Contents of Journal of Mechanical Engineering 62, 2 (2011) 




DARULA, R., ŽIARAN, S.: An experimental study of optimal measurement 
point location for gear wheel state-of-wear measurements by means of 
vibro-acoustic diagnostics                                              61                                                      

RAMANUJAM, R., RAJU, R.: Process parameter optimization in turning of
Al-SiCp composites using Taguchi based desirability function
analysis                                                                81

KLAS, R., POCHYLÝ, F.: The modification of the mixed flow pump with 
respect to its stability                                                93

DRON, J. P., COUSINARD, O., BOLAERS, F., CHIEMENTIN, X.: Setting up 
a temporal method to identify shock bearing defects, using vibration 
analysis of a transfer press within automotive field                   105



Abstracts



An experimental study of optimal measurement point location for gear wheel state-of-wear measurements by means of vibro-acoustic diagnostics

R. DARULA, S. ŽIARAN

An experimental diagnostics of gearboxes, and especially diagnostics of a state-of-wear of its gear wheels by means of vibro-acoustic diagnostics, can be based on processing of vibration signal carrying sufficient information value of a fault level. If the signal is weak, information of interest can be masked by noise and thus not recognized. Therefore, a choice of optimal measurement point is one of key factors taken into account in a design of an experiment.
To demonstrate a procedure of an experimental search of the optimal measurement point, an FZG test rig, used for experimental verification of gear wheel designs, is investigated. The point is searched analysing a dominant vibro-acoustic signal transfer path using: (a) overall signal quantity - i.e. the RMS value of vibration signal measured; (b) local quantity - i.e. the RMS value of vibration analysed within the specific frequency band in the vicinity of the frequency of interest (in gear wheel state-of-wear measurements - in a vicinity of a tooth meshing frequency and its harmonics). It is shown that the geometry of the machine of interest plays an important role in the optimal measurement point search. The more complicated the geometry, the more useful is the experimental approach in the measurement point search. The procedure resented in the article can be generalized for any machine of interest.


Process parameter optimization in turning of Al-SiCp composites using Taguchi based desirability function analysis

R. RAMANUJAM, R. RAJU

This paper outlines an experimental study for the optimization of turning parameters of Al-10%SiCp metal matrix composites (AlSiC - MMC) using desirability function analysis (DFA). Machining parameters such as cutting speed, feed rate and depth of cut are optimized with multiple performance considerations, namely surface roughness and power consumption. L27 orthogonal array was used for conducting the experiments. The optimum machining parameters have been identified by a composite desirability value obtained from desirability function analysis as the performance index, and significant contribution of parameters can then be determined by analysis of variance. Confirmation test is also conducted to validate the test result. Experimental results have shown that machining performance can be improved effectively through this approach.


The modification of the mixed flow pump with respect to its stability

R. KLAS, F. POCHYLÝ

This paper is focused on the computational fluid dynamics (CFD) simulation of the mixed flow pump (i.e. radiaxial pump) with the aim to detect the reasons of Y-Q characteristic instability. The main reasons of pressure pulsations were detected by means of the analysis of velocity and pressure fields inside the pump combined with the theoretical approach. Consequently, the modifications of spiral case and pump suction area were made based on the knowledge of flow conditions and the shape of dissipation function. The primary design of pump geometry was modelled as the base model serving for the comparison of individual modification influence. The basic experimental data are available for this geometry. This approach replaced the more complicated and with respect to convergence of all computational tasks more difficult calculation for the compressible liquid flow. The modification of primary pump consisted in inserting the three fins types. Subsequently, the evaluation of pressure pulsations, specific energy curves and visualization of velocity fields were chosen as the criterions for successful design.


Setting up a temporal method to identify shock bearing defects, using vibration analysis of a transfer press within automotive field

J. P. DRON, O. COUSINARD, F. BOLAERS, X. CHIEMENTIN

This paper takes part of a research contract in which the objective is to provide a monitoring process by vibration analysis of bearings on the transfer shaft, within automotive field. Presses have a specialty to work at low speed and to generate a shock type signal with very important amplitude, as a consequence of the stamp that hides the vibration signature of different mechanical components of the machine. A methodology is introduced for the acquisition and the signals treatment, outcoming from a press, with the objective to diagnose the bearings of the transfer shaft. However, the signals resulting from accelerometer sensors are the results of a mixture of sources of vibrations, sources being able to be allotted to one or more defects and are generally polluted by noise. This work presents the three principal methods of denoising and the study of their influence on the scalar parameters (kurtosis, crest factor) within the framework of the detection of defects of the chipping types of bearings on a form press.