Applied Mechanics and Materials Vols. 764-765

Abstract: Transparent inorganic-organic film with nanoparticle shows promising application in various technology field. In order to obtain transparent inorganic-organic composite film, the main challenge is to homogeneously disperse inorganic nanoparticle in polymer matrix without coagulation. This study demonstrated that silane-modification can obtain ZrO₂ with chemically bonded silane. The ZrO₂ nanoparticle shows good stability in various organic phase. Thus prepared inorganic-organic composite film has transparence as high as 80%.

Abstract: The femtosecond laser drilling for metal thin film is theoretically investigated in this paper. Femtosecond laser patterning of metal thin films is of technological significance because the fabrication of electrodes or metallization lines is a key process commonly required in the manufacturing of modern electronic devices. A femtosecond pulsed laser has a temporally short pulse that does not cause significant heat conduction in the material. This property of femtosecond laser pulse drilling makes sub-micron machining achievable with laser irradiation. Considering vaporization as the mechanism of the material removal, this paper employs two-temperature model to analyze the thermal process for femtosecond laser drilling of metal thin film. The variations of the drilling rate and squared diameter with laser fluence are compared with the available experimental data. This study also analytically validates that the drilling depth per pulse is governed by the optical penetration depth for low laser fluences and the squared crater diameter is linearly in proportion to the logarithm of laser fluence.

Abstract: In order to improve the toughness of the cured aromatic tetrafunctional epoxy resins in the premise of influencing the thermal properties as little as possible, the aromatic tetrafunctional epoxy named N,N,N’,N’-tetraglycidyl-4,4’-diaminodiphenyl ether (TGDDE) was modified by a dimer carboxylic acid (DFA), and then the epoxies were cured with methyl nadic anhydride (MNA). In the present work, the toughness was characterized with the impact resistance tested by pendulum impact testing. Besides, the thermal properties of the cured epoxy resin were investigated with the thermo-gravimetric analysis (TGA) and dynamic mechanical analysis (DMA). The impact testing results indicated that the toughness of the cured resins could be improved after the modification and increased with the increasing content of DFA. The thermal analysis showed that the thermal properties of the cured resins were not influenced obviously since the thermal stabilities of the products could be improved and the glass transition temperature of them were not influenced obviously when the tetrafunctional epoxy modified with appropriate content of DFA.

Abstract: The researches on strength of members bending-compression were evaluated through experimental tests on eccentrically load of high-strength steel (HSA800). This test was performed on H-shaped steels of high strength steel (HSA800) to verify the P-M correlations of members subjected to combined forces according to axial load ratios. And this strength evaluation test was performed for various P-M combinations on adjusted eccentric distance. The results showed that all the specimens was satisfied with P-M correlations according to design criteria.

Abstract: This paper deals with the use of special asphalt-rubber mixture, the Stress Absorbing Layer (SAL). Description of SAL and test methods is given in theoretical part of this paper. Several different mixtures were designed and selected ones subsequently tested. Low-temperature properties, rutting test, bending tensile relaxation, stiffness modulus and fatigue properties were determined. These parameters are stated for asphalt-rubber mixtures with aggregate sizes up to 5 mm, 8 mm or 16 mm.

Abstract: Direct heating billet within a die by using resistance heating method was developed to form the high strength material in one-step gradual forging process. During the forging process, the pressing speed of the upper die is controlled with the pace of the heating billet. In the proposed method, the forging die can be used as both the forming and heating of the billet. Based on this innovative forming method, experimental result shows that the billet could be heated quickly to 1000oC in about 5 seconds and the high strength material was successfully formed to the shape of bolt head in one-step gradual forging process. With the proposed mechanism, the rapidly heating and gradual deformation during the hot forging process can be successfully carried out.

Abstract: The current local stability criteria (KBC2009, AISC2010) are enacted through theoretical and experimental studies of ordinary steels, but the mechanical properties of high strength steels are different from ordinary steels. The high strength steel in the applicability of design criteria should be needed to review because of increasing market demanding for high strength steel in the high-rise and long span buildings. In this study, stub columns of H-shaped and box section with various steel grades subjected to concentric loading were investigated, and these steels were checked to the applicability of current local stability criteria. The difference between the ordinary steel and high strength steel was compared. As a result of comparison with various steel grades, most specimens were satisfied with the design criteria, but some specimens with lower tensile strength were not reached the required strength. It is considered that the uncertainty of material was the higher when the tensile strength of material was the lower.

Abstract: The pore distribution in cement mortar, which is highly related to compressive strength and permeability, vary with water-cement ratios and curing periods. This study used magnetic resonance imaging (MRI) to observe the pore distribution. Compressive strength tests, the rapid chloride-ion permeability test, and electrical resistivity tests were performed to determine the influence of pore distribution on durability. The results reveal that lower water-cement ratios and longer curing periods contributes to fewer pores in mortar specimens. SEM images illustrated how this may be influenced by the rate at which the hydration product, C-S-H colloids, is generated. In addition, the results of durability testing indicate that porosity and compressive strength, total charge passed, and resistivity display linear relationships, as porosity increases, the total charge passed increases, resistivity decreases, and compressive strength declines. The linear regression determined that the R² of all relationships exceeded 0.90, thereby demonstrating the feasibility of applying MRI to assess the durability of concrete.

Abstract: This work characterizes the mechanical and opto-electric properties of Aluminum-doped zinc oxide (AZO) thin films deposited by atomic layer deposition (ALD), where various depositing temperature, 100, 125, 150, 175, and 200 °C are considered. The transmittance, microstructure, electric resistivity, adhesion, hardness, and Young’s modulus of the deposited thin films are tested by using spectrophotometer, X-ray diffraction, Hall effect analyzer, micro scratch, and nanoindentation, respectively. The results show that the AZO thin film deposited at 200 °C behaves the best electric properties, where its resistance, Carrier Concentration and mobility reach 4.3×10^-4 Ωcm, 2.4×10²⁰ cm^-3, and 60.4 cm²V^-1s^-1, respectively. Furthermore, microstructure of the AZO films deposited by ALD is much better than those deposited by sputtering.

Abstract: This study aims at analyzing the influence of the maximum principal stress on Tungsten Carbide Steel die core in an extrusion die which caused the crack of die core, and then adjusts the dies assembly method in order to improve the service life of die. In this study, combining FEM simulation software with Taguchi Method L₉(3⁴) is to choose the cobalt content for die core materials, and the quantity of shrink fit while assembling the die core and die case as the reference parameters. When carrying out the simulation process, compared the changes of the maximum principal stress of the die core caused by the plastic deformation of die materials to achieve the minimum expected value as the goal be chosen the most optimal die combination. Then, the results obtained are to make dies in trial and mass-production practically; as a result, it can be achieved that the die life is improved from the original 1000pcs to 150000pcs, which is more 150 times better than before.