This paper presents the findings of comparative research conducted to find out the braking performance of a Mo/NiCrBSi coated automobile brake disc. The friction and wear behavior of the Mo/NiCrBSi coating (CD) used for the disc material was evaluated using a laboratory scale disc-pad dynamometer and compared with a reference disc (RD). The coating was deposited by means of the atmospheric plasma spray process on a grey cast iron substrate. Braking tests were performed according to the SAE-J2430 test standard. Disc microstructures were characterized by SEM and XRD. It was found that the bonding strength was good with an infinite rating between the accumulated coating layer and the substrate. The results show that the coated brake disc has a comparable coefficient of friction and that the amount of wear is lower than that of the reference disc. The addition of ductile phases to the disc coating was beneficial in reducing the coefficient of friction to an acceptable degree and also effectively improving wear resistance.
In braking systems, which consist of dry sliding lining against a pearlitic cast-iron disc, disc wear has a significant impact on the overall wear rate. In this work, dynamometer tests were conducted to find out the friction and wear behaviour of 20NiCrBSi-WC12Co cermet coating accumulated on the castiron disc by High velocity oxy-fuel spraying (HVOF) and the findings were compared with those of the uncoated disc. Braking tests of the coated and uncoated discs were performed on a full-scale brake dynamometer, which was designed in line with the SAE-J2430 Brake Effectiveness Procedure. Microhardness values, surface properties, scanning electron microscopy (SEM) analysis, energy dispersive x-ray (EDX) and x-ray diffraction (XRD) analysis of the discs were evaluated. As a result of these analyses, it was found out that cermet coating had a much higher microhardness and abrasion resistance with the combination of hard WC phase and mild Ni matrix compared to the conventional disc. The coated disc exhibited stable braking effectiveness with lower surface contact temperature. At the same time, this coating results in longer service life by reducing abrasive wear on the brake disc surface and a lower lining wear rate, reducing particle matter emissions to the environment.
Dry friction and wear behavior at high temperatures was investigated against an Al2O3 ball in order to characterize the wear rate, coefficient of friction (COF), hardness and thermal friction behavior at different temperatures in the wear-treated zones of the CuCrZr copper alloy. Experiments were fulfilled using a pin-on-disk wear device with the aid of a temperature modulated wear device at room temperature, 100, 200 and 300 °C. The loads applied during wear are given as 3N, 5N and 7N, respectively. In order to examine the morphological structure of the worn surfaces, appropriate samples were prepared and SEM (scanning electron microscopy) device was used. Similarly, EDS (energy dispersive x-ray spectrometry) was applied to worn surfaces to examine the abrasive-material interaction. Against the hardness of the material at 25 °C, the hardness value in measurements at 300 °C showed a small increase. The COF value increased at 100 °C and then decreased, while the wear rate increased significantly as the temperature increased. The temperature increase starting from RT up to 300 °C weakened the internal structure of the CuCrZr alloy and caused an increase in the wear rate. XRD test was used to show the phases that may occur in CuCrZr alloy due to temperature and heat treatment.
ÖzGünümüzde dünyada plastik üretimi 400 milyon tona ulaşmıştır. Bu büyük artışta plastik ürün tasarımı, kalıp imalatı ve plastik enjeksiyon makinelerinin rolü oldukça fazladır. Dolayısıyla üretimde oluşabilecek problemlerin önceden tespit edilmesi ve gerekli önlemlerin alınması üretim verimliliği bakımından büyük önem arz etmektedir. Plastik Enjeksiyon tezgâhları günümüzde üretimin yoğun olarak yapıldığı ve ürün kalitesinin makine performansına göre değerlendirildiği tezgâhlardır. Tezgâhların 7/24 saat çalışması ve bakım süreçlerinin zamanında yapılamaması, vida mili kırılması, hidromotor ve işlemci arızaları gibi üretimde problemlere neden olmaktadır. Bu problemlerin giderilmesi büyük maliyetler ve üretimde zaman kaybına neden olmaktadır. Özellikle vida mili arızasında tezgâh tamamen kontrol dışı olmakta ve 3-4 aylık zaman diliminde vida mili yenisi ile değiştirilerek tekrar çalışmaktadır. Bu çalışmada, plastik enjeksiyon tezgahlarında meydana gelen vida mili kırılma probleminin üretim esnasında oluşmaması için kesme kuvveti sinyallerinin akustik emisyon kullanılarak önceden tahmin edilmesi amaçlanmaktadır. Böylece yukarıda bahsedilen problemler önceden tespit edilerek üretimde meydana gelebilecek aksamaların önüne geçilmiş olacaktır.
One of the many methods used in the production of plastic materials is plastic injection method. The plastic injection method needs equipment difficult to choose, and it is also costly. Many negativities could be experienced during production. One of them is the water droplet problems on the surfaces of the mold. Provision of insufficient cooling on molds, ambient temperature, non-homogenous humidity, mechanical and other stresses occurring during production, cracks on the product, warpage and thermal residual all cause some stress-like defects. In this study, the effect of water droplets problem on production efficiency in the molds of Polyethylene Terephthalate (PET) raw materials manufactured in a private enterprise was examined. The percentage productivity table has been created based on different months of the year, August July and August. In the enterprise, 8 dehumidifiers were placed to 17 injection machines to create a homogeneous production temperature in the environment. Humidity and heat values obtained during production were monitored daily and recorded. In this study, which was conducted over two years and three months, positive results were obtained suggesting that the water droplets formed in injection molds has decreased with the effect of dehumidification devices, and the efficiency of injection production has also increased by 8%.
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