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Ultimate strength of austenitic stainless steel fillet-welded connections with weld metal fracture
Lee, HooChang,Hwang, BoKyung,Kim, TaeSoo Applied Science Publishers 2017 Thin-walled structures Vol.116 No.-
<P><B>Abstract</B></P> <P>This study investigates ultimate behaviors such as ultimate strength and weld metal fracture mechanism of austenitic stainless steel (304 type) fillet-welded connections with TIG (tungsten inert gas) welding through experimental method. Main variables of test specimens are weld length and welding direction against applied force. Specimens are fabricated with transverse fillet weld (TFW series), longitudinal fillet weld (LFW series) and full fillet weld FW series against loading direction. Specimens of TFW series, LFW series and FW series failed by tensile fracture, shear fracture and block shear fracture in the weld metal of connections. Test ultimate strengths were compared with predictions based on the design specifications, AISC (American institute of steel construction) and ASCE (American Society of Civil Engineers) and existing researcher's equations. Current design equations underestimated excessively the strength of welded connections with weld metal fracture. Consequently, modified design formula is suggested considering actual fracture path and the effect of stress triaxiality on welded connections and its validation was verified in this paper.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We performed experimental studies for fillet-welded connections. </LI> <LI> Specimens with austenitic stainless steel failed by block shear fracture. </LI> <LI> Weld metal of welded connection led to ultimate state. </LI> <LI> Current design codes overestimated overly the strength of welded connection. </LI> <LI> Strength equations were proposed considering actual fracture path. </LI> </UL> </P>
Experimental Studies on the Accuracy and Robustness of Yaw&G sensor
Hoochang Lee,Kwangho Yoo,Jaedoo Go,Jaekwang Lee,Wanil Kim 한국자동차공학회 2015 한국자동차공학회 부문종합 학술대회 Vol.2015 No.5
Yaw & G Sensor measures the vehicle motion of the rotation and the acceleration. Yaw & G Sensor output is mainly sent to ESC for the active safety. It seems obvious that the poor sensor output can mislead the malfunction of system which uses sensor output. Every company insists their sensor has the best performance, but unfortunately, there is no powerful method based on statistical analysis for an accuracy and a robustness. The focus of this paper is the experimental studies on the performance of Yaw & G Sensor using several practical tests. In this paper, a long-term bias stability is analyzed for an accuracy with linear fit line(best-fit line of offset) and allan variance. Plus, an anti-shock and anti-vibration is tested for a robustness with multi-types of shocks and sinusoidal acceleration wave.
Lee, HooChang,Hwang, BoKyung,Yang, WonJik,Kim, TaeSoo Elsevier 2019 Thin-Walled Structures Vol.141 No.-
<P><B>Abstract</B></P> <P>In this paper, the block shear fracture behavior of base metal in austenitic stainless steel (STS304, corresponds to ASTM 304 type) fillet-welded connection has been investigated through experimental and numerical methods. Even though the block shear fracture strength of welded connection thanks to stress triaxiality effect differs from those of bolted connection under monotonic tension, block shear strength equations of welded connection with base metal fracture in the design codes are identical to those of bolted connection. Main variables are weld method (TIG and Arc welding) and weld length (transverse and longitudinal to the direction of loading). It is found from study results that welding method did not affect the strength of welded connection. Block shear strengths by current codes (KBC2016, AISC2016 and EC3 1–3) and other researchers’ proposed equations were compared with those of experimental results and finite element analysis results. Finite element analysis (FEA) model was developed based on previously test data. Also, parametric study for investigating the weld length effect on strength has been performed with the developed finite element analysis procedures. Consequently, condition of weld length and end distance perpendicular to the direction of applied force for fracture mode transition boundary from tensile fracture to block shear fracture in welded connection was investigated. In addition, block shear strength equation with modified tensile stress and shear stress factors of base metal fracture in austenitic stainless steel (STS304) welded connection is suggested considering stress triaxiality.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Finite element analysis of stainless steel welded connections was conducted. </LI> <LI> Strength and fracture mode by analysis agreed with those of test results. </LI> <LI> Specimens failed by block shear fracture of base metal. </LI> <LI> Condition of fracture transition according to variables were investigated. </LI> <LI> Effective tensile and shear stress factors were suggested. </LI> </UL> </P>
3축 가속도센서를 이용한 도로 등판각 및 횡경사각 추정 방법
이후창(Hoochang Lee),윤정운(Jeongun Yoon),김건하(Gunha Kim),유광호(Kwangho Yoo),김완일(Wanil Kim) 한국자동차공학회 2015 한국자동차공학회 학술대회 및 전시회 Vol.2015 No.11
The climbing and road bank angle are the one of the most important information for active safety systems. But unfortunately, it isn’t easy to simply calculate since the angle is estimated from 2axis accelerometer which is also including driving acceleration and lateral slip angle. So current estimation algorithm requires complex equations and many variables from other sensors in order to extract the angles from measured acceleration. In this paper, a new angle estimation method based on 3axis accelerometer has been introduced with relatively simple equations. The performance of new approach has been evaluated by measuring the calculated angles.
동적 중복구조 활용을 통한 조향각 신호 신뢰성 향상 연구
김진우(Jinwoo Kim),유광호(Kwangho Yoo),김건하(Gunha Kim),이후창(Hoochang Lee),정준영(Joonyeong Jeong),이제광(Jekwang Lee),최윤희(Yunhee Choi),박현호(Hyunho Park) 한국자동차공학회 2015 한국자동차공학회 학술대회 및 전시회 Vol.2015 No.11
Steering angle signal widely uses for driving safety system and driver’s convenience system as well as the steering system. According to increased application range, it is important for complex systems to secure steering angle signal reliability. Current steering system uses major voting system by redundancy check for signal reliability. It has advantage of reliability securing. However when increasing redundancy check, calculation device (e.g. ECU) is also increasing processing load. In this paper, dynamic redundancy check has been introduced about simple processing structure for reduce processing load while keeping signal reliability.