Systems and methods to estimate nominal stress using finite element calculated stress

Abstract

Systems and methods described herein are configured to estimate nominal stress using finite element (FE) stress calculations, without hand calculations, specific mesh density requirements, or identifying specific geometric parameters such as plate thickness. The systems and methods described herein may be utilized to identify nominal stress in welded structures and components, and also in non-welded components that have stress raisers due to other causes. The systems and methods described herein also allow readily available FE stress results to be utilized in a consistent manner, as well as providing user feedback regarding the accuracy of the nominal stress approximations. Furthermore, the systems and methods described herein are generally faster and less error prone than conventional techniques, and are relatively insensitive to mesh density of the FE stress calculations.

1 . A method comprising:
 using finite element (FE) analysis to calculate stresses at a plurality of points from a base point along a base line of a structural component;   identifying two or more points of the plurality of points having a calculated stress that is determined to be unaffected by stress raising effects at the base point; and   estimating a nominal stress at the base point by extrapolating calculated stresses of the two or more points of the plurality of points to the base point.   
     
     
         2 . The method of  claim 1 , wherein identifying the two or more points of the plurality of points comprises comparing second derivatives of calculated stress for adjacent points of the plurality of points. 
     
     
         3 . The method of  claim 2 , wherein identifying each point of the two or more points of the plurality of points comprises identifying a subset of points adjacent each point, wherein a second derivative of each of the subset of points is within a threshold percentage of each other. 
     
     
         4 . The method of  claim 3 , wherein the subset of points comprises five points 
     
     
         5 . The method of  claim 3 , wherein the threshold percentage is 5%. 
     
     
         6 . The method of  claim 1 , wherein the method is not dependent upon a geometry of the structural component. 
     
     
         7 . The method of  claim 1 , wherein the method is not dependent upon a mesh density of the FE analysis. 
     
     
         8 . The method of  claim 1 , wherein the structural component comprises a welded component comprising a weld joint root at the base point. 
     
     
         9 . The method of  claim 1 , wherein the structural component comprises a non-welded component comprising a stress raiser at the base point. 
     
     
         10 . A method comprising:
 using finite element (FE) analysis to calculate stresses at a plurality of points from a base point along a base line of a structural component;   identifying two or more points of the plurality of points by evaluating second derivatives of calculated stress for adjacent points of the plurality of points; and   estimating a nominal stress at the base point by extrapolating calculated stresses of the two or more points of the plurality of points to the base point.   
     
     
         11 . The method of  claim 10 , wherein identifying each point of the two or more points of the plurality of points comprises identifying a subset of points adjacent the respective point, wherein a second derivative of each of the subset of points is within a threshold percentage of each other. 
     
     
         12 . The method of  claim 11 , wherein the subset of points comprises five points 
     
     
         13 . The method of  claim 11 , wherein the threshold percentage is 5%. 
     
     
         14 . The method of  claim 10 , wherein the method is not dependent upon a geometry of the structural component. 
     
     
         15 . The method of  claim 10 , wherein the method is not dependent upon a mesh density of the FE analysis. 
     
     
         16 . The method of  claim 10 , wherein the structural component comprises a welded component comprising a weld joint root at the base point. 
     
     
         17 . The method of  claim 10 , wherein the structural component comprises a non-welded component comprising a stress raiser at the base point. 
     
     
         18 . A non-transitory computer readable medium comprising instructions for estimating nominal stresses, wherein the instructions are configured to:
 use finite element (FE) analysis to calculate stresses at a plurality of points from a base point along a base line of a structural component;   identify two or more points of the plurality of points by evaluating second derivatives of calculated stress for adjacent points of the plurality of points; and   estimate a nominal stress at the base point by extrapolating calculated stresses of the two or more points of the plurality of points to the base point.   
     
     
         19 . The non-transitory computer readable medium of  claim 18 , wherein the instructions are configured to identify each point of the two or more points of the plurality of points by identifying a subset of points adjacent the respective point, wherein a second derivative of each of the subset of points is within a threshold percentage of each other. 
     
     
         20 . The non-transitory computer readable medium of  claim 18 , wherein the instructions are not dependent upon a geometry of the structural component. 
     
     
         21 . The non-transitory computer readable medium of  claim 18 , wherein the instructions are not dependent upon a mesh density of the FE analysis. 
     
     
         22 . The non-transitory computer readable medium of  claim 18 , wherein the structural component comprises a welded component comprising a weld joint root at the base point. 
     
     
         23 . The non-transitory computer readable medium of  claim 18 , wherein the structural component comprises a non-welded component comprising a stress raiser at the base point.