Langford Analytic · Knowledge Base
Test & Analysis Correlation
How physical measurements and numerical predictions are compared to establish whether an engineering model represents the real structure adequately — from correlation fundamentals and test design through strain gauge fundamentals, placement, orientation and rosettes, linear static FEA to strain gauge correlation, FE strain extraction, load scaling and linearity, correlation methods, discrepancy diagnosis, test fixtures and boundary conditions, instrumentation uncertainty, static structural test correlation, displacement and full-field correlation, modal test fundamentals, modal correlation with MAC, vibration test correlation, model updating without overfitting, correlation evidence and acceptance, to the complete chain from physical test to validated engineering model.
Test Planning & Instrumentation
Test & Analysis Correlation FundamentalsHow physical measurements and numerical predictions are compared to establish whether an engineering model represents the real structure adequately.Designing a Test for Analysis CorrelationHow test configuration and instrumentation should be chosen to challenge the important modelling assumptions.Strain Gauge FundamentalsHow resistance strain gauges measure directional surface strain and how bridge configuration, installation and temperature affect the measurement.Strain Gauge Placement & OrientationHow gauge location and direction determine what structural behaviour is actually measured.Strain Rosettes for Principal-Strain RecoveryHow multiple gauge directions are combined to recover a local in-plane strain state and principal strains.
Static Strain Correlation
Linear Static FEA to Strain Gauge CorrelationA complete engineering workflow for comparing measured test strain with directionally and spatially equivalent strain extracted from a linear static FE model.Extracting Comparable Strain from an FE ModelHow nodal, elemental, shell-surface and spatially averaged FE strain should be processed to represent what a physical strain gauge measures.Load Scaling, Linearity & Multi-Level Static TestingHow proportional response and load-normalised strain provide powerful checks of linear static model behaviour.Measured vs Predicted Strain: Correlation MethodsHow differences, ratios, slopes and measured-vs-predicted plots reveal the quality and pattern of strain correlation.Understanding Strain Correlation DiscrepanciesHow the pattern of test/FE disagreement can identify problems in loading, stiffness, instrumentation, fixtures or model assumptions.Test Fixtures, Boundary Conditions & Load IntroductionWhy fixtures and load introduction are part of the physical system and can dominate apparent correlation.Instrumentation Accuracy, Noise & Measurement UncertaintyHow calibration, installation, noise, drift and temperature affect confidence in measured data.Static Structural Test Correlation — Loads, Reactions, Displacement & StrainHow loads, reactions, displacement and strain are combined to evaluate global and local static model behaviour.Displacement, Deflection & Full-Field CorrelationHow physical deformation measurements complement strain data and provide direct evidence of structural stiffness and shape.
Dynamic Correlation
Modal Test FundamentalsHow experimental excitation and measured response identify natural frequencies, damping and structural modes.Modal Correlation: Frequency, Mode Shape & MACHow analytical and experimental dynamic modes are paired and compared using both frequency and deformation pattern.Vibration Test & Dynamic Response CorrelationHow sine, random vibration and frequency-response measurements are compared with dynamic models.
Model Updating & Evidence
Model Updating Without OverfittingHow test evidence should be used to improve physically uncertain model parameters without simply tuning the model to the data.Correlation Evidence, Uncertainty & Engineering AcceptanceHow correlation quality is assessed in the context of uncertainty and the engineering decision being supported.From Physical Test to Validated Engineering ModelHow test planning, measurement, correlation, model updating and independent evidence combine to increase model credibility.