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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.

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.

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.

The existence of ball-raceway relative motion imposes the simultaneous occurrence of spinning motion about an axis parallel to the normal in the contact point and a rolling motion about an axis contained in the common tangent plane intersecting the axis of the ball bearing. For the separate characterization of the two friction torques - spinning and rolling moments, the devices to be used must be specially designed. For finding the spin torque or the rolling torque, the test-rigs used must contain a housing washer and a ball between which only spinning or rolling motion, respectively, exists. A test rig for evaluation of the spinning moment assumes ensuring the rotation motion about the normal in the contact point and additionally allows for estimation of the friction torque. The main inconvenience of such a device is the necessity of bearings capable to ensure a fixed position for the axis of rotation of the ball. The work proposes a simple and precise method for estimation of the spin moment by analyzing the motion of an axi-symmetric body that is in contact with the housing washer of a thrust ball bearing. The experimental data are interpolated using a parabolic function which is a function characteristic to the rotation motion with constant friction torque. The (constant) angular acceleration is found from the law of motion and together with the moment of inertia of the body is used in estimation of the spinning torque. This moment is assumed equal to the one found experimentally and thus results the value of the coefficient of friction from the contact area. The concordance between the value of the coefficient of friction obtained by the present method and the values from literature validates the proposed technique.

The swash plate mechanism is one of the most exploited mechanisms from technical applications due to its constrictive simplicity. The kinematical analysis supposes establishing the motion of the plunger as function of the motion of the plate and of the constructive characteristics of the mechanism. The work presents the kinematical analysis of the mechanism performed by two methods. In the first way, the mechanism is replaced by a mechanism with lower pairs to which the Hartenberg-Denavit procedure is applied. In the second way, the definition conditions of the pair of first class, plunger-plate, are used. The results are obviously identical for the two methods but for the second approach, the labour required for the analysis is significantly reduced. The main outcome of the paper refers to the scheme of kinematical solving of a mechanism. The type of pairs should be a criterion and for the higher pairs, the use of direct condition of the structural definition is recommended.

In rigid dynamics theory the gyroscope has a special role, as one of the bodies with the most complex motion, having three degrees of freedom. As consequence of the complexity of the motion is the fact that only for three situations, the equations of motion can be analytically integrated. For all the three situations, it is assumed that the principal moments of inertia (PMI) with respect to the principal axes that are normal to the rotation axes, are equal, condition fulfilled by the shape of body of revolution of the gyroscope. The paper analyses the case when the two principal moments of inertia are unequal. The equations of motion are numerically integrated for different values of the ratio between the two PMI. The effect of the disparity between the two PMI upon the motion of the gyroscope is proved by comparison with the motion of the axisymmetric gyroscope, both obtained by numerical integration.

The paper proposes a method of cutting by generating of spur gears using a rack cutter with a modified geometry. The analytical equations of the tooth profile of the modified rack-gear cutter are deduced, both for involute zone and for filleting region, based on the remark that the profile is the envelope of successive positions of the tool. The undercutting radius for the modified profile is obtained from a system of transcendental equations which requires and a numerical method for solving it. Compared to the standard profile, the differences are insignificant. A program was written and the profiles of the teeth are represented for two shifting coefficients, for the standard and the modified tooth profiles.

The paper presents the cutting by generating of spur gears using a rack cutter with a modified geometry. In order to find the geometry of the new spur gears, a proper programme has been developed. The geometry of this spur gear is compared with one of a gear with the same parameters but obtained with a standard rack cutter. The differences between the two gears are insignificant but the new tool has a simpler geometry and a higher durability.

The collision between polyurethane prismatic foam and a dropping steel ball is investigated experimentally. Because the foam presents large deformations, an analytical model is not available. The impact is studied on a test rig from laboratory, for dry foam and for the mineral oil wetted foam. The post impact velocity is found measuring the flight time and the coefficient of restitution and lost energy are estimated. For the dry impact case the damping effect is smaller than for the case of oil-wetted target.

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.