Metallurgical Analysis and Simulation of a Service-Fractured Compressor Blade Made of ASTM S45000 Alloy
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TECHNICAL ARTICLE—PEER-REVIEWED
Metallurgical Analysis and Simulation of a Service-Fractured Compressor Blade Made of ASTM S45000 Alloy Reza Derakhshandeh-Haghighi
Submitted: 15 December 2016 / in revised form: 20 February 2017 ASM International 2017
Abstract Blades are key components of gas turbine compressors which are frequently subjected to centrifugal and vibratory loads. These cyclic loadings result in degradation of physical and mechanical properties of the blades. Moreover, the blades operate at high temperature and in aggressive environments which makes monitoring their properties hard, and as a consequence their useful life service is limited. In order to prevent early and sudden failure of compressor blades, it seems rational to find out the reason for limited service life of the blades. Experimental and metallurgical investigations on a servicefractured compressor blade combined with blade simulation and stress analysis resulted in calculation of cycles for fatigue crack initiation and propagation and understanding of the sudden failure of the blade made of custom 450 alloy in this case study during service. Keywords Compressor blade Corrosion Fatigue Failure analysis Simulation Custom 450 alloy
Introduction Turbo machines have been widely used in heavy industries such as aviation, energy, oil refining, petrochemical, coal chemical, natural gas transportation, metallurgy and other important areas [1]. Compressor blades are required to resist high mechanical loads imposed by high rotational speed in the form of large centrifugal loads and aerodynamic forces applied as a function of pressure rise through each stage of R. Derakhshandeh-Haghighi (&) Department of Materials Science and Engineering, Shiraz Branch, Islamic Azad University, Shiraz, Iran e-mail: [email protected]
the compressor section [2]. The failures of blades as the key components of turbo machines result in significant economic losses. The common modes of failure in compressor blades is fatigue failure as a result of improper assembly, fretting, mechanical abnormalities induced during manufacturing or by foreign and internal object damage during engine operation [3–5]. Corrosion pits facilitate fatigue crack initiation and propagation [6, 7]. Research on blade failures, especially on fatigue fracture as the main failure mode, is necessary for designing, manufacturing and application of compressor blades. Environmental factors combined with external loads on the blades lead to their early failure. The fatigue life of a material with different crack sizes can be calculated by the models with the parameters under operational conditions. In the prediction of fatigue life of compressor blades, the operational conditions are poorly monitored in the research. However, those parameters can be simulated effectively by finite element analysis [8–10]. The objective of the present study is to investigate the reason for sudden and early failure of a gas compressor blade working about 34,000 h in a sea water environment by consi
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