A Direct Method on the Evaluation of Cyclic Behaviour With Creep Effect

2012 ◽  
Author(s):  
Haofeng Chen ◽  
Weihang Chen ◽  
James Ure
Keyword(s):  
Plastic Strain ◽  
Creep Strain ◽  
Fatigue Damage ◽  
Mechanical Load ◽  
Direct Method ◽  
Load Condition ◽  
Strain Range ◽  
Plastic Strain Range ◽  
Cyclic Behaviour ◽  
Creep Fatigue

This paper describes a new Linear Matching Method (LMM) technique for the direct evaluation of cyclic behaviour with creep effects of structures subjected to a general load condition in the steady cyclic state. The creep strain and plastic strain range for use in creep damage and fatigue assessments, respectively, are obtained. A benchmark example of a Bree cylinder subjected to cyclic thermal load and constant mechanical load is analysed to verify the applicability of the new LMM to deal with the creep fatigue damage. The cyclic responses for different loading conditions and dwell time periods within the Bree boundary are obtained. To demonstrate the efficiency and effectiveness of the method for more complex structures, a 3D holed plate subjected to cyclic thermal loads and constant axial tension is analysed. The results of both examples show that with the presence of creep the cyclic responses change significantly. The new LMM procedure provides a general purpose technique for the evaluation of cyclic behaviour, the plastic strain range and creep strain for the creep fatigue damage assessment with creep fatigue interaction.

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.

scholarly journals On Creep Fatigue Interaction of Components at Elevated Temperature

2016 ◽  
Vol 138 (4) ◽  
Author(s):  
Daniele Barbera ◽  
Haofeng Chen ◽  
Yinghua Liu
Keyword(s):  
High Temperature ◽  
Mechanical Load ◽  
Direct Method ◽  
Bending Moment ◽  
Strain Range ◽  
Cyclic Plasticity ◽  
Element Analysis ◽  
Total Strain Range ◽  
Creep Fatigue ◽  
A Direct Method

The accurate assessment of creep–fatigue interaction is an important issue for industrial components operating with large cyclic thermal and mechanical loads. An extensive review of different aspects of creep fatigue interaction is proposed in this paper. The introduction of a high temperature creep dwell within the loading cycle has relevant impact on the structural behavior. Different mechanisms can occur, including the cyclically enhanced creep, the creep enhanced plasticity and creep ratchetting due to the creep fatigue interaction. A series of crucial parameters for crack initiation assessment can be identified, such as the start of dwell stress, the creep strain, and the total strain range. A comparison between the ASME NH and R5 is proposed, and the principal differences in calculating the aforementioned parameters are outlined. The linear matching method (LMM) framework is also presented and reviewed, as a direct method capable of calculating these parameters and assessing also the steady state cycle response due to creep and cyclic plasticity interaction. Two numerical examples are presented, the first one is a cruciform weldment subjected to cyclic bending moment and uniform high temperature with different dwell times. The second numerical example considers creep fatigue response on a long fiber reinforced metal matrix composite (MMC), which is subjected to a cycling uniform thermal field and a constant transverse mechanical load. All the results demonstrate that the LMM is capable of providing accurate solutions, and also relaxing the conservatisms of the design codes. Furthermore, as a direct method, it is more efficient than standard inelastic incremental finite element analysis.

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.

scholarly journals Isothermal Fatigue Behavior of Sn-Pb Solder Joints

1990 ◽  
Vol 112 (2) ◽  
pp. 94-99 ◽  
Author(s):  
T. S. E. Summers ◽  
J. W. Morris
Keyword(s):  
Fatigue Life ◽  
Plastic Strain ◽  
Strain Rate ◽  
Fatigue Behavior ◽  
Strain Range ◽  
Load Drop ◽  
Plastic Strain Range ◽  
Double Shear ◽  
Isothermal Fatigue ◽  
Fatigue Data

Isothermal fatigue data were collected for the compositions 5Sn-95Pb, 20Sn-80Pb, 40Sn-60Pb, 50Sn-50Pb and 63Sn-37Pb within the binary Sn-Pb system. All of these compositions are commercially available and include those most commonly used. Because Sn-rich solders are rarely used, they were not investigated here. The fatigue life was defined by a 30 percent load drop. The solders were tested in a double shear configuration joined to copper at 75° C. The displacement rate chosen was 0.01 mm/min, which corresponds to a strain rate of 1.5 × 10−4s−1 for our specimen configuration, over a 10 percent plastic strain range. Additionally, the microstructural changes during fatigue are presented. The various solder compositions studied exhibit strikingly different as-solidified microstructures. These differences are discussed in terms of their effect on the isothermal joint failure mechanism and joint isothermal fatigue life.

A Two Surface Model for Transient Nonproportional Cyclic Plasticity, Part 1: Development of Appropriate Equations

1985 ◽  
Vol 52 (2) ◽  
pp. 298-302 ◽  
Author(s):  
D. L. McDowell
Keyword(s):  
Plastic Strain ◽  
Kinematic Hardening ◽  
Strain Range ◽  
Cyclic Plasticity ◽  
Plastic Strain Rate ◽  
Internal Variables ◽  
Surface Model ◽  
Fading Memory ◽  
Plastic Strain Range ◽  
Hardening Modulus

A two surface stress space model is introduced with internal state variable repositories for fading memory of maximum plastic strain range and non-proportionality of loading. Evolution equations for isotropic hardening variables are prescribed as a function of these internal variables and accumulated plastic strain, and reflect dislocation interactions that occur in real materials. The hardening modulus is made a function of prior plastic deformation and the distance of the current stress point from the limit surface. The kinematic hardening rules of Mroz and Prager are used for the yield and limit surfaces, respectively. The structure of the model is capable of representing essential aspects of complex nonproportional deformation behavior, including direction of the plastic strain rate vector, memory of plastic strain range, cross-hardening effects, variation of hardening modulus, cyclic hardening or softening, cyclic racheting, and mean stress relaxation.

A Direct Method on the Evaluation of Ratchet Limit

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Haofeng Chen ◽  
Alan R. S. Ponter
Keyword(s):  
Cyclic Load ◽  
Mechanical Load ◽  
Low Cycle Fatigue ◽  
Direct Method ◽  
Numerical Technique ◽  
Load Condition ◽  
Numerical Procedure ◽  
Constant Load ◽  
Inelastic Analysis ◽  
Additional Constant

This paper describes a new linear matching method (LMM) technique for the direct evaluation of the ratchet limit of a structure subjected to a general cyclic load condition, which can be decomposed into cyclic and constant components. The cyclic load history considered in this paper contains multiload extremes to include most complicated practical applications. The numerical procedure uses the LMM state-of-the-art numerical technique to obtain a stable cyclic state of component, followed by a LMM shakedown analysis, to calculate the maximum constant load, i.e., the ratchet limit, which indicates the load carrying capacity of the structure subjected to a cyclic load condition to withstand an additional constant load. This approach is particularly useful in conjunction with the evaluation of the stable cyclic response, which produces the cyclic stresses, residual stresses, and plastic strain ranges for the low cycle fatigue assessment. A benchmark example of a holed plate under the combined action of cyclic thermal load and constant mechanical load is presented to verify the applicability of the new ratchet limit method through a comparison with published results by a simplified method assuming a cyclic load with two extremes. To demonstrate the efficiency and effectiveness of the method for a complicated cyclic load condition with multiload extremes, a composite thick cylinder with a radial opening subjected to cyclic thermal loads and a constant internal pressure is analyzed using the proposed ratchet limit method. Further verification by the ABAQUS step-by-step inelastic analysis demonstrates that the proposed new method provides a general-purpose technique for the evaluation of the ratchet limit and has both the advantages of programming methods and the capacity to be implemented easily within a commercial finite element code Abaqus.

Sign in / Sign up

Export Citation Format

Share Document