• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2002.10a
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• pp.379-384
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• 2002

The effect of size and volume fraction of ceramic particles with sliding velocity on the wear properties were investigated for the metal matrix composites fabricated by pressureless infiltration process. The particulate metal matrix composites exhibited about 5.5 - 6 times of excellent wear resistance compared with AC8A alloy at high sliding velocity, and as increasing the particle size and decreasing the volume fraction the wear resistance was improved. The wear resistance of metal matrix composites and AC8A alloy exhibited different aspects. Wear loss of AC8A alloy increased with sliding velocity linearly. whereas metal matrix composites indicated more wear loss than AC8A alloy at slow velocity region, however a transition point of wear loss was found at middle velocity region which show the minimum wear loss, and wear loss at high velocity region exhibited nearly same value with slow velocity region. In terms of wear mechanism, the metal matrix composites exhibited the abrasive wear at slow to high sliding velocity generally, however AC8A alloy showed abrasive wear at low sliding velocity and adhesive and melt wear at high sliding velocity.

• International Journal of Ocean System Engineering
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• v.3 no.2
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• pp.102-110
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• 2013

The purpose of this study was to improve the properties of epoxy resin using titanium oxide nanoparticles. The effects of particle weight fraction, dispersion agent, and curing agents with different molecular weights on the thermal and mechanical properties of titanium-oxide-reinforced epoxy resin were investigated. In addition, the effect of the particle dispersion condition on the mechanical properties of nanocomposites was studied. As a result, it was found that the glass transition temperature of film-shaped nanocomposites decreased with an in-crease in the nanoparticle content. Because nanoparticles interrupted the cross linkage between the epoxy resin and the amine curing agent, the cross-link density of the epoxy became lower and led to a decrease in $T_g$ in the nanocompo-sites. The tensile strength and modulus in film-shaped nanocomposites also increased with the particles content. But in the case of dog-bone-shaped nanocomposites, the values were not similar to the trend for the film-shaped nanocompo-sites. This was probably a result of the different nanoparticles dispersions in the epoxy resins resulting from the respective-thicknesses of the film and dog-bone-shaped samples.

• Computers and Concrete
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• v.13 no.2
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• pp.187-207
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• 2014

This paper mainly discusses the influence of the aggregate properties including grading, shape, content and distribution on the chloride diffusion coefficient, as well as the initiation time of steel corrosion from a probabilistic point of view. Towards this goal, a simulation method of random aggregate structure (RAS) based on elliptical particles and a procedure of finite element analysis (FEA) at meso-scale are firstly developed to perform the analysis. Next, the chloride diffusion coefficient ratio between concrete and cement paste $D_{app}/D_{cp}$ is chosen as the index to represent the effect of aggregates on the chloride diffusion process. Identification of the random distribution of this index demonstrates that it can be viewed as actually having a normal distribution. After that, the effect of aggregates on $D_{app}/D_{cp}$ is comprehensively studied, showing that the appropriate properties of aggregates should be decided by both of the average and the deviation of $D_{app}/D_{cp}$. Finally, a case study is conducted to demonstrate the application of this mesoscopic method in predicting the initiation time of steel corrosion in reinforced concrete (RC) structures. The mesoscopic probabilistic method developed in this paper can not only provide more reliable evidences on the proper grading and shape of aggregates, but also play an important role in the probability-based design method.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.4
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• pp.174-181
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• 2005

In order to investigate the behavior of fatigue crack growth of SiC-particulate- reinforced Al-Si alloy composites, fatigue tests using single edge notched tension(SENT) specimens were performed. Composite materials were manufactured by using both permanent die casting and extrusion processes with different volume fractions of $10\%\;and\;20\%$. $SiC_p-reinfurced$ Al-Si composites showed the increased levels of threshold stress intensity factor range, ${\Delta}K_{th}$, for the increased volume fractions of SiC particles, which implies the increased fatigue crack growth resistance at the threshold or low ${\Delta}K$ levels, compared to the unreinforced Al-Si alloy. In the Paris region, however, the composites showed the increased rate of crack growth resulting in the unfavorable effects on the fatigue crack growth resistance. Critical stress intensity factor range at unstable crack growth leading to final fracture decreased as the volume fraction of SiC particle increased, because of the reduced fracture toughness of the composites. Extruded materials showed higher threshold and critical values than the cast materials.

• Journal of Powder Materials
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• v.26 no.5
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• pp.383-388
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• 2019

To improve the mechanical properties of aluminum, graphene has been used as a reinforcing material, yielding graphene-reinforced aluminum matrix composites (GRAMCs). Dispersion of graphene materials is an important factor that affects the properties of GRAMCs, which are mainly manufactured by mechanical mixing methods such as ball milling. However, the use of only mechanical mixing process is limited to achieve homogeneous dispersion of graphene. To overcome this problem, in this study, we have prepared composite materials by coating aluminum particles with graphene by a self-assembly reaction using poly vinylalcohol and ethylene diamine as coupling agents. The scanning electron microscopy and Fourier-transform infrared spectroscopy results confirm the coating of graphene on the Al surface. Bulk density of the sintered composites by spark plasma sintering achieved a relative density of over 99% up to 0.5 wt.% graphene oxide content.

• Steel and Composite Structures
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• v.39 no.5
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• pp.493-509
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• 2021

There is not enough mixed finite element method (MFEM) model developed for static and dynamic analysis of functionally graded material (FGM) beams in the literature. The main purpose of this study is to develop a reliable and efficient computational modeling using an efficient functional in MFEM for free vibration and static analysis of FGM composite beams subject to high order shear deformation effects. The modeling of material properties was performed using mixture rule and Mori-Tanaka scheme which are more realistic determination techniques. This method based on the assumption that a two phase composite material consisting of matrix reinforced by spherical particles, randomly distributed in the beam. To explain the displacement components of the shear deformation effects, it was accepted that the shear deformation effects change sinusoidal. Partial differential field equations were obtained with the help of variational methods and then these equations were transformed into a novel functional for FGM beams with the help of Gateaux differential derivative operator. Thanks to the Gateaux differential method, the compatibility of the field equations was checked, and the field equations and boundary conditions were reflected to the function. A MFEM model was developed with a total of 10 degrees of freedom to apply the obtained functional. In the numerical applications section, free vibration and flexure problems solutions of FGM composite beams were compared with those predicted by other theories to show the effects of shear deformation, thickness changing and boundary conditions.

• Computers and Concrete
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• v.27 no.3
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• pp.185-197
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• 2021

Throughout the previous years, many efforts focused on incorporating non-biodegradable wastes as a partial replacement and sustainable alternative for natural aggregates in cement-based materials. Currently, rubberized concrete is considered one of the most important green concrete materials produced by replacing natural aggregates with rubber particles from old tires in a concrete mixture. The main benefits of this material, in addition to its importance in sustainability and waste management, comes from the ability of rubber to considerably damp vibrations, which, when used in reinforced concrete structures, can significantly enhance its energy dissipation and vibration behavior. Nowadays, the literature has many experimental findings that provide an interesting view of rubberized concrete's dynamic behavior. On the other hand, it still lacks research that collects, interprets, and numerically investigates these findings to provide some correlations and construct reliable prediction models for rubberized concrete's dynamic properties. Therefore, this study is intended to propose prediction approaches for the dynamic properties of rubberized concrete. As a part of the study, multiple linear regression and artificial neural networks will be used to create prediction models for dynamic modulus of elasticity, damping ratio, and natural frequency.

• Geomechanics and Engineering
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• v.28 no.6
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• pp.559-571
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• 2022

Deep soil mixing, DSM technique has been widely used to improve the engineering properties of problematic soils. Due to growing urbanization and the industrial developments, disposal of brick dust poses a big problem and causes environmental problems. This study aims to use brick dust in DSM application in order to minimize the waste in brick industry and to evaluate its effect on the improvement of the geotechnical properties. Three different percentages of cement content: (10, 15 and 20%) were used in the formation of soil-cement mixture. Unlike the other studies in the literature, various percentages of waste brick dust: (10, 20 and 30%) were used as partial replacement of cement in soil-cement mixture. The results indicated that addition of waste brick dust into soil-cement mixture had positive effect on the inherent strength and stiffness of loose sand. Cement replaced by 20% of brick dust gave the best results and reduced the final setting time of cement and resulted in an increase in unconfined compressive strength, modulus of elasticity and resilient modulus of sand mixed with cement and brick dust. The findings were also supported by the microscopic images of the specimens with different percentages of waste brick dust and it was observed that waste brick dust caused an increase in the interlocking between the particles and resulted in an increase in soil strength. Using waste brick dust as a replacement material seems to be promising for improving the geotechnical properties of loose sand.

• Advances in materials Research
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• v.12 no.3
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• pp.227-242
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• 2023

Polyester composites play a vital role in civil engineering applications, especially in bridge and car park structures. Therefore, the addition of waste silica-based fillers will both improve the mechanical and durability performance of composites and produce an environmentally friendly material. In this study, the mechanical performance of polyester composites was investigated experimentally and numerically by adding micro and nano-sized silica-based fillers, marble powder, silica fume and nano-silica. 24 cubes for the compression test and 18 prisms for the flexural test were produced in six different groups containing 30% marble powder, 5% silica fume and 1% nano-silica by weight. SEM/EDS testing was used to investigate the distribution of filler particles in the matrix. Experimentally collected results were used to validate tests in the Abaqus software. Additionally, the Extended Finite Element Method (XFEM) was used to estimate the fracture process for the flexural test. The results show that the added silica fume, marble powder and nano silica improves the compressive strength of polyester composites by 32-38% and the flexural tensile strength by 10-60% compared to pure polyester composite. The numerically obtained results matched well with the experimental data, demonstrating the accuracy and feasibility of the calibrated finite element model.

• Composites Research
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• v.21 no.6
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• pp.15-22
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• 2008

Reversed plane bending fatigue tests were conducted on SiC particle aluminum composite. The initiation and growth behaviors of small surface fatigue cracks were continuously monitored by the replica technique and investigated in detail. The fatigue life of MMC is shorter than that of matrix because there exists interface debonding of SiC particles and matrix on the whole face of the notch part in the casting metal matrix composite(MMC). The coalescence of micro-cracks was observed in the tests conducted at high stress levels. Due to the coalescence, a higher crack growth rate of small cracks rather than those of long cracks was recognized in da/dn-$K_{max}$ relationship.