Advanced Materials Research Vols. 301-303

Abstract: The finite element method combines with differential evolution algorithm to develop the displacement back analysis program. For the field excavation of Dalian subway tunnel, the ground subsidence, crown settlement and convergence displacement are monitoring measurement, then data fitting and regression analysis; Using the independent development program and monitoring data to back analysis so that we can address rock mechanics parameters are not accurate "bottleneck"; According to the inversion parameters, the forward analysis of the finite element numerical simulation, to form a comprehensive monitoring and information feedback system based on the field monitoring - displacement back analysis - being analyzed - field monitoring. The results show that the mechanical parameters of displacement back analysis program are very close to the project survey, while the monitoring and information feedback system has an important theoretical and practical value for safety of surrounding rock and stability of construction process.

Abstract: Differential evolution algorithm is a new global optimization algorithm. DE does not require an initial value, and it has rapid convergence, strong adaptability to a nonlinear function, the features of parallelcalculation, especially in adoption to the complex problem of multivariable optimization. The constitutive integration algorithm affecting the incremental calculation step, and convergence and accuracy of the results is a key of finite element analysis. It is usually divided into an explicit and implicit integration. Return mapping algorithm is an implicit integration to avoid solving the equivalent plastic strain directly so that we achieve a fast and accurate solution for the constitutive equations. Making use of DE and return mapping algorithm to program, the elasticplastic finite element simulation and parameter inversion, the inversion and simulation results are verificated, the results show that it is closed to the actual situation, indicating usefulness and correctness of the program.

Abstract: A method based on microwave digestion and inductively coupled plasma-mass spectrometry (ICP-MS) has been established for the sensitive determination of cadmium in bivalve molluscs. The application of the internal standards calibration improved the accuracy and precision values of the method. The relative standard deviation (RSD), the standard addition recovery value and the detection limit were determined as 4.25%, 94.74% and 0.005 μg/L, respectively. This method has been verified by the determination of cadmium in certified reference material kelp (GBW08517) and mussel (GBW08571). The method has been applied to determine the contamination concentration level of cadmium in seven kinds of bivalve mollusk samples. The results indicated that, among them, mud clam, scallop and oyster have relative high accumulation ability to cadmium.

Abstract: To solve problems of seal failure on composite transmission because of high temperature, an analytical and experimental analysis for the characteristics of leakage is presented. Basic on the principle of hydraulic resistance network, via establishing mathematical model of each section belonged to flow system, a leakage model of flow system is set up. Using the analytical model and the experimental methods, the factors of leakage are discussed. The results indicate that the characteristics of leakage depend on the working conditions, structural parameters of rotary seal and viscosity-temperature characteristics of lubricating medium.

Abstract: This paper introduces the methods and results of the overpressure in the thermal explosion, and analyzes the results according to the structure of the explosion cave. The experimental results show that the overpressure is close to that in detonation. It will generate electromagnetic radiation when the shell charge explodes, for the reason of electrokinetic’s effect and the friction of explosion product with the shell, and the electromagnetic radiation signal of shell charge and bare detonator are different from each other, including the duration and the complexity of signal.

Abstract: A laser instrument is designed to measure tunnel surface, which use a laser distance measure component as measuring sensor. The surface of the tunnel shape and the outline of the object can be measured by the instrument which can rotate around two axes mutually perpendicular. The measure data is processed and the graphic of the surface shape is generated. The hardware structure and composition of the instrument are analyzed, the hardware circuit is designed and components are chosen. Hardware control software and data process procedure are designed. The actual surface can be measured to draw out the 3D graphics. The advantages of this instrument are verified that has stable performance, quick measuring and convenient to use in practices.

Abstract: The rotor blade is an important component in wind turbine generator, it consists of glass fiber reinforced plastics (GFRP) and sandwich areas containing wood or plastic foam, different defects may be generated because of manufacturing problem. To improve the safety of wind turbine blades, pulsed thermography is being investigated in this study. Surface defects, such as air bubbles, edge bonding, etc. were easily and clearly detected on several full scale blades. Several specimens were manufactured to simulate the adhesive conditions between supporting spar and GFRP shells. The direct analysis of the original, 1^st or 2^nd derivatives was normally applied to judge any possible defects in the measured sample, and also used in quantitatively calculation. This study compared the relative thermal contrast (RTC) of the original and 1^st derivative for air bubbles at shallow depth and deficiency adhesive bonding at deep depth, the calculation of the RTC could give us the approximate best time to analysis defects of different depth and types. The comparison also indicated that it is better to use the 1^st derivative than the original to analysis the deep defects, however, there is no significant advantage in the analysis of shallow defects between the original and 1^st derivative.

Abstract: This paper presents a new non-destructive testing (NDT) for reinforced concrete structures, in order to identify the components of their reinforcement. A time varying electromagnetic field is generated close to the structure by electromagnetic devices specially designed for this purpose. The presence of ferromagnetic materials (the steel bars of the reinforcement) immersed in the concrete disturbs the magnetic field at the surface of the structure. These field alterations are detected by sensors coils placed on the concrete surface. Variations in position and cross section (the size) of steel bars immersed in concrete originate slightly different values for the induced voltages at the coils.. The values ​​for the induced voltages were obtained in laboratory tests, and multi-layer perceptron artificial neural networks with Levemberg-Marquardt training algorithm were used to identify the location and size of the bar. Preliminary results can be considered very good.

Abstract: The imaging and testing of ultrasonic SH (Shear Horizontal) guided waves may be used into testing and SHM (Structure Health Monitoring) of industrial plate with welding structure in service, which have much more important applied potential. During imaging and testing for steel plate with lap welding structure, photoelastic experiment on propagation of guided waves in Plexiglas plate was studied to clearly see the excellent advantages of SH guided waves. The mode of SH guided waves was analyzed to select the zero order mode SH0 and the SH guided waves transducer with SH0 mode was developed. Based on the synthetic aperture focusing method，a multichannel ultrasonic imaging and testing experimental system of ultrasonic SH guided waves was constructed，the imaging of plate with lap welding structure was mainly studied. The research results shows the ultrasonic SH guided waves and the transducers are fit for long distance testing for the plate with lap welding structure. The ultrasound scattering nearby the weld may cause a blind testing zone, about 150 mm wide, in which the less size corrosion defects at the blind zone could not be revealed in image, so as to lead to defects “no testing”. The imaging and testing of ultrasonic SH guided waves would be used for non-destructive testing of plate with lap welding structure, which image both can characterize the corrosion defects and lap welding structure, and realize the precise location of the weld. The proposed research provides important foundation for improving ultrasonic guided waves imaging and testing quality and SHM of industrial in-site plate with lap welding and larger size.

Abstract: For a new buried heated oil pipeline, the temperature field of the surrounded soil is natural. Therefore the temperature is usually low in this case. For the waxy crude oil whose pour point is higher than the ground temperature, if the new pipeline transports such oil directly after heating, crude oil may gel in pipeline because its temperature decrease dramatically due to heat exchange between the fluid and the surrounded soil. Hence, in practical situation hot water is often used to warm up the pipelines for most of the new long-distance buried pipelines. Crude oil transportation is determined after the soil temperature field around the pipeline is sufficiently high and the inlet water temperature meets the requirement.