Effect of Biaxial Stress on Crack Driving Force

2006 ◽  
Author(s):  
G. Shen ◽  
W. R. Tyson
Keyword(s):  
Internal Pressure ◽  
Driving Force ◽  
Axial Stress ◽  
Axial Strain ◽  
Biaxial Stress ◽  
J Integral ◽  
Longitudinal Stress ◽  
Secondary Stress ◽  
Stress Strain ◽  
Strain Equation

A stress-strain equation of Ramberg-Osgood type is proposed to correlate the longitudinal stress with longitudinal strain of a thin plate when a constant stress is applied transversely. The same approach can be used to correlate the axial stress with axial strain for a thin-walled pipe in axial tension with internal pressure. The proposed stress-strain equation relating the longitudinal stress and strain closely approximates that of deformation theory. The effect of a secondary stress (hoop stress) on the J-integral for a circumferential crack in a pipe under axial load and internal pressure is evaluated by finite element analysis (FEA). The results show that the J-integral decreases with internal pressure at a given axial stress but increases with internal pressure at a given axial strain. It is concluded that while a secondary stress may be safely neglected in a stress-based format because it decreases the driving force at a given applied stress, it should not be neglected in a strain-based format because it significantly increases the driving force at a given applied strain.

Combined-Stress Tests on 24S-T Aluminum-Alloy Tubes

1947 ◽  
Vol 14 (2) ◽  
pp. A147-A153
Author(s):  
W. R. Osgood
Keyword(s):  
Aluminum Alloy ◽  
Hoop Stress ◽  
Axial Stress ◽  
Axial Strain ◽  
Maximum Deviation ◽  
Shearing Stress ◽  
Stress Tests ◽  
Combined Stress ◽  
Stress Strain ◽  
Shearing Strain

Abstract Combined-stress tests were made on five 24S-T aluminum-alloy tubes, 1 3/4 in. ID × 0.05 in. thick. The ratios of circumferential (hoop) stress to axial stress were 0, 1/2, 1, 2, and ∞. The tubes were tested to failure and sufficient measurements of circumferential strain and axial strain were taken to plot stress-strain curves almost up to rupture. The results are presented in the form of two sets of stress-strain curves for each ratio of stresses, namely, maximum shearing stress plotted against maximum shearing strain, and octahedral shearing stress plotted against octahedral shearing strain. In each plot the maximum deviation of the curves is about ± 5 per cent. A method of evaluating small octahedral shearing strains from the data is given which does not assume Poisson’s ratio to be 1/2.

Comparison of Stress-Strain Relationships of FRP and Actively Confined High-Strength Concrete: Experimental Observations

2014 ◽  
Vol 919-921 ◽  
pp. 29-34 ◽  
Author(s):  
Jian Chin Lim ◽  
Togay Ozbakkloglu
Keyword(s):  
High Strength Concrete ◽  
Axial Stress ◽  
Axial Strain ◽  
High Strength ◽  
Confining Pressure ◽  
Confined Concrete ◽  
Lateral Strain ◽  
Stress Strain ◽  
Strength Concrete ◽  
Actively Confined Concrete

It is well established that lateral confinement of concrete enhances its axial strength and deformability. It is often assumed that, at a same level of confining pressure, the axial compressive stress and strain of fiber reinforced polymer (FRP)-confined concrete at a given lateral strain are the same as those in concrete actively confined concrete. To assess the validity of this assumption, an experimental program relating both types of confinement systems was conducted. 25 FRP-confined and actively confined high-strength concrete (HSC) specimens cast from a same batch of concrete were tested under axial compression. The axial stress-strain and lateral strain-axial strain curves obtained from the two different confinement systems were assessed. The results indicate that, at a given axial strain, lateral strains of actively confined and FRP-confined concretes correspond, when they are subjected to the same lateral confining pressure. However, it is observed that, at these points of intersections on axial strain-lateral strain curves, FRP-confined concrete exhibits a lower axial stress than the actively confined concrete, indicating that the aforementioned assumption is not accurate. The test results indicate that the difference in the axial stresses of FRP-confined and actively confined HSC becomes more significant with an increase in the level of confining pressure.

Influence of FRP-to-Concrete Gap Effect on Axial Strains of FRP-Confined Concrete Columns

2015 ◽  
Vol 1119 ◽  
pp. 760-765
Author(s):  
Thomas Vincent ◽  
Togay Ozbakkloglu
Keyword(s):  
Cross Sections ◽  
Axial Stress ◽  
Axial Strain ◽  
Strain Curve ◽  
Shrinkage Strain ◽  
Confined Concrete ◽  
Gap Effect ◽  
Stress Strain ◽  
Concrete Shrinkage ◽  
Concrete Interface

This paper reports on an experimental investigation on the influence of FRP-to-concrete interface gap, caused by concrete shrinkage, on axial compressive behavior of concrete-filled FRP tube (CFFT) columns. A total of 12 aramid FRP (AFRP)-confined concrete specimens with circular cross-sections were manufactured. 3 of these specimens were instrumented to monitor long term shrinkage strain development and the remaining 9 were tested under monotonic axial compression. The influence of concrete shrinkage was examined by applying a gap of up to 0.06 mm thickness at the FRP-to-concrete interface, simulating 800 microstrain of shrinkage in the radial direction. Axial strain recordings were compared on specimens instrumented with two different measurement methods: full-and mid-height linear variable displacement transformers (LVDTs). Results of the experimental study indicate that the influence of interface gap on stress-strain behavior is significant, with an increase in interface gap resulting in a decrease and increase in the compressive strength and ultimate axial strain, respectively. It was also observed that an increase in interface gap leads to a slight loss in axial stress at the transition region of the stress-strain curve. Finally, it is found that an increase in the interface gap results in a significant decrease in the ratio of the ultimate axial strains obtained from mid-section and full-height LVDTs.

Using MFL Corrosion Signals to Determine Biaxial Stress in Operating Pipelines

2000 ◽  
Author(s):  
Alfred E. Crouch
Keyword(s):  
Magnetic Flux ◽  
Internal Pressure ◽  
Pipe Wall ◽  
Axial Stress ◽  
Wall Stress ◽  
Biaxial Stress ◽  
Metal Loss ◽  
Pipe Surface ◽  
The Difference ◽  
Hoop Stresses

Previous work has shown that a corrosion assessment more accurate than B31.G or RSTRENG can be made if pipeline stresses are considered. A shell analysis can be carried out if both the corrosion profile and local pipe wall stresses are known. The corrosion profile can be approximated from analysis of magnetic flux leakage (MFL) signals acquired by an inline inspection tool (smart pig), but a measure of pipe wall stress has not been available. Approximations have been made based on pipe curvature, but a more direct measurement is desirable. Recent work has produced data that show a correlation between multi-level MFL signals from metal-loss defects and the stress in the pipe wall at the defect location. This paper presents the results of MFL scans of simulated corrosion defects in pipe specimens subjected to simultaneous internal pressure and four-point bending. MFL data were acquired at two different magnetic excitations using an internal scanner. The scanner’s sensor array measured axial, radial and circumferential magnetic flux components on the inner pipe surface adjacent to the defect. Comparison of the signals at high and low magnetization yields an estimate of the difference between axial and hoop stresses. If internal pressure is known, the hoop component can be determined, leaving data proportional to axial stress.

Partially Plastic Thick-Walled Cylinder Theory

1952 ◽  
Vol 19 (2) ◽  
pp. 133-140
Author(s):  
M. C. Steele
Keyword(s):  
Internal Pressure ◽  
Experimental Evidence ◽  
Closed Form ◽  
Strain Hardening ◽  
Axial Stress ◽  
Quantitative Comparison ◽  
Stress Strain ◽  
Von Mises ◽  
Walled Cylinder

Abstract Previous theories for partially plastic thick-walled cylinders under internal pressure are reviewed. A quantitative comparison is given for (a) compressibility versus incompressibility of material, and (b) von Mises’ versus Tresca’s theory of failure. The former reveals that deflections at the outside and bore surfaces agree closely, although considerable percentage differences may be found in the axial stresses and strains. Large differences (except for the axial stress) are found in comparing the two theories of failure. Based on the comparison and available experimental evidence, a theory is presented in closed form to include the Hencky stress-strain relations, incompressibility, and Ludwik’s strain-hardening function.

An Influence of Step Cyclic Loading due to Torsion on Tensile Curve Variation

2013 ◽  
Vol 535-536 ◽  
pp. 181-184
Author(s):  
Zbigniew L. Kowalewski ◽  
Tadeusz Szymczak
Keyword(s):  
Cyclic Loading ◽  
Strain Amplitude ◽  
Axial Stress ◽  
Axial Strain ◽  
Biaxial Stress ◽  
Main Task ◽  
Cyclic Shear ◽  
Tensile Curve ◽  
Engineering Steel ◽  
Stress Curve

The paper presents experimental results of tests carried out at room temperature on power engineering steel: 10H2M (11CrMo9-10) using thin-walled tubular specimens under biaxial stress state. The loading programme comprised different types of deformation, i.e. monotonic tension and cyclic torsion in the form of symmetric or asymmetric step-increasing strain amplitude. The main task of the paper was focused on investigation of an influence of the cyclic loading parameters on tensile curve variations. The magnitudes of axial strain and cyclic shear strain amplitude were small and did not exceed 1%. An analysis of the results showed a significant reduction of the axial stress (even equal 90% for the torsional amplitude ±0.8%, in both cases of cyclic loading). An influence of torsion frequency on the tensile stress curve was discovered within the range from 0.005Hz to 0.5Hz.

scholarly journals Non-Linear Analysis of Mode II Fracture in the end Notched Flexure Beam

2016 ◽  
Vol 46 (1) ◽  
pp. 53-64
Author(s):  
V. Rizov
Keyword(s):  
Strain Curve ◽  
Beam Theory ◽  
Integral Approach ◽  
J Integral ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Non Linear ◽  
Tension And Compression ◽  
Parametric Analyses ◽  
Strain Equation

Abstract Analysis is carried-out of fracture in the End Notched Flex- ure (ENF) beam configuration, taking into account the material nonlin- earity. For this purpose, the J-integral approach is applied. A non-linear model, based on the Classical beam theory is used. The mechanical be- haviour of the ENF configuration is described by the Ramberg-Osgood stress-strain curve. It is assumed that the material possesses the same properties in tension and compression. The influence is evaluated of the material constants in the Ramberg-Osgood stress-strain equation on the fracture behaviour. The effect of the crack length on the J-integral value is investigated, too. The analytical approach, developed in the present paper, is very useful for parametric analyses, since the simple formulae obtained capture the essentials of the non-linear fracture in the ENF con- figuration.

scholarly journals High-temperature creep rupture of low alloy ferritic steel butt-welded pipes subjected to combined internal pressure and end loadings

2005 ◽  
Vol 363 (1836) ◽  
pp. 2629-2661 ◽  
Author(s):  
F Vakili-Tahami ◽  
D.R Hayhurst ◽  
M.T Wong
Keyword(s):  
Internal Pressure ◽  
Constitutive Equations ◽  
Ferritic Steel ◽  
Loading Condition ◽  
Damage Mechanics ◽  
Axial Stress ◽  
Biaxial Stress ◽  
Type Iv ◽  
Modes Of Failure ◽  
Wide Range

Constitutive equations are reviewed and presented for low alloy ferritic steels which undergo creep deformation and damage at high temperatures; and, a thermodynamic framework is provided for the deformation rate potentials used in the equations. Finite element continuum damage mechanics studies have been carried out using these constitutive equations on butt-welded low alloy ferritic steel pipes subjected to combined internal pressure and axial loads at 590 and 620 °C. Two dominant modes of failure have been identified: firstly, fusion boundary failure at high stresses; and, secondly, Type IV failure at low stresses. The stress level at which the switch in failure mechanism takes place has been found to be associated with the relative creep resistance and lifetimes, over a wide range of uniaxial stresses, for parent, heat affected zone, Type IV and weld materials. The equi-biaxial stress loading condition (mean diameter stress equal to the axial stress) has been confirmed to be the worst loading condition. For this condition, simple design formulae are proposed for both 590 and 620 °C.

scholarly journals Numerical simulation of the dynamic distribution characteristics of the stress, strain and energy of coal mass under impact loads

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Hongqing Zhu ◽  
Shuhao Fang ◽  
Yilong Zhang ◽  
Yan Wu ◽  
Jinlin Guo ◽  
...  
Keyword(s):  
Dynamic Load ◽  
Axial Stress ◽  
Axial Strain ◽  
Radial Strain ◽  
Coal Mass ◽  
Impact Loads ◽  
Distribution Characteristics ◽  
Stress Strain ◽  
Dynamic Distribution ◽  
Strain Peak

Abstract To research the dynamic response characteristics of coal mass under impact loads, based on LS-DYNA software, rigid body bars are simulated to impact coal mass under different speed conditions, and the dynamic distribution characteristics of the stress, strain and energy of coal mass are analyzed. The results demonstrate that (1) the peaks of the axial and radial stresses and strain on the central axis and the radial line obey the power function distribution; at the same position, the axial and the radial stress peaks are close, and the axial strain peak is from much larger than the radial strain peak to close to. (2) The axial and radial stresses generate tensile stresses in the axial and radial propagation directions, respectively, and the coal mass is prone to damage under tensile stress. (3) When the speed is large, the axial stress–strain curve is similar to that of the dynamic load experiment. The axial stress peak, axial strain peak, critical effective stress, critical time and secant modulus have a linear relationship with the velocity. (4) When the dynamic load is large, most of the energy is in the form of kinetic energy, and the total energy loss also increases.

Fracture Mechanics Study of Cracked Pipe Bends Under Internal Pressure and Bending Moments

2006 ◽  
Author(s):  
Manish M. Joglekar ◽  
S. G. Joshi ◽  
B. K. Dutta
Keyword(s):  
Crack Initiation ◽  
Internal Pressure ◽  
Axial Stress ◽  
Crack Depth ◽  
Factor H ◽  
J Integral ◽  
Bending Moments ◽  
Dimensional Parameter ◽  
Axial Stress Distribution ◽  
Opening And Closing

The present work attempts to investigate some aspects of the fracture behavior of cracked pipe bends under the action of in-plane bending moments, with and without internal pressure. The results of the elastic-plastic FE analysis of the defect free elbow under the action of in-plane opening and closing bending moments are presented with the emphasis on the hoop and axial stress distribution at various salient locations in the elbow. A severity matrix is outlined subsequently, correlating the various possible cracked configurations and the loading patterns. Parametric studies on the cracked elbows are carried out, in which the parameters, such as ratio of crack depth to elbow thickness (a/t), angle of the part-through wall crack, bend factor ‘h’ and the internal pressure ‘P’ are varied. The variations of the J-integral versus load and load versus load line displacement are presented. The crack initiation load is determined from the material specific critical value of the J-integral. A non-dimensional parameter is suggested as ratio of plastic collapse load to the crack initiation load, which increases with the increase in the internal pressure both in case of the throughwall flawed elbow as well as in the part-throughwall flawed elbow.

Sign in / Sign up

Export Citation Format

Share Document