Gc max find find burner efect secundar
To working surfaces of such steel products for example, saw blade in woodworking the requirements of high wear-resistance at as greater excess as possible in hardness over opposite body of working cutting contact are provided. Application of diamond grinding with introduction of additional energy as electric discharges diamond-spark grinding in the technologies of reinforced steels allows to raise homogeneity of white layer structures, that will assist to increasing of stability of finished product operation.
Keywords: diamond, friction, microhardness, X-ray, roughness. Introduction The white layer white zones as gc max find find burner efect secundar etching hard buildup, appearing on a surface of steel components during contact thermomechanical influence, for a long time draws attention of researchers from the point of view of possible increase of life-limiting characteristics of operational contact surfaces. However to the beginning of the third quarter of XX century cautious negative estimations prevailed among metallophysicists as regards practical usage of white layer phenomenon.
There is characteristic point of view of worldfamous scientists I. Lyubarskiy and L. Palatnik [1]: «White zone does not possess satisfactory for effective resistance to deterioration properties, it is frequently formed as separate isolated sites on friction surface or in volume of metal, the non-uniform areas being concentrators of stresses that results in deterioration wear-resistance are formed; the nonequilibrium white zone possesses low fatigue resistance».
Here the same authors in the same work [1] emphasize: «the problem gc max find find burner efect secundar white zone is rather actual and wide and demands statement of the further investigations for more detailed studying» citing in author's translation from Russian.
The subsequent investigations of various authors testify to indefatigable temptation to use effect of white layer for the practical purposes. Here we shall note only some examples of successful promotion in this direction.
Questions of prediction and purposeful quality management of the processed surface under conditions of white layer formation are investigated by the European technological school []. Achievement of white layer microstructures during electroerosive processing of steel industrial equipment is considered as basic resource of strengthening [6].
At the Siberian University Russia, Novokuznetsk [7] even curing of fatigue damages of steels due to electric current pulses and practical technology based on this principle are justified on the basis of the mechanism of formation of local white zones in fatigue cracks.
Method of thermofriction strengthening of steel surfaces, using white layer phenomenon in real embodiments, relieved from the basic disadvantage quoted above on [1]: discontinuity flaw is completely eliminated and substantially - heterogeneity [8] is developed at Kharkov Polytechnic Institute.
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Diamond grinding with introduction of electric current pulses in zone of processing diamond-spark grinding allows both to independently form the strengthened white layers in steels [9], and to support such layers by means of finishing processing after preliminary thermoclutch strengthening with increase of their uniformity [10], that holds with electropulse technologies [5,6].
Diamond-spark grinding as finishing postprocessing after thermofriction strengthening Gc max find find burner efect secundar of research of influence of DSG on phase and stressed state of steels [9] are evidenced that control of quality of surface layer by means of combining of diamond grinding with sputter ion influence can be more directional including control of forming of both structures of second heat hardening and structures of tempering then in traditional technologies.
At that heat of machining surface is a little relative to TFP and it is equivalent to influence of backing, especially under grinding without current and gc max find find burner efect secundar preliminarily dressed wheel. Availability of use of diamond-spark grinding on operations of finishing following after thermofriction processing is confirmed of some practice of observation of white layer structures after diamond-spark grinding of steel [9] that can be explained exclusively thanks to action of electric discharges providing fast impulse heating of machined surface up to phase transformation temperatures.
DIAMOND-SPARK GRINDING IN FORMING OF FUNCTIONAL WHITE LAYERS OF INCREASED MICROHARDNESS IN STEELS
In electric contact patch maximum covering of machined surface greutatea pierde edita technologies of double speed diamond-spark grinding with gc max find find burner efect secundar speeds of working motions of both diamond wheel and machined piece it is to the point of melting and even to partial evaporating, with next enough quick cooling especially under influence of lubricoolant of efficient composition in combination with active technique of supply.
As it marked after known diamond-spark grinding experiment [9] just combination of high-speed and enough short-term heating with enough quick cooling can provide forming even more so an effective support of qualitative white layer in result of implementation of combined technologies.
This hypothesis also proceeds from probable smallness of individual - carbide fragments. As such fragments there are identified discovered by electron-microscope investigation in near-surface layers of past thermofriction processing steel, moreover on surface of martensate grains, particles of right geometric form with a size approximately µm [8], that practically is contignous with nanometer excursion, in gc max find find burner efect secundar case of upper bound of that is taken on a value nm, and with transformation in which of structure of materials are been connected greatest successes of modern materials science.
In light of electron-microscope investigations [8] it is noteworthy that grains gc max find find burner efect secundar of this parts with size µm themselves are more roundish and greatly smaller size about 1 2 µm than size of needled grains of martensite of parent before thermofriction processing texture.
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Latest research allowed to determine predominant component of white layer microstructure as deformed grainular martensite [8]. Conclusions Diamond-spark grinding, especially high-speed processing with cooling, is active mean of support of white layer after thermofriction processing. It is possible efficiently use diamond-spark grinding by combined control of electrical and mechanical operating modes taking into account technical requirements to accuracy and roughness, with short-term ironing sparking-out without current if necessary.
References: [1] Lubarskiy I. Metallophysics of Friction M. The surface integrity of turned and ground hardened bearing steel. Wearpp [3] Brinksmeter E. White layers in machining steel. White layer and thermal modeling of hard turned surfaces. Tarel nik, V. Matsinkovskiy, A. Belous, B. Structure Transformations at Electroerosion Treatment of Steels. Zuev, O. Sosnin, S. Podboronnikov, V. Gromov, S. Journal of Technical Physics,T. Due to measurement and computational tolerances, sufficiently accurate stoichiometric operation requires a closed loop control.
In this paper is described the problem of the spark-ignited engine model for lambda control.
Keywords: lambda control, platinum, rhodium, pipe. Introduction In SI engines, the air-fuel ration λ is either very lean at load or stoichiometric at medium and high load.
În timp ce din n - parafine se formează preferenĠial etilenă, din izoparafine ramificate se formează preferenĠial propilenă.
Due to turbulence and local inhomogeneity of the gas mixture, real combustions actually produces HC, CO and NO x at the same time. By means of a catalytic converter, these raw emission can be effectively reduced.
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Therefore, it is important to have an accurate closed loop lambda control to guarantee an average air-fuel ratio within a window smaller than 0. If the average accuracy can be held, such deviations go into both directions. Within the volume of the catalytic converter excursions of the air-fuel ratio in one direction are compensated by those in the opposite direction.
At the exhaust pipe tail, short time lambda deviations of a few percent do not deteriorate the emissions after the catalytic converter. The block-diagram of the lambda controlled SI engine is shown in Figure 1. The amount of injected fuel is controlled by the engine control unit which gets its feedback from the lambda sensor in the exhaust pipe as well as the mass air flow signal in the inlet pipe.
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Additional variables like engine speed and engine temperature are used in the control scheme. Due to turbulences and flame propagation, the air-fuel mixture is still uncompletely burned. The converter is integrated into the exhaust pipe. It consists of a ceramic or metal carrier substrate covered by a wash coat with an extremely large surface which is again covered with a thin layer of platinum and rhodium.
The ratio of platinum to rhodium is approximately 2 to 1. Depending on the engine size about 1 3 g of precious metals are used. They both support the chemical reactions: Platin supports more the oxidation of CO and HC and Rhodium supports more the reduction of the nitrogen gc max find find burner efect secundar NO x.
Reduction and oxidation processes are simultaneously running in the catalytic converter. Block diagram of a lambda controlled SI engine. At stationary engine operation, the conversion ratio is high, even if the converter would be already party damaged.
During transients, excursions in the air-fuel ratio occur, leading to high emissions. During the warm-up phase the engine and the exhaust pipe, temperatures are too low for chemical reactions and the conversion ratio is poor. The catalytic converter has to reach temperatures beyond C to be effective. There are several possibilities to accelerate the engine warm-up: A gc max find find burner efect secundar heating of the exhaust pipe can be obtained by an ignition angle retard of e.
After the warm-up period, this converter is bypassed; Fresh air is added to the exhaust gases by a secondary air-pump. The additional combustion process in the exhaust pipe heats up the catalytic converter; The catalytic converter is electrically heated. In order to reduce the required heating power, the heater is concentrated in the region of the converter where the exothermic reactions first starts.
Oxigen Sensor A lambda sensor is used to measure the concentration of oxygen O 2 in the exhaust pipe. The sensor is mounted in the collective exhaust pipe where the individual exhaust pipes from the cylinders end in. In engines with 6 or more cylinders two lambda sensors are used.
Zirconium Dioxide Sensor consists of 43 și doriți să pierdeți în greutate solid ceramic electrolyte zirconium dioxide which conducts oxygen ions at temperatures above C. Another sensor is based on strontium titanate.
Strontium titanate is a ceramic semiconductor material. Its conductivity in strontium titanate is less influenced by surface effects at high temperatures than in other materials. The dependence of the probe resistance from the temperature decreases at higher temperatures leaving the dependence on lambda only.
The strontium titanate sensor has a planar structure. An advance of the planar device is short response time of a few milliseconds after lambda deviations.
Because of its operation at temperatures around C it can be fitted closer to the engine. Engine model for lambda control. Inverted lambda characteristic with limiting range ± λ L.
Lambda control circuit The characteristic between the output voltage and the air-fuel ratio λ is not-linear. After operation for many years this characteristic slightly ages. Therefore the most stable measuring range of the characteristic is taken for the control. Figure 3 shows, that it is located in the steep linear range of the characteristic. The sensitivity factor in this rage is K L. Outside the measurement range the characteristic is cut-off. The center of the measurement range λ 0 is not at desired reference value λ ref but is determined exclusively by the stability of the characteristic.
Conclusions Lambda control is a very high priority for engine design because a change of the average would already increase the emission rates. Therefore, it is important to have an accurate closed loop lambda control to guarantee an average air-fuel ratio within a window smaller.
References: 1. Kienche, L. Starting with the idea that filling the matrix with various powders it is possible to change the electric behaviour some layered materials were formed having as reinforcement 15 layers of kevlar and carbon fibre simple type fabric.
The electric permittivity was evaluated using standard recommended method. Introduction While the major aim of composites is replacing the metals in aircraft, spacecraft and marine applications the electromagnetic properties of such materials are very important.
As it is well known metals show high electric conductivities while the composites excepting metal matrix, metal reinforced or metal-metal ones show poor electric conductivity. Both thermoset and thermoplastic polymers are also relatively sensitive to the action of aggressive media and show high values of water absorption.
The most common solution to improve the polymers properties is to fill them with various solid systems such as small metallic spheres or powders obtaining filled composites, according to [1]. The mechanical properties of composites are improved in the case of reinforcements reinforced composites or fibrous composites.
