Dynamic Strain Measurement System Research Articles

Safety assessment of buried gas pipeline subject to surface explosion: A case study in Wuhan, China

To ensure the safety of the underground gas pipeline in urban ground explosion construction and terrorist attack, a study of the safety of buried gas pipelines under surface explosions is inevitable. In this paper, an operating gas pipeline in Wuhan Economic Development Zone is taken as an example, and the surface explosion full-scale experiment is carried out in the open site. In the field experiment, small charge of No. 2 rock emulsion explosives were used to simulate ground construction blasting, the blasting vibration velocity tester (TC-4850) and dynamic strain measurement system (DH5956) are used to monitor data, the analysis of field data shows that the experimental data meet the general rules, which proves the reliability of the field experiment. Secondly, the numerical model of pipeline response characteristics under surface explosion is established, and the reliability of the model is verified by field monitoring data. In the numerical analysis, the operating pressure of 0.2 MPa is given to the pipeline following the actual working condition, and the response characteristics of the pipeline under the condition of large explosive charge blasting on the surface are discussed. Based on the simulation results, the dangerous section and dangerous point of the pipeline under the action of ground explosion are analyzed, and the functional relationship between the peak effective stress (PES) of pipeline dangerous point and the explosive charge on the surface is deduced. Finally, according to the pipeline control value of PES determined in relevant specifications, the controlled explosive charge of surface construction blasting is obtained. Further, the equivalent conversion analysis of No. 2 rock emulsion explosive and TNT explosive is carried out, and the TNT controlled explosive charge of ground terrorist attack is obtained.

Dynamic strain signal monitoring and calibration with neural network based on hierarchical orthogonal artificial bee colony

The dynamic strain monitoring system is an important means to reflect the deformation and evolution of the structure in the field of traffic and transportation visually. The exact measurement of dynamic strain measurement system is inseparable from the traceability system of high-precision strain gauge. In this paper, the resistance strain monitoring system installed on the web surface of the main girder box of Jiujiang bridge is calibrated online by using the parallel method at a similar location. By means of dynamic strain measurement system calibration sample signal feature extraction, put forward online calibration method based on neural network algorithm for dynamic strain signaler, move the noise of passive nonlinear signal under the circumstance of incentives, set up and designed a calibration method of HOABC-NN for dynamic signal analysis of on-line monitoring system. After verification, it is found that the algorithm is superior to the traditional neural network training method, the calibration precision is improved obviously, and can support the dynamic strain of bridge monitoring system online calibration

Modified cannulated screw fixation in the treatment of Pauwels type III femoral neck fractures: A biomechanical study

BackgroundAchieving satisfactory internal fixation for patients with Pauwels type III femoral neck fractures has become a critical problem. The purpose of this study was to compare a common standard internal reduction and fixation method for femoral neck fractures to the modified fixation methods. MethodsA computed tomography scan of the femur was performed to make a Three-dimensional (3D) model, and a fracture line was simulated in the femoral neck. 3Dfinite element analysis was carried out for different insertion methods of cannulated tension screws. Six healthy femur specimens were harvested from three formalin-fixed cadavers, and Pauwels type III femoral neck fracture was artificially created in bilateral femurs. The right side was treated with the inverted triangle construct method and the left side by the modified screw fixation method. After fixation, uniaxial compression and maximum load experiments on the bilateral femoral necks were carried out using the non-contact full-field dynamic strain measurement system (VIC-3D) on a pressure testing machine. FindingsBoth 3D finite element analysis and biomechanical study showed that the modified screw fixation method(group D) provided better anti-shearing and anti-rotation properties for Pauwels type III femoral neck fractures, and offered better interfragmentary compression. Therefore, this modified screw fixation method can offer patients a better option for treatment of Pauwels type III femoral neck fractures. InterpretationChanging the placement of the anterosuperior screw in the inverted triangle construct as perpendicular to the fracture line has the advantages in anti-shearing, anti-rotation and increasing interfragmentary compression.

A Simplified Analytical Solution for the Necking Semi-empirical Stresses based on Aramis System

To make comparison between classic necking stress solution Bridgman formula and ChenChi formula, the difference of necking surface profile assumptions in these two formulas were discussed theoretically. Then, the uniaxial tension experiment on 16 groups of carbon structural steels Q235 and Q345 were carried out at room temperature. Associate with the necking displacement measured by Aramis optical dynamic 3D strain measurement system, the parameter equation of necking surface profile was determined. The comparison results indicate that ChenChi formula is more accurate than Bridgman formula in calculating the necking stress distribution. Furthermore, to overcome the difficulty of measuring the radius curvature R in these formulas, an empirical formula of the geometric dimensions in the necking section was applied and the parameter was corrected based on the necking strain measured by Aramis system. As a result, the obtained equation in this study can provide an improved calculation method for the analysis of three-dimensional stress in necking and a reference for future research on the necking and ductile fracture of structural steels.

Fracturing Effect of Electrohydraulic Shock Waves Generated by Plasma-Ignited Energetic Materials Explosion

Electrohydraulic shock waves (ESWs) are widely applied to many fields such as sterilization, lithotripsy, food processing, and so on. Based on high-pulsed power technology, electrical explosion is increasingly utilized to generate shock waves with steep fronts and short duration. In order to further magnify the shock waves, we have proposed a new technique by using energetic materials (EMs) loads. This paper investigated the fracturing effect of the ESWs generated by plasma-ignited EMs explosion. During the ESWs fracturing process, a large-scale triaxial stress pressurizing equipment and a dynamic strain measurement system were applied to the shale samples. The most evident experimental results showed that a large number of cell-shaped multiple cracks developed after the ESWs fracturing process. In addition, interior crack morphology and fluorescent tracing proved the evidence of penetration cracks. These cracks contributed to a great reduction of fracture pressure in fracturing test, which laid a scientific foundation for ESWs technique to be a promising method of well stimulation in those low permeability reservoir and further optimized into a new plugging relief and injection gain technology.

Dynamic shape and strain measurements of rotating tire using a sampling moiré method

Shape measurements and strain distribution measurements are important for analyzing the behavior of a rotating tire. Recently, a two-dimensional phase analysis method using phase-shifting moire patterns, which are generated computationally from a two-dimensional grating image, was proposed. This method is well suited to the dynamic shape and strain measurement because the phase can be accurately obtained from a two-dimensional grating image. We show that it is possible to analyze the strain distribution and shape measurements of a moving object using a grating pattern attached to the surface of the specimen, and a dynamic shape and strain measurement system using the sampling moire method is developed in this paper. The principle of the method and the experimental results of the method when applied to a rotating object are shown.

Dynamic strain measurement system with fiber Bragg gratings and noise mitigation techniques

A low-cost fiber Bragg grating (FBG) vibrometer specifically suited for structural monitoring and aimed at the detection of low-amplitude vibrations is presented. The optical system exploits an intensity modulation principle of operation, while signal processing techniques are used to complement the transducer to improve the performances: a recursive least-squares adaptive filter improves the noise power mitigation by 14 dB, and an efficient spectral estimator permits operating spectral analysis even under high noise conditions. With these methods, a strain sensitivity of 5.6 nε has been achieved in the ±60 µε range. Experimental assessment tests carried out in typical structural monitoring contexts have demonstrated that the developed sensor is well suited to measure mechanical perturbations of different structures.

VALID STRAIN MEASUREMENTS FOR STRUCTURAL DYNAMICS TESTING. Part 2: Dynamic Strain Measurement System Transfer Functions and Linearity

VALID STRAIN MEASUREMENTS FOR STRUCTURAL DYNAMICS TESTING. Part 2: Dynamic Strain Measurement System Transfer Functions and Linearity