Analytical studies on Mode III fracture in flexoelectric solids

Due to the stress concentration near crack tips, strong flexoelectric effect would be observed there, which might lead to new applications of flexoelectricity in material science and devices. However, different from the flexoelectric effect in cantilever beams or truncated pyramids, at the crack tip, multiple components of strain gradients with nonuniform distribution contribute to the flexoelectric effect, which makes the problem extremely complex. In this paper, with the consideration of both direct and converse flexoelectricity, the electromechanical coupling effect around the tip of a Mode III crack is studied analytically. Based on the Williams' expansion method, the displacement field, polarization field, strain gradient field along with the actual physical stresses field are solved. A path independent J-integral for Mode III cracks in flexoelectric solids is presented. Our results indicate that the existence of flexoelectricity leads to a decrease of both the J-integral and the out-of-plane displacement in Mode III cracks, which means that the flexoelectric effect around the tip of Mode III cracks enhances the local strength of materials.

Assessment of Hydration Process And Mechanical Properties of Cemented Paste Backfill By Rebound Method

Backfilling mining method is a green mining method which is being used widely, nevertheless, the uniaxial compressive strength (UCS) of the cement backfill paste (CPB) on site is difficult to measure, and it is impossible to know the internal cementation, for this reason, the rebound method is improved and introduced in this paper. Standard specimens of CPB were made and cured for different curing age under standard curing conditions. The hardness test of each part of the CPB is completed, the unconfined compression test is carried out, and the functional model of the hardness of each part of the CPB is established, which was a function of radius and age. Based on the nonuniformity of the filling material, the failure mode of CPB is analyzed and verified in the test. The results show that the exponential function model is more suitable for the relationship between the external hardness and the overall strength, and this conclusion is of great significance in construction site. In addition, the corresponding relationship between hardness and local strength was calculated and verified, the results show that the simple model can predict the variation of local strength with hardness better, and the quadratic function model is the best choice.

Recommendations for deck primary supporting members design as applied to pillarless construction of ro-ro ships

Статья посвящена вопросам определения размеров набора грузовых стационарных палуб морских стальных судов типа Ro-Ro на ранних стадиях проектирования. В силу большого расстояния между поперечными переборками в случае отсутствия пиллерсов карлингсы палуб не являются опорами для рамных бимсов. Однако, как показывает практика, они всегда включаются в конструктивную схему палубы, так как позволяют разнести локальную нагрузку между соседними рамными бимсами, обеспечивают устойчивость их стенок, а также вовлекаются в работу в составе перекрытия при некоторых сценариях нагружения. В литературе отсутствуют рекомендации по выбору расчётной ширины их присоединенного пояска, расчётных значений изгибающих моментов и перерезывающих сил при восприятии нагрузки от разного типа груза. Исследование выполнялось на примере перекрытия грузовой палубы длиной 64,4 м на основе МКЭ. Были разработаны КЭ-модели палубы в балочной и оболочечно-балочной идеализациях. Вторая модель использовалась для оценки адекватности результата, получаемого на более простой модели. Рассмотрены 8 сценариев нагрузки. При определении ширины присоединенного пояска за величину условного пролёта принималось расстояние между точками, в которых величина изгибающего момента принимает нулевое значение. Показано, что карлингсы активно вовлекаются в работу при частичной загрузке трюма контейнерами в несколько ярусов, а также при работе погрузчика. Расчётная ширина их присоединенного пояска составила 0,60…0,75 расстояния между карлингсами при действии нагрузки от колёсной техники и оказалась близка к этому расстоянию при восприятии нагрузки от контейнеров при их поперечной укладке. Авторами предложено в качестве первого приближения значение расчётного изгибающего момента для карлингсов определять в долях от соответствующего значения для рамных бимсов. The paper deals with a design of deck primary structures of Ro-Ro vessels at early design stages. Due to the large distance between transverse bulkheads, in the case of no pillar construction, deck girders cannot be considered as supports for deck transverses. The common practice however, is to provide deck structures with deck girders anyway. It helps to distribute the local loads between transverses and to ensure the stability of deck transverses web plates. In addition, for a localized loads on deck structures girders to some extent contribute to local strength of the deck. Practically, deck girder scantlings are usually larger than those based on the minimum thickness, web depth and slenderness requirements of classification society rules. There are no publications proposing recommendations for deck girders design in pillarless structures of ro-ro ships at the early stages. Prescriptive recommendations should primarily include design bending moment value and effective breadth of the attached plate in different loading scenarios. The results presented in this paper are based on the linear finite element (FE) analysis of Ro-Ro deck having a length of 64.4 meters. Since the goal of the study was to develop recommendations for structural design aligned with prescriptive requirements of RS rules the research is provided with beam analysis carried out for 8 different loading scenarios. All of the reference calculations were made in FESTA-2020 software developed in SMTU as a part of CAD/СAE software ALMAZ-K. Verification is made with more sophisticated shell model analysis carried out in ANSYS with similar assumptions. The effective breadth of deck girders attached plate is calculated considering a distance between zero bending moment points as a nominal span. It is shown that the deck girders are highly stressed in loading cases with stacked containers and working fork lift. The calculated width of their attached plate which is in range from 0.60 to 0.75 of the distance between girders S under the load from the wheeled vehicles turns out to be close to Sin case of loading of transversely stacked containers. The authors propose to determine value of the design bending moment for deck girders at the early stages depending on span and loading of deck transverses.

On the edge of criticality: strength-dependent perturbation unveils delicate balance between fluctuation and oscillation in brain dynamics

Going beyond previous research, we use strength-dependent perturbation to obtain a deeper understanding of the mechanisms underlying the emergence of large-scale brain activity. Despite decades of research, we still have a shallow understanding of the role and generating mechanisms of the ubiquitous fluctuations and oscillations found in recordings of brain dynamics. Here, we used global strength-dependent perturbation to give a causal mechanistic description of human brain function providing a delicate balance between fluctuation and oscillation on the edge of criticality. After application of precise local strength-dependent perturbations and measuring the well-known perturbative complexity index, we demonstrated that the overall balance is shifted towards a fluctuating regime which is superior in terms of enhancing different functional networks compared to the oscillatory regime. This framework can generate specific, testable empirical predictions to be tested in human stimulation studies with strength-dependent rather than constant perturbation. Overall, our novel strength-dependent perturbation framework demonstrates that the human brain is poised on the edge of criticality, between fluctuations to oscillations, allowing for maximal flexibility.

Indigenous Experience as a Strategy to Develop Rural Tourism Identity

Rural tourism is often seen as a tourist attraction, where tourists make their visit only to catch a glimpse of the village’s potential. In contrast to this trend, the rural tourism of in Tanon sub village of in the Semarang regency (Central Java) attempts to offer more by developing its local strength as “Desa Menari” (lit. Dancing Village). It offers tour packages that invite tourists to experience a life in the village, interact with local communities, find happiness, and reinterpret life. The objective of this study is to find out how the local community uses indigenous experience as a strategy to develop rural tourism in the area. This study implemented the communication theory of identity (CTI) by applying qualitative method with a case study approach. After observation and in-depth interview were conducted to rural tourism community, this study found that rural tourism community actively introduces tourism based on local wisdom experiences through the conservation of tourism in Dusun Tanon, including the conservations of community arts, traditional games, and farmer. Indigenous experience as a village identity is constructed according to its purpose, i.e. spreading harmony, knitting inspiration, and reaping memory. This village identity includes personal identity, relational identity, and enacted identity that invite tourists to capture the process of self-meaning or journey into oneself as a psychological experience.

A System Identification and Implementation of a Soft Sensor for Freeform Bending

The primary goal of this study is the formulation of a soft sensor that predicts industrially relevant mechanical properties for freeform bending. This serves as the foundation of a closed-loop property control. It is hypothesized that by inline measurement of hardness, predictions regarding residual hoop stresses, local strength and strain level can be achieved. A novel hardness-based correlation scheme is introduced, which is implemented into an extended Kalman filter (EKF) and allows an inline prediction of local strength, residual hoop stresses and plasticity. Furthermore, the ultrasonic contact impedance (UCI) method is validated as a suitable inline measuring solution.

Towards finding a novel constant between local and bulk strength of friction stir processed aluminum alloys

Friction stir processing has gained remarkable success in producing ultrafine-grained structures and surface composites. In this context, the primary objective is to establish a linear relationship between local strength (i.e. hardness) and bulk mechanical strength (i.e. tensile strength) of friction stir processed aluminum alloys using experimental investigations on selected alloy system together with data reported in literature sources. Initially, authors generated a linear relation between hardness and strength of friction stir processed aluminum alloys under different cooling conditions. After friction stir processing, recrystallized fine grains were formed and better refinement was achieved in cooling-assisted friction stir processing. Irrespective of grain refinement, the strength and hardness of friction stir processed samples were found to be lower compared to the base metal due to the precipitation phenomenon during friction stir processing. At the same time, hardness and strength improved in cooling-assisted friction stir processing compared to natural-cooled friction stir processing due to better grain refinement going by the parameters of Hall–Petch equation. For friction stir processed samples, relevant constants were found using Hall–Petch equation. The experimental values of hardness and strength were well fitted with the formulated equations due to the formation of a homogeneous fine-grained structure. Also, two novel linear relations were successfully established between hardness and strength with proportionality constants of 1.9 and 2.7, respectively. On the other hand, it was also concluded that it is not possible to establish a linear relation between hardness and strength of surface composites due to structural inhomogeneity and agglomeration of reinforcement particles.

The Effectiveness of Additional Core Stability Exercises in Improving Dynamic Sitting Balance, Gait and Functional Rehabilitation for Subacute Stroke Patients (CORE-Trial): Study Protocol for a Randomized Controlled Trial

Background: Trunk impairment produces disorders of motor control, balance and gait. Core stability exercises (CSE) are a good strategy to improve local strength of trunk, balance and gait. Methods and analysis: This is a single-blind multicenter randomized controlled trial. Two parallel groups are compared, and both perform the same type of therapy. A control group (CG) (n = 110) performs conventional physiotherapy (CP) (1 h per session) focused on improving balance. An experimental group (EG) (n = 110) performs CSE (30 min) in addition to CP (30 min) (1 h/session in total). EG is divided in two subgroups, in which only half of patients (n = 55) perform CSE plus transcutaneous electrical nerve stimulation (TENS). Primary outcome measures are dynamic sitting, assessed by a Spanish version of Trunk Impairment Scale and stepping, assessed by Brunel Balance Assessment. Secondary outcomes are postural control, assessed by Postural Assessment Scale for Stroke patients; standing balance and risk of fall assessed by Berg Balance Scale; gait speed by BTS G-Walk (accelerometer); rate of falls, lower-limb spasticity by Modified Ashworth Scale; activities of daily living by Barthel Index; and quality of life by EQ-5D-5L. These are evaluated at baseline (T0), at three weeks (T1), at five weeks (end of the intervention) (T2), at 17 weeks (T3) and at 29 weeks (T4). Study duration per patient is 29 weeks (a five-week intervention, followed by a 24-week post-intervention).

The Plant-Like Structure of Lance Sea Urchin Spines as Biomimetic Concept Generator for Freeze-Casted Structural Graded Ceramics

The spine of the lance sea urchin (Phyllacanthus imperialis) is an unusual plant-akin hierarchical lightweight construction with several gradation features: a basic core–shell structure is modified in terms of porosities, pore orientation and pore size, forming superstructures. Differing local strength and energy consumption features create a biomimetic potential for the construction of porous ceramics with predetermined breaking points and adaptable behavior in compression overload. We present a new detailed structural and failure analysis of those spines and demonstrate that it is possible to include at least a limited number of those features in an abstracted way in ceramics, manufactured by freeze-casting. This possibility is shown to come from a modified mold design and optimized suspensions.