Computational analyses
Rollover stability (static and dynamic) of vehicles
Based on many years of experience and expertise, the Department offers analyses of rollover stability of vehicles on various types of undercarriages. Calculations of static rollover stability are based on our own original and well verified calculation algorithms. On that basis, our employees have developed computer programs that allow us to quickly determine the stability of various types of mobile machines. Among other things, they take into account the flexibility of the tyre wheels and the susceptibility of the soil.
For dynamic stability analyses, we use simulation models developed primarily in commercial MBS environments.
To verify the computational models, we use a dedicated test platform. Thanks to the hydrostatic system, it can be tilted at any angle and thus simulate the test reference vehicle being on a slope. For the wheels of the reference vehicle on the platform, we can record tangential and normal reactions and then compare them with corresponding values obtained computationally.
Directional stability (snaking) of vehicles
Directional stability is considered as undesirable by driver changing vehicles path and problems with keeping straight in line motion. High velocities, inappropriate mass position leads to reduced directional stability. Department proposed a new solution for keeping in line motion and allows for achieving higher velocities. Proposed methods are divided into 2 groups: active like using brakes of a vehicle or passive methods like optimising the steering system. Both systems are already tested in a computer software and on a laboratory vehicle.
Dynamics of a machines and vehicles by computer simulation
There is a growing number of computer simulation programmes on the market and companies offering to conduct such studies. The experience of members of the Department goes back to the 1990s, when the first such studies were conducted. In order to carry out such research, it is necessary to verify the simulation results and measurements obtained for different machines and devices. The knowledge of differences between various types of excitation, the use of software that has been verified many times, knowledge of weak/underdeveloped solutions in simulation programs allows to avoid erroneous simulation results. Many computer simulation programs have been tested in the Department and experience allows us to select the most beneficial for your needs.
Strength of load-bearing structures by the finite element method (FEM)
Designing load-bearing structures of machines and vehicles requires the use of computational methods that allow taking into account the complexity of structures, a wide spectrum of physical interactions, also non-linear, including contact phenomena.
The software (NE / Nastran) and the experience of the Department’s employees allow us to offer numerical strength calculations of load-bearing structures and assemblies of machines and vehicles using the finite element method in the field of linear and non-linear analyses.
Numerical simulations of soils using Dicrete Element Method
One of the fields of our expertise is testing and numerical simulations of soils. Thanks to the Discrete Element Method it is possible to predict: forces acting on work tools, work tool wear, discharge speed from hoppers, powder mixing process or even rock crushing.
Our laboratory is equipped with many devices for soil testing, such as triaxial apparatus, direct shear tester, oedometer, vibrating sieve and other that are used for determination of basic soil parameters as well as soil strength. Thanks to a well-equipped laboratory, we are able to provide input parameters for simulation models, i.e. conduct a so-called calibration of the model. DEM model calibration is the most often employed method for input parameter determination. It is an iteration method where the results of the simulation are compared with results of the experiment, and tuned (type of contact model, friction coefficient, adhesion forces, etc.) until the simulation reflects the experiment. With the knowledge of investigated process and the material, it is possible to extrapolate the established model parameters to other processes, which significantly reduces the total time of the research.
Below a simple simulation of a lunar rover wheel on loose soil, as a part of research on the influence of the shape and size of lugs on vehicle performance is presented.
The second video shows an exemplary simulation of hopper discharge of crushed quartz is shown. Thanks to similar simulations, it is possible to determine optimum geometry of the hopper, especially the hopper angle depending on the discharged material, as well as estimation of discharge speed depending on the hopper dimensions and auxiliary devices.
CFD analysis
The team conducts research and development activities in the field of computational fluid dynamics using Ansys software (CFX, Fluent). We perform CFD analyzes for hydraulic machines and components, as well as simulations of vehicle aerodynamics.
Among projects implemented so far, the following can be distinguished:
- Analysis of leakages in gaps in the external gear pump
The analysis of the fluid flow phenomena inside the gear pump for various pump parameters such, i.e. rotational speed, discharge pressure, suction pressure, as well as for different radial and axial gap sizes. Based on the performer calculations it was possible to determine the influence of pump operation parameters and gap sizes on volumetric efficiency. - CFD analysis of the vane pump
A series of simulations for various pump operating parameters were carried out. The influence of rotational speed and pressure in discharge channel on pressure changes in inter-vane chambers were analyzed. Furthermore, the occurrence of the cavitation phenomenon and its intensity was investigated. - Air flow analysis on a truck
The project involved performing CFD simulations on the flow over a truck in order to analyze velocity and pressure fields around the vehicle. Based on the obtained contour plots it was possible to investigate areas that reduce aerodynamic efficiency of the truck and modify them. In addition, the performed simulations allowed to obtain values of different factors, including aerodynamic drag coefficient.
