7 results about "Mean stress" patented technology

The invention relates to the technical field of tank cover packaging pressure control, and discloses a pressure uniformity control method for a tank cover packaging device, and the method comprises the following steps: arranging a plurality of pressure sensors in a packaging region, and collecting three-dimensional stress data; constructing a stress tensor model based on the collected data, and calculating the average pressure of the main shaft; constructing an optimization control function, and adjusting pressure output by taking stress tensor isotropy as a target; according to an adjusting strategy, stress diffusion in an initial loading stage is guided in combination with the elastic flexible structure layer; applying relaxation loading in an asynchronous microcycle according to the guidance of an optimal control function; and recording a loading history, dynamically updating loading parameters and performing compensation adjustment. According to the invention, by introducing the distribution design of the flexible structure which decreases progressively along the gradient direction, and by naturally diffusing and loading stress, the impact concentration phenomenon of a local loading point is significantly weakened, a stress transition zone in a complex structural member can be effectively organized, and the overall stress uniformity and stability in the packaging process are improved.

To predict a fatigue life of a thermoplastic resin capable of improving prediction accuracy in a range where a stress ratio R is 0 to 1.SOLUTION: A fatigue life prediction method comprising a step of creating a fatigue life prediction diagram of a thermoplastic resin having a stress ratio R of 0 to 1 based on the following formula (1). Where σ a is a stress amplitude, σ m is a mean stress, σ B is a value based on a rupture strength calculated from a result of a tensile test with a stress ratio R of 1, an index x is a value of more than 0 and less than 1.0, and σ w is an intercept obtained by substituting, into the above formula (1), a stress amplitude and a mean stress calculated from a result of a pulsating tensile fatigue test with a stress ratio R of 0 as σ a and σ m, respectively, a value based on the rupture strength as σ B, and a value of more than 0 and less than 1.0 as x. ) SELECTED DRAWING: Figure 2

This invention presents a method for establishing large deformation viscoelastic constitutive relations based on Prony technology. It addresses the problems of existing viscoelastic constitutive models lacking universality, and the complexity and programming difficulties associated with their mathematical relationships. The invention includes: decomposing the stress tensor into the sum of the deviatoric stress tensor and the mean stress; decomposing the strain tensor into the sum of the deviatoric strain tensor and the mean strain; and providing a convolutional expression for the deviatoric stress tensor and the mean stress. The increment of the deviatoric stress tensor is expressed as a function of the deviatoric strain increment, and the increment of the mean stress is expressed as a function of the mean strain increment. The tensor form of the incremental constitutive relation is written in matrix form. This method has been programmed, and the numerical results obtained from the program agree well with the experimental results in specimen-level experiments on solid rocket motor propellant grains.

The invention relates to the technical field of fatigue life prediction of metal materials, and provides a method for predicting the fatigue life of a thin-wall circular tube test piece in an elastic stability state, which comprises the following steps: S1, calculating the stress state at a dangerous point O in the thin-wall circular tube test piece according to the external load of the thin-wall circular tube test piece, and judging whether the thin-wall circular tube test piece is in the elastic stability state; s2, when it is judged that the thin-wall circular tube test piece is in an elastic stable state, extracting a stress state, searching a critical surface and an azimuth angle delta cr of the critical surface, and obtaining a maximum shear stress amplitude Ca, max and a shear average stress Cm, a on the critical surface; s3, constructing a calculation formula of a damage variable Q; and S4, calculating parameters in the fatigue life prediction model, and substituting the parameters, the maximum shear stress amplitude Ca, max and the shear average stress Cm, a of the critical plane into the fatigue life prediction model to calculate the fatigue life. According to the invention, the application space of the thin-wall circular tube test piece in more loading ranges is expanded, and more choices are provided for the field of metal fatigue research.

This invention provides a method and system for assessing the adaptability of a satellite to the mechanical environment during long-distance transportation after propellant loading, belonging to the field of spacecraft mechanical environment engineering technology. This method aims to solve the challenge of assessing the structural safety and leakage risk of propellant-loaded satellites during long-distance transportation under the coupling of static pressure stress within the propellant tank and dynamic stress during transport. The method includes: establishing a model of the satellite and packaging system; defining the transportation mechanical environment conditions; analyzing and calculating random vibration fatigue strength and impact strength, predicting propellant leakage rate, and conducting a comprehensive assessment. This method employs the mean stress correction theory and the quasi-static transformation method to solve the coupling problem of static and dynamic stresses in fatigue analysis and impact strength verification, respectively, and predicts leakage risk by comparing acceleration response with ground test data. This invention can comprehensively assess the safety of propellant-loaded satellite transportation and supports the optimization of spacecraft development processes.

The invention discloses a data processing method for predicting early-stage eccentric wear of a tire through tire grounding pressure distribution. The method comprises the following steps: step 1, performing static load simulation calculation on tire modeling, extracting stress distribution data, determining the number of ribs according to the number of pattern grooves, and extracting all stress distribution value data of each rib after tread deformation; 2, processing the extracted data, and calculating an average stress distribution value of each rib; step 3, evaluating the impression quality, the average pressure and the pressure distribution non-uniformity parameters by adopting a data processing method for predicting eccentric wear through pressure distribution; according to the method, impression and pressure distribution analysis is carried out on the tire, unit stress data are collected, parameters such as impression shapes, average pressure distribution and unevenness are evaluated by adopting a uniform distribution stress data processing method, the smaller the average pressure and pressure distribution unevenness value are, the better is, product optimization is realized by analyzing and processing the extracted data, and the product quality is improved. And the design period and the design cost are greatly reduced.

The invention discloses a method for determining the two-dimensional attribute of a fatigue load, and relates to the technical field of aero-engine structural member load spectrum compilation, and the method comprises the steps: carrying out the pairing of peak and valley points in an actual measurement load time history through a rain flow counting method according to a four-point rule, calculating the stress amplitude, stress mean and stress range of each closed cycle, and carrying out the calculation of the two-dimensional attribute of the fatigue load; obtaining the statistical attribute of the fatigue load; reconstructing a stress-strain hysteresis loop based on a rain flow counting result, and extracting order attributes from the hysteresis loop, including a father-son relationship of a load, a load grade and a load direction; and combining the statistical attribute with the order attribute to form a two-dimensional attribute of each cycle. According to the method, on the basis of the traditional rain flow counting statistical attribute, the sequence attribute of the fatigue load is determined based on the rain flow hysteretic loop containment relation, the sequence effect and the amplitude-mean value condition of the actual measurement load spectrum can be truly restored, the fatigue damage equivalence is guaranteed within the error range, and meanwhile the life prediction research method is enriched.