11,300 research outputs found
Experimental Investigation of Significance Parameters in Surface Grinding – Quality Evaluation
The resurgence of the high quality and precision parts
by manufacturing industries has enabled the development of ultraprecision
machine tools. Surface roughness and tolerances are the
most critical quality measures of any mating mechanical parts
produced. The quality evaluation requirement of manufactured
parts is becoming the prime factor as it determines not only the
esthetics values, but also the lifespan and function of its purpose.
Grinding is one the most popular methods of machining hard
materials which widely known as random point cutting. The main
aim of this experimental work is to investigate the significant
parameter(s) in surface grinding which affect the machined
surface roughness. Two work materials, namely, mild steel and
carbon steel have been investigated with two variables; feed rate
and depth of cut for the response of surface roughness totaling
eight experiments with three replications. Statistical approach
using Design of Experiment (DOE) has been carried out in this
investigation. The ANOVA results of the analysis have been based
to determine the significance and correlation of the input and
output parameters
Fatigue life of machined components
A correlation between machining process and fatigue strength of machined components clearly exists. However, a complete picture of the knowledge on this is not readily available for practical applications. This study addresses this issue by investigating the effects of machining methods on fatigue life of commonly used materials, such as titanium alloys, steel, aluminium alloys and nickel alloys from previous literature. Effects of turning, milling, grinding and different non-conventional machining processes on fatigue strength of above-mentioned materials have been investigated in detail with correlated information. It is found that the effect of materials is not significant except steel in which phase change causes volume expansion, resulting in compressive/tensile residual stresses based on the amounts of white layers. It is very complex to identify the influence of surface roughness on the fatigue strength of machined components in the presence of residual stresses. The polishing process improves the surface roughness, but removes the surface layers that contain compressive residual stresses to decrease the fatigue strength of polished specimens. The compressive and tensile residual stresses improve and reduce fatigue strength, respectively. Grinding process induces tensile residual stresses on the machined surfaces due to high temperature generation. On the other hand, milling and turning processes induce compressive residual stresses. High temperature non-conventional machining generates a network of micro-cracks on the surfaces in addition to tensile residual stresses to subsequently reduce fatigue strength of machined components. Embedded grits of abrasive water jet machining degrade the fatigue performance of components machined by this method
The tool:workpiece interaction when machining welded hardfacing using PCBN tools
The work presented in this thesis is concerned with turning chromium carbide based hardfacings using PCBN tools. The chip formation and tool wear process was studied by quick-stop and machining tests. Cutting temperature was investigated by means of a remote thermocouple and the chip-tool interface temperature was simulated by an ANSYS Finite Element Analysis model. Cutting performance of PBN tools from different suppliers was compared in field cutting tests. Hardness, microstructure and the adhesion between the workpiece and cutting tool material were assessed.ln the turning process, saw-tooth chips were formed, with a short chip:tool contact length. Quick-stop tests revealed that the machining process involved fracture of large carbides ahead of the cutting edge in the primary zone. Temperature measurements showed that the cutting temperature for the hard facing material was lower than that with titanium alloy but much higher than that with machining mild steel. The cutting temperature predicted at the tool chip interface was in the range of 600-700°C when cutting hard facing.The tool wear process was found to involve three main progressive stages - from small scale edge chipping to large scale flaking and fracture. Four types of wear were identified: flank wear, microchipping, flaking of the rake face and delamination of the flank face. Abrasion appears to be the principal flank wear mechanism and it showed a minimum value for different speeds but increased with feedrate. The main mechanism for microchipping involved failure through the CBN particle boundaries. Flaking of the rake face occurred in the later stages and transgranular fracture was the main mechanism.In field tests, PCBN material from various sources achieved different cutting performance, which reflected the structural differences in the PBN materials. A dense structure with strong particle binding is essential for satisfactory performance of PCBN in this application
Machining and grinding of ultrahigh-strength steels and stainless steel alloys
Machining and grinding of ultrahigh-strength steels and stainless steel alloy
Effect of Energy Consumption in Contact Zone on Machining Conditions Optimization in Precision Surface Grinding
The instantaneous energy consumption in grit-material interaction zone is one of important indicators to represent the efficiency of grinding. In contrast to methods based on chip crack and formation or energy consumption from experimental measurement, this paper presents an improved differential model of energy consumption that takes account of dynamic grinding force, forced-vibration induced by the eccentrically grinding wheel rotation and the phase difference between adjacent regenerative surface waviness. Further, the vibratory amplitude and relevant frequency elements of wheel-workpiece coupled system are analyzed to optimize the key machining conditions that involve in spindle speed, pack density of abrasive wheel and effective cutting space of adjacent contour grits in discrete transverse plane. It demonstrates that machining stability is the best, when the phase difference is /2 between continuously formed adjacent waviness generated by grain-workpiece interaction, i.e. the calculated value of instantaneous grinding energy consumption reaches to its maximum value. In comparison to stable situations, an unstable grinding process is excited when the phase difference value is 3/2, i.e. micro-grinding force and vibration reinforce each other. It proves that a satisfied stable grinding process can be controlled in real-time or in-situ by means of utilizing combination of optimal parameters, such as spindle speed, effective pack density and cutting space of abrasive grits. The presented mechanism is practical and can provide a good guidance for further studies on machine tool dynamics, time-domain or frequency-domain analysis of grinding vibration, and then on depth distribution of cut and ground surface accuracy
The performance of ultra-hard cutting tool materials in maching aerospace alloy TA48
A study has been made of the respective performance of cubic boron nitride (CBN) and polycrystalline diamond (PCD) cutting tool materials and compared to various coated and uncoated tungsten carbide grades when cutting titanium alloy workpieces. Two important experimental techniques were employed during the course of this work, firstly a quasi-static contact method was employed to establish the workpiece/tool interfacial temperature above which strongly adherent layers may be formed. This technique revealed that the critical temperatures which marked adhesion and welding, were 740, 820 and 800 °C for coated and uncoated carbides, and 760 and 900 °C for PCD and CBN tools respectively. Furthermore, the technique has been used to study the integrity of the bulk tool material, and/or individual coatings on their substrates, when welded junctions formed between the tool and workpiece are separated. With regard to the latter it was observed that in all cases fracture was initiated in the bulk of the harder tool material rather than in the workpiece or at the welded junction interface. Secondly, a quick-stop technique was used to study chip formation and tool wear when cutting with carbides, CBN and PCD tools under nominally the same conditions.The predominant wear mechanisms for each of the tool materials was found to be based on a diffusion/dissolution process. The wear process is discussed in detail for each of the tool materials and reasons advanced for observed differences in performance when removing material from a titanium alloy workpiece. The wear resistance and quality of the machined surface was found to be superior when cutting with the ultra-hard materials than with the carbide grades and in particular the PCD tool was found to produce exceptionally good surface finish. In the case of coated carbide tool grades rapid removal of the coated layers occurred leaving the substrate vulnerable to reaction with the workpiece material and this is considered to explain the seeming absence of beneficial effects when cutting with these grades
The performance of ultra-hard cutting tool materials in maching aerospace alloy TA48
A study has been made of the respective performance of cubic boron nitride (CBN) and polycrystalline diamond (PCD) cutting tool materials and compared to various coated and uncoated tungsten carbide grades when cutting titanium alloy workpieces. Two important experimental techniques were employed during the course of this work, firstly a quasi-static contact method was employed to establish the workpiece/tool interfacial temperature above which strongly adherent layers may be formed. This technique revealed that the critical temperatures which marked adhesion and welding, were 740, 820 and 800 °C for coated and uncoated carbides, and 760 and 900 °C for PCD and CBN tools respectively. Furthermore, the technique has been used to study the integrity of the bulk; tool material, and/or individual coatings on their substrates, when welded junctions formed between the tool and workpiece are separated. With regard to the latter it was observed that in all cases fracture was initiated in the bulk of the harder tool material rather than in the workpiece or at the welded junction interface. Secondly, a quick-stop technique was used to study chip formation and tool wear when cutting with carbides, CBN and PCD tools under nominally the same conditions.The predominant wear mechanisms for each of the tool materials was found to be based on a diffusion/dissolution process. The wear process is discussed in detail for each of the tool materials and reasons advanced for observed differences in performance when removing material from a titanium alloy workpiece. The wear resistance and quality of the machined surface was found to be superior when cutting with the ultra-hard materials than with the carbide grades and in particular the PCD tool was found to produce exceptionally good surface finish. In the case of coated carbide tool grades rapid removal of the coated layers occurred leaving the substrate vulnerable to reaction with the workpiece material and this is considered to explain the seeming absence of beneficial effects when cutting with these grades
An electrical matlab model of plasma electrolytic oxidation
Plasma Electrolytic Oxidation (PEO), a part of Plasma electrolytic Deposition (PED), has been developing for surface modification of metallic materials in the past 20 years. During PEO process, sample always connect with anode of DC power source, under high temperature, accelerating process of oxidation reaction to from an average and dense oxidation film. A general passage, Plasma electrolysis for surface engineering, written by A.L. Yerokhin, X. Nie gives us a trend of what happened during PEO process but did not determine specific material and value. Linxin Zhu’s Development of PEO invent a new boiling system and investigated relationship between surface roughness and coating and mentioned investigating on resistance of DC current at future work.
In this passage, focusing on the electrical model, PEO process is studied in both experimental and theoretic aspect. In practice, PEO industries could be distinguished by what terms it entered in according to different demand. And, the resistance in this term are quite different because of different structures at surface of sample. Theoretically, three types of electrical models have been built by MATLAB after analyzing the main influence factors of PEO process, which could help us explain how the structure and resistance change.
Experimentally, a Ti-6Al-4V piece was used as a sample to do all PEO experiments. Diversity results was obtained by change the conductivity of electrolyte and applied voltage. Others experimental parameters were controlled to be same as possible like surface roughness, contents of liquid solution and voltage increase speed. All the thing above purpose to make electrical model more reasonable and trustable.
All the experiments were recorded by a camera then select pictures in every second. Then input the statistics in the matrix in MATLAB as the original reference, which is used to compare to the simulation result. So that the simulation model could be adjusted until it meets the experiment results. Thus, the main factors which influence resistance could be inferred.
After analyzing, we found, at passive film stage, the majors resistance consists of resistance of electrolyte and passive oxidation film of anode (Ti-6Al-4V sample). Temperature would slightly influence resistance if electrolyte conductivity is big enough. The U-I in this stage is nearly a straight line. While, at the new oxidation film stage, current is significant increase because gradually dissolve of the passive oxidation film with time. So, the U-I curve is a trend of sharp increase. At the arcing stage, current decrease is because new oxidation film formed, and rest of the resistance is determined by temperature.
Besides, these PEO in three stage was simulated by MATLAB models according to the majority factors analyzed. The simulation results suitable for all kind of PEO in Ti-6Al-4V process with different conductivity but changeless surface roughness and increasing applied voltage. Prediction of optimizing applied voltage is possible with this model in PEO process in Ti-6Al-4V
Effect of different parameters on grinding efficiency and its monitoring by acoustic emission
Grinding efficiency is one of the most important considerations in the selection of grinding operation conditions because it has a significant impact on the productivity, quality, energy consumption and cost of production. Focusing on the core issues of grinding process, the paper presents some fundamental research findings in relation to grinding material removal mechanisms. The grinding efficiency is analysed by considering the rubbing, ploughing and cutting three stages of a single grit grinding process. By analysing the features of acoustic emission in single grit grinding tests, an evidence based scientific foundation has been established for monitoring grinding efficiency using acoustic emission. Accordingly, the energy consumption in the grinding is considered with the grit shape. Following the discussion of the models of temperature elevation and thermal stresses in grinding, the paper provides a logic depiction that explains why acoustic emission in grinding can be used for grinding thermal performance monitoring. As a result, the paper introduces a novel acoustic emission monitoring method that is capable to monitor grinding temperature and grinding wheel wear status
Multi-objective optimization of energy consumption and surface quality in nanofluid SQCL assisted face milling
Considering the significance of improving the energy efficiency, surface quality and material removal quantity of machining processes, the present study is conducted in the form of an experimental investigation and a multi-objective optimization. The experiments were conducted by face milling AISI 1045 steel on a Computer Numerical Controlled (CNC) milling machine using a carbide cutting tool. The Cu-nano-fluid, dispersed in distilled water, was impinged in small quantity cooling lubrication (SQCL) spray applied to the cutting zone. The data of surface roughness and active cutting energy were measured while the material removal rate was calculated. A multi-objective optimization was performed by the integration of the Taguchi method, Grey Relational Analysis (GRA), and the Non-Dominated Sorting Genetic Algorithm (NSGA-II). The optimum results calculated were a cutting speed of 1200 rev/min, a feed rate of 320 mm/min, a depth of cut of 0.5 mm, and a width of cut of 15 mm. It was also endowed with a 20.7% reduction in energy consumption. Furthermore, the use of SQCL promoted sustainable manufacturing. The novelty of the work is in reducing energy consumption under nano fluid assisted machining while paying adequate attention to material removal quantity and the product’s surface quality
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