Calculation Guidelines for Impact Testing
This SAE Recommended Practice presents a series of standard calculations and numerical methods for processing safety test instrumentation data that has been acquired during impact tests with instruments installed in ATD’s (crash test dummies), vehicle structures, and laboratory fixtures. The output data from performing these calculations may have applications that include energy analysis, biomechanical analysis, regulation compliance, or other purposes. However, application of the output data from these calculations is outside the scope of this document. It is the intent of this document to present a basic set of calculations that are applicable to test labs that follow the practices set forth by SAE J211-1, SAE J211-2, SAE J2570, and SAE J1733. For the calculations that are described in other sources, the relevant documents are referenced.
Rationale: The committee reviewed this Recommended Practice to determine what changes were necessary to include the set of calculations, methods, and indexes that are typically calculated by labs performing impact tests. The major changes are outlined below.
ECE R94 was added to the list of references.
FIA Procedure for the Approval of Safety Structures was added to the list of references.
Resultant: The resultant calculation was added to provide a method for combining sensor signals collected at a single location, where the signals provide measurement along mutually orthogonal axes.
Delta V: The delta V calculation was added to provide a method for calculating the total change in velocity of a point location on an object during an impact test. Verbiage was added to explicitly state that delta V is a point measurement relative to the earth fixed coordinate system. Delta V is not a measurement relative to a vehicle or dummy coordinate system.
Maximum Average Acceleration: The maximum average acceleration calculation was added to provide a method for calculating the acceptance criteria for the energy absorbing structures of a motorsport vehicle during a frontal and a rear crash test.
Impactor Load: Impactor load calculation was added to provide a method for calculating the force on the leading face of an impactor when load cells are installed internal to the impactor.
Impactor G-force: Impactor G-force calculation was added to provide a method for calculating the force on the leading face of an impactor when an impactor is instrumented with an accelerometer.
V*C: The viscous criteria section was modified to allow filtering of the chest compression data using a CFC 180 filter. ECE R94 and other organizations specify a CFC 180 filter for dummy chest deflection in lieu of the SAE J211-1 specified CFC 600 filter. Due to the sensitivity of the derivative calculation to signal noise, using the CFC 180 filter for V*C has become popular among several organizations and is in common use.
CWVP: The chest wall velocity predictor was added to provide a method for calculating the chest compressive velocity during impulsive and percussive events such as a mine blast.