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The Effects of Processing Residual Stresses on the Fatigue Crack Growth Behavior of Structural Materials

TL;DR: In this article, the effects of quenching residual stresses on fatigue crack propagation behavior of various materials were investigated, and an original residual stress analytical correction to fatigue crack growth data was developed, compared to existing corrective methodologies, and validated using residual stress free data.
Abstract: Residual stresses are a common and often undesired result of material processing, introduced through non-linear deformation and/or phase transformation of material under mechanical or thermo-mechanical loading. These macro stresses alter mechanical properties and the intrinsic fatigue crack growth characteristics of the material. Residual stress artifacts can introduce inconsistencies and significant errors when the true material behavior is needed for material development and optimization and for structural component design. The effects of quenching residual stresses on fatigue crack propagation behavior of various materials were investigated. In parallel, residual stresses similar in magnitude and distribution with the quenching residual stresses were generated using mechanical processes to decouple the effects of residual stresses from microstructural effects. Mechanical residual stress distributions predicted by 3D elastic-plastic finite element analysis showed good agreement with the stresses measured on fatigue crack growth testing specimens using fracture mechanics approaches. Crack propagation characteristics in fields with low and high residual stresses were studied using optical and scanning electron microscopy, and the effects of residual stress on crack path behavior were assessed. An original residual stress analytical correction to fatigue crack growth data was developed, compared to existing corrective methodologies, and validated using residual stress free data. Overall, the work provides tools to understand, control, and correct the effects of processing residual stresses on fatigue crack growth for accurate fatigue critical design and life predictions.
Citations
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Journal ArticleDOI
TL;DR: In this paper, a two-dimensional finite element (FE) model was established to simulate the residual stresses associated with the hole extrusion process and the numerical result showed a good agreement with the experimental data.

17 citations

Journal ArticleDOI
TL;DR: In this article, the failure reasons of a DY08 aluminum alloy elastic coupling connecting the motor of the multi-functional test bench with the experimental device was investigated based on the fact that the lifespan of coupling was not reached.

9 citations

Journal ArticleDOI
TL;DR: In this paper, wide-flange members are hot-rolled to their final shapes and subsequently air-cooled, during which residual stresses are developed due to nonuniform cooling.
Abstract: Wide-flange members are hot-rolled to their final shapes and subsequently air-cooled, during which residual stresses are developed due to nonuniform cooling. Both global and local flange-bu...

7 citations

25 Oct 2018
TL;DR: A comprehensive study of the mechanical fatigue subject is presented, with particular focus on the residual stresses issue, as their impact on the fatigue life expectations, the manufacturing processes behind their formation, their measurement methods and the most preforming way to account them in the fatigueLife estimates.
Abstract: The residual stresses were proven to play a relevant role in the fatigue life expectations of components and specimens. It is well established that almost every manufacturing process to some extent leads to the residual or internal stress fields formation. The challenge is to properly account for these internal stress fields in the fatigue life prediction. In this essay a comprehensive study of the mechanical fatigue subject is presented, with particular focus on the residual stresses issue, as their impact on the fatigue life expectations, the manufacturing processes behind their formation, their measurement methods and the most preforming way to account them in the fatigue life estimates. The most challenging issues in terms of the residual stress simulation in fatigue are presented through the previous works found in literature and finally in this thesis my personal contribution was given in the development of a Python program for the optimized insertion of a residual stress field on a finite element model, which will be potentially employed at FCA Automobiles for research purpose.

3 citations


Cites background or methods from "The Effects of Processing Residual ..."

  • ...This approach has been employed in [32,13,33,34,21,35,36,16,17,19,24], and anyway features some shortcomings and difficulties....

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  • ...The mechanical processes which the majority of the researches have dealt with, as to the FE modelling of residual stress fields are the shoot-peening treatments [22], welding processes [23, 21, 24, 25], four-points bending tests [26, 13, 27], or quenching processes [19]....

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  • ...SENT specimens [13, 14], welded plates [15, 16, 17], notched CT specimens [18 ,19, 20], M(T) specimens [21]....

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References
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Journal ArticleDOI
TL;DR: In this article, the authors investigated the effect of surface scratches on the mechanical strength of solids, and some general conclusions were reached which appear to have a direct bearing on the problem of rupture, from an engineering standpoint, and also on the larger question of the nature of intermolecular cohesion.
Abstract: In the course of an investigation of the effect of surface scratches on the mechanical strength of solids, some general conclusions were reached which appear to have a direct bearing on the problem of rupture, from an engineering standpoint, and also on the larger question of the nature of intermolecular cohesion. The original object of the work, which was carried out at the Royal Aircraft Estab­lishment, was the discovery of the effect of surface treatment—such as, for instance, filing, grinding or polishing—on the strength of metallic machine parts subjected to alternating or repeated loads. In the case of steel, and some other metals in common use, the results of fatigue tests indicated that the range of alternating stress which could be permanently sustained by the material was smaller than the range within which it was sensibly elastic, after being subjected to a great number of reversals. Hence it was inferred that the safe range of loading of a part, having a scratched or grooved surface of a given type, should be capable of estimation with the help of one of the two hypotheses of rupture commonly used for solids which are elastic to fracture. According to these hypotheses rupture may be expected if (a) the maximum tensile stress, ( b ) the maximum extension, exceeds a certain critical value. Moreover, as the behaviour of the materials under consideration, within the safe range of alternating stress, shows very little departure from Hooke’s law, it was thought that the necessary stress and strain calculations could be performed by means of the mathematical theory of elasticity.

10,162 citations


"The Effects of Processing Residual ..." refers background in this paper

  • ...Irwin [3], applying concepts of Griffith [4], realized that the stress intensity around a crack was the determining factor of static strength in the cracked state....

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  • ...A fail-safe understanding, the understanding of how existing flaws propagate and effect fatigue life, did not spring its roots until the late 1950’s. Irwin [3], applying concepts of Griffith [4], realized that the stress intensity around a crack was the determining factor of static strength in the cracked state....

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  • ...[4] Griffith, A. A., 1920, "The Phenomena of Rupture and Flow in Solids," Phil....

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Journal ArticleDOI
TL;DR: In this article, a relation between extent of plastic yielding and external load applied was investigated, and panels containing internal and edge slits were loaded in tension and lengths of plastic zones were measured.
Abstract: Y ielding at the end of a slit in a sheet is investigated, and a relation is obtained between extent of plastic yielding and external load applied. To verify this relation, panels containing internal and edge slits were loaded in tension and lengths of plastic zones were measured.

6,830 citations


Additional excerpts

  • ...Plasticity corrections can be applied as previously introduced by Irwin and others [47, 48]....

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Book
01 Jan 2000
TL;DR: The Stress Analysis of Cracks Handbook as mentioned in this paper provides a comprehensive, easy-to-access collection of elastic stress solutions for crack configurations, along with other relevant information, such as displacements, crack opening areas, basic stress functions source references, accuracy of solutions, and more.
Abstract: Nearly double the size of the previous edition, the third edition of this classic reference provides a comprehensive, easy-to-access collection of elastic stress solutions for crack configurations. For each configuration, The Stress Analysis of Cracks Handbook present crack tip stress intensity formulas along with other relevant information, such as displacements, crack opening areas, basic stress functions source references, accuracy of solutions, and more. Throughout, it stresses formulas for application to test configurations. The introductory section details the methods of developing the informatio A series of appendices represents special methods and special applications. Now in a hardbound format, the current Handbook offers a number of new features including: * Ne Stress Solutions * Cracked Configurations * Plates with Pinching Loads * Dislocations and Cracks Solutions * Plastic Zone Instability (Expanding a Potentially Interceding "Elastic" Failure Mechanism) * Estimation Methods for Stress Intensity Formulas * J-Integral Methods * Pure Shear Plasticity Solutions. The authors provide 30 new solution pages, plus modifications of older solutions. Contents Include: * Introductory Information Stress Analysis Results for Common Test Specimen Configurations with Cracks * Cracks Along a Single Line * Parallel Cracks * Cracks and Holes or Notches * Curved, Angled, Branched, or Radiating Cracks * Cracks in Reinforced Plates * Three-Dimensional Cracked Configurations * Crack(s) in a Rod or a Plate by Energy Rate Analysis * Strip Yield Model Solutions * Cracks(s) in a Shell * Appendices.

5,374 citations


"The Effects of Processing Residual ..." refers background in this paper

  • ...2), F2 is a function of specimen geometry [45], and af, b, d, and h are dimensions of the C(T) shown in Figure 3....

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Journal ArticleDOI
TL;DR: In this article, an analysis of the stress distribution acting on the fracture surfaces shows that the local compressive stress maxima may exceed the yield stress of the material and that crack closure may influence the shape of the striation pattern.

1,876 citations


"The Effects of Processing Residual ..." refers background in this paper

  • ...[8] Elber, W., 1970, "Fatigue Crack Closure Under Cyclic Tension," Engineering Fracture Mechanics, 2, pp. 37--45....

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  • ...Crack closure during cyclic loading was first documented by Christensen [7], and was later well established by Elber [8]....

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01 Jan 1961

1,286 citations


"The Effects of Processing Residual ..." refers background in this paper

  • ...In general crack thresholds increase, Paris slopes increase, and Paris intercepts decrease....

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  • ...%) for all alloys Page 35 Table 2.6 Front face notch displacements for all alloys and stress conditions Page 37 CHAPTER 3 Table 3.1 Avu coefficient matrix used in Equation (3.6) Page 49 CHAPTER 4 Table 4.1 Fatigue crack threshold, Paris Regime Slope, and Paris Regime Intercepts, and notch displacements for all alloys and stress conditions tested Page 61 Table 4.2 Average relative length and relative crack branching of entire crack path for low and high residual stress specimens tested at R=0.1, 0.5, and 0.7 Page 63 Table 4.3 ΔKeff, Kmax+Kres, and plastic zone radius calculations for low and high residual stress specimens tested at R=0.1, 0.5, and 0.7 at threshold Page 68 Table 4.4 Fatigue striation measurements taken at an average growth rate of 1 µm/cycle for low and high residual stress specimens tested at R=0.1, 0.5, and 0.7 Page 71 Table 4.5 Kmax+Kres and plastic zone radius calculations for low and high residual stress specimens tested at R=0.1, 0.5, and 0.7 at transition from regions of high to low crack deflection Page 78 CHAPTER 6 Table 6.1 Avu coefficients in Equation (6.4) Page 110 13 NONMENCLATURE a Crack length (measured from the center of specimen loading holes in the case of the compact tension (C(T)) specimen geometry) aeff Effective crack length including the radius of the plastic zone at the crack tip a0 Initial crack length at measurement increment used in the calculation of residual stress magnitudes using fracture mechanics approaches and weight functions for specimen geometry af Crack length measured from compact tension (C(T)) specimen front face ai-1 Crack length at previous measurement using fracture mechanics approaches of measuring the stress intensity due to residual stress, equivalent to aj-1 ai Crack length at current measurement using fracture mechanics approaches of measuring the stress intensity due to residual stress, equivalent to aj ai+1 Crack length at next successive measurement using fracture mechanics approaches of measuring the stress intensity due to residual stress, equivalent to aj+1 Avu Coefficient matrix used in conjunction with fracture mechanics approaches and specimen weight functions to calculate residual stress ACR Adjusted compliance ratio, the ratio of the difference between the secant compliance and initial compliance and the compliance in the absence of closure and the initial compliance b Total compact tension (C(T)) specimen width in the direction of crack growth B Compact tension (C(T)) specimen thickness C Paris intercept, the crack growth rate axis intercept of a line drawn tangent to the fatigue crack growth curve during Region II growth C0 Compliance in the absence of closure, above the opening load of a crack Ci (Initial) Compliance prior to the initiation of a crack Cs (Secant) Compliance of one compliance load-displacement record, including crack closure 14 d Vertical distance from the center of compact tension (C(T)) specimen loading pin holes to the mid-plane of the specimen d0 Distance between reference scribe marks on compact tension (C(T)) specimen front face prior to machining of crack initiation notch dnotch Distance between reference scribe marks on compact tension (C(T)) specimen front face after machining of crack initiation notch dP Front face scribe distance due to an applied load e% Elongation at failure E Modulus of elasticity f Analytical function used in analytical correction to fatigue crack growth data g(E * ) Function of material modulus of elasticity normalized to the modulus of elasticity of aluminum h Half of total compact tension (C(T)) specimen height normal to the direction of crack growth h(x,a) Geometry dependent weight function used in the calculation of residual stress from fracture mechanics approaches i Empirical constant used in analytical fatigue crack growth correction, interrelated to crack length and stress ratio j Empirical constant used in analytical fatigue crack growth correction, interrelated to stress ratio K Applied stress intensity, equivalent to Kapp and Kelastic Kclosure Stress intensity at which crack closure begins Kdisp Stress intensity necessary to achieve the front face notch displacement from the original distance between reference scribe marks on compact tension (C(T)) specimen front face prior to machining of crack initiation notch Kmax Maximum stress intensity Kmin Minimum stress intensity 15 Kplastic Stress intensity under an applied load calculated using the effective crack length Kplastic correction Difference between the applied stress intensity calculated using the crack length (elastic) and the stress intensity under an applied load calculated using the effective crack length Kres Stress intensity due to residual stress calculated using fracture mechanics approaches Kresidual Stress intensity due to residual stress calculated using restoring force approaches ΔK Applied stress intensity range, equivalent to ΔKapp ΔKcl Change in applied stress intensity range due to closure ΔKcorrection Analytical correction to applied stress intensity range which applies the stress intensity due to residual stress calculated using the restoring force concepts and an analytical function ΔKeff Effective stress intensity range ΔKth Crack growth threshold corresponding to a growth rate of 10 -7 mm/cycle ΔKFT Stress intensity range at specimen failure m Paris slope, the slope of a line drawn tangent to the fatigue crack growth curve during Region II growth m1(a/W) Elastic compliance solution to determine crack length for compact tension (C(T)) geometry defined in the ASTM E647 fatigue crack growth testing standard m2(a/W) Polynomial function to determine stress intensity with knowledge of applied load, crack length, and compact tension (C(T)) geometry defined in the ASTM E647 fatigue crack growth testing standard n Degree of plane stress N Number of cycles P Applied load rp Radius of the plastic zone ahead of the crack tip 16 R (Nominal) Stress ratio Reff Effective stress ratio at the crack tip u Normalized elastic compliance for the compact tension (C(T)) specimen defined in the ASTM E647 fatigue crack growth testing standard udisp Front face notch displacement from the original Distance between reference scribe marks on compact tension (C(T)) specimen front face prior to machining of crack initiation notch und Front face notch displacement resulting from machining of the crack initiation notch, equivalent to Δδ uP Front face notch displacement due to an applied load W Compact tension (C(T)) specimen width Z(a) Geometry dependent influence function used in application of the Cut Compliance method δ Displacement dδmax Change in maximum displacement dδP=0 Change in displacement at zero load, equivalent to dδres Δδ Notch clamping displacement measured for restoring force calculations, equivalent to und ν Poisson’s ratio ζres Residual stress ζUTS Ultimate tensile strength ζY Yield strength determined by 0.2% offset technique 17 CHAPTER 1: INTRODUCTION AND LITERATURE REVIEW Residual stresses are stresses that remain in materials after all external loadings and thermal gradients have been removed....

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  • ...In all the case of R=0.1 and 0.7 tests, high residual stress specimens experienced higher fatigue crack thresholds, higher Paris law slopes (m), lower Paris law intercepts (C), and larger front face notch displacements....

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  • ...61 Table 4.1 Fatigue crack threshold, Paris Regime Slope, and Paris Regime Intercepts, and notch displacements for all alloys and stress conditions tested Stress Ratio Stress Condition ΔKth (MPa√m) Paris Slope (m) Paris Intercept (C) Front Face Notch Displacement (mm) R=0.1 Low 3.713 4.475 1.139E-9 -0.015 High 4.875 5.403 8.383E-11 -0.088 R=0.5 Low 3.147 7.330 2.499E-11 -0.054 High 4.439 6.553 3.264E-11 -0.121 R=0.7 Low 1.907 5.091 4.614E-9 -0.024 High 3.252 8.066 1.342E-12 -0.158 Optical microscopy was performed on all six crack paths, and micrographs of threshold, lower Region II (da/dN=10 -5 mm/cycle), middle Region II (da/dN=10 -4 mm/cycle), and upper Region II (da/dN=10 -3 mm/cycle) were taken, shown in Figure 4.5....

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  • ...[38] Bergner, F., Zouhar, G., and Tempus, G., 2001, "The Material-Dependent Variability of Fatigue Crack Growth Rates of Aluminum Alloys in the Paris Regime," International Journal of Fatigue, 23, pp. 383--394....

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