Kamil Řehák

Experimental Validation Of The Gearbox NVH Parameters

Abstract The noise, vibration and harshness (NVH) plays an important role in the transmission area of automotive industry. To understand all the impacts on the gearbox’s global dynamic behavior it is necessary to gain information from a simplified model, create methods and get an appropriate and well correlated results with the experiment. The method itself can be afterwards reused for more complex transmission, which could be supported by other measurements. This paper deals with creation of a gearbox’s simplified model, including essential mechanisms as gear mesh stiffness, backlash, bearing stiffness and modal properties of the main components. Except for the presented model, more models with different difficulty levels are used. Numerical results are compared with data from experiment with good correlation.

Gear Drive System Simulation of Input Parameters Effect on Rattle

The understanding of gear dynamics is essential to design the power transmission with low vibration and noise radiation level. The virtual prototype is proposed for transmission dynamic investigation. This article deals with investigation of input parameters effect on gear rattle. The rattle noise is caused by hitting the tooth by each other, which can be noticed by vibrations evaluation on the gearbox housing. The evaluation is done by surface normal velocity comparison, which is connected to the emitted noise. The simulation results show that the torque and backlash has influence on the tooth contact loosening at the starting of rotation.

Gear Drive System Simulation with Different Model of Input Speed

Presented paper deals with investigation of the basic gearbox parameter effect on the surface normal velocity of the gearbox top cover. First the single stage gearbox was designed and manufactured for the inputs and results validation. Afterwards a dynamic model was built and each part of it was validated by an appropriate technical experiment. The presented part of investigation focuses on comparison of different kind of input speed—ideal smooth increasing input speed and variable input speed. The evaluation is done by amplitude of gearbox surface normal velocity. The main goal is to describe dynamic behaviour of whole gearbox by numerical simulation and find the numerical model recognisability. The simulation results show that the variable input speed has strong influence on dynamic behaviour.

Micro-CT Based Imaging and Numerical Analysis of Bone Healing

During distraction osteogenesis (bone lengthening) one phase is lengthening and a second phase is consolidation (fixed length, bone maturation). In this second phase of fracture healing, the callus consists of several tissue types. The response of callus bone to mechanical loading can determine the progress of treatment. The mechanical strain distribution could provide additional information of fracture healing in the same way as for bone remodeling. The architecture and tissue properties significantly affect the strength of the whole callus bone. This article focuses on imaging and numerical analysis of bone fracture healing based on input information obtained from micro-CT scans. The objective of this study is to focus on how different stiffness threshold values affect the load carrying tissue architecture and how this further influences the strain distributions within the callus. Finite element simulations are employed to investigate this. A rabbit tibia fracture callus was micro-CT scanned 30 days after osteotomy using an isotropic voxel size of 20 μm. Four computational models were created with different pixel threshold values to cover a wide range of callus tissue properties, with the purpose of finding an optimal threshold value. Optimal means here a finite element model which is computationally feasible and still contains the main load carrying tissue.The values of bone volume/total callus volume (BV/TV), bone area/total callus area (BA/TA), trabecular thickness, structure model index (SMI) were quantified to compare the differences between models. All finite element models were axially loaded to investigate the influence of threshold value on the callus reaction and influence of including the soft tissue. The BV/TV and BA/TA values indicate that for a certain threshold level, finite element models are suitable. However, a too high threshold leads to invalid finite element models. The finite element method (FEM) could be useful tool in understanding of fracture healing process.

Comparative Study of Mechanical Properties of Bone Tissue Based on the CT and the µCT Slices

This article deals with presentation of data processing obtained from imaging CT (computer tomography) and micro CT devices. These methods enable to perform bone tissue density analysis by non-invasive way. The image processing methods, by which it is possible to determine mechanical properties of bone tissue, are described in this paper. Further, a creation of a computational model with different bone density of cancellous tissue is described and afterwards the stress strain analysis is performed. The mandible segments with different bone density were used as samples. Results show significantly higher stresses are reached in a cancellous bone tissue with worse bone quality.

Study of Straight and Oblique Mandible Fracture Behavior in the Chin Section

. This work is focused on stress - strain analysis of a mandible fracture behavior in the case of straight and oblique fracture. For this problem the computational modelling was chosen with using finite element method. Mandible was created based on the 3D scanning and CT images. Using these procedures a STL model of mandible with cortical and cancellous bone tissue was created. A volume model of lower jaw with applied reconstruction plate was created in CAD software. Fracture in the chin region was modelled directly in the program ANSYS. The cancellous bone tissue is modeled with different mechanical properties, which corresponds to the varying quality of this tissue. An assessment of differences in the behavior of straight and oblique fracture is presented in this work.

Finite Element Analysis of Mandible Reconstruction Plate in the Case of Symphysis Fracture

The presented work is focused on stress - strain analysis of a reconstruction plate. For this problem the computational modelling was chosen with using finite element method. Mandible was created based on the methods of Reverse Engineering and CT images. Using these methods a STL model of mandible with cortical and cancellous bone tissue was created. A volume model of lower jaw with applied reconstruction plate was created in CAD software. A Symphysis fracture of lower jaw was modeled in calculation program ANSYS. The cancellous bone tissue is modeled with different mechanical properties, which corresponds to the varying quality of this tissue. In this work an influence of varying quality of cancellous bone tissue to von Mises stress is observed.