Papers by Keyword: Slipping

Abstract: Hot and cold deformation behavious and microstructure evolutions of Mn18Cr18N were investigated by thermo-mechanical modeling experiments and microstructure analysis. The results show that hot deformation flow stress curves characterized by the same work hardening and subsequent stress softening varied with temperatures and strain rates for both of as-cast and as-forged samples. And flow stresses are sensitive to strain rate. At strain rates lower than 0.01s^-1, the flow stresses are lower, and microstructure evolution controlled by dislocation mechanism dynamic recrystallization; At strain rates higher than 0.1s^-1, the flow stresses are higher, and microstructure evolution controlled by twinning mechanism dynamic recrystallization. But the dynamic recrystallzed fraction of the as-cast sample was much less than that of the as-forged sample. For cold deformation, the simple uniaxial tensile sample shows that the monotone increasing flow stress curve and monotone decreasing work-hanrdening rate. However, for the uniaxial and biaxial compression-tensile samples with different previous compression, the subsequent tensile yield stress, the maximum tensile stress, the reduction of cross sectional area and the elongation have extremums respectively at the previous compressive deformation of about 25%-30%. Microstructure evolution mechanisms during cold deformation were planar slipping and twinning.

Abstract: The orthocycloid represents a plane curve generated by a point belonging to a circle which is rolling without slipping along a line. Our original idea (not approached in the specialty literature) is to consider the rolling with slipping of a wheel on a rail, instead of the rolling of the gear “gearwheel –rack” as in the case of the orthocycloid generation. In this case the length of the arc considered on the circle is no longer equal to the segment from the line supporting the rolling. The tracer point belonging to the wheel will generate other curves but orthocycloids. Various curves were obtained. Analyses were made considering the braking due to the friction between the rolling surfaces and respectively the case when the lubricant layer generates a “skating like” rolling. The yielded curves start from the classical form of the orthocycloid and afterward are distorted exhibiting an increased number of loops. Some curves are similar to elongated orthocycloids, obtained in different conditions. The curves resulted from rolling by slipping can be used in various domains.

Abstract: The starting point consists in the modality to generate epicycloids when two external circles are considered. The mobile circle is rolling on the fix circle without slipping, such as two arcs belonging to these circles are equal. The specialty literature presents an example with a simple planetary gear in which the “satellite porting” arm provides the rolling of the mobile circle on the fix circle. Our original idea, not approached in the specialty literature, considers the rolling with slipping of the mobile circle on the fix circle. Instead of the gears providing the rolling without slipping, two wheels with smooth surfaces are used now. The case when the two involved arc are no longer equal is analysed. Between them appear either frictions generating braking or “skating like” rolling when the lubricant layer is too thick. An analysis of the theoretical case when the slipping has a sense opposite to that of a normal rolling is also performer. A significant class of curves was obtained. Some are even epicycloids obtained with slipping, with other parameters.

Abstract: The saturation of primary tensile twins in heavily textured Mg-alloy AZ31 is investigated, and their strain accommodation limit is evaluated. EBSD results suggest that the mean number of twins per grain saturate rapidly, followed by the stop of twin growth. Twinning saturation is included in a physical model of twin evolution.

Abstract: In this paper, effects of initial micro-structures on deformation behaviors of commercial pure titanium were elaborated by investigating the evolution of dislocation boundary and its adiabatic shear sensitivity. At the low to medium stain rates, the main plastic deformation mechanism of as-annealed commercial pure titanium is dislocation slipping. Meanwhile, geometrically necessary boundaries (GNBs) with different directions are generated and crossed with each other. However, new dislocation boundaries are formed in as-cold rolled plates, which are parallel to the initial ones induced by cold rolling. When the strain rate is up to 1000 s^-1, the initial dislocation boundary playes an adverse role in the adiabatic shear sensitivity of commercial pure titanium. The adiabatic shear band is the high-speed deformation characteristic micro-structure in commercial pure titanium. In addition, dynamic recrystallized grains are generated in the center of an adiabatic shear band, which is consistent with the sub-grain rotation mechanism.

Abstract: This paper shows how to calculate the speed of travel for a tractor equipped with an additional transmission (hydrostatic transmission). Determination is theoretically and experimentally, comparing the results. Theoretical calculation is done using MathCAD program. An experimental measurement is determined by the device called “fifth wheel", equipped with speed measuring transducer.

Abstract: Introduce the dynamic friction coefficient of clutch friction plate. Establish Mathematical model of starting process, carried out vibration analysis for frictional sliding process systematically, validated the analysis using Matlab/simulink software. Meanwhile, compared with the starting process by static friction coefficient. The results show that using dynamic friction coefficient to analyse starting process conforms to the actual working condition.

Abstract: In this paper, the slipping of belt conveyor for the normal stable operation and full load starting in between belt and rollers are investigated. The results illustrate that the resistance of the belt conveyor in the normal and stable operation is less than that of the full load starting operation due. The possibility of slipping in normal and stable operation is less than that of the slipping start running at full load condition. Therefore, in order to check the conveyor belt slipping, we should pay attention to the full load start condition, can not check under normal and stable operation of the skid. The application of soft-start technology to solve the problem of slipping when starting was also proposed.

Abstract: During the cold rolling of thin strip on the 1220mm five-stand tandem cold mills, scratch marks occur on the surfaces of strip and work roll. The surface quality of strip is degraded and the roll wear increases, which resulting in significant economic loss. In this paper, the mechanics of strip scratch marks was studied by carrying out both field experiments and theoretical analysis. Slippage Factor (SF) and Scratch Mark Factor (SMF) were presented to indicate the conditions of strip scratch marks. Meanwhile, mathematical models and simulation code were developed to optimise the rolling schedules and to improve the scratch marks. The practical application of the developed models to the 1220 mm five-stand tandem cold mills verifies the effectiveness of the developed models. The mathematical models can be applied to other similar tandem cold mills.