Geogrid Stabilization of Aggregates Evaluated via Local Stiffness Assessment

2021 ◽  
Author(s):  
Mingu Kang ◽  
Erol Tutumluer ◽  
Issam I. A. Qamhia ◽  
Han Wang ◽  
Jeb Tingle
Keyword(s):  
Local Stiffness

Comparative Evaluation of Foil Bearings With Different Compliant Structures for Improved Manufacturability

2017 ◽  
Author(s):  
K. Shalash ◽  
J. Schiffmann
Keyword(s):  
Cantilever Beam ◽  
Static Load ◽  
Measurement Tool ◽  
Reduced Order ◽  
Foil Bearings ◽  
Compliant Structure ◽  
Foil Bearing ◽  
Local Stiffness ◽  
Beam Foil ◽  
Bearing System

Potential geometrical deviations in bump foil bearings due to manufacturing uncertainty can have significant effects on both the local stiffness and clearance, and hence, affecting the overall bearing performance. The manufacturing uncertainty of bump type foil bearings was investigated, showing large geometrical deviations, using a developed measurement tool for the formed bump foils. A reduced order foil bearing model was used in a Monte Carlo simulation studying the effect of manufacturing noise on the onset of instability, highlighting the sensitivity of the rotor-bearing system to such manufacturing deviations. It was found that 30% of the simulated cases resulted improvements in stability, the remaining cases underperformed. Attempting to increase the robustness of the bearing, two other compliant structures replacing the classical gen-II bump foils were investigated from a manufacturing perspective. The first is a modified bump type Sinusoidal foil, and the second is the Cantilever beam foil. Consequently, quasi-static load-displacement tests were executed showing deviations in local clearance and stiffness for the classical bump type compliant structure compared to the other designs. It was found that the Cantilever beam foils yield more robustness compared to the bump type foils. Finally, an analytical model for the sequential engagement of the compliant structure is presented and validated with experimental measurements for both bump type and Cantilever structures.

scholarly journals The edge regions in tergites of the desert isopod Hemilepistus reaumuri: the transition from hard cuticle to flexible arthrodial membrane

2020 ◽  
Vol 126 (10) ◽  
Author(s):  
Franziska Ernst ◽  
Helge-Otto Fabritius ◽  
Erika Griesshaber ◽  
Wolfgang W. Schmahl ◽  
Andreas Ziegler
Keyword(s):  
Mechanical Properties ◽  
Anterior Part ◽  
Section Plane ◽  
Edge Region ◽  
Posterior Edge ◽  
Sagittal Section ◽  
Desert Habitat ◽  
Oriented Parallel ◽  
Local Stiffness ◽  
Hemilepistus Reaumuri

Abstract The arthrodial membrane is a thin and flexible type of cuticle that inserts at the edge regions of neighbouring rigid skeletal elements creating a flexible connection. In the present study, we analyzed the structure, mineral composition, calcite organization and local stiffness and hardness of edge regions that form transitions to the arthrodial membranes in the tergites of the desert isopod Hemilepistus reaumuri. For the transitions to the arthrodial membrane, the results show an increase in the thickness of the epicuticle at cost of the distal exocuticle and a calcite layer, an increase in the ratio of phosphorus to calcium and a decrease in the local mechanical properties. The posterior edge region contains an unusually large stack of unidirectionally oriented parallel fibrils projecting to the lateral sides. At the edge, it turns down into a long ventral cuticle overlapping an anterior part of the neighbouring tergite. It forms a thin arched gap between the tergites that can help reducing water loss through the arthrodial membrane and protects the arthrodial membrane upon predation. A thick ventral ridge near the transition to the arthrodial membrane carrying bristles can prevent sand grains from access to the arthrodial membrane. From the dorsal cuticle to the transition to the arthrodial membrane, calcite units become larger and single crystalline turning their c-axes orientation perpendicular to the sagittal section plane. Comparison with edge regions of the beach isopod Tylos europaeus reveal common characteristics of the edge region, but also specific adaptations to the desert habitat of H. reaumuri.

scholarly journals Stretching DNA origami: effect of nicks and Holliday junctions on the axial stiffness

2020 ◽  
Vol 48 (21) ◽  
pp. 12407-12414
Author(s):  
Wei-Hung Jung ◽  
Enze Chen ◽  
Remi Veneziano ◽  
Stavros Gaitanaros ◽  
Yun Chen
Keyword(s):  
Numerical Models ◽  
Double Helix ◽  
Single Particle Tracking ◽  
Holliday Junctions ◽  
Dna Origami ◽  
Axial Stiffness ◽  
Local Loss ◽  
Design Characteristics ◽  
Local Stiffness ◽  
Force Displacement

Abstract The axial stiffness of DNA origami is determined as a function of key nanostructural characteristics. Different constructs of two-helix nanobeams with specified densities of nicks and Holliday junctions are synthesized and stretched by fluid flow. Implementing single particle tracking to extract force–displacement curves enables the measurement of DNA origami stiffness values at the enthalpic elasticity regime, i.e. for forces larger than 15 pN. Comparisons between ligated and nicked helices show that the latter exhibit nearly a two-fold decrease in axial stiffness. Numerical models that treat the DNA helices as elastic rods are used to evaluate the local loss of stiffness at the locations of nicks and Holliday junctions. It is shown that the models reproduce the experimental data accurately, indicating that both of these design characteristics yield a local stiffness two orders of magnitude smaller than the corresponding value of the intact double-helix. This local degradation in turn leads to a macroscopic loss of stiffness that is evaluated numerically for multi-helix DNA bundles.

Elastoplastic Analysis of Layered Metal Matrix Composite Cylinders—Part I: Theory

1996 ◽  
Vol 118 (1) ◽  
pp. 13-20 ◽  
Author(s):  
R. S. Salzar ◽  
M.-J. Pindera ◽  
F. W. Barton
Keyword(s):  
Metal Matrix Composite ◽  
Matrix Composite ◽  
Stiffness Matrix ◽  
Metal Matrix ◽  
Plastic Response ◽  
Solution Strategy ◽  
Composite Tubes ◽  
Elastic Plastic ◽  
Stiffness Matrices ◽  
Local Stiffness

An exact elastic-plastic analytical solution for an arbitrarily laminated metal matrix composite tube subjected to axisymmetric thermo-mechanical and torsional loading is presented. First, exact solutions for transversely isotropic and monoclinic (off-axis) elastoplastic cylindrical shells are developed which are then reformulated in terms of the interfacial displacements as the fundamental unknowns by constructing a local stiffness matrix for the shell. Assembly of the local stiffness matrices into a global stiffness matrix in a particular manner ensures satisfaction of interfacial traction and displacement continuity conditions, as well as the external boundary conditions. Due to the lack of a general macroscopic constitutive theory for the elastic-plastic response of unidirectional metal matrix composites, the micromechanics method of cells model is employed to calculate the effective elastic-plastic properties of the individual layers used in determining the elements of the local and thus global stiffness matrices. The resulting system of equations is then solved using Mendelson’s iterative method of successive elastic solutions developed for elastoplastic boundary-value problems. Part I of the paper outlines the aforementioned solution strategy. In Part II (Salzar et al., 1996) this solution strategy is first validated by comparison with available closed-form solutions as well as with results obtained using the finite-element approach. Subsequently, examples are presented that illustrate the utility of the developed solution methodology in predicting the elastic-plastic response of arbitrarily laminated metal matrix composite tubes. In particular, optimization of the response of composite tubes under internal pressure is considered through the use of functionally graded architectures.

A Generalized Approach to the Dynamics of Cracked Shafts

1989 ◽  
Vol 111 (3) ◽  
pp. 257-263 ◽  
Author(s):  
Changhe Li ◽  
O. Bernasconi ◽  
N. Xenophontidis
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Experimental Method ◽  
The Finite Element Method ◽  
Nonlinear Formulation ◽  
Local Stiffness ◽  
Advanced Model ◽  
Cracked Shafts ◽  
Element Method

A new analytic-experimental method for describing crack breathing and obtaining shaft local stiffness change is presented. A generalized nonlinear formulation using the finite element method, which can be widely used for both horizontal and vertical cracked shafts, is derived. Some results previously explicited in other studies are confirmed and clarified. This advanced model can serve as a solid basis for further studies.

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