Using a Squid in Gravitational Field Measurement

The effects are examined for a weak static gravitational field on electrodynamic variables (current, magnetic induction, magnetic flux). Two schemes are proposed for experiments: recording the effects of a gravitational field potential difference on the magnetic flux Φ measured by means of a direct-current SQUID and determination of the change in magnetic flux in a SQUID in relation to the strength of the gravitational field g. Estimates are made of the effects that may be observed in these ways. __________ Translated from Izmeritel'naya Tekhnika, No. 9, pp. 18–21, September, 2005.     

Thermostressed state of a plate with angular inclusions

We reduce the problems of heat conduction and thermoelasticity for an isotropic plate with foreign elastic inclusions bounded by piecewise smooth curves to problems of conjugation of analytic functions on broken lines. Singular solutions of these problems and the corresponding complex potentials are constructed. Luts'k Industrial Institute, Luts'k. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 34, No. 3, pp. 67–72, May–June, 1998.     

Construction of a virtual multipole myocardium pseudo-ECG from synchronously measured electrograms in physiological tests

General formulas are suggested for the multipole pseudo-ECG. Pseudo-ECGs Φ(t) have been determined under physiological test conditions for preparations of the ventricular heart wall in warm-blooded animals (rabbit and ground squirrel). The virtually measured Φ(t) curves reproduce under the corresponding conditions the ECG patterns characteristic of all the main forms of evoked monomorphic and polymorphic tachyarrhythmia. __________ Translated from Izmeritel’naya Tekhnika, No. 12, pp. 57–62, December, 2007.     

Influence of stress concentrators on the fatigue and fracture characteristics of steels and welded joints

We study the effect of enhancement of the fatigue strength of welded joints in steel structures caused by the removal of the concentration of welding stresses. Main attention is given to the so-called method of contact treatment of the surface of welded joints close to the technology of arc welding. It is shown that the application of this method not only removes the defects of welded joints but also significantly increases their fatigue strength (by 20–100%). Welding Research Institute, VúZ, Bratislava, Slovakia. Published in Fizyko-Khimichna Mekhanika Materialiv, Vol. 34, No. 5, pp. 87–90, September–October, 1998.     

An electrochemical evaluation on the crevice corrosion of 430 stainless steel by micro capillary tubing method

The aim of this study was to investigate the initiation of crevice corrosion for ferritic 430 stainless steel in artificial crevice electrode cells using the IR drop mechanism. The 430 stainless steel artificial crevice electrodes were potentiodynamically polarized in solutions of sodium chloride with different concentrations. The potentiostatic polarization was measured for various artificial crevice sizes by measuring the potentials in the crevice by the depth profile technique using a micro capillary tube which was inserted into the crevice. The criterion for IR>Δ Φ^*, where Δ Φ^* is the difference between the applied potential, E_SURF, and the electrode potential of the active/passive transition, E_A/P, was also measured during the process of crevice corrosion. The potentials in the crevice were successfully measured from −220 mV versus SCE to −360 mV versus SCE, which is lower than that of the external surface potential of −200 mV versus SCE. Thus these results show that evaluation of corrosion using the IR drop mechanism in the crevice was more objective and easier to reproduce than the existing methods.     

Effect of the surface structure of a composite material on spatio-polarization characteristics of reflected radiation

The polarization degree, rotation of the polarization plane, and strength indicatrix of radiation with a wavelength of 0.63 μreflected from the surface of a unidirectional superhigh-modular organic plastic are investigated. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 70, No. 2, pp. 219–225, March–April, 1997.     

Influence of shear bond strength on compressive strength and stress–strain characteristics of masonry

The paper is focused on shear bond strength–masonry compressive strength relationships and the influence of bond strength on stress–strain characteristics of masonry using soil–cement blocks and cement–lime mortar. Methods of enhancing shear bond strength of masonry couplets without altering the strength and modulus of masonry unit and the mortar are discussed in detail. Application of surface coatings and manipulation of surface texture of the masonry unit resulted in 3–4 times increase in shear bond strength. After adopting various bond enhancing techniques masonry prism strength and stress–strain relations were obtained for the three cases of masonry unit modulus to mortar modulus ratio of one, less than one and greater than one. Major conclusions of this extensive experimental study are: (1) when the masonry unit modulus is less than that of the mortar, masonry compressive strength increases as the bond strength increases and the relationship between masonry compressive strength and the bond strength is linear and (2) shear bond strength influences modulus of masonry depending upon relative stiffness of the masonry unit and mortar.     

Boundary-value problem of electroelasticity for a piezoceramic elliptic cylinder and a layer with tunnel hollow

We consider a skew-symmetric stressed state of a piezoceramic layer weakened by a through elliptic hollow filled with air. The surfaces of the layer (or a finite elliptic piezoceramic cylinder) operating in contact with air are covered with a diaphragm rigid in its plane and flexible in the perpendicular direction. The stress vector {X ₁, X ₂, X ₃} acts on the lateral surface. The boundary-value problem of electroelasticity is reduced to a system of singular integral equations. This system is numerically solved by the method of mechanical quadratures. The integral representations of the solutions are constructed on the basis of the corresponding matrix of Φ-solutions. The distribution of normal circular stresses over the elliptic contour subjected to the action of normal or tangential stresses is investigated. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 43, No. 2, pp. 49–54, March–April, 2007.     

Influence of the mechanism and parameters of hardening of modified novolac phenol-formaldehyde resins on the physicomechanical properties of the composite

We study the influence of concentrations of the components of reactive compositions and the conditions of production and hardening of phenol-formaldehyde resins with the help of epoxy resins in the presence of polyvinylpyrrolidone on the physicomechanical, thermal, adhesion, insulation, and anticorrosion properties of the composites. The positive effect of modifications with polyvinylpyrrolidone and epoxy resin manifests itself within the following ranges of concentrations: 0.5–1 wt.% of polyvinylpyrrolidone and 25–30 wt.% of ED-20 in the presence of 1 wt.% of N, N-dimethylaniline. Thus, the adhesion strength of a glue based on the developed composition becomes four times higher and constitutes 5–6 MPa; the impact strength, static strength in bending, surface hardness, and the specific bulk electric resistance of the specimens hardened at 150–160°C for 25–30 min become 1.5–2.5 times higher and are equal to 5–6J/m², 15–17 MPa, 350–420 MPa, and (5.5–6.5)⋅10¹⁰ Ω⋅m, respectively. The behavior of these characteristics strongly depends on the conditions of hardening. We optimized the composition of modified phenol-formaldehyde resins, which made it possible to produce materials with predicted properties.     

Strength analysis of a split sleeve in a pipe containing a defect

We study the decrease in the strength of a pipe containing an artificial defect. On the basis of the analytic and numerical models, we consider the influence of the structural features of a split sleeve on its load-carrying ability. We also analyze the joint operation of a sleeve and a pipe containing an artificially made axial surface defect. The results of the numerical analysis are compared with the experimental data. Translated from Problemy Prochnosti, No. 2, pp. 102–111, March–April, 2009.     

Standardization of a shear test method for lead-free solder paste chip joints

The electronics industry is moving to replace Pb-based solder with Pb-free solder because of the growing environmental regulations governing the use of lead. Solder joints made from Pb-free solder paste do not yet have an evaluation method to classify its mechanical properties such as shear strength. In this study, we reflowed solder joints from Sn–3.0Ag–0.5Cu solder paste. To standardize the shear test method, we measured the shear strength of the solder joint of a 2012 ceramic chip at a shear rate of 3–60 mm/min and a shear height of 10–380 μm using different shaped shear jigs. We statistically analyzed the optimum number of shear tests by calculating the accumulative average value, standard deviation, and width of the confidence interval. The fracture surface was examined by scanning electron microscope and discussed in terms of the shear conditions.     

Analysis of the influence of elastic deformation on the electrode potential of a metal cylinder in a medium

We propose a new efficient procedure for the determination of the shift of the electrode potential on the boundary of an active medium with the surface of a stretched metal cylinder and determine the distributions of the electric potentials inside the cylinder, over its surface, and in the medium. We also establish the formulas for the evaluation of the electrode potential depending on the level of mechanical stresses and compute its values for copper and steel specimens. Karpenko Physicomechanical Institute, Ukrainian Academy of Sciences, L'viv. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 36, No. 1, pp. 47–50, January–February, 2000.     

Brazing of titanium to steel with different filler metals: analysis and comparison

Evaluations of vacuum brazed commercially pure titanium and low-carbon steel joints using one copper-based alloy (Cu–12Mn–2Ni) and two silver-based braze alloys (Ag–34Cu–2Ti, Ag–27.25Cu–12.5In–1.25Ti) have been studied. Both the interfacial microstructures and mechanical properties of brazed joints were investigated to evaluate the joint quality. The optical and scanning electron microscopic results showed that all the filler metals interact metallurgically with steel and titanium, forming different kinds of intermetallic compounds (IMC) such as CuTi, Cu2Ti, Cu4Ti3, and FeTi. The presence of IMC (interfacial reaction layers) at the interfacial regions strongly affects the shear strength of the joints. Furthermore, it was found that the shear strength of brazed joints and the fracture path strongly depend on the thickness of the IMC. The maximum shear strength of the joints was 113 MPa for the specimen brazed at 750 °C using an Ag–27.25Cu–12.5In–1.25Ti filler alloy.     

Improvement of the fatigue characteristics of VT1-0 titanium alloy by the surface mechanical and rapid thermal treatment

We study the influence of different modes of thermomechanical treatment of the surface of commercially pure titanium followed by its rapid thermal treatment on the characteristics of strength of the surface layers. It is shown that the highest strength of the surface layers is observed after treatment performed according to the following scheme: stabilizing annealing in a vacuum of about 10⁻⁵ Pa at 800°C for 1 h → deformation of the surface by ultrasonic impact treatment → rapid induction annealing of the surface at 600°C. The structural changes induced in the surface layers of VT1-0 alloy by this treatment are analyzed. It is discovered that the fatigue limit of the VT1-0 alloy increases by 50% as compared with the annealed state. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 42, No. 3, pp. 85–91, May–June, 2006.     

Electrochemical synthesis and characterization of CdSnSe thin films

The effects of deposition potentials on the electrochemical, structural, morphological and optical properties of the CdSnSe films are studied. X-ray diffraction patterns revealed a mix of cubic and orthogonal phases for the grown CdSnSe thin films. The refractive index, extinction coefficient, dielectric constant and thereby the optical band gap of the films are calculated from transmittance spectral data recorded in the range 400–1,200 nm by UV–Vis–NIR Spectrometer. The optical band gap energy of CdSnSe thin films is found to be in the range of 1.23–1.25 eV. Morphological studies revealed nano-rod shaped grains occupied over the entire surface of the film with average grain size of 150 nm. The influence of deposition potential on the microstructural properties of CdSnSe is also explained in the paper.     

Evaluation of fracture parameters of concrete from bending test using inverse analysis approach

In this study, an inverse analysis approach is developed to obtain the fracture parameters of concrete, including stress–crack opening relationship, cracking and tensile strength as well as fracture energy, from the results of a three-point bending test. Using this approach, the effects of coarse aggregate size (5–10, 10–16, 16–20 and 20–25 mm) and matrix strength (compressive strength of 40 and 80 MPa, respectively) on the fracture parameters are evaluated. For normal strength concrete, coarse aggregate size and cement matrix strength significantly influence the shape of σ–w curve. For a given total aggregate content, small aggregate size leads to a high tensile strength and a sharp post-peak stress drop. The smaller the coarse aggregate, the steeper is the post-peak σ–w curve. By contrast, in high strength concrete, a similar σ–w relationship is obtained for various aggregate sizes. The post-peak stress drop for high strength concrete is more abrupt than that for normal strength concrete. Also, the smaller the coarse aggregate size, the higher is the flexural strength. For both normal and high strength concrete, fracture energy and characteristic length are found to increase with increase of coarse aggregate size.     

Energy-based model of similarity of low-cycle fracture of a specimen and a structural component

Using the introduced notions of specific damage and equivalence of mechanical states in low-cycle loading, we propose an energy-based variant of similarity of fracture of a model specimen and a full-scale structural component. We recommend criteria of similarity to allow for scale and surface effects, stress concentration, and their joint impact on the endurance limit. The model is substantiated experimentally. Izhevsk State Technical University, Izhevsk, Russia. Translated from Problemy Prochnosti, No. 6, pp. 23–34, November–December, 1999.     

Long-term assessment of the implant titanium material—artificial saliva interface

This paper studies the long-term (20,000 exposure hours) behavior of titanium and Ti–5Al–4V alloy—Carter–Brugirard saliva interface and the short-term (500 exposure hours) resistance of titanium and Ti–5Al–4V alloy—Tani&Zucchi saliva interface. Potentiodynamic polarization method was applied for the determination of the main electrochemical parameters. Linear polarization measurements for to obtain the corrosion rates were used. Monitoring of the open circuit potentials (E _oc) for long-term have permitted to calculate the potential gradients due to the pH, ΔE _oc(pH) and to the saliva composition ΔE _oc(c) changes which can appear “in vivo” conditions and can generate local corrosion. Atomic force microscopy (AFM) has analyzed the surface roughness. Ion release was studied by atomic absorption spectroscopy (AAS). In Carter–Brugirard saliva both titanium and Ti–5Al–4V alloy present very stable passive films, long-term stability, “very good” resistance, low values of the open circuit potential gradients, which cannot generate local corrosion. In Tani&Zucchi artificial saliva, pitting corrosion and noble pitting protection potentials (which cannot be reached in oral cavity) were registered; titanium ion release is very low; surface roughness increase in time and in the presence of the fluoride ions, denoting some increase in the anodic activity.     

Joining of sialon ceramics by Sn-5 at % Ti based ternary active solders

The effect of a third element, such as silver, copper, indium, nickel or aluminium, on the joining of sialon ceramics with tin-5 at % titanium based ternary active solders was investigated. The content of the third element in the Sn-based solders was varied from 5–40% for Cu, from 5–10% for Ag and Al from 5–20% for In and from 1–5% for Ni. The joining was carried out in vacuum at 1100 K for 20 min. The four point bend testing of a butt joint of a ceramic/ceramic structure with dimensions 40 mm long, 3 mm wide and 4 mm high was used to study the bond strength between the ceramic and the Sn-based solders. The results show that the bond strength of the Sn-based solder with the sialon ceramic varied from 54–103 MPa. Small additions of Cu or Ag (about 5–10%), In (about 5–10%), or Ni (about 1–3%) to the solder is beneficial, but too much Ni (more than 5%) or In (more than 10%) is detrimental. On the other hand, Al in the active solder considerably decreased the bond strength of the solders with the ceramic. Suggestions are made for the selection of the third element in order to improve the bond strength of the soft solders with the ceramic. These include a high surface energy, improving the wetting of the solder on the ceramic and strengthening of the solder. This revised version was published online in November 2006 with corrections to the Cover Date.     

The interface electronic structure of thiol terminated molecules on cobalt and gold surfaces

The bonding strength and interfacial electronic properties of biphenyldimethyldithiol (HS–CH₂–C₆H₄–C₆H₄–CH₂–SH) adsorbed on Au(111) and polycrystalline cobalt are identified from combined photoemission and inverse photoemission. In order to develop a better understanding of the thiol functional group to metal surface interaction, the stable orientation, bonding site, bonding strength and interfacial electronic properties of methylthiol (S–CH₃) adsorbed on Au(111) and Co(0001) have been determined by ab initio density functional calculations. Both experiment and theory suggest that thiol bonding to cobalt surfaces is stronger compared to gold surfaces. The transfer of charge toward the adsorbed sulfur is greater for the thiols on cobalt than on gold.