• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2001년도 춘계학술대회 논문집(한국공작기계학회)
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• pp.72-77
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• 2001

The use of hexagonal ceramic inserts for copper extrusion dies offers significant technical and economic advantages over other forms of manufacture. In this paper the data on the loading of the tools is determined from a commercial FEM package as the contact stress distribution on the die-workpiece interface and as temperature distributions in the die. This data can be processed as load input data for a finite element die-stress analysis. Process simulation and stress analysis are thus combined during the design, and a data exchange program has been developed that enables optimal design of the dies taking into account the elastic deflections generated in shrink fitting the die inserts and that caused by the stresses generated in the process. The stress analysis of the dies is used to determine the stress conditions on the ceramic insert by considering contact and interference effects under both mechanical and thermal loads.

• 한국공작기계학회논문집
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• 제10권2호
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• pp.79-88
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• 2001

This paper suggests to predict the failure of helical gear extrusion die. The basic assumption that constitutes the frame-work for any combined stress failure theory is that failure is predicted to occur when the maximum value of stress becomes equal to or exceeds the value of the same modulus that produces failure in a simple uniaxial stress test using the same material. The stresses which were calculated to each critical points are applied maximum normal stress theory and distor-tion energy theory. The theroretical analysis and experimental results for Samanta process and New process dies were com-pared.

• 한국생산제조학회지
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• 제9권3호
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• pp.76-82
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• 2000

It is well known that during the oxygen cutting process residual thermal stresses are produced in weldment. The local non-uniform heating and subsequent cooling which takes place during any welding process causes complex thermal strains and stresses to finally lead to residual stresses exceed to the yield stress. High tensile stresses combined with applied structural load in the region near the welded joint can given rise to distortion brittle fracture change of the fatigue strength and stress corrosion cracking. The appropriate treatment of the welded component which reduces the peak of he welding residual stresses is believed to lower risk of the fracture during the service of the structure. In this study the impact loading in oxygen cutting frame was applied to reduce the residual stress. After applying the impact loading redistribution of resid-ual stress was measured by cutting method and the effect of fatigue was tested.

• 대한기계학회논문집A
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• 제30권2호
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• pp.112-119
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• 2006

Due to their intrinsic anisotropy, composite materials show quite complicated damage mechanism with their fiber orientation and stacking sequence and especially, their fatigue damage process is sequential occurrence of matrix cracking, delamination and fiber breakage. In the study, to propose new model capable of describing damage mechanism under fatigue loading, fatigue analysis of composite laminates based on damage mechanics, are performed. The average stress is disassembled with stress components of matrix, fiber and interlaminar interface through stress analysis. Each stress components are used to assess static damage analysis based on continuum damage mechanics (C.D.M.). Fatigue damage curves are obtained from hysteresis loop and assessed by the fatigue damage analysis. Then, static and fatigue damage analysis are combined. Expected results such as stress-cycle relation are verified by the experimental results of fatigue tests.

• 대한기계학회논문집A
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• 제32권12호
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• pp.1123-1131
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• 2008

This paper provides V-factor estimation under combined mechanical and thermal load for circumferential cracks. Results are based on finite element analyses and effect of types and magnitudes of the thermal stress, crack geometry, the loading mode and plastic strain hardening on variations of the V-factor are investigated. The results of finite element analyses are compared with R6 values. As a result, it is shown that R6 gives generally conservative results. The conservatism is especially increased for the combination of large mechanical and thermal load. As a result, new estimation method which uses failure assessment line in R6 is proposed for V-factor and gives less conservative results.

• 소성∙가공
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• 제17권1호
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• pp.19-26
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• 2008

In the present work, the ratcheting behavior under uniaxial cyclic loading is analyzed. A comparison between the published and the results from the present model is also included. In order to simulate the ratcheting behavior, Two-Back Stress model is proposed by combining the non-linear Armstrong-Frederick rule and the non-linear Phillips hardening rule based on kinematic hardening equation. It is shown that some ratcheting behaviors can be obtained by adjusting the control material parameters and various evolutions of the kinematic hardening parameter can be obtained by means of simple combination of hardening rules using simple rule of mixtures. The ultimate back stress is also derived for the present combined kinematic hardening models.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1999년도 가을 학술발표회 논문집
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• pp.87-94
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• 1999

The structural behavior of welded steel box columns subjected to axial compression and combined load of axial and horizontal load is described. The nonlinear stress-strain relation of the material and residual stress resulted from welds were included in the analysis. Inelastic buckling analysis of hollow rectangular sections of various width-thickness and slenderness ratios was carried out using the semi-analytical and spline finite strip method to investigate the local and global bucking stress and mode interaction. The buckling stress was compared with test results and design curves. Post-buckling behavior was traced by the finite element program(ADINA) and compared with experimental results. The comparison showed that the ultimate stress can be used for the design purpose.

• Structural Engineering and Mechanics
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• 제58권4호
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• pp.689-705
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• 2016

The Drucker-Prager yield criterion is combined with an equilibrium equation to provide the elastic-plastic stress distribution within rotating annular hyperbolic discs and the residual stress distribution when the angular speed becomes zero. It is verified that unloading is purely elastic for the range of parameters used in the present study. A numerical technique is only necessary to solve an ordinary differential equation. The primary objective of this paper is to examine the effect of the parameter that controls the deviation of the Drucker-Prager yield criterion from the von Mises yield criterion and the geometric parameter that controls the profile of hyperbolic discs on the stress distribution at loading and the residual stress distribution.

• Clinical and Experimental Pediatrics
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• 제45권10호
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• pp.1251-1262
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• 2002

목 적 : 간질아동 부모들이 경험하는 스트레스 수준을 살펴보고 부모 및 아동의 특성과 부모가 겪는 스트레스의 관계를 파악하고자 하였다. 방 법: 부산 대구 경북지역 소재 4개 대학병원 간질클리닉에서 간질로 진단 치료를 받고 있는 간질 아동의 부모를 조사대상으로 구조화된 설문지를 이용한 면접조사 및 반송우편을 이용한 조사를 하였다. 결 과 : 간질아동 부모의 스트레스 수준은 그리 높게 나타나지는 않았으며, 간질아동 부모간에 스트레스 수준의 유의한 차이는 나타나지 않았다. 항경련제 종류의 수와 부모의 스트레스 수준간에는 상관관계를 보였고, 모의 경우에 간질아동을 양육하는 시간이 많을수록 스트레스가 증가하며, 아동의 나이가 어릴수록 모가 느끼는 스트레스가 높은 것으로 나타났다. 항경련제 종류의 수가 증가하거나 환아가 특수학교에 다니는 경우, 환아가 복합 간질을 가졌을 경우, 그리고 환아에게 장애가 동반되었을 때 부와 모 모두에서 스트레스가 높게 나타났다. 또한 모의 경우에는, 간질아동 양육 시간이 많은 경우, 환아의 나이가 어릴 경우, 경련의 빈도가 빈번할 경우, 그리고 아동의 갑작스러운 사망을 우려하는 경우에도 스트레스 수준이 높게 나타났고, 부의 경우에는 간질의 치료기간이 장기간일 경우에도 스트레스 수준이 높게 나타났다. 결 론 : 간질아동의 질병 관련 특성에 의하여 부모의 스트레스 수준이 좌우됨을 알 수 있었고, 주로 난치성 간질이나 장애를 동반한 'epilepsy-plus' 간질아동의 부모에게서 스트레스 수준이 높았으며, 이런 간질아동 부모들에 대한 사회심리학적 접근이 고려되어야 할 것으로 생각된다.

• Journal of Yeungnam Medical Science
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• 제20권1호
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• pp.36-44
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• 2003

Background: To evaluate the efficacy of EMG biofeedback and pelvic floor electrical stimulation in the stress urinary incontinence patients by Kontinence HMT2000. Materials and Methods: A group of 14 patients with stress urinary incontinence were treated with combined biofeedback and intravaginal electrical stimulation during 12 sessions from 2 weeks to 6 weeks. Results: At immediate post treatment, subjective cure rate was 28% and improvement rate was 57% and failure rate was 15%. Thus the overall success rate for this treatment was 85%. The result of 3 months after treatment showed cure rate 14% and improvement rate was 43%. Intravaginal pressure increased by an average of 11.9 cmH2O. Increased vaginal pressure was found in 93% of the patients and more than 50% increment of intravaginal pressure was 71%. Conclusions: Combined biofeedback and pelvic floor electrical stimulation by use of Kontinence HMT2000 is effective for the patients who have good compliance, relative low degree stress urinary incontinence. In order to attain good results, a well structured program that teaches specific muscle exercise and the patients should be followed by regular interval reinforcement treatment.