Global ETD Search

291	Effect of temperature on early stage adhesion during TiAlN sliding against Inconel 718 and Stainless steel 316L : High temperature tribology Ali, Ahsan January 2023 (has links) High-performance materials such as stainless steels and nickel based super alloys are widely used in demanding applications where high mechanical and thermal properties are required. The applications of super alloys are mainly found in jet engines, power plants and gas turbines demanding high fatigue strength, corrosion and oxidation resistance as well as wear resistant properties. In order to use them, they go through various machining processes such as milling, turning, cutting, polishing etc. until the final product is achieved. Modern manufacturing industries employs various machining tools and technologies to improve the machining process of heat resistant super alloys. However, there are still challenges which needs to be addressed. Among them, adhesive wear of the machining tools is one of the main wear mechanism during the tribological interaction of tool and workpiece, preventing them to achieve the desired quality and surface finish of the end product. Moreover, it damages the tool reducing its lifecycle and in return, increasing the production cost. Among the cutting tools tungsten carbide (WC/Co) tools coated with TiAlN coating due to their good high temperature performance are extensively used. Nonetheless, these coatings still face issue like adhesive wear, abrasion, oxidation at higher temperature damaging the tools and subsequent machining. Therefore, it is imperative to understand the initiation mechanism of adhesive wear during the tribological interaction of super alloys and coated cutting tool material. In this research work, the tribological response of two coatings deposited by physical vapour deposition (PVD), having the composition Ti60Al40N and Ti40Al60N have been studied against two super alloys material, i.e. Inconel 718 and stainless steel 316L. A high temperature SRV (Schwingung (Oscillating), Reibung (Friction), Verschleiß (Wear)) reciprocation friction and wear test set up was employed to investigate the friction behaviour, wear rate and dominant wear mechanisms. For Ti60Al40N coating, the experimental results revealed that generally, friction increases in case of sliding against Inconel 718 up to 400 °C and drops at 760 °C. A high wear volume at room temperature and a decrease to a minimum at 760 °C has been observed for Inconel 718. On the other side, Stainless steel 316L (SS 316L) faces a continuous rise in friction coefficient with highest value at 760 °C during sliding against Ti60Al40N coating. Wear is highest at 400 °C for SS 316L pin. The worn surfaces shows that both workpiece materials experience increase in material transfer due to adhesive wear with rise in temperature. At 400 °C, adhesion is the primary wear mechanism for both workpiece materials. A further rise in temperature to 760 °C promotes the adhesive wear through oxides formation on both material surfaces. Similarly, Ti40Al60N coating shows the same friction behaviour with change in average steady state friction values for both material of Inconel 718 and SS 316L. Both workpiece materials responds in a similar way to wear volume loss, i.e. lowest at room temperature and highest at 760 °C. For Inconel 718, transfer of coating constituents on to the Inconel 718 pin surface was detected and associated with coating rupture and peeling, exacerbating with rise in temperature. Adhesion, abrasion, and oxidation are primary wear mechanisms at 400 °C and 760 °C. For SS 316L, coating transfer only happen at 400 °C. No damage of coating at 40 °C, a complete damage at 400 °C, and formation of dense porous oxides layers at 760 °C have been noticed. At 400 °C, adhesion, abrasion, and chipping while at 760 °C, adhesion, three body abrasion, ploughing and oxidation are the main wear mechanisms. High temperature tribology Early-stage adhesion Adhesive wear Friction Wear resistant coatings TiAlN Tungsten carbide (WC/Co) Difficult to machine super alloys Inconel 718 Stainless steel 316L High-performance materials Abrasion Oxidation Chipping Ploughing Characterization Reliability and Maintenance Tillförlitlighets- och kvalitetsteknik Aerospace Engineering Rymd- och flygteknik
292	Ätiologie und Epidemiologie pathologischer Veränderungen an den Skeletfunden der neolithischen Populationen aus Calden, Rheine und Großenrode / Etiology and epidemiology of pathological changes on the skeletal remains of the Neolithic populations from Calden, Rheine and Großenrode Cyris, Jan Christian 17 August 2020 (has links) No description available. 610 Trichterbecherkultur Wartbergkultur Paläopathologie Archäologie Anthropologie Soester Gruppe Karies Parodontopathien apikale Prozesse Megalithik Neolithik Jäger und Sammler Ackerbauern Zahnabrasion Schmelzhypoplasie Ernährungszustand Meningitis Sinusitis degenerative Gelenkerkrankungen Trauma Gewalt Fraktur Cribra orbitalia Arthrose Arthritis Histologie Lebensbedingungen Funnelbeaker culture Wartberg culture Palaeopathology Archaeology Anthropology Soester group caries periodontal diseases apical process megalithic neolithic hunters and gatherers sedentary farmers abrasion enamel hypoplasia nutritional status meningitis sinusitis degenerative joint disease trauma violence fracture Cribra orbitalia arthrosis arthritis histology living conditions
293	Placement of Controls in Construction Equipment Using Operators´Sitting Postures : Process and Recommendations Jalkebo, Charlotte January 2014 (has links) An ergonomically designed work environment may decrease work related musculoskeletal disorders, lead to less sick leaves and increase production time for operators and companies all around the world. Volvo Construction Equipment wants to deepen the knowledge and investigate more carefully how operators are actually sitting whilst operating the machines, how this affects placement of controls and furthermore optimize controls placements accordingly. The purpose is to enhance their product development process by suggesting guidelines for control placement with improved ergonomics based on operators’ sitting postures. The goal is to deliver a process which identifies and transfers sitting postures to RAMSIS and uses them for control placement recommendations in the cab and operator environments. Delimitations concerns: physical ergonomics, 80% usability of the resulted process on the machine types, and the level of detail for controls and their placements. Research, analysis, interviews, test driving of machines, video recordings of operators and the ergonomic software RAMSIS has served as base for analysis. The analysis led to (i) the conclusion that sitting postures affect optimal ergonomic placement of controls, though not ISO-standards, (ii) the conclusion that RAMSIS heavy truck postures does not seem to correspond to Volvo CE’s operators’ sitting postures and (iii) and to an advanced engineering project process suitable for all machine types and applicable in the product development process. The result can also be used for other machines than construction equipment. The resulted process consists of three independent sub-processes with step by step explanations and recommendations of; (i) what information that needs to be gathered, (ii) how to identify and transfer sitting postures into RAMSIS, (iii) how to use RAMSIS to create e design aid for recommended control placement. The thesis also contains additional enhancements to Volvo CE’s product development process with focus on ergonomics. A conclusion is that the use of motion capture could not be verified to work for Volvo Construction Equipment, though it was verified that if motion capture works, the process works. Another conclusion is that the suggested body landmarks not could be verified that they are all needed for this purpose except for those needed for control placement. Though they are based on previous sitting posture identification in vehicles and only those that also occur in RAMSIS are recommended, and therefore they can be used. This thesis also questions the most important parameters for interior vehicle design (hip- and eye locations) and suggests that shoulder locations are just as important. The thesis concluded five parameters for control categorization, and added seven categories in addition to those mentioned in the ISO-standards. Other contradictions and loopholes in the ISO-standards were identified, highlighted and discussed. Suggestions for improving the ergonomic analyses in RAMSIS can also be found in this report. More future research mentioned is more details on control placement as well as research regarding sitting postures are suggested. If the resulted process is delimited to concern upper body postures, other methods for posture identification may be used. Motion capture controls placement posture identification construction equipment operator environment volvo ce depth sensor inertial optical zone of reach zone of comfort H-point SIP Seat index point product development ergonomics Work Related Musculoskeletal Disorders Human Machine Interaction HMI WRMD Anthropometry Catia RAMSIS GEometric Kinematic backhoe loader wheel loader articulated hauler excavator Faro-Arm CMM Skeleton points skin points sitting posture operating posture categorization V model visual fields percentile road condition skill level sight point Abrasion speed visibility FOV field of view primary secondary tertiary ZoC ZoR mid-eye Design aid safety heavy truck

Page generated in 0.0428 seconds