One of the most effective way of electrochemical machining (ECM) accuracy increase is to carry out process with application of voltage pulses. In one of the variants of ECM, ultra short (nono- or ...picosecond range) voltage pulses are applied. It gives possibility to achieve high localization of electrochemical dissolution process and allows to machine microparts with accuracy less than 0.01 mm. However, because of the process principles, this variant of ECM has number of limitations which stop its wider application in micromanufacturing industry. Based on the literature review, the physical principles of ultrashort voltage pulses electrochemical machining were presented and anodic dissolution localization issues were discussed. Also, differences between other electrochemical machining variants were underlined. It gave possibility to identify limitations and future perspectives of industrial applications.
The progression of the industry, alongside the continuous enhancement of operational efficiency and the reduction of production costs, is paving the way for novel solutions in the realm of storage ...and transportation systems. The incorporation of new technologies and solutions, such as mobile robots, has culminated in the establishment of Smart Warehouses. It facilitates the reduction of non-value adding activities for companies. One of the methods of improving the efficiency of such systems is the more effective use of autonomous mobile robots. The article presents an inventive concept of an autonomous mobile robot capable of undertaking transport tasks both on the shop floor and within high-bay warehouses. The new concept of the drive mechanism enables it to navigate on surfaces and move along rail guides. By using an elevator, the robot can be lifted to higher levels within the warehouse. The well-conceived structural solution of the robot allows the elevator's placement anywhere within the warehouse, eliminating the need for constructing a pit. The use of a mobile robot with the proposed structure will enable the execution of transport tasks without necessitating reloading. Such an approach has the potential to increase efficiency and reduce the costs of storage processes.
Display omitted
•Multiphysics model of surface strengthening in burnishing was developed.•Twining-induced plasticity was identified as most dominant hardening mechanism.•Austenite-ferrite phase ...change has contribution to strengthening up to limited depth.•Burnishing depth was identified as most influential parameter influencing hardening up to deep layers.
In the present work, a physic-based analytical model has been developed to find the hardening mechanism contributed to surface property enhancement during burnishing process. The model takes into account the effects of grain size evolution, phase change and plasticity-induced twinning. Here, the deformation parameters were firstly modeled using the expanding cavity model and theory of incremental plasticity. Then, the strengthening mechanism are identified based on developed physics based material model. Series of experiments were carried out to confirm the hardness values obtained from the model. Finally, the developed multiphysics model were utilized to identify the influence of burnishing parameters on hardness distribution and contributed mechanisms. The obtained results indicated that the there is good agreement between the measured and predicted values of hardness. On the other hand, it was found that the twinning-induced plasticity followed by phase change (from austenite to ferrite) have more dominant influence on hardening compared to grain size evolution; however, the latter only affects the hardening up to limited depth. In addition, the burnishing depth has been identified as most influential parameter that affects hardness and hardened depth.
The paper focuses on the fundamentals of electrochemical machining technology de-elopement with special attention to applications for micromachining. In this method, a material is removed during an ...anodic electrochemical dissolution. The method has a number of features which make it attractive technology for shaping parts with geometrical features in range of micrometres. The paper is divided into two parts. The first one covers discussion on: general characteristics of electrochemical machining, phenomena in the gap, problems resulting from scaling down the process and electrochemical micromachining processes and variants. The second part consists of synthetic overview of the authors' research on localization of pulse electrochemical micromachining process and case studies connected with application of this method with use of universal cylindrical electrode-tool for shaping cavities in 1.4301 stainless steel. The latter application was conducted in two following variants: electrochemical contour milling and shaping carried out with sidewall surface of rotating tool. In both cases, the obtained shape is a function of electrode tool trajectory. Selection of adequate machining strategy allows to obtain desired shape and quality.
The paper focuses on the problem of selecting the correct tool geometry in high-speed milling of 316L stainless steel. Carbide milling cutters with two configurations of helix angle (40/42 degrees ...for tool#1 and 35/38 degrees for tool#2) with different cutting edge radiuses rn (i.e. 4 µm, 6 µm, 8 µm, 10 µm and 12 µm) were prepared and their impact on cutting force and roughness were analyzed. The obtained results revealed that the small changes in cutting edge radius rn have a significant effect on both cutting forces and surface roughness. In this context, irrespective to the type of the tool, increasing the cutting edge radius results in further cutting force. However, increasing the cutting edge radius shows different behavior on roughness while using different tool helix angles. For the tool#1, it was found that the surface roughness increases by increasing the cutting edge radius from 6 μm to 12 μm; while in the samples machined by tool #2, increase in cutting edge radius results in reduction of roughness. It was also found that irrespective to the values of cutting edge radius, the cutting force while using tool #1 is slightly less than the tool#2. In addition, the induced milling surface roughness of the samples machined by tool#2 is significantly less than the tool#1 where the mean value of Ra was reduced from 2.55 µm to 0.35 µm.
In many machining applications, the appropriate selection of cutting toolsin relation to the type of material being machined, the machining parametersand the required shape and dimensional accuracy ...is of particular importance.This especially applies to operations requiring the use of specific tools, i.e. toolsthat are not included in the standard offer but are tailor-made according tothe individual needs of the customer. The article focuses on the machiningproblems of selected austenitic grades of stainless steel and the selection oftechnologies (i.e. machining parameters and strategies and tool geometry)concerning the design and use of special monolithic carbide milling cutters.The possibilities of manufacturing elements from austenitic steels with highshape and dimensional accuracy and high surface layer quality are limited.Due to their high ductility, the tendency to create growths on the cutting edgeand the high compression strength coefficient, these materials pose a serioustechnological challenge. The analysis of phenomena presented in the articleforms the basis for developing guidelines for designing the machining processusing special monolithic carbide cutters dedicated for specific applications.
Hardening of surface layers are one of main goals of surface sever plastic deformation (SSPD) process. Grain refinement is majorly a dominant mechanism that results in hardening of surface layers ...when the material is subjected to room temperature SSPD. Accordingly, development of predictive models of microstructure refinement is gaining interest. In the present study, analytical predictive model is developed to predict the through depth grain size and hardness in one of famous SSPD technique namely ultrasonic burnishing process. Here, firstly the deformation parameters (i.e. strain and strain rate) are modeled by means of the concept of elasto-plastic contact mechanics taken into account the superposition of static and dynamic loads. Then, grain refinement is predicted through sequence of dislocation density evolution (DDE) followed by dynamic recrystallization (DRX). In order to verify the results derived by analytical model, series of confirmatory experiments were carried out on aluminum 6061-T6. The X-ray diffraction (XRD) method was utilized to obtain the grain size in different layers from the surface of the burnished sample. The obtained results indicated that the developed model of microstructure evolution were consistent well with experimental measurement in terms of gradient grain size and micorhardness distribution. The confirmed simulation model was further utilized to understand how the process factors i.e. static force, vibration amplitude and ball size influence the evolution of microstructure. It was found the finer grain structures distributed at further depth can be obtained while static force and vibration amplitude adopt their maximum range value; while the ball diameter and feed rate are set on minimal values.
•A new analytical model for identifying the mechanism of ultrasonic burnishing was established.•The modeled strain and strain rates were utilized to simulate microstructure evolution.•Dislocation density evolution and dynamic recrystallization were taken into accounts as mechanisms of grain refinement.•The effect of process factors on gradient microstructure and hardness distribution were studied.
Abstract
Following sustainability in manufacturing, the machining chain can be optimized by either reducing the time and energy consumption of each operation or eliminating the unnecessary operations ...subjected to keeping the quality of the final product as consistent. However, the roadblock in designing an optimum machining chain is lack of prediction tool to interact between the included operations. In this paper, an integrated algorithm is developed to simulate the surface roughness generation and following modification caused by milling and burnishing, respectively. Predict the surface roughness generation by milling process and its alternation after burnishing. The algorithm works on the basis of clouds of points which were generated in the engagement region of tool and workpiece and their transformation from tool to workpiece coordinate systems. Moreover, some mechanical attributes of the process regarding effect of surface work hardening and elastic rebound were added to the algorithm to enhance the accuracy of simulation. To verify the results, a series of burnishing experiments with multi-roller rotary tool have been carried out on the surface of the finish-milled samples and the surface roughness change was taken into investigation. The obtained results showed that by applying the work hardening and springback effect to predictive algorithm the prediction accuracy of roughness at submicron level enhances up to 50%. It was also found that the most influential parameters influencing the surface roughness after milling-burnishing sequence are milled surface roughness, burnishing force and pass number. In addition, results showed that applying burnishing after rough machining consumes lots of energy to achieve nanoscale surface finish. Accordingly, the sequence of rough-milling, finish-milling and burnishing results in achieving sound surface finish within significantly shorter period of time and applied force.
The paper investigated an electrochemically-assisted microturning process. Depending on the variant of electrochemical assistance, material can be removed with simultaneous electrochemical and ...mechanical action or electrochemical assistance can change the conditions of the cutting by changing the mechanical properties of the machined material. The experimental part includes discussion of the study methodology and a comparison of straight turning results in the case of machining 1.4301 stainless steel with and without electrochemical assistance. Based on this study, we can confirm that electrochemical assistance brings significant benefits in both variants, especially when the depth-of-cut is in the range of 1 µm.
•Multiphysics theoretical modeling of UAB was developed.•The model correlates process factors to fatigue life.•Roughness, hardness and residual stress were included in the model.•The modeled life ...cycles were compatible well with experimental values.
Burnishing is type of contact based non-metal removal finishing processes that is used to enhance the service performance of hard material like Ti-6Al-4V through modification of roughness, exerting work hardened surface layer and inducing compressive residual stress. However, the design of process aiming at anti-fatigue machining is a big challenge, since on one hand the experimental trial and errors of fatigue tests are time consuming and costly, on the other hand there is lack of predictive models that directly correlate the process factors to lifetime. Therefore, to study the fatigue behavior of burnished samples, a holistic predictive framework is required. The present study takes lead to solve the problem by developing a model which correlates the surface integrity and fatigue life of the materials processed. Here firstly the roughness, microhardness and residual stress of the burnished samples are modeled and correlated to process factors through multiphysics of burnishing. Then they were correlated to fatigue life by using stress-based approach that includes surface geometrical, mechanical and metallurgical aspects. The accuracy of developed models were compared with the series of experiments which were carried out on as-turned Ti-6Al-4V. The results revealed that the developed analytical model can predict the lifetime of the burnished samples with acceptable accuracy where the average prediction error for 16 data sets is 13.6 % within the range of 6.3 % to 22 %. The verified model was then utilized to identify the mechanism of lifetime variation and to understand how the process factors determines the fatigue life. It was obtained that the static force as a parameter contributed to loading has greatest impact on variation of fatigue life by adjusting all the surface integrity aspects i.e. roughness, microhardness and residual stress. It was also found that the main impact of feed rate on fatigue life is attributed to its influence surface roughness at high static force.
PDF
