Langford Analytic · Knowledge Base
Ballistics & Penetration
High-velocity impact produces a highly localised structural response governed by inertia, contact, stress-wave propagation, material strain-rate behaviour and rapidly evolving damage. Depending on the structure and impact environment, the response may range from local indentation to cracking, plugging, petalling, delamination, penetration or complete perforation. This section covers the engineering methods used to model externally defined impact threats, assess structural response and determine the residual integrity of protective and containment structures — from ballistic impact fundamentals and low-speed vs high-speed response regimes through contact mechanics, impact angle, target thickness, boundary conditions, multi-layer targets, contact algorithm selection, stress-wave propagation, wave reflection and transmission, mechanical impedance, thin and thick structure response, high-strain-rate material behaviour, strain-rate sensitivity, plasticity, adiabatic heating, material failure models and failure-model calibration — treating projectile mass, shape and velocity as externally specified analysis inputs and focusing on the structural response of the target.
High-Velocity Impact Fundamentals
Ballistic Impact Structural Analysis FundamentalsStructural assessment of externally specified high-velocity impact events, covering contact, inertia, stress waves, local deformation, material failure, penetration/perforation response, residual strength and verification.Low-Speed vs High-Speed ImpactHow contact duration, structural response time, inertia and stress-wave transit distinguish low-speed, intermediate and high-rate impact regimes.Kinetic Energy in Impact AnalysisUse of kinetic energy as an impact-analysis bookkeeping quantity, including initial energy, plastic work, fracture, internal energy, residual motion and explicit-FEA energy checks.Momentum in Structural ImpactMomentum and impulse checks for high-rate structural impact, including target motion, support reaction, fragment motion and complementary use with energy balance.Impact Duration & Structural Response TimeHow contact duration, wave transit, modal period and event sequencing determine whether impact response is local, global, quasi-static or wave dominated.Local vs Global Structural Response to ImpactSeparation and interaction of local indentation/damage with global bending, membrane action, support response and residual vibration in impact-loaded structures.
Contact & Impact Mechanics
Contact Mechanics in High-Rate ImpactContact mechanics for short-duration impact analysis, including normal contact, friction, stiffness, large deformation, separation, penalty controls and verification of force transfer.Impact Angle & Structural ResponseStructural effects of oblique impact, including normal and tangential velocity components, asymmetric contact, sliding, bending, ricochet-like separation and target-response verification.Target Thickness & Impact ResponseHow target thickness changes structural response regime, wave timing, bending/membrane participation, rear-face response and numerical modelling requirements under a specified impact.Boundary Conditions in Impact AnalysisSelection and verification of impact-analysis boundaries, including support stiffness, model extent, wave reflection, symmetry, remote constraints and realistic structural interfaces.Multiple Structural Layers Under ImpactStructural response of layered systems under specified impact, including interface wave transmission, layer separation, backing support, sequencing, load spreading and residual assessment.Contact Algorithm Selection in Explicit FEASelection, setup and verification of explicit-FEA contact for impact, including penalty behaviour, general versus pair contact, self-contact, friction, erosion interaction and numerical sensitivity.
Stress Waves & High-Rate Response
Stress-Wave Propagation in ImpactStress-wave propagation during externally specified high-velocity impact, covering characteristic wave speeds, particle motion, transit time, reflection, transmission, dispersion, numerical resolution and structural interpretation.Wave Reflection at Free SurfacesFree-surface stress-wave reflection in impact analysis, including the traction-free boundary condition, sign reversal, rear-surface motion, tensile-wave interaction, numerical requirements and structural verification.Wave Transmission Across Material InterfacesStress-wave transmission and reflection at material interfaces, covering impedance mismatch, normal-incidence coefficients, bonded and compliant interfaces, layered structures, numerical modelling and verification.Mechanical Impedance in Impact ProblemsMechanical and wave impedance concepts for impact analysis, explaining stress-to-particle-velocity impedance, structural dynamic impedance, mismatch effects, layered systems and practical finite-element interpretation.Stress-Wave Effects in Thin StructuresStress-wave behaviour in thin plates and shells under short-duration impact, including through-thickness reverberation, bending and membrane response, dispersion, local-to-global transition, numerical modelling and verification.Stress-Wave Effects in Thick StructuresStress-wave response of thick sections under short-duration impact, covering through-thickness transit, confined stress states, rear-surface reflection, local damage, three-dimensional modelling and verification.
Material Behaviour at High Strain Rate
High-Strain-Rate Material BehaviourHigh-strain-rate constitutive behaviour for impact analysis, covering rate sensitivity, hardening, thermal coupling, pressure effects, dynamic test data, model selection, uncertainty and finite-element implementation.Strain-Rate Sensitivity of MetalsStrain-rate sensitivity of metallic materials in dynamic structural analysis, including flow-stress trends, data interpretation, rate-dependent constitutive modelling, calibration range and numerical verification.Plasticity in High-Velocity ImpactPlastic deformation in high-velocity structural impact, covering elastic-plastic wave behaviour, hardening, rate and temperature coupling, multiaxial stress, energy absorption, constitutive modelling and verification.Adiabatic Heating in High-Rate DeformationAdiabatic temperature rise during rapid plastic deformation, including plastic-work conversion, thermal softening, localisation, constitutive coupling, energy checks and finite-element verification.Material Failure Models for Impact FEAFailure and damage modelling for high-rate structural FEA, covering initiation, evolution, stress-state and rate dependence, tensile failure, erosion, mesh objectivity, calibration and validation.Failure-Model Calibration & Test DataA defensible workflow for calibrating high-rate material failure models from traceable test data, covering test matrix design, inverse identification, parameter identifiability, mesh dependence, uncertainty and independent validation.
Penetration & Perforation Response
Penetration vs PerforationThe engineering distinction between indentation, partial penetration, complete perforation and residual structural response — and why the difference matters for structural assessment.Structural Penetration MechanismsThe engineering mechanisms of structural penetration — plastic flow, local deformation, cracking, plugging, petalling, shear localisation and how the mechanism depends on the target structure.Plugging Failure in Metallic PlatesThe plugging failure mechanism in metallic plates — local shear, plug formation, the role of target thickness and material behaviour, strain-rate effects and FEA interpretation.Petalling Failure in Thin Metallic PlatesThe petalling failure mechanism in thin metallic plates — local bending, radial tearing, plastic deformation and the structural interpretation of petal formation.Ductile Hole EnlargementDuctile hole enlargement as a penetration mechanism — plastic flow, local stretching, material ductility, the deformation process and the residual geometry after impact.Rear-Surface Spall & DamageRear-surface spall and damage in thick targets under high-velocity impact — stress-wave reflection, tensile failure, structural significance and inspection considerations.Residual Deformation After High-Rate ImpactThe residual deformation of structural targets after high-rate impact — local dent, permanent bending, membrane deformation, residual stress and the implications for serviceability and remaining structural margin.Residual Structural Strength After ImpactAssessing the residual structural strength after high-rate impact — remaining section, cracks, plastic strain, distortion, fatigue implications and inspection-informed reassessment.
Composite & Sandwich Impact
High-Velocity Impact of Composite StructuresThe structural response of composite materials to high-velocity impact — fibre failure, matrix cracking, delamination, local crushing, perforation and residual strength.Delamination Under High-Rate ImpactDelamination growth in composite laminates under high-rate impact — interlaminar stress, wave propagation effects, local contact, delamination growth and hidden damage.Fibre & Matrix Failure Under ImpactFibre and matrix failure modes in composites under high-rate impact — fibre tension and compression, matrix damage, shear, progressive damage and strain-rate considerations.Impact Response of Sandwich PanelsThe impact response of sandwich panels — face sheet response, core crushing, local indentation, delamination and rear-face response under high-velocity impact.Composite Residual Strength After ImpactResidual strength of composite structures after high-velocity impact — hidden damage, compression-after-impact concepts, remaining stiffness and strength, inspection and analysis/test correlation.
Layered & Containment Structures
Layered Structural Systems Under High-Rate ImpactThe response of layered structural systems to high-rate impact — multiple layers, gaps, interfaces, energy absorption, stress-wave interaction and load spreading.Backing Structures & Secondary Load PathsThe role of backing structures and secondary load paths in layered impact systems — front layer, backing structure, supports, attachment loads, residual motion and secondary structural response.Containment Structures Under Fragment ImpactThe response of containment structures to externally specified fragment impact — local impact, casing response, penetration and perforation, energy absorption and residual containment function.Machinery Casing Impact & ContainmentThe structural response of machinery casings to internally released component impact — casing deformation, rupture, mount and interface loads, and the structural containment assessment.Combined Impact & Pressure LoadingStructural response to combined impact and pressure loading — impact followed by pressure, pressure followed by impact, damaged structural state, load sequencing and nonlinear response.
Explicit FEA, Damage & Numerical Methods
Explicit FEA for Penetration & PerforationExplicit FEA for penetration and perforation analysis — explicit integration, contact, high deformation, material failure, element deletion, time step, energy balance and verification.Mesh Strategy for High-Velocity ImpactMesh strategy for high-velocity impact FEA — local refinement, element size, through-thickness discretisation, localisation capture, mesh dependency and computational cost.Element Erosion & Deletion in Impact AnalysisElement erosion and deletion in high-rate impact FEA — the numerical purpose, damage criteria, mass and energy loss, contact consequences, sensitivity and the danger of nonphysical results.Energy Balance in Penetration FEAThe energy balance in penetration FEA — initial kinetic energy, internal energy, kinetic energy, contact energy, artificial energy, deleted-element energy and the interpretation of energy conservation.Verification & Validation of High-Rate Impact ModelsVerification and validation of high-rate impact models — mass, velocity, energy, momentum, contact, mesh sensitivity, material calibration, deformation, damage pattern, test comparison and uncertainty.Defensible Ballistic Impact Structural Analysis WorkflowThe cornerstone closing article — the complete workflow from defined impact requirement through target geometry, materials, externally specified impactor inputs, material rate data, preliminary physics checks, contact, mesh, explicit solution, damage, penetration response, energy balance, residual condition, test correlation, sensitivity, verification and reporting.