• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 2002.10a
• /
• pp.504-507
• /
• 2002

Glass fiber reinforced PET (Poly-Ethylene-Terephthalate) matrix composite was manufactured by rapid press consolidation technique as functions of temperature, pressure and time in pre-heating, consolidation and solidification stages. The optimal manufacturing conditions for this composite were discussed based on the void content, tensile, interlaminar shear, and impact properties. A tensile test was attempted to investigate the mechanical properties of the composite. It is found that the level of crystallinity and microstructure affects on the tensile properties substantially.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.8 no.3
• /
• pp.349-355
• /
• 2020

The purpose of this study is to investigate the effects of types and amounts of fibers on the compressive strength and tensile behavior high strength fiber-reinforced composites under a static load and impact resistance properties of composites under a high-velocity projectile impact load. Three kinds of mixtures were designed and specimens were manufactured. compressive strength, uniaxial tension, and high velocity projectile impact load tests were performed. Test results showed that the amount of fiber has a greater effect on the tensile strength an d tensile strain capacity than the compressive strength, an d the tensile strain capacity was improved by using hybrid fibers. It was also found that the amount of steel fiber had a great influence on the impact resistance capacity of panels. Although the impact resistance capacity of panels could be improved by using hybrid fibers, the difference of impact resistance capacity between specimens was found to be larger than the case of use of single fiber.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.3 no.2
• /
• pp.43-47
• /
• 1979

This paper presents the effect of stress relief annealing on mechanical properties in single Vee-groove welding joint. In this experiment, the investigation of annealing effect on mechanical properties of test material carried out by changing the annealing temperature from $600^{\circ}C$ to $900^{\circ}C$ under the given conditions. The results pbtained by this study are as follows: (1) Under the constant welding conditions, the tensile strength of test welded joint decrease in accordance with the increase of annealing temperature. The experimental results show that the reduction rate of tensile strength is about 35.09% of base metal strength. (2) Microhafdness distribution of welded joint bring about the maximum hardness near the bended line of welding joint. (3) Izod impact energy of welded joint in increase in according to the rise of annealing temperature and the peak energy of impact test occurs at $800^{\circ}C$

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.40 no.3
• /
• pp.281-288
• /
• 2016

The ballistic performance data of composite materials is distributed due to material inhomogeneity. In this paper, the uncertainty in residual velocity is obtained experimentally, and a method of predicting it is established numerically for the high-speed impact of a bullet into laminated composites. First, the failure strain distribution was obtained by conducting a tensile test using 10 specimens. Next, a ballistic impact test was carried out for the impact of a fragment-simulating projectile (FSP) bullet with 4ply ([0/90]s) and 8ply ([0/90/0/90]s) glass fiber reinforced plastic (GFRP) plates. Eighteen shots were made at the same impact velocity and the residual velocities were obtained. Finally, simulations were conducted to predict the residual velocities by using the failure strain distributions that were obtained from the tensile test. For this simulation, two impact velocities were chosen at 411.7m/s (4ply) and 592.5m/s (8ply). The simulation results show that the predicted residual velocities are in close agreement with test results. Additionally, the modeling of a composite plate with layered solid elements requires less calculation time than modeling with solid elements.

• Macromolecular Research
• /
• v.15 no.1
• /
• pp.44-50
• /
• 2007

This study investigated the effect of ultrasound irradiation on the blend of poly(lactic acid) (PLA) and poly(butylene adipate-co-terephthalate) (PBAT). The blends of PLA/PBAT(50/50) (PBAT50) were prepared in a melt mixer with an ultrasonic device attached. Thermal, rheological, and mechanical properties, morphology, and biodegradability of the sonicated blends were analysed. The viscosity of the sonicated blends was increased by the ultrasound irradiation owing to the strong interaction. The morphology of the sonicated blends was significantly dependent on the duration o the ultrasound irradiation. For PBAT50, the phase size reduction was maximized when the blends were ultrasonically irradiated for 30 sec. At longer duration of ultrasound irradiation, the PBAT phase underwent flocculation. Measurement of the tensile properties showed an increased breakage tensile stress and an enhanced Young's modulus when the blends were properly irradiated. This improvement was ascribed to better adhesion between the PLA matrix and the PBAT domain and to better dispersion of the PBAT phase. However, the tensile properties were maximized after excessive energy irradiation, which was ascribed to an emulsifying effect leading to coalescence of the PBAT phase. Impact strength was increased to reach a peak with the ultrasound irradiation, and was higher than the untreated sample for all sonicated samples due to the difference of failure mechanism between the tensile test and the impact test.

• Journal of Welding and Joining
• /
• v.30 no.5
• /
• pp.22-26
• /
• 2012

Butt-joints of A6061-T6 and AZ31 plates were successfully manufactured by using a friction stir welding method. Off-set free joints and off-set joints were fabricated to investigate the effect of the tool plunge position on the mechanical properties of the joints. Hardness test, tensile test and charpy impact test was performed to evaluate the mechanical properties of the joints. Off-set condition resulted in increase of mechanical properties of the joints. The variation of the hardness distribution in the SZ was also stabilized in the off-set condition. Tensile strength of the off-set joint was about 85% against to that of the AZ31 base metal. Impact absorption energy by Charpy-Impact-Test of the off-set joint also increased by almost 2 times against to that of the AZ31 base metal.

• Nuclear Engineering and Technology
• /
• v.31 no.6
• /
• pp.561-571
• /
• 1999

Microstructure and mechanical properties of five Cr-Mo steels for nuclear industry applications have been investigated. Transmission electron microscopy, energy dispersive spectrometer, differential scanning calorimeter, hardness, tensile, and impact test were used to evaluate the Cr and W effect on the microstructure and mechanical properties. Microstructures of Cr-Mo steels after tempering are classified into three types : bainitic 2.25Cr-lMo steel, martensitic Mod.9Cr-lMo, HT9M, and HT9W steels, and dual phase HT9 steel. The majority of the precipitates were found to be M$_{23}$C$_{6}$ carbides. As minor phases, fine needle-like V(C,N), spherical NbC, fine needle-like Cr-rich Cr$_2$N, and Cr-rich M$_{7}$C$_3$were also found. Addition of 2wt.% W in Cr-Mo steels retarded the formation of subgrain and dissolution of Cr$_2$N precipitates. Hardness and ultimate tensile strength increased with increasing Cr content. Though Cr content of HT9W steel was lower than that of HT9 steel, the hardness of HT9W was higher due to the higher W content. W added HT9W steel had the highest ultimate tensile strength above $600^{\circ}C$. But impact toughness of W added steel (HT9W) and high Cr steel (HT9) was low.w.w.

• Korean Journal of Materials Research
• /
• v.29 no.3
• /
• pp.189-195
• /
• 2019

The effect of C, Mn, and Al additions on the tensile and Charpy impact properties of austenitic high-manganese steels for cryogenic applications is investigated in terms of the deformation mechanism dependent on stacking fault energy and austenite stability. The addition of the alloying elements usually increases the stacking fault energy, which is calculated using a modified thermodynamic model. Although the yield strength of austenitic high-manganese steels is increased by the addition of the alloying elements, the tensile strength is significantly affected by the deformation mechanism associated with stacking fault energy because of grain size refinement caused by deformation twinning and mobile dislocations generated during deformation-induced martensite transformation. None of the austenitic high-manganese steels exhibit clear ductile-brittle transition behavior, but their absorbed energy gradually decreases with lowering test temperature, regardless of the alloying elements. However, the combined addition of Mn and Al to the austenitic high-manganese steels suppresses the decrease in absorbed energy with a decreasing temperature by enhancing austenite stability.

• Journal of Ocean Engineering and Technology
• /
• v.30 no.4
• /
• pp.268-276
• /
• 2016

This paper presents a study on the crashworthiness of the scaled-down stiffened panels used on a Korean icebreaker. In order to validate the crashworthiness of the panels, this paper provides various mechanical properties such as the results of a CVN test, quasi-static tensile test, and high-speed tensile test at arctic temperatures. Two types of steels (EH32 and FH32) were chosen for the material tests. CVN tests revealed that the two steels were equivalent up to −60℃ in terms of their impact energy absorption capacity. However, the toughness of FH32 was significantly superior to that of EH32. EH32 showed slightly higher flow stresses at all temperature levels compared to FH32. The improvement ratios of the yield strengths, tensile strengths, plastic hardening exponents, etc. for FH32, which were obtained from quasi-static tensile tests, showed an apparent ascending tendency with a decrease in temperature. Dynamic tensile test results were obtained for the two temperatures levels of 20℃ and −60℃ with two plastic strain rate levels of 1 s⁻¹ and 100 s⁻¹. A closed form empirical formula proposed by Choung et al. (2011;2013) was shown to be effective at predicting the flow stress increase due to a strain rate increase.

• Journal of the korean Society of Automotive Engineers
• /
• v.10 no.2
• /
• pp.46-53
• /
• 1988

Effect of Notch Shape and Hardness Ratio on Characteristics of Impact Fracture in Dual Phase Steels. In this study, it is investigated the effect of notch shape and hardness ratio on the characteristics of impact fracture in dual phase steels. The impact test was carried out at the temperature range from -40.deg. C to room temperature with Instrumented Charpy Impact Tester. The main results obtained are as follows; 1, The maximum impact bending strength (.sigma.$_{max}$) increases with the tensile strength. Also, the impact energy depends on .sigma.$_{max}$. 2, In room temperature, the impact energy depends on crack-initiation energy (E$_{i}$) in case of the high hardness ratio (R=3.4), whereas depends on crack-propagation energy (E$_{p}$) in case of the low hardness ratio (R=1.8) and the dependence of crack-initiation energy of the impact characteristics decreases with increasing test temperature. These phenomena are result from the difficulty of cleavage facet formation.ion.ion.