Research

Research

The research of the Engineering Mechanics group focuses on the development of constitutive models and computational methods for advanced engineering applications. Having a wide range of expertise in numerical and theoretical solid and fluid mechanics, the group aims to provide comprehensive simulation tools for analysis and design through the development of multiscale and multi-physics methods.

The following subjects are studied within the group of engineering mechanics:

Adaptive Discretization for Fluid Structure Interaction

Fluid-structure interaction encapsulates several of the most daunting challenges in concurrent computational science, as it constitutes a multiphysics, multiscale, free-boundary problem. The disparity of the fluid and structure subsystems is reflected in a wide range of length and time scales in the aggregated problem. Moreover, the interaction occurs at a free boundary, which yields a complicated interconnection between the governing initial-boundary-value problems, and the domains on which these are defined.

Delamination Buckling of Fibre-Metal Laminates

A fibre-metal laminate is a hybrid material consisting of alternating layers of metal and fibre-reinforced prepreg. An example of such a material is GLARE; a combination of aluminium and glass fibre-reinforced epoxy. This material has better fatigue properties than traditional aluminium alloys and will therefore be applied to large parts of the fuselage of the A380 aircraft.

Earthquake hazard assessment through stochastic failure mechanics and satellite observations

The introduction of satellite radar interferometry in the 1990’s resulted in a significant boost of geophysical analyses of earthquakes, volcano and glacier dynamics, and land subsidence. The fine spatial resolution unravelled unprecedented detail in the stress and strain patterns related to these phenomena, leading to a better insight in the driving mechanisms. Moreover, compared to conventional geodetic survey methods, also the high temporal revisit rate, low cost, and non-intervening nature of the satellite images resulted in improved insight in the dynamics of these geophysical events.

Simulation of environmentally assisted failure of metals

The combined influence of stress and an aggressive environment leads to a form of localised damage that is commonly known as Stress Corrosion Cracking (SCC). Electrochemical actions tend to intensify the crack growth and to decrease the resistance to final fracture. This form of corrosion attack has led to catastrophic failures in structural and aircraft systems. While the understanding of SCC phenomena has increased in the past century and models based on heuristic and mechanistic aspects have been developed, experimental data on SCC exhibit a considerable scatter and application to practice is limited.

Explosive Loaded Composite Plates

The Royal Netherlands Navy is considering composite antenna masts for their future naval ships, see figure 1 for an example. These composite masts will combine several properties in order to enhance the survivability under enemy attack and to lower the Radar Cross Section (RCS) signature of the ship. Because of the high value payload in these masts (communication and radar equipment) and the low electronic transmission loss, the use of advanced glass fibre composites is useful.

Qualification Methodology of Hard Coating-Substrate Systems

The development of new coatings with thickness of only a few microns and high hardness creates the need to extend the techniques used to characterize their mechanical properties. Micro- and nano-indentation tests are commonly used to measure mechanical properties, however there is a large scatter in values reported from different research groups. Although indentation tests can be useful to obtain qualitative data, they do not always provide accurate quantitative data, particularly for brittle materials such as hard coatings.

Design and Development of High Temperature Coating System for Engines

The project is aimed at developing the fundamental elements for the design, simulation and testing of a high-temperature coating system for aerospace jet engines. The overall goal of the proposed research is to improve the durability of the coating system and to allow higher engine operation temperatures. To this end, it is crucial to obtain detailed knowledge about the thermal, mechanical and chemical processes occurring within the coating/substrate system during its life span.

Design of Optimized TRIP Steels

Transformation-induced plasticity steel (TRIP-steel) constitutes a special class of high performance multiphase steels, which can be distinguished from other materials of this type by the controlled inclusion of islands of a metastable phase, retained austenite. Recent academic and industrial research has concentrated on the stability of retained austenite islands during mechanical loading. Physical models have shown that this stability, and therefore the macroscopic mechanical properties of the material, depends on a large number of highly interrelated parameters. Very recently, experimental proof has been obtained for some of the theoretical predictions on the stability of individual islands.

Adaptive Multiscale Methods for Hybrid RANS/LES

There is considerable impetus to improve aircraft performance through the use of lighter, more flexible smart structures. In many cases, however, such designs are limited by the necessity of avoiding undesirable fluid-structure interaction phenomena which are dependent on the dynamics of high-Reynolds-number turbulent flows. Such interactions are notoriously intractable, due to the enormous range of flow length scales present at high Reynolds numbers. For practical computations, specialised techniques must be developed.

Stochastic analysis for fracture of piezoelectric components

The reliability of piezoelectric devices is an outstanding issue that will become of major importance as industry gets more concerned with the development MEMS. Uncertainty in the behaviour of piezoelectric materials exists, for instance, in the electro-mechanical coupling and the dielectric behaviour, in the fracture and fatigue properties and in the bonding to the host structure . These issues are essentially of a physically non-linear nature.

Variational Multiscale Large-Eddy Simulation for Deforming Domains

The dynamics of many types of fluid-structure interactions are dependent on the unsteady behaviour of turbulent flows. In most cases of interest, however, the flow is of relatively high Reynolds number, and thus contains features which transcend an wide range of length scales. These include the largest eddies which most directly influence the forces felt by the structure (figure 1, left) down to minute viscosity-dominated eddies (figure 1, below), which account for the majority of the flow's energy dissipation.

Stochastic finite element modelling of fibre-metal laminates

Fibre metal laminates (FML) combine properties of both monolithic metal alloys and fibre-reinforced composites. These laminates consist of alternating layers of fibre-reinforced epoxy and metal alloy layers. The metal alloy layers protect the fibre-reinforced epoxy layers from the often harsh operating environment, while the fibre-reinforced layers in turn provide an effective barrier to eventual fatigue cracks from propagating through the laminate.