Meltem Altin Karatas, Hasan Gokkaya and Muammer Nalbant
The aim of this paper is to optimize the machining parameters to obtain the smallest average surface roughness values during drilling of the carbon fiber-reinforced polymer (CFRP…
Abstract
Purpose
The aim of this paper is to optimize the machining parameters to obtain the smallest average surface roughness values during drilling of the carbon fiber-reinforced polymer (CFRP) composite material with abrasive water jet (AWJ) and analyze the damage of the delamination.
Design/methodology/approach
CFRP composite material had been fabricated having fiber orientations frequently used in the aerospace industry (0°/45°/90°/−45°). Three different stand-off distances (1, 2 and 3 mm), three different water pressures (1,800, 2,800 and 3,800 bar) and three different hole diameters (4, 8 and 12 mm) were selected as processing parameters. The average surface roughness values were obtained, and delamination damage was then analyzed using Taguchi optimization. Drilling experiments were performed using the Taguchi L27 orthogonal array via Minitab 17 software. The signal/noise ratio was taken into account in the evaluation of the test results. Using the Taguchi method, the control factors giving the mean surface roughness values were determined. Analysis of variance was performed using the experimental results, and the effect levels of the control factors on the average surface roughness were found.
Findings
It was found that water pressure and hole diameter had a higher effect on average surface roughness, while water pressure and stand-off distance were effective on delamination.
Practical implications
Owing to their excellent thermal and mechanical properties, the CFRP composite materials show greater potential for their applications in aircraft and aerospace industry.
Originality/value
The novel approach is to reduce cost and spent time using Taguchi optimization as a result of AWJ drilling the material in this fiber orientation ([0°/45°/90°/−45°]s, which is often used in the aerospace industry).
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Murat Tunç, Hasan Gökkaya, Gökhan Sur and Ali Riza Motorcu
The purpose of the paper is to investigate photochemical machining characteristics of stainless steel (AISI 304-SS304) parts with a novel design are investigated experimentally…
Abstract
Purpose
The purpose of the paper is to investigate photochemical machining characteristics of stainless steel (AISI 304-SS304) parts with a novel design are investigated experimentally from the aspect of process parameters. The effects of phototool pattern geometry, ultraviole (UV) exposure time and etching time on of AISI 304 were evaluated.
Design/methodology/approach
The designed semi-automated photochemical manufacturing (PCM) equipment consists of 4 units, which include UV exposure, etching, developing and surface cleaning units. Experimental procedure has been designed via Taguchi method. Results were evaluated via Analysis of Variance (ANOVA) method.
Findings
Etching time is the most effective factor in PCM quality of AISI 304 stainless steel. Surface roughness is sensitive to geometrical pattern of the phototool for PCM of AISI 304 UV exposure time is less influential on the PCM quality for stainless steel.
Research limitations/implications
The designed PCM equipment prototype is not fully automated, which requires automation for part replacements into units. The effects of the temperature inside chemical processing units on process characteristics cannot be evaluated due to equipment limitations. The effects of surface cleaning time inside surface cleaning unit are not analyzed.
Originality/value
The utilized PCM equipment is semi-automated equipment, with which the process parameters such as etching time, surface cleaning time, UV exposure time and developing time can be controlled. Different from literature, the effects of phototool pattern geometries on the photochemical machining quality parameters are evaluated for the processing of AISI 304. The effects of processing parameters on dimensional accuracy, which is not common in the literature for AISI 304 stainless steel, are also evaluated.
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Meltem Altin Karataş, Hasan Gökkaya, Sıtkı Akincioğlu and Mehmet Ali Biberci
The purpose of this study is to optimize processing parameters to get the smallest average surface roughness (Ra) and delamination damage (Fd) values during drilling via abrasive…
Abstract
Purpose
The purpose of this study is to optimize processing parameters to get the smallest average surface roughness (Ra) and delamination damage (Fd) values during drilling via abrasive water jet (AWJ) of the glass fiber-reinforced polymer composite material produced at [0°/90°]s fiber orientation angles.
Design/methodology/approach
Drilling experiments were done via AWJ with three-axis computer numerical control (CNC) control system. Machine processing parameters such as water pressure of 3,600, 4,300, 4,800 and 5,300 bar; stand-off distance of 1, 2, 3 and 4 mm; traverse rate of 750, 1,500, 2,000 and 3,000 mm/min; and hole diameters of 8, 10, 12 and 14 mm have been selected. The effects of processing parameters in drilling experiments were investigated in conformity with the Taguchi L16 orthogonal array and the data obtained were analyzed using Minitab 17 software. The signal/noise (S/N) ratio was taken as a basis for evaluating the test results. Optimum processing conditions were determined by calculating the S/N ratio for both Ra and Fd in conformity with the “smaller is better” approximation. The effects of processing parameters on Ra and Fd were statistically investigated using analysis of variance, S/N ratio and Taguchi-based gray relational analysis. Ra and Fd were predicted by evaluating with the ANN model and were predicted with the least amount of error.
Findings
It has been determined that the most effective parameter for Ra and Fd is the water pressure and then the stand-off distance.
Originality/value
The novel approach is to reduce cost and the time spent by using Taguchi optimization as a result of AWJ drilling the material in this fiber orientation [0°/90°]s.
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Ahsana Aqilah Ahmad, Jaharah A. Ghani and Che Hassan Che Haron
The purpose of this paper is to study the cutting performance of high-speed regime end milling of AISI 4340 by investigating the tool life and wear mechanism of steel using the…
Abstract
Purpose
The purpose of this paper is to study the cutting performance of high-speed regime end milling of AISI 4340 by investigating the tool life and wear mechanism of steel using the minimum quantity lubrication (MQL) technique to deliver the cutting fluid.
Design/methodology/approach
The experiments were designed using Taguchi L9 orthogonal array with the parameters chosen: cutting speed (between 300 and 400 m/min), feed rate (between 0.15 and 0.3 mm/tooth), axial depth of cut (between 0.5 and 0.7 mm) and radial depth of cut (between 0.3 and 0.7 mm). Toolmaker microscope, optical microscope and Hitachi SU3500 Variable Pressure Scanning Electron Microscope used to measure tool wear progression and wear mechanism.
Findings
Cutting speed 65.36%, radial depth of cut 24.06% and feed rate 6.28% are the cutting parameters that contribute the most to the rate of tool life. The study of the tool wear mechanism revealed that the oxide layer was observed during lower and high cutting speeds. The former provides a cushion of the protective layer while later reduce the surface hardness of the coated tool
Originality/value
A high-speed regime is usually carried out in dry conditions which can shorten the tool life and accelerate the tool wear. Thus, this research is important as it investigates how the use of MQL and cutting parameters can prolong the usage of tool life and at the same time to achieve a sustainable manufacturing process.
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Shih-Hao Lu, Rohit Raj, Anupama Mahajan, Ajay Jha, Priyanka Verma, Hsia-Ping Lan and Sumanjeet Singh
The study aims to add to the existing literature on food supply chains by specifically taking into the redesigning of the alignment of storage, packaging and distribution…
Abstract
Purpose
The study aims to add to the existing literature on food supply chains by specifically taking into the redesigning of the alignment of storage, packaging and distribution practices in the modern complex supply chain. The redesign of the food supply chain’s storage, distribution and packaging is a transformative endeavor ultimately aimed at enhancing efficiency, sustainability and reliability.
Design/methodology/approach
In order to identify, classify and prioritize the main challenges, this study conducted an extensive analysis of the literature and experts’ opinions in the areas of academia, information technology and the food supply chain (FSC) using combined compromise solution method (CoCoSo) and complex proportional assessment (COPRAS).
Findings
The top three classes of key indicators revealed in this study are dynamic route optimization and on-demand delivery pods (RD4), implementation of active packaging with nanotechnology (RP3) and collaborative last-mile (RD2). The findings reveal that dynamic route optimization and on-demand delivery pods (RD4) and collaborative last-mile (RD2) are maintaining a balance between collaborative delivery networks through route optimization which is a very discussable theme in recent literature.
Originality/value
The research provides fresh insights into how perishable food shelf life parameters and the use of distribution networks within the short supply chain can be taken into consideration when redesigning the storage, packaging and distribution system for food supply chains.
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Michele Meoli, Andrea Signori and Silvio Vismara
– The purpose of this paper is to relate the fees paid to IPO underwriters to the nature and quality of the services they provide.
Abstract
Purpose
The purpose of this paper is to relate the fees paid to IPO underwriters to the nature and quality of the services they provide.
Design/methodology/approach
Controlling for the characteristics of the firm going public, the risk associated with the offering, and the reputation of the underwriter, the authors study on a sample of Italian IPOs whether a formal commitment by underwriters to provide ancillary services allows them to charge higher fees.
Findings
The authors document that asking underwriters to stabilize stock price is costly to the issuer, while to support liquidity is not. The authors’ also show that underwriters stabilize IPOs that really need it, whereas the provision of liquidity support does not seem to be always aligned with the issuer’s interest.
Originality/value
Investigating the Italian underwriting market is instructive for two main reasons. First, the institutional setting in IPOs is similar to most continental European countries, but significantly different from the US market. For instance, allocation policies in US IPOs are discretionary for both retail and institutional investors, while in Europe shares cannot be discretionarily allocated to retail investors. Second, the Italian market offers the opportunity to study the going-public decision outside the typical Anglo-Saxon financial systems. This is of interest because while both the UK and the USA have well-developed equity markets and a related industry of financial intermediation centered on providing equity, our analysis sheds light on financial intermediation of IPOs in a bank-centered system.