Papers by Keyword: Electrical Resistance

Abstract: An unravelling porous asphalt concrete was developed by adding steel wool and heating it with induction energy. The purpose of this paper is to examine the effects of the steel wool distribution on the properties of this unravelling porous asphalt concrete. The mixture was mixed for 10 min, 12 min, 15 min or 20 min respectively, and then samples were prepared with a gyratory compactor. The steel wool distribution at different mixing time was compared with CT scanning analysis. The electrical resistance, indirect tensile strength and induction heating speed of samples with different mixing time were also studied. It was found that a better distribution of steel wool in porous asphalt concrete increased its indirect tensile strength, but decreased its electrical conductivity and induction heating speed. 15 min mixing is sufficient to disperse steel wool to a homogenous distribution.

Abstract: The purpose of this paper is to discuss the influence of mineral additives i.e. metakaolin, silica fume, rice ash and fly ash incorporating with nanocarbontubes mortar composites. The effects on compressive strength at 28 days were also discussed and presented. Cement content of 500 kg/m³, water/cement ratio of 0.6 and aggregate/cement ratio of 2.75 were adopted for the mix propotion. 1%, 3% and 5% of nanocarbontubes in mortar were combined with 15% of mineral additives. The results show that mixtures of nanocarbontubes with 15% of metakaolin produce better strength compared to normal mortar. Meanwhile with addition of fly ash and rice husk ash the strength were decreased. The electrical resistance for all mixes at 28 days were also discussed and presented. The higher percentages of nanocarbon with addition of all mineral additives resulted in lower electrical resistance properties

Abstract: The paper deals with the study of dominant frequencies of an Impact-Echo method response signal obtained from a reinforced concrete beam with a steel rod diameter of 8 mm. Tension pulse was produced in axis of the rod at one end and detected in axis at opposite end of rod. Dominant frequencies of the response signal will be the main criterions for the reinforced concrete rebar corrosion progress. The article presents the results of measurements obtained after 12 months controlled degradation in aqueous NaCl solution. The results were compared with measurements of electrical resistance of reinforcing steel by using the Thomson double bridge.

Abstract: The paper deals with the study of dominant frequencies of an Impact-Echo method response signal obtained from a reinforced concrete beam with a steel rod diameter of 8 mm. Tension pulse was produced in axis of the rod at one end and detected in axis at opposite end of rod. Dominant frequencies of the response signal will be the main criterions for the reinforced concrete rebar corrosion progress. The article presents the results of measurements obtained after 12 months controlled degradation in aqueous NaCl solution. The results were compared with measurements of electrical resistance of reinforcing steel by using the Thomson double bridge.

Abstract: Advanced fiber-reinforced polymer composites are known to possess outstanding specific strength and stiffness and their use in structural applications continues to expand. Most structural composites are susceptible to the formation of micro-scale damage in polymer matrix under adverse conditions which has significant implications on the durability and performance of fiber composites. Thus, it is imperative to detect the initiation and evolution of damage in composites long before their catastrophic failure. In this report, our recent research in sensing of micro-crack in matrix in situ and in real time for glass fiber composites was reviewed. Carbon nanotubes were dispersed into glass fiber composites by three roll mill technique. A resistance parameter was utilized to quantitatively characterize damage initiation and propagation. Damage mechanisms and development were investigated under tension, fatigue loadings. This research demonstrates the feasibility and benefits of electrical resistance measurements in the sensing of micro-scale damage for fiber composites using carbon nanotubes and offers the potential for in-service health monitoring of composite structures.

Abstract: The increase in the number of electronic and electric systems used in the automotive industry necessitates a high level of electric power. To respond to this high electric power demand, it will be necessary to increase the voltage of the batteries and the current and to use new power connectors. A connector provides a separable interface between two subsystems of an electronic system. The main function of the connector is to transmit a signal or distribute power. For power connectors, heating can lead to an increase in contact resistance and sometimes even to contact surface melting and thus to connector damage. In this study, vibration tests and heat evolution of a commercial power connector used in the automotive industry was undertaken. The connector includes two spring lamellas on each side and the pin is flat. The pin is introduced between the two lamella springs and is submitted to vibration tests. Using an experimental set-up, the mechanical insertion force, the temperature and the resistance evolution can be measured. To quantify these parameters at the contact zone, a numerical modeling, using the finite element software Ansys, is used to give the change of the insertion force during several insertion-extraction cycles and to solve the differential equations for heat transfer in a transitory mode.

Abstract: An important parameter in MEMS design is the electrical contact resistance. This depends on material conductibility, on the geometry of the contacting surfaces, on the applied load and on the current passing through the contact. This work aims to experimentally investigate the dependence between: electrical contact resistance and contact load force, contact resistance and contact area and contact perimeter for constant current through a microcontact.

Abstract: A sensing element made of conductive composite created by an entangled network of electrically conductive carbon nanotubes embedded in polyurethane was used for simultaneous measurements of the pressure between the shoe and floor as well as the extension of the leg at the knee joint during marching. The results recorded as sensor resistance change show reasonable reversibility of the basic sensor characteristics, which gives potential for practical applications.

Abstract: The influence of tensile load on electrical resistance and acoustic emission (AE) energy of carbon fabric/epoxy-matrix composites were investigated in this study. The experiment results showed that both electrical resistance and AE energy of carbon fabric/epoxy-matrix composites increased with the increase of tensile load. When tensile damage in composites was brought about, the growth rate of AE energy and electrical resistance increased significantly, and the growth rate of AE energy and electrical resistance can be used as the basis of monitoring tensile damage in composites. In addition, compared with AE technology, the electrical resistance measurement by monitoring tensile damage in composites was simpler, and the results were more reliable too.

Abstract: This paper studied the effect of carbon fiber dosage, concrete age, size of defect, and eater pressure on the electrical conductivity of carbon fiber reinforced concrete (CFRC). Insulating films were buried in the concrete to simulate inside cracking. The carbon fiber was added as the conductive material of the concrete. The electrical conductivity was measured with a two-electrode method with a DC power. The test results show that concrete age, defect area and the external water pressure are the main factors influencing the electrical conductivity of CFRC, while the number and location of defects have less effect.