Six-degree-of-freedom whole-body vibration exposure levels during routine skidder operations.

This research focuses on quantifying six-degree-of-freedom (6-DOF) whole-body vibration (WBV) exposure levels that occur in Northern Ontario skidders during routine field operating tasks. 6-DOF vibration running root-mean-square (RMS) acceleration levels at the operator/seat interface were determined for eight skidders while driving loaded, driving unloaded, picking up a load, dropping off a load and ploughing logs under field operating conditions. The acceleration data were weighted in accordance with ISO 2631-1:1997 and evaluated for both health and comfort outcomes. The mean running RMS weighted translational and rotational accelerations all exceeded 0.36 m/s(2) and 0.14 rad/s(2). The greatest average accelerations occurred while driving unloaded with this condition displaying translational vibration total values (VTV) that exceeded the upper limit of the ISO 2631-1:1997 health caution zone within an average of 2.3 h. Utilizing 6-DOF VTV, virtually all operating conditions would be designated as uncomfortable. STATEMENT OF RELEVANCE: This study provides one of the most comprehensive reports on vibration exposures in seated vehicle operators. The results are geared towards ergonomists with discussions on health effects and measurement concerns, while providing the raw vibration exposure data that will be useful to vehicle, component and vibration sensor designers.

Contact mechanics of the ovine stifle during simulated early stance in gait. An in vitro study using robotics.

Ovine stifle joint contact pressures and contact areas were measured in vitro using a six degree-of-freedom (DOF) robotic system. The robot generated static joint loads of 1.875 times body weight (BW) compression, 0.15 BW medial shear and 0.625 BW cranial shear at 6.5 degrees of flexion for four specimens, simulating the early stance phase of gait (walking). This condition represents a period of intense loading and was implemented as a worst-case loading scenario for the joint at this gait. We determined that the medial and lateral compartments bore 5.5 +/- 0.9 MPa and 4.4 +/- 1.1 MPa of mean pressure, respectively, on 107.7 +/- 28.7 mm(2) and 60.8 +/- 56.3 mm(2) of area, respectively. The unique contribution of this study is that stifle contact pressures and areas were determined during loading which simulated physiological levels (early stance phase of gait). This information is important to our understanding of the stresses that must be borne by repair tissues/constructs that are implanted into human and animal tibio-femoral joints.