Whole-body vibration is vibration transmitted into the human body when using heavy construction machinery like bulldozers or when traveling by bus or train. The vibration is transmitted via the supporting surfaces and depends on the person’s position: seated (legs, back and buttocks), standing (legs), recumbent (back and head).
Regular exposure to whole body vibration causes following health effects:
The longer a person is exposed to the vibrating environment, the greater the risk of health effects. Measuring the whole-body vibration is a legal duty and is required to be able to limit the daily exposure and vibration dose values.
Industries and applications concerned
Measuring the whole-body vibration levels is a legal duty and needs to be done by the manufacturers of the products listed below, to limit the daily exposure. Following industries are concerned with whole body vibration: manufacturing, construction, transportation, agriculture.
Following products are concerned with whole body vibration:
Buses, subway trains, locomotives, helicopters, trucks, (tractor/trailer), bulldozers and other earth moving machinery, power shovels, forklifts, cranes, wheel loaders.
Whole-body vibration is measured at all the supporting surfaces (floor, seat, back) and is measured in three
orthogonal axes for each surface using a triax sensor. The measurement of vibration exposure can be divided into different stages:
- Measurement of the time signals of all acceleration channels. In case of standing and recumbent position this means 3 acceleration channels (X, Y, Z direction measured at the floor), in case of sitting position this means 9 acceleration channels (X, Y, Z direction each time measured at the floor, the back and the seat).
- The time signals are weighted with the appropriate time domain filters as specified in the ISO2631 standard:
- Wk for foot location of the seat
- Wd (X,Y) an Wk (Z) for seat location of the seat
- Wc for back location of the sea
- The vector sum for each location is calculated using the k-factors as specified in the ISO2631 standard:
- 0.25 for foot X and Y, 0.4 for foot Z
- 1 for seat X, Y and Z
- 0.8 for head X, 0.5 for head Y, 0.4 for head Z
- For all directions and for the vector sum, the weighted RMS values are calculated.
- For each vector sum, the weighted VDV (vibration dose values) are displayed and a color coding shows exceeding of the ISO standardized limits:
- Green = VDV below action value (9.1 m/s1.75)
- Yellow =VDV between action value (9.1 m/s1.75) and limit value (21 m/s1.75)
- Red = VDV above limit value (21 m/s1.75)
- In the different displays, one can see the following:
- Time signals for all accelerations (for checking correctness of input signals)
- Real-time VDV values for every measurement location on the seat with color coding VDV values from last measurement
- Separate summary sheet with VDV values for every measurement location on the seat from last measurement
- Separate Validity sheet to check the validity of the data (complete measurement overview)
The LMS Test.Xpress solution for whole-body vibration testing
The LMS Test.Xpress system consists of a measurement front-end (LMS SCADAS Mobile SCM01 or SCM05) and the LMS Test.Xpress analyzer software.
The LMS Test.Xpress Human Body Vibration Filters apply the ISO2631 time domain filters to the incoming vibration signals. Those filters are available both online as well as offline in case of post processing raw data.
The number of channels can go from 4 to 40, thus allowing:
- Measurement of all directions from all the triax sensors in one run
- Combination of whole-body ISO2631 with hand-arm ISO5349 measurements
- Measure extra channels (speed, temperature, noise, …)
- Later in-depth analysis of the measurement data as all time signals are saved
The Vibration Dose Values (VDV) are calculated and displayed in real time and a color coding clearly indicates
exceeding of the exposure and/or limit values as specified in the ISO standard.
At the end of the measurement, embedded MS Office reporting allows to finish the report on the spot.
The whole measurement and reporting is controlled by use of a simple toolbar, and as all critical settings are blocked by a password there is no risk for errors or unwanted changes.
Supported standards for whole-body vibration
The LMS Test.Xpress system supports the following WBV standards:
- ISO 2631-1 General requirements
- ISO 2631-2 Whole Body Vibration in Buildings
- ISO 2631-3 Motion sickness
- ISO 2631-4 Whole Body Vibration in Transport