42 results about "Strength theory" patented technology

The present invention provides a multiaxial short crack propagation life prediction method based on a critical surface method, and relates to the field of multiaxial fatigue strength theory. The algorithm comprises the steps of: (1) selecting a plane, which contains the maximum shearing strain range, as a critical surface, and using the damage parameters on the critical surface to characterize a short crack propagation driving force; (2) based on the shear-type multiaxial fatigue damage parameters, establishing an equivalent crack stress intensity factor applicable to the multiaxial stress state; (3) fitting the short crack propagation rate data under uniaxial loading to obtain an uniaxial short crack propagation curve; and (4) carrying out plastic zone size correction on the crack tip, and calculating the short crack propagation life by a fracture mechanics method. The method can well descript the influence of non-proportional loading on crack propagation. The results show that the method can well predict the short crack propagation life under multiaxial proportional and non-proportional loading.

The present invention discloses a multi-axial fatigue life prediction method based on the weighted average maximum shear strain amplitude plane, and relates to the field of the multi-axial fatigue strength theory. The method comprises: synthesizing the multi-axis amplitude-varying load history into a von Mises equivalent strain history by using the equivalent von Mises strain formula, and carrying out Wang- Brown cycle counting on the von Mises equivalent strain history; determining the critical plane under the multi-axial amplitude-varying load by using the proposed weight average maximum shear strain amplitude plane; calculating fatigue damage parameters on the critical surface in each half-cycle obtained by counting; carrying out damage calculation by using the Wang and Brown damage models or the Fatemi and Socie damage models; and accumulating the calculated damage in each half-cycle by using the Miner's linear cumulative law, and calculating the fatigue life. The proposed life prediction method is validated by four kinds of materials, and the results show that the proposed method can predict the failure plane and fatigue life under the multi-axial amplitude-varying load.

The invention discloses a fatigue short crack propagation life prediction method under multi-axis variable amplitude loading, and relates to the multi-axis fatigue strength theory field. The algorithmincludes the following steps: (1) using the Wang-Brown multi-axis cycle counting under stress loading to obtain a plurality of half cycles, and realizing multi-axis constant amplitude loading of eachhalf cycle; (2) using the weighted average maximum shear stress method to determine a weight critical surface for the characteristic that the critical surface is not fixed; (3) obtaining the crack propagation amount of a single variable amplitude load block by using a multi-axis fatigue short crack propagation model on the weight critical surface; and (4), performing plastic zone size correctionon crack tips, and calculating the short crack propagation life by the fracture mechanics method. The method can well describe the influence of multi-axis variable amplitude loading on crack propagation. The results show that the method can predict the short crack propagation life under multi-axis variable amplitude loading.

The invention discloses a method for predicting the hydration damage degree of shale. The method includes the following steps that: S1, target shale block standard rock samples are prepared, and are subjected to soaking treatment; S2, after being dried, the standard rock samples are subjected to a triaxial mechanics experiment; S3, on the basis of the results of the triaxial mechanics experiments,the Poisson's ratio-water immersion time curve and elastic modulus-water immersion time curve of the standard rock samples are obtained; S4, the internal friction angles of the standard rock samplesare determined according to the Mohr-Coulomb strength theory, and a relational expression of the internal friction angles and immersion time is obtained; S5, post-water immersion Weibull distributionparameter m is obtained through the softening constitutive model of Weibull distribution under water immersion, and the rock compressive strength F0 of the shale which has been damaged by hydration isobtained; and S6, the hydration damage degree of the shale is calculated. With the method adopted, the influence of hydration damage on shale rock mechanical parameters under different confining pressure and hydration time conditions can be quantitatively expressed, and therefore, the hydration damage degree can be quantitatively predicted.

The invention discloses a strength check method for an asphalt pavement. The method comprises the step of carrying out planar isobaric/axial compression, planar isobaric/axial tension, planar tension-compression, planar compression/axial compression, planar tension-compression/axial compression, planar tension-compression/axial tension and planar anisobaric/axial compression tests on the basis of a three-axis test system and a three-axis test method for an asphalt mixture to obtain a multi-axis strength test result for the asphalt mixture. According to the new method for carrying out strength check on an asphalt pavement according to an asphalt mixture breakage criterion in a complex stress state, the problem that the existing one-dimensional strength theory is incapable of objectively reflecting the breakage characteristics and the resistance of a pavement structure is solved, and the refinement level of an asphalt pavement design is improved.

The invention relates to a method for judging piping seepage damage of a foundation pit containing confined water of a soft soil layer, in particular to a method for judging piping seepage damage of a foundation pit containing aquitard confined water of a soft soil layer. The method comprises the following steps of: deducing a piping seepage damage equation of pit bottom soil according to the soil stability condition of a seepage surface at the foundation pit bottom, and then collating the piping seepage damage equation to obtain a critical piping damage seepage gradient; then establishing a foundation pit two-dimensional seepage computation model to compute a maximum seepage gradient of the pit bottom soil; and judging whether the pit bottom soil has seepage damages or not. Compared with the prior art, the invention overcomes the defect that piping damage phenomena such as quick sand, flowing soil or sand boil similar to boiling, which occur at the bit bottom, can not be explained by applying the strength theory and other methods.

The invention discloses a bearing force test method of bridge ultra-long large-diameter pile, which is a middle shearing test based on Mohr-Clone strength theory to find the pile side friction force, is based on three value methods of normal stresses between pile soils, considers the effect of yield strength of around soils, and calculates out three pile limit bearing forces according to the side stress caused by self weight, normal stress generated by finite element digit calculation, and normal stress generated by coupling weight and finite element. The inventive test has simple operation, without large loading device and limited loading weight, while the invention can drill and sample on site, process indoor test, completely simulate real project geological character of pile ground, and completely consider similarity as similar simulation of real condition, the material, size, and bearing state of test sample, pile and around soil, with low cost, reliable data, or the like.

The invention provides a strength theory based welding design method, and belongs to the technical field of welding. The welding design method comprises steps as follows: (1), actual measurement; (2), CAE (computer-aided engineering) analysis on a welding simulation part; (3) CAE analysis on a whole welding workpiece; and (4), improvement of an established welding method for a corresponding welding seam to reduce the maximum stress sigma max till the minimum safety factor N of the welding seam falls into the corresponding safety factor range of the welding seam. The welding design method can pointedly reduce stress levels of some welding seams and improve the safety factor, so that the welding debugging process is simple, and load-carrying property of the welding seams are effectively and integrally improved.

The invention discloses a notched piece local stress and strain determination method considering multi-axial load non-proportionality and relates to the field of multi-axial fatigue strength theory. According to the method, finite element analysis software is utilized to establish a finite element model of a notched piece; convergence analysis is performed on a mesh number of the finite element model of the notched piece; the finite element analysis software is utilized to calculate a local stress concentration coefficient of a notch under the action of a unit external load, and a virtual stress course of a notch region is calculated; a virtual strain course at the notch is determined through a linear elastic theory or linear elastic finite element analysis; a proposed evaluation method ofnon-proportionality factors is utilized to determine local non-proportionality of the notch under a multi-axial cyclic load; and true stress and true strain at the notch are solved through a notch virtual stress correction method and a constitutive relation. Through the method, local strain of the notch under the multi-axial load can be well predicted.

The invention discloses a filling mining critical-fullness-rate design method. The method includes: A, obtaining a theoretical design value of a solid-filling coal-mining fullness rate according to afilling mining objective and a control object; B, establishing an overlying stratum structure model and an elastic-foundation beam model; C, calculating a load of a n-th stratum on a first stratum according to a composite-beam principle; D, adopting a stiffness discriminating condition of stratum separation occurrence and a force differential principle of a beam to construct a deflection differential equation of the n-th stratum; E, simplifying fractured n-1 strata to a total elastic-foundation coefficient k, and establishing a relationship of the k and a filling-body elastic-foundation coefficient k<g> and a relationship of the k<g> and the fullness rate phi; F, solving a deflection curve equation expression by boundary conditions of a clamped-clamped beam; G, obtaining a relationship ofthe elastic-foundation coefficient k and stratum allowable-stress [sigma<t>] according to a first strength theory; and H, obtaining a critical fullness rate of fracturing occurrence of the n-th stratum by the elastic-foundation coefficient k.

The invention discloses a method for establishing a unified strength theory of unsaturated soil. According to the double-stress state variable theory and the absorption strength characteristic of the unsaturated soil, a double-shear element model suitable for the unsaturated soil is established, then the unified strength theory of the unsaturated soil under a complex stress state is established, the characteristics of the particular case, the plane limit line and the space limit face of the unified strength theory are analyzed, the document rigidity and flexibility true triaxial test of unsaturated sand is used for verification. The method for establishing the unified strength theory of the unsaturated soil completes and enriches the basic theory of the unsaturated soil, and has important theoretical significance and engineering application value.

The invention discloses a design method of a synchronous counterweight cover type explosion-proof door, and belongs to the field of mine ventilation system design. The method for calculating the thickness of the steel plate for the explosion-proof cover plate is given according to the strength theory in the design of the pressure container. The concept of the weight ratio and the stroke ratio is introduced for the first time, a method for calculating the weight ratio and the stroke ratio range is given to reasonably determine the weight, the stroke of the explosion-proof cover and the stroke of the balancing weight of the balancing weight system, and the height of the redirection wheel frame and the height of the balancing weight frame can be further determined through the stroke of the explosion-proof cover and the stroke of the balancing weight. The design and calculation method for the synchronous counterweight cover type explosion-proof door is simple in calculation, the calculation amount during design is reduced, concepts of the counterweight ratio and the stroke ratio are creatively provided, blindness of design of the synchronous counterweight cover type explosion-proof door can be avoided, and the design and calculation method has high engineering practice feasibility and effectiveness.

The invention discloses a Mohr-Coulomb theory based mechanical stability quantitative analysis method for the exploitation of an aquo-complex. The method comprises the following steps: (1) calculatingthrough numerical simulation to obtain the condition of stress distribution of a reservoir stratum in the exploitation of the aquo-complex; (2) establishing a quantitative index for a mechanical stability coefficient s on the basis of the Mohr-Coulomb shearing strength theory; (3) substituting the stress distribution obtained in the step (1) into the mechanical stability coefficient s, and obtaining distribution of the mechanical stability coefficient; and (4) quantitatively analyzing the mechanical stability of the reservoir stratum on the basis of the mechanical stability coefficient obtained in the step (3). The method overcomes the defects that the traditional Mohr-Coulomb shearing strength theory only can qualitatively analyze in the analysis of the mechanical stability in the exploitation of aquo-complex, the concept of the stability coefficient is used to quantitatively describe the mechanical stability, the stability within the full research scope is quantitatively described,the method is more convenient and intuitive to use, the quantitative analysis result is more accurate, and the method has higher practical reference and application values.

The invention relates to the technical field of a full section rock heading machine, in particular to a variable thickness full section rock heading machine cutterhead. The variable thickness full section rock heading machine cutterhead adopts edge supporting, when the center deflection of the cutterhead is 0, and t0 is obtained according to the relationship between the cutterhead center thicknesst0 and the thickness t1 of the cutterhead supported position; and t1 is determined by an existing determination method for the thickness of a cutterhead of a constant thickness full section rock heading machine or determined according to a cutterhead strength theory. The variable thickness full section rock heading machine cutterhead aims to solve the technical problem of poor deformation uniformity of the cutterhead when the full section rock heading machine carries out heading operation in the prior art.

The invention discloses a fatigue monitoring counting method based on an extreme value window, and relates to the field of the multiaxial fatigue strength theory. The counting object of a traditionalrain flow counting method is extended from the equivalent stress extreme point of a single time point to the extreme value window containing several time points. The traditional rain flow counting process considering the equivalent stress is changed into a three-dimensional rain flow counting process that simultaneously considers the six-direction stress data of the multiaxial variable amplitude load history. The invention proposes a new cycle amplitude determining method, a stress extreme point eliminating method, and a stress history rearrangement inspection method for the extreme value window and a formula thereof. The extreme value window is introduced to fully consider the phase difference between the stresses in a multiaxial stress state when calculating each cycle amplitude, so thatthe traditional rainflow counting method using equivalent stress synthesis is changed into a three-dimensional rainflow counting method that considers six-direction stress at the same time. Accordingto the fatigue monitoring counting method based on the extreme value window, the extreme value window is introduced, and the six-direction stress can be considered at the same time, so that the cyclecounting result of the multiaxial load history is more accurate and reliable.

A method for determining the ultimate bearing capacity of a gravel pile mainly comprises the steps that on the basis of the coulomb strength theory, the included angle between a fracture surface and the maximum principal stress acting direction is determined; and when the gravel pile is under the action of an upper load, the lateral confinement constraint force of foundation soil on the pile bodyis considered, the influence of pile body self-weight stress is also considered, the pile body stress is simplified to the direction of the inter-pile soil fracture surface, and a stress balance modelis established, so that the mutual relation between the gravel pile single-pile bearing capacity and foundation soil and the pile body self-weight stress is obtained, and then the more accurate gravel pile single-pile bearing capacity is obtained. The method is simple in calculation, more comprehensive in consideration of influence factors, and more in accordance with engineering practice in calculation result, provides accurate and reliable basis for engineering design and construction, and avoids waste.

The invention relates to a method for designing a gun monocular barrel based on a third strength theory. The method comprises the following steps of (I) calculating a high and low temperature pressure curve of a gun barrel; (II) calculating a theoretical strength curve of the barrel; (III) calculating a theoretical shape of the barrel; and (IV) adjusting the shape of the barrel. According to the method for designing the gun monocular barrel based on the third strength theory, the method for designing the gun monocular barrel in China is broadened, thereby being beneficial to exchange between China and various countries in the world in the aspect of gun monocular barrel design; and the method can be used for development of the gun monocular barrel in academies, scientific research institutes and weapon manufacturers.

The invention provides a high-strength high-rigidity guide upright column, and belongs to the technical field of machine tools. The high-strength high-rigidity guide upright column comprises an upper solid column section, a lower solid column section and a hollow column casing, wherein the upper solid column section, the lower solid column section and the hollow column casing are positioned on one same axis; the upper part of the upper solid column section is a working section; the lower part of the lower solid column section is also a working section; the lower part of the upper solid column section is inserted into the upper end of the hollow column casing from top to bottom; the upper solid column section and the hollow column casing are in interference fit; the upper part of the lower solid column section is inserted into the lower end of the hollow column casing from bottom to top; the lower solid column section and the hollow column casing are in interference fit; the depth that the upper solid column section and the lower solid column section are respectively inserted into the hollow column casing is 3-5 times of the respective diameters of the upper solid column section and the lower solid column section. According to the mechanical bending strength theory, the bending-resistant section modulus of a hollow column rod with equal cross sections is greater than that of a solid column rod with equal cross sections, that is when the identical bending-resistant section modulus requirement is met, the weight of the hollow column rod needs to be less than that of the solid column rod; particularly, in a wide table surface hydraulic machine, the bending-resistant cross section modulus of the upright column adopting a hollow column casing structure is increased when being compared with that of a solid upright column with equal mass, the unbalance loading prevention capacity of the upright column is also increased, and the product verification results show that the unbalance loading prevention capacity of the upright column is 2-4 times of that of an ordinary solid upright column.

The invention provides a method of calculating a total process deformation curve of rock mass. The method comprises obtaining structure data of the rock mass, calculating total process deformation data of the rock mass and drawing a total process stress-drain curve of the rock mass. With the weak link strength theory of rock mass mechanics as the basis, the invention obtains structure data of therock mass by comprehensively considering geological conditions of the rock mass, and through SMRM computing software, calculates total process deformation data of the rock mass; and finally, through SMRM computing software again, draws total process deformation data of the rock mass into the total process stress-strain curve of the rock mass, so as to provide rock mass information closer to authentic structure and environmental state for engineering construction and offer important reference data for engineering construction, such that engineering construction design is more reasonable.