The aim of this paper is to develop a mathematical model for an unconventional worm gear consisting of a globoid worm and a worm wheel where the teeth are bearings. Using rolling elements such the teeth of the worm wheel (ball bearings) transforms the sliding friction to rolling friction during the process of worm gear meshing, improving power. The geometry of the component elements of the gear is analyzed in correlation with its kinematics. After the creation of the mathematical model, it is validated both analytically (through complex graphic representations) and experimentally (by creating, for a particular case, the 3D model and the concrete physical model (prototype) of the gear through 3D printing).

This paper aims to review researchers’ concerns over time (from the 1980s to the present) regarding the transmission of mechanical vibrations in the workplace to the limbs, with a preponderant focus on the hand–arm system and some of the effects over time. These concerns are strictly approached from the point of view of their effects on different races, types of jobs, and forms of tools handled in the workplace. In this regard, when we refer to unwanted vibrations (harmful to a person) in the industrial environment, these are vibrations that can produce harmful effects on an individual’s health, leading to occupational diseases such as white finger syndrome. Some of the terms specific to the studies reviewed, such as vibration perception and biodynamic force, among others, are explained in this paper as needed. Studies in the field have shown that vibrations are transmitted differently when the arm is bent at the elbow joint compared to when it is outstretched; also, the transmission of vibrations is influenced by other factors, such as the temperature of the working environment, the gender and age of the person who is using the vibrating devices, and last but not least, the time of their use and the frequency. The conclusions presented by the specialized literature often refer to existing standards, in particular SR EN ISO 5349/2003. Finally, in this paper, conclusions are drawn regarding how to analyze the transmission of vibrations over time, and some recommendations are given for avoiding or minimizing them, which can be added to the already-existing standards.

Nowadays environmental concerns and the constant demands of obtaining efficient designs when tackling complex structural problems forced mechanical engineers to use the optimal design methodology. In this paper, a Genetic Algorithm is used to minimize the mass of a helical gear pair mechanism - a key component of an Electric Continuously Variable Transmission - eCVT used as automatic power transmission of various hybrid cars. Designing such mechanisms is an iterative process in which it is necessary to make some tentative choices (for example, the impact of a certain choice of gear width and center distance may yield a minimum mass gearing, but the selection of these values for that parameters may cascade through subsequent steps of the gear design process to ultimately lead to a helical gearing that does not meet the specific strength or manufacturing conditions). The objective function considered here i.e. the mass of the helical gears pairs is computed exactly through a unique method developed by the authors. The optimal design problem is described by a set of 5 design variables (i.e. integer, discrete, and real), and the objective function is subjected to a set o 17 highly non-linear constraints. The results obtained by using GA show significant improvement over the results obtained by traditional design (a 24.21% mass reduction).

At the final step of the injection process (of a plastic product with cavities) when the part is on the point to be ejected the adhesion phenomena occurs between the core and the plastic part. The mold adhesion effect has a significant influence on the mold design ejection system and over the whole process. This paper presents a computation methodology of the demolding moment for two cases of plastic injected parts with internal trapezoidal thread. Knowing the value of this moment offer us the possibility to adopt the right design solution of the ejector system and of the entire mold. As further work the author will try to validate this method through a set of practical experiments.

The purpose of this paper is to present a vibration dissipation device that sends vibration signals from the manipulated tool in the workplace to the operator’s hand by improving its ergonomic appearance and materials. Compared with another vibration dissipation device, this one was previously designed and patented. This paper is based on two studies: one theoretical and the other experimental (the latter regarding the material used). The first part is represented by the design and simulation of the device and a static analysis by FEA in SolidWorks 2022. The stresses to which the materials of the device’s bracelets are subjected are studied in this article; then, the resistance of the device’s materials to the tensile and deformation stresses they are subjected to is presented. All these studies complement DIAV equipment’s functionality in terms of its components’ design and assembly. Emphasis is placed on its shape and ease of assembly and the operator’s dexterity in mechanical processes so that DIAV does not limit them. In addition, from the point of view of its design, emphasis is placed on its fixation so that it is easy to assemble and is within reach of any operator. The appropriate choice of materials for the components of the DIAV device is of major importance both in terms of strength, ergonomics, and weight. The experimental results validate the theoretical results obtained through the FEA simulation in SolidWorks, and this fact confirms the usefulness and functionality of the DIAV device from the perspective of vibration attenuation.