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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…
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.
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.
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.
Owing to their excellent thermal and mechanical properties, the CFRP composite materials show greater potential for their applications in aircraft and aerospace industry.
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).
The purpose of this paper is to relate the fees paid to IPO underwriters to the nature and quality of the services they provide.
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.
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.
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.