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In this study, the effects of machining parameters on the material removal rate (MRR) and surface roughness (Ra) were investigated during the cutting of Al/B4C/Gr hybrid composites by wire electrical discharge machining (WEDM). Wire speed (WS), pulse-on time (Ton) and pulse-off time (Toff) were chosen as the control factors. The L27 (33) orthogonal array in the Taguchi method was used in the experimental design and for the determination of optimum control factors. Response surface methodology was also used to determine interactions among the control factors. Variance analysis (ANOVA) was applied in the determination of the effects of control factors on the MRR and Ra. According to the ANOVA results, the most effective parameters on MRR and Ra were wire speed with a 85.94% contribution ratio, and pulse-on-time with a 47.7% contribution ratio. The optimum levels of the control factors for MRR and Ra were determined as A3B3C3 and A1B1C2. In addition, second-order predictive models were developed for MRR and Ra; correlation coefficients (R2) were calculated as 0.992 and 0.63.

In this research, the tool-chip interface temperature (T-CTI), the tool temperature (T-T) and the average surface roughness (R-a) were measured experimentally during the turning of AISI 4140 alloy steel with TiAlN-TiN, PVD-coated, WNVG 080404-IC907 tungsten carbide inserts using an IR pyrometer technique, a K-type thermocouple and a portable surface-roughness measurement device, respectively. The workpiece material was heat treated by an induction-hardening process and hardened up to a value of 50 HRC. The Taguchi method L18 (21 x 37) was used for the determination of the optimum control factors. The depth of cut, the cutting speed and the feed rate were taken as control factors. The analysis of variance was applied in order to determine the effects of the control factors on the tool-chip interface temperature, the tool temperature and the surface roughness. The optimum combinations of the control factors for T-CTI, T-T and R-a were determined as a(2)v(1)f(3), a(1)v(3)f(2) and a(2)v(3)f(1), respectively. Second-order predictive models were developed with a linear-regression analysis, and the coefficients of correlation for T-CTI, T-T and R-a were calculated as R-2 = 92.8, R-2 = 68.1 and R-2 = 82.6, respectively.

Bu çalışmada, Waspaloy süper alaşımının tel erozyon yöntemi ile işlenmesinde (WEDM) kesme parametrelerinin ortalama yüzey pürüzlülüğü üzerindeki etkileri araştırılmış ve en düşük yüzey pürüzlülük değerlerini veren en uygun kesme parametreleri belirlenmiştir. Kontrol faktörleri olarak; tel gerginliği, tel ilerleme hızı, ilerleme miktarı ve dielektrik sıvı sirkülasyon basıncı seçilmiş ve Taguchi Metodu (TM) kullanılarak L18 (21 x33 ) ortogonal dizin oluşturulmuştur. Kesme parametrelerinin yüzey pürüzlülüğü üzerindeki istatistiksel etkileri, varyans analizi (ANOVA) yöntemi ile belirlenmiştir. Yüzey pürüzlülüğünü tahmin etmek amacıyla Lineer Regresyon yöntemi ile ikinci dereceden tahminsel denklem geliştirilmiştir. Geliştirilen ikinci dereceden tahminsel yüzey pürüzlülük denkleminin kullanılması ile % 95 güven seviyesinde (R2 =0,936) teorik ortalama yüzey pürüzlülük (Ra) değerleri elde edilmiştir. Varyans analizi sonuçları ve ana etki grafiklerinin değerlendirilmesinden, ortalama yüzey pürüzlülüğü üzerinde en etkili parametreler sırasıyla; ilerleme miktarı, dielektrik sıvı basıncı ve tel ilerleme hızı olarak belirlenmiş, tel gerginliğinin anlamlı bir etkisinin olmadığı gözlemlenmiştir. Waspaloy'un WEDM’de kesilmesinde; yüzey pürüzlülüğü aritmetik ortalamasının 2,683-4,052 m aralığında değiştiği belirlenmiştir. In this study, the effects of cutting parameters on the surface roughness in Wire Electrical Discharge Machining (WEDM) of Waspaloy have been investigated and optimal cutting parameters for lowest surface roughness values were determined. As control factors; wire tension, wire feed speed, feed rate and dielectric flushing pressure have been selected and a Taguchi L18 (2(1)x3(3)) orthogonal array was used for experimentation. The statistical effects of cutting parameters on the surface roughness have been determined by using analysis of variance (ANOVA). The second order predictive equation has been developed via Linear Regression Analysis. Using the second-order predictive surface roughness equation developed in the result of this study, the theoretical average surface roughness (R-a) values at a confidence level of 95 percent (R-2=0.936) have been obtained. When evaluating the main effects plots and ANOVA results, the feed rate was found the most efficient factor on the Ra, while dielectric flushing pressure and wire speed were the following ranking factors. The wire tension was seemed to have not of a statistically influence on the R-a. The arithmetic average surface roughness R-a of the WEDM-cut workpiece has been obtained between 2.683 to 4.052 mu m intervals for Waspaloy.

This study researched the effects of machining parameters on surface roughness and material removal rate in the wire electrical discharge cutting of high-density Al/B4C metal matrix composites produced via the hot pressing method. Wire tension, reinforcement percentage, wire speed, pulse-on time and pulse-off time were set as the control factors. The Taguchi L18 (21 × 34) orthogonal array was used in the experiment design and determination of the optimum control factors. Variance analysis was applied to determine the effects of the control factors on the surface roughness and material removal rate. The results showed the most effective parameters to be pulse-on time (30.22%) for surface roughness and wire speed (83.20%) for material removal rate, and the optimum levels of the control factors to be A2B1C2D1E1 and A2B2C3D2E2, respectively. Predictive equations were then developed by applying linear regression analysis, and the adjusted correlation coefficients were calculated as 0.61 for surface roughness and 0.785 for material removal rate.

This paper presents an investigation regarding the ballistic performance of protection panels of different fabric ply numbers used in body armours. Twaron CT 710 type fabric layers of differing numbers are joined by using three stitch types to form the panels and then the panels are subjected to ballistic tests according to NIJ standards. Ballistic performance of the panels is determined by measuring trauma depth and trauma diameter. The energy absorbed by the fabric layers and the energy transmitted to the back of the fabric layers are determined from the trauma depth and trauma diameter values using a different approach. It is shown that the fabric ply number and stitching type have significant effects on ballistic properties and the effect of conditioning is limited.

Bu çalışmada, Ç1050 ve Ç4140 çeliklerinin kaplamasız ve kaplamalı seramik kesici takımlarla işlenmesinde, kesme parametreleri ile iş parçası ve takım sertliklerinin, takım ömrü ve takım aşınması üzerindeki etkileri araştırılmıştır. Taguchi Tekniği kullanılarak en yüksek takım ömrü değerlerini veren optimum kontrol faktörleri belirlenmiştir. Tahminsel takım ömrü denklemleri çıkartılmıştır. Ayrıca, aşınmış uçların SEM görüntüleri incelenerek takım aşınma tipleri belirlenmiştir. Deneysel sonuçlar, sırasıyla iş parçası sertliği, kesme hızı, kesme hızı-ilerleme miktarı etkileşimi, kesme hızı-iş parçası sertliği etkileşimi, talaş derinliği-kesici takım sertliği etkileşimi, ilerleme miktarı-iş parçası sertliği etkileşimi ve ilerleme miktarının takım ömrü üzerinde en etkili faktörler olduğunu göstermiştir. Faktör etkileşimlerinin yer aldığı ikinci dereceden tahminsel denklem daha güvenilir sonuçlar vermiştir. Ç1050 ve Ç4140 çeliklerinin seramik takımlarla işlenmesinde çentik, yan kenar ve krater aşınması gözlenmiştir. In this study, the effects of cutting parameters and the effects of workpiece hardness and tool hardness on tool life and tool wear have been investigated in machining of AISI1050 and AISI4140 steels by uncoated and coated ceramic cutting tools. Optimum cutting conditions for maximum tool life were determined using the Taguchi technique. Predictive tool life equations were derived. In addition, types of tool wear were observed by shown worn surfaces with a scanning electron microscope (SEM). The results indicated that the workpiece hardness, cutting speed, cutting speed-feed rate interaction, cutting speed-workpiece hardness interaction, dept of cut-cutting tool hardness interaction, feed rate-workpiece hardness interaction and feed rate were found out to be the most effective factors among control factors on tool life. It is observed that the second order predictive equation provided more reliable results. In machining AISI1050 and AISI4140 steels, notch wear, flank wear and crater wear observed on ceramic tools. Gazi Üniversitesi TEF-07/2003-38

The surface roughness model was developed in terms of main cutting parameters such as cutting speed, feed rate and depth of cut, using response surface methodology. Machining tests were carried out in turning AISI 1050 hardened steels by cubic boron nitride (CBN) cutting tools under different conditions. The model predicting equations for surface roughness of R-a, R-z, and R-max were developed using an experimental data when machining steels. The results indicate that the feed rate was found out to be dominant factor on the surface roughness, but it decreased with decreasing cutting speed, feed rate, depth of cut for these tools. In addition, average surface finish of Ra value produced by CBN cutting tool was about 0.823 mu m when machining hardened steels. However, the Ra value decreased about 0.55 mu m in terms of trial conditions. Moreover, a good agreement between the predicted and experimental surface roughness was observed within reasonable limit. (C) 2007 Elsevier Ltd. All rights reserved.