11 research outputs found
Research on the variability of the burnishing force during processing surfaces with 3D shape by using simultaneous 5-axis ball-burnishing process implemented on CNC milling machine
oai:ojs2.aj-tuv.org:article/20The present research is focused on continuously measuring the variability of the burnishing force during conducting ball-burnishing process for specimens with surfaces with 3D shape, by using CNC milling machine with dual rotary table installed. For measuring the burnishing force and its variability, the specifically developed ball-burnishing tool with miniature force sensor was used. To assess the degree of influence of the main regime parameters on the variability of the burnishing force, the four factors full factorial experiment design with two levels per factor and four replications per run has been carried out. The experimental results are processed statisti-cally and techniques such as Pareto and ANOVA were used after that, for sorting them by degree of significance. Some conclusions about the magnitude and the causes of the obtained variability also are given.The present research is focused on continuously measuring the variability of the burnishing force during conducting ball-burnishing process for specimens with surfaces with 3D shape, by using CNC milling machine with dual rotary table installed. For measuring the burnishing force and its variability, the specifically developed ball-burnishing tool with miniature force sensor was used. To assess the degree of influence of the main regime parameters on the variability of the burnishing force, the four factors full factorial experiment design with two levels per factor and four replications per run has been carried out. The experimental results are processed statisti-cally and techniques such as Pareto and ANOVA were used after that, for sorting them by degree of significance. Some conclusions about the magnitude and the causes of the obtained variability also are given
Research on the influence of the five-axis ball-burnishing process regime parameters on the resulted cells properties from regularly shaped roughness
The current study presents the results from the experimental research conducted on the influence of the regime parameters on the process for a five-dimensional Ball Burnishing (BB) finishing process with the help of a CNC milling machine on the Regular Reliefs (RR) obtained on complex functional surfaces. The elements of the technological system, necessary for the formation of RR of type IV on the complex surfaces, are presented. A planned factorial experiment is realized, through which the significantly affecting parameters of the BB process on the size and shape of the RR cells, are determined. The results obtained are statistically confirmed by a dispersion analysis (ANOVA) carried out. Conclusions, regarding the possibilities of obtaining RRs of type IV on complex surfaces through a process of five-axis simultaneous BB, are made
Artificial neural network and response surface methodology based analysis on solid particle erosion behavior of polymer matrix composites
Polymer-based fibrous composites are gaining popularity in marine and sports industries because of their prominent features like easy to process, better strength to weight ratio, durability and cost-effectiveness. Still, erosive behavior of composites under cyclic abrasive impact is a significant concern for the research fraternity. In this paper, the S type woven glass fibers reinforced polymer matrix composites (PMCs) are used to analyze the bonding behavior of reinforcement and matrix against the natural abrasive slurry. The response surface methodology is adopted to analyze the effect of various erosion parameters on the erosion resistance. The slurry pressure, impingement angle and nozzle diameter, were used as erosion parameters whereas erosion loss, i.e., weight loss during an erosion phenomenon was considered as a response parameter. The artificial neural network model was used to validate the attained outcomes for an optimum solution. The comparative analysis of response surface methodology (RSM) and artificial neural network (ANN) models shows good agreement with the erosion behavior of glass fiber reinforced polymer matrix composites
INVESTIGATION OF SURFACE ROUGHNESS AND MICROHARDNESS IN BALL BURNISHING PROCESS OF AZ31B MAGNESIUM ALLOY
Magnesium alloys which are lightweight and high strength materials have some limitations due to their insufficient corrosion resistance and low surface quality. To overcome these limitations, especially improving surface properties ball burnishing process was applied to magnesium alloy with different parameters like force, number of passes, feed rate and speed. For reducing number of experiments Taguchi method was used and optimum burnishing condition was determined according to S/N ratios. The results of surface roughness and hardness tests show that feed rate and force was found significant parameters for improving surface quality. When lower feed rate and higher force parameters was choosen best surface roughness value was obtained
Advances in CAD/CAM/CAE Technologies
CAD/CAM/CAE technologies find more and more applications in today’s industries, e.g., in the automotive, aerospace, and naval sectors. These technologies increase the productivity of engineers and researchers to a great extent, while at the same time allowing their research activities to achieve higher levels of performance. A number of difficult-to-perform design and manufacturing processes can be simulated using more methodologies available, i.e., experimental work combined with statistical tools (regression analysis, analysis of variance, Taguchi methodology, deep learning), finite element analysis applied early enough at the design cycle, CAD-based tools for design optimizations, CAM-based tools for machining optimizations
Optimization of total trihalomethanes' (TTHMs) and their precursors' removal by granulated activated carbon (GAC) and sand dual media by response surface methodology (RSM)
A response surface methodology (RSM) applying central composite design with rotatable full factorial (14 non-center and six center points) was used to discern the effect of granular activated carbon (GAC), sand and pH on total trihalomethanes (TTHMs) and humic acid (HA) removal from drinking water. Results showed efficient TTHMs and HA removal by GAC while a sand column showed little effect for TTHMs but was significant for total organic carbon (TOC) removal. With GAC and a sand column of 4 cm, a pH increase from 6 to 8 caused an increase in TTHM removal from 79.8 to 83.6% while a decrease in HA removal from 26.6 to 6.6% was observed. An increase in GAC column depth from 10 to 20 cm caused a slight increase in TTHM removal from 99.4 to 99.7%, while TOC removal was increased from an average of 38.85% to 57.4% removal. The developed quadratic model for TTHM removal (p = 0.048) and linear model for TOC removal (p = 0.039) were significant. GAC column depth (p < 0.0117) and column depth2 (p < 0.039) were the most significant factors. A 98% TTHMs, 30%TOC and 51% residual chlorine removal were optimized at 9 cm GAC and 4 cm sand column depth at pH 8 with desirability factor (D) 0.64
Study and characterisation of surface integrity modification after ultrasonic vibration-assisted ball burnishing
Tesi en modalitat de cotutela: Universitat Politècnica de Catalunya i Université Toulouse III Paul Sabatier. Aplicat embargament des de la data de defensa fins a gener de 2020Premi extraordinari doctorat UPC curs 2017-2018. Àmbit d’Enginyeria IndustrialThis dissertation is an experimental research project into the mechanical effects of the ultrasonic vibration-assisted ball burnishing process on the surface integrity of surfaces machined through ball-end milling. Due to the lack of commercial tools able to perform this process, the study includes firstly the design and characterization of a prototype to that effect. An experimental analysis is then undertaken, applying the process to AISI 1038 and Ti-6Al-4V surfaces of high industrial and aeronautical value. The experimental campaign is designed based on a Taguchi orthogonal array that includes five factors, namely: preload, number of passes, feed velocity, strategy and initial surface texture. Results are analyzed in terms of topological characteristics, residual stress and hardness, in order to identify and understand the impact of process parameters on surface integrity, to define the best parameters for performing the process and to assess the positive effects caused by the introduction of vibrations as a means of assistance.
Results reveal that the initial texture is the most influential parameter on all outcomes. Texture results show that the vibrations can enhance the roughness and texture results, as long as they have sufficient low initial amplitude. Furthermore, only the preload and number of passes influence the results, with a pair of values being found in all cases that serve a threshold from which further plastic strain is detrimental for the final surface topology. In terms of residual stress, all parameters are influential in the results, especially the burnishing strategy, through which a certain component of the residual stress tensor can be adequately reinforced. Finally, the burnishing operation proves to modify the hardness of deep layers down to 0.5 mm, applying the vibration-assisted process. .e main conclusion is that the optimal parameters for performing the process are different with regards to the optimization objective.
Some useful combinations are proposed for performing the process depending on the desired targetEsta tesis es un estudio experimental que versa sobre los efectos del proceso de bruñido con bola asistido por vibraciones ultrasĂłnicas sobre la integridad superficial de superficies mecanizadas mediante fresa hemisfĂ©rica. Dada la indisponibilidad de herramientas comerciales capaces de efectuar este proceso, el estudio incluye en primer lugar el diseño y caracterizaciĂłn de un prototipo a tal efecto. Posteriormente, se realiza un análisis experimental aplicando el proceso sobre superficies de dos aleaciones de interĂ©s industrial y aeronáutico, AISI 1038 y Ti-6Al-4V, siguiendo un diseño de experimentos fraccionario basado en una matriz ortogonal de Taguchi. Para ello, cinco factores son incluidos en el modelo, a saber: la precarga, el nĂşmero de pasadas, la velocidad de avance, la estrategia de bruñido, y la textura de la superficie de partida. Los resultados se evalĂşan en tĂ©rminos de textura, tensiones residuales y dureza, para identificar y comprender el impacto de este proceso y de sus parámetros de operaciĂłn sobre la integridad superficial, para definir los mejores parámetros a aplicar para cada material, y con el fin de evaluar los efectos positivos provocados por la introducciĂłn de las vibraciones como medio de asistencia. Los resultados revelan que la textura inicial es el parámetro que define en mayor medida el estado de las superficies finales. Los resultados de textura evidencian que las vibraciones pueden mejorar en mayor medida la topologĂa de las superficies objetivo, siempre que Ă©stas sean suficientemente finas. Además, sĂłlo la precarga y el nĂşmero de pasadas influyen en el resultado, encontrando en todo caso un par de valores limĂtrofe a partir del cual las superficies se ven dañadas. Los resultados de tensiones residuales muestran que todos los parámetros son influyentes en el resultado final, especialmente la estrategia de bruñido, con la que puede modificarse la direcciĂłn preferencial del tensor de tensiones superficial. Finalmente, el bruñido demuestra modificar la dureza positivamente hasta capas de aproximadamente 0,5 mm, aplicando el proceso asistido con vibraciones. Se concluye que los parámetros Ăłptimos de proceso son diferentes en funciĂłn del objetivo de optimizaciĂłn, y deben definirse en base a dos variables de partida: el material objetivo y la textura que Ă©ste presenta antes del proceso.Cette thèse Ă©tudie les effets du processus de brunissage Ă bille assistĂ© par vibrations ultrasoniques sur l’intĂ©gritĂ© surface des surfaces usinĂ©es par fraisage hĂ©misphĂ©rique. Compte tenu de l’inexistence d’outils commerciaux capables de rĂ©aliser ce processus, l’étude dĂ©bute par la conception et la caractĂ©risation d’un prototype capable de l’exĂ©cuter. Par la suite, une analyse expĂ©rimentale est menĂ©e, en utilisant le procĂ©dĂ© sur les surfaces de deux alliages d’intĂ©rĂŞt industriel et aĂ©ronautique, AISI 1038 et Ti- 6Al-4V. Pour cela, un plan d’expĂ©riences est elaborĂ© Ă base d’une matrice orthogonale Taguchi.
Cinq facteurs sont inclus dans le modèle : la prĂ©charge, le nombre de passes, la vitesse d’avance, la stratĂ©gie de brunissage et la texture initiale de la surface prĂ©alablement usinĂ©e. Les rĂ©sultats sont Ă©valuĂ©s en termes de texture finale, de contrainte rĂ©siduelle et de duretĂ©, pour identifier et comprendre l’impact de ce procĂ©dĂ© et des paramètres opĂ©ratoires sur l’intĂ©gritĂ© de surface, pour dĂ©finir les meilleurs paramètres Ă appliquer pour chaque matĂ©riau, et pour Ă©valuer les effets positifs provoquĂ©s par l’introduction de vibrations comme moyen d’assistance. Pour cela, la notion d’intĂ©gritĂ© de surface est rappelĂ©e, voire redĂ©finie dans le cas de la texture de surface. En effet, les critères classiquement utilisĂ©s se rĂ©vèlent inaptes Ă caractĂ©riser les surfaces obtenues, et une nouvelle mĂ©thodologie d’analyse des topologies de surface est proposĂ©e. Les rĂ©sultats obtenus suite Ă la rĂ©alisation du plan d’expĂ©riences rĂ©vèlent que la texture initiale est le paramètre prĂ©pondĂ©rant. Les rĂ©sultats de la topologie de surface montrent que les vibrations peuvent amĂ©liorer la rugositĂ© et la texture des surfaces dans la mesure oĂą l’état de surface initial est sufisamment fin. Ensuite, seule la prĂ©charge et le nombre de passes influencent le rĂ©sultat, avec, dans tous les cas, un couple de valeurs limites Ă partir desquelles les surfaces sont endommagĂ©es. Les rĂ©sultats des contraintes rĂ©siduelles montrent que tous les paramètres influent sur le rĂ©sultat final, en particulier la stratĂ©gie de brunissage, avec laquelle la direction prĂ©fĂ©rentielle du tenseur de la contrainte superficielle peut ĂŞtre modifiĂ©e. Enfin, le brunissage montre une modification positive de la duretĂ© Ă des couches d’environ 0,5 mm en appliquant le processus assistĂ© avec vibrations. Nous concluons que les paramètres de processus optimaux sont difĂ©rents en fonction de l’objectif d’optimisation, et que certaines combinaisons peuvent ĂŞtre utiles en fonction de ces objectifs.Aquesta tesi Ă©s un estudi experimental que tracta sobre els efectes del procĂ©s de brunyit amb bola assistit per vibracions ultrasòniques sobre la integritat superficial de superfĂcies mecanitzades amb fresa hemisfèrica. Degut a la indisponiblitat d’eines comercials capaces d’aplicar aquest procĂ©s, l’estudi inclou en primer lloc el disseny i la caracteritzaciĂł d’un prototip capa d’executar-lo. Posteriorment, es realitza una anĂ lisi experimental aplicant el procĂ©s sobre superfĂcies de dues aliatges d’internes industrial i aeronĂ utic, AISI 1038 i Ti-6Al-4V, seguint un disseny d’experiments basat en una matriu ortogonal Taguchi. Per això, cinc factors sĂłn inclous en el model: la precĂ rrega, el nombre de passades, la velocitat d’avenç, l’estratègia de brunyit i la textura de la superfĂcie inicial. Els resultats s’avaluen en termes de textura final, tensions residuals i duresa, per identificar i comprendre l’impacte d’aquest procĂ©s i dels seus parĂ metres d’operaciĂł sobre la integritat superficial, definir els millors parĂ metres a aplicar per a cada material, i amb l’objectiu d’avaluar els efectes positius provocats per la introducciĂł de les vibracions com a mitjĂ d’assistència.
Els resultats evidencien que la textura inicial Ă©s el parĂ metre que defineix en major mesura l’estat de les superfĂcies finals. Els resultats de textura indiquen que les vibracions poden millorar en major mesura la rugositat i textura de les superfĂcies, sempre que aquestes siguin suficientment fines. A mĂ©s, nomĂ©s la precĂ rrega i el nombre de passades influeixen sobre el resultat, trobant en tot cas un parell de valors lĂmits a partir del qual les superfĂcies sĂłn empitjorades. Els resultats de tensions residuals mostren que tots els parĂ metres sĂłn influents sobre el resultat final, especialment l’estratègia, amb la què es pot millorar la direcciĂł preferencial del tensor de tensions superficial. Finalment, el brunyit demostra modificar la duresa positivament fins a capes d’aproximadament 0.5 mm de profunditat, aplicant el procĂ©s assistit amb vibracions.
Es conclou que els parà metres òptims de procés són diferents en funció de l’objectiu d’optimització, i es proposen algunes combinacions que poden ser útils en funció del mateix.Award-winningPostprint (published version
Study and characterisation of surface integrity modification after ultrasonic vibration-assisted ball burnishing
Tesi en modalitat de cotutela: Universitat Politècnica de Catalunya i Université Toulouse III Paul Sabatier. Aplicat embargament des de la data de defensa fins a gener de 2020Premi extraordinari doctorat UPC curs 2017-2018. Àmbit d’Enginyeria IndustrialThis dissertation is an experimental research project into the mechanical effects of the ultrasonic vibration-assisted ball burnishing process on the surface integrity of surfaces machined through ball-end milling. Due to the lack of commercial tools able to perform this process, the study includes firstly the design and characterization of a prototype to that effect. An experimental analysis is then undertaken, applying the process to AISI 1038 and Ti-6Al-4V surfaces of high industrial and aeronautical value. The experimental campaign is designed based on a Taguchi orthogonal array that includes five factors, namely: preload, number of passes, feed velocity, strategy and initial surface texture. Results are analyzed in terms of topological characteristics, residual stress and hardness, in order to identify and understand the impact of process parameters on surface integrity, to define the best parameters for performing the process and to assess the positive effects caused by the introduction of vibrations as a means of assistance.
Results reveal that the initial texture is the most influential parameter on all outcomes. Texture results show that the vibrations can enhance the roughness and texture results, as long as they have sufficient low initial amplitude. Furthermore, only the preload and number of passes influence the results, with a pair of values being found in all cases that serve a threshold from which further plastic strain is detrimental for the final surface topology. In terms of residual stress, all parameters are influential in the results, especially the burnishing strategy, through which a certain component of the residual stress tensor can be adequately reinforced. Finally, the burnishing operation proves to modify the hardness of deep layers down to 0.5 mm, applying the vibration-assisted process. .e main conclusion is that the optimal parameters for performing the process are different with regards to the optimization objective.
Some useful combinations are proposed for performing the process depending on the desired targetEsta tesis es un estudio experimental que versa sobre los efectos del proceso de bruñido con bola asistido por vibraciones ultrasĂłnicas sobre la integridad superficial de superficies mecanizadas mediante fresa hemisfĂ©rica. Dada la indisponibilidad de herramientas comerciales capaces de efectuar este proceso, el estudio incluye en primer lugar el diseño y caracterizaciĂłn de un prototipo a tal efecto. Posteriormente, se realiza un análisis experimental aplicando el proceso sobre superficies de dos aleaciones de interĂ©s industrial y aeronáutico, AISI 1038 y Ti-6Al-4V, siguiendo un diseño de experimentos fraccionario basado en una matriz ortogonal de Taguchi. Para ello, cinco factores son incluidos en el modelo, a saber: la precarga, el nĂşmero de pasadas, la velocidad de avance, la estrategia de bruñido, y la textura de la superficie de partida. Los resultados se evalĂşan en tĂ©rminos de textura, tensiones residuales y dureza, para identificar y comprender el impacto de este proceso y de sus parámetros de operaciĂłn sobre la integridad superficial, para definir los mejores parámetros a aplicar para cada material, y con el fin de evaluar los efectos positivos provocados por la introducciĂłn de las vibraciones como medio de asistencia. Los resultados revelan que la textura inicial es el parámetro que define en mayor medida el estado de las superficies finales. Los resultados de textura evidencian que las vibraciones pueden mejorar en mayor medida la topologĂa de las superficies objetivo, siempre que Ă©stas sean suficientemente finas. Además, sĂłlo la precarga y el nĂşmero de pasadas influyen en el resultado, encontrando en todo caso un par de valores limĂtrofe a partir del cual las superficies se ven dañadas. Los resultados de tensiones residuales muestran que todos los parámetros son influyentes en el resultado final, especialmente la estrategia de bruñido, con la que puede modificarse la direcciĂłn preferencial del tensor de tensiones superficial. Finalmente, el bruñido demuestra modificar la dureza positivamente hasta capas de aproximadamente 0,5 mm, aplicando el proceso asistido con vibraciones. Se concluye que los parámetros Ăłptimos de proceso son diferentes en funciĂłn del objetivo de optimizaciĂłn, y deben definirse en base a dos variables de partida: el material objetivo y la textura que Ă©ste presenta antes del proceso.Cette thèse Ă©tudie les effets du processus de brunissage Ă bille assistĂ© par vibrations ultrasoniques sur l’intĂ©gritĂ© surface des surfaces usinĂ©es par fraisage hĂ©misphĂ©rique. Compte tenu de l’inexistence d’outils commerciaux capables de rĂ©aliser ce processus, l’étude dĂ©bute par la conception et la caractĂ©risation d’un prototype capable de l’exĂ©cuter. Par la suite, une analyse expĂ©rimentale est menĂ©e, en utilisant le procĂ©dĂ© sur les surfaces de deux alliages d’intĂ©rĂŞt industriel et aĂ©ronautique, AISI 1038 et Ti- 6Al-4V. Pour cela, un plan d’expĂ©riences est elaborĂ© Ă base d’une matrice orthogonale Taguchi.
Cinq facteurs sont inclus dans le modèle : la prĂ©charge, le nombre de passes, la vitesse d’avance, la stratĂ©gie de brunissage et la texture initiale de la surface prĂ©alablement usinĂ©e. Les rĂ©sultats sont Ă©valuĂ©s en termes de texture finale, de contrainte rĂ©siduelle et de duretĂ©, pour identifier et comprendre l’impact de ce procĂ©dĂ© et des paramètres opĂ©ratoires sur l’intĂ©gritĂ© de surface, pour dĂ©finir les meilleurs paramètres Ă appliquer pour chaque matĂ©riau, et pour Ă©valuer les effets positifs provoquĂ©s par l’introduction de vibrations comme moyen d’assistance. Pour cela, la notion d’intĂ©gritĂ© de surface est rappelĂ©e, voire redĂ©finie dans le cas de la texture de surface. En effet, les critères classiquement utilisĂ©s se rĂ©vèlent inaptes Ă caractĂ©riser les surfaces obtenues, et une nouvelle mĂ©thodologie d’analyse des topologies de surface est proposĂ©e. Les rĂ©sultats obtenus suite Ă la rĂ©alisation du plan d’expĂ©riences rĂ©vèlent que la texture initiale est le paramètre prĂ©pondĂ©rant. Les rĂ©sultats de la topologie de surface montrent que les vibrations peuvent amĂ©liorer la rugositĂ© et la texture des surfaces dans la mesure oĂą l’état de surface initial est sufisamment fin. Ensuite, seule la prĂ©charge et le nombre de passes influencent le rĂ©sultat, avec, dans tous les cas, un couple de valeurs limites Ă partir desquelles les surfaces sont endommagĂ©es. Les rĂ©sultats des contraintes rĂ©siduelles montrent que tous les paramètres influent sur le rĂ©sultat final, en particulier la stratĂ©gie de brunissage, avec laquelle la direction prĂ©fĂ©rentielle du tenseur de la contrainte superficielle peut ĂŞtre modifiĂ©e. Enfin, le brunissage montre une modification positive de la duretĂ© Ă des couches d’environ 0,5 mm en appliquant le processus assistĂ© avec vibrations. Nous concluons que les paramètres de processus optimaux sont difĂ©rents en fonction de l’objectif d’optimisation, et que certaines combinaisons peuvent ĂŞtre utiles en fonction de ces objectifs.Aquesta tesi Ă©s un estudi experimental que tracta sobre els efectes del procĂ©s de brunyit amb bola assistit per vibracions ultrasòniques sobre la integritat superficial de superfĂcies mecanitzades amb fresa hemisfèrica. Degut a la indisponiblitat d’eines comercials capaces d’aplicar aquest procĂ©s, l’estudi inclou en primer lloc el disseny i la caracteritzaciĂł d’un prototip capa d’executar-lo. Posteriorment, es realitza una anĂ lisi experimental aplicant el procĂ©s sobre superfĂcies de dues aliatges d’internes industrial i aeronĂ utic, AISI 1038 i Ti-6Al-4V, seguint un disseny d’experiments basat en una matriu ortogonal Taguchi. Per això, cinc factors sĂłn inclous en el model: la precĂ rrega, el nombre de passades, la velocitat d’avenç, l’estratègia de brunyit i la textura de la superfĂcie inicial. Els resultats s’avaluen en termes de textura final, tensions residuals i duresa, per identificar i comprendre l’impacte d’aquest procĂ©s i dels seus parĂ metres d’operaciĂł sobre la integritat superficial, definir els millors parĂ metres a aplicar per a cada material, i amb l’objectiu d’avaluar els efectes positius provocats per la introducciĂł de les vibracions com a mitjĂ d’assistència.
Els resultats evidencien que la textura inicial Ă©s el parĂ metre que defineix en major mesura l’estat de les superfĂcies finals. Els resultats de textura indiquen que les vibracions poden millorar en major mesura la rugositat i textura de les superfĂcies, sempre que aquestes siguin suficientment fines. A mĂ©s, nomĂ©s la precĂ rrega i el nombre de passades influeixen sobre el resultat, trobant en tot cas un parell de valors lĂmits a partir del qual les superfĂcies sĂłn empitjorades. Els resultats de tensions residuals mostren que tots els parĂ metres sĂłn influents sobre el resultat final, especialment l’estratègia, amb la què es pot millorar la direcciĂł preferencial del tensor de tensions superficial. Finalment, el brunyit demostra modificar la duresa positivament fins a capes d’aproximadament 0.5 mm de profunditat, aplicant el procĂ©s assistit amb vibracions.
Es conclou que els parà metres òptims de procés són diferents en funció de l’objectiu d’optimització, i es proposen algunes combinacions que poden ser útils en funció del mateix.Award-winningPostprint (published version
Study and characterisation of surface integrity modification after ultrasonic vibration-assisted ball burnishing
Cette thèse étudie les effets du processus de brunissage à bille assisté par vibrations ultrasoniques sur l'intégrité de surface des surfaces usinées par fraisage hémisphérique.
Compte tenu de l'inexistence d'outils commerciaux capables de réaliser ce processus, l'étude débute par la conception et la caractérisation d'un prototype capable de l'exécuter.
Par la suite, une analyse expérimentale est menée, en utilisant le procédé sur les surfaces de deux alliages d'intérêt industriel et aéronautique, AISI 1038 et Ti- 6Al-4V. Pour
cela, un plan d'expériences est élaboré à base d'une matrice orthogonale Taguchi. Cinq facteurs sont inclus dans le modèle : la précharge, le nombre de passes, la vitesse
d'avance, la stratégie de brunissage et la texture initiale de la surface préalablement usinée. Les résultats sont évalués en termes de texture finale, de contrainte résiduelle
et de dureté, pour identifier et comprendre l'impact de ce procédé et des paramètres opératoires sur l'intégrité de surface, pour définir les meilleurs paramètres à appliquer
pour chaque matériau, et pour évaluer les effets positifs provoqués par l'introduction de vibrations comme moyen d'assistance. Pour cela, la notion d'intégrité de surface est
rappelée, voire redéfinie dans le cas de la texture de surface. En effet, les critères classiquement utilisés se révèlent inaptes à caractériser les surfaces obtenues, et une
nouvelle méthodologie d'analyse des topologies de surface est proposée.
Les résultats obtenus suite à la réalisation du plan d'expériences révèlent que la texture initiale est le paramètre prépondérant. Les résultats de la topologie de surface
montrent que les vibrations peuvent améliorer la rugosité et la texture des surfaces dans la mesure où l'état de surface initial est suffisamment fin. Ensuite, seule la
précharge et le nombre de passes influencent le résultat, avec, dans tous les cas, un couple de valeurs limites à partir desquelles les surfaces sont endommagées. Les résultats
des contraintes résiduelles montrent que tous les paramètres influent sur le résultat final, en particulier la stratégie de brunissage, avec laquelle la direction préférentielle
du tenseur de la contrainte superficielle peut être modifiée. Enfin, le brunissage montre une modification positive de la dureté à des couches d'environ 0,5 mm en appliquant le
processus assisté avec vibrations. Nous concluons que les paramètres de processus optimaux sont différents en fonction de l'objectif d'optimisation, et que certaines
combinaisons peuvent ĂŞtre utiles en fonction de ces objectifs.This dissertation is an experimental research project into the mechanical effects of the ultrasonic vibration-assisted ball burnishing process on the surface integrity of
surfaces machined through ball-end milling. Due to the lack of commercial tools able to perform this process, the study includes firstly the design and characterisation of a
prototype to that effect. An experimental analysis is then undertaken, applying the process to AISI 1038 and Ti-6Al-4V surfaces of high industrial and aeronautical value. The
experimental campaign is designed based on a Taguchi orthogonal array that includes five factors, namely: preload, number of passes, feed velocity, strategy and initial surface
texture. Results are analysed in terms of topological characteristics, residual stress and hardness, in order to identify and understand the impact of process parameters on
surface integrity, to define the best parameters for performing the process and to assess the positive effects caused by the introduction of vibrations as a means of assistance.
Results reveal that the initial texture is the most influential parameter on all outcomes. Texture results show that the vibrations can enhance the roughness and texture
results, as long as they have sufficient low initial amplitude. Furthermore, only the preload and number of passes influence the results, with a pair of values being found in
all cases that serve a threshold from which further plastic strain is detrimental for the final surface topology. In terms of residual stress, all parameters are influential in
the results, especially the burnishing strategy, through which a certain component of the residual stress tensor can be adequately reinforced. Finally, the burnishing operation
proves to modify the hardness of deep layers down to 0.5 mm, applying the vibration-assisted process. The main conclusion is that the optimal parameters for performing the
process are different with regards to the optimisation objective. Some useful combinations are proposed for performing the process depending on the desired target
Ultra-high precision diamond turning of advanced contact lens polymers
Contact lens polymer-based materials are extensively used in the optical industry owing to their excellent corrosion resistance, the possibility of mass production and their ability to be processed without external lubrication. Owing to the fast growth in optical industries, contact lens (CL) requires high accuracy and a high surface quality. The demand for high-accuracy and minimal surface roughness drives the development of ultra-high precision machining technology with regard to single point diamond turning (SPDT). Ultra-high precision diamond turning is an advanced manufacturing technique employed in the machining of CLs owing to its capability of producing high optical surfaces with complex shapes and nanometric accuracy. Yet, even with the advances in ultra-high precision machining (UHPM), it is not continuously easy to achieve a highquality surface finish during polymers machining as the adhesion of the tool chip around the tool dictates the presence of electrostatic charges. The electrostatic charges encountered by a cutting tool when turning advanced CLs are important as they reflect the quality and condition of the tool, machine, fixture, and sometimes even the finished surface, which is responsible for tool wear and poor surface quality. This study investigates the role of cutting parameters, namely cutting speed, feed rate and depth of cut on surface roughness (Ra), electrostatic charge (ESC) and material removal rate (MRR), which determines machine economics and the quality of machining contact lens polymers. The experiments were mainly conducted on two different advanced polymeric materials: polymethyl methacrylate (PMMA) and Optimum Extreme (Roflufocon E) CLs. Experimentation was carried out on the Nanoform 250 ultra-grind turning machine with a monocrystalline diamond-cutting tool for machining the PMMA and Roflufocon E CL polymers, covering a wide range of machining parameters. Before conducting the experiments, a design of experiment was conducted according to the response surface methodology (RSM) that is based on the Box-Behnken Design (BBD). In addition, the research study focused on the determination of the optimum cutting conditions leading to minimum Ra and ESC as well as maximum productivity in the SPDT of the PMMA and Roflufocon E CL polymers, using a monocrystalline diamondcutting tool. The optimization was based on RSM together with the desirability function approach. In addition, a mathematical model was developed for Ra, ESC and MRR using a RSM regression analysis for PMMA and Roflufocon E CL polymers by means of Design Expert software. RSM allowed for the optimization of the cutting conditions for minimal Ra and ESC as well as maximal MRR, which provides an effective knowledge base for process parameters to enhance process performance in the SPDT of CL polymers. Furthermore, this study also deals with the development of Ra, ESC and MRR prediction models for the diamond turning of PMMA and Roflufocon E CL polymers, using the fuzzy logic based artificial intelligence (AI) method. The fuzzy logic model has been developed in terms of machining parameters for the prediction of Ra, ESC and MRR. To judge the accuracy and ability of the fuzzy logic model, an average percentage error was used. The comparative evaluation of experiments and the fuzzy logic approach suggested that the obtained average errors of Ra, ESC and MRR using the fuzzy logic system were in agreement with the experimental results. Hence, the developed fuzzy logic rules can be effectively utilized to predict the ESC, Ra and MRR of PMMA and Roflufocon E CL polymers in automated optical manufacturing environments for high accuracy and a reduction of computational cost. Moreover, owing to the brittle nature of optical polymers, the Roflufocon E CL polymer requires ductile-mode machining for improved surface quality. Molecular Dynamics (MD) simulation methods are thus applied to investigate the atomistic reaction at the tool/workpiece surface to clearly study and observe conditions occurring at nanometric scale in polymer machining. This research study is particularly concerned with the comparative analysis of experiments and a MD study of the Roflufocon E optical polymer nano cutting approach to the atomistic visualization of the plastic material flow at the tool/workpiece interface during cutting. The simulated MD acting force, machine stresses, and the temperature at the cutting region were evaluated to access the accuracy of the model. Hence, the nanomachining simulations were found to have a correlation to the experimental machining results