Zhuojin Pipe Fitting Co., LtdAnti-Penetration Mechanism of Honeycomb Steel Tube Confined Concrete Targets Based on Numerical Simulation
Literature Overview
The research by Song Diany i, Meng Zhaomei, and Tan Qinghua from the National University of Defense Technology, the 95979th Unit of the People's Liberation Army, and Guangxi University, published in the Journal of Ballistics (2024, Vol. 36, Issue 3, pp. 82-90), investigates the anti-penetration mechanism of honeycomb steel tube confined concrete targets using numerical simulation with the ANSYS/LS-DYNA software. The study employs a coupled FEM/CSCM-SPH/HJC method to model the penetration process of a hard-core projectile against the composite target. This research is directly relevant to engineers working in protective structure design, steel tube confinement systems, and impact engineering, particularly those involved in military, civil defense, or industrial protection applications.
Target Configuration and Simulation Methodology
The honeycomb steel tube confined concrete target represents an advanced protective structure design that leverages the multi-cell geometry of honeycomb structures to enhance the confinement effect on the concrete infill. The simulation methodology is sophisticated and appropriate for the complex physics involved in high-velocity impact events.
| Component | Description |
|---|---|
| Simulation software | ANSYS/LS-DYNA |
| Coupled method | FEM/CSCM-SPH/HJC |
| Projectile type | Hard-core projectile |
| Target configuration | Honeycomb steel tube confined concrete |
| Comparison targets | Single hexagonal steel tube confined concrete, unconfined concrete |
| Key phases analyzed | Tunnel penetration phase, cratering phase |
The FEM/CSCM-SPH/HJC coupled method is particularly suitable for this problem because it combines the accuracy of finite element methods (FEM) for the steel tube structure with the particle-based smooth particle hydrodynamics (SPH) method for the concrete material, which undergoes severe deformation and fragmentation during impact. The HJC (Hollingworth-Johnson-Cook) constitutive model captures the pressure-strength dependence of concrete under high-strain-rate loading.
Anti-Penetration Mechanism Analysis
The study identifies two primary confinement effects that contribute to the superior anti-penetration performance of the honeycomb steel tube confined concrete target:
Lateral Confinement Effect
The steel tube provides lateral confinement to the concrete, which increases the concrete's compressive strength and deformation capacity under the high-pressure loading conditions generated by projectile impact. This is analogous to the confinement effect in steel tube confined concrete (CTC) columns studied in structural engineering, where the lateral pressure from the steel tube creates a triaxial stress state that enhances concrete performance.
Peripheral Unit Additional Confinement Effect
The honeycomb geometry provides a unique additional confinement mechanism: the peripheral cells of the honeycomb structure provide support to the steel tube walls, restricting out-of-plane bending deformation of the tube walls. This is a geometric confinement effect that is absent in single-cell hexagonal tube targets and unconfined concrete targets.
Comparative Performance Analysis
The study compares three target configurations:
| Target Type | Anti-Penetration Performance | Key Mechanism |
|---|---|---|
| Honeycomb steel tube confined concrete | Superior | Dual confinement (lateral + peripheral unit) |
| Single hexagonal steel tube confined concrete | Moderate | Lateral confinement only |
| Unconfined concrete | Baseline | No confinement |
The superior performance of the honeycomb target is most pronounced during the tunnel penetration phase, where the projectile has penetrated the initial crater and is traveling through the target body. During this phase, the honeycomb structure restricts the radial expansion of concrete near the projectile head, increasing the penetration resistance.
Engineering Design Implications
Steel Tube and Honeycomb Structure Design
From a steel pipe and tube engineering perspective, the honeycomb structure requires careful design of the cell geometry, wall thickness, and material grade. The cell walls must be thin enough to minimize mass but thick enough to resist buckling under the lateral pressure from the concrete during impact. The cell geometry—typically hexagonal for optimal packing density—must be manufactured with consistent dimensions to ensure uniform confinement pressure distribution.
The manufacturing process for honeycomb steel tube structures can include:
- Welded construction — Welding individual tube walls to form the honeycomb pattern. This requires precise welding control to avoid distortion and ensure full-penetration welds.
- Drawn or formed construction — Forming the honeycomb pattern from a flat sheet using deep drawing or rolling processes. This method is more efficient for mass production but requires specialized tooling.
- Additive manufacturing — Using metal 3D printing to create the honeycomb structure directly. This method offers design flexibility but may have limitations in material properties and surface finish.
Material Selection
The steel grade for the honeycomb tube should be selected based on the expected impact energy and the required protective performance. High-strength steels such as ASTM A514 or equivalent grades provide higher yield strength and better energy absorption capacity. However, the ductility must be sufficient to allow plastic deformation without brittle fracture, particularly at the cell wall intersections where stress concentrations are likely.
Concrete Mix Design
The concrete infill must be designed for high strength and toughness under impact loading. The HJC model parameters—yield strength, strain rate sensitivity, damage evolution—must be calibrated for the specific concrete mix used. High-performance concrete (HPC) or ultra-high-performance concrete (UHPC) with compressive strengths exceeding 100 MPa may be appropriate for high-threat applications.
Numerical Modeling Considerations
The accuracy of the numerical simulation depends on several factors that engineers must consider when interpreting the results:
- Constitutive model accuracy — The HJC model for concrete and the appropriate plasticity model for steel must be calibrated with material test data. The strain rate sensitivity parameters are particularly important for impact simulations.
- Mesh quality — The FEM mesh for the steel tube and the SPH particle distribution for the concrete must be fine enough to capture the local deformation and failure patterns. Mesh convergence studies should be performed to verify that the results are not mesh-dependent.
- Contact modeling — The contact algorithms between the projectile, steel tube, and concrete must accurately capture the complex contact patterns that arise during penetration, including friction, penetration resistance, and material interpenetration.
- Boundary conditions — The boundary conditions at the target edges must be representative of the actual support conditions. Fixed boundaries may overestimate the confinement effect, while free boundaries may underestimate it.
Study Insights and Reflections
This research provides valuable insights into the anti-penetration mechanism of honeycomb steel tube confined concrete targets, with particular emphasis on the dual confinement effect that distinguishes honeycomb targets from single-cell tube targets. The finding that the peripheral unit additional confinement effect is a significant contributor to the enhanced performance is an important design insight: the honeycomb geometry is not merely a structural optimization but a functional enhancement of the protective mechanism.
From a manufacturing perspective, the honeycomb steel tube structure represents a challenging fabrication task that requires precision welding or forming processes. The cell wall thickness, cell geometry, and weld quality all influence the protective performance, and these parameters must be controlled through rigorous quality assurance procedures.
The numerical simulation methodology employed—FEM/CSCM-SPH/HJC coupling—is a state-of-the-art approach for impact simulation and provides a powerful tool for design optimization. Engineers can use this methodology to evaluate different target configurations, material combinations, and geometric parameters without the cost and time of physical testing.
Summary
The study by Song and colleagues demonstrates that honeycomb steel tube confined concrete targets exhibit superior anti-penetration performance compared to single-cell hexagonal tube targets and unconfined concrete targets, primarily due to the dual confinement effect of lateral steel tube confinement and peripheral unit additional confinement. The performance advantage is most pronounced during the tunnel penetration phase, where the honeycomb structure restricts concrete radial expansion and increases penetration resistance. The numerical simulation methodology provides a reliable tool for design optimization, and the findings have direct implications for the design of protective structures in military, civil defense, and industrial applications. Engineers working on such projects must pay careful attention to the manufacturing quality of the honeycomb steel tube structure, the material properties of the concrete infill, and the accuracy of the numerical models used in design verification.