• Transactions of Materials Processing
• /
• v.15 no.4 s.85
• /
• pp.311-318
• /
• 2006

One of the most important quality problems in flat plate leveled from hot rolled coils in cut-to-Iength lines is bowing and cambering when they are cut in small width parts. It is verified analytically and experimentally that residual stress remained in plate is th ε source of the problem. In order to produce low residual stress flat plate from hot rolled coils, the proper conditions of leveling are studied and two things are implemented. One is proper plastic deformation area ratio to reduce residual stress within customer requirement by applying suitable plastic deformation and maintain leveling load within structural strength limit of leveler. The other is maintaining uniform plastic deformation along the width of the plate during leveling. Customer requirement for residual stress is met by applying above 70% of plastic deformation area ratio and uniform deformation along width of coil by adjusting back up rolls according to deformation analysis of work roll and back up roll assembly and leveling tests.

• Journal of Ocean Engineering and Technology
• /
• v.10 no.2
• /
• pp.106-119
• /
• 1996

The ceramic has various high mechanical properties such as heat, abrasion, corrosion resistance and high temperature strength compared with metal. It also has low speciffic weight, low thermal expansibillity, low thermal conductivity. However, it could not be used as structural material since it is brittle and difficult for the machining. Therefore, there have been many researches to attempt to join ceramic with metal which is full of ductillity in order to compensate the weakness of ceramic.The problem is that residual stress develops around the joint area while the ceramic/metal joint material is cooled from high joining temperature to room temperature due to remarkable difference of thermal expansion coefficients between ceramic and metal. Especially, the residual stress at both edges of the specimen reduces the strngth of joint to a large amount by forming a singular stress field. In this study, two dimensional finite element method is attempted for the thermal elastic analysis. The joint residual stress of ceramic/metal developed in the cooling process is investigated and the change of joint residual stress resulted from the repetitive heat cycle is also examined. In addition, it is attempted to clarify the joint stress distribution of the case of tensile load and of the case of superposition of residual stress and actual loading stress.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.19 no.4
• /
• pp.539-547
• /
• 2010

Laser shock peening is useful to improve fatigue characteristic of multiple number of metals and alloys. This process induces a compressive residual stress on the metal surface, and when tensile load is applied, growth of crack is delayed and which changes the characteristic of the metal surface. It is an innovative surface treatment technique for strengthening metals. Specimens of SM45C are used in this study. The effect of an inertial tamping layer on the residual stress field using laser shock peening setup and Nd:YAG laser power is evaluated. Residual stress distribution measured by X-ray diffraction. As a result of this study it can be presented that following condition of Nd:YAG laser power and inertial tamping layer parameters, compressive residual stress is generated on the surface of the SM45C. Results to experimental data indicate that laser shock peening has great potential as a means of improving the mechanical performance of the metal surface.

• Structural Engineering and Mechanics
• /
• v.77 no.4
• /
• pp.559-569
• /
• 2021

This study was conducted to investigate the residual bearing capacity of steel-concrete composite beams under high-cycle fatigue loading through experiments and theoretical analysis. Six test beams with stud connectors were designed and fabricated for static, complete fatigue, and partial fatigue tests. The failure modes and the degradation of several mechanical performance indicators of the composite beams under high-cycle fatigue loading were analyzed. A calculation method for the residual bearing capacity of the composite beams after certain quantities of cyclic loading cycles was established by introducing nonlinear fatigue damage models for concrete, steel beam, and shear connectors beginning with the material residual strength attenuation process. The results show that the failure mode of the composite beams under the given fatigue load appears to be primarily affected by the number of cycles. As the number of fatigue loadings increases, the failure mode transforms from mid-span concrete crushing to stud cutting. The bearing capacity of a 3.0-m span composite beam after two million fatigue cycles is degraded by 30.7% due to premature failure of the stud. The calculated values of the residual bearing capacity method of the composite beam established in this paper agree well with the test values, which indicates that the model is feasibly applicable.

• Structural Engineering and Mechanics
• /
• v.75 no.4
• /
• pp.455-464
• /
• 2020

Reinforcement corrosion is one of the major problems in the durability of reinforced concrete structures exposed to aggressive environments. Deterioration caused by reinforcement corrosion reduces the durability and the safety margin of concrete structures, causing excessive costs in managing these structures safely. This paper aims to investigate the effects of reinforcement corrosion on the load bearing capacity deterioration of the corroded reinforced concrete structures. A new analytical method is proposed to predict the crack growth of cover concrete and evaluate the residual strength of concrete structures with corroded reinforcement failing in bond. The structural performance indicators, such as concrete crack growth and flexural strength deterioration rate, are assumed to be a stochastic process for lifetime distribution modelling of structural performance deterioration over time during the life cycle. The Weibull life evolution model is employed for analysing lifetime reliability and estimating remaining useful life of the corroded concrete structures. The results for the worked example show that the proposed approach can provide a reliable method for lifetime performance assessment of the corroded reinforced concrete structures.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2009.05a
• /
• pp.103-104
• /
• 2009

This paper focuses on the characteristics on long-term deflection and creep recovery of reinforced concrete beams under a sustained load of 25kN. In order to investigate the residual strengthen of the RC beam, a static flexural experiment was conducted. The result of the RC beam preloaded was compared with that of a RC beam, which was not preloaded.

• Proceedings of the KSME Conference
• /
• 2001.11a
• /
• pp.93-98
• /
• 2001

Fatigue strength evaluation was carried out for the core support structure of a low voltage circuit breaker. The impact load acting on the core support was calculated based on the strains measured during operation. A three-dimensional finite element analysis was performed to determine local peak stresses for fatigue evaluation. Fatigue safety factors were calculated using the modified Goodman, Gerber, Soderberg, and modified Findley lines, considering the magnitude of the residual stress and impact load.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1996.04a
• /
• pp.697-703
• /
• 1996

Fatigue strength of high strengthsteels are variable with many different surface treatment. It is well known that residual compressive stress retard fatigue crack growth rate(or arrest crack). High strngth steels are manufactured by following process. Heat treatment, shot peening and chromium plating process. High strength steel(HRC40 or above) which are subjected to fatigue load and dynamic load, chromium plated parts shall be peened in accordance with requirements and baked after plating. The purpose of this paper is to compare and discuss the influence of surface treatment and hydrogen embrittlement on fatigue strength of high strength steel. Therefore, fatigue test was performed to investigate influence of surface treatment. The results shows that shot peening is very effect method in creasing fatigue life and after plating, baking process is essential to prevent hydogen failure. In this paper, the experimental investigation is made to clarify the influence of shot peening conditions and baking process on fatigue strength of high strength steel.

• Journal of the Korean Ceramic Society
• /
• v.40 no.7
• /
• pp.667-671
• /
• 2003

Tape cast laminar composites with alumina/zircon(reaction-bonded mullite/zirconia) as an inner layer and alumina/zirconia or mullite/zirconia as an outer layer have been fabricated by hot-pressing. The mechanical properties(hardness and Young's modulus) and microstructure of laminar composites were examined using a nanoindentation technique and Scanning Electron Microscopy (SEM), respectively. The indentation load-displacement curve revealed the existence of residual stress in laminar composites.

• Proceedings of the KIEE Conference
• /
• 1998.07b
• /
• pp.417-419
• /
• 1998

In a large diesel engine actuator position servo system, it is impossible to isolate an actuator fault from a load torque with conventional fault detection isolation (FDI) schemes because they are propagated through a channel. This paper deals with a parity equation based residual generation to isolate them in the system. The actuator fault is modelled by a multiplicative type fault that can be characterized as discrepancies between the nominal and actual plant parameters, whereas the load torque is modelled by an additive disturbance. The transformation implemented in the residual generator should be determined on-line to achieve the isolation. Simulation studies show the practical applicability of the FDI scheme.