Cohesive Zone Model Modification Techniques According to the Mesh Size in Finite Element Models of Stiffened Panels with Debonding

When catastrophic failure phenomena in aircraft structures, such as debonding, are numerically analyzed during their design process in the frame of “Damage Tolerance” philosophy, extreme requirements in terms of time and computational resources arise. Here, a decrease in these requirements is achieved by developing a numerical model that efficiently treats the debonding phenomena that occur due to the buckling behavior of composite stiffened panels under compressive loads. The Finite Element (FE) models developed in the ANSYS© software (Canonsburg, PA, USA) are calibrated and validated by using published experimental and numerical results of single-stringer compression specimens (SSCS). Different model features, such as the type of the element used (solid and solid shell) and Cohesive Zone Modeling (CZM) parameters are examined for their impact on the efficiency of the model regarding the accuracy versus computational cost. It is proved that a significant reduction in computational time is achieved, and the accuracy is not compromised when the proposed FE model is adopted. The outcome of the present work leads to guidelines for the development of FE models of stiffened panels, accurately predicting the buckling and post-buckling behavior leading to debonding phenomena, with minimized computational and time cost. The methodology is proved to be a tool for the generation of a universal parametric numerical model for the analysis of debonding phenomena of any stiffened panel configuration by modifying the corresponding geometric, material and damage properties.

The failure behavior of buckling pin valve: Theoretical, numerical, and experimental study

At present, buckling pin in the bypass of piping as pressure relief valve has been gradually utilized in the low-concentration coal-bed methane (CBM), which bends to release pressure when the main valve fails leading to pipeline blockage. However, current researches mainly focused on the buckling behavior of hydraulic cylinder rod or rod string, and less consideration was given to the operational reliability of buckling pin valves. This paper deduced the calculation formula of the critical failure load based on Euler formula in the buckling pin under buckling load. Besides, three finite element models (FEM) based on Johnson−Cook constitutive model were compared to predict failure strength of buckling pin which were verified by experiment. In addition, the defect sensitivity analysis of the buckling pin under different initial geometric defects rate was carried out. The results showed that a) the experimental value of the critical failure load in the buckling pin was 206.04 N and the bending position was in the middle of the buckling pin; b) the analysis result adopting explicit dynamic method was in best agreement with the experimental results within deviation of 0.24%; and c) the initial geometric defect of buckling pin should be controlled within 1%. This study provides an important reference to predict the critical failure load of the buckling pin valve and achieve safe transportation of low-concentration CBM.

Investigation of the buckling behavior of a control arm with Si particle reinforced aluminum based metal composite material

Control arms are subjected to static and dynamic loads in car during their lifetime. Recent increases in loads in which control arms are subjected, are not complying with the low-weight design targets expected by auto makers. In this study, buckling behavior of control arms which have been produced with Si particle reinforced aluminum based metal composite material have been investigated and compared with the performance of control arms that are produced with standard aluminum alloy. The results revealed that mechanical properties of control arm housings with 10% Sip MMC material are lower than standard 6110 alloy due to different process parameters. Elasticity of modulus of control arm housings with 10% Sip MMC material are approximately 7% higher than standard aluminum alloys. Buckling results of control arms with 10% Sip MMC material are around 25% lower that control arms with standard 6110 alloy. Also, a second darker phase was found in the microstructure.

Global Buckling Behavior of CFST Columns with Assembling Errors

Concrete-filled steel tubular (CFST) column has been widely used in engineering practice. In the process of assembling two columns to form a slender member, assembling errors (AE) are inevitably produced at the section of connection. When the AE are too large, the global buckling resistance of slender column would be significantly affected. Therefore, it is necessary to investigate the influence of AE on the stability performance of slender CFST columns. In this study, an axial compressive test involving three CFST columns with AE (AE-CFST columns) was conducted. A refined finite element (FE) model is established for further parametric analysis. Based on a simplified analytical model by analyzing the isolated steel connecting plate, a theoretical formula is proposed for predicting the critical thickness [Formula: see text] of the connecting plate. When the thickness [Formula: see text] of the connecting plate meets its requirement, the failure at the section of connection caused by AE could be effectively prevented. Stability design curves considering the influence of AE ratio (the ratio between assembling error and sectional depth of column) are proposed based on numerous FE examples. It is found that the proposed design curves are reliable for the design of AE-CFST columns with different AE ratios.

Beulverhalten von ringversteiften Kreiszylinderschalen unter Axialdruck – Teil 1: Versuche und geometrische Imperfektionsanalyse/Buckling behavior of ring-stiffened cylinder shells under axial pressure – Part 1: Tests and geometric imperfection analysis

Moderne Behälter werden oft als ringversteifte Kreiszylinderschalen ausgeführt. Der traglaststeigernde Effekt eng liegender Ringsteifen unter Axialdruck erfuhr in der Forschung bis heute nur geringe Beachtung. Er ist bisher ungeregelt und infolge unnötig hohen Materialeinsatzes bleiben Stahlbehältern Marktanteile und bessere Nachhaltigkeit verwehrt. Anhand von Versuchen und einer numerischen Studie werden die neuesten Forschungsergebnisse des Einflusses der Ringsteifen auf das Axialbeulverhalten von Kreiszylinderschalen erläutert. Die Ergebnisse zeigen, dass die ringversteiften Kreiszylinder unter Axialdruck nach der aktuellen Bemessungspraxis unwirtschaftlich bemessen werden.   Im Teil 1 dieses Beitrags werden Versuche im verkleinertem Maßstab durchgeführt, um den Einfluss der Ringsteifen auf das Beulverhalten der Kreiszylinderschalen unter Axialdruck zu erforschen. Gemäß einem Vergleich von Versuchsergebnissen wird eine mehrfach höhere Tragfähigkeit ringversteifter Schalen gegenüber unversteiften Schalen ermittelt. Die geometrischen Imperfektionen des Probekörpers werden durch eine 3D-Scan-Technologie gemessen und danach mittels der Methode der Fourier-Reihen analysiert. Im Teil 2 folgen die numerische Simulation und das Ableiten eines Ingenieurmodells.

Deterministic and probabilistic buckling response of fiber–metal laminate panels under uniaxial compression

Purpose The purpose of this paper is to study the deterministic elastic buckling behavior of cylindrical fiber–metal laminate panels subjected to uniaxial compressive loading and the investigation of GLAss fiber-REinforced aluminum laminate (GLARE) panels using probabilistic finite element method (FEM) analysis. Design/methodology/approach The FEM in combination with the eigenvalue buckling analysis is used for the construction of buckling coefficient–curvature parameter diagrams of seven fiber–metal laminate grades, three glass-fiber composites and monolithic 2024-T3 aluminum. The influences of uncertainties concerning material properties and laminate dimensions on the buckling load are studied with sensitivity analyses. Findings It is found that aluminum has a stronger impact on the buckling behavior of the fiber–metal laminate panels than their constituent uni-directional or woven composites. For the classical simply supported boundary conditions, it is found that there is an approximately linear relation between the buckling coefficient and the curvature parameter when the diagrams are plotted in double logarithmic scale. The probabilistic calculations demonstrate that there is a considerable probability to overestimate the buckling load of GLARE panels with deterministic calculations. Originality/value In this study, the deterministic and probabilistic buckling response of fiber metal laminate panels is investigated. It is shown that realistic structural uncertainties could substantially affect the buckling strength of aerospace components.