Propagation Law Research Articles

Statistical Characteristic of the Transition Temperature Shift for Reactor Pressure Vessel Steel

Abstract In the ductile?brittle transition temperature range, the Charpy absorbed energy exhibits an inherent variation, which causes uncertainty in the transition temperature shift. In the current codes for the evaluation of fracture toughness of reactor pressure vessel steels, margins are considered to account for the uncertainty in the transition temperature shift. Although they have been statistically determined, their adequacy is only inductively assured by specific surveillance program databases. In this study, a model was proposed to describe the statistical characteristics of the transition temperature shift. An equation to describe the standard deviation of the associated transition temperature was theoretically derived from a previously proposed variation model of the Charpy absorbed energy according to the law of propagation of uncertainty. The obtained standard deviations were then compiled into procedures to estimate the transition temperature shift according to the sufficiency of the parameters required for the evaluation (shape of Charpy curve and sample size). The standard deviations of the transition temperature shift assumed in past studies/present codes were compared with those predicted using the proposed model. In the range of upper shelf energy greater than 100 J, the standard deviations in past studies/present codes.

Mechanical responses research of subway stations under explosion impact load

As the subway station space is closed and the passenger flow is large, subway explosion-proof has always been the focus of station safety personnel. Here we built typical two-story and two-span underground stations model by using LS-DYNA. Through ALE algorithm and fluid structure coupling method, propagation law of shock wave in subway station and damage state of station structures were analyzed in the case of 16.3 kg TNT explosion. It is found that the shock wave mainly propagates along the lateral direction of the station after the superposition and attenuation of the surrounding structures. The maximum displacements of supporting columns, subway stairways, hallway flooring and platform flooring are 1.34 mm, 16.83 mm, 5.354 mm and 112.8 mm respectively. And the overall structure of the station is complete, but local areas are damaged and collapsed. In addition, in order to strengthen the antidetonation stability of subway station structure, the joint of column and platform floor, the joint of column and station hall floor and the reinforcement of stairs should be considered. This paper mainly provides a theoretical basis for the explosion-proof design of station structure.

The law of axial compressive damage of wood components with T-shaped and L-shaped cracks

ABSTRACT Wood components are easy to crack, which has great influence on their performance. So it is particularly essential to monitor and clarify the crack propagation law. In this paper, T- and L-shaped cracks were prefabricated on wood components, and acoustic emission (AE) and digital imaging correlation (DIC) technology were combined to monitor and analyse the damage of wood components under axial compression. The effects of different crack types on the damage forms, mechanical properties, damage index and propagation characteristics of acoustic emission signals were studied. It shows that the damage to L-cracked wood components was more serious than that of T-cracked wood and the acoustic emission signal strengthened as the load increased and the degree of rupture intensified. By establishing the corresponding relationship between the initiation and propagation behavior of wood microcracks and the acoustic emission parameters and surface strain, a measurement and evaluation system for in-situ monitoring the crack damage evolution of wood components with parallel and transverse cracks based on acoustic emission technology and digital image correlation method was successfully constructed. The test results provide a reference for further study on the damage mechanism and in-situ monitoring method of crack evolution behavior of wood with cracks.

Study on the vibration characteristics and influence range of buried dam pipeline

To alleviate water resource shortages and tensions and meet the water diversion needs of different river basins, buried (cross-dam) pipelines have become an essential component of water diversion projects. They are installed in levee projects in key river basins such as the Yellow River, Jingjiang River, and Beijiang River. Due to the complex engineering structure and multiple sources of vibration excitation, if vibrations propagate along the pipeline axis towards the surrounding levee, they could have an adverse impact on the stability and safe operation of the levee. To accurately identify the vibration and transmission characteristics of the buried pipeline dikes, determine its primary vibration sources, and clarify the propagation laws of pipeline vibrations within the levee, this study, based on prototype observation data and utilizing signal fusion processing technology, investigates the inherent vibration characteristics of the buried pipeline dikes from the perspectives of excitation, transmission, and response. At the same time, by introducing the “finite element-infinite element” theory, a coupled finite element-infinite element model is established for the pipeline, levee, anchor piers, support piers, foundation, and infinite half-space. This model is then used to analyze the site response induced by flow-induced vibration in buried pipeline levee structures. The results show that the primary vibration frequencies of the buried pipeline dike structure are the unit rotation frequency of 74.4 Hz and the blade vibration frequency of 24.8 Hz. These vibration sources originate from the pump unit and propagate outward along the pipeline axis. Using the transmission range of the vibration source as the basis for determining the vibration impact range, it was established that the horizontal vibration impact of the buried pipeline extends 10 m on either side of the pipeline axis, while the vertical vibration impact extends 7.5 m below the dike crest.

Single-cell bilayer design of a terahertz six-channel metasurface for simultaneous holographic and grayscale images

Metasurfaces have exhibited excellent capabilities in controlling main characteristics of electromagnetic fields. Thus, a lot of significant achievements have been attained in many areas especially in the fields of hologram and near-field imaging. However, some of these designs are implemented in a manner of interleaved subarrays that complicates the design and makes them difficult to achieve integration. Here, an innovative stacking technique of metasurface is combined with vanadium dioxide (VO2) to achieve independent imaging of six channels in terahertz band. Our research combines intensity modulation controlled by the Malus’s law and phase modulation of geometry and propagation to merge amplitude, phase, and polarization manipulation of electromagnetic wave. A “six-in-one” meta-device is constructed by combining phase change properties of VO2 to realize simultaneous near-field grayscale imaging and far-field holography. This design has advantages of wide bandwidth and low crosstalk. Based on the advantage of low crosstalk, single-cell bilayer design allows the number of independent channels to be doubled within an acceptable error range. The proposed metasurface introduces a fresh viewpoint for the design of multi-purpose meta-devices, and has broad application prospects in information encryption and multi-channel image display.

Study on the crack propagation morphology and initiation law of coal rock under the action of underwater electric pulse

Based on the symmetric initiation mechanism of double-wing cracks in coal rock mass induced by high-pressure electro-recoil water pressure, fracturing experiments have been performed on coal rock mass under different water pressures and discharge conditions using high-voltage electric pulse hydraulic fracturing devices. Combined with CT scans, the crack spatial distribution inside the post-break coal rock mass was analyzed and found that the edge of the water injection hole is prone to produce double-wing cracks along the drilling hole diameter. ABAQUS is used to verify the physical test and extend the test conditions, the geometric parameter change, morphological expansion rule and crack initiation mechanism of double-wing crack in coal rock mass under different discharge conditions and ground stress conditions are studied. The results show that the cracks around the borehole of coal rock mass crack symmetrically under the action of high-voltage electric pulse in water. When the impact load of the high-voltage electric pulse is small(3 MPa hydrostatic pressure, 7 kV discharge voltage), cracks crack symmetrically around the drilling hole, and when the impact load is large(3 MPa hydrostatic pressure, 13 kV discharge voltage), most of the cracks inside the specimen crack symmetrically along the radial or tangential wings of the drilling hole, and the cracks change from multiple pairs of double-wing cracks to a pair of double-wing cracks with the weakening of the shock wave energy until only one single wing crack remains. With the increase of discharge voltage, the length, width, area and complexity of the cracks in both wings will increase in different degrees. With the increase of in-situ stress difference, the crack is more inclined to the direction of the maximum principal stress and eventually expands along the direction of the maximum principal stress. The results further shed light on the initiation and propagation laws of double-wing crack during high-voltage electrical pulse fracturing of coal rock in water and provide theoretical support for efficient extraction of coalbed methane from high-voltage electrical pulse fracturing of coal rock mass in water in China.

The propagation laws of hydraulic fractures under the influence of natural fracture zones

This paper uses the finite-discrete element method (FDEM) to establish a fluid–solid coupling model for the propagation of multi-cluster hydraulic fractures. The validity of the proposed model is verified using the analytical solution and onsite microseismic data. The results show that with the approach angle increases, the propagation of hydraulic fracture transitions from a single capture mode to the mixed modes of capture, crossing and blocking. The total length of hydraulic fractures is negatively correlated with the approach angle and cohesion of natural fracture, and positively correlated with the distribution density and bandwidth of natural fracture. The length of shear fractures initially increases and then decreases with the increase in approach angle, showing negatively, positively, and positively correlated with cohesion, length, and bandwidth, respectively, while the trend of tensile fracture length is opposite to it. The tortuosity of hydraulic fractures (which is used to characterize the complexity of fracture morphology) initially decreases and then increases with the increase in the approach angle, negatively correlated with the cohesion of natural fracture, and positively correlated with the distribution density and bandwidth of natural fractures. Comparatively, the fracture propagation morphology is the most complex at the approach angle of 45°, which is more conducive to full reservoir enhancement. Conversely, under conditions of high cohesion, narrow width, and low-density distribution of natural fractures, the fracture morphology is relatively simple, all of which are unfavorable for reservoir enhancement in the target segment.

Uncertainty Estimation Based on Error Propagation Law for Multi-Robot Pose Graph Merging

Uncertainty Estimation Based on Error Propagation Law for Multi-Robot Pose Graph Merging

Measurement Errors Propagation Laws and Schemes Comparative Study in Sensor Location Problem Based on Turning Ratios

Measurement Errors Propagation Laws and Schemes Comparative Study in Sensor Location Problem Based on Turning Ratios

Horizontal Detection Range Estimation of Deep-Sea Acoustic Shadow Area Based on Vertical Phased Emission Array

To scan the horizontal range of the deep-sea shadow zone with high accuracy and efficiency, enabling active target detection, a horizontal detection range estimation method based on phased sound focusing technology is presented. The model of the phased emission sound field is derived, along with the theoretical estimation formula for the horizontal detection range, by combining the half-power beamwidth of the beam curve at the phased-emitter end with the ray propagation law of deep-sea acoustics. The corresponding relationships among each discrete phased angle, the horizontal distance, and the detection range of the focused beam boundary are detailed. The estimation formula for the horizontal detection range is then improved to account for the sea surface reflection effect, and angle optimization is applied to the transmitted beam curve to counteract the boundary error accumulation effect of the focused sound beam as the sound ray propagates. To address the issue of reduced scanning efficiency at large phased angles, the grating lobe-focused sound beam generated by phased emission array parameters is used to achieve angle scanning within the close deep-sea sound shadow zone, increasing the phased angle scanning efficiency. Finally, the deep-sea phased emission active target detection experiments were carried out, and the echo signal generated by the phased focused sound beam and received by the vertical receiving array was recorded. Numerical simulation and echo signal processing show that the high-efficiency angle scanning of the entire deep-sea sound shadow zone is achieved by the proposed estimation method.

Propagation Law of Hydraulic Fractures in Continental Shale Reservoirs with Sandstone–Shale Interaction

There are significant lithological and stress differences between continental shale layers, posing challenges for hydraulic fractures (HFs) to propagate through the formations, leading to weak fracture effects. To address this, this article adopts the finite element and cohesive force element methods to formulate a three-dimensional numerical model for hydraulic fracture (HF) propagation through layers, considering interlayer lithology and stress variations. The accuracy of the model was verified by physical experiments, and the one-factor analysis method was used to creatively reveal the complex mechanism of the effect of geological and engineering variables on the diffusion of HFs in continental shale reservoirs. The results show that high interlayer stress difference, high interlayer tensile strength difference, low interlayer Young’s modulus difference and large interlayer thickness are not conducive to the penetration of HFs, but increasing the injection rate and the viscosity of fracturing fluid can effectively improve the penetration of HFs. The influence ranking of each factor was determined using the grey relational degree analysis method: interlayer stress difference > interlayer Young’s modulus difference > interlayer tensile strength difference > interlayer thickness > injection rate > fracturing fluid viscosity.

Research on the Modulation Characteristics of LiNbO3 Crystals Based on the Three-Dimensional Ray Tracing Method

To further study the electro-optical modulation characteristics of LiNbO3 crystals and analyze their modulation performance, a method for studying the modulation characteristics of LiNbO3 crystals, based on the three-dimensional ray tracing method, is introduced. With the help of the refractive index ellipsoidal theory, the optical properties of LiNbO3 crystals under the influence of the Pockels effect are systematically investigated. The research results show that the optical properties of LiNbO3 crystals under the action of an external electric field can be divided into two cases: the crystal optical axis is parallel to the clear light direction, and the crystal optical axis is perpendicular to the clear light direction. Subsequently, starting from Maxwell’s equation and the matter equation, the analytical expressions of optical parameters such as refractive index, wave vector, light vector, optical path, and phase delay in electro-optical crystals are derived. Finally, the propagation law of LiNbO3 crystals when the light is incident in any direction, i.e., when the optical axis of the crystal is parallel to the clear direction and perpendicular to the clear direction, and the light intensity and field of view of the LiNbO3 crystal for electro-optical modulation are discussed.

Numerical simulation and experimental investigation of the propagation law of plasma pulse shock waves

Abstract Plasma pulse shock wave rock-breaking technology represents a novel approach to rock fracturing. Present research on this subject largely addresses rocks and electrodes, yet often neglects the critical influence of shock waves in the rock-breaking process. Therefore, it is necessary to further study the propagation law of the shock wave and its reflection and transmission. This paper undertakes experimental simulations using the RHT rock model to explore the propagation process of plasma pulse shock waves based on two variables: the medium and the shape of the electrode. Integrated with one-dimensional stress wave theory, the study examines the impact of four specific parameters—dielectric thickness, surrounding rock height, surrounding rock density, and surrounding rock porosity—on the reflection and transmission rates of shock waves. Pressure data collected from experimental platform are utilized to validate the study’s conclusions. The findings indicate that the propagation behaviors of shock waves differ significantly between water and air mediums. The shape of the electrode causes significant differences in the pressure exerted by the shock wave at the same location. Both the thickness of the dielectric and the porosity of the surrounding rock show a positive correlation with the reflection coefficient and a negative correlation with the transmission coefficient, while the density of the surrounding rock exhibits an inverse relationship. The height of the surrounding rock is irrelevant to both reflection and transmission coefficients.

Fracture Propagation Laws and Influencing Factors in Coal Reservoirs of the Baode Block, Ordos Basin

The expansion of hydraulic fractures in coalbed methane (CBM) reservoirs is key to effective stimulation, making it essential to understand fracture propagation and its influencing factors for efficient resource development. Using petrological characteristics, logging data, microseismic monitoring, and fracturing reports from the Baode Block on the eastern Ordos Basin, this study systematically investigates the geological and engineering factors influencing hydraulic fracture propagation. The real-time monitoring of fracture propagation in 12 fractured wells was conducted using microseismic monitoring techniques. The results indicated that the fracture orientations in the study area ranged from NE30° to NE60°, with fracture lengths varying between 136 and 226 m and fracture heights ranging from 8.5 to 25.3 m. Additionally, the fracturing curves in the study area can be classified into four types: stable, descending, fluctuating, and falling. Among these, the stable and descending types exhibit the most effective fracture propagation and are more likely to generate longer fractures. In undeformed–cataclastic coals and bright and semi-bright coals, long fractures are likely to form. When the Geological Strength Index (GSI) of the coal rock ranges between 60 and 70, fracture lengths generally exceed 200 m. When the coal macrolithotype index (Sm) is below 2, fracture lengths typically exceed 200 m. When the difference between the maximum and minimum horizontal principal stresses exceeds 5 MPa, fractures with length >180 m are formed, while fracture heights generally remain below 15 m. From an engineering perspective, for the study area, hydraulic fracturing measures with a preflush ratio of 20–30%, an average sand ratio of 13–15%, and a construction pressure between 15 MPa and 25 MPa are most favorable for coalbed methane production.

Analysis of crack propagation due to fatigue using the Stable Generalized Finite Element Method (SGFEM)

This work aims to present a combination of the stable generalized finite element method (SGFEM) and of the displacement correlation method (DCM) for analyzing 2D crack propagation problems due to fatigue. The SGFEM allows to model fracture mechanics problems without excessive refinement and/or concern of the mesh-to-crack alignment. Additionally, this method maintains the numerical conditioning under control. The DCM, in turn, is computationally very efficient when compared to traditional energy based methods (like J integral) and herein is even improved by means of a linear least square extrapolation. The maximum circumferential tension criterion and well-known propagation laws available in literature are adopted for considering the crack propagation. Experimental and numerical benchmark examples are proposed and the obtained results are compared against results provided by a commercial software widely adopted in the aeronautics industry.

Theoretical Study on Impact Compression Behavior and Reaction Characteristics of Reactive Materials

Abstract Reactive Materials (RMs) is usually inert at normal temperature and pressure, but when it is subjected to enough impact energy, it can be rapidly transformed into a high-temperature and high-pressure environment, which triggers a chemical reaction and releases a large amount of energy. In order to study the impact compression behavior and reaction characteristics of RMs, this paper established a typical Al/PTFE RMs impact reactivity calculation equation based on the Arrhenius reaction rate model and combined with Avrami-Erofeev’s n-dimensional nuclear/growth control reaction model. And theoretical calculations were conducted on the impact response and reaction characteristics of typical Al/PTFE RMs. The reliability of the model was verified by comparing the calculated results with the simulation results. At the same time, the propagation process of shock wave pressure peak under explosive load in RMs was numerically simulated using software, and the propagation law was studied. The results showed that the impact pressure had a significant impact on the energy release characteristics of typical Al/PTFE active materials. The calculation results of the critical reaction threshold for impact are in good agreement with the simulation results, indicating the reliability of the model. The size of the explosive charge remained unchanged, and as the propagation distance of the shock wave increases, the peak pressure of the shock wave attenuated slowly in the Al/PTFE RMs. During the explosive loading process, the Al/PTFE RMs did not undergo complete chemical reactions, and only a portion of the RMs underwent chemical reactions.

Numerical investigation of the multi-physics coupling effect of supersonic projectile on the cross section of terminal ballistics

Abstract This study investigates the multiphysics effects the shock waves from the supersonic projectile on the cross section of its terminal ballistics, and this purpose is to effectively extract attitude information of projectiles in terminal ballistics。Firstly, the acoustic effects are used to study the propagation and attenuation laws of shock waves on the terminal ballistic plane, comparing the spectral characteristics of acoustic pressure signals and photoelectric signals; Secondly, through numerical simulations using COMSOL, the study analyses shock wave attenuation, refractive index changes, and pressure distribution at different Mach numbers. Results show that shock waves significantly affect the refractive index, which can be effectively detected using optical methods. The proposed method demonstrates improved accuracy over conventional techniques, particularly in capturing critical flight parameters of supersonic projectiles. This research lays the groundwork for developing advanced measurement techniques for hypersonic weapon systems, addressing current limitations in projectile detection and measurement accuracy.

ABAQUS-based research on the parameters of highway subgrade vibratory compaction and vibration wave propagation laws

Vibratory rollers are generally used in the process of highway subgrade compaction. In the paper, the vibratory roller—subgrade finite element model was established to simulate the field construction by using ABAQUS. We used Hilbert–Huang Transform to analyze the compaction in the field test from the time–frequency domain. By changing the parameters of the vibratory roller and the filler, the comprehensive influence of the parameters such as the elastic modulus of the filler, rolling speed, excitation force, vibration frequency and thickness of the filler on the compaction quality of the subgrade was investigated. We studied the propagation pattern of vibration waves in three-dimensional space. The study shows that the signals of different frequency bands in the Hilbert spectrum represent the compaction degrees of fillers in different zones. The peak acceleration generally decreases with the increase of horizontal and vertical distance, but there is an increase at the boundary of the vibration field. There is an optimal combination of the excitation force, vibration frequency and thickness of the filler. The vibration waves propagate in the form of an ellipsoid in three dimensions, and the amplitude decreases with distance.

Experimental Study on Fatigue Properties of Q420 Bridge Steel in a Deicing Salt Corrosion Environment in Western China

The corrosive environment in the western region will adversely affect the fatigue performance of bridges. In order to determine the influence of the corrosion environment in western China on the fatigue failure of bridges, this paper simulated corrosion environment characteristics in northwest China, conducted alternating corrosion and high-cycle fatigue experiments on Q420 bridge steel, and used Origin (2019b 64Bit) to fit S-N curves of specimens with different corrosion periods to study the influence of corrosion damage in western China on their fatigue properties. Based on the damage theory, the corrosion fatigue failure degree of Q420 bridge steel was analyzed, and the crack propagation law was revealed by microscopic scanning of the fracture. The findings indicate that the damage to Q420 bridge steel progressively worsens with more prolonged corrosion exposure in the deicing salt conditions of western China. The 60-day corrosion resulted in a rust rate ηs of 2.17% and a corrosion rate K of 1.413 mm/a. The fatigue life of Q420 bridge steel is significantly affected by the coupling of stress level and corrosion damage. After 60 days of corrosion, the specimen’s fatigue limit decreases by 12.28%, which accelerates the fatigue property degradation rate of the specimen. The damage index effectively represents the internal damage behavior of materials under corrosion fatigue conditions. Fatigue damage escalates as the corrosion period extends, and the number of fatigue bands decreases, with the stress corrosion threshold σth diminishing by 1.77%, 3.55%, 4.61%, and 6.38% across various corrosion durations. The research results are significant for the fatigue failure prediction and reliability analysis of Q420 bridge steel in a deicing salt corrosion environment in western China.

Numerical Computation-Based Analysis of Blasting Vibration Effects and Slope Stability in an Open-Pit Quarry

With the large-scale exploitation of mineral resources, the safety problems of open-pit slopes and dumps become increasingly prominent. In this work, the safety demonstration of the interaction between the eastside slope of an open-pit quarry and the dump was carried out. Firstly, the influence of blasting vibration on the stability of the eastside slope and the dump was analyzed, and the propagation law of blasting vibration wave and the attenuation law of velocity were obtained. Secondly, the finite element analysis of the seepage field of the slope was carried out, and the basic seepage parameters of the rock and soil were determined. Then, the limit equilibrium analysis method was used to quantitatively calculate the stability of the eastside slope of the stope under the load of the dump to assess landslide risk. The results show that no landslides would occur at the dump or affect the performance of the slope, and that the slope was able to reach the required safety reserve factor. Then, through the finite element analysis of the 3-3 profile, it was found that the deformation caused by the excavation unloading of the eastside slope was mainly concentrated in the lower part of the slope, and the displacement variation caused by the top area of the slope was about 0~10 mm. The research verified the stability of slope and dump, which provides technical support for slope project design and blast operation in open-pit quarries.