Plastic Biaxial Stress-Strain Relations for Alcoa 24S-T Subjected to Variable-Stress Ratios

1950 ◽  
Vol 17 (4) ◽  
pp. 372-376
Author(s):  
Joseph Marin ◽  
B. J. Kotalik
Keyword(s):  
Type Theory ◽  
Stress Ratio ◽  
Biaxial Stress ◽  
Test Results ◽  
Principal Stresses ◽  
Stress Strain ◽  
Axial Tension ◽  
Stress Ratios ◽  
Predicted Values ◽  
Plastic Stress

Abstract Usually plastic biaxial stress-strain relations for metals have been determined for tests in which the ratios of the principal stresses have been maintained essentially constant. This paper presents biaxial plastic stress-strain relations for both constant and variable-stress ratios. The purpose of conducting the variable-stress-ratio tests is to attempt to prove whether the flow- or deformation-type theory is the correct theory for predicting plastic stress-strain relations. The paper also gives a comparison between the actual and theoretically predicted values of the biaxial yield, ultimate and fracture strengths, and the biaxial ductility. Various ratios of biaxial tensile stresses were investigated by subjecting tubular specimens to axial tension and internal pressure. The test results showed that the yield-strength values agree best with the distortion-energy theory. For the prediction of the plastic stress-strain relations the deformation-type theory was found to be in approximate agreement with the test results for both the constant- and variable-stress-ratio tests.

The Effect of Stress Ratio on Fatigue Crack Growth in a Biaxial Stress Field

1977 ◽  
Vol 99 (1) ◽  
pp. 137-143 ◽  
Author(s):  
S. Y. Zamrik ◽  
M. A. Shabara
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Stress Field ◽  
Crack Growth ◽  
Stress Ratio ◽  
Biaxial Stress ◽  
Stress System ◽  
Mean Stress ◽  
Principal Stresses ◽  
Stress Ratios

The effect of stress ratio (mean stress) on fatigue crack growth in a biaxial stress field was investigated. The biaxiality was introduced by means of anticlastic bending of rhombic plates. A crack initiator in the form of an EDM slot was embedded in the top surface of plate specimen. The crack tip was subjected, as a result of specimen bending, to two principal stresses, one tensile and normal to the crack and the other parallel to it but in a compressive direction. Three mean stress ratios of R = Kmin/Kmax were applied, one in a zero to tension mode, the second in a completely reversed cycling where the stress ratio R = −1, and the third in an intermediate ratio of R = −0.5. All stress ratios were imposed in an existing biaxial stress field. Uniaxial concepts such as Walker’s approach were analyzed and applied to biaxial stress system. Experimental results have shown that fatigue crack growth is influenced by both variables: mean stress ratio and stress biaxiality ratio. Each variable was isolated by using the concept of effective stress intensity range ΔK. The crack growth and the fracture mode under each type of loading are discussed and analyzed.

Transverse-sensitivity errors in biaxial-stress fields

1972 ◽  
Vol 7 (1) ◽  
pp. 41-43 ◽  
Author(s):  
V C Saxena ◽  
K E Machin
Keyword(s):  
Stress Ratio ◽  
Biaxial Stress ◽  
Stress Fields ◽  
Strain Gauges ◽  
Principal Stresses ◽  
Transverse Sensitivity

Expressions for the errors in principal stresses and stress ratio due to transverse sensitivity of the strain gauges have been determined in terms of the stress ratio. The results are also represented in the form of curves.

Study of Strength Criterion for Dynamic Compression of Concrete under Biaxial Equal Proportion Loading

2010 ◽  
Vol 163-167 ◽  
pp. 1819-1822
Author(s):  
Guan Ping ◽  
Peng Liu ◽  
Tao Xu
Keyword(s):  
Experimental Data ◽  
Stress Ratio ◽  
Dynamic Compression ◽  
Strength Criterion ◽  
Biaxial Stress ◽  
Strain Rates ◽  
Equal Proportion ◽  
Stress Space ◽  
Principal Stress Space ◽  
Stress Ratios

The dynamic compressive experiments of cubic concrete specimens under various biaxial equal proportion loading were preformed. The biaxial equal proportion stress in the tests were kept constant at 1:0, 1:0.5 and 1:1, respectively, and the tested strain rate ranged from 10−5/s to 10−2/s. Based on the experimental results, the influence of the strain rates on compressive characteristics of concrete under various biaxial stress ratios were researched. The unified strength criterion in terms of principal stress space considering the influence of strain rates and biaxial stress ratio is proposed. The fitting curves by the present strength criterion agree well with experimental data.

Evaluation of Fatigue Crack Growth at Piping of Austenitic Stainless Steel Under Biaxial Stress

2019 ◽  
Author(s):  
Shogo Harada ◽  
Takanori Kitada ◽  
Takao Nakamura
Keyword(s):  
Fatigue Test ◽  
Nuclear Power ◽  
Power Plants ◽  
Stress Ratio ◽  
Low Cost ◽  
Fatigue Curve ◽  
Biaxial Stress ◽  
The Other ◽  
Test Machine ◽  
Stress Ratios

Abstract The fatigue degradation in Nuclear Power Plants (NPPs) is evaluated by a design fatigue curve that is published in ASME code which is based on the results of uniaxial fatigue test data. On the other hand, stress that occurs at actual piping elements, such as elbows, is not uniaxial stress but biaxial stress, with different stress ratios. Stress ratio is defined as the ratio of stress range in one axis to that in the other axis. In this study, a pressurized disc fatigue test machine is developed in order to conduct biaxial fatigue test under different stress ratio more easily and low-cost. A newly designed test specimen is adopted to generate biaxial stress under different stress ratios near the center of the specimen. This test machine can generate a specific biaxial stress with different stress ratios at specimen by adjusting air pressure and shape of the specimen.

Determination of Theoretical Plastic Stress-Strain Relations for Variable Combined Stress Ratios

1952 ◽  
Vol 19 (4) ◽  
pp. 485-488
Author(s):  
L. W. Hu ◽  
Joseph Marin
Keyword(s):  
Graphical Methods ◽  
Stress Tests ◽  
Combined Stress ◽  
Stress Strain ◽  
Simple Tension ◽  
Stress Ratios ◽  
Theoretical Stress ◽  
Stress Invariant ◽  
Plastic Stress

Abstract To distinguish between the various theories of plastic flow defining plastic stress-strain relations under combined stresses, it is necessary to conduct combined stress tests in which the ratio of the stress components does not remain constant during the test. To compare these results with the flow theory of the second stress-invariant type, graphical methods have been used to determine the combined plastic stress-strain relations based upon the simple tension plastic stress-strain relations. This paper presents an analytical procedure for the determination of these theoretical stress-strain relations. For certain stress conditions the graphical methods have the disadvantage of yielding inaccurate results—an objection not present in the proposed method. Furthermore, the proposed analytical method is less time-consuming than the graphical methods.

Computational Models for Multilayered Composite Shells with Application to Tires

1996 ◽  
Vol 24 (1) ◽  
pp. 11-38 ◽  
Author(s):  
G. M. Kulikov
Keyword(s):  
Type Theory ◽  
Computational Models ◽  
Geometrical Nonlinearity ◽  
Higher Order ◽  
Stress Strain ◽  
Strain Fields ◽  
First Order ◽  
Timoshenko Type ◽  
Joint Influence ◽  
Discrete Layer

Abstract This paper focuses on four tire computational models based on two-dimensional shear deformation theories, namely, the first-order Timoshenko-type theory, the higher-order Timoshenko-type theory, the first-order discrete-layer theory, and the higher-order discrete-layer theory. The joint influence of anisotropy, geometrical nonlinearity, and laminated material response on the tire stress-strain fields is examined. The comparative analysis of stresses and strains of the cord-rubber tire on the basis of these four shell computational models is given. Results show that neglecting the effect of anisotropy leads to an incorrect description of the stress-strain fields even in bias-ply tires.

Experimental study of the strength and durability of metal-composite high-pressure tanks

2019 ◽  
Vol 85 (1(I)) ◽  
pp. 49-56 ◽  
Author(s):  
A. M. Lepikhin ◽  
V. V. Moskvichev ◽  
A. E. Burov ◽  
E. V. Aniskovich ◽  
A. P. Cherniaev ◽  
...  
Keyword(s):  
High Pressure ◽  
Strain State ◽  
Full Scale ◽  
Fracture Mechanisms ◽  
Metal Composite ◽  
Test Results ◽  
Stress Strain ◽  
Pneumatic Pressure ◽  
Stress Strain State ◽  
Composite Tank

The results of unique experimental studies of the strength and service life of a metal-composite high-pressure tank are presented. The goal of the study is to analyze the fracture mechanisms and evaluate the strength characteristics of the structure. The methodology included tests of full-scale samples of the tank for durability under short-term static, long-term static and cyclic loading with internal pneumatic pressure. Generalized test results and data of visual measurements, instrumental and acoustic-emission control of deformation processes, accumulation of damages and destruction of full-scale tank samples are presented. Analysis of the strength and stiffness of the structure exposed to internal pneumatic pressure is presented. The types of limiting states of the tanks have been established experimentally. Change in the stress-strain state of the tank under cyclic and prolonged static loading is considered. Specific features of the mechanisms of destruction of a metal-composite tank are determined taking into account the role of strain of the metal liner. The calculated and experimental estimates of the energy potential of destruction and the size of the area affected upon destruction of the tank are presented. Analysis of test results showed that the tank has high strength and resource characteristics that meet the requirements of the design documentation. The results of the experiments are in good agreement with the results of numerical calculations and analysis of the stress-strain state and mechanisms of destruction of the metal-composite tank.

scholarly journals Numerical simulation on the simultaneous stress interference of parallel multiple hydraulic fractures

2021 ◽  
pp. 014459872110019
Author(s):  
Weiyong Lu ◽  
Changchun He
Keyword(s):  
Principal Stress ◽  
Hydraulic Fracture ◽  
Stress Ratio ◽  
Fracture Network ◽  
Hydraulic Fractures ◽  
Fracture Spacing ◽  
Induced Stress ◽  
Minimum Principal Stress ◽  
Fracturing Process ◽  
Stress Ratios

During horizontal well staged fracturing, there is stress interference between multiple transverse fractures in the same perforation cluster. Theoretical analysis and numerical calculation methods are applied in this study. We analysed the mechanism of induced stress interference in a single fracture under different fracture spacings and principal stress ratios. We also investigated the hydraulic fracture morphology and synchronous expansion process under different fracture spacings and principal stress ratios. The results show that the essence of induced stress is the stress increment in the area around the hydraulic fracture. Induced stress had a dual role in the fracturing process. It created favourable ground stress conditions for the diversion of hydraulic fractures and the formation of complex fracture network systems, inhibited fracture expansion in local areas, stopped hydraulic fractures, and prevented the formation of effective fractures. The curves of the maximum principal stress, minimum principal stress, and induced principal stress difference with distance under different fracture lengths, different fracture spacings, and different principal stress ratios were consistent overall. With a small fracture spacing and a small principal stress ratio, intermediate hydraulic fractures were difficult to initiate or arrest soon after initiation, fractures did not expand easily, and the expansion speed of lateral hydraulic fractures was fast. Moreover, with a smaller fracture spacing and a smaller principal stress ratio, hydraulic fractures were more prone to steering, and even new fractures were produced in the minimum principal stress direction, which was beneficial to the fracture network communication in the reservoir. When the local stress and fracture spacing were appropriate, the intermediate fracture could expand normally, which could effectively increase the reservoir permeability.

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