rss_2.0Acta Mechanica et Automatica FeedSciendo RSS Feed for Acta Mechanica et Automatica Mechanica et Automatica Feed and Experimental Study of a Passive Frequency-Dependent Vehicle Suspension Damper<abstract> <title style='display:none'>Abstract</title> <p>The recent trends in the automotive industry have enforced chassis solutions beyond the reach of conventional systems. Thus, extending the functionality of passive hydraulic dampers is vital in improving their effectiveness while maintaining low production and operating costs. This paper presents a general structure of a passive shock absorber with so-called frequency-dependent (FD) damping characteristics and points to constitutive elements of the valves used in this type of an adaptive damper. A mathematical description of FD damper is provided together with a model developed in the Siemens AMESim environment. The performance of the model was verified against the data from tests with a real, commercially available FD shock absorber. Furthermore, in order to emphasise its efficiency, the authors have carried out a study involving quarter car models (QCM) with and without the FD damper, respectively. The results have clearly shown major advantages of utilising FD dampers in a suspension.</p> </abstract>ARTICLEtrue Solitary Waves for Thin-Film Ferroelectric Material Equation Arising in Dielectric Materials<abstract> <title style='display:none'>Abstract</title> <p>In this paper, the thin-film ferroelectric material equation (TFFME), which enables the propagation of solitary polarisation in thin-film ferroelectric materials is investigated, will be expressed through the non-linear evolution models. Ferroelectrics are dielectric materials that explain wave propagation non-linear demeanors. The non-linear wave propagation form is administrated by TFFME. To investigate the characterisations of new waves and solitonic properties of the TFFME, the modified exponential Jacobi technique and rational exp(−ϕ(η))-expansion technique are used. Plenty of alternative responses may be achieved by employing individual formulas; each of these solutions is offered by some plain graphs. The validity of such schemes and solutions may be exhibited by assessing how well the relevant schemes and solutions match up. The effect of the free variables on the manner of acting of reached plots to a few solutions in the exact forms was also explored depending upon the nature of non-linearities. The descriptive characteristics of the reached results are presented and analysed by some density, two- and three-dimensional figures. We believe that our results would pave the way for future research generating optical memories based on non-linear solitons.</p> </abstract>ARTICLEtrue Behaviour of Cross-Shaped Dimples on Sliding Surfaces Under Hydrodynamic Lubrication<abstract> <title style='display:none'>Abstract</title> <p>This study reports on the tribological behaviour of sliding surfaces having cross-shaped micro-dimples on a surface. One wall is smooth and moving at a constant speed against the other fixed wall with dimples. The laser machine helps to create the desired dimples on the surface of the fixed wall. For the purpose of generating hydrodynamic pressure and tribological behaviour, the effects of cross-shaped dimples and oriented cross-shaped dimples have been compared with circular-shaped dimples. Additionally, the impact of sliding speed, dimple area density and depth on tribological behaviour was examined. The findings show that compared with a circular-shaped dimple, an unconventional cross-shaped and orientated cross-shaped dimple generates a higher net hydrodynamic pressure in the fluid domain and offers superior stability between the sliding surfaces. It has been demonstrated that geometrical factors like dimple depth and area density as well as operational factors like sliding speed have a substantial impact on the hydrodynamic average pressure and tribological behaviour of sliding surfaces. The experimental findings indicate that, for the same geometric and operating parameters, cross- and orientated cross-shaped dimples have a 20%–25% lower friction coefficient between the sliding surfaces than circular dimples. The results of the experiment support those of the analysis and CFD.</p> </abstract>ARTICLEtrue of Pore Architecture of 3D Printed Open Porosity Cellular Structures on Their Resistance to Mechanical Loading: Part I – Experimental Studies<abstract> <title style='display:none'>Abstract</title> <p>The development of additive manufacturing (AM) techniques has sparked interest in porous structures that can be customized in terms of size, shape, and arrangement of pores. Porous lattice structure (LS, called also lattice struct) offer superior specific stiffness and strength, making them ideal components for lightweight products with energy absorption and heat transfer capabilities. They find applications in industries such as aerospace, aeronautics, automotive, and bone ingrowth applications. One of the main advantages of additive manufacturing is the freedom of design, control over geometry and architecture, cost and time savings, waste reduction, and product customization. However, the designation of appropriate struct/pore geometry to achieve the desired properties and structure remains a challenge. In this part of the study, five lattice structs with various pore sizes, with two volume fractions for each, and shapes (ellipsoidal, helical, X-shape, trapezoidal, and triangular) were designed and manufactured using selective laser sintering (SLS) additive manufacturing technology. Mechanical properties were tested through uniaxial compression, and the apparent stress-strain curves were analyzed. The results showed that the compression tests revealed both monotonic and non-monotonic stress-strain curves, indicating different compression behaviors among the structures. The helical structure exhibited the highest resistance to compression, while other structures showed similarities in their mechanical properties. In Part II of this study provides a comprehensive analysis of these findings, emphasizing the potential of purpose-designed porous structures for various engineering applications.</p> </abstract>ARTICLEtrue of an Influence of Liquid Velocity Above the Needle on the Bubble Departures Process<abstract> <title style='display:none'>Abstract</title> <p>In the present paper, the influence of liquid flow above the needle on a periodic or chaotic nature of the bubble departures process was numerically investigated. During the numerical simulations bubbles departing from the needle was considered. The perturbations of liquid flow were simulated based on the results of experimental investigations described in the paper [<xref ref-type="bibr" rid="j_ama-2024-0044_ref_001">1</xref>]. The numerical model contains a bubble growth process and a liquid penetration into a needle process. In order to identify the influence of liquid flow above the needle on a periodic or chaotic nature of bubble departures process, the methods data analysis: wavelet decomposition and FFT were used. It can be inferred that the bubble departure process can be regulated by altering the hydrodynamic conditions above the needle, as variations in the liquid velocity in this area affect the gas supply system’s conditions. Moreover, the results of numerical investigations were compared with the results of experimental investigation which are described in the paper [<xref ref-type="bibr" rid="j_ama-2024-0044_ref_002">2</xref>]. It can be considered that, described in this paper, the numerical model can be used to study the interaction between the bubbles and the needle system for supplying gas during the bubble departures from two needles, because the interaction between the bubbles is related to disturbances in the liquid flow above the needle.</p> </abstract>ARTICLEtrue Temperature Mechanical Properties of 6082 Aluminium Alloy as a Function of Tempering Temperature: Experimental and Numerical Approach<abstract> <title style='display:none'>Abstract</title> <p>Our study involved a combination of practical experiments and numerical simulations using the Abaqus computational software. The main aim was to enhance our understanding of the mechanical characteristics exhibited by 6082 aluminium alloy when exposed to tensile forces. To achieve this, we produced 18 samples of standardized dimensions utilizing a parallel lathe. These samples then underwent a thermal treatment comprising a solution treatment, water quenching and various tempering procedures at different temperatures (280°C, 240°C, 200°C, 160°C and 120°C), resulting in a range of hardness levels. To obtain the experimental results, we conducted tensile tests on a specialized machine, which were subsequently supplemented with numerical analyses. By adopting this approach, we gained valuable insights into the behaviour of aluminium alloy 6082, specifically regarding its mechanical properties such as hardness, tensile strength, elongation and necking coefficient. This newfound knowledge holds potential significance in the realm of designing and optimizing aluminium structures that operate within high-temperature environments.</p> </abstract>ARTICLEtrue of Parameters of the Mixture and Heat Generation of the DD15 Diesel Engine of the Sandvik LH514 Loader in the Process of Using Alternative Fuels Based on RME<abstract> <title style='display:none'>Abstract</title> <p>Today, there is a growing shortage of commercial motor fuels in the world. This is due to the tendency to regulate the extraction of hydrocarbons, which are the main raw materials for their production; and, therefore, to reduce the import of oil, alternative types of fuel for diesel engines based on oils and animal fats are becoming widespread today. In this regard, intensive work is underway to convert internal combustion engines to biofuel-based ones both in countries with limited fuel and energy resources and in highly developed countries that have the opportunity to purchase liquid energy carriers. Biodiesel fuel (biodiesel, PME, RME, FAME, EMAG, etc.) is an environmentally friendly type of biofuel obtained from vegetable and animal fats and used to replace petroleum diesel fuel. According to the results of modelling, in the process of using RME B100 biodiesel fuel, we found a reduction in nitrogen dioxide emissions by 21.5% and a reduction in soot emissions by 34.5%. This will positively affect the environmental performance of the Sandvik LH514 loader, which is especially relevant in closed environments such as mines. So, according to the results of studies of the operation of the DD15 engine of the Sandvik LH514 loader on commercial and RME B100 biodiesel fuel, it was established that the use of biodiesel fuel leads to a deterioration of the mixture, due to which heat generation is reduced and, as a result, fuel consumption increases and engine power decreases, but the aspect of environmental indicators constitutes the significant improvement demonstrated by the present work.</p> </abstract>ARTICLEtrue Assessment of Critical Factors during Patient Lifting: Shoulder Girdle and Cumulative Moment Ergonomic Evaluation<abstract> <title style='display:none'>Abstract</title> <p>This study examines the ergonomics of the patient lifting motion often used by healthcare professionals, focusing on the shoulder area, as manual weight management is still an important part of daily work. Data acquisition was made with the 17 IMU sensors, Movella Xsens system. A total of 25 quality measurements were acquired for further data processing. A mathematical model with the defined assumptions is presented in this research calculating shoulder moment-kinematics. The load engagement profile was determined based on the hip extension as a variable size for different test subjects and trials. Shoulder flexion-extension range of motion (ROM) variance was estimated, determining each test subject’s technique, together with shoulder moment and cumulative shoulder moment. Cumulative shoulder load varied from -31.46% to 27.78% from the mean shoulder moment value. During the estimated accumulation of a 5-year work span, the difference in worst to best techniques accumulated to 1.86 times. Recommendations on how the technique and the further scope of the research could be improved were given.</p> </abstract>ARTICLEtrue of Parameters of the Vibration-Based Energy Harvesting System Located in the Micro-Power Generator<abstract> <title style='display:none'>Abstract</title> <p>This article presents the optimisation process of some key parameters such as the size of the macro-fibre composite (MFC) and the optimal impedance load matching the piezoelectric harvester located in the prototype of the micro-power generator to enhance the vibration-based energy harvesting effect. For this, the distributed parameter model of this structure, including MFCs of the 8514 P2, 5628 P2 and 8528 P2 types, with a homogenous material in the piezoelectric fibre layer was determined. The numerical analysis of the FEM model of the flexure strip with piezo-composite indicated that the highest amplitude of voltage &gt;7 V is generated by the proposed device with the piezo of the 8528 P2 type, while the lowest amplitude (close to 1.1 V) was noted for the piezo of the 8514 P2 type. Experiments were carried out on the laboratory stand to verify the obtained results. In addition, it was shown that the power output of the real EH system with the piezo of the MFC 8528 type, connecting with the matched resistive load (<italic>R</italic> = 120 kΩ), led to a significant increase in the value of the generating voltage up to 500 mW versus EH system with the piezo of 8514 P2 and 5628 P2 types. Finally, the effectiveness of this system was found to be close to 33% for the EH system with the piezo of the 8528 P2 type.</p> </abstract>ARTICLEtrue Semi-Analytical Approach for Duffing Equation<abstract> <title style='display:none'>Abstract</title> <p>This research endeavour-investigates the enhanced adaptation of the Laplace-based variational iteration method (VIM) tailored specifically for tackling the Duffing Equation. This is accomplished by incorporating the Lagrange multiplier as a strategic tool to effectively address the inherent natural frequency within the Duffing Equation. Using a meticulous comparative analysis, here are juxtapose the analytical outcomes generated by the modified VIM approach with the numerical solution obtained through the application of the renowned Runge-Kutta Fehlberg method (RKF45), implemented by using the powerful mathematical software, MAPLE. Furthermore, by exploring the profound influence of diverse initial conditions on the resulting solution, a diverse array of distinct graphical representations is presented.</p> </abstract>ARTICLEtrue Research Issues of Prototype Floating Systems<abstract> <title style='display:none'>Abstract</title> <p>The paper presents a solution that can be used as a temporary supplement to the existing infrastructure in cases of natural disasters, during structure or bridge repair, in military applications and in areas where it is necessary to provide a floating system crossing. The genesis of the proposed structure and its development, as well as examples of applications of the basic module, referred to as the river module – the floating cassette with the pneumatic pontoon – are presented. The original solutions, such as the bow–stern modules, designed using modern, light and durable materials acting as deflectors, are also described. Examples of the use of floating structures composed of identical/repeatable modules–cassettes are shown. The results of experimental tests of two prototype river modules sets are presented as a validation for numerical studies. Selected aspects of static, kinematic and dynamic analyses using finite element and multibody simulations are presented. The numerical simulation of the prototype floating bridge with an assessment of the impact of clearances and an estimation of the kinematic parameters of the floating ribbon with various configurations are described.</p> </abstract>ARTICLEtrue Stresses in A Multi-Layered Spherical Tank with a Slowly Graded Structure<abstract> <title style='display:none'>Abstract</title> <p>The central-symmetrical problem of thermoelasticity for a multi-layered spherical tank is considered. The thermal stresses were caused by a temperature difference between the inner and outer surfaces of the tank. Two approaches to solving this problem have been proposed. In the first approach, the boundary problem defined in the components of a considered inhomogeneous spherical tank was solved. In the second approach, the homogenization method with microlocal parameters was used. Good agreement between the solutions was obtained.</p> </abstract>ARTICLEtrue Modelling and Simulation of the Shear-Slitting Process of Electrical Steels<abstract> <title style='display:none'>Abstract</title> <p>Despite the development of laser processing, the mechanical cutting process is still widely used in the formation of electric steels that are very sensitive to thermal phenomena. However, proper process control is difficult due to the large number of factors determining the quality of the products. As a result, the quality of the cut edge is characterised by the presence of burrs, the removal of which increases the production costs. Due to their magnetic properties, these materials should not be exposed to excessive stresses and deformations. The article presents the possibilities of predicting the characteristic features of the cut edge as well as stress distributions in this area. Original shear-slitting finite element method (FEM) models were developed, the results of which were verified experimentally. The proposed method based on stress triaxiality analysis enables precise analysis of stress states in the cutting zone and the boundaries of the slip fracture transition in the separating fracture, as well as determining the method of material cracking. Variable control factors such as cutting clearance, rake angle of the upper knife, and cutting speed were taken into account in the models. Parametric analysis of the process was carried out and it was determined how the process parameters should be selected in order to obtain the appropriate quality of the product. The developed analysis results can be useful on production lines for proper process control.</p> </abstract>ARTICLEtrue Analysis of Chemically Reacting Species and Radiation Effects on MHD Free Convective Flow Through a Rotating Porous Medium<abstract> <title style='display:none'>Abstract</title> <p>The present study deals with the effects of radiation and mass transfer on a laminar unsteady free convective flow of a viscous, incompressible, electrically conducting and chemically reacting fluid past a vertical surface in a rotating porous medium. It is assumed that the surface is rotating with angular velocity Ω. The governing mathematical equations are developed and solved by adopting complex variable notations and the analytical expressions for velocity, temperature and concentration fields are obtained. The effects of various parameters on mean primary velocity, mean secondary velocity, mean temperature, mean concentration, transient primary velocity, transient secondary velocity, transient temperature and transient concentration have been discussed and shown graphically. Further, the consequences of different parameters on rate of heat transfer coefficient (Nusselt number), rate of mass transfer coefficient (Sherwood number) and drag coefficient (mean skin-friction) are analysed. It is observed that the mean and transient primary velocities increase with the radiation parameter E, while reverse phenomena are observed for the Schmidt number, Sc, and the chemical reaction parameter, γ. The results may be useful in studying oil or gas and water movement through an oil or gas field reservoir, underground water migration, and the filtration and water purification processes.</p> </abstract>ARTICLEtrue and Analytical Approaches on Air Spring Absorbers Made of LDPE Polymer<abstract> <title style='display:none'>Abstract</title> <p>Damping and energy-consuming elements can be found in many technical applications. This means these component types can prevent fractures or injuries in the case of products or people, respectively. In the last time, many modern applications and inventions associated with the reduction of the effects of an impact are observed especially in the mode of transportation safety area. The significant development of the automotive industry, increasing popularity of motorbikes, electric bikes and scooters, sports field, etc., require new solutions for personal safety protection. Human head and neck protection, and other body parts protection are typical groups of solutions from biomechanics and mechanical engineering. Authors have investigated LDPE-made pneumatic absorbers under axial impact force. Based on the experimental approach and analytical model, mechanical characteristics are presented. Impact force value, deceleration and damping for different loading conditions are shown. Because safety systems’ impact protective features can be matched to impact conditions, results indicated that absorber damping could possibly be a good solution for them, shaping the impact characteristics according to safety requirements.</p> </abstract>ARTICLEtrue System of 1-D Subalgebras and Conserved Quantities of A Nonlinear Wave Equation in Three Dimensions Arising in Engineering Physics<abstract> <title style='display:none'>Abstract</title> <p>The construction of explicit structures of conserved vectors plays diverse crucial roles in the study of nonlinear science inclusive of the fact that they are invoked in developing appropriate numerical schemes and for other mathematical analyses. Therefore, in this paper, we examine the conserved quantities of a nonlinear wave equation, existing in three dimensions, and highlight their applications in physical sciences. The robust technique of the Lie group theory of differential equations (DEs) is invoked to achieve analytic solutions to the equation. This technique is used in a systematic way to generate the Lie point symmetries of the equation under study. Consequently, an optimal system of one-dimensional (1-D) Lie subalgebras related to the equation is obtained. Thereafter, we engage the formal Lagrangian of the nonlinear wave equation in conjunction with various gained subalgebras to construct conservation laws of the equation under study using Ibragimov’s theorem for conserved vectors.</p> </abstract>ARTICLEtrue of Human Gait Based on Ground Reaction Forces and Combined Data From Two Gait Laboratories<abstract> <title style='display:none'>Abstract</title> <p>In a world in which biometric systems are used more and more often within our surroundings while the number of publications related to this topic grows, the issue of access to databases containing information that can be used by creators of such systems becomes important. These types of databases, compiled as a result of research conducted by leading centres, are made available to people who are interested in them. However, the potential combination of data from different centres may be problematic. The aim of the present work is the verification of whether the utilisation of the same research procedure in studies carried out on research groups having similar characteristics but at two different centres will result in databases that may be used to recognise a person based on Ground Reaction Forces (GRF). Studies conducted for the needs of this paper were performed at the Bialystok University of Technology (BUT) and Lublin University of Technology (LUT). In all, the study sample consisted of 366 people allowing the recording of 6,198 human gait cycles. Based on obtained GRF data, a set of features describing human gait was compiled which was then used to test a system’s ability to identify a person on its basis. The obtained percentage of correct identifications, 99.46% for BUT, 100% for LUT and 99.5% for a mixed set of data demonstrates a very high quality of features and algorithms utilised for classification. A more detailed analysis of erroneous classifications has shown that mistakes occur most often between people who were tested at the same laboratory. Completed statistical analysis of select attributes revealed that there are statistically significant differences between values attained at different laboratories.</p> </abstract>ARTICLEtrue the Thermal Properties of the Insulating Structures of A Flight Data Recorder<abstract> <title style='display:none'>Abstract</title> <p>This paper deals with the problems faced during the research on the insulating structures used in the thermal shielding of flight recorders. These structures are characterised by specific properties determined by, among other aspects, their porosity. The complex and coupled heat-exchange phenomena occurring under the operating conditions of the recorders, and in numerous cases combined with mass exchange, require dedicated test methods. The paper characterises the origin of the research problem, presents a methodology for comprehensive testing of the thermal propertiesand uses the example of determining the insulating properties of the Promalight microporous structure ®-1000R. The authors focussed on thermal diffusivity tests performed by means of the oscillatory excitation method. The measurements were conducted on a test stand to determine the effect the type of gas filling had on the porous structure and the pore filling gaspressure effect on the temperature characteristics of apparent thermal diffusivity. The authors also conducted research on the structure’s resistance to direct flame exposure. The analysis of the obtained results enable recognition and characterisation of the key phenomena of heat and mass transfer; the numerical results exert a significant influence on their application.</p> </abstract>ARTICLEtrue of Some Thermophysical Properties of SN500 Lubrication Oil Blended with SIO2, AL2O3 and TIO2 Nano-Additives, Using Fuzzy Logic<abstract> <title style='display:none'>Abstract</title> <p>Nano-additives are generally blended with the base lubricant oil, to enhance the lubricant characteristics such as wear, coefficient of friction (CoF), thermal conductivity, density, and flash and fire points of the lubricant. In this research, nano-additives of SiO2, Al2O3 and TiO2 are blended with the base SN500 oil with different proportions of mixture. When these three nanoparticles are used together in base oil, they enhance most of the desirable properties of a lubricant; 27 samples with three different levels of a mixture of nano-additives are identified using factorial design of experiments. The experimental outcomes for the selected three characteristics of interest of density, flash point and fire point are determined. Conducting experiments for ‘n’ number of samples with different proportions of mixture of nano-additives is a cumbersome, expensive and time-consuming process, in order to determine the optimum mix of nano-additives for the desirable level of characteristics of interest. In this research, attempt has been made to apply fuzzy logic to simulate a greater number of samples with different proportions of a mixture of three nano-additives with the respective outcomes of characteristics of three thermophysical properties. Out of the numerous samples simulated using fuzzy logic, the sample with the optimum mix of three nano-additives of SiO2, Al2O3 and TiO2 blended with the base oil is identified for the desirable level of characteristics of interest of density, flash point and fire point. The values of the identified sample are found to be at the desirable level of 0.9008 gm/ml, 231°C and 252°C, respectively.</p> </abstract>ARTICLEtrue Gain PI/PID Controllers for FOPTD/SOPTD Processes Under Load Disturbance<abstract> <title style='display:none'>Abstract</title> <p>In practical applications, an engineer is sometimes expected to execute the step test for tuning the controller without waiting much for the steady-state or a low level of disturbances. Hence, knowing that the initial settings may not be quite reliable, he/she detunes the controller by reducing its gain as a precaution against possible poor behaviour of the closed-loop system. It is up to their experience to choose by how much to detune. Therefore, the development of a practically oriented approach that would assist the engineer to choose the degree of gain reduction is the goal of this paper. The approach assumes that process parameters are determined by the least-squares approximation of the step response. Accuracy of the approximation is evaluated by a relative approximation error involving integrals of the error and the process response itself. The SIMC tuning rules are applied to choose the initial controller settings. The approach relies on detecting by simulation the worst case that may happen when the step response is triggered at any time. Detuning nomograms specify by how much to reduce the initial gain for PI-FOPTD and PID-SOPTD designs, given the relative approximation error. Two long-lasting lab experiments involving temperature control identify a plant, verify the load disturbance model through multiple step tests and demonstrate usage of the approach in the closed-loop system.</p> </abstract>ARTICLEtrue