An experimental device was designed and developed to study the friction coefficient between a steel rod and two drive rollers on which it is supported. The motion of the steel rod is achieved by ...means of two rods mounted on bearing and driven by two engines. The two rollers have rotational motions with equal and opposite as sign angular velocities. These cause a harmonic motion of the horizontal rod. By measuring the oscillation period of the steel rod, the coefficient of sliding friction between the rod and the drive roller is obtained.
The paper presents the manner of finding the conjugate profile of a circular tooth of a spur gear. A synthesis of the method of enveloping applied to the cam mechanisms is presented in order to ...relate it the profile of the spur gears. The main argument of employing cam mechanisms is the possibility of obtaining any follower law of motion using a minimum number of parts- the cam and the follower. In the case of the mechanisms with flat face follower, the cam is obtained as an envelope of successive positions of the follower. The gear mechanisms are a particular case of cam mechanisms. The major requirement imposed to this mechanism is to transmit the rotational motion between two shafts with a constant transmission ratio. From here it results that the profile a geared wheel can be completely identified when there are known the distance between the axes, the transmission ratio and the profile of one of the wheels. The most used curve as tooth flank is the involute of a circle, due to the fact that this curve has as conjugate curve an involute, too. Although the involute profiles are common in most of the technical appliances, there are cases when they cannot satisfy the functional constraints of certain devices. As example, in the mechanical watches technology, large transmission ratios are needed and the gears with small number of teeth are used as routine. But this necessity is better fulfilled by cycloidal profiles than the involute ones. The circular profiles for the spur gear are the oldest gears due to the simple profile. The exact conjugate profile of a circular tooth obtained by enveloping by means of dedicated software is presented.
The paper presents some problems which might occur at different stages of the 9R(3RRR) planar mechanisms study (workspace characterizing, forward and direct kinematics, singularities analysis). At ...each of this stage, it has been identified certain problem which can occur and that need more attention and effort to be solved. In the paper classical methods, and formulas, known from technical literature, have been used, but occurred situations was depicted detailed and illustrated by graphical representations.
One of the problems of the modern era that we are facing nowadays, besides the pollution caused by fuel burning, is the level of noise pollution in constant growth in agglomerated cities. The main ...source of noise is the transport sector where the number of passenger cars had dramatically increased in recent years. Most of the vehicles around the world are powered by internal combustion engines equipped with a fuel injection system and a small percentage with an electric one. Researchers have shown that noise pollution affects human health from a psychological and physical point of view. Due to the manufacturing process of high-pressure pumps, some pumps mounted on the engine and running under certain conditions can produce a higher audible noise than the engine. The paper presents an experimental investigation on a high-pressure pump that provides a comparison between the noise level at the beginning of its lifetime and that resulting after an endurance test performed on a special test bench. It has been found that the greatest contributor to noise emissions is the high-pressure pump outlet valve when it opens. To improve the sound quality of the high-pressure pump, it is essential to further develop the outlet valve design and better control over the manufacturing process.
A dynamical system with one degree of freedom is modelled in two manners: the first one considers that only the dynamical sliding friction is present and the second considers the presence of both ...dynamic friction and static friction. It is difficult to apply the model of revealed static friction only for the zero relative velocity. For this reason, an approximate model for the static friction was identified, that accepts that the static friction occurs when the magnitude of relative velocity in contact decreases under a certain value, the critical value. The integration of the equations of motion of the two models reveals that for important values of the relative velocity, the two models estimate the same behaviour of the system. An experimental set-up was used to validate the theoretical results.
The high-pressure pump is a component of the automotive common-rail system and has as main assemblies: housing, driveshaft, gaskets and front plate. Literature presents analyses of the threaded ...fastening assemblies, especially for those with the critical joints with screws, those involving torque and angle. The assembly process that we have studied performs the sealing of the components with the gasket through the screws, thus preventing the fuel from leaking from the pump. Our paper presents an analysis of the influence of the tightening process with screws of the housing, gasket and front plate. The experiment was conducted using the Zeiss measuring system and the screwdriver Janome. The tests analysis demonstrates that screwing process can influence the distortion.
The paper aims finding the conjugate profile of a circular profile tooth from a gear mechanism with fixed parallel axes and constant transmission ratio. There are presented three manners of attaining ...the goal. The first two methods are based on the general methodology of gear wheel toothing by envelope machining presented in the first part of the work, considering elementary mechanisms with fixed axes and then a planetary one. The last method is based on applying the Reuleaux's fundamental law of gearing and has the advantage of obtaining both the conjugate profile of the gear with circular profile and the line of action which is useful in the study of gearing phenomena.
Based on an observation from a previous work, the authors use the degree of passive freedom of a mechanism with roller follower to propose a new type of mechanism. In the new mechanism, the roller is ...replaced by a jointed element that forms two contacts with the cam. The obtaining of the cam profile is the main disadvantage of the cam mechanisms but in the present work, by using a cam formed by two connected discs, it is aimed to be avoided. The method is illustrated by designing the mechanism in CAD software followed by the simulation of its movement. To optimize the movement of the final element, the equivalent mechanism with lower pairs is used which has the advantage that the lengths of the elements are constant. The kinematics of the final element is particularly sensitive to the variation of the dimensions of the mechanism, fact illustrated by an example.
Upon the efficiency of gear transmissions Alaci, S; Ciornei, F C; Pentiuc, R D ...
Journal of physics. Conference series,
01/2020, Letnik:
1426, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The work proposes an experimental method and device for finding the efficiency of the spur gear mechanism. A simple device that can measure the work lost by friction only in teeth contacts was ...constructed. The test rig was designed to ensure measurements for two configurations with the same inertial characteristics but for different gear friction conditions. The principle is based on the difference of energy losses for the two mounting cases that provides the energy lost by friction between flanks. Recording the variation of the decreasing rotational speed for the case of constant actuating torque, the frictional losses can be deduced. The values of the efficiency obtained are smaller than in literature. The method is simple and rapid and the experimental results validate the theoretical model.
The study of the dynamical behavior of a system becomes really complex when friction forces are introduced in calculus since they directly depend on the values of the normal reactions and on the ...motion of the system, but the motion, at its turn, depends upon the forces from the system. The analysis is more difficult when dry friction, characterized by inequalities, is present between the parts of the system. When inequalities are involved in dynamical equilibrium equations, theoretically simultaneous equilibrium states may occur. In scientific literature there are famous examples supporting this statement. The present paper presents the dynamical study of a simple system, namely a ball obliged to roll in a groove with flat walls. It is proved experimentally that the motion of the ball is a planar one. The dynamical analysis of the system with planar motion leads to an undeterminate system of equations and therefore the spatial approach of the system is required. After writing the equations of the spatial motion of the ball, an incompatible system of equations is obtained.
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