It remains unclear whether local stiffening or uniform thickening provides a safer balance between global deformation control and hole-edge stress margin under impact loading. This study compares 4/4 mm baseline, 4/4 mm locally stiffened, and 5/5 mm uniformly thickened 6061-T6 shells under 300 g, 2 ms base acceleration using transient finite element analyses with identical geometry, material, supports, loading, mesh, and solver settings. Within this linear-elastic relative-comparison framework, the locally stiffened shell reduces maximum deformation by 16.06%, yet increases selected hole-edge peak stress by 27.76% and unaveraged nodal peak equivalent stress by 32.52%, lowering minimum stress-margin indicator to 0.60216. In contrast, uniform thickening reduces deformation by 42.36%, decreases hole-edge stress by 5.25% and nodal peak stress by 17.34%, and raises the indicator to 0.96538. Boundary-condition sensitivity confirms that support idealization does not reverse this trend. A supplementary elastoplastic analysis using a bilinear isotropic hardening model shows that plasticity reduces peak nodal stress of the critical stiffened shell by 19.4%, confines yielding to a sub-millimeter hole-edge band, and preserves linear-elastic ranking for comparative design assessment. Therefore, displacement reduction alone is insufficient for evaluating impact-loaded perforated shells. For design under this impact condition, uniform thickening is preferable for balanced performance, while local stiffening requires hole-edge reinforcement and elastoplastic assessment.
Ballistic equivalent thickness conversion is key in armor design and damage assessment, but traditional fixed ratio or curve-fitting methods have limited applicability, neglecting energy dissipation and hardening. Cavity expansion theory, validated for ballistic limit prediction, has not been inversely applied to establish ballistic equivalence between different targets. Using mathematical inversion, we derive an explicit analytical solution for the equivalent thickness of ductile metal plates struck by ogive-nose armor-piercing projectiles. Validated with 950+ independent penetration equivalence cases from public databases, the model achieves 7.4% MAPE for ductile hole-growth metals without empirical calibration, outperforming traditional empirical models. When inertial effects are negligible, the equivalent thickness ratio depends only on quasi-static cavity expansion resistances, independent of projectile parameters. The derived formula eliminates experimental calibration, supports lightweight protective design, and aids equivalent testing and optimization for vehicle and ship protective panels.
This study examines the flexural performance of partially encased concrete cellular beams (PECCBs), in which continuous openings are introduced into the web of the main steel component (MSC). To evaluate the influence of web openings and their geometries on structural behavior, six PECCBs with different configurations and one conventional partially encased concrete beam (PECB) were tested. The parameters investigated included three cellular geometries (circular, square, and hexagonal), two opening ratios, and three flange thicknesses. Experimental results indicated that conventional PECB specimens primarily failed through concrete crushing and flange buckling, whereas PECCBs exhibited lower flange tensile failure with concrete damage or upper flange buckling in compression. The presence of cellular webs enhanced the overall energy absorption capacity, with circular openings delivering the best performance, followed by hexagonal and square shapes. The cracking load was governed by both the opening ratio and geometry, with the highest value of 27.14 kN & centerdot;m obtained for circular-cellular beams. Based on the test results, a cracking load prediction formula and an analytical deflection model were developed using the discounted web thickness method. Comparisons with JGJ 138-2016 and T/CECS 719-2020 demonstrated that the proposed deflection model achieved superior accuracy, with an average error of 4.20% and a standard deviation of 0.045.
Suspension bridges experience significant stress cycles from wind loads, leading to fatigue damage. Traditional rainflow counting methods perform poorly under non-stationary wind loads, especially when stress responses exhibit abrupt state changes, often causing incomplete cycle identification or amplitude misjudgment. This paper proposes a Time-Domain-State Dual-Layer Rainflow Counting (TSD-RFC) method. The method decomposes the non-stationary response into multiple quasi-stationary segments, applying classical three-point rainflow counting within each segment to identify primary fatigue cycles. Additionally, for state transition segments, an independent cycle counting layer captures large-amplitude stress cycles induced by wind speed fluctuations. Compared with traditional rainflow counting, TSD-RFC identifies stress cycles more accurately, particularly in high-amplitude regions, and effectively distinguishes cycles caused by state transitions. In fatigue assessment at a wind speed of 20 m/s, TSD-RFC yields approximately 11.39% higher fatigue damage than traditional methods, demonstrating its clear advantage under non-stationary wind loads.
Ground contact explosions cause limited deformation and crater formation, an issue critical for forensic explosion analysis and blast-resistant structural design. In this study, a multiscale numerical model based on the Coupled Eulerian-Lagrangian (CEL) method was developed in Abaqus/Explicit to model craters formed by contact explosions on the ground. The model was calibrated using controlled field tests on low-plasticity clay-silt (CL) soil with 1, 2, and 3 kg of TNT equivalent and validated using a vehicle-induced explosion in Elaz & imath;& gbreve; in 2016 with approximately 2 tons of TNT equivalent. Soil behavior was defined using the Mohr-Coulomb plasticity model and explosive behavior using the Jones-Wilkins-Lee (JWL) state equation. Crater diameter, depth, depth/diameter ratio, and blast index were evaluated across three orders of explosive mass. Numerical results were consistent with field measurements; error rates were below 5% for small-scale and below 8% for large-scale explosions. As the explosive mass increases, craters become wider and deeper. The CEL-based approach provides a reliable tool for forensic explosion analysis and the evaluation of ground behavior under extreme loading.
