Search Results (18)

The design of the suspension system affects handling and stability, vibrations of the steered wheels, vehicle ride comfort, and tyre tread wear. One of the most important vibration parameters is acceleration; high acceleration values can have an adverse effect on both the driver and passengers, as well as on the components of the vehicle’s suspension and handling. This paper presents the results of the effects of acceleration on the components of a front-independent MacPherson suspension system. Data on the accelerations were obtained from theoretical and experimental studies. A simulation study was conducted, taking into account the elastic and damping characteristics of the elastic components. The experimental study was conducted under laboratory conditions by using a suspension tester, BEISSBARTH, and a measuring system developed with LabVIEW 2021 SP1 and MATLAB R2022b software. The experiments were conducted with different tyre pressures and by using bushings made from different materials. The experimental tests were conducted with two rubber bushings within the mounting of the arm, as well as a rubber bushing and a polyurethane bushing. The experimental results were compared and analyzed. Two theoretical models were considered: one is a mathematical model, and the other is a simulation model which uses the finite element method. Numerical dynamic analysis of the suspension was performed using the SolidWorks 2023. Full article

Evaluating noise, vibration, and harshness (NVH) performance is crucial in vehicle development. However, NVH evaluation is often subjective and challenging to achieve through numerical simulation, and typically prototypes are required. Dynamic driving simulators are emerging as a viable solution for assessing NVH performance in the early development phase before physical prototypes are available. However, most current simulators can reproduce vibrations only in a single direction or within a limited frequency range. This paper presents a comprehensive design optimization approach to enhance the dynamic response of a full-spectrum driving simulator, addressing these limitations. Specifically, in complex driving simulators, vibration crosstalk is a critical and common issue, which usually leads to an inaccurate dynamic response of the system, compromising the realism of the driving experience. Vibration crosstalk manifests as undesired vibration components in directions other than the main excitation direction due to structural coupling. To limit the system crosstalk, a flexible multibody dynamics model of the driving simulator has been developed, validated, and employed for a global sensitivity analysis. From this analysis, it turns out that the bushings located below the seat play a crucial role in the crosstalk characteristics of the system and can be effectively optimized to obtain the desired performances. Bushings’ stiffness and locations have been used as design variables in a multiobjective optimization with the aims of increasing the direct transmissibility of the actuators’ excitation and, at the same time, reducing the crosstalk contributions. A surrogate model approach is employed for reducing the computational cost of the process. The results show substantial crosstalk reduction, up to 57%. The proposed method can be effectively applied to improve the dynamic response of driving simulators allowing for their extensive use in the assessment of vehicles’ NVH performances. Full article

In deep-hole boring processes, boring bars with a large length-to-diameter ratio are typically employed. However, excessive overhang significantly reduces the boring bar’s stiffness, inducing vibrational effects that severely degrade machining precision and surface quality. To address this, the research objective is to suppress vibrations using a tunable-parameter boring bar. This paper proposes a novel Tunable Dynamic Vibration Absorber (TDVA) boring bar and designs its fundamental parameters. Based on the derived dynamic model, the vibration characteristics of the proposed boring bar are analyzed, revealing the variation in damping performance under different excitation frequencies. By establishing the relationship between TDVA stiffness, damping, and the axial compression of rubber bushings, optimal parameter combinations can be precisely identified for specific excitation frequencies. Ultimately, adjusting the TDVA’s axial compression displacement (0.1–0.5 mm) significantly expands the effective machining frequency range compared to conventional designs while maintaining operational reliability. This study proposes a novel Tunable Dynamic Vibration Absorber (TDVA) that innovatively integrates axial compression to achieve coupled stiffness and damping adjustments, addressing the rigidity–adaptability trade-off in deep-hole boring tools. Full article

In recent years, transformer failures caused by the aging of bushing sealing materials have become increasingly common in power systems, posing significant risks to the safe and stable operation of transformers. Microencapsulated self-healing technology offers a promising solution by repairing microcracks and extending the service life of rubber sealing materials. This study developed polyurea-formaldehyde microcapsules encapsulating polydimethylsiloxane (PDMS) self-healing agents based on a Pt/PDMS curing system. A two-component microencapsulated self-healing system was further established for fluoro-silicone rubber materials. The feasibility of self-healing in these composite materials was validated through tensile property tests. Additionally, the effects of varying microcapsule contents and two-component ratios on material performance were systematically investigated, leading to the optimization of the mechanical and self-healing properties of the microcapsule/fluoro-silicone rubber composites. The results demonstrated that using SYLGARD™ 184 as the healing agent, with a two-component microcapsule ratio of 6:4 (A:B) and a microcapsule content of 10 phr, yielded a remarkable self-healing performance, achieving a healing efficiency of approximately 63%. The results of this paper can provide reference for the development of long-life rubber sealing materials. Full article

The aim of this article is to assess which elements of street design impact subjective well-being in the central area of a city in southern Chile, based on residents’ perceptions. Fifty-six semi-structured walking interviews were conducted to obtain records of pedestrians’ self-reported perceptions of their environment. To categorize the emotions reported in the interviews, the Circumplex Model of Affect was used to organize and classify the declared emotions. The results revealed that street design elements such as heritage buildings with well-maintained facades with intense colors in their coatings, spacious front gardens, wooden facades, low fences, wide sidewalks, soft or rubberized floors, and trees with colorful fruits and leaves promote a greater dominance of high-intensity positive emotions such as enjoyment, joy, happiness, liking, and pleasure. In contrast, neglected or abandoned building facades, blind fronts with graffiti or murals, high fences, tall buildings, treeless or vegetation-free sidewalks, untrimmed bushes, and narrow and poorly maintained sidewalks promote negative emotions of both high and low activation such as fear, anger, dislike, rage, unsafety, discomfort, and stress. The article concludes with the development of an emotional map of momentary experiences, identifying places of well-being and discomfort in public spaces. The value of this map is discussed as a tool to inform urban design in the promotion of healthier pedestrian environments in Latin American cities. Full article

This paper deals with joining dissimilar materials using thermal drilling technology as well as the combination of thermal drilling and adhesive bonding. The base materials for the experimental work were deep-drawn low-carbon steel DC04, HSLA steel TL 1550-220 + Z, and structural aluminum alloy EN AW-6082 T6 (AlSi1MgMn). The geometry of the formed joints was tested metallographically as the load-bearing shear capacity under the tensile shear test of single-lapped joints and the resistance of the joints against corrosion-induced disbonding in a climate chamber. The energy dissipated by the joints up to fracture was calculated from the load–displacement curves. The hybrid joints were compared with the bonded joints with the same overlap area in terms of the load-bearing capacity and energy dissipated at joint failure. The hybrid joints formed by thermal drilling and adhesive bonding with a rubber-based adhesive confirmed the synergistic effect—the adhesive provides the high load-bearing capacity of the joint, and the bushing formed by thermal drilling increases the dissipated energy of the joint at failure. The exposure of the joints in the climatic chamber did not cause a relevant reduction in the characteristics of the joints. Full article

This research focused on the rubber bushings of the rear sub-frame in an electric vehicle. A dynamic model was developed to represent the bushing, incorporating an elastic element, a frictional element, and a viscoelastic element arranged in series using a fractional-order Maxwell and a Kelvin–Voigt model. To identify the parameters of the bushing model, an improved adaptive chaotic particle swarm optimization algorithm was employed, in conjunction with dynamic stiffness test data obtained at an amplitude of 0.2 mm. The test data obtained at different amplitudes (0.2 mm, 0.3 mm, 0.5 mm, and 1 mm) were fitted to the model, resulting in fitting errors of 1.13%, 4.07%, 4.42%, and 28.82%, respectively, when compared to the corresponding test data in order to enhance the accuracy of the model fitting; the Sobol sensitivity analysis method was utilized to analyze the parameter sensitivity of the model. Following the analysis, the parameters α, β, and $k_2$, which exhibited high sensitivity, were re-identified. This re-identification process led to a reduction in the fitting error at the 1 mm amplitude to 7.45%. The improved accuracy of the model plays a crucial role in enhancing the simulation accuracy of design of experiments (DOE) analysis and verifying the vehicle’s performance under various conditions, taking into account the influence of the bushing. Full article

This paper proposes a fluid-structure interaction (FSI) numerical calculation method for investigation of the elastohydrodynamic lubrication performance of the rubber-plastic double-layer water-lubricated journal bearings. The accuracy and rapidity of the FSI method are improved by studying the effect of mesh density and by comparing the calculation results with those in the literature. Based on the proposed method, a series of numerical simulations are carried out to reveal the influence of operating conditions and structural parameters on the lubrication performance of the rubber-plastic bearings. Numerical results show that the bush deformation of the rubber-plastic bearing is between that of the rubber bearing and the plastic bearing, and the deformation area is close to that of the rubber bearing. The bearing load carrying capacity increases significantly with the rotational speed, eccentricity ratio, bearing length, and decrease with the clearance. But the influences of the plastic layer elastic modulus and thickness on bearing load are unremarkable. The effect of bush deformation on bearing load is noticeable when the eccentricity ratio is more than 0.8. The results are expected to provide design references for the bearings. Full article

There has been a rise in the prevalence of atopic dermatitis (AD) globally, especially in low-and middle-income countries such as Nigeria. The condition has been linked to genetic predisposes, living conditions, and environmental factors. Environmental factors are considered a significant contributor to AD in low- and middle-income countries. This study determined the prevalence of AD in south-western Nigeria and identified risk factors in home and school environments that children aged 6 to 14 years are exposed to. A cross-sectional study was adopted, and the total sample size was 349. Four randomly selected health facilities were used for the study. A questionnaire was used to determine the risk factors in the population. Data analysis was performed using the latest version of Statistical Package for Social Science (SPSS). The prevalence of atopic dermatitis in this study is 25%. Atopic dermatitis was found to be common in females (27%). According to the univariate analysis, children who lived where trucks pass on the street almost daily had the highest cases of atopic dermatitis (28%). Children with rugs in their houses (26%) and those whose houses are surrounded by bushes (26%) had higher cases of atopic dermatitis. Children who played on school grass (26%), attended creche with rubber toys (28%), and attended school where wooden chairs (28%) and chalkboards (27%) are used had a higher number of AD. Bivariate analysis showed an association between AD with a mother’s monthly income (p = 0.012) and eating potatoes (p = 0.005), fruits (p = 0.040), and cereal (p = 0.057). In the multivariate analysis, the consumption of fruits (p = 0.02), potatoes (p < 0.001), and cereal (p = 0.04) were identified as risk factors associated with AD. It is envisaged that the study will serve as a basis for possible research on evidence-based and primary prevention options. Hence, we recommend health education activities to empower communities to protect themselves against environmental risk factors that are preventable. Full article

Rubber bush (Calotropis procera), a perennial invasive milkweed, infests large swathes of pastoral land in northern Australia and Queensland, diminishing pasture productivity. The seeds of rubber are small with fluffy pappi that confer buoyancy during wind dispersal. Long-distance seed dispersal (LDD) by wind is dependent in part on seed terminal velocity, the height of release above the ground, the surrounding vegetation, and wind parameters such as speed and vertical turbulence. Using empirical dispersal data, spatial population distribution, and historical knowledge of three experimental sites, we examine how seed traits can interact with environmental features to promote dispersal. We expected naturalised rubber bush populations to have the following: (1) higher spatial autocorrelation on open plains where dispersal distances are maximised compared to hilly habitats or those with tall vegetation; (2) southeast to northwest directional bias aligned to prevailing winds; and (3) patchy satellite populations ahead of an infilled continuous main front. Seed dispersal kernels were estimated by releasing seeds from dehiscent fruit for four periods of ten minutes each at three locations from a fixed height while monitoring wind speed. Five alternative models were fitted to the seed dispersal data, of which the log-logistic (Kolgomorov–Smirnov test p = 0.9998), 3-parameter Weibull model (K-S p = 0.9992), and Weibull model (K-S p = 0.9956) provided the best fit in that order. Stem size distribution was similar at the leading edges of populations at all sites (F_{10, 395} = 1.54; p = 0.12). The exponential semivariogram model of the level of spatial autocorrelation was the best fit and was adopted for all sites (Tennant Creek (TC), Helen Springs (HS) and Muckaty (MU) sites (R² = 63.8%, 70.3%, and 93.7%, respectively). Spatial autocorrelation along the predicted southeast-to-northwest bearing was evident at all sites (TC kriging range = 236 m; HS = 738 m and MU = 1779.8 m). Seed dispersal distance was bimodal and dependent on prevailing wind conditions, with short distance dispersal (SDD) up to 55 m, while the furthest propagules were 1.8 km downwind in open environments. Dispersal directions and distances were pronounced on plains with short or no vegetation, compared to hilly locations or areas with tall vegetation. In designing management strategies, it should be noted that invasion risk is greater in frequently disturbed open landscapes, such as pastoral landscapes in Northern Australia. Infestations on open xeric grassland plains with shrubby vegetation should be a priority for rubber bush control to maintain high levels of productivity in beef production systems. Full article

Inspired by the convex hull structure of the dung beetle head’s surface, we extracted the non-smooth surface morphology of its head and designed a rubber bushing with a representative structure according to the bionics principle. According to the fitting results of the test data, Ogden N3-Prony N3 was selected as the hyper-viscoelastic constitutive model of the rubber material. Then, the two-direction (radial, axial) motion characteristics of the flexible friction pair in the rubber bushing were systematically analyzed from the aspects of stress, strain and thermal effect through the combination of numerical simulation and experimental research. Finally, the bionic design with the best drag reduction and wear resistance was determined. Full article

Conventional bearing systems and materials, which are important components of machine elements, have often failed to fulfil requirements, especially in places where sealing is required. In such cases, sliding bearings with PTFE- and NBR-based polymer and elastomer materials operating in water or oil are preferred. In this study, the performance of two alternative rubber-based materials, synthetic styrene butadiene rubber (SBR) and natural rubber smoked sheet (RSS), as a sliding bearing was experimentally investigated in terms of frictional resistance using pin-on-disc and pin-on-cylinder devices. In the study, very low friction forces emerged at low sliding speeds compared to PTFE and NR operating in water. The friction force values and friction coefficients obtained are presented in diagrams and tables. Full article

The experimental investigation of viscoelastic behavior of cyclically loaded elastomeric components with respect to the time and the frequency domain is critical for industrial applications. Moreover, the validation of this behavior through numerical simulations as part of the concept of virtual prototypes is equally important. Experiments, combined measurements and test setups for samples as well as for rubber-metal components are presented and evaluated with regard to their industrial application. For application in electric vehicles with relevant excitation frequencies substantially higher than by conventional drive trains, high-frequency dynamic stiffness measurements are performed up to 3000 Hz on a newly developed test bench for elastomeric samples and components. The new test bench is compared with the standard dynamic measurement method for characterization of soft polymers. A significant difference between the measured dynamic stiffness values, caused by internal resonance of the bushing, is presented. This effect has a direct impact on the acoustic behavior of the vehicle and goes undetected by conventional measurement methods due to their lower frequency range. Furthermore, for application in vehicles with internal combustion engine, where the mechanical excitation amplitudes are significantly larger than by vehicles with electric engines, a new concept for the identification of viscoelastic material parameters that is suitable for the representation of large periodic deformations under consideration of energy dissipation is described. This dissipated energy causes self-heating of the polymer and leads to the precocious aging and failure of the elastomeric component. The validation of this concept is carried out thermally and mechanically on specimen and component level. Using the approaches developed in this work, the behavior of cyclically loaded elastomeric engine mounts in different applications can be simulated to reduce the time spent and save on the costs necessary for the production of prototypes. Full article

Rubber bushings and mounts are vastly used in automotive applications as support and interface elements. In suspension systems, they are commonly employed to interconnect the damping structure to the chassis. Therein, the viscoelastic nature of the material introduces a desirable filtering effect to reduce mechanical vibrations. When designing a suspension system, available literature often deals with viscoelastic mounts by introducing a linear or nonlinear stiffness behavior. In this context, the present paper aims at representing the rubber material using a proper viscoelastic model with the selection of different in-wheels motors. Thus, the mount dynamic behavior’s influence in a suspension is studied and discussed thoroughly through numerical simulations and sensitivity analyses. Furthermore, guidelines are proposed to orient the designer when selecting these elements. Full article

The novelty of the present study is that it investigates the effect of propeller shaft deflection, caused by the propeller self-weight and interfacial mixed forces, on the fluid–solid–heat (FSH) coupling performance of water lubricated rubber stern bearing (WLRSB). In the FSH coupling model, the generalized average Reynolds equation and the Kogut–Etsion asperity contact model are used to determine the hydrodynamic and the elastic–plastic contact behaviors of WLRSB. In the thermal analysis, the journal, water film, and rubber bushing are considered as an integrated system (JWR system) using the Euler method. To prove the correctness of the developed model, the predicted results are verified by comparisons with the experimental results given in the literature. In addition, to assess the effect of the force-driven deflection during FSH simulation, comparisons of the FSH predictions between the aligned journal case and the deflected journal case are carried out. The results indicate that, especially under a heavy load condition, the deflection of the stern shaft should be incorporated into the lubrication gap between the journal–rubber interface during the analysis of FSH performance of the JWR system. Full article