Piston scuffing fault and its identification in an IC engine by vibration analysis Ashkan Moosavian a,b , G. Najafi a,⇑ , Barat Ghobadian a , Mostafa Mirsalim b , Seyed Mohammad Jafari b , Peyman Sharghi b a Biosystems Engineering Department, Tarbiat Modares University (TMU), Jalale-E-Aleahmad Highway, Tehran, Iran b Workshops, Engine and Vehicle Labs Unit, Irankhodro Powertrain Company (IPCO), Tehran, Iran article info Article history: Received 4 April 2015 Received in revised form 15 August 2015 Accepted 7 September 2015 Keywords: Piston scuffing fault Engine Vibration analysis Continuous wavelet transform Fault diagnosis Three-body abrasive wear mechanism abstract In this paper, the effects of piston scuffing fault on engine performance and vibrations are investigated. A procedure based on vibration analysis is also presented to identify piston scuffing fault. To this end, an internal combustion (IC) engine ran under a specific test procedure. The engine parameters and vibration signals were measured during the experiments. To produce piston scuffing fault, three-body abrasive wear mechanism was employed. The experimental results showed that piston scuffing fault caused the engine performance to reduce significantly. The vibration signals were analyzed in time-domain, frequency-domain and time–frequency domain. Continuous wavelet transform (CWT) was used to obtain time–frequency representations. ‘‘dmey” wavelet was selected as the optimum wavelet type for this research among different wavelet types using the three criteria of energy, Shannon entropy and energy to Shannon entropy ratio. The results of CWT analysis by ‘‘dmey” wavelet showed that piston scuffing fault excited the frequency band of 2.4–4.7 kHz in which the frequency of 3.7 kHz was affected more. Finally, seven different features were extracted from the engine vibration signals related to the frequency band of 2.4–4.7 kHz. The results indicated that maximum, mean, RMS, skewness, kurtosis and impulse factor of the engine vibration related to the found frequency band increased significantly due to piston scuffing fault. The obtained results showed that the proposed method identified piston scuffing fault and discovered the vibration characteristics of this fault like frequency band. The results also demon- strated the possibility of using engine vibrations in piston scuffing fault identification. Ó 2015 Elsevier Ltd. All rights reserved. 1. Introduction Scuffing is gross damage in which local welds are formed between the sliding surfaces [1]. When two sliding metallic sur- faces contact and rub to each other, the friction and temperature of the area between these surfaces increase dramatically. High temperature in contact area and also the existence of structural weakness which could happen during production process cause the deterioration of the material strength [2]. Due to contact stres- ses acted to the sliding surfaces, plastic deformation occurs in materials, plastic flows are activated in layer and sub-layers, and materials go into liquid–solid phase [2]. As the result of reciprocat- ing sliding and generation of adhesion forces, softened materials detach from the surface and stick to the opposite surface, means mutual material transfer occurs. In this situation, some chemical interactions take place between the stuck materials in the presence of lubricant [2,3]. The result of this process is formation of harder and rougher layers on the two sliding surfaces. If the contact between the sliding surfaces continues, the described process will progress with an increasing rate. Scuffing fault could occur in all sliding mechanisms such as gears and piston/cylinder. When scuffing fault occurs in the piston and cylinder of an engine, it is called piston scuffing fault. This fault is among the main piston failures in both spark-ignition (SI) and compression- ignition (CI) engines which is a result of wear mechanism. There are three important wear mechanisms namely corrosion, abrasion and adhesion [4]. Abrasion occurs during the running-in period of engine which is a dominant wear mechanism for piston/cylinder system. Abrasive wear is damage to a component surface caused by the motion of a harder surface or hard particles trapped at the interface. There are two types of abrasive wear, namely, two- body and three-body abrasive wear. Two-body abrasion takes place when a hard surface slides on a softer counter surface. When wear is produced by free hard particles trapped at the area http://dx.doi.org/10.1016/j.apacoust.2015.09.002 0003-682X/Ó 2015 Elsevier Ltd. All rights reserved. ⇑ Corresponding author at: P.O. Box: 14115-111, Iran. Tel.: +98 21 48292322; fax: +98 21 48292200. E-mail address: g.najafi@modares.ac.ir (G. Najafi). Applied Acoustics 102 (2016) 40–48 Contents lists available at ScienceDirect Applied Acoustics journal homepage: www.elsevier.com/locate/apacoust