89 results about "Discrete element simulation" patented technology

The invention relates to a contact judgment method of spherical particles and triangular meshes in discrete element simulation. The contact judgment method of the spherical particles and the triangular meshes in the discrete element simulation comprises steps of searching neighbor meshes of a target particle to confirm a boundary triangle unit which performs intersecting detection with the target particle; confirming primary contacting information between the target particle and the boundary triangle unit in combination with a symbolic assembly of triangular Voronoi space and center-of-mass coordinates; and judging effectiveness of the primary contacting information, eliminating invalid contacting information and adding the effective contacting information into a contacting linked list to calculate the contact force of particles through a discrete element simulation program. The contact judgment method of the spherical particles and the triangular meshes in the discrete element simulation has the advantages of avoiding respectively building contact judgment algorithms for every kind of basic graphic elements; providing a method for directly positioning an area generating contact to save execution steps of the contact judgment; building judging criteria for eliminating the invalid contact information among multiple contact information; and finally effectively solving the contact judgment problem of the spherical particles and complex geometry boundaries in the discrete element simulation.

The invention discloses a seepage simulation method for constructing a coal body based on finite element-discrete element CT (Computer Tomography). The method comprises the following steps: performing industrial CT scanning to obtain a three-dimensional data body of the coal body, performing three-dimensional reconstruction, and removing an ''island block'' to obtain a general three-dimensional geometric model which can be called by simulation software; writing a coal body fracture discrimination algorithm by a discrete element simulation method, and determining whether the coal body is deformed, even fractured under the action of hydraulic pressure stress; meanwhile, realizing migration of coal body fragments formed after fracture in the coal body along with moisture flow based on an finite element simulation method by a mobile grid method; and performing numerical simulation of a moisture seepage pressure field, a seepage speed field and a coal body moisture increment at the same time in order to reveal deformation and fracture phenomena of the coal body and a migration rule of moisture in a water injection process of a porous medium coal bed to the maximum extent.

Discrete Element Modeling (DEM) of rock subject to high confining pressures, such as in a subterranean drilling environment, may be used to predict performance of cutting structures used in drill bits and other drilling tools, as well as of the tools themselves. DEM may also be used to create “virtual” rock exhibiting specific drillability characteristics with or without specific reference to any actual rock, for purposes of assessing cutting efficiency of various cutting structure configurations and orientations, as well as of drilling tools incorporating same.

The invention discloses a temperature field analysis method of a bituminous mixture test piece on the basis of discrete element simulation, belongs to the technical field of bituminous mixture, and solves the problem that a finite element method can not accurately analyze the internal temperature field of the bituminous mixture test piece in a high-temperature environment. The temperature field analysis method comprises the following steps: firstly, forming the bituminous mixture test piece, collecting a digital image of irregular aggregate distribution, and converting the digital image into a digital test piece of a two-dimensional CAD (Computer-Aided Design) image format after the digital image is subjected to image processing; then, importing discrete element software, independently generating irregular aggregate and bituminous mortar according to the positions of aggregate blocks and the bituminous mortar, and constructing a two-dimensional test piece discrete element model; simulating a situation that the test piece is heated in the high-temperature environment, setting a boundary condition of the test piece model, the thermophysical property parameters of the aggregate and the bituminous mortar and the internal contact thermal resistance of a unit; and applying certain constant-high-temperature and room-temperature heat flow around the test piece model, recording the temperature change situations of each point in the test piece at different moments, drawing a comparison graph, and combining with a temperature field and a heat flow distribution cloud chart generated by the software to analyze the temperature field of the bituminous mixture test piece.

The invention discloses a particle flow numerical simulation method for reflecting the distribution of the real engineering soil-rock mixture. The method comprises the following steps: taking photos to obtain the real image of the soil-rock mixture on the project site; using the processing technology to recognize rocks and extract their boundary coordinates; combined with particle sieving and image data, obtaiing the particle size distribution of soil-rock mixture; testing the strength and deformation of soil and rock and deformation parameters.; establishing a numerical model of particle flowin soil-rock mixture; calibrating parameters of particle flow numerical model and carrying numerical tests of mechanical properties of soil-rock mixture specimens. The method is convenient to implement and can be programmed to model intelligently, and can overcome the limitation of test size and meet the requirement of engineering. It is suitable for DEM simulation of binary media such as earth-rock mixture and concrete.

The invention provides a hierarchical-extension discrete element simulation method. The method comprises the steps that based on formation rock mechanical properties and basement fault positions of areal formation, a discrete element numerical simulation formation is constructed, wherein the discrete element numerical simulation formation comprises a simulation formation, and the simulation formulation has a hierarchical-extension superposed deformation structure of an intermediate ductile layer; and the simulation formulation accurately simulates the rock mechanical properties of the real formation through adjustment of filling material properties, construction and/or structures. Through the hierarchical-extension discrete element simulation method, the model construction mode is simple,the simulation mode is easy to realize, and the simulation result has good accuracy.

The invention discloses a discrete element numerical simulation method for viscous sandy soil hydraulic erosion damage. The method comprises the steps of:establishing an initial calculation space areaand a viscous sandy soil numerical model; initializing a numerical model and balancing stress; compiling a strength degradation criterion linear bonding contact model based on a time effect to simulate a clay phase between aggregate particles in the viscous sandy soil; selecting a contact model as a mesomechanics model of contact between aggregate particles, and valuing mesoscopic parameters of the contact model; calibrating the numerical model through a direct shear strength test; establishing a flow field to simulate the hydraulic erosion damage process of the viscous sandy soil; and obtaining a numerical simulation result of the hydraulic erosion damage test. According to the method, the viscous sand hydraulic erosion damage is simulated through the discrete elements, the thought is simplified, the viscous sand hydraulic erosion damage process can be truly simulated on the mesoscopic level under the conditions that the calculated amount is reduced as much as possible and the calculation efficiency is improved, the migration situation of soil particles is observed and recorded, and the result is accurate.

The invention provides a structure surface wear simulation method based on a discrete element method. The structure surface wear simulation method includes the following steps that S1, the structure surface shape is obtained, and a target surface is divided into a triangular mesh composed of a plurality of triangular units; S2, discrete element simulation is conducted on the triangular units, the scattered particle collision processes of the triangular units are simulated, and thus the collision energy data of all the triangular units are computed and recorded; S3, the sizes of the materials stripped out of the surfaces of all the triangular units are computed according to the collision energy data obtained in S2, and thus the height variable quantity of the centers of mass of all the triangular units is obtained according to the material sizes; S4, the target surface is fitted again according to the height variable quantity of the centers of mass of all the triangular units obtained in S3. The structure surface wear simulation method based on the discrete element method provides reference for structural design, functional design, service life design and the like of scattered material processing equipment.

The invention discloses a discrete element simulation method for a rock-soil triaxial test flexible film boundary. The discrete element simulation method adopts a particle set arranged in a hexagonalhoneycomb structure to represent a flexible film, and a linear bonding model is adopted among particles, and an upper loading plate and a lower loading plate adopt rigid walls. The discrete element simulation method has the outstanding advantages that (1) the film particles can effectively represent parameters such as the elasticity modulus, the Poisson's ratio and the thickness of the physical film; (2) the film can be freely deformed in the sample loading process, and the hydrostatic confining pressure can be stably and accurately transmitted; and (3) the volume deformation of the sample canbe accurately recorded in real time in the loading process. The discrete element simulation method is simple in implementation process and suitable for simulating conventional triaxial tests of various granular materials such as sandy soil and rockfill materials. Practice shows that the discrete element simulation method can accurately simulate the shape change, the stress-strain relationship andthe volume strain condition of the sample in the triaxial test process of the granular material, and can provide powerful support for macroscopic parameter test and mechanical property research of the granular material.

The invention discloses a method for constructing a breakable grain particle discrete element simulation model. The method comprises the following steps that 1, measuring the three-dimensional characteristic size of grain particles; 2, generating a grain particle three-dimensional model by using a computer; 3, preliminarily establishing a grain particle discrete element simulation model through discrete element software; 4, introducing a virtual cylinder bonding key into the discrete element simulation model obtained in the step 3; 5, taking a force and deformation curve obtained by a conventional physical and mechanical test as a target; repeatedly adjusting mesoscopic parameters of the discrete element simulation model; the force obtained by calculation and actual measurement of the simulation model is matched with the deformation curve; according to the method, the characteristic that the cereal grains have crushable and viscoelastic mechanical properties is considered at the same time, so that the discrete element simulation model of the cereal grains is closer to actual cereal grains, and the method can be widely applied to cereal grain crushing mechanism research in the grainprocessing process.

The invention discloses a verification device and method for simulating a concrete slump form by discrete elements, and belongs to the technical field of building material performance detection. The verification device comprises a supporting frame, a pair of Y-direction guide rails arranged on the supporting frame in parallel, a first driving brake assembly arranged on the Y-direction guide rails,an X-direction guide rail of which the two ends are fixedly connected with the first driving brake assembly, a second driving brake assembly arranged on the X-direction guide rail, and a distance measuring instrument arranged below the second driving brake assembly and a control terminal which comprises a control module, a data acquisition and calculation module and a data processing module. According to the verification device and method, by measuring the distance of a surface measuring point after the concrete slump, calculating the three-dimensional coordinate of the measuring point, converting the three-dimensional coordinate of the measuring point into a polar coordinate, fitting the polar coordinate into a longitudinal section diagram of the concrete slump form simulated by discreteelements, the concrete slump form simulated by the discrete elements is verified, and a quantitative evaluation index has the reasonability.

The present invention relates to a multi-ball particle two-layer grid search contact detection method in discrete element simulation. The method comprises the following steps: a global space is divided into square or cube girds with the size of D; performing a first layer grid search, if the enveloping ball of a target particle is intersected with the enveloping ball of a certain candidate particle, the first layer grid search is completed, or else, the intersection detection between the enveloping ball of the target particle and the enveloping balls of other candidate particles is performed; and when the enveloping ball of the target particle and the enveloping balls of other candidate particles are intersected, a square or cube local space with the size of D+d is divided into square or cube grids with the size of d for the usage of a second layer grid search, and the contact between the cell ball of the target particle and the cell balls of the candidate particles is detected. The multi-ball particle two-layer grid search contact detection method in discrete element simulation keeps the time consuming of the contact detection without increasing while significantly decreasing memory consumption of the contact detection and provides an effective technological means for the large-scale application of the multi-ball particle discrete element simulation in the industrial field.

the invention discloses a numerical simulation method for aging degradation of mechanical properties of carbonate rock under water action which includes such step as establishing a generalized model of mechanical property deterioration mechanism of carbonate rock under the action of water, setting up the generalized model of mechanical property deterioration mechanism of carbonate rock under the action of water, setting up the generalized model of mechanical property degradation mechanism of carbonate rock under the action of water. Step 22, establishing a discrete element model of aging deterioration of mechanical properties of carbonate rock under different immersion conditions according to the mechanism generalization model obtained in the step 1, and obtaining a quantitative correlation of mechanical properties with time of bonding between blocks of polygonal blocks under different immersion conditions; step 3, calibrating that mechanical parameters of the discrete element model; Carbonate rock mechanics tests under different immersion conditions and immersion time were carried out to calibrate the mechanical parameters of the discrete element model in step 2. Step 4, simulating the mechanical properties of carbonate rock under different immersion conditions by using the calibrated parameters of the discrete element model. The invention truly reflects the carbonate rock-water water interaction principle, a two-stage deterioration model and its discrete element simulation method are proposed.

The invention discloses an accurate control method for surrounding rock of a coal mine tunnel crossing fault area, which comprises the following steps of: (1) carrying out ground stress inversion on afault damage area to determine a ground stress distribution rule of the tunnel crossing fault area; (2) taking mudstone of the surrounding rock fault zone of the roadway, carrying out a remolding test, and determining the physical and mechanical properties of the surrounding rock by adopting a geological strength index (GSI) method; (3) adopting a discrete element simulation method to preferablyselect a fault zone surrounding rock control scheme, and determining a precise surrounding rock control method for a fracture zone of the coal mine tunnel crossing fault ; and (4) observing the mine pressure of the roadway surrounding rock. Aiming at the characteristics of quick rock stratum lithology change and rock stratum crushing of a fault fracture zone, the stress distribution rule and the surrounding rock type of the roadway are mastered through geomechanics and a numerical simulation method, and accurate control over the surrounding rock of the roadway is achieved.

The invention discloses an automatic calibration method for discrete element hertz contact parameters during geotechnical material simulation, and the method comprises the following steps: substituting a target macroscopic parameter calibrated by a discrete element into an analytical formula to calculate a particle shear modulus and a Poisson's ratio, taking the particle shear modulus and the Poisson's ratio as initial estimation values of particle parameters, and establishing a numerical triaxial or biaxial test to obtain a macroscopic Young modulus and a Poisson's ratio; calculating the sizeof an error function, and judging whether particle parameters are updated or not; adopting different strategies according to different iteration times; during primary iteration, manually giving smalldisturbance in direct proportion to an initial estimated value; and adopting an adaptive moment estimation strategy to update parameters in multiple iterations. An embodiment shows that after finiteiteration of a single-particle-size or multi-particle-size discrete element sample, errors of calibration parameters are effectively controlled within a certain range. The calibration method has the advantages of automatic calibration capability, strong convergence capability and high calibration efficiency, and can effectively solve the calibration problem of the Hertz deformation parameter whenthe discrete element simulates the rock-soil body material.

The invention provides a discrete element modeling method for stochastic void defect materials based on hyperelliptic equation, which can randomly generate ellipse, rhombus, star or rectangular cavitydefects with different flatness by controlling parameters, and is used for discrete element simulation research of hard and brittle materials. The concrete steps are as follows: defining the main physical parameters of the material, generating particles in a closed calculation area and assigning microscopic contact property parameters to the particles, and randomly determining a certain number ofvoid defect centers with random positions; Based on the hyperelliptic equation, the hole defect patterns with different shapes are constructed at each center point. Delete the particles in each holedefect pattern, select the appropriate contact model, delete the wall of the closed area, and form the discrete element model of the hole defect. The method of the invention is simple and feasible, and the size, shape, angle and flatness of the formed hole defects are controllable, so that the generated material model is closer to the reality, so that the simulation calculation result is more accurate, and the simulation effectiveness is improved.

The invention discloses a compression penetration test numerical simulation method based on particle discrete elements and lattice Boltzmann, and the method comprises the following steps: S1, carrying out three-dimensional particle discrete element simulation of a sand rain method and a quasi-vibration compaction method, and preparing virtual compression samples with different relative densities; s2, applying axial pressure to the virtual compression sample step by step, and performing three-dimensional particle discrete element numerical simulation of a lateral confinement compression test to obtain a discrete element numerical model after compression stabilization under each stage of pressure; s3, respectively slicing the discrete element numerical model after pressure compression at each stage, processing a slice image, and establishing a corresponding pore structure model; and S4, carrying out lattice Boltzmann numerical simulation of seepage aiming at the established pore structure model. According to the invention, the defects of the existing indoor compression penetration test technology are overcome, the principle is simple, the implementation is convenient, the calculation efficiency is high, the application effect is good, and the feasibility and superiority of the compression penetration test numerical simulation method based on the particle discrete element and the lattice Boltzmann are verified.

The invention provides a numerical simulation method of a powder flow field of a coaxial powder feeding nozzle of laser additive re-manufacturing, and relates to the technical field of laser manufacturing. The method comprises the following steps: firstly, obtaining physical powder parameters and material parameters and structural parameters of the coaxial powder feeding nozzle; and secondly, performing parameter calibration to obtain simulation experimental parameters, establishing a three-dimensional calculation model of the coaxial powder feeding nozzle according to the structural parameters of the coaxial powder feeding nozzle, establishing a powder particle model and a discrete element simulation model of powder particle motion of the coaxial powder feeding nozzle by using a discreteelement method, then establishing a gas-powder two-phase model of the coaxial powder feeding nozzle by using a computational fluid mechanics method, and then obtaining a gas-powder flow field distribution condition of the coaxial powder feeding nozzle. According to the numerical simulation method of the powder flow field of the coaxial powder feeding nozzle of laser additive re-manufacturing provided by the invention, the influence of the action relationship between the gas-powder two-phase, the physical properties of the discrete phase powder particles, and other factors on the powder flow field is fully considered, so that the powder flow field distribution condition of the coaxial powder feeding nozzle is accurately obtained.

The invention relates to a discrete element method-based double-layer porous asphalt pavement drainage characteristic analysis method, and belongs to the technical field of double-layer porous asphaltpavement drainage characteristics. By means of the discrete element simulation technology, the problems that irregular geometrical shapes and surface textures of aggregate are difficult to explain bya continuous medium pavement model, and adhesive force, viscoelastic plasticity, pore microstructure and drainage performance between an upper surface layer and a lower surface layer in a porous asphalt pavement influence each other are solved. According to the method, a double-layer porous asphalt pavement model is established mainly through discrete element software, coupling calculation is conducted on the double-layer porous asphalt pavement model and fluid dynamics software, and the double-layer porous asphalt pavement drainage characteristic rule is obtained through analysis. Accordingto the method, the irregular geometrical shape of the aggregate, the asphalt adhesive force and the granularity and the viscoelastic plasticity of the mixture can be well expressed, the asphalt mortarand gap three-phase structure formed by the drainage asphalt mixture serving as coarse aggregate, fine aggregate and an asphalt cementing material is effectively simulated, and the improvement of a model and drainage characteristic research accuracy is facilitated.

The invention provides a seepage failure discrete element simulation method which comprises the following steps: in fluid-free solid particle simulation, applying a force related to the hydraulic gradient of a flow field, namely a gradient force, to replace the acting force of a fluid on particles so as to perform simplified simulation on a seepage failure phenomenon. On the basis of achieving thefluid-solid coupling effect, the fluid-solid coupling calculation process can be omitted, and the simulation calculation speed is increased.