• Advances in concrete construction
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• v.2 no.1
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• pp.13-27
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• 2014

The principal objective of this study is to deepen the characterization studies already led on sand concretes in previous works. Indeed, it consists in studying the effect of the sand type on the main properties of sand concrete: fracture and mechanical properties. We particularly insist on the determination of the fracture characteristics of this material which apparently have not been studied. To carry out this study, four different types of sand have been used: dune sand (DS), river sand (RS), crushed sand (CS) and river-dune sand (RDS). These sands differ in mineralogical nature, grain shape, angularity, particle size, proportion of fine elements, etc. The obtained results show that the particle size distribution of sand has marked its influence in all the studied properties of sand concrete since the sand having the highest diameter and the best particle size distribution has given the best fracture and mechanical properties. The grain shape, the angularity and the nature of sand have also marked their influence: thanks to its angularity and its limestone nature, crushed sand yielded good results compared to river and dune sands which are characterized by rounded shape and siliceous nature. Finally, it should further be noted that the sand concrete presents values of fracture and mechanical properties slightly lower than those of ordinary concrete. Compared to mortar, although the mechanical strength is lower, the fracture parameters are almost comparable. In all cases, the sand grains are debonded from the paste cement during the fracture which means that the crack goes through the paste-aggregate interface.

• Bulletin of the Society of Naval Architects of Korea
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• v.27 no.3
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• pp.100-106
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• 1990

Microcracking of type 304 stainless steel at $593^{\circ}C(1,100^{\circ}F)$ has been studied, in particular, initiation, growth, and coalescence of fatigue and creep microcracks on smooth specimens and small notch specimens via surface replicas and photomicrographs. Quantitative information, such as, initiation period, growth, and coalescence behavior, statistical distributions of crack length, density of cracks, distribution patterns and crack growth properties, were obtained. From this study, the fracture process, fatigue life, and creep life prediction characterized by the growth of surface microcracks have been analysed by a new approach unifying the conventional approaches based on the final fracture of materials with the fracture mechanics approach. Knowledge of these parameters is critical for the application of fracture mechanics to fatigue and creep life assessment, and the damage evaluation of structures at elevated temperature.

• Journal of the Korean Ceramic Society
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• v.31 no.9
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• pp.941-948
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• 1994

An underwater grout on material resistance against segregation in water were studied by water soluble polymer (methyl cellulose and acrylic acid ester and styrene). The mechanical properties of the grout agents were investigated through the observation of the microstructure and application of fracture mechanic. When the soluble polymer MC+AAES added with 0.6 wt% to the underwater grout agents the compressive strength, flexural strength and Young's modulus were about 58 MPa, 10 MPa and 3.2 GPa respectively, and critical stress intensity was about 0.8 MNm-1.5. It can be considered that the strength improvement and fracture toughness increase may be due to the pore decrease and bonding force by material resistance against segregation in water.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.39 no.2
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• pp.158-163
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• 2003

Thermosetting matrix composites have disadvantages in terms of moulding time, repairability and manufacturing cost. Thus the high-performance thermoplastic composites to eliminate such disadvantages have been developed so far. As a result of environmental and economical concerns, there is a growing interest in the use of thermoplastic composites. However, since their mechanical properties are very sensitive to the environment such as moisture, temperature etc., those behaviors need to be studied. Particularly the temperature is a very important factor influencing the mechanical behavior of thermoplastic composites. The effect of temperature have not yet been fully quantified. Since engineering applications of reinforced composites necessitate their fracture mechanic characterization, work is in progress to investigate the fracture and related failure behavior. An approach which predicts the tensile strength was perpormed in the tensile test. The main goal of this work is to study the effect of temperature on the result of tensile test with respect to GF/PE composite. The tensile strength and failure mechanisms of GF/PE composites were investigated in the temperature range 6$0^{\circ}C$ to -5$0^{\circ}C$. The tensile strength increased as the fiber volume fraction ratio increased. The tensile strength showed the maximum at -5$0^{\circ}C$, and it tended to decrease as the temperature increased from -5$0^{\circ}C$. The major failure mechanism was classified into the fiber matrix debonding, the fiber pull-out, the delamination and the matrix deformation.

• Advances in materials Research
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• v.4 no.2
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• pp.87-96
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• 2015

In this paper, three-dimensional finite element method is used to analyze the J integral for repaired cracks in plates with bonded composite patch and stiffeners. For elastic the effect of cracks, the thickness of the patch ($e_r$) and properties of the patch are presented for calculating the J integral. For elastic-plastic a several calculations have been realized to extract the plasticized elements around the crack tip of repaired and un-repaired crack. The obtained results show that the presence of the composite patch and stiffener reduces considerably the size of the plastic zone ahead of the crack. The effects of crack size and the inter-distance of repaired cracks were analysed.

• Proceedings of the Korean Institute of Resources Recycling Conference
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• 2003.10a
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• pp.134-138
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• 2003

The purpose of this paper is to recycle the fly ash to the valuable resources and settle environment problems which was caused by the fly ash produced from the thermal power plant. Making the fly ash-cement matrix reused fly ash in large quantities, we looked into minutely the physical properties - the elastic modulus, the compressive strength - to increase the usefulness as the building materials for the structure widely. In this paper, the variables are the water-binder(39, 42, 45%), the fine aggregate ratio(37, 41, 45%). Because the fracture energy is influenced by the strength, it is showed to decrease with the increase of W/B and S/a. Besides, we will be able to know that basic properties of the fly ash-cement matrix are similar to that of concrete. But, it is needed to carry out durability experiment on the drying shrinkage, creep, freezing and thawing test to use structural materials.

• International Journal of Naval Architecture and Ocean Engineering
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• v.10 no.3
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• pp.393-402
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• 2018

While interacting with a sloping structure, an ice floe may fracture in different patterns. For example, it can be local bending failure or global splitting failure depending on the contact properties, geometry and confinement of the ice floe. Modelling these different fracture patterns as a natural outcome of numerical simulations is rather challenging. This is mainly because the effects of crack propagation, crack branching, multi fracturing modes and eventual fragmentation within a solid material are still questions to be answered by the on-going research in the Computational Mechanic community. In order to simulate the fracturing of ice floes with arbitrary geometries and confinement; and also to simulate the fracturing events at such a large scale yet with sufficient efficiency, we propose a semi-analytical/empirical and semi-numerical approach; but with focus on the global splitting failure mode in this paper. The simulation method is validated against data we collected during the Oden Arctic Technology Research Cruise 2015 (OATRC2015). The data include: 1) camera images based on which we specify the exact geometry of ice floes before and after an impact and fracturing event; 2) IMU data based on which the global dynamic force encountered by the icebreaker is extracted for the impact event. It was found that this method presents reasonably accurate results and realistic fracturing patterns upon given ice floes.

• Journal of the Korea Concrete Institute
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• v.17 no.3 s.87
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• pp.329-334
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• 2005

The use of Polymer Concrete (PC) is growing very rapidly in many structural and construction applications such as box culverts, hazardous waste containers, trench lines, floor drains and the repair and overlay of damaged cement concrete surfaces in pavements, bridges, etc. However, PC has a defect economically because resin which be used for binder is expensive. Therefore the latest research is being progressed to replace existing resin with new resin which can reduce the high cost. Here, Polymer concrete using the recycled PET(polyethylene terephthalate) has some merits such as decrease of environmental destruction, decrease of environmental pollution and development of new construction materials. The variables of this study are amount of resin, curing condition and maximum size of coarse aggregate to find out mechanic properties of this. Stress-strain curve was obtained using MTS equipment by strain control. The results indicated that modulus of elasticity was increased gradually in an ascending branch of curve, as an increase of resin content. Compressive strength was the highest for resin content of $13\%$. And Compressive strength was increased as maximum size of coarse aggregate increases. The strain at maximum stress increases with an increase of resin content and size of coarse aggregate. For the descending branch of stress-strain curve the brittle fracture was decreased when it was cured at the room temperature compared to high temperature.