Application of the Linear Matching Method to the Integrity Assessment for the High Temperature Response of Structures

2003 ◽  
Author(s):  
Haofeng Chen ◽  
Alan R. S. Ponter
Keyword(s):  
Residual Stress ◽  
Stress Field ◽  
Temperature Response ◽  
Assessment Method ◽  
Life Assessment ◽  
Residual Stress Field ◽  
Matching Method ◽  
Integrity Assessment ◽  
Linear Matching Method

The paper describes a first attempt to produce a complete system of calculations that cover the entire range of assessments required in the Life Assessment method R5 based on a new programming method, the Linear Matching Method, and using shakedown and related concepts. We show that two solutions types are possible, the first assuming a constant residual stress field that provides shakedown and related limits. The second method involves the evaluation of the amplitude of the changing residual stress field. This provides the first stage for the ratchet limit and the amplitude of plastic strain. By adaptation the elastic follow-up factor corresponding to creep dwell periods may also be evaluated.

The Application of the Linear Matching Method to the Life Assessment Method R5: A Comparison

2005 ◽  
Author(s):  
Haofeng Chen ◽  
A. R. S. Ponter ◽  
R. A. Ainsworth
Keyword(s):  
Failure Modes ◽  
Limit Load ◽  
Detailed Comparison ◽  
Assessment Method ◽  
Life Assessment ◽  
Distinct Advantage ◽  
Matching Method ◽  
Creep Fatigue ◽  
Linear Matching Method

The Life Assessment Method R5 is widely used for the assessment of power plant at high temperatures. The procedure involves the application of a sequence of rules that provide margins of safety against a range of possible failure modes, plastic collapse, ratchetting, fatigue failure, creep rupture and creep/fatigue interaction. Within R5 this is achieved by using limit load and shakedown methods, combined with Neuber’s rule and the evaluation of elastic follow-up factors. In recent years, the Linear Matching Method has been developed so that it is capable of providing optimal solutions for each of these criteria, thereby giving less conservative margins of safety, but adopting the same use of material data as R5. The paper describes a detailed comparison between the approach currently used in R5 and the result of the application of the Linear Matching Method, for the entire range of failure modes and for a simple example. The purpose of this comparison is to assess the circumstances where Linear Matching Methods may have a distinct advantage over current methods. The example consists of a square plate containing a circular hole. The plate is subjected to uniaxial loading and a radial varying temperature field. For all failure modes the Linear Matching Method gives less conservative results compared with standard R5 methods. The differences can be very significant, particularly for the prediction of strength limits; limit load, shakedown load and ratchet limit. Significantly lower and less conservation elastic follow-up factors were also obtained. The comparison demonstrates the advantages of the Linear Matching Method in this context.

An Energy-Based Residual Stress Field Reconstruction Approach Using Limited Measurements

2015 ◽  
Author(s):  
H.-B. Liu ◽  
Y.-P. Li ◽  
Y.-Q. Wang ◽  
X.-J. Sheng
Keyword(s):  
Residual Stress ◽  
Stress Distribution ◽  
Stress Field ◽  
Structural Integrity ◽  
Spline Interpolation ◽  
Residual Stress Field ◽  
Strain Compatibility ◽  
Integrity Assessment ◽  
Field Reconstruction ◽  
Initial Stress Field

To characterize the residual stress distribution is very crucial for workpiece fatigue lifetime and structural integrity assessment. An energy-based residual stress field reconstruction approach using limited measurements is proposed. Firstly, the Ferguson spline interpolation technique is employed as the stress interpolation base of the 2-order stress tensor. Then, an initial stress field can be reconstructed using the overall boundary conditions by minimizing strain energy. Further, the stress distribution is modified according to strain compatibility equation. At last, a typical stress unit from the artificial stress field constructed by FEM, was picked up as an input set to verify the validation of the developed model and algorithm numerically. It was demonstrated that the energy-based scheme was efficient and reliable to reconstruct the residual stress field from limited measurements.

Methods for the Evaluation of Creep Relaxation and the Amplitude of Reverse Plastic Strain for Bodies Subjected to Cyclic Loading

2003 ◽  
Author(s):  
Haofeng Chen ◽  
Alan R. S. Ponter
Keyword(s):  
Residual Stress ◽  
Cyclic Loading ◽  
Stress Field ◽  
Plastic Strain ◽  
Dwell Time ◽  
Mechanical Load ◽  
Computation Method ◽  
Residual Stress Field ◽  
Plasticity Mechanism

An extension of the upper bound shakedown theorem to load histories in excess of shakedown has been applied in previous papers [1, 2] to the evaluation of a ratchet limit and the varying plastic strain magnitudes associated with a varying residual stress field by the Linear Matching Method. In the present paper, this technique is further applied to the evaluation of creep-reverse plasticity mechanism for bodies subjected to cyclic loading including creep effects. The accumulated creep strain, the varying flow stress and the corresponding varying residual stress field during a creep dwell time are evaluated. The elastic follow-up factors are calculated thereafter. In order to verify the applicability of the proposed method, a monotonic creep computation method based upon the rapid cycle solutions is introduced for comparison. A holed plate subjected to cyclic thermal load and constant mechanical load is assessed in detail as a typical example. The consistent solutions of the accumulated creep strains, the varying flow stresses and the elastic follow-up factors with creep dwell time by these different methods confirm the applicability of the proposed new methods.

scholarly journals Modeling of the Behavior of a Welded Joint Subjected to Reverse Bending Moment at High Temperature

2006 ◽  
Vol 129 (2) ◽  
pp. 254-261 ◽  
Author(s):  
Alan R. S. Ponter ◽  
Haofeng Chen
Keyword(s):  
Experimental Data ◽  
Fatigue Damage ◽  
Assessment Method ◽  
Parent Material ◽  
Life Assessment ◽  
Maximum Temperature ◽  
Assessment Procedure ◽  
Analytic Model ◽  
Matching Method ◽  
Linear Matching Method

The paper is concerned with the modeling of the behaviour of welds when subjected to severe thermal and mechanical loads where the maximum temperature during dwell periods lies in the creep range. The methodology of the life assessment method R5 is applied where the detailed calculations are carried out using the linear matching method (LMM), with the objective of generating an analytic model. The linear matching method has been developed to allow accurate predictions using the methodology of R5, the UK life assessment method. The method is here applied to a set of weld endurance tests, where reverse bending is interrupted by creep dwell periods. The weld and parent material are both Type 316L(N) material, and data were available for fatigue tests and tests with 1 and 5h dwell periods to failure. The elastic, plastic, and creep behavior of the weld geometry is predicted with the LMM using the best available understanding of the properties of the weld and parent material. The numerical results are translated into a semi-analytic model. Using the R5 standard creep/fatigue model, the predicted life of the experimental welds specimens are compared with experimental data. The analysis shows that the most severe conditions occur at the weld/parent material interface, with fatigue damage concentrated predominantly in the parent material, whereas the creep damage occurs predominantly in the weld material. Hence, creep and fatigue damage proceed relatively independently. The predictions of the model are good, except that the reduction in fatigue life due to the presence of the weld is underestimated. This is attributed to the lack of separate fatigue date for the weld and parent material and the lack of information concerning the heat affected zone. With an adjustment of a single factor in the model, the predictions are very good. The analysis in this paper demonstrates that the primary properties of weld structures may be understood through a number of structural parameters, defined by cyclic analysis using the linear matching method and through the choice of appropriate material data. The physical assumptions adopted conform to those of the R5 life assessment procedure. The resulting semi-analytic model provides a more secure method for extrapolation of experimental data than previously available.

An Experimental Procedure to Determine the Interaction between Applied Loads and Residual Stresses

2013 ◽  
Vol 768-769 ◽  
pp. 733-740 ◽  
Author(s):  
Greame Horne ◽  
Matthew J. Peel ◽  
Danie G. Hattingh ◽  
Thomas Connolley ◽  
Michael Hart ◽  
...  
Keyword(s):  
Residual Stress ◽  
Stress Field ◽  
Permanent Deformation ◽  
High Energy ◽  
Image Correlation ◽  
Residual Stress Field ◽  
Full Field ◽  
Residual Stress State

This paper presents a novel experiment to quantify both the initial residual stress state in a specimen and its redistribution due to plasticity induced by in-situ loading. The rate of relaxation of the residual stress with respect to permanent deformation is a measure of the elastic follow-up associated with the residual stress field. Residual stress measurements were made using high energy dispersive X-ray diffraction. Digital image correlation, verified by strain gauges, was used to measure full-field deformation on the specimen. The specimen was loaded and unloaded in-situ incrementally to promote plasticity, allowing the relaxation rate of the residual stress to be quantified. An elastic follow-up factor was calculated for the residual stress field, that indicated loading conditions of the residual stress field between fixed-displacement and fixed-load.

Numerical and experimental investigations of effects of residual stresses on crack behavior in Aluminum 6082-T6

2012 ◽  
Vol 226 (9) ◽  
pp. 2178-2191 ◽  
Author(s):  
Mohammadreza Farahani ◽  
Iradj Sattari-Far ◽  
Davood Akbari ◽  
Rene Alderliesten
Keyword(s):  
Fracture Toughness ◽  
Residual Stress ◽  
Finite Element ◽  
Stress Field ◽  
Residual Stresses ◽  
Crack Growth ◽  
Crack Tip ◽  
Residual Stress Field ◽  
Integrity Assessment ◽  
Crack Tip Constraint

In the structural integrity assessment, residual stresses play an important role. The residual stresses affect both the crack driving forces and the crack-tip constraint. To investigate the interaction of residual stresses with mechanical loading during the onset of crack growth in Aluminum 6082-T6, modified single edge-notched bending specimens were used. Aluminum 6082 has the highest strength of the 6000 series alloys with excellent corrosion resistance. A residual stress field was created in the specimens by pre-loading. To accurately quantify the residual stress field created during this test procedure, the strains were measured during loading and unloading and compared with finite element results. After the introduction of the residual stress field, the specimens were tested under three-point bending to determine the load versus displacement behavior and fracture toughness. Also, a post-processor for finite element calculation was developed to enable determination of the J-integral values for the specimens having residual stresses. The constraint parameters Q and R were calculated at the crack-tip to describe the stress field in this region. The parameter Q is used to characterize the loading and geometry constraint, and the parameter R is used for characterizing the crack-tip constraint due to residual stresses. It is observed that tensile residual stresses around the crack-tip increase the crack-tip constraint and decrease the fracture toughness of the bodies. By increasing the external load, the constraint parameter R goes toward zero and the effects of residual stresses on the crack growth resistance become negligible.

scholarly journals Residual stresses in thermite welded rails: significance of additional forging

2020 ◽  
Vol 64 (7) ◽  
pp. 1195-1212
Author(s):  
B. Lennart Josefson ◽  
R. Bisschop ◽  
M. Messaadi ◽  
J. Hantusch
Keyword(s):  
Residual Stress ◽  
Stress Field ◽  
Residual Stresses ◽  
Weld Metal ◽  
Welding Process ◽  
Surface Zone ◽  
Fe Model ◽  
Uneven Surface ◽  
Residual Stress Field ◽  
High Dynamic

Abstract The aluminothermic welding (ATW) process is the most commonly used welding process for welding rails (track) in the field. The large amount of weld metal added in the ATW process may result in a wide uneven surface zone on the rail head, which may, in rare cases, lead to irregularities in wear and plastic deformation due to high dynamic wheel-rail forces as wheels pass. The present paper studies the introduction of additional forging to the ATW process, intended to reduce the width of the zone affected by the heat input, while not creating a more detrimental residual stress field. Simulations using a novel thermo-mechanical FE model of the ATW process show that addition of a forging pressure leads to a somewhat smaller width of the zone affected by heat. This is also found in a metallurgical examination, showing that this zone (weld metal and heat-affected zone) is fully pearlitic. Only marginal differences are found in the residual stress field when additional forging is applied. In both cases, large tensile residual stresses are found in the rail web at the weld. Additional forging may increase the risk of hot cracking due to an increase in plastic strains within the welded area.

A mechanism study on characteristic curve of residual stress field in Ti–6Al–4V induced by wet peening treatment

2015 ◽  
Vol 86 ◽  
pp. 761-764 ◽  
Author(s):  
Kang Li ◽  
Xue-song Fu ◽  
Rui-dong Li ◽  
Wen-long Zhou ◽  
Zhi-qiang Li
Keyword(s):  
Residual Stress ◽  
Stress Field ◽  
Characteristic Curve ◽  
Mechanism Study ◽  
Residual Stress Field
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