Dynamics of the deformation of a spherical pore in a plastic material

1983 ◽  
Vol 24 (1) ◽  
pp. 111-115
Author(s):  
A. V. Attetkov ◽  
V. V. Selivanov ◽  
V. S. Solov'ev
Keyword(s):  
Plastic Material ◽  
Spherical Pore

Masonry: the brittle or plastic material?

2019 ◽  
pp. 22-28
Keyword(s):  
Plastic Material ◽  
Experimental Studies ◽  
Point Of View ◽  
Plastic Properties ◽  
Plastic Deformations ◽  
Base Materials ◽  
Stress States ◽  
Creep Deformations ◽  
Structural Point

The results of experimental studies of masonry on the action of dynamic and static (short-term and long-term) loads are presented. The possibility of plastic deformations in the masonry is analyzed for different types of force effects. The falsity of the proposed approach to the estimation of the coefficient of plasticity of masonry, taking into account the ratio of elastic and total deformations of the masonry is noted. The study of the works of Soviet scientists revealed that the masonry under the action of seismic loads refers to brittle materials in the complete absence of plastic properties in it in the process of instantaneous application of forces. For the cases of uniaxial and plane stress states of the masonry, data on the coefficient of plasticity obtained from the experiment are presented. On the basis of experimental studies the influence of the strength of the so-called base materials (brick, mortar) on the bearing capacity of the masonry, regardless of the nature of the application of forces and the type of its stress state, is noted. The analysis of works of prof. S. V. Polyakov makes it possible to draw a conclusion that at the long application of the load, characteristic for the masonry are not plastic deformations, but creep deformations. It is shown that the proposals of some authors on the need to reduce the level of adhesion of the mortar to the brick for the masonry erected in earthquake-prone regions in order to improve its plastic properties are erroneous both from the structural point of view and from the point of view of ensuring the seismic resistance of structures. It is noted that the proposal to assess the plasticity of the masonry of ceramic brick walls and large-format ceramic stone with a voidness of more than 20% is incorrect, and does not meet the work of the masonry of hollow material. On the basis of the analysis of a large number of research works it is concluded about the fragile work of masonry.

The Issue of Plastic and Microplastic Pollution in Soil

2019 ◽  
Vol 56 (3) ◽  
pp. 484-487 ◽  
Author(s):  
Valentina Constanta Tudor ◽  
Dorina Nicoleta Mocuta ◽  
Ruxandra Florina Teodorescu ◽  
Dragos Ion Smedescu
Keyword(s):  
Water Pollution ◽  
Organic Matter ◽  
Soil Pollution ◽  
Aquatic Environment ◽  
Negative Impact ◽  
Plastic Material ◽  
Soil Biota ◽  
Toxic Substances

Soil pollution with plastics represents a great threat to plants, animals, but especially to humans, as a very small quantity of the plastic which is discarded daily is recycled or incinerated in waste facilities, much of it reaching landfills where their decomposition lasts up to 1000 years and during this time the toxic substances penetrate the soil and the water. If, initially, the pollution with plastics has been identified and recognized in the aquatic environment, recent studies show that plastics residues exist in huge quantities in the soil. The present study focuses on the analysis of factors that pollute soil, so the various studies that have been carried out claim that soil pollution with plastic is much higher and increases in an aggressive manner, being estimated to be 4 to 23 times higher than water pollution with plastics, and the accumulation of microplastics in the soil has a negative impact on soil biota. Thus, once the plastic material accumulates in the soil, it is assimilated to organic matter and the mineral substitutes of the soil and persists for several hundred years.

EXPERIENCE OF RECONSTRUCTION OF THE BREAST WITH THE USE OF THORACODORSAL FLAP

2018 ◽  
Vol 64 (2) ◽  
pp. 206-210
Author(s):  
Petr Krivorotko ◽  
Vladimir Semiglazov ◽  
Aleksey Belyaev ◽  
Kirill Nikolaev ◽  
Tengiz Tabagua ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Plastic Material ◽  
Breast Cancer Patients ◽  
Anterior Axillary Line ◽  
National Medical ◽  
Results Of Treatment ◽  
Implant Placement ◽  
Quality Of Medical Care ◽  
Low Incidence

Purpose: To analyze the results of treatment and the quality of medical care for breast cancer patients with breast reconstruction using thoracodorsal flap (TDF). Material and methods: The study was conducted on the basis of the N.N. Petrov National Medical Research Center of Oncology at the Department of Breast Tumors for the period 2016-2017. When using the reconstruction of the breast with the help of TDF the feature was the complete intersection of the muscle in the anterior-axillary line before closing the defect of the breast tissue but with the preservation of the thoracodorsal vascular sheaf. Surgical treatment was provided to 67 patients with breast cancer including after neoadjuvant therapy. Results: One-time reconstruction was performed in 16 (23.8%) patients under the organ-preserving surgery, mastectomy in two (2.9%) patients and mastectomy with implant placement in 27 (40.2%) patients. Delayed reconstruction of the breast: TDF in combination with the implant - 20 (29.8%), the use of TDF without an implant - 2 (2.9%) patients. Complications were observed in 6 (8.9%) patients. Conclusion: Reconstruction of the breast with TDF is the method of choice and priority for patients who underwent radiation therapy with a lack of integumentary tissues to cover the implant. TDF is a «good» plastic material and could be used in patients with severe defect of breast shape after organ-preserving surgery and mastectomy. TDF is characterized by a low incidence of complications. The use of TDF does not worsen the rehabilitation of patients and does not shift the timing of adjuvant treatment.

scholarly journals Right paraduodenal hernia with extensive bowel gangrene treated with staged surgery: a Bogota bag followed by resection in a low-resource setting

2021 ◽  
Vol 14 (4) ◽  
pp. e239250
Author(s):  
Vijay Anand Ismavel ◽  
Moloti Kichu ◽  
David Paul Hechhula ◽  
Rebecca Yanadi
Keyword(s):  
Plastic Material ◽  
Successful Outcome ◽  
Paraduodenal Hernia ◽  
Transparent Plastic ◽  
Low Resource ◽  
Entire Small Bowel ◽  
Resource Setting ◽  
Low Resource Setting ◽  
Right Paraduodenal Hernia ◽  
Bowel Gangrene

We report a case of right paraduodenal hernia with strangulation of almost the entire small bowel at presentation. Since resection of all bowel of doubtful viability would have resulted in too little residual length to sustain life, a Bogota bag was fashioned using transparent plastic material from an urine drainage bag and the patient monitored intensively for 18 hours. At re-laparotomy, clear demarcation lines had formed with adequate length of viable bowel (100 cm) and resection with anastomosis was done with a good outcome on follow-up, 9 months after surgery. Our description of a rare cause of strangulated intestinal obstruction and a novel method of maximising length of viable bowel is reported for its successful outcome in a low-resource setting.

scholarly journals Plastic forming processes of transverse non-homogeneous composite metallic sheets

2021 ◽  
Vol 11 (1) ◽  
pp. 294-302
Author(s):  
Gal Davidi
Keyword(s):  
Inner Core ◽  
Plastic Material ◽  
Radial Solution ◽  
Algebraic Differential Equation ◽  
Forming Process ◽  
Perfectly Plastic ◽  
Plastic Forming ◽  
Validity Limit ◽  
Significant Achievement

Abstract In this work an analysis of the radial stress and velocity fields is performed according to the J 2 flow theory for a rigid/perfectly plastic material. The flow field is used to simulate the forming processes of sheets. The significant achievement of this paper is the generalization of the work by Nadai & Hill for homogenous material in the sense of its yield stress, to a material with general transverse non-homogeneity. In Addition, a special un-coupled form of the system of equations is obtained where the task of solving it reduces to the solution of a single non-linear algebraic differential equation for the shear stress. A semi-analytical solution is attained solving numerically this equation and the rest of the stresses term together with the velocity field is calculated analytically. As a case study a tri-layered symmetrical sheet is chosen for two configurations: soft inner core and hard coating, hard inner core and soft coating. The main practical outcome of this work is the derivation of the validity limit for radial solution by mapping the “state space” that encompasses all possible configurations of the forming process. This configuration mapping defines the “safe” range of configurations parameters in which flawless processes can be achieved. Several aspects are researched: the ratio of material's properties of two adjacent layers, the location of layers interface and friction coefficient with the walls of the dies.

Theory and Application of the Parallel-Plate Plastimeter. Part 2

1935 ◽  
Vol 8 (4) ◽  
pp. 587-596 ◽  
Author(s):  
J. R. Scott
Keyword(s):  
Plastic Flow ◽  
Parallel Plate ◽  
Plastic Material ◽  
Compressive Load ◽  
Flow Equation ◽  
Simple Type ◽  
Plastic Properties ◽  
Further Development ◽  
Rubber Stock ◽  
Existing Data

Abstract In Part I (loc. cit.) the behavior of a plastic material in the parallel-plate (Williams) plastimeter was studied, and an expression was deduced showing how the rate of decrease in thickness of the sample during compression depends on the volume of the sample, its plastic properties, the compressive load, and the thickness itself. Subsequently, observations were published which showed that the basic principle adopted in this study was incorrect in certain particulars. Peek (loc. cit.), using these observations as a basis, deduced a new expression for the rate of decrease in thickness, though this is too complex for convenient practical use, except in an approximate simplified form. It has now been shown that the expression deduced in Part I, in spite of the inaccurate basis used, is sufficiently near to the truth to render substantially correct the conclusions there stated concerning the plastic properties of unvulcanized rubber stocks. By adopting the more accurate basis used by Peek, moreover, expressions for the rate of decrease in thickness can be deduced for materials showing more complex types of plastic flow than that considered in Part I or by Peek; this had proved impossible by the method previously used. The expression obtained by Peek for the simple type of plastic flow, as well as those now deduced for the more complex types, can be expressed in a form that furnishes a simple and rapid method of examining and analyzing experimental results. As a result of the work described in this paper, it is thus possible to determine, from results obtained with the parallel-plate plastimeter, whether or not a material such as unvulcanized rubber stock exhibits any of the types of plastic flow represented in the general form by Equation 1, and, if so, to find the values of the plastic constants of the material. The procedure is similar to that described in Part I, and consists simply in comparing, by superposition, a set of standard curves drawn on transparent paper with the curve plotted from experimental data. This further development of the method of studying plastic properties by means of the parallel-plate plastimeter should greatly increase its utility as an instrument of research. It has not yet been possible to apply the new method to a systematic study of rubber stocks, but from an examination of existing data it appears that these stocks, tested at 90° C., agree approximately with various forms of the generalized plastic flow equation already referred to.

scholarly journals Study of the Biodegrability of Degradable/Biodegradable Plastic Material in a Controlled Composting Environment

2012 ◽  
Vol 19 (3) ◽  
pp. 347-358 ◽  
Author(s):  
Magdalena Vaverková ◽  
František Toman ◽  
Dana Adamcová ◽  
Jana Kotovicová
Keyword(s):  
Plastic Material ◽  
Laboratory Scale ◽  
Biodegradable Plastic ◽  
Preliminary Evaluation ◽  
The Czech Republic ◽  
Chain Stores ◽  
Plastic Bags ◽  
Plastic Materials ◽  
Scale Test

Study of the Biodegrability of Degradable/Biodegradable Plastic Material in a Controlled Composting EnvironmentThe objective of this study was to determine the degrability/biodegradability of disposable plastic bags available on the market that are labeled as degradable/biodegradable and those certified as compost. The investigated materials were obtained from chain stores in the Czech Republic and Poland. Seven kinds of bags (commercially available) were used in this study. One of them was a disposable bag made of HDPE and mixed with totally degradable plastic additive (TDPA additive). Another was a disposable made of polyethylene with the addition of pro-oxidant additive (d2w additive). One was labeled as 100% degradable within various periods of time, from three months up to three years, and four were certified as compostable. The test was carried out in a controlled composting environment. The biodisintegration degree of the obtained pieces was evaluated following a modified version of ČSN EN 14806 Norm "Packaging - Preliminary evaluation of the disintegration of the packaging materials under simulated composting conditions in a laboratory scale test" and a modified version of ČSN EN ISO 20200 "Plastics - Determination of the degree of disintegration of plastic materials under simulated composting conditions in laboratory-scale test" (ISO 20200:2004). The emphasis was put on determination whether the bags are degradable/biodegradable or not.

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