Machining and grinding of ultrahigh-strength steels and stainless steel alloys

Machining and grinding of ultrahigh-strength steels and stainless steel alloy

Vibration assisted machining: Modelling, simulation, optimization, control and applications

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University, 30/11/2010.Increasing demand for precision components made of hard and brittle materials such as glasses, steel alloys and advanced ceramics, is such that conventional grinding and polishing techniques can no longer meet the requirements of today's precision manufacturing engineering. Particularly, in order to undertake micro-milling of optical glasses or other hard-machining materials, vibration assisted machining techniques have been adopted. However, it is essential and much needed to undertake such processes based on a scientific approach, i.e. the process to be quantitatively controlled and optimized rather than carried out with a trial-and-error manner. In this research, theoretical modelling and instrumental implementation issues for vibration assisted micro-milling are presented and explored in depth. The modelling is focused on establishing the scientific relationship between the process variables such as vibration frequency, vibration amplitude, feedrate and spindle speed while taking into account machine dynamics effect and the outcomes such as surface roughness generated, tool wear and material removal rate in the process. The machine dynamics has been investigated including a static analysis, machine tool-loop stiffness, modal analysis, frequency response function, etc, carried out for both the machine structure and the piezo-actuator device. The instrumentation implementation mainly includes the design of the desktop vibration assisted machining system and its control system. The machining system consists of a piezo-driven XY stage, air bearing spindle, jig, workpiece holder, PI slideway, manual slideway and solid metal table to improve the system stability. The control system is developed using LabVIEW 7.1 programming. The control algorithms are developed based on theoretical models developed by the author. The process optimisation of vibration assisted micro-milling has been studied by using design and analysis of experiment (DOE) approach. Regression analysis, analysis of variance (ANOVA), Taguchi method and Response Surface Methodology (RSM) have been chosen to perform this study. The effects of cutting parameters are evaluated and the optimal cutting conditions are determined. The interaction of cutting parameters is established to illustrate the intrinsic relationship between cutting parameters and surface roughness, tool wear and material removal rate. The predicted results are confirmed by validation experimental cutting trials. This research project has led to the following contribution to knowledge: (1) Development of a prototype desktop vibration assisted micro-milling machine. (2) Development of theoretical models that can predict the surface finish, tool wear and material removal rate quantitatively. (3) Establishing in depth knowledge on the use of vibration assisted machining principles. (4) Optimisation of cutting process parameters and conditions through simulations and machining trials for through investigation of vibration assisted machining.Financial support was obtained from Brunel University

Cost Basis of Grinding vs. Machining Machines

Grinding and machine tool machining are seperated by a gap in technological knowledge. This project investigated the gap between the two areas in a functional comparison. The two methods were found to be comparable with regards to hard materials and high precision. The difference in price was accounted for by production volume. Grinding may find a way to keep a competitive edge in the marketplace if a common ground for function and performance provide for cheaper parts in the industry

High speed milling technological regimes, process condition and technological equipment condition influence on surface quality parameters of difficult to cut materials

[ES] La calidad superficial en las piezas mecanizadas depende del acabado superficial, resultado de las marcas dejadas por la herramienta durante el proceso de corte. Las aproximaciones teóricas tradicionales indican que estas marcas están relacionadas con los parámetros de corte (velocidad de corte, avance, profundidad de corte...), el tipo de máquina, el material de la pieza, la geometría de la herramienta, etc. Pero no todos los tipos de mecanizado y selección de materiales pueden dar un resultado ambiguo. Hoy en día, de manera progresiva, se están utilizando las técnicas de fresado de Alta Velocidad sobre materiales de difícil mecanizado cada vez más. El fresado de Alta Velocidad implica a un considerable número de parámetros del proceso que pueden afectar a la formación topográfica 3D de la superficie. La hipótesis de que los parámetros de rugosidad superficial dependen de las huellas dejadas por la herramienta, determinadas por las condiciones de trabajo y las propiedades del entorno, condujo al desarrollo de una metodología de investigación personalizada. Este trabajo de investigación muestra como la combinación de los parámetros, inclinación del eje de la herramienta, deflexión geométrica de la herramienta y comportamiento vibracional del entorno, influencian sobre el parámetro de rugosidad superficial 3D, Sz. El modelo general fue dividido en varias partes, donde se ha descrito la influencia de parámetros del proceso adicionales, siendo incluidos en el modelo general propuesto. El proceso incremental seguido permite al autor desarrollar un modelo matemático general, paso a paso, testeando y añadiendo los componentes que más afectan a la formación de la topografía de la superficie. En la primera parte de la investigación se seleccionó un proceso de fresado con herramientas de punta plana. Primero, se analiza la geometría de la herramienta, combinada con múltiples avances, para distinguir los principales parámetros que afectan a la rugosidad superficial. Se introduce un modelo de predicción con un componente básico para la altura de la rugosidad, obtenida por la geometría de la herramienta de corte. A continuación, se llevan a cabo experimentos más específicamente diseñados, variando parámetros tecnológicos. Esto empieza con el análisis de la inclinación del eje de la herramienta contra la mesa de fresado. Los especímenes de análisis son muestras con cuatro recorridos de corte rectos con corte en sentido contrario. Las trayectorias lineales con diferentes direcciones dan la oportunidad de analizar la inclinación del husillo de fresado en la máquina. Un análisis visual reveló diferencias entre direcciones de corte opuestas, así como marcas dejadas por el filo posterior de la herramienta. Considerando las desviaciones de las marcas de corte observadas en las imágenes de rugosidad superficial obtenidas a partir de las medidas, se introdujo un análisis sobre el comportamiento dinámico del equipo y de la herramienta de corte. Las vibraciones producen desviaciones en la mesa de fresado y en la herramienta de corte. Estas desviaciones fueron detectadas e incluidas en el modelo matemático para completar la precisión en la predicción del modelo. Finalmente, el modelo de predicción del parámetro de rugosidad Sz fue comprobado con un mayor número de parámetros del proceso. Los valores de Sz medidos y predichos, fueron comparados y analizados estadísticamente. Los resultados revelaron una mayor desviación de la rugosidad predicha en las muestras fabricadas con diferentes máquinas y con diferentes avances. Importantes conclusiones sobre la precisión del equipo de fabricación han sido extraídas y de ellas se desprende que la huella de la herramienta de corte está directamente relacionada con los parámetros de la topografía de la superficie. Además, la influencia de la huella está afectada por la geometría de la herramienta de corte, la rigidez de la herramienta y la precisión del equipo. La geometría de la herramienta conforma la base del parámetro Sz, desviación de la altura de la superficie. Las conclusiones alcanzadas son la base para recomendaciones prácticas, aplicables en la industria.[CA] La qualitat superficial en les peces mecanitzades depèn de l'acabat superficial, resultat de les marques deixades per l'eina durant el procés de tall. Les aproximacions teòriques tradicionals indiquen que aquestes marques estan relacionades amb els paràmetres de tall (velocitat de tall, avanç, profunditat de tall...), el tipus de màquina, el material de la peça, la geometria de l'eina, etc. Però no tots els tipus de mecanitzat i selecció de materials poden donar un resultat ambigu. Avui en dia, de manera progressiva, s'estan utilitzant les tècniques de fresat d'Alta Velocitat sobre materials de difícil mecanització cada vegada més. El fresat d'Alta Velocitat implica un considerable nombre de paràmetres del procés que poden afectar la formació topogràfica 3D de la superfície. La hipòtesi que els paràmetres de rugositat superficial depenen de les empremtes deixades per l'eina, determinades per les condicions de treball i les propietats de l'entorn, va conduir al desenvolupament d'una metodologia d'investigació personalitzada. Aquest treball de recerca mostra com la combinació dels paràmetres, inclinació de l'eix de l'eina, deflexió geomètrica de l'eina i comportament vibracional de l'entorn, influencien sobre el paràmetre de rugositat superficial 3D, Sz. El model general va ser dividit en diverses parts, on s'ha descrit la influència de paràmetres addicionals del procés, sent inclosos en el model general proposat. El procés incremental seguit permet a l'autor desenvolupar un model matemàtic general, pas a pas, testejant i afegint els components que més afecten a la formació de la topografia de la superfície. En la primera part de la investigació es va seleccionar un procés de fresat amb eines de punta plana. Primer, s'analitza la geometria de l'eina, combinada amb múltiples avanços, per distingir els principals paràmetres que afecten la rugositat superficial. S'introdueix un model de predicció amb un component bàsic per a l'altura de la rugositat, obtinguda a través de la geometria de l'eina de tall. A continuació, es duen a terme experiments més específicament dissenyats, variant paràmetres tecnològics. Això comença amb l'anàlisi de la inclinació de l'eix de l'eina contra la taula de fresat. Els espècimens d'anàlisi són mostres amb quatre recorreguts de tall rectes amb tall en sentit contrari. Les trajectòries lineals amb diferents direccions donen l'oportunitat d'analitzar la inclinació del fus de fresat en la màquina. Una anàlisi visual revelà diferències entre direccions de tall oposades, així com marques deixades pel tall posterior de l'eina. Considerant les desviacions de les marques de tall observades en les imatges de rugositat superficial obtingudes a partir de les mesures, es va introduir una anàlisi sobre el comportament dinàmic de l'equip i de l'eina de tall. Les vibracions produeixen desviacions en la taula de fresat i en l'eina de tall. Aquestes desviacions van ser detectades i incloses en el model matemàtic per completar la precisió en la predicció de el model. Finalment, el model de predicció de el paràmetre de rugositat Sz va ser comprovat amb un major nombre de paràmetres del procés. Els valors de Sz mesurats i predits, van ser comparats i analitzats estadísticament. Els resultats van revelar una major desviació de la rugositat predita en les mostres fabricades amb diferents màquines i amb diferents avanços. Importants conclusions sobre la precisió de l'equip de fabricació han estat extretes i d'elles es desprèn que l'empremta de l'eina de tall està directament relacionada amb els paràmetres de la topografia de la superfície. A més, la influència de la empremta està afectada per la geometria de l'eina de tall, la rigidesa de l'eina i la precisió de l'equip. La geometria de l'eina conforma la base del paràmetre Sz, desviació de l'altura de la superfície. Les conclusions assolides són la base per recomanacions pràctiques, aplicables en la indústria.[EN] Surface quality of machined parts highly depends on the surface texture that reflects the marks, left by the tool during the cutting process. The traditional theoretical approaches indicate that these marks are related to the cutting parameters (cutting speed, feed, depths of cut...), the machining type, the part material, the tool geometry, etc. But, different machining type and material selection can give a variable result. In nowadays, more progressively, High Speed milling techniques have been applied on hard-to-cut materials more and more extensively. High-speed milling involves a considerable number of process parameters that may affect the 3D surface topography formation. The hypothesis that surface topography parameters depends on the traces left by the tool, determined by working conditions and environmental properties, led to the development of a custom research methodology. This research work shows how the parameters combination, tool axis inclination, tool geometric deflection, cutting tool geometry and environment vibrational behavior, influence on 3D surface topography parameter Sz. The general model was divided in multiple parts, where additional process parameters influence has been described and included in general model proposed. The incremental process followed allows the author to develop a general mathematical model, step by step, testing and adding the components that affect surface topography formation the most. In the first part of the research a milling procedure with flat end milling tools was selected. First, tool geometry, combined with multiple cutting feed rates, is analyzed to distinguish the main parameters that affect surface topography. A prediction model is introduced with a basic topography height component, performed by cutting tool geometry. Next, specifically designed experiments were conducted, varying technological parameters. That starts with cutting tool axis inclination against the milling table analysis. The specimens of analysis are samples with 4 contrary aimed straight cutting paths. Linear paths in different directions give a chance to analyze milling machine spindle axis topography, as well as marks left from cutting tool back cutting edge. Considering the deviations of cutting marks observed in the images of the surface topography obtained through the measurements, the milling equipment and cutting tool dynamical behavior analysis were introduced. Vibrations produce deviations in the milling table and cutting tool. These deviations were detected and included in the mathematical model to complete the prediction model accuracy. Finally, the prediction model of the topography parameter SZ was tested with increased number of process parameters. Measured and predicted SZ values were compared and analyzed statistically. Results revealed high predicted topography deviation on samples manufactured with different machines and with different feed rates. Relevant conclusions about the manufacturing equipment accuracy have been drawn and they state that cutting tool's footprint is directly related with surface topography parameters. Besides, footprint influence is affected by cutting tool geometry, tool stiffness and equipment accuracy.Logins, A. (2021). High speed milling technological regimes, process condition and technological equipment condition influence on surface quality parameters of difficult to cut materials [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/164122TESI

Cryogenic storage systems design, fabrication and evaluation. Volume 2 - Appendices. 1. Summary of cryogenic storage system evaluation. 2. Ardeform pressure vessel program Final report

Cryogenic storage system and pressure vessel desig

Proceeding Of Mechanical Engineering Research Day 2016 (MERD’16)

This Open Access e-Proceeding contains a compilation of 105 selected papers from the Mechanical Engineering Research Day 2016 (MERD’16) event, which is held in Kampus Teknologi, Universiti Teknikal Malaysia Melaka (UTeM) - Melaka, Malaysia, on 31 March 2016. The theme chosen for this event is ‘IDEA. INSPIRE. INNOVATE’. It was gratifying to all of us when the response for MERD’16 is overwhelming as the technical committees received more than 200 submissions from various areas of mechanical engineering. After a peer-review process, the editors have accepted 105 papers for the e-proceeding that cover 7 main themes. This open access e-Proceeding can be viewed or downloaded at www3.utem.edu.my/care/proceedings. We hope that these proceeding will serve as a valuable reference for researchers. With the large number of submissions from the researchers in other faculties, the event has achieved its main objective which is to bring together educators, researchers and practitioners to share their findings and perhaps sustaining the research culture in the university. The topics of MERD’16 are based on a combination of fundamental researches, advanced research methodologies and application technologies. As the editor-in-chief, we would like to express our gratitude to the editorial board and fellow review members for their tireless effort in compiling and reviewing the selected papers for this proceeding. We would also like to extend our great appreciation to the members of the Publication Committee and Secretariat for their excellent cooperation in preparing the proceeding of MERD’16

Liquid rocket metal tanks and tank components

Significant guidelines are presented for the successful design of aerospace tanks and tank components, such as expulsion devices, standpipes, and baffles. The state of the art is reviewed, and the design criteria are presented along with recommended practices. Design monographs are listed

Implementation of hierarchical design for manufacture rules in manufacturing processes

In order to shorten the product development cycle time, minimise overall cost and smooth transition into production, early consideration of manufacturing processes is important. Design for Manufacture (DFM) is the practice of designing products with manufacturing issues using an intelligent system, which translates 3D solid models into manufacturable features. Many existing and potential applications, particularly in the field of manufacturing, require various aspects of features technology. In all engineering fields geometric modelling wluch accurately represents the shape of a whole engineering component has become accepted for a wide range of applications. To apply DFM rules or guidelines in manufacturing processes, they have to be systematised and organised into a hierarchical rule system. Rules at the higher level of the hierarchical system are applied to more generic manufacturing features, and specific rules are applied to more detailed features. This enables the number of rules and amount of repetition to be minimsed. Violation of the design for manufacture rules in the features, their characteristics and manufacturing capabilities are further examined in this hierarchical system. Manufacturabillty analysis, such as production type, materials, tolerances, surface finish, feature characteristics and accessibility, are also taken into consideration. Consideration of process capabilities and limitations during the design process is necessary in order to minimise production time and as a result, rnanufactunng cost. The correct selection of manufacturing processes is also important as it is related to the overal cost. As a result of this research, a hierarchical design for manufacture rule system is proposed which would aid designers in avoiding designs that would lead to costly manufacturing processes

Investigation on micro-cutting mechanics with application to micro-milling

This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University LondonNowadays technology development places increasing demands on miniature and micro components and products, and micro-milling is one of the most flexible machining processes in manufacturing 3D structures and complex structured surfaces. A thorough and scientific understanding on fundamentals of the micro-milling process is essential for applying it in an industrial scale. Therefore, in-depth scientific understanding of the micro-cutting mechanics is critical, particularly on size effect, minimum chip thickness, chip formation, tool wear and cutting temperature, etc. so as to fulfil the gap between fundamentals and industrial scale applications. Therefore, three key fundamental research topics are determined for this research, and a comprehensive study on those topics is conducted by means of modeling, simulation, experiments. The topics include chip formation process in micro-milling, novel cutting force modeling in multiscale and study on the tool wear and process monitoring. The investigation into chip formation process in micro-milling consists of three stages; the micro-cutting process is firstly simulated by means of FEA with a primary focus on finding the minimum chip thickness for different tool/material pair and explaining the size effect; the simulation results are then validated by conducting micro-cutting experiment on the ultra-precision lathe. Experiments are carried out on aluminium 6082-T6 with both natural diamond and tungsten carbide tool. By knowing the minimum chip thickness for different tool/material pair, the chip formation process is investigated by performing comparative study by using the diamond and tungsten carbide micro-milling tools. As the minimum chip thickness for diamond micro-milling tool is smaller than that for tungsten carbide tool compared to nominal chip thickness, MCT is ignored in diamond micro-milling. Thus the comparative study is conducted by utilizing both tools with perfectly sharpened cutting edge and tools with the rounded cutting edge in micro-milling. The chips are inspected and associated with cutting force variations in the micro-milling process. The findings are further consolidated by comparing with research results by other researchers. The cutting force modeling is developed in three different aspects, e.g. cutting force on the unit length or area and cutting force on the unit volume in order to better understand the micro-cutting mechanics in aspects of size effect, tool wear mechanism and the cutting energy consumption. The mathematical modeling firstly starts with a novel instantaneous chip thickness algorithm, in which the instantaneous chip thickness is computed by taking account of the change of tool geometry brought about by the tool runout; then the collected cutting forces are utilized to calibrate the model coefficients. For accurate measurement on cutting forces, the Kalman Filter technique is employed to compensate the distortion of the measured cutting force. Model calibration is implemented using least-square method. The proposed cutting force model is then applied in micro-milling to represent the conditions of tool wear and the cutting energy consumption. Further study on the surface generation simulation is based on force model and its comparison with the machined surface is also performed. Cutting experiments using the new tungsten carbide tool are carried out and the tool wear is monitored offline at different machining stages. The dominant tool wear types are characterised. Tool wear is investigated by mainly analysing cutting force at different tool wear status. Frequency analysis by Fourier Transform and Wavelet Transform are carried out on the force signals, and features closely related to the tool wear status are identified and extracted. The potential of applying these features to monitoring the tool wear process is then discussed. Experimental studies to machine the structured surface and nano-metric level surface roughness are presented, the machining efficiency, dimensional accuracy and tool-path strategies are optimised so as to achieve the desired outcomes. Moreover, investigation on cutting temperature in micro-cutting is also studied to some extent by means of simulation; the influence of cutting edge radius on cutting temperature is particularly investigated. Investigation on above aspects provides systematic exploration into the micro-milling process and can contribute substantially to future micro-milling applications.China Scholarship Council and Korean Institute of Machinery and Material

Use of scale models to determine the structural dynamic characteristics of space vehicles

Scale model designs for determining structural dynamic characteristics of future spacecraf