Buckling vs. Crack Growth: Numerical Simulation

2000 ◽  
Author(s):  
T. Siegmund
Keyword(s):  
Numerical Simulation ◽  
Crack Growth ◽  
Local Failure ◽  
Small Thickness ◽  
Mechanical Integrity ◽  
Thin Walled Structures ◽  
Aspect Ratios ◽  
Thin Walled

Abstract Thin walled structures are characterized by configurations that possess large aspect ratios, i.e. large in-plane dimensions and small thickness dimensions. The present work aims on investigations of the mechanical integrity of such structures thereby focusing on the competition and interaction between global failure due to buckling and local failure due to crack growth.

Development of a New Model for the Varying Dynamics of Flexible Pocket-Structures During Machining

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Mouhab Meshreki ◽  
Helmi Attia ◽  
József Kövecses
Keyword(s):  
Dynamic Models ◽  
Ritz Method ◽  
Computation Time ◽  
Dynamic Effect ◽  
Dynamic Responses ◽  
Prediction Errors ◽  
Continuous Change ◽  
Thin Walled Structures ◽  
Aspect Ratios ◽  
Thin Walled

Many of the aerospace components are characterized by having pocket-shaped thin-walled structures. During milling, the varying dynamics of the workpiece due to the change of thickness affects the final part quality. Available dynamic models rely on computationally prohibitive techniques that limit their use in the aerospace industry. In this paper, a new dynamic model was developed to predict the vibrations of thin-walled pocket structures during milling while taking into account the continuous change of thickness. The model is based on representing the change of thickness of a pocket-structure with a two-directional multispan plate. For the model formulation, the Rayleigh–Ritz method is used together with multispan beam models for the trial functions in both the x- and y-directions. An extensive finite element (FE) validation of the developed model was performed for different aspect ratios of rectangular and nonrectangular pockets and various change of thickness schemes. It was shown that the proposed model can accurately capture the dynamic effect of the change of thickness with prediction errors of less than 5% and at least 20 times reduction in the computation time. Experimental validation of the models was performed through the machining of thin-walled components. The predictions of the developed models were found to be in excellent agreement with the measured dynamic responses.

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