Force Fp Research Articles

ENERGY-BASED CHARACTERIZATION OF PRECISION HARD MACHINING USING PARTIALLY WORN CBN CUTTING TOOLS

This paper highlights the performance of precision hard turning with CBN cutting tools from energy point- of-view with additional tool wear effect. For this purpose several wear tests were performed during which the tool nose wear VBC and the corresponding changes of component forces Fc, Ff and Fp were continuously measured. Based on the measured forces and geometrical characteristic of the uncut layer, specific cutting and ploughing energy were determined for several combinations of cutting parameters. Consequently, changes of energy consumption resulting from tool wear evolution for variable feed rate, depth of cut and tool nose radius were presented.

Hydrostatic pressure effect on superconductivity and vortex pinning mechanism of Sr(Fe0.88Co0.12)2As2 single crystal

The external pressure effect on superconducting transition temperature (Tc) was investigated by dc magnetic and electrical resistivity studies for Sr(Fe0.88Co0.12)2As2 single crystal down to 2 K. The observed large diamagnetic signal and zero resistance clearly indicate bulk superconductivity with sharp Tc of ∼16.5 K (0 GPa). Onset of Tc is suppressed monotonically down to 5.2 K under pressure up to 2.8 GPa. The evaluation of Tc was observed by the application of magnetic fields and critical field was estimated to be rather high of about 10 T. These observed results reveal a large vortex region that replicates high anisotropy of the systems. The observed coherence length ξGL(0) was estimated to be ∼57 Å. We evaluated the thermally activated flux flow activation energy (U0) at 100 K using the Arrhenius equation. Finally, the temperature and pressure dependent critical current density Jc(T) and reduced flux pinning force (fp) were analyzed by collective pinning model with different magnetic fields.

Dependence of the passive force Fp from the revolutions, back engagement of cutting edge ae, working engagement of the cutting edge ap during milling

In this contribution is analysed the force component of final force (passive force) by peripheral milling operation. Therefore, the main parameters that had influence to independent variable were revolutions, back engagement of a cutting edge ae, working engagement of the cutting edge ap. The article deals with the issue of milling in material AlMgSi0.5 (aluminium alloy). Specifically evaluates the force component with respect to change of revolutions (4000/min., 5000/min., 6000/min.), working engagement of the cutting edge ap (1 mm, 2 mm, 3 mm) and back engagement of a cutting edge ae (5 mm, 10 mm, 15 mm). The Alfaflex process fluid with 7% concentration was supplied in an amount of about cca 10 l/min.

Dependence of the passive force Fp from the revolutions, back engagement of cutting edge ae, working engagement of the cutting edge ap during milling

Dependence of the passive force Fp from the revolutions, back engagement of cutting edge ae, working engagement of the cutting edge ap during milling

The effects of Mg doping on the microstructure and transport properties of internal tin-processed brass matrix Nb3Sn superconductors

The addition of Zn into Cu matrix has been proved to enhance the Sn activity and accelerate the formation of a Nb3Sn layer in internal tin-processed Nb3Sn wires. However, in our samples, Ti is doped in Sn cores, and during the reaction, Ti was observed to accumulate between the inner and outer sub-elements of the 1980-Nb-core multi-filamentary brass matrix wires. With the addition of Mg into the brass matrix, Ti accumulation between the sub-elements was significantly suppressed, which promoted Ti incorporation into the Nb3Sn layers. Meanwhile, the formed Nb3Sn layers exhibited smaller grain sizes. Compared to the brass (Cu-12wt%Zn) matrix wires, an improvement of critical current density (Jc) was found in the Cu-12Zn-0.2Mg matrix wires due to the incorporation of Ti into the Nb3Sn layer and the refinement of the Nb3Sn grain size. The irreversibility field (Birr) and maximum bulk pinning forces (Fp,max) were calculated from the Kramer plot by analyzing the Jc(B) curves. A small amount of Mg (0.2 wt%) doping into the Cu-12Zn matrix wires can increase the Birr value by about 0.5 T and the Fp,max value by about 3 ∼ 4 GN m−3 after the wires were heat treated between 670 °C and 730 °C. The non-Cu Jc of the Cu-12Zn-0.2Mg matrix wires reaches the maximum value of 1533 A mm−2 @12 T after heat treatment at 685 °C and decreases at higher temperatures.

Mechanical properties of maize kernel horny endosperm, floury endosperm and germ

ABSTRACT Mechanical damage of maize kernel caused by external forces during processing is closely related to its internal mechanical properties. In this research, three main tissues’ (horny endosperm, floury endosperm and germ) mechanical properties of three maize varieties (Jinyu818, Zhengdan958 and Dafeng30) and five stages of moisture contents (11.78–34.73% w.b.) were evaluated using puncture test. Results showed that there was no (p > .05) or weak significant (0.01 < p < .05) difference between varieties, while significant moisture and tissue material effects were observed. For rupture force (Frp ), ultimate strength (σb ), toughness (Trp ), initial firmness (Finf ), average firmness (Favf ), modulus of elastic (E), apparent modulus of elastic (AME), bioyeiled force (Fby ), bioyeiled strength (σs ) and penetration force (Fp ), outer layer tissue (horny endosperm) of maize kernel at lower stage of moisture contents were higher than those of inner layer tissues (floury endosperm and germ) at higher moisture contents. While for bioyeiled deformation (Dby ) and rupture deformation (Drp ) values, results showed that inner layer tissues at with higher moisture content were the highest. Pearson’s correlation analysis showed that most of the parameters had a significant correlation (p < .01, r > 0.80) with each other. This study can be considered as a contribution towards further studying and minimizing the mechanical damage of the maize kernel when applying external force during and post harvesting.

Investigation of the Deep Hole Drill Stability When Using a Steady Rest

Rotary cutting tools, which are relatively long and thin spindles for deep hole machining turn out to be unstable when the cutting force FP reaches a certain critical value Fkp The behaviour of the deep hole drill stability when using a steady rest is investigated; and a diagram of the critical parameters Ic-D showing the boundary of the drill stability zone when using a steady rest located in the centre of the shank bit is represented.

An Analysis of the Origin of the Interaction Force between Electric Charges, including Justification of the ln&amp;lt;i&amp;gt;r&amp;lt;/i&amp;gt; Term in the Completed Coulomb’s Law, in HM16 Ether

In this study, we demonstrate the correctness of our 2010 hypothesis regarding the need to complete Coulomb’s FC law with the term lnr, resulting in the completed FCC force. For this purpose, we consider the electrical interactions between charged microparticles (MPs), which develop as fundamental vibrations (FVs) in ether, producing the vibrational strains ε and γ and the resulting stresses σ and τ, as percussions of ether cells (ECs) upon the MP surface. The stresses σ and τ produce a resultant force FP, due to the percussions which constitute the real electric force FCC. The spatial effect of ether on FP is demonstrated by an analytical method, considering the electrical interaction between MPs through various equidistant spatial paths li of FVs, modelled on the basis of the Huygens principle for waves. For this issue, we utilized a numerical calculation, which could be generalized. But this spatial effect of the ether leads at a very slow decreasing of the FP forces ratio rF when doubling the distance l, in contrast to Coulomb’s FC forces whose ratio rF decreases accentuate with doubling l. Accordingly, the necessity of including the term ln r in the FCC force, which is limited to 1.0 for doubling l, at long distances, was justified.

Experimental Investigation of the Shear Behavior of a Concrete Beam without Web Reinforcements Using External Vertical Prestressing Rebars

The shear performance of concrete beams is known to be an important mechanical feature; hence, enhanced shear resistance is critical for determining a beam’s performance in terms of security and service life. This paper presents a study on the shear behavior of concrete beams without web reinforcement strengthened by external vertical prestressing rebars (EVPRs). Experimental data were obtained from seven test beams with varying influencing factors (stirrup ratio ρsEP, arrangement spacing s, prestressing force Fp, and compressive stress degree γp of the EVPRs) to determine their effects on the shear behavior. The results reveal that the EVPRs can significantly improve the shear capacity and ductility of concrete beams without web reinforcement. Furthermore, the failure mode is changed from brittle diagonal tension to relatively ductile shear compression, and the flexural cracks and shear cracks are more fully developed. The shear capacity becomes enhanced as the ρsEP and γp are increased; vertical compressive stress provided by the EVPRs can reduce the principal tensile stress of the concrete structure to prevent the shear cracking and enhance the shear resistance of the concrete. Meanwhile, in the stage from the formation of the critical shear crack (CSC) to the shear failure, the EVPRs can be used as stirrups to share the shear load. It can be concluded that EVPRs can effectively improve the shear performance of concrete beams.

Equiaxial nano-crystals Nb3Al superconductor prepared by optimized mechanically alloying

The influence of the original nominal chemical composition, milling time, sintering temperature and holding time was studied systematically on the phase formation, microstructure and superconductivity of mechanically alloyed Nb3Al. By optimizing the process, we have successfully prepared high-performance Nb3Al superconductor. Samples with original nominal composition of Nb-27 at.%Al were milled for 3 h and sintered at 900 °C for 1 h, resulting in an entire A15 superconducting phase, except a few negligible Nb2Al phase. The superconducting critical transition temperature (Tc) and the upper critical field at absolute zero (Hc2(0)) reached 15.7 K and 28.1 T, respectively. It should be noted that the superconducting critical current density (Jc) was still as high as 6.3 × 104 A cm−2 at a temperature of 4.2 K under an applied magnetic field of 7 T, as well as a maximum flux pinning force (Fp,max) of 6.23 × 109 N m−3 in the whole magnetic field range at 4.2 K. All of the results could be attributed to the microstructure of the sample with equiaxial nano-crystals.

Enhanced flux-pinning performance of YBCO films derived from a fluorine-free sol-gel process with ceria addition

In this work, a facile and effective method which can significantly improve the flux-pinning performance of YBCO films was reported. YBCO/CeO2 composite films were prepared on LaAlO3 (LAO) single crystal substrates through a fluorine-free sol-gel approach with a certain amount of ceria addition. During the nucleation and growth of YBCO films, CeO2 reacted with the barium-contained phase in YBCO precursors to generate the nanosized BaCeO3 phase and thus the redundant Y2O3 and CuO phases remained, leading to the wrong stacking of Cu atoms to form the stacking faults of Cu-O planes, which has been demonstrated by XRD, TEM, SEM and EDS results. The variation of critical current density (Jc) and flux-pinning force (Fp) with the percentage of ceria addition was investigated, and the results show that YBCO film with the amount of 5 mol% of ceria addition exhibits the highest Jc and the strongest Fp at the same temperature and applied magnetic fields. In addition, the stacking faults effectively reduced the degree of dependency of Jc of YBCO film on the applied magnetic field especially at low temperature.

Thermally activated flux creep in nanocrystalline δ-MoN thin films

We study the vortex dynamics in a nanocrystalline 420 nm thick δ-MoN film on Si (100). The film was grown at room temperature by reactive sputtering and following it is crystallized by thermal annealing at 973 K for one hour. The microstructure shows grains with sizes between 30 nm and 65 nm. The film displays a Tc of 11.2 K. The magnetic field dependence of the critical current density Jc at intermediate and low fields (related to the upper critical field) displays a power-law regime. The self-field Jc at 4.5 K is ≈2 MA cm−2. The pinning force Fp exhibits a maximum at h ≈ 0.3, which is in agreement with vortex pinning produced by grain boundaries. An Anderson-Kim mechanism describes the temperature dependence of the flux creep rates. The U0 values range from ≈2500 K for μ0H = 0.02 T to ≈1300 K for μ0H = 0.5 T.

Multi-objective robust optimization design of a front-end underframe structure for a high-speed train

ABSTRACTA multi-objective robust design optimization of a front-end underframe structure for application in high-speed trains is proposed and the structural parameter uncertainty is considered. A finite element model of the structure is developed and verified by dynamic impact experiments. The sensitivity analysis demonstrates that the thicknesses of the centre sill have significant influences on structural crushing behaviours. The specific energy absorption and the initial peak crushing force (Fp) are taken as optimization objectives. Compared with the baseline structure, the 6-sigma robust design shows that the Fp and the structural mass are reduced by 54.86% and 13.06%, respectively, and the robust optimum is more reliable. The 6-sigma robust optimal solution has an efficient energy-absorbing capacity while satisfying the design constraint. Thus, 6-sigma robust optimization can be applied for high-speed trains.

Vortex pinning in artificially layered Ba(Fe,Co)2As2 film

Static high critical current densities (Jc) > 1 MA/cm2 with magnetic field parallel or perpendicular to c-axis were realized in Co-doped/undoped multilayerd BaFe2As2 films. We made a current bridge by FIB to allow precise measurements, and confirmed that the boundary quality using FIB was considerably better than the quality achieved using a laser. The presence of a high in-plane Jc suggested the existence of c-axis correlated vortex pinning centers. To clarify the relationship between the Jc performance and superstructures, we investigated the magnetic flux pinning mechanism using scaling theory of the volume pinning force Fp(H). The Jc(H) curves, Fp/Fp,max vs. h = H/Hirr curves, and parameters p and q depended on the characteristics of the flux pinning mechanism. It was found that the dominant pinning mechanism of Co-doped/undoped multilayerd BaFe2As2 films was Δl-pinning and the inserted undoped BaFe2As2 layers remained non-superconducting. The dominant pin geometry varied when the magnetic field direction changed. It was concluded that the artificially layered BaFe2As2 film is a 3-D superconductor due to its long correlation length compared to the thickness of the non-superconducting layer.

Angular dependence of the critical current density and the temperature scaling of the flux pinning force in YBCO thin film

In this paper, the critical current Jc(Θ) have been investigated as a function of magnetic-field angle Θ. Θ is the angle between the c-axis and the applied magnetic field direction. This investigation concerned three temperature values (60 K, 78 K and 81 K). The normalized pinning force fp versus the normalized magnetic field h was also studied (fp = Fp / Fpmax and h = H / Hmax). The Fp expression was determined based on the Kramer model.The studied sample was a single crystal of YBaCuO thin film deposited by the ablation laser method on the surface (100) of a SrTiO3 substrate.The results of this work show the existence of point core pinning of the normal centers in the low field regime and the occurrence of the flux creep in high field regime.

Tool stability analysis for deep hole drilling

A large number of parts have deep holes, therefore, rotary cutting tools, which represent relatively long and thin columns are used for holemaking. In this article we analyze the behavior of such tools under the influence of an axial compression load, in our case, the axial cutting force Fp , which differs fundamentally from the compression of short tools. Moreover, experience shows that when the cutting force Fp reaches a certain critical value equal to Fkp , a long straight column becomes unstable.

Preparation of Nb3Al Superconducting Tapes by a Powder-in-Tube Method Combined with Hot-Pressed Sintering

The precursors of Nb-Al tape were fabricated by a powder-in-tube (PIT) technique. Supersaturated solid solutions of Nb-Al powder were obtained by high-energy ball milling, followed by a powder-in-tube process to prepare series of Nb3Al precursor tapes. Compared with sintering under normal pressure, the hot-pressing sintering greatly increased the critical current density of the tapes. The results showed that the Nb3Al tapes prepared via the powder-in-tube method and hot-pressed sintering could significantly improve the J c performance, and the value of J c (8 K, 0 T) was higher than 6 × 105 A/cm2. The Nb3Al tapes after pressing under the pressure of 20 MPa and sintering at 950 ∘C for 3 h had the best magnetic flux pinning performance, and the sample reached the maximum flux pinning force (F p,max) of 3.28109 N/m3 in the magnetic field of 2.2 T.

Crashworthiness analysis and optimization of a cutting-style energy absorbing structure for subway vehicles

This study proposes a cutting-style energy absorbing structure to improve the crashing performance of subway vehicles through experiment and numerical simulations. The structure consists of an anti-creeper device, energy absorption tube, cutting knife and clamp. A finite element (FE) model of a cutting-style energy absorbing structure is created and validated by full-scale experimental data. Based on the validated simulation model, the influence of the design parameters, which include the cutting depth (d), the cutting edge angle (CEA) and the chip central angle (CCA), on the impact performance is analyzed. The parametric study found that the design parameters influence the peak cutting force (Fp) and energy absorption (EA). In addition, the structure has prominent advantage in lowering the peak interface force. Finally, the response surface method (RSM) is adopted to achieve maximum EA and minimum Fp simultaneously. The optimized results show that the objectives compete with each other, and the weighting factors are of considerable significance to the most satisfactory Pareto fronts solutions. In this paper, the minimum distance selection method (TMDSM) is adopted to determine the most satisfactory solution. It can be concluded that when CCA = 18.18°, CEA = 23.87°, and d = 2.87mm, the structure shows the best impact performance and EA = 275.9kJ and Fp = 887.2kN.

Flux pinning properties of YBa2Cu3O7–δ thin films containing a high density of nanoprecipitates: A comparative study to reveal size effects

Temperature dependence of critical current density Jc(H, T) was measured in moderate magnetic fields (H ⊥ film) in two thermally co-evaporated YBa2Cu3O7–δ (YBCO) thin films (A, B) and two YBCO films (C, D) deposited using a pulsed-laser deposition method. All sample films were grown epitaxially with the c-axis perpendicular to the surface of a single-crystalline substrate. Transmission electron microscopy observation revealed that these four films contained a high density of nanoprecipitates with typical sizes of 3.6 – 5.0 nm (A), 5.0 – 7.1 nm (B), 7.0 – 10.1 nm (C) and 8.7 – 14.3 nm (D). Films A and B contained very fine nanoprecipitates, whose typical diameters Dtyp are smaller than double the estimated Ginzburg-Landau coherence length 2ξab at T = 77 K, and exhibited a steep increase of Jc with decreasing temperature. Whereas, film D, which contained relatively large nanoprecipitates (Dtyp > 2ξab at T ≤ 70 K), exhibited a gradual increase in Jc. This led to a remarkable crossing of the Jc(T) curves. The temperature dependence of Jc(H//c) under a fixed magnetic field is approximated by Jc ∼ (1 – T/Tc)m(1 + T/Tc)2 where the index m is larger for films containing finer precipitates; that is, m(A) > m(B) > m(C) > m(D). This means that finer nanoprecipitates generally cause steeper Jc increase at low temperatures, which is the origin of the observed crossing phenomenon. The experimental results are reasonably explained by several theoretical models based on the direct summation of elementary pinning forces fp calculated by core pinning interactions.

Analysis of the micro turning process in the Ti-6Al-4V titanium alloy

The great challenge of the modern industry is carrying out an online prediction in the shop floor during the machining to define the exact instant of tool breakage and simultaneously improve the quality of manufactured products. This work shows a study to examine the effect of the feed rate, depth of cut, cooling system, and type of tool on the responses: surface roughness, passive force (Fp), feed rate force (Ff), cutting force (Fc), and micro hardness in the turning of Ti-6Al-4V titanium alloy. Experimental tests were carried out with workpieces 4 mm in diameter, and the surface roughness, micro hardness, and cutting efforts were analyzed. The analysis of variance was used to define the influence of input parameters on the responses. The results showed that the lowest surface roughness was achieved using the carbide tool with code TPMT and the lower input parameters, but the most important parameter was feed rate. The cutting efforts were influenced by feed rate and depth of cut. On the other hand, the cooling system does not show good efficiency in the cutting efforts. However, the geometry of the tool and the Minimum Quantity Lubrication system were more effective to cause the hardening in micro scale at the surface of the material.