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.

scholarly journals Bending Response of 3D-Printed Titanium Alloy Sandwich Panels with Corrugated Channel Cores

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 556
Author(s):  
Zhenyu Zhao ◽  
Jianwei Ren ◽  
Shaofeng Du ◽  
Xin Wang ◽  
Zihan Wei ◽  
...  
Keyword(s):  
Titanium Alloy ◽  
Heat Dissipation ◽  
Sandwich Panels ◽  
Face Sheet ◽  
Collapse Mechanism ◽  
Corrugated Channel ◽  
Four Point Bending ◽  
Numerical Predictions ◽  
Load Carrying ◽  
3D Printed

Ultralight sandwich constructions with corrugated channel cores (i.e., periodic fluid-through wavy passages) are envisioned to possess multifunctional attributes: simultaneous load-carrying and heat dissipation via active cooling. Titanium alloy (Ti-6Al-4V) corrugated-channel-cored sandwich panels (3CSPs) with thin face sheets and core webs were fabricated via the technique of selective laser melting (SLM) for enhanced shear resistance relative to other fabrication processes such as vacuum brazing. Four-point bending responses of as-fabricated 3CSP specimens, including bending resistance and initial collapse modes, were experimentally measured. The bending characteristics of the 3CSP structure were further explored using a combined approach of analytical modeling and numerical simulation based on the method of finite elements (FE). Both the analytical and numerical predictions were validated against experimental measurements. Collapse mechanism maps of the 3CSP structure were subsequently constructed using the analytical model, with four collapse modes considered (face-sheet yielding, face-sheet buckling, core yielding, and core buckling), which were used to evaluate how its structural geometry affects its collapse initiation mode.

Pressuremeter Testing of Normally Consolidated Clays—The Effects of Varying Test Technique

1986 ◽  
Vol 2 (1) ◽  
pp. 125-132
Author(s):  
W. F. Anderson ◽  
I. C. Pyrah ◽  
F. Haji-Ali
Keyword(s):  
Test Methods ◽  
Time Dependent ◽  
Clay Soils ◽  
Shear Creep ◽  
Test Technique ◽  
Pressuremeter Test ◽  
Numerical Predictions ◽  
Cylindrical Cavities ◽  
Undrained Conditions ◽  
Insight Into

AbstractAlthough BS 5930:1981 describes both Menard and self-boring pressuremeter tests, little guidance is given on test methods. A number of techniques, both stress controlled and strain controlled, have been used and it has been shown that for clays the test technique has a significant influence on the derived strength and modulus parameters.When a pressuremeter test is carried out in a clay, it is assumed that shearing occurs under undrained conditions. However, in addition to immediate shear strain, some creep and local consolidation will occur in the soil around the expanding borehole. These two phenomena are time-dependent and variations in test technique will affect the test data and hence the derived strength and modulus values.To obtain a better understanding of these effects, pressuremeter tests have been studied both experimentally and numerically. Experimentally, pressuremeter tests have been simulated by expanding cylindrical cavities in samples of three clays prepared with known stress history and the results compared with numerical predictions where the effects of immediate shear, creep and consolidation can be separated. The experimental results compare well with the numerical predictions.This has given a new insight into the behaviour of clay soils during pressuremeter tests. The results indicate that any simple standardization of pressuremeter test technique should be approached with caution.

Insight into the core–shell structures of Cu–In–S microspheres

2013 ◽  
Vol 26 ◽  
pp. 23-30 ◽  
Author(s):  
Angela S. Wochnik ◽  
Anna Frank ◽  
Christoph Heinzl ◽  
Jonas Häusler ◽  
Julian Schneider ◽  
...  
Keyword(s):  
Shell Structures ◽  
Core Shell ◽  
The Core ◽  
Insight Into

Asymmetric Postbuckling Behavior of Hemispherical Shell Structure Under Axial Compression

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Shanshuai Wang ◽  
Shuhui Li ◽  
Ji He ◽  
Yixi Zhao
Keyword(s):  
Stainless Steel ◽  
Axial Compression ◽  
Shell Structure ◽  
Load Capacity ◽  
Plastic Hinge ◽  
Shell Structures ◽  
Postbuckling Behavior ◽  
Asymmetric Deformation ◽  
Deformation Stage ◽  
Hemispherical Shell

In real physical experiments, three typical deformation stages including elastic deformation stage, symmetric deformation stage, and asymmetric deformation stage appear step by step when the stainless steel hemispherical shell structure is under axial compression loading. During the asymmetric deformation stage, the rolling-plastic-hinge-radius which characterizes the size of the deformation area evolves along the circumferential direction with the compressive displacement. For the hemispherical shell structures with apparent asymmetric deformation stage, the double-buckling phenomenon of the structures in experiments can be clearly detected. The traditional theoretical analysis based on the assumption with circumferentially constant rolling-plastic-hinge-radius is not suitable to predict this phenomenon. For these hemispherical shell structures, load capacity and absorbed energy predicted by the traditional analysis are usually higher than experimental results in the asymmetric deformation stage. In this paper, a new description based on experimental observation for the evolution of rolling-plastic-hinge-radius has been proposed. Minimum energy principle was employed to obtain the postbuckling behavior. The energy evolution of different buckling stages during compression loading is investigated to evaluate the structure load capacity. Stainless steel hemispherical specimens with different sizes are tested under axial compression between two rigid plates to verify the theoretical modification. Good agreement is achieved between proposed model and experimental results. The theoretical model proposed in this paper can be used in prediction of postbuckling behavior for different deformation patterns in the asymmetric deformation stage. It also provides higher flexibility and efficiency for the postbuckling behavior prediction of hemispherical shell structures.

Influence of micro-grooves on the lubrication performance of a misaligned bearing

2019 ◽  
Vol 234 (6) ◽  
pp. 887-899
Author(s):  
Yanxiang Han ◽  
Yonghong Fu
Keyword(s):  
Angular Position ◽  
Surface Texturing ◽  
Mass Conservation ◽  
Groove Depth ◽  
Film Rupture ◽  
Practical Applications ◽  
Numerical Predictions ◽  
Lubrication Performance ◽  
Load Carrying ◽  
Manufacturing Tolerances

Surface texturing for improving the lubrication performance of journal bearings has been widely investigated in the last two decades. In practical applications, the misalignment of a journal bearing occurs due to the asymmetric bearing load, elastic deflection, manufacturing tolerances, and installation errors. However, there has been little discussion on the influence of grooves on the lubrication performance of misaligned bearings. In the present work, numerical predictions of lubrication performances are presented to test the influence of the grooves. Based on the JFO boundary condition, a mass conservation algorithm is implemented to automatically determine the position of oil film rupture and reformation. The load-carrying capacity, friction force, friction coefficient, and bearing moment are computed numerically. The influence of angular position of the groove is first conducted in a misaligned bearing. Subsequently, the groove depth and width are investigated with different values of [Formula: see text] and [Formula: see text] ratios, respectively.

Compactness variability of metal deployable load-carrying shell structures

2020 ◽  
Author(s):  
V.S. Volkov ◽  
O.V. Makhnenko ◽  
S.M. Kandala ◽  
O.A. Volkova ◽  
Y.V. Borovyk
Keyword(s):  
Shell Structures ◽  
Load Carrying

Centrifugal Flow in a Rotor-Stator Cavity

2005 ◽  
Vol 127 (4) ◽  
pp. 787-794 ◽  
Author(s):  
Sébastien Poncet ◽  
Roland Schiestel ◽  
Marie-Pierre Chauve
Keyword(s):  
Laser Doppler Anemometer ◽  
Second Order ◽  
Control Parameters ◽  
Complex Flows ◽  
Order Model ◽  
Pressure Transducers ◽  
Numerical Predictions ◽  
Two Component ◽  
First Time ◽  
Insight Into

The present work considers the turbulent flow inside an annular rotor-stator cavity with and without centrifugal throughflow. Extensive measurements performed using a two-component laser-Doppler anemometer technique, and pressure transducers are compared to numerical predictions based on one-point statistical modeling using a low-Reynolds-number second-order full-stress transport closure. A study of the flow control parameters is performed, and, for the first time, a better insight into the transition from Batchelor to Stewartson types of flow is gained from this study. The advanced second-order model is confirmed to be the adequate level of closure to describe such complex flows.

Experimental and Numerical Investigation of Aluminum Alloy Plates With Initial Crack Under Repeated Dynamic Impact Loads

2018 ◽  
Author(s):  
Fangjuan Duan ◽  
Weiguang Liu ◽  
De Xie ◽  
Jingxi Liu ◽  
Zhiqiang Hu
Keyword(s):  
Aluminum Alloy ◽  
Numerical Simulations ◽  
Carrying Capacity ◽  
Initial Crack ◽  
Impact Loads ◽  
Load Carrying Capacity ◽  
Repeated Impact ◽  
Alloy Plate ◽  
Numerical Predictions ◽  
Load Carrying

Ships and offshore structures are often exposed to various types of repeated impact loads, such as wave slamming, floating ice impacts and ship collisions which will cause large deformation or even fracture. With imperfections due to the process of construction or damage caused by accidents, the load carrying capacity of structures will decrease. This paper investigates the load carrying capacity of aluminum alloy plate with an initial crack under repeated impact loads by means of experiments and numerical simulations. In the experiments, the prepared specimens with crack and without crack are impacted repeatedly up to plate perforation by releasing a hemispherical-headed cylindrical hammer. Numerical simulations are carried out with ABAQUS/Explicit software. The numerical models are built according to the actual experimental conditions. Comparison of the numerical predictions with the experimental results shows reasonable agreement. It is found that aluminum alloy plates under repeated impacts are sensitive to initial cracks. The fracture mode and plastic deformation of aluminum alloy plates can also be affected.

On Numerical Results of Reticulated Shell Buckling

1992 ◽  
Vol 7 (4) ◽  
pp. 299-319 ◽  
Author(s):  
Heinrich Rothert ◽  
Norbert Gebbeken
Keyword(s):  
Path Following ◽  
Shell Structures ◽  
Element Analysis ◽  
Economical Analysis ◽  
Shell Buckling ◽  
Stiffness Matrices ◽  
Load Carrying ◽  
The Stability ◽  
Stability Of Structures ◽  
Path Following Algorithms

This paper is mainly focused on the numerical methods which are used to calculate realistically the load-carrying behaviour of reticulated shell structures. It is generally assumed that for an economical analysis, aimed at the saving of material, the material non-linearity has to be taken into consideration if dead loads prevail. For this in the context of finite element analysis the stiffness matrices of elastic and elastic-plastic rod elements are presented. In order to ensure the stability of structures it is indispensable to detect limit loads such as snap-through loads and bifurcation loads. Assuming that snap-through phenomena are quasi static, path-following algorithms can be implemented to trace the load-deflection curves in the postbuckling domain. The testing of the reliability and stability of the algorithms requires a sufficient number of numerical examples. Few will be presented.

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