Modeling the wind circulation around mills with a Lagrangian stochastic approach

This work aims at introducing model methodology and numerical studies related to a Lagrangian stochastic approach applied to the computation of the wind circulation around mills. We adapt the Lagrangian stochastic downscaling method that we have introduced in [3] and [4] to the atmospheric boundary layer and we introduce here a Lagrangian version of the actuator disc methods to take account of the mills. We present our numerical method and numerical experiments in the case of non rotating and rotating actuator disc models. We also present some features of our numerical method, in particular the computation of the probability distribution of the wind in the wake zone, as a byproduct of the fluid particle model and the associated PDF method

Finite element analysis of micro end mill and simulation of burr formation in machining al6061-t6

The recent technological progressions in industries have offered ascent to the continually growing requests for microstructures, sensors, and parts. Micro-milling is a promising method to create these scaled down structures, sensors, and parts. Yet, micromilling still confronts some significant difficulties, tormenting further provision of this innovation. The most noticeable around them is micro burr formation. Burrs created along the completed edges and surfaces in micro-milling operation have huge effect on the surface quality and performance of the completed parts and microstructures. In any case, deburring of micro-parts is not conceivable because of bad accessibility and tight tolerances in micro segments. One of the methods to minimize micro burr formation in micro milling is by enhancing the geometry of the device. As minimization of micro burrs still remains a key test in micro machining, not many researchers have worked in this field. The main aim of the research work is to present finite element analysis of flat end mill micro cutters used in micro milling by varying geometry of the tools. Apart from this, study has been done in detail on burr formation in micro milling and what factors affect it. Burr formation simulation has been carried out while varying the tool geometry. The outcome of the research will be a static finite element analysis of micro burrs formed during micro-milling which can help in determining tool life and a detailed dynamic analysis of micro burrs formed during micro-milling operation in Al6061-T6 which can benefit the aerospace industry in various ways. The results obtained during the analysis may be used for further research for burr minimization through tool optimization and process control

Three-Dimensional Finite Element Analysis of Conventional and Ultrasonic Vibration Assisted Micro-Drilling on PCB

Recent advancement in society’s demands has forced industries to produce more and more precise micro parts. With an advancement in engineering sciences, current manufacturers in various fields such as aerospace, medical, electronics, automobile, biotechnology, etc. have achieved the potential to fabricate miniaturized products, but with numerous technical challenges. Dimensional accuracy and surface integrity of the machined components are the key challenges and at the same time, cost minimization is strongly desired. To meet these challenges and demands, improvements in machining regarding new procedures, tooling, tool materials and modern machine tools are highly essential. Micromachining has shown potential to achieve the fast-growing needs of the present micro manufacturing sector. Additionally, new machining techniques like ultrasonic machining, laser drilling, etc. have been developed as an alternative source to reduce obstructions caused during macro/micro machining. The present research aims to perform three-dimensional (3D) finite element dynamic analysis for micro-drilling of multi-layer printed circuit boards (PCBs). Both conventional and ultrasonic vibration assisted micro-drilling (UVAMD) FE simulations have been compared to predict and evaluate the effect of process parameters on the output responses like stress generation and reaction forces and burr formation on the workpiece surfaces. The Lagrangian based approach is followed for the FE simulation including the mass and inertial properties of the proposed FE model. The predicted FE results are compared with the past experimental work for thrust force evaluation and burr formation on workpiece surfaces. The present work is supported with modal and harmonic analysis of stepped and conical horns along with micro drill bit. Here, horns made up of Aluminum 6061-T6, Titanium and Mild steel are chosen with micro drill bit of 0.3 mm diameter with varying tool materials (Tungsten carbide and High speed steel). The effects of natural frequencies with different mode shapes within the range of 15-30 kHz are shown. The frequency responses of micro drill with displacement conditions have been presented for longitudinal modes. The present simulation results will be helpful to conduct proper experimentation in order to achieve efficient machining and surface finish. The results enumerate that the drilling parameters have a strong influence on thrust forces and stresses occurring in micro-drilling. Ultrasonic assisted micro-drilling has a good potential in reduction of forces generated by vii selecting proper machining parameters. The FE simulation of UVA micro machining can further be enhanced and extended to various materials like plastics, sheet metal, other PCBs, etc. to predict the performance with varying machining and geometrical parameters

A FEA simulation study of ball end mill for fixed 3+1 / 3+2 axis machining of Ti-6Al-4V.

This paper presents a Finite Element Analysis (FEA) simulation study conducted on ball endmill for fixed 3 + 1 and 3 + 2 axis orientations for machining Ti-6Al-4 V. This work adopts a tungsten carbide (WC) ∅18.6 mm diametrical/6fluted ball endmill to analyse maximum principal elastic strain (ϵmax-max-principal-elastic), maximum principal stress (σmax-principal)along with cutting tools forces in the axial (Fz), radial (Fy), tangential (Fx) and total (Ftotal) directions. The machining orientations considered for 3 + 1 and 3 + 2 axis are (i) tilt angles of 5°, 10°, 15° & 20° and (ii) lead angles of 5°, 10° & 15° with a constant fixed tilt angle of 10°. The cutting speed and feed rate per tooth is taken as 450 m/min and 0.5 mm/tooth. These are based on a high speed machining (HSM) scenario and has been dynamically simulated for a maximum of 175,000 cycles. From the simulation study considered at 16-20 valid cutting points, it can be noticed that in 3 + 1 axis, for a tilt angle of 10° and 3 + 2 axis for a Tilt 10°/Lead 10° the σmax-principaland ϵmax-max-principal-elasticare higher when compared with all tilt/lead angles. In case of total forces (Ftotal) from all 3 directions (Fx, Fyand Fz) not much variation can be noticed for different tilt/lead angles, but higher values are recorded with 3 + 1 axis at 5° tilt angle and 3 + 2 axis at tilt/lead angle of 10°. The paper provides a critical comparative study on the 3 + 1/ 3 + 2 axis orientations highlighting the cutting strain/stress with tool forces at valid cutting points considering entry, middle and exit region of the blank by emphasizing the importance of cutting tool design parameters

Digital Cutting Force Modeling for Milling Operations

Process improvement in milling through improved understanding of machining dynamics is an on-going research endeavor. The objective of this project is to advance digital modeling of the milling process by incorporating tool-specific geometry in the machining analysis. Structured light scanning will be used to perform tool geometry measurements and produce a 3D model. The 3D model data will include the spatial location of the cutting edges, as well as the rake and relief profiles from the tool cross section. The rake and relief profiles will be imported, together with the work material flow stress model, into a finite element analysis of orthogonal (2D) cutting. The predicted forces will be used to calculate the coefficients for a mechanistic cutting force model. These cutting force coefficients and the location of the cutting edges, as well as the tool-holder-spindle-machine structural dynamics, will be incorporated in a time domain simulation that will be used to predict the milling forces and vibrations. Cutting tests will be performed to validate the performance predictions for this digital modeling approach

Effects of cutting conditions on forces and force coefficients in plunge milling operations

The modeling of milling forces is a crucial issue to understand milling processes. In the literature, many force models and experiments to identify force coefficients are found. The objective of this article is to develop a new approach, based on the traditional average force method, able to measure and compute the cutting coefficients for end mills used in plunging operations. This model has been used to evaluate the effect of the radial engagement on the cutting coefficients themselves, proposing a new strategy to update these values for different cutting parameters. This dependency of the cutting coefficient is particularly important for the determination of the stability lobe diagrams, used to predict the chatter conditions. In this article, the method to assess the cutting coefficients, the results of the experimental tests, and the effect of condition-dependent cutting coefficients on process stability are presented

Quasistatic deflection analysis of slender ball-end milling cutter

This work was supported by the National Natural Science Foundation of China (Grant No. 51975333), Jinan University and Institute Innovation Team Program (Grant No. 2020GXRC025), and Taishan Scholars Project of Shandong Province (ts201712002).Peer reviewedPostprin

On 3-D inelastic analysis methods for hot section components (base program)

A 3-D Inelastic Analysis Method program is described. This program consists of a series of new computer codes embodying a progression of mathematical models (mechanics of materials, special finite element, boundary element) for streamlined analysis of: (1) combustor liners, (2) turbine blades, and (3) turbine vanes. These models address the effects of high temperatures and thermal/mechanical loadings on the local (stress/strain)and global (dynamics, buckling) structural behavior of the three selected components. Three computer codes, referred to as MOMM (Mechanics of Materials Model), MHOST (Marc-Hot Section Technology), and BEST (Boundary Element Stress Technology), have been developed and are briefly described in this report