Effect of Matching Buckling Loads on Post-Buckling Behavior in Compliant Mechanisms

2021 ◽  
Author(s):  
A. Numić ◽  
T. W. A. Blad ◽  
F. van Keulen
Keyword(s):  
Compliant Mechanisms ◽  
Relative Length ◽  
Optimal Designs ◽  
Element Analysis ◽  
Buckling Loads ◽  
Actuation Force ◽  
Stepped Beam ◽  
Buckling Behavior ◽  
Post Buckling ◽  
Novel Method

Abstract In this paper, a novel method for stiffness compensation in compliant mechanisms is investigated. This method involves tuning the ratio between the first two critical buckling loads. To this end, the relative length and width of flexures in two architectures, a stepped beam and parallel guidance, are adjusted. Using finite element analysis, it is shown that by maximizing this ratio, the actuation force for transversal deflection in post-buckling is reduced. These results were validated experimentally by identifying the optimal designs in a given space and capturing the force-deflection characteristics of these mechanisms.

Delamination Suppression in Sandwich Beams Using Translaminar Reinforcements

1999 ◽  
Author(s):  
Brian T. Wallace ◽  
Bhavani V. Sankar ◽  
Peter G. Ifju
Keyword(s):  
Axial Compression ◽  
Sandwich Beam ◽  
Sandwich Beams ◽  
Thickness Direction ◽  
Compression Tests ◽  
Honeycomb Core ◽  
Element Analysis ◽  
Buckling Loads ◽  
Buckling Behavior ◽  
Post Buckling

Abstract The present study is concerned with translaminar reinforcement in a sandwich beam for preventing buckling of a delaminated face-sheet under axial compression. Graphite/epoxy pins are used as reinforcement in the thickness direction of sandwich beams consisting of graphite/epoxy face-sheets and a Aramid honeycomb core. Compression tests are performed to understand the effects of the diameter of the reinforcing pins and reinforcement spacing on the ultimate compressive strength of the delaminated beams. A finite element analysis is performed to understand the effects of translaminar reinforcement on the critical buckling loads and post-buckling behavior of the sandwich beam under axial compression.

The effects of cutouts on buckling behavior of composite plates

2012 ◽  
Vol 19 (3) ◽  
pp. 323-330 ◽  
Author(s):  
Ahmet Erkliğ ◽  
Eyüp Yeter
Keyword(s):  
Fiber Orientation ◽  
Polymer Matrix Composites ◽  
Orientation Angle ◽  
Composite Plates ◽  
Buckling Load ◽  
Matrix Composites ◽  
Element Analysis ◽  
Buckling Loads ◽  
Buckling Behavior ◽  
Fiber Orientation Angle

AbstractCutouts such as circular, rectangular, square, elliptical, and triangular shapes are generally used in composite plates as access ports for mechanical and electrical systems, for damage inspection, to serve as doors and windows, and sometimes to reduce the overall weight of the structure. This paper addresses the effects of different cutouts on the buckling behavior of plates made of polymer matrix composites. To study the effects of cutouts on buckling, loaded edges are taken as fixed and unloaded edges are taken as free. Finite element analysis is also performed to predict the effects of different geometrical cutouts, orientations, and position of cutouts on the buckling behavior. The results show that fiber orientation angle and cutout sizes are the most important parameters on the buckling loads. For all types of cutouts the buckling loads decrease dramatically by increasing the fiber orientation angle. It is observed that minimum buckling load is reached when 45° fiber angle is used, and after this angle critical buckling load begins to increase. Also, it is concluded that while fiber orientation angle is 0°, elliptical cutout has the highest buckling load and while fiber orientation angle is 45°, circular cutout has the highest buckling load.

Comparative Study of Post-Buckling Load Redistribution in Stiffened Aircraft Panel With and Without Material Nonlinearity

2018 ◽  
Author(s):  
Enes Aydin ◽  
Altan Kayran
Keyword(s):  
Finite Element ◽  
Material Nonlinearity ◽  
Stiffened Panel ◽  
Effective Width ◽  
Element Analysis ◽  
Buckling Behavior ◽  
The Finite Element Analysis ◽  
Post Buckling ◽  
Buckling Coefficient ◽  
Clamped Edge

In this article, a comparative study is presented on the post-buckling load redistribution in stiffened aircraft panels modeled with and without material nonlinearity. In the first part of the study, a baseline stiffened panel is generated for further investigation of the material nonlinearity on the post-buckling behavior and on the effective width of the stiffened panel. In this respect, a stiffener section which provides classical clamped edge condition is designed by matching the compression buckling coefficient determined by the finite element analysis closely with the analytically determined buckling coefficient of the clamped edge panel. Post-buckling analysis of the stiffened panel is then performed utilizing linear and nonlinear material models in the finite element analysis and the effect of material plasticity on the post-buckling behavior of the panel is ascertained. The load distribution in the stiffened panel is investigated just before the buckling of the panel and before the collapse of the panel in the post-buckled stage. The effective widths of the panel are calculated before the collapse of the panel using the load distributions determined by the finite element analyses of the panel models with and without material nonlinearity and comparisons are made with the effective width calculated by the classical effective width formulation. It is shown that material nonlinearity accounts for higher effective width and in general the classical empirical approach gives the smallest effective width.

scholarly journals A Simplified Analysis of the Post-buckling Behavior of a Compressed Reinforcing Bar

10.14311/650 ◽  
2004 ◽  
Vol 44 (5-6) ◽  
Author(s):  
P. Kabele
Keyword(s):  
Plastic Material ◽  
Axial Loading ◽  
Central Line ◽  
Material Behavior ◽  
Multiscale Approach ◽  
Rigid Plastic ◽  
Element Analysis ◽  
Reinforcing Bar ◽  
Buckling Behavior ◽  
Post Buckling

Recently, a computational methodology based on a sequential multiscale approach, which facilitates numerical simulation of an R/C building demolition has been developed. In this type of analysis, it is necessary to capture the behavior of compressed reinforcement bars until complete rupture, which occurs due to extensive bending in the post-buckling regime. To this end, a simplified analytical model of the post-buckling behavior of a compressed bar is proposed. The simplification consists namely in considering rigid-plastic material behavior, neglecting axial contraction of the central line, and approximating the shape of the deformed central line in the plastic hinges by a circular arch. Consequently, the axial loading force, bar end displacement, and extreme strain can be expressed in relatively simple closed forms. The results obtained with the proposed model show very close agreement with those obtained by a detailed and realistic finite element analysis, which justifies the use of the simplifying assumptions. 

The Ultimate Strength of Stiffened Panel with Overall Buckling

2011 ◽  
Vol 308-310 ◽  
pp. 1297-1301
Author(s):  
Bao Zhang ◽  
Qin Sun
Keyword(s):  
Ultimate Strength ◽  
Orthotropic Plate ◽  
Plate Theory ◽  
Stiffened Panel ◽  
Buckling Mode ◽  
Element Analysis ◽  
Buckling Behavior ◽  
Eigenvalue Method ◽  
Post Buckling ◽  
Overall Buckling

The post-buckling behavior of a stiffened panel is investigated in this paper. Firstly, the buckling mode of the stiffened panel is obtained using the linear buckling eigenvalue method. Then, the collapsing strength of the stiffened panel is calculated using the ultimate strength method based on large deflection orthotropic plate theory. In addition, nonlinear finite element analysis is performed to predict the post-buckling behavior of the stiffened panel. By comparing the model prediction and the analytical results of ultimate strength, it is shown that good accuracy can be achieved, especially for the method referring to membrane stress in mid-thickness of equivalent orthotropic plate. It suggests that the proposed method can predict the ultimate strength of whole stiffened panel accurately and effectively.

An Experimental Study of Buckling and Post-Buckling of Laterally Constrained Rods

1995 ◽  
Vol 117 (2) ◽  
pp. 115-124 ◽  
Author(s):  
P. V. R. Suryanarayana ◽  
R. C. McCann
Keyword(s):  
Experimental Study ◽  
Horizontal Wells ◽  
Current Theory ◽  
Buckling Loads ◽  
Buckling Behavior ◽  
Experimental Apparatus ◽  
Compressive Loads ◽  
Weight On Bit ◽  
Post Buckling ◽  
Safe Load

The effects of friction and curvature on buckling, post-buckling, and unbuckling behavior of rods laterally constrained within an enclosure are studied experimentally. The experimental apparatus, measurement procedures, and uncertainty analysis are described. Results indicate that friction significantly delays the onset of buckling, and causes noticeable hysteresis in the post-buckling behavior. As a result, the unbuckling loads are always less than the corresponding buckling loads. The drag-related loss, which eventually leads to lock-up, is also measured and reported in this work. Friction is also a cause of post-buckling snapping and reversals in the direction of wrap of the helix. As expected, the effects of friction become less significant as the inclination decreases. It is shown that predictions of current theory agree with experimentally measured unbuckling rather than buckling loads. When friction is significant, current theory underestimates the compressive loads at which buckling occurs in straight or curved wellbores. Ignoring friction or curvature limits the estimated weight on bit well below the safe load that can be used in many drilling and completion operations in extended reach or horizontal wells. Moreover, the hysteresis effect of friction means that once buckling has occurred, the compressive loads must be reduced to values much below the buckling initiation loads to fully straighten the buckled pipe.

Buckling of curved panels under combined shear and compression

1998 ◽  
Vol 212 (3) ◽  
pp. 183-196 ◽  
Author(s):  
C A Featherston ◽  
C Ruiz
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Boundary Conditions ◽  
Experimental Results ◽  
Flat Plates ◽  
Element Analysis ◽  
Buckling Loads ◽  
Analytical Work ◽  
Post Buckling ◽  
Curved Panels

The analytical work which has been carried out to determine the buckling load and post-buckling behaviour of curved panels under various types of loading and different boundary conditions is not as comprehensive as that for flat plates. Only elementary loading and boundary conditions have been analysed. In addition to this, many of the theories developed have not been tested experimentally. This paper outlines a series of tests carried out to determine the accuracy of the theoretical buckling loads. The experimental results are then used to examine whether or not finite element analysis can be used as an alternative to determine collapse loads and post-buckling behaviour, especially in cases where no theoretical solutions exist.

Buckling Behavior of Tire Breaker Structure

1983 ◽  
Vol 11 (1) ◽  
pp. 3-19
Author(s):  
T. Akasaka ◽  
S. Yamazaki ◽  
K. Asano
Keyword(s):  
Elastic Foundation ◽  
Elastic Moduli ◽  
Wave Length ◽  
Bending Moment ◽  
Experimental Results ◽  
Automobile Tire ◽  
Buckling Behavior ◽  
Post Buckling ◽  
Steel Cord ◽  
Interlaminar Shear

Abstract The buckled wave length and the critical in-plane bending moment of laminated long composite strips of cord-reinforced rubber sheets on an elastic foundation is analyzed by Galerkin's method, with consideration of interlaminar shear deformation. An approximate formula for the wave length is given in terms of cord angle, elastic moduli of the constituent rubber and steel cord, and several structural dimensions. The calculated wave length for a 165SR13 automobile tire with steel breakers (belts) was very close to experimental results. An additional study was then conducted on the post-buckling behavior of a laminated biased composite beam on an elastic foundation. This beam is subjected to axial compression. The calculated relationship between the buckled wave rise and the compressive membrane force also agreed well with experimental results.

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