A study on resonance characteristics of hydraulic structures and buildings conducted using small-size models

Introduction. The study focuses on resonance characteristics of a hydraulic engineering structure, such as a groin, land retention works on an artificial island, and a school building. Any structure, exposed to dynamic effects of natural or man-induced origin, can be validly simulated as a mechanical resonator. Models are made of materials that have electro-elastic properties allowing to measure responses to induced oscillations, or changes in an alternating electric field, and reevaluate the physical characteristics later. Materials and methods. Small-size physical models of structures are made of electro-elastic materials, such as organic glass and ABS plastic, used for 3D printing. A laboratory test bench, composed of an oscillator and a personal computer, used as an oscillograph, was applied to conduct the testing. Mathematical modeling was performed using SolidWorks software packages. Oscillation modes and structural responses, featuring different response amplitudes, were identified. Models of structures were studied in different contexts, including restraint and free bearing. Results. It has been found that frequencies of the first mode of oscillations in a restrained model correspond to the fourth mode of a model in case of free bearing. Mutual correlation of eigenfrequencies of oscillations in small-size models, made of ABS plastic and organic glass, is demonstrated. Conclusions. The applicability of ABS plastic as the material of small-size physical models of buildings and structures has been proven for the purpose of identifying resonance frequencies of the prototypes. The co-authors have developed an integrated physical and mathematical modeling method that entails the use of SolidWorks software packages. This method allows to identify resonance frequencies, which are most dangerous for structures. Different structure support patterns allow to apply the geometric scale to obtain resonance frequencies when translating small-size model results to natural values and, hence, identify the vulnerability of structures to dynamic effects.

Tribological properties of FeS/Cu-Bi copper-based bearing materials fabricated by mechanical alloying

Purpose This paper aims to fabricate a FeS/Cu-Bi copper-based lead-free bearing material to maintain good friction-reducing and anti-adhesive properties under boundary lubrication conditions. Design/methodology/approach The materials were fabricated by mechanical alloying and powder metallurgy and tested under dry friction conditions using HDM-20 wear tester. Findings The results show that mechanical alloying can improve the antifriction and wear resistance of the materials. The 6 per cent FeS and 6 per cent Bi in the copper-based bearing materials fabricated by mechanical alloying have a better synergism which contributes to the friction and wear properties of copper matrix. Originality/value This new approach solves the problems of Bi and FeS mutual segmentation, mutual agglomeration and poor interface bonding.

Еxperimental Studies of Sliding Bearings of Locomotive Turbochargers by Their Level of Vibration

The diagnostic features and sources of vibration of sliding bearings of diesel locomotive turbochargers (disappearance of the negative allowance on bearing bushings, self-oscillation in the bearing, self-oscillation when the negative allowance on the bearing bushing disappears, excitation of blade harmonics, etc.) are described in brief. The results of experimental studies of diesel locomotive turbochargers equipped with cylindrical and elliptical sliding bearings are shown. The specific spectra of vibration velocity of the bearing housings (cylindrical and elliptical) in the low-frequency range are presented. Bearing frequencies have been detected in the low-frequency vibration spectrum of the turbocharger housing with cylindrical bearings, and the connection of the detected diagnostic features with defects in sliding bearings has been established. Blade frequencies of the compressor and turbines on turbochargers with cylindrical and elliptical sliding bearings have been found in the high-frequency part of the vibration spectrum. These frequencies are necessary for identifying rotor harmonics and bearing frequencies. It has been established that for a defect-free bearing of turbochargers with elliptical and cylindrical sliding bearings, the vibration velocity of the rotor harmonics and the bearing frequency should not exceed the rated values.

Seizure Improved Lead-Free Electroplated Bearing Overlay System for Heavy-Duty Truck and Off-Highway Applications

The move to lead-free bearing materials is well known, and upcoming legislation, such as the restriction of hazardous substances, is increasing the drive to extend this trend toward heavy-duty diesel truck and off-highway applications. During the development of lead-free systems, new electroplated overlays and bronze-based substrates have been developed by various suppliers, but little attention has been given to the interlayer or diffusion barrier between the overlay and substrate materials. This interlayer is particularly necessary for tin-based solutions as it prevents the rapid diffusion of overlay species into the bronze substrate. The present development focuses on improving this often overlooked element in the system and provides a further robustness that could even be adapted to lead-based systems where increased performance is required. The incorporation of hexagonal boron nitride (hBN) as a solid lubricant in the nickel interlayer changes dramatically the interlayer properties and provides more typical bearing-like behavior for seizure resistance and scuff performance compared to nickel alone. The paper details the findings of respective rig tests as well as an actual engine test supporting the change in material characteristics and the associated improvement in seizure resistance.

Seizure Improved Lead-Free Electroplated Bearing Overlay System for Heavy Duty Truck and Off-Highway Applications

The move to lead-free bearing materials is well known and upcoming legislation, such as the Restriction of Hazardous Substances (RoHS), is increasing the drive to extend this trend towards heavy duty diesel truck and off-highway applications. During the development of lead-free systems, new electroplated overlays and bronze-based substrates have been developed by various suppliers, but little attention has been given to the interlayer or diffusion barrier between the overlay and substrate materials. This interlayer is particularly necessary for tin-based solutions as it prevents the rapid diffusion of overlay species into the bronze substrate. The present development focuses on improving this often overlooked element in the system and provides a further robustness that could even be adapted to lead-based systems where increased performance is required. The incorporation of hexagonal boron nitride as a solid lubricant in the nickel interlayer changes dramatically the interlayer properties and provides more typical bearing-like behavior for seizure resistance scuff performance compared to nickel alone. The paper details findings of respective rig tests as well as an actual engine test supporting the change in material characteristics and the associated improvement in seizure resistance.