Advanced Materials Research Vols. 1025-1026

Abstract: Objective: To investigate the effect of thermocycling on the shear bond strength of the three no-mixed bonding adhesives.

Abstract: Nonlatex orthodontic elastics have been developed as alternative products for latex allergic patients. However, to date, the studies on nonlatex elastics are limited and controversial. Therefore, further investigation of the mechanical properties of nonlatex elastics should be conducted.

Abstract: As a result of the strict restrictions on the use of power supply under the mine disaster, the Open loop cycle CO₂ refrigeration system is used in the Mine Rescue Cabin. Traditional system have got a couple of equipment malfunctions frequently, such as the Ice-block in Cold-start, Cold-frost and Overheating. In this paper, a new type of refrigeration system is designed after the Thermodynamic analysis of extreme limit condition. The new system avoids the Ice-block and the cold-frost by limit the refrigerant flow, it also can improve the capability of the evaporator. It has a important reference value to the research and application of the open loop cycle CO₂ refrigeration system in the extreme condition.

Abstract: In this study, a hydraulic servo system for mold oscillating mechanism was investigated. In order to check the efficiency and the stability of system, its geometrical designs, which change the natural characteristic of system, including a spool volume, area of piston, and so on were analyzed by a non-linear model. The model was composed of the equation of orifice, the continuity equation, and the force equilibrium including a variable effective bulk modulus belonging to operating oil, gas, and cylinder. All simulations were conducted by the MATLAB SIMULINK, and simulated as specific conditions corresponding real operation conditions in the steel industry. According to the analysis, the relation between a controller, servo design, and system performance was investigated with physical means. And, the fact that not compared to other design variables, the entrance shape on spool was dominant to determine the stability and the performance of system, was found. Furthermore, a fault detection method, and optimization problem including this work were discussed.

Abstract: 1024x768 This research aimed to investigate possible differences in values of longitudinal modulus of elasticity for wood species usually employed for structural purposes, as Castanheira (Bertholletia excelsa), Cambará (Erisma uncinatum), Cumaru (Dipteryx odorata), Jatobá (Hymenaea stilbocarpa), Garapa (Apuleia leiocarpa) and Peroba Rosa (Aspidosperma polyneuron), obtained from compression and tension parallel to grain, and static bending tests. Recommendations of the Brazilian standard ABNT NBR 7190:1997, Annex B, were followed. Statistical analysis results for the cited properties, had equivalent averages for the six wood species analyzed. This confirms that any of the three tests can be used to obtain the longitudinal elastic modulus and which could avoid the necessity of evaluating stiffness values for wood by more than one kind of mechanical test. Normal 0 21 false false false PT-BR X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Tabela normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;}

Abstract: Abstract. The study aimed to analyze the longitudinal modulus of elasticity (E_m), based on static bending tests, in different spans and confirm that it’s necessary adopt as 21 the ratio between span and height of the cross section of the specimen to turn no significant the influence of shear stress on vertical deflection. So, simplified equation to determine E_m can be employed. Specimens of Pinus elliottii var. elliottii and Pinus elliottii var. elliottii × Pinus cariabeae hondurensis (hybrid), came from Itapeva region, São Paulo State, Brazil, were considered. Bending tests were conducted in Labs of Experimental Campus Itapeva, UNESP, adapting recommendations of Brazilian Code ABNT NBR 7190. Twelve specimens of each species were tested. The trend lines for the plotted graphics showed clearly a nonlinear behavior until the neighborhood of ratio 21 and no expressive variations after this point, confirming that normative recommendations are correct.

Abstract: In order to improve the properties of a co-extruded wood-plastic composite (WPC), five different carbon-based fillers, namely graphite (G), expandable graphite (EG), carbon nanotubes (CNTs), carbon black (CB) and carbon fibres (CFs) were introduced into the shell layer of polypropylene (PP)-based WPC. The addition of CB, G, EG and CNTs improved the tensile strength by 45%, 25%, 5% and 32%, respectively; the addition of carbon fibres decreased the tensile strength by 22%. However, the tensile modulus of the composites decreased for all filler types. The incorporation of CNTs and CFs increased the impact strength by 11% and 21%, respectively; the impact strength of CB, EG and G-loaded WPCs decreased by 7%. The incorporation of CB, EG, G, CNTs improved the hardness by 25%, 9%, 25% and 59%, respectively; the addition of CFs decreased the hardness slightly. The wettability of the composite decreased with the CB, CNTs and CFs loadings. The presence of EG increased water absorption, whereas thickness swelling decreased compared to the reference.

Abstract: In-situ tensile properties during the solidification of three commercial aluminium die casting alloys, ADC5, ADC6 and ADC12, were investigated by utilizing a high temperature tensile testing machine. Mid-length portions of the tensile specimens were melted by electromagnetic induction heating. The in-situ data was recorded in the temperature range in which the melt zone was cooling down to the solidified state and immediately after solidification. The technique allows measurement and evaluation of tensile strength and elongation of the alloys at the temperature ranges critical to many manufacturing processes. The relationship between fraction of solid and temperature during the solidification of each alloy was predicted using the Gulliver-Scheil model applied with the thermodynamic database, i.e., Thermo-Calc. Zero Strength Temperature (ZST) and Zero Ductility Temperature (ZDT) of each alloy were determined from the experiments and were correlated to the calculated fractions of solid. The morphology of the specimens’ fractured surfaces was also investigated. The tensile behavior during solidification in this study was used for characterization of hot tearing behavior in each alloy.

Abstract: Fumed silica particles (SiO₂) were directly added into poly (butylene succinate) (PBS) by melt mixing process. The effects of amount of fumed silica particles on mechanical properties of PBS/fumed silica composites, those are tensile strength, tensile modulus, impact strength as well as flexural strength, were investigated. It was found that the mechanical properties decreased with increasing fumed silica loading (0-3 wt%). In order to increase polymer-filler interaction, fumed silica was treated with 3-glycidyloxypropyl trimethoxysilane (GPMS), and its structure was analyzed by FT-IR spectrophotometry. The PBS/modified was found to possess better tensile strength, tensile modulus, impact strength and flexural strength that those of PBS/fumed silica composites.

Abstract: Nanocomposite is one of the most favorable approaches to improve mechanical properties of polymers. This study prepared polymer composite of PLA and LLDPE with different amount of rice husk silica (0.5 and 1 wt%). The composites were prepared by melt-mixing in a twin-screw extruder and processed into film by a chill roll cast extruder. The mechanical properties were investigated through tensile testing and tear testing. The result show that the tensile modulus of PLA decreased with 1wt% rice husk silica. Similarly, tensile modulus of LLDPE dropped with the addition of silica. However, with the addition 0.5 and 1 wt% rice husk silica, the elongation at break of PLA and LLDPE composites increases significantly.