Machining Chips Research Articles

Effects of Shape of Machining Chips Inserted in Mold on Mechanical Properties of Centrifugal Casts of High Strength Brass Containing Machining Chips

Effects of Shape of Machining Chips Inserted in Mold on Mechanical Properties of Centrifugal Casts of High Strength Brass Containing Machining Chips

Investigating the microstructure and morphology of chips in dry, flood coolant and MQL machining of Ti-6Al-4V alloy

Investigating the microstructure and morphology of chips in dry, flood coolant and MQL machining of Ti-6Al-4V alloy

Investigating the microstructure and morphology of chips in dry, flood coolant and MQL machining of Ti-6Al-4V alloy

The objective of this research is to investigate the morphology and microstructure of the chips formed during milling of Ti-6Al-4V alloy using conventional flood coolant and sustainable dry and MQL machining conditions. It was found that the chips formed in dry machining suffered a higher degree of serration indicating higher chip temperature and ineffective cooling of the chips. The bi-modal structure of Ti-6Al-4V remained the same in the bulk part of the chips. However, phase transformations were seen for all three machining conditions at the shearing plane of the chips. The chips formed in dry machining had comparatively higher percentage of β-phase due to phase transformation. For the chips obtained in flood coolant machining, the transformed β-phase possibly returned to martensitic α-phase due to rapid cooling. The MQL machined chips had the least transformation of β-phase, indicating minimal changes in mechanical properties of the machined parts in sustainable MQL machining.

Compaction of machining chips: Extended experiments and modeling

The process of compaction of machining chips inside a cylindrical processing chamber is investigated. This process can be either an independent process or the first step in the Friction Extrusion Process (FEP) where the consolidated chips are softened due to frictional heating and are turned into a wire through an extrusion hole in the die. The current study provides an extension to our previous study in order to determine experimentally the Poisson's ratio as a function of the relative density during compaction. This determination is done through measurements of strains on the outer surface of the processing chamber containing the machining chips. The elastic theory of a thick-walled cylinder under internal pressure is employed to relate the surface strain measurements to stress and strain states at the processing chamber-chips interface. Also, the loading machine compliance effect is removed from the compaction and uniaxial test results whereas in the previous work it is implicitly assumed that the loading machine is rigid so that the measured axial deformation is taken to be entirely due to the deformation of the compacted chips. The porous elastic-plastic material model developed previously is extended to model the mechanical behavior of the chips during the compaction process. Simulation predictions of the axial stress-strain curves are performed and the predicted data are found to have a good agreement with experimental data.

Effects of different implant materials and surface microgrooves on the biological behavior of gingival fibroblasts

Objective: To study the effect of microgroove surface modification of titanium and zirconia on the biological behavior of gingival fibroblasts in order to find suitable surface materials for the transmucosal part of the dental implant. Methods: Twenty specimens were divided into four groups: smooth titanium (Ti-S), smooth zirconia (ZC-S), microgroove titanium (Ti-MG) and microgroove zirconia (ZC-MG) (five specimens in each group). Microgroove modification of titanium and zirconia surfaces was carried out by using fine machining chip system in the last two groups. The width of groove ridge was 60 μm, the width of groove was 60 μm, the depth of groove was 10 μm. The surface morphologies (the groove width and depth) were observed by scanning electron microscope (SEM), the surface roughness, static contact angle and elemental of specimens in each group were detected by SEM, atomic force microscope (AFM), optical contact angle measuring device and energy-dispersion X-ray analysis (EDX). Morphology of human gingival fibroblast (HGF) that arranged along the groove was analyzed using laser scanning confocal microscope by immunofluorescence staining. Differences in cell proliferation were analyzed and compared using cell counting kit. Expression level of intergrin α(5), β(1) and collagen Ⅰ mRNA were compared among different groups by quantitative real-time PCR for 6 h and 3 d. Results: The surface roughness of smooth titanium group and smooth zirconia group was (63.23± 2.55) and (26.78±3.11) nm, respectively. Microgroove zirconia group showed the best hydrophilicity: the static contact angle was 51.2°±2.0°. HGF was arranged along the groove surface, and cell proliferation results showed that proliferation on microgroove zirconia was more significant than that on other groups from 6 h to 7 d (P<0.05). Intergrin α(5) mRNA has the highest expression in microgroove zirconia (P<0.05) in the early adhesion (6 h), and there was no significant difference in the surface expression of intergrin β(1) and collagen Ⅰ mRNA in the early adhesion (6 h) of each group. However, in the late adhesion (3 d), intergrin α(5), β(1) and collagenⅠ mRNA expression in microgroove surface groups were higher than those of the smooth groups (P<0.05). Conclusions: Microgroove zirconia surface has small roughness and good hydrophilicity, which can guide HGF to line up in the groove, and this is beneficial to the HGF proliferation and the expression of structural proteins and functional proteins.

Enhanced Corrosion Resistance of Recycled Aluminum Alloy 6061 Chips Using Hot Extrusion Followed by ECAP

The oxidation of aluminum machining chips retards the successful recycling through the conventional remelting route. A promising approach to overthrow this problem is the utilization of solid state recycling in converting aluminum machining chips directly into semifinished products to eliminate the cost of the remelting process and reduce CO2 emissions. Therefore, in recent work, chips of aluminum alloy (AA6061) were recycled by compaction and then extrusion conducted at 500°C, followed by equal channel pressing (ECAP) to study the resultant material properties and its microstructure. Moreover, the present investigation explores the influence of ECAP after hot extrusion on the corrosive behaviour of the recycled samples in saline solution (NaCl) by electrochemical impedance spectroscopy (EIS) and linear polarization (LP). The results demonstrated a remarkable enhancement of the recycled chips’ properties subjected to hot extrusion followed by the ECAP process. Furthermore, the successive ECAP passes leads to increased film thickness and decreased corrosion rate.

Production of seamless tube from aluminum machining chips via double-step friction stir consolidation

At this present work, the feasibility of producing seamless tubes through recycling of aluminum machining chips via the double-step friction stir consolidation (FSC) process was investigated. This process was done in two distinct steps. At the first step, the chips are loaded into the container and slightly compacted, and then a rotating tool with a designated diameter is plunged into the chips at a chosen rotational speed and feed rate. Due to the frictional heating, the softened materials are compressed and merged to form a consolidated cylindrical bulk material eventually. In the second step, a rotating tool that is smaller in diameter than the first tool is again plunged into the recycled round bars at a selected rotational speed and feed rate, forcing the material radially outwards and afterwards forming tubes. The results show that the process is a feasible solution for producing structurally sound, void-free tubes directly from machining chips at two simple steps. A numerical model was implemented to predict the evolution of the main field variables including temperature, density, and strain in the process.

Analysis of the Tribological Properties of Commercial Pure (CP) Aluminum Developed by Chip Consolidation through Equal Channel Angular Pressing (ECAP)

The goal of this research work is to study the role of equal channel angular pressing on consolidation behavior of machined chips of CP Al through ECAP. The chips are collected by orthogonal cutting with cutting edge angle 75° and depth of cut 0.2 mm. The ECAP die with Φ = 90° (channel angle) and Ψ = 20° (corner angle) is used for consolidation of machined chips. The consolidation is done by pre-heating the chips at 200°C upto four passes through processing route BC. The maximum density of 99% and hardness of 94 HV was obtained after 4 ECAP passes. Tribological properties is evaluated by Pin-on-disc dry wear testing for three different loads at a constant sliding speed 750 RPM and distance of 5 kms. Chip consolidated CP Al is inferior in wear resistance with as-received CP Al owed to localised debonding of chips with the sliding disc.

Determination of the Optimal Path of Three Axes Robot Using Genetic Algorithm

Drilling is a chip machining process widely used in manufacturing .The term drilling includes all methods for making cylindrical holes in a work piece with chip cutting tools. There are many applications where drilling is used, such as drilling holes in PCBs. Robotic systems are used today to perform the drilling process. A problem that affects the use of these systems is the drilling sequence, as there are usually a number of points to visit. The determination of the drilling sequence is similar to the problem of synchronization of movement and travel time. The main objective is to optimize the time and trajectory of the three axes robot equipped with an automatic drill that seeks the best performance. In this paper, we have built a genetic optimization and problem solving algorithms to shorten the machining time to drill a given group of holes and reduce machining costs in order to improve the efficiency of the machining process as well robotic machining with three axes without degradation of the precision of the movement. The results of the experiments show that the proposed approach is feasible and practical. It is particularly useful in planning and scheduling systems for real-time manufacturing processes.

Microstructure and Tensile Behavior of Al7075/Al Composites Consolidated from Machining Chips Using HPT: A Way of Solid-State Recycling

Microstructure and Tensile Behavior of Al7075/Al Composites Consolidated from Machining Chips Using HPT: A Way of Solid-State Recycling

Corrosion resistance of aluminum alloy AA7022 wire fabricated by friction stir extrusion

Abstract Friction stir extrusion (FSE) is known as an innovative manufacturing technology that makes it possible to directly produce wire via consolidation and extrusion of metal chips or solid billets. In this study, wire samples were produced using aluminum alloy AA7022 machining chips by the use of the FSE. To this end, the microstructures and mechanical properties of the base material (BM) and the extruded samples were investigated. The corrosion resistance of the given samples was also determined using potentiodynamic polarization technique. The results showed that the samples manufactured at higher rotational speeds possessed good surface quality, the process temperature and the grain size similarly increased following the rise in rotational speed, and the mechanical properties consequently decreased. Using the FSE led to crystallite refinement, increase in volume fraction of grain boundaries, as well as re-distribution of precipitates affecting corrosion resistance. Furthermore, the findings of the corrosion tests revealed that the produced samples by the FSE had adequate corrosion resistance and the growth in die rotation rate augmented current density and subsequently reduced corrosion resistance.

Study of saw-tooth chip in machining of Inconel 718 by metallographic technique

The present research work aims to understand the chip formation mechanisms in Inconel 718 machining through metallographic technique. The influence of machining speed on shear band and chip shape have been analyzed. Characterization of the shear band has been conducted by analyzing the shear band thickness, strain, strain rate, stress and micro-hardness. Additionally, chip reduction coefficient parameters and chip segmentation ratio parameters have been analyzed to understand the type of chip formation at various machining speeds. The observations and analysis of the same indicated that the formation of the saw-tooth chip is due to high-strain localization within the chip and crack initiation at the free surface of the chip. Thinner shear bands are observed at higher machining speed (120 m/min), and thicker shear bands are observed at lower machining speed (40 m/min). The magnitude of chip segmentation parameters indicates that crack generation increases with increase in machining speed.

Quality Parameters of 3D Print Products by the DMLS Method

Additive technologies are a dynamically evolving category of manufacturing methods for a wide range of industries, particularly engineering and related fields. Compared to traditional technologies based on chip machining, molding and casting, they offer new production options, particularly for complex shape components. At the same time, however, there are differences and limits that must be taken into account when designing functional machine parts. The important quality parameters of the products are in particular the dimensions and the quality of the surface. These factors are of fundamental importance for the subsequent assembly and function of a component in a plant assembly. They determine, together with the structural material properties, the usability of the component and the economic efficiency of the production in order to achieve the finished product with the minimum need for postprocessing the finished part. The submited text presents the results of the quality parameter research carried out on 3D print products made by the DMLS method, where the focus is put on the assessment of linear dimensions and the surface quality of samples from three selected materials and a combination of two print modifications. The measurement results are compared to generally valid standards and tabulated values to verify and eventually modify table values for use when designing a design solution with the use of 3D print products.

Serrated Chips Formation in Micro Orthogonal Cutting of Ti6Al4V Alloys with Equiaxial and Martensitic Microstructures.

The formation of serrated chips is an important feature during machining of difficult-to-cut materials, such as titanium alloy, nickel based alloy, and some steels. In this study, Ti6Al4V alloys with equiaxial and acicular martensitic microstructures were adopted to analyze the effects of material structures on the formation of serrated chips in straight line micro orthogonal machining. The martensitic alloy was obtained using highly efficient electropulsing treatment (EPT) followed by water quenching. The results showed that serrated chips could be formed on both Ti6Al4V alloys, however the chip features varied with material microstructures. The number of chip segments per unit length of the alloy with martensite was more than that of the equiaxial alloy due to poor ductility. Besides, the average cutting and thrust forces were about 8.41 and 4.53 N, respectively, for the equiaxed Ti6Al4V alloys, which were consistently lower than those with a martensitic structure. The high cutting force of martensitic alloy is because of the large yield stress required to overcome plastic deformation, and this force is also significantly affected by the orientations of the martensite. Power spectral density (PSD) analyses indicated that the characteristic frequency of cutting force variation of the equiaxed alloy ranged from 100 to 200 Hz, while it ranged from 200 to 400 Hz for workpieces with martensites, which was supposedly due to the formation of serrated chips during the machining process.

Recycling and melting process of the zirconium alloy chips

The aim of this work is study on the recycling process of zirconium alloy chips and the results aiming the efficiency in the cleaning process; the quality control; the obtaining of the pressed electrodes and finally the melting in a Vac-uum Arc Remelting furnace (VAR). The recycling process begins with magnetic separation of possible ferrous al-loys chips contaminant, the washing of the cutting fluid that is soluble in water, washing with an industrial degreas-er, followed by a rinse with continuous flow of water under high pressure and drying with hot air. The first evalua-tion of the process was done by an Energy Dispersive X-rays Fluorescence Spectrometry (EDXRFS) showed the presence of 10 wt. % to 17 wt. % of impurities due the mixing with stainless steel machining chips. The chips were then pressed in a custom-made matrix of square section (40 x 40 mm - 500 mm in length), resulting in electrodes with 20% of apparent density of the original alloy. The electrode was then melted in a laboratory scale VAR furnace at the CCTM-IPEN, producing a massive ingot with 0.8 kg. It was observed that the samples obtained from In-dústrias Nucleares do Brasil (INB) are supposed to be secondary scrap and it is suggested careful separation in the generation of this material. The melting of the chips is possible and feasible in a VAR furnace which reduces the storage volume by up to 40 times of this material, however, it is necessary to correct the composition of the alloy for the melting of these ingots.

Defining parameters for control of extruding wire by friction process

Friction stir extrusion is an innovative direct-recycling technology for metal machining chips. During the process a specifically designed rotating tool is plunged into a cylindrical matrix containing the scraps to be recycled. The stirring action of the tool prompts solid bonding related phenomena allowing the back extrusion of a full dense rod. This process results to be particularly relevant because allows the reuse of the scrap without any previous treatment. Experiments have been carried out in order to investigate the influence of the process parameters on the extrudes quality and a numerical model has been developed in order to simulate the evolution of the material flow.

A new sustainable direct solid state recycling of AA1090 aluminum alloy chips by means of friction stir back extrusion process

Friction stir extrusion is an innovative process designed to recycle metal chips from various machining operations. In this research, the feasibility of solid-state recycling of pure aluminum AA1090 machining chips using FSE process is investigated. In the early stage, a FE simulation was conducted in order to optimize the die design (spiral scroll of the plunge, hole size and bearing distance) and the process parameters in terms of plunge rotational speed and extrusion rate. The AA1090 aluminum chips were produced by turning off an as-received bar without lubrication. The chips were compacted on a MTS machine up to 150KN of load. The resulting chip-billets had a diameter of 40mm and 30mm high. The chip-based billet was FS Extruded at 1000rpm rotational speed and 0.8mm/s of plunge displacement. The extruded samples were analyzed by optical microscope in order to see the material flow and to characterize the microstructure. Finally, micro-hardness Vickers profiles were carried out, in both longitudinal and transversal direction, in order to investigate the homogeneity of the mechanical properties of the extrudate.

Development of a magnesium-alumina composite through cold consolidation of machining chips by high-pressure torsion

High pressure torsion offers unique conditions for the consolidation of metallic particles at room temperature owing to the high hydrostatic compressive stresses combined with the high shear strain. A Mg-Al2O3 composite was produced by consolidation of machining chips of pure magnesium with 10% in volume of alumina particles. The consolidation process was investigated by optical and scanning electron microscopy and X-ray microtomography. It is shown that shear deformation concentrates along thick alumina particle layers in the initial stage of deformation. A significant fraction of the hard phase particles are pushed into the outflow in quasi-constrained HPT and a homogeneous composite is achieved after significant straining. The composite exhibits a refined microstructure, a higher hardness and improved resistance against room temperature creep compared to pure magnesium.

Finite element simulation of saw-tooth chip in high-speed machining based on multiresolution continuum theory

Because the deformation is very large and highly localized in the adiabatic shear bands (ASB) of the saw-tooth chip in high-speed machining (HSM), the physical results of the width and spacing of ASB in saw-tooth chip cannot be given by the traditional finite element method (FEM) due to the mesh dependency. Therefore, a 3D finite element model of HSM based on multiresolution continuum theory (MCT) with a simple algorithm of hourglass control was brought out to predict the saw-tooth chip. The comparison between the simulation results and experimental ones of chip deformation and cutting forces shows the validity of the established model. The formation of saw-tooth chip is analyzed, and the changes of chip morphology with cutting parameters were given. The results show that the MCT model has the ability to capture the width and spacing of shear band of saw-tooth chip in HSM by using a length scale to build the relationship between the macro materials behavior and the microstructure. It can also clearly show the formation of saw-tooth chip. An interesting thing is that during the forming of two adjacent shear bands, there is a transition shear band. The stress of MCT model is slightly larger than that of traditional FEM, but the strain is little smaller and the temperature is little lower. For the cutting force, the simulation results of MCT model are more consistent with experimental ones than that of traditional FEM. The simulation results of chip morphology under the condition of different cutting parameter are consistent with that of experiment.

Microstructure and texture development during solid consolidation recycling of Ti-6Al-4V

Ti-6Al-4V machining chips were recycled using equal channel angular pressing (ECAP). The microstructural and texture evolution of the recycled Ti-6Al-4V have been investigated using scanning electron microscopy, electron backscattered diffraction and transmission electron microscopy. For samples consolidated at 500 °C with a back-pressure of 100 MPa, the as-pressed density reached up to 99.9% after 8 passes. Pronounced grain refinement was also observed with increasing number of passes. The morphology of the grains has been changed from elongated and coarse to equiaxed and ultrafine as the number of passes increases. Strong textures were also introduced during multiple passes via Bc route. Texture has been developed with basal planes parallel to the inclination direction which is at 21° of the extrusion direction. After 4 and 8 passes, basal planes were rotated towards the transverse direction. No oxide can be detected at the chip-chip boundaries when the Ti-Al-4 V machining chips was consolidated at 500 °C. When the sample was processed at 550 °C, significant grain growth and clear oxide layers at the chip-chip interface were observed. In addition, the c-axis were rotated towards the longitudinal direction due to the non-basal slip activity. TEM observation revealed the <a→+c→> dislocations presence in the 550 °C ECAP-processed sample.