Applied Mechanics and Materials Vols. 365-366

Abstract: An important and basic issue of compound material surface analysis was raised in this paper, that was, the picking basic element which that material microstructures were well characterized according to the research subject of material. Here, the five kinds of basic element were proposed for picking, they were separately ellipse, regular triangle, rectangle, square and circle. At first, the counting methods and rules of area radio base on elements and pictures, and the formula of the merging difference was introduced, then block experiment design in modern statistics was used to pick among the five elements. At last, through experiment and analysis, the result of picking was that ellipse element was most appropriate one among five elements. Meanwhile, it was pointed in this paper with regard to the area radio of picture based on element that the approaching extent of the ellipse was most suitable among five elements.

Abstract: The purpose of this study is to explore the influence of the sodium hydroxide (NaOH) treatment duration on the physical properties of the composite filling material. This study uses Intermediate Restorative Material (IRM^®) as matrix and 2 % of polylactic acid (PLA) fiber as reinforcing material to make the IRM^®/PLA composite filling material. Before being infused into the IRM^® matrix, the 2-mm long PLA fiber is treated by NaOH solution for 5, 10, 15, 20, 30, 60, or 90 minutes. The setting time and compressive strength of resulting composite filling materials are evaluated, determining the optimum treatment duration is 60 minutes. The compressive strength is increased by 41 %.

Abstract: The effect of solution and aging temperatures on microstructure and tensile property of Ti-5Al-5Mo-5V-3Cr-1Fe Alloy was investigated. The results showed that the tensile strength lowered, when the solution and aging temperature rose respectively. The alloy with different heat treatments showed better tensile strength totally, i.e. the minimum level of ultimate and yield strength passed 1280 MPa and 1245MPa. The highest ultimate tensile strength could reach 1445 MPa. After (α+β) solution and aging treatment, the microstructure consists of primary α phase and transformed β phase with fine secondary α phase precipitating to improve the tensile strength effectively.

Abstract: The search for new technological concepts in the field of injection of thermoplastic polymers, in order to optimize the process and reduce cycle time, faced us with a new concept in moulding, where two different technologies are proposed to be unified. The fabric impregnated with thermoplastic is an example of a quite new product that combines the potential of polymers with long reinforcing fibres. In order to process this new product, injection of polymers and thermoforming will be applied in only one operation. To allow cycle time prediction for this new technique, changes will be made in the formulation of conventional injection cycle time, in order to comprise the new necessary stages. In this work a new approach is proposed to obtain moulded parts of thermoplastic polymers with functional fabric only in a single processing cycle. The description of the new stages and its mathematical formulation is made, in function of the time needed to complete each one. The results presented come from processing parameters optimization using the Particle Swarm Optimization (PSO) algorithm.

Abstract: In order to study the residual stress distribution in the titanium alloy laser rapid forming parts, the incremental-step hole drilling method is improved. Choose a calibration sample which has the same material as the test sample to conduct internal residual stress measurement by incremental-step hole drilling method. Conduct stress-release heat treatment (insulation 4 hours in 750 centigrade, furnace cooling) to the calibration sample before the measurement to uniform the internal stress. Calculate calibration compensation coefficient according to the calibration sample stress measurement result, and use the compensation coefficient to compensate the stress measurement result of the laser rapid forming sample. This method improves the reliability of internal residual stress measurement by incremental-step hole drilling method. Then use this method to measure the stress of laser rapid forming sample. The result shows that both the residual stress in the X direction and the Y direction is larger when the depth ranges from 1 mm to 3 mm. When the depth is greater than 3 mm, the residual stress decreases gradually with the hole depth increasing. The maximum value in the X direction is 147.13 MPa, and the maximum value in the Y direction is 236.32 MPa.

Abstract: In order to eliminate the bubbles during composites manufacturing, a special performance was designed. And the effects of the speed of the resin injection on bubble content were investigated. The results demonstrate that the speed of resin injection has distinct effects on the bubble content. When the speed of resin injection is slightly higher than the speed of capillary injection, the bubble content of the test pieces with latitudinal fiber bundles is more than the test pieces without latitudinal fiber bundles. But when the speed of the resin injection is slower than the speed of capillary injection, the bubble content of the test pieces with latitudinal fiber bundles is less than the test pieces without latitudinal fiber bundles. These results will provide a reference for the design of RTM process parameters.

Abstract: Drilled, cold expanded with ring indented method was employed for crack-tip on the both sides and front side of the specimens, thus build up the residual compressive stresses, strain hardening and plasticity induced closure, and lead toward crack growth retardation. The compact tension specimens of AISI 304 stainless steel were used drilled, cold expanded with ring indented in the fatigue test. The experimental methods were drilled (Φ=2mm ) and cold expanded (Φ=2.074mm) and both sides at 2mm and 1mm position of the crack-tip in the specimen, then apply 0kN, 6KN, and 9kN test loads, respectively. The experimental results showed that, for the same test position, the number of delay cycles result from cold expanded than that of drilled and the number of delay cycles are 220798. For the same position, the stronger test load is, the greater crack growth retardation effect is. And, This study proposed some useful information on utilizing cold expanded with ring indented method for AISI 304 Stainless Steel crack growth retardation.

Abstract: The morphology of poly (vinyl alcohol) (PVA)/graphene nanosheet (GNS) electrospun fibers was studied. GNSs were prepared from chemically reduced graphene oxide using freeze drying. The effect of adding GNSs on solution viscosity and conductivity were investigated. The PVA nanofibers with GNSs have smaller diameters than those without GNSs.

Abstract: Recently, due to the harsh demands for automobile lightweight and safety, more and more attention is focused on the warm forming process of various high strength steel sheet. In the present work, aiming to the formed parts safety problems caused by elevating temperature, take B340/590DP steel as the research object, the dent resistance of the warm-forming parts with free-form surface is studied. Firstly, combing the warm tensile tests under various conditions with the secondary room temperature tensile tests, a secondary yield constitutive model is established for the researched material by the regression analysis method, which reveals the influences of temperature, strain rate and pre-deformation on the secondary yield behaviors. Secondly, based on the plastic deformation theory and the free-form curves and surfaces theory, a dent resistance evaluation system is proposed for the warm-forming high-strength steel parts with free-form surface. Finally, design a dent resistance model experiment, validate the dent resistance of the warm-forming B340/590DP steel specimens, and determine the relevant coefficient value in the proposed dent resistance evaluation system by means of the obtained experiment data. The research results can be used directly to select the reasonable warm-forming process conditions, control and improve the warm-forming parts quality and performances.

Abstract: This article provides a method to determinate boron (B) impurity in silicon by inductively coupled plasma emission spectrometry (ICP-AES), in which the element spectral and analytical parameters were optimized. Three factors that influence testing results were discussed, including the amount of mannitol (C6H14O6) addition, concentration of nitric acid (HNO3) and evaporated temperature. As a result, the experimental parameters and conditions were optimized. The method of the detection limit, recovery and precision were all awarded with satisfactory results.