Economic Systems Research

Abstract The objective of the current study is to investigate the formation mechanism of rail corrugation. According to the actual wheel-rail motion relationship, that is, considering the influence of the angle of attack (AoA), a single degree of freedom friction pair model considering different friction attributes was established. The system stick-slip oscillation characteristics under different friction attributes were analyzed by using the model, so as to explore the generation reason of corrugation. Meantime, combined with the parameter analysis of the power system, the corresponding control measures for the stick-slip oscillation were put forward to slow down the formation and development of corrugation. The results show that the lateral and vertical dynamics play important role on its stick-slip oscillation characteristics. The corrugation formation on the metro small radius curve is related to the unstable stick-slip oscillation induced by the negative slope friction creep property of wheel-rail interface. The parameter analysis illustrates that the unstable stick-slip oscillation can be effectively controlled by increasing the damping coefficient, increasing the modal stiffness, appropriately reducing the static vertical force of the contact interface and increasing the lateral velocity (AoA) within a certain range. Practically, knowing the formation mechanism of rail corrugation is conducive to understanding the evolution process of rail corrugation; meantime, by referring to the results of parameter analysis, the active control of stick-slip oscillations can be realized, thereby controlling the growth of rail corrugation.

Abstract The contribution is devoted to the making of bimetallic semi-finished products for the production of elements, which are used to joining dissimilar materials, metal sheets to plastics, using the Resistance Element Soldering. During the making of bimetallic semi-finished products by gravity casting, defects occurred and, moreover, the proposed method of casting was not very productive. Therefore, centrifugal casting of bimetallic semi-finished products was proposed, which enables the production of a larger number of semi-products with higher quality in one casting cycle. The method was verified by preparing bimetallic semi-finished products Cu-Sn91Zn9 and Cu-Sn60Pb40. The non-destructive X-ray test proved the reliability of the centrifugal casting in the serial production of high quality bimetallic semi-finished products.

Abstract This paper aims to investigate the impact of braking with brake blocks on the fatigue lifetime of the train wheel web. Braking generates heat, causing uneven thermal stress and residual stresses as it cools. This can lead to the initiation of fatigue cracks in the wheel web. Therefore, the main issue is the numerical modelling of the railway wheel loaded by mechanical and thermal loads. A complex fatigue investigation is proposed to validate the numerical models and determine critical areas of the wheel web where fatigue cracks can initiate.

Abstract This study aims to evaluate the durability of as-cast Ti-6Al-7Nb in femoral stem application using fatigue analysis. As-cast Ti-6Al-7Nb rod specimens were tested experimentally with load range of 120%, 100%, 90%, 80%, 70%, 50%, 30%, and 20% relative to the yield strength. The fatigue limit was identified on a range of 141 - 211 MPa, represented by two run-out specimens running until high fatigue cycle (HFC) of 107 without failure. ProFatigue contributed to expose the estimation of the expected failure cycle on fatigue limit stress of as- cast Ti-6Al-7Nb based on Weibull modelling. It was predicted by probability failure (Pfail) of 50%. The failure cycles were revealed at 2.144 x 107 and 2.823 x 109 cycles on amplitude stress of 211 and 141 MPa, respectively. The reliability of the designed femoral stem for Indonesian people has been analyzed under ISO 7206 configuration through finite element analysis by adopting the material properties of as-cast Ti-6Al-7Nb. The static linear analysis demonstrated the maximum stress concentration of 136 MPa occurring over the medial region of the femoral stem, showing lower stress levels compared to the fatigue limit of as-cast Ti-6Al-7Nb. Furthermore, the lifetime analysis computed that the design could withstand cyclic loading until 2.51 x 109 cycles with fatigue safety factor and damage factor in 1.763 and 0.398, respectively. Results concluded that the investment casting is evident to become an alternative manufacturing method of femoral stem made of Ti-6Al-7Nb.

Abstract Classical analysis methods have shown that flexural, in-plane, deflections due to shear strain in the flange pack of preloaded bolted joints produce bending moments and tensile loads on bolts within the joint. These bending moments and tensile loads are most noticeable in joints that are required to support large in-plane loads and torsional moments. The shear loads on the bolt associated with the flexural deflections can result in the bolt head, or nut, slipping relative to the flanges. This slippage will in turn result in mechanical loosening of the joint. The bending moments associated shear loads and tensile loads produced by the combination of both out-of-plane and in-plane external loads and torsional moments are in addition to the bolt preload. These additional loads, combined with a high initial bolt preload, can cause yielding of the bolt, which can also result in relaxation of the initial preload. This article reviews earlier work in determining the tensile bolt stresses induced in preloaded bolts by the external loads and presents methods of calculating the amount of preload relaxation that could occur from each mechanism discussed.

Abstract The presented studies made it possible to clarify the calculation model of the diesel engine clutch with packages of sleeve springs. The stressed state of the spring packets is considered, while it is proposed to place the point of application of the radial force, which bends the spring package, in the zone of its greatest flexibility. Calculations performed according to the obtained expressions showed a coincidence with the results of experimental studies by other authors within 4% and with simulations conducted using automated design systems.

Abstract This paper deals with the calibration of the polymer material PPC3TF2 using the PRF (Parallel Rheological Framework) material model implemented in the commercial software Abaqus. In order to reduce computational time, the unit cube model was used for the simulations. The coefficients initially calculated in Excel were used as input values to create the material model. For the most accurate results, the coefficients were optimized in Isight software.

Abstract This article presents the development and implementation of the IPASIOU automated system for producing orthopaedic insoles. The IPASIOU system utilizes CAD/CAM technologies, digital scanning, and automated manufacturing processes to enhance the quality and availability of individually made orthopaedic insoles. The paper discusses the technological solution, results, and implications of the IPASIOU system, highlighting its potential for advancing the fields of orthotics and prosthetics.

Abstract The paper presents a low-cost driver fatigue detection camera system for older car models that do not have built-in fatigue detection systems. Based on a review of current solutions and image processing methods for face and eye detection, the Viola-Jones method for face detection and the cascade regression for eye detection were selected to enable real-time detection via smartphones and avoid the high cost of traditional systems. The proposed system has been successfully tested with real-time video under laboratory conditions.

Abstract Article deals with the calculation issues of deflection and stress in the rail and pins, which are a part of the anchoring design for rack-railway tracks. The rack-railway track, is intended for the transport of excessively heavy loads and people inside mines. A longitudinal track dip can be up to ± 35deg. Practical application is focused on the calculations of pins and rails, for which a novel combination of analytical approaches and FEM is used, with dynamic loading and the theory of beams on an elastic foundation. The methodology is explained in details and the first results are listed. Everything stated in this article can be used to design transport systems not only in mining/underground constructions.

Abstract The purpose of the proposed modernization was to create the possibility of harvesting assortments simultaneously with stripping the bark in longitudinal strips to accelerate the natural drying of wood without reducing the productivity of the device compared to its counterparts. The goal was achieved and the forest harvester equipped with the new device was able to harvest debarked logs.

Abstract Synthesis gases produced from municipal waste or plastic waste pose a great alternative source of energy, as they are not only reducing dependency on the fossil fuels, but also diversify energy sector and reduce the amount of a landfilled waste. This is directly related to the recent initiatives and legislation related to the greening of transport. The presented contribution focuses on the influence of six selected synthesis gases on the internal parameters of an internal combustion engine intended for cogeneration. The investigated gases fall into the category of medium-energy gases (8 – 14 MJ.kg−1). The experimental measurements have shown that mainly the proportion of hydrogen in the mixture has an effect on shortening the burning time and also on the maximum rate of pressure increase. A higher proportion of CO and H2 increased the maximum combustion pressure with slightly reduced power. The concentration of CH4 directly affected the volumetric value of the heating value of the mixture with a subsequent direct effect on the IMEP or engine torque. The engine operating at full load at speed of 1500 min−1, when running on the selected mixtures in comparison with the operation on natural gas, decreased its engine torque in the range between 13 and 20% and increased its hourly fuel consumption from 2.31 kg.h−1 for natural gas to the span of 7.90 - 12.30 kg.h−1 for measured gases. During the measurement of the control characteristic all investigated synthesis gases have developed an abnormal (detonation) combustion near the optimum pre-ignition angle.

Abstract The purpose of the published research is to investigate the dependence of the technological parameters (cutting speed, focal length, and gas pressure) of fiber laser cutting to obtain the minimum deviation of the diameters of the parts from the nominal dimensions. The result is a mathematical model and optimized values for setting the fiber laser cutting machine’s technological parameters for the given material type. The optimized laser cutting parameters also depend on the kind of material. The entire research is focused on developing a global auto-calibration system for optimizing laser cutting parameters for different thicknesses and types of materials.

Abstract Based on the flow modeling and operational experience of the previous cylindrical loop reactor, we designed a sheet reactor combined with a loop reactor. The design with a cylindrical cross-section was applied to an equivalent cross-section (sheet) of several squares arranged next to each other. In accordance with the sedimentation processes experienced in the outlet branch, we created an algae trap, thereby reducing the flow to the level necessary for sedimentation. With this, I would like to achieve the already experienced, nearly 10-fold increase in algae concentration compared to the one in the mainstream.

Abstract The article shows how the orthotropic material properties of the textile composite layer change if the ratio of longitudinal and transversal fiber bundles in the textile is modified in the case of a composite reinforced with plain weave textile. I determine the material properties using model-cell and finite element simulation. The density of the longitudinal fiber bundles is the same in each of the five examined layer models. I change the ratio of the fiber bundles of the textile by varying the distance of the transversal roving’s in each model.