Thermo-mechanical-abrasive-chemical coupled simulation method for ignition of energetic material micro-hot-spot

Abstract

The application discloses a thermal-force-abrasion-chemical coupling simulation method for micro hot spot ignition of energetic materials, and comprises the following steps: S1, establishing a thermal-force-chemical multi-field coupling control model corresponding to a friction geometry model of the energetic materials; S2, designing an abrasion sub-module to quantify the removal amount of the materials in the friction process; S3, defining a friction contact area in the thermal-force-chemical multi-field coupling control model, and adopting a partition-differentiated adaptive mesh technology to perform mesh dynamic updating on the friction contact area; S4, constructing boundary conditions of the thermal-force-chemical multi-field coupling control model and solving the boundary conditions; and S8, extracting critical temperature data of the friction contact area, and using the critical temperature data to evaluate the micro hot spot ignition risk of the energetic materials. The application innovatively introduces the abrasion effect, and constructs a more perfect "thermal-force-abrasion-chemical" coupling model, so that the authenticity and accuracy of the micro hot spot ignition process of the energetic materials are realized.

Description

Technical Field

[0001] This invention relates to the field of micro-hotspot-induced ignition at the interface of energetic materials. More specifically, this invention relates to a thermo-mechanical-wear-chemical coupling simulation method for micro-hotspot ignition in energetic materials. Background Technology

[0002] Energetic materials, with their high energy density and ability to release enormous amounts of energy instantaneously, have become the core material foundation for modern national weapon systems and defense deterrence capabilities. However, throughout the entire lifecycle of energetic materials—from preparation and processing to transportation and use—their interfaces are often subjected to complex frictional interactions. This not only triggers localized high temperatures but also leads to material wear, collectively increasing the risk of deformation, damage, and even accidental ignition, seriously threatening their safety in use. Although the ignition behavior of energetic materials under frictional interactions is a key scientific question for assessing their safety performance, current research still lacks a deep understanding of the coupling mechanism of "thermal-mechanical-wear-chemical" processes, and related analytical methods are not yet perfect, making it difficult to accurately predict and reliably assess the ignition process of microscopic hot spots.

[0003] Microscopic hotspots refer to the core areas where microscopic irregularities on the surface of energetic materials are more prone to significant stress and heat concentration under friction during ignition, thus becoming the core areas for hotspot formation and ignition. Given that the ignition process of microscopic hotspots is essentially accompanied by chemical thermal decomposition, the ignition of microscopic hotspots in energetic materials is a coupled "thermo-mechanical-chemical" driven process. In existing friction-induced ignition models for energetic materials, for example, Wang Ran et al. (Friction-induced ignition study of HTPB propellant based on a coupled chemo-mechano-thermodynamic model under ultrahigh acceleration overload conditions[J]. CaseStud. Therm. Eng. 2023, 52: 103708.) established a coupled "thermo-mechanical-chemical" model for HTPB propellant considering different velocity, pressure, and roughness conditions, systematically studying its friction-induced ignition process. The study revealed the ignition response level of the propellant sample under different friction conditions and determined the corresponding ignition threshold.

[0004] Furthermore, the invention patent CN119294200A, "A Thermo-Mechanical-Chemical Coupled Simulation Calculation Method Based on Friction-Induced Ignition of Energetic Materials," provides a method for measuring the friction-induced ignition behavior of energetic materials during friction, studying the critical conditions for friction-induced ignition, and achieving comprehensive monitoring of the "thermo-mechanical-chemical" coupled physicochemical processes of energetic materials during friction. It also allows for the simulation and study of friction-induced ignition problems of different energetic materials. However, these friction-induced ignition models for energetic materials only describe macroscopic ignition behavior and do not consider the influence of wear during friction. During friction, once the contact pressure exceeds the elastic boundary of the energetic material, wear or removal of the material occurs. Material wear can continuously change the interface contact area and pressure, thus affecting the temperature rise caused by friction, and consequently affecting the microscopic hot spot ignition behavior of the energetic material. Therefore, the coupled simulation calculations in the existing technology cannot accurately express the ignition behavior of energetic materials. Summary of the Invention

[0005] One object of the present invention is to solve at least the above-mentioned problems and / or defects, and to provide at least the advantages described below.

[0006] To achieve these objectives and other advantages of the present invention, a thermo-mechanical-wear-chemical coupling simulation method for microscopic hot spot ignition of energetic materials is provided, characterized by comprising: S1. Establish a thermo-mechanical-chemical multi-field coupled control model corresponding to the tribogey model of energetic materials; S2. Based on the Archard wear theory, a wear sub-module is designed to quantify the amount of material removed during the friction process. S3. Define the frictional contact region in the thermo-mechanical-chemical multi-field coupled control model; S4. Adaptive meshing technology with zoned differentiation is used to dynamically update the mesh in the friction contact area; S5. Construct the boundary conditions of the thermo-mechanical-chemical multi-field coupled control model and solve it. Determine whether the solution has converged. If it has converged, obtain the simulation result cloud map including temperature field distribution data and wear morphology, and proceed to S6. Otherwise, return to S4. S6. Extract transient temperature data during the sliding process from the temperature field distribution data in S5 to evaluate the ignition risk of micro hotspots in energetic materials. The wear submodule discretizes the entire wear process into n incremental steps, and the local wear depth increment Δ in each incremental step... h Local wear volume increment Δ V They are obtained respectively through the following formulas: In the above formula, p To contact pressure, K The wear coefficient is a dimensionless coefficient. H For material hardness, Δ s Δ represents the increment of the sliding distance within the current increment step. A This represents the local contact area represented by the node within the current increment step; Total wear depth h and total wear volume V Obtained through the following formula: .

[0007] Preferably, in S3, the partition differentiation refers to: Local mesh refinement is performed in rough surface regions with concentrated contact stress and drastic temperature gradient changes to capture the coupled "thermal-mechanical-wear" response during the friction process; In regions far from the contact interface, a gradual transition to a sparser mesh is used to improve solution efficiency; For complex micro-convex structural domains, tetrahedral elements are used for discretization; for regular smooth surface regions, hexahedral structured meshes are used for discretization.

[0008] Preferably, in S3, the grid is dynamically updated in the following way: S30. In each increment step, obtain the real-time wear amount of each contact node from the wear submodule. If the accumulated wear amount reaches the critical threshold based on the element feature size, or meets the preset increment step frequency, automatically trigger the mesh update program. S31. Identify wear areas that have undergone significant deformation based on the cumulative wear of each contact node; S32. Re-mesh and selectively refine the mesh within the wear area, while smoothing the adjacent cells in the wear area to achieve geometric update of the friction contact area; S33. After the geometry update of the friction contact region is completed, all historical field variables on the old mesh are mapped to the new mesh, and one iteration cycle is completed. The significant deformation is triggered when the cumulative wear reaches 5% of the unit feature size. The region where the cumulative wear of the corresponding node enters the critical range is recorded as the significant deformation region. If significant deformation is triggered by the incremental step frequency, then all nodes with accumulated wear at that moment are marked as significant deformation nodes.

[0009] Preferably, in S32, the re-division and selective densification are achieved by using the local wear depth increment as a normal displacement condition for the surface nodes through ALE technology, thereby driving the nodes to move and reproducing the material removal effect.

[0010] Preferably, the movement of the driving nodes is smoothly transferred from the surface displacement to the internal mesh nodes through a set of diffusion equation solvers; The diffusion equation solver uses the surface node normal displacement caused by wear as a boundary condition that must be satisfied, and smoothly and coherently transfers the surface node caused by wear to all internal mesh nodes in the computational domain, so as to obtain a displacement field corresponding to the global smooth node displacement distribution. The displacement field is superimposed onto the original coordinates of the mesh nodes to obtain a new mesh with accurate surface geometry updates and smooth transition of internal node distribution.

[0011] Preferably, the contact area, wear volume, and node temperature data of the friction contact area are post-processed, the ignition temperature of the micro hot spot is calculated based on the node temperature distribution data, and its temperature rise rate is statistically analyzed to obtain the critical temperature characteristics for assessing ignition risk.

[0012] The present invention has at least the following beneficial effects: Traditional simulation methods often neglect wear as a key influencing factor when analyzing the micro-hot spot ignition behavior of energetic materials. However, wear between the substrate and the friction pair is inevitable in actual friction processes and will significantly change the "thermal-mechanical-chemical" coupling process. Therefore, the present invention innovatively introduces the wear effect and constructs a more complete "thermal-mechanical-wear-chemical" coupling model. Furthermore, it considers the influence of different wear coefficients caused by the anisotropy of energetic materials on the ignition behavior of energetic materials. It can realistically reproduce the interface geometry, contact state and real-time evolution of the material surface during the friction process, thereby achieving the realism and accuracy of energetic materials in the micro-hot spot ignition process.

[0013] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0014] Figure 1 This is a flowchart of the microscopic hot spot ignition behavior of energetic materials under wear conditions, considering the "thermal-mechanical-wear-chemical" coupling. Figure 2 This is a schematic diagram of the mesh division of energetic materials in an embodiment of the present invention. Figure 3 This is a cloud map showing the surface temperature distribution of the HMX friction model during the sliding process in an embodiment of the present invention. Figure 4This is a schematic diagram of the HMX crystal contact area under different load conditions for wear of the friction pair and the substrate in an embodiment of the present invention. Figure 5 This is a schematic diagram of the HMX crystal contact pressure under different load conditions for wear of the friction pair and substrate in an embodiment of the present invention. Figure 6 This is a schematic diagram of the wear volume of the HMX crystal under different load conditions for wear of the friction pair and the substrate in an embodiment of the present invention. Figure 7 This is a schematic diagram showing the temperature rise of HMX crystal micro-hot spots under different load conditions during wear of the friction pair and substrate in an embodiment of the present invention. Figure 8 This is a schematic diagram of the contact area and contact pressure of the HMX crystal under different wear coefficients in an embodiment of the present invention. Figure 9 This is a schematic diagram of the wear volume of the HMX crystal under different wear coefficients in an embodiment of the present invention. Figure 10 This is a schematic diagram showing the temperature rise of HMX crystal micro-hot spots under different wear coefficients in an embodiment of the present invention. Detailed Implementation

[0015] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0016] Existing frictional temperature rise models are mostly limited to the "thermal-mechanical-chemical" coupling effect, failing to fully consider the crucial factor of material wear. In actual friction processes, when the contact pressure exceeds the elastic limit of the energetic material, material wear and removal will inevitably occur. This wear process dynamically changes the interfacial contact state and pressure distribution, thus significantly affecting the frictional temperature rise and subsequent ignition behavior. Furthermore, the surface of energetic materials is not ideally smooth but contains numerous micro-protrusions. Throughout the ignition process, these micro-protrusions preferentially generate micro-hot spots, which then gradually expand to the entire surface. Therefore, introducing a surface micro-protrusion model into the simulation is crucial for accurately reproducing the actual ignition process.

[0017] To fill the gaps in existing technologies and address the challenges of difficult and high-risk experimental observation, this invention provides a coupled "thermal-mechanical-wear-chemical" simulation method for the ignition of microscopic hotspots in energetic materials. This method can safely and effectively simulate the entire process from hotspot formation to explosion, thus providing crucial reference for improving processing techniques and assessing safety.

[0018] Example 1 As attached Figure 1As shown, a coupled "thermal-mechanical-wear-chemical" simulation method for the ignition of microscopic hot spots in energetic materials includes the following steps: Step 1: Based on actual research needs, construct a tribogeyser model of the energetic material using the SolidWorks platform. Since friction between surfaces of energetic materials typically occurs between micro-protrusions and relatively flat surfaces, to reasonably simplify the simulation process and highlight the main physical mechanisms, the friction system is idealized as a sliding contact between a single micro-protrusion and a plane.

[0019] Step two: Import the geometric model created in SolidWorks into ANSYS software, set the physical property parameters of the energetic material, and construct a multi-field coupled control model of the energetic material HMX / HMX. The physical parameters of the HMX crystal are set to cover mechanical, thermal, and tribological properties, including density, elastic modulus, Poisson's ratio, coefficient of thermal expansion, specific heat capacity, thermal conductivity, and coefficient of friction.

[0020] In the "thermo-mechanical-chemical" multi-field coupled control model of energetic materials, based on Fourier's heat transfer law and the principle of energy conservation, the transient heat conduction differential equation describes the temperature variation of the object's interior with time and space. Solving the heat conduction differential equation under certain conditions yields the temperature distribution of the object. The heat conduction differential equation for the material is as follows: (1) In the formula, ρ , C , These are the density, specific heat capacity, and thermal conductivity of the energetic material, respectively. T The friction-induced "thermal-mechanical-wear" temperature at the interface of energetic materials. Q i It is the heat generated by the exothermic reaction of the chemical thermal decomposition of HMX per unit time.

[0021] During sliding, the work done by interfacial friction is partially converted into heat energy. This frictional heat, as a local heat source, is generated at the contact interface and flows to the two contacting frictional bodies according to the laws of heat conduction. q It can be represented as: (2) In the formula, Friction work-heat conversion coefficient μ It is the coefficient of friction. P It is a normal load. vThis refers to the sliding speed. Assuming all frictional work is converted into internal energy and distributed across the two interfaces, and treating frictional heat as the boundary heat flow input, since the heat distribution coefficient depends on the density, specific heat capacity, and thermal conductivity of the mating materials, and both the mating pair and the substrate material are HMX crystals with identical thermophysical parameters, the ratio of their heat distribution coefficients is determined to be 0.5. Therefore, by calculating the generated heat, the "thermal-mechanical-wear" temperature of the mating pair and the substrate during the friction process can be accurately derived. T .

[0022] Step 3: Based on the classic Archard wear theory, develop corresponding wear user subroutines to quantify the amount of material removed during the friction process.

[0023] The Archard wear model, a classic theory in tribology, successfully describes the relationship between wear volume and load, sliding distance, and material hardness on a macroscopic scale. However, the classic Archard model is a global, empirical model, and its formula is expressed as: (3) In the formula, V For wear volume, K The wear coefficient is a dimensionless coefficient. F For normal load, s The sliding distance, H The value represents the material hardness. However, the limitation of the Archard wear model lies in its inability to accurately simulate the local wear depth at a single contact point during the wear process. In actual contact, the contact pressure distribution is uneven, leading to significant differences in wear behavior across different regions of the material surface. Therefore, to accurately predict the morphological evolution of a specific wear region in finite element analysis, a localization correction must be made to the classic Archard model.

[0024] To apply it to finite element simulations, we transform the Archard wear model into an incremental form for each computational node (or contact point). Within each computational increment step, the corresponding wear volume increment Δ V It can be represented as: (4) In the formula, Δ s This represents the incremental sliding distance within the current increment step.

[0025] Since wear is a dynamic process, the contact area and surface morphology change after each incremental step. Therefore, the wear volume increment Δ V This can be further characterized by changes in local contact area and depth: (5) In the formula, Δ A Δ represents the local contact area represented by the node within the current increment step. h This represents the wear depth increment of the node in the current step.

[0026] By combining equations (5) and (6), we can obtain: (6) In the formula, F / ∆ A This can be expressed as contact pressure. p Substituting into the above formula, we obtain the formula for the local wear depth increment applicable to finite element calculations: (7) This formula is the core of the simulation. It directly correlates the macroscopic wear coefficient with the microscopic nodal pressure and sliding distance, thus allowing the calculation of the wear amount of each node at each time step. In the finite element method, the entire wear process is discretized into n incremental steps, with the total wear depth... h and total wear volume V This can be obtained by summing the results of all increment steps: (8) (10) The key parameter in the model is the wear coefficient. K Calculations were performed using a nano-scratch test, which directly yielded a curve showing the wear depth as a function of sliding distance. Due to the experimental process... H remain unchanged. p It can be calculated based on Hertzian contact pressure. Therefore, the wear coefficient of energetic materials can be calculated. K To realize the dynamic evolution of geometry during wear, this study embeds the improved Archard model into the finite element software via a user subroutine and employs ALE adaptive meshing technology.

[0027] Since the triboelectric wear behavior of HMX crystals is significantly affected by crystal anisotropy, the temperature rise and ignition behavior of its surface during the friction process are likely to also exhibit anisotropic characteristics. In order to study the ignition sensitivity of HMX (011) and (110) crystal planes, measurements were taken along three crystallographic directions of 0°, 45° and 90° for each crystal plane, and the wear coefficients obtained are shown in Table 1.

[0028] Table 1: Wear coefficient of each crystal face in different crystallographic directions Step 4: Define the HMX crystal mating surface as the contact surface in the contact pair, and the HMX crystal substrate plane as the target surface in the contact pair.

[0029] Since the surface of the HMX crystal is a smooth curved surface and the substrate is a smooth plane, the constructed HMX / HMX friction model belongs to the surface-to-surface contact type. According to the contact definition rules, in the multiphysics coupling environment, the surface of the HMX crystal is set as the contact element CONTAC174, and the substrate plane of the HMX crystal is set as the target element TARGE170.

[0030] Furthermore, key parameters such as the normal stiffness of the contact interface (consisting of the contact surface and the target surface) are defined and set. The value of the normal stiffness is based on the actual surface morphology characteristics of the HMX crystal and is equivalently set through a scaling factor. Given that the micro-protrusions will undergo significant elastoplastic deformation during friction, the normal stiffness scaling factor of the contact model is set to 1 to accurately simulate contact behavior and ensure the realism of the calculated contact stress and deformation response. This model aims to simulate heat generation and conduction during friction, and must be set as a thermo-structural coupling problem to capture the bidirectional interaction between frictional heat generation and thermally induced deformation. For the contact algorithm, the augmented Lagrangian algorithm is adopted. This algorithm, by automatically updating the contact pressure in each equilibrium iteration, can significantly improve convergence while maintaining computational efficiency comparable to the penalty function algorithm, and obtain more accurate contact force and penetration control results, thereby effectively improving the numerical stability and reliability of the coupled solution.

[0031] Step 5: In the solution process, to adapt to the geometric deformation caused by material wear, adaptive meshing technology is used to dynamically update the mesh of the wear area of ​​the HMX / HMX finite element model.

[0032] In the finite element simulation of friction and wear, to improve computational accuracy and efficiency, a partitioned differentiated meshing strategy is adopted based on the model's geometric characteristics. For complex micro-convex structural domains, highly adaptable tetrahedral elements are used for discretization to ensure accurate fitting of complex morphologies. For regular smooth surface regions, a more computationally efficient and convergent hexahedral structured mesh is selected. Local mesh refinement is performed in rough surface regions with concentrated contact stress and drastic temperature gradients to accurately capture the coupled "thermal-mechanical-wear" response during friction. In regions far from the contact interface, a sparser mesh is gradually applied, significantly improving solution efficiency while maintaining computational accuracy. After meshing, the built-in quality check function in the meshing module is used to perform a quality check on the entire mesh (the quality check is implemented using the mesh quality check module in Ansys software) to ensure the absence of negative volumes, high distortion, and other mesh defects, thus guaranteeing the numerical stability of subsequent calculations. The meshing results for the HMX / HMX friction model are shown below. Figure 2 As shown (it should be noted that, Figure 2In this diagram, V represents speed, P represents pressure, A represents the HMX friction pair, and B represents the HMX substrate.

[0033] Specifically, this step, to accurately simulate the geometric evolution caused by continuous material removal, employs an adaptive mesh dynamic update strategy deeply coupled with the physical model. Its core lies in utilizing the ALE mesh adaptive method to intelligently adjust the computational domain while maintaining the overall mesh topology. This process begins with real-time monitoring and calculation of surface nodes within each increment step. The user subroutine accesses the contact pressure and sliding increment of each contact node and calculates the corresponding normal wear depth based on the localized Archard model. When the cumulative wear of a node reaches a critical threshold based on the element feature size, or when a preset increment step frequency is met, the system automatically triggers the mesh update procedure.

[0034] The update process does not involve global mesh reconstruction, but rather performs highly localized optimization operations. The system first accurately identifies wear regions with significant deformation, then re-meshes and selectively refines the mesh only within these affected areas, while smoothing adjacent elements to maintain good mesh quality. During this process, the ALE (Adaptive Element Removal) technique uses the calculated wear depth increment as the normal displacement condition for surface nodes, driving these nodes to move precisely, thus geometrically reproducing the material removal effect. To adapt the internal mesh to this surface deformation, a diffusion equation solver smoothly transfers the surface displacement to the internal mesh nodes, effectively avoiding element distortion. This diffusion equation solver is the core execution unit of the adaptive mesh update technology, using the surface node normal displacement caused by wear as a necessary boundary condition, smoothly and coordinately transferring it to all internal mesh nodes within the computational domain, thereby obtaining a globally smooth node displacement distribution. Superimposing this calculated displacement field onto the original coordinates of the mesh nodes yields a new mesh with accurately updated surface geometry and a smoothly transitioned internal node distribution. This process mathematically guarantees that the rate of change of the displacement field within the domain is minimized, thereby effectively avoiding excessive distortion or deformation of the elements caused by severe local deformation, and ensuring the numerical stability and accuracy of subsequent calculation steps.

[0035] After the geometry update is complete, a crucial step is to accurately map all historical field variables from the old mesh, such as pressure, area, and temperature, onto the new mesh. This ensures the physical consistency and numerical stability of the solution process. At this point, a complete iteration cycle is finished. The updated geometry and physical fields provide a completely new computational foundation for the next incremental step. This forms a fully automated closed-loop feedback system of "wear calculation - trigger judgment - mesh update - variable mapping," ultimately achieving high-fidelity and high-stability dynamic simulation of complex wear evolution processes.

[0036] Step six: Set the boundary conditions for the friction model. First, constrain all degrees of freedom at the bottom of the energetic material substrate to simulate a fixed support. Then, apply a normal load to the top of the friction pair while simultaneously controlling its tangential sliding velocity to simulate the actual frictional motion process. The analysis process of the friction model includes two steps: In the first analysis step (application of normal load), during this quasi-static phase, a fixed constraint is applied to both the HMX crystal mating pair and the HMX crystal substrate. Subsequently, a quasi-statically increasing normal load is applied to the top edge of the HMX crystal mating pair until a preset stable load value is reached. This analysis step aims to simulate the smooth establishment process of pressure between the contact interfaces, ensuring the rationality of the initial stress state of the model.

[0037] The second analysis step (steady-state friction process) maintains a constant normal load on the top edge of the HMX crystal, fixes all degrees of freedom on the bottom edge of the HMX crystal substrate, and applies a constant sliding speed to the HMX crystal friction pair to simulate a stable sliding friction process. Simultaneously, complete thermal boundary conditions need to be defined: the ambient temperature and the initial temperature of the HMX / HMX crystal model are set, and the heat dissipation mechanism during the friction process is clarified. Heat dissipation mainly includes thermal convection with the surrounding medium, and thermal conduction through the contact interface and the interior of the material.

[0038] Step seven: After completing all parameter settings, execute the calculation. When the HMX crystal interface temperature reaches the thermal decomposition threshold, a chemical decomposition reaction of HMX will be triggered, releasing a large amount of heat, far exceeding the frictional heat. This chemical heat generated during the thermal decomposition of energetic materials... Q The following formula can be used for calculation: (11) In the formula, t 1 represents the time when the HMX surface temperature reaches 220 °C, at which the chemical thermal decomposition begins. t 2 represents the ignition time of the HMX crystal. q m The total energy per unit mass of energetic materials. A Pre-exponential factor, E a The Arrhenius activation energy of energetic materials. R This is the universal gas constant. T This refers to the "thermal-mechanical-wear" temperature of the microscopic hotspot at the interface of energetic materials. The generated heat can be converted into the chemical thermal decomposition temperature ΔT using the following formula. T : (12) In the formula, c The specific heat capacity of energetic materials, mThis refers to the mass of energetic materials. Therefore, the "thermo-mechanical-wear-chemical" temperature of the microscopic hotspot of energetic materials is the "thermo-mechanical-wear" temperature. T Add the chemical thermal decomposition temperature Δ T .

[0039] If non-convergence occurs during the solution process, the boundary conditions or mesh generation need to be readjusted. When the numerical simulation converges, the temperature field distribution data of the friction system and the morphological simulation cloud map of the worn surface can be output as key results for subsequent analysis.

[0040] Step eight involves entering the post-processing module, where a self-developed code system extracts transient temperature data of the friction contact area during the sliding process. Since the HMX crystal begins to undergo thermal decomposition at 220 ℃, the code uses this temperature as a critical point to automatically identify and filter all nodes whose temperatures exceed this threshold. Based on the temperature distribution data of these nodes, the micro-hotspot ignition temperature is calculated, and its temperature rise rate is statistically analyzed to obtain the critical temperature characteristics for assessing ignition risk.

[0041] The ignition mechanism of energetic materials depends on the formation and evolution of microscopic hot spots. Under friction, high-temperature hot spots are first generated locally within the material. Subsequently, these hot spots diffuse energy to the surrounding area through heat conduction, ultimately triggering the ignition reaction of the entire model. (See attached image) Figure 3 As shown, during the sliding process, the highest temperature on the surface of the HMX / HMX crystals is always concentrated at the frictional contact interface between the two crystals. This is mainly because HMX has a low thermal conductivity and the frictional action time is extremely short, causing frictional heat to accumulate rapidly at the micro-protrusions without time to diffuse to the surroundings. It is this significant heat concentration effect that makes ignition behavior very likely to occur at this frictional interface, and as the friction time increases, the temperature of the micro-hot spots in the friction concentration area also gradually increases.

[0042] Example 1 proposes a coupled "thermal-mechanical-wear-chemical" simulation method for the microscopic hot spot ignition of energetic materials based on the friction-induced ignition behavior of energetic materials under wear conditions. This method systematically reveals the coupling mechanism between the material wear process and surface temperature rise and ignition behavior. It provides a reliable theoretical tool and numerical basis for a deeper understanding of the frictional temperature rise law and ignition mechanism of energetic materials, and has important guiding significance for improving the accuracy of their safety design and evaluation.

[0043] Example 2 Building upon Example 1, the significant impact of this key mechanical parameter on the tribological behavior and temperature rise effect of the HMX crystal surface was explored in depth by systematically adjusting the normal load. Specifically, a direct increase in the normal load means an increase in the normal pressure between the contact interfaces of the friction pair, which leads to a linear increase in frictional force. This results in more mechanical energy input at the same sliding speed and also increases the actual contact area, making heat generation more concentrated and intense.

[0044] According to the appendix Figure 4 and attached Figure 5 As shown, under the conditions of a sliding speed of 1 m / s and a friction coefficient of 0.24, when the normal load gradually increases from 60 MPa to 100 MPa, the contact area and contact pressure on the HMX crystal surface change with sliding time. The dashed line in the figure represents the case without wear, while the solid line represents the case where the HMX crystal, as a friction pair and substrate, undergoes wear. Under the condition without wear, except for a momentary increase in contact area and contact pressure during the application of the normal load, both remain basically constant after entering the stable sliding contact stage. Under the condition of wear, as sliding continues, the contact area gradually increases, while the contact pressure decreases accordingly. This phenomenon is attributed to the continuous removal of material due to wear, which reduces the height of the HMX crystal friction pair and expands the actual contact area. Under a constant normal load, the load per unit area decreases, thus causing a decrease in the average contact pressure. (Appendix) Figure 6 The wear volume of the HMX crystal under different load conditions varies with normal load on the wear of the friction pair and substrate. In the absence of wear, the wear volume is zero under different normal loads. However, under wear conditions, when the normal load increases from 60 MPa to 100 MPa, the wear volume correspondingly increases from 65.41 μm³ to 109.03 μm³, clearly showing a linear growth trend in wear volume with increasing normal load.

[0045] Appendix Figure 7This paper presents the variation of microscopic hot spot temperature of the HMX crystal with friction time under different normal load conditions. It can be observed that under a normal load of 60 MPa, considering HMX crystal wear, the highest temperature recorded on the HMX surface at the end of the sliding process is 398 °C. However, without considering wear of the friction pair, the temperature rise rate exhibits a sharp increase and eventually diverges to infinity. Without considering HMX crystal wear, the HMX crystal exhibits ignition behavior, while considering wear, it does not. The local ignition temperature and ignition time are defined as the temperature and time points corresponding to the rate of temperature change approaching infinity. Without considering HMX crystal wear, when the normal load increases from 60 MPa to 100 MPa, the ignition temperature increases from 441 °C to 460 °C, and the ignition time decreases from 55.2 μs to 20.2 μs. Under the same friction conditions, when the HMX crystal wears, no ignition behavior occurs at the HMX contact surface at a normal load of 60 MPa. When the normal load increased from 80 MPa to 100 MPa, the ignition temperature increased from 454 ℃ to 467 ℃, and the ignition time decreased from 32 μs to 20.8 μs. The results show that material wear has a significant impact on the ignition temperature and ignition time of HMX. Compared with the unworn state, the ignition temperature increases after the material wears, which makes the ignition temperature of energetic materials more accurate during the ignition process.

[0046] Example 3 Building upon Example 1, the significant impact of the wear coefficient, a key interfacial characteristic parameter, on the tribological behavior and temperature rise effect of the HMX crystal surface can be explored in depth by systematically adjusting the wear coefficient. An increase in the wear coefficient directly reflects the intensification of interfacial wear, which significantly improves the material removal rate, leading to a dynamic evolution of the friction interface morphology and thus altering the actual contact state and heat source distribution. Therefore, studying the changes in the wear coefficient is crucial for revealing the material degradation mechanism, interface evolution law, and its feedback effect on thermo-mechanical coupling behavior during friction. This provides clear guidance for evaluating the interfacial stability and thermal safety of materials under long-term service conditions.

[0047] According to the appendix Figure 8 and attached Figure 9 As shown, under the conditions of a normal load of 80 MPa, a sliding speed of 1 m / s, and a friction coefficient of 0.24, when the wear coefficient increases from 2.7 × 10⁻⁶... -4 Increased to 4.4 × 10 -4 The changes in contact area, contact pressure, and wear volume on the HMX crystal surface during wear are observed. This is as follows: when the wear coefficient increases from 2.7 × 10⁻⁶... -4 Increased to 4.4 × 10 -4At that time, the total wear of the HMX crystal on the surface of the friction pair and the substrate increased from 102.32 μm. 3 Increased to 184.31 μm 3 The contact area is 109 μm 2 Increased to 123 μm 2 The contact pressure decreased from 468 MPa to 395 MPa. These changes indicate that a higher wear coefficient corresponds to a more significant wear condition, specifically manifested as greater wear, expanded contact area, and decreased contact pressure, indicating an intensified wear.

[0048] Appendix Figure 10 This shows the variation of microscopic hot spot temperature of the HMX crystal with friction time under different wear coefficients. As the wear coefficient increases, the ignition time after wear is significantly prolonged. K From 2.7×10 -4 Increased to 4.4 × 10 -4 At that time, the ignition temperature increased from 450 ℃ to 456 ℃, and the ignition time increased from 24.7 μs to 34.4 μs. The increase in the wear coefficient reduced the ignition sensitivity of the HMX crystal, making it more difficult to ignite.

[0049] Example 3 establishes a multi-field coupled model of "thermal-mechanical-wear-chemical" for the micro-hot spots of HMX crystals, achieving accurate simulation of the ignition process of micro-hot spots in HMX crystals under wear conditions. This method comprehensively considers the complex interactions between mechanical action, heat accumulation, material wear, and chemical reaction, significantly improving the accuracy and predictive ability of simulating the ignition process of HMX micro-hot spots. It provides important theoretical tools and calculation basis for further revealing the frictional temperature rise and ignition mechanism of energetic materials, and has positive guiding significance for improving the reliability of their safety design and evaluation.

[0050] The above solution is merely an illustration of a preferred example and is not limited thereto. When implementing this invention, appropriate substitutions and / or modifications can be made according to the user's needs.

[0051] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. It can be applied to various fields suitable for the present invention. Other modifications can be readily made by those skilled in the art. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and examples shown and described herein.

Claims

1. A thermo-mechanical-wear-chemical coupling simulation method for microscopic hot spot ignition of energetic materials, characterized in that, include: S1. Establish a thermo-mechanical-chemical multi-field coupled control model corresponding to the tribogey model of energetic materials; S2. Based on the Archard wear theory, a wear sub-module is designed to quantify the amount of material removed during the friction process. S3. Define the frictional contact region in the thermo-mechanical-chemical multi-field coupled control model; S4. Adaptive meshing technology with zoned differentiation is used to dynamically update the mesh in the friction contact area; S5. Construct the boundary conditions of the thermo-mechanical-chemical multi-field coupled control model and solve it. Determine whether the solution has converged. If it has converged, obtain the simulation result cloud map including temperature field distribution data and wear morphology, and proceed to S6. Otherwise, return to S4. S6. Extract transient temperature data during the sliding process from the temperature field distribution data in S5 to evaluate the ignition risk of micro hotspots in energetic materials. The wear submodule discretizes the entire wear process into n incremental steps, and the local wear depth increment Δ in each incremental step... h Local wear volume increment Δ V They are obtained respectively through the following formulas: In the above formula, p To contact pressure, K The wear coefficient is a dimensionless coefficient. H For material hardness, Δ s Δ represents the increment of the sliding distance within the current increment step. A This represents the local contact area represented by the node within the current increment step; Total wear depth h and total wear volume V Obtained through the following formula: 。 2. The thermo-mechanical-wear-chemical coupling simulation method for microscopic hot spot ignition of energetic materials as described in claim 1, characterized in that, In S3, the partition differentiation refers to: Local mesh refinement is performed in rough surface regions with concentrated contact stress and drastic temperature gradient changes to capture the coupled "thermal-mechanical-wear" response during the friction process; In regions far from the contact interface, a gradual transition to a sparser mesh is used to improve solution efficiency; For complex micro-convex structural domains, tetrahedral elements are used for discretization; for regular smooth surface regions, hexahedral structured meshes are used for discretization.

3. The thermo-mechanical-wear-chemical coupling simulation method for microscopic hot spot ignition of energetic materials as described in claim 1, characterized in that, In S3, the method for dynamically updating the grid is as follows: S30. In each increment step, obtain the real-time wear amount of each contact node from the wear submodule. If the cumulative wear amount reaches 5% based on the element feature size, or meets the preset increment step frequency, automatically trigger the mesh update program. S31. Identify wear areas that have undergone significant deformation based on the cumulative wear of each contact node; S32. Re-mesh and selectively refine the mesh within the wear area, while smoothing the adjacent cells in the wear area to achieve geometric update of the friction contact area; S33. After the geometry update of the friction contact region is completed, all historical field variables on the old mesh are mapped to the new mesh, and one iteration cycle is completed. The significant deformation is triggered when the cumulative wear reaches 5% of the unit feature size. The region where the cumulative wear of the corresponding node enters the critical range is recorded as the significant deformation region. If significant deformation is triggered by the incremental step frequency, then all nodes with accumulated wear at that moment are marked as significant deformation nodes.

4. The thermo-mechanical-wear-chemical coupling simulation method for microscopic hot spot ignition of energetic materials as described in claim 3, characterized in that, In S32, the re-division and selective densification are achieved by using the local wear depth increment as the normal displacement condition of the surface nodes through ALE technology to drive node movement and reproduce the material removal effect. To adapt the internal mesh to this surface deformation, a diffusion equation solver smoothly transfers the surface displacement to the internal mesh nodes, effectively avoiding element distortion.

5. The thermo-mechanical-wear-chemical coupling simulation method for microscopic hot spot ignition of energetic materials as described in claim 4, characterized in that, The driving node movement is achieved by smoothly transferring the surface displacement to the internal mesh nodes through a set of diffusion equation solvers; The diffusion equation solver uses the surface node normal displacement caused by wear as a boundary condition that must be satisfied, and smoothly and uniformly transfers the surface node displacement caused by wear to all internal mesh nodes in the computational domain to obtain a displacement field corresponding to the global smooth node displacement distribution.

6. The thermo-mechanical-wear-chemical coupling simulation method for microscopic hot spot ignition of energetic materials as described in claim 1, characterized in that... The contact area, wear volume, and node temperature data of the friction contact area are post-processed. Based on the distribution data of node temperature, the ignition temperature of the micro hot spot is calculated, and its temperature rise rate is statistically analyzed to obtain the critical temperature characteristics for assessing ignition risk.

Images