AUTOMOTIVE Options

C60

C180

C600

C1000

BUT

BUT(p)

FIR

HIC

Calculates the Head Impact Criteria from an acceleration time history. The user is prompted for the time window and the acceleration conversion factor.

Normally this option writes the HIC value to the screen. If required the values may also be written out to a file using the WRITE TO FILE option.

The time unit for the input curve should be seconds. T/HIS looks at the range of the x-axis values and if the range is >10 then T/HIS will assume the x-axis values are in ms and it will automatically divide the x-axis values by 1000.

If the y-axis values are not in (G) then an optional factor can be specified that T/HIS will DIVIDE the y-axis values by to convert them to (G).

Example factors for different units are :

In addition to calculating and reporting the HIC value the time window and value can be displayed on the graph using the Show HIC Value option.

See Appendix E for more details on the Head Impact Criteria calculation.

HIC(d)

\( HIC(d) = 0.75446 * (\textrm{free motion headform HIC}) + 166 \)

3ms CLIP

Calculates the 3ms clip value from an acceleration time history. Normally this option writes the value to the screen, and produces a curve of the clip region.

By default the screen value will be labeled as " 3ms = value ". This label can be modified by specifying a different Screen Label.

If required the values may also be written out to a file using the WRITE TO FILE option. In addition to calculating and reporting the 3ms clip value the time window and value can be displayed on the graph using the Show 3ms Clip Value option.

See Appendix E for more details on the 3ms clip calculation.

EXC

Calculate and displays an EXCeedence plot. This is a plot of force (y-axis) versus cumulative time (x-axis) for which the force level has been exceeded. By default the Automatic option will create an exceedence plot using either the +ve OR the -ve values depending on which the input curve contains most of. The Positive option will calculate the exceedence plot using only the points with +ve y values. The Negative option will calculate the exceedence plot using only the points with -ve y values.

VC

ASI

Acceleration Severity Index. This value is used to assess the performance of road side crash barriers.

This option requires 3 acceleration input curves. The user is prompted for the acceleration limits in the 3 directions.

The calculation method can be set to 2010 (BS EN 1317-1:2010) or 1998 (BS EN 1317-1:1998). See Appendix E for more details on this calculation.

THIV

Theoretical Head Impact Velocity and the Post Impact Head Deceleration. These values are used to assess the performance of road side crash barriers.

This option requires 3 input curves, a longitudinal and lateral acceleration and a rotation rate. The user is prompted for the constants Dx, Dy and X0. See Appendix E for more details on these calculations.

NIJ

Biomechanical neck injury predictor. Used as a measure of injury due to the load transferred through the occipital condyles.

This option requires 3 input curves. 1 to represent Shear force, 1 to represent Axial force and a third to represent bending moment in the dummy's upper neck loadcell. Enter these curves in the corresponding input boxes.

The 4 critical constants used to calculate NIJ; Fzc (Tension), Fzc (Comp), Myc (Flexion) and Myc (Extension) default to the values specified by the test creators. These can be changed by entering different values into the respective boxes.

Enter the e distance into the e (distance) box.

Select which curves you wish to output to in the Output box.

For more information on the calculation of NIJ, refer to Biomechanical neck injury predictor (NIJ).

TTI

This option requires 3 input curves. 1 to represent the Upper Rib Acceleration, 1 to represent the Lower Rib Acceleration and a third to represent the Lower Spine (T12) Acceleration. Enter these curves in the corresponding input boxes.

The output can either be written to the screen, appearing in a listing box, or written to a file specified in the File: input box, or both.

If the Write To Screen option is toggled on, the following window will appear:

For more information on the calculation of TTI, refer to The Thoracic Trauma Index (TTI).

NOR(y)

NOR(x)

REG

It is necessary for a curve to have a constant time step between points for it to be filtered. This option takes an existing curve and prompts the user for a new time step. The points of the output curve are calculated by linear interpolation. Regularising a curve may alter its peak values, and could change filtered output slightly.

VEC

VEC(2D)

ACU

This option evaluates the following equation:

\( ACU(T) = \int_{T-n}^{T} (a(t) - m)dt \\ \begin{align*} \textrm{Where } m &= \textrm{user-defined offset} \\ n &= \textrm{time to integrate over} \end{align*} \)

COR1

The Correlation function provides a measure of the degree to which two curves match. When comparing curves by eye, the quality of correlation may be judged on the basis of how well matched are the patterns of peaks, the overall shapes of the curves, etc, and can allow for differences of timing as well as magnitude. Thus a simple function based on the difference of Y-values (such as T/HIS ERR function) does not measure correlation in the same way as the human eye. The T/HIS correlation function attempts to include and quantify the more subtle ways in which the correlation of two curves may be judged.

The input parameters for the COR1 function have been chosen so as to produce a strict judgement of the correlation (see Appendix F for more details).

COR2

COR3

This function first normalises the curves using two factors either specified by the user or defaults calculated by the program (the maximum absolute X and Y values of both graphs). For each point on the first normalised curve, the shortest distance to the second normalised curve is calculated. The root mean square value of all these distances is subtracted from 1 and then multiplied by 100 to get an index between 0 and 100. The process is repeated along the second curve and the two indices are averaged to get a final index. The higher the index the closer the correlation between the two curves.

Note that the choice of normalising factors is important. Incorrect factors may lead to a correlation index outside the range of 0 to 100 (see Appendix F for more details).

WIF

Compares curves using the Weighted Integrated Factor method (WIFAC).  A value between 0 and 100 is calculated, the higher the index the closer the correlation between the two curves.

See Appendix F for more details.

BES

OLC

The Occupant Load Criterion (OLC) is a parameter used to assess the MPDB-to-vehicle impact in the Euro NCAP Compatibility assessment. This operation requires two inputs:

1. The X-acceleration curve of the Barrier Model's Centre of gravity (CoG). 
2. The Initial Velocity of the Barrier Model's CoG, which can be specified by either selecting the velocity curve or providing the initial velocity as an numerical input.

There is also an option to auto-regularise and auto-filter the input curves, before calculating the OLC. The filter class can be chosen from the available Filter Curves using options.

The OLC operation outputs five curves: 

1. Velocity Curve of the Virtual Occupant Model with OLC value and vertical lines to signify the end of the free flight phase and the end of the ideal restraint phase. 
2. Velocity Curve of the Barrier Centre of Gravity.
3. Displacement Curve of the Barrier Centre of Gravity.
4. Displacement Curve of the Virtual Occupant Model.
5. Relative Displacement between the two Displacement curves.

The display option for OLC value and vertical lines for the end of the free flight phase and the end of the ideal restraint phase can be toggled using the Show OLC value option in Tools → Settings → General.

For more information on the calculation of OLC, refer to Appendix E → Occupant Load Criterion (OLC).

TI 

Tibia Index (TI) is an injury criterion for the lower leg area used to predict the leg injuries.

TI requires three input curves: Axial Curve, X Moment Curve and Y Moment Curve

Additionally, two constant inputs: Critical Force \(F_{zc}\) and Critical Bending Moment \(M_{rc}\).

These Critical constant values vary depending on the Occupant type. For the standard occupant types, \(F_{zc}\) and \(M_{rc}\) values are updated automatically. Otherwise, if the occupant type Other is selected then the Critical force and Critical Bending Moment values can be provided manually.

The unit system of the selected input curves is also displayed in this panel. The values of critical constants for the standard occupant types are internally converted to the unit system shown.

There is also an option to auto-regularise and auto-filter the input curves, before calculating the TI. The filter class can be chosen from the available Filter Curves using dropdown. 

The TI operation outputs a single Tibia Index Curve.

For more information on the calculation of Tibia Index, refer to Appendix E → Tibia Index (TI).

DMG 

The DAMAGE criterion (or DMG for short) is a brain injury metric which is based on deformation output from a second-order system of equations.

DMG requires three input curves: Head Rotation Velocity X, Head Rotation Velocity Y, Head Rotation Velocity Z. 

The unit system of the selected input curves is also displayed in this panel. The scaling factor, stiffness and damping constants value are internally converted to the unit system shown.

There is also an option to auto-regularise and auto-filter the input curves, before calculating the DMG. The filter class can be chosen from the available Filter Curves using options.

There is also an option to choose the calculation method used to solve the second order differential equation:

1. Runge Kutta 4 uses a fourth-order approximation to calculate the solution at each time step, providing good accuracy for most problems.
2. Runge Kutta Fehlberg 45 is an adaptive step size version of Runge Kutta 4. It automatically adjusts the step size based on the solution's behaviour, balancing accuracy and computational efficiency. 
3. Newmark Beta Method is a method to solve structural dynamics problems, particularly for second-order equations of motion. 

The DAMAGE operation outputs four curves:

1. DAMAGE Curve Resultant
2. DAMAGE Curve X component 
3. DAMAGE Curve Y component
4. DAMAGE Curve Z component

For more information on the calculation of DAMAGE Criterion, refer to Appendix E → DAMAGE Criterion (DMG).