PERIDYNAMICS

Peridynamics

The peridynamic theory provides the capability for improved modeling of progressive failure in materials and structures. Further, it paves the way for addressing multi-physics and multi scale problems. Even though numerous journal articles and conference papers exist in the literature on the evolution and application of the peridynamic theory, it is still new to the technical community. Please see below for numerous application areas of peridynamics performed by PDRC researchers.

composite materials

Damage initiation and its subsequent propagation in fiber-reinforced composites are not understood as clearly as they are, for example, for metals because of the presence of stiff fibers embedded into the soft matrix material, causing inhomogeneity. Under the assumption of homogeneity, a lamina has orthotropic elastic properties. Even though this assumption is suitable for stress analysis, it becomes questionable when predicting failure. Most composite structures include notches and cutouts, not only reducing the strength of the composites but also serving as potential failure sites for damage initiation. They also promote common failure modes of delamination, matrix cracking, and fiber breakage. These failure modes are inherent to the inhomogeneous nature of the composite, thus the homogeneous material assumption taints failure analyses.

Researchers: Dr. Cagan Diyaroglu, Ms. Yan Gao, Mr. Yakubu Kasimu Galadima, Ms. Jeeyeon Heo

Damage in a composite lamina subjected to underwater shock loading

CORROSION DAMAGE MODELLING

Due to their unpredictability, rapid growth and difficulty of detection, localised forms of corrosion represent a threat to human life and the environment. The current empirical and semi-empirical approaches used by engineers to hinder corrosion damage have several disadvantages and limitations. In this regard, numerical approaches can be a valuable complement. However, the majority of the numerical techniques currently available in the literature are based on partial differential equations, which become invalid in the presence of field’s discontinuities such as cracks and sharp concentration gradients. In order to overcome these limitations, a recently introduced continuum theory of mechanics based on integro-differential equations, peridynamics, is used modelling of polycrystalline fracture, stress-corrosion cracking, pitting corrosion and crack propagation from corrosion pits in materials exposed to different corrosive environments.

Researchers: Dr. Dennj De Meo, Mr. Andrzej Czerwonka, Mr. Mingyang Li, Mr. Zhenghao Yang, Mr. Ademolu Richard, Ms. Olena Karpenko

ICE-STRUCTURE INTERACTIONS

The Arctic is considered as the Middle East of the future. Around 30% of the world’s undiscovered gas and 13% of the world’s undiscovered oil are expected to be stored in the North Arctic Circle. Despite of its advantages, utilization of the Arctic region for sailing brings new challenges due to its harsh environment. Therefore, ship structures must be designed to withstand ice loads in case of a collision between a ship and ice takes place. Such incidents can cause significant damage on the structure which can yield flooding and sinking of the ship. In order to capture the macro-scale behaviour of ice, well-known Finite Element Method (FEM) has been used in various previous studies. The effectiveness of computational techniques such as finite elements in modelling material failure has lagged far behind their capabilities in traditional stress analysis. This difficulty arises because the mathematical foundation on which all such methods are based assumes that the body remains continuous as it deforms. By taking into account all these challenging issues, a state-of-the-art technique, peridynamics can be utilized for ice-structure interaction modelling.

Researchers: Mr. Bozo Vazic, Mr. Xu Ji, Ms. Wei Lu

Crack evolution inside an electronic package

Electronic packages

The components of Integrated Circuit (IC) devices are susceptible to moisture absorption at different stages of the production environment which can lead to hygrothermal stresses during the surface mounting process. The moisture concentration in electronic packages can be determined based on the wetness approach. If the saturated concentration value is dependent on temperature or time, the analogy between the wetness equation and the standard diffusion equation is not valid and requires special treatment. Peridynamics is utilized for the solution of wetness field equation in the case of saturated concentration varying with time.

Researchers: Dr Cagan Diyaroglu

EXTREME LOADING ON STRUCTURES

Efficient quantitative assessment of damage to structures is an active need that hasn’t been satisfactorily addressed. From a defense perspective, damages to structures stem from two main modes of loading: explosions leading to airblast loading on a structure, and direct strikes causing damage through penetration. In some cases both modes coexist. Both of these loading modes have the potential to cause extensive damage on both the external and internal structure. Detection of damage in structures may be straight-forward through visual inspection (cracks, holes, etc.). However, quantification of damage is a daunting task. In addition to the damage that is visible, there exists further damage internal to components and at joints of components. On-site evaluation of damage that is not visible involves expensive specialized equipment, and may not be fully satisfactory in visualization of internal damage. Therefore, damage assessment process stands to benefit from its augmentation by computational modelling and analysis.

Researchers: Dr. Cagan Diyaroglu, Ms. Yan Gao, Ms Jeeyeon Heo

Impact damage assessment of reinforced concrete

fire damage modeling

Composite materials are increasingly used in marine industry as in many other sectors including aerospace and automotive. For instance fiberglass reinforced plastic (FRP) materials have many advantages over other traditional metallic materials such as (i) resistance to the marine environment, (ii) lightweight, (iii) high strength, (iv) seamless construction, (v) low maintenance and (vi) durability. Moreover, composite materials can provide a step change in vessel efficiency both in terms of energy use and maintenance costs. Although these materials have many advantages, one of the biggest disadvantages of composites is their poor fire performance. Composite materials are usually composed of glass or carbon fibre and polymer matrix material and they are flammable. Therefore, understanding the damage and failure in fire condition is a crucial issue for safety since the damage induced by fire may result in collapse of the marine structure which may cause injuries and deaths.

Researcher: Ms. Yan Gao

fatigue

Fatigue is the weakening of a material caused by repeatedly applied loads. It is the progressive and localized structural damage that occurs when a material is subjected to cyclic loading. The nominal maximum stress values that cause such damage may be much less than the strength of the material typically quoted as the ultimate tensile stress limit, or the yield stress limit. Fatigue occurs when a material is subjected to repeated loading and unloading. If the loads are above a certain threshold, microscopic cracks will begin to form at the stress concentrators.

Researchers: Mr. Ning Zhu, Dr. Cemal Kochan, Mr. Kyutack Hong, Ms. Olena Karpenko

Damage in SOFCs as a result of high temperatures

fracture in lithium-ion batteries and fuel cells

Hybrid propulsion system has become popular in marine industry due to increasingly strict emission control standards. Hence, as one component in the system, marine batteries become attractive in marine design. Solid Oxide Fuel Cells (SOFCs) and lithium ion battery are the most promising energy storage devices in the electric propulsion system or HPS. Since silicon particles expands around 400% in volume during lithation, the battery electrodes will experience large volumetric change during normal battery cycling. As a result, misdistribution of stress may form inside the battery electrode. Therefore, degradation and delamination may happens in the battery electrode after many cycling process of marine battery.

Researcher: Dr. Hanlin Wang

Hydrodynamic pressure distribution acting on a containership.

FLUID-STRUCTURE INTERACTION

Fluid–structure interaction (FSI) is the interaction of some movable or deformable structure with an internal or surrounding fluid flow. Fluid–structure interactions are a crucial consideration in the design of many engineering systems, e.g. aircraft, spacecraft, engines and bridges. Aircraft wings and turbine blades can break due to FSI oscillations. Fluid–structure interactions also occur in moving containers, where liquid oscillations due to the container motion impose substantial magnitudes of forces and moments to the container structure that affect the stability of the container transport system in a highly adverse manner.

Researchers: Dr. Cagan Diyaroglu, Dr. Adnan Kefal, Mr. Yildirim Dirik, Mr. Cong Nguyen, Mr. Mingyang Li

ADDITIVE MANUFACTURING

Metal-based additive manufacturing, or three-dimensional (3D) printing, is an emerging technology across various industries including the marine industry. Manufacturing metal components layer by layer increases design freedom and manufacturing flexibility. Therefore, complex geometries can be easily created, product customisation can be enhanced and time to market can be shortened. However, currently only a few number of alloys can be reliably printed. Metal-based additive manufacturing often involves the deposition of layers of an alloy feedstock in the form of powders or wires, which are melted together by a rapidly moving heat source to form a solid mass. The rate of solidification is often an order of magnitude higher than that is seen during conventional casting techniques, and the process of building up layers causes non-uniform cooling. This leads to thermal stresses in the alloy which can generate cracks known as hot tears.

Researchers: Ms. Olena Karpenko, Mr. Bingquan Wang

NONLOCAL CONTINUUM MECHANICS

Nonlocal continuum mechanics is becoming increasingly popular with the development of new materials and systems such as carbon nanotubes and graphene. Nonlocal continuum mechanics has a length scale parameter which doesn’t exist in classical techniques. Therefore, it can represent non-classical physical phenomena. Moreover, it is computational more adventageous with respect to atomistic techniques since it is a continuum approach.

SOFT MATERIALS

Soft materials are important in a wide range of technological applications. They may appear as structural and packaging materials, foams and adhesives, detergents and cosmetics, paints, food additives, lubricants and fuel additives, rubber in tires, etc. In addition, a number of biological materials (blood, muscle, milk, yogurt, jello) are classifiable as soft matter. Liquid crystals, another category of soft matter, exhibit a responsivity to electric fields that make them very important as materials in display devices (LCDs).

Researcher: Ms. Yunke Huang

MATERIAL DESIGN

With the advancement of manufacturing techniques including 3-D printing, designing new materials with superior properties are now possible. Computational techniques can play a crucial role in the design process.

Researchers: Mr. Wenxuan Xia, Mr. Zhenghao Yang, Mr. Yakubu Kasimu Galadima

Variation of oxidation state in a rectangular G30/PMR-15 lamina with a pre-existing crack

oxidation damage in composites

Surface oxidation degrades the durability of polymer marix composites operating at high temperatures due to the presence of strong coupling between the thermal oxidation and structural damage evolution. The mechanism of oxidation in polymer matrix composites leads to shrinkage and damage growth. The thermo-oxidative behavior of composites introduces changes in diffusion behavior and mechanical response of the material.

Crack propagation paths in a fuel pellet

nuclear materials

Nuclear fuel pellets are used to generate heat for power generation as a result of fission process. Therefore, it is essential to understand its thermal transport for enhancing power output and preventing potential accidents. Uranium dioxide (UO2) is the main component of the fuel pellet. Its composition can have both an excess and deficiency of oxygen relative to stoichiometric UO2. Studies by show that in hyper-stoichiometric Urania (UO2 + x), the oxygen ions tend to accumulate in the regions of high temperature gradient or the Soret effect (the transport of oxygen atoms due to a temperature gradient). It is experimentally found that the thermal conductivity of UO2 decreases with temperature and with increasing non-stoichiometry. The fuel pellets are placed in a cladding and there exists a gap between fuel pellet and the cladding. The cooling water passing through the fuel elements extracts heat from the nuclear fuels. However, significant microstructural changes and deterioration of the fuel pellet occur due to the fission process. As a result, the degraded physical state of the fuel becomes the limiting factor for long term and transient reactor performance.

nanomechanics: graphene fracture & nanoindentation

Traditionally, there exist two main approaches to simulate the mechanical behavior of materials at the nano-scale. The first approach is based on Classical Continuum Mechanics (CCM) when the continuum assumption is valid. When nano-scale effects become significant, it is no longer applicable since it does not have a length-scale parameter. Furthermore, its equation of motion is not suitable for problems including discontinuities since the spatial derivatives are not defined in such cases. The second approach is based on Molecular Dynamics (MD). It is a powerful tool as long as the interactions between atoms and molecules are well defined. However, even with current powerful supercomputers, the total simulation time and size of the models are still limited. Therefore, it is necessary to use a methodology that is based on continuum mechanics and have a length scale parameter to capture the nano-scale effects. Furthermore, it should be applicable for problems with discontinuities. Peridynamics is a suitable approach for this since it is a continuum mechanics formulation with a length scale parameter.

Researcher: Dr. Cagan Diyaroglu, Mr. Ning Zhu

hydraulic fracturing

The hydraulic fracturing process creates and propagates cracks in a porous medium by injecting fluid pressure. It has gained significant attention as a result of its use in oil and gas extraction from unconventional shale resources. In this particular application, a mixture of hydraulic fluid, sand, and chemicals is pumped into a well to create cracks in low-permeable shale, and keep them open after the removal of the fluid. Once the process is complete, the permeability of the shale increases significantly; thus, oil and/or gas starts to flow through the well. Another application of hydraulic fracturing concerns heat extraction from geothermal resources. Similar to the technique used in oil and gas extraction, the permeability of hot rocks is enhanced by pumping cold water into the rock. Cold water can be pumped from one well (injection well), and hot water can be extracted from the other well (production well). This technique, known as Hot Dry Rock (HDR), is used in the production of electricity.

Propagation of Cracks in Photovoltaic Panels

Cracking in PV panels can cause performance degradation in PV panels.

Researchers: Mr. Andrew Premchander, Dr. Islam Amin, Dr. Selda Oterkus, Dr. Erkan Oterkus and Dr. Nabil Ahmed Shawky Elminshawy