Study on diffusion and mechanical behaviour of calcium-based solid waste mineralization grouting materials in the goaf

Neutron scattering is one of the most powerful characterization techniques available for materials research, and its proven capabilities and anticipated potentials justify the 1.4-billion dollar construction of the Spallation Neutron Source (SNS) at the Oak Ridge National Laboratory (ORNL) as well as a number of multi-million dollar facility upgrades at the Los Alamos Neutron Science Center (LANSCE), Intense Pulsed Neutron Source (IPNS), and High Flux Isotope Reactor (HFIR) in the US, and at ISIS, the Rutherford Appleton Laboratory in UK. However, while the multi-billion dollar constructions are on-going all around the world, currently there is no concerted effort within the US in advancing the science and education in the application of neutron scattering in materials research, specifically in the study of mechanical behavior of advanced materials. To be better positioned in the scientific research at the international level, it is important to develop a network with international counterparts. Therefore, a group of the most active researchers in the neutron-scattering materials-research field will form an international network through the International Materials Institutes (IMI)-Advanced Neutron Scattering netWork for Education and Research (ANSWER) with a focus on mechanical behavior of materials. The IMI provides a synergistic effort in advancing the fundamental understanding of mechanical behavior of materials at the atomic level using state-of-the-art neutron sources in the world.

This study aims to advance the understanding of particle shape effects on the mechanical behaviours of granular materials by using 3D printed soil. A holistic particle geometry parameter (Sh), which integrated the 3D information of a particle (i.e. volume, surface area, and size) was developed to describe the particle shape and correlate with the granule’s shear behaviours. Test results revealed that higher Sh had positive correlations with the shear strength and dilation angle but exhibited negative correlations with packing densities. Under a constant relative density, particle shape showed coupled effects on the mechanical and volumetric behaviours of granular materials. The Regular Hexahedron (RH) granules exhibited the highest shear strength with the optimal shape parameter. In addition, an empirical correlation between Sh and maximum mobilised friction angle (ϕmax ) was established, which provided insights for discrete element method (DEM) simulations in considering the influences of particle shape.

Finite element modelling of rubber-like polymers based on chain statistics

Chapter 20 - Severe Plastic Deformation of Materials

Analysis of acoustic emission signature during aluminous cement setting to characterise the mechanical behaviour of the hard material

Impact of train speed on the mechanical behaviours of track-bed materials

There are a significant number of factors which have impact on the scale effect in the mechanical behaviour of composite materials. In this paper, the influence of the microstructure on this phenomenon is examined. In particular, how the results of the uniaxial compression test are affected by the microstructure geometry is verified. For the purposes of this study, two different materials are chosen, i.e. pure gypsum and mortar. Firstly, the microstructures of the two considered materials are compared with the use of different microstructure measures, i.e. attenuation profiles, porosity and pore size distributions, calculated based on the images obtained from the X-ray microCT. Then, a series of uniaxial compression tests is performed for a large number of cylindrical specimens made of the two materials under study. Four different sample diameters are assumed in order to investigate the size effect in the considered composites. For both materials, the results of uniaxial compressive strength and the Young modulus are presented. The relationship between the microstructure of the material and the scale effect in mechanical properties is proved. The scale effect is more demonstrable in the case of the material which exhibits a more heterogeneous microstructure.

Discontinuous FE approach and lattice models to describe cracking behaviour in fibre-reinforced brittle materials

Effect of particle type on the shear behaviour of granular materials

Artificial cementation bonds were created in a model clayey material by adding 4% of Portland cement to kaolin clay. The mechanical behaviour of the model material was compared with the behaviour of the pure reconstituted kaolin clay. Submersible LVDT's and bender elements were used in identifying the elastic stiffness and the destructuration of the specimens. The triaxial CIUP tests were carried out in determining the shear strength. The aim of the laboratory study was to obtain a complete picture of the mechanical behaviour of the model material, which can be used for calibration, evaluation and further development of constitutive models.

The Boundary Element Method (BEM) is one among the most popular simulation techniques employed to simulate mechanical behaviour of materials, including smart engineering materials. Although BEM is a quite well-established numerical technique, literature tells that the method may not be well suited to simulate structures where one or two of the dimensions is much smaller than the remaining dimension/s (for a 3D problem). Hence in this work, deflection of a cantilever beam is simulated using constant boundary elements to get a feel of the accuracy of the BEM when used to simulate such type of structures. Although the concept is not new, the study assumes significance because studies which list the results in detail are not readily found in the literature. In this study, the results are obtained for different mesh resolutions also. The results indicate that - as expected - constant boundary elements are not a good choice for simulating the mechanical behaviour of smart materials when the structural member to be simulated is thin. Although it is a known fact that constant boundary elements converge very slowly, the present study helps to get a clearer picture on the accuracy and the convergence rate that one can expect from constant boundary elements. This paper heavily borrows content from this author’s PhD thesis [1]. The geometry considered in this paper is a beam. One may also note that the author is publishing another paper [2] (“Simulation of Mechanical Behaviour of Materials using Constant Boundary Elements - A Discussion on the Accuracy of Results for Bars”) that is very similar to this paper except that the geometry considered in that paper is a bar.

The principles and examples of state-of-the-art experimental methods for measuring the fracture mechanics parameters are presented in this paper. The methodology of experimental analysis of the fracture mechanics parameters includes investigation of fracture behaviour of metallic materials using modified specimens with initial crack under tensile load, with the primary goal of determining the characteristics of fracture processes for the case of thin plates, using basic fracture mechanics postulates. The methodology also includes the application of experimental fracture mechanics procedures as defined by standards, using three-dimensional stereo-metric mechanical behaviour measurement methods. Fracture behaviour of metallic materials, mainly 316L stainless steel and titanium alloy Ti-6Al-4V specimens, is analyzed by using a digital image correlation (DIC) system for measuring strain and displacement in the material. GOM three-dimensional optical system and Aramis software are used to perform experimental analysis of selected specimens. As this system is used to measure strain and crack tip opening displacement (CTOD) parameter on the modified compact tension specimen C(T) and notch specimens, a basic review of measuring procedures and result processing is given, alongside other possible applications for this system. The presented results show strain and displacement fields during crack tip opening, crack growth, and the moment of fracture of specimens, which are not possible using traditional measurement methods. The analysis of results shows that it is possible to measure displacements during crack tip opening with a great precision, and thus obtain the CTOD parameter. The results show that the selected measuring method obtains good results in the analysis of mechanical behaviour and fracture mechanics parameters of metallic materials.

Material behaviour in metal cutting: strains, strain rates and temperatures in chip formation

Emerging Methods in Mechanical Behavior

[EN] The understanding of the mechanical behaviour of natural intact soils is central to engineers when designing new structures. The research carried in this thesis focused on investigating the effects of the naturally occurring in-situ structure on the mechanical behaviour of two shallow recently deposited Holocene alluvial materials, the Bormida River silts (BRS) from Italy and the Valencia silty soils (VSS) from the alluvial plains of the Turia River, Spain. These types of deposits are frequently characterised by highly heterogeneous in-situ structures.
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\nA large range of soils with different size distributions from sands to silty clays were investigated. Oedometer and triaxial tests were carried out on intact, slurry and compacted samples. The first step was to characterise the behaviour of the materials at their reconstituted state to define the reference framework for investigating the effect of the in-situ structure of the intact specimens. The effects of the sample preparation technique on the mechanical behaviour were examined, in particular its influence on the uniqueness of the normal compression line and critical state line. The initial structure created during the preparation of the specimens was totally removed after compression and shearing regardless of the sample preparation method. Only one soil displayed a clear effect of the sample preparation technique, the oedometer compression lines of which remained parallel to each other even at a very high stress levels for the case of the slurry samples. This result showed that contrary to what is stated in the literature the sample preparation technique can created very robust initial structures resulting in a transitional behaviour.
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\nClears effects of the in-situ structure of the intact samples of the BRS and VSS were observed on the oedometer compression behaviour even at very high stress levels with stress sensitivity values still larger than unity at the end of the tests. It appeared that the effects were more noticeable as the degree of heterogeneity inside the specimens increased at a meso-structure level as it was the case of some samples of the VSS materials which exhibited a certain layering. Small effects of the in-situ structure were seen at large shearing strains and only on the wet side of the critical state.