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1

Electrical resistivity analysis for the internal capillary water migration mechanism of porous stone

Yang Haiqing, Chen Chiwei, Zhao Gang, Zhou Jiayuan

Acta Geophysica

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2024

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Vol. 72, no. 1

213-–231

EN

Porous stone that has been exposed to the natural environment for a long time has developed a variety of diseases under the influence of environmental and geological factors. Especially, migration of soluble salt solution in porous stone and salt crystallization will inevitably lead to the deterioration of stone surface. To investigate the spatial and temporal evolution features of porous stone during capillary water migration, a series of capillary water absorption tests with different types of porous sandstone were performed. The process of capillary water absorption and stone surface deterioration characteristics was observed by high-density resistivity method. The results indicate that the process of capillary rise can be divided into stages of rapid rising, transition, and slow rising. According to the analysis of electrical resistivity measurements at millimeter scale, there was a negative correlation between capillary rise rate and sample total porosity, and the rising trend of the dry-wet interface was presented as the saddle shape. Then, a novel capillary rise model was proposed considering the variation in pore saturation. Moreover, it has been demonstrated that the migration and crystallization of soluble salt solution were the main causes for the change of micropore structure, resulting in increased deterioration of porous stone during the dry-wet cycles. This present study serves as some references for the protection and restoration of porous stone.

2

Electrical characteristics of dry cement – based composites modified with coconut husk ash nanomaterial

Robert Ubong Williams, Etuk Sunday Edet, Ekong Sylvester Andrew, Agbasi Okechukwu Ebuka, Ekpenyong Nsikak Edet, Akpan Samuel Sunday, Umana Eme Aniefiok

Advances in Materials Science

|

2022

|

Vol. 22, nr 2(72)

64--77

EN

Coconut husk is generated yearly as waste in large quantities but majorly under-utilized. Also, as a result of high embodied carbon, cement production is one of the largest contributors to construction sector carbon footprint. Since accumulation of unmanaged agro-waste like coconut husk has an increased environmental concern due to its pollution effect, recycling it into sustainable construction materials is a viable solution for future generation. In this study, experiments were performed to investigate the influence of coconut husk ash nanomaterial (CHAN) inclusion on electrical characteristics of plain cement paste (BCP) and mortar (CSM) samples at curing ages of 7 and 28 days. The results showed increase in electrical resistivity, thermal constant, and activation energy with curing duration for heating and cooling cycles of BCP and CSM. With inclusion of CHAN, the developed cement paste (CAP) and mortar (CASM) possessed lower values in all cases compared to their counterparts. Also, during heating at 28 days, both the CAP and CASM exhibited decrease in thermal constant. Though electrical resistance of all the samples varied inversely with temperature, CAP and CASM were found to possess greater potentials to make building structures intrinsically smart. Hence, in addition to solving disposal problems, utilization of coconut husks as described herein could enhance development of safe, inexpensive, and sustainable buildings that have large temperature sensing volume.

3

Frequency domain electromagnetic and electrical resistivity geophysical investigation of tar sands deposits in the Ijebu Waterside area, Eastern Dahomey Basin, southwestern Nigeria

Osinowo Olawale Olakunle, Okechukwu Ifeayinchukwu

Geology, Geophysics and Environment

|

2021

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Vol. 47, no. 4

217--226

EN

The use of electromagnetic conductivity and electrical resistivity geophysical techniques has been employed in this study to investigate the occurrence, thickness, and spatial distribution of bitumen deposit around Makun-Omi in the Ijebu Waterside area of southwestern Nigeria. Subsurface apparent conductivity distribution data obtained using Geonic 34-3 equipment along fifteen traverses which sounded from different depths of 7.5, 15, 30 and 60 m at inter-coil separation of 10, 20 and 40 m in vertical and horizontal coupling modes and ground resistivity distribution measurements, obtained using Geopulse Tiger Allied resistivity meter at fourteen Vertical Electrical Sounding (VES) stations, were processed and employed to characterize the subsurface in terms of tar sands distribution. The conductivity and resistivity distribution in the form of a 3D earth model, iso-depth maps, 2D sections generated from the processed conductivity and resistivity data indicate relatively low conductivity <20 mS/m and high resistivity >1300 Ωm values around tar/bitumen impregnated sands which mostly occurred in the southern part of the study area. Clearly defined conductivity and resistivity anomalies which delineate the lateral and vertical occurrence of tar impregnated sands underscore the efficacy of integrating electromagnetic and electrical resistivity geophysical techniques to identify occurrence of economic deposits of tar sands in parts of southwestern Nigeria.

4

Estimation of electrical resistivity using artifcial neural networks: a case study from Lublin Basin, SE Poland

Ważny Jakub, Stefaniuk Michał, Cygal Adam

Acta Geophysica

|

2021

|

Vol. 69, no. 2

631--642

EN

Artifcial neural networks method (ANNs) is a common estimation tool used for geophysical applications. Considering borehole data, when the need arises to supplement a missing well log interval or whole logging-ANNs provide a reliable solution. Supervised training of the network on a reliable set of borehole data values with further application of this network on unknown wells allows creation of synthetic values of missing geophysical parameters, e.g., resistivity. The main assumptions for boreholes are: representation of similar geological conditions and the use of similar techniques of well data collection. In the analyzed case, a set of Multilayer Perceptrons were trained on fve separate chronostratigraphic intervals of borehole, considered as training data. The task was to predict missing deep laterolog (LLD) logging in a borehole representing the same sequence of layers within the Lublin Basin area. Correlation between well logs data exceeded 0.8. Subsequently, magnetotelluric parametric soundings were modeled and inverted on both boreholes. Analysis showed that congenial Occam 1D models had better ftting of TM mode of MT data in each case. Ipso facto, synthetic LLD log could be considered as a basis for geophysical and geological interpretation. ANNs provided solution for supplementing datasets based on this analytical approach.

5

Badania oporności elektrycznej zbrojonego betonu klasy XD3 z azotanem wapnia i superplastyfikatorami pod kątem korozji zbrojenia powodowanej przez chlorki

Abdulsada Shaymaa Abbas, Török Tamás I.

Cement Wapno Beton

|

2020

|

R. 25, nr 4

330--343

PL

W pracy przedstawiono badania zawartości chloru w betonie i proces korozji, w oparciu o pomiary oporu przewodnictwa elektrycznego i potencjału półogniwa próbek betonowych. Te analizy opierały się na doświadczalnych pomiarach próbek w funkcji czasu zanurzenia w 3,5% roztworze NaCl w wodzie, w temperaturze pokojowej, przez 18 miesięcy, zgodnie z europejskimi normami. Przygotowano mieszanki betonowe o różnym składzie, do których dodawano inhibitor, jakim był azotan wapnia i dwa rodzaje superplastyfikatorów. Wyniki doświadczeń pokazały, że po sześciu miesiącach zanurzenia próbki miały dużą zawartość jonów chlorkowych. Próbki C4 z dodatkiem 3% inhibitora i superplastyfikatora w formie Oxydtronu, jak również C3 z tym samym dodatkiem inhibitora i superplastyfikatora MAPEI Dynamon SR 31, wykazały dobrą odporność na korozję, w stosowanym roztworze NaCl. Znalazło to również potwierdzenie w serii pomiarów przewodnictwa elektrycznego i potencjału półogniwa, przeprowadzonych po doświadczalnym okresie 18 miesięcy.

EN

This work presents a study of the total chloride contents in concrete and the corrosion process by testing electrical resistivity and half-cell potential of concrete samples. The analysis was based on an experimental investigation of the samples with the time of immersion in 3.5% mass NaCl aqueous solution at room temperature for 18 months, according to European Standards. For this study, different mixtures of concrete were prepared by adding two types of superplasticizers and calcium nitrate inhibitor, in different concentrations. The results of the Cl- ions test showed that all the samples, after an immersion testing period of six months, contained high concentrations of Cl- ions. Samples C4 with 3% calcium nitrate inhibitor and Oxydtron superplasticizer as well as C3 with 3% calcium nitrate inhibitor and Mapei Dynamon SR 31 superplasticizer, showed good resistance to corrosion, in the tested environment. It was also proved by the results of several sets of measurements of the electrical resistivity and half-cell potentials carried on the concrete test samples, to the end of the 18 months testing period.

6

Production and investigation of mechanical properties and electrical resistivity of cement-matrix nanocomposites with graphene oxide and carbon nanotube reinforcements

Najafishad S., Manesh H. D., Zebarjad S. M., Hataf N., Mazaheri Y.

Archives of Civil and Mechanical Engineering

|

2020

|

Vol. 20, no. 2

397--409

EN

In this study, two groups of the cement-matrix nanocomposites (CMNC) were produced. The first group was reinforced with either carbon nanotubes (CNT) or graphene oxide (GO), where the equivalent weight% of cement equaled 0.05, 0.1, and 0.15. The second group was reinforced with the hybrid CNT–GO, where the equivalent weight% of cement equaled 0.05 CNT–0.1 GO and 0.1 CNT–0.05 GO. Before producing nanocomposites, the distribution of the nanoreinforcement in water had been investigated using spectrophotometric analysis, scanning electron microscopy, and transmission electron microscopy. The physical and mechanical behaviors of different samples of the produced nanocomposites were evaluated by electrical resistivity and compressive strength tests. The effects of the types and the percentages of the nanoreinforcements on the electrical and mechanical properties of the produced nanocomposites were measured. The results showed that the electrical resistivity of the produced composites decreased with increasing the percentage of CNT, whereas the compressive strength of the cement paste initially increased and then decreased. Also, with increasing the percentage of GO, the compressive strength of the produced composites increased, while the electrical resistivity decreased. Moreover, in comparison with the composites reinforced with either CNT or GO, by using the hybrid reinforcement (CNT/GO), the compression strength increased, while the electrical resistivity decreased.

7

Silicon Carbide Fabrication by Infiltration of Molten Fe-Si Alloy Through Two-Step Reaction Sintering

Hanada Yoshitsugu, Xiao Yang, Sonoda Akio, Kang Hyo-Gyoung, Nagayoshi Hideaki, Yamamoto Atsuo, Tokunaga Tatsuya

Archives of Metallurgy and Materials

|

2019

|

Vol. 64, iss. 4

1645--1652

EN

Wider application of silicon carbide (SiC) is anticipated for increasing the durability of various structural facilities. For this study, SiC was fabricated with decreased electrical resistivity for precision electrical discharge machining. Two-step reaction sintering by infiltration of molten Fe-Si alloy was applied for SiC fabrication. The procedure included first sintering at 973 K in Ar gas atmosphere and second sintering by spontaneous infiltration of molten Fe-75%Si alloy at 1693 K in vacuum. The sintered structure porosity became very low, forming 3C-type SiC. Results confirmed that molten Fe-75%Si alloy infiltration occurred because of reaction sintering. The electrical resistivity of the sintered SiC infiltrated by molten Fe-75%Si alloy can be improved to be two orders of magnitude lower than that by molten Si, consequently maintaining the high performance of SiC.

8

Prediction of Microstructure of Grey Cast Irons by Electrical Resistivity Measurements

Petrič M., Mrvar P., Kastelic S.

Archives of Metallurgy and Materials

|

2019

|

Vol. 64, iss. 1

365--369

EN

The paper describes the influence of graphite shape, size and amount to electrical properties of different cast irons. Experiments of electrical resistivity measurements were conducted during solidification of four different melts in different time intervals from melt treatment by inoculation and nodularization. Metallographic analyses were made in order to determine the shape, size, distribution and amount of graphite and correlate results with electrical resistivity measurements. It was found out that nodular graphite is giving the lowest electrical resistivity and is decreased during solidification. Electrical resistivity of lamellar cast iron is increased during solidification since lamellas interrupt metal matrix severely. There is no significant difference in resistivity of vermicular cast iron from nodular cast iron. Smaller size of graphite and lower amount of graphite and higher amount of metal matrix also decrease resistivity.

9

Effect of MgB2 additives on structure, electrical and thermal properties of Eu1Ba2Cu3O7

Akduran N.

Materials Science Poland

|

2018

|

Vol. 36, No. 4

609--615

EN

The effect of MgB2 addition on the Eu1Ba2Cu3O7 (EBCO) ceramics was systematically studied. Series of Eu1Ba2Cu3O7 + x(MgB2) samples (x = 0 wt.%, 0.05 wt.%, 0.1 wt.%, 1 wt.%, 3 wt.%) were prepared using traditional solid state method. X-ray powder diffraction measurements were used for phase identification. The lattice parameters and orthorombicity decreased with MgB2 addition. A standard four point measurement method was used to determine transition temperatures Tc of superconducting samples. Tc values of the samples were decreasing with MgB2 concentration. TGA results indicate thermal stability of doped samples.

10

Electrical and piezoresistive sensing capacities of cement paste with multi-walled carbon nanotubes

Yoo D. Y., You I., Lee S. J.

Archives of Civil and Mechanical Engineering

|

2018

|

Vol. 18, no. 2

371--384

EN

This study examined the feasibility of using multi-walled carbon nanotubes (MWCNTs) in cement paste for piezoresistive sensors. Two types of MWCNTs with different carbon content (>90% and >99%) were incorporated into cement paste at 1% by weight of binder (1 wt%). Plain cement paste and cement composites including 1 wt% graphite nanofiber (GNF) and graphene (G) were also considered for comparisons of the electrical conductivity. The test results indicate that the MWCNTs more effectively improved the conductivity of the cement paste than GNF and G. In addition, composites with MWCNTs with lower flowability had less resistivity than those with higher flowability. The size effect in electrical resistivity was observed in the cement pastes with and without the carbon-based nanomaterials, but it was mitigated by incorporating MWCNTs in the cement paste. The stresses and strains under cyclic compression and monotonic tension were well simulated by the measured fraction change in the resistivity of the composites with 1 wt% MWCNTs. The gauge factor (GF) for the composites with 1 wt% MWCNTs was higher than that of commercially available strain gauges, and it was affected by the loading condition: a higher GF obtained under compression than under tension.

11

Comparison of compressive strength and electrical resistivity of cementitious composites with different nano- and micro-fillers

Jiang S., Zhou D., Zhang L., Ouyang J., Yu X., Cui X., Han B.

Archives of Civil and Mechanical Engineering

|

2018

|

Vol. 18, no. 1

60--68

EN

Cementitious composites with 0–1.5 wt.% Nano-SiO2 (NS), nano-TiO2 (NT), carbon nanotubes (CNTs), carbon nanofibers (CNFs) and carbon microfibers (CFs) are fabricated and tested. The enhancing effects of different fillers on the compressive strength and electrical resistivity of composites are compared, and the underlying modification mechanisms of fillers to composites are investigated by analyzing the difference in the morphology of fillers and rheology of composites. The compressive strength of composites containing 0.1% NS, 0.5% NT, 0.1% CNTs and 0.5% CFs by weight of cement presents approximately 12.5%, 20.8%, 16.8% and 21.4% higher than that of control sample, respectively. It is revealed that CFs also have improving effect on the compressive strength of composites besides flexural strength. When the composites with nano-fillers cannot be processed to ideal state, the reinforcing effect of nano-fillers is no better but even worse than that of micro-fillers. Composites with CNTs, CNFs and CFs possess good electrical conductivity. Composites with CNFs and CFs have a percolation threshold of electrical resistivity below 0.5%, while the percolation threshold of electrical resistivity of composites with CNTs is about 1%. Although CNFs do not have significant effect on compressive strength of composites, they have the best improvement to electrical resistivity.

12

Geoelectric method applied in correlation between physical characteristics and electrical properties of the soil

Filho A. M. S., Silva C. L. B., Oliveira M. A. A., Pires T. G., Alves A. J., Calixto W. P., Narciso M. G.

Transactions on Environment and Electrical Engineering

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2017

|

Vol. 2, No. 2

37--44

EN

This paper presents the study of the relationship between electrical properties and physical characteristics of the soil. Measures of apparent electrical resistivity of the soil were made for different types of soil, varying moisture content gradually while maintaining a constant compaction, and then varying the compaction and relating it to a constant humidity. Development of a correlation surface is proposed in order to identify granulometry of the soil from moisture and compaction measurements. For the study of spatial variability, two areas were chosen to allow the change of moisture content and compaction in order to verify the measurement capacity of apparent electrical resistivity of the soil as methodology to identify change in soil dynamics. Results obtained show correlations among apparent electrical resistivity of the soil, moisture, soil compaction and clay content.

13

Enhanced thermal conductivity of graphene nanoplatelets epoxy composites

Jarosinski L., Rybak A., Gaska K., Kmita G., Porebska R., Kapusta C.

Materials Science Poland

|

2017

|

Vol. 35, No. 2

382--389

EN

Efficient heat dissipation from modern electronic devices is a key issue for their proper performance. An important role in the assembly of electronic devices is played by polymers, due to their simple application and easiness of processing. The thermal conductivity of pure polymers is relatively low and addition of thermally conductive particles into polymer matrix is the method to enhance the overall thermal conductivity of the composite. The aim of the presented work is to examine a possibility of increasing the thermal conductivity of the filled epoxy resin systems, applicable for electrical insulation, by the use of composites filled with graphene nanoplatelets. It is remarkable that the addition of only 4 wt.% of graphene could lead to 132 % increase in thermal conductivity. In this study, several new aspects of graphene composites such as sedimentation effects or temperature dependence of thermal conductivity have been presented. The thermal conductivity results were also compared with the newest model. The obtained results show potential for application of the graphene nanocomposites for electrical insulation with enhanced thermal conductivity. This paper also presents and discusses the unique temperature dependencies of thermal conductivity in a wide temperature range, significant for full understanding thermal transport mechanisms.

14

Multifunctionality of cement based composite with electrostatic self-assembled CNT/NCB composite filler

Zhang L., Han B., Ouyang J., Yu X., Sun S., Ou J.

Archives of Civil and Mechanical Engineering

|

2017

|

Vol. 17, no. 2

354--364

EN

In this paper, electrostatic self-assembled carbon nanotube (CNT)/nanocarbon black (NCB) composite is employed as filler for developing multifunctional cement-based composites. The performances of the composites with different content of filler are investigated. The electrochemical impedance spectroscopy and equivalent circuit are used to explore the conductive and mechanical mechanisms of the composites. Experimental results indicate that the compressive strength and elasticity modulus of the composites sharply decrease when the filler content exceeds 0.77 vol.%. The percolation threshold zone of the electrical conductivity of the composites ranges from 0.39 vol.% to 1.52 vol.%. The piezoresistive properties of the composites with 2.40 vol.% filler are stable and sensitive, and the maximum fractional change of electrical resistivity is 25.4% when the stress amplitude is 10 MPa. The composites feature sensitive and linear thermal resistance effect when the filler content is 0.77 vol.%. Electromagnetic shielding effectiveness of the composites with 2.40 vol.% filler at 18 GHz is 5.0 dB, which is 2.2 times of that of the control samples. The composites exhibit high absorbing electromagnetic wave performances in the frequency range of 2–18 GHz, and the minimum reflectivity reaches −23.08 dB with 0.77 vol.% filler.

15

Application of electrical resistivity imaging (ERI) for the assessment of peat properties: a case study of the Całowanie Fen, Central Poland

Kowalczyk S., Żukowska K. A., Mendecki M. J., Łukasiak D.

Acta Geophysica

|

2017

|

Vol. 65, no. 1

223--235

EN

Complex studies were carried out to recognize the fen structure and peat properties in the Całowanie Fen area, belonging to the Natura 2000 network. The studies were conducted in two study areas that differ significantly in terms of peat thickness. Electrical resistivity imaging (ERI) was used to identify the properties of the peat and its substrate, such as thickness and electrical resistivity. Comparison of the field studies with the laboratory tests has shown that the ash content rises electrical resistivity in peat. In addition, the study has shown that the application of non-invasive geophysical methods in protected areas is justified. The fen, as a medium containing mostly water, was a proper test area for the ERI measurements.

16

Przykłady zastosowania pomiarów oporności elektrycznej w geotechnice środowiskowej

Lech M., Bajda M., Markowska-Lech K., Skutnik Z.

Zeszyty Naukowe Instytutu Gospodarki Surowcami Mineralnymi i Energią PAN

|

2016

|

nr 93

83--94

PL

Do rozpoznania warunków geotechnicznych podłoża budowli i do oceny oddziaływania na środowisko projektowanych budowli rutynowe metody badań mogą być niewystarczające lub wręcz nieodpowiednie. Bardzo pomocne mogą być metody geofizyczne, które zweryfikowane innymi metodami badawczymi znajdują w ostatnich latach szerokie zastosowanie w praktyce inżynierskiej, zarówno w geotechnice, jak i w badaniach środowiskowych. Do zalet metod geofizycznych zaliczyć można nieniszczący i nieinwazyjny charakter, niskie koszty i szybkie uzyskanie wyników, możliwość ich stosowania w różnorodnych materiałach, w tym w gruntach, skałach litych, materiałach odpadowych i utworach antropogenicznych. W artykule przedstawione zostaną wyniki badań przeprowadzonych metodą tomografii elektrooporowej ERT oraz badania sondą RCPT, która stanowi połączenie w jednym urządzeniu pomiarowym sondy statycznej CPTU powszechnie stosowanej w badaniach geotechnicznych z modułem do pomiaru oporności elektrycznej ośrodka gruntowego. Zaprezentowane w artykule wyniki pomiarów elektrooporowych wykorzystano do oceny stanu technicznego obiektów hydrotechnicznych, rozpoznania przebiegu stropu iłów w podłożu budowli, rozpoznania głębokości i budowy podłoża oraz oceny zanieczyszczenia gruntów w sąsiedztwie składowisk odpadów. Ponadto, w artykule przestawiono wyniki badań RCPT w celu szczegółowego rozpoznania budowy geologicznej podłoża oraz do oszacowania porowatości iłów plioceńskich z terenu Warszawy. Z zaprezentowanych w pracy wyników można wywnioskować, że badania te mogą być użyteczne do oceny jakościowej budowli inżynierskich i rozpoznania budowy ich podłoża. Ocena ilościowa np. porowatości gruntów wymaga natomiast znajomości oporności elektrycznej wody gruntowej a zależność przedstawiona w artykule ma zastosowanie lokalne ze względu na różnorodność czynników wpływających na otrzymywane wyniki.

EN

Standard test methods may not be suitable or sufficient to determine the geotechnical conditions of the structure’s subbase and the effects of the designed structures on the environment. Geophysical test methods, validated with other methods, may prove useful and have, in the recent years, found many new applications in engineering practice, both in geotechnical engineering and environmental surveys. The advantages of the geophysical methods include a non-destructive and non-invasive nature of the test, low costs and quick results, as well as compatibility with different materials, including soils, solid rocks, wastes and anthropogenic formations. The article presents the results of electrical resistivity tomography (ERT) and resistivity cone penetration test (RCPT), which is a combination of a static CPTU probe, commonly used in geotechnical surveys with a module for soil resistivity tests. The results of electric resistivity tests were used to rate the condition of hydro-engineering structures, determine the profile of the upper surface of clay deposits in the subbase, investigate the subbase and ground contamination near a landfill. The article also presents the RCPT results for a detailed determination of the geological structure of the subbase and the porosity of the Pliocene clay deposits in the Warsaw area. The results show that the tests can be used in a qualitative analysis of contamination of the ground and water subbase, condition rating of the hydro-engineering structures and investigation of the structure’s subbase. The electrical resistivity tests can also be used in a quantitative analysis, e.g. to determine the soil porosity, however they require a known value for the electrical resistivity of water and the relationships are limited to local use due to the variety of factors affecting the results.

17

Młody beton

Kohutek Z. B.

Przegląd Budowlany

|

2016

|

R. 87, nr 11

32--33

PL

Beton, niedługo po zabudowaniu w wielkoprzestrzenny fundament, masywny przyczółek itp., jest narażony na samouszkodzenie (głównie – rozległe spękania), spowodowane ekspansją ciepła hydratacji cementu. Zapobiec temu można poprzez selekcję i odpowiednią proporcję składników w zestawieniu receptury, a także – prowadząc specjalną pielęgnację betonu. W artykule porównano pogląd na problematykę „młodego betonu” – obecny i sprzed niespełna 40 lat.

EN

Concrete, shortly after being embedded in a spatially large foundation, massive abutments etc., is exposed to self-mutilation (mainly – spatially expansive cracks) caused by the expansion of heat created during the cement hydration. The above phenomenon can be avoided by selecting proper composition and proportions in the concrete mix, and through implementation of special care for the concrete. The article compares the “young concrete” problem area, taking into account the current state of research and the views present around 40 years ago.

18

Evaluation of the Mechanical Properties of Gray Cast Iron Using Electrical Resistivity Measurement

Bieroński M., Krasa O., Koza M., Książek D., Kuś R.

Archives of Foundry Engineering

|

2016

|

Vol. 16, iss. 4

29--32

EN

In this paper an attempt to determine the relationship between the electrical resistivity and the tensile strength and hardness of cast iron of carbon equivalent in the range from 3.93% to 4.48%. Tests were performed on the gray cast iron for 12 different melts with different chemical composition. From one melt poured 6 samples. Based on the study of mechanical and electro-resistive determined variation characteristics of tensile strength, hardness and resistivity as a function of the carbon equivalent. Then, regression equations were developed as power functions describing the relationship between the resistivity of castings and their tensile strength and hardness. It was found a high level of regression equations to measuring points, particularly with regard to the relationship Rm=f(ρ). The obtained preliminary results indicate the possibility of application of the method of the resistance to rapid diagnostic casts on the production line, when we are dealing with repeatable production, in this case non variable geometry of the product for which it has been determinated before a regression equation.

19

Rezystywność skrośna kompozytów epoksydowych ze stopami niskotopliwymi

Wierzbicki Ł., Stabik J.

Przetwórstwo Tworzyw

|

2015

|

T. 21, Nr 1 (163)

50--53

PL

W pracy przedstawiono wyniki pomiarów rezystancji skrośnej, kompozytów o osnowie epoksydowej napełnianych stopami niskotopliwymi. W badaniach wykorzystano stop Lipowitz’a i stop Wood’a oraz żywicę epoksydową (Epidian 6) sieciowaną tri-etyleno-tetra-aminą (utwardzacz Z1). Wykonane kompozyty zawierały odpowiednio 20, 40, 60 i 80 % wagowo wymienionych stopów. Ideą przedstawionych w pracy badań, jest sprawdzenie możliwości wykorzystania ciekłego napełniacza metalicznego do modyfikacji właściwości elektrycznych materiałów polimerowych. Uzyskane wyniki badań eksperymentalnych potwierdzają taką możliwość.

EN

The paper presents the results of measurements of volume resistivity of epoxy matrix composites filled low melting point alloys. In the research, Lipowitz and Wood’s alloys were used and an epoxy resin (Epidian 6) cured with tri-ethylene-tetra amine (Z1 hardener). Composites were made with 20, 40, 60 and 80% by weight contents of the alloy. The idea of the presented research was to check the possibility of using molten metal fillers to modify the electric properties of polymeric materials. The research results confirm such possibilities.

20

Ocena stanu technicznego wałów przeciwpowodziowych z wykorzystaniem metod geofizycznych i modelowania numerycznego

Popielski P., Chadaj M., Krysiak M., Smoliński B., Kowalczyk S., Mieszkowski R.

Prace Naukowe Politechniki Warszawskiej. Inżynieria Środowiska

|

2015

|

z. 70

33--55

PL

W pracy przeanalizowano możliwość wykorzystania nowoczesnych metod geofizycznych W ocenie stanu technicznego wałów przeciwpowodziowych. Omówiono pokrótce podstawy teoretyczne pomiarów georadarowych, metody elektrooporowej oraz badań sejsmicznych. Zaprezentowano i przeanalizowano otrzymane wyniki pomiarów. Na podstawie zgromadzonych danych przeprowadzono obliczenia numeryczne rozpatrywanych przekrojów obwałowań w oprogramowaniu Z_Soil.PC, pod kątem zjawisk filtracyjnych i stateczności konstrukcji. We wnioskach końcowych podsumowano wady i zalety poszczególnych metod badawczych. Przedstawiono istniejące ograniczenia i możliwości zastosowania w praktyce.

EN

The paper gives an example of using modern geophysical methods to evaluate the technical condition of levees. The theoretical bases of GPR measurements, electrical resistivity and seismic methods are briefly discussed. Test results for two embankments are presented. Based on the collected data, numerical calculations of the analyzed embankment sections were performed with the Z_SoiI.PC programme. The phenomena of filtration conditions and constructiori stability were examined. In the conclusions section, advantages and disadvantages of each method are given, along with existing limitations and possibilities of practical applicability.