Simulation of a micro-milling single crystal copper process based on crystal plastic constitutive theory

This study investigated the application of ultrasonic atomization lubrication system with Nanofluid additive implemented in micro-milling process on SKD11 die steel. The graphene nanoparticles are employed as the additive of Nanofluid. Ultrasonic atomization system not only can effectively improve the agglomeration phenomena of Nanoparticles in Nanofluids but also provide the benefit of particle lubrication. For this experiment, Taguchi method was adopted and L 9 34 orthogonal array was used to explore the optimal parameters. Targeting micro-milling force evaluation as the only focus, the control parameters included the average thickness and weight percentage concentration of Nano-graphene, the amount of ultrasonic atomization, and the angle of nozzle are analyzed. Based on the analysis, the optimal combination of Nano-graphene with ultrasonic atomization micro-lubrication was found, and then compared to the case of MWCNTs with ultrasonic atomization micro-lubrication and the other case of basal liquid with ultrasonic atomization micro-lubrication. According to the experiment results, the Nanofluid with Nano-graphene added can further reduce the micro-milling force of micro-milling process that suppress the burr generated by the processing. It can achieve the goal of tool life improvement and high workpiece quality. The micro-milling force using Nano-graphene with ultrasonic atomization micro-lubrication is reduced by 7.8% and 12.9% compared to the other two lubricating fluids, respectively.

In present investigations, efforts have been undertaken to explore the impact of micromilling cutting variables during the micromilling of Ti6AL7Nb alloy using Tungsten Carbide [WC/Co] cutting tool. The exploratory trials have been undertaken with dry micromilling environment for various process variables like surface speed, feed velocity, deepness of cut, etc. The main intention for this experimental tests are to establish effects of multiple process variables on micromilling forces and surface textures. The micromilling forces and surface texture are measured at distinct micromilling environment. The outcomes incurred signified the micromilling forces and surface roughness intensifies with increase in feed velocity and reduces for increase in cutting velocity. It is established that feed velocity have dominating effects on micromilling forces and surface textures morphology, however, the deepness of cut is least effective process variable. The cut fragments generation and gradual evolvement suggests that spring mode, continuous and fragmented chips are formed during micromilling process.

Slip-discreteness-corrected strain gradient crystal plasticity (SDC-SGCP) theory

Crystal plasticity finite element simulations of pyramidal indentation in copper single crystals

We review the state of the art of process modeling for discrete event simulation, make a number of observations and identify a number of issues that have to be tackled for promoting the use of process modeling in simulation. Process models are of particular interest in model-based simulation engineering approaches where the executable simulation model (code) is obtained with the help of textual or visual models. We present an illustrative example of model-based simulation development.

Previously, the infrared permittivity tensor of monoclinic β-Ga2O3 crystals has been determined using ellipsometry reflection measurements from two differently oriented monoclinic β-Ga2O3 crystals with surfaces parallel to (010) and (−201). The (010) surface places the crystallographic a-c plane in the table of the instrument. The permittivity tensor consists of four complex values, and in order to compute it, four or more combinations of measurements are required at selected table rotations and incidence angles. However, the (010) orientation also places the transverse optical (TO) modes with Au symmetry parallel to the z-axis of the instrument, and we find that these modes are not fully excited and, hence, not measurable due to underlying selection rules. This makes additional measurements on surfaces other than (010) necessary. The second orientation has been the (−201) crystal, which places the crystallographic b axis in the plane of the table to access the transverse Au phonons. In prior work, the overall tensor has been determined by combining measurements of the two crystal orientations [Schubert et al., Phys. Rev. B 93, 125209 (2016)]. The goal of the work here is to find single crystal orientations for which all TO modes can be determined from measurements. The use of a set of measurements employed for such a single crystal is inextricably linked to the choice of incidence angles and table rotations. Consequently, determining suitable angles for these is linked to the selection of a crystal orientation, which is, therefore, an integral part of the overall goal. The TO contribution to the permittivity strongly dominates at or near the TO mode wavenumber resonances and, therefore, are used in this work to identify suitable orientations for a single crystal. Any such crystal orientation will also provide measurements useful to compute permittivity across the entire measured wavenumber range. In principle, any crystal orientation that does not place the direction of any TO mode at or near the z-axis may be suitable due to the underlying physics and mathematics of the problem. We discuss which of these measurement parameters contain the most sensitivity for the (111) orientation. For accuracy, we seek the best or very good orientations. Our investigation follows a previously demonstrated approach where at a single wavelength, the full tensor of an orthorhombic absorbing crystal was obtained from a low-symmetry surface of stibnite [Schubert and Dollase, Opt. Lett. 27, 2073 (2002)]. We discuss which of these measurement parameters contain the most sensitivity for the (111) orientation. The methods presented here will also be useful for other monoclinic materials as well as other materials of different crystal structures, including orthorhombic and triclinic materials.

Dislocation structures and crystal orientations of copper single crystals deformed by equal-channel angular pressing

Normally, FTire model parameters are determined by experimental tests. However, because of the high cost of experiment equipment and limitations in rig design and operating conditions, it is hard to obtain all the required data by experimental tests, especially for some large tires, such as the running wheel tires of straddle-type monorail vehicles. To solve this problem, a method based on finite element (FE) simulations is put forward. To achieve the goal, a three-dimensional FE model of a 345/85R16 radial tire is developed using ABAQUS software. In addition, a modified exponential decay friction model, derived from tire tread rubber friction tests, is put forward and applied in the following FE simulations using the ABAQUS user subroutine FRIC. To verify the accuracy of the present model, tire vertical stiffness test, lateral stiffness test, and tire contour geometry measurement are designed. Through the comparison of measurements and FE simulations, it turns out that the model is capable of predicting tire properties accurately. Tire static, steady-state, modal, and dynamic cleat tests are modeled. Finally, data such as vertical stiffness, cornering stiffness, and natural frequencies are derived from FE simulations. Based on the data derived from FE simulations, the FTire model parameters are identified and then validated by comparing the force responses of the FTire simulation in the ADAMS/Tire test rig and FE simulations. The results show that there is an acceptable agreement between them, reflecting that the method is feasible.

Static recrystallization simulations starting from predicted deformation microstructure by coupling multi-phase-field method and finite element method based on crystal plasticity

Elastic-plastic deformation behavior of austenitic, martensitic, and austenitic-martensitic high-Mn steels is investigated by using crystal plasticity theory. The development of expandable pipes made of two-phase steel for oil and gas well applications is needed for improved and efficient recovery of hydrocarbons from difficult reservoirs. The current research is aimed at improving the down-hole post-expansion material properties of expandable pipes. A mathematical model is first developed based on finite-deformation crystal plasticity theory assuming that slip is the prime mode of plastic deformation. The developed model is then numerically implemented by using the finite element software ABAQUS, through a user defined subroutine. Finite element simulations are performed for austenitic, martensitic, and austenitic-martensitic steels having different proportions of martensite in an austenite matrix. Three primary modes of loading are considered: uniaxial tension, compression and simple shear. The variation in yield strength, hardening pattern and dissipated energy is observed and analyzed.

One dimensional chemical shift modulated correlation spectroscopy of single-crystals

Micromechanical analysis of martensite distribution on strain localization in dual phase steels by scanning electron microscopy and crystal plasticity simulation

Micromilling can fabricate miniaturized components using micro-end mill at high rotational speeds. The analysis of machining stability in micromilling plays an important role in characterizing the cutting process, estimating the tool life, and optimizing the process. A numerical analysis and experimental method are presented to investigate the chatter stability in micro-end milling process with variable milling tool geometry. The schematic model of micromilling process is constructed and the calculation formula to predict cutting force and displacements is derived. This is followed by a detailed numerical analysis on micromilling forces between helical ball and square end mills through time domain and frequency domain method and the results are compared. Furthermore, a detailed time domain simulation for micro end milling with straight teeth and helical teeth end mill is conducted based on the machine-tool system frequency response function obtained through modal experiment. The forces and displacements are predicted and the simulation result between variable cutter geometry is deeply compared. The simulation results have important significance for the actual milling process.

Ni3Al based single crystal alloy IC6SX was prepared by election spiral crystal method. The effect of the conical transition section of the single crystal on the microstructure of the single crystal was studied in this work. The results showed that, in the crystal growth process, the effect of the conical transition section on the orientation of single crystal was significant. The yield ratio of the single crystal alloy specimen with <001> orientation could be improved significantly by adding cone transition section. With the angle of the cone transition section increasing from 20 º to 43 º, the dendrite arm spacing increased gradually, and dendrite morphology was coarsened and the third dendrite arm appeared.

Prediction of micro-milling forces with finite element method