scholarly journals Tectonophysical criteria for forecasting the locations of quartz crystal deposits (case of Subpolar Ural)

2020 ◽  
Vol 11 (1) ◽  
pp. 31-38
Author(s):  
L. A. Sim
Keyword(s):  
Stress State ◽  
Stress Field ◽  
Uniaxial Tension ◽  
Quartz Crystal ◽  
Stress Fields ◽  
Mineral Deposits ◽  
Tectonic Stresses ◽  
Quartz Veins ◽  
General Stress ◽  
Type Of Stress State

Spatial reconstruction of tectonic stresses within the Subpolar Ural quartz crystal-containing province was conducted by the kinematic method [Gushchenko, 1973, 1979] based on the main indicators of tectonic stresses on slickensides. Local stress states (LSS) and general stress fields for large blocks were reconstructed by the method described in [Sim, Marinin, 2015]. In the blocks with numerous occurrences of quartz crystal (Pelingichey and Omega-Shor blocks), the general stress fields is characterized by a stress state close to uniaxial tension, i.e. the Lode-Nadai coefficient µ=–1. In these blocks, thick quartz veins are perpendicular to the tension axis of the general stress field. In the block without quartz crystal (West Saled), the general stress field is characterized by a triaxial stress state or pure shear state (–1˂µσ˂+1). The LSS of the quartz crystal deposits show the following: the stress state of µ=–1 is typical of quartz veins without quartz crystal nests, and a special kind of stress state is reconstructed near the nests with piezoelectric material. It is named a variation of the type of stress state (VTSS), which means that within one tectonic stage, the type of stress state changes approximately as follows: µσ=+1 (40 %), µσ=–1 (40 %), and –1˂µσ˂+1. It means that in the piezoelectric mineral deposits, pulsating tectonic stresses provided for a fluid flow of hydrothermal solutions at the intersection of ore-bearing and ore-controling faults when tension (µ=–1) was replaced with compression (µ=+1), while the orientations of compression and tension axes remained unchanged. Apparently, such a regime was caused by alternating activation of the above-mentioned faults. The tectonic stress reconstructions were performed for 33 mineral deposits and occur­rences of quartz crystal. VTSS was determined in 32 deposits; one mineral occurrence is characterized by uniaxial tension. Therefore, we propose using VTSS (variation of the type of stress state) as a criterion for predicting the locations of quartz crystal deposits.

scholarly journals Influence of paleodislocation intensity and modern movements on the stressed state of massif

2020 ◽  
Vol 168 ◽  
pp. 00060
Author(s):  
Dmytro Pymonenko
Keyword(s):  
Stress State ◽  
Stress Field ◽  
Stressed State ◽  
Central Region ◽  
Experimental Studies ◽  
Physicomechanical Properties ◽  
Stress Fields ◽  
Tectonic Processes ◽  
Statistical Relationships ◽  
Main Components

To study the nature of the forces determining the stress state of the massif, the results of experimental studies of determining numerical values and spatial orientation of the main components of the active stress field using the local hydraulic fracturing method in coal mines of Central Region of Donbas are compared with maps characterizing the intensity of the distribution of paleo-and modern tectonic processes in the area of Donbas. Statistical relationships between indicators characterizing the stress state and the physicomechanical properties of rock are established. The results of performed studies show that the stress fields measured under the conditions of the mines of the Central Region of Donbas are mainly due to modern movements, but the paleological disturbances of tectonic blocks with disjunctive dislocations have a significant effect on the change in the stress state of the massif.

Fatigue crack propagation in biaxial stress fields

1977 ◽  
Vol 12 (1) ◽  
pp. 23-28 ◽  
Author(s):  
C D Hopper ◽  
K J Miller
Keyword(s):  
Fatigue Crack ◽  
Stress State ◽  
Stress Field ◽  
Crack Propagation ◽  
Bulk Material ◽  
Fatigue Cracks ◽  
Propagation Rate ◽  
Biaxial Stress ◽  
Stress Fields ◽  
Biaxial Stress State

The propagation of fatigue cracks in notched and un-notched biaxially stressed plates is investigated. The rate of propagation is found to be affected by both the stress field associated with the notch and the biaxial stress state of the bulk material. It is found that the propagation rate of a crack from a notch may be predicted by the use of a theoretical notch contribution factor in conjunction with propagation data for a crack in un-notched material.

The Effect of Two Rigid Spherical Inclusions on the Stresses in an Infinite Elastic Solid

1966 ◽  
Vol 33 (1) ◽  
pp. 68-74 ◽  
Author(s):  
Joseph F. Shelley ◽  
Yi-Yuan Yu
Keyword(s):  
Stress Field ◽  
Uniaxial Tension ◽  
Elastic Solid ◽  
Displacement Function ◽  
Hydrostatic Tension ◽  
Series Form ◽  
Spherical Inclusions ◽  
Spherical Cavities ◽  
In Series ◽  
The Common

Presented in this paper is a solution in series form for the stresses in an infinite elastic solid which contains two rigid spherical inclusions of the same size. The stress field at infinity is assumed to be either hydrostatic tension or uniaxial tension in the direction of the common axis of the inclusions. The solution is based upon the Papkovich-Boussinesq displacement-function approach and makes use of the spherical dipolar harmonics developed by Sternberg and Sadowsky. The problem is closely related to, but turns out to be much more involved than, the corresponding problem of two spherical cavities solved by these authors.

Design Optimisation of a Ferritic Ring Weld Specimen Using FE Modelling

2009 ◽  
Author(s):  
Christopher M. Gill ◽  
Paul Hurrell ◽  
John Francis ◽  
Mark Turski
Keyword(s):  
Heat Treatment ◽  
Residual Stress ◽  
Finite Element ◽  
Neutron Diffraction ◽  
Stress Field ◽  
Finite Element Modelling ◽  
Post Weld Heat Treatment ◽  
Stress Fields ◽  
Element Modelling ◽  
Weld Heat

This paper describes the design optimisation of an SA508 ferritic steel ring weld specimen using FE modelling techniques. The aim was to experimentally and analytically study the effect of post weld heat treatment upon a triaxial residual stress field. Welding highly constrained geometries, such as those found in some pressure vessel joints, can lead to the formation of highly triaxial stress fields. It is thought that application of post weld heat treatments will not fully relax hydrostatic stress fields. Therefore a ferritic multi-pass ring weld specimen was designed and optimised, using 2D finite element modelling, to generate a high magnitude triaxial stress field. The specimen thickness and weld-prep geometry was optimised to produce a large hydrostatic stress field and still allow efficient use of neutron diffraction to measure the residual stress. This paper reports the development of the test specimen geometry and compares the results of welding FE analysis and neutron diffraction measurements. Welding residual stresses were experimentally determined using neutron diffraction; both before post weld heat treatment. Three dimensional moving heat source weld finite element modelling has been used to predict the residual stresses generated by the welding process used. Finite element modelling examined the effect of phase transformation upon the residual stress field produced by welding. The relaxation of welding stresses by creep during post weld heat treatment has also been modelled. Comparisons between the modelled and measured as-welded residual stress profiles are presented. This work allows discussion of the effect of post weld heat treatment of triaxial stress fields and determines if finite element modelling is capable of correctly predicting the stress relaxation.

scholarly journals Local stress fields in solids estimated by acoustical emission method

2021 ◽  
Vol 2103 (1) ◽  
pp. 012064
Author(s):  
V L Hilarov ◽  
E E Damaskinskaya
Keyword(s):  
Time Series ◽  
Acoustic Emission ◽  
Stress Field ◽  
Estimation Method ◽  
Local Stress ◽  
Stress Fields ◽  
Emission Method ◽  
Macroscopic Fracture ◽  
Stress Estimation ◽  
Kinetic Concept

Abstract Based on the Zhurkov’s kinetic concept of solids’ fracture a local internal stress estimation method is introduced. Stress field is computed from the time series of acoustic emission intervals between successive signals. For the case of two structurally different materials the time evolution of these stresses is examined. It is shown that temporal changes of these stresses’ accumulation law may serve as a precursor of incoming macroscopic fracture.

scholarly journals General Stress Fields of Orthotropic Plate with Mode II Crack

2020 ◽  
Vol 746 ◽  
pp. 012015
Author(s):  
Long Zhang ◽  
Purong Jia ◽  
Yongyong Suo ◽  
Cheng Jia
Keyword(s):  
Orthotropic Plate ◽  
Stress Fields ◽  
Mode Ii ◽  
General Stress ◽  
Mode Ii Crack

scholarly journals Efficiency of Plasticity Correction in the Hole-Drilling Residual Stress Measurement

Materials ◽  
2020 ◽  
Vol 13 (15) ◽  
pp. 3396
Author(s):  
Tomáš Návrat ◽  
Dávid Halabuk ◽  
Petr Vosynek
Keyword(s):  
Residual Stress ◽  
Stress State ◽  
Uniaxial Tension ◽  
Relative Error ◽  
Computational Simulation ◽  
Equivalent Stress ◽  
Biaxial Stress ◽  
Hole Drilling ◽  
Plane Shear ◽  
Plasticity Effect

This paper focuses on the analysis of the plasticity effect in the measurement of the residual stress by the hole-drilling method. Relaxed strains were evaluated by the computational simulation of the hole-drilling experiment using the finite element method. Errors induced by the yielding were estimated for uniaxial tension, plane shear stress state and equi-biaxial stress state at various magnitudes of residual stress uniformly distributed along the depth. The correction of the plasticity effect in the evaluation of residual stress was realized according to the method proposed by authors from the University in Pisa, which was coded in MATLAB. Results obtained from the MATLAB script were compared to the original input data of the hole-drilling simulation and discussed. The analyses suggested that the plasticity effect is negligible at the ratio of applied equivalent stress to yield stress, being 0.6, and that the correction of the plasticity effect is very successful at the previous ratio, being 0.9. Failing to comply with the condition of the strain gauge rosette orientation according to the principal stresses directions causes an increase in the relative error of corrected stresses only for the case of uniaxial tension. It affects the relative error negligibly for the plane shear and equi-biaxial stress states.

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