6 results about "Yield surface" patented technology

The application relates to a constitutive calculation method and device for improving a GTN model, equipment and a medium, comprising the following steps: obtaining initial porosity of a target material at a current increment step in a finite element implicit calculation process; judging whether the initial porosity is greater than a preset minimum porosity threshold; if the initial porosity is greater than the preset minimum porosity threshold, completing constitutive calculation of the target material at the current increment step based on a preset improved GTN yield criterion. The preset improved GTN yield criterion is used to calculate constitutive material parameters of the target material. In the increment step of the finite element implicit calculation, the application first carries out minimum threshold validity checking on the initial porosity, and only when the porosity meets the physical rationality requirement, the improved GTN yield criterion is used to carry out material constitutive calculation, so that the yield surface shape continuously changes when the porosity changes from a positive value to a negative value in the iteration process, and the technical problem that the traditional GTN model cannot converge due to the numerical iteration divergence caused by the negative porosity is solved.

The present application relates to a method for establishing a constitutive model of soil based on a prototype test and a test device used by the method, the method comprising the following steps: placing a sealed bag in a soil column test hole, injecting fluid into the sealed bag to load the soil, measuring the lateral displacement of the deep soil, calculating the yield cylindrical surface radius of the soil, the radial compressive stress at yield, and the principal stress state of the soil unit according to the circular hole expansion theory and the Lame equation, establishing the yield criterion, the subsequent yield surface, and the failure criterion, dividing the soil in the plastic deformation area into multiple concentric soil cylinders according to the graded loading, calculating the size and radial displacement of each soil cylinder from outside to inside, combining the test hole sidewall radial displacement test value, calculating the elastic parameters required by the incremental method in the elastic-plastic mechanics according to the test loading grade, establishing the constitutive model, assuming that the yield surface is a plane and the intermediate principal stress is ignored, degrading the yield criterion into the Mole-Coulomb criterion, and verifying the constitutive model through a prototype test.

The application provides a kind of automobile deep drawing steel yield surface determination method and system, it is related to the technical field of mechanics test yield surface determination, it aims at solving the defects that traditional uniaxial tensile test cannot reflect the anisotropic yield behavior of deep drawing steel.The method adopts the technical scheme of uniaxial tensile test combined with cross-shaped biaxial tensile test: prepare uniaxial tensile test sample in rolling direction and perpendicular to rolling direction and cross-shaped biaxial tensile test sample; obtain real stress-real plastic strain curve and plastic work under different plastic strain by uniaxial tensile test; load different proportion of biaxial tensile test on cross-shaped test sample, obtain biaxial stress-strain data; based on the principle of equivalent plastic work per unit volume, back-calculate the stress value corresponding to each loading proportion, draw yield locus curve.Precisely characterize the yield surface evolution law and anisotropic deformation behavior of deep drawing steel under complex stress state.The automobile deep drawing steel yield surface determination system is applied to the automobile deep drawing steel yield surface determination method.

This invention discloses a method for constructing a multi-scale fracture assessment index for rocks under true three-dimensional stress, comprising the following steps: S1, establishing a yield function F based on the Mogi-Coulomb three-dimensional strength criterion; S2, constructing a formula for assessing the degree of multi-scale fracture of rocks based on the strength envelope of the three-dimensional strength criterion and the geometric relationship between the yield surface and the stress point; S3, assessing the degree of rock mass fracture based on the range of the multi-scale fracture assessment index. This invention proposes a method for constructing a multi-scale fracture assessment index for rocks, providing a theoretical basis for safety evaluation and stability analysis of high-stress deep rock engineering.

The application provides an elastoplastic unified description method and system considering the nonlinear characteristics of surrounding rock of intermediate principal stress, and belongs to the technical field of computer-aided design. Through the true triaxial mechanical property test of surrounding rock, the full stress-strain curve of surrounding rock is obtained, the characteristic stress points of the stress-strain curve are extracted, and the stress-strain curve is divided into stages; based on the characteristic stress points, the characteristic yield surface in the stress space is constructed; based on the stage characteristics of the stress-strain curve, the plastic deformation capacity representation functions of different stages are respectively constructed, and the plastic deformation capacity representation functions are used for describing the plastic deformation capacity of the stress-strain curve; and the nonlinear hardening-softening equation is constructed to describe the evolution characteristics of the characteristic yield surface. The scheme can more comprehensively and accurately describe the nonlinear characteristics of the stress-strain curve under different minimum principal stresses and intermediate principal stresses.

The invention discloses a method and system for constructing a critical state constitutive model of over-consolidated gas-bearing clay, and the method comprises the following steps: 1, dispersing the gas-bearing clay into two phases of a saturated soil matrix and a gas cavity according to a composite material theory, and obtaining a stress-strain relationship; step 2, establishing a local drainage equation of pore water flowing into the gas cavity; step 3, constructing a teardrop type yield surface function with an adjustable shape; 4, weakening parameters are introduced, weakening items are obtained, and a hardening law with a weakening effect is obtained; 5, according to the stress and strain relation, the local drainage equation, the yield surface function and the hardening law, a critical state elastic-plastic constitutive model of the over-consolidated gas-containing clay is obtained; and 6, according to the test data of the gas-containing kaolin, reversely calibrating parameters and weakening parameters for modifying the shape of the yield surface. The method aims at obtaining the constitutive model capable of accurately describing the mechanical response of the high-precision over-consolidated gas-containing clay in the complex stress state.