Predicting impact forces on pipelines from deep-sea fluidized slides:A comprehensive review of key factors

Deep-sea pipelines play a pivotal role in seabed mineral resource development,global energy and resource supply provision,network communication,and environmental protection.However,the placement of these pipelines on the seabed surface exposes them to potential risks arising from the complex deep-sea hydrodynamic and geological environment,particularly submarine slides.Historical incidents have highlighted the substantial damage to pipelines due to slides.Specifically,deep-sea fluidized slides(in a debris/mud flow or turbidity current physical state),characterized by high speed,pose a significant threat.Accurately assessing the impact forces exerted on pipelines by fluidized submarine slides is crucial for ensuring pipeline safety.This study aimed to provide a comprehensive overview of recent advancements in understanding pipeline impact forces caused by fluidized deep-sea slides,thereby identifying key factors and corresponding mechanisms that influence pipeline impact forces.These factors include the velocity,density,and shear behavior of deep-sea fluidized slides,as well as the geometry,stiffness,self-weight,and mechanical model of pipelines.Additionally,the interface contact conditions and spatial relations were examined within the context of deep-sea slides and their interactions with pipelines.Building upon a thorough review of these achievements,future directions were proposed for assessing and characterizing the key factors affecting slide impact loading on pipelines.A comprehensive understanding of these results is essential for the sustainable development of deep-sea pipeline projects associated with seabed resource development and the implementation of disaster prevention measures.

BOP shear force evaluation under complex scenarios

As the“throat”of the drilling well control system,ram blowout preventers(BOPs)can effectively prevent blowout accidents.However,the ram shear mechanism under complex working conditions is unclear,and it is difficult to evaluate the ram BOP shear force,leading to frequent shear failure accidents in oilfields.Aiming at the above problems,this paper takes the double-V ram BOP as the research object,and integrates the methods of theoretical analysis,simulation modeling,and test verification to analyze the shear force in the pipe shear process under both static and moving conditions.A ram BOP shear force evaluation method is proposed based on equivalent stress.Finally,by comparing with calculation data and experimental data,the error between them is less than 5%,demonstrating the applicability and effectiveness of the proposed method.The research results can provide a theoretical basis for oilfield operations of ram BOPs.

Effect of diode-laser parameters on shear force of micro-joints soldered with Sn-Ag-Cu lead-free solder on Au/Ni/Cu pad

Soldering experiments with Sn-3.5Ag-0.5Cu lead-free solder on Au/Ni/Cu pad were carried out by means of diode-laser and IR reflow soldering methods respectively.The influence of different heating methods as well as output power of diode-laser on shear force of micro-joints was studied and the relationship between the shear force and microstructures of micro-joints was analyzed.The results indicate that the formation of intermetallic compound Ag3Sn is the key factor to affect the shear force and the fine eutectic network structures of micro-joints as well as the dispersion morphology of fine compound Ag3Sn,in which eutectic network band is responsible for the improvement of the shear force of micro-joints soldered with Sn-Ag-Cu lead-free solder.With the increases of output power of diode-laser,the shear force and the microstructures change obviously.The eutectic network structures of micro-joints soldered with diode-laser soldering method are more homogeneous and the grains of Ag3Sn compounds are finer in the range of near optimal output power than those soldered with IR reflow soldering method,so the shear force is also higher than that using IR reflow soldering method.When the output power value of diode-laser is about 41.0 W,the shear force exhibits the highest value that is 70% higher than that using IR reflow soldering method.

Electro-elastic Fields of Piezoelectric Materials with An Elliptic Hole under Uniform Internal Shearing Forces

The existing investigations on piezoelectric materials containing an elliptic hole mainly focus on remote uniform tensile loads. In order to have a better understanding of the fracture behavior of piezoelectric materials under different loading conditions, theoretical and numerical solutions are presented for an elliptic hole in transversely isotropic piezoelectric materials subjected to uniform internal shearing forces based on the complex potential approach. By solving ten variable linear equations, the analytical solutions inside and outside the hole satisfying the permeable electric boundary conditions are obtained. Taking PZT-4 ceramic into consideration, numerical results of electro-elastic fields along the edge of the hole and axes, and the electric displacements in the hole are presented. Comparison with stresses in transverse isotropic elastic materials shows that the hoop stress at the ends of major axis in two kinds of material equals zero for the various ratios of major to minor axis lengths; If the ratio is greater than 1, the hoop stress in piezoelectric materials is smaller than that in elastic materials, and if the ratio is smaller than 1, the hoop stress in piezoelectric materials is greater than that in elastic materials; When it is a circle hole, the shearing stress in two materials along axes is the same. The distribution of electric displacement components shows that the vertical electric displacement in the hole and along axes in the material is always zero though under the permeable electric boundary condition; The horizontal and vertical electric displacement components along the edge of the hole are symmetrical and antisymmetrical about horizontal axis, respectively. The stress and electric displacement distribution tends to zero at distances far from the elliptical hole, which conforms to the conclusion usually made on the basis of Saint-Venant’s principle. Unlike the existing work, uniform shearing forces acting on the edge of the hole, and the distribution of electro-elastic fields inside and outside the elliptic hole are considered.

Near Crack Line Elastic-Plastic Analysis for an Infinite Plate Loaded by a Pair of Point Shear Forces

The near crack line analysis method was used to investigate a crack loaded by a pair of point shear forces in an infinite plate in an elastic-perfectly plastic solid. The analytical solution was obtained, that is the elastic-plastic fields near crack line and law that the length of the plastic zone along the crack line is varied with external loads. The results are sufficiently precise near the crack line and are not confined by small scale yielding conditions.

Normal values of shear wave velocity in liver tissue of healthy children measured using the latest acoustic radiation force impulse technology

BACKGROUND Several studies have demonstrated the feasibility and effectiveness of using ultrasound elastography to assess liver tissue stiffness.Virtual touch imaging quantification(VTIQ)based on acoustic radiation force impulse imaging has been developed as a latest and noninvasive method for assessing liver stiffness in children.AIM To determine the standard value in healthy children,and to identify possible factors that might influence the VTIQ measurement.METHODS With the ethical approval,202 children between 1 month and 15 years old were included in this study.None of them had any liver or systematic diseases.All children had a normal ultrasound scan and normal body mass index(BMI)range.The subjects were divided into four age and BMI groups.The effects of gender,age,liver lobe,measurement depth,and BMI on liver elasticity were investigated.RESULTS A significant correlation was found between age and shear wave velocity(SWV)value.At measurement depths of 1.5 cm and 2.0 cm in the left lobe,there were significant differences among the age groups.SWV values were significantly negatively correlated with the measurement depth.Gender,liver lobe,and BMI showed no significant effect on the SWV values.Age and BMI may influence the quality of the elastogram.CONCLUSION VTIQ is a noninvasive technique that is feasible to measure liver stiffness in children.The afore-mentioned velocity value obtained utilizing VTIQ method could be used as reference value for normal liver stiffness in children.

A Modified Monte Carlo Model of Speckle Tracking of Shear Wave Induced by Acoustic Radiation Force for Acousto-Optic Elasticity Imaging

A modified Monte Carlo model of speckle tracking of shear wave propagation in scattering media is proposed. The established Monte Carlo model mainly concerns the variations of optical electric field and speckle. The two- dimensional intensity distribution and the time evolution of speckles in different probe locations are obtained. The fluctuation of speckle intensity tracks the acoustic-radiation-force shear wave propagation, and especially the reduction of speckle intensity implies attenuation of shear wave. Then, the shear wave velocity is estimated quantitatively on the basis of the time-to-peak algorithm and linear regression processing. The results reveal that a smaller sampling interval yields higher estimation precision and the shear wave velocity is estimated more efficiently by using speckle intensity difference than by using speckle contrast difference according to the estimation error. Hence, the shear wave velocity is estimated to be 2.25 m/s with relatively high accuracy for the estimation error reaches the minimum （0.071）.

Elastoplastic analysis for infinite plate with centric crack loaded by two pairs of point shear forces

The near crack line analysis method was used to investigate a crack loaded by two pairs of point shear forces in an infinite plate in an elastic-perfectly plastic solid, and the analytical solution was obtained. The solutions include: the unit normal vector of the elastic-plastic boundary near the crack line, the elastic-plastic stress fields near crack line, law that the length of the plastic zone along the crack line is varied with an external loads, and the bearing capacity of an infinite plate with a center crack loaded by two pairs of point shear forces. The results are sufficiently precise near the crack line because the assumptions of the small scale yielding theory have not been made and no other assumption have been taken.

Effect of the particle temperature on lift force of nanoparticle in a shear rarefied flow

The nanoparticles suspended in a shear flow are subjected to a shear lift force,which is of great importance for the nanoparticle transport.In previous theoretical analysis on the shear lift,it is usually assumed that the particle temperature is equal to the temperature of the surrounding gas media.However,in some particular applications,the particle temperature can significantly differ from the gas temperature.In the present study,the effect of particle temperature on the shear lift of nanoparticles is investigated and the corresponding formulas of shear lift force are derived based on the gas kinetic theory.For extremely small nanoparticles(with radius R<2 nm)or large nanoparticles(R>20 nm),the influence of the particle temperature can be neglected.For the intermediate particle size,the relative error induced by the equal gas–particle temperature can be significant.Our findings can bring an insight into accurate evaluation of the nanoparticle transport properties.

Derivation of energy-based base shear force coefficient considering hysteretic behavior and P-delta effects

A modified energy-balance equation accounting for P-delta effects and hysteretic behavior of reinforced concrete members is derived. Reduced hysteretic properties of structural components due to combined stiffness and strength degradation and pinching effects, and hysteretic damping are taken into account in a simple manner by utilizing plastic energy and seismic input energy modification factors. Having a pre-selected yield mechanism, energy balance of structure in inelastic range is considered. P-delta effects are included in derived equation by adding the external work of gravity loads to the work of equivalent inertia forces and equating the total external work to the modified plastic energy. Earthquake energy input to multi degree of freedom（MDOF） system is approximated by using the modal energy-decomposition. Energybased base shear coefficients are verified by means of both pushover analysis and nonlinear time history（NLTH） analysis of several RC frames having different number of stories. NLTH analyses of frames are performed by using the time histories of ten scaled ground motions compatible with elastic design acceleration spectrum and fulfilling duration/amplitude related requirements of Turkish Seismic Design Code. The observed correlation between energy-based base shear force coefficients and the average base shear force coefficients of NLTH analyses provides a reasonable confidence in estimation of nonlinear base shear force capacity of frames by using the derived equation.

Diatom-induced impact on shear strength characteristics of finegrained soils

Diatomaceous soils,composed of diatom microfossils with biological origins,have geotechnical properties that are fundamentally different from those of conventional non-diatomaceous fine-grained soils.Despite their high fines content,diatomaceous soils typically exhibit remarkably high shear resistance,approaching that of sandy soils.However,the exact role that diatoms play in controlling the mechanical properties of fine-grained soils and the underlying mechanisms remain unclear.In light of this,the shear strength response of diatomaceous soils was systematically investigated using consolidated undrained triaxial compression tests on diatomekaolin mixtures(DKMs)with various diatom contents and overconsolidation ratios.The micro-and nano-scale structures of the soil samples were characterized in detail using scanning electron microscope(SEM)and atomic force microscope(AFM)to interpret the abnormal shear strength parameters of diatomaceous soils.The results indicated that the presence of diatoms could contribute to significantly higher strength,e.g.the friction angle of DKMs was improved by 72.7%to 37and the value of undrained shear strength tripled with diatom content increasing from 20%to 100%.Such significant improvement in soil strength with diatom inclusion could be attribute to the hard siliceous skeleton of diatoms and the interlocking between particles with rough surfaces,which were quantitatively analyzed by the surface roughness parameters with AFM.Furthermore,a conceptual model established based on the macro-mechanical tests and microscopic observations portrays a microstructural evolution of soils with increasing diatoms.The microstructure of soils was gradually transformed from the matrix-type to the skeletal one,resulting in a continual augmentation in shear strength through mutual interactions between diatom microfossils.This paper provides new insights into the multi-scale structural properties of diatoms and significantly advances our understanding of the mechanical behavior of diatomaceous soils.

Growth and aggregation control of spinel by shear-force-based melting modification of stainless steel slag

To improve the efficiency of melting modification for stainless steel(SS) slag, a shear force was introduced in this work and its effects on the spinel and silicate melt were experimentally investigated. The results indicated that the use of shear force changed the nucleation and growth behaviors of spinel and that the effects of shear force varied with its intensity. The aggregation behavior of spinel under different shear-force conditions was studied, revealing that large spinel clusters could be formed when the stirring speed was controlled. However, no notable change in the melt structure of the silicate was detected in this study. The optimal stirring speed for the melting modification treatment was 50 r·min^(-1), which substantially promoted spinel growth and aggregation, resulting in modified SS slag with excellent chromium sequestration capability.

Analysis of Photoelectric Hybridization Measurement on Shearing Force for Flat Shearer

This paper introduces a kind of photoelectric hybridization measuring process.Owing to the characteristics of the compact form of shearing equipment to be analyzed and the connecting rod existing in two directional stress state during operation etc.,it is hard to obtain results by means of single electrical testing process.For this reason,this paper derives a group of calculation formulas of hybridization measuring process through comprehensive discussion of photoelectric analysis and electrical testing theories,thus providing an analytical method for actual measurement of complex engineering problems.

Study on adhesively-bonded surface of tapered double cantilever specimen made of aluminum foam affected with shear force

Aluminum foam is widely used in diverse areas to minimize the weight and maximize the absorption of shock energy in lightweight structures and various bio-materials.It presents a number of advantages,such as low density,incombustibility,non-rigidity,excellent energy absorptivity,sound absorptivity and low heat conductivity.The aluminum foam with an air cell structure was placed under the TDCB Mode II tensile load by using Landmark equipment manufactured by MTS to examine the shear failure behavior.The angle of the tapered adhesively-bonded surfaces of specimens was designated as a variable,and three models were developed with the inclined angles differing from one another at 6°,8° and 10°.The specimens with the inclined angles of 6°,8° and 10° have the maximum reaction forces of 168 N,194 N when the forced displacements are 6,5 and 4.2 mm respectively.There are three specimens with the inclined angles of 10°,8° and 6° in the order of maximum reaction force.As the analysis result,the maximum equivalent stresses of 0.813 MPa and 0.895 MPa happened when the forced displacements of 6 mm and 5 mm proceeded at the models of 6° and 8°,respectively.A simulation was carried out on the basis of finite element method and the experimental design.The results of the experiment and the simulation analysis are shown not different from each other significantly.Thus,only a simulation could be confirmed to be performed in substitution of an experiment,which is costly and time-consuming in order to determine the shearing properties of materials made of aluminum foam with artificial data.

Elastic-plastic analytical solution for centric crack loaded by two pairs of point shear forces in finite plate

The near crack line analysis method was used to investigate a centric crack loaded by two pairs of point shear forces in a finite plate, and the analytical solution was obtained. The solution includes the unit normal vector of the elastic-plastic boundary near the crack line, the elastic-plastic stress fields near the crack line, the variations of the length of the plastic zone along the crack line with an external load, and the bearing capacity of a finite plate with a centric crack loaded by two pairs of point shear forces. The results are sufficiently precise near the crack line because the assumptions of small scale yielding theory have not been made and no other assumptions are taken.

SHEAR EFFECTS ON LARGE AMPLITUDE FORCED VIBRATIONOF SYMMETRICALLY LAMINATED RECTILINEARLYORTHOTROPIC CIRCULAR PLATES

In this paper, nonlinear forced vibration of symmetrically laminated rectilinearly orthotropic circular plates excited by a harmonic force q(0)cos omega t including effects of transverse shear deformation is discussed. The analytical solution for the relationship between forcing frequency and amplitude of vibration is obtained by Galerkin's method. Finally, the paper analyses the effect of the transverse shear on the vibration of the plate and gives the ratio of nonlinear period to linear period for nonlinear free vibration of the plate.

Cyclic testing of moment-shear force interaction in reinforced concrete shear wall substructures

Previous quasi-static cyclic tests of shear walls,which routinely used an incremental lateral displacement test protocol with a constant axial load,failed to reflect the character of moment-shear force interaction of prototype buildings.To study the effect of the moment-shear force interaction on the seismic performance of shear walls,three identical 2-story shear wall specimens with different loading patterns were constructed at 1/2 scale,to represent the lower portion of an 11-story high-rise building,and were tested under reversed cyclic loads.The axial force,shear force and bending moment were simultaneously applied to simulate the effects of gravity loads and earthquake excitations on the prototype.The axial force and bending moment delivered from the upper structure were applied to the top of the specimens by two vertical actuators,and the shear force was applied to the specimens by two horizontal actuators.A mixed force-displacement control test program was adopted to ensure that the bending moment and the lateral shear were increased proportionally.The experimental results show that the moment-shear force interaction had a significant effect on the failure pattern,hysteretic characteristics,ductility and energy dissipation of the specimens.It is recommended that moment-shear force interaction should be considered in the loading condition of RC shear wall substructures cyclic tests.

Role of Interatomic Force to Critical Resolved Shear Stress of Single Crystals

Experimental results of the temperature dependence of critical resolved. shear stresses (CRSS)of Mo, Fe, Al and Mg single crystals are shown. Associating reports in recent years, we point out that the approximate exponential relationship between CRSS and the absolute temperatureat least in the region of the steep temperature dependence range of many materials is more common, even for bcc, fcc, and hcp single crystals. polycrystals and other covalent crystals,provided that the slip plane and slip direction are kept the same. Successful explanation with atomic force law shows that the interatomic forces (electronic structure) play a decisive role in determining the temperature dependence of yield stresses for a large number of materials.

Effect of external shearing force on exfoliation structure and properties of high-performance epoxy/clay nanocomposites

To further investigate the influence of organic modifiers （primary amine with catalytic hydrogen and quaternary alkylammonium salt） on exfoliation behavior of clay tactoids, high-speed emulsifying and homogeneous mixing（HEHM） and ball milling were used to exert external shearing force on two organic clay tactoids (termed as (（MMT）DDA) and (（MMT）DBDA), respectively), which were organically modified with DoDecyl Amine（DDA） and Dodecyl Benzyl Dimethyl Ammonium chloride（DBDA）,respectively. The effects of external shearing force on microstructure and properties of both resultant nanocomposites were investigated by X-ray diffractometry（XRD）, transmission electron microscopy（TEM） and thermogravimetric analysis（TGA）. The results show that whether the clay tactoids are organically modified with catalytic primary amine or quaternary alkylammonium salt, the large agglomerates will not be finely dispersed or exfoliated by conventional mixing （magnetic stirring）. After being vigorously sheared by （HEHM） or ball milling, the dispersion and exfoliation of clay tactoids are increasingly promoted for both (（MMT）DDA) and (（MMT）DBDA), and the mechanical properties of the high-performance epoxy/clay nanocomposites are enhanced. For epoxy/(（MMT）DDA) nanocomposites, impact strength can be increased up to 44.5 kJ/m2 from 32.1 kJ/m2, which is about 39% higher than that of pristine matrix, and the flexural strength is enhanced by about 4%. A similar enhancement for epoxy/(（MMT）DBDA) nanocomposites has also been achieved. Improvement on thermal stability of epoxy/clay nanocomposites is dependent on the exfoliation of clay layers and molecular structure of the modifiers. The onset temperature is increased with the clay loading decreasing from 5% or higher content to 3%（mass fraction）, and the DBDA modifier with the heat-resistant benzyl may also improve the stability of epoxy/(（MMT）DBDA) nanocomposites.

Study on the Distribution Law of Horizontal Seismic Forces between Slab-Column and Shear Wall

In slab column-shear wall structures,both the whole structure′s seismic behavior and failure mode are greatly influenced by the distribution of horizontal seismic forces between slab-column and shear wall.In this paper,a pushover analysis of topical slab column-shear wall structure was carried out,the seismic shear force that the slab-column and shear wall should undertake was worked out,the influences of plastic internal force redistribution and structure stiffness characteristic value on horizontal seismic distribution were studied and the calculation formula was given.The analysis results showed that with the yield of the shear walls,the story shear force was undertaken by slab-columns correspondingly increased while with the decrease of characteristic value of stiffness of a structure,and the horizontal seismic force was undertaken by slab-columns correspondingly decreased.According to the code,the design of horizontal force distribution may be cause insecurity problems,so it is necessary to give the distribution law of horizontal seismic forces in slab-column shear wall structures as the supplement to the corresponding regulation of the Code.