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The book presents interesting examples of recent developments in this area. Among the studied materials are bulk metallic glasses, metamaterials, special composites, piezoelectric smart structures, nonwovens, etc.

The last decades have seen a large extension of types of materials employed in various applications. In many cases these materials demonstrate mechanical properties and performance that vary significantly from those of their traditional counterparts. Such uniqueness is sought – or even specially manufactured – to meet increased requirements on modern components and structures related to their specific use. As a result, mechanical behaviors of these materials under different loading and environmental conditions are outside the boundaries of traditional mechanics of materials, presupposing development of new characterization techniques, theoretical descriptions and numerical tools. The book presents interesting examples of recent developments in this area. Among the studied materials are bulk metallic glasses, metamaterials, special composites, piezoelectric smart structures, nonwovens, etc.



Finite Element Modelling of 2D Brittle Fracture: The Phase-Field Approach

The prevention of fracture-induced failure is a major constraint in engineering design, and numerical simulations of fracture processes often play a key role in design decisions. Although huge efforts have been made to develop novel and more accurate models of fracture and an enormous progress has been achieved in the recent years, the development of an adequate scheme for the numerical simulation of crack initiation and propagation is still a significant challenge for the scientific community. The goal of this paper is twofold: (i) to give an overview of current numerical methods available in the literature for the analysis of brittle fracture problems; (ii) to present a finite element phase-field scheme for the analysis of brittle fracture problems. This scheme relies on recently developed strategies for incorporating an additional phase-field to account for fracture. The spatial finite element discretization is formulated by means of the classical Galerkin method, whereas an implicit Euler method with adaptive time-stepping is adopted for the temporal discretization. To demonstrate the capabilities of the model, some numerical experiments are modelled.
H. A. F. A. Santos, V. V. Silberschmidt

Crystalline Deformation in the Small Scale

In the last two decades, experimental observations demonstrated—and numerical simulations confirmed—that plastic deformation in the small scale, i.e. at the micron or sub-micron scales, is different from that at the macro-scale; this phenomenon is known as size effect. It was observed mostly in indentation, torsion and bending experiments, being ascribed to strong gradients of strain in such deformation processes. The size effect was also reported in uniaxial micro- and nano-pillar compression experiments in spite of their inherent lack of (or limited) macroscopic strain gradients. In the present study, we first review some critical and essential experimental studies that were conducted over the years to analyse various mechanisms that govern deformation in the small scale. In the second part, different modelling approaches describing this phenomenon are briefly reviewed.
Murat Demiral, Anish Roy, Vadim V. Silberschmidt

Methods of Stochastic Mechanics for Characterization of Deformation in Randomly Reinforced Composite Materials

This chapter reveals certain aspects of theoretical statistical approach to studying mechanical behavior of randomly reinforced composite materials, particularly focusing on microstructural characterization and methods of description of stress and strain fields in components of material. Mechanical properties of microstructural components are defined with conventional phenomenological equations and criteria while the effective properties of composite and characteristics of microscopic deformation fields are computed using the solutions of stochastic boundary value problems (SBVPs). Microstructural description is based on a concept of the representative volume elements (RVE) and is implemented with the correlation functions of the second and higher orders. Statistical moments of microstructural fields are used as the characteristic of deformation and fracture processes and analytically connect the microstructural correlation functions with the SBVP solution. Using the Green’s functions these solutions have been obtained in elastic and elastoplastic formulations. The numerical calculations for a case study of porous composites with different microstructural properties were obtained for various loading conditions. Some milestones of emerging and development of the described methods are also addressed.
Mikhail A. Tashkinov

Optimization of the Damping Properties of Electro-Viscoelastic Objects with External Electric Circuits

The paper deals with optimization of dynamic characteristics of smart structures based on piezoelectric materials with external electric circuits comprising resistance, capacitance and inductance. The dynamic parameters to be optimized are resonance frequencies and damping properties. For numerical estimation of the dynamic characteristics of the model system, a natural vibration problem of an electroviscoelastic solid with differing external electric circuits is proposed. Model examples are given to demonstrate the efficiency of the natural vibration problem in finding dynamically optimum piezoelectric smart structures with external electric circuits.
V. P. Matveenko, M. A. Yurlov, N. A. Yurlova

Bulk Metallic Glasses: Mechanical Properties and Performance

In this paper, a history of development of bulk metallic glasses (BMGs) was presented, followed by a review of fundamental mechanisms of their deformation and fracture. In this study, observations of fracture surfaces of the Zr-Cu-based BMG exposed to a 3-point test revealed features that are different from those observed in crystalline materials. Indentation techniques were extensively used to characterise elastic deformation of the studied BMG alloy, followed by a systematic analysis of initiation and evolution of shear-band localisation in the indented material. Our results, obtained with the suggested wedge-indentation technique, demonstrated initiation of shear bands in the material volume. This technique can be particularly useful for development of appropriate constitutive models to analyse plastic events in amorphous materials in the small-length scale. A current state of constitutive models of deformation and fracture behaviour of BMGs are presented together with modelling challenges. Simulation of simple tensile and compressive tests were conducted with JH-2, JHB and Drucker-Prager constitutive models by employing identical boundary conditions, type of element and specimen’s geometry. Based on the obtained simulation results, the JH-2 model was considered as not suitable for quasi-static analysis due to ambiguity of the data produced with it for uniaxial tensile and compressive conditions. However, it is concluded that the extended Drucker-Prager and JHB models can be used to study deformation modes in BMGs.
V. Nekouie, G. Abeygunawardane-Arachchige, A. Roy, V. V. Silberschmidt

Constitutive Properties of Pure Indium in Wide Temperature Range

For microelectronic devices used in low-temperature applications, understanding of their reliability and performance has become an important research subject covering their service under severe or extreme conditions. Along with challenges due to continuing miniaturisation of such devices, various properties and relevant thermo-mechanical response of interconnection materials to temperature excursions at micro-scale became a critical factor that can affect reliable performance of microelectronics in various applications. Pure indium, as an excellent interconnection material, has been used in the pixellated detector systems, functioning at cryogenic temperatures. The properties and behaviour of indium joints determine the functionality and performance of the detector system directly since higher resolution of the sensor is achieved by bonding it with a readout assembly via ultra-fine indium bumps. In this study, deformation behaviour of indium joints was investigated by considering effects of its microstructure, including the joint size (thin and thick joints) and substrate type (In/Cu and In/Ni/Cu joints), and temperature. A constitutive relationship was thus established to describe the deformation properties of indium joints under a wide range of homologous temperatures.
Xiaojin Cheng, Changqing Liu, Vadim V. Silberschmidt

Metamaterials with Negative Poisson’s Ratio: A Review of Mechanical Properties and Deformation Mechanisms

Compared to conventional materials, materials with a negative Poisson’s ratio are endowed with many specific mechanical features; consequently, there are many potential applications for them. For the last two decades, many efforts have been made on this sort of metamaterial both experimentally and theoretically. This paper provides a brief review of those studies with a focus on mechanical properties and deformation mechanisms of the metamaterials. The latter are explained using a structure of a multi-phase metamaterial system for a more comprehensive understanding and as an inspiration for future works. Additionally, respective manufacturing methods and applications are also summarised.
Xiaonan Hou, Vadim V. Silberschmidt

Deformation and Damage of Thermally Bonded Nonwoven Networks

Nonwovens, composed of randomly-oriented polymer-based fibres, possess unique properties, with features common to paper, plastic and textile materials. From various types of bonding technologies used in the nonwovens industry. This chapter focuses on thermal bonding and respective fabrics as it is one of the most widely used techniques. Understanding a mechanical behaviour of polymer-based nonwoven materials that includes large-strain deformation and damage can help to evaluate a response of nonwoven fibrous networks to various loading conditions. The main deformation and damage mechanisms are analysed by means of experimental assessment of fabrics in tension alongside damage evolution based on progressive failure of fibres. Finite-element simulation strategies to gain insight into their behaviour and to achieve quantitative exploration of a design space for these materials are also discussed in this chapter.
Farukh Farukh, Emrah Demirci, Memiş Acar, Behnam Pourdeyhimi, Vadim V. Silberschmidt
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