The article presents the results of investigations into the depth of the plastically deformed surface layer in the roller burnishing process. The investigation was carried out in order to obtain information on the dependence relationship between the depth of plastic deformation, the pressure on the roller and the braking torque. The research was carried out according to the original method developed by the authors, in which the depth of plastic deformation is increased by applying a braking torque to the burnishing roller. In this method, it is possible to significantly increase (up to 20%) the depth of plastic deformation of the surface layer. The tests were carried out on a specially designed device on which the braking torque can be set and the force of the rolling resistance of the roller during burnishing can be measured. The tests were carried out on specimens made of C45 heat-treatable carbon steel. The dependence of the depth of the plastically deformed surface layer was determined for a given pressure force and variable braking moments. The depth of the plastically deformed layer was measured on the deformed end face of the ring-shaped samples. The microhardness in the sample cross-section and the evolution of the microstructure were both analysed.

The influence of dynamic loads resulting from human motor activity and electrocorrosion inside the human body on the strength parameters of artificial joint elements has not yet been investigated. Hip joint arthroplasty is the most common surgical procedure in the world that allows doctors to remove pain and restore motor skills in people with severe hip diseases, after accidents, and in the elderly. Based on the reports, this article assesses changes in the number of implanted endoprostheses in the years 2005–2019 and determines the trends and estimated changes in the number of implanted hip prostheses in the following decades. The study assesses changes in selected strength parameters of UHMW-PE polyethylene inserts of hip joint endoprostheses during their use in the human body. The research was carried out on appropriately collected samples from UHMW-PE cups removed from the human body with a known history and lifetime from 4 to 10 years. Patients’ body weight ranged from 735 [N] to 820 [N], and the declared physical activity was similar in the entire research group. As part of the research, the values of changes in dynamic modules and the mechanical loss coefficient were determined in relation to the share of the crystalline and amorphous phases of artificial UHMW-PE cups, removed from the human body after different periods of exploitation under similar operating conditions. The analysis of selected strength parameters was performed at a temperature of 40 °C, which corresponds to the working conditions inside the human body. On the basis of numerical studies, the influence of changes in material parameters on the deformation of the artificial acetabulum during the patient’s motor activity, which is one of the causes of fatigue destruction, was determined.

This article investigates the potential of using polymer-based Fused Filament Fabrication (FFF) 3D printing to manufacture structural components. This study aimed to explore the application of this technology within manufacturing processes. This research focused on material analysis, using a gear wheel from a lawn mower’s drive system as a case study. To achieve the purpose of this study, a reverse engineering process was carried out to create 2D and 3D documentation based on a physical piece. The geometric model created in the CAD environment was optimized for volume. It was intended to keep the material expenditure unchanged, which is intensified during the 3D printing process due to the need to apply an adhesive layer and supports. The final design process of the geometric model of the prototype was subjected to numerical analyses in terms of total deformation and reduced stresses for materials commonly used as filaments in the FDM/FFF 3D printing technology. The basic filaments PLA, ABS, and PA6 and PA12 were analyzed in this study. The results of the analyses showed that two of the four selected filaments had to be rejected due to significant deterioration in strength properties. Finally, the prototype workpieces were printed using materials approved for the manufacturing process.

The article presents the original technology of the extrusion of hollow curved pipes. The curvature radius of pipe axis was obtained directly during extrusion by eccentric alignment of the annular calibration gap of the extrusion die. Theoretical relationships describing the radius of curvature of the extruded part as a function of the eccentricity e of position of the annular calibration gap in the die were developed. A die with replaceable inserts with eccentricity e equal to 1, 2, 3, 5, 7 mm was designed and fabricated. Experimental tests were carried out to extrude lead pipes with an outer diameter of 20 mm and an inner diameter of 18 mm. Measurements of the radii of the curvature of the extruded pipes were consistent with the values calculated from the developed theoretical relationships. Numerical modelling of the proposed method of extrusion in a finite element-based QForm 3D program was carried out. The finite element method (FEM) numerical calculations were carried out for lead. Numerical simulations and experimental studies have shown that, by changing the value of the eccentric gap, the radius of curvature of the extruded pipe can be controlled.

Burnishing is one of the most effective methods of improving the strength of the surface layer of shafts as a result of strain strengthening of the material. This article presents an analytical approach to determining the the depth of the plastically deformed top layer of shaft based on Belyaev's theory. Contact of two bodies with an asymmetric stress state was assumed. A classic (symmetrical) solution was also considered. The aim of the research was to compare the calculated values of the depth of the plastically deformed top layer determined using these two methods. The calculations considered burnishing of shafts with a diameter of 48 mm made of steel with a yield stress of Re = 450 MPa and Re = 900 MPa. A burnishing tool with a Si3N4 ceramic tip was used for burnishing. It was found that in the range of low contact forces, the calculated values of the depth of the plastically deformed top layer using the asymmetric solution and the classical method are similar. It was also found that the relationship between the depth of the plastically deformed top layer and the contact force can be explained by a power equation with an accuracy of R2 > 0.999.

Purpose: This paper presents the application of numerical methods, for preoperative planning and determining the force and placement of distraction springs, as well as the cranial incision sites, in a newborn with a congenital disability involving cranial suture fusion. Methods: The study employs a multifaceted methodology based on the work of an interdisciplinary team. The procedure involves: (1) patient-specific Finite Element Method (FEM) numerical analysis to simulate varying distraction spring forces and allocations, (2) non-invasive 3D optical surface scanning for the precise analysis of post-operative anatomical changes, and (3) clinical verification of the numerical predictions. Results: Numerical studies were verified against clinical trials, resulting in substantial changes in the head shape of a 4-month-old child, an expansion of the external cranial vault, and a measurable improvement in the cephalic index and overall skull geometry. Conclusions: Based on this single-patient numerical case study, it is hypothesized that the design of craniosynostosis treatment planning can be configured to introduce personalized force into critical areas. The proposed alternative spring allocation suggests potential biomechanical advantages, including stress reduction and improved shape optimization. However, these findings serve as a proof-of-concept and require validation in larger clinical trials. Achieving a clinical effect that is sustained over time by reducing stress values can also be significant, because the bone remodeling process can be designed so that bones multiply along the direction of principal stresses, thereby allowing for the optimization of the skull shape envisioned by the neurosurgeon.