FEM analysis of arch cast partials

This paper presents FEM analysis of arch cast partials. Functional tests of such prostheses were carried out. Loads and strains they are subject to were taken into account. An original, proprietary test stand was devised to test cast partials

Measurement system for testing the alar cast partials

The paper presented the issues related to the study of the alar cast partial. For this purpose, the author’s test station with a dedicated measurement system (with particular emphasis on its dynamics)

Vibroacoustic symptom of the exhaust valve damage of the internal combustion engine

Modern vehicles are equipped with highly developed electronic computer systems allowing diagnostics of control system elements, but – notwithstanding – deprived of the diagnostic function of purely mechanical defects. The reason of this situation is less and less number of breakdown vehicles. However, mechanical defects still occur, which is confirmed by the information from car repair workshops, and their too late finding increases repair costs. From the economic point of view, supplementing computer systems with diagnostics functions seems justified. The existence of such gap was the reason for undertaking several active experiments, aimed at explaining whether there is a possibility of improving the existing systems by an additional diagnostics function. The results of the possibility of applying quantitative estimation measures of the selected vehicle state are presented in the paper. Directions of further investigations and stages of diagnostic experiments, which would confirm the effectiveness of the proposed measures are provided in the hereby paper. This paper also constitutes the attempt of answering the question whether the similar algorithm application is possible in vehicles of the newest generation, equipped with adaptive systems of on board diagnostics

Time-varying group delay as a basis for clustering and segmentation of seismic signals

In this paper the applications of group delay in seismic vibration signals analysis are discussed. A method which bases on the autoregressive model with sliding-window is used to track volatility of signal’s properties in time. The analysis of time-frequency maps of group delay can be used in a process of distinguishing signals of different characteristics. Moreover, the method is robust for the different parameters of the sliding-window AR model. In the article applications of the time-frequency maps of group delay in a signal segmentation and clustering are also discussed. In seismic analysis an ability to distinguish signals with different seismic nature is very important, especially in case of safety in copper-ore underground mines. Creation of tools for revealing the origin of vibration will have positive impact on evaluation of hazard level

Analysis of vibration time histories in the time domain for propulsion systems of minesweepers

This paper presents the results of research carried out on the basis of vibration analysis for propulsion systems of ships used on the same basin. Six propulsion systems, identical in terms of mechanics, placed on three seagoing vessels, have been analyzed. The considered files have been divided into catalogues, separately for each measurement point, each direction, each rotational speed, and separately for usable and unusable shaft lines. Thus, it was possible to obtain vibration time histories of particular shaft lines for every combination point/direction/rotational speed. The mean value and standard deviation have been calculated separately for usable and unusable shaft lines and for each combination and each calculated characteristic. Next, the characteristic of time histories was calculated in the time domain: integral, mean value, energy, mean power (rms squared), simple moment of I order, simple moment of II order, central moment of I order, central moment of II order, normalized simple moment of I order, normalized simple moment of II order, normalized central moment of I order, normalized central moment of II order, as well as the abscissa of the signal square gravity center, variance of the signal square, the signal equivalent diameter. It has been established that the characteristic for standard deviation lower than 15 % of the mean value is of concentrated type. On this basis the abscissa of the signal square gravity center, variance of the signal square and the value of normalized correlation function have been determined. A module and the sum of standard deviations have been calculated from the difference of mean values for usable and unusable objects for each combination and characteristic. Basing on this, it has been determined whether a given characteristic is reliable, that is, whether the module from the difference of mean values is higher than the sum of standard deviations

Vibroactivity analysis of a dual fuel diesel engine based on the knock sensor signal and measuring pressure in the combustion chamber

A study conducted by a team of authors attempts to identify the occurrence of knocking based on the vibro-acoustic signal from the knock sensor and the signal from the pressure sensor glow plug (PSG). The reason the authors decided to discuss the issue is increasing interest in the use of information contained in the generated vibration and acoustic emissions as well as reducing acoustic emissions as one of the environmental threats. The adopted form of experiment and analysis enables determining the validity of testing of NVH multifuel engines. Information based on the vibro-acoustic signal allows to determine the qualitative and quantitative occurrence of the phenomenon of knocking in case of proper analysis. Both the energy spectrum of the vibration and the summation value of the successive bands of the spectrum confirm the occurrence of knock resulting from the analysis of the pressure in the combustion chamber and allow to relate to its intensity

Assessment of the vibroactivity level of SI engines in stationary and non-stationary operating conditions

Combustion engines are one of the main sources of vibration and noise in vehicles. The level of engine vibroactivity is affected by aspects such as rotational speed and technical condition. Tests were carried out as part of the research, designed to assess the level of vibroactivity of SI engines in stationary and non-stationary conditions. During the bench tests, the engine’s rotational speed and its technical condition were changed by simulating a slightly enlarged valve clearance. As a result of the experiments it was determined that local changes in the amplitude of engine vibrations caused by the combustion process, clearances or misfire can be used as diagnostic information about the condition of the engine. It has been shown that the local level of vibration is dependent on the point of measurement, the angle of the crankshaft rotation and valve timing, and that for diagnostic tests, measurements performed in stationary engine operating conditions are more useful. The tests have also shown how the change of engine condition affects the level of noise and vibration generated, and how these levels change during the acceleration of the engine

Application of alpha-stable distribution approach for local damage detection in rotating machines

In this paper a novel method for informative frequency band selection for local damage detection is presented. Local damage in bearings/gearbox provides specific vibration signature, i.e. train of impulses with cycle related to fault frequency. The proposed approach is based on the α-stable distribution, which is an extension of the Gaussian one. The choice of this distribution is motivated by its superiority towards other distributions when modeling impulsive data. We introduce here the new selector (to select informative frequency band) which is based on the stability parameter α. Moreover we propose also the new time-frequency maps based on the measures of dependence adequate for α-stable distribution, namely autocodifference and autocovariation maps. The introduced methodology is illustrated by analysis of simulated and real vibration signals from heavy-duty rotating machinery. The results prove that proposed approach allows detection of multiple damages in signal and location of informative frequency band related to these damages. Moreover the analyzed examples indicate the α-stable distribution approach for some cases can give better results in contrast to the classical methodology based on the spectral kurtosis

Some basic tips in vehicle chassis and frame design

The article describes important stage of the vehicle production, which is design of chassis and frames. There is some historical information for showing development in vehicle production. Many of vehicles properties are strictly connected with the chassis or frame. Dynamic properties and static or geometric parameters of the vehicle depends on chassis or frames. It was described an interesting method IPPD adopt to automotive industry. Also some examples of SSS for design concept in vehicle production have been depicted. Some short information about chassis and frames types used in special vehicles can be helpful for young engineers or technical students. These issues are very important for vehicle designers and engineers and has to be take into focused consideration in all productions processes, especially during assumptions and constructions of chassis or frames