Wyniki wyszukiwania - BazTech

1

Effect of engine oil degradation in city type of operation part 1: Extreme case of operation in the city

Marko M., Štiavnicky M.

Zeszyty Naukowe Instytutu Pojazdów / Politechnika Warszawska

|

2013

|

z. 5/96

67--76

EN

The paper deals with the impact of deterioration factors on the degradation of motor oils from the viewpoint of its selected parameters in vehicles operation. Vehicles were operated on the roads, on the off road ground even under the so called intermittent operation with a number of cold starts and “go-stop“ type of driving. Motor oils were tested using TRIBO-I tribodiagnostic kit. The paper points on the change in parameter values after contamination of engine lubrication system of the vehicle with fuel, water and glycol compounds.

PL

Artykuł dotyczy wpływu najbardziej istotnych czynników wpływających na degradację olejów silnikowych, z punktu widzenia wybranych parametrów w eksploatacji pojazdów. Pojazdy były eksploatowane na drogach, poza drogami utwardzonymi, w warunkach pracy przerywanej z dużą liczba zimnych rozruchów oraz w czasie jazdy w warunkach "go-stop". Oleje silnikowe badano za pomocą zestawu do tribodiagnostyki “TRIBO-I”. W referacie zwrócono na zmiany wartości parametrów po zanieczyszczeniu układu smarowania silnika pojazdu: paliwem, wodą i związkami glikolu.

2

Trefftz radial basis functions (TRBF)

Kompiš V., Štiavnicky M., Žmindák M., Murčinková Z.

Computer Assisted Mechanics and Engineering Sciences

|

2008

|

Vol. 15, No. 3/4

239-249

EN

The TRBF's are radial functions satisfying governing equation in the domain. They can be used as interpolation functions of the field variables especially in boundary methods. In present paper discrete dipoles are used to simulate composite material reinforced by stiff particles using with boundary point collocation method which does not require any meshing and any integration. The better the interpolation (unction satisfies also the boundary conditions, the more efficient it is. In examples it is shown that a triple dipole (which is a TRBK) located into the center of the particle can approximate the inter-domain boundary conditions very good, if the particles are not very close to each other and their size is not very different. In general problem the model can be used as very good start point for international improvements in refined model. (Composite reinforced by short fibres with very large aspect ratio continuous TRBF were developed. They enable to reduce problem considerably and to simulate complicated interactions for investigation such composites.

3

Trefftz functions for 3D stress concentration problems

Murčinková Z., Kompiš V., Štiavnicky M.

Computer Assisted Mechanics and Engineering Sciences

|

2008

|

Vol. 15, No. 3/4

305-318

EN

The paper deals with solution of 3D problems with stress concentration using the Trefftz functions. The modelled stress concentrators are holes and cavities of spherical and ellipsoidal shapes. Moreover, the random spherical cavity microstructure is modelled. The Method of External Finite Element Approximation (MEFEA) is applied to simulate detailed stress state of mentioned stress concentrators. This boundary-type method was developed to build special approximation fund ions that are associated with surface which causes the stress concentration. The method does not need discretization by classical finite elements, however, instead of elements the domain is divided into Trefftz type subdomains. The displacement and force boundary conditions are met only approximately whereas the governing equations are fulfilled exactly in the volume for linear elasticity, making it possible to assess accuracy in terms of error in boundary conditions.

4

Trefftz functions in FEM, BEM and meshless methods

Kompiš V., Štiavnicky M.

Computer Assisted Mechanics and Engineering Sciences

|

2006

|

Vol. 13, No. 3

417-426

EN

The paper contains three different multi-domain formulations using Trefftz (T-) displacement approximation/interpolation, namely the hybrid-displacement FEM, reciprocity based FEM (multi-domain BEM) and the Boundary Meshless Method (BMM) for a single and multi-domain (MD) formulation. All three methods can lead to compatible formulation with the isoparametric FEM, when the displacements along the common boundaries are defined by same interpolation function. All three T-formulations enable to define more complicated elements/subdomains (the T-element can be also a multiply connected region) with integration along the element boundaries, only.