Applied Mechanics and Materials Vols. 496-500

Abstract: 50% solid content of nano-SiO₂/silicon modified polyacrylate composite emulsion was synthesized by emulsion polymerization and sol-gel technique with MMA, BA, silane coupling agent (KH-570) and tetraethoxysilane (TEOS) as the main raw material. The influence of some parameters on the properties of emulsion and film were studied, such as initiator, emulsifier, 3-methacryloxypropyltrimethoxysilane(KH-570), tetraethoxysilane(TEOS). The results showed that as the dosage of tetraethoxysilane (TEOS) and organic silicon(KH-570) increased, the stability of emulsion polymerization decreased; The emulsion with good polymerization stability and film with good water resistance were obtained when the mass of initiator is 0.5%, the mass of compound emulsifier is 4%, of which the ratio of OP-10/SDBS/DNS-86=5:3:2, the mass of KH-570 is 2% and the mass of TEOS is 1%.

Abstract: The paraffin, pre-treated paraffin and hydroxyl-terminated polybutadiene (HTPB) were measured by Differential Scanning Calorimetry (DSC) and Thermogravimetry (TG) in different conditions. Thermal degradation characteristics of the paraffin, pre-treated paraffin and HTPB were studied; Influences of different pressure and different temperatures on thermal degradation characteristics of pre-treated paraffin were analyzed. Experiments show that the decomposition temperature of pre-treated paraffin is higher than that of the untreated paraffin, but lower than that of HTPB; the initial reaction temperature, the reaction exothermic peak temperature and the reaction heat release of pre-treated paraffin were all affected by pressure and heating rate; Kinetic parameters of pre-treated paraffin in oxygen atmosphere were calculated.

Abstract: Carbon nanotubes (CNTs) possess extremely high stiffness, strength and resilience, and may provide the ultimate reinforcing materials for the development of nanocomposites. In this paper, nanostructure is modeled as a linearly elastic composite medium, which consists of a homogeneous matrix having hexagonal representative volume elements (RVEs) and homogeneous cylindrical nanotubes. Formulas to extract the effective material constants from solutions for the RVE under axial as well as lateral loading conditions are derived based on the continuum mechanics approach. Numerical examples using the FEM are presented, which demonstrate that the load carrying capacities of the CNTs in a matrix are significant. For the RVEs having long carbon nanotube, better values of stiffness in axial direction are found as compared to stiffness in the lateral direction. Also, It is found that the square RVEs tend to overestimate the effective Youngs moduli of the CNT-based composites, and the hexagonal RVEs may be the preferred models for obtaining more accurate results.

Abstract: With systematic change in the riser size, together with variation of thickness and length, A201 aluminum alloys were cast in 100% silica sand molds. The higher the thermal gradient, the lower the porosity content was measured in the A201 aluminum alloy plate casting. And the faster the solidus velocity, the more the porosity content in this study. The porosity content of A201 aluminum alloy was influenced by both of thermal gradient and solidus velocity at same time in this study. Basically, high thermal gradient with slow solidus velocity seems get lower porosity content in A201 aluminum alloy castings.

Abstract: Two spherical composite adsorbents namely polyacrylonitrilepotassium cobalt hexacyanoferrates (PAN-KCoCF) and polyacrylonitrilepotassium nickel hexacyanoferrates (PAN-KNiCF) were synthesized. The effects of liquid flow rate, bed height and presence of other cations on the adsorption of cesium were investigated by conducting fixed-bed columns. The results showed that the column performed well at lowest flow rate for PAN-KNiCF. Flow rate examined had little influence on the adsorption of PAN-KCoCF. The breakthrough time decreased with decreasing bed height for both PAN-KCoCF and PAN-KNiCF. In addition, the existence of K⁺, Na⁺, NH₄⁺, Ca²⁺ and Mg²⁺ in solution caused a reduction of maximum adsorption capacity for both of the composites. The bed depth service time (BDST) model and the Thomas model were used to analyze the experimental data and the model parameters were evaluated. Good agreement of the experimental breakthrough curves with the model predictions was observed.

Abstract: In this paper, the porous NiTi alloys were prepared by microwave sintering, and the effects of NH₄HCO₃ contents on the microstructure of the porous NiTi alloys were studied. The microstructure of the porous NiTi alloys was investigated by optical microscopy, Archimedes drainage method, surface roughmeter and X-ray diffraction. The results showed that the porous NiTi alloys were mainly composed of NiTi, Ni₃Ti, Ti₂Ni and Ni, and the diffraction peaks of the non-equiatomic phases (Ni₃Ti, Ti₂Ni and Ni) increased with increasing the NH₄HCO₃ contents. At the same time, the porosity, pore size and surface roughness of the porous NiTi alloys increased with the increase of the NH₄HCO₃ contents.

Abstract: In the author’s opinion, Spot Welding Procedures Chart D.1 (hereafter referred to as Figure D.1) in Appendix D of International Standard ISO 15609-5 [1] is not accurate in principle. This figure is not suitable for materials need exerting forging force for spot welding such as aluminum alloy, especially hard aluminum alloy, for it does not correctively reflect loading moment of forging force. In the author’s opinion, the loading moment of forging force given by Figure D.1 is too late, which will lead to the generation of crack. In addition, two important reasons equally considered to advance loading moment of forging force are: (1) different spot welding equipments have different response time for welding pressure; (2) electric response speed is faster than that of mechanical or pneumatic mechanism, that is to say, response speed of current shall be faster than implementation speed of forging force. Is this paper, we discuss such above-mentioned kinds of different situations. We suggest advancing the forging force in Figure D.1 to the maintenance course of welding current. We propose an amended spot welding course schematic diagram and a simplified schematic diagram.

Abstract: In this paper, Si was added to the Al alloy to research its effect on the wettability between SiC and Al at 1000°C. The results showed that the contact angle decreased with the increase of Si content in the Al alloys and it droped from 570 to 370 with the Si content from 0 to 12wt% and reached equillibrium with the further addition of Si to 18wt%. The improvement mechanism of Si on the wettabitliy is also discussed in this paper.

Abstract: Near-net-shaping hot isostatic pressing (NNS-HIP) method was used for once-forming complex monolithic Ti6Al4V alloy bladed disks manufacturing. The complex monolithic bladed disks were formed successfully in a near-net-shape manner using the proposed HIP mold scheme in this study. The results showed that there were fine and homogeneous strip α+β phases and no obvious pores or cracks were detected. A "layered" phenomenon was observed in as-built part microstructure. The tensile strength value of specimens from the NNS-HIP bladed disks in the same furnace reached 900MPa, which was higher than the values of parts manufactured using casting and forging processes. The fracture morphology analysis showed that the sample had a ductile fracture. This study provides a reference to the NNS-HIP for the bladed disk parts manufacturing.

Abstract: The evaluation of properties of rolls of old and new generations is made. Using method of work calculation and rolls service properties after experimental checking the material and properties of working rolls which are used in finishing rolling group of CWRM-1700 JSC ArcelorMittal Temirtau until year 2001 and later are estimated.