New contributions to granite characterization by ultrasonic testing

Ultrasonic characteristics and equivalent crack width of coal and rock bodies around boreholes during progressive failure

The ultrasonic characteristics of the coal and rock bodies around boreholes during failure are closely related to the crack propagation law. To investigate the ultrasonic characteristics and crack propagation law of coal and rock bodies around boreholes, different grouting samples with boreholes were taken to carry out ultrasonic test during progressive failure. The ultrasonic amplitude, velocity and attenuation coefficient of the samples were analyzed. According to the ultrasonic time difference formula, the equivalent crack width of the sample during the failure process is calculated. The influence of grouting material on the crack propagation law is quantitatively analyzed. The results show that: (1) The peak stress, elastic energy at the peak, ultrasonic parameters and crack propagation of the coal and rock bodies around boreholes show obvious differences influenced by the strength of the grouting material. (2) During the loading process, the arrival time of the first wave of the sample with holes is 5μs later than that of the grouting sample, and the ultrasonic energy attenuates fastest in the time domain, and the coda wave is not developed. (3) During the progressive failure, the ultrasonic velocity and attenuation coefficient of all show three stages of stability(0~0.6σp), slow change(0.6σp~0.8σp) and rapid change(0.8σp~1.0σp). According to the "sudden decrease" of velocity and the "sudden increase" of attenuation coefficient to judge the crack propagation of sample. (4) The equivalent crack width of the sample increases exponentially with the increase of stress level. At the time of reaching the peak stress, the equivalent crack width of SH-BH increases about 0.027mm~0.032mm, SH-PU about 0.01mm~0.014mm, and SH-CEM about 0.002mm~0.006mm.

Nondestructive assessment of local microcracking degree in orthoclase and plagioclase feldspars using spectral analysis of backscattered laser-induced ultrasonic pulses

The laser-ultrasonic method for nondestructive assessment of a microcracking degree in laboratory specimens of orthoclase and plagioclase feldspars is proposed. The influence of the local concentration of microcracks on the spectral efficiency of backscattering of pulses of longitudinal ultrasonic waves in the studied specimens (the so-called "structural noise power") is studied. A specially designed laser-ultrasonic transducer used in experiments combines laser excitation of probe broadband ultrasonic pulses in a black polyethylene film and piezoelectric detection of both probe pulses and that scattered in the specimen. We study specimens of a potash feldspar and soda-calcium plagioclase with nonuniformly distributed local microcracks. The cracking domains were identified by optical microscopy as well as using the attenuation coefficient of longitudinal ultrasonic waves measured in these domains. The increase in the ultrasonic attenuation coefficient was associated with a higher concentration of microcracks, which efficiently scatter acoustic waves. At the same time, the domains with a higher ultrasonic attenuation exhibited an increased structural noise power. The direct correlation between the growth of the structural noise power and a higher local concentration of microcracks can be used as a basis of a system of nondestructive ultrasonic monitoring of occurrence and evolution of local microcracks in rocks and geomaterials under external loads of different nature.

Dry-cured loin characterization by ultrasound physicochemical and sensory parameters

The aim of this study was to evaluate the ability of ultrasound inspection and quality determinations to characterize two commercial categories of dry-cured pork loin, labelled as green (GL) and red (RL). For this objective, ultrasound inspection was carried out for two different frequencies (500 and 1000 kHz), considering parameters of ultrasonic pulse velocity (UPV), frequency components related to the fast Fourier transform (FFT), and variables related to the attenuation. Physicochemical (moisture and fat content, water activity, instrumental color), instrumental texture (TPA) and sensory analyses (QDA) were also carried out. Moreover, quality and ultrasonic parameters were subjected to a correlation analysis (Pearson). Several physicochemical, instrumental texture and sensory parameters allowed to discriminate the dry-cured loin category. Moreover, high significant correlations were found among quality and acoustics parameters. Thus, ultrasound inspection can determine quality parameters indirectly without the limitations of traditional methodologies, postulating as a tool for characterizing dry-cured loin samples of different category with a promising predictive nature. This work has showed new findings for dry-cured meat products that may be of interest to the meat industry.

Ultrasonic Properties of a Stone Architectural Heritage and Weathering Evaluations Based on Provenance Site

In this study, we performed customized ultrasonic measurements of the stone block foundation of the Sungnyemun Gate, which is representative of the stone architectural heritage in the Republic of Korea. Furthermore, the weathering evaluation standards, which are extensively used in stone heritage, were improved considering the type of rock and its provenance site. In particular, the absolute weathering grade used the ultrasonic velocity (P-wave) of a universal hard rock, whereas the relative weathering grade used the differences between the ultrasonic velocities of the materials in the stone block foundation of the Sungnyemun Gate (weathered stone) and the fresh rocks in the provenance. Among these, the absolute weathering grade was observed to be constant regardless of the type of rock; however, the relative weathering grade varied depending on the type dof rock. Because the average ultrasonic velocity of the original blocks of the stone block foundation of the Sungnyemun Gate was 2665 m/s, it was estimated that their ultrasonic velocity reduced by approximately 2.1 m/s per year as compared to that observed in case of fresh rocks (average 3932 m/s) in the provenance site. Furthermore, the weathering evaluation exhibited that there were approximately two stages of difference between the original blocks and the new blocks. As compared to the relative weathering grade, the absolute weathering grade was observed to underestimate the overall ultrasonic velocity of the stone block foundation of the Sungnyemun Gate. This study presents a customized method for performing ultrasonic measurements and for evaluating weathering. It is assumed that the results of this study will be extensively used in diagnosing and monitoring the stone architectural heritage.

New findings of edible oil characterization by ultrasonic parameters

The basic objective of the study was to confirm the usefulness of non-destructive ultrasonic testing in evaluating different edible oil samples. The experimental study was carried out for three types of edible oils (olive, sunflower, and corn) in which a 1.0 MHz ultrasound transducer was immersed. Density and viscosity values of the samples were determined simultaneously with the ultrasound tests. By themselves, ultrasound inspection, density, and viscosity, were able to characterize and distinguish each type from the others, but only the ultrasound inspection has a non-destructive nature. Moreover, significant correlations among density and viscosity with the acoustic parameters were found. The results postulate that ultrasound inspection is a fast and non-destructive tool to characterize and discriminate different types of edible oils.

Improving the Autogenous Self-Sealing of Mortar: Influence of Curing Condition

With the construction of projects under severe environments, new and higher requirements are put forward for the properties of concrete, especially the autogenous self-sealing property, which is greatly affected by the curing environment and the state of the water. Herein, six types of curing conditions, including in air with a relative humidity of 30%, 60%, and 95%; flowing water; wet-dry cycles; and static water, are designed to investigate the autogenous self-sealing of mortar under different curing conditions. The results showed that the self-sealing ratios are higher than 60% and the cracks are closed for the mortar undergoing the wet-dry cycles and the static water. However, the self-sealing ratios of mortar are lower than 10% and the cracks are almost unchanged when the mortar is cured in the air with a relative humidity (RH) of 30% and 60%. The static liquid water is more conducive to the continued hydration of cement and the formation of CaCO₃ than the flowing water. The research provides guidance for the design of concrete and the improvement of autogenous self-sealing when the concrete serves in different environments.

Application of ultrasound for quality control of Torta del Casar cheese ripening

This work aimed to establish the ultrasound parameters that can be useful to classify the defects in the soft cheese Torta del Casar during ripening. During ripening by ultrasound, 1 standard and 3 defective cheese batches (anomalous microbial population, inadequate pressing curd, and excessive pressing curd) were evaluated. Ultrasound parameters related to velocity, attenuation, and frequency were calculated and correlated with the physicochemical and rheological properties of the cheeses. Ultrasound data were considered variables in linear discriminant analysis to attempt cheese classification at different periods of the ripening process. Defective soft cheeses could be discriminated from standard ones with good accuracy, mainly at the final stages of ripening. The differentiation of cheese samples from 2 of the defective cheese batches (anomalous microbial population and inadequate pressing curd) from the standard was mainly attributed to different values of the attenuation-related parameters, whereas for samples from the other defective batch (excessive pressing curd), some parameters related to velocity and frequency were responsible for such discrimination.

Research on the Improvement of Concrete Autogenous Self-healing Based on the Regulation of Cement Particle Size Distribution (PSD)

Overgrinding of Portland cement brings excessive shrinkage and poor self-healing ability to concrete. In this paper, through the ultrasonic test and optical micrograph observation, the self-healing properties of concrete prepared by cement with different particle size distributions were studied. Besides, the effect of carbonation and continued hydration on self-healing of concrete was analyzed. Results show that, for the Portland cement containing more particles with the size 30~60 μm, the concrete could achieve a better self-healing ability of concrete at 28 days. For the two methods to characterize the self-healing properties of concrete, the ultrasonic test is more accurate in characterizing the self-healing of internal crack than optical micrograph observation. The autogenous self-healing of concrete is jointly affected by the continued hydration and carbonation. At 7 days and 30 days, the autogenous self-healing of concrete is mainly controlled by the continued hydration and carbonation, respectively. The cement particle size could affect the continued hydration by affecting un-hydrated cement content and the carbonation by affecting the Ca(OH)₂ content. Therefore, a proper distribution of cement particle size, which brings a suitable amount of Ca(OH)₂ and un-hydrated cement, could improve the self-healing ability of concrete.

Contributions to ultrasound monitoring of the process of milk curdling

Ultrasound evaluation permits the state of milk being curdled to be determined quickly and cheaply, thus satisfying the demands faced by today's dairy product producers. This paper describes the non-invasive ultrasonic method of in situ monitoring the changing physical properties of milk during the renneting process. The basic objectives of the study were, on the one hand, to confirm the usefulness of conventional non-destructive ultrasonic testing (time-of-flight and attenuation of the ultrasound waves) in monitoring the process in the case of ewe's milk, and, on the other, to include other ultrasound parameters which have not previously been considered in studies on this topic, in particular, parameters provided by the Fast Fourier Transform technique. The experimental study was carried out in a dairy industry environment on four 52-l samples of raw milk in which were immersed 500kHz ultrasound transducers. Other physicochemical parameters of the raw milk (pH, dry matter, protein, Gerber fat test, and lactose) were measured, as also were the pH and temperature of the curdled samples simultaneously with the ultrasound tests. Another contribution of this study is the linear correlation analysis of the aforementioned ultrasound parameters and the physicochemical properties of the curdled milk.

Efficient feature selection for neural network based detection of flaws in steel welded joints using ultrasound testing

This work studies methods for efficient extraction and selection of features in the context of a decision support system based on neural networks. The data comes from ultrasonic testing of steel welded joints, in which are found three types of flaws. The discrete Fourier, wavelet and cosine transforms are applied for feature extraction. Statistical techniques such as principal component analysis and the Wilcoxon-Mann-Whitney test are used for optimal feature selection. Two different artificial neural network architectures are used for automatic classification. Through the proposed approach, it is achieved a high discrimination efficiency by using only 20 features to feed the classifier, instead of the original 2500 A-scan sample points.