Appendix I: SPD File Format Specification

Test data for the behavior of a bushing in one direction is provided to the MIT in a System Performance Data (SPD) file. The SPD file is an ASCII file with information in Tiem-Orbit format. It consists of the following five blocks:

HEADER
UNITS
EXPERIMENTAL DETAILS
FREQUENCY DATA
STATIC DATA

The data in the SPD file is NOT case sensitive. Upper case, lower case or mixed case may be used as needed to increase readability of the file.

HEADER Block

This is a mandatory block.

This block contains information about the file type, version and file format. The key words that are used in this block are:

FILE_TYPE = 'spd'
FILE_VERSION = '1.0'
FILE_FORMAT = 'ASCII'

UNITS Block

This is a mandatory block.

This block contains information about the system of units used for the date in the file. The key words that are used in this block are:

LENGTH = quoted_string
Valid length units: ‘mm’, ‘m’, ‘meter’, ‘cm’, ‘mile’, ‘foot’, ‘inch’
ANGLE = quoted_string
Valid angle units: ‘degree’ and ‘radian’
FORCE = quoted_string
Valid force units: ‘newton’, ‘kg_force’, ‘knewton’, ‘pound_force’, ‘kpound_force’, ‘dyne’, ‘ounce_force’
MASS = quoted_string
Valid mass units: ‘kg’, ‘gram’, ‘pound_mass’, ‘kpound_mass’, ‘slug’, ‘ounce_mass’
TIME = quoted_string
Valid time units: ‘second’, ‘sec’, ‘millisecond’, ‘minute’, ‘hour’

EXPERIMENTAL DETAILS Block

This is a mandatory block.

This block contains information about the component that was tested and the dates when the tests were conducted. The key words that are used in this block are:

TEST_DATE = quoted_string
TEST_USER = quoted_string
FILE_DATE = quoted_string
FILE_USER = quoted_string
PART_NUMBER = quoted_string
DIRECTION = quoted_string

TEST_DATE: Contains a string that identifies the date when the experiment was done. It can be any string. An example is:
TEST_DATE = ‘2011/01/15’
TEST_USER: Contains a string that identifies the user that created the test data. It can be any string. An example is:
TEST_DATE = ‘2011/01/15’
FILE_DATE: Contains a string that defines when this SPD file was created. It can be any string. An example is:
FILE_DATE = ‘2011/01/15’
FILE_USER: A string that identifies the user who is using the test data. An example is:
FILE_USER = ‘Ingo Nolden’
PART_NUMBER: A string that uniquely identifies a part number that is associated with this bushing. It can be any string. An example is:
PART_NUMBER = ‘Altair_314159_GearBox’
DIRECTION: Used to identify the testing direction for the SPD file. The value of this string must be one of the following: ‘FX’, ‘FY’, ‘FZ’, ‘TX’, ‘TY’ and ‘TZ’.
DESIGN_TYPE: Identifies the type of bushing for which the test data is being provided. The value of this string must be one of the following: ‘RUBBER’ or ‘HYDRO’.
APPLICATION_TYPE: Specifies the specific application for which the bushing is being used. It can be any string. An example is:
APPLICATION_TYPE = ‘Gear Box’

FREQUENCY DATA Block

This block contains the details of the frequency domain test. The input signal is always a sinusoidal displacement of a given magnitude and frequency. Furthermore the test may be performed at a specific preload. Often this is zero. The quantities that are measured for this input are the dynamic stiffness and the loss angle. An additional data, displacement offset is not used currently.

Thus each line of the dynamic data block contains six columns of data per measurement.

The measured input displacement magnitude
The input frequency
The dynamic stiffness magnitude
The loss angle
The displacement offset
The preload

The frequency data-block is optional. It is needed by the MIT for the generation of the dynamic model of the bushing. If this data is not present, only the static characteristics are written out.

STATIC DATA Block

The static data block is mandatory.

This block contains the details of the quasi-static tests. The data for the direction identified in the EXPERIMENT_DETAILS data block contains two columns of data:

The input displacement
The output force

Example SPD File

The file below shows a fictitious example for measurements made for a bushing. This example is provided to emphasize the different blocks of data in the SPD file.

Important: The data should not be interpreted as being realistic.

$------------------------------------------------------------------- HEADER 
[HEADER]
FILE_TYPE     =  'spd'
FILE_VERSION  =  1.0
FILE_FORMAT   =  'ASCII'

$------------------------------------------------------------------- UNITS
[UNITS]
LENGTH = 'mm'
ANGLE  = 'degree'
FORCE  = 'newton'
MASS   = 'kg'
TIME   = 'second'

$-------------------------------------------------------EXPERIMENT_DETAILS
[EXPERIMENT_DETAILS]
TEST_DATE        = 'Unknown'
TEST_USER        = 'Unknown'
FILE_DATE        = '18/05/2015 (dd/mm/yyyy)'
FILE_USER        = 'John Doe - III'
PART_NUMBER      = '3141592653'
DIRECTION        = 'FZ'
DESIGN_TYPE      = 'Hydro'
APPLICATION_TYPE = 'Gear Box'

$--------------------------------------------------------------------------DATA
[FREQUENCY_DATA]
{    d_mag        freq       k_mag         loss_angle    offset       preload   }
     0.10000      1.00000    129.49730      1.90437      0.00000      0.00000 
     0.10000      2.00000    124.87106      4.17876      0.00000      0.00000 
     0.10000      6.00000    132.52306     19.56765      0.00000      0.00000 
     0.10000     10.00000    165.48866     36.18596      0.00000      0.00000 
     0.10000     14.00000    253.20040     25.81164      0.00000      0.00000 
     0.10000     18.00000    261.76914     14.11530      0.00000      0.00000 
     0.10000     22.00000    257.30352      9.58230      0.00000      0.00000 
     0.10000     26.00000    253.91557      7.35016      0.00000      0.00000 
     0.10000     30.00000    251.72323      6.01642      0.00000      0.00000 
     0.30000      1.00000    129.84541      2.61325      0.00000      0.00000 
     0.30000      2.00000    126.41526      5.48099      0.00000      0.00000 
     0.30000      6.00000    141.48654     19.26517      0.00000      0.00000 
     0.30000     10.00000    170.43227     29.36106      0.00000      0.00000 
     0.30000     14.00000    235.15798     21.53400      0.00000      0.00000 
     0.30000     18.00000    246.16590     12.55937      0.00000      0.00000 
     0.30000     22.00000    245.22880      8.84298      0.00000      0.00000 
     0.30000     26.00000    243.87993      6.92413      0.00000      0.00000 
     0.30000     30.00000    242.90718      5.73891      0.00000      0.00000 
     1.00000      1.00000    129.59747      3.42382      0.00000      0.00000 
     1.00000      2.00000    127.64017      6.93225      0.00000      0.00000 
     1.00000      6.00000    151.81227     18.61976      0.00000      0.00000 
     1.00000     10.00000    178.31125     20.15408      0.00000      0.00000 
     1.00000     14.00000    207.82846     13.93181      0.00000      0.00000 
     1.00000     18.00000    219.85961      9.82250      0.00000      0.00000 
     1.00000     22.00000    223.77251      7.55890      0.00000      0.00000 
     1.00000     26.00000    225.34344      6.17990      0.00000      0.00000 
     1.00000     30.00000    226.13383      5.24682      0.00000      0.00000 

[STATIC_DATA]
{  displacement    force }
   -13.3          -11000
   -13             -6300
   -12             -3669
   -11             -2541
   -10             -1923
    -9             -1594
    -8             -1309
    -7             -1021
    -6              -784
    -5              -604
    -4              -473
    -3              -360
    -2              -246
    -1              -123
     0                 0
     1               104
     2               197
     3               279
     4               355
     5               436
     6               599
     7              1014
     8              1824
     9              3058
     10             4671
     10.5           6400
     10.7           9000
     10.8          11100