Search Results (21)

This paper presents an experimental method for determining the suitable bore diameter of bearing housings made of polymer designated as PA6, which enables multiple bearing replacement processes. Preceded by analytical calculation, four distinct series of housing samples (each with varying production tolerances) were subjected to testing, where each series comprised three housing samples with identical tolerance specifications. The assembly and disassembly processes of press-fit joints were thoroughly monitored using a force sensor, complemented by equipment for measuring the roughness of contact surfaces. Based on the experimental findings, a recommendation is provided for an appropriate interference fit for the tested bearing housing, providing a suitable solution for multiple maintenance processes. As a summary, the idea of this research is to define the prototype solution for the interference fit of a rolling bearing installed in a PA6 housing. Methods used to examine the proposed solution were surface topography and roundness measuring of PA6 housings, while the press-fitting and dismantling tests of rolling bearings in/from PA6 housings were used to verify it. Full article

This paper investigates the suppression of the cohesive cracking mode (CCM) in the sintered silver (s-Ag) die layer by intentionally introducing anisotropic porosity through two press sintering methods. Full press (FP) and local press (LP) bonding represent the s-Ag formed by pressing the die-attached assemblies (DAAs) on either the entire top surface or only on the silicon carbide (SiC) top surface, respectively. The fabricated DAAs were encapsulated with epoxy molding compounds. Degradation was evaluated using a nine-point bending test (NBT) under cyclic force between 0 and 270 N with a triangle waveform for 3 min per cycle at 150 °C. Scanning tomography images after 500 NBT cycles showed that the LP reduced the inner degradation ratio by up to 21.1% compared to the FP. Cross-sectional scanning electron microscopy revealed that the FP progressed cracking in the s-Ag die layer, whereas the LP showed no evidence of cracking. A finite element analysis revealed that in the FP, the accumulated plastic strain (APS) was concentrated in the s-Ag layer within the inner SiC chip. In contrast, the APS of the LP was preferentially concentrated outside the SiC chip. This preferential localization of damage outside the chip presents a promising approach for enhancing the reliability of packaging products. Full article

The interference fit is a common process for the assembly of mechanical parts on a shaft for diverse mechanical engineering applications. One of the manufacturing methods consists of introducing a shaft into a hub by applying a force being the hub diameter lower than the shaft diameter. This way, contact pressure is generated at the shaft–hub interface at the end of the process, enabling torque transmission. Thus, a non-uniformly distributed stress state appears at the shaft–hub interface with significant stress peaks at the hub edges. In addition, as a consequence of the manufacturing process, local plasticity is generated in the hub on the insertion side causing changes in stress distributions. In this paper, an analysis based on finite elements simulations is carried out to reveal the influence of, on one hand, manufacturing parameters such as friction on stress concentrations at the interface and, on the other hand, geometrical parameters such as hub chamfer angle, considering chamfer hubs and conventional hubs. To achieve this goal, different simulations of the mechanical manufacturing process of the axial assembly of press fits are carried out to reveal the stress fields at the interface. Thus, stress concentrations under different friction conditions from a case without friction to a dry friction case are revealed and analyzed. The results show, on one hand, the friction coefficient as a highly influential factor, causing asymmetrical stress distributions with high stress concentrations that reduce the mechanical performance of press fits and, on the other hand, the beneficial impact of chamfer hubs for lowering stress concentrations. Full article

Polycarbonate (PC) is a highly recyclable thermoplastic with high impact strength that bodes well to re-melting extrusion and shredding for positive environmental impact. For the goal of improving impact strength further, layered carbon fiber (CF) reinforcement has been added between PC sheets by hot pressing at 6.0 MPa and 537 K for 8 min. An addition of cross-weave CF layer reinforcement to PC increased Charpy impact value, a_uc of the untreated [PC]₄[CF]₃ composite over that of untreated PC resin reported at all accumulative probabilities, P_f. At medial-P_f of 0.50, a_uc was increased 3.13 times (213%), while statistically lowest impact value a_s at P_f = 0 calculated by 3-parameter Weibull equation was boosted 2.64 times (164%). To optimize a_uc, effect of homogeneous electron beam irradiation (HLEBI) treatment of 43.2, 129, 216, 302, or 432 kGy at 170 kV acceleration voltage to the CF plies before assembly with PC then hot press was also investigated. The 216 kGy HLEBI dose appears to be optimum, raising a_s at P_f = 0 about 6.5% over that of untreated [PC]₄[CF]₃ and agrees with a previous study that showed 216 kGy to be optimum for static 3-point bending strength, when quality can be controlled. Electron spin resonance (ESR) data confirms 216 kGy HLEBI generates strong peaks in CF and PC indicating dangling bond (DB) generation. Bending strength increase was higher than that of impact due to lower test velocity and higher deformation area spreading along specimen length, allowing more DBs to take on the load. X-ray photoelectron spectroscopy (XPS) data of CF top ~10 nm surface layer in the sizing confirms C–O–H, C–H, and C–O peak height from 216 kGy exhibited little or no change compared with untreated. However, 432 kGy increased the peak heights indicating enhanced adhesion to PC. However, 432 kGy degraded a_s at P_f = 0 of the [PC]₄[CF]₃, and is reported to decrease impact strength of PC itself by excess dangling bond formation. Thus, the 432 kGy created increased PC/CF adhesion, but degraded the PC resin. Therefore, 216 kGy of 170 kV-HLEBI appeared to be a well-balanced condition between the PC-cohesive force and PC/CF interface adhesive force when fabricating [PC]₄[CF]₃. Full article

The study introduces new technologies of microfinishing, which are primarily aimed at cylindrical surfaces but with machining effectiveness, precision, and surface longevity. In the newly proposed dual-zone microfinishing method, symmetrical abrasive film feeding systems are adapted with a lever mechanism and a pivoting pressing assembly to simultaneously conduct processing in two zones. With such a design, uniform force distribution is ensured, while mechanical deformation is reduced to raise the utility of the abrasive film and lower scraps for better economic performance. Also, the application of microfinishing operations combined with carbon layer deposition using graphite-impregnated abrasive films is introduced as a novel method. This process combines surface refinement and the forming of wear-resistant carbon coatings into one single operation, resulting in increased wear resistance and reduced forces of friction. Further stabilization of the conditions for microfinishing is achieved by immersing the processing zone in a fluid medium due to increased lubrication, improvement in heat dissipation, and the optimization of surface properties. It is particularly suitable for high-precision applications and a maintenance-free environment such as military, vacuum, and low-temperature systems. The experimental results show the effectiveness of the proposed methodologies, underscoring their ability to create remarkably smooth surfaces and very robust carbon textures simultaneously. Full article

Press fits are a simple and effective method for assembling a shaft into a hub for different applications in the mechanical engineering field. This method consists of forcing to pass a shaft into a hub via axial insertion. As a result of the difference in the diameters of both components of the shaft and hub, a radial interference is generated, causing a contact pressure at the interface shaft–hub. Contact pressure and the friction coefficient are key factors influencing the maximum transmitted torque. So, in this study, different scenarios for the assembly of a press fit were simulated using finite elements (FE) in order to reveal the influence of this key parameter on the manufacturing-induced stresses in the hub. This way, different friction conditions were considered in terms of the friction coefficient from the frictionless case to a case of high dry friction. In addition, different hub geometries were analyzed including conventional hubs and chamfer hubs with optimal geometry that allows lowering the localized stress concentrations at the hub edges. This way, a more realistic estimation of the final stress state of a press fit is obtained. According to the obtained results, the friction coefficient is revealed as a key parameter in the resulting stress field, causing a non-uniform distribution of stress that can affect the mechanical performance of the press-fit assembly. Full article

As an emerging grinding equipment, roller presses are widely used in Cement industry. The current problem with roller press is that the rolls surface is prone to wear and needs to be replaced regularly. This greatly reduces the service life of the roller press and affects the development of the roller press. Therefore, how to reduce the wear on the surface of the roller press and increase the service life of the roller press is an urgent problem that needs to be solved for the current roller press. Current research mainly focuses on the mechanism research of roller press wear and the optimization of rolls surface structure. In this paper, the extrusion force between the stud-lining and the material is calculated by analyzing the stress of the studded rolls under actual working conditions and the compression and rebound characteristics of material layer. The failure modes of studded rolls are mainly divided into two parts. On the one hand, it is fatigue cracking of the roller shaft and stud-lining. On the other hand, it is cracking at the contact between the stud-lining and the stud, and the fracture of the stud. Because the failure modes of the studded rolls are divided into two parts, the studded rolls are divided into two parts for simulation by using ANSYS 18.0. Firstly, the static analysis is carried out on the roller shaft and the stud-lining, and the distribution cloud diagram of the stress and contact pressure of the roller shaft and the stud-lining is obtained, and the stress concentration area is optimized. After optimization, the contact pressure between the roller shaft and the stud-lining is reduced by about 50%. The maximum equivalent stress of the roller shaft and stud-lining has also been reduced. Secondly, a static analysis was conducted on the stud-lining and studs. Since the stud-lining of the studded rolls are composed of stud holes arranged in a certain order. Therefore, stress concentration is prone to occur around the stud hole. The simulation experiment was carried out by changing the optimization schemes such as the assembly method of the stud and the stud-lining, the distance between the studs, and the length of the stud. To reduce the stress concentration of stud and stud-lining. After optimizing the model of the stud and stud-lining, the maximum equivalent stress of the stud-lining and stud decreased by about 10% and 25% respectively. Through the optimized design of roller shafts, stud-lining and studs. The service life of the studded rolls can be effectively improved and the production cost can be reduced. This can provide a reference for the design of the studded rolls. Full article

Ultrahigh-molecular-weight polyethylene (UHMWPE) is used in the defence industry mainly owing to its properties, such as excellent dimensional stability, excellent ballistic performance, and light weight. Although UHMWPE laminates are generally studied under impact loads, it is crucial to understand better the optimal machining conditions for assembling auxiliary structures in combat helmets or armour. This work analyses the machinability of UHMWPE laminates by drilling. The workpiece material has been manufactured through hot-pressing technology and subjected to drilling tests. High-speed steel (HSS) twist drills with two different point angles and a brad and spur drill that is 6 mm in diameter have been used for this study. Cutting forces, failure, and main damage modes are analysed, making it possible to extract relevant information for the industry. The main conclusion is that the drill with a smaller point angle has a better cutting force performance and less delamination at the exit zone (5.4 mm at a 60 m/min cutting speed and a 0.05 mm/rev feed) in the samples. This value represents a 46% improvement over the best result obtained in terms of delamination at the exit when using the tool with the larger point angle. However, the brad and spur drill revealed a post-drilling appearance with high fuzzing and delamination. Full article

In this paper, we address the most pressing challenges faced by the manufacturing sector, particularly the manufacturing of small and medium-sized enterprises (SMEs), where the transition towards high-mix low-volume production and the availability of cost-effective solutions are crucial. To overcome these challenges, this paper presents 14 innovative solutions that can be utilized to support the introduction of agile manufacturing processes in SMEs. These solutions encompass a wide range of key technologies, including reconfigurable fixtures, low-cost automation for printed circuit board (PCB) assembly, computer-vision-based control, wireless sensor networks (WSNs) simulations, predictive maintenance based on Internet of Things (IoT), virtualization for operator training, intuitive robot programming using virtual reality (VR), autonomous trajectory generation, programming by demonstration for force-based tasks, on-line task allocation in human–robot collaboration (HRC), projector-based graphical user interface (GUI) for HRC, human safety in collaborative work cells, and integration of automated ground vehicles for intralogistics. All of these solutions were designed with the purpose of increasing agility in the manufacturing sector. They are designed to enable flexible and modular manufacturing systems that are easy to integrate and use while remaining cost-effective for SMEs. As such, they have a high potential to be implemented in the manufacturing industry. They can be used as standalone modules or combined to solve a more complicated task, and contribute to enhancing the agility, efficiency, and competitiveness of manufacturing companies. With their application tested in industrially relevant environments, the proposed solutions strive to ensure practical implementation and real-world impact. While this paper presents these solutions and gives an overview of their methodologies and evaluations, it does not go into their details. It provides summaries of comprehensive and multifaceted solutions to tackle the evolving needs and demands of the manufacturing sector, empowering SMEs to thrive in a dynamic and competitive market landscape. Full article

The purpose of the investigations was to assess the influence of repeated sleeve assembly on the wear of forced-in joint elements. The test methodology assumed operating a forced-in joint in rotational bending conditions, dismantling the joint after every thousand fatigue cycles, and then joint reassembling. The total number of fatigue cycles was 106, or as many as needed for fatigue cracking. The macroscopic observations of the shaft surface demonstrated the traces of fretting wear in the form of randomly spaced grey and dark brown stains at the axle seat circumference close to the joint edge. The size and number of the wear traces would increase with the number of fatigue cycles. The top layer wear also depended on the number of sleeve/shaft assembly processes. The microscopic observations confirmed fretting wear, which developed on the shaft surface. Numerous instances of surface microabrasion as well as micropullouts and surface scratches were observed. Material build-ups were also observed, which would crack and migrate. The chemical analysis of the composition of wear products demonstrated the presence of iron and oxygen atoms, which confirms the oxidation of wear products. The measurement of the maximum force needed to remove the sleeve from the shaft after the next fatigue cycle showed the need to use a greater force each time; however, a smaller force was needed to press the sleeve onto the shaft. As a result of the development of fretting wear, shafts would become fatigue-worn after 3.6 × 10⁶ fatigue cycles. Full article

In the traditional pre-joining technology of aircraft panels, bolts are generally employed for pre-joining. Due to the length and width of panels, bilateral manual operations are required to operate bolts. In this case, there are problems such as low work efficiency, unstable quality, cumbersome operation, and inconvenient installation-removal. This paper takes a temporary fastener with one-side installation-removal as a research object and conducts in-depth research on three levels of quick-pressing: unloading, stable self-locking, and easy automatic installation. Firstly, by coordinating the ratchet and the spring, the restoring force of the spring is used to make the cylindrical top-rod rotary and realize the telescopic function to achieve quick loading and unloading of fasteners; subsequently, through the cooperation between the buckle and the spring, loading and unloading self-locking is attained; afterwards, through the threaded joining and the same cylinder design between the external profile components, the convenience of fasteners for automatic transportation is realized. When assembling two thin-walled parts of the aircraft, only continuous one-side pressing of fasteners is needed to carry out the tightening and unloading work, namely, one-pressing installation and one-pressing removal, which could solve the problems caused by the bilateral operation of traditional bolts and part tolerances. After the application of the fasteners into the pre-joining process of aircraft panels, the experiment results have shown that this temporary fastener provided a good clamping effect, could be quickly and efficiently installed and removed by continuous one-pressing, and avoided the problems of complexity and high cost for pre-joining processes. Full article

An implicit, elastoplastic, finite element method (FEM) with multi-body treatment function was applied to accurately analyze the real-world shaft clinching of a duplex-pair tapered roller (DPTR) wheel-bearing unit (WBU) under minimal assumptions during modeling. The inner races were viewed as elastoplastically deformable and were fitted to the hub shaft before clinching by imposing a thermal load reflecting the mechanical load of press-fitting. The forming roller (i.e., the power source) was considered to be force-prescribed, similar to the approach on real shop floors. The predictions focused on the homogenizing stage, during which the two inner races bear the preload. At this time, local plastic deformation occurred at the end of the hub shaft and in the armpit area and the cavity was either maintained or enlarged. The predicted cavity size in case of force-prescribed forming roller increased, compared with the velocity-prescribed forming roller. The residual stress became axisymmetric and was divided into two parts by the cavity. These findings allow engineers to control the pre-stresses imparted to the inner races of tapered roller bearing assemblies. Full article

This paper presents a method to include unmodeled dynamics of load or a robot’s end-effector into algorithms for collision detection or general understanding of a robot’s operation context. The approach relies on the application of a previously developed modification of the Dynamic Time Warping algorithm, as well as a universally applicable algorithm for identifying kinematic parameters. The entire process can be applied to arbitrary robot configuration, and it does not require identification of dynamic parameters. The paper addresses the two main categories of contact tasks with unmodelled dynamics, which are determined based on whether the external contact force has a consistent profile in the end effector or base coordinate. Conclusions for representative examples analysed in the paper are applicable to tasks such as load manipulation, press bending, and crimping for the first type of forces and applications such as drilling, screwdriving, snap-fit, bolting, and riveting assembly for the latter category. The results presented in the paper are based on realistic testing with measurements obtained from an industrial robot. Full article

Rapid prototyping has become increasingly popular over the past years. However, its application is heavily confined to a part size that fits the small build volume of additive machines. This paper presents a universal design method to overcome this limitation while preserving the economic advantages of rapid prototyping over conventional processes. It segments large, thin-walled parts and joins the segments. The method aims to produce an assembly with minimal loss to the performance and characteristics of a solid part. Based on a set of requirements, a universal segmentation approach and a novel hybrid joint design combining adhesive bonding and press fitting are developed. This design allows for the force transmission, positioning, and assembly of the segments adaptive to their individual geometry. The method is tailored to fused deposition modeling (FDM) by minimizing the need for support structures and actively compensating for manufacturing tolerances. While a universal application cannot be guaranteed, the adaptive design was proven for a variety of complex geometries. Using automotive trim parts as an example, the usability, benefits, and novelty of the design method is presented. The method itself shows a high potential to overcome the build volume limitation for thin-walled parts in an economic manner. Full article

In engineering application, the hot press assembly technology is often used to improve the stability of the rotor structure, but the conventional design methods cannot effectively evaluate the influence of this process on the rotor strength, which easily causes the rotor strength to exceed its safety margin range, and seriously it will lead to the failure of the rotor structure. This paper takes the cylindrical magnet surface-mounted high-speed permanent magnet synchronous motor rotor as the research object. Firstly, the influence of the assembly pressing force on the rotor stresses and interference is analyzed; then, comprehensively considering the assembly pressing force, speed and temperature, the rotor strength’s design method with high structural stability is proposed. Finally, based on the proposed method, the rotor strength of a 100 kW/30,000 rpm high-speed motor is designed, and the feasibility of the design is verified by over-speed experiment. Full article