機(jī)械畢業(yè)設(shè)計(jì)外文翻譯-切割參數(shù)對(duì)芯片影響形成垂直切割論文-預(yù)覽頁(yè)
【正文】 件切削力在圖10中以圖形方式呈現(xiàn)。切向力的數(shù)學(xué)模型的確定是由實(shí)驗(yàn)設(shè)計(jì)的方法。事實(shí)上,這個(gè)參數(shù)圖讓我們知道提要輪流的價(jià)值對(duì)于一個(gè)給定的切削速度和一個(gè)給定的切削力。 chemical analysis obtained by EDS analysisa) b) c)Fig. 2. a) Specimen form, (b) orthogonal cutting, and c) the carbides in the matrix of the materials create grooves by wear on the toolFig. 3. a) Chip formation at Vc=100 m/min, f = mm/rev, ap=2mm。 (a) Vc = 50 m/min。C/s[8]. Obviously, the quantity of the heat transferred towards the chip is more important than that of the 8b indicates the evolution of the hardness of the chip structure depending on the cutting speed for a given feed rate off = mm/rev. These results are the mean values taken from the five measurements for each cutting speed. According to theseresults obtained here, it is suggested that there is a nearly total dissolution of carbides due to the high temperature generated byplastic deformation at very high cutting speeds. The more the amount of carbon in the matrix increases, the more the meltingpoint of the steel decreases. Additionally, when the tool leaves after each cutting stage, the material undergoes abnormal coolingconditions through its microstructure. Large amount of austenite cannot find enough time to transform at high cutting speeds and a considerable amount of fresh martensite or remained austenite arefound in the structure not only in white layer but also within the microstructure of the chip.As for white and dark layers, a large number of experimental investigations have been carried out in the literature in order to understand the formation mechanisms and properties of white and dark layers in many material removal processes, such as turning, reaming, grinding and electrical discharge machining [1620]. Quasi these papers were carried out very similar results the evaluation of white layer. As far as the white layer is concerned, three different theories explaining the mechanism of white layer formation have emerged from the literature: I) rapid heating and quenching, which results in sudden phase transformation, II) severe plastic deformation, which produces a homogenous microstructure with a very fine grain size III) surface reaction with the environment, such as in nitriding processes [2029].However, some of the authors have indicated that the dark layer formation seems to be a result of microstructural changes in the heataffected zone as a consequence of the rapid heating and quenchingFig. 7 (a, b). SEM observation of white layer of a part of the chip obtained from steel X160CrMoV1, (Vc = 110 m/min, f = mm/rev, ap = 2 mm)In fact, this work represents an initial attempt to explain the white layer formation. We confirmed here that very defined and considerable thickness of the white layer occurs during the hard machining.However, we did not detect here a dark layer formation under the experimental conditions. As formerly indicated, the formationof the white and dark layers depends on not only heat treatmentdue to the operational parameters (cutting force, cutting speed, etc.) but also the materials parameters and some other important metallurgical aspects, such as the grain size, grain elongation, etc.Analyse of cutting forcesThe cutting forces recorded by the dynamometric table shows that the tangential force Ft and the feed force Fa decrease when the cutting speed Vc increases (Figure 9) that is due to mainly to the reduction in friction between “tool amp。 by fixing two parameters and to provide for the point on the curve to choose the third one. This parametric approach diagram will be useful for the manufacturers working on the steel X160 CrMoV12 as received or quenched conditions.教師評(píng)語(yǔ)教師簽名：2015 年 月 日
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