{"title":"An Enriched Equilibrium Finite Element Method for Crack Problems With Direct Access to Stress Intensity Factors and Strict Error Estimation","authors":"Qisheng Zheng, Jike Liu, Li Wang","doi":"10.1002/nme.70097","DOIUrl":"https://doi.org/10.1002/nme.70097","url":null,"abstract":"<div>\u0000 \u0000 <p>This paper proposes an enriched equilibrium finite element method (EFEM) for addressing crack problems within the framework of linear elastic fracture mechanics and complementary energy principle. The key ingredient of enriched EFEM is to construct the equilibrated stress field using equilibrated tractions along with asymptotic enrichment. Specifically, an auxiliary field is employed to capture the asymptotic singular behavior of the near-tip stress field, while the traction-based equilibrium finite element accounts for the residual terms. The remarkable property of the proposed enriched EFEM is that the stress intensity factors (SIFs) and the stress fields are directly obtained with high accuracy, even on a very coarse mesh. Moreover, in combination with the compatible solution acquired by the enriched finite element method (FEM), strict estimation of the discretization error is obtained for crack problems by dual analysis. Numerical examples are finally conducted to verify the performance of the proposed method on strict error estimation and accurate computation of the SIFs.</p>\u0000 </div>","PeriodicalId":13699,"journal":{"name":"International Journal for Numerical Methods in Engineering","volume":"126 15","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144751670","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Celine Lauff, Maximilian Krause, Matti Schneider, Thomas Böhlke
{"title":"On the Influence of the Fiber Curvature on the Stiffness of Long Fiber Reinforced Composites","authors":"Celine Lauff, Maximilian Krause, Matti Schneider, Thomas Böhlke","doi":"10.1002/nme.70094","DOIUrl":"https://doi.org/10.1002/nme.70094","url":null,"abstract":"<p>The degree of curvature of fiber inclusions in fiber-reinforced composites impacts the elastic properties of the composite, but numerical studies of this effect are limited by the lack of efficient microstructure generators with fiber curvature control. We propose an extension to the fused Sequential Addition and Migration algorithm (<i>Int. J. Numer. Methods Eng.</i>, 125(22), e7573, 2024) to allow for the direct control of the average fiber curvature. To this end, we prescribe an averaged curvature parameter for the entire microstructure, while also constraining local curvature for every fiber to a maximum value. While local curvature is unambiguously defined, the choice of the averaged curvature parameter is not obvious. We introduce as a novel curvature measure the deviation from straight curve (DSC), which computes as the trace of the local second-order fiber orientation tensor's covariance for a single fiber. Averaging this over all fibers leads to a scalar averaged curvature parameter. Using this parameter, we define an optimization procedure for generating curved-fiber reinforced microstructures. We compare the microstructure generation capabilities of the proposed extension with the prior algorithm without curvature control and find that the extended algorithm is capable of realizing a significantly wider spectrum of curvatures. Finally, we study the influence of fiber curvature on elastic properties, and find that for an example composite of glass-fiber reinforced polypropylene, increased fiber curvature leads to a reduction of the Young's modulus by as much as 10%.</p>","PeriodicalId":13699,"journal":{"name":"International Journal for Numerical Methods in Engineering","volume":"126 15","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/nme.70094","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144751671","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ahmed Manguri, Domenico Magisano, Robert Jankowski
{"title":"Gradient-Based Weight Minimization of Nonlinear Truss Structures With Displacement, Stress, and Stability Constraints","authors":"Ahmed Manguri, Domenico Magisano, Robert Jankowski","doi":"10.1002/nme.70096","DOIUrl":"https://doi.org/10.1002/nme.70096","url":null,"abstract":"<p>This paper presents an effective and robust computational method of gradient-based methodology for weight minimization of geometrically nonlinear structures, considering 3D trusses as exemplary case study. The optimization framework can accommodate multiple different constraints: (i) bounds on the cross-sectional area of each design element, (ii) prescribed ranges for displacements and stresses, and (iii) nonlinear stability for geometries such as arches and domes. For large structures, this results in numerous optimization variables and constraints, including the highly nonlinear (ii) and (iii). Such constraints are evaluated consistently and simultaneously by combining path-following finite element analysis and null vector method. Typically, the gradient of the nonlinear structural response is approximated numerically, which is computationally intensive and can introduce inaccuracies deteriorating the optimization process. In contrast, this work derives a fully analytical gradient evaluation for nonlinear deformation, stress, and stability constraints. This is implemented directly within the finite element solver, enhancing robustness and computational efficiency of the optimization. Validation examples range from simple benchmarks to large structures.</p>","PeriodicalId":13699,"journal":{"name":"International Journal for Numerical Methods in Engineering","volume":"126 14","pages":""},"PeriodicalIF":2.7,"publicationDate":"2025-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/nme.70096","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144716693","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Product of Exponentials (POE) Splines on Lie-Groups: Limitations, Extensions, and Application to \u0000 \u0000 \u0000 S\u0000 O\u0000 (\u0000 3\u0000 )\u0000 \u0000 $$ SO(3) $$\u0000 and \u0000 \u0000 \u0000 S\u0000 E\u0000 (\u0000 3\u0000 )\u0000 \u0000 $$ SE(3) $$","authors":"Andreas Müller","doi":"10.1002/nme.70088","DOIUrl":"https://doi.org/10.1002/nme.70088","url":null,"abstract":"<p>Existing methods for constructing splines and Bézier curves on a Lie group <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>G</mi>\u0000 </mrow>\u0000 <annotation>$$ G $$</annotation>\u0000 </semantics></math> involve repeated products of exponentials deduced from local geodesics, w.r.t. a Riemannian metric, or rely on general polynomials. Moreover, each of these local curves is supposed to start at the identity of <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>G</mi>\u0000 </mrow>\u0000 <annotation>$$ G $$</annotation>\u0000 </semantics></math>. Both assumptions may not reflect the actual curve to be interpolated. This paper pursues a different approach to construct splines on <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>G</mi>\u0000 </mrow>\u0000 <annotation>$$ G $$</annotation>\u0000 </semantics></math>. Local curves are expressed as solutions of the Poisson equation on <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>G</mi>\u0000 </mrow>\u0000 <annotation>$$ G $$</annotation>\u0000 </semantics></math>. Therewith, the local interpolations satisfies the boundary conditions while respecting the geometry of <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>G</mi>\u0000 </mrow>\u0000 <annotation>$$ G $$</annotation>\u0000 </semantics></math>. A <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>k</mi>\u0000 <mtext>th</mtext>\u0000 </mrow>\u0000 <annotation>$$ kmathrm{th} $$</annotation>\u0000 </semantics></math>-order approximation of the solutions gives rise to a <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>k</mi>\u0000 <mtext>th</mtext>\u0000 </mrow>\u0000 <annotation>$$ kmathrm{th} $$</annotation>\u0000 </semantics></math>-order product of exponential (POE) spline. Algorithms for constructing 3rd- and 4th-order splines are derived from closed form expressions for the approximate solutions. Additionally, spline algorithms are introduced that allow prescribing a vector field the curve must follow at the interpolation points. It is shown that the established algorithms, where <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>k</mi>\u0000 <mtext>th</mtext>\u0000 </mrow>\u0000 <annotation>$$ kmathrm{th} $$</annotation>\u0000 </semantics></math>-order POE-splines are constructed by concatenating local curves starting at the identity, cannot exactly reconstruct a","PeriodicalId":13699,"journal":{"name":"International Journal for Numerical Methods in Engineering","volume":"126 14","pages":""},"PeriodicalIF":2.7,"publicationDate":"2025-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/nme.70088","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144705347","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}