Innovative Mechanical Engineering

A MATHEMATICAL MODEL FOR DETERMINING THE ROUGHNESS OF LASER-MACHINED SURFACES

Constantin Cristinel Girdu — 2024-04-17

The paper aims to determine the influence of input parameters on surface roughness in CO₂ laser cutting. The material used is Hardox 450 steel in the form of plates with a thickness of 12 mm. Adjustment parameters that ensure cutting, laser power (3700,3900) W, pressure (0.55,0.75) bar, and cutting speed (1250,1650) mm/min were identified through trial tests.Based on the current state of research in the field, a mathematical model is proposed to describe the relationship between roughness and input parameters. The designed model is validated with statistical methods. The results show that the pressure of the assistant gas is the most influential factor with regard to surface roughness. The laser surface treatment of manganese steel is a promising technique for increasing roughness if the pressure is used at the minimum input level of 0.55 bar. For low production costs, the combination of 3700 W power, 1250 mm/min speed, and 0.55 bar pressure is recommended for cutting Hardox 450 steel.

WAVELET TRANSFORM PACKET FOR SIGNAL ANALYSIS USING STANDARD DEVIATION AND SIGNAL SPECTRUM

Nikola Vorkapic — 2024-04-17

The paper presents the research results and the possibilities of applying the standard deviation and amplitude spectrum for chatter vibration detection using the wavelet transform packet as a tool for signal decomposition that was recorded during machining. An analysis of the signal spectrum was additionally performed, which is represented by a spectrogram. Two experiments were performed, where the cutting force signal and acceleration signal, recorded during the machining processes, were analyzed. The recorded signals were decomposed using the wavelet transform packet with the mother wavelet 'db4', and then the standard deviation in the time domain and the amplitude spectrum in the frequency domain were calculated for each level of the decomposed signal. The application of wavelets in this study is intended to enable a better assessment of the quality of standard deviation and amplitude spectrum in chatter vibration detection.

EFFECT OF SURFACE PREPARATION ON THE SHEARSTRENGTH OF ALUMINIUM ALLOYADHESIVE SINGLE-LAP JOINTS

Nataša Zdravković — 2024-04-17

Surface preparation for adhesive bonding is crucial for optimum bonding performance and has a major impact on the quality and durability of bonded joints. The effects of two different mechanical surface preparations (with Scotch-Brite abrasive pad and P180 sandpaper) on the strength properties of bonded joints were investigated. The prepared surface of aluminium alloy AW 5754 was characterized based on surface roughness parameters (Ra and Rz), wettability and mechanical properties (tensile lap-shear strength). Adhesively bonded single-lap joints were produced, and fracture surfaces were observed. It was found that the bonded joints of aluminium alloy AW 5754 had different strengths based on the surface preparation method and adhesive utilized. This indicates that joining aluminium alloys using the same adhesive and different surface preparations results in significant differences in the strength of bonded joints.

OPTIMIZATION OF CURVED FLEXURE HINGE PARAMETERS FOR ENHANCED MECHANICAL PERFORMANCE

Dušan Stojiljković — 2024-04-17

Flexure hinges are integral components of compliant mechanism design and as such are an important factor in various engineering applications, contributing to their enhanced mechanical performance and longevity. One newly researched type of flexure hinges is the curved flexure hinge with a wide range of opportunities for possible advancement and applications. This paper presents an investigation into the mechanical performance of curved flexure hinges, with a specific focus on the impact of flexure hinge orientation. The utilization of orientation variations introduces a unique parameter to the optimization process. This diversity allows for a comprehensive design space exploration, potentially leading to novel hinge configurations that exhibit superior mechanical characteristics. By using Finite Element Analysis (FEA) this research aims to advance the understanding of how curved flexure hinge design collectively influences strain, deflection angle and deformation characteristics. By employing a Multi-Objective Genetic Algorithm (MOGA) optimization, this study aims to identify the optimal orientation of a curved flexure hinge as a part of the parallel crankcompliant mechanism that simultaneously maximizes rectilinear motion and minimizes parasitic deviation.

CUTTING ENERGY AND SURFACE TEMPERATURE ANALYSIS IN GAS COMBUSTION HEATING ASSISTED TURNING

Branislav Sredanović — 2024-04-17

Developments inthe mechanical engineering industryare accompanied by the development of new solutions in material machining technologies. One of the directions of this development is combining different processes,with regard to obtaining the required machining process performance. The machining performance rating is commonly based on energy consumption analysis, process productivity, and machining efficacy, at the least. In this paper, an analysis of the steel turning process assisted by gas combustion heating was performed.This combined machining process is widely available, on the one hand, but is unstable and causes negative changes in the workpiece surface layer, on the other. The cutting energy was analyzed, as well as the consumption of energy due to the heating of the workpiece. Based on the experimental data, statistical analysis was carried out, and mathematical models of process performance indicators were developed. By using the developed mathematical models, optimization was carried out in order to obtain the appropriate process parameters, which would result in the lowest heat input and the used energy.