0000000000027821
AUTHOR
Florin Ciofu
FMEA - BASIC CONCEPT IN PRODUCT QUALITY
Failure modes and effects analysis (FMEA) is a systematic procedure for analyzing a system (the entire system or just an assembly, subassembly or component) to identify potential failure modes, causes and effects of each failure on system operation. A somewhat different definition was formulated by Goddard Space Flight Center (USA) : FMEA is a procedure whereby every credible way of defeating each item from the lower decomposition level to the highest level is analyzed to determine effects on the system and classify each potential way of failure according to the severity of its effect.
Aluminium-steel plating by press welding
A series of researches related to aluminium-steel plating by press welding are presented in the paper. In this sense, the influence of the roughness of the aluminium and steel test samples was taken into account, but also of the post-welding heat treatment on the characteristics of the joints made. S355 steel specimens and AlMgSi0.7 F27 aluminium specimens were analyzed. The samples were processed and roughness Ra = 2.51-51.09 µm were obtained. Also, after making the joints, a postwelding heat treatment was applied which consisted of a heating at a temperature of 425 °C with a duration of 6.5 hours and a slow cooling to room temperature. Six distinct samples were made in terms of surface ro…
Metallographical Aspects of the Application of Special Paint Layers for the Protection of Machine Part Sections against the Effect of lonitriding
The paper presents aspects concerning the appreciation of the protection through special paints based on copper powders used against plasma nitriding. First of all the choice of copper is motivated as an important metallic component of protecting paints, with the characteristics that the copper presents in the context of the physical and chemical phenomena (from the cathode and from gas volume) specific for the ionic nitriding process. The paper contains comparatively some characteristics (the duration of drying on the coat, the compatibility of the components, the capacity of extension and of avoiding the leakage, the power of covering, the capacity of joining, and the emitting of gases, t…
Changes of Structure and Physical-Mechanical Properties in Alloy Steels Thermochemically Treated by Plasma Nitriding
Plasma nitriding is a method of surface modification using a glow discharge technology to introduce nitrogen into the surface of a metal, which subsequently diffuses into the material. The main advantages of plasma nitriding over conventional nitriding processes are: reduced cycle time, controlled growth of the surface layer, elimination of white layer, reduced distortion, no need of finishing, pore-free surfaces and mechanical masks instead of copper plating. The process is especially suitable for complex parts that are intensively solicited by wear, fatigue, contact pressure, shocks, possibly also to corrosion. It is applied in order to bring the metallic products in a state favourable fr…
EXPERIMENTAL STUDY ON THE FLUID FLOWIN THE CONDUCTS
Fluids are high mobility environments that, under the action of external forces, are continuously and irreversibly deformed. The flow of fluid through a pipe is ensured by a pressure difference between its ends. The presented paper aims to experimentally determine the velocity profile of flowing a Newtonian fluid through a circular section pipe by measuring the local speed at five points on the pipe radius.
Increasing the Wear Resistance of Metallic Materials by applying Thermochemical Treatments
Wear is defined as mechanical or physical damage to a contact surface by another as a result of a relative movement. The structure of the steels has a great influence on abrasion resistance, so that certain thermo-chemical treatments applied to steels, besides the structural changes, are also aimed at changes in the chemical composition in the superficial layers as a result of diffusion with certain elements. A highly used thermo-chemical treatment is the aluminization, especially as a process for increasing the wear resistance, of the hot oxidation resistance, in order to replace the expensive refractory alloys with heating resistance up to 800-1000 °C with cheaper materials.