scholarly journals Determination of Surface Stresses in X20Cr13 Steel by the Use of a Modified Hardness Measurement Procedure with Vickers Indenter

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 4844
Author(s):  
Bogusław Hościło ◽  
Krzysztof L. Molski
Keyword(s):  
Linear Relationship ◽  
Hybrid Approach ◽  
Strain Range ◽  
Experimental Tests ◽  
Characteristic Parameter ◽  
Hardness Measurement ◽  
Measurement Procedure ◽  
Plastic Strain Range ◽  
Elastic Plastic ◽  
Vickers Indenter

The paper presents a method for estimating the value of equibiaxial stress in a surface layer of a material by using a modified hardness measurement procedure with a Vickers indenter. A certain characteristic parameter was defined and related to the surface stress. A hybrid approach, based on experimental tests and accompanied by the complementary results obtained by the finite element modelling of X20Cr13 steel in elastic–plastic range, confirmed a linear relationship between the value of the characteristic parameter and the magnitude of equibiaxial stress at the surface. This linear relationship was valid in both elastic and elastic–plastic strain range beyond the yield stress of the material.

Strain Measures for Fatigue Assessment Using Elastic-Plastic FEA

2005 ◽  
Author(s):  
W. Reinhardt
Keyword(s):  
Strain Range ◽  
Fatigue Curve ◽  
Fatigue Analysis ◽  
Plastic Strain Range ◽  
Elastic Plastic ◽  
Asme Code ◽  
The Mean ◽  
Mean Cycle ◽  
Strain Measures ◽  
Cycle Temperature

In the ASME Code, Section III NB-3228.4(c) requires that if an elastic-plastic fatigue analysis is performed, the fatigue curve shall be entered with the numerically maximum principal total (elastic plus plastic) strain range multiplied by one-half the modulus of elasticity of the material at the mean cycle temperature. This paper discusses the choice of the principal strain range as well as other possible strain range measures for elastic-plastic fatigue analysis. Several generic observations that form the basis for the discussion are outlined.

Elastic-plastic strain distributions at fillet welds

1996 ◽  
Vol 31 (3) ◽  
pp. 215-230 ◽  
Author(s):  
K S Elliott ◽  
H Fessler
Keyword(s):  
Strain Range ◽  
Post Weld Heat Treatment ◽  
Steel Plates ◽  
Plastic Strains ◽  
Weld Toes ◽  
Thick Plates ◽  
Full Size ◽  
Elastic Plastic ◽  
Tensile Forces ◽  
Fringe Patterns

Steel plates 25 mm thick were fillet-welded to 50 mm thick plates according to good offshore welding practice. The thinner plates were inclined at 90° or 60° to the thicker ones to represent, at full size, the crown or saddle positions of a structural tubular T joint. Slices 4 mm or 10 mm thick were cut from these weldments and the elastic, elastic-plastic and residual plastic strains in the surfaces of these sections were measured using photoelastic coatings and moiré interferometry. The slices were loaded by tensile forces on the 25 mm wide parts, reacted at pin joints near the ends of the 50 mm wide part. The positions and directions of loading were arranged to load the welds in the same way as in a tubular T joint, loaded in tension. Yielding initiated at the weld toes and could be clearly identified in the moiré fringe patterns. It progressed into the plates, being inhibited by the heat-affected zone. Maximum plastic strains also occurred at the weld toes. Measurements of residual plastic strains showed that the actual strain range, which ‘drives’ fatigue failure, differs from predictions based on elastic analyses. Post-weld heat treatment is beneficial, but extending the weld along the plate reduces the strain concentrations much more.

A Dislocation Model for Fatigue Crack Initiation

1981 ◽  
Vol 48 (1) ◽  
pp. 97-103 ◽  
Author(s):  
K. Tanaka ◽  
T. Mura
Keyword(s):  
Grain Size ◽  
Crack Initiation ◽  
Slip Band ◽  
Fatigue Crack Initiation ◽  
Strain Range ◽  
Material Surface ◽  
Dislocation Model ◽  
Plastic Strain Range ◽  
Stress Cycles ◽  
Distributed Dislocations

The slip band formed in a grain on the material surface is a preferential site for crack initiation during low strain fatigue of polycrystalline metals. The forward and reverse plastic flow within the slip band is modeled in the present study by dislocations with different signs moving on two closely located layers, and it is assumed that their movement is irreversible. Based on the model, the monotonic buildup of dislocation dipoles piled up at the grain boundary is systematically derived using the theory of continuously distributed dislocations. This buildup is associated with the progress of extrusion or intrusion. The number of stress cycles up to the initiation of a crack of the grain size order is defined as the cycle when the stored strain energy of accumulated dislocations reaches a critical value. The relation between the initiation life and the plastic strain range derived theoretically is in agreement with a Coffin-Manson type law, and that between the fatigue strength and the grain size is expressed in an equation of the Petch type.

A Direct Method on the Evaluation of Cyclic Steady State of Structures With Creep Effect

2014 ◽  
Vol 136 (6) ◽  
Author(s):  
Haofeng Chen ◽  
Weihang Chen ◽  
James Ure
Keyword(s):  
Fatigue Damage ◽  
Mechanical Load ◽  
Direct Method ◽  
Load Condition ◽  
Hysteresis Loops ◽  
Strain Range ◽  
Cyclic Behavior ◽  
Direct Evaluation ◽  
Plastic Strain Range ◽  
Creep Fatigue

This paper describes a new extension of the linear matching method (LMM) for the direct evaluation of cyclic behavior with creep effects of structures subjected to a general load condition in the steady cyclic state, with the new implementation of the cyclic hardening model and time hardening creep constitutive model. A benchmark example of a Bree cylinder and a more complicated three-dimensional (3D) plate with a center hole subjected to cyclic thermal load and constant mechanical load are analyzed to verify the applicability of the new LMM to deal with the creep fatigue damage. For both examples, the stabilized cyclic responses for different loading conditions and dwell time periods are obtained and validated. The effects of creep behavior on the cyclic responses are investigated. The new LMM procedure provides a general purpose technique, which is able to generate both the closed and nonclosed hysteresis loops depending upon the applied load condition, providing details of creep strain and plastic strain range for creep and fatigue damage assessments with creep fatigue interaction.

Critical Review of Strain Measures for Characterisation of Fatigue Damage in ASME Section III Fatigue Assessments

2019 ◽  
Author(s):  
Daniel Leary ◽  
Chris Currie ◽  
Keith Wright
Keyword(s):  
Strain Range ◽  
Pressure Vessels ◽  
Total Strain ◽  
Multiaxial Loading ◽  
Critical Plane ◽  
Total Strain Range ◽  
Elastic Plastic ◽  
Fatigue Evaluation ◽  
Von Mises ◽  
Strain Measures

Abstract Rules for fatigue evaluation of nuclear pressure vessels and piping components are provided in Subsection NB of Section III of the ASME code. The code prescribed fatigue procedure requires the comparison of an alternating stress amplitude with fatigue allowables (design fatigue curves), usually derived through uniaxial specimen testing. For elastic assessments of multiaxial loading, typical from thermal shocks, a Tresca stress is used to characterise the stress field into a single effective stress measure for comparison with ASME fatigue allowables. For nonlinear elastic-plastic assessments, Appendix XIII-3440(b) of Section III specifies that “the numerically maximum principal total strain range” (interpreted as Maximum Total Principal (MTP) strain range) should be used for comparison with fatigue allowables. Two alternative methods for the characterisation of multiaxial strain fields are presented in the ASME code. Section VIII Division 2 provides alternative rules for the construction of pressure vessels, with Part 5 specifying the use of a Von Mises based Effective Strain Range (ESR) for elastic-plastic analysis. Section III Division 5 Subsection NBB provides rules for the assessment of components at elevated temperatures, also specifying the use of a Von Mises based Equivalent Total Strain Range (ETSR) measure. The two alternative strain measures are differentiated by their treatment of the elastic strain contribution. In the ESR method an equivalent elastic strain is calculated and summated with the plastic strain component. In the ETSR method the total strain (elastic plus plastic) is used thus evaluating the elastic and plastic contributions simultaneously. More complex critical plane approaches have also been proposed in recent years to better characterise multiaxial loading conditions. This paper presents a comparison of the various ASME specified strain measures and simplified critical plane approaches for fatigue evaluation of complex multiaxial loading. In support of this comparison, predictions of initiation lives to 0.254 mm defect in the stepped pipe specimen reported in PVP2004-2748 are provided to quantify the additional conservatism contained in elastic-plastic fatigue assessments of nuclear components. Predictions use the methodology presented in the companion paper PVP2019-93847 for the generation of short crack fatigue curves and the associated modification to environmental enhancement factors. It is concluded that use of the ASME specified strain measures, in conjunction with lower bound stress-strain data, conservatively underestimate the initiation life to a 0.254 mm defect by a factor of four for the example considered. However, use of more complex critical plane strain measures were observed to provide significant improvement in prediction accuracy of elastic-plastic fatigue evaluations.

Low-Cycle Fatigue of AISI 1010 Steel at Temperatures up to 1200°F (649°C)

1977 ◽  
Vol 99 (3) ◽  
pp. 432-443 ◽  
Author(s):  
C. E. Jaske
Keyword(s):  
Plastic Strain ◽  
Fatigue Resistance ◽  
Stress Amplitude ◽  
Low Cycle Fatigue ◽  
Strain Range ◽  
Cyclic Stress ◽  
Cyclic Life ◽  
Stress Strain ◽  
Plastic Strain Range ◽  
Tensile Hold

This program was undertaken to develop isothermal low-cycle fatigue information for AISI 1010 steel in air. Such information is needed to help predict acceptable conditions for equipment and structures operating at elevated temperatures. Tensile properties and cyclic stress-strain behavior were also developed. For lives between 103 and 106 cycles to failure, fatigue curves were developed at 70, 400, 600, 800, 1000, and 1200°F (21, 204, 316, 427,538, and 649°C). Data for these curves were obtained from constant-amplitude, fully reversed strain-cycling tests of axially loaded specimens. Results from the same experiments were used to define cyclic stress-strain curves at each of the above temperatures. Dynamic strain aging caused a maximum amount of cyclic hardening at 600°F (316°C). In terms of stress amplitude, the maximum fatigue strength was at 600°F (316°C). In terms of either total strain range or plastic strain range, the maximum fatigue resistance was at 400°F (204°C). At temperaures above 600°F (316°C), fatigue resistance decreased as temperature increased. Tensile hold periods caused a significant reduction in cyclic life at 800 and 1000°F (427 and 538°C) but had no noticeable effect on cyclic life at 600°F (316°C). Fatigue resistance was quantified in terms of power functions relating fatigue life to both plastic strain range and stress amplitude, and cyclic stress-strain response was quantified in terms of a power function relating stress amplitude to plastic strain amplitude. The method of strain-range partitioning provided good cyclic life predictions for the limited number of tensile hold-time experiments, although other types of hold periods were not evaluated.

Plastic and Creep Analyses of the Superheater Header Tubeplate Using Linear Matching Method

2004 ◽  
Author(s):  
Haofeng Chen ◽  
Alan R. S. Ponter
Keyword(s):  
Complex Geometry ◽  
Strain Range ◽  
Inelastic Strain ◽  
Cyclic Hardening ◽  
Matching Method ◽  
Plastic Strain Range ◽  
Integrity Assessment ◽  
Perfectly Plastic ◽  
Shakedown Limit ◽  
Linear Matching Method

In 2003 ASME PVP conference, a series of numerical procedures for integrity assessment based upon recently developed Linear Matching Method were presented [1]. A typical example of holed plate was used to verify these procedures for the evaluation of plastic and creep behaviours of complex geometry components based on linear solutions, which can be easily implemented into the commercial FE code ABAQUS through user subroutines. In this paper, a more complex 3D tubeplate in a typical AGR superheater header is analysed for the shakedown limit, reverse plasticity, ratchet limit and creep relaxation based on application of the Linear Matching Method. Both the perfectly plastic model and the cyclic hardening model are adopted for the evaluation of the plastic strain range. For the evaluation of accumulated creep strains, flow stresses and elastic follow-up factors with differing dwell times at the steady cyclic state, a creep-reverse plasticity model is adopted. The total inelastic strain range over the cycle at the steady cyclic state is calculated. By comparing these results with ABAQUS step-by-step inelastic analyses, the applicability of the methods is verified.

Sign in / Sign up

Export Citation Format

Share Document