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DURABILITY IMPROVEMENT OF A CYLINDER HEAD IN CONSIDERATION OF MANUFACTURING PROCESS
Kim, B.,Chang, H.,Lee, K.,Kim, C. The Korean Society of Automotive Engineers 2007 International journal of automotive technology Vol.8 No.2
The durability of a cylinder head is influenced by the thermal and mechanical history during the manufacturing process, as well as engine operation. In order to improve the durability of cylinder head, both load from engine operation and the preload conditions from the manufacturing process must be considered. The aluminum cylinder head used for a HSDI diesel engine is investigated to reduce the possibility of high cycle fatigue crack in this study. FE analysis is performed to elucidate the mechanism of high cycle fatigue crack in the HSDI diesel cylinder head. Two separate approaches to increase the durability of the cylinder head are discussed: reducing load from engine operation and re-arranging preload conditions from the manufacturing process at the critical location of the cylinder head. Local design changes of the cylinder head and modification of pretension load in the cylinder head bolt were investigated using FE analysis to relieve load at the critical location during engine operation. Residual stress formed at the critical location during the manufacturing process is measured and heat treatment parameters are changed to re-arrange the distribution of residual stress. Results of FE analysis and experiments showed that thorough consideration of the manufacturing process is necessary to enhance the durability of the cylinder head.
ESTIMATION OF RESIDUAL STRESS IN CYLINDER HEAD
KIM B.,EGNER-WALTER A.,CHANG H. The Korean Society of Automotive Engineers 2006 International journal of automotive technology Vol.7 No.1
Residual stresses are introduced in aluminum cylinder head during quenching at the end of the T6 heat treatment process. Tensile residual stress resulted from quenching is detrimental to fatigue behavior of a cylinder head when it is overlapped with stresses of engine operation load. Quenching simulation has been performed to assess the distribution of residual stress in the cylinder head. Analysis revealed that in-homogeneous temperature distribution led to high tensile residual stress at the foot of the long intake port, where high stresses of engine operation load are expected. Measurements of residual stress have been followed and compared with the calculated results. Results successfully proved that high tensile residual stress, which was large enough to accelerate fatigue failure of the cylinder head, are formed during quenching process at the end of heat treatment at the same critical position. Effect of quenching parameters on the distribution of residual stress in cylinder head has been investigated by choosing different combination of heat treatment parameters. It was demonstrated that changes of quenching parameters led to more homogeneous temperature distribution during cooling and could reduce tensile residual stress at the critical region of the cylinder head used in this study.
Spiral-shaped electromagnetic bandgap structure for simultaneous switching noise suppression
Kim, B.,Kim, D.-W. IET 2009 Electronics letters Vol.45 No.5
<P>A spiral-shaped electromagnetic bandgap (EBG) structure is proposed to suppress simultaneous switching noise effectively when the power plane drives high-speed ICs. The new EBG structure is locally or periodically utilised on the power plane. Even with reduced unit cell size, its port-to-port transmission characteristic shows a much wider stopband than other conventional EBG structures.</P>