Jan Maciejewski, PhD, DSc
Publications
CV
Research fields
Contact
Research field
Laboratory test of the soil-tool interaction
An experimental program are executed on the specialized laboratory stand equipped with a soil bin, located at the Technical University of Kielce, Poland.
The main type of laboratory tests:
- Analysis of the rigid walls interaction in the soil digging processes
- Optimization of the soil cutting and tool filling processes using the excavator bucket
- The influence of the teeth wear in the digging processes
- Soil compaction in the rolling process
- Passive Earth Pressure Problems: wedge, punch indentation, influence of a non-uniform soil mass on the failure mode
Theoretical analysis of the soil-tool interaction:
- Simulation of soil compaction process under rigid cylinder using FEM and multisurfaces soil model
- Application of the kinematically admissible solutions and incremental analysis to the description of the soil cutting problems
- An Upper-bound analysis for the geomaterials with non-linear failure condition and anisotropic geomaterials
Soil and Rock Anisotropy
In the cooperation with prof
Zenon Mróz , the new constitutive model of anisortopic materials
was elaborated. The model based on the critical plane concept. The damage or shear
strength distribution is an essential element in generating the yield or
failure condition. In several paper were demonstrated that the form of the
respective failure surfaces depends essentially on the relative orientation of
stress and anisotropy axes. The damage evolution rules can also be postulated
using the critical plane concept and expressing the rules in terms of contact
variables. Those approach provides
much simpler description of anisotropic damage or deformation induced texture
than that based on the representation formulas in terms of stress, structure
and mixed invariants.
Numerical simulation of SPD processes
Severe plastic deformation (SPD) processing
techniques, namely, equal-channel angular
pressing (ECAP) and cyclic extrusion-compression (CEC) were
investigated by using the FEM ADINA 8.3. The major aspect examined is the non-uniformity of
the accumulated, equivalent plastic strain after processing with the
use of
different shapes of the die. The
quantitative effect of several parameters on the plastic flow was
presented in the paper: Maciejewski, Kopeĉ and Petryk (2007).It is found that
the diameter ratio of the chambers and narrower channel in the CEC
method, and also the inclination angle of connecting
conical parts, can affect strongly the degree
of strain non-uniformity.
Technological
metal forming processes of extrusion with imposed cyclic
torsion or shear deformation are of actual research and engineering interest in
view of their advantages with respect to monotonic loading processes (KOBO process). The
significant reduction of required forming load, growth of ductility and finer
grain structure of extruded material are the main beneficial factors. An
analysis of an axisymmetric extrusion process assisted by cyclic torsion
induced by cyclically rotating die with specified rotation amplitude and frequency was investigated. Assuming the kinematically admissible flow mode upper-bound analysis was
presented in the paper: Maciejewski and Mróz (2008). The evolution of extrusion force and torsion moment with process
control parameters such as ratio of extrusion and torsion rates, amplitude of torsion was
studied and the corresponding localized plastic
flow mode was specified. The effect of material hardening, viscosity and thermal
softening was analyzed. The presented analysis allows for specification of
process control parameters.
Constitutive modelling of metal under combined loading paths
In the cooperation with prof Mroz a constitutive model for metals was developed, with
the aim to simulate cyclic deformation under axial extension or compression
assisted by cyclic torsional (or shearing) straining of specified amplitude.
Such mode of deformation was recently implemented in technological processes
such as extrusion, forging and rolling. The constitutive model accounting for combined hardening
(isotropic-kinematic) with both hardening and recovery effects is presented and
calibrated for four materials: pure copper, aluminium alloy (PA7), austenitic
and carbon steel. The experimental data are used to specify model parameters of
materials tested and next the cyclic
response for different shear strain amplitudes is predicted and confronted with
empirical data. The model prediction of ratcheting effect is also discussed in paper Maciejewski & Mróz (2007).
