System and method for estimating nominal stress using finite element calculated stress

Abstract

The systems and methods described herein are configured to estimate nominal stresses using finite element (FE) stress calculations without manual calculations, specific mesh density requirements, or identification of specific geometric parameters, such as plate thickness. The systems and methods described herein can be used to identify nominal stresses in welded structures and components, as well as in non-welded components that have stress concentrations for other reasons. The systems and methods described herein also allow for the use of easily available FE stress results in a consistent manner, as well as providing user feedback on the accuracy of the nominal stress approximation. In addition, the systems and methods described herein are generally faster and less error-prone than conventional techniques, and are relatively insensitive to the mesh density of the FE stress calculations.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to and the benefit of U.S. Provisional Application No. 62 / 751,186, filed on October 26, 2018, entitled “Systems and Methods to Estimate Nominal Stress Using Finite Element Calculated Stress,” which is hereby incorporated by reference in its entirety for all purposes. Background Art

[0003] The present disclosure generally relates to the estimation of nominal stresses in welded structures and components or in non-welded components having stress raisers for other reasons. More specifically, embodiments of the present disclosure relate to the estimation of nominal stresses using finite element (FE) calculated stresses.

[0004] This section is intended to introduce the reader to various aspects of the art that may be related to various aspects of the present disclosure, which are described below. It is believed that this discussion helps to provide the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Therefore, it should be understood that these statements are to be read in this context and not as admissions of prior art.

[0005] Welding fatigue prediction standards usually allow the use of nominal stress metrics. However, stresses in welded structures are usually calculated using FE calculation methods, which do not directly calculate nominal stresses. Instead, nominal stresses must usually be estimated based on, for example, separate calculations. For example, some conventional methods of approximating nominal stresses include using FE-generated forces and moments in combination with manual calculations, while other methods use coarse FE meshes to minimize the local stress rise effects at the root of the weld joint, and other methods extrapolate FE-calculated stresses based on certain geometric parameters (such as plate thickness), which may not be easily identifiable in practical applications. Typically, these conventional methods tend to be relatively time-consuming, error-prone, or, in the case of using coarse FE mesh methods, somewhat arbitrary or lengthy. Summary of the invention

[0006] Some embodiments that are commensurate in scope with the original claimed subject matter are summarized below. These embodiments are not intended to limit the scope of the present disclosure, but these embodiments are only intended to provide a brief summary of certain disclosed embodiments. In fact, the present disclosure can encompass various forms that may be similar or different from the embodiments set forth below.

[0007] In one embodiment, a method includes using FE analysis to calculate stress at a plurality of points from a base point along a baseline of a structural component. The method also includes identifying two or more points of the plurality of points having calculated stresses that are determined to be unaffected by stress riser effects at the base point. The method also includes estimating a nominal stress at the base point by extrapolating the calculated stresses of the two or more points of the plurality of points to the base point.

[0008] In another embodiment, a method includes calculating stress at a plurality of points from a base point along a baseline of a structural component using FE analysis. The method also includes identifying two or more points in the plurality of points by evaluating second derivatives of the calculated stresses of adjacent points in the plurality of points. The method also includes estimating a nominal stress at the base point by extrapolating the calculated stresses of the two or more points in the plurality of points to the base point.

[0009] In yet another embodiment, a non-transitory computer-readable medium includes instructions for estimating nominal stress. The instructions are configured to calculate stress at a plurality of points along a baseline of a structural component from a base point using FE analysis. The instructions are further configured to identify two or more points in the plurality of points by evaluating second-order derivatives of the calculated stresses of adjacent points in the plurality of points. The instructions are further configured to estimate the nominal stress at the base point by extrapolating the calculated stresses of the two or more points in the plurality of points to the base point. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] These and other features, aspects and advantages of the present disclosure will become better understood when the following detailed description is read with reference to the accompanying drawings, wherein like characters refer to like parts throughout the drawings, and wherein:

[0011] Figure 1 illustrates an embodiment of a control system configured to estimate nominal stress in a structural component according to an embodiment of the present disclosure;

[0012] Figure 2 is a perspective view of a welded structural component according to an embodiment of the present disclosure, which can be seen through Figure 1 The control system estimates the nominal stress for the welded structural component;

[0013] Figure 3 is a perspective view of a non-welded structural component according to an embodiment of the present disclosure, which can be Figure 1 The control system estimates the nominal stress for the non-welded structural component;

[0014] Figure 4A The diagram shows a method according to an embodiment of the present disclosure along the path such as Figure 2 and 3A graph of stress values ​​at various points of a baseline of a structural component such as the structural component illustrated in FIG.

[0015] Figure 4B The embodiment according to the present disclosure is illustrated Figure 4A an enlarged view of the graph illustrated in FIG.

[0016] Figure 5 is a flow chart of a method for estimating nominal stress in a structural component according to an embodiment of the present disclosure, which method can be performed by Figure 1 control system execution; and

[0017] Figure 6 The diagram shows a method according to an embodiment of the present disclosure along the path such as Figure 2 and 3 Graphs of the spline fitted stress and the filtered second derivative of the stress at various points of the baseline of a structural component such as the structural component illustrated in FIG. DETAILED DESCRIPTION

[0018] One or more specific embodiments of the present disclosure will be described below. In an effort to provide a brief description of these embodiments, all features of the actual implementation may not be described in the specification. It should be understood that in the development of any such actual implementation, as in any engineering or design project, many implementation-specific decisions must be made to achieve the developer's specific goals, such as in accordance with system-related and business-related constraints, which may vary from implementation to implementation. In addition, it should be understood that such development work may be complex and time-consuming, but for ordinary technicians who benefit from the present disclosure, this will still be a routine task of design, production and manufacturing.

[0019] When introducing elements of various embodiments of the present disclosure, the articles "a," "an," and "the" are intended to mean that there are one or more elements. The terms "comprising," "including," and "having" are intended to be inclusive, and mean that there may be additional elements in addition to the listed elements. Additionally, it should be understood that reference to "one embodiment" or "an embodiment" of the present disclosure is not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features.

[0020] Embodiments described herein include systems and methods for estimating nominal stresses using FE stress calculations without manual calculations, specific mesh density requirements, identification of specific geometric parameters (such as plate thickness) or finite element representations of welds. The systems and methods described herein can be used to identify nominal stresses in the parent metal of welded structures and components, as well as in non-welded components that have stress concentrations for other reasons. The systems and methods described herein also allow the use of easily available FE stress results in a consistent manner, as well as providing user feedback on the accuracy of the nominal stress approximation. In addition, the systems and methods described herein are generally faster and less error-prone than conventional techniques described herein, and are relatively insensitive to the mesh density of FE stress calculations. As described herein, the term "nominal stress" is intended to exclude certain stress concentration effects. Therefore, as described herein, it is assumed that the nominal stress along any one baseline exhibits linear behavior at a distance from a base point (such as a weld joint root or stress concentration), where the nonlinear effects from the base point are no longer dominant. In some embodiments, multiple baselines may be employed, and the nominal stress is assumed to exhibit linear behavior along each baseline. Additionally, in certain embodiments, a linearity check may be performed to verify that the stress exhibits linear behavior at a certain distance from a base point.

[0021] Figure 1 An embodiment of a control system 10 configured to estimate a nominal stress in a structural component 12 according to an embodiment of the present disclosure is illustrated. As illustrated, in certain embodiments, the control system 10 includes a storage device 14 (e.g., a non-transitory computer-readable medium) and a processor 16 configured to execute computer-readable instructions stored on the storage device 14. In certain embodiments, the processor 16 may include a plurality of processors, one or more general-purpose microprocessors, one or more special-purpose microprocessors, and / or one or more application-specific integrated circuits (ASICs), or some combination thereof. For example, in certain embodiments, the processor 16 may include one or more reduced instruction set (RISC) processors, advanced RISC machine (ARM) processors, performance-optimized processors with enhanced RISC (PowerPC) processors, field programmable gate array (FPGA) integrated circuits, graphics processing units (GPUs), or any other suitable processing devices.

[0022] In some embodiments, the storage device 14 may include volatile memory (such as random access memory (RAM)), non-volatile memory (such as read-only memory (ROM)), flash memory, or any combination thereof. The storage device 14 may store a variety of information that may be used for various purposes. For example, in some embodiments, the storage device 14 may store processor-executable instructions (e.g., firmware or software) for execution by the processor 16, such as instructions for estimating the nominal stress in the structural component 12. In addition, in some embodiments, the processor 16 may store information related to the nominal stress in one or more storage devices 18. For example, in some embodiments, the one or more storage devices 18 (e.g., non-volatile storage) may include ROM, flash memory, hard drive, or any other suitable optical, magnetic or solid-state storage medium, or a combination thereof. In addition, in some embodiments, the processor 16 may be configured to output a control signal 20 that may be used to control the manufacture of one or more subsequent structural components 12.

[0023] As described in greater detail herein, the processor 16 may execute instructions stored in the storage device 14 that are related to calculating stresses at a plurality of points of the structural component 12 using the FE analysis algorithm 22. To this end, in certain embodiments, the processor 16 may utilize one or more models 24 of the structural component 12, which may be stored, for example, in the storage device 14 or one or more storage devices 18 and / or may be received from an information source 26 external to the control system 10. In certain embodiments, once the processor 16 has calculated the stresses at the plurality of points of the structural component 12 using the FE analysis algorithm 22, the processor 16 may identify two or more points of the plurality of points along a baseline (e.g., in a linear direction) of the structural component 12 that have corresponding calculated stresses that are not affected by stress riser effects at a base point of the structural component 12 (e.g., a weld joint root of a welded structural component 12 where welded components are closest to one another, a stress concentration of a non-welded structural component 12, or some other point where stress riser effects may occur). As described in more detail herein, in certain embodiments, the processor 16 may identify two or more points along the baseline of the structural component 12 as having corresponding calculated stresses that are not affected by stress riser effects at the base points of the structural component 12 by, for example, evaluating second derivatives of the calculated stresses at adjacent points among the plurality of points of the structural component 12 .

[0024] It should be noted that in some embodiments, the weld bead geometry need not be included in the FE idealization using the FE analysis algorithm 22. Rather, in some embodiments, the weld joint may be idealized using coincident nodes or joint contact without penetration. Additionally, in some embodiments, the instructions executed by the processor 16 may assume that stresses are due only to external forces and moments; however, in other embodiments, a more complex stress analysis may be performed. It is also noted that in some embodiments, the instructions executed by the processor 16 may assume that stresses at locations sufficiently far from the weld joint root or other stress concentrations will decrease linearly with distance from the weld joint root, stress concentration or other point where stress riser effects may occur; however, again, in other embodiments, a more complex stress analysis may be performed. In some embodiments, the processor 16 may perform a linearity check to verify that stresses do in fact exhibit linear characteristics at a distance from a base point.

[0025] In certain embodiments, once the processor 16 has identified two or more points along the baseline of the structural component 12 that have corresponding calculated stresses that are not affected by stress riser effects at the base point of the structural component 12, the processor 16 may estimate the nominal stress at the base point of the structural component 12, for example, by extrapolating the calculated stresses at the identified two or more points back to the base point of the structural component 12. Thus, as described in more detail herein, the processor 16 may estimate the nominal stress at the base point of the structural component 12 with little sensitivity to the mesh density used in the FE analysis algorithm 22. More specifically, the embodiments described herein use a relatively simple extrapolation of the calculated stresses along the baseline of the structural component 12 (e.g., in any linear direction) based on two or more points along the baseline that are determined by the processor 16 to have corresponding calculated stresses that are not affected by stress riser effects at the base point of the structural component 12.

[0026] The embodiments described herein may be equally applicable to estimating nominal stresses in welded structural components 12 as well as non-welded structural components 12. For example, Figure 2 is a perspective view of a welded structural member 12 according to an embodiment of the present disclosure, which can be seen through Figure 1 The control system 10 estimates the nominal stress for the welded structural component 12. Figure 2, the welded structural component 12 includes a base member 28 and an auxiliary member 30 welded to the base member 28 via a fillet weld 32 on the opposite side of the auxiliary member 30. However, it will be understood that the embodiments described herein may be equally applicable to estimating the nominal stress at other types of welds. As described herein, in certain embodiments, the weld joint root (e.g., the intersection between the base member 28 and the auxiliary member 30 for the weld 32) may be considered a base point 40 at which the stress may be determined by the fillet weld 32. Figure 1 The control system 10 estimates the nominal stress.

[0027] In contrast, Figure 3 is a perspective view of a non-welded structural component 12 according to an embodiment of the present disclosure, which can be seen through Figure 1 The control system 10 estimates the nominal stress for the non-welded structural component 12. Figure 3 As shown in FIG, the non-welded structural component 12 includes a single (eg, integral) structural component 34. However, as shown, Figure 3 The integral structural member 34 of the non-welded structural component 12 includes one or more stress concentrations 36 (e.g., holes or other structural features) at which the nominal stress may be different due to the structural nature of the one or more stress concentrations 36. As described herein, in some embodiments, Figure 3 The one or more stress concentrations 36 of the non-welded structural component 12 shown in FIG. 1 may be considered as base points 40 at which stress concentrations may be determined by Figure 1 The control system 10 estimates the nominal stress.

[0028] like Figure 2 and 3 As shown in FIG. 1 , regardless of the specific type of base point (eg, weld 32 or stress concentration 36 ), the structural component 12 may be composed of Figure 1 The control system 10 (e.g., by the processor 16 executing the FE analysis algorithm 22) is analyzed as having a certain mesh density to calculate the stress at certain points (e.g., intersections of the mesh) of the structural component 12. However, as described in more detail herein, embodiments of the present disclosure are able to estimate the nominal stress at the base points 40 of the structural component 12 without being significantly affected by the specific mesh density used by the FE analysis algorithm 22. Specifically, as well as Figure 2 and 3As illustrated in FIG. 1 , in certain embodiments, once the stresses at multiple points of the structural component 12 are calculated using the FE analysis algorithm 22, the processor 16 may consider the FE-calculated stresses for each individual point along a straight baseline 38 (e.g., in a linear direction) extending from a base point 40 (e.g., at the root of a weld joint associated with a weld 32 or stress concentration 36) along the baseline 38 to a distal point that is a linear distance away from the base point 40.

[0029] As described in greater detail herein, embodiments of the present disclosure are capable of estimating the nominal stress at a base point 40 of a structural component 12 regardless of the specific geometric features of the structural component 12. More specifically, by estimating the nominal stress at a base point 40 of the structural component 12 by considering the FE calculated along a baseline 38 extending from the base point 40, the embodiments described herein eliminate the need to consider specific geometric features of the structural component 12 by instead identifying points along the baseline 38 having calculated stresses that are determined to be unaffected by stress riser effects at the base point 40.

[0030] To further illustrate Figure 1 how the control system 10 estimates the nominal stress at the base point 40 of the structural component 12, Figure 4A The diagram shows a method according to an embodiment of the present disclosure along the path such as Figure 2 and 3 Graph of stress values ​​at various points of the baseline 38 of a structural component 12 such as the structural component 12 illustrated in FIG. In particular, Figure 4A A series 42 of FE calculated stress values ​​at various locations along the baseline 38 of the structural component 12 (e.g., as determined by the processor 16 of the control system 10 using the FE analysis algorithm 22) are illustrated. It will be appreciated that a value of 0 for the position axis is similar to a value of 0 for the structural component 12 (e.g., at a position axis corresponding to the position axis). Figure 2 The weld joint root associated with the weld 32 of the welded structural component 12 shown in FIG. Figure 3 ) base point 40 at the stress concentration point 36 of the non-welded structural component 12 shown in FIG.

[0031] like Figure 4A , the processor 16 of the control system 10 may identify two or more points 44 of the series 42 of FE-calculated stress values ​​where the FE-calculated stress values ​​are not affected by stress riser effects at the base point 40 of the structural component 12. Figure 4A40 of the structural component 12, the processor 16 may then extrapolate the FE-calculated stress values ​​of the two or more points 44 back to a value of 0 on the position axis, which also corresponds to the base point 40 of the structural component 12. The processor 16 of the control system 10 then determines that the intersection 48 of the extrapolated line 46 with the stress axis is the estimated nominal stress value for the base point 40 of the structural component 12.

[0032] In certain embodiments, to identify two or more points 44 having FE-calculated stress values ​​that are not affected by the stress riser effect at the base point 40 of the structural component 12, the processor 16 of the control system 10 may compare the rate of change (e.g., second derivative) of the slope of the series 42 of FE-calculated stress values ​​for adjacent points along the position axis (e.g., which also correspond to points along the base line 38 of the structural component 12). It will be appreciated that the slope of the calculated stress at any given point along the position axis will be equal to the slope of the calculated stress at that particular point. , and the rate of change of the slope of the calculated stress at any given point along the position axis (e.g., the second derivative) will be equal to , where s equals the calculated stress (ie, along the stress axis), and x equals the distance from the base point 40 along the baseline 38 of the structural component 12 (ie, along the position axis).

[0033] To further illustrate Figure 1 how the control system 10 of the structural component 12 identifies two or more points 44 having FE-calculated stress values ​​that are not affected by the stress riser effect at the base point 40 of the structural component 12, Figure 4B The embodiment according to the present disclosure is illustrated Figure 4A In particular, Figure 4B Twelve different points 50, 52, 54, 56, 58, 60, 62, 64, 66, 68, 70 and 72 of the series 42 of FE calculated stress values ​​are illustrated.

[0034] In some embodiments, the processor 16 of the control system 10 may identify the point 62 as one of the two or more points 44 having a FE-calculated stress value that is not affected by the stress riser effect at the base point 40 of the structural component 12. In particular, in some embodiments, the processor 16 of the control system 10 may make this determination based on the fact that a given number of points adjacent to the point 62 have second-order derivatives that deviate from the second-order derivative at the point 62 by no more than a threshold percentage. For example, in some embodiments, the processor 16 of the control system 10 may determine that the points 58, 60, 62, 64, and 66 all have second-order derivatives that deviate from each other by no more than 10%, no more than 5%, no more than 2%, no more than 1%, or less. Therefore, the processor 16 of the control system 10 may determine that the point 62 is one of the two or more points 44 having a FE-calculated stress value that is not affected by the stress riser effect at the base point 40 of the structural component 12. It will be appreciated that in such an embodiment, the processor 16 of the control system 10 identifies the point 62 as one of the two or more points 44 having FE-calculated stress values ​​that are not affected by the stress riser effects at the base point 40 of the structural component 12 by analyzing a subset of points adjacent to the point 62 (e.g., the point 62 itself, along with two points on either side of the point 62) such that five points are included in the subset of points. However, it will be appreciated that in other embodiments, any number of points may be used for the subset of points, such as three points, seven points, nine points, or more.

[0035] Figure 5 is a flow chart of a method 74 for estimating nominal stress in a structural component 12 according to an embodiment of the present disclosure. The method 74 may be performed by Figure 1 In particular, as described in more detail herein, Figure 1 The processor 16 of the control system 10 may be configured to execute instructions stored in the storage device 14 of the control system 10, wherein the instructions are configured to execute Figure 5 The method 74 is shown in FIG. Figure 5 As illustrated in block 76 of FIG. 1 , in some embodiments, the instructions may include instructions for using the FE analysis algorithm 22 to calculate a baseline 38 along the structural component 12 from the base point 40 (eg, as shown in FIG. 1 ). Figure 2 The weld joint root associated with the weld 32 of the welded structural component 12 as shown in FIG. Figure 3 For example, in some embodiments, the processor 16 of the control system 10 may be configured to execute the FE analysis algorithm 22 based on one or more models 24 of the structural component 12 to calculate the stress at multiple points along the baseline 38 of the structural component 12.

[0036] In addition, if Figure 5 As illustrated in block 78 of , in some embodiments, the instructions may include instructions for identifying two or more points 44 of the plurality of points along the base line 38 of the structural component 12 that have FE-calculated stress values ​​that are determined to be unaffected by the stress riser effect at the base point 40 of the structural component 12. For example, in some embodiments, the processor 16 of the control system 10 may be configured to identify the two or more points 44 that have FE-calculated stress values ​​that are determined to be unaffected by the stress riser effect at the base point 40 of the structural component 12 by comparing second-order derivatives of the FE-calculated stress values ​​of adjacent points, such as with respect to Figure 4B Described in more detail.

[0037] In addition, if Figure 5 As illustrated in block 80 of FIG. 1 , in some embodiments, the instructions may include instructions for estimating the nominal stress at the base point 40 of the structural component 12 by extrapolating the FE-calculated stress values ​​for the identified two or more points 44 of the plurality of points back to the base point 40 of the structural component 12, e.g., as described with respect to FIG. Figure 4A As described herein, in certain embodiments, the control system 10 may use the estimated nominal stress at the base point 40 of the structural component 12, for example, to output a control signal (e.g., a control signal 20, such as Figure 1 ), which may be used to control the manufacture of one or more subsequent structural components 12. For example, in some embodiments, if the processor 16 of the control system 10 estimates the nominal stress at the root of the weld joint associated with the weld 32 of the welded structural component 12 to be higher (or lower) than expected, the processor 16 may output a control signal (e.g., a control signal 20, such as Figure 1 ), for the subsequent manufacture of the welded structural component 12.

[0038] In certain embodiments, modeling and simulation performed by the control system 10 may begin by creating a baseline 38 (or multiple baselines 38) perpendicular to the weld region of interest. Figure 2 , the weld region of interest may include a weld joint root associated with weld 32 (e.g., at the intersection of components 28 30), and a baseline 38 perpendicular to the weld region of interest may include a straight baseline 38 extending from a base point 40. Typically, baseline 38 is directly located at the component of interest (i.e., the component that will be damaged first, e.g., Figure 2, 28). The control system 10 may then create a simulation study and apply materials for the components 28, 30, one or more loads 82 on the components 28, 30, and the boundary conditions of the components 28, 30. The control system 10 may then model component contacts reflecting the weld 32, such as joint contacts on the edges of the welded components 28, 30 and no-penetration contacts between the components 28, 30. The control system 10 may then mesh the structural component 12. In certain embodiments, mesh control (e.g., in conjunction with a fine mesh option) may be applied by the control system 10 in the weld region of interest. The control system 10 may then perform the study and ensure, for example, that the structural component 12 reacts appropriately to the load 82 by considering the displacement deformation results to ensure that the structural component 12 is appropriately constrained. The control system 10 may then check the von Mises (or other) stress results by probing the baseline 38. In certain embodiments, the control system 10 may ensure that the first node value probed resides on the root of the weld joint. Note that when using a metric other than von Mises stress, in some embodiments control system 10 may ensure that the selected metric references a coordinate system oriented relative to baseline 38. Control system 10 may then extract stress and position values ​​along baseline 38.

[0039] Once the stress and position values ​​are extracted by the control system 10, the data manipulation performed by the control system 10 may begin by evenly spacing the position data if it is not already evenly spaced. The control system 10 may then spline fit the stress versus position data (e.g., in some embodiments, using fourth-order splines). The control system 10 may then double-difference the stress with respect to the position (e.g., in some embodiments, using a central difference method). The control system 10 may then filter the double-differenced data (e.g., in some embodiments, using a Butterworth filter with a low-pass, forward and backward method with a cutoff frequency of 0.07 and a stop frequency of one), and plot both the spline-fitted stress versus position data and the filtered second-order derivative of the stress versus position data. Figure 6 The diagram shows a method according to an embodiment of the present disclosure along the path such as Figure 2 and 3 8 and a graph of the filtered second derivative of stress 86 at various points of the baseline 38 of a structural component 12 such as illustrated in FIG. The control system 10 may then calculate the absolute difference of the filtered second derivative of stress 86 between each value of x (e.g., to two decimal places in certain embodiments).

[0040] The control system 10 may then identify a first instance along the position (i.e., x) axis where a certain number of consecutive points (e.g., in some embodiments, three consecutive points, five consecutive points, seven consecutive points, nine consecutive points, or more) have an absolute difference in the filtered second derivative of the stress 86 between adjacent points that is less than a given threshold percentage (e.g., in some embodiments, less than 10%, less than 5%, less than 2%, less than 1%, or less). It will be appreciated that this first identified instance is Figure 4A In some embodiments, the control system 10 may identify a second point 44 at a set distance from the first identified point 44 (e.g., in some embodiments, 1.5 times the position value along the position axis), and both identified points 44 may be determined to have corresponding calculated stresses that are not affected by the stress riser effect at the base point 40 of the structural component 12.

[0041] In some embodiments, if the control system 10 determines that the calculated stress associated with the second identified point 44 is greater than a given threshold value (e.g., greater than 10%, greater than 5%, greater than 2%, greater than 1%, or less, in some embodiments) of the calculated stress associated with the first identified point 44, the control system 10 may rerun the analysis only on the data preceding and including the first identified point 44 along the position axis. In other words, the control system 10 may treat the data beyond the first identified point 44 as exhibiting nonlinearity that should be excluded from the analysis. In other cases, the control system 10 may perform the analysis using two (or more) identified points 44 (and, in some embodiments, all data between those points 44). Figure 4A In some embodiments, the control system 10 can ensure that the R-squared value of the linear regression is greater than a given threshold (e.g., in some embodiments, greater than 0.7, greater than 0.75, greater than 0.8, greater than 0.85, greater than 0.9, or greater). Figure 4A Described in more detail, the y-intercept value of the linear regression (ie, the value of the linearized stress at a position value of 0) represents the estimated nominal stress at the base point 40 .

[0042] As described herein, embodiments of the present disclosure provide advantages over conventional systems and methods for determining nominal stresses in the following respects: no manual calculations are required; no specific geometry of the structural component 12 is required in the FE representation used by the FE analysis algorithm 22; the mesh density used by the FE analysis algorithm 22 has little effect on the estimated nominal stress; and the extrapolation of the nominal stress does not require identification of specific geometric parameters (such as plate thickness). In addition, as described in more detail herein, the nominal stress in a non-welded structural component 12 having stress concentrations 36 due to geometric features, load application, or other features can also be estimated in a manner similar to the welded structural component 12.

[0043] Although only certain features of the present disclosure have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is therefore to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the present disclosure. The technology presented and claimed herein is referenced and applied to material objects and specific examples of a practical nature, which provably improve the art, and is therefore not abstract, intangible, or purely theoretical. In addition, if any claim attached to the end of this specification contains one or more elements designated as "means for [performing] ... [function]" or "steps for [performing] ... [function]", it is intended to interpret such elements in accordance with 35 U.S.C. § 112 (f). However, for any claim containing elements designated in any other manner, it is intended not to interpret such elements in accordance with 35 USC § 112 (f).

Claims

1. A method comprising: calculating stresses at a plurality of points along a baseline of the structural component from a base point using finite element analysis via the control system; identifying, via the control system, two or more points of the plurality of points having calculated stresses determined to be unaffected by stress riser effects at the base point, wherein identifying the two or more points of the plurality of points includes comparing second order derivatives of the calculated stresses of adjacent points of the plurality of points, and wherein identifying each of the two or more points of the plurality of points includes identifying a subset of points adjacent to each point, wherein the second order derivative of each of the subset of points is within a threshold percentage of each other; estimating, via the control system, a nominal stress at the base point by extrapolating the calculated stresses at the identified two or more of the plurality of points to the base point; and Via the control system, welding process variables of the control system are adjusted based at least in part on the estimated nominal stress. The method of claim 1 , wherein the subset of points comprises five points. The method of claim 1 , wherein the threshold percentage is 5%.

4. The method of claim 1, wherein the method is independent of the weld bead geometry of the structural component.

5. The method of claim 1, wherein the method is not significantly affected by a specific mesh density of the finite element analysis.

6. The method of claim 1, wherein the structural component comprises a welded component including a weld joint root at the base point.

7. A method comprising: calculating stresses at a plurality of points along a baseline of the structural component from a base point using finite element analysis via the control system; identifying, via the control system, two or more of the plurality of points by evaluating second order derivatives of calculated stresses of adjacent points in the plurality of points; wherein identifying each of the two or more of the plurality of points comprises identifying a subset of points adjacent to the respective point, wherein the second order derivative of each of the subset of points is within a threshold percentage of each other; estimating, via the control system, a nominal stress at the base point by extrapolating the calculated stresses at the identified two or more of the plurality of points to the base point; and Via the control system, welding process variables of the control system are adjusted based at least in part on the estimated nominal stress. The method of claim 7 , wherein the subset of points comprises five points.

9. The method of claim 7, wherein the threshold percentage is 5%.

10. The method of claim 7, wherein the method is independent of the weld bead geometry of the structural component.

11. The method of claim 7, wherein the method is not significantly affected by a specific mesh density of the finite element analysis.

12. The method of claim 7, wherein the structural component comprises a welded component including a weld joint root at the base point.

13. A non-transitory computer readable medium comprising instructions for estimating a nominal stress and controlling a control system, wherein the instructions are configured to: calculating stresses at a plurality of points along a baseline of the structural component from a base point using finite element analysis; identifying two or more of the plurality of points by evaluating second-order derivatives of calculated stresses of adjacent points in the plurality of points, wherein the instructions are configured to identify each of the two or more of the plurality of points by identifying a subset of points adjacent to the respective point, wherein the second-order derivative of each of the subset of points is within a threshold percentage of each other; estimating a nominal stress at the base point by extrapolating the calculated stresses of the two or more points of the plurality of points to the base point; as well as A welding process variable of the control system is adjusted based at least in part on the estimated nominal stress.

14. The non-transitory computer readable medium of claim 13, wherein the instructions are independent of a weld bead geometry of the structural component.

15. The non-transitory computer readable medium of claim 13, wherein the instructions are not significantly affected by a particular mesh density of the finite element analysis.

16. The non-transitory computer readable medium of claim 13, wherein the structural component comprises a weld component including a weld joint root at the base point.

17. The non-transitory computer-readable medium of claim 13, wherein the subset of points includes five points.

18. The non-transitory computer-readable medium of claim 13, wherein the threshold percentage is 5%.

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