Imperfection-Sensitivity of Long Antisymmetric Cross-Ply Cylindrical Panels Under Shear Loads

1987 ◽  
Vol 54 (2) ◽  
pp. 292-298 ◽  
Author(s):  
David Hui ◽  
I. H. Y. Du
Keyword(s):  
Modulus Ratio ◽  
Postbuckling Behavior ◽  
Imperfection Sensitivity ◽  
Geometric Imperfections ◽  
Material Parameters ◽  
Shear Loads ◽  
Number Of Layers ◽  
Cylindrical Panels ◽  
Shear Buckling ◽  
Shell Geometry

This paper examines the theoretical postbuckling behavior and imperfection-sensitivity of antisymmetrically laminated open, long, cylindrical panels under shear loads. The longitudinal edges may be simply-supported or clamped. It is found that the cylindrical panels may be sensitive to the presence of geometric imperfections depending primarily on the reduced-flatness parameter and Young’s modulus ratio. The shear buckling load and the postbuckling coefficients are plotted as a function of the shell geometry, number of layers, and material parameters. The paper is the first in the literature to examine the postbuckling behavior of open laminated cylindrical panels under shear loads.

scholarly journals Imperfection Sensitivity of Externally Pressurized Spherical Shells

1967 ◽  
Vol 34 (1) ◽  
pp. 49-55 ◽  
Author(s):  
J. W. Hutchinson
Keyword(s):  
General Theory ◽  
Shell Thickness ◽  
Middle Surface ◽  
External Pressure ◽  
Postbuckling Behavior ◽  
Imperfection Sensitivity ◽  
Spherical Shells ◽  
Small Deviations ◽  
Severe Effect ◽  
Shell Geometry

The initial postbuckling behavior of a shallow section of a spherical shell subject to external pressure is studied within the context of Koiter’s general theory of postbuckling behavior. Imperfections in the shell geometry are shown to have the same severe effect on the buckling strengths of spherical shells as has been demonstrated for axially compressed cylindrical shells. Large reductions in the buckling pressure result from small deviations, relative to the shell thickness, of the shell middle surface from the perfect configuration.

Shell Stability

1983 ◽  
Vol 50 (4b) ◽  
pp. 935-940 ◽  
Author(s):  
C. D. Babcock
Keyword(s):  
Dynamic Buckling ◽  
Recent History ◽  
Postbuckling Behavior ◽  
Imperfection Sensitivity ◽  
Plastic Buckling ◽  
Shell Stability ◽  
Current Trends ◽  
Shell Buckling ◽  
History Of ◽  
Subject Areas

Recent advances in shell buckling research are reviewed. Five separate subject areas are covered: elastic postbuckling behavior and imperfection sensitivity, plastic buckling, dynamic buckling, experiments and computations. Recent history of the research is presented emphasizing important advances in understanding. Areas of needed research and current trends are pointed out.

Initial Postbuckling Behavior of Imperfect, Antisymmetric Cross-Ply Cylindrical Shells Under Torsion

1987 ◽  
Vol 54 (1) ◽  
pp. 174-180 ◽  
Author(s):  
David Hui ◽  
I. H. Y. Du
Keyword(s):  
Cylindrical Shells ◽  
Elastic Stability ◽  
Buckling Load ◽  
Postbuckling Behavior ◽  
Imperfection Sensitivity ◽  
Torsional Buckling ◽  
Buckling Mode ◽  
Young’S Moduli ◽  
Coupling Behavior ◽  
Parameter Variations

This paper deals with the initial postbuckling of antisymmetric cross-ply closed cylindrical shells under torsion. Under the assumptions employed in Koiter’s theory of elastic stability, the structure is imperfection-sensitive in certain intermediate ranges of the reduced-Batdorf parameter (approx. 4 ≤ ZH ≤ 20.0). Due to different material bending-stretching coupling behavior, the (0 deg inside, 90 deg outside) two-layer clamped cylinder is less imperfection sensitive than the (90 deg inside, 0 deg outside) configuration. The increase in torsional buckling load due to a higher value of Young’s moduli ratio is not necessarily accompanied by a higher degree of imperfection-sensitivity. The paper is the first to consider imperfection shape to be identical to the torsional buckling mode and presents concise parameter variations involving the reduced-Batdorf paramter and Young’s moduli ratio.

scholarly journals Evaluation of the effectiveness of representative methods for determining Young's modulus and hardness from instrumented indentation data

2006 ◽  
Vol 21 (1) ◽  
pp. 225-233 ◽  
Author(s):  
Dejun Ma ◽  
Taihua Zhang ◽  
Chung Wo Ong
Keyword(s):  
Young’S Modulus ◽  
Young's Modulus ◽  
Maximum Error ◽  
Instrumented Indentation ◽  
Modulus Ratio ◽  
Material Parameters ◽  
Correction Scheme ◽  
Single Standard ◽  
Hardness Values ◽  
Hardening Coefficient

The effectiveness of Oliver & Pharr's (O&P's) method, Cheng & Cheng's (C&C’s) method, and a new method developed by our group for estimating Young's modulus and hardness based on instrumented indentation was evaluated for the case of yield stress to reduced Young's modulus ratio (σy/Er) ≥ 4.55 × 10−4 and hardening coefficient (n) ≤ 0.45. Dimensional theorem and finite element simulations were applied to produce reference results for this purpose. Both O&P's and C&C's methods overestimated the Young's modulus under some conditions, whereas the error can be controlled within ±16% if the formulation was modified with appropriate correction functions. Similar modification was not introduced to our method for determining Young's modulus, while the maximum error of results was around ±13%. The errors of hardness values obtained from all the three methods could be even larger and were irreducible with any correction scheme. It is therefore suggested that when hardness values of different materials are concerned, relative comparison of the data obtained from a single standard measurement technique would be more practically useful. It is noted that the ranges of error derived from the analysis could be different if different ranges of material parameters σy/Er and n are considered.

scholarly journals The shear buckling and postbuckling behavior of laterally pressured curved panels

2019 ◽  
Author(s):  
Mohammad Mehdi Alinia ◽  
Arash Saeidpour ◽  
Mozhdeh Amani
Keyword(s):  
Shear Capacity ◽  
Radius Of Curvature ◽  
Postbuckling Behavior ◽  
Plane Shear ◽  
Theoretical Formulation ◽  
Curved Panel ◽  
Shear Buckling ◽  
Parametric Studies ◽  
Ultimate Shear Capacity ◽  
Curved Panels

Curved panels are widely used in different structures from fuselage of planes to curved bridge girders. An accurate understanding of buckling and postbuckling behavior of curved panels under different loadings is essential for efficient structural design. The shear buckling and postbuckling behavior of laterally pressured thin curved panels under gradually increasing in-plane shear forces is investigated. The magnitude of the lateral forces, the radius of curvature and the aspect ratio of panels are considered in the parametric studies. A classic theoretical formulation of curved panels buckling load is reexamined and compared to experimental results. The results showed that inward pressure eliminates the snap-through phenomenon and the softening stage in the response of shallow curved panels. However, the buckling characteristics are not significantly affected in the moderately curved panels under small pressures. In addition, the magnitude of inward pressures that would affect the shear buckling and postbuckling behavior of panels depends on their radius of curvature. The ultimate shear capacity of a highly curved panel is considerably reduced due to the increasing presence of inward pressures. The failure mode of highly curved panels are associated with the occurrence of unstable buckling; and as a result, the released strain energy prevents the occurrence of hardening stages.

scholarly journals Nudging Axially Compressed Cylindrical Panels Toward Imperfection Insensitivity

2019 ◽  
Vol 86 (7) ◽  
Author(s):  
B. S. Cox ◽  
R. M. J. Groh ◽  
A. Pirrera
Keyword(s):  
Numerical Continuation ◽  
Shell Structures ◽  
Postbuckling Behavior ◽  
Numerical Predictions ◽  
Highly Nonlinear ◽  
Flat Structures ◽  
Load Carrying ◽  
Cylindrical Panels ◽  
Stable Equilibria ◽  
Insight Into

Curved shell structures are known for their excellent load-carrying capability and are commonly used in thin-walled constructions. Although theoretically able to withstand greater buckling loads than flat structures, shell structures are notoriously sensitive to imperfections owing to their postbuckling behavior often being governed by subcritical bifurcations. Thus, shell structures often buckle at significantly lower loads than those predicted numerically and the ensuing dynamic snap to another equilibrium can lead to permanent damage. Furthermore, the strong sensitivity to initial imperfections, as well as their stochastic nature, limits the predictive capability of current stability analyses. Our objective here is to convert the subcritical nature of the buckling event to a supercritical one, thereby improving the reliability of numerical predictions and mitigating the possibility of catastrophic failure. We explore the elastically nonlinear postbuckling response of axially compressed cylindrical panels using numerical continuation techniques. These analyses show that axially compressed panels exhibit a highly nonlinear and complex postbuckling behavior with many entangled postbuckled equilibrium curves. We unveil isolated regions of stable equilibria in otherwise unstable postbuckled regimes, which often possess greater load-carrying capacity. By modifying the initial geometry of the panel in a targeted—rather than stochastic—and imperceptible manner, the postbuckling behavior of these shells can be tailored without a significant increase in mass. These findings provide new insight into the buckling and postbuckling behavior of shell structures and opportunities for modifying and controlling their postbuckling response for enhanced efficiency and functionality.

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