Three post-glacial marine clays from eastern Canada and one marine clay from Japan have been studied by Mössbauer spectroscopy to ascertain their iron mineralogy. Small amounts of hematite (in two samples) and magnetite (in one sample) were found in the Canadian clays, and hematite was detected in the Japanese clay. The major spectral components were ferrous and ferric doublets, consistent with X-ray powder diffraction results that show chlorite, mica, and amphibole in the Canadian samples and smectite in the Japanese sample. Citrate-dithionite extraction removed hematite and most of the magnetite from these samples. Acid-base extraction also removed chlorite and some mica from the Canadian samples. Samples treated by these extractions had appreciably lower geotechnical yield stresses at given water contents.

Particle–particle interactions in natural clays can be evaluated by their rheological behavior, but the results are often affected by the physicochemical properties of the clays. The behaviors of two fundamentally different types of clays (low-activity and high-activity) differ with respect to salinity and a time factor (duration of shearing at a given shear rate): illite-rich Jonquiere clay (low-activity clay, Canada) and montmorillonite-rich Wyoming bentonite (high-activity clay, USA). The purpose of the present study was to investigate these different behaviors. Most natural clays exhibit shear-thinning and thixotropic behavior with respect to salinity and the volumetric concentration of the solids. Natural clays also exhibit time-dependent non-Newtonian behavior. In terms of index value and shear strength, lowactivity and high-activity clays are known to exhibit contrasting responses to salinity. The geotechnical and rheological characteristics as a function of salinity and the shearing time for the given materials are compared here. The clay minerals were compared to estimate the inherent shear strengths, such as remolded shear strength (which is similar to the yield strength). Low-activity clay exhibits thixotropic behavior in a time-dependent manner. High-activity clay is also thixotropic for a short period of shearing, although rare cases of rheopectic behavior have been measured for long periods of shearing at high shear rates. The change from thixotropic to rheopectic behavior by bentonite clay has little effect at low shearing speeds, but appears to have a significant effect at higher speeds.

This paper proposes a methodology for architecting microstructures with extremal stiffness, yield, and buckling strength using topology optimisation. The optimised microstructures reveal an interesting transition from simple lattice-like structures for yield-dominated situations to hierarchical lattice structures for buckling-dominated situations. The transition from simple to hierarchical is governed by the relative yield strength of the constituent base material as well as the volume fraction. The overall performances of the optimised microstructures indicate that maximum strength is determined by the buckling strength at low-volume fractions and yield strength at higher-volume fractions, regardless of the base material’s relative yield strength. The non-normalised properties of the optimised microstructures show that higher base material Young’s modulus leads to both higher Young’s modulus and strength of the architected microstructures. Furthermore, the polynomial order of the maximum strength lines with respect to mass density obtained from the optimised microstructures reduces as base material relative yield strength decreases, reducing from 2.3 for buckling-dominated thermoplastic polyurethane to 1 for yield-dominated steel microstructures.

In this study, precipitate phase transformation behavior, microstructure, and properties of the Cu–1Cr–1Co–0.4Si (wt%) alloy were investigated. Precipitate phase transformation kinetic equations of the alloy under room temperature rolling (RTR) 90% deformation and aging at different temperatures (440–520 °C) were established. The alloy yielded excellent mechanical and electrical properties under RTR 90% deformation and aging at 440 °C for 1 h, and the corresponding hardness, yield strength (YS), ultimate tensile strength (UTS), elongation, and electrical conductivity were 181.6 HV, 573.6 MPa, 653.7 MPa, 7.3%, and 51.6% International Annealed Copper Standard, respectively. The precipitate phase transformation behavior determined the size and volume fraction of the precipitate phase fv, which played a key role in improving the YS. Impurity scattering caused by surplus Si atoms was mainly responsible for decreasing the electrical conductivity. Therefore, these results can provide a reliable theoretical guidance to prepare Cu–Cr–based alloys with high strength and high electrical conductivity.

The finite element method (FEM) was used to study the elastic-plastic contact in the coating systems with interlayer. The results reveal that with the increase of interlayer thickness, the maximum shear stress of coating/interlayer and interlayer/substrate interfaces decreases. Moreover, the sharply changed shear stress between the interfaces of coating/interlayer and interlayer/substrate decreases too. There is no further decrease when interlayer thickness increase to 0.04 mm and above. With the increasing of interlayer elastic modulus, the shear stress of coating/interlayer interface decreases while the shear stress of interlayer/substrate interface increases. Meanwhile, the higher elastic modulus leads to the intensive tensile stress concentration on the interface of coating/interlayer. Hence, the interlayer with appropriate elastic modulus not only reduces the shear stress of coating/interlayer and interlayer/substrate interfaces but also decreases the tensile stress of coating/interlayer interface. The mechanical properties of coating systems were investigated with different interlayer yield strength. The effective hardness and elastic modulus increase with the increase of interlayer yield strength, which is good to protect the substrate from the deformation. In addition, higher indentation load can lead to the decrease of effective hardness and elastic modulus.

Cell morphology and relative density (ρrel) are two crucial intrinsic parameters controlling the mechanical properties of metal foams (MFs) and directly depend on their structure (closed/open-cell) and composition (affecting processing parameters). Here, we report on compressive studies of MFs of aluminum (Al) and 7075-T6 alloy processed via a customized route at strain rate, έ = 0.002 and 2.0 s−1. In both sets of MFs, the strength and apparent elastic modulus (E) monotonically increased with ρrel at both έ. At έ = 2.0 s−1, an increase in cell size (Cs) enhanced the strength of both sets of MFs, while at έ = 0.002 s−1, only the alloy foams showed strength increment. The densification strain (εd) of Al foams at έ = 0.002 s−1 monotonically decreased with increasing ρrel, whereas the alloy foams collapsed before the onset of densification. None of the MFs showed any particular trend of εd at έ = 2.0 s−1. The studies conclude that the mechanical properties of MFs with similar morphology, foam parameters, and processing route depend on έ and Cs. Absorption energy (W) and absorption efficiency (Im) of the two sets of MFs were also compared.

Nanoindentation techniques are commonly used to characterize nanomechanical properties of microscaled and nanoscaled materials. Nanoindentation using a cylindrical flat-tip indenter has a constant contact area which makes it a reliable source to find material’s yield strength as well as other mechanical properties. However, an angular misalignment of the indenter with the specimen results in experimental error. In this work, the effects of angular misalignment on the nanoindentation testing with a cylindrical flat-tip indenter were numerically analyzed. A three-dimensional nanoindentation solid model was generated, computer modeling based on finite element analysis was conducted. The angle of misalignment ranged from 0° to 1°. Young’s modulus and hardness were evaluated. Based on the hemispherical stress–strain distribution assumption of an elastic plastic indentation, corrected depths and modifiers were proposed for adjusting material’s 0.1% offset and 0.2% offset yield strengths. Low carbon steel AISI 1018 was selected as sample material for indentation testing and modeling validation.

Material property measurements at the micro-/nanoscale are required for within many materials systems, such as thin-films, coatings, nanostructured materials, and interface/interphase. An innovative approach through micro-/nano-indentation testing with a cylindrical flat-tip indenter and coupled with computer modeling was proposed to characterize the material's elastic–plastic properties. A mechanical model proposed for directly extracting the yield strength of the tested materials, based on the hemi-spherical stress–strain distribution assumption, was analytically derived and numerically validated. Specimens being tested are aluminum alloy, low carbon steel, and alloy steel. A micro-/nano-indentation solid model was constructed and computer modeling was conducted. The load point in the indentation load–depth curve and the modifier for extracting the yield strength were identified through computer modeling and validated by indentation tests. The material properties measured by indentation were compared with tensile tests. The indentation testing errors induced by residual stresses in specimens were investigated by a residual stress measurement system.