Browsing by Author "Yilmaz, SS"

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    Tribological properties of boronized ferrous based PM journal bearings
    Ünlü, BS; Yilmaz, SS; Kurgan, N; Varol, R
    Ferrous based PM (powder metallurgical) materials are widely used in journal bearings since they provide a good tribological performance. These bearings are self-lubricating and can be used in places where lubricating is not possible. This also applies to the shaft material which shows adhesive wear. Tribological properties can be improved and adhesive wear can be decreased by boronizing. In this study, tribological properties of ferrous based boronized and non-boronized Fe-graphite, FeCu-graphite and CuSnFe-graphite bearings manufactured by PM method have been determined and compared. Boronizing treatment was carried out at 950 degrees C for 4 hours. The SAE 1050 steel shaft was used as counter abrader. Experiments were carried out at 20 N loads and 1500 rpm every 30 minutes for 2.5 hours.
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    The effect of surface hardening treatments on the mechanical properties of iron based P/M specimens
    Yilmaz, SS; Varol, R
    In this study, boronizing and/or shot peening surface treatments were applied individually or in combination to the P/M steel specimens. The composition of specimens was 3% Cu + 0.2% C + balance Fe%. Tensile strength, hardness values and surface properties of treated specimens were determined. Boronizing + shot peening surface treatment was found to be the most convenient surface treatment for P/M steel materials based on test results. However, it is important to avoid high peening intensities for shot peening of boronized surfaces because shot peening deteriorates the boronized surface of P/M steel specimens. As a result. surface hardness values such as 1800-2500 HV were achieved after boronizing, the difference between the matrix materials with a hardness of 200 HV was quite high. (c) 2010 Elsevier B.V. All rights reserved.
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    Effect of Boronizing and Shot Peening on the Fatigue Properties of an Iron Based FeCu-Graphite P/M Material
    Yilmaz, SS; Ünlü, BS; Kurgan, N; Varol, R
    Iron based materials manufactured by powder metallurgy (P/M) method are widely used in industry. These materials are very important in applications where no machining is required, they can also be used as journal bearing material due to their self-lubricated property, and can be used for applications in the medical industry. In this study, powder metal parts were manufactured from composites based on FeCu-graphite by P/M method. Fatigue test was carried out on manufactured samples, which were only treated by boronizing or boronizing and shot peeing. The fatigue properties of these parts were investigated by a rotating bending fatigue test rig.
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    Tribological behaviors of polymer based journal bearings manufactured from particle reinforced bakelite composites
    Ünlü, BS; Atik, E; Yilmaz, SS
    Polymer based materials are widely used do to their good corrosion resistance, self lubrication, and wear resistance properties at low speeds, but are not suitable for lubrication in journal bearings. High performance engineering polymers offer desired properties for journal bearings and give good tribological results. In this study, tribological behaviors of polymer based composite bearings manufactured from particle reinforced bakelite have been investigated and evaluated. Reinforcement significantly improved wear resistance of bronze-bakelite composite bearings. (C) 2009 Published by Elsevier Ltd.
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    Investigation of the effect on boride layer of powder particle size used in boronizing with solid boron-yielding substances
    Meriç, C; Sahin, S; Yilmaz, SS
    In this study, the effect of particle size of powder used in the boronizing process with solid boron-yielding substances on the boride layer was investigated. Hot-shaped AISI 1020, AISI 1030, AISI 1040, and AISI 1050 structural steels were used as the base materials. EKabor HM powder was used as the boronizing agent, and was classified into four groups according to particle size. The boronizing process was carried out with each group at 900 degreesC for 2, 3, 4, and 5 h. The microstructure, microhardness, and layer thickness of the boronized materials were investigated. (C) 2001 Elsevier Science Ltd. All rights reserved.
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    Microstructural and Mechanical Properties of Pure Aluminum, 5083 and 7075 Alloys Joined by Friction Stir Welding
    Yilmaz, SS
    In this study, microstructural and mechanical properties of pure aluminum, 5083 and 7075 alloys joined by friction stir welding were investigated. Hardness, tensile, bending and impact tests were applied to the welded samples. In addition, optical and SEM tests were carried out. The effects of welding speed on microstructure and mechanical properties were investigated in these materials. Then, the optimal conditions for friction stir welding were determined for pure aluminum, 5083 and 7075 alloys. The maximum hardness was observed for 7075 while the minimum hardness was observed for pure aluminum.
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    The prevalence of childhood psychopathology in Turkey: a cross-sectional multicenter nationwide study (EPICPAT-T)
    Ercan, ES; Polanczyk, G; Ardic, UA; Yuce, D; Karacetin, G; Tufan, AE; Tural, U; Aksu, H; Aktepei, E; Arman, AR; Basgülk, S; Bilac, O; CosKunm, M; Celik, GG; Demirkaya, SK; Dursun, BO; Durukan, I; Fidan, T; Fis, NP; Gençoglan, S; Gökçen, C; Görker, I; Görmez, V; Gündogdu, OY; Gurkan, CK; Hergüner, S; Hesapçioglu, ST; Kandemir, H; Kiliç, BG; Kilinçaslan, A; Mutluer, T; Nasiroglu, S; Özcan, ÖÖ; Öztürk, M; Öztop, D; Sapmad, SY; Süren, S; Sahin, N; Tahiroglu, AY; Toros, F; Ünal, F; Vural, P; Yazici, IP; Yazici, KU; Yildirim, V; Yulaf, Y; Yüce, M; Yüksel, T; Akdemir, D; Altun, H; Ayik, B; Bilgic, A; Bozkurt, ÖH; Çakir, ED; Çeri, V; Demir, NÜ; Dinç, G; Irmak, MY; Karaman, D; Kinik, MF; Mazlum, B; Memik, NÇ; Özdemir, DF; Sinir, H; Tasdelen, BI; Taskin, B; Ugur, Ç; Uran, P; Uysal, T; Üneri, Ö; Yilmaz, S; Yilmaz, SS; Açikel, B; Aktas, H; Alaca, R; Aliç, BG; Almaidan, M; Ari, FP; Aslan, C; Atabay, E; Ay, MG; Aydemir, H; Ayranci, G; Babadagi, Z; Bayar, H; Bayhan, PÇ; Bayram, Ö; Bektas, ND; Berberoglu, KK; Bostan, R; Canli, MA; Cansiz, MA; Ceylan, C; Coskun, N; Coskun, S; Çakan, Y; Demir, I; Demir, N; Demirdögen, EY; Dogan, B; Dönmez, YE; Dönder, F; Efe, A; Eray, S; Erbilgin, S; Erden, S; Ersoy, EG; Eseroglu, T; Firat, SK; Gök, EE; Güler, G; Güles, Z; Günes, S; Günes, A; Günay, G; Özgür, BG; Güven, G; Goksoy, SC; Horozcu, H; Irmak, A; Isik, U; Kahraman, Ö; Kalayci, BM; Karaaslan, U; Karadag, M; Kilic, HT; Kiliçaslan, F; Kinay, D; Kocael, O; Koç, EB; Mutlu, RK; Lushi-San, Z; Nalbant, K; Okumus, N; Özbek, F; Özdemir, FA; Özdemir, H; Özkan, S; Özyurt, EY; Polat, B; Polat, H; Sekmen, E; Sertçelik, M; Sevgen, FH; Sevince, O; Süleyman, F; Shamkhalova, Ü; Simsek, NE; Tanir, Y; Tekden, M; Temtek, S; Topal, M; Topal, Z; Türk, T; Uçar, HN; Uçar, F; Uygun, D; Uzun, N; Vatansever, Z; Yazgili, NG; Yildiz, DM; Yildiz, N
    Aim: The aim of this study was to determine the prevalence of childhood psychopathologies in Turkey. Method: A nation-wide, randomly selected, representative population of 5830 children (6-13 years-old) enrolled as a 2nd,3rd or 4th grade student in 30 cities were evaluated for presence of a psychiatric or mental disorder by a Sociodemographic Form, Kiddie Schedule for Affective Disorders and Schizophrenia for School Age Children-Present and Lifetime Version (K-SADS-PL), and DSM-IV-Based Screening Scale for Disruptive Behavior Disorders in Children and Adolescents scales. Impairment criterion was assessed via a 3 point-Likert scale by the parent and the teacher independently. Results: Overall prevalence of any psychopathology was 37.6% without impairment criterion, and 17.1% with impairment criterion. Attention-deficit hyperactivity disorder was the most frequent diagnosis, followed by anxiety (19.5% and 16.7% without impairment, 12.4% and 5.3% with impairment, respectively). Lower education level and presence of a physical or psychiatric problem of the parents were independent predictors of any psychopathology of the offspring. Conclusion: This is the largest and most comprehensive epidemiological study to determine the prevalence of psychopathologies in children and adolescents in Turkey. Our results partly higher than, and partly comparable to previous national and international studies. It also contributes to the literature by determining the independent predictors of psychopathologies in this age group.
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    Prevalence of Childhood Affective disorders in Turkey: An epidemiological study
    Karacetin, G; Arman, AR; Fis, NP; Demirci, E; Ozmen, S; Hesapcioglu, ST; Oztop, D; Tufan, AE; Tural, U; Aktepe, E; Aksu, H; Ardic, UA; Basgul, S; Bilac, O; Coskun, M; Celik, GG; Demirkaya, SK; Dursun, OB; Durukan, I; Fidan, T; Gencoglan, S; Gokcen, C; Gokten, ES; Gorker, I; Gormez, V; Gundogdu, OY; Gurkan, CK; Herguner, S; Kandemir, H; Kilic, BG; Kilincaslan, A; Mutluer, T; Nasiroglu, S; Ozcan, OO; Ozturk, M; Sapmaz, SY; Suren, S; Sahin, N; Tahiroglu, AY; Toros, F; Unal, F; Vural, P; Yazici, IP; Yazici, KU; Yildirim, V; Yulaf, Y; Yuce, M; Yuksel, T; Akdemir, D; Altun, H; Ayik, B; Bilgic, A; Bozkurt, OH; Cakir, ED; Ceri, V; Demir, NU; Dinc, G; Irmak, MY; Karaman, D; Kinik, MF; Mazlum, B; Memik, NC; Ozdemir, DF; Sinir, H; Tasdelen, BI; Taskin, B; Ugur, C; Uran, P; Uysal, T; Uneri, OS; Yilmaz, S; Yilmaz, SS; Acikel, B; Aktas, H; Alaca, R; Alic, BG; Almbaidheen, M; Ari, FP; Aslan, C; Atabay, E; Ay, MG; Aydemir, H; Ayranci, G; Babadagi, Z; Bayar, H; Bayhan, PC; Bayram, O; Bektas, ND; Berberoglu, KK; Bostan, R; Cakan, Y; Canli, MA; Cansiz, MA; Ceylan, C; Coskun, N; Coskun, S; Demir, I; Demir, N; Demirdogen, EY; Dogan, B; Donmez, YE; Donder, F; Efe, A; Eray, S; Erbilgin, S; Erden, S; Ersoy, EG; Eseroglu, T; Firat, SK; Gok, EE; Goksoy, SC; Guler, G; Gules, Z; Gunay, G; Gunes, S; Gunes, A; Guven, G; Horozcu, H; Irmak, A; Isik, U; Kahraman, O; Kalayci, BM; Karaaslan, U; Karadag, M; Kilic, HT; Kilicaslan, F; Kinay, D; Koc, EB; Kocael, O; Mutlu, RK; San, Z; Nalbant, K; Okumus, N; Ozbek, F; Ozdemir, FA; Ozdemir, H; Ozgur, BG; Ozkan, S; Ozyurt, EY; Polat, B; Polat, H; Sekmen, E; Sertcelik, M; Sevgen, FH; Sevince, O; Shamkhalova, U; Suleyman, F; Simsek, NE; Tanir, Y; Tekden, M; Temtek, S; Topal, M; Topal, Z; Turk, T; Ucar, HN; Ucar, F; Uygun, D; Uzun, N; Vatansever, Z; Yazgili, NG; Yildiz, DM; Yildiz, N; Ercan, ES
    Aim: To determine the prevalence of affective disorders in Turkey among a representative sample of Turkish population. Methods: This study was conducted as a part of the The Epidemiology of Childhood Psychopathology in Turkey (EPICPAT-T) Study, which was designed by the Turkish Association of Child and Adolescent Mental Health. The inclusion criterion was being a student between the second and fourth grades in the schools assigned as study centers. The assessment tools used were the K-SADS-PL, and a sociodemographic form that was designed by the authors. Impairment was assessed via a 3 point-Likert type scale independently rated by a parent and a teacher. Results: A total of 5842 participants were included in the analyses. The prevalence of affective disorders was 2.5 % without considering impairment and 1.6 % when impairment was taken into account. In our sample, the diagnosis of bipolar disorder was lacking, thus depressive disorders constituted all the cases. Among depressive disorders with impairment, major depressive disorder (MDD) (prevalence of 1.06%) was the most common, followed by dysthymia (prevalence of 0.2%), adjustment disorder with depressive features (prevalence of 0.17%), and depressive disorder-NOS (prevalence of 0.14%). There were no statistically significant gender differences for depression. Maternal psychopathology and paternal physical illness were predictors of affective disorders with pervasive impairment. Conclusion: MDD was the most common depressive disorder among Turkish children in this nationwide epidemiological study. This highlights the severe nature of depression and the importance of early interventions. Populations with maternal psychopathology and paternal physical illness may be the most appropriate targets for interventions to prevent and treat depression in children and adolescents.
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    Effect of boronizing and shot peening in ferrous based FeCu-Graphite powder metallurgy material on wear, microstructure and mechanical properties
    Yilmaz, SS; Ünlü, BS; Varol, R
    Ferrous based materials manufactured by powder metallurgy (P/M) method are widely used in industry. These materials are very important because they do not require machining, have self-lubricated properties as journal bearing material, find applications in medical industry. In this study, powder metal parts were manufactured from ferrous based FeCu-Graphite composites by P/M method. Wear and mechanical test samples were manufactured and boronizing and boronizing + shot peening was applied to samples. Wear properties of these parts were investigated by wearing at 17 N load and 50 rpm on pin-on-disc wear test rig under dry conditions. Moreover, mechanical properties of powder parts were investigated in detail. (C) 2010 Elsevier Ltd. All rights reserved.