No abstract

No abstract

The repeatability of the air-cooled piston engine cylinder assembly failure due to a crack in the cylinder head, as well as its severity from the aspect of crew and passenger safety were the main motives for our research. In this paper an integrity assessment of a cylinder assembly with a crack was performed. By modeling cracks of different lengths in the cylinder head and considering the values of stress intensity factors and J-integral values at a given crack length on the one hand and determining the critical values of these fracture mechanics parameters on the other hand, the stability of the crack was examined. As part of the research, the dependence of the crack length on the stress intensity factor was established. The methodology proposed in this paper can be adapted to assess the integrity of other similar structural elements.

Aluminum alloys are widely used in military and aviation industry due to their properties such as low density and high strength. During the aircraft operation there are mechanical failures of various structural components caused by numerous mechanisms such as corrosion, material defects, high cycle fatigue and the like. One of the frequent mechanical failures on air-cooled piston engines is the cylinder head cracking. This paper is the continuation a comprehensive research of the Lycoming IO-360-B1F aircraft cylinder head failure. The failure of this type has already occurred during flight and about 50 failures like this have been registered from around the world, some of them with a fatal outcome and therefore require detailed research. The paper consists of machining of the tested specimens and their testing at many different locations and in many different laboratories throughout Bosnia and Herzegovina, Serbia and Slovenia. This paper is based on a research that includes the experimental analysis of mechanical properties of Aluminum alloy 242.0 which is a constituent material of the cylinder head of the Lycoming IO-360-B1F aircraft engine on which a crack appeared. Based on chemical, metallographic, static and dynamic experimental tests of the material properties, Aluminum alloy 242.0 static and fatigue properties were obtained, S-N curve was formed and endurance limit was determined. Results of numerical simulations of experiments, confirmed by experimental results, were performed to make numerical procedures reliable due to further research. The results of the research are planned to be implemented in numerical modeling of the cylinder assembly stress-strain state under workload and in further numerical research of Lycoming IO-360-B1F cylinder assembly integrity assessment.

No abstract