Workpiece Material Research Articles

Surface topography irregularities generated by broaching

Surface topography irregularities generated by broaching are analysed. Experimental tests were carried out on three workpiece materials: AISI 1045, Ti-6Al-4V, and Inconel 718, varying the cutting speed, rise per tooth, and rake angle. The experimental results combined with numerical simulation demonstrate that surface topography irregularities result from mechanical rather than thermal effects. Higher surface topography variations are obtained when the force magnitude increases, and when its direction is more perpendicular to the machined surface. Additionally, the Young's modulus of both the workpiece and tool materials plays a fundamental role in topography quality, reducing irregularities when the Young's modulus is increased.

Effect of material inhomogeneity on chatter stability

Chatter vibrations in milling are a widely researched topic in manufacturing science. The models used to predict and mitigate chatter use assumptions for the model inputs. Assuming the workpiece material is homogenous, is such an assumption. In this study, the effect of workpiece material variation on chatter stability is studied. Upon the observation of varying stability limits during milling operations of aluminium blocks, it is shown that the workpiece material inhomogeneity affects the chatter stability. To support this hypothesis, the surface hardness of the workpieces is measured using the Leeb rebound hardness test method. It is shown that the location-dependent chatter stability limits, calculated using the local cutting coefficients, capture the position-dependent stability nature of the experimental data.

Experimental investigation on the performance variations of three different work piece materials in EDM with variation of thermo-physical properties

Experimental investigation on the performance variations of three different work piece materials in EDM with variation of thermo-physical properties

Optimization of process parameters in ultrasonic machining using integrated AHP-TOPSIS method

The process by virtue of which holes and cavities are formed in a metal work piece with the help of shaped tools, high frequency mechanical motion and abrasive slurry is known as Ultrasonic Machining Process. Its working principle is completely different from the other traditional machining processes such as laser beam machining and electrical discharge devices. This is developed machine removal processes in which the work material is less damaged by the thermal energy and it also introduce significant level of residual stress which is important for survival of the work material. This character of the process makes USM more enhanced and better machine job characteristics. This characteristic is also required for determining the optimal control parameter settings of an USM process’s is a non-traditional machining process in which abrasive content in slurry are driven against work by tool oscillating at low amplitude and high frequency. In this research paper stainless steel is used as tool material in the whole process and zirconia bio ceramic plate is taken as a work piece material. The process parameters are considered as feed rate, slurry concentration, power rating and grit size. Through this work, it is found that responses highly correlated with correlation coefficient, which justifies the application of MCDM as an optimization tool. The optimization studies are carried out on an ultrasonic machining process with multi response characteristics depend on the multi criteria decision making methodology (MCDM), using technique for order preference by similarity to ideal solution (AHP-TOPSIS) approach are described in this paper. The final results of this paper indicate the effectiveness of USM using MCDM method for different USM parameters to produce high quality parts made of zirconia Bio-ceramics with excellent productivity.

An overview of the machinability of alloy steel

Machinability is an important aspect for the machining of any materials. In general, it is controlled by means of tool life, surface roughness, power consumption, chip morphology, cutting forces, cutting fluid and material removal rate. Furthermore, it is also affected the microstructure, grain size, hardness, yield, tensile strength and chemical composition of the work piece material and tool materials. Advanced materials such as alloy steel, structural ceramics, and hardened steel are difficult to machine using conventional tool materials. The machining parameters such as depth of cut, cutting velocity and feed rate play a very important role to achieve high quality of surface finish on the machined surface. High interface temperatures at the tool tip and work piece material resulted poor surface finish and increases cutting forces and tool wear. A high cutting speeds with high feed and depth of cut causes high heat generation which reduces the tool substrates bonding strength resulting in accelerated tool wear and reducing tool life. In this article influence of heat treatment to enhance machinability alloy steel reviewed in terms of tool life, surface roughness, cutting forces and chip morphology. This article will be very useful for the students, research scholar and industrialist working in the area of machining.

Nanosecond laser-induced controllable oxidation of TiB2–TiC ceramic composites for subsequent micro milling

Laser-induced controllable oxidation coupled with micro-milling (LOMM) provides a feasible way to machine difficult-to-machine materials such as TiB 2 –TiC ceramic composites. The oxidation mechanism of the material under laser irradiation represents the fundamental issue of LOMM. In this paper, laser-induced controllable oxidation of spark plasma sintered TiB 2 –TiC ceramic composites as the workpiece material was studied. A three-dimensional finite element model was established based on ABAQUS/CAE 6.14 software to simulate the effect of laser parameters on temperature field distribution and was verified by experiments. The influence of laser processing parameters and assisted gas atmospheres on the oxidation behavior of TiB 2 –TiC ceramic composites was investigated. Results revealed that the irradiated temperature which had a significant impact on oxidation behavior, increased with an increment of the laser fluence and decreased with an increment of scanning speed with other laser parameters fixed. In addition, based on experimental analysis, the thickness of the oxide-layer increased with an increase of laser fluence and reduced with increasing laser scanning speed. At a laser fluence of 10.78J/cm 2 and scanning speed of 1 mm/s as well as in an oxygen-rich atmosphere, a loose and porous oxide-layer was produced on the irradiated surface. Cross-section thicknesses of the oxide-layer and sub-layer reached 63 μm and 22 μm, respectively. Moreover, the thickness of the oxide-layer was 22 μm in air surroundings and hardly be found in argon and nitrogen atmospheres under identical laser parameters, which indicated that oxygen content had a significant influence on the oxidation reaction of the material. The products of the oxide-layer were mainly composed of rutile- and anatase-TiO 2 . Furthermore, the hardness of the sub-layer was 9.6 ± 0.7 GPa at a laser fluence of 10.78J/cm 2 and scanning speed of 1 mm/s, which was far lower than that of the substrate with a hardness of 20 ± 0.7 GPa. This study provides a theoretical basis for subsequent micro-milling.

Magnetic field assisted finishing (MFAF) process for internal finishing of alumina ceramic tube

Nowadays, fine surface finish is in great demand for many industrial applications. An MFAF process is discussed in this conference paper to achieve a highly finished internal surface of non-ferromagnetic Alumina ceramic tube. Conventional grinding and polishing techniques cannot be used to finish this material because they cannot achieve high surface precision and produce surface defects like micro cracks. Therefore, MFAF process is an alternative method as it minimizes the surface damage because of flexible finishing conditions. MFAF Process, has flexible abrasive brush which can easily finish complex geometry of the workpiece. The workpiece material is alumina ceramic which is in higher demand as a substrate in electronic device applications. The MFAF process was done on alumina ceramic tube and 3 parameters, each having 2 different levels was selected. The parameters considered in the study are chuck speed (rpm), quantity of Diamond abrasive and iron power, machining time. 4 experiments with different levels of parameters were conducted. After finishing experiment using MINITAB 19 software, optimum parameters were determined. From the results of experiment, it was concluded that quantity of diamond abrasive and iron powder did not have much influence on finishing time compare to the chuck speed (r.p.m).

Holistic process monitoring with machine learning classification methods using internal machine sensors for semi-automatic drilling

Since one third of rivet holes during aircraft assembly are produced with semi-automatic drilling units, in this work reliable and efficient methods for process state prediction using Machine Learning (ML) classification methods were developed for this application. Process states were holistically varied in the experiments, gathering motor current and machine vibration data. These data were used as input to identify the optimal combination of five data feature preparation and nine ML methods for process state prediction. K-nearest-neighbour, decision tree and artificial neural network models provided reliable predictions of the process states: workpiece material, rotational speed, feed, peck-feed amplitude and lubrication state. Data preprocessing through sequential feature selection and principal components analysis proved to be favourably for these applications. The prediction of the workpiece clamping distance revealed frequent misclassifications and thus, was not reliable.

Effect of a Single Particle in Abrasive Waterjet Machining on 42CrMo4 Modifications

Waterjet machining is a powerful tool for processing of a variety of materials from ductile to brittle ones. However, it is a complicated machining process to control and predict its results on the workpiece due to the interaction of high dynamic abrasive particles with the workpiece surface and with each other simultaneously. A proper approach to decrease this complication is to investigate the effect of a single particle on the workpiece surface instead of multiple particles with their complex interactions. Therefore, the aim of this study is to understand the mechanism of abrasive waterjet machining by considering the effect of single particles of different abrasives with different attacking angles on two different microstructural conditions of a steel alloy. Here, 42CrMo4 is selected as the workpiece material for its ability to have different modifications from ductile to brittle characteristics. First, the effect of process parameters on the impact characteristics of the waterjet is studied. In the next step, the effect of particle velocity on the workpiece material modification is investigated. Furthermore, the effect of impact angle on the material modification and shape of the generated footprints is explored. Moreover, the effect of kinetic and kinematic properties of abrasive particle on burr formation in the ductile modification of 42CrMo4 is investigated.

Process Signatures–Knowledge-based approach towards function-oriented manufacturing

Surface layer properties are of crucial importance for the functional performance of manufactured components. For the vision of a function-oriented production, the relevant surface layer properties for the considered functional properties (e.g. fatigue strength, corrosion resistance) are to be generated by an adequate selection and adjustment of manufacturing processes. In order to accomplish this in a resource-efficient manner, extensive knowledge about the impact of manufacturing processes on the workpiece material is required. During the process, the material responds to external loads (e.g. process forces, heat fluxes in the contact zone) which induce internal material loads (e.g. strain, temperatures, chemical potential), which finally are responsible for the resulting material modifications (e.g. changes in hardness, residual stress, chemical composition). The correlations between material modifications and internal material loads are aggregated in Process Signatures. This keynote shows exemplary Process Signature Components and their use in generating targeted surface layer properties. The key scientific challenges are developments towards a deeper understanding of the underlying mechanisms leading to modifications in the microstructure and the derivation of suitable descriptive quantities for the relevant internal material loads, which can usually only be obtained from process simulations. Based on this, a prediction and knowledge-based generation of depth profiles of surface layer properties is possible, wherefore first approaches are presented in this keynote.

Multi-objects optimization in μ-EDM using AlCrN coated tungsten carbide electrode by Deng's method

In machining, the use of appropriate optimization method will significantly contribute in improving the economic and technical efficiency. Currently, there are many techniques used for multi-objective decisions in electrical discharge machining (EDM) and micro-EDM. This may create mistakes in choosing the optimal solution for each problem and mislead the optimum solution. Therefore, it is necessary to have research directions to be able to come up with a reasonable optimal method. In this study, the author has studied multi-targeting decisions in micro-EDM using coated electrode. Experiments were performed using Ti-6Al-4V as a workpiece material and AlCrN coated Tungsten carbide (WC) micro tool electrode. Deng's method was used to decide the optimized level of depth of machining (Z Co-Ordinate) and overcut (OC) in micro-EDM using the coated electrode. Research results are analyzed and evaluated with several other multi-objective decision methods. The results indicated that Deng's method was the suitable method for this study and the machined surface quality of the coated electrode was also analyzed.

Measurement and analysis of the thermal load in the bore subsurface zone during BTA deep hole drilling

To machine bores with larger diameters (D > 40mm) and a length to diameter ratio greater than ten (lb/D > 10) the BTA deep hole drilling process is often used. The cutting action of the cutting edge and the burnishing of the guide pads influence the resulting surface and the subsurface zone of the machined bore. The guide pads support the BTA drill head against the machined bore to prevent straightness deviations. A thermo-mechanical load, which results from the cutting and burnishing, influences the surface of the bore and effects the surface integrity, i.e. micro hardness, residual stress state, microstructure or the surface roughness, of the bore. In this paper, a measurement strategy to determine the thermal load in the subsurface zone using thermocouples is presented. Furthermore, a fiber-optic ratio pyrometer was used to measure the temperature in the contact zone between the cutting edge and the wall of the bore. The experiments were carried out using different workpiece materials, tool coatings and cutting parameters. The measurements are analyzed and set in context with previous studies.

Fracture in self-lubricating inserts: A case study

A case study is carried out to reveal the fracture mechanism of self-lubricating inserts. The insert is made up of 98.5 wt% Zirconia Toughened Alumina (ZTA) reinforced with 1.5 wt% CuO. The insert is fabricated through the powder metallurgy route, followed by the hot isostatic pressing (HIP) technique (for densification). After densification, the insert is shaped and sized according to ISO SNUN 120408. The workpiece material used for machining is AISI 4340 steel. A conventional NH-26 lathe is used for machining as well as for creating facture inside the insert. In this investigation, the machining operations are carried out till the failure of inserts does not take place. The fracture analysis suggested a synonymous fracture mechanism that occurs for brittle facture (facture without any deformation). The fracture analysis seen through FESEM images observed that the initiation of crack that happened without any dislocation movement results in chipping, cracking, and flaking on the surface. The crack is initialized due to the generation of high localized stresses. The stresses were developed due to the continuous movement of chips concentrated slightly away from the cutting edges. The developed stresses are relieved by creating small cracks beneath the surface. These cracks are propagated in the radial direction without any dislocation-induced plasticity. The mechanism is well confirmed through the FESEM images of fracture specimens.

Calculation of heating drawing regimes of anisotropic material

Relationships for calculating of the kinematics, power, pressure and continuity of the workpiece material during heating drawing are proposed. The workpiece material is assumed to be viscoplastic, transversally isotropic. The energy equation of equilibrium and the equations of damage kinetics are used. The calculated results are presented.

Simulation of AWJ drilling process using the FEA coupled SPH models: A preliminary study

Abrasive Water Jet machining (AWJM) is one of the most prominent non-traditional machining processes in manufacturing as its ability to machine a variety of materials including ceramics and hard metals without developing any thermal stresses over the target materials. However, the accuracy of the machined materials is challenging to predict due to the lack of study of the machining parameters. In addition, the machining cost is restricted to conduct the real time experiments with different combinations. Therefore, in this research work Smoothed Particle Hydrodynamics (SPH) coupled Finite Element Analysis method is used to examine the effect of change in velocity and stand-off distance on hole diameter and shear stress on Nickel-based superalloys while piercing small holes using the AWJ. In this work, the abrasives and waterjet features are modeled using SPH, and the Finite Element Analysis (FEM) is used to model the target material. A contact called “ERODING_NODES_TO_SURFACE” is set between the workpiece material and SPH particles to simulate the AWJ machining and a software package called LS-DYNA is used to perform the whole simulation. The results of this study bring the suitable parameter settings to produce the quality holes in nickel-based superalloys by using the AWJ with piercing mode.

Performance of ceramic cutting tool with groove and cross-chevron surface textures filled with semi-solid lubricants

In this work, the integration of surface texturing and extended self-lubrication for machining grey cast iron materials is made for a hassle-free and toxic-free working environment for industrial workers. The Cross-chevron and line textures were fabricated on the tool's rake, and flank faces using Nd: YAG laser texturing machine. Turning experiments are made using an untextured ceramic tool (UT), cross-chevron and line textured tool (TT), semi-solid lubricants MoS2, Graphite, and SAE 40 oil solutions filled texture tool (STL) under dry conditions. The investigational results showed reduced main cutting force, feed force, average friction co-efficient for semi-solid lubricant filled texture tool than other considered tools. Due to the lesser adherability of grey cast iron (workpiece material) with the surface textured tool and texture gaps filled with semi-solid lubricants, a significant reduction in cutting forces were observed at higher cutting speeds. The authors found that the texture surfaces and the texture gaps filled with lubricant at a far distance away from the cutting edge were not helpful during the trial experiments.

Crack study of recasting layer on workpiece surface in Micro-EDM

In this paper, the crack phenomenon of different materials was studied according to the surface morphology of recasting layer of micro EDM workpiece. In this paper, high-speed steel and titanium alloy are used as workpiece materials, and the RC pulse power supply is used for electric discharge machining. The surface and profile of the recast layer of the workpiece are examined by scanning electron microscopy. The difference between the two in the crack phenomenon of the recast layer in micro electric spark machining is analyzed. Finally, some improvement measures are put forward to solve the problem of recasting layer crack on the surface of micro EDM workpiece.

White Layer Thickness Variation in Die Sinking EDM

Surfaces that were machined by Electrical Discharge Machining (EDM) inevitably exhibit a thin layer of resolidified material, commonly called “white layer”. It is usually regarded as disadvantage of ED machining as it induces tensile residual stresses to the parent material and therefore facilitates the formation of cracks. It therefore was subject to a number of scientific investigations that often dealt with its (non-)crystalline structure or the stress induction. Some research groups have also focused on the thickness of the white layer. However, the variation of its thickness has not yet been investigated comprehensively and therefore constitutes the focus of this work. Experiments were conducted on a conventional sinking EDM machine. A heat-treatable steel was used as a workpiece material and graphite was used for the tool electrode. The influence of the discharge duration te as well as the discharge current ie on the white layer formation were investigated. Results show that significant thickness variations occur on every ED machined surface and that increasing discharge energy leads to an increase of both, white layer thickness as well as its variation.

Surface Roughness Prediction in Grinding Ti using ANFIS Hybrid Algorithm

Intelligent manufacturing is needed, and many techniques and tools have been developed with this in mind. Over time, many of these techniques have been combined, and hybrid approaches have provided better results in shorter times, leading to a more precise prediction of outcomes when compared to the use of individual tools. This research focused on grinding Ti-6Al-4V workpiece material with a Carbon nanotube (CNT) incorporated grinding wheel. The Adaptive Neuro-Fuzzy Inference System (ANFIS) was used to predict surface roughness which was taken as the output of choice for this study. A new hybrid of ANFIS with Genetic Algorithm (ANFIS-GA) was then proposed to see if this prediction method could obtain greater precision. The regression analysis predicted the experimental model’s linear relationship to surface roughness, and the effect of grinding process parameters on surface roughness was analysed using the sensitivity analysis method.

Prediction of machine tool wear using the weighted k-nearest neighbor method and Neural network model with acceleration response

In the manufacturing industry, with the decrease in the working population, there is a demand for intelligent manufacturing processes (smart factory). When focusing on cutting, predicting and detecting tool wear during machining is an important technical issue for autonomy. However, the tool wear of cutting tools varies from machining to machining even under the same machining conditions, with the same type of tool, and with the same material and shape of workpiece. Therefore, even if a representative wear prediction model is constructed to predict tool wear, the prediction accuracy is low and not practical. In this research, we will verify whether the amount of tool wear can be predicted by a neural network, which is a type of machine learning, using the vibration data obtained during cutting and the past. The accuracy of the proposed method is also verified by comparing the wear volume prediction by one representative neural network with the wear volume prediction by the combination of the proposed multiple neural network.