Measurement of WAVE VELOCITY in materials is very important .It has applications in ULTRASONIC thickness gauging as well as estimating the elastic constants of materials. The aim of the current paper is to improve the accuracy of WAVE VELOCITY measurements by signal processing techniques. For this purpose, the SAGE algorithm, which is a model-based estimation technique, is implemented. Using SAGE, the overlapping echoes are separated and consequently the time-delay between these echoes is estimated more accurately. The signal processing scheme reduces the adverse effects of noise too. To demonstrate the effectiveness of the proposed technique, an AISI 4140 steel block with four steps of thicknesses 10, 15, 20, and 25 mm was tested by the immersion ULTRASONIC testing technique. The time-delay between echoes obtained from each step was measured fifty times and by averaging these measurements, the actual time-delay and its uncertainty were estimated. The thickness of the block at each step was also measured by a micrometer. Using the time-delay and thickness data, the WAVE VELOCITY and its uncertainty were estimated for each of the four thicknesses. The results show that this technique can reduce the uncertainty of WAVE VELOCITY measurements significantly.

Ultrasound test is a widely used non-destructive method for determining the mechanical and metallurgical properties of materials. In this method, ULTRASONIC WAVE VELOCITY or attenuation coefficient is measured and measurement accuracy is very important. In this paper, variations of longitudinal WAVE VELOCITY are studied in the presence of a thermal gradient both theoretically and numerically using a 2D model. A linear temperature distribution is assumed and the length of the work piece and the temperature of the hot side are considered as varying parameters. A new 2D theoretical model is developed for this problem. The test piece is made of st37 steel. To evaluate the proposed equation, we assume constant temperatures and the length of the work piece are varied in the range of 0.05-0.1 m. Then, we study the effect of the temperature of the hot side from 398-998 K. By ANSYS software, a novel two-dimensional finite element model (FEM) is developed in axisymmetric state for this problem. The results of the theoretical model are compared with those obtained from the numerical model and very good agreement is observed.

Pattern matching is a method that used for quality control in production lines. In this study, the pattern of ULTRASONIC WAVE propagation in rubber compounds was used. ULTRASONIC test is a non-destructive test. In addition to identifying defects, non-destructive tests are used to study material characteristics such as the mechanical and structural properties. The main advantage of non-destructive tests is detecting defects and characteristics of materials without changing the test piece. In this research, this method was used to investigate passenger radial tire tread compound formulation. To investigate the radial passenger tire tread compound formulation at first 14 samples with different formulations were prepared and for each of the samples the propagation VELOCITY of the longitudinal sound WAVEs was measured. Another sample with a new formulation was developed and longitudinal WAVE VELOCITY was measured for validation of proposed method. The validation results show that the proposed method can accurately predict longitudinal WAVE propagation VELOCITY in radial passenger tire tread compounds. Thus, this method can be used for validation of compound formulation in rubber production lines.

Preparation of Iso-VELOCITY and Iso-Depth maps for different shear WAVE velocities in Tehrans alluvium is the main subject of this paper. In this regard, data obtained through geoseismic and geotechnical investigations was used. The collected geotechnical data of about 1000 boreholes including results of 26 new drilled boreholes are considered and combined with the results of 95 refraction surveys and 9 down hole surveys in the studied area. Furthermore the combination of geoseismic surveys, collected geotechnical data and in-situ measurements in drilled boreholes are used to propose a new classification of Tehrans soils based on shear WAVE VELOCITY and N(SPT). A comparison also is made between results of Standard Penetration Test (SPT) in drilled boreholes and shear WAVE velocities obtained from geoseismic surveys. The new correlations established between N (SPT) and shear WAVE VELOCITY for different types of fine-grained soils in south of Tehran are proposed.

Non-destructive tests can identify and investigate the defects and properties of the test piece without changing the physical and mechanical properties of the sample. In this study, the non-destructive inspection method of ULTRASONIC WAVEs was used to investigate the rubber formulation. In this method, the time between the transmission and the reflection of ULTRASONIC WAVEs is measured and using this time propagation VELOCITY is calculated. As components percent of the rubber are changed the physical and mechanical properties of rubber are altered and as a result, the VELOCITY of ULTRASONIC propagation is changed. To investigate the rubber formulation at first 12 samples with different formulations were prepared and for each of the samples the propagation VELOCITY of the longitudinal sound WAVEs was measured. In order to establish the mathematical model between used elements percent in the rubber formulation and longitudinal WAVE VELOCITY the multiple linear regression was used. To evaluate the accuracy another sample with a new formulation was developed and longitudinal WAVE VELOCITY was measured. The comparison between the results of the test and those of the regression model showed a low error in the predicted result by the proposed model; therefor, the ULTRASONIC WAVEs can be used to investigate the rubber formulation and the rubber production lines can use this non-destructive test to control tire quality online.

Long-range guided WAVE inspection systems are often used in low frequency– thickness ranges below the cut-off frequencies of higher WAVE modes to simplify data interpretation. In this paper, the potential of high-order guided WAVE modes for the inspection of plate structures is considered. The characteristics of high-order lamb WAVE modes and their corresponding sensitivity and detectability are investigated. Using a commercially available software package, finite element simulations are carried out to model the propagation of A1 and S1 WAVE modes in steel plate. Using a variable angle transducer, experimental pulse– echo measurements are also conducted to evaluate the measurement errors when implementing higher order modes A1 and S1 on a 2-mm thick steel plate at 4 MHz. mm. Experimental measurements show that when using S1 mode for short-range measurements, the relative error is less than 10%.

High sensitivity, high accuracy and almost no limitations on type of test material has made ULTRASONIC testing (UT) a desirable nondestructive testing method. ULTRASONIC WAVE VELOCITY and attenuation are two important parameters that affect an ULTRASONIC test. Attenuation is the loss of WAVE energy and reduction in WAVE amplitude during the propagation of WAVEs through the material. In this paper, the attenuation coefficient is measured in an St37 specimen at a frequency of 1 MHz. The test is conducted in pulse-echo mode with immersion technique. The sources of error are identified, and the measurement uncertainty is calculated. In this measurement, the sources of error include errors due to measuring the length of the part and the amplitude of the echoes reflected from the back surface of the part. The attenuation coefficient is 39. 33 dB/m and the measurement uncertainty is ± 8. 8 dB/m. The noise in the pulser-reciever system is found to be the main source of error in the measurement of amplitudes of reflected echoes from which the attenuation coefficient is calculated.

In this labratory study, the effect of joint density (number and spacing) on the pressure WAVE VELOCITY was researched in pyroclastic rocks. After determining the physical properties, the P-WAVE velocities of intact rock samples were measrued. Then, an artificial joint perpendicular to the measuring direction was created in each sample, and the WAVE VELOCITY tests were repeated. These tests were continued up to 5 joints with two sets of 2 and 5 cm spacing. Consequently, the data were analyzed using the statistical methods. The results show that the P-WAVE VELOCITY was decreased by increasing the number of joints in both spacing sets, and thus an inverse linear relationship was obtained. However, as the number of joints increases, the reduction rates of WAVE VELOCITY were different at two spacing sets. More precisely, up to 3 joints, the reduction rate in the 5 cm spacing set was more than that in the other set. Nonetheles, after the third joint, the decreasing rate in the 2 cm spacing set became greater. Generally, the shorter spacing had a more reduction (attenuation) in the P-WAVE VELOCITY. In this regard, at a total of 5 joints, the reduction rate of the P-WAVE VELOCITY in 2 cm spacing set was more than that in the other set.