Plasticity and the crack opening displacement in shells

Plastic deformation and crack opening displacement in thin walled, cylindrical shell

The use of COD and plastic instability in crack propagation and arrest in shells

The initiation, growth, and possible arrest of fracture in cylindrical shells containing initial defects are dealt with. For those defects which may be approximated by a part-through semi-elliptic surface crack which is sufficiently shallow so that part of the net ligament in the plane of the crack is still elastic, the existing flat plate solution is modified to take into account the shell curvature effect as well as the effect of the thickness and the small scale plastic deformations. The problem of large defects is then considered under the assumptions that the defect may be approximated by a relatively deep meridional part-through surface crack and the net ligament through the shell wall is fully yielded. The results given are based on an 8th order bending theory of shallow shells using a conventional plastic strip model to account for the plastic deformations around the crack border

On the effect of orthotropy in a cracked cylindrical shell

A pressurized cylindrical shell containing a longitudinal crack is considered. The shear modulus of the sheet may be evaluated from the measured Young's moduli and the Poisson's ratios rather than being an independent material constant. Two examples, one for a mildly orthotropic (titanium) and the other for a strongly orthotropic (graphite) material approximately satisfying the condition of special orthotropy are given. The results show that the stress intensity factors are rather strongly dependent on the degree of orthotropy

A rare case of aggressive angiomyxoma of vulva since childhood

Aggressive angiomyxoma is a locally invasive benign mesenchymal tumour usually occurring in women of reproductive age and is rare in children. It carries a high risk of recurrence and hence needs to be differentiated from other masses. The diagnosis is difficult clinically and is almost always histological. Here is a rare case of aggressive angiomyxoma of vulva in a 15 year old female presented with presented with mass in vulva on left side since birth and increased to the present size since 3 years. The swelling was painless, no local rise of temperature, no visible veins. Attained menarche 2 years ago and cycles are regular with normal flow

Expert interpretation of bar and line graphs: The role of graphicacy in reducing the effect of graph format.

The distinction between informational and computational equivalence of representations, first articulated by Larkin and Simon (1987) has been a fundamental principle in the analysis of diagrammatic reasoning which has been supported empirically on numerous occasions. We present an experiment that investigates this principle in relation to the performance of expert graph users of 2 × 2 'interaction' bar and line graphs. The study sought to determine whether expert interpretation is affected by graph format in the same way that novice interpretations are. The findings revealed that, unlike novices—and contrary to the assumptions of several graph comprehension models—experts' performance was the same for both graph formats, with their interpretation of bar graphs being no worse than that for line graphs. We discuss the implications of the study for guidelines for presenting such data and for models of expert graph comprehension

Self-healing by Diels-Alder cycloaddition in advanced functional polymers: A review

The ability of artificial materials to be healed efficiently, mimicking the living organisms, exhibits a great deal of potential advantages that can revolutionise the operation and maintenance of materials used in various applications. Such self-healable smart materials have been extensively researched in the last few decades, leading to the development of different physical and chemical synthesis approaches. Among these methods, chemical techniques based on reversible cycloadditions or disulfide bonding provide obvious advantages in terms of repeatability, which holds prime importance in determining the commerciality of the healing approach. This review compiles the recent advances in the field of self-healing polymers where the healing ability is introduced by reversible cycloaddition reactions while focusing mainly on the Diels-Alder (DA) reaction. DA is a [4 + 2] cycloaddition reaction where diene and dienophile pairs are used to fabricate thermally reversible crosslinked networks. These covalent bonds provide the necessary reversibility to the healing matrix and impart the desired strength to the polymeric material. There is a considerable body of recent literature where DA bonding has been employed either on its own or along with other healing mechanisms to impart self-healing to polymers. However, lack of a systematic review discussing these works makes it difficult for a beginner to cope with advancements in this field. Most early studies have focused on the healing stimuli and efficiency of healing in polymers but with this review, we would like to explore the healing thermodynamics governing the rupture–repair process in DA polymers along with the use of advanced spectroscopic techniques to study them and their applicability in thermosets, epoxy resins, biopolymers, and polymer nanocomposites. Novel applications for such advanced functional polymers, multifunctional healable polymers, and the outlook for future research, opportunities and challenges in the area are also discussed

Multifunctional steel surface through the treatment with graphene and h-BN

The search for improved surface properties of engineering alloys is always a matter of interest. Herein, we introduce a surface treatment based on depositing a non-continuous layer of two-dimensional (2D) nanomaterials via a simple and scalable method. 2D nanosheets of hexagonal boron nitride (h-BN) and graphene nanoplatelets (GNP) were sprayed on mild steel, followed by mild heat treatment. The nanosheets are strongly attached to the surfaces and even diffused to submicron under the surface, as proved by various analytical techniques. The mechanical, tribological and corrosion evaluations show significant simultaneous enhancement in a set of surface properties. From the friction tests with sliding steel-steel tribo-pairs under dry conditions, the graphene treatment decreases the friction coefficient and wear area by 21% and 31%, respectively. Interestingly, it is revealed that under dry and lubricated conditions, graphene-doped h-BN exhibits outstanding anti-wear properties synergistically compared to stand-alone 2D materials. The possible wear mechanism is investigated and found to be based on the formation of a tribofilm

Sustainable regeneration of high-performance LiCoO2 from completely failed lithium-ion batteries

Utilising the solid-state synthesis method is an easy and effective way to recycle spent lithium-ion batteries. However, verifying its direct repair effects on completely exhausting cathode materials is necessary. In this work, the optimal conditions for direct repair of completely failed cathode materials by solid-state synthesis are explored. The discharge capacity of spent LiCoO2 cathode material is recovered from 21.7 mAh g−1 to 138.9 mAh g−1 under the optimal regeneration conditions of 850 °C and n(Li)/n(Co) ratio of 1:1. The regenerated materials show excellent electrochemical performance, even greater than the commercial LiCoO2. In addition, based on the whole closed-loop recycling process, the economic and environmental effects of various recycling techniques and raw materials used in the battery production process are assessed, confirming the superior economic and environmental feasibility of direct regeneration method