Mechanical model of errors of probes for numerical controlled machine tools

CNC machine tool probes are not only used to set up the workpiece before machining and to control it after machining, but also to determine volumetric errors of the machine tool. That’s why there is a necessity not only for knowledge of the complete on-machine measurement system errors, but also for the knowledge about probe’s errors in separation from machine tools. This paper presents a theoretical model of errors of probes for CNC machine tools. It takes into account such unique features of the machine tool probes as the transducer with support on the whole circumference and as wireless communication. 3 probes: RMP60, MP700 and IRP32.00-MINI were tested using moving master artifact method, out of machine tool, to verify the model described. The triggering radius values obtained experimentally were compared with values calculated using theoretical model, resulting with a compliance up to 92%.     

Dynamic characteristics and model updating of damaged slab from ambient vibration measurements

This paper reports a field investigation using ambient vibration testing on a damaged floor slab of a reinforced concrete frame building. Due to unexpected heavy rainfall, the hill slope at the rear of building failed triggering a major landslide and causing major damage to the perimeter beams and parts of the slab on the first floor. The modal parameters namely natural frequencies and mode shapes were acquired using output only identification technique and the results obtained from the undamaged and damaged floor slabs were compared. It was observed that there was a 25–53% drop in natural frequencies of the damaged slab compared to the undamaged slab, with a much bigger drop for the lower modes. The irregularities in mode shapes identified correlates with the location of the cracks as revealed from visual examination on the damaged slab. Two finite element models of the slab were created using a finite element software package. The damaged slab was updated manually so as to match the modal parameters obtained experimentally. The results from this study further highlight the possibility and feasibility of using non-destructive vibration testing for condition monitoring of structures over more conventional testing techniques.     

Quantification of handwriting performance: Development of a force acquisition pen for measuring hand-grip and pen tip forces

Suitable apparatuses for exploring the kinetics of handwriting performance are limited, which hinders a thorough understanding of the control mechanisms between the hand and a pen. This study proposes a force acquisition pen (FAP) that detects the contact forces between digits and the pen barrel, as well as the force between the pen tip and writing surface. Tests of the validity and reliability of the FAP and the variability of the acquired kinetic information of handwriting performance were conducted. Acceptable validity (R² > 0.9986, p < 0.0001) and reliability (intraclass correlation coefficients >0.79) were obtained, indicating the feasibility of the proposed pen. From the force information acquired from the digits and pen tip, kinetic parameters were determined for a detailed investigation of the coordination and control mechanism between the digits and a pen.     

Surfactant-polymer interactions: Mixed micelles of hexadecylpyridinium bromide and trimethyltetradecylammonium bromide in aqueous poly(vinylpyrrolidone) solution

The conductance of hexadecylpyridinium bromide (HPyBr) and trimethyltetradecylammonium bromide (TTAB) mixtures over the entire mole fraction range of HPyBr (α_HPyBr) was measured in aqueous poly(vinylpyrrolidone) (PVP) solution containing 1, 5, and 10 wt% PVP at 30°C. Each conductivity curve showed two breaks corresponding to two aggregations throughout the whole mole fraction range of HPyBr and TTAB mixtures except for pure TTAB for which a single break corresponding to the conventional critical micelle concentration was observed. The two aggregation processes in the presence of low amounts of PVP were mostly similar to those in pure water, however, 10 wt% PVP shifted the break, corresponding to the second aggregation, toward the higher value. This was attributed to HPyBr/PVP interactions, which were also evident from the appearance of a second break in the conductivity (κ) plot of pure HPyBr in aqueous 10 wt% PVP. From conductivity data, various micellar parameters in the presence of PVP were determined and discussed from the standpoint of micelle-polymer interactions. The mixing behavior of HPyBr and TTAB corresponding to the first break in the presence of PVP was ideal for the most part and identical to that in pure water.     

Strain ratcheting and stress relaxation around interference‐fitted single‐holed plates under cyclic loading: experimental and numerical investigations

Longitudinal strain ratcheting and stress relaxation in interference‐fitted single‐holed plates were investigated both experimentally and numerically. In the experimental part single‐holed plates made from Al‐alloy 7075‐T6 were force‐fitted with oversized pins to create 1% and 2% nominal interference fit sizes. Then these plates (specimens) were instrumented with dynamic strain gauges in longitudinal direction around the hole to measure the strain during interference fit and strain ratcheting during subsequent cyclic loading. In the numerical part, 2D finite element code has been written to simulate the interference fit process and subsequent cyclic loading to obtain strains and stresses around the force fitted hole. To predict the strain ratcheting, Ohno–Wang kinematic hardening model was applied for simulation of stress/strain path. The strain ratcheting predicted from the finite element code and experimental test results were compared. The results showed that there is a good agreement between the measured and numerically evaluated strains, and the strain ratcheting is bigger for higher cyclic load level, but it is smaller for larger interference size.     

Effects of substrate composition and roughness on mechanical properties and conformality of parylene C coatings

Nanoindentation was used to determine reduced elastic modulus E_r and hardness H of 16 μm thick Parylene C coatings vapor‐deposited on mill‐finished samples of aluminum, copper, nickel steel, and stainless steel. Profilometry was used to compare average surface roughnesses of the polymeric coatings to the roughnesses of the underlying metals, thereby providing a quantitative index for determining conformality. Roughness, elasticity, and hardness of coatings were found to be affected by both chemical composition and surface roughness of four different metallic substrates. Standard nanoindentation evaluations of E_r and H distributions for the various metals were found to be positively skewed, which precluded use of simple averages for purposes of comparison. However, analysis of the nanoindentation and profilometry data by use of alternative techniques indicated that coatings were consistently smoother and flatter than their underlying substrates, i.e., they were not truly conformal, and nanomechanical properties of Parylene C were affected by the chemical composition of the substrates independently of the effects of substrate roughness. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Influence of Y doping on structural,vibrational, optical and magnetic properties of BiFeO3 ceramics prepared by Mechanical Activation

Y substituted BiFeO₃ (Bi_1−xY_xFeO_3; x=0.0–0.1) polycrystalline ceramics were synthesized by Mechanical Activation. The effect of varying composition of Y substitution on the structural, vibrational, optical and magnetic properties of doped BiFeO₃ (BFO) ceramics has been investigated. Rietveld refinement of X-ray diffraction patterns reveals that all samples crystallize in distorted rhombohedral structure with R3c symmetry and no structural transition has been observed. Raman spectroscopy also confirmed the distorted perovskite structure with R3c space group. Optical studies in the spectral range 1–4.5 eV were dominated by two d-d and three charge transfer (C-T) transitions. The optical band gap decreases from 2.11 to 2.01 eV with increasing Y substitution. Room temperature magnetic measurements showed weak ferromagnetic ordering and enhancement in magnetization with increasing Y concentration. Mechanical activation leads to significantly altered magnetic properties, particularly in higher Y-doping samples. The Mössbauer spectra demonstrate the suppression of spiral spin modulation of the magnetic moments resulting in enhanced ferromagnetism with increasing doping concentration. Significant increase in Néel temperature T_N in the substituted compounds was discussed on the basis of structural distortions.     

Protein adsorption on titanium dioxide: Effects on double layer and semiconductor space charge region studied by EIS

The semiconductor properties of an n-type TiO₂ oxide surface and its modification by protein adsorption using electrochemical impedance spectroscopy (EIS) were studied. Impedance spectra under steady state conditions were obtained as a function of electrode potential and human serum albumin (HSA) concentration in solution. The effect of the adsorption potential on the EIS response was also analyzed (E_ads −0.70, −0.50 and −0.080 V vs. saturated calomel electrode). The impedance spectra were modeled using different equivalent circuits, and data analysis were performed by data fitting in the whole frequency range, as well as in the low and high frequency ranges. The electric representation that better fit experimental data consisted of two equivalent subcircuits composed by a combination of constant phase elements (cpe₁ and cpe₂) and resistances (R_s and R₁). The cpe₁ element represented the distributed capacity in the semiconductor oxide. The cpe₂ element was associated with diffusional processes. We have analyzed EIS data based on a theoretical calculation of interface apparent capacitance (C_app) from the cpe₁ parameters (Q₁ and ?₁) and resistance elements. The changes in capacitance, produced by the presence of HSA, were associated to changes in the space charge layer capacitance of the semiconductor, as a result of the energy band bending near the surface. The values obtained for the R₁ element from the theoretical fitting procedures (in the high and whole frequency range) were correlated to the electric resistance inherent to the semiconductor properties having a value of 6.10³ Ω cm².     

Mathematical Statistics and Probability Theory

The standardized difference in estimated Bayes risk between two subsets of groups of allocation variables is proposed as a test statistic for additional classification accuracy. This test is used in a minimal-best-subset algorithm that aims to select the optimal subset for the data at hand—that is, the smallest subset retaining most of the classification accuracy. A multivariate normal example confirms that all-possible-subsets and minimal-best discrimination procedures based on Wilks's lambda and Rao's test usually do not identify the best subsets according to estimated Bayes risk. The minimal-best discrimination subset was suboptimal in all of 100 bootstrapped samples: It contained too many groups in every case. In contrast, the minimal-best classification selected an optimal subset for 82 out of 100 bootstrap examples; appending a test of additional accuracy of the minimal-best subset versus the overall-best subset led to an optimal subset in the other 18 cases by suggesting the addition of more groups.