Application of artificial neural networks to the evaluation of the ultimate strength of uniaxially compressed welded stiffened aluminium plates

peer reviewedA series of elastoplastic large-deflection finite element analyses is performed on stiffened aluminium plates with flat-bar stiffeners under in-plane longitudinal compression loads. Then, the closed-form ultimate compressive strength formula is derived for stiffened aluminium plates by regression analysis. Finally, artificial neural network methodology is applied to predict the ultimate strength of uniaxially compressed stiffened aluminium plates. It is found that artificial neural network models can produce a more accurate prediction of the ultimate strength of the stiffened aluminium plates than can the existing empirical formula

Ultimate strength

Concern for the ductile behaviour of ships and offshore structures and their structural components under ultimate conditions. Attention shall be given to the influence of fabrication imperfections and in-service damage and degradation on reserve strength

The influence of residual stress on the ultimate strength of longitudinally compressed stiffened panels

Welding-induced residual stress is known to reduce the ultimate compressive strength of moderately slender stiffened panels under longitudinal compression. This paper contributes a quantified measure of this strength reduction and draws some qualitative observations linking the significance of the residual stress influence to the collapse mode of the panel. A series of nonlinear finite element analyses are completed which covers a range of plate slenderness ratios (β = 1.0 − 4.0) and column slenderness ratios (λ = 0.2 − 1.2) typical for application to ship structures. Two residual stress scenarios are compared to a baseline stress-free condition. The first scenario includes residual stress in the plate only and the second scenario includes residual stress applied in the plate and the stiffener web. A modified edge function approach, which can be used in combination with a rule-based approach to account for the effects of residual stress, is examined with reference to the numerical results. A significant ultimate strength reduction due to residual stress is found in most test cases. It is found that residual stress in the plate causes a reduction of the ultimate compressive strength of stiffened panels regardless of failure modes. However, the residual stress in the stiffener web dominates the strength reduction of stiffened panels where collapse is triggered by beam-column buckling. Conversely it has little influence on the stiffened panels which collapse in a plate buckling mode. In addition, the modified edge function approach is demonstrated as conservative compared to the present numerical results, with its applicability confined to stocky panels

Engineering Principles

Over the last decade, there has been substantial development of welding technologies for joining advanced alloys and composites demanded by the evolving global manufacturing sector. The evolution of these welding technologies has been substantial and finds numerous applications in engineering industries. It is driven by our desire to reverse the impact of climate change and fuel consumption in several vital sectors. This book reviews the most recent developments in welding. It is organized into three sections: “Principles of Welding and Joining Technology,” “Microstructural Evolution and Residual Stress,” and “Applications of Welding and Joining.” Chapters address such topics as stresses in welding, tribology, thin-film metallurgical manufacturing processes, and mechanical manufacturing processes, as well as recent advances in welding and novel applications of these technologies for joining different materials such as titanium, aluminum, and magnesium alloys, ceramics, and plastics

Development of Non-Destructive Testing by Eddy Currents for Highly Demanding Engineering Applications

Defect detection with Non-Destructive Testing (NDT) is essential in accidents prevention, requiring R&TD to generate new scientific and procedural knowledge for new products with high safety requirements. A current challenge lies in the detection of surface and sub-surface micro defects with NDT by Eddy Currents (EC). The main objective of this work was the development of applied research, technological innovation and experimental validation of EC customized systems for three highly demanding inspection scenarios: micro defects in tubular geometries; brazed joints for the automotive industry; and high-speed moving composite materials. This objective implied starting from the scientific fundamentals of NDT by EC to design and simulate EC probes and the prototypes developed were tested in industrial environment, reaching a TRL ≈ 5. Another objective, of a more scientific and disruptive nature, was to test a new technique for the creation of EC in the materials to be inspect, named Magnetic Permeability Pattern Substrate (MPPS). This technique consists on the development of substrates/films with patterns of different magnetic permeabilities rather than the use of excitation bobbin coils or filaments of complex geometry. The experimental results demonstrated that the prototypes developed for the three industrial applications studied outperformed the state of the art, allowing the detection of target defects with a very good signal-to-noise ratio: in tubular geometries defects with depth of 0.5 mm and thickness of 0.2 mm in any scanning position; in the laser brazed weld beads pores with 0.13 mm diameter and internal artificial defects 1 mm from the weld surface; in composite materials defects under 1 mm at speeds up to 4 m/s and 3 mm lift-off. The numerical simulations assisted the probe design, allowing to describe and characterize electrical and magnetic phenomena. The new MPPS concept for the introduction of EC was validated numerically and experimentally

Novel Approaches for Nondestructive Testing and Evaluation

Nondestructive testing and evaluation (NDT&E) is one of the most important techniques for determining the quality and safety of materials, components, devices, and structures. NDT&E technologies include ultrasonic testing (UT), magnetic particle testing (MT), magnetic flux leakage testing (MFLT), eddy current testing (ECT), radiation testing (RT), penetrant testing (PT), and visual testing (VT), and these are widely used throughout the modern industry. However, some NDT processes, such as those for cleaning specimens and removing paint, cause environmental pollution and must only be considered in limited environments (time, space, and sensor selection). Thus, NDT&E is classified as a typical 3D (dirty, dangerous, and difficult) job. In addition, NDT operators judge the presence of damage based on experience and subjective judgment, so in some cases, a flaw may not be detected during the test. Therefore, to obtain clearer test results, a means for the operator to determine flaws more easily should be provided. In addition, the test results should be organized systemically in order to identify the cause of the abnormality in the test specimen and to identify the progress of the damage quantitatively

Modelling, Test and Practice of Steel Structures

This reprint provides an international forum for the presentation and discussion of the latest developments in structural-steel research and its applications. The topics of this reprint include the modelling, testing and practice of steel structures and steel-based composite structures. A total of 17 high-quality, original papers dealing with all aspects of steel-structures research, including modelling, testing, and construction research on material properties, components, assemblages, connection, and structural behaviors, are included for publication