철도차량 차륜의 압축잔류응력 특성 및 마모한계 연구

김재영(Jae Young Kim),박상수(Sang Soo Park),김재문(Jae Moon Kim) 한국도시철도학회 2021 한국도시철도학회논문집 Vol.9 No.4

본 논문에서는 휠의 압축잔류응력이 휠의 마모한계에 대한 주요요인임을 증명하기 위한 연구를 수행하였다. 국내 철도차량의 강재 차륜(이하 차륜)에 대한 마모한계는 철도차량 제조사의 구조강도설계 측면에서 관리되어 왔으나 차륜의 잔류압축응력에 대한 연구는 미미한 실정이다. 차륜의 압연공정과 열처리과정에서 압축잔류응력의 발생 원리를 연구하였다. 그리고 압축잔류응력이 차륜의 피로파괴에 미치는 영향을 연구하고 압축잔류응력에 대한 표준규격과 검사방법을 고찰하였다. 이러한 연구 및 검토과정에서 압축잔류응력이 철도차량 차륜의 마모한계를 결정하는 주요 근거임을 입증하였다. In this paper, a study was conducted to prove that the compressive residual stress of the wheel is the main factor for the wear limit of the wheel. The wear limit for steel wheels (hereafter wheels) of domestic railway vehicles has been managed in terms of structural strength design by railway vehicle manufacturers, but studies in terms of the residual compressive stress of the wheels are insignificant. The principle of the generation of compressive residual stress in the rolling process and heat treatment process of the wheel was studied. In addition, the effect of the compressive residual stress on the fatigue failure of the wheel was studied, and the standard specifications and inspection methods for the compressive residual stress were considered. In the course of these studies and reviews, it was verified that the compressive residual stress is the main basis for determining the wear limit of the railway vehicle wheel.

5083-0 Al합금 鎔接材의 잔류응력에 관한 硏究

권관구(Gwan-Gu Gwon) 산업기술교육훈련학회 2012 산업기술연구논문지 (JITR) Vol.17 No.4

The purpose of this thesis was to investigate the welding characteristics and the residual stress behavior of SS41, commonly using power station, aircraft and ship. The experimented material was GMA welded in order to look over the residual stress distribution was measured under perfect restraint and nonrestraint welding conditions. From these test, we reached conclusion as followings ; The welding residual stress welded specimens was much higher in restraint condition than in nonrestraint. In case of restraint welding, the σx direction residual stress was measured the tensile residual stress. In case of nonrestraint welding, it was rapidly changed to compressive residual stress at about 15mm from welding bead center. In case of nonrestraint welding, the σy direction residual stress was measured the tensile residual stress. In case of restraint welding, it was changed to compressive residual stress at 40~45mm from welding bead center.

다중충돌 쇼트피닝에서 변형률 속도와 소재 경도가 잔류응력에 미치는 영향에 관한 연구

김태우(Tae Woo Kim),양조예(Zhao Rui Yang),나두현(Doo Hyun Na),이영석(Youngseog Lee) 대한기계학회 2011 大韓機械學會論文集A Vol.35 No.11

쇼트피닝 공정은 쇼트볼이 소재에 충돌을 일으킬 때 생기는 압축잔류응력에 의해 소재의 피로 강도를 향상 시키는데 그 목적이 있다. 본 연구는 변형률 속도 민감도 변화가 압축잔류응력에 미치는 영향을 분석하기 위해서 수행되었다. 본 연구자는 변형률 속도 민감도의 영향을 고려한 쇼트피닝 다중 충돌을 ABAQUS 6.9-1 를 사용하여 모사하였다. 사용된 소재는 AISI 4340 강종이다. 본 연구자는 변형률 속도 민감성이 높은 재료와 낮은 재료를 비교하였다. 결과적으로 변형률 속도 민감성이 증가하면 압축잔류응력은 감소하였다. 또한 경도가 낮은 소재의 압축잔류응력이 경도가 높은 소재보다 더 크게 발생하였다. Shot ball impacts to materials cause residual compressive stress on their surfaces. Improving the fatigue strength of a material that has this residual compress stress is the purpose of the shot peening process. A numerical study was performed to evaluate the effect of the strain rate sensitivity and hardness of the shot ball on the residual compressive stress. We calculated the residual compressive stress due to multiple impact shot peening using ABAQUS 6.9-1. AISI 4340 steel was the material used in this study. We compared the effects of high strain rate sensitivities and low strain rate sensitivities and found that when the material’s sensitivity to the strain rate increased, the residual compressive stress decreased. In addition, the residual compressive stress of low-hardness material is higher than that of high-hardness material.

TiNi/Al6061 형상기억복합재료의 고온에서의 손상거동에 대한 AE 특성

이진경,박영철,구후택 한국비파괴검사학회 2002 한국비파괴검사학회지 Vol.22 No.1

금속복합재료(MMC) 내부에서의 강화재와 기지재사이의 열팽창계수의 차이에 의해 발생하는 인장잔류응력은 복합재료의 인장강도를 저하시키는 심각한 문제중의 하나이다. 따라서 본 연구에서는 TjNi/Al6061 형상기억복합재료내부의 인장잔류응력의 문제를 해결하기 위하여 강화재로써 TiNi 합금을 사용하였다. TiNi 합금은 형상기억효과를 이용하여 복합재료내부에 압축잔류응력을 발생시킴으로써 인장강도를 증가시키는 역할을 한다. 복합재료내부에 압축잔류응력을 발생시키기 위하여 예변형(pre-strain)을 가하였다. 본 연구에서는 예변형의 변화에 따른 압축잔류응력의 영향을 평가하였으며 AE 기법을 이용하여 고온에서의 복합재료의 미시적 손상거동과 예변형의 영향을 평가하였다. It has been known that tensile residual stresses occurring by the thermal expansion coefficient mismatch between fiber and matrix is a cause of the weak strength of metal matrix composites(MMCs). In order to solve this problem, TiNi alloy fiber was used as a reinforced material in TiNi/Al6061 shape memory alloy composite in this study. TiNi alloy fiber improves the tensile strength of the composite by causing compressive residual stress in matrix on the basis of its shape memory effect. Pre-strain was imposed to generate the compressive residual stresses inside the TiNi/Al6061 shape memory alloy composites. AE technique was used to quantify the microscopic damage behavior of the composite at high temperature. The effect of applied pre-strains on the AE behavior was also evaluated.

Shot peening 가공에 의한 노치재의 응력분포와 피로강도의 개선

이승호,김희송 한국공작기계학회 1998 한국생산제조학회지 Vol.7 No.5

Second step shot peening was applied on both smooth specimen and U-notch specimen in order to investigate the stress distribution and the improvement in fatigue strength. Various experiments and measurements such as rotary bending fatigue test and the measurement of compressive residual stress were performed. The results showed that the fatigue strength of second step shot peened specimens increased by 34 percent compared to that of unpeened ones. Compressive residual stress also considerably increased, which resulted in the increase of fatigue strength. Finite element analysis showed that shot peening is effective decreasing the bending stress by external force. The effectiveness of shot peening reducing the compressive residual stress was anticipated by the superposition of the concentrated stress and the compressive residual stress.

스프링강의 피로파괴에 미치는 압축잔류응력의 영향

진영범(Young-Beom Jin),박경동(Keyung-Dong Park) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.4

Recetly the steel parts used for automiles and trains are required to be used under higher stress than ever before in need of the weight down. However, there are a lot of problems with developing such materials that require expensive tools, and a great deal of time and effort. Therefore, the improvement of fatigue strength and fatigue life are mainly focused on by adopting residual stress. And got the following characterisics from crack growth test carried out stress ratio. Fatigue life shows more improvement in the Un-peening material. And compressive residual stress of surface on the Shot-peening processed operate resistance force of fatigue. So we cam obtain fallowings. (1) The fatigue crack growth rate on stage Ⅱ is conspicuous with the size of compressive residual stress and is dependent on Paris equation. (2) Although the maximum compressive residual stress is deeply and widely formed from surface, fatigue life does not improve than when maximum compressive residual stress is formed in surface. (3) The threshold stress intensity factor range is increased with increasing compressive residual stress.

다중충돌 쇼트피닝에서 변형률속도와 쇼트볼 경도가 잔류응력에 미치는 영향에 관한 연구

김태우(TAEWOO KIM),이영석(YOUNGSEOG LEE) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11

When a shot ball impacts with material, residual compress stress occurs. Improving fatigue strength of material with this residual compress stress is the purpose of shot peening process. Numerical study was performed to evaluate the effect of strain rate on the residual compressive stress. We calculated the residual compressive stress of shot peening multiple impact using ABAQUS with strain rate. Shot ball was deformable body. Material used in this study was AISI4340 steel. There were two method as follow. i) higher sensitivity of strain rate ii). lower sensitivity of strain rate. we compared residual compressive stress of two method. when sensitivity of strain rate increased, residual compressive stress is less. there are same material with yield stress, the sensitiveness of strain rate has a strong influence on residual compressive stress.

스프링강의 피로크랙 진전거동에 미치는 압축잔류응력의 영향

박경동(Keyoung-Dong Park),정찬기(Chan-Gi Jung) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.3

Nowadays, many components used in machinery industry is required lightness and high strength. Therefore, the effects of compressive residual stress by shot-peening which is method to improve fatigue lift of (JISG SUP-9), which used in suspension of automobile, on fatigue crack growth characteristics was investigated with considering fracture mechanics. So, we can obtain followings. (1) The fatigue crack growth rate on stage Ⅱ is conspicuous with the size of compressive residual stress and is dependent on Paris equation. (2) Although the maximum compressive residual stress is deeply and widely formed from surface, fatigue life does not improve than when maximum compressive residual stress is formed in surface. (3) The threshold stress intensity factor range is increased with increasing compressive residual stress. (4) In fracture surface of fatigue crack growth it is investigated that compressive residual stress remarkably retards fatigue crack growth.

압축잔류응력이 차량용 스프링강(SUP-9)의 파괴인성에 미치는 영향

박원조(WonJo Park),김추용(ChoYong Kim),허선철(SunChul Huh),이광영(KwangYoung Lee) 한국자동차공학회 2004 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-

Recently, many components used in machinery industry demand lightness and high strength. The shot-peening method is used in order to improve fatigue life of spring steel(SUP-9) which is used in suspension of automobile. The compressive residual is induced in shot-peening process. This paper investigated the effect of the compressive residual stress on the fracture toughness. The test of Fracture toughness had been conducted at room temperature, high temperature(100℃, 200℃) and low temperature(-60℃, -100℃) from SUP-9 Steel was process by shot-peening. so we survey fractography of SUP-9 Steel by SEM.

압축잔류응력 분포에 따르는 무해한 균열 크기 평가

김민헌(Min-Heon Kim),박환성(Hwan-Seong Park),김동규(Dong-Kyu Kim),남기우(Ki-Woo Nam) 대한기계학회 2019 대한기계학회 춘추학술대회 Vol.2019 No.11

This study is to evaluate the harmless crack size according to the compressive residual stress as a basic study to evaluate the safety of hydrogen storage tank. The harmless crack dimension depends on the residual stress and the crack aspect ratio(As). As = 1.0 and 0.6 were determined as crack depth at large residual stresses and crack lengths at medium and small residual stresses. As = 0.3 was determined as the crack depth regardless of the magnitude of the residual stress. The harmless crack size by shot peening was different depending on the residual stress and the crack aspect ratio.