An improved three-dimensional multibody model of the human spine for vibrational investigations

2015 ◽  
Vol 36 (4) ◽  
pp. 363-375 ◽  
Author(s):  
Pier Paolo Valentini ◽  
Ettore Pennestrì
Keyword(s):  
Three Dimensional ◽  
Multibody Model ◽  
Human Spine

Efficient Simulation of Gear Contacts Including Transient Elastohydrodynamic Effects

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Peter Fietkau ◽  
Bernd Bertsche
Keyword(s):  
Three Dimensional ◽  
Direct Determination ◽  
Simulation Method ◽  
Elastic Half Space ◽  
Operating Conditions ◽  
Multibody Simulation ◽  
Multibody Model ◽  
Gear Contact ◽  
Oil Films ◽  
Lubrication Conditions

This paper describes an efficient transient elastohydrodynamic simulation method for gear contacts. The model uses oil films and elastic deformations directly in the multibody simulation, and is based on the Reynolds equation including squeeze and wedge terms as well as an elastic half-space. Two transient solutions to this problem, an analytical and a numerical one, were developed. The analytical solution is accomplished using assumptions for the gap shape and the pressure in the middle of the gap. The numerical problem is solved using multilevel multi-integration algorithms. With this approach, tooth impacts during gear rattling as well as highly loaded power-transmitting gear contacts can be investigated and lubrication conditions like gap heights or type of friction may be determined. The method was implemented in the multibody simulation environment SIMPACK. Therefore it is easy to transfer the developed element to other models and use it for a multitude of different engineering problems. A detailed three-dimensional elastic multibody model of an experimental transmission is used to validate the developed method. Important values of the gear contact like normal and tangential forces, proportion of dry friction, and minimum gap heights are calculated and studied for different conditions. In addition, pressure distributions on tooth flanks as well as gap forms are determined based on the numerical solution method. Finally, the simulation approach is validated with measurements and shows good consistency. The simulation model is therefore capable of predicting transient gear contact under different operating conditions such as load vibrations or gear rattling. Simulations of complete transmissions are possible and therefore a direct determination of transmission vibration behavior and structure-borne noise as well as of forces and lubrication conditions can be done.

An Improved Olympic Hole-Filling Method for Ultrasound Volume Reconstruction of Human Spine

2012 ◽  
pp. 259-271 ◽  
Author(s):  
D. E. O. Dewi ◽  
T. L. R. Mengko ◽  
I. K. E. Purnama ◽  
A. G. Veldhuizen ◽  
M. H. F. Wilkinson
Keyword(s):  
Three Dimensional ◽  
3D Ultrasound ◽  
Hole Filling ◽  
Filling Process ◽  
Volume Reconstruction ◽  
Acquisition Process ◽  
Human Spine ◽  
Filling Method ◽  
Averaging Filter

Hole-filling in ultrasound volume reconstruction using freehand three-dimensional ultrasound estimates the values for empty voxels from the unallocated voxels in the Bin-filling process due to inadequate sampling in the acquisition process. Olympic operator, as a neighbourhood averaging filter, can be used to estimate the empty voxel. However, this method needs improvement to generate a closer estimation of the empty voxels. In this paper, the authors propose an improved Olympic operator for the Hole-filling algorithm, and apply it to generate the volume in a 3D ultrasound reconstruction of the spine. The conventional Olympic operator defines the empty voxels by sorting the neighbouring voxels, removing the n% of the upper and lower values, and averaging them to attain the value to fill the empty voxels. The empty voxel estimation can be improved by thresholding the range width of its neighbouring voxels and adjusting it to the average values. The method is tested on a hole-manipulated volume derived from a cropped 3D ultrasound volume of a part of the spine. The MAE calculation on the proposed technique shows improved result compared to all tested existing methods.

An Improved Olympic Hole-Filling Method for Ultrasound Volume Reconstruction of Human Spine

2010 ◽  
Vol 1 (3) ◽  
pp. 28-40 ◽  
Author(s):  
D. E. O. Dewi ◽  
T. L. R. Mengko ◽  
I. K. E. Purnama ◽  
A. G. Veldhuizen ◽  
M. H. F. Wilkinson
Keyword(s):  
Three Dimensional ◽  
3D Ultrasound ◽  
Hole Filling ◽  
Filling Process ◽  
Volume Reconstruction ◽  
Acquisition Process ◽  
Human Spine ◽  
Filling Method ◽  
Averaging Filter

Hole-filling in ultrasound volume reconstruction using freehand three-dimensional ultrasound estimates the values for empty voxels from the unallocated voxels in the Bin-filling process due to inadequate sampling in the acquisition process. Olympic operator, as a neighbourhood averaging filter, can be used to estimate the empty voxel. However, this method needs improvement to generate a closer estimation of the empty voxels. In this paper, the authors propose an improved Olympic operator for the Hole-filling algorithm, and apply it to generate the volume in a 3D ultrasound reconstruction of the spine. The conventional Olympic operator defines the empty voxels by sorting the neighbouring voxels, removing the n% of the upper and lower values, and averaging them to attain the value to fill the empty voxels. The empty voxel estimation can be improved by thresholding the range width of its neighbouring voxels and adjusting it to the average values. The method is tested on a hole-manipulated volume derived from a cropped 3D ultrasound volume of a part of the spine. The MAE calculation on the proposed technique shows improved result compared to all tested existing methods.

Sign in / Sign up

Export Citation Format

Share Document