This paper deals with the synchromesh behaviour of the manual car gearbox. Firstly, the state of the art on Borg-Warner-type synchronizers is presented. Then, the gear-changing process is studied and eight main operating phases are defined. The phases are described using classical tribological, mechanics, and thermodynamics theories. Models are interconnected to describe synchronizer behaviour and they are included in a numerical simulation software. Measured data are compared with the results of simulation software. Then, stick-slip phenomenon during gear changing is studied. Stick-slip is supposed to be present in two contact zones: sleeve splines and the synchronizer cone. The effects in both zones are discussed. Finally, the double bump phenomenon is studied. Double bump is assumed to be the maximum axial operating force coming from short successive phases at the end of the gear-changing process. Due to the angular integer division of splines and to the non-definite angular position of mechanical parts, sliding sleeve displacement into the ring and gear claw clutch splines gives secondary angular rotation and large increases in the axial operating force. The model can explain large variations and random dispersion of the measured double bump force peaks.
This paper, the first of two companion papers, proposes a general methodology for accurate modeling of the nonlinear behavior of ball and roller bearings. The models give stiffness matrices which can be introduced into standard finite element models of complex mechanical systems, with the aim of predicting mechanical behavior and load and strain distributions. In the case of an “isolated” ball bearing, the results obtained with the proposed approach are compared to results from the literature. Applications are implemented to evaluate the influence of external loadings on the stiffness matrices of tapered roller bearings mounted in a rigid mechanical environment.
From a practical point of view, in machining applications, chatter vibration constitutes a major problem during the cutting process. It is becoming increasingly difficult to suppress chatter during cutting at high speeds. Many investigators have regarded chatter vibrations as a “natural” phenomenon during the cutting process and a part of the process itself. In classical machining operations with thick-walled workpieces chatter vibrations occur when the cutting depth exceeds stability limits dependent on the machine tool. On the other hand, in the case of thin-walled cylindrical workpieces, chatter vibration problems are not so simple to formulate. The main purpose of this study is to qualify the dynamic behavior of a thin-walled workpiece during the turning process. It contains two parts: the cutting process simulation and the definition of experimental stability criteria. In the first part, a numerical model, which simulates the turning process of thin-walled cylindrical workpieces, is proposed. This model also permits obtaining workpiece responses to excitation generated by cutting forces. Finally, the stability of the process is discussed.
Chatter vibrations in the cutting process have a central place in many machining applications. A numerical and theoretical approach of self-excited vibrations during the turning process of thin-walled hollow workpieces has been presented in the accompanying paper. Furthermore, a finite element model has been proposed to simulate the dynamics of the system. The response to a Dirac excitation, presented as Nyquist curves, is proposed in order to characterize the dynamics of the turning process and the stability criterion. In this the second part of two related papers, the main objective is to validate the simulated dynamic behavior by using the experimental approach. The results of machining tests performed on thin-walled tubes with steel and aluminum alloys, using different operating conditions (dimensions, geometry and setting conditions) are presented and discussed.
A numerical method for the contact analysis of uniform tooth height epicyclical spiral bevel gears stemming from the Klingelnberg’s Cyclo-Palloid System is proposed. The analysis is based on simultaneous generations of gear surfaces and contact simulation. A theoretical contact identification program has been developed. Conjugated tooth contact is examined. Longitudinal settings of contact patterns or contact across the surfaces from tooth root to tooth top were obtained as a function of machine-settings. The influences of each cutting parameter were isolated and were discussed.
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