• Journal of Biomedical Engineering Research
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• v.18 no.1
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• pp.1-8
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• 1997

This study was performed to evaluate the effect of resin and filler type on the compressive strength of light-activated composite resins. Experimental composite resins containing either amorphous spherical silica or crushed quartz in two matrix resins of BisGMA/TEGDMA and UTMA/TEGDMA were prepared and the specimens of 3 m in diameter and 6m in length were made. Compressive test was subjected to a crosshead speed of 0.5 mm/min, and the fracture surFaces were examined by SEM. The compressive strength of UTMA-based composite resin was higher than that of BisGMA-based composite resin. The loading rate of spherical silica was higher than that of crushed silica when the size dis- tribution of fillers was same. Strength decrease of Bis-GMA-based composite resin was severer than that of UTMA-based composite resin in a $37^{\circ}$c water environment. Fracture surface showed that the composite resin failure developed along the matrix resin and the filler/resin interface region.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04a
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• pp.359-364
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• 1998

The interfacial zone in concrete materials is extensive, geometrically complex, and constitutes inherently weak zones that limit the concrete performance. Motar-aggregate interfaces play a major role in the fracture processing in concrete composites. Also, the interfacial bond considerably influence mechanical properties of concrete such as modulus of elasticity, strength, and fracture energy, Characterization of the interfacial properties is, therefore, essential to overcome the limitations associated with the interfaces. an objective of this paper is to investigate the corelationship between the fracture toughness of mortar-aggregate interface and the concrete properties such as strengths and elastic moduli. It is observed from the test results that interface fracture toughness is closely related with the compressive strength rather than other properties. At early ages, the development of both tensile strength and elastic modulus are much greater thatn that of both interface fracture toughness and compressive strength.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.11-30
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• 2000

Structural properties of reinforced concrete, such as bond and shear strength, that depend on the tensile properties of concrete are much lower for high-strength concrete than would be expected based on relationships developed for normal-strength concretes. To determine the reason for this behavior, studies at the University of Kansas have addressed the effects of aggregate type, water-cementitious material ratio, and age on the mechanical and fracture properties of normal and high-strength concretes. The relationships between compressive strength, flexural strength, and fracture properties were studied. At the time of test, concrete ranged in age from 5 to 180 days. Water-cementitious material ratios ranged from 0.24 to 0.50, producing compressive strengths between 20 MPa(2, 920 psi) and 99 MPa(14, 320psi). Mixes contained either basalt or crushed limestone aggregate, with maximum sizes of 12mm(1/2in). or 19mm(3/4in). The tests demonstrate that the higher quality basalt coarse aggregate provides higher strengths in compression than limestone only for the high-strength concrete, but measurably higher strengths in flexure, and significantly higher fracture energies than the limestone coarse aggregate at all water-cementitious material ratios and ages. Compressive strength, water-cementitious material ratio, and age have no apparent relationship with fracture energy, which is principally governed by coarse aggregate properties. The peak bending stress in the fracture test is linearly related to flexural strength. Overall, as concrete strength increases, the amount of energy stored in the material at the peak tensile load increases, but the ability of the material to dissipate energy remains nearly constant. This suggests that, as higher strength cementitious materials are placed in service, the probability of nonductile failures will measurably increase. Both research and educational effort will be needed to develop strategies to limit the probability of brittle failures and inform the design community of the nature of the problems associated with high-strength concrete.

• Journal of Technologic Dentistry
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• v.42 no.2
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• pp.129-137
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• 2020

Purpose: The aim of this study is to observe the compressive fracture strength of the crown according to the direction of the occlusal force of the mandibular canine and carnassial of the small dog. Methods: The abutment models of mandibular canine and carnassial were prepared, specimens of zirconia, PMMA and Ni-Cr alloy were produced. The experimental jig was fabricated with Co-Cr alloy and buried in acrylic resin after make tilt to specified angle. The specimen was attached to a jig and loaded using a universal testing machine until the specimen fractured. Results: The compressive fracture strengths of CXZ and CXP specimens were found to be 999.21 ± 31.15 N on average and 731.42 ± 59.13 N on average. And CZZ and CZP specimens were 730.48 ± 70.14 N on average and 377.65 ± 11.87 N on average. CXN and CZN specimens were not fractured. In addition, MZZ and MZP specimens were 746.46 ± 50.75 N and 258.64 ± 31.86 N on average. The MZN specimens were not fractured. Conclusion: Zirconia has compressive fracture strength that can be applied to small dog's canine and Carnassial prosthetics, while PMMA has inadequate strength to small dog's carnassial prosthesis.

• Advances in nano research
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• v.15 no.6
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• pp.495-511
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• 2023

In this research, the impact of micro-silica, nano-silica, and polypropylene fibers on the fracture energy of self-compacting concrete was thoroughly examined. Enhancing the fracture energy is very important to increase the crack propagation resistance. The study focused on evaluating the self-compacting properties of the concrete through various tests, including J-ring, V-funnel, slump flow, and T50 tests. Additionally, the mechanical properties of the concrete, such as compressive and tensile strengths, modulus of elasticity, and fracture parameters were investigated on hardened specimens after 28 days. The results demonstrated that the incorporation of micro-silica and nano-silica not only decreased the rheological aspects of self-compacting concrete but also significantly enhanced its mechanical properties, particularly the compressive strength. On the other hand, the inclusion of polypropylene fibers had a positive impact on fracture parameters, tensile strength, and flexural strength of the specimens. Utilizing the response surface method, the relationship between micro-silica, nano-silica, and fibers was established. The optimal combination for achieving the highest compressive strength was found to be 5% micro-silica, 0.75% nano-silica, and 0.1% fibers. Furthermore, for obtaining the best mixture with superior tensile strength, flexural strength, modulus of elasticity, and fracture energy, the ideal proportion was determined as 5% micro-silica, 0.75% nano-silica, and 0.15% fibers. Compared to the control mixture, the aforementioned parameters showed significant improvements of 26.3%, 30.3%, 34.3%, and 34.3%, respectively. In order to accurately model the tensile cracking of concrete, the authors used softening curves derived from an inverse algorithm proposed by them. This method allowed for a precise and detailed analysis of the concrete under tensile stress. This study explores the effects of micro-silica, nano-silica, and polypropylene fibers on self-compacting concrete and shows their influences on the fracture energy and various mechanical properties of the concrete. The results offer valuable insights for optimizing the concrete mix to achieve desired strength and performance characteristics.

• Smart Structures and Systems
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• v.12 no.2
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• pp.137-155
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• 2013

Brittle fracture of structures excited by earthquakes can be prevented by adding a tuned mass damper (TMD). This TMD must be optimum and suitable to the physical conditions of the structure. Compressive strength of concrete is an important factor for brittle fracture. The application of a TMD to structures with low compressive strength of concrete may not be possible if the weight of the TMD is too much. A heavy TMD is dangerous for these structures because of insufficient axial force capacity of structure. For the preventing brittle fracture, the damping ratio of the TMD must be sufficient to reduce maximum shear forces below the values proposed in design regulations. Using the formulas for frequency and damping ratio related to a preselected mass, this objective can be only achieved by increasing the mass of the TMD. By using a metaheuristic method, the optimum parameters can be searched in a specific limit. In this study, Harmony Search (HS) is employed to find optimum TMD parameters for preventing brittle fracture by reducing shear force in additional to other time and frequency responses. The proposed method is feasible for the retrofit of weak structures with insufficient compressive strength of concrete.

• Magazine of the Korea Concrete Institute
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• v.11 no.2
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• pp.95-103
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• 1999

The reduction phenomena of concrete compressive strength with the size of specimens have been extensively investigated, but till now the adequate analysis technique is not fixed. The existing research results show that the bigger the member size, the smaller the strength. This means the nonlinear fracture mechanics theory is needed in order to analyze the fracture behaviors of concrete and the size effect. There is a few model equations that is to predict the size effect of compressive strength of standard and non-standard cylindrical specimen. However, theses equations did not considered the difference of fracturing mechanism which depends on the strength level. In this paper, model equations to predict compressive strength of concrete considering the size effect and strength level are suggested. The size effect model suggested in this paper shows good prediction compared with the existing test data of various concrete size and strength level.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.406-409
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• 2004

In this study, we investigated compressive characteristics of seawater-absorbed carbon-epoxy composite under hydrostatic pressure environment. The hydrostatic pressures applied were 0.1 MPa, 100 MPa, 200 MPa, and 270 MPa. The results showed that the compressive elastic modulus increased about 10 % as the hydrostatic pressure increased from 0.1 MPa to 200 MPa. The modulus increased 2.3 % more as the pressure increased to 270 MPa. Fracture strength and fracture strain increased with pressure in a linear fashion. Fracture strength increased 28 % and fracture strain increased 8.5 % as the hydrostatic pressure increased from 0.1 MPa to 270 MPa.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.335-340
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• 2002

By the recently, Environmental pollution is serious by the highly economic growth and expansion of lively country basic industry. Especially, in case of industrial waste and life waste leaped into a pollution source. Also, research for processing of waste and recycling countermeasure is a pressing question on national dimension because it is prohibited an ocean disposal and reclamation. In this study, it looked for fracture characteristic value of recycling a coal ash to decrease environmental pollution by picky and exhaustion of natural resources and to reduce self-weight to prepare for a tall building and earthquake. So a coal ash examined to be possible to do as construction material. It achieved compressive strength test and three points bending test with initial notch depth rate and age for variables to show a basic research data. From the basis of the three points bending test, the fracture parameters - notch sensitivity, fracture energy, initial compliance were experimentally proposed. From the results of the compressive strength test, the elastic modulus was experimentally proposed. Also on the basis of the three points bending test, the fracture parameters - notch sensitivity, fracture energy, initial compliance were experimentally proposed. The results that the strength and fracture energy value are lower than concrete or mortar is described in this paper. Also, it shows that the deflection at fracture decreases as the age increases and the notch sensitivity decrease. However, it is judged to be available to construction material if research is continuously gone forward.

• Magazine of the Korea Concrete Institute
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• v.7 no.4
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• pp.129-136
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• 1995

Thls research Includes est~mat~ons of the relat~on ktween the strength of concrete and the fracture energy for river sand concrete and crushed sand concrete using the wedge sphtting test method. Furthermore the fracture energy and the characteristic length of two types of concrete were compared and d~scussed. Fracture behaviors of crushed sand concrete and natural sand concrete had the similar trend in fracture characteristics. The fracture energy was increased with the increase of compressive strength in the strength range of 20-60MPa, but was not increased for the concrete more than 6OM.Pa of compressive strength.