Influence of metal working fluid on chip formation and mechanical loads in orthogonal cutting

Metal working fluids are used in machining processes of many hard-to-cut materials to increase tool life and productivity. Thereby, the metal working fluids act on the thermal and on the mechanical loads of the tool. The changing mechanical loads can mostly be attributed to the changing friction between rake face and chip and changes in the chip formation, e.g., the contact length between rake face and chip. However, analyzing those effects is challenging, since a detailed look at the chip formation process is prevented by the metal working fluid. In this paper, a novel planing test rig is presented, which enables high-speed recordings of the machining process and process force measurements while using metal working fluids. Experiments reveal that process forces are reduced with increasing pressure of the metal working fluid. However, the average friction coefficient only changes slightly, which indicates that the reduced process forces are mainly the result of reduced contact lengths between rake face and chip

Coolant boiling and cavitation wear – a new tool wear mechanism on WC tools in machining alloy 718 with high-pressure coolant

In recent years, research interest in liquid coolant media applied to the tool–workpiece interface (the tertiary shear zone) has grown considerably. In particular, attention has increased for work where the media has been applied under high-pressure. This is most likely triggered by the positive results reported on similar applications, but with coolant media directed towards the rake face of the cutting tool (the secondary shear zone). The most typical applications have not surprisingly been related to the machining of Heat Resistant Super Alloys (HRSA) or other “difficult to machine” alloys where the main intention has been to extend tool life and improve surface finish through reduced shear zone temperatures.Concurrently, these achievements have revealed a knowledge gap and unlocked a new research area in understanding the effects and influences of coolant media applied on super-heated surfaces under high-pressure conditions. The aim of this study is to investigate the “coolant boiling and cavitation” phenomena that emerges during the application of coolant under high-pressure to the flank face of an uncoated WC tool while turning Alloy 718. The experimental campaign was conducted in three aspects: varying flank (coolant media) pressure; varying spiral cutting length (SCL); and varying cutting speed.The results revealed that the location and size of the coolant-boiling region correlated with flank wear, coolant pressure and vapour pressure of the coolant at the investigated pressure levels. Further, the results showed that coolant applied with a lower pressure than the vapour pressure of the coolant itself caused the “Leidenfrost” effect. This then acts as a coolant media barrier and effectively reduces the heat transport from the cutting zone.Further, erosion pits were observed on small areas of the cutting tool, resembling the typical signs of cavitation (usually found in much different applications such as pumps and propellers). The discovered wear mechanism denoted as “Cavitation Wear” was used as base for the discussion aimed to deepen the understanding of the conditions close to the sliding interface between the tool and the workpiece. Even though “Cavitation Wear” has been widely reported in hydraulic systems like pumps and water turbines, it is a new phenomenon to be seen on cutting tools while using high-pressure flank cooling

Heat Transfer And Pressure Drop Measurements In A High-Solidity Pin-Fin Array With Variable Hole Size Incremental Impingements

Gas turbines play a very critical role in the current energy sector in both power generation and in propulsion for almost the entire commercial and military aviation industry. Higher efficiencies can be developed from gas turbines, either land based or aero-propulsion by raising both the pressure and the temperature of combustion gases which discharge into the turbine section, which is also known as the Turbine Entry Temperature (TET). Turbine blade materials simply cannot operate safely at current TETâs of 3000 °F without implementing comprehensive cooling schemes developed in the industry over the years. Normally some of the compressed air is extracted from the compressor discharge and forced into internal cooling passages including serpentine passages in blades to cool the hottest engine components to a safer range in metal temperatures. Often, a portion of air is forced out from an array of tiny holes concentrated in the leading edge of blade aimed to provide internal cooling and a thin layer of protection from hot combustion gases while the rest of the coolant is delivered internally for convection to cool component surfaces to a sustainable temperature. However, the leading edge is quite susceptible to deposition of contaminants from the combustion products which can buildup and plug film cooling discharge holes. In addition, the surface of the leading region experiences intense turbulence, and the turbulence disrupts the film cooling layer from forming stably and protecting the blade surfaces

A bibliography /with abstracts/ on gas-lubricated bearings Interim report

Gas lubricated bearings - annotated bibliograph

Future Space-Transport-System Components under High Thermal and Mechanical Loads

This open access book presents the findings of Collaborative Research Center Transregio 40 (TRR40), initiated in July 2008 and funded by the German Research Foundation (DFG). Gathering innovative design concepts for thrust chambers and nozzles, as well as cutting-edge methods of aft-body flow control and propulsion-component cooling, it brings together fundamental research undertaken at universities, testing carried out at the German Aerospace Center (DLR) and industrial developments from the ArianeGroup. With a particular focus on heat transfer analyses and novel cooling concepts for thermally highly loaded structures, the book highlights the aft-body flow of the space transportation system and its interaction with the nozzle flow, which are especially critical during the early phase of atmospheric ascent. Moreover, it describes virtual demonstrators for combustion chambers and nozzles, and discusses their industrial applicability. As such, it is a timely resource for researchers, graduate students and practitioners

Design of an Original Methodology for the Efficient and Economic Appraisal of Existing and New Technologies in Form Grinding Processes including Helical

The purpose of this research was to create and design a methodology for new product evaluation with an interest in the affects that they could have on form and helical grinding. The design uses a relatively small and commonly available grinding machine so that testing could be done without need for an expensive helical grinding machine typical of that utilised in industry. The contact conditions of the helical grinding process were considered, and the workpiece geometry was designed to closely replicate the form and entry and exit conditions found in helical form grinding of screw compressor rotors. The equipment design allows the grinding forces to be measured in axial, normal and tangential planes. This will allow the variation in axial forces to be explored and allow any variation in hydrodynamic forces to be investigated during the entry and exit regions. Grinding trials showed the importance of the need to measure the true depth of cut for a grinding pass. A novel method of measuring the depth of cut was designed that will allow an accurate measurement of the form position before and after a grinding pass. Replication methods for the workpiece and grinding wheel form were designed to allow capture on the grinding machine to facilitate an economic appraisal method that allows testing to be carried out in a short period of time. A 3D printed coolant nozzle was designed with an air scraper to overcome the air barrier around the periphery of the grinding. The aim of the design was to reduce the need for a high pressure grinding fluid jet and allowing less turbulent flow to enter the grinding nip at lower pressures. A preliminary cost model was created with inputs that relate to form grinding and allow the user to investigate different process parameters and arrive at a cost per part

THIESEL 2020.Thermo-and Fluid Dynamic Processes in Direct Injection Engines.8th-11th September

'The THIESEL 2020 Conference on Thermo-and Fluid Dynamic Processes in Direct Injection Engines planned in Valencia (Spain) for 8th to 11th September 2020 has been successfully held in a virtual format, due to the COVID19 pandemic. In spite of the very tough environmental demands, combustion engines will probably remain the main propulsion system in transport for the next 20 to 50 years, at least for as long as alternative solutions cannot provide the flexibility expected by customers of the 21st century. But it needs to adapt to the new times, and so research in combustion engines is nowadays mostly focused on the new challenges posed by hybridization and downsizing. The topics presented in the papers of the conference include traditional ones, such as Injection & Sprays, Combustion, but also Alternative Fuels, as well as papers dedicated specifically to CO2 Reduction and Emissions Abatement.Papers stem from the Academic Research sector as well as from the IndustryXandra Marcelle, M.; Desantes Fernández, JM. (2020). THIESEL 2020.Thermo-and Fluid Dynamic Processes in Direct Injection Engines.8th-11th September. Editorial Universitat Politècnica de València. http://hdl.handle.net/10251/150759EDITORIA

Phoebus-2 materials Final report

Physical metallurgy, fabrication, and mechanical properties of Phoebus 2 rocket nozzle material