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2025,
45(7):
071001.
doi: 10.11883/bzycj-2024-0500
Abstract:
To investigate the crashworthiness and energy absorption characteristics of aircraft fuselage substructures and to conduct structural crashworthiness design, this study focuses on a typical metal aircraft fuselage as the research object. A drop test of a typical fuselage substructure was performed, and the energy absorption characteristics were evaluated based on both experimental and simulation analysis results. Subsequently, an energy absorption design for the fuselage substructure was developed. The influence of structural layout parameters on the crash response of the new fuselage substructure was examined through simulation analysis. Comparisons were made regarding structural deformation, impact force-time curves, acceleration responses, and energy absorption for fuselage substructures with different layout parameters. The results indicate that during the crash process of the original structure, the primary energy absorption modes include plastic deformation and fracture in the column, frame, and beam connection areas, bending deformation of cabin floor beams, and failure of connectors. Since all columns bend and break near the connection areas, the other parts of the columns are almost entirely free of plastic deformation, resulting in limited energy absorption by the columns. The new substructure proposed in this study features a novel configuration that fully leverages the advantages of metal plastic deformation. Compared to the original configuration, the new substructure exhibits more uniform deformation while maintaining the same total mass of the fuselage structure. It significantly reduces the peak load and acceleration at the early stage of the crash. The proportion of energy absorption by the frame and energy-absorbing components has increased markedly. After optimization, the average overload of the new fuselage substructure is reduced by 30.8% compared to the original configuration. The average acceleration of the two mass points on the cabin floor of the new fuselage substructure is reduced by 25.0% and 37.6%, respectively, compared to the original configuration. These findings provide valuable insights and references for the crashworthiness design of aircraft fuselage substructures.
To investigate the crashworthiness and energy absorption characteristics of aircraft fuselage substructures and to conduct structural crashworthiness design, this study focuses on a typical metal aircraft fuselage as the research object. A drop test of a typical fuselage substructure was performed, and the energy absorption characteristics were evaluated based on both experimental and simulation analysis results. Subsequently, an energy absorption design for the fuselage substructure was developed. The influence of structural layout parameters on the crash response of the new fuselage substructure was examined through simulation analysis. Comparisons were made regarding structural deformation, impact force-time curves, acceleration responses, and energy absorption for fuselage substructures with different layout parameters. The results indicate that during the crash process of the original structure, the primary energy absorption modes include plastic deformation and fracture in the column, frame, and beam connection areas, bending deformation of cabin floor beams, and failure of connectors. Since all columns bend and break near the connection areas, the other parts of the columns are almost entirely free of plastic deformation, resulting in limited energy absorption by the columns. The new substructure proposed in this study features a novel configuration that fully leverages the advantages of metal plastic deformation. Compared to the original configuration, the new substructure exhibits more uniform deformation while maintaining the same total mass of the fuselage structure. It significantly reduces the peak load and acceleration at the early stage of the crash. The proportion of energy absorption by the frame and energy-absorbing components has increased markedly. After optimization, the average overload of the new fuselage substructure is reduced by 30.8% compared to the original configuration. The average acceleration of the two mass points on the cabin floor of the new fuselage substructure is reduced by 25.0% and 37.6%, respectively, compared to the original configuration. These findings provide valuable insights and references for the crashworthiness design of aircraft fuselage substructures.
2025,
45(7):
071411.
doi: 10.11883/bzycj-2024-0227
Abstract:
The small-scale test has several advantages, such as low cost, low risk, and short duration, and has been widely applied in aerospace and other fields. Taking the lower structure of a typical civil aircraft fuselage as the research object, this study conducted theoretical analysis and experimental methodology of scaling on the impact crashworthiness of civil aircraft structures. Using a dimensional analysis, the complex dynamics of the fuselage crash were simplified to identify key physical parameters and processes. The main objects, critical physical parameters, and physical processes involved in the aircraft crash were discussed, leading to the extraction of key basic physical parameters and the derivation of primary dimensionless numbers that control the crash response of the fuselage structure. Based on the Buckingham Π theorem, the scaling factor for civil aircraft crashes was derived, establishing the small-scale experimental methodology. A 1/4 scale experimental model was designed and fabricated, and an impact test at a speed of 6 m/s was performed. The velocity, acceleration, ground impact load, deformation, and failure modes of key components in both full-scale and small-scale crash tests were obtained and compared. The applicability and accuracy of the small-scale theory in the crash experiment of the civil aircraft fuselage frame section were verified. The results show that the deformation and failure modes of the frames and columns of the 1/4 scale model are in good agreement with those of the full-scale model. The peak crash load prediction error of the small-scale structure for the full-scale prototype structure is 14.4%, the peak seat acceleration prediction error is 14.8%, and the peak acceleration prediction error at the beam is 13.1%. The small-scale tests can effectively predict the deformation, failure process, and dynamic response of key parts of the full-scale prototype structure. Therefore, the small-scale test could be used to verify and evaluate the crash performance of civil aircraft structures.
The small-scale test has several advantages, such as low cost, low risk, and short duration, and has been widely applied in aerospace and other fields. Taking the lower structure of a typical civil aircraft fuselage as the research object, this study conducted theoretical analysis and experimental methodology of scaling on the impact crashworthiness of civil aircraft structures. Using a dimensional analysis, the complex dynamics of the fuselage crash were simplified to identify key physical parameters and processes. The main objects, critical physical parameters, and physical processes involved in the aircraft crash were discussed, leading to the extraction of key basic physical parameters and the derivation of primary dimensionless numbers that control the crash response of the fuselage structure. Based on the Buckingham Π theorem, the scaling factor for civil aircraft crashes was derived, establishing the small-scale experimental methodology. A 1/4 scale experimental model was designed and fabricated, and an impact test at a speed of 6 m/s was performed. The velocity, acceleration, ground impact load, deformation, and failure modes of key components in both full-scale and small-scale crash tests were obtained and compared. The applicability and accuracy of the small-scale theory in the crash experiment of the civil aircraft fuselage frame section were verified. The results show that the deformation and failure modes of the frames and columns of the 1/4 scale model are in good agreement with those of the full-scale model. The peak crash load prediction error of the small-scale structure for the full-scale prototype structure is 14.4%, the peak seat acceleration prediction error is 14.8%, and the peak acceleration prediction error at the beam is 13.1%. The small-scale tests can effectively predict the deformation, failure process, and dynamic response of key parts of the full-scale prototype structure. Therefore, the small-scale test could be used to verify and evaluate the crash performance of civil aircraft structures.
2025,
45(7):
071412.
doi: 10.11883/bzycj-2024-0315
Abstract:
Structural damages in solid propellants can lead to combustion anomalies and affect ballistic performance. Utilizing synchrotron radiation X-ray computed tomography technology and an in-situ mechanical loading test system, the macro-meso structures of nitrate ester plasticized polyether (NEPE) solid propellant were observed in-situ at compressive rates of 0.1, 1.0, and 5.0 mm/s. The compressive process employed an intermittent loading mode. With loading paused each time the preset displacement was reached to enable scanning imaging, thereby capturing the state of the propellant at specific phases during compression. Following the in-situ imaging experiment, the tomographic images of the samples were processed through projection correction and phase recovery using PITRE and PITRE_BM software, followed by image bit-depth conversion to obtain 8-bit 2D grayscale slices. Through 3D reconstruction, the typical damages and evolutionary behaviors of the solid propellant were analyzed, exploring the macroscopic deformation as well as the distribution and propagation patterns of internal micro-cracks. Results indicate that most micro-cracks nucleate and grow at the interface between filled particles and the matrix, with meso-pore evolution being rate-dependent. Unlike the continuous damage growth under tensile loading, the nucleation, growth, and closure of pores occur simultaneously during compression. Under high-rate uniaxial compressive loading, the solid propellant exhibits characteristic trumpet-shaped deformation, with spatially distributed cracks primarily located around the propellant. Macroscopic surface damage results from micro-crack propagation between near-surface particles and the matrix, with crack propagation related to the spatial location of filled particles. Transversal and axial crack propagation modes exist under dynamic compressive loading, with the transition from vertically to horizontally oriented cracks in the matrix leading to crack closure.
Structural damages in solid propellants can lead to combustion anomalies and affect ballistic performance. Utilizing synchrotron radiation X-ray computed tomography technology and an in-situ mechanical loading test system, the macro-meso structures of nitrate ester plasticized polyether (NEPE) solid propellant were observed in-situ at compressive rates of 0.1, 1.0, and 5.0 mm/s. The compressive process employed an intermittent loading mode. With loading paused each time the preset displacement was reached to enable scanning imaging, thereby capturing the state of the propellant at specific phases during compression. Following the in-situ imaging experiment, the tomographic images of the samples were processed through projection correction and phase recovery using PITRE and PITRE_BM software, followed by image bit-depth conversion to obtain 8-bit 2D grayscale slices. Through 3D reconstruction, the typical damages and evolutionary behaviors of the solid propellant were analyzed, exploring the macroscopic deformation as well as the distribution and propagation patterns of internal micro-cracks. Results indicate that most micro-cracks nucleate and grow at the interface between filled particles and the matrix, with meso-pore evolution being rate-dependent. Unlike the continuous damage growth under tensile loading, the nucleation, growth, and closure of pores occur simultaneously during compression. Under high-rate uniaxial compressive loading, the solid propellant exhibits characteristic trumpet-shaped deformation, with spatially distributed cracks primarily located around the propellant. Macroscopic surface damage results from micro-crack propagation between near-surface particles and the matrix, with crack propagation related to the spatial location of filled particles. Transversal and axial crack propagation modes exist under dynamic compressive loading, with the transition from vertically to horizontally oriented cracks in the matrix leading to crack closure.
2025,
45(7):
071413.
doi: 10.11883/bzycj-2024-0477
Abstract:
K447A, a nickel-based superalloy, is widely used in critical hot-end components of aerospace engines due to its excellent high-temperature performance. Through quasi-static and high strain rate compression experiments within the temperature range of 25 ℃ to1000 ℃, the dynamic mechanical properties of K447A superalloy were systematically investigated. The effects of temperature and strain rate on its plastic flow behavior and material microstructure were analyzed. By examining the stress-strain curves under quasi-static conditions and utilizing electron backscatter diffraction (EBSD), the microstructural characteristics of specimens deformed at various strain rates and temperatures were analyzed. The results reveal that during the plastic deformation of K447A, strain hardening, temperature softening, and strain rate strengthening phenomena coexist. As the strain rate increases from quasi-static levels to 5000 s−1, the temperature sensitivity index (s) gradually decreases, indicating a diminishing temperature softening effect at higher strain rates. Notably, at an elevated strain rate of 800 ℃, an anomalous stress peak appears in the flow stress-strain curve of the K447A alloy, suggesting complex interactions between temperature and strain rate during deformation. Furthermore, the strain rate sensitivity coefficient (p) increases with temperature, highlighting a more pronounced strain rate strengthening effect at elevated temperatures. Microstructural changes within the material, which are influenced by the coupling of strain rate and temperature, are also examined. An increase in strain rate leads to grain refinement, while higher temperatures result in a decrease in the proportion of low-angle grain boundaries, facilitating dynamic recrystallization within the material. To accurately describe the flow stress influenced by the interplay of temperature and strain rate, a modified Johnson-Cook constitutive model was developed. This revised model demonstrates improved predictive capability compared to the original formulation, effectively capturing the plastic flow behavior of K447A across a broad range of temperatures and strain rates. The predictive error is significantly reduced from 26.36% to 9.05%, underscoring the model’s enhanced accuracy and reliability in simulating the mechanical performance of K447A alloy under varying operational conditions.
K447A, a nickel-based superalloy, is widely used in critical hot-end components of aerospace engines due to its excellent high-temperature performance. Through quasi-static and high strain rate compression experiments within the temperature range of 25 ℃ to
2025,
45(7):
071414.
doi: 10.11883/bzycj-2024-0448
Abstract:
To enhance the evaluation and prediction for service performance of hot-end components in equipment under the dynamic loads, a comprehensive study was conducted on Ni-based single crystal superalloys with diverse microstructures. This study involved a series of split Hopkinson tensile bar (SHTB) tests and related scanning electron microscopy (SEM) characterization. The influences of various factors, including the volume fraction of precipitation particles, phase coarsening, loading angle and strain rate, etc., on the dynamic tensile properties of superalloys were systematically investigated. Moreover, the relationships between these factors and the fracture morphology of alloys were thoroughly discussed. The results indicated that the microstructural features and strain rate have significant effect on the dynamic tensile properties of alloys, leading to a complex anisotropic characteristic occur in their dynamic tensile behaviors after phase coarsening. In general, the yielding strength displays a positive relationship with the tensile strength. As the volume fraction of precipitation particles or the strain rate increases, the alloy specimen gradually exhibits brittle fracture characteristics, with an increase in strength and a decrease in elongation. Besides, phase coarsening derived from the aging treatment significantly weakens the strength of alloys while enhancing their elongation, i.e., the specimens progressively show mixed fracture characteristics after phase coarsening, and both yielding strength and tensile ultimate strength gradually decrease while the elongation increases with the degree of phase coarsening. Furthermore, the strength and elongation of alloys at the loading angle of 55° are lower than those at the loading angle of 0°. Comparatively, for alloys with high volume fraction of precipitation particles and high degree of phase coarsening, the elongation achieves the maximum value at the loading angle of 55°. The corresponding variation characteristics are closely related to the fibrous zone and the cleavage plane on the fracture surface. Meanwhile, the variations in microstructure of materials and loading conditions affect the microcrack nucleation and fracture mode within the specimen, leading to various dynamic tensile properties in Ni-based single crystal superalloys. The present research and related results provide theoretical guidance and experimental data support for improving the mechanical performance of Ni-based single crystal superalloys and optimizing the design of hot-end components.
To enhance the evaluation and prediction for service performance of hot-end components in equipment under the dynamic loads, a comprehensive study was conducted on Ni-based single crystal superalloys with diverse microstructures. This study involved a series of split Hopkinson tensile bar (SHTB) tests and related scanning electron microscopy (SEM) characterization. The influences of various factors, including the volume fraction of precipitation particles, phase coarsening, loading angle and strain rate, etc., on the dynamic tensile properties of superalloys were systematically investigated. Moreover, the relationships between these factors and the fracture morphology of alloys were thoroughly discussed. The results indicated that the microstructural features and strain rate have significant effect on the dynamic tensile properties of alloys, leading to a complex anisotropic characteristic occur in their dynamic tensile behaviors after phase coarsening. In general, the yielding strength displays a positive relationship with the tensile strength. As the volume fraction of precipitation particles or the strain rate increases, the alloy specimen gradually exhibits brittle fracture characteristics, with an increase in strength and a decrease in elongation. Besides, phase coarsening derived from the aging treatment significantly weakens the strength of alloys while enhancing their elongation, i.e., the specimens progressively show mixed fracture characteristics after phase coarsening, and both yielding strength and tensile ultimate strength gradually decrease while the elongation increases with the degree of phase coarsening. Furthermore, the strength and elongation of alloys at the loading angle of 55° are lower than those at the loading angle of 0°. Comparatively, for alloys with high volume fraction of precipitation particles and high degree of phase coarsening, the elongation achieves the maximum value at the loading angle of 55°. The corresponding variation characteristics are closely related to the fibrous zone and the cleavage plane on the fracture surface. Meanwhile, the variations in microstructure of materials and loading conditions affect the microcrack nucleation and fracture mode within the specimen, leading to various dynamic tensile properties in Ni-based single crystal superalloys. The present research and related results provide theoretical guidance and experimental data support for improving the mechanical performance of Ni-based single crystal superalloys and optimizing the design of hot-end components.
2025,
45(7):
071415.
doi: 10.11883/bzycj-2024-0453
Abstract:
With the deterioration of the natural climate, hail impact has become a threat that cannot be ignored by civil aircraft. To study the hail impact damage characteristics of high-performance carbon fiber composites used for civil aircraft, we first investigated the impact force characteristics of ice spheres under high-speed impact through experiments, and the impact force time history curves of ice spheres under different speeds were obtained using an air cannon test system. At the same time, to make the speed range of the ice sphere more extensive, some existing experiment data were introduced as a comparison to obtain the linear growth relationship between the peak impact force and the kinetic energy of the ice sphere. Subsequently, a single ice sphere impact test was conducted on the T800/3200 carbon fiber composite laminates. It was found that the concave of the front core damage area forms a 45° angle with the boundary of the target plate, which is related to the carbon fiber layup mode, and the damage degree depends on the initial speed of the ice sphere. To further quantify the relationship between the damage degree of the laminate and the kinetic energy of the ice sphere, ultrasonic C-scanning was used to obtain the damaged area of the target plate, and the damage percentage was extracted by software analysis. The results show that the percentage of internal interlayer delamination increases linearly with the kinetic energy of the ice sphere. After that, repeated impact tests of ice spheres were carried out on the target plate with the same thickness, and as expected, the macro damage degree increased with the number of impacts. Finally, the front and back surfaces of the composite laminates were completely delaminated, resulting in a large number of fibers being pulled out and displaying a penetrating through-thickness damage pattern. The deflection of the center point of the target plate was selected as the quantitative damage index, and according to the data analysis of the measured results, it was found that there is a quadratic relationship between the deflection of the center point of the carbon fiber plate and the accumulated kinetic energy of the ice sphere. The apex of the parabola can well reflect the accumulated kinetic energy required for the target plate penetration.
With the deterioration of the natural climate, hail impact has become a threat that cannot be ignored by civil aircraft. To study the hail impact damage characteristics of high-performance carbon fiber composites used for civil aircraft, we first investigated the impact force characteristics of ice spheres under high-speed impact through experiments, and the impact force time history curves of ice spheres under different speeds were obtained using an air cannon test system. At the same time, to make the speed range of the ice sphere more extensive, some existing experiment data were introduced as a comparison to obtain the linear growth relationship between the peak impact force and the kinetic energy of the ice sphere. Subsequently, a single ice sphere impact test was conducted on the T800/3200 carbon fiber composite laminates. It was found that the concave of the front core damage area forms a 45° angle with the boundary of the target plate, which is related to the carbon fiber layup mode, and the damage degree depends on the initial speed of the ice sphere. To further quantify the relationship between the damage degree of the laminate and the kinetic energy of the ice sphere, ultrasonic C-scanning was used to obtain the damaged area of the target plate, and the damage percentage was extracted by software analysis. The results show that the percentage of internal interlayer delamination increases linearly with the kinetic energy of the ice sphere. After that, repeated impact tests of ice spheres were carried out on the target plate with the same thickness, and as expected, the macro damage degree increased with the number of impacts. Finally, the front and back surfaces of the composite laminates were completely delaminated, resulting in a large number of fibers being pulled out and displaying a penetrating through-thickness damage pattern. The deflection of the center point of the target plate was selected as the quantitative damage index, and according to the data analysis of the measured results, it was found that there is a quadratic relationship between the deflection of the center point of the carbon fiber plate and the accumulated kinetic energy of the ice sphere. The apex of the parabola can well reflect the accumulated kinetic energy required for the target plate penetration.
2025,
45(7):
071416.
doi: 10.11883/bzycj-2024-0355
Abstract:
The characteristics of flash radiation during hypervelocity impact processes were investigated using a flash radiation test system established on a two-stage light gas gun platform. The study explored how impact velocity, projectile diameter, and target chamber vacuum level affect the frequency and time characteristics of flash radiation. The flash radiation test system was designed to precisely measure the frequency and time domain of the flash radiation emitted during hypervelocity impacts. The system is composed of a two-stage light gas gun capable of achieving high impact velocities, a vacuum chamber to control the environmental pressure, and a high-speed spectrometer to capture the emitted radiation. The experimental setup enabled the systematic variation of impact velocity, projectile diameter, and target chamber vacuum level, allowing for a comprehensive study of their individual and combined effects on flash radiation characteristics. The results indicate that the flash radiation in the frequency domain exhibits a dual-component structure, comprising discrete line spectra with fixed wavelengths and continuous spectra. Higher impact velocities and larger projectile diameters, which increase the initial kinetic energy of the impact, enhance the radiation intensity of the flash. Additionally, higher environmental pressures of target chamber increase the frictional heating between the projectile and the gas, further increasing flash radiation intensity. During the decay phase of the flash, increasing the impact velocity raises the plasma concentration, prolongs the duration of the flash, but accelerates the flash temperature decay. In contrast, the projectile diameter has an insignificant effect on the duration and temperature of the flash. Reducing the environmental pressure of target chamber decreases the attenuation during the flash radiation process and extends the duration of the flash. In conclusion, the study provides a comprehensive understanding of the factors influencing flash radiation during hypervelocity impacts. The findings highlight the importance of impact velocity and projectile diameter in determining the intensity and duration of flash radiation and reveal the significant role of environmental pressure of target chamber in modifying the radiation characteristics. These results offer valuable insights for the design and analysis of hypervelocity impact experiments and contribute to the broader understanding of impact physics.
The characteristics of flash radiation during hypervelocity impact processes were investigated using a flash radiation test system established on a two-stage light gas gun platform. The study explored how impact velocity, projectile diameter, and target chamber vacuum level affect the frequency and time characteristics of flash radiation. The flash radiation test system was designed to precisely measure the frequency and time domain of the flash radiation emitted during hypervelocity impacts. The system is composed of a two-stage light gas gun capable of achieving high impact velocities, a vacuum chamber to control the environmental pressure, and a high-speed spectrometer to capture the emitted radiation. The experimental setup enabled the systematic variation of impact velocity, projectile diameter, and target chamber vacuum level, allowing for a comprehensive study of their individual and combined effects on flash radiation characteristics. The results indicate that the flash radiation in the frequency domain exhibits a dual-component structure, comprising discrete line spectra with fixed wavelengths and continuous spectra. Higher impact velocities and larger projectile diameters, which increase the initial kinetic energy of the impact, enhance the radiation intensity of the flash. Additionally, higher environmental pressures of target chamber increase the frictional heating between the projectile and the gas, further increasing flash radiation intensity. During the decay phase of the flash, increasing the impact velocity raises the plasma concentration, prolongs the duration of the flash, but accelerates the flash temperature decay. In contrast, the projectile diameter has an insignificant effect on the duration and temperature of the flash. Reducing the environmental pressure of target chamber decreases the attenuation during the flash radiation process and extends the duration of the flash. In conclusion, the study provides a comprehensive understanding of the factors influencing flash radiation during hypervelocity impacts. The findings highlight the importance of impact velocity and projectile diameter in determining the intensity and duration of flash radiation and reveal the significant role of environmental pressure of target chamber in modifying the radiation characteristics. These results offer valuable insights for the design and analysis of hypervelocity impact experiments and contribute to the broader understanding of impact physics.
2025,
45(7):
071421.
doi: 10.11883/bzycj-2024-0522
Abstract:
A study was conducted to investigate the crash impact response of the lower fuselage structure of a typical civil aircraft with an auxiliary fuel tank installed. The results of vertical crash tests conducted at impact velocities of 1.53, 2.78 and 5.96 m/s were obtained. These results include the influence of installing auxiliary fuel tanks on the impact response and the structural deformation and damage of the lower fuselage structure. The validity of the corresponding finite element model was verified through a correlation analysis between the simulation and test results. The impact energy absorption form during the vertical crash process was analyzed through simulation results. The results show that the structure mainly deforms elastically with only slight plastic deformation under the impact condition of 1.53 m/s. Under the impact condition of 2.78 m/s, the fuselage frames, skin, and T-shaped support components of the cargo floor are mainly deformed by bending, and the total structures were slightly compressed. The T-shaped support components connected to the left cargo floor slide rails extended upward and did not touch the fuel tank. Under the impact condition of 5.96 m/s, the lower fuselage structures were seriously compressed and the left diagonal brace was fractured under pressure. The auxiliary fuel tank sank to the cargo floor. The simulation analysis can effectively model the deformation and damage of the structure during the vertical crash process at different impact velocities. The impact force on the ground and the trend of acceleration at typical locations obtained by analysis are in good agreement with the test results. The analysis results show that the fuselage frame is the main deformation and energy absorption component in the crash of the lower fuselage structure equipped with auxiliary fuel tanks. The skin and auxiliary fuel tank are the secondary structures that participate in deformation and energy absorption. As the auxiliary fuel tank is filled with more fuel, the simulation results show that the energy absorption capacity of the auxiliary fuel tank and the lower fuselage structure components increases, i.e., the degree of damage becomes more serious. The research results can provide support for the anti-crash design, analysis, and verification of the fuselage structure of civil aircraft with auxiliary fuel tanks installed.
A study was conducted to investigate the crash impact response of the lower fuselage structure of a typical civil aircraft with an auxiliary fuel tank installed. The results of vertical crash tests conducted at impact velocities of 1.53, 2.78 and 5.96 m/s were obtained. These results include the influence of installing auxiliary fuel tanks on the impact response and the structural deformation and damage of the lower fuselage structure. The validity of the corresponding finite element model was verified through a correlation analysis between the simulation and test results. The impact energy absorption form during the vertical crash process was analyzed through simulation results. The results show that the structure mainly deforms elastically with only slight plastic deformation under the impact condition of 1.53 m/s. Under the impact condition of 2.78 m/s, the fuselage frames, skin, and T-shaped support components of the cargo floor are mainly deformed by bending, and the total structures were slightly compressed. The T-shaped support components connected to the left cargo floor slide rails extended upward and did not touch the fuel tank. Under the impact condition of 5.96 m/s, the lower fuselage structures were seriously compressed and the left diagonal brace was fractured under pressure. The auxiliary fuel tank sank to the cargo floor. The simulation analysis can effectively model the deformation and damage of the structure during the vertical crash process at different impact velocities. The impact force on the ground and the trend of acceleration at typical locations obtained by analysis are in good agreement with the test results. The analysis results show that the fuselage frame is the main deformation and energy absorption component in the crash of the lower fuselage structure equipped with auxiliary fuel tanks. The skin and auxiliary fuel tank are the secondary structures that participate in deformation and energy absorption. As the auxiliary fuel tank is filled with more fuel, the simulation results show that the energy absorption capacity of the auxiliary fuel tank and the lower fuselage structure components increases, i.e., the degree of damage becomes more serious. The research results can provide support for the anti-crash design, analysis, and verification of the fuselage structure of civil aircraft with auxiliary fuel tanks installed.
2025,
45(7):
071422.
doi: 10.11883/bzycj-2024-0371
Abstract:
The containment process of aero-engine casing is very complex, which involves large deformation, material viscoplasticity and nonlinear dynamic response of structural elements. To meet the fan casing containment assessment requirements of engine, a new method combining ballistic impact test and finite element analysis is proposed to evaluate the casing containment capability. A blade-liked projectile was used to impact the half ring simulator to obtain the impact resistance of the titanium alloy casing. The high-speed cameras were positioned perpendicular to the projectile's trajectory to accurately capture and measure its velocities both before and after impact.. The DIC (digital image correlation) technology is used to determine the deformation field of the half ring simulator. Based on the contact-impact dynamics software, a corresponding numerical simulation model was established. The residual velocity of the projectile, radial deformation of the target, and the morphology of structural damage of numerical predictions are compared with those of experimental results. The good agreement between the two results indicated the accuracy of the numerical method. Under the low energy impact, the projectile was rebound, and the half ring absorbed energy with bulge. Whereas in the high energy impact, the projectile penetrated the half ring target and result in tear in the rear surface. Finally, the validated numerical simulation method was employed to simulate the real fan blade/casing containment process, and the effect of the blade rotate speed and the blade size on casing containment are studied. The results show that the fan casing in rotating state can contain more impact energy than that in ballistic impact test. It is suggested that the design for the ballistic impact test can be scaled to 0.76 times the size of the real containment system. Additionally, a parametric correlation model is developed between the casing containment capacity and the characteristics of the released blade, especially the rotate speed and size. It is found that the internal energy of the casing is in a quartic relationship with the blade released speed and a quadratic relationship with the blade size. Moreover, as the blade size increases, the critical containment speed of the casing decreases exponentially.
The containment process of aero-engine casing is very complex, which involves large deformation, material viscoplasticity and nonlinear dynamic response of structural elements. To meet the fan casing containment assessment requirements of engine, a new method combining ballistic impact test and finite element analysis is proposed to evaluate the casing containment capability. A blade-liked projectile was used to impact the half ring simulator to obtain the impact resistance of the titanium alloy casing. The high-speed cameras were positioned perpendicular to the projectile's trajectory to accurately capture and measure its velocities both before and after impact.. The DIC (digital image correlation) technology is used to determine the deformation field of the half ring simulator. Based on the contact-impact dynamics software, a corresponding numerical simulation model was established. The residual velocity of the projectile, radial deformation of the target, and the morphology of structural damage of numerical predictions are compared with those of experimental results. The good agreement between the two results indicated the accuracy of the numerical method. Under the low energy impact, the projectile was rebound, and the half ring absorbed energy with bulge. Whereas in the high energy impact, the projectile penetrated the half ring target and result in tear in the rear surface. Finally, the validated numerical simulation method was employed to simulate the real fan blade/casing containment process, and the effect of the blade rotate speed and the blade size on casing containment are studied. The results show that the fan casing in rotating state can contain more impact energy than that in ballistic impact test. It is suggested that the design for the ballistic impact test can be scaled to 0.76 times the size of the real containment system. Additionally, a parametric correlation model is developed between the casing containment capacity and the characteristics of the released blade, especially the rotate speed and size. It is found that the internal energy of the casing is in a quartic relationship with the blade released speed and a quadratic relationship with the blade size. Moreover, as the blade size increases, the critical containment speed of the casing decreases exponentially.
2025,
45(7):
071423.
doi: 10.11883/bzycj-2024-0363
Abstract:
The hose-drogue aerial refueling process involves the complex coupling of aerodynamic force, fuel flow, and flexible structure deformation. Solving these interactions requires advanced simulation techniques and significant computational resources, which posed challenges to the accuracy and safety of practical implementations. A novel fluid-solid coupling model and methodology integrating aerodynamic loads, wake vortex effects, hose flexibility, airflow and internal fuel flow were developed to analyze structural deformation of hose-drogue assembly during docking and fuel transfer phases, overcoming limitations of traditional kinetic equation modeling. The aerodynamic forces of the paradrogue were obtained by performing separate CFD modeling on the paradrogue and conducting steady-state calculations. Meanwhile, the stabilizing moment of the paradrogue was equivalently converted into the lateral and rotational boundary condition at the center point of the paradrogue. Subsequently, based on the Hallock-Burnham model, the analytical expressions of the aerodynamic loads on the hose-drogue assembly under the action of the wake vortex alone were derived, and the aerodynamic loads were applied to hose-drogue assembly by ABAQUS subroutine. With the proposed model, the multi-stage operational processes of hose-drogue aerial refueling including steady-state, docking-state and refueling-state were calculated. Fluid-solid coupling simulations, which were conducted through co-simulation, demonstrated excellent agreement with experimental data, particularly under the steady-state. Furthermore, the influence of fuel flow characteristics, docking parameters and flight parameters were systematically identified. The results show that the matching relationship between the docking speed and retracting acceleration is the main influencing factor of whiplash load, and the retracting acceleration is positively correlated with the magnitude of the optimally matched docking velocity. In addition, the flight parameters are the secondary influencing factors. When the fuel flow is not considered, it is established at each altitude that the higher the flight speed, the lower the whiplash load. Fuel flow dynamics acts as a disturbing factor that partially perturbs the established relationship between whiplash loads and key operational parameters. However, these disturbances do not fundamentally alter the overall trend, and therefore, analyses under specific conditions are imperative to account for the effects of the fuel flow in different situations.
The hose-drogue aerial refueling process involves the complex coupling of aerodynamic force, fuel flow, and flexible structure deformation. Solving these interactions requires advanced simulation techniques and significant computational resources, which posed challenges to the accuracy and safety of practical implementations. A novel fluid-solid coupling model and methodology integrating aerodynamic loads, wake vortex effects, hose flexibility, airflow and internal fuel flow were developed to analyze structural deformation of hose-drogue assembly during docking and fuel transfer phases, overcoming limitations of traditional kinetic equation modeling. The aerodynamic forces of the paradrogue were obtained by performing separate CFD modeling on the paradrogue and conducting steady-state calculations. Meanwhile, the stabilizing moment of the paradrogue was equivalently converted into the lateral and rotational boundary condition at the center point of the paradrogue. Subsequently, based on the Hallock-Burnham model, the analytical expressions of the aerodynamic loads on the hose-drogue assembly under the action of the wake vortex alone were derived, and the aerodynamic loads were applied to hose-drogue assembly by ABAQUS subroutine. With the proposed model, the multi-stage operational processes of hose-drogue aerial refueling including steady-state, docking-state and refueling-state were calculated. Fluid-solid coupling simulations, which were conducted through co-simulation, demonstrated excellent agreement with experimental data, particularly under the steady-state. Furthermore, the influence of fuel flow characteristics, docking parameters and flight parameters were systematically identified. The results show that the matching relationship between the docking speed and retracting acceleration is the main influencing factor of whiplash load, and the retracting acceleration is positively correlated with the magnitude of the optimally matched docking velocity. In addition, the flight parameters are the secondary influencing factors. When the fuel flow is not considered, it is established at each altitude that the higher the flight speed, the lower the whiplash load. Fuel flow dynamics acts as a disturbing factor that partially perturbs the established relationship between whiplash loads and key operational parameters. However, these disturbances do not fundamentally alter the overall trend, and therefore, analyses under specific conditions are imperative to account for the effects of the fuel flow in different situations.
2025,
45(7):
071424.
doi: 10.11883/bzycj-2024-0265
Abstract:
To enhance the hypervelocity impact protection performance of Whipple shields against high-speed space debris, an aluminum spherical micro-airbag array metastructure was designed without incorporating additional energy-absorbing materials such as porous materials or carbon fibers. This metastructure was fabricated using 3D printing technology. The protective performance of the Whipple shield was investigated and analyzed by constructing a numerical model of a spherical projectile with an initial velocity of 7.5 km/s impacting both the single-layer aluminum plate and the aluminum spherical micro-airbag metastructure. The finite element method is often inadequate for accurately calculating large plastic deformations and fracture damage problems, particularly when mesh distortions are involved. Therefore, the material point method (MPM) was employed in this study to simulate hypervelocity impact scenarios. After verifying the reliability of the MPM calculations through experiments, a three-dimensional numerical simulation of hypervelocity impacts on the Whipple shield was conducted. The mechanism of energy absorption and dissipation by the aluminum spherical micro-airbag metastructure was elucidated through a comparative analysis of the perforation size, debris cloud morphology, and key parameters such as velocity, momentum, energy, and temperature with those of a single-layer aluminum plate subjected to hypervelocity impact. The results indicate that the Whipple shield with the aluminum spherical micro-airbag metastructure reduces the axial kinetic energy of the projectile by 300 J more than the single-layer aluminum plate. In addition, the maximum expansion radius of the debris cloud is 32.2 mm larger than that of the single-layer aluminum plate. These findings demonstrate that the Whipple shield with the aluminum spherical micro-airbag metastructure significantly enhances protection against hypervelocity impacts from space debris. Moreover, when compared with relevant experimental data, the material point method simulation proves to be an effective computational tool for researching and developing new types of Whipple shields.
To enhance the hypervelocity impact protection performance of Whipple shields against high-speed space debris, an aluminum spherical micro-airbag array metastructure was designed without incorporating additional energy-absorbing materials such as porous materials or carbon fibers. This metastructure was fabricated using 3D printing technology. The protective performance of the Whipple shield was investigated and analyzed by constructing a numerical model of a spherical projectile with an initial velocity of 7.5 km/s impacting both the single-layer aluminum plate and the aluminum spherical micro-airbag metastructure. The finite element method is often inadequate for accurately calculating large plastic deformations and fracture damage problems, particularly when mesh distortions are involved. Therefore, the material point method (MPM) was employed in this study to simulate hypervelocity impact scenarios. After verifying the reliability of the MPM calculations through experiments, a three-dimensional numerical simulation of hypervelocity impacts on the Whipple shield was conducted. The mechanism of energy absorption and dissipation by the aluminum spherical micro-airbag metastructure was elucidated through a comparative analysis of the perforation size, debris cloud morphology, and key parameters such as velocity, momentum, energy, and temperature with those of a single-layer aluminum plate subjected to hypervelocity impact. The results indicate that the Whipple shield with the aluminum spherical micro-airbag metastructure reduces the axial kinetic energy of the projectile by 300 J more than the single-layer aluminum plate. In addition, the maximum expansion radius of the debris cloud is 32.2 mm larger than that of the single-layer aluminum plate. These findings demonstrate that the Whipple shield with the aluminum spherical micro-airbag metastructure significantly enhances protection against hypervelocity impacts from space debris. Moreover, when compared with relevant experimental data, the material point method simulation proves to be an effective computational tool for researching and developing new types of Whipple shields.
2025,
45(7):
071425.
doi: 10.11883/bzycj-2024-0454
Abstract:
Impact damage and fatigue are emerging challenges in the defense industry and civil infrastructure. The more pronounced material size effect induced by advanced manufacturing processes makes mechanical analysis and life prediction in these contexts more complex. Currently, there is no convenient and effective method for predicting and designing the cross-scale impact damage and fatigue performance of metal materials. This research is based on the metallic plasticity mechanisms in the impact damage and fatigue processes, investigating the material performance under the influence of the material size effect during the impact damage process. A non-local, cross-scale impact and damage constitutive theory for metallic materials was developed, and an impact damage and fatigue simulation method for advanced manufactured metals was established. This method used the conventional theory of mechanism-based strain gradient (CMSG) to describe the size effect and was built on the Johnson-Cook impact dynamics model and Lemaitre impact damage model to describe cross-scale impact dynamics and damage evolution. This approach could be conveniently implemented in finite element analysis with the VUMAT and relevant subroutines. The present work established uniaxial and U-notch bending finite element models and verified the influence of work hardening, strain rate hardening, size effect, and damage effect on static and impact dynamic response of metals. Simulation results indicated the material behavior corresponds to the material characteristic and constitutive design. The distribution and evolution of the stress, strain, strain gradient, and damage before and after material failure are also discussed. The results show that the inhomogeneous deformation caused by advanced manufacturing processes leads to higher strain gradients, which further increase the flow stress through work hardening and strain rate hardening effects and strengthen the material. However, this also causes the material to enter the damage stage earlier, leading to reduced impact and fatigue-bearing capacity or premature failure. These findings are consistent with the inherent trade-off between strength and toughness of metallic materials.
Impact damage and fatigue are emerging challenges in the defense industry and civil infrastructure. The more pronounced material size effect induced by advanced manufacturing processes makes mechanical analysis and life prediction in these contexts more complex. Currently, there is no convenient and effective method for predicting and designing the cross-scale impact damage and fatigue performance of metal materials. This research is based on the metallic plasticity mechanisms in the impact damage and fatigue processes, investigating the material performance under the influence of the material size effect during the impact damage process. A non-local, cross-scale impact and damage constitutive theory for metallic materials was developed, and an impact damage and fatigue simulation method for advanced manufactured metals was established. This method used the conventional theory of mechanism-based strain gradient (CMSG) to describe the size effect and was built on the Johnson-Cook impact dynamics model and Lemaitre impact damage model to describe cross-scale impact dynamics and damage evolution. This approach could be conveniently implemented in finite element analysis with the VUMAT and relevant subroutines. The present work established uniaxial and U-notch bending finite element models and verified the influence of work hardening, strain rate hardening, size effect, and damage effect on static and impact dynamic response of metals. Simulation results indicated the material behavior corresponds to the material characteristic and constitutive design. The distribution and evolution of the stress, strain, strain gradient, and damage before and after material failure are also discussed. The results show that the inhomogeneous deformation caused by advanced manufacturing processes leads to higher strain gradients, which further increase the flow stress through work hardening and strain rate hardening effects and strengthen the material. However, this also causes the material to enter the damage stage earlier, leading to reduced impact and fatigue-bearing capacity or premature failure. These findings are consistent with the inherent trade-off between strength and toughness of metallic materials.
2025,
45(7):
071426.
doi: 10.11883/bzycj-2024-0513
Abstract:
Cortical bone, as a critical component of the human skeletal system, effectively disperses and absorbs external impact forces, protecting the internal medullary cavity, surrounding soft tissues, and organs from damage. In order to investigate the mechanical response of cortical bone under impact loading, quasi-static and dynamic compression experiments were conducted on porcine cortical bone at varying strain rates using a universal material testing machine and a split Hopkinson pressure bar apparatus. The compression deformation characteristics of cortical bone were observed by employing ultra-depth three-dimensional microscopy and digital image correlation techniques. A viscoelastic damage constitutive model was applied to fit the experimental data, and the model parameters were determined. The results demonstrate that the compression process of cortical bone is characterized by the initiation and propagation of microcracks, and mechanical properties of the material exhibit significant strain-rate dependence. The elastic modulus, yield stress, and compressive strength increase significantly with increasing strain rates. Under quasi-static loading, the stress-strain curve consists of distinct elastic and plastic deformation stages. In contrast, under high-strain-rate loading, the stress-strain response remains purely elastic at strains below 0.2%, but transitions into a highly nonlinear regime with increasing compression. Notably, no significant plastic deformation occurs under dynamic loading, revealing pronounced viscoelastic behavior. Comparison between the experimental data and theoretical curves from the constitutive model shows good agreement, with minimal deviations between predicted and measured values. The model accurately captures the compressive mechanical behavior of cortical bone across different strain rates. This study provides theoretical references for the treatment of impact-induced human injuries and protective designs.
Cortical bone, as a critical component of the human skeletal system, effectively disperses and absorbs external impact forces, protecting the internal medullary cavity, surrounding soft tissues, and organs from damage. In order to investigate the mechanical response of cortical bone under impact loading, quasi-static and dynamic compression experiments were conducted on porcine cortical bone at varying strain rates using a universal material testing machine and a split Hopkinson pressure bar apparatus. The compression deformation characteristics of cortical bone were observed by employing ultra-depth three-dimensional microscopy and digital image correlation techniques. A viscoelastic damage constitutive model was applied to fit the experimental data, and the model parameters were determined. The results demonstrate that the compression process of cortical bone is characterized by the initiation and propagation of microcracks, and mechanical properties of the material exhibit significant strain-rate dependence. The elastic modulus, yield stress, and compressive strength increase significantly with increasing strain rates. Under quasi-static loading, the stress-strain curve consists of distinct elastic and plastic deformation stages. In contrast, under high-strain-rate loading, the stress-strain response remains purely elastic at strains below 0.2%, but transitions into a highly nonlinear regime with increasing compression. Notably, no significant plastic deformation occurs under dynamic loading, revealing pronounced viscoelastic behavior. Comparison between the experimental data and theoretical curves from the constitutive model shows good agreement, with minimal deviations between predicted and measured values. The model accurately captures the compressive mechanical behavior of cortical bone across different strain rates. This study provides theoretical references for the treatment of impact-induced human injuries and protective designs.
