Danuta Miedzińska

Numerical verification of three point bending experiment of magnetorheological elastomer (MRE) in magnetic field

In the article a method of numerical verification of experimental results for magnetorheological elastomer samples (MRE) is presented. The samples were shaped into cylinders with diameter of 8 mm and height of 20 mm with various carbonyl iron volume shares (1,5%, 11,5% and 33%). The diameter of soft ferromagnetic substance particles ranged from 6 to 9 μm. During the experiment, initially bended samples were exposed to the magnetic field with intensity levels at 0,1T, 0,3T, 0,5T, 0,7 and 1T. The reaction of the sample to the field action was measured as a displacement of a specimen. Numerical calculation was carried out with the MSC Patran/Marc computer code. For the purpose of numerical analysis the orthotropic material model with the material properties of magnetorheological elastomer along the iron chains, and of the pure elastomer along other directions, was applied. The material properties were obtained from the experimental tests. During the numerical analysis, the initial mechanical load resulting from cylinder deflection was set. Then, the equivalent external force, that was set on the basis of analytical calculations of intermolecular reaction within iron chains in the specific magnetic field, was put on the bended sample. Correspondence of such numerical model with results of the experiment was verified. Similar results of the experiments and both theoretical and FEM analysis indicates that macroscopic modeling of magnetorheological elastomer mechanical properties as orthotropic material delivers accurate enough description of the materials behavior.

EXPERIMENTAL AND ANALYTICAL RESEARCH ON RESONANCE PHENOMENA OF VIBRATING HEAD WITH MRE REGULATING ELEMENT

Abstract A vibratory pile hammer (VPH) is a mechanical device used to drive steel piles as well as tube piles into soil to provide foundation support for buildings or other structures. In order to increase the stability and the efficiency of the VPH work in the over-resonance frequency, a new VPH construction was developed at the Military University of Technology. The new VPH contains a system of counter-rotating eccentric weights, powered by hydraulic motors, and designed in such a way that horizontal vibrations cancel out, while vertical vibrations are transmitted into the pile. This system is suspended in the static parts by the adaptive variable stiffness pillows based on a smart material, magnetorheological elastomer (MRE), whose rheological and mechanical properties can be reversibly and rapidly controlled by an external magnetic field. The work presented in the paper is a part of the modified VPH construction design process. It concerns the experimental research on the vibrations during the piling process and the analytical analyses of the gained signal. The results will be applied in the VPH control system.

NUMERICAL INVESTIGATIONS ON VIBRATING MOTION WITH INERTIAL LOAD OF VIBRATORY PILE HAMMER STIFFLY COUPLED WITH EXCAVATOR

A vibratory pile hammer (VPH) is a mechanical device used to drive steel piles as well as tube piles into soil to provide foundation support for buildings or other structures. In order to increase the stability and the efficiency of the VPH work in the over-resonance frequency, a new VPH construction was developed in the Military University of Technology. The new VPH contains a system of counter-rotating eccentric weights, powered by hydraulic motors, and designed in such a way that horizontal vibrations cancel out, while vertical vibrations are transmitted into the pile. This system is suspended in the static parts by the adaptive variable stiffness pillows based on a smart material, magnetorheological elastomer (MRE), which rheological and mechanical properties can be reversibly and rapidly controlled by an external magnetic field. The work presented in the paper is a part of the modified VPH construction design process. It concerns the development of the numerical model of the VPH and soil interaction that will describe resonance conditions, resonance frequencies with consideration of soil susceptibility, coupling phenomenon and elastomer changeable stiffness. On the base of developed theoretical equations, the frequency of VPH piling will be regulated to assure the over-resonance work.

Multiscale Modelling Method for Chosen Functionally Graded Material

The paper deals with the numerical and experimental analyses of functionally graded material structures which are represented by a surface layer of the steel sample hardened during the laser treatment process. A functionally graded parameter of the researched structure was assumed as the hardness value experimentally measured with the use of a Vickers hardness test method. The microstructure of the tested layer was also analyzed for the Vickers test verification. Two homogenization methods were used for the purpose of layer substitute properties for numerical calculations. The first one was to divide the FGM domain into a number of layers in the direction of material gradation and then apply a numerical homogenization method within each layer. The resulting material model describes the FGM as a composite of homogeneous layers. The second method was based on the Mori-Tanaka homogenization theory and was carried out with the use of Digimat software, which is the nonlinear multi-scale materials and structures modelling platform. Both methods were compared and showed good correspondence.

Experimental Investigations of MREs Behavior under the Cyclic Load

In the paper the experimental results of the dynamic tests of the MRE samples cured without and under magnetic field are presented and compared. The samples (55 mm diameter and 70 mm) were made of the polyurethane elastomer PU 70/30 with the admixture of the ferromagnetic particles (in this case – carbonyl iron spheres with the diameter of about 9 μm). The samples with ferromagnetic particles were cured without as well as under the external, parallel to the vertical axis of the sample, magnetic field of the 300 mT intensity. The experiments were carried out on the materials testing machine for static and dynamic loads INSTRON 8802. The machine was additionally equipped with the measurement head of 4kN scope and the magnetic coil that produces the magnetic field of the intensity up to 500 mT. Cycled load was applied to the MRE samples. In the case of the dynamic tests the sinusoid cyclic variable load was used. The applied load frequency was 1 Hz in each presented test. The samples were cyclically compressed of the 10, 15, 20 and 25 % of their height. On the base of the obtained results the force maximum values and the dumping coefficient (the energy dissipation coefficient) in each dynamic tests were calculated. The hysteresis loops in the load – displacement charts that were observed during the cyclic tests. The influence of the internal structure of the researched material on its strength behaviour is taken into consideration.

FEM Modeling of Failure of a Foam Single Cell

. The paper deals with the numerical analysis of foam materials. Open cell foam is investigated. Numerical simulations enable prediction of failure process and assessment of effective properties of the modeled foam structures [1]. Metal as well as polyurethane foams exhibit interesting properties. They are light, possess good acoustic and/or magnetic isolation, have ability to absorb energy of vibration and impacts [2]. They are used for sandwich panels, hit absorbers (i.e. as elements of buffer constructions in rail vehicles), fillers of construction parts, bodies of vehicles (i.e. floating combat vehicles), dividing walls on vessels and others. Specially prepared open cell foams demonstrate auxetic properties [3] and shape memory effect [4]. Such materials are very good for seats in aircrafts, which may protect pilots and passengers during crashes and restrict heavy backbone injuries. Foams are also applied for filtering purposes. Foams themselves or in combination with different types of fillers (i.e. elastomers) or ceramic reinforcement may be used for impact energy absorbing panels for military purposes (protection against explosion shock wave and splinters).

Analysis of influence of temperature on wellbore tubing dimensions

The construction of exploitation wellbore is complex, it consists of several columns of pipelines which perform different tasks. It is very important to preclude flow of reservoir fluid between wellbore and ground. Tubing is a kind of a pipeline which is very important element of oil and gas wellbore construction. It allows to transport fracturing medium between wellbore station and underground deposit. Manufacture quality and correct mounting of tubing in the wellbore are the key for effective exploitation. However, during work those pipes are subjected to changeable loads which results in temperature value changes for example. That temperature variations can be caused by cold medium transport inside the pipe. In the paper, analyses of influence of temperature value changes on the tubing shrinkage were presented. Numerical analyses of section of pipe vertically located in the wellbore and loaded with changeable temperature were carried out. The calculations were made with the use of coupled structural and thermal analyses. Received results of tubing shrinkage for fragment of pipe were adapted to the column of pipes of 3000 m length. Results of numerical analyses were verified with the analytical calculations. Material of tubing was assumed as steel P110 which is often applied in the wellbore construction.

Research on heat flow in granite sample using thermal imaging camera

Research on heat flow in granite sample and sample of aluminium foam with the use of a thermal imaging camera is presented in the paper. Temperature distribution on the surface of the sample as a function of time was obtained on the basis of data from the thermal imaging camera. Thermovision is one of the most universal technology, which is applied for detection of infrared radiation. This technique allows observing and record infrared radiation emitted by objects located in the surrounding environment. This technology allows obtaining, in a short time, temperature distribution on the surface of the sample. The thermograms (pictures showing on the surface of the object) are types of photos showing temperature distribution on the tested object surface which is achieved on the base of a specified range of electromagnetic radiation. Accurate measurement of the temperature distribution on the heated granite sample surface was obtained using a thermal imaging camera FLIR SC 6000. Thermal imaging camera was connected to the computer equipped with control software FLIR ResearchIR Max. Heat source was applied in the experiment as a cast iron hotplate with high efficiency heating, gradual control and 1500W power. Obtained results showed regular temperature distribution over the surface of researched sample.

Non-destructive testing of polyethylene composite by terahertz radiation

We report on the terahertz time-of-flight analysis of an internal structure of an ultra-high molecular weight polyethylene (UHMWPE) composite material, which is based on the BT10-tape from Dyneema®. This type of composite is very hard and resistant and therefore it is often used to manufacture personal armors such as bulletproof vests and helmets. The multilayer structure of the UHMWPE composite was investigated by means of a raster scanning time domain spectroscopy technique in a reflection configuration. The mechanism of the formation of many shifted in time THz pulses (reflected from the internal layers of the sample) originates from the periodic modulation of the refractive index along the propagation of the radiation. This modulation is connected with alternate layers of fibers, each having different direction (perpendicular to each other one). As a result, the detailed three dimensional profile of the 20-mm-thick sample was obtained. Moreover, it is also possible to identify internal defects i.e. delaminations in the internal structure of this composite material.

Development of Porosity Measurement Method Based on Modern Microscopic Techniques

The aim of the research, presented in the paper, is to show and to assess the porosity structure in accordance to the dimensions of carbon dioxide particle. The characteristic surface morphology of the sample and the visualisation of the coal porous structure have been obtained using the atomic force microscope (AFM). The presented study of the coal microstructure is a part of the concepts of the project which aim is to develop the guidelines for design of the innovative technology of shale gas recovery with the use of liquid CO2. The technology will be based on Military University of Technology invention which considers gaseous hydrocarbons recovery from at least two levels of lateral wellbores with the use of supercritical CO2, what will result with wellbore productivity increase, because CO2 will cause desorption of CH4 from the porous structure of shale rock and the thermodynamic transformation of CO2 in the reservoir will help the rock fracturing. The heat energy added for the fracturing process will be taken from the surrounding rock mass.