Taşıtlarda kullanılan debriyaj sistemlerinin termo-mekanik özelliklerinin iyileştirilmesi
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Date
2018-05-10
Authors
Çakmak, Tolga
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Publisher
Uludağ Üniversitesi
Abstract
Bu çalışmada, ağır vasıta araçlardaki kuru kavramalı debriyaj sistemlerinin termal ve mekanik şartlar altında sergilediği performans özelliklerinin iyileştirilmesine yer verilmiştir. Uygulama olarak yüksek tonajdaki kamyon ve otobüs grubunda kullanılan 430 mm çapındaki ürün değerlendirilmiştir. Çalışmada eğimli yolda, tekrarlı ardışık duruş kalkış için araç testleri ve bu testlerin simülasyonları üzerinde analizler yapılmıştır. Debriyajın termo-mekanik özelliklerinde iyileştirme için ısıl kapasitesi en yüksek ürün olan döküm baskı plakasına yoğunlaşılmış, bu parçada yapılan iyileştirmelerin sistem performansı üzerine etkisi incelenmiştir. Bu çalışmada özgün olarak incelenen konulardan biri, debriyaj döküm baskı plaka yüzeyi ile hava arasındaki ısı taşınım katsayısının, deneysel olarak ölçülmesiyle elde edilen veriler doğrultusunda dönme hızı ve geometrik özelliklere bağlı bir fonksiyon olarak tanımlanmasıdır. Böylece henüz tasarım aşamasında bir öngörüde bulunulması hedeflenmiştir. Diğer özgün kısım eğimli yolda çok fazla sayıda duruş kalkış içeren araç testi için açığa çıkan enerji ve kaçırma süresi verilerinin sunulmasıdır. Araç testleri süresince debriyaj muhafazası sıcaklık artışının, bir boyutlu sistem, üç boyutlu sonlu elemanlar ve hesaplamalı akışkanlar dinamiği analizleri ile benzetimi yapılmıştır. Benzetimler sayesinde debriyaj baskı plakası sürtünme yüzeyi sıcaklığı ve sistemin dayanabileceği toplam çevrim sayısı için öngörüde bulunulmuştur. Tezin asıl konusu olan termo-mekanik iyileştirmede, tasarım ve malzeme olarak iki konu ele alınmıştır. Tasarımda, daha önce debriyaj baskı plakasına uygulanmamış havalandırma kanallarının taşınımla ısı transferine olumlu etkisi irdelenmiştir. Malzemede ise kimyasal kompozisyondaki değişiklik ile iletimle ısı transferinde gerçekleşen iyileşme gösterilmiştir. Geleneksel ürüne kıyasla %28 daha hafif olan havalandırma kanallı prototipin, mekanik ve termal performansı, mevcut ürün ile karşılaştırılmıştır. Parçaların soğuma hızı, ardışık kavramalar sonrası sürtünme yüzeyindeki termal çatlak direnci ve yüksek dönme hızlarındaki mekanik patlama performansı, tezgah testleri ile araştırılmıştır.
In this study, improvement of the performance characteristics of dry clutch systems in heavy duty vehicles under thermal and mechanical conditions is investigated. As an application, 430 mm diameter product used in high tonnage truck and bus vehicles was evaluated. In the study, vehicle tests for repeated successive stop and take offs on the slope road and simulations of these tests were analyzed. For the thermo mechanical properties improvement of the dry clutch, pressure plate that has the most thermal absorption capacity, has been focused and the effect of improvements made on this component on the system performance has been evaluated. In this study, one of the points examined originally is the determination of the convection heat transfer coefficient between clutch casting pressure plate surface and air as a function of rotational speed and geometrical properties on the basis of experimental data. Thus, having estimation during design phase was targeted. Another original section is the presentation of energy dissipation and slippage duration results for the vehicle test that includes many repetitive take offs on a slope road. Temperature rise of the clutch housing air during the vehicle tests was simulated with 1D system, 3D finite element and computational fluid dynamics analyses. Simulations enabled to estimate the friction surface temperature and the number of cycles that clutch system could withstand. The main theme of the thesis; thermo-mechanical improvement has been evaluated within two aspects; design and material. In the design, the positive effect on the convection heat transfer by the ventilation channels, which had not been applied to the clutch pressure plate previously, was investigated. In the material, the improvement in conductive heat transfer was demonstrated by the change in chemical composition. The mechanical and thermal performance of the 28% lightweight prototype has been compared with the existing product. The cooling rate of the parts, the thermal crack resistance on the friction surface after consecutive engagements, and the mechanical burst performance at high rotational speeds have been investigated with the bench tests.
In this study, improvement of the performance characteristics of dry clutch systems in heavy duty vehicles under thermal and mechanical conditions is investigated. As an application, 430 mm diameter product used in high tonnage truck and bus vehicles was evaluated. In the study, vehicle tests for repeated successive stop and take offs on the slope road and simulations of these tests were analyzed. For the thermo mechanical properties improvement of the dry clutch, pressure plate that has the most thermal absorption capacity, has been focused and the effect of improvements made on this component on the system performance has been evaluated. In this study, one of the points examined originally is the determination of the convection heat transfer coefficient between clutch casting pressure plate surface and air as a function of rotational speed and geometrical properties on the basis of experimental data. Thus, having estimation during design phase was targeted. Another original section is the presentation of energy dissipation and slippage duration results for the vehicle test that includes many repetitive take offs on a slope road. Temperature rise of the clutch housing air during the vehicle tests was simulated with 1D system, 3D finite element and computational fluid dynamics analyses. Simulations enabled to estimate the friction surface temperature and the number of cycles that clutch system could withstand. The main theme of the thesis; thermo-mechanical improvement has been evaluated within two aspects; design and material. In the design, the positive effect on the convection heat transfer by the ventilation channels, which had not been applied to the clutch pressure plate previously, was investigated. In the material, the improvement in conductive heat transfer was demonstrated by the change in chemical composition. The mechanical and thermal performance of the 28% lightweight prototype has been compared with the existing product. The cooling rate of the parts, the thermal crack resistance on the friction surface after consecutive engagements, and the mechanical burst performance at high rotational speeds have been investigated with the bench tests.
Description
Keywords
Debriyaj, Kavrama süresi, Açığa çıkan enerji, Gri dökme demir, Clutch, Engagement duration, Energy dissipation, Gray cast iron
Citation
Çakmak, T. (2018). Taşıtlarda kullanılan debriyaj sistemlerinin termo-mekanik özelliklerinin iyileştirilmesi. Yayınlanmamış doktora tezi. Uludağ Üniversitesi Fen Bilimleri Enstitüsü.