Wyniki wyszukiwania - BazTech

1

Quasi-Static Investigations of 240-Bloom Gelatine for Ballistic Tests

Fikus Bartosz, Basiński Norbert

Problemy Mechatroniki : uzbrojenie, lotnictwo, inżynieria bezpieczeństwa

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2023

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Vol. 14, Nr 1 (51)

61--72

EN

The paper presents the results of investigations of ballistic gel properties in quasi-static conditions. Specimens were prepared using the 240 Bloom gelatine, which was determined by product availability. Tests were carried out making use of a material testing machine to estimate the influence of gel share on stress-strain characteristics. Considered values of a gel mass content were equal to 10, 12, and 14%. Assumed parameters were determined on the material calibration stage conducted with steel balls with a diameter of 4.5 mm. The most significant influence of a gel content on mechanical properties of specimens were observed for a share of 10% and 12%. The conducted preliminary tests are a part of investigations aimed at assessment if it is possible to calibrate the ballistic gel making use of mechanical characteristics obtained in quasi-static tests without shooting.

PL

Niniejsza praca stanowi opis oraz wyniki prac realizowanych w ramach badań quasi-statycznych żelatyny (o sile żelowania 240 Bloom) przeznaczonej do testów balistycznych, która jest najczęściej stosowanym substytutem tkanek miękkich w badaniach balistyki końcowej. W ramach prac przeprowadzono proces przygotowania materiału do badań, jego kondycjonowania, kalibracji oraz badań w warunkach quasi-statycznych w celu określenia modułu sprężystości wzdłużnej oraz modułu sprężystości objętościowej. Na podstawie wstępnych badań kalibracyjnych podjęto decyzję o przebadaniu próbek o zawartości żelatyny równej 10 %, 12 % oraz 14 %. Rezultaty badań (krzywe siła-przemieszczenie) pozwoliły na ocenę odkształceń oraz naprężeń (inżynierskich oraz rzeczywistych) występujących w badanym materiale. To z kolei pozwoliło na ocenę wartości wyżej wspomnianych modułów sprężystości. Należy zwrócić uwagę na relatywnie duży rozrzut uzyskanych wyników, co może sugerować konieczność dalszych prac nad precyzją wykonania próbek. Uzyskane wyniki wykazały łatwość oraz efektywność zastosowanej metodyki przygotowania próbek, jak również znaczący wpływ zawartości żelatyny na moduł sprężystości wzdłużnej (szczególnie w przypadku dwóch niższych wartości zawartości żelatyny). Zdecydowania mniejszą rozbieżność zauważono w przypadku modułu sprężystości objętościowej. Ponadto, okazało się, że przygotowanie próbek o udziale masowym 20 % jest nieuzasadnione ze względu na dużą czasochłonność całości procesu.

2

Potential method in the coupled linear quasi-static theory of thermoelasticity for double porosity materials

Mikelashvili M.

Archives of Mechanics

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2023

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Vol. 75, nr 5

559--590

EN

This paper concerns the coupled linear quasi-static theory of thermoelasticity for materials with double porosity under local thermal equilibrium. The system of equations of this theory is based on the constitutive equations, Darcy’s law of the flow of a fluid through a porous medium, Fourier’s law of heat conduction, the equations of equilibrium, fluid mass conservation and heat transfer. By virtue of Green’s identity the uniqueness theorems for classical solutions of the internal and external quasi-static boundary value problems (BVPs) are proved. The fundamental solution of the system of steady vibration equations in the considered theory is constructed and its basic properties are established. Then, the surface and volume potentials are presented and their basic properties are given. Finally, on the basis of these results the existence theorems for classical solutions of the above mentioned BVPs are proved by means of the potential method (boundary integral equation method) and the theory of singular integral equations.

3

Parametric Study of Geometry Effect on Response to Applied Loadings of Metallic Honeycomb Structures by Virtual Testing of Mesoscale Models

Pietras D., Sadowski T.

Archives of Metallurgy and Materials

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2018

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Vol. 63, iss. 2

953--961

EN

In this paper were conducted virtual tests to assess the impact of geometry changes on the response of metallic hexagonal honeycomb structures to applied loadings. The lateral compressive stress state was taken into consideration. The material properties used to build numerical models were assessed in laboratory tests of aluminium alloy 7075. The modelling at meso-scale level allow to comprehensive study of honeycomb internal structure. The changes of honeycomb geometry elements such as: fillets radius of the cell edges in the vicinity of hexagonal vertexes, wall thickness were considered. The computations were conducted by using finite element method with application of the ABAQUS finite element method environment. Elaborated numerical models allowed to demonstrate sensitivity of honeycomb structures damage process response to geometry element changes. They are a proper tools to perform optimization of the honeycomb structures. They will be also helpful in designing process of modern constructions build up of the considered composite constituents in various branches of industry. Moreover, the obtained results can be used as a guide for engineers. Conducted virtual tests lead to conclusion that simplification of the models of internal honeycomb structure which have become commonplace among both engineers and scientist can lead to inaccurate results.

4

Comparative analysis of buckling load of circular and corrugated tubes by utilizing key performance indicators

Rahim M. R., Akhtar S., Bharti P. K.

International Journal of Applied Mechanics and Engineering

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2017

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Vol. 22, no. 3

789--797

EN

The performance of buckling load of tubular structures under quasi-static axial loading is quite appreciable, numerous tubes of various cross-section have been extensively investigated and corrugated sections have been designed to further improve the performance. In this paper, a carefully designed set of key performance indicators (KPIs) is utilized to assess and compare the buckling load of circular and corrugated tubes. A series of diagrams related to KPIs with various parameters of tubes are presented to demonstrate the influence of sectional configuration on the performance of tubes as well as the effect of the material on the potential of the same. The work is inestimable to engineering designs and applications, and further studies on the buckling load of other configurations.

5

Preparation of a new AAC-concrete sandwich block and its compressive behavior at quasi-static loading

Abed F., Aidan A., Hegazi N., Ibrahim N., Al-Dabagh S.

Engineering Transactions

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2017

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Vol. 65, iss. 2

371--389

EN

Autoclaved aerated concrete (AAC) is an environmentally friendly material that has several advantages such as heat insulation, sound insulation, and light weight which reduce the energy consumption of a structure during its construction and when using it. However, the compressive strength of AAC is relatively low in comparison with concrete masonry units that are used as building blocks. This paper provides insight into a newly proposed AAC-concrete sandwich composite. The main aim of this research is to produce a lightweight eco-friendly loadbearing building block. Construction and demolition wastes including the cement and fine powder waste were utilized to generate the AAC-concrete composite. The proposed sandwich composite was tested in a number of stages. Firstly, a preliminary test was conducted to test the proposed sandwiching technique. Three sets of plain sandwich specimens were prepared, each with a different combination of AAC thickness and concrete thickness. It was found that the proposed composite had a higher compressive strength than AAC and a lower density than the normal concrete. Secondly, different concrete and mortar mixes were prepared and studied to identify the mix that would yield the best sandwich composite. This best mix was identified and used throughout the experiment. Thirdly, different sandwiching techniques were applied to enhance bonding at the AAC-concrete interface. The proposed sandwiching techniques were as follows: (1) inserting grooves at the AAC-concrete interface and (2) wrapping the AAC block with wire mesh. Multiple cube specimens with 10 cm side length were prepared and tested for their compressive strength. It was found that the wire mesh provided a more effective bonding. Finally, additional grooved and plain sandwich cube specimens with 20 cm side length were prepared and tested under different quasi-static loading rates. Unlike plain sandwich block, the compressive behavior of grooved sandwich showed a slight increase in its capacity at higher quasi-static rate. Almost all specimens in this study failed in a similar manner that is, by debonding at the AAC-concrete interface, followed by crushing.

6

Quasi-static Planar Deformation in av Medium Composed of Elastic and Thermoelastic Solid Half Spaces Due to Seismic Sources in an Elastic Solid

Vashisth A. K., Rani K., Singh K.

Acta Geophysica

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2015

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Vol. 63, no. 3

605--633

EN

A two-dimensional problem of quasi static deformation of a medium consisting of an elastic half space in welded contact with thermoelastic half space, caused due to seismic sources, is studied. Source is considered to be in the elastic half space. The basic equations, governed by the coupled theory of thermoelasticity, are used to model for thermoelastic half space. The analytical expressions for displacements, strain and stresses in the two half spaces are obtained first for line source and then for dip slip fault. The results for two particular cases, adiabatic conditions and isothermal conditions, are also obtained. Numerical results for displacements, stresses and temperature distribution have also been computed and are shown.

7

Hybrid piezoelectric motor based on electroactive lubrication principle

Rouchon J. F., Harribey D., Tran D. H., Ryndzionek R., Sienkiewicz Ł., Ronkowski M.

Prace Naukowe Instytutu Maszyn, Napędów i Pomiarów Elektrycznych Politechniki Wrocławskiej. Studia i Materiały

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2012

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Vol. 66, nr 32, t. 1

326-332

EN

A novel conception of hybrid piezoelectric motor is presented in this paper. Proposed conception required synchronized work of quasi-static and resonant piezoelectric actuators that results in a rotary movement. The motor's working principle is explained and the main characteristics are described. Studied topology is compared to the existing piezoelectric motors with regards to its field of applications. The assembling process of the motor is briefly explained with emphasis put on the frequency and impedance tuning of the piezoelectric actuators. Next, the power supply system is described. Finally, conclusions are presented concerning the features of the hybrid piezoelectric motor and possible solutions of the faced problems.

8

Dynamic response analysis of light weight pyramidal sandwich plates subjected to water impact

Hao Wang Hao, Fei Zhao, Jun Liu Jun, Yuan Tian Yuan

Polish Maritime Research

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2012

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nr 4

31-43

EN

The fluid-solid interaction (FSI) dynamic responses for a Light Weight Pyramidal Sandwich Plate Structure (LWPSPS) under different water-entry velocities (1m/s-6m/s) are investigated numerically and theoretically. The characteristics of impact pressure and structure deformation are obtained by using LS-DYNA code based on the proposed 3D multi-physics (air-water-solid) FEM model. Numerical results show that the average water impact pressure of LWPSPS is much lower than that of the monolithic plate with same mass. Moreover, a phenomenon called “local air cushion” is observed for LWPSPS which does not exist for a monolithic plate. Theoretical hydroelasticity analysis demonstrates that the FSI effect of LWPSPS is weak when the ratio of water impact duration time to wet natural vibration period is greater than 4. In the study, an engineering estimation method to predict the maximum deformation of the LWPSPS is proposed, in which the total deformation is divided into two parts, i.e. local field deformation and global field deformation, and they are both computed using analytical model. Good agreement between the numerical results and ones obtained from the proposed engineering estimation method is achieved. Furthermore, the geometric variation sensitiveness analysis is also conducted.