International Journal of Machining and Machinability of Materials (10 papers in press)

Regular Issues

• Quality improvement in mechanical micro drilling of titanium alloy under dry conditions  
  by Somashekhar S. Hiremath, Prashanth P 
  Abstract: Titanium alloy (CpTi) grade II is considered a hard-to-cut material due to low thermal conductivity, work hardening behavior, and affinity with cutting tool materials. In this study, micro-holes are machined on titanium alloy (Cp Ti) grade II under dry conditions. Experiments are carried out by varying the machining parameters like cutting speed (5 m/min, 6.9 m/min, and 8.8 m/min), feed (5
  Keywords: mechanical micro-drilling; exit burr height; taper angle; response surface methodology; exit thrust force; titanium alloy (Cp – Ti) grade –II.
  
  
• Effect of Nano-void Position on Surface Integrity in Nanomachining of Single Crystal Copper  
  by Seyed Vahid Hosseini, Mehdi Heidari, Hadi Parvaz, Mehrdad Vahdati 
  Abstract: In this paper, molecular dynamics simulations were performed to study the effect of nano-size voids in different locations relative to the surface on nanomachining characteristics and surface integrity. Using EAM potential, MD simulations were performed with two approaches: material removal and relaxation of the work material, to find a low defect permanent configuration after the rigid tool has traversed the machined area. Results show that high hydrostatic pressure induced by tool edge diffuses atoms into the void during the machining process. Investigation of residual stress for subsurface void workpiece represents that higher compressive stress remains in the surface due to the tendency of void for spring back. Besides, in the nanomachining process, surface atoms are greatly disordered and dislocation loops glide deep into substrate atoms. After relaxation, if void pitting contains no other atoms, the machined surface is reorganized as FCC lattice similar to a pure workpiece.
  Keywords: Nanomachining; Molecular dynamics; Nano-void; Residual stress; Surface integrity.
  
  
• Fabrication of Ti-6Al-4V thin sheet using wire-EDM and its characterisation  
  by M. Baburaj, K. Manoj Kumar, Nithin Tom Mathew, S. Ragu Nathan 
  Abstract: An appreciable demand for thin titanium sheets is observed in the recent years due to technological development in various sectors. The existing sawing methods are uneconomical to produce high aspect ratio sheets with good dimensional accuracy. The current work focuses on extracting thin sheet of 380 mm x 50 mm x 0.2 mm from Ti-6Al-4V using wire electric discharge machining and investigated the dimensional and surface variations. The preliminary study using usual wire EDM procedure resulted in poor dimensional accuracy for a thickness in the range of 500 m due to the lateral movement of sheet free end. Hence, in this work, a support system is attached to workpiece to minimise sheet movement and to improve the flushing during extraction. This helped to reduce the thickness variation up to 6% for a 0.2 mm Ti-6Al-4V sheet. The root mean square roughness is found to be consistent up to a height of 240 mm from the top surface. Also, majority of the measured skewness are positive. Altogether, the results of the study can be applied to fabricate thin sheets for additive manufacturing process.
  Keywords: wire-EDM; Ti-6Al-4V; thickness; surface roughness.
  DOI: 10.1504/IJMMM.2021.10041507
   
  
• Multi-Objective Parameter Optimization to Improve Machining Performance on Deep Drilling Process  
  by Esmaeil Damavandi, Amin Kolahdooz, Yousef Shokoohi, Seyyed Ali Latifi Rostami, Seyyed Mohammadbagher Tabatabaei 
  Abstract: Cutting parameters and factors should be selected wisely to increase the quality of a product. Therefore, the optimisation of the deep drilling process was investigated by utilising the Taguchi method on three materials by three different tools. The influences of cutting speed and workpiece temperature are investigated on machining power, surface roughness and tool wear. The results revealed that the application of preheating could provide lower power consumption and a relatively good finished surface. In continue, analysis of variance demonstrated that all factors are effective, but the workpiece material and speed are the most influential parameters on surface roughness and power consumption, respectively. Workpiece material influenced about 72.24% on machining performance, and its effect was more than tool material (3.64%). For machining power, the effect of speed (55.41%) was higher than others. The preheating and lower speeds reduced tool wear of titanium coated and cobalt coated drills.
  Keywords: precooling; preheating; machining performance; surface roughness; machining power.
  DOI: 10.1504/IJMMM.2021.10041677
   
  
• Finite Element Analysis Machining Assessment Study of AL-6XN and Inconel 718 alloys  
  by Mohanad Alabdullah, Ashwin Polishetty, Guy Littlefair 
  Abstract: This paper presents a finite element study to assess machinability of AL-6XN alloy by benchmarking against the machinability of Inconel 718 alloy. Johnson-Cook model was used to represent the alloys plastic strain behaviour, at cutting speeds (65 m/min and 94 m/min). Outcomes reveal that percentage increase of the plastic strain at the beginning of cutting, for Inconel 718 alloy was higher by 18% and 4% at speeds of 65 m/min and 94 m/min respectively. The percentage increase in plastic strain for the AL-6XN alloy during the cutting was higher by 36% and 10% at the same cutting speeds. The shear zone temperature percentages of the AL-6XN alloy increased by 31% and 9.5% at 65 m/min and 94 m/min cutting speed respectively, when the tool removed chips. Results indicated that the AL-6XN alloy is suitable for industrial applications (due to the alloy elevated ductility) fabricated at elevated cutting speeds.
  Keywords: machinability; finite element analysis; FEA; assessment; stress; strain; temperature.
  DOI: 10.1504/IJMMM.2021.10042061
   
  
• Influence of ultrasonic burnishing on the surface integrity of planar plates  
  by Juha Huuki, Henrik Siren 
  Abstract: Ultrasonic burnishing is one of several surface treatment methods. The method is a relatively new treatment process used for finishing workpieces to produce good surface quality. This paper presents ultrasonic burnishing as a mechanical surface treatment for improving the quality of planar plates. This process improves the surface quality by increasing the surface hardness of the workpiece and reducing its surface roughness. However, it is essential to know the effect of the method on residual stresses in the material. This study investigated at the residual stresses produced in two different materials: AISI 420 steel and aluminium (Alumec AA7075-T651). The magnitude of stresses was examined using an X-ray diffractometer. This study also evaluated the hardness and surface quality of the finished workpiece.
  Keywords: ultrasonic burnishing; finishing; hardness; residual stress measurements; surface roughness; surface quality; X-ray diffractometer; AISI 420; aluminium.
  DOI: 10.1504/IJMMM.2021.10042434
   
  
• A new method for defining the ploughing forces in processing of brittle materials with the formation of discontinuous chips  
  by Alexey Popov 
  Abstract: When monitoring cutter wear during microcutting, it is necessary to consider the ploughing force of the tool flank face (PFs). The method of measurement differs based on the wear of the cutting tools and cannot be applied to determine PFs. When we cut brittle materials using a tool with wear there are significant fluctuations in the cutting forces due to the unstable chip formation, so the cutting forces cannot be measured. A new method for defining PFs when cutting brittle materials with the formation of discontinuous chips has been proposed in this study. The reliability of the new method has been confirmed by comparing PFs obtained with the help of different methods of cutting materials with the formation of continuous chips.
  Keywords: machining; cutting edge; ploughing; cutting forces; microcutting.
  DOI: 10.1504/IJMMM.2021.10042435
   
  
• Minimum Cutting Depth and Cutting Depths’ Effects to Chip’s Shape and Size in Orthogonal Cutting of CFRP  
  by Farid Miah, Fréderic Lachaud, Emmanuel De Luycker 
  Abstract: Studying chip’s shape and size is an important part in carbon fibre reinforced polymer (CFRP) cutting technique as the generated chip’s size and shape are closely linked to the chip generation process. In this present research work, an experimental analysis has been done to analyse the cutting depths’ effect to the generated chip’s shape and size. Five different cutting depths from 0.1 mm to 1 mm were used in the tests. A strong influence of cutting depth as well as fibre orientation to chip’s shape and size was found. Apart from that, the answer of what is the minimum cutting depth below which a tool cannot cut the materials smoothly was studied. Four fibre orientations have been used separately; and the minimum cutting depth was studied at each fibre orientation. The results showed that the minimum cutting depth is not the same at each fibre orientation.
  Keywords: orthogonal cutting; carbon fibre reinforced polymer; CFRP; cutting depth; fibre orientation; chip size.
  DOI: 10.1504/IJMMM.2022.10042948
   
  
• Prediction of surface roughness and delamination in spiral milling of CFRP laminates by SAPSO-BP neural network  
  by Haifeng Ning, Hualin Zheng, Xiufen Ma, Bo Feng, Xinman Yuan 
  Abstract: Due to the anisotropy carbon fibre reinforced polymer (CFRP) materials, problems such as poor surface quality of the hole wall and delamination often occur in the traditional hole-making process. In this study, the Taguchi method was used to design a CFRP spiral-milling experiment using uncoated and diamond-coated carbide cutters. The analysis of variance and signal-to-noise ratio analysis were used to study the influence of process parameters on the surface roughness and delamination factors. Prediction models for surface roughness and delamination factors were established using improved particle-swarm neural network. The results showed that the diamond-coated milling cutters are more suitable for CFRP processing. The order of importance of the process parameters is as follows: axial-feed speed > horizontal-feed speed > spindle speed > revolution radius. The prediction model for the surface roughness and delamination factors developed in this study achieves high accuracy.
  Keywords: CFRP; surface roughness; delamination factor; spiral milling; SAPSO-BP neural network.
  DOI: 10.1504/IJMMM.2021.10044093
   
  
• Sensitivity Analysis and Multi-objective Optimization of Effective parameters on Force and Temperature in Ultrasonic-assisted Bone Drilling  
  by Abbas Pak, Hamed Yaghuti, Vahid Tahmasbi 
  Abstract: The use of ultrasonic vibrations to reduce the temperature and force in bone drilling is one of the most important advanced processes that have attracted the attention of bone surgeons. In this paper, the influence of the process parameters on temperature variations and force changes were investigated using response surface methodology (RSM). Moreover, using the statistical method of Sobol sensitivity, the effect of each input factor on and its sensitivity to temperature and force were studied. Simultaneous optimisation was also performed to achieve the lowest temperature and force in the minimum time of the bone drilling. The results showed that the main parameters influencing the temperature were rotational speed, vibration amplitude (33%) and feed rate (19%). The vibration amplitude, rotational speed, and feed rate, explaining 48%, 40%, and 12% of the variations, had the most significant effects on force in the ultrasonic-assisted bone drilling, respectively.
  Keywords: bone drilling; ultrasonic vibrations; multi-objective optimisation; response surface methodology; RSM; temperature; force.
  DOI: 10.1504/IJMMM.2022.10044094