4 results about "Multiple stress" patented technology

The invention discloses a roadway roof damage time prediction method and system, and belongs to the technical field of mine rock mechanics and safety engineering. Comprising the following steps: recognizing a roof rock stratum structure and lithology of each layer through drilling peeping, and drilling a representative rock sample; determining the crack initiation strength and peak strength of the rock sample through a uniaxial compression test; selecting a plurality of stress levels between the axial strain and the acoustic emission signal to carry out a creep test, synchronously monitoring the axial strain and the acoustic emission signal, and determining an accelerated creep starting moment as the damage time under the stress according to the abrupt change characteristics of the axial strain and the acoustic emission signal; establishing a stress-failure time relation model of each lithology; finally, selecting a corresponding model to predict the damage time of rocks at different layers of the roof according to the actual rock stratum structure and ground stress state of the roadway; according to the method, accurate and reliable time prediction of the progressive damage process of the roadway roof is realized.

The invention relates to a metal material strain rate effect measurement method based on multiple stress relaxation, which comprises the following steps: carrying out a standard quasi-static stretching or compression test on a material sample at a constant strain rate to obtain a stress-strain curve; analyzing a strain range according to a stress-strain curve, and determining a stress relaxation frequency N to be developed and a corresponding relaxation strain value sequence epsilon i, i = 1... N; a material sample is taken to be subjected to a tensile or compression test at a set strain rate, stress relaxation lasts for relaxation time delta t when the strain sequentially reaches values in each relaxation strain value sequence, and after each stress relaxation, the tensile or compression test is performed according to the set strain rate; obtaining a stress-plastic strain rate curve corresponding to each relaxation strain epsilon i; and obtaining a stress-strain curve corresponding to each strain rate. Stress-strain curves corresponding to different plastic strain rates in a quasi-static range can be obtained through a single sample.

The present application aims to reveal the influence mechanism of stress level and stress gradient on the behavior of metal material hot salt corrosion, and provides a force-chemical coupling test method and device of metal material considering stress gradient, aiming at the technical defects that mechanical load and corrosion environment are difficult to be controlled simultaneously in the existing research. First, a variable cross-section tensile deposited salt sample is designed, which can form different stress level and stress gradient distribution areas under a single loading condition. Second, the hot salt corrosion test under external stress is carried out under the condition of controlled temperature by artificially depositing the molten salt formed in the simulation of marine environment on the surface of the sample and applying external tensile load. Finally, the corrosion morphology, oxide film structure and element distribution of the sample are systematically characterized and quantitatively analyzed. The test method of the present application is simple, highly repeatable, can realize the comparative analysis of corrosion behavior under multiple stress states, and significantly improves the efficiency and accuracy of stress-corrosion synergistic effect research.

The invention provides a shield tunnel aerodynamic effect stress field response characteristic calculation method and device, and relates to the technical field of shield tunnels, and the method comprises the steps: obtaining a plurality of stress value data of a plurality of longitudinal sections of a tunnel; respectively calculating to obtain an average value of each section; respectively calculating to obtain a first correction coefficient set and a second correction coefficient set of each section; respectively constructing a circumferential stress characteristic model of the aerodynamic effect of each section; fitting the circumferential stress characteristic models of the plurality of sections to obtain a full-tunnel stress characteristic model; and the angle and the longitudinal distance of the to-be-measured point location are substituted into the full tunnel stress characteristic model, and the stress value and the acceleration value of the aerodynamic effect of the to-be-measured point location are calculated respectively. According to the method, the stress value and the acceleration value, generated by the aerodynamic effect, of each point position of the whole tunnel can be obtained only by arranging a limited number of monitoring devices to the multiple sections of the tunnel, and the arrangement number of the monitoring devices of the tunnel is reduced.