woven flax fiber composites

The present study is focused on tribological and multiscale analysis for the machined surfaces of bi-directional flax fibers reinforced polypropylene composites. This is to track the multiscale effect of the helix angle of the cutting tool, related to its kinematic, on the cutting mechanisms. The results show that the helix angle has significant effect on the tribological performances which affect the tribo-contact interaction between the flax fibers and the cutting edge. The fibers orientation in the woven reinforcement has significant effect on the surface quality. The multiscale analysis reveals the pertinent scales that activate the helix angle effect

Experimental study of coated tools effects in dry cutting of natural fiber reinforced plastics

This work aims to investigate the tribological effects of coated tools on the surface finish of natural fiber reinforced plastics (NFRPs) during profile milling process with particular emphasis on the natural fiber cutting mechanisms and tool wear. Both up-milling and down-milling configurations were considered. The cutting experiments were carried out on unidirectional flax fibers reinforced polypropylene resin (UDF/PP) using three different cutting tools. Uncoated tungsten carbide, titanium diboride (TiB2) coated and diamond coated were used to conduct profile milling tests. Tribological cutting contacts were evaluated by measuring the specific cutting energy. Surface state was acquired by a scanning electronic microscope (SEM) and an optical microscope (OM). Surface topography was measured using a 2D Surfascan stylus profilometer. Machined NFRP surface finish was characterized using standard and multiscale analysis based on wavelets transform. Results show that the cutting edge radius made by tool coating has a significant effect on surface finish. Natural fiber shearing is more efficient once the removed chip thickness exceeds the cutting edge radius value. Moreover, it had been demonstrated that the pertinent scales for surface finish analysis are between 50 μm and 1 mm which correspond to the multiscale fiber reinforcement structure. Furthermore, and unlike the uncoated tool, TiB2 and diamond coatings allow a good wear resistance of the cutting tools against the tribological solicitations of flax composite machining

Multiscale assessment of structured coated abrasive grits in belt finishing process

This paper outlines the link between grit morphology and surface roughness of belt-finished workpieces.It features a comparative analysis of a new generation of abrasive belts with diverse abrasive structures,and a multi-scale roughness characterization of abrasive belt wear on a variety offinished surfaces. Theultimate thickness of the mechanically deformed layer and surface profile projections depends, to a greatextent, on the abrasive mechanisms of friction and wear employed in thefinishing process. By modifyingthe physical mechanisms (cutting, plowing or sliding), it is possible to achieve a concomitant change inthe rate of material removal and, consequently, to the specific surface roughness of thefinished parts.Our research shows that the active roughness scale resulting from beltfinishing is stronglydependent on the grit orientation and the binder distribution. The results are promising for increasingthe efficiency of the abrasion processes and for improving the surface texturing offinished parts