Crack detection in single-crystalline silicon wafers using impact testing

This paper presents acoustic measurements obtained by mechanically exciting vibratory modes in single-crystalline silicon wafers with hairline periphery cracks of different type and location. The data presented shows a dependence of natural frequencies, peak amplitudes and damping levels of four audio vibration modes in the frequency range up to 1000 Hz on crack type and crack location. Data from defective wafers exhibit lower natural frequencies, higher damping levels, and lower peak amplitudes. The results suggest an impact test method may be useful for solar cell crack detection and quality control.     

Analysis of the energy extracted by a harvester based on a piezoelectric tile

In this paper, we analyze the maximum energy that can be extracted from a piezoelectric harvester subject to pulsed excitation, with an interface circuit composed by a standard bridge rectifier. We show that the optimal voltage of the DC load of the bridge rectifier is a fraction, comprised between 1/3 and ½, of the open-circuit voltage, depending on the piezoelectric losses and excitation time. A simple analytical model is provided, whose accuracy has been assessed against SPICE simulations. Furthermore, preliminary experimental tests carried out over a commercial piezoelectric tile confirm the validity of the proposed model.     

Thermal effect on microstructure vibration of SiO2 thin films

The microstructure of amorphous SiO₂ thin film is a random network structure in which a large amount of [SiO₄] is interconnected with a specific SiOSi bond angle. The SiO₂ thin films used in this paper were prepared by ion beam sputtering and electron beam evaporation deposition techniques. Two-dimensional correlation spectroscopy analysis techniques were used in this study. By measuring the infrared temperature spectrum, we obtained the two-dimensional correlation synchronous spectrum and asynchronous spectrum, and decomposed the in-phase and out-phase asymmetric stretching vibration characteristics of SiOSi. As the temperature increases, the spectral transmittance of the vibrating peak decreases, and the relative change of in-phase asymmetric stretching vibration absorption peak is higher than that of the out-phase asymmetric stretching vibration absorption peak.     

Comparison of absolute magnitude estimation and relative magnitude estimation for judging the subjective intensity of noise and vibration

The method of magnitude estimation is used in psychophysical studies to obtain numerical values for the intensity of perception of environmental stresses (e.g., noise and vibration). The exponent in a power function relating the subjective magnitude of a stimulus (e.g., the degree of discomfort) to the physical magnitude of the stimulus shows the rate of growth of sensations with increasing stimulus magnitude. When judging noise and vibration, there is no basis for deciding whether magnitude estimation should be performed with a reference stimulus (i.e., relative magnitude estimation, RME) or without a reference stimulus (i.e., absolute magnitude estimation, AME). Twenty subjects rated the discomfort caused by thirteen magnitudes of whole-body vertical vibration and 13 levels of noise, by both RME and AME on three occasions. There were high correlations between magnitude estimates of discomfort and the magnitudes of vibration and noise. Both RME and AME provided rates of growth of discomfort with high consistency over the three repetitions. When judging noise, RME was more consistent than AME, with less inter-subject variability in the exponent, n_s. When judging vibration, RME was also more consistent than AME, but with greater inter-subject variability in the exponent, n_v. When judging vibration, AME may be beneficial because sensations caused by the RME reference stimulus may differ (e.g., occur in a different part of the body) from the sensations caused by the stimuli being judged.     

Simple method for measuring vibration amplitude of high power airborne ultrasonic transducer: Using thermo-couple

Vibration amplitude of transducer’s elements is the influential parameters in the performance of high power airborne ultrasonic transducers to control the optimum vibration without material yielding. The vibration amplitude of elements of provided high power airborne transducer was determined by measuring temperature of the provided high power airborne transducer transducer’s elements. The results showed that simple thermocouples can be used both to measure the vibration amplitude of transducer’s element and an indicator to power transmission to the air. To verify our approach, the power transmission to the air has been investigated by other common method experimentally. The experimental results displayed good agreement with presented approach.     

Built-up edge investigation in vibration drilling of Al2024-T6

Adding ultrasonic vibrations to drilling process results in an advanced hybrid machining process, entitled “vibration drilling”. This study presents the design and fabrication of a vibration drilling tool by which both rotary and vibrating motions are applied to drill simultaneously. High frequency and low amplitude vibrations were generated by an ultrasonic transducer with frequency of 19.65 kHz. Ultrasonic transducer was controlled by a MPI ultrasonic generator with 3 kW power. The drilling tool and workpiece material were HSS two-flute twist drill and Al2024-T6, respectively. The aim of this study was investigating on the effect of ultrasonic vibrations on built-up edge, surface quality, chip morphology and wear mechanisms of drill edges. Therefore, these factors were studied in both vibration and ordinary drilling. Based on the achieved results, vibration drilling offers less built-up edge and better surface quality compared to ordinary drilling.     

The calculation of electrical parameters of AT-cut quartz crystal resonators with the consideration of material viscosity

Electrical parameters like resistance and quality factor of a quartz crystal resonator cannot be determined through vibration analysis without considering the presence of material dissipation. In this study, we use the first-order Mindlin plate equations of piezoelectric plates for thickness-shear vibrations of a simple resonator model with partial electrodes. We derive the expressions of electrical parameters with emphasis on the resistance that is related to the imaginary part of complex elastic constants, or the viscosity, of quartz crystal. Since all electrical parameters are frequency dependent, this procedure provides the chance to study the frequency behavior of crystal resonators with a direct formulation. We understand that the electrical parameters are strongly affected by the manufacturing process, with the plating techniques in particular, but the theoretical approach we presented here will be the first step for the precise estimation of such parameters and their further applications in the analysis of nonlinear behavior of resonators. We calculated the parameters from our simple resonator model of AT-cut quartz crystal with the first-order Mindlin plate theory to demonstrate the procedure and show that the numerical results are consistent with earlier measurements.     

An experimental study of the effects of resilient bars on plate vibration

Resilient bars can provide a low-cost, effective improvement to sound insulation performance. They are commonly used in timber-framed floor/ceiling assemblies in North America and Europe. Resilient bars are often modelled as springs isolating the two connected plates thereby forming a mass-spring-mass system. However, as a furring system of plates, resilient bars may modify the vibration energy distribution across a connected plate by acting as stiffeners. The authors investigate this issue by measuring acceleration levels at different locations relative to the fixing positions and thereby derive vibration waveforms for the connected plate in a small-scale structural simulation of a floor-ceiling system. The results were compared with timber-joist-ribbed, and timber-brander-ribbed, structures. The vibration modes of a suspended plate were also measured for comparative purposes. The results indicated that resilient bars did not perform as stiffeners whereas joists and timber branders did effectively stiffen their connected plates. Resilient bars neither forced orthotropic plate behaviour at low frequencies, nor separated the plate into sub-plates at higher frequencies. Resilient-bar-ribbed plates may also differ from independent plates. The modal behaviour of resilient-bar-ribbed plates is more complex and their effect on modal density and radiation efficiency are worthy of further research.     

Effects of tire inflation pressure and tractor velocity on dynamic wheel load and rear axle vibrations

The objective of this study was to evaluate the effects of agricultural tire characteristics on variations of wheel load and vibrations transmitted from the ground to the tractor rear axle. The experiments were conducted on an asphalt road and a sandy loam field using a two-wheel-drive self-propelled farm tractor at different combinations of tractor forward speeds of approximately 0.6, 1.6 and 2.6 m/s, and tire inflation pressures of 330 and 80 kPa. During experiments, the vertical wheel load of the left and right rear wheels, and the roll, bounce and pitch accelerations of the rear axle center were measured using strain-gage-based transducers and a triaxial accelerometer. The wavelet and Fourier analyses were applied to measured data in order to investigate the effects of self-excitations due to non-uniformity and lugs of tires on the wheel-load fluctuation and rear axle vibrations. Values for the root-mean-square (RMS) wheel loads and accelerations were not strictly proportional and inversely proportional to the forward speed and tire pressure respectively. The time histories and frequency compositions of synthesized data have shown that tire non-uniformity and tire lugs significantly excited the wheel load and accelerations at their natural frequencies and harmonics. These effects were strongly affected by the forward speed, tire pressure and ground deformation.