Modeling of cutting force prediction in machining high-volume SiCp/Al composites

Variations in cutting forces significantly influence the tool wear and part quality in machining high-volume SiC-particle-reinforced aluminum matrix (SiCp/Al) composites. Properties of the reinforcement SiC particles, such as size and volume fraction, contribute to the change in the cutting forces. This paper presents a cutting force model based on the geometrical and mechanical nature of the tool and workpiece, considering the effect of the SiC reinforcement particles. The cutting force is predicted as three components (F_z, F_x, and F_y) and the resultant cutting force F_τs. The cutting force was considered to generate three deformed zones: (a) shear deformed zone, (b) friction deformed zone on the chip–tool interface, (c) plow deformed zone. The effect of SiC reinforcement particles on friction deformed zone is analyzed emphatically. The friction force from friction deformed zone was obtained by calculating the sliding friction force and rolling friction force. To verify the feasibility and validity of the predicted model of cutting force, cutting experiments were performed with different combinations of cutting speed, feed rate, depth of cut, and tool nose radius. The predicted cutting force values demonstrate good agreement with the measured experimental cutting force values in most cutting conditions. The average percentages of the prediction error were 1.93%, 6.20%, and 10.48% for the F_z, F_x, and F_y components, respectively, thus proving the validity and accuracy of the predicted model of cutting forces.     

Influence of mechanical activation,ion implantation,and filler type on the formation of a transfer film in tribounits of UHMWPE-based composites

The supermolecular structure of composites obtained by reinforcing an ultrahigh-molecular-weight polyethylene with C and Al₂O₃ nanofibers, Cu and SiO₂ nanoparticles, and Al₂O₃ and AlO (OH) microparticles has been studied by means of X-ray diffraction analysis, infrared spectroscopy, and optical and electron microscopy. It is shown that the filler type (nano-, submicro-, or micro-) determines the character of the supermolecular structure, the evolution of friction transfer films, and the wear resistance of the composites.     

Artificial Intelligence in numerical modeling of nano sized ceramic particulates reinforced metal matrix composites

Artificial neural network models have the capacity to eliminate the need for expensive experimental investigation in various areas of manufacturing processes, including the casting methods. An understanding of the inter-relationships between input variables is essential for interpreting the sensitivity data and optimizing the design parameters. Aluminum is the best metal for producing metal matrix composites which are known as one of the most useful and high-tech composites in our world. Combining aluminum and nano Al₂O₃ particles will yield a material with high mechanical and tribological properties. In this investigation, the accuracy of various artificial neural network training algorithms in FEM modeling of Al₂O₃ nano particles reinforced A356 matrix composites has been studied.     

Microstructure of a-SiOx:H

A set of a-SiO_x:H (0.52 <x< 1.58) films are fabricated by plasma-enhanced-chemical-vapor-deposition (PECVD) method at the substrate temperature of 250°C. The microstructure and local bonding configurations of the films are investigated in detail using micro-Raman scattering, X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). It is found that the films are structural inhomogeneous, with five phases of Si, Si₂O:H, SiO:H, Si₂O₃:H and SiO₂ that coexist. The phase of Si is composed of nonhydrogenated amorphous silicon (a-Si) clusters that are spatially isolated. The average size of the clusters decreases with the increasing oxygen concentration x in the films. The results indicate that the structure of the present films can be described by a multi-shell model, which suggests that a-Si cluster is surrounded in turn by the subshells of Si₂O:H, SiO:H, Si₂O₃:H, and SiO₂.     

The effect of CNT modification on the mechanical properties of polyimide composites with and without MoS<Subscript>2</Subscript>

The aim of this work was to investigate the effect of surface modification of carbon nanotubes (CNTs) on the mechanical properties of polyimide (PI) composites with and without MoS₂. A three-phase system of CNT/PI/ MoS₂ laminates were fabricated with an extrusion-grade PI to produce CNT-reinforced laminates with MoS₂ volume fractions of 1–5%. The tensile and impact properties of CNT/PI composites and CNT/PI/MoS₂ laminates were also measured and compared. Results showed that the introduction of CNTs as reinforcing additives improved the tensile properties of the composites, but worsened their impact properties. Furthermore, the addition of MoS₂ increased the impact strength of the CNT/PI composites greatly. The optimum contents of CNT and MoS₂ have been found.     

Synthesis and characterization of C3N4 crystal (I)

A successful experimental synthesis of pure crystalline β- and α-C₃N₄ films on Si(100) substrate was carried out by bias-assisted hot filament chemical vapor deposition (bias-HFCVD). It is found that a mixed-phase C₃-_I-Si_xN_y buffer layer was formed between the Si substrate and the C-N film. A “lattice match selection” was proposed to study the growth mechanism of C₃N₄ clusters composed of many crystal columns with hexagonal facets. Project supported by the National Natural Science Foundation of China and the Chinese Academy of Sciences.     

Synthesis and characterization of C3N4 hard films

C₃N₄ films have been synthesized on both Si and Ft substrates by microwave plasma chemical vapor deposition (MPCVD) method. X-ray spectra were calculated for single phase α-C₃N₄ and β-C₃N₄ respectively. The experimental X-ray spectra of films deposited on both Si and Pt substrates showed all the strong peaks of α-C₃N₄ and β-C₃N₄ so the films are mixtures of α-C₃N₄ and β-C₃N₄. The N/C atomic ratio is in the range of 1.0–2.0. X-ray photoelectron spectroscopy (XPS) analysis indicated that the binding energy of Is and N ls are 286.2 eV and 399.5 eV respectively, corresponding to polarized C-N bond. Fourier transform infrared absorption (FT-IR) and Raman spectra support the existence of C-N covalent bond in the films. Nano-indentation hardness tests showed that the bulk modulus of a film deposited on Pt is up to 349 GPa     

On the classes of hereditarily ℓp Banach spaces

Let X denote a specific space of the class of X _α,p Banach sequence spaces which were constructed by Hagler and the first named author as classes of hereditarily ℓ_p Banach spaces. We show that for p > 1 the Banach space X contains asymptotically isometric copies of ℓ_p. It is known that any member of the class is a dual space. We show that the predual of X contains isometric copies of ℓ_p where 1/p + 1/q = 1. For p = 1 it is known that the predual of the Banach space X contains asymptotically isometric copies of c ₀. Here we give a direct proof of the known result that X contains asymptotically isometric copies of ℓ₁.     

Water uptake and mechanical characteristics of wood fiber-polypropylene composites

The influence of mixing process (in a two-roll mill, high-speed mixer, or twin-screw extruder) on the strength properties of polypropylene/wood fiber composites was studied. The best results were obtained for composites compounded in a twin-screw extruder. The water uptake and the influence of moisture on the flexural strength (σ_fl) and modulus (E_fl) were studied by immersion of the composites in water at 20, 50, and 90°C. Most strongly the moisture affected the value of E_fl, but the degree of water uptake and the change in σ_fl and E_fl also depended on temperature and the presence of a modificator—maleated polypropylene (MAH). MAH improved the strength properties of the composites both in dry and wet states and also decreased the extent of water uptake and swelling in cyclic (soaking/drying) tests. Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 42, No. 1, pp. 101–114, January–February, 2006.     

Preparation, structure, magnetic properties and special magnetoresistance effect of Lao.67Sr0.33Mn03+δ/Pr0.7Cao.3 Mn03+δ/Lao.67Sro.33Mn03+δ trilayered thin films

The La_0,67Sr_0.33Mn0_{3 +δ}/Pr_0.7Ca_o.3Mn0_3+δ/La_0.67Sr_0.33Mn0_3+δ(LPL) trilayered films on (100)LaA-1O₃ substrates are prepared by using direct current (DC) magnetron sputtering method. The results obtained by means of X-ray powder diffractometer show that all films are the high quality epitaxial films. The results gained by SQUID magnetometer indicate that there is a magnetic coupling in the LPL trilayered films. The resistivities of LSMO, PC-MO and LPL films are measured using standard four-probe method and analyzed log_p-1/T curve. From the results it is concluded that the middle-layered PCMO which is ferromagnetic may play a role of intra-magnetic field, which weakens the paramagnetism of LSMO film, lowersp _max and enlargesT _p which is the transition temperature from metal to insulator, just as the applied magnetic field does. And the middle-layered PCMO may induce the change of the density of states in the LSMO’s gap. The two reasons above make the resistivity andT _p of the samples in zero field change with the thickness of PCMO layers. Project supported by the Chinese Academy of Sciences and the Foundation of State Science and Technology Commission of China.     

Fibrous Filler-Matrix Interaction in Oxide Composites

The interaction between a fibrous alumina filler and a hydrated zirconia matrix during the fabrication of ceramic composites is studied. The influence of the crystal structure and porosity of the filler on the properties of the ZrO₂-Al₂O₃ composite material is investigated. It is found that, as a result of addition of alumina fibers of cubic and monoclinic structures (- and -phases), the ZrO₂ hydrogel interacts with fibers and solid ZrO₂ solutions of tetragonal structure are formed. These solutions exist over the range of 600 to 1200°C and, at annealing above 1200°C, due to crystallographic transitions the of - and -phases, they break down, namely Al₂O₃ transforms into -corundum and ZrO₂ into a monoclinic modification. However, the material does not fail and a stable porous ceramic composite is formed. To manufacture a composite with improved mechanical characteristics, fibrous alumina fillers with the structure of -corundum must be used.     

Distribution results for lattices in SL(2,ℚ p )

In this paper we study the ergodic properties of the linear action of lattices Γ of SL(2,ℚ_p) on ℚ_p × ℚ_p and distribution results for orbits of Γ. Following Serre, one can define a “geodesic flow” for an associated tree (actually associated to GL(2,ℚ_p)). The approach we use is based on an extension of this approach to “frame flows” which are a natural compact group extension of the geodesic flow.     

The genus of space curves

LetC be a curve contained in ℙ _k ³ (k of any characteristic), which is locally Cohen-Macaulay, not contained in a plane and of degreed. We prove thatp _a (C)≤≤((d−2)(d−3))/2. Moreover we show existence of curves with anyd, p _a satisfying this inequality and we characterize those curves for which equality holds.

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Sunto Si dimostra che seC⊃ℙ _k ³ (k di caratteristica qualunque) é una curva, non piana, localmente Cohen-Macaulay, di gradod, allorap _a (C)≤((d−2)(d−3))/2. Si mostra che questa limitazione è ottimale, e si classificano le curve di genere aritmetico massimale.

     

Complemented copies of ℓ<Subscript>p</Subscript> spaces in tensor products

We give sufficient conditions on Banach spaces X and Y so that their projective tensor product X ⊗_π Y, their injective tensor product X ⊗_ɛ Y, or the dual (X ⊗_π Y)^* contain complemented copies of ℓ_p.     

Experimental and Numerical Investigations of Al/Mg Compounds

Al/Mg compounds produced by hydrostatic extrusion exhibit unique characteristics regarding high strength and low weight, which are required by safety part applications in lightweight constructions. Between the two materials an interface in form of a brittle intermetallic phase consisting of Al₂Mg₃ and Al₁₂Mg₁₇ arises during the production process. However, a certain plastic deformability of the semi-finished product is essential for further forming processes. Even under multi-axle load during a radial upsetting process, the interface maintains a full material joint although a fragmentation and a new secondary interface between the fragments can be observed. Due to the evaluations of light microscopy images and Eulerian Hencky strain values at the interface, which are obtained with the help of the Digital Image Correlation, a relation between the strain and the boundary layer's appearance seems reasonable. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Alcune classi di gruppi abeliani misti di rango 1

Riassunto Si definisce una classe diZ _p-moduliQ _β, simili aip-gruppiP _β studiati daE. A. Walker, che danno una caratterizzazione delle sequenze esatte bilanciate diZ _p-moduli e degliZ _p-moduli bilanciati proiettivi. Si definiscono poi dei gruppi misti di rango 1,R _h, che sono un'estensione al caso globale deiQ _β e che generalizzano i gruppi razionali. Per gliR _h vale un teorema analogo a quello di classificazione coi tipi di Baer ed essi danno inoltre una caratterizzazione delle sequenze esatte bilanciate di gruppi e dei gruppi bilanciati proiettivi.

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Summary We define a class ofZ _p-modulesQ _β, like thep-groupsP _β studied byE. A. Walker, that give a characterization of balanced exact sequence ofZ _p-modules and balanced projectiveZ _p-modules. We introduce also some mixed groups of rank one,R _h, which are an extension to the global case ofQ _β and which generalize rational groups. Moreover, forR _h, there is a theorem, which is analogous to Baer's theorem of classification by types. GroupsR _h give too a characterization of balanced exact sequence of groups and of balanced projective groups.

     

Besov spaces andK-functionals inL p, 0<p<1*

We investigate Besov spaces and their connection with trigonometric polynomial approximation inL _p[−π,π], algebraic polynomial approximation inL _p[−1,1], algebraic polynomial approximation inL _p(S), and entire function of exponential type approximation inL _p(R), and characterizeK-functionals for certain pairs of function spaces including (L _p[−π,π],B _s ^a(L _p[−π,π])), (L _p(R),_s ^a(L_p(R))), , and , where 0<s≤∞, 0<p<1,S is a simple polytope and 0<α<r. This project is supported by the National Science Foundation of China.     

Interface interaction and inter-osmosis effect of Fe x (SiO2)1-x nanocomposite materials on magnetic properties

Fe _x (SiO₂)_1-x nanocomposites prepared by using mechanical alloying method were reported. The microstructure character and magnetic properties of Fe _x (SiO₂)_1-x nanocomposite samples with different Fe content and different ball milling time were studied by using X-ray diffraction (XRD), transmission electron microscopy (TEM), Mössbauer spectroscopy, and Faraday magnetic balance in a wide temperature range. The results indicate that the rnicrostructure and magnetic properties are closely related to ball milling time and Fe content. When Fe content is less than 20 wt%, the sample after 80-h ball milling has very complex microstructure. Small α-Fe grains and Fe cluster are implanted in SiO₂ matrix. And there are not only isolated α-Fe granular and Fe cluster, but also nanometer scaled sandwich network-like structure. Fe _x (SiO₂)_1-x nanocomposite samples display a rich variety of physical and chemical properties as a result of their unique nanostructure, strong interface interaction and inter-osmosis effect in Fe-SiO₂ boundaries, and the grain size effect.     

Maggiorazioni interpolatorie negli spaziH λ m,p (Ω)

Sommario Si dimostrano alcune maggiorazioni che si possono riguardare come una generalizzazione della classica maggiorazione di Poincaré. Se ne deducono, a scopo illustrativo, delle maggiorazioni interpolatorie per funzioni u ∈H _λ ^{m, p} e u ∈ H^{2, p} ∩L ^{P0, λ}. Questo lavoro è stato parzialmente finanziato da ? the United States Air Force ? in continuazione del contratto AF EOAR, grant 65-42.