• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2011년도 추계학술대회 논문집
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• pp.687-692
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• 2011

Experimental analysis has been carried out on noise reduction of subsonic jet flow with chevron nozzle to investigate relationships between geometry variation of chevron nozzles and jet noise reduction. Including base nozzle, seven nozzles are tested at Mach number 0.9. Parametric variables are chevron count, chevron length, and chevron shape. From these experiment, the more chevron count increase, the more jet noise reduction gain. Varying the chevron length, short chevron nozzle increase the jet noise at certain direction all the more. Chevron shape is also considered as important factor to reduce the jet noise.

• 소성∙가공
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• 제6권3호
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• pp.221-226
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• 1997

Chevron crack in cold extrusion has been studied in view of deformation conditions and material characteristics. There is V formed chevron crack is occasionally occurred in core part of shaft by multistage free extrusion. Although many research results were reported and theoretical analyses were accompanied, in this study we discussed practical method to prevent chevron crack in the field of working conditions and material characteristics. We have found that chevron crack is eliminated under condition of high hydrostatic state in deformation and decreased segregation, refinement of micro structure of materials.

• International Journal of Precision Engineering and Manufacturing
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• 제3권3호
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• pp.69-75
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• 2002

Measuring dynamic fracture toughness of brittle and small ceramic specimen is very difficult in a SHPB (Split Hopkinson Pressure Bar). As a countermeasure to this difficulty, a dynamic fracture toughness measuring method by the Chevron-notch ceramic specimen was proposed. Tested chevron specimens were of Chevron notch angles of 90$^{\circ}$, 100$^{\circ}$ and 110$^{\circ}$. Through finite element analysis, shape parameters of the Chevron-notch specimens according to notch angles were calculated. And the static fracture tough1ess of the Chevron-notch alumina specimen was measured as 3.8MPa√m similar to that of CT specimen with a precrack. Dynamic fracture toughness was 4.5MPa√m slightly higher than the static one. It was shown in this study that the proposed Chevron-notch specimens are valid to measure dynamic fracture toughness of extremely brittle materials such as ceramic.

• 한국철도학회논문집
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• 제4권4호
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• pp.123-130
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• 2001

A chevron rubber spring is used in primary suspension system for rail vehicle. The chevron spring support the load carried and reduces vibration and noise in operation of rail vehicle. The computer simulation using the nonlinear finite element analysis program MARC executed to predict and evaluate the load capacity and stiffness for the chevron spring. The appropriate shape and the material properties are proposed to adjust the required characteristics of chevron spring in the three modes of flexibility. Also, several samples of chevron spring are manufactured and experimented. It is shown that the predicted values agree well the results obtained from experiment.

• 한국추진공학회지
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• 제17권6호
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• pp.89-96
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• 2013

이젝터-디퓨저 시스템의 성능을 효과적으로 향상시키는 연구는 복잡성과 어려움을 고려하여 중요한 과제이다. 이 연구에서는, 성능 향상을 위해 이젝터-디퓨져 시스템의 이차유동 입구에 Chevron를 설치하여 재설계하였다. 이젝터 내부의 초음속 유동과 충격파를 모사하기 위해 Fluent를 사용하여 수치해석을 수행하였다. 주된 수치해석 결과로부터 Chevron은 이젝터 유동에 긍정적인 영향을 얻었다. 그리고 Chevron의 유무에 따라 이젝터 성능을 비교하였고, chevron의 최적 수는 성능 향상을 위해 설명하였다. 이젝터-디퓨져 시스템의 성능은 유인비, 압력회복 뿐만 아니라 전압손실 관점에서 분석하였다.

• 한국소음진동공학회논문집
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• 제27권2호
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• pp.162-167
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• 2017

The chevron rubber spring is used for subway vehicle as a primary suspension. Generally, the primary suspension has an influence to the running performance and not so much effect on the ride comfort in railway vehicle. But the stiffness of chevron spring is harder and harder as time goes on because of rubber characteristics. Therefore the dynamic characteristics such as ride comfort and derailment coefficient should be reviewed according to the stiffness variation of chevron rubber spring. In this paper the effect of chevron rubber spring on dynamic characteristics was studied by considering multi-body dynamics of railway vehicle on one straight line and seven curved lines.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2001년도 춘계학술대회 논문집
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• pp.186-192
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• 2001

A chevron rubber spring is used in primary suspension system for rail vehicle. The chevron spring has function which support the load carried and reduce vibration and noise in operation of rail vehicle. The computer simulation using the non-linear finite element analysis program MARC executed to predict and evaluate the load capacity and stiffness for tile chevron spring. The appropriate shape and material properties are proposed to adjust the required characteristics of chevron spring in the three modes of flexibility. Also, several samples of chevron spring are manufactured and experimented. It is shown that the predicted values agree well tile results obtained from experiments.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2011년도 춘계학술대회 논문집
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• pp.611-612
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• 2011

• 대한족부족관절학회지
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• 제10권2호
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• pp.234-237
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• 2006

Purpose: Authors analyzed and compared the treatment result of distal chevron osteotomy between with and without adductor tenotomy. Materials and Methods: 36 patients (60 feet) with a minimum follow-up of one year were involved in this retrospective study. The chevron osteotomy without adductor tenotomy was performed for 20 patients (30 feet) and chevron osteotomy with adductor tenotomy was done for 16 patients (30 feet). The first metatarsophalangeal (MTP) angle and angle between first and second metatarsal longitudinal axis (IM) was measured. The difference of these angles were measured pre-and postoperatively and compared using Student's T-test. Results: In the group of chevron osteotomy with adductor tenotomy, the mean first MTP angle corrected $29^{\circ}$ pre-operatively to $9^{\circ}$ and the mean first IM angle corrected $16^{\circ}$ pre-operatively to $12^{\circ}$. In the group of chevron osteotomy without adductor tenotomy the mean first MTP angle corrected $31^{\circ}$ pre-operatively to $11^{\circ}$ (P>0.05) and the mean first IM angle corrected $13^{\circ}$ pre-operatively to $11^{\circ}$ (P>0.05). Deep peroneal neuroma were found in 3 cases of chevron osteotomy with adductor tenotomy. Conclusions: Adductor tenotomy should be performed in selected patient with chevron osteotomy to prevent deep peroneal neuroma.

• Structural Engineering and Mechanics
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• 제64권3호
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• pp.301-310
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• 2017

For further development of passive control systems to dissipate larger seismic energy and prevent the structures from earthquake losses, this paper proposes an innovative two-level control system to improve behavior of chevron braced steel frames. Combining two Knee Braces, KB, and a Vertical Link Beam, VLB, in a chevron braced frame, this system can reliably sustain main shock and aftershocks in steel structures. The performance of this two-level system is examined through a finite element analysis and quasi-static cyclic loading test. The cyclic performances of VLB and KBs alone in chevron braced frames are compared with that of the presented two-level control system. The results show appropriate performance of the proposed system in terms of ductility and energy dissipation in two different excitation levels. The maximum load capacity of the presented system is about 30% and 17% higher than those of the chevron braced frames with KB and VLB alone, respectively. In addition, the maximum energy dissipation of the proposed system is about 78% and 150% higher than those of chevron braced frames with VLB and KB respectively under two separate levels of lateral forces caused by different probable seismic excitations. Finally, high performance under different earthquake levels with competitive cost and quick installation work for the control system can be found as main advantages of the presented system.