• International Journal of Naval Architecture and Ocean Engineering
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• v.9 no.1
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• pp.66-76
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• 2017

This paper is concerned with investigating the plastic material properties of steel plate formed by line heating method, and is aimed at implementing more rational design considering the accidental limit states such as collision or grounding. For the present study, line heating test for marine grade steel plate has been carried out with varying plate thickness and heating speed, and then microscopic examination and tensile test have been carried out. From the microscopic, it is found that the grain refined zones like ferrite and pearlite are formed all around the heat affected zone. From the tensile test results, it is seen that yield strength, tensile strength, fracture strain, hardening exponent and strength coefficient vary with plate thickness and heat input quantity. The formulae relating the material properties and heat input parameter should be, therefore, derived for the design purpose considering the accidental impact loading. This paper ends with describing the extension of the present study.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.696-697
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• 2006

This paper presents the densification and microstructure evolution of bilayer components made from 316L stainless steel and M2 High speed steel during co-sintering process. The sintering was carried out at temperatures ranging from $1230-1320^{\circ}C$ in a reducing atmosphere. The addition of boron to 316L was examined in order to increase the densification rate and improve the sintering compatibility between the two layers. It was shown that the mismatch strain bettwen the two layers induces biaxial stresses during sintering, influencing the densification rate. The effect of boron addition was also found to be positive as it improves the bonding between the two layers.

• Composites Research
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• v.34 no.5
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• pp.311-316
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• 2021

In this study, TiC/steel metal matrix composites were fabricated by powder metallurgy process using Fealloy powders with 3 wt.% Cr and 10 wt.% Cr, respectively, as matrix material. Subsequently, the composite samples were heat treated by the annealing and quenching-tempering(Q-T), respectively, to understand the effect of heat treatment on the mechanical properties of the composites. The correlation between microstructure and structural strength depending on the chromium content and the heat treatment conditions was studied through tensile, compressive, and transverse rupture test and microstructural analysis. In the case of TiC/steel composite containing 10 wt.% Cr, the tensile strength and transverse rupture strength at room temperature were significantly lowered by the influence of coarse chromium carbide formed at the TiC/steel interface. On the other hand, both TiC/steel composites containing 3 wt.% Cr and 10 wt.% Cr showed much higher compressive strength of about 4 GP after quenching-tempering compared to the annealed specimens regardless of the presence of the chromium carbide.

• Journal of the Korean Society of Safety
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• v.21 no.4 s.76
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• pp.33-41
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• 2006

Material degradation should be considered to assess integrity and residual life of high temperature equipments. However, the property data reflecting degradation are not sufficient for practical use. In this study measuring properties for 1Cr-1Mo-0.25V forging steel generally used for turbine rotor was carried out. Degradation was simulated by isothermal ageing. heat treatment and variation of microstructure was observed. Mechanical properties such as tensile strength, impact energy, hardness and fracture toughness were measured. Assuming a semi-elliptical surface crack at the bore hole in a turbine rotor, material risk was estimated by using the aged material property data obtained in this study. Safety margin was decreased and life of the rotor was exhausted. This procedure can be used in assessing the residual life of a turbine rotor due to material degradation.

• Journal of Power System Engineering
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• v.19 no.5
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• pp.60-66
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• 2015

Embrittlement of material by hydrogen charging should be cleared for safety of storage vessel of hydrogen and components deal with hydrogen. A stainless steel is generally used as materials for hydrogen transportation and storage, and it has a big advantage of corrosion resistance due to nickel component in material. In this study, microscopic damage behavior of stainless steel according to the hydrogen charging time using nondestructive evaluation was studied. The surface of stainless steel became more brittle as the hydrogen charging time increased. The parameters of nondestructive evaluation were also changed with the embrittlement of stainless steel surface by hydrogen charging. Ultrasonic test, which is the most generalized nondestructive technique, was applied to evaluate the relationship between the ultrasonic wave and mechanical properties of stainless steel by hydrogen charging. The attenuation coefficient of ultrasonic wave was increased with hydrogen charging time because of surface embrittlement of stainless steel. In addition, acoustic emission test was also used to study the dynamic behavior of stainless steel experienced hydrogen charging. AE event at the hydrogen charged specimen was obviously decreased at the plastic zone of stress-strain curves, while the number of event for the specimen of hydrogen free was dramatically generated when compared with the specimens underwent hydrogen charging.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.3
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• pp.267-274
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• 2010

Unlike the structure which has a homogeneous material property, a composite structure is coupled with materials which have different properties, namely, steel and concrete. At actual modeling, the real behavior cannot be predicted without consideration of those material characteristics. Therefore, by putting the interface element between concrete and steel, a slip of steel and concrete is made predictable. Interface element can be used properly not by an ordinary constitutive relation, but by a non-linear constitutive relation considering actual adhesion and slip. A contact surface between plate-shape steel box and concrete is described by using this interface element. Furthermore, because the general 8 node conforming element is inappropriate for describing a bending buckling behavior of steel box, the EAS(Enhanced Assumed Strain) solid-shell element is used to describe a bending behavior of plate-shape steel box.

• Steel and Composite Structures
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• v.44 no.1
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• pp.33-47
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• 2022

This paper presents a finite element model for predicting the monotonic behaviour of bolted endplate joints connecting steel-concrete composite walls and steel beams. The demountable Hollo-bolts are utilised to facilitate the quick installation and dismantling for replacement and reuse. In the developed model, material and geometric nonlinearities were included. The accuracy of the developed model was assessed by comparing the numerical results with previous experimental tests on hollow/composite column-to-steel beam joints that incorporated endplates and Hollo-bolts. In particular, the Hollo-bolts were modelled with the expanded sleeves involved, and different material properties of the Hollo-bolt shank and sleeves were considered based on the information provided by the manufacture. The developed models, therefore, can be applied in the present study to simulate the wall-to-beam joints with similar structural components and characteristics. Based on the validated model, the authors herein compared the behaviour of wall-to-beam joints of two commonly utilised composite walling systems (Case 1: flat steel plates with headed studs; Case 2: lipped channel section with partition plates). Considering the ease of manufacturing, onsite erection and the pertinent costs, composite walling system with flat steel plates and conventional headed studs (Case 1) was the focus of present study. Specifically, additional headed studs were pre-welded inside the front wall plates to enhance the joint performance. On this basis, a series of parametric studies were conducted to assess the influences of five design parameters on the behaviour of bolted endplate wall-to-beam joints. The initial stiffness, plastic moment capacity, as well as the rotational capacity of the composite wall-to-beam joints based on the numerical analysis were further compared with the current design provision.

• Journal of the Society of Naval Architects of Korea
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• v.60 no.2
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• pp.65-75
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• 2023

Ships operated at sea for a long time are subjected to various kinds of loads, which may cause various types of damage. Such damages will eventually reduce the strength of hull structures. Therefore, it is necessary to estimate and evaluate the residual strength and remaining fatigue life of aging ships in order to secure structural safety, establish a reasonable maintenance plan, and make a judgment of life extension. For this purpose, the corrosion damage and local denting damage should be measured, fatigue damage estimation should be performed, and material properties of aged steel should be identified. For this study, in order to investigate the mechanical properties of aged steel, steel plates were obtained from a naval ship that reached the end of her life span. The specimens were manufactured from the obtained steel plates, and static and dynamic tensile tests, fatigue tests, and metallographic tests were performed. The mechanical properties obtained from the aged steel plates were compared with those of new steel plates to quantify the aging effect on the mechanical properties of marine steel materials.

• Steel and Composite Structures
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• v.26 no.5
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• pp.583-594
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• 2018

Although a lot of experimental and analytical investigations have been carried out for steel bridge piers made of SS400 and SM490, the formulas available for SS400 and SM490 are not suitable for evaluating ultimate load and deformation capacities of steel bridge piers made of high strength steel (HSS) SM570. The effect of various parameters is investigated in this paper, including plate width-to-thickness ratio, column slenderness ratio and axial compression force ratio, on the ultimate load and deformation capacities of steel bridge box piers made of SM570 steel subjected to cyclic loading. The elasto-plastic behavior of the steel bridge piers under cyclic loads is simulated through plastic large deformation finite element analysis, in which a modified two-surface model (M2SM) including cyclic hardening is employed to trace the material nonlinearity. An extensive parametric study is conducted to study the influences of structural parameters on the ultimate load and deformation capacities. Based on these analytical investigations, new formulas for predicting ultimate load and deformation capacities of steel bridge piers made of SM570 are proposed. This study extends the ultimate load and deformation capacities evaluation of steel bridge piers from SS400, SM490 steels to SM570 steel, and provides some useful suggestions.

• Magazine of the Korean Society of Agricultural Engineers
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• v.27 no.2
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• pp.47-56
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• 1985

Wasting fiberous residues from the cutting processes of steel materials at an iron-Works were mixed with concrete. The strength and toughness of steel fiber concrete with different steel contents were tested in a laboratory. The test results showed that the steel fiber residues can be used for the reinforcement of concrete. The potential applications of such product include floor constructions for facilities like dairy barns, grain storages, and machinery shops. The test results are as follows. 1. The compressive strengths of steel fiber concrete with one percent steel content by volume were 20 percent greater than that of plain concrete. The treatments also increased the concrete toughness by 96 percent. 2. When applied to tensile forces, the steel fiber concrete showed the increased strengths by 20 percent, and the toughness by 48 percent. 3. The steel content levels greater than or equal to 1.5 percent by volume resulted in the decreases of the compressive and tensile strengths of steel fiber concrete by 10 percent as compared to plain concrete. The concrete toughness increased with the steel contents. 4. The reinforcement effects of steel fiber depend on the quality of fiber material being used. Good steel fiber for concrete reinforcement appears to be uniform in shape and component, fine and long, and round-shaped.