• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.3
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• pp.71-77
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• 2018

This paper suggests how to improve the fatigue strength of an axle shaft, which is the vulnerable part of an axle shaft system for a 3.5-ton commercial vehicle. The axle shaft is composed of a universal joint with a spider and yoke, yoke shaft, and so on. Structural analysis of the initial axle shaft was conducted to select the exact area for structural strength fatigue improvement, and as a result, the inner/outer yoke shaft and spider were selected. Four cases considered design variables, such as length and thickness, to verify the enhanced durability of the axle shaft, and fatigue analysis was conducted. Finally, we suggest that the axle shaft system satisfied the working conditions for a 3.5-ton commercial vehicle.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.5
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• pp.128-134
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• 2021

A press-fitted shaft is an essential part used in industrial machines, and it is generally used to transmit large quantities of power. Very high contact pressure occurs at the end parts of the contact between the shaft and boss, which are press-fitted shaft components. Such contact pressure not only damages the contact surface of a press-fitted shaft but also reduces its fatigue strength. To improve a press-fitted shaft's fatigue strength, the contact pressure on the contact surface, which directly affects the fatigue strength, should be minimized. Thus, in this study, the design configuration optimization of the end part of the boss was based on the approximate optimization method and was aimed at minimizing the contact pressure at the end of a press-fitted shaft. Comparison of the contact pressure and the contact stress of a conventional press-fitted shaft with those of the optimized press-fitted shaft showed that the boss design of the optimized press-fitted shaft effectively improved the fatigue life.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1031-1036
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• 2007

Torsional vibration analysis is necessary at design stage to ensure the reliability of a system particularly when the driven machine is a reciprocating compressor. This paper contains the results of torsional vibration analysis and fatigue strength evaluation for 540 kW compressor driving motor. Torsional vibration analysis showed that the $2^{nd}$ torsional mode of the entire shaft system has the possibility of resonance with the $14^{th}$ order excitation of compressor and twin line frequency of motor at operating speed. Therefore, the analyses were required to ensure the structural reliability of the motor. The fatigue strength was evaluated for the shaft and inner fans using the results of forced vibration analysis. It is concluded that the motor has sufficient fatigue strength under normal operating condition.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.7 no.3
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• pp.61-67
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• 1998

To find out the reason of fracture, specimens were made from the fractured winding shaft and the mechanical properties as well as their microstructures were investigated. Several heat treatments. including caburizing and tempering were carried out to improve the microstructure, mechanical properties, fatigue crack propagation and rotating bending fatigue characteristics. Through these experiments, following conclusions were obtained. (1) Carburized and tempered specimens showed greatly improved mechanical properties including impact energy, hardness and strength. (2) The fatigue strength of the carburized and tempered specimens increased more than twice than that of the original fractured winding shaft. (3) Crack propagation of the carburized and tempered specimens were faster than that of the original fractured speciens under the same △K. However, it is believed that, in the early stage, the fatigue crack initiation and growth for the carburized and tempered specimen is more difficult.

• Journal of Ocean Engineering and Technology
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• v.11 no.2
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• pp.28-38
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• 1997

The corrosion fatigue test was conducted in air to investigate the corrosion fatigue strength of SM 30 C steel by which was corroded in the under sea and surface in the conditions of 3.0% NaCl salt solution. The fatigue tests were carried out on a rotary bending testing machine of cantilever type. The corrosion effect of the sea surface conditionwas served more than that of the under sea condition which was due ti the periodic contact of air thus accelerate the corrosion. The difference of the fatgue strength between sea surface and under sea conditions decreased with increase of stree level and corroded period. Inthe case of the solid shaft and thickness 2mm of hollow shaft, the difference of corrosion fatigue strength decreased as stress level and corrosion periodic increasing. Onthe contrary in the case of thickness 1mm of hollow sgaft, the difference of it increased as stress level, corrosionn periooodic increasing and also the condition of corrosion chaanged. The main factors affecting the degradation of fatigue strength due to corrosion were the reduction of sectional area and the increase of surface roughness. The interference phenomenon increase with stress level got higher.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.8 s.185
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• pp.154-162
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• 2006

By laying its drum horizontally, front-loaded washing machine mostly used in Europe that uses the head of the water to launder was appropriate for washing only small amount of laundry. However, the demands of customers are requiring front-loaded washing machine to handle big capacity laundry as well, and have faster rotation speed to increase drying ability. To meet such demands, more stress from bending and twisting are complexly loaded onto the shaft supporting the horizontal drum, causing problems in fracture strength and fatigue life. Shafting system is mainly divided into flange and shaft. Flange is located between the drum and shaft, transferring power from the shaft to drum, and acting as a supporter of the back of the drum. Shaft is connected from the flange to insert production, transferring power from the motor to drum, and mainly acting as stiffness against the horizontal weight of the shafting system. In this paper, strength analysis and experiment were executed on both the shaft and flange of front-loaded washing machine to suggest the design improvement of shafting system for big capacity, high-rotation drying. Also, verification of this evaluation was executed on fracture strength and fatigue life for studied shaft system.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.7 s.124
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• pp.572-578
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• 2007

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.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1033-1038
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• 2003

A wind turbine obtains its power input by converting the force of the wind into a torque (turning force) acting on the rotor blades. The amount of energy which the wind transfers to the rotor depends on the density of the air, the rotor area, and the wind speed. Because it has long term operating life and very complex load condition, the fatigue strength of each component must be considered. In this paper, we calculated the load condition by wind using a combined blade elemental theory and a FEM based analytical approach was use to evaluate the fatigue strength of a Hub of wind turbine. The effect of tensile mean stress was taken into account by the modified Goodman diagram. Using this approaches, we evaluated the fatigue strength of hub and main shaft and improved the design.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.6
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• pp.567-573
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• 2017

The drive shaft of passenger vehicle has an important role in transmitting the torque between the power train system and the wheels. Torsional fatigue failures occur generally in the connection parts of the spline edge of the drive shaft, when there is significant fatigue damage under repeated twisting loads. A heat treatment, an induction hardening process, has been adopted to increase the torsional strength as well as the fatigue life of the drive shaft. However, it is still unclear how the extension of the induction hardening process in a used material relates to its shear-strain fatigue life range. In this study, a shear-strain controlled torsional-fatigue test with a specially designed specimen was conducted by an electro-dynamic torsional fatigue test machine. A finite element analysis of the drive shaft was carried out using the results obtained by the fatigue experiment. The estimated fatigue life was verified through a twisting load test of the real drive shaft in a test rig.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.2
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• pp.80-89
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• 1996

Fatigue life of a notched shaft was evaluated in order to estimate the durability and integrity of the notched shaft in design stage. Cumulative fatigue dama- ge analysis was performed using local strain approach based on the assumption that the fatigue life of a notched component is approximately same as that of a smooth specimen is subjected to the same strain at the notched component. In this paper, shafts with different notch root radius of 1, 2㎜ resulting in different values of stress concentration factors were tested under||rotating bending fatigue loading condition. Theoretical stress concentration factor for each notch type was calculated using finite element method. Fatigue life prediction program, FALIPS, written in C language was developed using the strain-life curve, and the local strain approach integrating Neuber's rule, cyclic stress-strain, and hysteresis loop equations. The fatigue life evaluated using the fatigue notch factor obtained from the experimentally determined fatigue strength showed very large scattering with nonconservatism, but the fatigue notch factors derived from the stress concentration factors and Peterson's equation reduced the considerablely accurate fatigue life evaluation within a factor of three.