Influence of the built-up edge on the stress state in the chip formation zone during orthogonal cutting of AISI1045

In-situ strain measurements with high energy synchrotron radiation during orthogonal cutting of AISI1045 were carried out. Thereby it was possible to determine the stress state in the chip formation zone during the cutting process. As such, observations regarding the formation of built-up edges during the cutting process have been made. The formation of a built-up edge on the cutting tool is a common phenomenon during cutting of mild steel and other ductile materials, in particular at low cutting speeds. This may result in increased tool wear and a decrease in the resulting surface quality. By analyzing the chip roots of the in-situ experiments, it was possible to determine the geometry of the built-up edges on tools with a rake angle of γ = 0° and cutting edge radii of rβ = 30 μm and rβ = 60 μm. Using the obtained data a simulation model which represents the built-up edge could be established with two versions of the built-up edge: a solid one as part of the rigid tool and an elastic one in front of the tool. Using FEM cutting simulations with and without built-up edges, it was possible to show the influence of a built-up edge on the chip formation and the stress state in the chip formation zone. With this data, a comparison of the results of the cutting simulations with those of the in-situ experiments was conducted

Influence of the Built-up Edge on the Stress State in the Chip Formation Zone During Orthogonal Cutting of AISI1045

AbstractIn-situ strain measurements with high energy synchrotron radiation during orthogonal cutting of AISI1045 were carried out. Thereby it was possible to determine the stress state in the chip formation zone during the cutting process. As such, observations regarding the formation of built-up edges during the cutting process have been made. The formation of a built-up edge on the cutting tool is a common phenomenon during cutting of mild steel and other ductile materials, in particular at low cutting speeds. This may result in increased tool wear and a decrease in the resulting surface quality. By analyzing the chip roots of the in-situ experiments, it was possible to determine the geometry of the built-up edges on tools with a rake angle of γ = 0° and cutting edge radii of rβ = 30 μm and rβ = 60 μm. Using the obtained data a simulation model which represents the built-up edge could be established with two versions of the built-up edge: a solid one as part of the rigid tool and an elastic one in front of the tool. Using FEM cutting simulations with and without built-up edges, it was possible to show the influence of a built-up edge on the chip formation and the stress state in the chip formation zone. With this data, a comparison of the results of the cutting simulations with those of the in-situ experiments was conducted

Cutting simulation with consideration of the material hardening in the Shear Zone of AISI1045

By the use of high energy synchrotron X-ray diffraction it was possible to determine the stress state in the chip formation zone during orthogonal cutting of AISI1045. The analysis of the diffractograms showed a hardening of the material during the movement through the shear zone. For this reason nano indentation experiments on prepared chips have been carried out. With these experiments, the material hardening has been confirmed. The nano indentation experiments were reproduced by FEM simulations and it was possible to determine flow curves of the hardened material above the shear zone based on existing flow curves of AISI1045. Thus, cutting simulations have been carried out, which considered the material hardening in the shear zone. The simulation results were then compared with the results of the in-situ strain measurements

Mechanical and thermal stability of hard nitride coatings

Cotutela Universitat Politècnica de Catalunya i Linköping UniversityTesi per compendi de publicacionsHard coating 's thermal stability is essential due to the high temperature environment of high-speed cutting applications, while the induced phase and microstructure evolution affects the mechanical properties. In this thesis, the mechanical stability of arc-evaporated hard nitride coatings annealed at high temperature is analyzed and connected to the phase evolution. In addition to hardness, fracture toughness is evaluated by surface and cross-sectional investigations by scanning/transmission electron microscopy of damage events by mechanical tests. The crack resistance of Ti1-xAixN with a range of Al content (x = 0.23-0.82) is studied by contact fatigue tests, where the difference in the microstructure plays a major role. Superior mechanical properties are found in annealed Ti0.63AI0.37N at 900 oC due to the spinodal decomposition. The mechanical and high-temperature properties of hard coatings can be enhanced by alloying or multi-layering. Quaternary Ti-Al-X-N (X = Cr, Nb and V) alloys are studied, and superior toughness is found in TiAI(Nb )N in both the as-deposited and annealed (1100 oC) states. The h-AIN formation in TixAI0.37Cr1-0.37-xN (x = 0.03 and 0.16) is analyzed by in-situ x-ray scattering during annealing. The kinetic energy for h-AIN formation is found to be dependent on the microstructure evolution during annealing, which varies with coating composition. High Al content h-ZrAIN/c-TiN and h-ZrAIN/c-ZrN multilayers are investigated through scratch tests followed by focused ion-beam analysis of the crack propagation. A c-Ti(Zr)N phase forms in h-ZrAIN/c-TiN multilayers at high temperatures and that contributes to enhanced hardness and fracture toughness by keeping the semi-coherency at the sub-interfaces. Finally, an in-situ analysis of coatings by x-ray scattering during a turning process is carried out. lt demonstrates the possibility of observation of stress evolution and thermal expansion of the coatings or the work piece material during machining. This experiment provides real-time information on the coating behavior during cutting.La estabilidad térmica del recubrimiento es esencial debido a que estos recubrimientos durante su aplicación son utilizados a elevada temperatura y a alta velocidad. Durante dicho proceso, la evolución microestructural afecta a las propiedades mecánicas. En dicha tesis, la estabilidad mecánica de los recubimientos duros base nitruro producidos mediante arco y recocidos a elevada temperatura son analizados y se correlacionado con su transformación de fase. La dureza, la resistencia a la fractura son evaluados mediante la observación tanto superficial como transversal mediante microscopia electrónica de barrido. La resistencia a la propagación de grieta de Ti1−xAlxN con un contenido en Al que fluctúa entre 0.23-0.82 se estudia mediante ensayos de fatiga por contacto, donde la diferencia microstructural juega un papel importante. Las mejores propiedades mecánicas se encentran en las muestras con un 0.63 de Ti donde se ha realizado un proceso de recocido a 900o C debido a la descomposición espinoidal. Las características mecánicas y de alta temperatura de recubrimientos duros pueden ser mejoradas si tenemos un recubrimiento multicapa. Aleaciones cuaternarias de Ti-Al-X-N (X = Cr, Nb y V) son estudiada, y una mejor tenacidad de fractura se encuentra para la muestra TiAl(Nb)N sin tratamiento de recocido como recocida a 1000ºC. La formación del AlN con una estructura hexagonal en la muestra TixAl0.37Cr1−0.37−xN (x = 0.03 y 0.16) son analizadas mediante ensayos in-situ de difracción de rayos X durante el proceso de recocido. Cabe mencionar que la energía cinética para la formación de la AlN con una estructura hexagonal depende del proceso de recocido, la cual hace variar la composición química del recubrimiento. Multicapas de h (hexagonal)-ZrAlN/c (cúbica)-TiN con un elevado contenido de Al son estudiadas mediante ensayos de rayado y la generación de daño es observado mediante la técnica del haz de iones focalizados. Las formas de la fase de c-Ti(Zr)N en las multicapas de (h)-ZrAlN/c-TiN formadas a elevadas temperaturas contribuyen a mejorar la dureza y la tenacidad de fractura manteniendo la semicoherencia en las intercaras entre cada capa. Finalmente, se realiza un análisis in-situ de los diferentes recubrimientos me diante dispersión de rayos X durante un proceso de torneado. En este caso, se demuestra la posibilidad de observar la evolución de las tensiones residuales y de la expansión térmica durante el proceso de conformado. Dicho experimentos proporciona información en tiempo real sobre el comportamiento del recubrimiento en condiciones de servicio.Hårda skikts högtemperaturstabilitet är viktig på grund av den höga temperaturskikten utsätts för under skärande bearbetning, och den utveckling av faser och mikrostruktur som då sker påverkar skiktets mekaniska egenskaper. I den här avhandlingen har den mekaniska stabiliteten hos arcförångade, hårda metallnitridskikt som värmebehandlats vid höga temperaturer studerats. Förutom hårdhet har även skiktens seghet utvärderats genom yt- och tvärsnittsstudier av den sprickbildning som uppstår vid mekanisk provning med hjälp av svep- och transmissionselektronmikroskopi. Segheten hos Ti1−xAlxN skikt med varierande Al-halt (x = 0.23-0.82) studerades genom utmattningsprovning och resultaten visar att förändringar i mikrostrukturen spelar en stor roll. Ti0.63Al0.37N skikten hade överlägsna mekaniska egenskaper; på grund av en fördelaktig kornstorlek i de obehandlade skikten och efter värmebehandling som ett resultat av det spinodala sönderfall som skett. De mekaniska egenskaperna och högtemperaturegenskaperna hos hårda skikt kan förbättras genom legering eller genom multilagring. I den här avhandlingen har kvarternära Ti-Al-X-N (X = Cr, Nb eller V) skikt studerats och TiAl(Nb)N skikten hade en överlägsen seghet i både obehandlat och värmebehandlat (1100oC) tillstånd. Bildandet av h-AlN i TixAl0.37Cr1−0.37−xN (x = 0.03 and 0.16) skikt studerades genom in situ röntgenspridning under värmebehandling. Den energi som krävs för att bilda h-AlN beror av mikrostrukturutvecklingen under värmebehandling vilken i sin tur beror av skiktens kemiska sammansättning. h-ZrAlN/c-TiN och h-ZrAlN/c-ZrN multilager med hög Al-halt undersöktes genom reptester följda av tvärsnittsstudier av sprickbildningen genom en analys med en fokuserad jonstråle (FIB). En c-Ti(Zr)N fas bildas vid höga temperaturer i h-ZrAlN/c-TiN multilagren och det bidrar till förhöjd hårdhet och förbättrad seghet på grund av en bibehållen koherens mellan lagren. Slutligen har in situ röntgenspridningsstudier av ytskikt utförts vid svarvning. Studien visar på möjligheten att observera spänning och värmeutvidgning av skikten eller arbetsmaterialet under bearbetning. Experimenten ger information om skiktens beteende under bearbetning i realtid.Postprint (published version

In situ strain measurement in the chip formation zone during orthogonal cutting

The strain and stress state in the chip formation zone determines the chip formation. However, it is difficult to obtain experimental data about the strain/stress fields during machining. For this reason, present chip formation models highly simplify the chip formation process. In order to extend the knowledge regarding the chip formation mechanisms, an experimental method for the in situ measurement of the elastic deformations within the chip formation zone during the cutting process has been developed. Using these deformations, the stress state can subsequently be calculated. The method is based on X-ray diffraction using high-energy synchrotron X-radiation during machining the workpiece in an orthogonal cutting process with low cutting speed. The diffraction patterns are captured with a 2D detector. A comparison of the experimentally determined stresses at different measuring positions within the chip formation zone with results from a FEM cutting simulation shows a good qualitative and partially also quantitative consistency. Possibilities for the further performance increase of the method are identified so that the method can be used for the verification and extension of existing chip formation models in future.JRC.DDG.F.4-Safety of future nuclear reactor

Detaillierte Analyse der Aufbauschneidenbildung bei der Trockenzerspanung von Stahl C45E mit Berücksichtigung des Werkzeugverschleißes

In dieser Arbeit wurde ein tieferes Verständnis der Aufbauschneidenbildung bei der trockenen Zerspanung entwickelt. Die Aufbauschneidenbildung wurde in relevanten Zerspanparameterbereichen in-situ radiographisch und röntgenographisch analysiert. Gleichzeitig konnte die Mikrostruktur in Abhängigkeit der Zerspanparameter mittels neuester Methoden der Mikrostrukturanalytik ex-situ untersucht werden. Eine Korrelation zwischen Aufbauschneidenbildung und Werkzeugverschleiß konnte abgeleitet werde

Detaillierte Analyse der Aufbauschneidenbildung bei der Trockenzerspanung von Stahl C45E mit Berücksichtigung des Werkzeugverschleißes

Anhand dieser Arbeit wurde mittels neuester Methoden ein tiefergehendes Verständnis der Aufbauschneidenbildung entwickelt. Die Aufbauschneidenbildung konnte zum ersten Mal in einem relevanten Zerspanparameterbereich in-situ radiographisch und röntgenographisch untersucht werden. Zudem wurde die Mikrostruktur innerhalb der Aufbauschneide mittels neuer materialwissenschaftlicher Methoden analysiert. Eine Korrelation zwischen Aufbauschneidenbildung und Werkzeugverschleiß konnte abgeleitet werden