Formulation and Finite Element Implementation of Dynamically Consistent Gradient Elasticity

Author(s):  
H. Askes ◽  
I.M. Gitman ◽  
T. Bennett
Meccanica ◽  
2021 ◽  
Author(s):  
Tobias Kaiser ◽  
Samuel Forest ◽  
Andreas Menzel

AbstractIn this contribution, a finite element implementation of the stress gradient theory is proposed. The implementation relies on a reformulation of the governing set of partial differential equations in terms of one primary tensor-valued field variable of third order, the so-called generalised displacement field. Whereas the volumetric part of the generalised displacement field is closely related to the classic displacement field, the deviatoric part can be interpreted in terms of micro-displacements. The associated weak formulation moreover stipulates boundary conditions in terms of the normal projection of the generalised displacement field or of the (complete) stress tensor. A detailed study of representative boundary value problems of stress gradient elasticity shows the applicability of the proposed formulation. In particular, the finite element implementation is validated based on the analytical solutions for a cylindrical bar under tension and torsion derived by means of Bessel functions. In both tension and torsion cases, a smaller is softer size effect is evidenced in striking contrast to the corresponding strain gradient elasticity solutions.


Author(s):  
R E Cornwell

There are numerous situations in machine component design in which curved beams with cross-sections of arbitrary geometry are loaded in the plane of curvature, i.e. in flexure. However, there is little guidance in the technical literature concerning how the shear stresses resulting from out-of-plane loading of these same components are effected by the component's curvature. The current literature on out-of-plane loading of curved members relates almost exclusively to the circular and rectangular cross-sections used in springs. This article extends the range of applicability of stress concentration factors for curved beams with circular and rectangular cross-sections and greatly expands the types of cross-sections for which stress concentration factors are available. Wahl's stress concentration factor for circular cross-sections, usually assumed only valid for spring indices above 3.0, is shown to be applicable for spring indices as low as 1.2. The theory applicable to the torsion of curved beams and its finite-element implementation are outlined. Results developed using the finite-element implementation agree with previously available data for circular and rectangular cross-sections while providing stress concentration factors for a wider variety of cross-section geometries and spring indices.


2014 ◽  
Vol 100 ◽  
pp. 138-154 ◽  
Author(s):  
Lanhao Zhao ◽  
Jia Mao ◽  
Xin Bai ◽  
Xiaoqing Liu ◽  
Tongchun Li ◽  
...  

2020 ◽  
Vol 2020 (0) ◽  
pp. J03139
Author(s):  
Shotaro KIKUCHI ◽  
Hiroaki MIYOSHI ◽  
Seishiro MATSUBARA ◽  
Dai OKUMURA

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