Reliability-based code calibration applied to thin elements made of UHPFRC

A semi-probabilistic approach used in current design codes requires calibrated partial factors to secure safety of structures and people. The current code calibration procedure has an inefficient and imprecise iterative loop and it also neglects economical aspects which should be an integral part of any code calibration. This paper suggests a modified approach to the reliability-based code calibration which eliminates disadvantages of the original procedure and it is defined in a way to take advantage of the current computation means such as parallel and cloud computing. The modified approach was used to calibrate the partial factors for the structural verification of UHPFRC thin elements predominantly loaded in bending. The described example proves efficiency of the modified approach and it illustrates the advantages of the reliability-based code calibration. Indeed, the design method of UHPFRC with the calibrated partial factors allows better exploitation of the material without compromising the safety requirements. Because of the straightforward procedure, independent reliability and design computations, and selection of the ideal partial factors at the end of the calibration procedure, the modified approach is an ideal option for various code calibrations. It is worth noting that the modified approach can “grow” with development of material, knowledge, applications, and safety requirements due its simple updating which was not possible before. Moreover, the removal of the iterative loop allows using Monte Carlo methods (among other options) which are normally time-consuming and impractical for code calibration.     

Performance of Emulsion Explosives

Some performance of a number of emulsion explosives containing glass micro-baloons were studied experimentally and theoretically. For each of the explosives, detonation velocity was measured and calculated and ballistic mortar tests and cylinder expansion tests were carried out. The results obtained enables a comparison of the usefulness of both testing methods. The influence of some metal nitrates contained in the emulsion matrix on the performance and detonation parameters of the explosives was examined. Key words: explosives, glass micro-balloons, nitrates of metals, detonation parameters, performance.     

Problems with welding steel T24 intended for membrane walls of boilers

We present the issues connected with the manufacture of waterwalls made of modern 7CrMoVTiB10-10 (T24) steel by submerged and TIG welding methods. We give the results of mechanical testing and structural examination of parent materials and welding consumables used for the manufacture of welded joints as well as the results of weldability and crack resistance testing for T24 steel. Possible reasons for cracking in welded joints as well as the usability of T24 steel for construction of responsible elements of waterwalls in advanced power boilers is discussed.     

On the mechanical stability of mesoporous silica SBA-15

Mesoporous silica SBA-15 was synthesised at 80 °C. The calcined solids were exposed to a unilateral external pressure in the range 16–191 MPa in order to monitor the impact of the mechanical pressure on the properties of SBA-15. N₂ adsorption–desorption measurements, XRD and UV-Raman spectroscopy was used in order to evaluate the changes occurring in the SBA-15. For the XRD measurement, an internal Si standard was used to correct the position of the SBA-15 patterns. It appeared that the elevated pressure has no influence on the hexagonal cell parameter a. Through the N₂ sorption measurements the fraction of the preserved mesoporous structure was estimated to be 60% when the highest pressure has been used. As the remaining part of the material is irreversibly disintegrated into small particles, the pressed sample is considered to be heterogeneous. However, the preserved fraction is slightly modified, showing a smaller pore width and plugs located within the mesopores. The plugs most likely originate from a disintegrated fraction of the SBA-15. UV-Raman spectroscopy shows that the relative intensity of the band associated with the siliceous network (ω₁) has decreased on the pressed samples resulting in a less ordered material possessing an enhanced population of silanols as compared to parent SBA-15. We propose that the disorder introduced by pressing is responsible for the observed expansion of the SBA-15 walls, which is detected for the samples treated at higher pressures (112, 191 MPa).     

Toward a 2D/3D Finite-Element–Based Digital Shadow for the Approximation of Metrologically Inaccessible Dynamic Fields of State Variables during Heavy Plate Rolling

While innovations in metal forming technology are closely linked to material science, automation, and mechatronization in recent decades, nowadays, and in the upcoming years, they are supposed to be driven by digital transformation and virtualization. Motivated by this expectation and the fact that the dynamic, process-relevant thermophysical state variables in plates during rolling are difficult or even impossible to measure, a modularly structured 2D/3D model, integrated into a digital shadow, is built and validated against a metrologically accessible process data. The decisive innovation of the presented modeling strategy is the investigation of the state during longitudinal rolling in the fillet, depending on the width direction. The fillet marks the heavy plate without head and tail crops, developed during longitudinal rolling. Application of the simulation tool reveals significant temperature gradients near the plate surfaces, both horizontally and vertically, but also a region of nearly constant temperature near the core. The development of the fillet cross-section shape, including the emergence of bulges or contractions at the side surfaces, is predicted within the simulation. The digital shadow is scalable and has a parameterized structure so that rolling schedules of different compositions can be simulated.     

New Aspects of the Impact Reactivity of Nitramines

The impact reactivity (“the first reaction”) of 16 nitramines was determined as the drop energy E_d, required for 50% initiation probability. Relationships have been found between the E_d values, on the one hand, and heats of fusion, ¹⁵N NMR chemical shifts of aza atoms in reaction centers, parameters of low‐temperature thermolysis, and oxygen balances of nitramines studied, on the other. Taking these relationships the E_d values were predicted for four nitramines, from which three have not been synthesized yet. On the basis of the said relationships it was stated that the impact reactivity of nitramine molecules depends on the electronic configuration within their reaction centers and on their conformational stability and intensity of their intermolecular interactions. The reaction centers here are the same as in the case of initiation of the nitramines by shock. It is found that ϵ‐HNIW possesses higher thermal and impact reactivities in comparing with those of β‐modification.     

Synthesis of Glycolysis Inhibitor PFK15 and Its Synergistic Action with an Approved Multikinase Antiangiogenic Drug on Human Endothelial Cell Migration and Proliferation

Activated endothelial, immune, and cancer cells prefer glycolysis to obtain energy for their proliferation and migration. Therefore, the blocking of glycolysis can be a promising strategy against cancer and autoimmune disease progression. Inactivation of the glycolytic enzyme PFKFB3 (6-phosphofructo-2-kinase/fructose-2,6-biphosphatase) suppresses glycolysis level and contributes to decreased proliferation and migration of cancer (tumorigenesis) and endothelial (angiogenesis) cells. Recently, several glycolysis inhibitors have been developed, among them (E)-1-(pyridin-4-yl)-3-(quinolin-2-yl)prop-2-en-1-one (PFK15) that is considered as one of the most promising. It is known that PFK15 decreases glucose uptake into the endothelial cells and efficiently blocks pathological angiogenesis. However, no study has described sufficiently PFK15 synthesis enabling its general availability. In this paper we provide all necessary details for PFK15 preparation and its advanced characterization. On the other hand, there are known tyrosine kinase inhibitors (e.g., sunitinib), that affect additional molecular targets and efficiently block angiogenesis. From a biological point of view, we have studied and proved the synergistic inhibitory effect by simultaneous administration of glycolysis inhibitor PFK15 and multikinase inhibitor sunitinib on the proliferation and migration of HUVEC. Our results suggest that suppressing the glycolytic activity of endothelial cells in combination with growth factor receptor blocking can be a promising antiangiogenic treatment.     

Complete damage in elastic and viscoelastic media and its energetics

A model for the evolution of damage that allows for complete disintegration is addressed. Small strains and a linear response function are assumed. The “flow rule” for the damage parameter is rate-independent. The stored energy involves the gradient of the damage variable, which determines an internal length-scale. Quasistatic fully rate-independent evolution is considered as well as rate-dependent evolution including viscous/inertial effects. Illustrative 2-dimensional computer simulations are presented, too.     

Umweltschutz wirtschaftlich betrachtet

Ohne Zusammenfassung     

Decomposition of some polynitro arenes initiated by heat and shock Part I. 2,4,6-Trinitrotoluene

Samples of 2,4,6-trinitrotoluene (TNT) exposed to heat or to shock and residues after their detonation have been analyzed chromatographically (LC-UV and LC/MS). It was found that the main identified decomposition intermediates are identical in all the three cases. 4,6-Dinitro-2,1-benzoisoxazole and 2,4,6-trinitrobenzaldehyde are the most reactive from them. It has been stated that the chemical micro-mechanism of the primary fragmentations of shock-exposed TNT molecules and/or its detonation transformation should be the same as in the case of its low-temperature thermal decomposition.