As surface wear is one of the major failure mechanisms in many applications that include polymer gears, lifetime prediction of polymer gears often requires time-consuming and expensive experimental testing. This study introduces a contact mechanics model for the surface wear prediction of polymer gears. The developed model, which is based on an iterative numerical procedure, employs a boundary element method (BEM) in conjunction with Archard’s wear equation to predict wear depth on contacting tooth surfaces. The wear coefficients, necessary for the model development, have been determined experimentally for Polyoxymethylene (POM) and Polyvinylidene fluoride (PVDF) polymer gear samples by employing an abrasive wear model by the VDI 2736 guidelines for polymer gear design. To fully describe the complex changes in contact topography as the gears wear, the prediction model employs Winkler’s surface formulation used for the computation of the contact pressure distribution and Weber’s model for the computation of wear-induced changes in stiffness components as well as the alterations in the load-sharing factors with corresponding effects on the normal load distribution. The developed contact mechanics model has been validated through experimental testing of steel/polymer engagements after an arbitrary number of load cycles. Based on the comparison of the simulated and experimental results, it can be concluded that the developed model can be used to predict the surface wear of polymer gears, therefore reducing the need to perform experimental testing. One of the major benefits of the developed model is the possibility of assessing and visualizing the numerous contact parameters that simultaneously affect the wear behavior, which can be used to determine the wear patterns of contacting tooth surfaces after a certain number of load cycles, i.e., different lifetime stages of polymer gears.

With the ever-increasing number of polymer materials and the current number of commercially available materials, the polymer gear design process, regarding the wear lifetime predictions, is a difficult task given that there are very limited data on wear coefficients that can be deployed to evaluate the wear behavior of polymer gears. This study focuses on the classic steel/polymer engagements that result in a wear-induced failure of polymer gears and proposes a simple methodology based on the employment of optical methods that can be used to assess the necessary wear coefficient. Polymer gear testing, performed on an open-loop test rig, along with VDI 2736 guidelines for polymer gear design, serves as a starting point for the detailed analysis of the wear process putting into service a digital microscope that leads to the evaluation of the wear coefficient. The same wear coefficient, as presented within the scope of this study, can be implemented in a rather simple wear prediction model, based on Archard’s wear formulation. The developed model is established on the iterative numerical procedure that accounts for the changes in tooth flank geometry due to wear and investigates the surface wear impact on the contact pressure distribution to completely describe the behavior of polymer gears in different stages of their lifetime. Although a simple one, the developed wear prediction model is sufficient for most engineering applications, as the model prediction and experimental data agree well with each other, and can be utilized to reduce the need to perform time-consuming testing.

Product design and manufacturing leverage 3D scanning for various applications. This study aims to investigate the effectiveness of 3D scanning in furniture production by surveying the literature and showcasing four real-world case studies. The literature review reveals that 3D data acquired from real-world objects have applications in research, rapid prototyping, restoration, and preservation of antique furniture, optimizing CNC machining processes, and measuring furniture components for quality control. The case study descriptions demonstrated the circumstances, rationale, and methodology for 3D scanning. All the case studies analyzed stem from the collaboration between the Laboratory for Product Development and Design at the Faculty of Mechanical Engineering at the University of Sarajevo and various furniture production enterprises from Bosnia and Herzegovina. The conclusions highlight that 3D scanning in the furniture sector is advantageous for developing computer-aided design models from early-stage design prototypes, validating the dimensional accuracy of manufactured components by comparing with CAD models, safeguarding and reconstructing vintage furniture, and remanufacturing formerly produced goods that lack complete technical records (reverse engineering).

The current paper investigates the effects of geometric design parameters on the fatigue failure of the drive axle housing using the Finite Element Method (FEM). The study examines the effects of various factors on the fatigue life of the drive axle housing, such as axle housing wall thickness, housing cross-sectional rounding radius, and rounding radius of the central part of the housing. Based on the known material properties and dynamic loads, a CAD/FEM model of the drive axle housing was developed, and a structural analysis was carried out. Based on the results of the structural analysis, critical places on the housing were determined, and fatigue analysis and lifetime prediction were performed. Through a series of simulations, the study reveals that increasing housing wall thickness can significantly improve fatigue performance. Similarly, increasing the rounding radius at the housing cross-section, as well as the rounding radius at the central part of the housing can also lead to improved fatigue performance. However, the effect of increasing the value of these two radii is not as significant as the effect of the wall thickness. These findings give useful information regarding the design and manufacture of drive axle housings for vehicles, intending to reduce the likelihood of fatigue failure.

Bridge crane is exposed to dynamic loads during its non-stationary operations (acceleration and braking). Analyzing these operations, one can determine unknown impacts on the dynamic behavior of bridge crane. These impacts are taken into consideration using selected coefficients inside the dynamic model. Dynamic modelling of a bridge crane in vertical plane is performed in the operation of the hoist mechanism. The dynamic model is obtained using data from a real bridge crane system. Two cases have been analyzed: acceleration of a load freely suspended on the rope when it is lifted and acceleration of a load during the lowering process. Physical quantities that are most important for this research are the values of stress and deformation of main girders. Size of deformation at the middle point of the main crane girder is monitored and analyzed for the above-mentioned two cases. Using the values of maximum deformation, one also obtains maximum stress values in the supporting construction of the crane.

(1) Background: With the ever-increasing number of polymer materials and limited data on polymer gear calculations, designers are often required to perform extensive experimental testing in order to establish reliable operational data for specific gear applications. This research investigates the potential of a Polyvinyldene fluoride (PVDF) polymer material in gear applications, considering various loading conditions and different types of gear transmission configurations, including both self-mated mesh and steel/PVDF mesh. (2) Methods: PVDF gear samples were tested on a specially designed test rig that enables active torque control and temperature monitoring in order to obtain the necessary design parameters and failure modes. Each test for certain load conditions was repeated five times, and to fully investigate the potential of PVDF gear samples, comparative testing was performed for Polyoxymethylene (POM) gear. (3) Results: Tribological compatibility, tooth load capacity, and lifespan assessment, along with the types of failure, which, for some configurations, include several types of failures, such as wear and melting, were determined. Temperature monitoring data were used to estimate the coefficient of friction at the tooth contact of analyzed gear pairs, while optical methods were used to determine a wear coefficient. (4) Conclusions: The tribological compatibility of polymer gear pairs needs to be established in order to design a gear pair for a specific application. PVDF gear samples mated with steel gear showed similar lifespan properties compared to POM samples. Temperature monitoring and optical methods serve as a basis for the determination of the design parameters. PVDF is an appropriate material to use in gear applications, considering its comparable properties with POM. The particular significance of this research is reflected in the establishment of the design parameters of PVDF gear, as well as in the analysis of the potential of the PVDF material in gear applications, which gives exceptional significance to the current knowledge on polymer gears, considering that the PVDF material has not previously been analyzed in gear applications.

: Modern technologies are essential parts of Industry 4.0. From automation, robotics, digitalization and additive manufacturing (3D printing) up to 3D scanning and reverse engineering. 3D scanning has a wide range of usage in today product development and design processes. This paper will present several real case studies of 3D scanning in reverse engineering andnew product development and design processes. Paper explores importance of 3D scanning technology, as integral part of Industry 4.0. Seven case studies are explored in more detail. Five of these case studies are realized in Laboratory for Product development and design at University of Sarajevo – Faculty of mechanical engineering as a part of the projects realized in cooperation with several companies from Bosnia and Herzegovina, while two of them are realized in Protodevs company in Sarajevo. Artec Eva 3D scanner and Artec Studio software were used for most of the presented case studies.

The aim of this work is to investigate the impact of geometry on the mechanical stability of characteristic structural solutions of plates for internal bone fixation using the finite element method (FEM). Based on the realistic construction of plates for internal bone fixation, 3D geometric and FEM models were formed, and then structural analysis was carried out in the CAD/CAE system CATIA V5. Five different types of plates for internal bone fixa - tion were tested under two types of loads: axial pressure and torque in the case of application to the femur. During the structural analysis, stresses and displacements were monitored at characteristic points of the structure. The most attention was paid to the relative displacements of the bone model fragments, because the stiffness of the plates for the internal fixation of the bone was determined based on them. At the end of the paper, the results of all analyzed plates are presented, their mutual comparison as well as the conclusion in which, based on everything done, it was stated which plate would be the most favorable solution for a given case of bone fracture.

This study performed a mechanical stability analysis for the impact of axial pressure on an Ultra X external unilateral fixation device applied to a tibia with an open fracture. The real construction of the fixation device was used to create a 3D geometric model using a Finite Element Method (FEM) model, which was made to perform structural analysis in the CATIA V5 (Computer Aided Three-dimensional Interactive Application) CAD/CAE system. Specific stresses and displacements were observed at points of interest using structural analysis. The focus was on the relative displacements of the proximal and distal bone segments in the fracture zone. These displacements were used to calculate the stiffnesses of the bone in the fracture zone and the fixation device itself. The results obtained provide the necessary information regarding the stability of the Ultra X fixation device.

This paper presents a comparative analysis of the biomechanical characteristics of an external fixator with a frame made of two different materials (stainless steel and composite material) during anterior–posterior bending. Before the test itself, two representative configurations of the Sarafix fixator were selected for application on the lower leg and upper extremities under the designations B50 and C50, which are most widely used in orthopedic practice. The examination of the biomechanical characteristics of the external fixator was carried out using the structural analysis of the construction performance of the Sarafix fixator using the finite element method, the results of which were verified through experimental tests. The developed experimental and FEM models study the movement of the fracture crack and enable the determination of the stiffness of structural designs as well as the control of the generated stresses at the characteristic locations of the fixator. The results show that the fixator with a carbon frame has lower stresses at critical points in the construction compared to the fixator with a steel frame, in the amount of up to 49% (at the measuring point MT+) or up to 46% (at the measuring point MT−) for both fixture test configurations. The fixator with a carbon frame has greater displacements at the fracture site compared to the fixator with a steel frame, in the amount of up to 45% (for configuration B50) or up to 31% (for configuration C50). The stiffness of the structure for both test configurations of the fixator is lower in the fixator with a carbon frame compared to the fixator with a steel frame by up to 27%. Based on the findings of this study, we can conclude that a fixator with a steel frame has better biomechanical characteristics compared to a carbon frame.