Search results

In general two main types of criteria are essential for the sizing of aircraft structural panels, namely, stability and damage tolerance. The way these criteria act and interact is very different for metallic and composite building blocks. While interaction of both types of criteria is relatively clear for composite parts, this is normally not the case for metallic ones. What is common for both is the fact that, if an interaction occurs, the impact is essential. The paper aims to discuss these issues.

This is a survey paper.

There is a strong mutual influence of buckling and damage in many cases.

It shows the significance of both, buckling and damage as a combined phenomenon.

The purpose of this paper is to present the first results of tests where cracks lie in the tension field of a shear forced aluminium panel. The paper's main focus is on the crack propagation behavior and possible 3D‐effects caused by the bending of the plate. A simplified numerical approach is presented to confirm the observed phenomena.

Experiments have been performed to investigate the influence of buckling on accidental damages. A simplified numerical approach is presented and compared to the experimental results.

It can be shown that the crack propagates due to buckling of the plate. The principal stress of the neutral axis of the plate has significant influence on the crack propagation.

Investigations of stability problems and damage tolerance behavior of metallic structures have been realized but mainly separately. This paper shows that cracks propagate due to buckling and that both phenomena influence one another considering accidental damages. The paper presents the first experimental and numerical results of cracked aluminium panels subjected to cyclic shear load.

In former work, test results of cracks in aluminium panels under cyclic shear buckling showed that cracks in the tensile stress field of a buckle propagate. The main influencing factor for the crack growth rate is the maximum principle stress. A simplified approach for crack propagation analyses based on this finding showed limitations for application on larger cracks because it disregarded the increasing out-of-plane deformation for larger cracks as well as stress redistributions. The purpose of this paper is to improve the results of the simplified approach with the help of finite element method (FEM).

An approach for crack propagation based on FEM is presented taking into account the mutual interaction of cracks and buckling. The finite element (FE) model, which is described in detail, respects the boundary conditions of the test-set-up. Different initial crack positions, loads and panel thicknesses are analyzed. Results of the stress intensity factors KI calculated by the ABAQUS® FE model provide a function which is used to run a crack propagation analysis based on Forman law.

The results of the FE-based crack propagation solution are in good agreement with test results and improve the prediction of the simplified approach. It is not restricted in terms of panel thickness, crack position or applied shear load.

Limitations of the FE-based crack propagation solution compared to the experimental results are discussed. These are, the sensitivity of crack propagation analyses to initial crack length and deviations of the experimental settings from the ideal FE model.

The interaction of cracks and buckling in aluminium shells is mainly disregarded both in research and industrial work, but can be of interest considering, accidental damages in fuselage side shells. Cracks propagate under shear load as it was shown in former work. The FE modeling of the tests presented in this paper proves the mutual interactions of crack propagation and buckling deformation.

Gives a bibliographical review of the finite element methods (FEMs) applied for the linear and nonlinear, static and dynamic analyses of basic structural elements from the theoretical as well as practical points of view. The range of applications of FEMs in this area is wide and cannot be presented in a single paper; therefore aims to give the reader an encyclopaedic view on the subject. The bibliography at the end of the paper contains 2,025 references to papers, conference proceedings and theses/dissertations dealing with the analysis of beams, columns, rods, bars, cables, discs, blades, shafts, membranes, plates and shells that were published in 1992‐1995.

A new approach to the problem of minimum‐weight design of stiffened compression panels is presented. It is predominantly based on the plate instability mode in which the sheet and stiffeners, having been stressed to the same degree, simultaneously buckle over a long wavelength with the length of a buckle equal to the pin‐ended length of a panel. Charts to determine the buckling stresses of the modes required for the minimum‐weight design are given. Formulae and charts are presented to compute the effective moment of inertia of a stiffener, a most important quantity, over a wide range of panel proportions, for Z‐section and integrally machined unflanged stiffeners. The principles of minimum‐weight design are discussed and illustrated by the lightest Z‐stiffener panels selected from extensive test data. Comparison of the theoretical stresses of the optimum panels and many other panels of different proportions with those obtained by tests shows good agreement. The principle of dimensional similarity, which is implicit in the buckling mode referred to above, eliminates the effects of size. Results obtained either from theory or tests can therefore be applied to different size panels of like proportions.

The purpose of this paper is to make an analytical comparison of two vertical tail models from a structural point of view.

The original vertical tail design of PZL-106BT aircraft was used for Computer aided design (CAD) modeling and for creating the finite element model.

The nodal displacements, Von-Mises stresses and Buckling factors for two vertical tail models have been found using the finite element method. The idea of a possible Multidisciplinary concept assessment and design (MDCAD) concept was presented.

The used software analogy introduces an idea of having an automated calculation procedure within the framework of MDCAD.

The aircraft used for calculation had undergone a modification in its vertical tail length, as there was an urgent need to calculate for the plane’s manufacturer, PZL Warszawa – Okecie.

THE FIRST MEETING of the LA Council in each year confirms the nomination of the new president by arranging his investiture with the badge of office by the outgoing incumbent. Last year Sir Fred Dainton had to buckle at the knees to allow Douglas Foskett to slip the blue ribbon over his head; this time he had to stretch up a little to negotiate Godfrey Thompson's ginger curls. The new president might have been only too willing to do the buckling but he was carrying the effects of a seasonal bug and once started on his way down, might never have stopped.

Universities globally have faced the introduction of research performance assessment systems that provide monetary and ranking rewards based on publication outputs. This study aims to seek an understanding of the implementation of performance-based research funding (PBRF) and its impact on the heads of departments (HoDs) and accounting academics in New Zealand (NZ) tertiary institutions. The study explores NZ accounting academics’ experiences and their workload; the relationship between teaching and research in the accounting discipline and any issues and concerns affecting new and emerging accounting researchers because of PBRF.

Applying an institutional theoretical lens, this paper explores accounting HoDs’ perceptions concerning the PBRF system’s impact on their academic staff. The research used semi-structured interviews to collect data from NZ’s eight universities.

The key findings posit that many institutional processes, some more coercive in nature, whereas others were normative and mimetic, have been put in place to ensure that academics are able to meet the PBRF requirements. HoDs suggest that their staff understand the importance of research, but that PBRF is a challenge to new and emerging researchers and pose threats to their recruitment. New academics must “hit the ground running” as they must demonstrate not only teaching abilities but also already have a track record of research publications; all in all, a daunting experience for new academics to overcome. There is also a teaching and research disconnect. Furthermore, many areas where improvements can be made in the design of this measurement tool remain.

The PBRF system has significantly impacted on accounting academics. Central university research systems were established that subsequently applied coercive institutional pressures onto line managers to ensure that their staff performed. This finding offers scope for future research to explore a better PBRF that measures and rewards research productivity but without the current system’s unintended negative consequences.