Molten Marks Research Articles

조직 분석(ASTM E1382)에 의한 용융흔 정량적 판별 연구

The molten marks of electrical wiring found at the fire site can be helpful in inferring the cause of the fire and the ignition point, and it is a very important piece of evidence. However, in the fire department, there are few cases of quantitative analysis and study on the texture of molten marks. In this study, based on the ASTM E1382 standard, using an analysis program called iSolution DT, the image taken with an electron microscope is analyzed and quantitatively determined. In a energized state, the electric wiring was short-circuited at 25°C and 600°C to form molten marks. The primary melt scar shorted at 25°C showed a small columnar structure major axis ratio (GAR), and the secondary melt scar shorted at 600°C showed a large major axis ratio (GAR). As a result, it will be very helpful in quantitatively classifying primary and secondary melt traces using isolution DT.

Microstructural Examination of Molten Marks on Copper Wire for Fire Investigation

Fire investigators have attempted to study fire behaviors through microstructural examination of molten marks on copper wire. However, there have not been many studies on the metallurgical examination of real-world cases. This research examined the surface morphology and microstructure in the longitudinal section of molten marks on copper wire from various fire scenes to explain how they formed and identify the surrounding materials. The results show that the foreign elements discovered via EDS on the surface of molten marks vary depending on their environment. Molten mark microstructures differed even if they were collected from the same fire scene; a distinct microstructure implies different molten mark formations. Moreover, the presence of residual elements in the microstructure indicates the existence of surrounding materials during formation in a fire. Therefore, microstructural diversity and the presence of residual elements may guide fire investigators in explaining the formation of molten marks and the fire environment for fire investigation.

Analysis of Visual Characteristics of Short-circuited Arc Sites

Identifying the cause of fire at a fire site is an important fire prevention measure to prevent recurrence. In particular, information about molten marks of the copper wire is essential to check whether electric power is being supplied at the fire site. This study aims to analyse the visual characteristics of arc sites formed by a short circuit to identify the molten marks at the fire site. When a short circuit occurs, electromagnetic force is generated by the short circuit current, and the arc repulsion force is generated by the contact arc. In this study, the effects of the forces, which act on the short-circuited melted area, on the formation of copper molten marks were investigated. Copper molten marks formed by a short circuit were experimentally fabricated, and the visual characteristics based on the force that was applied to the melted area were identified and classified based on features. The results showed that the melted area was affected by both the arc repulsion and electromagnetic forces, resulting in the visual differences between the short-circuited arc sites and flame-melted ones, which are affected by gravity and molecular force. These results provide a theoretical basis for discriminating between arc sites formed by a short circuit and flame-melted marks at the fire site. The validity of this study was verified via a comparative analysis using shape and cross-sectional microstructure of molten marks collected at the fire site.

Discrimination of Copper Molten Marks through a Fire Reproduction Experiment Using Microstructure Features.

The copper molten marks at a fire site provide important clues for determining the causes of fire. Four factors have been presented to quantitatively discriminate copper molten marks, namely the fraction of (001) component perpendicular to the demarcation line, the grain aspect ratio, the fraction of Σ3 boundaries, and the fraction of maximum grain size. However, only laboratory-level results of these parameters have been presented, and their applicability in actual fires is yet to be verified. In this study, a fire reproduction experimental system was configured to generate molten marks similar to those in actual fire sites. The molten marks were measured by electron backscatter diffraction and applied to the four discriminant factors. The results obtained similar characteristics to those of the laboratory unit, confirming the applicability of the four discriminant factors. Discriminant equations and processes that can distinguish the primary and secondary arc beads were derived using the molten marks generated in the laboratory and reproduction experiments. Furthermore, a probabilistic discrimination method and classification model developed by machine learning were proposed. Therefore, the use of the discriminants in actual fires can improve the reliability of the statistics and prevent the recurrence of similar fires.

Potential Method to Distinguish Copper Molten Marks Using Boundary and Grain Characteristics.

The microstructure of molten marks changes according to ambient temperatures, when a short circuit occurs. Investigation of microstructural changes is important for understanding the properties of copper and examining the cause of a fire. In this study, the boundary characteristics and grain-size distribution of molten marks—primary-arc beads (PABs), which short-circuited at room temperature (25 °C), and secondary-arc beads (SABs), which short-circuited at high temperatures (600 °C, 900 °C)—were compared using electron backscatter diffraction. The distribution of Σ3 boundaries was compared, and it was found that SABs have a higher fraction of Σ3 boundaries than PABs. Moreover, it was confirmed that the ratio of maximum grain size (area) to the total area of the molten mark in SABs is larger than that in PABs. Thus, reliable discriminant factors were suggested, such as the fraction of Σ3 boundaries and normalized maximum grain size, which can distinguish PABs and SABs. The four discriminant factors, such as the (001)//LD, GAR, fraction of Σ3 boundaries, and fraction of maximum grain size to the total molten-mark area, were verified using the machine learning of t-SNE and Pearson correlation analyses.

전기화재 원인분석을 위한 실험실 데이터를 활용한 1차, 2차 단락흔 및 열흔 판별용 CNN 알고리즘 설계

In this paper, a new CNN algorithm is proposed to determine the direct cause of electric fires. We create 10,000-15,000 three types of data that can occur at a fire scene in our laboratory, and then train and verify it through the proposed CNN algorithm. As a result of the experiment and analysis, the classification accuracy of the primary and secondary arc beads was 86.2%, the accuracy of arc beads and molten marks was 93.6%. And also, the classification accuracy of the primary and secondary arc beads and molten marks was 92.4%. The results of this study are meaningful in that fire forensics can provide accurate identification results in a shorter time through artificial intelligence algorithms compared to the existing methods of identification through visual classification and physicochemical material analysis methods. In particular, the classification between primary and secondary arc beads is known to be a very difficult problem. However, the results of this study provided more than 86% classification ability.

Microstructural Study of Arc Beads in Aluminum Alloy Wires with an Overcurrent Fault.

To clarify the understanding and analysis of arc molten marks in electrical faults of aluminum alloy wires, this paper simulates overcurrent faults of aluminum alloy wires at currents of 128 A–224 A and uses thermogravimetry-differential scanning calorimetry (TG-DSC), optical microscope (OM), scanning electron microscope (SEM) and X-ray energy spectroscopy (EDS) to characterize the effects of current on the microstructure of arc beads. The results show that there are small and large amounts of Al-Si and Al-Fe binary phases in the metallographic structure of the aluminum alloy wires at the rated current, the grains are fine, and there are no significant grain boundaries. After an overcurrent fault occurs in the wires, a high-temperature arc causes the second phase in the aluminum alloy to disappear, a cellular dendritic metallographic structure appears, the grain boundaries become more well-defined, and composition segregation occurs at the grain boundaries. Using Image-Pro-Plus software to quantify the grain characteristics, the average grain size is found to gradually decrease as the current increases. In addition, by comparing and analyzing the characteristics of arc beads in aluminum wires and aluminum alloy wires under the same conditions, alloying elements are found to have a refining effect on the grain boundaries, and there are coarse precipitates at the grain boundaries in the aluminum wire arc beads.

New Approach to Distinguish Copper Molten Marks Based on Quantitative Microstructure Analysis Using Electron Backscatter Diffraction

Molten marks identified at a fire site can aid in determining the cause of a fire. Quantitative analysis of such molten marks has not yet been reported, despite several identification methods for molten marks being proposed based on optical micrographs. Herein, we propose a new methodology to establish the quantitative microstructure parameters of the molten marks using electron backscatter diffraction (EBSD). The globules were generated by heating the copper conductor to 1100°C in a non-energized state. Then, the arc beads were prepared by shorting the copper wire at 25°C and 900°C in an energized state. The globules did not show evident demarcation lines and indicated that the microstructure consisted of globular or dendritic grains; this demonstrated that their characteristics were distinctly different from those of arc beads. However, the primary arc beads (PABs) shorted at 25°C exhibited a strong (001) texture perpendicular to the demarcation line and comprised large fractions of columnar grains with a small grain aspect ratio (GAR). The microstructure of secondary arc beads (SABs) shorted at 900°C presented a mixture of elongated and equiaxed grains with a large GAR and no specific development of texture. The GAR and (001) fraction perpendicular to the demarcation line could be discriminant parameters of PABs and SABs. Consequently, EBSD methods can be newly applied for the classification of globules, PABs, and SABs based on the quantitative microstructure information and orientation distribution.

분석화학을 통한 전선 용융흔의 분석기법 향상에 관한 연구

With the steady increase in electricity use, electric fires account for more than 20% of the total number of fires each year. Electrical fires are caused by electrical arcs or sparks inside the cover of wires, but they are also caused by external flames melting the cover of wires into contact with each other. In electric fires, melting of wires is usually found, which is commonly referred to as short circuit. The molten marks are divided into the primary one that occurs inside the wire and causes the fire directly, the secondary one caused by external fire, and the heat melt found in the unenergized state. Scientific criteria for the distinction between primary and secondary molten mark is presented by using qualitative and quantitative analysis, through analytical chemistry such as SEM and EDS, XRD and EA.

Study on Discrimination between Primary and Secondary Molten Marks by Analyzing the Crystal Structure of the Carbon in Carbonized Residue

Study on Discrimination between Primary and Secondary Molten Marks by Analyzing the Crystal Structure of the Carbon in Carbonized Residue

Study on Discrimination between Primary and Secondary Molten Marks by DAS

Study on Discrimination between Primary and Secondary Molten Marks by DAS

Study on Discrimination between Primary and Secondary Molten Marks at Attachment Plugs and Receptacles

Study on Discrimination between Primary and Secondary Molten Marks at Attachment Plugs and Receptacles

옥외용 LED 조명의 전기화재 위험성 평가기법에 관한 연구

In this paper, we experimented and analyzed about electric fire risk assessment methods of LED lightings for outdoor. LED lighting is composed of AC power lines, AC/DC converter, DC power lines and LED lamps. There are some risk factors of electric fire in LED lighting such as short circuit between power lines or power line and ground, dielectric breakdown, leakage current, abnormal voltage inflow, poor contacts(connections), etc. As a result of this study, insulation coverings of wire was ignited due to dielectric breakdown between power lines and molten marks were formed in copper conductor. LED lighting was blown out while short circuit, beside that, electrical disorder did not occur. When abnormal voltage was inflowed, electronic components such as varistor, condenser were damaged. Partial heating was produced and insulation was melted and carbonized by arc and heating while poor contacts were happened. We expect that the results of this study would be helpful for electrical safety of LED lightings for outdoor.

Microscopic Investigation of a Copper Molten Mark by Optical Microscopy (OM) and Atomic Force Microscopy (AFM)

A wide variety of physical and chemical detecting methods have been proposed for discriminating between and electric arc bead that caused a fire, versus one that was caused by the fire itself. The simplest proposed method claims that examination of the molten marks in a bead under a microscope will suffice to make the distinction. Generally, copper molten marks of the bead are examined by using optical (OM) and scanning electron microscopy (SEM). In this paper, OM and AFM were employed to investigate a molten mark formed in laboratory. AFM observation reveals that AFM could be an auxiliary method to investigate the copper molten mark formed in the fire in order to confirm the reasons of the fire.

Structural Engineering and Fire Dynamics: Advances at the Interface

At most fire scenes, electric short circuit (ESC) arc beads that may be provide useful information on the cause and development of the fire are found. Various physical or chemical methods have been proposed for identifying these electric short circuit beads to be either the cause of a fire (primary arc beads) or one caused by the flames of the fire (secondary arc beads). Little was studied, however, on their identification using the different distribution of O and C in the molten marks. In this study, the concentration of O and C in the surface region and subsurface was quantified by X-ray photoelectron spectroscopy (XPS). Corresponding to the sputtering depth, the molten product on a primary ESC arc bead may be distinguished as three portions: surface layer with drastic decrease of carbon content; intermediate layer with gentle change of oxygen content, gradually diminished carbon peak, and consisted of Cu2O; transition layer without Cu2O and with rapid decrease of oxygen content. While the molten product on a secondary ESC are bead may be distinguished as two portions: surface layer with carbon content decreasing quickly; subsurface layer without Cu2O and with carbon, oxygen content decreasing gradually. Thus, it can be seen that there was an obvious interface between the layered surface product and the substrate for the first type of bead, while as to the second type of bead there was no interface. As a result, the quantitative results can be used to identify these electric short circuit beads to be either the cause of a fire (a primary ESC) or one caused by the flames of the fire (a secondary ESC), as complementary technique for judgments of fire cause.

Surface Analysis of Electrical Arc Residues in Fire Investigation

At most fire scenes, electric short circuit (ESC) arc beads that may be provide useful information on the cause and development of the fire are found. Various physical or chemical methods have been proposed for identifying these electric short circuit beads to be either the cause of a fire (primary arc beads) or one caused by the flames of the fire (secondary arc beads). Little was studied, however, on their identification using the cupreous oxides formed in the molten marks. In this study, the concentration of metallic Cu and Cu2O in the surface region and subsurface was quantified by X-ray photoelectron spectroscopy (XPS). As a result, it can be examined to distinguish the primary and secondary arc beads by comparing the distribution of the substances of Cu and Cu2O.

A Study on Discrimination between Primary and Secondary Molten Marks on Blades of Electric Plugs by DAS

Molten marks on electric plugs or wall sockets found in fire sites often are great help, when we investigate the cause of the fires. It is known that the distance between each second arm of crystals called DAS (Dendrite Arm Spacing), that we see on the cross section of those molten marks, change depending on the atmospheric temperature at the time of a short circuit. Also it is already known that DAS between primary and secondary marks are clearly different. We created reference data to make use of DAS for practical investigation. In this study, we showed the relation between atmospheric temperature and DAS by making samples of molten marks at various temperatures. And we examined if this method was able to help assume the surrounding temperature at the time when the molten mark was produced. As a result, we found that the method has some possibility. We developed a new method for assuming the atmospheric temperature at the time of the short circuit using the reference data.

Study on discrimination between primary and secondary molten marks using carbonized residue

In most places where a fire started, electric molten marks that may be the cause of the fire are found. Various methods have been studied for identifying these electric molten marks to be either the cause of a fire (a primary molten mark (PMM)) or one caused by the flames of the fire (a secondary molten mark (SMM)). Little was studied, however, on their identification using the carbonized residue remaining in the molten marks. In this study, therefore, it was examined whether it was possible to discriminate between the PMMs and SMMs by analyzing the crystal structure of the carbon in the carbonized residue, which came from PVC insulation, remaining in the primary and the SMMs. As a result, it has been found that PMMs contain both graphitized carbon and amorphous carbon, whereas SMMs only contain amorphous carbon.

Discrimination between Primary and Secondary Molten Marks on Electric Wires by DAS

Discrimination between Primary and Secondary Molten Marks on Electric Wires by DAS