Improving the surface finish of concave and convex surfaces using a ball burnishing process

The ball burnishing process is done to improve the surface finish of workpieces that have been previously machined. In this article we present the results of tests performed with this process that was applied to workpieces with a convex or concave surface of two different materials: aluminum A92017 and steel G10380. An experiment to do the tests was designed. The results of measurements of surface roughness are presented in this paper as well. These results are compared to those measured in the workpieces before being burnished. After that conclusions are drawn about the improvement of surface roughness applied to the workpieces through the ball burnishing process. The main innovation of this paper is that we work with concave and convex geometries. We also obtain a table of recomended parameter values for the process

Combination of acoustic emission and vibratory measure-ments to characterize an ultrasonic vibration assisted ball burnishing tool for a lathe

In this paper, a resonant system that produces a movement of low amplitude and ultrasonic frequency is used to achieve the vibration assistance in a ball-burnishing process. A full vibration characterization of this process performed in a lathe was done. It is carried out by a new tool designed in the research group of the authors. Its purpose is to demonstrate that the machine and the tool do not have any resonance problem during the process and to prevent possible failures. The analysis of this dynamic behaviour permits to validate the suitability of the tool when it is anchored to a numerical control lathe. This is very important for its future industrial implementation. It is also intended to confirm that the system adequately transmits vibrations through the material. To do this, a methodology to validate the dynamic tool behaviour was developed. Several techniques that combine the usual and ultrasonic vibration ranges through static and dynamic measurements were merged: vibration and acoustic emission measurements. An operational deflection shape (ODS) exercise has been also performed. Results show the suitability of the tool used to transmit the assistance vibrations, and that no damage is produced in the material in any case.Postprint (author's final draft

Investigation of the Effect of Surface Burnishing on Stress Condition and Hardening Phenomena

The purpose of this paper is to present a comprehensive study of the stress state and hardening characteristics of low-alloyed aluminium cylindrical specimens subjected to the diamond burnishing process. Diamond burnishing has a surface hardening effect on structural steels. In the present study, our aim was to check whether this surface hardening effect is also observed for other (less hard) material grades, such as low-alloy aluminium. We also aimed to determine the technological parameters at which the greatest relative increase in hardness can be achieved by burnishing. In addition to the hardness test, the changes in the residual stress state due to burnishing were also analysed. Both hardness and residual stress tests were performed in two variants. Of the 4 technological parameters (burnishing speed, feed, burnishing force and number of passes), the burnishing speed was set to constant for one variant and number of passes was set to constant at the other variant, while two levels were chosen for the other parameters. A special formula was developed to determine the relative improvement in residual stress and hardness. Our experiments were performed using a full factorial experimental design. The results show that diamond burnishing has surface hardening effect and increases of residual stress on an aluminium alloy when applying adequate technological parameters

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

Monitoring of Processing Conditions of an Ultrasonic Vibration-Assisted Ball-Burnishing Process

Although numerous references present the beneficial effects on surface integrity of ultrasonic vibration-assisted ball burnishing (UVABB), nothing has been reported about the dynamic behavior of the UVABB tool, workpiece, and machine triad during the process. In this paper, a dynamic monitorization through a set of 5 accelerometers is tested to analyze the interactions between the tool–workpiece–machine mechanical assembly. A UVABB tool attached to a milling machine and equipped with a piezoelectric stack that is able to assist the process with a 40-kHz vibration is tested on a milled C45 steel surface. First, the natural frequencies of the mechanical system are obtained through hammer impact tests. Then, the vibratory signals transmitted during the execution of the process are monitored and compared to those: two feed velocities and two burnishing preloads, all with and without vibration-assistance. Results show that the proposed accelerometer set is valid to assess the behavior of a UVABB process. The system’s natural frequencies are not varied by vibration-assistance and are not excited when the piezoelectric is functioning. It is confirmed that UVABB is safe for the machine and the tool, and there is no unexpected excited frequencies due to the piezoelectric excitation.Ministerio de Ciencia, Innovación y Universidades de España RTI2018-101653-B-I00Gobierno regional de Cataluña IU68-016744Unión Europea IU68-01674

Wear resistance and friction analysis of Ti6Al4V cylindrical ball-burnished specimens with and without vibration assistance

The objective of the research is to analyze the impact of the ultrasonic vibration assistance on the wear resistance due to the topography enhancement caused on Ti6Al4V cylindrical samples after surface modification through a ball burnishing process. The process parameters considered for this study are the burnishing force, the number of passes, and the addition of a 40 kHz ultrasonic assistance, which are thought to enhance the surface topography and increase the hardener effect in terms of depth. A complete screening design of 3 factors was performed, revealing that the number of passes and the vibration assistance are the most important parameters for minimizing the wear volume loss, being 170 N of burnishing force, 3 passes, and the addition of the vibration assistance as the best combination found. However, no significant difference in the friction force was observed. The topography results show that there is a decrease in the average roughness from 1.50 to 0.45 µm with optimal burnishing conditions. It was also analyzed the microstructure originated after the turning, the conventional ball burnishing, and the vibration-assisted ball burnishing, being the last optimal in terms of depth affectation to the microstructure. Therefore, these results confirm an improvement in terms of wear enhancement, friction reduction, and topography results when vibration assistance is added to a conventional ball burnishing process.Peer ReviewedObjectius de Desenvolupament Sostenible::9 - Indústria, Innovació i InfraestructuraPostprint (published version

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

A novel force control strategy for improved surface integrity in low plasticity burnishing

Ball burnishing is a cold work process where a hard ceramic or diamond ball rolls on a metal surface and flattens the roughness peaks under high local pressure. The small deformation created on the surface imposes compressive residual stresses and raises hardness in a shallow sub-surface layer, leading to improved fatigue, corrosion, and foreign object damage performances. Trial-and-error type experimental work to determine the optimum process parameters for a cold-forming process like ball burnishing for acceptable performance is costly. Therefore, the article aims to investigate the effects of various force control strategies in the double-sided low plasticity burnishing (LPB) process to find the effects on deformation and residual stresses on thin Ti6Al4V flat sheets. A 3D static-implicit finite element model was developed with an elastic-rigid plastic flow curve. Simulations were conducted to predict residual stresses and deformationі on the surface. As a result, it was proven that ball burnishing can produce a deterministically controlled surface. An increased vertical force produced higher deformation normal to the surface and, therefore, a deeper pool. As the ball proceeded further, a plowing effect developed such that when a 3.5–4.8 m deep pool was formed (at a vertical force of 150 N), a peak of 2.8 m was produced at the front end. Overall, the deformation on the surface and the residual stresses were directly interrelated. Parallel to the deformation on the surface, residual stresses on and beneath the surface also showed some variation. Nevertheless, the predicted residual stress variations were not big. They did not switch to the tensile mode in the burnished zone. Therefore, the whole sheet surface should be burnished to obtain all the compressive residual stresses

Liquid Impingement Erosion Performance of Low Plasticity Burnished Ti6Al4V

Abstract In power generation industry, inlet fog cooling is used for the turbine inlet cooling (TIC). However, this approach also leads to liquid impingement erosion (LIE) of the rotating blades in the compressor, resulting in performance degradation and reduction of service life of gas turbines. Previous studies have introduced Laser shock peening (LSP) and shot peening (SP) as potential solutions for LIE of Ti64. However, no study has been done on the LIE performance of the low plasticity burnished Ti64. Full factorial design of experiments was conducted to investigate the effects of LPB process parameters (Feed Rate, Spindle Velocity, Number of Passes, Pressure) on the residual stress distribution, microhardness and surface roughness of Ti64. The surface microhardness and the surface roughness of the Ti64 were improved after the LPB treatment. Moreover, a large magnitude of compressive residual stress layer was induced by LPB treatment on the surface of the Ti64. However, the results of the LIE tests showed that LPB treatment has little or no effect on the LIE performance of Ti64

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 ultrasónicas sobre la integridad superficial de superficies mecanizadas mediante fresa hemisférica. Dada la indisponibilidad de herramientas comerciales capaces de efectuar este proceso, el estudio incluye en primer lugar el diseño y caracterización de un prototipo a tal efecto. Posteriormente, se realiza un análisis experimental aplicando el proceso sobre superficies de dos aleaciones de interés 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 número de pasadas, la velocidad de avance, la estrategia de bruñido, y la textura de la superficie de partida. Los resultados se evalúan en términos de textura, tensiones residuales y dureza, para identificar y comprender el impacto de este proceso y de sus parámetros de operación 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 introducción 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 topología de las superficies objetivo, siempre que éstas sean suficientemente finas. Además, sólo la precarga y el número de pasadas influyen en el resultado, encontrando en todo caso un par de valores limítrofe 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 dirección 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 óptimos de proceso son diferentes en función del objetivo de optimización, y deben definirse en base a dos variables de partida: el material objetivo y la textura que éste presenta antes del proceso.Cette thèse étudie les effets du processus de brunissage à bille assisté par vibrations ultrasoniques sur l’intégrité 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 elaboré 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 sufisamment 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 diférents en fonction de l’objectif d’optimisation, et que certaines combinaisons peuvent être utiles en fonction de ces objectifs.Aquesta tesi és un estudi experimental que tracta sobre els efectes del procés de brunyit amb bola assistit per vibracions ultrasòniques sobre la integritat superficial de superfícies mecanitzades amb fresa hemisfèrica. Degut a la indisponiblitat d’eines comercials capaces d’aplicar aquest procés, l’estudi inclou en primer lloc el disseny i la caracterització d’un prototip capa d’executar-lo. Posteriorment, es realitza una anàlisi experimental aplicant el procés sobre superfícies de dues aliatges d’internes industrial i aeronàutic, AISI 1038 i Ti-6Al-4V, seguint un disseny d’experiments basat en una matriu ortogonal Taguchi. Per això, cinc factors són inclous en el model: la precàrrega, el nombre de passades, la velocitat d’avenç, l’estratègia de brunyit i la textura de la superfície inicial. Els resultats s’avaluen en termes de textura final, tensions residuals i duresa, per identificar i comprendre l’impacte d’aquest procés i dels seus paràmetres d’operació sobre la integritat superficial, definir els millors paràmetres a aplicar per a cada material, i amb l’objectiu d’avaluar els efectes positius provocats per la introducció de les vibracions com a mitjà d’assistència. Els resultats evidencien que la textura inicial és el paràmetre que defineix en major mesura l’estat de les superfícies finals. Els resultats de textura indiquen que les vibracions poden millorar en major mesura la rugositat i textura de les superfícies, sempre que aquestes siguin suficientment fines. A més, només la precàrrega i el nombre de passades influeixen sobre el resultat, trobant en tot cas un parell de valors límits a partir del qual les superfícies són empitjorades. Els resultats de tensions residuals mostren que tots els paràmetres són influents sobre el resultat final, especialment l’estratègia, amb la què es pot millorar la direcció 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 procés assistit amb vibracions. Es conclou que els paràmetres 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