Publication: Disk balata çiftindeki sıcaklık dağılımının frenleme üzerine etkisinin incelenmesi
Abstract
Frenler; hareket halindeki taşıtı yavaşlatmak, taşıtın hızını kontrol altında tutmak, durdurmak ve duran taşıtı yerinde sabit tutmak amacıyla kullanılır. Fren sistemi, fren çiftinin sürtünmesine bağlı olarak aracın mekanik enerjisini ısı enerjisine dönüştüren en önemli aktif güvenlik sistemidir. Fren çiftinin frenleme esnasında ve neticesinde ısı transferi iletim, taşınım ve ışınımla gerçekleştirilmektedir. Günümüzde yaygın olarak kullanılan disk frenlerde diskin açısal hızına bağlı olarak sürekli değişen ısı taşınım katsayısının fren çiftlerinin soğumasına etkisi önemlidir. Isı taşınım katsayısındaki değişimi sayısal yaklaşımlarla hesaplamak mümkündür. Bu çalışmada, sonlu elemanlar yöntemi ile ANSYS® yazılımını kullanarak disk frenin termo-mekanik davranışı incelenmiştir. Öncelikle ısı taşınım katsayısındaki değişim sayısal yaklaşımla hesaplanmış ve akabinde bir binek otomobilin disk-balata fren çiftinin SAE J2522 Kapsamlı Fren Etkinlik Test standardından elde edilmiş deneysel verileri kullanılarak kararlı hal termik analiz gerçekleştirilmiştir. Elde edilen ısıl sonuçlar ve deneysel veriler geçişli yapısal analizde kullanıldıktan sonra toplam deformasyon ve Von-Misses gerilme değerleri değerlendirilmiştir. Frenleme sırasındaki disk sıcaklığının maksimum değere ulaştığı bölgelerde, deformasyonların da maksimuma ulaşması sonuçların birbiriyle ilişkili olduğunu ortaya koymuştur. Genel olarak frenlemenin sonunda, başlangıç durumuna göre sıcaklık farkındaki düşüşte; taşınımın etkisinin %91,15 ile 91,74 arasında azaldığı tespit edilmiştir.
Brakes; it is used to slow down the moving vehicle, keep the vehicle's speed under control, stop it and keep the stationary vehicle stable. Brake system is the most significant active safety system that converts the vehicle's mechanical energy into heat energy based on braking pair’s friction. The heat transfer of the brake pair during and as a result of braking is carried out by conduction, convection and radiation. In disc brakes, which are widely used today, the effect of the heat transfer coefficient, which constantly changes depending on the angular velocity of the disc, on the cooling of the brake pairs is important. It is possible to calculate the change in heat convection coefficient with numerical approaches.In this study, the thermo-mechanical behavior of the disc brake was investigated by using ANSYS® software with the finite element method. Firstly, the change in heat convection coefficient was calculated by a numerical approach, and then steady-state thermal analysis was performed using the experimental data obtained from SAE J2522 Comprehensive Brake Efficiency Test standard of the disc-pad brake pair of a passenger car. After the thermal results obtained and experimental data were used in the transient structural analysis, the total deformation and Von-Misses stress values were evaluated. In the regions where the disc temperature during braking reaches its maximum value, the deformations reaching the maximum revealed that the results are related to each other. Generally, at the end of braking, the drop in temperature difference relative to the initial state has been determined the decreased effect of convection between 91.15% and 91.74%.
Brakes; it is used to slow down the moving vehicle, keep the vehicle's speed under control, stop it and keep the stationary vehicle stable. Brake system is the most significant active safety system that converts the vehicle's mechanical energy into heat energy based on braking pair’s friction. The heat transfer of the brake pair during and as a result of braking is carried out by conduction, convection and radiation. In disc brakes, which are widely used today, the effect of the heat transfer coefficient, which constantly changes depending on the angular velocity of the disc, on the cooling of the brake pairs is important. It is possible to calculate the change in heat convection coefficient with numerical approaches.In this study, the thermo-mechanical behavior of the disc brake was investigated by using ANSYS® software with the finite element method. Firstly, the change in heat convection coefficient was calculated by a numerical approach, and then steady-state thermal analysis was performed using the experimental data obtained from SAE J2522 Comprehensive Brake Efficiency Test standard of the disc-pad brake pair of a passenger car. After the thermal results obtained and experimental data were used in the transient structural analysis, the total deformation and Von-Misses stress values were evaluated. In the regions where the disc temperature during braking reaches its maximum value, the deformations reaching the maximum revealed that the results are related to each other. Generally, at the end of braking, the drop in temperature difference relative to the initial state has been determined the decreased effect of convection between 91.15% and 91.74%.