• Proceedings of the Korean Institute of Building Construction Conference
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• 2012.05a
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• pp.255-256
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• 2012

In this study, strain properties of high strength concrete using light weight aggregate which is widely used in recent years are evaluated. For these purpose, thermal strain, transient creep were measured in prestressed condition as 0, 20, 40% of specimen strength at target temperature with 60MPa specimens which was using normal and light weight aggregate. As a result, light weight aggregate is more advantageous for the control of strain than normal aggregate because of its low thermal expansion.

• Design & Manufacturing
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• v.12 no.2
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• pp.34-39
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• 2018

The biggest topics in the automobile industry are light weightening and fuel efficiency improvement. There's a lot of research going on. It is focused on light weight materials. Light weight material is seen as the best way to reduce fuel consumption and to solve the problem of environmental pollution and resource depletion. For the light weight materials, new materials such as aluminum, magnesium, and carbon-hardening materials can be found. Research on the joining techniques of dual materials, improvement of material properties by improving the method of manufacture of existing materials, and studies on ultra-high strength steel sheets are expected to take up the most weight in lightweight materials. As the strength of the ultra-high strength steel sheets increases during forming, it is difficult to obtain dimensional precision due to the increase in elastic restoring force compared to mild or high strength steel sheets. Spring back is known to be affected by a number of factors due to poor plastic molding, and can be divided into the effects of the material spraying and the process. The study on the plasticitic variables were studied as plasticitic factors that can be controlled by a part company. Tensile testing of ultra-high strength materials was conducted to derive properties for plasticitic analysis and to analyze spring back with two factors controlling the height of the bead and blank holding force by adding tensile force and controlling the flow rate.

• Restorative Dentistry and Endodontics
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• v.32 no.5
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• pp.445-458
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• 2007

The purpose of this study was to evaluate the bond strength of a new Single step system with different curing mode composites, and to evaluate the effect of the intermediate resins which have different hydrophilicity on bonding ability by means of the micro shear bond testing and TEM examination for the adhesive interface. The adhesive used in this study was an experimental single step system (Bisco Inc., Schaumburg IL). Experimental groups were produced by using six kinds of intermediate resin having different hydrophilicity that was hydrophilic, hydrophobic and most hydrophobic resin and as filled or not after applying adhesive. Each experimental group was further divided into two subgroups whether the adhesive was light cured or not. Dual cured composite (Bis Core, Bisco Ltd., Schaumburg, IL) was placed on the adhesive layer as light cure or self cure mode. The results or bond strength were statistically analyzed using one way ANOVA and multiple comparisons are made using Tukey's test at ${\alpha}\;<\;0.05$ level. The results of this study were as follows ; 1. The application of intermediate resin did not increase the bond strength for light cured composite. 2. The bond strength of an experimental adhesive with self cured composite was significantly increased by the application of intermediate resin layer. 3. The bond strength of adhesive was irrespective of the cure or not of itself before intermediate resin layer applied. 4. As applied hydrophilic resin layer was, the initial bond strength was higher than both hydrophobic and most hydrophobic one used but there was no significance. Using a single step adhesive with dual/self cured composite, the incompatibility between both of them should be solved by the application of intermediate hydrophobic resin to reduce the adhesive permeability. However, Single step adhesive can be used in the light cured composite restoration without any decrease of the initial bond strength.

• Restorative Dentistry and Endodontics
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• v.18 no.1
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• pp.84-94
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• 1993

The purpose of this study was to evaluate flexure strength of composite resin inlay according to heat treatment and duration in comparasion with visible light-cured resin. In this study, materials were used 1 visible light-cured resin and 3 kinds of composite resin inlays. Control group was visible light cured resin (Photo Clearfil Posterior) and experimental groups were composite resin inlays (Brilliant Dentin, Brilliant Enamel and Clearfil CR Inlay). Experimental groups were divided 3 groups: First group was Brilliant Dentin and second group was Brilliant Enamel and -third group was Clearfil CR Inlay. Used experimental groups were calculated flexural strength according to heat treatment and duration. The following results were obtained: 1. Experimental groups were higher flexural strength than control group. 2. At $100^{\circ}C$ when heat treatment carried out 7 minutes flexural strength elevated third group, second group, first group in turn and when heat treatment carried out 15 minutes flexural strength elevated third group, second group, first group in turn but no difference was showed between first and second group. 3. At $125^{\circ}C$ when heat treatment was carried out 7 minutes flexural strength elevated third group, second group, first group in turn and when heat treatment was carried out 15 minutes flexural strength elevated third group, first group, second group in turn but no difference was showed between first and second group. 4. In spite of heat treatment and duration the third group was highest flexural strength in the others groups.

• Restorative Dentistry and Endodontics
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• v.17 no.1
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• pp.36-54
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• 1992

The purpose of this study was to compare the shear bond strengths to ground dentin surfaces of four dentinal bonding agents in 193 teeth. Various dentin surfaces treated with four dentin bonding agents were attached with two restorative composite resins. The effectiveness of the bonding were tested by the monitoring the shear bond strength. The shear bond strengths were measured after 2 hours and 24 hours after surface conditioning with four dentin bonding agents. Effects of EDTA, the additive illumination, and sealer treatments without primer on bond strength to dentin surfaces were assessed. In addition the effects of the thickness of specimens ranging from 0.65 mm to 1.95 mm and the ratio of catalyst and base paste on the bond strength of chemical cure composite resin were estimated. The shear bond strength was determined by testing specimens in the Instron universal testing machine (Model No. 1122) at a crosshead speed of 1.0 mm/min. Following condusions were drawn: 1. The highest mean shear bond strengths of chemical cure composite resin to dentin conditioning with dentin bonding agents aged 2 hours were obtained, and then that was decreased with time followed by EDTA treatment. 2. In light cure composite resin, the shear bond strength was increased following dentin conditioning with bonding agents with time, irradiation time and EDTA treatment except in SB group. 3. The thicker the composite resin specimen was, the less the shear bond strength in chemical cure composite resin was. 4. In light cure composite resin, there was a little change in shear bond strength following dentin conditioning with bonding agents. 5. In chemical cure composite resin, the shear bond strength was the highest in the ratio of 1/1 of catalyst and base part. 6. Without a dentin primer, shear bond strength to dentin conditioned only with UB sealer was the highest among four sealers in light cure composite resin.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.249-253
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• 2003

In recent years, developments of light weight vehicle are one of the most important issues in automotive makers. New materials and new processes have been studied on the point of weight saving of chassis worldwide. Associated with materials, applications of high strength steel, aluminium, magnesium are being developed. On the point of new processes, tailored welded blank and hydroforming have been applied. In this paper, focusing to both material and process, we have applied hydroforming process to the engine cradle. In addition to that, three kinds of high strength steel have been applied to the development of light weight material for hydroforming. All the studies have been carried by FEM.

• Transactions of Materials Processing
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• v.26 no.1
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• pp.55-62
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• 2017

This paper proposes the process to develop a light-weighting automotive door assembly using high strength steel with low cost penalty. In recent years, the automotive industry is making an effort to reduce the vehicle weight. In this study, inner panels for automotive front door using thinner sheets and quenchable boron steel were designed to reduce the weight of conventional one. In order to evaluate the stiffness properties for the proposed door design, the several static tests were conducted using the finite element method. Based on the simulation results, geometry modifications of the inner panels were taken into account in terms of thickness changes and cost saving. Furthermore, a prototype based on the proposed design has been made, and then static stiffness test carried out. From the results, the proposed door is proved compatible and weight reduction of 11.8% was achieved. It could be a reference process for automotive industry to develop the similar products.

• Journal of Dental Rehabilitation and Applied Science
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• v.26 no.3
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• pp.311-322
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• 2010

The purpose of this study was to evaluate the bond strengths between IPS e.max Press and four different types of resin cements that often used for esthetic restoration. Disc shaped IPS e.max Press blocks(N=40, diameter: 12mm, thickness: 3mm) were fabricated according to the manufacture's instruction and cleaned with ultrasonic cleaner. They were embedded into an autopolymerizing acrylic resin. Fourty cylinder shaped resin block(Filtek Z350, diameter: 4.5mm, thickness: 3mm) were fabricated using a plastic tube. Each specimens were randomly divided into 4 experimental group and bonded each other using 4 different resin cements(Variolink II(light-cure), Variolink II(dual-cure), Calibra, Super-Bond C&B) according to the manufactures' recommendations. All the specimens were stored in normal saline at $37^{\circ}C$ for 24 hours before test. Universal testing machine at a crosshead speed of 1mm/min was used to evaluate the shear bond strength. The data were statistically analyzed using one-way ANOVA(P<.01). Multiple comparison was done by the Tukey HSD test. The shear bond strength of Super-Bond C&B to e.max was significantly lower than those of Calibra, Variolink II(light-cure), Variolink II(dual-cure) (P<.01). The shear bond strength of Calibra, Variolink II(light-cure), Variolink II(dual-cure) to e.max were not significantly different. The shear bond strengths of light-cure/dual-cure cement were higher than that of self-cure cement.

• Restorative Dentistry and Endodontics
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• v.21 no.1
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• pp.280-288
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• 1996

The purpose of this study was to assess comparatively the shear bond strength on dentin of four dentin bonding agents used in conjunction with light-curing composite resins. Clearfil New Bond, Scotchbond Multipurpose Dentin Adhesive, All-Bond 2 and X-R Bond were applicated on labial dentin surfaces just below dentin - enamel juction of bovine incisor teeth. After shear bond strength testing with the universal testing machine, the bonding interface of the specimens were observed under light stereomicroscope. Following results were obtained. 1. The shear bond strength was high in the order of B,C,D,A and group B Scotchbond Multipurpose Dentine Adhesive revealed greater bond strength than Clearfil New Bond and X-R Bond. (p<.001) 2. When using ANOVA and Duncan's multiple range test, there were statistical differences among the four groups, except between group Band C,group D and A. 3. There was no relationship between mode of failure and shear bond strength.

• Polymer(Korea)
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• v.37 no.2
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• pp.196-203
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• 2013

Surface modification of meta-aramid fibers was performed by phosphoric acid treatment. Surface morphology and element composition of untreated and treated fibers were analyzed by scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). Effects of surface modification on the mechanical strength of aramid papers made from meta-aramid fibers and fibrid were investigated. Surface modification conditions were optimized by response surface analysis (RSA). Results show that phosphoric acid treatment increases the surface roughness and oxygen content of aramid fibers. They improve the interface bonding strength between aramid fibers and fibrid, which improves the tensile strength of aramid papers. The results of response surface analysis indicate that the tensile strength of aramid papers increases by 47.5% and reaches the maximum when meta-aramid fibers are treated with 21.1wt% phosphoric acid solution at $39.3^{\circ}C$ for 36.7 min.