scholarly journals TEMPERATURE ERROR WHEN DETERMINING THE TIME PARAMETER OF A FIRE DETECTOR WITH A THERMORESISTIVE SENSITIVE ELEMENT

2021 ◽  
Vol 6 (166) ◽  
pp. 151-155
Author(s):  
Ya. Kozak
Keyword(s):  
Electric Current ◽  
Current Pulse ◽  
Mathematical Description ◽  
Sensitive Element ◽  
A Priori ◽  
Time Parameter ◽  
Temperature Error ◽  
Electric Current Pulse ◽  
Sensing Element ◽  
Fire Detector

For fire detectors with a thermoresistive sensing element, a mathematical description of the reaction to the thermal action of an electric current pulse flowing through such a sensing element and having the shape of a right triangle is obtained. The mathematical description is constructed using the Laplace integral transformation and is shown to be a superposition of two Heaviside functions. The parameters of these functions are determined by the transmission coefficient and time constant of the thermoresistive sensitive element of the fire detector and the amplitude and duration of the electric current pulse. It is shown that the ratio of the output signals of the thermoresistive sensitive element of the fire detector at two a priori given moments of time can be used to determine the time parameter of the fire detector. The values ​​of a priori set moments of time, in which the temperature of the thermoresistive sensitive element of the fire detector is determined, are selected under the condition of simplicity of technical implementation. If there is a change in ambient temperature, it leads to a temperature error as a function of the time parameter of the fire detector. For such an error, a mathematical description is obtained in the general case, as well as for the case when the thermal influence on the thermoresistive sensitive element of the fire detector is due to the flow of an electric current pulse in the form of a right triangle. It is shown that the value of the temperature error has a minimum at the values ​​of the ratio of the output signals of the thermoresistive sensitive element of the fire detector at two a priori time points belonging to the range The value of this error does not exceed 4.9% with variations in ambient temperature, the value of which does not exceed 2.0%.

scholarly journals PULSE METHOD FOR DETERMINATION OF TIME PARAMETERS THERMAL FIRE DETECTOR

2021 ◽  
Vol 4 (164) ◽  
pp. 166-170
Author(s):  
Ya. Kozak
Keyword(s):  
Electric Current ◽  
Time Constant ◽  
Sensitive Element ◽  
Integral Transformation ◽  
Pulse Method ◽  
Auxiliary Parameter ◽  
Sensing Element ◽  
Fire Detector ◽  
Time Parameters ◽  
Analytical Expressions

For thermal fire detectors with a thermoresistive sensitive element, the method of determining its time parameters is justified. The time parameters of operation and the time constant of the thermal fire detector are considered as time parameters. The method is based on the use of the Joule-Lenz effect, for the implementation of which single pulses of electric current are passed through the thermoresistive sensitive element of the fire detector. Pulses having the shape of a quarter sinusoid or a quarter cosinusoid are used as such test signals. Using the Laplace integral transformation, analytical expressions are obtained, which represent the formalization of the reaction of the thermoresistive sensitive element of the fire detector to the corresponding test signals. These analytical expressions are used to obtain the functional dependences of the fire detector time constants on the pulse duration of the electric current and the auxiliary parameter. The auxiliary parameter is the ratio of the values ​​of the output signal of the thermal fire detector at two fixed points in time. This choice of auxiliary parameter allows to ensure invariance with respect to the transfer coefficient of the thermal fire detector with a thermoresistive sensing element. The fixed moments of time are chosen to be equal to half and three quarters of the duration of the pulses of electric current flowing through the thermoresistive sensitive element of the fire detector. The time of operation of the thermal fire detector is determined in the form of two additive components, one of which is a time constant of the fire detector, and the other is determined by the values ​​of normalized parameters in accordance with existing regulations. A sequence of procedures is given, which together represent a method of determining the time parameters of thermal fire detectors of this type.

scholarly journals Substantiating the pulse method for determining the time parameter of fire detectors with a thermoresistive sensing element

2021 ◽  
Vol 6 (5 (114)) ◽  
Author(s):  
Yuriy Abramov ◽  
Oleksii Basmanov ◽  
Yaroslav Kozak
Keyword(s):  
Mathematical Model ◽  
Transfer Function ◽  
Electric Current ◽  
Integral Transformation ◽  
A Priori ◽  
Single Pulse ◽  
Pulse Method ◽  
Time Parameter ◽  
Sensing Element ◽  
Equations Of Mathematical Physics

This paper substantiates the pulse method for determining the time parameter for fire detectors with a thermoresistive sensing element ‒ the time constant. The method is based on using the Joule-Lenz effect, which manifests itself when an electric current pulse passes through the thermoresistive sensing element of fire detectors. Thermal processes in such a sensing element are described by a mathematical model that belongs to the class of equations of mathematical physics. The solution to the differential equation of this class was derived using the Hankel integral transformation and is represented as a series relative to the Bessel functions. The resulting solution is used to construct a mathematical model of a thermoresistive sensing element in the form of a transfer function, which takes the form of the transfer function of the inertial link. To trigger the thermoresistive sensing element of fire detectors, a single pulse of electric current in the shape of a rectangular triangle is used. The integral Laplace transformation was applied to mathematically describe the response of a thermoresistive sensing element to the thermal effect of such a test influence. To obtain information about the time parameter of fire detectors with a thermoresistive sensing element, the ratio of its output signals is used, which are measured in the a priori defined moments. A two-parametric expression was built to determine the time parameter of fire detectors; a verbal interpretation of the pulse method to determine it was provided. The implementation of this method ensures the invariance of the time parameter of fire detectors with a thermoresistive sensing element relative to the amplitude of a single pulse of an electric current, as well as relative to the parameter that is included in its transfer coefficient.

Refinement of inclusions in molten steel by electric current pulse

2015 ◽  
Vol 31 (13) ◽  
pp. 1555-1559 ◽  
Author(s):  
W. B. Dai ◽  
J. K. Yu ◽  
C. M. Du ◽  
L. Zhang ◽  
X. L. Wang
Keyword(s):  
Electric Current ◽  
Current Pulse ◽  
Molten Steel ◽  
Electric Current Pulse

Electric Current Pulse Welding of Titanium with 18-10 Stainless Steel

2009 ◽  
Vol 83-86 ◽  
pp. 1251-1253 ◽  
Author(s):  
E.G. Grigoryev ◽  
V.N. Bazanov
Keyword(s):  
Stainless Steel ◽  
Electric Current ◽  
Current Pulse ◽  
Contact Zone ◽  
Welded Joints ◽  
High Speed ◽  
Welded Joint ◽  
Electric Current Pulse ◽  
Pulse Effect ◽  
Different Thickness

The purpose of the work was to determine the capabilities of the pulse effect of electric current and pressure to produce welded joints of various component parts of different thickness from 18-10 stainless steel and titanium. Application of electric current pulses on the surfaces of contacting metallic conductors leads to considerable changes in the surface structure. Depending on the initial state of the surfaces and parameters of the pulse effect this can result in melting without formation of joints, formation of a strong welded joint with characteristics no worse than those of welded metals, and in destruction of the contact zone. A combination of a short electric pulse with simultaneous application of mechanical pressure in the weld zone causes high-speed deformation of the contact zone. The process of joint formation itself does not cause any appreciable diffusion during welding. The greatest energy emission and the maximal heating occur on the contacting surfaces being welded with the passage of an electric current pulse through the welding zone. Simultaneously with intensive heating, and due to applied pressure, high-speed deformation of materials takes place and a strong welded joint is formed. Optimal parameters for the welding of titanium and 18-10 stainless steel have been determined on the basis of the tests conducted. Investigations into the welding of titanium and 18-10 stainless steel have shown that application of a short electric current pulse and pressure produces stronger welded joints composed of both similar and different metals of considerably different thickness.

scholarly journals Effect of Electric Current Pulse on Microstructure and Corrosion Resistance of Hypereutectic High Chromium Cast Iron

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2220 ◽  
Author(s):  
Haiyang Lv ◽  
Rongfeng Zhou ◽  
Lu Li ◽  
Haitao Ni ◽  
Jiang Zhu ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Cast Iron ◽  
Electric Current ◽  
Current Pulse ◽  
Electric Current Pulse ◽  
High Chromium ◽  
High Chromium Cast Iron ◽  
Microcrack Propagation ◽  
Primary Carbides ◽  
Chromium Cast Iron

The effect of electric current pulse on the microstructure and corrosion resistance of hypereutectic high chromium cast iron was explored. The morphology of carbides in solidification microstructure was observed by an optical microscope and a scanning electron microscope and the composition was determined by an electron probe micro-analyzer. The microhardness of primary carbides and corrosion resistance of samples were also compared. Under the active of electric current pulse, the microstructure of hypereutectic high chromium cast iron was homogenized and its performance improved accordingly. On treatment by electric current, the morphology of primary carbides changed from thick long rods to hexagonal blocks or granular structures. The interlayer spacing of eutectic carbide decreased from ~26.3 μm to ~17.8 μm. Size statistics showed that the average diameter of primary carbide decreased from ~220 μm to ~60 μm. As a result, microhardness increased from 1412 HV to 1511 HV. No obvious microcrack propagation was found at the microindentation sites. The average length of microcracks decreased from ~20.7 μm to ~5.7 μm. Furthermore, corrosion resistance was remarkably enhanced. The average corrosion rate decreased from 2.65 mg/cm2·h to 1.74 mg/cm2·h after pulse current treatment.

scholarly journals Effect of High Density Electric Current Pulse on Solidification of Cu-37.4 wt.%Pb Monotectic Alloy Melt

2019 ◽  
Vol 26 (1) ◽  
pp. 34-40
Author(s):  
Teng MA ◽  
Guihong GENG ◽  
Xiaosi SUN ◽  
Xi HAO ◽  
Weixin HAO
Keyword(s):  
Wear Resistance ◽  
Electric Current ◽  
Current Pulse ◽  
Metal Cluster ◽  
High Density ◽  
Formation Mechanisms ◽  
Electric Current Pulse ◽  
Monotectic Alloy ◽  
Scanning Calorimetry ◽  
Cluster Theory

The effect of high-density electric current pulse (ECP) on the solidification of Cu-37.4 wt.%Pb monotectic alloy melt was investigated. The microstructure formation mechanisms of ECP were clarified according to liquid metal cluster theory. The results demonstrated that with ECP treatment, the microstructure of Cu-Pb monotectic alloy became finer, the distribution of Pb phase in the matrix was more even and the solute trapping was significantly apparent. Based on the metal liquid cluster theory under ECP, the solid solubility increase result might be due to the salvation clusters increase under the action of pulse current, leading to the binding force increase among solute atoms and solvent atoms. Simultaneously, the aforementioned results were verified through the Differential Scanning Calorimetry (DSC) curve analysis. The results of hardness test, anti-friction test and wear- resistance test show that the ECP can enhance the hardness, improve the properties of anti-friction and wear-resistance of the alloy.

Effect of electric current pulse type on springback, microstructure, texture, and mechanical properties during V-bending of AA2024 aluminum alloy

2020 ◽  
pp. 1-36
Author(s):  
Nafiseh Mohammadtabar ◽  
Mohammad Bakhshi-jooybari ◽  
Hamid Gorji ◽  
Roohollah Jamaati ◽  
Jerzy A. Szpunar
Keyword(s):  
Mechanical Properties ◽  
Aluminum Alloy ◽  
Electric Current ◽  
Current Pulse ◽  
Fiber Texture ◽  
Electric Current Pulse ◽  
Electric Pulses ◽  
Current Pulses ◽  
Electric Current Pulses ◽  
Pulse Type

Abstract The present work focused on the effect of the electric current pulse type on the springback, microstructure, texture, and mechanical properties during the V-bending process of AA2024 aluminum alloy. In order to investigate this effect, three different forming conditions including conventional V-bending and electrically assisted V-bending with square and sinusoidal pulses were considered. The results indicated that the amount of springback significantly decreased from 45.5° (for the sample formed via conventional V-bending) to 24° by applying the sinusoidal pulse. Microstructural observations revealed lower stored energy in the samples formed by electric current pulses which resulted in larger grain size compared to the samples formed without electric pulses. In addition, the result showed that the intensity of the (111)||BLD (bend line direction) fiber texture reduced after applying electric current pulses whereas it was very strong in the sample formed without electric pulses. It was suggested that the electric current pulses led to change the slip plane of the dislocations from {111} to {110} through cross slip. The applying electric current pulses decrease the ultimate tensile strength (UTS) from 471.1 MPa (for the conventional tensile test) to 448.0 and 426.7 MPa for the square and sinusoidal pulses, respectively. On the other hand, the electric pulses improved the formability of the AA2024 alloy owing to the activation of more slip systems, inhibition of dislocation pinning, the promotion of dislocation movement, and the acceleration of restoration mechanisms.

Improvement of pitting corrosion resistance of stainless steel by electric current pulse

2017 ◽  
Vol 33 (12) ◽  
pp. 1417-1420 ◽  
Author(s):  
D. B. Jia ◽  
W. B. Dai ◽  
G. P. Tang ◽  
C. Z. Xu ◽  
X. Z. Tian ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Corrosion Resistance ◽  
Electric Current ◽  
Current Pulse ◽  
Pitting Corrosion ◽  
Electric Current Pulse ◽  
Pitting Corrosion Resistance
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