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Monitoring of thermal information of heated media is important for ensuring the reliability of high temperature processes in various industries. Ultrasound thermometry, which is a temperature measurement method by ultrasound, is expected as a potential candidate for such monitoring. In this work, an effective ultrasound thermometry utilizing both pulse-echo measurements and unsteady heat conduction analysis is applied to real-time monitoring of temperature profiles and heat fluxes of a heated steel. This method provides non-invasive measurements of such thermal information. To examine the feasibility of the method to condition monitoring, the internal temperature profile of a steel plate whose back surface is being heated, and cooled is monitored every 70 ms. Furthermore, the ultrasonic method is utilized to monitor heat fluxes of bonded materials of aluminum and copper, and reasonable results on transient variation in heat flux are then obtained. Thus, it is considered that the ultrasonic method could be applicable to condition monitoring of various heated materials.

In this study, we present application of the level-set type topology optimization analysis for the cavity shape estimation problem in structures based on the non-destructive hammering test. The cavity shape is identified so as to minimize a performance function. The performance function is defined as the square sum of the residual between computed and the observed displacements on structure surface. In this study, accuracy of identified cavity shape is investigated by changing numerical parameters in the topology optimization.

Mechanical properties including elastic modulus and hardness are sensitive to spacial gaps among grains in polycrystalline organic semiconducting films. Densification behavior of copper pht...

It is essential to characterize fuel debris fragments that are to be retrieved from reactors at the Fukushima Daiichi power station prior to their large-scale retrieval. Using nanoindentation (NI) test, we have determined the mechanical properties of boron carbide (B 4 C) particles currently used to simulate hard covalent materials as included in the debris. We also examined the measurable minimum size among the particles sized to three types and found suitable sample preparation methods. While the minimum size was limited to 1000 μm among the particles fixed with grease in molding process, it was brought down to 500 μm by alternative polyvinyl alcohol (PVA) films. Indentation moduli of these successfully measured B 4 C particles are consistent with a referential value of 431 GPa with a difference of 3.5%. Furthermore, the hardness values of the particles are slightly lower than a referential value of 21.8 GPa within uncertainty of 9%. The particle surfaces were polished enough with only the roughest #240 abrasive papers, and surface flatness was a key issue for the successful indentation but not surface roughness. As a result of the detachment caused during polishing, both 500 μm particles and 100 μm particles fixed with the grease were insufficiently flattened, and then the indenter was slipped on the inclined surfaces during the NI tests. The values of modulus and hardness are at the minimum for the 100 μm particles at decreasing rates of 46% and 42% to the referential values. The thin uniform PVA films reduced the projection amount of the 500 μm particles from the surrounding resin and prevented the particle detachment during polishing. Residual resin was distinguished from an underlaying B 4 C particle using the NI tests.

The fundamental study on the ultrasonic characterization of non-Gaussian rough surface of a material is carried out. In this study, a theoretical relationship among ultrasonic reflection coefficient at normal incidence, root mean square roughness Rq, and skewness Rsk (which is the measure of symmetrical level of a height distribution) has been derived. In the derivation, a Gaussian curve fitting to the non-Gaussian height distribution of a rough surface is effectively performed so that the Kirchhoff theory of wave scattering from a rough surface can be utilized. In order to verify the validity of the derived relationship, air-coupled ultrasonic pulse-echo measurements with normal incident configuration at center frequency of 0.35 MHz have been conducted to a series of sandpapers having various Rq and Rsk values. From the measured ultrasonic reflection coefficient of each sandpaper, the Rq values of the sandpapers have been estimated from the derived relationship with known values of skewness of the sandpapers and then compared to those measured by a mechanical stylus profiler. It is found that the Rq values estimated by the ultrasonic method and the stylus profiler almost agree with each other. Thus, the validity of the derived theoretical relationship is demonstrated.

An ultrasonic lateral displacement sensor utilizing air-coupled ultrasound transducers is proposed. The normally-distributed far field of an ultrasound transducer in a lateral direction is taken advantage of for measuring lateral displacement. The measurement system is composed of several air-coupled ultrasound transducers as a receiver and several transmitters. The transmitters are immobilized at a fixed point, whereas the receiver set-up is separately arranged on the opposite side. In order to improve measurement accuracy, a correction method that utilizes polynomial approximation is introduced. The difference between the corrected lateral displacement and the reference displacement is estimated to be 0.2 mm at maximum for the two transmitters system. A good responsiveness is demonstrated by conducting a dynamic response experiment. When five transmitters are arranged, their measurement range is easily extended up to ±60 mm with an accuracy of 0.7 mm. In both cases, the fluctuations to the measurement ranges show less than 1%. These results indicate that the developed sensor system is useful for measuring relative lateral displacement of a seismically isolated building in the field of structural health monitoring.

Mechanical properties such as bending strength represent critical issues for the manufacture and practical use of flexible organic semiconducting films. In this study, we have used isostatic presses to densify pentacene films and compared the densification behavior and mechanical properties of the films. Although most pores formed between the grains were crushed in the pressed films, thickness reduction of the films was nondetective. And the nondetection is attributed to original dense cylindrical structure of the as-coated films which is predicted to produce a porosity 9.3% and a thickness reduction 80 nm. Both the indentation modulus (15.0 GPa) and the indentation hardness (0.643 GPa) of the as-coated films were reduced by up to 25% and 23% in the WIP films. The resultant critical bending radius of the WIP films of 4.29 mm is approximately the same as that of the as-coated films because of simultaneous falls in both modulus and hardness. The decreasing modulus and hardness in the isostatically pressed films are concluded to be caused by relaxation of the pentacene grain anisotropy accompanied by buckling of the grains.

A novel noncontact method to measure both surface and internal temperatures of a heated cylindrical rod end is proposed. In the method a laser ultrasonic technique providing noncontact measurements of ultrasonic waves in such heated rod is employed. To quantitatively determine both the surface and internal temperatures near the rod end, an effective ultrasonic thermometry has been developed by considering the propagation direction and path of the ultrasonic waves in the rod generated by pulsed-laser irradiation. The thermometry is basically a combined method consisting of ultrasonic wave velocities measurements based on pitch-catch configurations and a one-dimensional finite difference calculation for unsteady heat conduction. The advantage of the method is that there is no need to know the thermal boundary condition at the heating surface where the thermal state is often unstable and unknown. To demonstrate the feasibility of the proposed method, experiments with an aluminum rod whose end surface is heated by a gas burner are carried out. A laser ultrasonic system consisting of a pulsed laser generator (Nd:YAG, 1064 nm, 180 mJ) and a laser Doppler vibrometer (He-Ne, 633 nm

A method for measuring liquid-level utilizing wedge wave generated by a pulsed laser is presented. The sound velocity of wedge wave is slow compared to the other types of guided waves, so the measurement accuracy which is closely related to the time resolution of measurement equipment can be improved. This method is utilizing the difference of wedge wave velocity in the air and in the water. It is demonstrated that the liquid level is proportional to the elapsed time difference of the propagated wedge wave. The wedge wave velocities in the air were experimentally obtained 1375 m/s for mode 1 and 2362 m/s for mode 2. It is confirmed that mode 1 is suitable for the measurement because of its slowness and clear signal. The liquid-level sensing was carried out by laser ultrasonic technique using aluminum 30° wedge in the water. The relationship between the liquid-level and the elapsed time of the wedge wave showed high linearity. The standard deviation of data plots was 0.88 mm, the measurement resolution was...

Annealing is reported as an effective process to improve electrical properties of organic semiconducting films. The mechanical properties of pentacene and tris(8-hydroxyquinoline) aluminum (Alq3) films annealed at 140°C were investigated in this study by nanoindentation testing. AFM observations of as-coated and annealed pentacene films indicate grain growth from 160 to 258 nm. The annealing process decreases pentacene and Alq3 film hardness by 23 and 36% from those of the as-coated films, 0.643 and 0.523 GPa. Grain growth and decreasing hardness are attributed to thermal diffusion and recrystallization of molecules.

A nanoindentation technique with a spherical indenter of tip radius 10 μm is applied to the evaluation of stress-strain curve at a local area of a pure iron under the uniaxial compressive stress exerted through the iron, and the influence of the compressive stress on the estimated stress-strain curve has been examined. A continuous multiple loading method is employed to determine the stress-strain curve. In the method, a set of 21 times of loading/unloading sequences with increasing terminal load are made and load-displacement curves with the different terminal loads from 0.1 mN to 100 mN are then continuously obtained and converted to a stress-strain curve. To examine the stress dependence of the stress-strain curve, the estimation by the nanoindentetion is performed under different uniaxial compressive stresses up to 250 MPa. It has been found that the stress-strain curve determined by the nanoindentation shifts upward as the compressive stress increases and the quantity of the shift is almost equal to the uniaxial stress acting on the iron specimen. It is also noted that the yield stress (0.2 % proof stress) estimated from the stress-strain curve increases almost proportionally to the uniaxial stress and the increase ratio tends to decrease as the stress reaches around 200 MPa.

In the fields of materials science and engineering, measuring temperature has become one of the most fundamental and important issues. In particular, there are growing demands for monitoring temperature gradient and its transient variation of materials being processed at higher temperatures because the temperature state during processing crucially influences the quality of final products. Such temperature monitoring is also required for rotating machining processes such as tuning, milling and friction stir welding (FSW). In this work, a new noncontact method for monitoring temperature distribution of a heated rotating cylindrical object is presented. A laser-ultrasonic technique is employed in the method. Surface temperature measurements for the cylindrical object using the laser-ultrasonic technique and heat conduction analyses are combined together for making quantitative evaluation of temperature distribution in the radial direction of the cylindrical object. To demonstrate the feasibility of this method, an experiment with a steel cylinder of 100 mm in diameter rotating at 300 min-1 and heated up to 100 °C on the surface is carried out. A pulsed laser generator and a laser Doppler vibrometer are used for generating and detecting surface acoustic waves (SAWs) on the steel cylinder, respectively. Measured SAWs are used for determining both surface and internal temperatures of the cylinder. As a result, the estimated temperature distributions during heating almost agree with those measured by an infrared radiation camera.

High-density, ultrasmall-pitch electronic applications require miniaturized solder bumps with improved thermomechanical performance. In addition, novel techniques which are able to precisely characterize these solder bumps are needed. One approach to meeting both of these requirements is to make use of recently developed nanocomposite solders with enhanced creep resistance, and to characterize these solders using a nanoindentation technique. In the present study, the creep behavior of ceria-reinforced nanocomposite solder foils fabricated by the accumulative roll-bonding process was characterized using a depth-sensing nanoindentation technique. It was found that the creep resistance of the composites increased with increasing volume fraction of CeO2 reinforcement, and it was deduced that the creep deformation of this nanocomposite proceeded by deformation of the matrix, with the role of the reinforcement being to increase the creep resistance by reducing the effective stress acting on the matrix. The values of the creep exponent suggested that the dominant creep deformation mechanisms involved were diffusion creep and grain boundary sliding.

The alignment film abrasion caused by the rubbing process was quantitatively evaluated via atomic-force microscopy (AFM). First, a patterned alignment film structure, which was molded through the imprint method, was artificially formed. Then, the surface topography of the alignment film was evaluated via AFM after rubbing, and the degree of abrasion of the alignment film was estimated by subtracting the value after rubbing from the value before rubbing. It was recognized that the degree of abrasion increased with an increase in the rubbing strength. The relationship between the number of rubbing cycles and the degree of abrasion of the alignment film was also estimated.

Spot welding is widely used in the various fields of engineering and industries. Since the size, shape and mechanical properties of a nugget which is a zone melted and re-solidified during welding are closely related to the strength of the welded structure, quantitative evaluations of them are strongly required. In this work, an air-coupled ultrasound technique with focused transducers has been used for non-contact measurements of spot welds of steel plates. One-dimensional scanning in transmission configuration using a pair of focused air-coupled ultrasonic transducers operating with tone burst waves at 0.3 MHz is performed to obtain the amplitude profile of the transmitted ultrasound through the nugget area of a spot weld. A simple method for determining the nugget size from the profile of the transmitted ultrasound is proposed. To verify the validity of the method, calibration samples which imitate spot welds having different sizes of nuggets are prepared and used for demonstrating nugget size determinations. In addition, the proposed method has been applied to evaluate several spot welds fabricated with different electric currents (5 kA – 9 kA).

The mechanical properties of Y2Ti2O7 ceramics have been systematically characterized. Y2Ti2O7 shows higher hardness (12.1 GPa) than Y2O3 and TiO2. The Young’s modulus of Y2Ti2O7 (262 GPa) is close to that of TiO2 and 50% higher than that of Y2O3. The fracture toughness (1.9 MPa m1/2) and bending strength (206 MPa) are comparable with those of Y2O3 but half those of TiO2. The indentation size effect on the hardness in nanoindentation tests is discussed based on the Nix–Gao model.