Strength and Compressibility of Ammonia-Soda Residue from the Solvay Sodium Plant

This work presents the discussion of the results for an experimental study conducted to characterise the mechanical behaviour of ammonia-soda residue (ASR). The calcareous sludge is an alkaline waste formed during the production of soda ash and deposited at the area of the former Solvay Sodium Plant factory in Krakow, Poland. Isotropically consolidation drained (CID) triaxial tests and constant rate of strain (CRS) consolidation tests include the full saturation with water, completion of the consolidation, and the loading/strain rate choice. For this purpose, ASR undisturbed samples were collected from the ground and submitted to laboratory experiments. These samples show a distinct difference in the initial bulk density, the initial level of compaction, initial void ratio, and the natural water content. The CD triaxial tests were conducted under three different levels of confining pressure; in turn, CRS tests were run with two appropriate input strain rates. According to the physical state of ASR and the depth of sampling, two different evolutions of the critical state in the stress–strain space were observed. In the light of the assessed stress–strain–strength behaviour, key design engineering parameters of ASR were calculated.

Experimental verification of the isotropy postulate at deformation of steel 45 along orthogonal curvilinear trajectories of constant curvature

Представлены результаты экспериментальных исследований по проверке достоверности одного из основных законов пластичности - постулата изотропии А.А. Ильюшина в условиях ортогональных сложных нагружений по криволинейным окружным траекториям постоянной кривизны. Экспериментальные исследования выполнены на тонкостенных трубчатых образцах из материала сталь 45 на автоматизированном расчетно-экспериментальном комплексе СН-ЭВМ. Программы нагружения трубчатых образцов задавались в девиаторном пространстве деформаций А.А. Ильюшина при одновременном комбинированном действии на образец растяжения-сжатия и кручения. В экспериментах реализовано четыре траектории деформирования, представляющие собой окружности, начинающиеся из начала координат. Установлено, что для реализованных сложных траекторий постоянной кривизны постулат изотропии выполняется как по скалярным, так и векторным свойствам. The results of experimental studies on validation Ilyushin’s isotropy postulate under the conditions of orthogonal complex loads along curvilinear trajectories of constant curvature. Experimental studies were carried out on thin-walled tubular specimens made of steel 45 on SN-EVM testing machine. Loading programs for tubular specimens were set in the deviatorial strain space of A.A. Ilyushin under the combined action of tension-compression and torsion on the specimens. Experimental data are obtained for four strain trajectories, which are circles starting from the origin. It is found that for the realized complex trajectories of constant curvature the isotropy postulate is fulfilled in terms of scalar and vector properties.

BMO and Elasticity: Korn’s Inequality; Local Uniqueness in Tension

In this manuscript two BMO estimates are obtained, one for Linear Elasticity and one for Nonlinear Elasticity. It is first shown that the BMO-seminorm of the gradient of a vector-valued mapping is bounded above by a constant times the BMO-seminorm of the symmetric part of its gradient, that is, a Korn inequality in BMO. The uniqueness of equilibrium for a finite deformation whose principal stresses are everywhere nonnegative is then considered. It is shown that when the second variation of the energy, when considered as a function of the strain, is uniformly positive definite at such an equilibrium solution, then there is a BMO-neighborhood in strain space where there are no other equilibrium solutions.

Metallization of diamond

Experimental discovery of ultralarge elastic deformation in nanoscale diamond and machine learning of its electronic and phonon structures have created opportunities to address new scientific questions. Can diamond, with an ultrawide bandgap of 5.6 eV, be completely metallized, solely under mechanical strain without phonon instability, so that its electronic bandgap fully vanishes? Through first-principles calculations, finite-element simulations validated by experiments, and neural network learning, we show here that metallization/demetallization as well as indirect-to-direct bandgap transitions can be achieved reversibly in diamond below threshold strain levels for phonon instability. We identify the pathway to metallization within six-dimensional strain space for different sample geometries. We also explore phonon-instability conditions that promote phase transition to graphite. These findings offer opportunities for tailoring properties of diamond via strain engineering for electronic, photonic, and quantum applications.

Development of Stress- and Strain-Based Fracture Forming Limit Curves of Sheet Aluminium-Alloy AA2024-T3 through Various Approaches

In this work, four fracture criteria—namely, Fracture Forming Limit Curve (FFLC), Fracture Forming Limit Stress Curve (FFLSC), Fracture Locus (FL) and Fracture Locus Embedded with Bao-Wierzbicki Ductile Damage Criterion (BW-FL)—are comparatively deployed to forecast breakage of deformed AA2024-T3 sheet aluminium-alloy. An FFLC can be experimentally formed by conducting a set of Nakajima stretch-forming based tests. To obtain an FFLSC, such an FFLC drawn in the strain space has to be entirely mapped onto the stress space. This can computationally be accomplished with the help of those well-known plasticity-relevant models like the Hill’48 anisotropic yield criterion and the Swift hardening law. Likewise, both BW-FL and FL in terms of stress triaxialities and critical plastic strains can mathematically be derived from the FFLC incorporated with the Hill’48 anisotropic yield criterion. Hole expansion and tree-point bending tests are carefully carried out both experimentally and simulatively to verify those four generated fracture limits. The more innovative FFLSC and FL demonstrate more accurate prediction on rupture of AA2024-T3 sheet aluminium-alloy than the conventional FFLC. The BW-FL however performs the worst.