• International Journal of Naval Architecture and Ocean Engineering
• /
• 제9권5호
• /
• pp.509-524
• /
• 2017

Experiments and a numerical simulation were conducted to investigate the deformation and impact behavior of a corroded pipe, as corrosion, fatigue, and collision phenomena frequently occur in subsea pipelines. This study focuses on the deformation of the corrosion region and the variation of the geometry of the pipe under impact loading. The experiments for the impact behavior of the corroded pipe were performed using an impact test apparatus to validate the results of the simulation. In addition, during the simulation, material tests were performed, and the results were applied to the simulation. The ABAQUS explicit finite element analysis program was used to perform numerical simulations for the parametric study, as well as experiment scenarios, to investigate the effects of defects under impact loading. In addition, the modified ASME B31.8 code formula was proposed to define the damage range for the dented pipe.

• Nuclear Engineering and Technology
• /
• 제47권1호
• /
• pp.102-114
• /
• 2015

Background: A technique developed to produce artificial intergranular stress corrosion cracks in structural components was applied to thick, forged alloy 600 base and alloy 182 weld metals for use in the qualification of nondestructive examination techniques for welded components in nuclear power plants. Methods: An externally controlled procedure was demonstrated to produce intergranular stress corrosion cracks that are comparable to service-induced cracks in both the base and weld metals. During the process of crack generation, an online direct current potential drop method using array probes was used to measure and monitor the sizes and shapes of the cracks. Results: A microstructural characterization of the produced cracks revealed realistic conformation of the crack faces unlike those in machined notches produced by an electrodischarge machine or simple fatigue loading using a universal testing machine. Conclusion: A comparison with a destructive metallographic examination showed that the characteristics, orientations, and sizes of the intergranular cracks produced in this study are highly reproducible.

• Corrosion Science and Technology
• /
• 제7권1호
• /
• pp.6-12
• /
• 2008

Non-metallic composite overwrap repair methods utilize resin based fiber-reinforced composite materials, which have higher specific strength to weight ratio and stiffness, superior corrosion and fatigue resistance, and substantially reduced weight when compared to carbon steel. Non-metallic repair methods/systems can allow desired functional properties to be achieved at a respectable economic advantage. For example, non-metallic composite repair systems have at least a 50 year design stress of 20 ksi and approximately 25% of the short term tensile strength of fiberglass. For these systems, the contribution of the repaired steel to the load carrying capability need not be considered, as the strength of the repair itself is sufficient to carry the internal pressure. Worldwide experience in the Oil & Gas industry confirms the integrity, durability, inherent permanency, and cost-effectiveness of non-metallic composite repair or rehabilitation systems. A case study of a recent application of a composite repair system in Saudi Aramco resulted in savings of 37% for offshore subsea line and 75% for onshore above grade pipeline job. Maintaining a pipeline can be costly but it is very small in comparison to the cost of a failure. Pipeline proponents must balance maintenance costs with pipeline integrity. The purpose is not just to save money but also to attain a level of safety that is acceptable. This technology involves the use of an epoxy polymer resin based, fiber-reinforced composite sleeve system for rehabilitation and /or repair pipelines.

• Nuclear Engineering and Technology
• /
• 제53권2호
• /
• pp.657-665
• /
• 2021

Nondestructive evaluation methods play an important role in ensuring component integrity and safety in many industries. Operator fatigue can play a critical role in the reliability of such methods. This is important for inspecting high value assets or assets with a high consequence of failure, such as aerospace and nuclear components. Recent advances in convolution neural networks can support and automate these inspection efforts. This paper proposes using residual neural networks (ResNets) for real-time detection of corrosion, including iron oxide discoloration, pitting and stress corrosion cracking, in dry storage stainless steel canisters housing used nuclear fuel. The proposed approach crops nuclear canister images into smaller tiles, trains a ResNet on these tiles, and classifies images as corroded or intact using the per-image count of tiles predicted as corroded by the ResNet. The results demonstrate that such a deep learning approach allows to detect the locus of corrosion via smaller tiles, and at the same time to infer with high accuracy whether an image comes from a corroded canister. Thereby, the proposed approach holds promise to automate and speed up nuclear fuel canister inspections, to minimize inspection costs, and to partially replace human-conducted onsite inspections, thus reducing radiation doses to personnel.

• 한국산업융합학회 논문집
• /
• 제7권4호
• /
• pp.399-405
• /
• 2004

Currently, the use of carbon steel in a high temperature environment, such atomic reactor, increases. Test piece was heated in electric furnace and the prescribed temperature was controlled within ${\pm}1^{\circ}C$. Debris that falls apart from cracked section due to friction is accumulated inside. Then, as it causes fretting corrosion (formation of oxide layer), it contributes to crack closure.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2002년도 가을 학술발표회 논문집
• /
• pp.637-640
• /
• 2002

The deterioration of RC deck slabs has been a serious problem and high portion of budget has been a spent for repair and strengthening of deck slab. The concrete deck slabs are subject to direct application of vehicle loading and accumulation of fatigue damage. Besides, various environmental causes. In this paper, an probabilistic study is carried out to predict exact load effects and structural capacity of deck slab during its service life, and estimate an appropriate remaining life of deck slab. To achieve this purpose the live load model is developed using by influence line including deterioration of deck slab, and deterioration model of bridge deck slab is developed. In addition, the fatigue life of reinforced concrete deck slabs considering corrosion of reinforcement are estimated based on experimental formula. This study will help rational decisions for the management and repair of reinforced concrete deck slabs.

• Journal of Advanced Marine Engineering and Technology
• /
• 제34권5호
• /
• pp.661-669
• /
• 2010

The effects of laser peening on metallic materials have been investigated with water-penetrable frequency-doubled Nd:YAG laser. Laser pulses of 200 mJ energy and 8 ns duration focused on samples underwater with 0.8 mm spot diameter. X-ray study showed that compressive residual stress was imparted on SKD61 from the surface to nearly 2 mm depth. Stress corrosion cracking (SCC) was prohibited for sensitized SUS304 even in a severely corrosive environment fatigue lives of SUS316L and SM490A welded samples were prolonged significantly in the high-cycle regime. Since 1999, laser peening has been applied to prevent SCC in operating nuclear power plants in Japan.

• 대한용접접합학회:학술대회논문집
• /
• 대한용접접합학회 2006년 추계학술발표대회 개요집
• /
• pp.277-279
• /
• 2006

Due to the numerous environmental factors, cracks and corrosion are frequently occured especially in old steel bridge, which deteriorate the structural integrity; thus bring about the problems of structural safety of the steel bridge. Therefore, repair and reinforcement are required for the damaged structure. the replacement repair welding method is spotlighted for its brilliant features, i.e. it can be achieved without incurring traffic dislocation. the method cuts the damaged parts and replaces them with new steel plate by welding under live loads. However, the mechanical behavior of the welded joints under cyclic loads due to the traffic which passes along bridge is not clarified. In this paper, the fatigue strength of the replacement repair welded joints was investigated in order to improve reliability in the repair welded joints of old steel bridge.

• 한국생산제조학회지
• /
• 제9권3호
• /
• pp.76-82
• /
• 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.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
• /
• pp.469-474
• /
• 2003

Recently, to overcome the disadvantages of RC decks, advanced countries such as Japan and USA, and Europe are using prestressing connection precast decks and loop connection precast decks. The prestressing connection precast deck, however, has a weakness against steel corrosion, because of unreliable enforced grouting. The relatively low loading and fatigue capacities of the loop connection precast deck make it difficult to be used for the bridge that requires high fatigue resistance due to the frequent over loaded vehicles. This research proposes the improved connecting method for the precast decks to minimize its shortcomings based on both numerical analyses and full scale model tests. The proposed method maximizes the advantages of precast decks and extends it's service life.