Applied Mechanics and Materials Vols. 80-81

Abstract: In this paper, a low-temperature self-mixing combustion synthesis method was introduced to prepare spinel LiMn₂O₄. Low-melting raw materials and fuel (acetate salts as starting materials and urea as fuel) were molten to a homogeneous liquid mixture at ~100°C. The mixture was then ignited and calcined at a higher temperature, final products were obtained. The products were determined by X-ray diffraction (XRD) and scanning electric microscope (SEM). XRD analysis indicated that product with higher purity was obtained at 550°C for 5h when the molar ratio of Li:Mn:urea=1:2:4. The impurity Mn₂O₃ was appeared in the products when the igniting temperature >600°C, and the content of Mn₂O₃ increased with the increasing igniting temperatures. SEM investigation indicated that the particles of the products were small and agglomerated. The igniting temperature monitoring indicated that the combustion reaction rate increased with increasing igniting temperature, and this did not favor for the formation of LiMn₂O₄.

Abstract: Continuous carbon fiber reinforced silicon carbide composite material (C/SiC) is one of the most effective candidate materials for hot structures in aeronautic and aerospace applications. Its performances in the complicated service environments are widely concerned. A database, aiming at optimized design of C/SiC, was developed. The database collected original data on the fabrication, microstructure of C/SiC, as well as abundant data on performance experiments including tension, compression, shear, fatigue, creep, oxidation, high-temperature fatigue, and so on. The logic structure of the database, modeled by unified modeling language, provides a data link that connecting the processing, microstructure and performance of C/SiC, so that users can conveniently create a test result set to build the mathematical model of material design. Efficient software was developed to realize management, browsing and extension of the database.

Abstract: Three-dimensional molecular dynamics simulations are performed to investigate the AFM-based nanometric cutting process of single crystal copper. The effects of cutting velocities (180, 360, and720 m/s) on the cutting force, the ratio of the thrust force and cutting force and subsurface layers. The results show that the dislocations nucleate beneath the tool, and propagate along the [-11-1] direction in the (111) plane. The effects of the nanocutting action from the tool on the subsurface damaged layers decrease gradually as the distance from the tool tip increases. With the increasing cutting speed, the cutting forces increase accordingly. However, the ratio of the the ratio the thrust force and cutting force decrease as the cutting speeds increase. With the proceeding of the cutting process, that tends to the same on the whole.

Abstract: A disposable, magnetism-controlled, and amperometric immunosensor was fabricated for the determination of C reactive protein (CRP). Firstly, Fe₃O₄ (core)/Au (shell) nanoparticle (GMP)–coated multiwalled carbon nanotubes (MWCNT–GMP) were prepared. Then, monoclonal antibody (anti-CRP) was immobilized on MWCNT–GMP to prepare MWCNT–GMP/anti-CRP composite magnetic probes. At last, the probes was adsorbed on the surface of N,N''-bis-(2-hydroxy-methylene)-o-phenylenediamine cobalt (CoRb) modified, screen-printed carbon electrodes through external magnetic field.The amount of CRP in the serum sample was determined by one-step immunoassay. When different concentrations of CRP were added into25μL of phosphate-buffered solution (pH7.0) containing10^-4M H₂O₂, the percentage of DPV cathodic peak current decrease (CR%) exhibited a linear relationship with the concentration of CRP in the range of 0.3–100 μg L^-1.The detection limit was 0.16 μg L^-1(3б).The immunosensor was used to determine CRP in serum samples of patients with heart diseases, and the results were consistent with those of the traditional ELISA method. The proposed amperometric immunosensor was sensitive, rapid, magnetic field–controlled, and disposable; therefore, it could be used to determine even traces of CRP in the blood serums of patients with heart diseases.

Abstract: Binary Fe-Al alloy ingots with 29 at. %Al were prepared with commercially pure Fe and Al in a vacuum induction furnace. The specimens used in the internal friction measurement were cut using an electric sparkle machine from the ingots into a dimension 68×1.7×0.9 mm3. The heat treatment was performed in such regimes as heating temperature 900°C and holding time 1 hour in an argon atmosphere followed by furnace cooling or air cooling. The air-cooled samples were then aged at 350°C for different time to achieve the different degree of disorder. The internal fiction-temperature spectra of the air-cooled Fe₇₁Al₂₉ alloy were measured during both heating and cooling using a computer-controlled automatic inverted torsion pendulum through free-decay and forced vibration methods. It has been found that three internal friction peaks appear during heating at 180°C termed as P1, 340°C termed as P2 and 510°C termed as P3 in air-cooled specimens, respectively. P1 and P2 peaks disappear and P3 is retained during cooling. XRD results show that the air-cooled Fe₇₁Al₂₉ alloy is disordered and the furnace-cooled specimen possesses ordered structures. The air-cooled specimen presents similar diffraction peaks to the furnace-cooled specimen after it is heated to 650°C and then in-situ cooled to room temperature. Ageing has great influence on the P1 and P2 peaks for the air-cooled Fe₇₁Al₂₉ alloy. The height of P1 and P2 peaks is decreased with increasing aging time, which is due to the reduction in the disorder degree of the air-cooled specimen.

Abstract: The relation between corrosion depth and width with corrosion time is according with the power function. The corrosion pits can be seen as ellipse balls through the examination of QUESTAR three-dimensional optics microscope. Corrosion can decrease the fatigue life of materials and is the main reason of fatigue crack form and grow; through AFGROW analyze we can see that the AFGROW software can simulate crack growth life well and the error is low, the crack growth life and critical crack length are conservative than experiment values.

Abstract: The junction and flow distributing of Yangtze River’s main stream or branch, the underground gate valve of every interception and reservoir are all placed branch. In order to find flow parameters of algorithms when the water system needs the pipeline bifurcation layout, the fluid energy equation was built based on the differential equation of fluid motion because it force only the steady flow and the gravity in the quality. By further analysis of the equation, derive that fluid total energy equation when merging flow bifurcation layout in a underground drainage piping as an example, demonstrate the use of the equation. Theoretical calculations were consistent with actual measurements and provided a theoretical basis for the engineering design and calculation.

Abstract: In production practice，the preferred methods of determining interference fit of hole and axle are mainly empirical methods such as analogy ，which exist a wide range of errors. This paper discusses in detail the selection standard of common interference fit by stress analysis of hole and axle interference fit，puts forward the concept of allowable shearing stress of interference fit which refers to allowable shearing stress in machine design，and determines the preferred method of exact interference fit.

Abstract: The alien stone turning-milling compound machining center is a new generation gap multifunctional compound machining center. It is used to process rotating part of alien stone products and three-dimensional sculpture products. The pillar and guiding rail are the key parts of the machining center. The straightness error of the pillar and guide rail seriously impacts the linear motion precision of beam parts. Comparison the straightness of guiding rail with pillar or without pillar, it shows that the results meet the standard of GB/T16462-1996. So it ensures the accuracy of the linear motion precision of beam parts. It lays a solid foundation for achieving the design function and machining precision.

Abstract: In this paper, 6 eccentric structural models are selected as examples, a great many elastic earthquake response analyses are carried out. The biggest action effect which an earthquake brings about when acting in one direction along certain angle is found out, and is defined as a normal value. Simultaneously, the present two commonly used methods using bidirectional horizontal earthquake input, with identical horizontal component earthquake waves, are used to calculate effect value. The results are compared, and they indicate that it's suitable for the proportion of the two component earthquake acceleration peak values to be adjusted to 1:0.3，when carrying out the bidirectional horizontal earthquake input with the same earthquake wave.