Structural stress analysis
First Claim
Patent Images
1. A method of analyzing structural stress σ
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s in a localized fatigue-prone region of a structure from a representation of the structure, said method comprising;
determining a through-thickness stress distribution σ
x(y) along a selected cross section of said structure, wherein a localized fatigue-prone region lies adjacent to said selected cross section, and wherein said stress distribution σ
x(y) is determined from said representation of said structure;
determining a first component σ
M of said structural structural stress σ
s in said localized fatigue-prone region by performing an operation having a result substantially equivalent to a result of the following first integration
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Abstract
Structural stress in a fatigue-prone region of a structure is determined by using the nodal forces and displacement values in the fatigue-prone region, or equilibrium-equivalent simple stress states consistent with elementary structural mechanics in the fatigue-prone region. The determination is substantially independent of mesh size and is particularly well-suited for applications where S-N curves are used in weld fatigue design and evaluation, where S represents nominal stress or stress range and N represents the number of cycles to failure.
24 Citations
37 Claims
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1. A method of analyzing structural stress σ
-
s in a localized fatigue-prone region of a structure from a representation of the structure, said method comprising;
determining a through-thickness stress distribution σ
x(y) along a selected cross section of said structure, wherein a localized fatigue-prone region lies adjacent to said selected cross section, and wherein said stress distribution σ
x(y) is determined from said representation of said structure;determining a first component σ
M of said structural structural stress σ
s in said localized fatigue-prone region by performing an operation having a result substantially equivalent to a result of the following first integration - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 27)
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s in a localized fatigue-prone region of a structure from a representation of the structure, said method comprising;
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11. A method of analyzing structural stress σ
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s in a localized fatigue-prone region of a structure from a three-dimensional finite element solid model of the structure, said method comprising;
identifying at least one local element for structural stress extraction, wherein said local element lies adjacent to said localized fatigue-prone region; determining stress resultants fx′
fz′
, and my′
for said local element from said finite element solid model of said structure, wherein said stress resultants represent the sectional forces and moments for said local element; andcalculating structural stress σ
s in said localized fatigue-prone region utilizing the following equation; - View Dependent Claims (28)
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s in a localized fatigue-prone region of a structure from a three-dimensional finite element solid model of the structure, said method comprising;
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12. A technique for analyzing structural stress σ
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s in a localized fatigue-prone region of a structure defining a substantially monotonic through thickness stress distribution, said technique comprising;
measuring displacement in the vicinity of said fatigue-prone region by configuring at least one measuring device to measure displacement along a first cross section of said structure offset a distance L from said fatigue-prone region, and measure displacement along a second cross section of said structure offset a distance L−
l from said fatigue prone region;decomposing stress measurements at said strain gauges as follows - View Dependent Claims (29)
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s in a localized fatigue-prone region of a structure defining a substantially monotonic through thickness stress distribution, said technique comprising;
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13. A technique for analyzing structural stress σ
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s in a localized fatigue-prone region of a structure defining a non-monotonic through thickness stress distribution, said technique comprising;
measuring displacement in the vicinity of said fatigue-prone region by configuring at least one measuring device to measure displacement along a first cross section of said structure offset a distance L from said fatigue-prone region, measure displacement along a second cross section of said structure offset a distance L−
l from said fatigue prone region, andmeasure displacement along a third cross section of said structure, wherein said third cross section defines an approximately linear structural stress distribution, decomposing stress measurements at said strain gauges as follows - View Dependent Claims (30)
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s in a localized fatigue-prone region of a structure defining a non-monotonic through thickness stress distribution, said technique comprising;
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14. A computer-readable medium encoded with a computer program for analyzing structural stress σ
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s in a localized fatigue-prone region of a structure, said program being operative to;
determine a through-thickness stress distribution σ
x(y) along a selected cross section of said structure, wherein a localized fatigue-prone region lies adjacent to said selected cross section;determine a membrane component σ
M and a bending component σ
B of said structural stress σ
s in said localized fatigue-prone region from said through thickness stress distribution σ
x(Y), wherein said membrane and bending components comprise simple structural stress distributions that are equilibrium-equivalent to said through thickness stress distribution σ
x(y); andcalculate said structural stress σ
s by combining said first component σ
M of said structural stress and said second component σ
B of said structural stress.
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s in a localized fatigue-prone region of a structure, said program being operative to;
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15. A computer-readable medium encoded with a computer program for analyzing structural stress σ
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s in a localized fatigue-prone region of a structure, said program being operative to;
identify at least one local element for structural stress extraction, wherein said local element lies adjacent to said localized fatigue-prone region; determine stress resultants fx′
, fz′
, and my′
for said local element from said finite element solid model of said structure, wherein said stress resultants represent the sectional forces and moments for said local element; andcalculate structural stress σ
s in said localized fatigue-prone region utilizing the following equation
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s in a localized fatigue-prone region of a structure, said program being operative to;
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16. A system for analyzing structural stress σ
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s in a localized fatigue-prone region of a structure, said system including a controller programmed to;
determine a through-thickness stress distribution σ
x(y) along a selected cross section of said structure, wherein a localized fatigue-prone region lies adjacent to said selected cross section;determine a membrane component σ
M and a bending component σ
B of said structural stress σ
s in said localized fatigue-prone region from said through-thickness stress distribution σ
x(y), wherein said membrane and bending components comprise simple structural stress distributions that are equilibrium-equivalent to said through thickness stress distribution σ
x(y); andcalculate said structural stress σ
s by combining said first component σ
M of said structural stress and said second component σ
B of said structural stress. - View Dependent Claims (31)
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s in a localized fatigue-prone region of a structure, said system including a controller programmed to;
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17. A system for analyzing structural stress or in a localized fatigue-prone region of a structure, said system including a controller programmed to:
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identify at least one local element for structural stress extraction, wherein said local element lies adjacent to said localized fatigue-prone region; determine stress resultants fx′
, fz′
, and my′
for said local element from said finite element solid model of said structure, wherein said stress resultants represent the sectional forces and moments for said local element; andcalculate structural stress σ
s in said localized fatigue-prone region utilizing the following equation - View Dependent Claims (32)
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18. A system for analyzing structural stress σ
-
s in a localized fatigue-prone region of a structure, said system comprising;
at least one measuring device configured to measure displacement in the vicinity of said fatigue-prone region by measuring displacement along a first cross section of said structure offset a distance L from said fatigue-prone region, and measuring displacement along a second cross section of said structure offset a distance L−
l from said fatigue prone region; anda controller programmed to decompose stress measurements at said strain gauges as follows - View Dependent Claims (33)
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s in a localized fatigue-prone region of a structure, said system comprising;
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19. A system for analyzing structural stress σ
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s in a localized fatigue-prone region of a structure, said system comprising;
at least one measuring device configured to measure displacement in the vicinity of said fatigue-prone region by measuring displacement along a first cross section of said structure offset a distance L from said fatigue-prone region, measuring displacement along a second cross section of said structure offset a distance L−
l from said fatigue prone region; andmeasuring displacement along a third cross section of said structure, wherein said third cross section defines an approximately linear structural stress distribution; and a controller programmed to decompose stress measurements at said strain gauges as follows
σ
bB=(σ
TB−
σ
m)
σ
bC=(σ
TC−
σ
m)where said superscript B corresponds to a measurement at said first cross section, said superscript C corresponds to a measurement at said second cross section, said subscript T corresponds to a measurement at a top surface of said structure, and σ
m is a through thickness mean stress measurement taken at said third cross section; andapproximate structural stress σ
s, in said fatigue-prone region as follows
σ
s=σ
TB+L/l(σ
bC−
σ
bB)where the distances L and l are measured in terms of fractions of thickness t. - View Dependent Claims (34)
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s in a localized fatigue-prone region of a structure, said system comprising;
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20. A method of analyzing structural stress in a localized fatigue-prone region of a structure, said method comprising:
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determining a through-thickness stress distribution along a selected cross section of said structure, wherein a localized fatigue-prone region lies adjacent to said selected cross section and said through-thickness stress distribution is determined from a finite element model of said structure; determining a membrane component and a bending component of said structural stress in said localized fatigue-prone region from said through thickness stress distribution, wherein said membrane and bending components comprise simple structural stress distributions that are equilibrium-equivalent to said through thickness stress distribution; and calculating said structural stress by combining said first component of said structural stress and said second component of said structural stress, wherein said membrane component and said bending component are determined such that said structural stress calculation is substantially independent of the size, shape and distribution of mesh elements defining said finite element model of said structure. - View Dependent Claims (21, 22, 23, 35)
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24. A method of analyzing structural stress a, in a localized fatigue-prone region of a structure, said method comprising:
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determining a through-thickness stress distribution σ
x(y) along a selected cross section of said structure, wherein a localized fatigue-prone region lies adjacent to said selected cross section;determining a membrane component σ
M and a bending component σ
B of said structural stress σ
s in said localized fatigue-prone region from said through thickness stress distribution σ
x(y), wherein said membrane and bending components comprise simple structural stress distributions that are equilibrium-equivalent to said through thickness stress distribution σ
x(y); andcalculating said structural stress σ
s by combining said first component σ
M of said structural stress and said second component σ
B of said structural stress. - View Dependent Claims (25, 26, 36)
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37. A method of analyzing structural stress σ
-
s in a localized fatigue-prone region of a structure from a representation of the structure, said method comprising;
determining a through-thickness stress distribution σ
x(y) along a selected cross section of said structure, wherein a localized fatigue-prone region lies adjacent to said selected cross section, and wherein said stress distribution σ
x(y) is determined from said representation of said structure;determining a first component σ
M of said structural structural stress σ
s in said localized fatigue-prone region by performing an operation having a result substantially equivalent to a result of the following first integration
-
s in a localized fatigue-prone region of a structure from a representation of the structure, said method comprising;
Specification