Analisa Pengaruh Tekanan Dan Temperatur Ruang Bakar Terhadap Tegangan Pada Silinder Head Motor Diesel 4 Langkah 125 HP

Reverse engineering adalah salah satu metode dalam mendesain motor diesel, dimana motor diesel yang sudah ada digunakan sebagai referensi dalam membuat desain. Ruang bakar pada motor diesel menghasilkan tekanan dan temperatur tinggi yang dapat menyebabkan tegangan pada silinder head. Kerusakan fatal pada silinder head dapat terjadi karena tegangan yang terlalu besar. Maka dari itu, diperlukan analisa distribusi tegangan yang disebabkan oleh tekanan dan temperatur dari ruang bakar pada hasil desain silinder head. Pada penelitian ini dilakukan analisa tegangan mekanik, thermal, dan total (mekanik-thermal) dengan menggunakan Finite Element Method (FEA) serta pemilihan material, hingga diperoleh hasil desain silinder head yang optimum. ================================================================================== Reverse engineering is one of the methods to design the diesel engines, for instance the existing diesel engine is used as a reference to design the cylinder head. The combustion chamber of diesel engine produce high pressure and high temperature which can cause stress on the cylinder head. The worst damage is able to be occurred if the stress in cylinder head is very high. Because of that reason a research of stress distribution in cylinder head design caused by combustion chamber pressure and temperature is very important. In this research is analized about mechanical stress, thermal stress, and total stress (mechanics-thermal) using Finite Element Method (FEM) and materials selection. As the results of the research is found the optimum design of the cylinder head

Development of methodology for integrity assessment of air-cooled aircraft piston engine exposed to high-cyclic mechanical and thermal load

Istraživanje u ovoj disertaciji obuhvata kompleksnu analizu cilindarskog sklopa avionskog vazdušno hlađenog klipnog motora koji je otkazao usljed pojave prsline na glavi cilindra. Eksperimentalni dio istraživanja sastoji se od određivanja statičkih i dinamičkih karakteristika legure aluminijuma 242.0, kao sastavnog materijala glave cilindra, na sobnoj i na povišenoj temperaturi. Numerička analiza uključuje određivanje naponsko-deformacionog stanja cilindarskog sklopa na sobnoj i na povišenoj temperaturi, kao i analizu zamora navedenog sklopa na povišenoj temperaturi. Rezultati pomenutih analiza odnose se na utvrđivanje potencijalnog uzroka pojave prsline na glavi cilindra. Nastavak istraživanja podrazumijeva numeričko određivanje kritične vrijednosti faktora intenziteta napona i J-integrala. Modeliranjem prslina različitih dužina u glavi cilindra, te računajući za svaki pojedinačni slučaj vrijednosti faktora intenziteta napona i vrijednosti J-integrala, a poznavajući prethodno navedene kritične vrijednosti ovih parametara mehanike loma izvršena je procjena integriteta cilindarskog sklopa. U okviru istraživanja određen je ugao pravca propagacije prsline, kao i zavisnost brzine rasta prsline od opsega faktora intenziteta napona. Dobijeni rezultati su od velikog značaja za dalja istraživanja u oblasti mehanike loma i zamora vezana za problematiku pojave prsline i otkaza konstruktivnih elemenata izrađenih od legure aluminijuma 242.0, ali i od drugih materijala. Navedena metodologija u ovoj disertaciji može se primijeniti za procjenu integriteta bilo kog konstruktivnog elementa.The research in this dissertation consists of a complex analysis of the cylinder assembly of an air-cooled aircraft piston engine that failed due to a crack appearance on the cylinder head. Experimental part of the research consists of determination of the aluminum alloy 242.0 static and dynamic properties at room and at elevated temperature. This alloy is the constituent material of the cylinder head. Numerical analysis includes determining the stress-strain state of the cylinder assembly at room and at elevated temperature and fatigue analysis of the assembly at elevated temperature. The output of the aforementioned analysis refers to determination of the potential cause of the crack appearance on the cylinder head. The continuation of the research includes numerical determination of the critical values of the stress intensity factor and J-integral. By modeling the cracks of varying length in the cylinder head and considering the values of the stress intensity factors and the J-integral for each of the individual crack and knowing stress intensity factor and J-integral critical values mentioned above the integrity assessment of the cylinder assembly was performed. Within the research the crack propagation angle was determined, as well as the dependence of the crack growth rate on the stress intensity factor range. The results obtained are of great importance for further research in the field of fracture mechanics and fatigue related to the problem of cracking and failure of structural elements made of aluminum alloy 242.0, but also of any other material. The methodology that will be developed in this dissertation is able to be applied to estimate the integrity of any constructive element