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Nonlinear in-plane buckling of small-curved and large-curved FG porous microbeams via strain gradient-based isogeometric collocation formulations

202428 citationsOpen accessUniversity of South Africa

In plain language

This research explores the nonlinear in-plane stability and buckling characteristics of curved microbeams subjected to thermomechanical loads. The microbeams are made from functionally graded porous metal reinforced with nanofillers, configured with clamped ends across small, medium, and large curvatures. Using strain gradient elasticity combined with a third-order shear flexible beam framework, an isogeometric collocation formulation was developed to analyse microsize-dependent equilibrium states. Results show that small-curved microbeams display no initial buckling limit load until subjected to an adequate temperature rise. Medium-curved microbeams undergo limit instability buckling, where strain gradient elasticity predicts a 6.21 percent higher upper limit load and a 15.07 percent higher lower limit load than classical theory. Large-curved microbeams experience bifurcation buckling, similarly yielding increases of 8.23 percent for upper limit loads and 12.94 percent for lower limit loads when microstructural effects are accounted for.

Key takeaways

  • Small-curved porous microbeams reinforced with nanofillers show no initial limit load, requiring a sufficient temperature rise before buckling instability appears.
  • Medium-curved microbeams undergo limit instability buckling, with strain gradient elasticity increasing upper and lower limit loads by 6.21 percent and 15.07 percent over classical predictions.
  • Large-curved microbeams demonstrate bifurcation buckling, with strain gradient elasticity raising upper and lower limit loads by 8.23 percent and 12.94 percent.
  • Isogeometric collocation formulations using Greville abscissae provide high accuracy and continuity for higher-order approximations of curved microstructures.

Why it matters

Predicting how curved micro-components buckle under mechanical and thermal stresses is vital for structural integrity in micro-engineering. Conventional models can miscalculate load limits because they ignore microscopic size effects. By demonstrating that microstructural gradient effects notably enhance buckling thresholds across different beam curvatures, this work provides computational techniques that ensure more precise structural analysis for advanced porous composite materials.

Commercialisation angle

The abstract does not indicate an application pathway.

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Abstract

In the current investigation, for the first time, the changes in the limit loads and equilibrium branches associated with the nonlinear in-plane stability characteristics of curved microbeams are explored in the presence of different microstructural gradient tensors. In this regard, multiple microsize-dependent equilibria are analyzed relevant to thermomechanical loaded small-curved, medium-curved, and large-curved microbeams made of functionally graded porous (FGP) metal reinforced with nanofillers possessing clamped end supports. To this purpose, based upon the strain gradient elasticity within the framework of the third-order shear flexible curved beam model, the isogeometric collocation formulations incorporating Greville abscissae are constructed resulting in higher-continuity characters as well as remarkable accuracy for higher-order approximations. It is deduced that for the small-curved FGP reinforced microbeam, no limit load can be found due to the absence of the buckling phenomenon, but after rising the temperature by an enough amount, the initial instability mode appears. However, for the medium-curved FGP reinforced microbeam, the limit instability mode of buckling occurs which results in the normalized upper limit load equal to 0.7161 based on the classical theory and 0.7606 based on the strain gradient elasticity (6.21% enhancement). Also, it results in the normalized lower limit load equal to 0.3060 based on the classical theory and 0.3521 based on the strain gradient elasticity (15.07% enhancement). On the other hand, for the large-curved FGP reinforced microbeam, the bifurcation mode of buckling occurs which results in the normalized upper limit load equal to 1.0494 based on the classical theory and 1.1358 based on the strain gradient elasticity (8.23% enhancement). Also, it results in the normalized lower limit load equal to 0.2225 based on the classical theory and 0.2513 based on the strain gradient elasticity (12.94% enhancement).

Research topics

  • Nonlocal and gradient elasticity in micro/nano structures
  • Composite Structure Analysis and Optimization
  • Numerical methods in engineering

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DOI: 10.1016/j.compstruct.2024.117969

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