Assessment of four strain energy decomposition methods for phase field fracture models using quasi-static and dynamic benchmark cases

Strain energy decomposition methods in phase field fracture models separate strain energy that contributes to fracture from that which does not. However, various decomposition methods have been proposed in the literature, and it can be difficult to determine an appropriate method for a given problem. The goal of this work is to facilitate the choice of strain decomposition method by assessing the performance of three existing methods (spectral decomposition of the stress or the strain and deviatoric decomposition of the strain) and one new method (deviatoric decomposition of the stress) with several benchmark problems. In each benchmark problem, we compare the performance of the four methods using both qualitative and quantitative metrics. In the first benchmark, we compare the predicted mechanical behavior of cracked material. We then use four quasi-static benchmark cases: a single edge notched tension test, a single edge notched shear test, a three-point bending test, and a L-shaped panel test. Finally, we use two dynamic benchmark cases: a dynamic tensile fracture test and a dynamic shear fracture test. All four methods perform well in tension, the two spectral methods perform better in compression and with mixed mode (though the stress spectral method performs the best), and all the methods show minor issues in at least one of the shear cases. In general, whether the strain or the stress is decomposed does not have a significant impact on the predicted behavior.

A Novel Multitask Scheduling and Distributed Collaborative Computing Method of Edge Nodes in the Internet of Things

In this paper, we propose a novel multitask scheduling and distributed collaborative computing method for quality of service (QoS) guaranteed delay-sensitive services in the Internet of Things (IoT). First, we propose a multilevel scheduling framework combining the process and thread scheduling for reducing the processing delay of multitype services of a single edge node in IoT, where a preemptive static priority process scheduling algorithm is adopted for different types of services and a dynamic priority-based thread scheduling algorithm is proposed for the same type of services with high concurrency. Furthermore, for reducing the processing delay of computation-intensive services, we propose a distributed task offloading algorithm based on a multiple 0-1 knapsack model with value limitation with the collaboration of multiple edge nodes to minimize the processing delay. Simulation results show that the proposed method can significantly reduce not only the scheduling delay of a large number of time-sensitive services in single edge node but also the process delay of computation-intensive service collaborated by multiple edge nodes.

Mode I stress intensity factor with various crack types

Presence of cracks in mechanical components needs much attention, where the stress field is affected by cracks and the propagation of cracks may be occurred causing the damage. The objective of this paper is to present an investigation of crack type effect on crack severity in a finite plate. Three cases of cracked plate with three different types of cracks are assumed in this work, i.e., single edge crack, center crack and double edge crack. 2D numerical models of cases of cracked plate are established in finite element analysis (FEA), ANSYS software by adopting PLANE 183 element. Values of FEA mode I stress intensity factor SIF and Von-Mises stress at crack apex are determined for cases of cracked plate under tensile stress with different values. To identify the crack severity, the comparison of FEA results for different cracked cases is made. The comparison showed that, single edge cracked plate (SECP) has the maximum values of mode I SIF and Von-Mises stress at crack apex, i.e. the greatest crack severity is considered. Also, values of FEA Von-Mises stress at crack apex for center cracked plate (CCP) are moderate and for double edge cracked plate (DECP) are the minimum. Besides, in case of high crack lengths, it is found that, FEA results of mode I SIF in case of (CCP) are higher than those of in case of (DECP). Consequently, crack severity is considered as moderate in case of (CCP) and the minimum in case of (DECP). Empirical formulas are used to approximately estimate mode I SIF for all the case studies of cracked plate in this study and the results are compared to those of FEA. A good agreement between analytical and FEA results has been showed by this comparison.

BLADED WEAPONS FROM GRAVE 16 DATING TO THE MIGRATION PERIOD AT THE DZHURGA-OBA CEMETERY IN THE EASTERN CRIMEA

Описывается погребение - кенотаф № 16 из могильника Джурга-Оба в Восточном Крыму. По найденным в нем вещам (элементы ременной гарнитуры) это погребение датируется второй половиной V - первой половиной VI в. Здесь было обнаружено оружие с прямым однолезвийным клинком, которое можно идентифицировать как скрамасакс. В его конструкции и декоре есть элементы как восточного происхождения (железная гарда), так и западного (накладки на ножны с декором в виде птичьих голов). Погребения со скрамасаксами немногочисленны в Северном Причерноморье и, возможно, отражают сасанидскую воинскую традицию. The paper publishes a cenotaph grave 16 from the Dzhurga-Oba cemetery in the Eastern Crimea. Based on the items retrieved from the grave (belt sets details), the grave is dated to the second half of the 5 - first half of the 6 centuries. Among the finds there is a straight single-edge knife that can be identified as scramasax. Its design and decoration reveal some elements of Oriental origin (iron guard) and Western origin (scabbard plates featuring bird heads as a decoration). The graves with scramasax are not numerous in the North Pontic region, possibly, they reflect a Sasanid military tradition.

Stability of supratransmission waves in a crystal of A3B stoichiometry upon interaction with single dislocations

Supratransmission waves are stable objects that can exist in different discrete environments. In this paper, we consider the interaction of such waves with single edge dislocations of various configurations in a crystal with A3B stoichiometry. The model was a Pt3Al crystal, the potential obtained by the embedded atom method was used to describe the interaction of its atoms. Quantitative characteristics of the wave were obtained before and after the interaction. It is found that the degree of energy dissipation by dislocations depends on the mutual orientation of the wave front and the extra plane of the dislocation. Numerical estimates are made for four different configurations. The results obtained can be useful in studying the propagation of soliton-type waves in defect crystals of various compositions.