Method for judging close contact with fire source based on slight thermal damage of chemical fiber
Through the combination of macro observation and scanning electron microscopy, the slight thermal damage traces of chemical fiber clothing fibers are identified, which solves the problem of difficult to identify the degree of fiber thermal damage in fire, and realizes effective identification of the suspect's close contact with fire sources, improving the The reliability of criminal investigation evidence.
Patent Information
- Application Number
- CN202311854678.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-29
- Publication Date
- 2025-01-07
- Estimated Expiration
- 2043-12-29
AI Technical Summary
In fires, it is difficult for the prior art to effectively identify whether the suspect is in close contact with the fire source, especially when the degree of fiber thermal damage is mild, and the traces of thermal damage that are difficult to distinguish with the naked eye can lead to difficulties in personal identification.
Using a combination of macro observation and scanning electron microscope (SEM), the chemical fiber clothing fabric is subjected to macro observation, gold spraying and SEM scanning, and the magnification is adjusted to observe abnormal conditions on the fiber surface, and determine whether there are slight thermal damage marks in the fiber, and then Determine whether the personnel are in close contact with the fire source.
A new method of personal identification and identification of fire personnel is provided, which can effectively identify whether the suspect is in close contact with the fire source, improve the investigative ability of criminal investigators in fire-related cases, and enhance the proving power of evidence.
Smart Images
Figure CN117805163B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a method for identifying slight thermal damage to clothing fibers, in particular to a method for identifying close contact of a person with a fire source based on slight thermal damage to chemical fibers, and belongs to the technical field of technical identification of physical evidence in fire-related cases. Background Art
[0002] In arson fires, although the nature of the fire can be confirmed, it is difficult to identify the suspect and whether the relevant person is present. Therefore, it is very convincing to use the thermal damage on human clothing to determine whether a person is in close contact with the fire source and present at the fire scene. For example, when using an accelerant to ignite the fire, it is very likely that thermal damage will be left on the fabric fibers of the suspect's cuffs and collar. In reality, the damage to the fabric fibers directly affected by the flame is already clearly visible (see J, KRAUβW. Damage caused to fibres by vapourcloud explosions[J]. Forensic science international, 2004, 141(2-3): 77-83. and LEUNG EH, HALLIDAY DX. "Flashburning"—Interpreting the presence of heat damage to a suspect's clothing and footwear in the investigation of fires[J]. Science&Justice, 2010, 50(4): 187-191). In the area outside the flame where heat is mainly transferred by thermal radiation, thermal damage will also be caused to the fabric fibers. The degree of damage is relatively minor and difficult to distinguish with the naked eye. This is a typical situation objectively existing in the fire scene. The traces formed are called slight thermal damage traces of chemical fibers.
[0003] In summary, it is necessary to create a method for determining slight thermal damage to chemical fiber fabrics to help criminal investigators identify suspects during fire-related case investigations. Summary of the invention
[0004] In view of the above-mentioned defects of the above-mentioned prior art, the present invention proposes a method for judging whether a person is in close contact with a fire source based on slight thermal damage to chemical fibers. The method first determines whether thermal damage may exist by macroscopic observation and hardness comparison, and finally uses a scanning electron microscope (SEM) observation method to inspect and identify traces of slight thermal damage to the fabric fibers at the microscopic level.
[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:
[0006] The method for judging whether a person is in close contact with a fire source based on slight thermal damage to chemical fibers comprises the following steps:
[0007] Step 1: Conduct macroscopic observation of chemical fiber clothing fabrics and extract parts that may have slight heat damage marks by analyzing the fire scene process;
[0008] Step 2: After the clothing fragment sample is sprayed with gold, its surface is observed through a scanning electron microscope (SEM);
[0009] Step 3: Adjust the magnification of the scanning electron microscope (SEM) to 500-1000, focus on the surface of the clothing fragment sample, and observe the surface morphology of the clothing fiber;
[0010] Step 4: Find the abnormality of the surface morphology along the fiber orientation of the fabric;
[0011] Step 5: For abnormal areas, adjust and increase the magnification of the scanning electron microscope (SEM) to observe the surface;
[0012] Step 6: Observe and record the slight traces of heat damage in abnormal areas on the surface of the fabric fiber to determine whether the person is in close contact with the fire source.
[0013] Furthermore, in the step one, the analysis method is: the personnel need to use the hand to hold the fire source to ignite the fire. In this process, because the fire starts quickly, a certain amount of heat loss occurs in some typical parts of the clothing along the direction of the flame spread. The typical parts include the cuffs that are closer to the ignition flame when using the hand to ignite the fire, the trouser legs and trouser corners that are in a lower position (when the low-position combustion aid flows and burns), and the fibers of the upper front part of the body during the rapid spread of the flame.
[0014] Furthermore, in step 4, the abnormal surface morphology includes melting, adhesion or damage.
[0015] Furthermore, in the step five, the magnification of the scanning electron microscope (SEM) is adjusted and increased to be greater than 1000 times to further analyze the trace characteristics of the details.
[0016] Furthermore, in step six, the specific method for judging whether the person is in close contact with the fire source is as follows: by scanning with a scanning electron microscope (SEM), if there is melt adhesion in the abnormal area on the surface of the fabric fiber, it is judged that the person is in close contact with the fire source; if the surface shape of the fabric fiber remains the same, it is judged that the person is not in close contact with the fire source.
[0017] Furthermore, in step six, the melt bonding is manifested as adhesion of more than 10 microns in length between different fibers.
[0018] The method proposed by the present invention for judging close contact of a person with a fire source based on slight thermal damage to chemical fibers has the following beneficial effects:
[0019] The present invention proposes a new method for personal identification and appraisal of personnel at a fire scene, which can be used to identify suspects and effectively identify whether relevant personnel were present at the scene during the occurrence and development of a fire. It has strong evidentiary power in determining whether a person has been in close contact with a fire source through slight thermal damage to chemical fibers in clothing, and is of great significance for inspection and appraisal, providing a new investigative technical means for criminal investigators in personal identification methods in fire-related cases. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Figure 1 This is a comparison chart of chemical fiber and pure cotton blended fabric before and after heat treatment;
[0021] Figure 2 This is a comparison chart of chemical fiber textiles before and after heat treatment;
[0022] Figure 3 This is the SEM comparison of polyester fabric before and after heat treatment;
[0023] Figure 4 This is a comparison of polyester-cotton fabric before and after heat treatment;
[0024] Figure 5 It is slight heat damage to polyester fiber. DETAILED DESCRIPTION
[0025] The following is combined with Figure 1-5 The present invention is further described in detail with specific implementations to facilitate a clear understanding of the present invention, but they do not constitute a limitation on the present invention.
[0026] Example 1
[0027] Figure 1 , 2 This is a comparison chart of chemical fiber fabrics or blended fabrics before and after radiation heat treatment, divided into black and white, and the leftmost is a normal fabric for comparison. It can be seen that the surface of normal chemical fiber fabrics is flat, without wrinkles, unevenness, adhesion and fusion. As the temperature rises, it can be found that the fabric gradually becomes uneven, curled and curled, and the wrinkles are obvious. At a temperature of about 250°C, fabrics with severe heat damage are found, and it can be seen that the fibers are obviously melted. From all the experimental samples, some fabrics have very obvious signs of heat damage, but there are still fabrics that are similar to the shape before heat treatment, and it is difficult to observe the signs of heat damage with the naked eye. Accordingly, this phenomenon shows that investigators sometimes find it difficult to judge whether the suspected fabric has been subjected to high temperature when the conditions are unknown, and the objects of this innovation are mainly concentrated on chemical fiber fabrics with heat treatment temperatures of 170°C-220°C, which may have slight signs of heat damage.
[0028] Figure 3 This is a comparison of polyester before and after radiation heat treatment. It can be seen that the surface of normal fibers is relatively flat, each fiber is distinct, and there is no adhesion or fusion. However, in fabrics with obvious heat damage, it can be seen that the fibers are melted, and there are signs of partial fusion between different fibers, and even more serious areas have been fused as a whole.
[0029] Figure 4 This is a comparison of chemical fiber blends before and after radiation heat treatment. It can be seen that the surface of normal polyester-cotton fibers is relatively flat, each fiber is distinct, and there is no adhesion or fusion between cotton and polyester fibers. For fabrics with obvious heat damage, due to the low melting point of chemical fibers, it can be seen that the fibers are melted, and for blended fabrics, chemical fibers will adhere to cotton fibers after melting and softening.
[0030] Figure 5 The morphology of chemical fiber after heat treatment between 170℃ and 220℃ observed under a scanning electron microscope is shown. It can be seen that the shape of the polyester fiber remains basically the same, but there is adhesion between different fibers, as marked in the box.
[0031] Analysis shows that these marks can be attributed to the melting phase change of polyester after heating, which causes the fibers to stick together and become fixed and irreversible after cooling. It can be determined that the fabric fibers have suffered slight heat damage, and the marks can provide a basis for investigators to determine whether someone has been in close contact with a heat source.
[0032] The specific identification method includes the following steps:
[0033] Step 1: Make a macroscopic observation of the fabric of the cuffs and collar of the clothing, and extract the parts that may form slight heat damage marks of polyester by analyzing the process of the suspect setting fire; the analysis method is: when the suspect sets fire, he usually needs to use his hands to ignite the fire source. In this process, because the fire starts quickly, some heat damage occurs in some typical parts of the clothing along the direction of the flame spread. Typical parts include the cuffs that are closer to the flame when using hands to ignite, the lower trouser legs and trouser corners (when the low-level oxidant flows and burns), and the fibers of the upper front part of the body during the rapid spread of the flame. .
[0034] Step 2: After the clothing fragment sample is sprayed with gold, its surface is observed through a scanning electron microscope (SEM).
[0035] Step 3: Adjust the SEM magnification to 500-1000, focus on the surface of the clothing fragment sample, and observe the surface of the fabric fiber.
[0036] Step 4: Look for surface abnormalities along the fabric fibers. Surface abnormalities include melting, adhesion or damage.
[0037] Step 5: For the abnormal area, adjust and increase the magnification of the scanning electron microscope (SEM) to observe the surface. The magnification of the scanning electron microscope (SEM) after adjustment and increase is greater than 1000 times, which can further analyze the trace characteristics of its details.
[0038] Step 6: Observe and record the slight traces of heat damage in abnormal areas on the surface of the fabric fiber to determine whether the person is in close contact with the fire source.
[0039] The specific method for judging whether the personnel have been in close contact with the fire source is as follows: by scanning with a scanning electron microscope (SEM), if there is melting or adhesion in the abnormal area on the surface of the fabric fiber, which is manifested as adhesion of more than 10 microns between different fibers, then it is judged that the personnel have been in close contact with the fire source; if the surface shape of the fabric fiber remains the same, then it is judged that the personnel have not been in close contact with the fire source.
[0040] The above is only a preferred embodiment of the present invention, and does not impose any formal limitation on the structure of the present invention. The layout type and the number of uses of the present invention are not limited to this example, and can be optimized and selected according to the actual project. Any modification, equivalent change and decoration of the above embodiment based on the technical principle of the present invention that does not deviate from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.
Claims
1. A method for judging whether a person is in close contact with a fire source based on slight thermal damage to chemical fibers, characterized in that: The steps include: Step 1: macroscopic observation of chemical fiber clothing fabrics is performed, and parts that may form slight heat damage marks are extracted by analyzing the process of personnel in the fire scene; in the step 1, the analysis method is: personnel need to use their hands to hold the fire source to ignite, and in this process, due to the rapid ignition, certain heat losses occur in some typical parts of the clothing along the direction of the flame spread, and the typical parts include the cuffs that are closer to the flame when using hands to ignite, the trouser legs and trouser corners at a lower position, and the fibers of the upper front part of the body during the rapid spread of the flame; Step 2: After the clothing fragment sample is sprayed with gold, its surface is observed through a scanning electron microscope (SEM); Step 3: Adjust the magnification of the scanning electron microscope (SEM) to 500-1000, focus on the surface of the clothing fragment sample, and observe the surface morphology of the clothing fiber; Step 4: searching for abnormalities in the surface morphology of the fabric along the fiber orientation; in the step 4, the abnormal surface morphology includes melting, adhesion or damage; Step 5: For the abnormal area, adjust and increase the magnification of the scanning electron microscope (SEM) to observe the surface; in the step 5, the magnification of the scanning electron microscope (SEM) after adjustment and increase is greater than 1000 times, and further analyze the trace characteristics of the details; Step six: observe and record the traces of slight heat damage in the abnormal area on the surface of the fabric fiber, and then judge whether the person is in close contact with the fire source; in the step six, the specific method for judging whether the person is in close contact with the fire source is: through scanning with a scanning electron microscope SEM, if there is melt adhesion in the abnormal area on the surface of the fabric fiber, it is judged that the person is in close contact with the fire source; if the shape of the surface of the fabric fiber remains the same, it is judged that the person is not in close contact with the fire source; in the step six, the melt adhesion is manifested as adhesion of more than 10 microns between different fibers.