35 results about "Reference stress" patented technology

A method of determining the elastoplastic behavior of components, in particular of gas turbine plants, at high temperatures. First of all, the linear-elastic behavior is determined and the inelastic behavior is taken into account on the basis of the linear-elastic results by using the Neuber rule, the anisotropic characteristics of the components, as occur in particular through the use of single-crystalline materials, are taken into account in a simple manner by using a modified anistropic Neuber rule in the formσ*2=σep2⁡(1+A⁢C⁢αER⁢(A⁢⁢σep2σ02)n-1)whereA=inelastic anisotropic correction term,A=⁢12[F⁡(Dyy-Dzz)2+G⁡(Dzz-Dxx)2+⁢H⁢(Dxx-Dyy)2+2⁢L⁢⁢Dyz2+2⁢⁢MDz⁢⁢x2+2⁢⁢NDx⁢⁢y2] where F, G, H, L, M and N are the Hill constants,C=elastic anisotropic correction term, C=D•E−1•Dσ*=determined linear stress,σep=estimated inelastic stress,D=direction vector of the elastic and inelastic stressesE−1=inverse stiffness matrix,ER=reference stiffness,σ0=reference stress, and σα, n=material constants.

The invention discloses a magnetic liquid manipulating method. Due to pressure latency, offset exists between pressure data which are used for reference and are processed by an FPGA chip and real pressure derived data. An ARM chip compares the reference pressure data with the real pressure derived data to acquire response data. The reference pressure data are corrected. Pressure data given by a pressure piston are changed. The drive performance of a magnetic liquid micro-displacement drive is improved. The ARM chip applies a manipulating command on a dynamic balance valve of a second processing unit according to reference stress derived data to change the opening of an electronic switch. The gas incoming speed of a pressure piston is changed. Pressure applied by the pressure piston on the magnetic liquid micro-displacement drive is changed. According to the invention, the defect that a method used for manipulating the cohesion progress of magnetic liquid cementing is unavailable in the prior art is avoided.

The invention provides a judgment method of a dual adaptation critical point of expansion direction connection structure DFR (Detail Fatigue Rating). The judgment method comprises the following steps: (1) determining an expansion direction connection structure DFR value: obtaining the DFR value according to a formula DFR=DFRbase*A*B*C*C*D*E*Rc; and (2) calculating ([Tau]s / [Delta]g)*(ts / tp): aiming at the specific position of the calculated expansion direction connection structure in an airplane, calculating to obtain the fatigue stress spectra of the position, extracting DFR reference stress [Delta]g, shearing stress [Tau]s in the spectra corresponding to the DFR reference stress [Delta]g, the basic thickness ts of a wallboard and the thickness tsp of the wallboard boss of a connection position, and calculating to obtain the numerical value of the ([Tau]s / [Delta]g)*(ts / tp).

The invention discloses a method for establishing a database of surface crack stress intensity factors based on a weight function, which is used to improve the calculation efficiency of defect crack expansion, thereby providing a basis for linear elastic fracture mechanics analysis in surface probability damage tolerance evaluation. Specifically, finite element parametric modeling is used to calculate the reference stress intensity factor under a given stress gradient based on the J-integral stress intensity factor theory. The calculation accuracy is not affected by the number of crack tip grids, and the calculation results are accurate; based on the weight function theory, the establishment The efficient calculation method of stress intensity factors under arbitrary stress gradients for structures with different geometric configurations makes up for the limitations of the stress intensity factor manual; compared with the traditional stress intensity factor database, the weight function method based on the present invention The structure configuration of the surface crack stress intensity factor database has increased, and the calculation error of the stress intensity factor of the applicable structure is within 5%.

The invention discloses a method for predicting the remaining fatigue life of concrete components, which is a simpler and more convenient way to effectively predict the fatigue life of concrete under variable amplitude fatigue loads. The basic concept is that the damage condition of concrete when loaded for ni cycles under the stress level Si is equivalent to that when loaded for n1 cycles under the reference stress level S1. For any i, the number of cycles nit of concrete loading under the reference stress level S1 can be obtained when it is equivalent to loading the concrete damage of ni cycles under the stress level Si.

The invention discloses a method for establishing a database of surface crack intensity factors based on point weight functions. By integrating the stress and weight functions of all points on the surface crack surface, the stress intensity factors of surface cracks under complex stress gradients are calculated at high speed, thereby Provides the basis for linear elastic fracture mechanics analysis in surface probabilistic damage tolerance assessment. Specifically, finite element parametric modeling is used to establish a cubic structure configuration. Based on the J-integral stress intensity factor theory, the reference stress intensity factor under a given stress gradient is calculated. The calculation accuracy is not affected by the number of crack tip grids. The calculation results Accurate; compared with the general weight function method, the point weight function method overcomes the limitation of only considering the unidirectional change of stress at the crack depth, is suitable for more complex stress situations, and makes up for the limitations of the stress intensity factor manual. The probabilistic damage tolerance assessment of life parts provides technical support, which has important engineering significance and practical value.

The invention discloses a safety assessment method for a high-temperature pressure pipeline with crack type defects. The safety assessment method for the high-temperature pressure pipeline with crack type defects includes steps that 1, gathering data; 2, definitely evaluating the life span; 3, determining load and temperature; 4, analyzing elastic stress; 5, characterizing crack; 6, assessing initial crack leakage and rupture; 7, judging whether the initial crack is safe; 8, judging whether the initial crack is free of creep analysis; 9, calculating reference stress and stress intensity factors; 10, calculating creep rupture life based on the initial crack size; 11, judging whether the creep rupture life is long enough; 12, judging whether the creep is steady creep; 13, calculating steady state creep crack growth; 14, calculating unsteady state creep crack growth; 15, calculating the creep rupture life based on the current crack size; 16, judging whether the current creep rupture life is long enough; 17, assessing the current crack leakage and rupture; 18, refining and evaluating; 19, judging whether the assessed object is safe. The safety assessment method for the high-temperature pressure pipeline with crack type defects can be used for assessing the safety of the high-temperature pressure pipeline with crack type defects under creep load effect.