• Title/Summary/Keyword: Peening

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Damage Analysis of Leaf Spring for Transport Utility Vehicles (운송 차량용 판 스프링의 파손 해석)

  • Kim, Tae-Song;Kang, Seok-Hee;Kwon, Yung-Kug;Yun, Seo-Hyun;Nam, Ki-Woo
    • Journal of the Korean Society of Industry Convergence
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    • v.25 no.6_2
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    • pp.1047-1053
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    • 2022
  • The leaf spring for a truck absorbs shocks or vibrations from the road surface while driving with the elastic force of the material and prevents the shock from being transmitted to the vehicle body. It is subjected to cyclic stress, and fatigue fracture occurs frequently. This study analyzes fractured leaf spring from a 25 ton truck that has been operating for about a year. In the fractured portion, which is the origin of crack, inclusions were observed, and fatigue failure was caused by cyclic stress. In the stress calculation and FE analysis, the stress at the center of the leaf spring was obtained to be 54~65% of the yield strength of the base material and damaged material. It is most important to prevent the mixing of impurities in the steel manufacturing for leaf springs. The large stress portion of the leaf spring needs to introduce compressive residual stress by peening etc.

Evaluation of Harmless Crack Size according to Residual Stress Depth of Induction Hardened SCM440 Steel (유도경화한 SCM440 강의 잔류응력 깊이에 따르는 무해화 균열 크기 평가 )

  • Jong-Kyu Park;Ki-Hang Shin;Byoung-Chul Choi;In-Duck Park;Ki-Woo, Nam
    • Journal of the Korean Society of Industry Convergence
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    • v.26 no.4_2
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    • pp.571-576
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    • 2023
  • In this study, the harmless crack size(ahml) according to the residual stress depth was evaluated using the fatigue limit of SCM440 steel by quenching-tempering(QT) and induction hardening(IH), and threshold stress intensity factor of QT steel. Because the residual stress increased rapidly as the crack depth increased, ahml was determined at the depth of all the crack aspect ratio(As) regardless of Type I-III, and ahml also increased according to the residual stress depth. ahml was minimal at As=1.0 and maximal at As=0.1, but was almost similar on each Type. ahml was small the dependence on As.

A study on the Fracture of Coil Spring (파쇄기용 코일스프링의 파손에 관한 연구)

  • Jeong, Hyung-Sik;An, Se-Won;Lee, Jong-Hyung;Choi, Seong-Dae
    • Journal of the Korean Society of Industry Convergence
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    • v.9 no.1
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    • pp.51-59
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    • 2006
  • The study is diagnosis about fatigue failure phenomenon of heating coil spring (sup9) and heat treatment method that is used to crusher. Because more than 80~90% of damage announcement of breakdown of machine and construction is been caused in fatigue present state, fatigue failure became important leading person at design. Calculated design load is imposed repeatedly that fatigue breakdown is safe. Is phenomenon that change load is imposed in the construction continuously. Used coil spring applies heat 30minute by Quenching temperature $860^{\circ}C$ if see manufacturing process and temperature of gasoline of $50^{\circ}C$ keep after quench that know tempering a $460^{\circ}C$ 90minute a product be. If doto apply heat $950^{\circ}C$ material at rolling process historically before quenching, austenite formation clay pipe being done AGS(Austenite Grain Size) by 2.5~4 become. Apply heat quenching 30minute by $820^{\circ}C$ by improvement method and after quench that keep $50^{\circ}C$ in oil tempering if do $450^{\circ}C$, 90minute spring ideal formation sorbite formation of the river form and condition that satisfy most more than AGS 7 appeared. Also, we can secure authoritativeness through MT since shot peening processing.

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A Study of Fatigue Crack Growth Behaviour for Ferrite-Bainite Dual Phase Steel (Ferrite-Bainite dual phase 강의 피로균열진전 특성 평가)

  • Kim, Deok-Geun;Cho, Dong-Pil;Oh, Dong-Jin;Kim, Myung-Hyun
    • Journal of Welding and Joining
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    • v.34 no.1
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    • pp.41-46
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    • 2016
  • With the recent increase in size of ships and offshore structures, there are more demand for thicker plates. As the thickness increases, it is known that fatigue life of the structures decrease. To improve the fatigue life, post weld treatments techniques, such as toe grinding, TIG dressing and hammer peening, are typically employed. However, these techniques require additional construction time and production cost. Therefore, it is of crucial interest steels with longer fatigue crack growth life compared to conventional steels. This study investigates fatigue crack growth rate (FCGR) behaviours of conventional EH36 steel and Ferrite-Bainite dual phase EH36 steel (F-B steel). F-B steel is known to have improved fatigue performance associated with the existence of two different phases. Ferrite-Bainite dual phase microstructures are obtained by special thermo mechanical control process (TMCP). FCGR behaviours are investigated by a series of constant stress-controlled FCGR tests. Considering all test conditions (ambient, low temperature, high stress ratio), it is shown that FCGR of F-B steel is slower than that of conventional EH36 steel. From the tensile tests and impact tests, F-B steel exhibits higher values of strength and impact energy leading to slower FCGR.

Variation of Axial Tension-Compression Fatigue Characteristics by UNSM on Ti-6Al-4V (Ti-6Al-4V재의 UNSM처리에 의한 축인장압축피로특성변화)

  • Suh, Chang-Min;Cho, Sung-Am;Pyoun, Young-Sik;Suh, Min-Soo
    • Journal of Ocean Engineering and Technology
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    • v.25 no.6
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    • pp.42-48
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    • 2011
  • The present study makes three original contributions to nanoskinned Ti-6Al-4V materials. The nanoskins were fabricated on Ti-6Al-4V material using various surface treatments: deep rolling (DR), laser shot peening (LSP), and ultrasonic nanocrystal surface modification (UNSM). These surface treatments are newly developed techniques and are becoming more popular in industrial fields. A fatigue strength comparison at up to 106 cycles was conducted on these nanoskinned Ti-6Al-4V materials. Fatigue tests were carried out using MTS under axial loading tension-compression fatigue (R = -1, RT, 5 Hz, sinusoidal wave). The analysis of the crack initiation patterns in the nanoskinned Ti-6Al-4V materials found an interior originating crack pattern and surface originating crack type. Microscopic observation was mainly used to investigate the fatigue fractured sites. These surface modification techniques have been widely adopted, primarily because of the robust grade of their mechanical properties. These are mainly the result of the formation of a large-scale, deep, and useful compressive residual stress, the formation of nanocrystals by the severe plastic deformation (SPD) at the subsurface layer, and the increase in surface hardness.

Effect of Rotating Speed and Air Flow Rate on Material Removal Characteristics in Abrasive Fluidized Bed Machining of Polyacetal (폴리아세탈의 입자유동베드 가공에서 회전속도와 공기 유량이 재료제거 특성에 미치는 영향)

  • Jang, Yangjae;Kim, Taekyoung;Hwang, Heondeok;Seo, Joonyoung;Lee, Dasol;Lee, Hyunseop
    • Tribology and Lubricants
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    • v.33 no.5
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    • pp.214-219
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    • 2017
  • Abrasive fluidized bed machining (AFBM) is similar to general abrasive fluidized machining (AFM) in that it can perform polishing of the outer and inner surfaces of a 3-dimensional shape by the flow of particles. However, in the case of AFM, the shear force generated by the flow of the particles causes material removal, while in AFBM, the abrasive particles are suspended in the chamber to form a bed. AFBM can be used for deburring, polishing, edge contouring, shot peening, and cleaning of mechanical parts. Most studies on AFBM are limited to metals, and research on application of AFBM to plastic materials has not been performed yet. Therefore, in this study, we investigate the effect of rotating speed of the specimen and the air flow rate on the material removal characteristics during AFBM of polyacetal with a horizontal AFBM machine. The material removal rate (MRR) increases linearly with increase of the rotating speed of the main shaft because of the shear force between the particles of the fluidized bed and the rotation of the workpiece. The reduction in surface roughness tends to increase as the rotating speed of the main shaft increases. As the air flow rate increases, the MRR tends to decrease. At a flow rate of 70 L/min or more, the MRR remains almost constant. The reduction of the surface roughness of the specimen is found to decrease with increasing air flow rate.

Variation of Fatigue Properties in Nanoskinned Ti-6Al-4V - Rotating Bending and Axial Loading Tension-Compression Cycle - (Ti-6Al-4V 재의 UNSM 처리에 의한 피로특성변화 - 회전굽힘 피로시험과 축하중 인장압축 피로시험 비교 -)

  • Suh, Min-Soo;Pyoun, Young-Shik;Suh, Chang-Min
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.36 no.4
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    • pp.443-449
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    • 2012
  • Nanoskins were fabricated on a Ti-6Al-4V material by carrying out various surface treatments, i.e., deep rolling, laser shot peening, and ultrasonic nanocrystal surface modification (UNSM). These surface treatments are newly developed techniques and are becoming more popular for industrial applications. Fatigue tests were carried out using material test system (MTS); these tests included the axial loading tension-compression fatigue test (R = -1, RT, 5 Hz, sinusoidal wave) and rotating bending fatigue test (R = -1, RT, 3200 rpm). The analysis of the crack initiation pattern in the UNSM-treated material indicated that the crack was interior originating in the axial loading tension-compression cycle, and was surface originating in the bending fatigue test. UNSM treatment significantly improved the fatigue strength for the regime of above $10^6$ cycles that S-N curve of rotating bending stress clearly show the performance of a 5 mm titanium specimen after UNSM treatment is similar to that of an untreated 6 mm titanium specimen.

Effect of cavitation on surface damage of 16.7Cr-10Ni-2Mo stainless steel in marine environment (해양 환경 하에서 16.7Cr-10Ni-2Mo 스테인리스강의 표면 손상에 미치는 캐비테이션의 영향)

  • Chong, Sang-Ok;Han, Min-Su;Kim, Seong-Jong
    • Corrosion Science and Technology
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    • v.14 no.5
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    • pp.239-246
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    • 2015
  • Stainless steel is generally known to have characteristics of excellent corrosion resistance and durability, but in a marine environment it can suffer from localized corrosion due to the breakdown of passivity film due to chloride ion in seawater. Furthermore, the damage behaviors are sped up under a cavitation environment because of complex damage from electrochemical corrosion and cavitation-erosion. In this study the characteristics of electrochemical corrosion and cavitation erosion behavior were evaluated on 16.7Cr-10Ni-2Mo stainless steel under a cavitation environment in natural seawater. The electrochemical experiments have been conducted at both static conditions and dynamic conditions inducing cavitation with different current density parameters. The surface morphology and damage behaviors were compared after the experiment. After the cavitation test with time variables morphological examinations on damaged specimens were analyzed by using a scanning electron microscope and a 3D microscope. the galvanostatic experiment gave a cleaner surface morphology presented with less damage depth at high current density regions. It is due to the effect of water cavitation peening under the cavitation condition. In the cavitation experiment, with amplitude of $30{\mu}m$ and seawater temperature of $25^{\circ}C$, weight loss and cavitation-erosion damage depth were dramatically increased after 5 hours inducing cavitation.

Effect of cavitation for electrochemical characteristics in seawater for austenitic 304 stainless steel (오스테나이트계 STS 304강의 해수 내 전기화학적 특성에 미치는 캐비테이션의 영향)

  • Kim, Seong-Jong;Lee, Seung-Jun;Chong, Sang-Ok
    • Journal of Advanced Marine Engineering and Technology
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    • v.37 no.5
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    • pp.484-492
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    • 2013
  • With the industrial acceleration in a lot of countries of the world, the demand for anti-corrosion and anti-abrasion material increases continuously. Particularly, stainless steel with the fine surface and excellent corrosion resistance is widely used in various industrial fields including ship, offshore structures tidal power plant, and etc. In marine environment, however, it is easy to generate by the corrosion damage by $Cl^-$ ion and cavitation damage due to high rotation speed on stainless steel. Therefore, in this research, the cavitation erosion-corrosion test (Hybrid test) was performed for 304 stainless steel specimen used in the high flow rate seawater environment. And the cavitation damage behavior in the corrosive environment was analyzed overall. The high hardness was shown due to the formation of compressive residual stress by the water cavitation peening effect in cavitation condition. However, high current density in the potentiodynamic polarization experiment presented with the breakdown of the passive film caused by physical impact. Therefore, both electrochemical characteristics and mechanical properties must be taken into account to improve the cavitation resistance in seawater.

Damage Analysis of Train Rail Fishplate (전동차 선로 이음매 판의 파손 해석)

  • Seo-Hyun Yun;Byoung-Chul Choi;Ki-Hang Shin;Ki-Woo Nam
    • Journal of the Korean Society of Industry Convergence
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    • v.26 no.2_2
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    • pp.341-347
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    • 2023
  • The subway is one of the most common and important means of transportation in modern society. In order to use the subway safely, tracks are necessary, but trains are prone to derailment and collisions. In order for the train to run safely on the track, the fishplate that connects the line connection is used. The damaged railway was a fishplate for connecting subway lines used for 11 years, and damage analysis and countermeasures were presented. Beach marks were observed on both fracture surfaces, and striations appeared at the range of crack propagation. The damaged part is Cr carbide, which has a higher hardness than the base metal, and is judged to be embrittled and destroyed by fatigue. The SM50C fishplate was subjected to a cyclic stress of about 59% of the upper limit of tensile-compression fatigue limit, but inclusions were the cause of failure. In order to prevent fatigue failure of the SM50C steel fishplate, the occurrence of inclusions should be minimized and processed to have a homogeneous structure when manufacturing the fishplate. In addition, compressive residual stress is given through surface modification such as peening to control crack generation. It is necessary to minimize the change in shape that can become a stress concentration part along with accurate fastening of the bolt, and to design the stress distribution to be as uniform as possible.