T. Figlus

The Use of Denoising and Analysis of the Acoustic Signal Entropy in Diagnosing Engine Valve Clearance

The paper presents a method for processing acoustic signals which allows the extraction, from a very noisy signal, of components which contain diagnostically useful information on the increased valve clearance of a combustion engine. This method used two-stage denoising of the acoustic signal performed by means of a discrete wavelet transform. Afterwards, based on the signal cleaned-up in this manner, its entropy was calculated as a quantitative measure of qualitative changes caused by the excessive clearance. The testing and processing of the actual acoustic signal of a combustion engine enabled clear extraction of components which contain information on the valve clearance being diagnosed.

Application of a Continuous Wavelet Transform for the Diagnosing of Excessive Valve Clearance of the Combustion Engine

Combustion engines are the components of means of transport which during service are exposed to the occurrence of excessive clearances. The diagnosing of the condition of the engine requires developing methods which could be useful during both continuous and single checks of the engine. Application of measurements and acoustic signal processing may facilitate a quick diagnosis of the engine without any additional disassembly work. As part of the study, research was conducted to develop a non-invasive method of diagnosing excessive clearance of the combustion engine. Based on the recorded acoustic signals of the combustion engine and reference signals of the momentary crankshaft position, a method was developed to diagnose an increased valve clearance in the combustion engine. In this method, processing of the recorded acoustic signals by means of the continuous wavelet transform was applied together with a comparison of their instantaneous energy, depending on the crankshaft rotation angle and timing angles, as well as the scale parameters of time and frequency distributions.

MEASURING OF MECHANICAL RESISTANCES OF A HEAVY GOOD VEHICLE BY COASTDOWN TEST

Mechanical resistance consists of rolling tire resistance and power losses of vehicle drive train. Rolling resistance is done by deformation of vehicle tires on road surface. Power losses represent resistances of bearings and wheels rolling and oil wading. This resistance acts continuously during vehicle wheels rotation. The value of this driving resistance is possible to test by different methods. Laboratory tests on rotating drum or dynamometer are usually used. This paper deals about rare method – coastdown exterior driving test. It was done with a casual truck trailer set. Results of this test method show the value of this resistance forces which are converted into a coefficient of mechanical resistance and discussed in the point of view of rolling resistance coefficient values.

Failure Progress of 3D Reinforced GFRP Laminate during Static Bending, Evaluated by Means of Acoustic Emission and Vibrations Analysis

The work aimed to assess the failure progress in a glass fiber-reinforced polymer laminate with a 3D-woven and (as a comparison) plain-woven reinforcement, during static bending, using acoustic emission signals. The innovative method of the separation of the signal coming from the fiber fracture and the one coming from the matrix fracture with the use of the acoustic event’s energy as a criterion was applied. The failure progress during static bending was alternatively analyzed by evaluation of the vibration signal. It gave a possibility to validate the results of the acoustic emission. Acoustic emission, as well as vibration signal analysis proved to be good and effective tools for the registration of failure effects in composite laminates. Vibration analysis is more complicated methodologically, yet it is more precise. The failure progress of the 3D laminate is “safer” and more beneficial than that of the plain-woven laminate. It exhibits less rapid load capacity drops and a higher fiber effort contribution at the moment of the main laminate failure.