Energy version of the kinetic equations of isothermal creep and long-term strength

2014 ◽  
Vol 55 (1) ◽  
pp. 172-181 ◽  
Author(s):  
V. P. Radchenko ◽  
M. N. Saushkin ◽  
S. V. Gorbunov
Keyword(s):  
Kinetic Equations ◽  
Term Strength ◽  
Energy Version ◽  
Isothermal Creep

Energy version of creep and long-term strength theory

1974 ◽  
Vol 6 (1) ◽  
pp. 41-46 ◽  
Author(s):  
O. V. Sosnin ◽  
I. K. Shokalo
Keyword(s):  
Term Strength ◽  
Strength Theory ◽  
Energy Version

scholarly journals Long-Term Strength Prediction of Wood Based Composites Using the Kinetic Equations

2021 ◽  
Vol 24 (3) ◽  
pp. 9-18
Author(s):  
Sergiy Kulman ◽  
Liudmyla Boiko ◽  
Ján Sedliačik
Keyword(s):  
Damage Mechanics ◽  
Blow Up ◽  
Kinetic Equations ◽  
Elastic State ◽  
Term Strength ◽  
Forecast Horizon ◽  
One Stage ◽  
Kinetic Transition ◽  
Viscoelastic State

The existing behaviour models of the structures under constant load (creep) have a fairly wide forecast horizon and low accuracy. As a rule, they consider the transition from an undestroyed state of an element to a destroyed one, in one stage. The purpose of this study is to substantiate and develop a new approach to predicting long-term strength based on kinetic equations, which, in turn, should consider the multistage nature of the process of gradual destruction of structure elements. To achieve this purpose, the study solves the tasks of creating a multistage kinetic transition of individual structure elements from an initially elastic state to a viscoelastic state, and then to a fractured state. When describing this process, the authors employed the methods of formal kinetics and the theory of continuum damage mechanics, including the method of basic diagrams. Wood-based composites were used as the materials under study. Based on the results of the conducted full-scale and computational experiments, the study discovers that a mathematical model based on kinetic equations adequately describes the behaviour of the materials under study for long-term strength; the proposed two-stage model determines the forecast horizon much more accurately than the available one-stage models. The kinetic parameters that determine the rate of transition of a structural element from an elastic state to a viscoelastic state, and then to a destroyed state, were determined based on experimental base chart. The time to fracture was determined at three-point bending at a load equal to 70% of the flexural strength at temperatures of 20°C and 60°C, constant humidity RH 65% and moisture content MC 8%. When building control charts, the load increased by another 15%. The method allows narrowing the forecast horizon and determining the moment of transition of a structure from a stationary state to a blow-up regime with a higher accuracy

scholarly journals NUMERICAL STUDY OF THE PROCESS OF HIGH-TEMPERATURE CREEP AND LONG-TERM STRENGTH OF STRUCTURAL ALLOYS UNDER UNIAXIAL TENSION

2021 ◽  
Vol 83 (3) ◽  
pp. 294-310
Author(s):  
I.V. Smetanin
Keyword(s):  
High Temperature ◽  
Damage Accumulation ◽  
Kinetic Equations ◽  
Structural Materials ◽  
High Temperature Creep ◽  
Term Strength ◽  
Thermomechanical Loading ◽  
Initial Strength ◽  
Temperature Creep

The main regularities of deformation processes are consideredand degradation of the initial strength properties of structural materials (metals and their alloys) by the mechanism of long-term strength. To describe the processes of high-temperature creep and long-term strength of polycrystalline structural alloys, an approach based on the concept of “hidden” or “internal” parameters is used, which can give a qualitative and quantitative description of experimental data. This approach has two important advantages: it allows you to cover a wide range of behavior of structural materials and at the same time it is very convenient for analyzing the stress-strain state. The mathematical model of the mechanics of a damaged medium used in this work, describing the processes of inelastic deformation and damage accumulation during creep, consists of three interrelated components: evolutionary relations that determine the inelastic behavior of the material, considering the dependence on the destruction process; kinetic equations describing the process of damage accumulation; criteria for the strength of the damaged material. The variant of the determining relations of viscoplastic deformationof polycrystalline structural alloys is based on the idea of the existence of a family of equipotential creep surfaces in the stress space and the principle of gradiency of the creep strain rate vector to the corresponding surface at the loading point.This version of the equations of state reflects the main regularitiesthe process of viscoplastic deformation of the material under proportional and disproportionate modes of combined thermomechanical loading. The variant of the kinetic equations of damage accumulation is based on theintroduction of a scalar damage parameter, is based on energy principles, and considers the main effects of the formation, growth and fusion of microdefects for arbitrary complex modes of thermomechanical loading. As a criterion of the strength of the damaged material, the condition for reaching the critical value of the damage value is used. The results of experimental studies of short-term high-temperature creep of several structural alloys (copper, stainless steel X18H10T) at constant temperature values and various levels of forces set in the samples are presented. To assess the degree of reliability and determine the limits of applicabilitymodels of the mechanics of the damaged medium numerical studies of the process of high-temperature creep and long-term strength of these structural alloys are carried out and the numerical results obtained are compared with the data of field experiments. The results of comparing the calculated and experimental data allow us to conclude that the proposed determining relationships are reliable when the initial strength properties of structural materials are degraded by the mechanism of long-termstrength. It is shown that the model used qualitatively and with the accuracy necessary for practical calculations quantitatively describes the main effects of the process of viscoplastic deformation and damage accumulation in polycrystalline structural alloys under high-temperature thermomechanical loading.

Subcritical Crack Growth and Long-Term Strength in Rock and High-Strength and Ultra Low-Permeability Concrete

2009 ◽  
Vol 58 (6) ◽  
pp. 525-532 ◽  
Author(s):  
Yoshitaka NARA ◽  
Masafumi TAKADA ◽  
Daisuke MORI ◽  
Hitoshi OWADA ◽  
Tetsuro YONEDA ◽  
...  
Keyword(s):  
Crack Growth ◽  
Subcritical Crack Growth ◽  
High Strength ◽  
Low Permeability ◽  
Term Strength

Long-term strength retrogression of silica-enriched oil well cement: A comprehensive multi-approach analysis

2021 ◽  
Vol 144 ◽  
pp. 106424 ◽  
Author(s):  
Xueyu Pang ◽  
Jiankun Qin ◽  
Lijun Sun ◽  
Ge Zhang ◽  
Honglu Wang
Keyword(s):  
Oil Well ◽  
Term Strength ◽  
Oil Well Cement ◽  
Well Cement
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