In-Situ Characterization of Burr Formation in Finish Machining of Inconel 718

One of the undesirable byproducts that occur during the machining process is the development of burrs, which are defined as rough excess material that forms around the geometric discontinuities of a part. Burrs are especially problematic because they have negative impacts across the triple bottom line: economic, environmental, societal. For one, they are expensive to remove because the deburring process is entirely manual and requires skill. Further, burr material is typically discarded which is adding to the already mounting waste generated from machining such as in coolant and chip disposal. Lastly, there are many societal implications, such as operator injury during assembly and the failure of parts in service because of leftover burrs that turned into stress concentrations. Therefore, optimizing the machining process to minimize burrs and promote sustainable manufacturing is a central challenge for manufacturers today. However, the burr formation mechanism is complex, and research on the phenomenon is scarce. The current state of the art focuses almost exclusively on drilling and micro-milling processes, with very little work investigating burr formation in the conventional machining processes of turning and milling. Research as it pertains to materials that are difficult-to-machine like nickel and titanium-based superalloys is even less common, as most of the literature focuses on softer materials like aluminum and steel alloys. Superalloys are especially crucial to the aerospace industry, comprising most of the components in jet engines. Thus, the objective of this study was to characterize burr formation for nickel-based superalloy Inconel 718 using a custom-built in-situ testbed capable of ultra-high-speed imaging in orthogonal cuts. Experiments were carried out to measure the variation in burr development with respect to several cutting parameters: uncut chip thickness, tool-wear, and cutting speed. Firstly, the exit and side burr geometry were measured after each machining trial for a variety of different metrics. Results showed that all cutting parameters have an influence on the burr geometry, although not every cutting parameter had statistical significance on certain burr metrics. For instance, it was found that side burrs were much more sensitive to tool-wear than exit burrs. Then, by combining digital image correlation (DIC) with a physics-based model, the flow stress was calculated during exit burr formation and results revealed that the stress at the exit burr root was approximately equal to the flow stress. Finally, this study investigates the fracture phenomenon during exit burr formation—it was found that besides the requirement of high strain rate and depth of cut, negative exit burrs, there is a microstructural size effect, which had not been reported by prior work

A novel finite element approach to modeling hard turning in due consideration of the viscoplastic asymmetry effect

A novel material model for strain rate and temperature dependent asymmetric viscoplastic deformation behavior considering transformation induced plasticity (TRIP) as a crucial phenomenon influencing the hard turning process-oriented ductility was developed. Within the framework of viscoplasticity and continuum damage mechanics, the well-established Johnson-Cook flow stress model has been upgraded by the concept of weighting functions accounting for the asymmetric viscoplastic material behavior under different stress conditions during hard machining of chrome bearing steel AISI 52100. Moreover, the extended Johnson-Cook model incorporates the ductility alteration caused by transformation induced plasticity by applying the Leblond-approach. Based on the theoretical proceeding, a material routine for flow stress computation considering the viscoplastic asymmetry has been developed and applied within hard turning simulations using the commercial Finite-Element-Method (FEM) software DEFORM. In addition, the hard turning simulation model accounts for the phase transitions between martensite and austenite during the process-related material heating as well as austenite and white layer as a consequence of the so-called reverse martensite transformation. A decisive actuating variable concerning the feasibility and accuracy of the performed hard turning modelling is the austenite start temperature, which has been determined in consideration of the externally applied stress. Within the scope of the material modelling, a novel quantity referred to as stress mode factor has been introduced in order to enable the identification of areas in the cutting zone subjected to heterogeneous load conditions. The stress mode factor appraisal within the aforementioned bearing steel material routine discloses a new path to establish the influence of dissimilar stress states on the work piece heat balance as well as the impact of transformation induced plasticity on the stress distribution in the cutting zone

Robotic arm system with computer vision for colour object Sorting

This study presents the development of robotic arm with computer vision functionalities to recognise the objects with different colours, pick up the nearest target object and place it into particular location. In this paper, the overview of the robotic arm system is first pre-sented. Then, the design of five-degrees of freedom (5-DOF) robotic arm is introduced, followed by the explanation of the image proc-essing technique used to recognize the objects with different colours and obstacle detection. Next, the forward kinematic modelling of the robotic arm using Denavit-Hartenberg algorithm and solving the inverse kinematic of the robotic arm using modified flower pollination algorithm (MFPA) are interpreted. The result shows that the robotic arm can pick the target object accurately and place it in its particular place successfully. The concern on user safety is also been taken into consideration where the robotic arm will stop working when the user hand (obstacle) is detected and resume its process when there is no obstacle

Development of software for easy prediction of process parameters in air bending with local heating

This paper presents a new software tool for sheet metal forming, based on an analytical model of the process. The advantages of this kind of tool, compared with numerical models based on finite element codes, are described. The analysis is focused on sheet metal bending at high temperature that is a promising method for metal forming, improving sheet formability and machines range of use.Publicad