DESIGN AND VIBRATIONS IN THE ROTARY HAMMER

The vibrations generated by manual machines can cause occupational diseases with both vascular and osteoarticular affectations, also known as hand-arm vibration syndrome. The pneumatic rotary hammer is one of these machines, widely used in the construction sector. In the bibliography consulted, it is found that the transmission of vibrations from the handle to the hand-arm system depends on both the composition of the material and the design of the handle. Although there are already improvements in this damping of vibrations received through the handles, there is a great field for its optimization, redesign and the search for new materials not yet used in the handles of pneumatic hammers. This article presents a methodology for the study of new materials used in the grip, including the analysis of the design, real tests for the characterization of the materials and their simulation by finite elements. The results obtained show that the design is a decisive factor for both vibration damping and weight. The redesigned grip that generates more damping at 33 seconds with a weight of 0.51kg is the "R1" with a value of 0.6346% better than the original grip, "Segeda original", with a weight of 0.55kg and with a damping value of 0.605%. Keywords: industrial design, pneumatic hammer, handle, elastomers, vibrations

Properties of vehicle support suspensions

The processes of damping of vibrations of sprung masses with polyurethane foam support cushions in the frequency range of vibrations with an optimal transfer function are investigated. The amplitude-phase-frequency characteristics of the masses are determined during vibrations with the subsequent presentation of transient processes, according to which the damping time of the vibrations of the sprung masses is determined. The used support cushions made of polyurethane foam reduce the minimum damping time of vibrations of the sprung masses on 1520 %, they are more wear-resistant and have greater damping properties than rubber support cushions. Keywords: spectral density, exposure frequency, transmission coefficient, deformation coefficient, vibration damping time, polyurethane foam. [email protected]

SYSTEM OF TENSION ALIGNMENT OF TWO CIRCUITS OF THE DRIVE BELT OF THE MOVEMENT OF THE 3D PRINTER CARRIAGE

Existing drive belt tensioning systems in FDM 3D printers are considered. A comparative analysis of tensioning systems has been carried out, which has shown that the existing systems are characterized by the phenomenon of asymmetry of the action of forces during the stretching of the drive belt. A new design has been proposed and developed, which is a unit mounted in a 3D printer that equalizes the forces of tension of the drive belt and damping of vibrations in an FDM 3D printer.

A Review on Ergonomics in Agriculture. Part II: Mechanized Operations

Background: Musculoskeletal disorders (MSDs) have long been recognized as the most common risks that operation of agricultural machineries poses, thus, undermining the ability to labor and quality of life. The purpose of this investigation was to thoroughly review the recent scholarly literature on ergonomics in agricultural mechanized operations; Methods: Electronic database research over the last ten years was conducted based on specific inclusion criteria. Furthermore, an assessment of the methodological quality and strength of evidence of potential risk factors causing MSDs was performed; Results: The results demonstrated that ergonomics in agriculture is an interdisciplinary topic and concerns both developed and developing countries. The machines with driving seats seem to be associated with painful disorders of the low back, while handheld machines with disorders of the upper extremities. The main roots of these disorders are the whole-body vibration (WBV) and hand-arm transmitted vibration (HATV). However, personal characteristics, awkward postures, mechanical shocks and seat discomfort were also recognized to cause MSDs; Conclusions: The present ergonomic interventions aim mainly at damping of vibrations and improving the comfort of operator. Nevertheless, more collaborative efforts among physicians, ergonomists, engineers and manufacturers are required in terms of both creating new ergonomic technologies and increasing the awareness of workers for the involved risk factors.