Method for detecting compressive strength of solid propellant in viscous state

Abstract

The invention provides a method for detecting the compressive strength of a solid propellant in a viscous state. The method comprises the following steps: step 1, processing the size of a sample: processing the solid propellant to be detected into a medicine column; step 2, heat preservation treatment: putting the grain prepared in the step 1 into an environmental box, and preserving heat, so that the solid propellant to be detected in the grain is in a viscous state. The grain subjected to heat preservation treatment in the second step is put into an environment box of a universal material testing machine, the temperature of the environment box is the same as the heat preservation temperature, and the compression resistance test is conducted till the compression resistance value reaches 102% or above of the qualified value required by the product. And 4, flaw detection test: sending the grain pressed in the step 3 into an industrial CT, and carrying out DR imaging scanning in the industrial CT to obtain a DR scanning picture. And 5, result judgment: observing whether damage such as cracks and gaps occurs in the DR scanning picture, if not, judging that the compressive strength of the product is qualified, otherwise, judging that the compressive strength of the product is unqualified. The method solves the problems that the compressive strength value of the solid propellant in the viscous state cannot be directly obtained through a compressive test, and then whether the product is qualified cannot be judged, and has the advantages of being visual, reliable, accurate in result and the like.

Description

Technical Field

[0001] This invention belongs to the field of energetic materials testing technology, and relates to compressive strength testing, specifically to a method for testing the compressive strength of solid propellants in a viscous flow state. Background Technology

[0002] Solid propellant grains (hereinafter referred to as propellant grains) are an important component of solid rocket motors. During production, transportation, and flight, propellant grains are subjected to loads such as temperature, vibration, acceleration overload, and ignition pressurization, exhibiting a state of compressive stress. Therefore, propellant grains must have a relatively relaxed mechanical response behavior under certain compressive loads; otherwise, the propellant will crack, leading to runaway combustion and engine damage. Compressive strength is the main indicator for evaluating the structural integrity (i.e., no cracking) of propellant grains under compressive loads. Currently, the pass / fail status of propellant grain compressive strength is mainly determined by comparing the measured compressive strength value with the product requirements. The standard mainly used for compressive strength testing is Method 415.1 "Compressive Strength Compression Method" in the known standard "GJB770B-2022 Test Methods for Pyrotechnics". The test principle of this standard is to apply a static compressive load to the longitudinal axis of the specimen at a specified test temperature and loading rate until the maximum load appears on the stress-strain curve, and then stop. Finally, the maximum load divided by the contact area is taken as the compressive strength value. This determination method is highly suitable for solid propellants, is simple to operate, and yields accurate and reliable results. However, at higher temperatures, some solid propellants, such as nitrocellulose (NC), hydroxyl-terminated polybutadiene (HTPB), and their modified materials, undergo a glass transition, causing the propellant grain to change from a glassy state to a viscous flow state. This results in the absence of a maximum load when static loads are applied, making it impossible to obtain the compressive strength value of the propellant grain. Typical load-displacement curves for glassy and viscous flow propellant grains are shown in [reference needed]. Figure 1 Therefore, existing standards are not applicable to determining the compressive strength compliance of solid propellants in viscous flow conditions. To address the shortcomings of existing methods, a more applicable and accurate new testing method needs to be developed. Summary of the Invention

[0003] To address the shortcomings of existing technologies, the present invention aims to provide a method for testing the compressive strength of solid propellants in a viscous flow state. This method solves the technical problem that existing testing methods cannot directly obtain the compressive strength value of solid propellants in a viscous flow state through compressive testing, thus failing to determine whether the product is qualified. To solve the above-mentioned technical problems, the present invention adopts the following technical solution.

[0004] A method for testing the compressive strength of solid propellants in viscous flow conditions, comprising the following steps.

[0005] Step 1, Sample size processing: The solid propellant to be tested is processed into a propellant grain.

[0006] Step 2, heat preservation treatment: The propellant column prepared in step one is placed in an environmental chamber and kept at a constant temperature to ensure that the solid propellant to be tested in the propellant column is in a viscous flow state.

[0007] Step 3, Compression Test: After the heat preservation treatment in step two, the explosive column is placed in the environmental chamber of the universal testing machine. The temperature of the environmental chamber is the same as the heat preservation temperature. A compressive strength test is carried out until the compressive strength value reaches more than 102% of the qualified value required by the product.

[0008] Step 4, flaw detection test: The compressed drug cartridge from step three is then sent to an industrial CT scanner for DR imaging to obtain DR scan images.

[0009] Step 5, Result Determination: Observe whether cracks, voids or other damage appear in the DR scan image. If no damage is found, the product is deemed to have qualified compressive strength; otherwise, it is deemed unqualified.

[0010] The present invention also has the following technical features.

[0011] In step one, the height of the drug column is 20.00 mm.

[0012] In step two, the heat preservation is carried out at 60°C for 1.5 hours.

[0013] In step three, the compression test is conducted at a loading rate of 10 mm / min.

[0014] Compared with the prior art, the present invention has the following technical effects.

[0015] This invention uses a universal testing machine to compress the propellant grain to over 102% of the specified value, then uses industrial CT to observe the formation of cracks and voids in the propellant grain after compression, finally determining the product's compressive strength value for compliance. This method solves the problem that the compressive strength value of solid propellants in a viscous flow state cannot be directly obtained through compression testing, thus making it impossible to determine whether the product is qualified. This method has the advantages of being intuitive, reliable, and providing accurate results. Attached Figure Description

[0016] Figure 1 This is a typical load-displacement curve.

[0017] Figure 2 This is the compressive strength test curve.

[0018] Figure 3 This is a DR scan image.

[0019] The specific content of the present invention will be further explained in detail below with reference to the embodiments. Detailed Implementation

[0020] It should be noted that, unless otherwise specified, all raw materials and instruments used in this invention are known in the prior art and are commercially available. All testing methods used in this invention, unless otherwise specified, are conventional methods.

[0021] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments. All equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0022] Example: This embodiment provides a method for testing the compressive strength of solid propellants in a viscous flow state. The method includes the following steps: Step 1, Sample size processing: The solid propellant to be tested is processed into a propellant grain.

[0023] Step 2, heat preservation treatment: The propellant column prepared in step one is placed in an environmental chamber and kept at a constant temperature to ensure that the solid propellant to be tested in the propellant column is in a viscous flow state.

[0024] Step 3, Compression Test: After the heat preservation treatment in step two, the explosive column is placed in the environmental chamber of the universal testing machine. The temperature of the environmental chamber is the same as the heat preservation temperature. A compressive strength test is carried out until the compressive strength value reaches more than 102% of the qualified value required by the product.

[0025] Step 4, flaw detection test: The compressed drug cartridge from step three is then sent to an industrial CT (X-Ray Computed Tomography) machine for DR (Digital Radiography) imaging scans to obtain DR scan images.

[0026] Step 5, Result Determination: Observe whether cracks, voids or other damage appear in the DR scan image. If no damage is found, the product is deemed to have qualified compressive strength; otherwise, it is deemed unqualified.

[0027] In this invention, cracks and voids inside the propellant grain are detected using DR scanning imaging with an industrial CT scanner. This detection method combines the test curves from a material testing machine with DR scanning images from an industrial CT scanner to determine whether the product's compressive strength is up to standard.

[0028] Application example: This application example provides a method for testing the compressive strength of solid propellants in a viscous flow state based on the above embodiments. In this application example, the universal testing machine used is the MTS 5504 type, known in the art; the industrial CT uses the APTIPT15110 type, a known industrial CT non-destructive testing device; the solid propellant uses a commonly used modified double-base propellant, which refers to a propellant in which solid oxidizers, high-energy explosives, and metallic fuels are added to the double-base propellant components to improve energy performance. Its main components include nitrocellulose, nitroglycerin, aluminum powder, inorganic oxides (such as ammonium perchlorate), organic nitramine compounds (such as octogen or RDX), stabilizers, and combustion catalysts. The method includes the following steps.

[0029] Step 1, Sample size processing: The modified double-base propellant was processed into propellant grains with a height of 20.00 mm, with a dimensional tolerance within 0.10 mm. The diameter of the propellant grains was determined using the standard diameter for the compressive strength test conducted on a universal testing machine.

[0030] Step 2, heat preservation treatment: The propellant grains prepared in step one are placed in an environmental chamber and kept at 60°C for 1.5 hours to bring the solid propellant to be tested into a viscous flow state. The environmental chamber of the universal testing machine must also be kept at the same temperature.

[0031] Step 3, Compression Test: After the insulation treatment in step two, the propellant column was placed in the environmental chamber of a universal testing machine. The temperature of the environmental chamber was the same as the insulation temperature. A compressive strength test was conducted at a loading rate of 10 mm / min until the compressive strength value reached more than 102% of the product's required qualified value. The test curve is shown in [reference needed]. Figure 2 As shown.

[0032] Step 4, flaw detection test: The compressed drug cartridge from step three is then sent to an industrial CT scanner for DR imaging, yielding DR scan images, such as... Figure 3 As shown.

[0033] Step 5, Result Determination: Observation as Figure 3 The DR scan image shown does not have obvious defects such as cracks and voids, so it can be determined that the compressive strength of the product is better than the qualified line.

Claims

1. A method for testing the compressive strength of solid propellants in a viscous flow state, characterized in that, The method includes the following steps: Step 1, Sample size processing: The solid propellant to be tested is processed into a propellant grain; Step 2, heat preservation treatment: The propellant column prepared in step one was placed in an environmental chamber and kept at a constant temperature to ensure that the solid propellant to be tested in the propellant column was in a viscous flow state. Step 3, Compression Test: After the heat preservation treatment in step two, the catalytic column is placed in the environmental chamber of the universal testing machine. The temperature of the environmental chamber is the same as the heat preservation temperature. A compressive strength test is carried out until the compressive strength value reaches more than 102% of the qualified value required by the product. Step 4, flaw detection test: The compressed drug column from step three is sent to an industrial CT scanner for DR imaging to obtain DR scan images. Step 5, Result Determination: Observe whether cracks, voids or other damage appear in the DR scan image. If no damage is found, the product is deemed to have qualified compressive strength; otherwise, it is deemed unqualified.

2. The method for testing the compressive strength of solid propellants in viscous flow as described in claim 1, characterized in that, In step one, the height of the drug column is 20.00 mm.

3. The method for testing the compressive strength of solid propellants in viscous flow as described in claim 1, characterized in that, In step two, the heat preservation is carried out at 60°C for 1.5 hours.

4. The method for testing the compressive strength of solid propellants in viscous flow as described in claim 1, characterized in that, In step three, the compression test is conducted at a loading rate of 10 mm / min.

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