Potentials for Improving Efficiency of Combustion Engines Due to Cylinder Liner Surface Engineering

AbstractDespite new developments like E-mobility or hybrid concepts, the combustion engine will remain of great importance in individual mobility. The article highlights the recent trends, i.e. moving away from monolithic materials in the crankcase towards coated liners with adapted surface structures generated by honing processes. Results of tribological tests are presented for determined surface modifications and different materials to decrease frictional losses. Methods of process monitoring are outlined together with discussion of results from running-in experiments and boundary layer characterisation. Thus, conclusions for the specific finishing of cylinder running surfaces are drawn to improve the honing process

Grinding and fine finishing of future automotive powertrain components

The automotive industry is undergoing a major transformation driven by regulations and a fast-paced electrification. A critical analysis of technological trends and associated requirements for major automotive powertrain components is carried out in close collaboration with industry – covering the perspectives of OEMs, suppliers, and machine builders. The main focus is to review the state of the art with regard to grinding, dressing, texturing and fine-finishing technologies. A survey of research papers and patents is accompanied by case studies that provide further insights into the production value chain. Finally, key industrial and research challenges are summarized

A comparative analysis of ceramic and cemented carbide end mills

Milling of ferrous metals is usually performed by applying cemented carbide tools due to their high hardness, temperature and wear resistance. Recently, ceramic tool materials have been on the rise and enhanced the efficiency in machining. As ceramics are brittle-hard materials, tool manufacturing requires a sound knowledge in order to meet the tool requirements such as sharp cutting edges and wear resistance. In this study, milling tools made of the high performance ceramic SiAlON were compared to tools made from cemented carbide. For both tool materials, the influence of a prepared cutting edge was investigated. Both the tool manufacturing process and the cutting edge preparation processes are presented, followed by the application of those tools within milling experiments. In order to evaluate the efficiency of both tool types, the cutting forces and the cumulative process energy demand were analyzed. Additionally, surface roughness of the machined workpieces and tool wear were examined. It was found that the ceramic tools, although process forces were higher than for cemented carbide tools, exhibited by far lower energy consumption, less tool wear and finally generated lower surface roughness. © 2020, The Author(s)

Micromagnetic Analysis of Thermally Induced Influences on Surface Integrity Using the Burning Limit Approach

Particularly for highly stressed components, it is important to have precise knowledge of the surface and subsurface properties and, thus, of the functional properties after final grinding at the end of a complex process chain in order to avoid rejected parts. Therefore, non-destructive testing methods have been the subject of research for several years. The Barkhausen noise analysis, as a micromagnetic measuring method, has the potential to characterize the subsurface area up to an analyzing depth δ non-destructively with micromagnetic parameters. In addition to micromagnetic multiparameter approaches, which allow post-process mode clear statements about the subsurface area state, the present research work deals with the concept of a connection of a single Barkhausen noise parameter with grinding process parameters. In combination with the analytical approach of Malkin for the thermal surface and subsurface area influence, which is based on the process parameters of grinding processes, a distinction between good and rejected ground parts can be achieved. The results show that, by post-process measurements of the Barkhausen noise on case-hardened workpieces made of steel 18CrNiMo7-6 (No. 1.6587, AISI 4820) and machined by a cylindrical grinding process, incipient changes in the residual stress state up to industrial-relevant limits, which distinguish between good and rejected parts, is possible. In the future, a combination of the Malkin grinding burning limit and sufficient condition monitoring based on in-process measurements of Barkhausen noise will be investigated. The application limits of the analytical approach of Malkin as well as the measurement of the Barkhausen noise in-process have to be determined

Modelování drah brusného kotouče při výrobě šroubovitého vrtáku

Moderní řezné nástroje z rychlořezné oceli nebo slinutého karbidu jsou v současnosti vyráběny broušením na CNC nástrojařských bruskách. Protože se při programování těchto obráběcích strojů jedná o velmi komplikovaný proces, jsou jejich řídící systémy obvykle vybaveny programovacím rozhraním ve formě soustav tabulek, do kterých jsou zadávány jednotlivé parametry vyráběného nástroje. Protože tento systém programování není dostatečně pružný, jsou některé řídící systémy vybaveny možností načítat externí NC programy, s jejichž pomocí je možné vyrábět buď speciální nástroje, nebo modifikovat výrobní proces stávajících nástrojů. Protože při výrobě řezných nástrojů je nezbytné uvažovat s tvarem obalových ploch, které proces programování činí značně obtížným, je výhodné vytvořit matematický popis drah brusného kotouče, který umožní dráhy snáze modifikovat s ohledem na časté změny, které jsou nezbytné při konstrukci monolitního řezného nástroje

An Investigation on Internal Material Loads and Modifications in Precision Turning of Steel 42CrMo4

The functional properties of a workpiece are determined by a modification of the surface and subsurface materials. In this work, the correlation between thermo-mechanical material loads and the modification of the residual stresses is presented. While the resulting residual stresses were measured by X-ray diffraction after machining experiments, the material loads were determined using a process simulation. The experimental data (measured process forces and results from previous experiments) are used to validate the simulation, which is then applied to calculate the internal thermo-mechanical loads of the maximal temperature and the equivalent von-Mises-stresses per volume element during the machining experiments. In conclusion, a higher depth impact of mechanical loads compared to a lower depth impact of thermal loads in precision machining is observed. For the sake of novelty, the thermo-mechanical loads were plotted and interpreted in a three-dimensional fashion. Finally, cross sections of this mutual representation at certain constant material loads—thermal and mechanical—result in a process signature, which can prospectively improve the prediction of functional workpiece properties

In-Process Measurement of Barkhausen Noise for Detection of Surface Integrity during Grinding

The Barkhausen noise (BN) analysis is a method increasingly used for the post-process assessment of thermo-mechanical surface damages from grinding and has several advantages compared with the established nital etching method. In-process measurement of the BN has not been used industrially yet, but the basics have already been developed and promise time savings by avoiding time spent on inspections after grinding. Furthermore, it bears potential for the optimization of grinding processes and, in perspective, a process control. In the present work, the suitability of in-process BN analysis for the detection of thermo-mechanically influenced near-surface regions was assessed. Case-hardened workpieces were ground, and BN signals were related to the properties of the surface and subsurface area, in particular residual stresses, microstructure and surface hardness after grinding. The results show a clear dependency of BN on surface layer properties that allows for an in-process detection of detrimental changes in the surface state. Special attention was paid to the differences between in-process and post-process measured signals, and the suitability of the different measurement parameters for in-process detection was investigated