Biological response of an in vitro human 3D lung cell model exposed to brake wear debris varies based on brake pad formulation

Wear particles from automotive friction brake pads of various sizes, morphology, and chemical composition are significant contributors towards particulate matter. Knowledge concerning the potential adverse effects following inhalation exposure to brake wear debris is limited. Our aim was, therefore, to generate brake wear particles released from commercial low-metallic and non-asbestos organic automotive brake pads used in mid-size passenger cars by a full-scale brake dynamometer with an environmental chamber simulating urban driving and to deduce their potential hazard in vitro. The collected fractions were analysed using scanning electron microscopy via energy-dispersive X-ray spectroscopy (SEM-EDS) and Raman microspectroscopy. The biological impact of the samples was investigated using a human 3D multicellular model consisting of human epithelial cells (A549) and human primary immune cells (macrophages and dendritic cells) mimicking the human epithelial tissue barrier. The viability, morphology, oxidative stress, and (pro-)inflammatory response of the cells were assessed following 24 h exposure to similar to 12, similar to 24, and similar to 48 A mu g/cm(2) of non-airborne samples and to similar to 3.7 A mu g/cm(2) of different brake wear size fractions (2-4, 1-2, and 0.25-1 A mu m) applying a pseudo-air-liquid interface approach. Brake wear debris with low-metallic formula does not induce any adverse biological effects to the in vitro lung multicellular model. Brake wear particles from non-asbestos organic formulated pads, however, induced increased (pro-)inflammatory mediator release from the same in vitro system. The latter finding can be attributed to the different particle compositions, specifically the presence of anatase.Web of Science9272351233

A cutting force model based on kinematics analysis for C/SiC in rotary ultrasonic face machining

Ceramic matrix composites (CMC) superior properties and are used in the harsh conditions of high temperature and pressure, in aerospace and other industries. However, due to inhomogeneous and anisotropic properties of the composites, the machining is still challenging to achieve desired efficiency and quality. For advanced materials, Rotary ultrasonic machining is considered as a process with high efficiency technology. The cutting force is a critical factor required to be effectively predicted and controlled to reduce processing defects in composites. In this research, the rotary ultrasonic machining was used for face machining of carbon reinforced silicon carbide matrix composites (C/SiC), with a conical shaped tool. The kinematics between individual diamond abrasive and the workpiece material was analyzed to illustrate the separation characteristics in the cutting area. The condition for the intermittent machining during RUFM was obtained by establishing the mathematical relation between cutting parameters and vibration parameters. The indentation fracture theory was adopted to calculate the penetration depth into the workpiece by diamond abrasives in the RUFM. The relationship of cutting force and processing parameters including spindle speed, feed rate, and cutting depth were investigated. The comparison of the experimental and simulation data of the cutting force, showed that most of the tests, the errors were below 15 %. It is therefore stipulated that the cutting force model developed in this paper can be applied to predict cutting forces and optimize the process in the RUFM of C/SiC

Leichtbaubremsen aus C/C-SiC Keramiken

Zu den wichtigsten Sicherheitsbauteilen von Fahrzeugen gehören die Bremsscheiben, die beim Abbremsen die entstehende Wärme speichern und anschließend in möglichst kurzer Zeit wieder an die Umgebung abführen sollen. Steigende Antriebsleistungen und höhere Geschwindigkeiten moderner Fahrzeuge erfordern temperaturstabile Bremssysteme, die außerdem den Anforderungen des Leichtbaus genügen müssen. Aufgrund seiner ausgewogenen Eigenschaften und seiner niedrigen Herstellungskosten stellt Grauguß in seinen verschiedenen Modifikationen trotz hoher Materialdichte und begrenzter Temperaturbeständigkeit heute noch erste Wahl der Bremsenkonstrukteure dar. In besonders gewichts-sensitiven Anwendungen des Rennsports und im Flugzeugbau haben sich jedoch die wesentlich leichteren Carbon/Carbon-Werkstoffe bereits durchgesetzt und etabliert. Einem breiteren Serieneinsatz dieser Materialien stehen allerdings gravierende Nachteile bei kalter und nasser Bremse und die hohen Materialkosten entgegen. Neue Faserkeramiken auf C/C-SiC Basis versprechen deutliche Vorteile bezüglich Verschleiß- und Reibwertverhalten. Durch ihre Herstellung in einem schnellen und kostengünstigen Fertigungsverfahren können zukünftig diese CMC-Werkstoffe eine echte Leichtbau-Alternative zu metallischen Bremsscheiben darstellen und völlig neue Perspektiven für Hochleistungs- und Leichtbaubremsen in der Fahrzeug- bzw. Antriebstechnik eröffnen