시간영역에서 과도 비틀림 진동에 의한 저속 2행정 디젤엔진의 축계 피로강도 평가

다국어 초록 (Multilingual Abstract)

Two stroke low speed diesel engines are widely used for marine propulsion or as power plant prime mover. These engines have many merits which includes higher thermal efficiency, mobility and durability. Yet various annoying vibrations occur sometimes in ships or at the plant itself. Of these vibrations, torsional vibration is very important and dictates a careful investigation during the engme's initial design stage for safe operation. With the rule and limit on torsional vibration in place, shaft strength fatigue due to torsional vibration however demands further analysis which possibly can be incorporated in the classification societies' rule and limit. In addition, the shaft's torsional vibration stresses can be calculated equivalently from accumulated fatigue cycles number due to transient torsional vibration in time domain. In this paper, authors suggest a new estimation method combined with Palmgren-Miner equation. A 6S70MC-C ($25,320ps{\times}91rpm$) engine for ship propulsion was selected as a case study. Angular velocity was measured, instead of shaft's strain, for simplified measurement and it was converted to torsional vibration stress for accumulated fatigue cycle numbers in shafting life time. Likewise, the accumulated fatigue calculation was compared with shaft fatigue strength limit. This new method can be further realized and confirmed in ship with two stroke low speed diesel engine.

참고문헌 (Reference)

1 Korean Register of Shipping, "Vibration of Shaftings, Rule Book Part 5 Chapter 4"

2 MAN B&W, "Vibration Characteristics of Two stroke Low Speed Diesel Engines"

3 Jenzer, J., "Vibration Aspect (Some vibration aspects of modern ship installations)"

4 Davies, P. D., "Torsional Vibration-Case Study of a Shaft Failure"

5 Dynamics Lab. of Mokpo National Maritime University, "Torsional Vibration Measurement of Hyundai-Samho Ship, Document No. MDL-06062"

6 Lee, D. C., "Theoretical Analysis about Transient Torsional Vibrations of Two Stroke Low Speed Diesel Engines" 830-835, 2002

7 Sasaki, S., "Recent Vibration Problems and Its Trend" 40 (40): 37-41, 2005

8 Stephens, R. I., "Metal Fatigue in Engineering" Jon Wiley Sons. Inc 2001

9 Germanischer Lloyd, "Harmonisation of Rules Regarding Vibration Analysis and Shafting Layout" 2002

10 International Association of Classification Societies, "Dimensions of Propulsion Shafts and Their Permissible Torsional Vibration Stresses" IACS 2005

11 Det Norske Veritas, "Calculation of Shafting in Marine Application" 2001