Purpose: The objective of the study is to build a mathematical model that will be used to determine the value of the propulsions torque required to drive a human–wheelchair system under varied conditions. Materials and methods: To this end, the mechanics of the system’s movement were described with equations taking into account forces acting on it. As a result forces acting on individual axles of the wheelchair’s wheels were determined. This formed a basis for solving the developed model. In the next step experimental and literature based research was performed in order to determine values of the developed model’s parameters. It was then introduced into the environment of numerical computation. As a result, we could carry out a number of simulations allowing us to trace propulsion torque curves for various driving conditions. Results: This in turn was a basis on which a preliminary validation of the developed mathematical model was performed. Conclusions: Presented the mathematical model can be applied during work related to the design of manually propelled wheelchairs.

This article presents the results of a numerical experimental study on the simulation of the dry ice compaction process. The first part of the article presents a description of the material used, material models and the methodology of experimental research. In the second part, numerical and experimental study results are presented. For the purpose of comparison, a parametric method based on the residual sum of squares was used. The application of the indicated method fills the gap in the available literature as the authors are not aware of any existing data from previous studies on the method of comparing the results of numerical tests in terms of the obtained results and the change of the value of the tested parameter as a function of another variable. The results of this study can be useful in research work aimed at further development of the process of extrusion and compaction of dry ice using Drucker-Prager/Cap and modified Cam-Clay material models for instance for optimization of geometric parameters of parts and components of the main assembly of the machine used in the process of dry ice extrusion.

How to reduce consumption of energy in manufacturing has become a topical issue nowadays. Certain manufacturing processes are known for being highly energy-intensive and compression of materials belongs to this group. This article presents the simulation of the process of compression of dry ice snow with the use of the Mohr–Coulomb model. Two simulation variants were considered in this research. In the first one, constant input parameters were used and in the second one, the input parameters were variable, depending on the changing density of the compressed material. The experimental data were compared with the predicted values to find that the model using constant input parameters was inferior as regards to the goodness of fit. On the other hand, the model with variable input parameters was less accurate in predicting the maximum compression force acting in the process. The last section of this article deals with simulations performed with the Drucker–Prager Cap and modified Cam-Clay models. Finally, it was concluded that the Mohr–Coulomb model yields a more accurate representation of the compression process while requiring less information on the variation of the material parameters.

The article presents the preliminary results of numerical simulations of the densification process of shredded waste wood. The purpose of the simulation was to evaluate the possibility of using the Drucker-Prager-Cap model in the field of modeling plastic deformation of shredded biomaterials. The experimental studies allowed the verification of numerical simulations. In the research, the stamp-cylinder assembly of a special construction was used, adapted for assembly on a strength machine. The tests carried out are to constitute guidelines for the construction of machinery and devices for compacting biomass.

This article presents the outcome of research on modelling the process of the extrusion of crystalline dry ice. The purpose of this process is to densify the material and obtain pellets of several millimeters in diameter. This reduces the sublimation rate in ambient conditions of the material whose temperature in a solid state is 195 K. A lower sublimation rate means a reduction of the loss of product in its final applications, which include refrigeration and reduction of atmospheric emissions of gaseous CO₂. A ram-type extruder was considered in this analysis, in which dry ice was extruded through a single-hole die of varying geometry. The article presents the results of numerical analyses of the extrusion process, using a simulation method based on the Smoothed Particle Hydrodynamics (SPH) approach. The results from simulations were verified by the experimental data in terms of the maximum force required to complete the process, in order to assess the applicability of the proposed method in further research on dry ice compression.

Presently, there are many different available material models. Some are used for modeling loose materials such as soil and sand. Such models could be usable for modeling the behavior of fragmented biomaterials e.g. sawdust. The subject of the present article is the M-C model, one of the models for describing the characteristics of plasticity in a material. The article presents the method of determining the material constants used in this model, including the cohesion coefficient and angle of internal friction. The results and types of experimental examinations necessary for the purpose of the implemented task are also presented herein. The study was carried out for the oak and pine sawdust mix.