• 한국기계가공학회지
• /
• 제19권7호
• /
• pp.60-66
• /
• 2020

In order to improve fatigue life of transmission gear carburizing is normally used. Carburizing is a very good process to achieve low cost and high performance. The machined gears are heated up to carburizing temperature and then cooled rapidly in an oil bath to produce high surface hardness. The gears may undergo excessive thermal distortion during heating and rapid cooling. In order to predict the distortion during heating and rapid cooling, a coupled thermo-mechanical simulation is needed. In the current research, the simulation of heating and cooling was performed. The results show that the thermal distortion and the residual stresses are well predicted by the coupled simulation. In addition, induction heating and rapid cooling simulation is carried out to predict the thermal distortion. The amount of distortion is compared. It is shown that induction heating is very effective to reduce thermal distortion.

• 대한용접접합학회:학술대회논문집
• /
• 대한용접접합학회 2009년 추계학술발표대회
• /
• pp.96-96
• /
• 2009

The purpose of this study is to clarify the transitional behavior and main factor of excessive welding distortion caused by fabrication process of STS 304 vacuum vessel having double curvature for the efficient quality control of vacuum vessel. In order to do it, the predictive equations of the welding distortion in simple weldment of vacuum vessel were established by conventional finite element analysis. And the principal factor controlling the welding distortion was identified by evaluating the welding distortion of vacuum vessel in each fabrication process with FEA and simplified thermo elastic method. Based on the results, the principal factors of distortion of vacuum vessel were clarified as angular distortion and transverse shrinkage which are a source of excessive out-of plane distortion in the double curved vacuum vessel. It was expected that the FE analysis results of this study could contribute to establish the proper control method of welding distortion for double curved vacuum vessel.

• 대한용접접합학회:학술대회논문집
• /
• 대한용접접합학회 2004년도 춘계 학술발표대회 개요집
• /
• pp.234-236
• /
• 2004

The purpose of this study is to establish the predictive equation of welding distortion at the thick AA5083 alloy weldment. In order to do it, the extensive FE analysis was peformed to identify the principal factor controlling welding distortion. Based on the results, the predictive equations of transverse shrinkage and angular distortion at the thick AA5083 alloy weldment were formulated as the function of heat intensity (Q), in-plane(Di) and bending(Db) rigidity.

• 한국소음진동공학회논문집
• /
• 제18권4호
• /
• pp.473-479
• /
• 2008

With the advent of mobile phone, digital multimedia broadcasting(DMB) service is to be realized for multimedia data communication. For an acoustic part, a smaller and lighter microspeaker is also soon to be realized as an MP3 song player and a speakerphone. Sound quality in the microspeaker is becoming more important in mobile phones. It is evaluated by total harmonic distortion(THD). THD is the proportion of higher order frequencies output response to sinusoidal input signal. It is affected by uneven magnetic distribution and nonlinear response of diaphragm. In this paper, harmonic distortion is analyzed by considering magnetic and mechanical coupling effects. Simulated results of THD are compared with experimental data. Results show that THD in lower frequency range is higher due to high displace on voice coil and high mechanical response of high order frequency.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2008년도 춘계학술대회논문집
• /
• pp.236-241
• /
• 2008

With the advent of mobile phone, Digital multimedia broadcasting (DMB) service is to be realized for multimedia data communication. For an acoustic part, a smaller and lighter microspeaker is also soon to be realized as an MP3 song player and a speakerphone. Sound quality in the microspeaker is becoming more important in mobile phones. It is evaluated by total harmonic distortion (THD). THD is the proportion of higher order frequencies output response to sinusoidal input signal. It is affected by uneven magnetic distribution and nonlinear response of diaphragm. In this paper, harmonic distortion is analyzed by considering magnetic and mechanical coupling effects. Simulated results of THD are compared with experimental data. Results show that THD in lower frequency range is higher due to high displace on voice coil and high mechanical response of high order frequency.

• 전자공학회논문지B
• /
• 제32B권7호
• /
• pp.1003-1009
• /
• 1995

In This Paper, Linearization problem is discussed to reduce distortion of a nonlinear system based on Schetzen's pth-orfer inverse theorem. We propose a nonlinear adaptive prefiltering algorithm which can reduse nonlinear distortion up to pth order by tandemly connecting a pth-order Volterra filter before the nonlinear system under the consideration and by adjusting the filter coefficients adaptively. The feasibility of applying the proposed algorithm to a nonlinear system is conformed via computer simulation by observing significant reduction of total nonlinear distortion for the case of random input and sinusoidal input excitation.

• Journal of Welding and Joining
• /
• 제28권4호
• /
• pp.41-48
• /
• 2010

The purpose of this study is to establish the control method of the global bending distortion caused by fabrication process of hatch-cover in a container ship. In order to do it, the transitional behavior of global bending distortion in the deck of hatch-cover during fabrication process was measured by 3-dimensional measuring instrument. From the results, the principal factor controlling the global bending distortion was identified as the bending moment associated with the longitudinal shrinkage force and transverse shrinkage caused by welding and flame heating and the change of the centroid axis of hatch-cover in each fabrication process. Therefore, in this study, with the predictive equations of the longitudinal shrinkage force and transverse shrinkage caused by welding and flame heating and the simplified thermo elastic method, the predictive method for the global bending distortion was established and verified by comparing with the measured result. Based on the results, the amount of reverse bending distortion of main stiffeners was determined to prevent the global bending distortion of hatch-cover.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2007년도 제28회 춘계학술대회논문집
• /
• pp.339-345
• /
• 2007

입구유동 왜곡 상황에서 엔진의 성능 저하여부를 평가하기 위하여 입구유동 왜곡시험을 한국항공우주연구원에서 수행하였다. 본 논문에서는 입구압력 왜곡에 대한 시험만이 고려되었으며 입구왜곡 시험 기술의 절차를 개발하는 동안 엔진 시험용 시험 자료를 구축하기 위하여 다양한 시험 조건에서 다양한 왜곡용 스크린에 대한 설계와 평가를 거쳤다. 엔진 입구왜곡 시험 결과는 작동점이 성능저하를 일으키는 방향으로 변동하는 것을 보여주었으며 입구왜곡에 의한 엔진 성능의 저하 여부를 확인하였다.

• International Journal of Korean Welding Society
• /
• 제5권1호
• /
• pp.29-34
• /
• 2005

Finite element analysis (FEA) and experimental studies on an elastic bending method have been performed in order to control the angular distortion at the fillet weldment for curved panel. Process parameters for the elastic bending method such as clamping span and release time were analyzed with reference to welding condition and geometric effect of the curved panel, which can minimize or prevent the angular distortion by producing a proper skin stress to the fillet weldment. The amounts of the angular distortion decrease almost in a linear manner with an increase in the skin stress. The skin stress required for non-angular distortion at the fillet weldment is strongly dependent on the plate thickness, not the heat intensity applied. The clamping span for obtaining uniform skin stress was defined as functions of the plate thickness and length of the free edge. Clamp should be removed after the fillet weldment is cooled down to room temperature for non-angular distortion. Effectiveness of the elastic bending method established was verified by its application to an actual curved panel.

• Journal of Welding and Joining
• /
• 제21권5호
• /
• pp.518-524
• /
• 2003

The block assembly of ship consists of a series of heat processes such as cutting, bending, welding, residual stress relaxation and fairing. With the fast development of computers, the thermal elasto-plastic analysis method has become a versatile tool for practical applications in the ship production. If numerical analysis is proved to be an advantageous tool to predict the residual deformation due to various heat processes, the optimum methods which can remove the welding distortion can be presented at each assembly stage, which will result in great progress in improving the accuracy of block assembly. In order to minimize the weld-induced angular distortion in thick weldments, this paper proposes the optimum groove design for various plate thickness as the distortion control method. The validity of this method has been substantiated by a number of numerical simulations and experiments.