Search

The aim of this study was to compare the mechanical properties of carbon-fiber-reinforced polymer (CFRP) composites produced using three popular technologies. The tests were performed on composites produced from prepregs in an autoclave, the next variant is composites produced using the infusion method, and the third variant concerns composites produced using the vacuum-assisted hand lay-up method. For each variant, flat plates with dimensions of 1000 mm × 1000 mm were produced while maintaining similar material properties and fabric arrangement configuration. Samples for testing were cut using a plotter in the 0° and 45° directions. Non-destructive tests (NDTs) were carried out using the active thermography method, demonstrating the correctness of the composites, i.e., the absence of structural defects for all variants. Static peel strength tests were carried out for samples with different directional orientations. The tests were carried out at temperatures of +25 °C and +80 °C. At room temperature, similar strengths were demonstrated, which for the 0° orientation were 619 MPa, 599 MPa and 536 MPa for the autoclave, vacuum and infusion variants, respectively. However, at a temperature of +80 °C, only the composite produced in the autoclave maintained the stability of its properties, showing a strength of 668 MPa. Meanwhile, in the case of the composite produced by the infusion method, a decrease in strength at an elevated temperature of 46.5% was demonstrated, while for the composite produced by the hand lay-up method, there was a decrease of 46.2%. For the last two variants, differential scanning calorimetry (DSC) analysis of epoxy resins constituting the composite matrices was carried out, showing a glass transition temperature value of 49.91 °C for the infusion variant and 56.07 °C for the vacuum variant. In the three-point static bending test, the highest strength was also demonstrated for the 0ᵒ orientation, and the bending strength was 1088 MPa for the autoclave variant, 634 MPa for the infusion variant and 547 MPa for the vacuum variant. The fatigue strength tests in tension at 80% of the static strength for the infusion variant showed an average fatigue life of 678.788 × 103 cycles for the autoclave variant, 176.620 × 103 cycles for the vacuum variant and 159.539 × 103 cycles for the infusion variant. [ABSTRACT FROM AUTHOR]

Friction is an unfavourable phenomenon in deep-drawing forming processes because it hinders the deformation processes and causes deterioration of the surface quality of drawpieces. One way to reduce the unfavourable effect of friction in deep-drawing processes is to use lubricants with the addition of hard particles. For this reason, this article presents the results of friction tests of dual-phase HCT600X+Z steel sheets using the flat die strip drawing test. Sunflower oil and rapeseed oil with the addition of 1, 5 and 10 wt.% of silicon dioxide (SiO2) particles were used as lubricants. Tests were also carried out in dry friction conditions and lubricated conditions using SiO2-modified oils and oils without the addition of particles, as a reference. Tests were carried out at different pressure values between 2 and 8 MPa. The effect of friction on the change in sheet surface roughness was also examined. For the entire range of pressures analysed, pure sunflower oil showed lower efficiency in reducing the coefficient of friction compared to pure rapeseed oil. In the pressure range of 4–8 MPa, the lubricants with 5 wt.% and 10 wt.% of particles were more effective in reducing friction than the biolubricant with the addition of 1 wt.% of SiO2. The lowest average roughness was observed for lubrication with sunflower oil containing 5 wt.% of particles. In relation to rapeseed oil, the addition of 10 wt.% of SiO2 provided a sheet surface with the lowest average roughness. [ABSTRACT FROM AUTHOR]

Presented work deals with the prediction of the forming limit of food can obtained with deep drawing, reverse drawing and expansion operations. Two commonly used materials of TH330 steel and AA5352 aluminium alloy for packaging can production were studied. Finite element simulation (FEM) is an essential tool in the packaging industry to prevent different sheet metal forming difficulties such as failure under complex nonlinear strain paths and plastic anisotropic earing. In order to characterise the material plastic properties and to specify failure criteria, the uniaxial tensile, hydraulic bulge test, as well as the routines for obtaining forming limit curves were carried out. The input material data required for various material models are also described. Utilisation of advanced material models in numerical simulation require a large number of input data. Prediction of failure location in drawing and expansion of axi-symmetric cups were estimated for each material. The FEM results were verified by real experiments.

The emerging trend of employing 4 or more axes multi-purpose and gantry industrial robots in large format additive manufacturing presents numerous opportunities as well as challenges. The capacity to handle substantial material quantities and rapidly produce prototypes, instrumentation, and final products of considerable dimensions necessitates the formulation of a well-suited production strategy. This involves setting production parameters to minimize material consumption and production time, considering the limitations of the utilized technologies, and ensuring the final product's quality. While slicers are commonly employed for establishing manufacturing strategies and production parameters, most additive manufacturing slicers are optimized for planar 3 axes 3D printing. This limitation hinders their ability to generate non-planar and freeform toolpaths. To overcome this constraint, this paper delves into the utilization of parametric modelling as a potent tool in the realm of non-planar additive manufacturing. It explores the possibilities offered by Rhinoceros Grasshopper software in designing toolpath strategies and fabricating non-planar layers. The paper addresses the associated challenges and limitations of parametric modelling, including computational complexity and the requirement for specialized software and expertise. It emphasizes the crucial need to strike a balance between design complexity and manufacturability to ensure the successful implementation of non-planar additive manufacturing processes. [ABSTRACT FROM AUTHOR]

This paper presents the result of a study evaluating the influence of alternative path generation strategy on structure and some mechanical properties of parts produced by Fused Deposition Modeling (FDM) technology. Several scientific investigations focused on resolving issues in FDM parts by modifying a path generation strategy to optimize its mechanical properties. In this study, an alternative strategy was proposed with the intention of minimizing internal voids and, thus, to improve mechanical properties. Polycarbonate samples made by this alternative path generation strategy were subjected to tensile strength test and metro-tomography structure evaluation. The results reveal that the structure observed on build models differs from a structure expected from path generation predicted by software Insight 9.1. This difference affected the tensile strength of samples.

Almost all electrical machine consists of the stator and rotor cores, which are made of stacked non-oriented electric steel sheets. Punching and blanking are the two commonly used shear cutting technologies. The efficiency and performance of an electrical machine depend on the magnetic properties of its magnetic core. The shear cutting process causes the formation of residual stresses in cut segments next to the cutting line from the nonoriented electrical sheet metal, resulting in increased iron losses. The extent of deterioration in the magnetic material properties depends on the amount of induced stresses, which is affected by the used process parameters during shear cutting and the mechanical properties of the electrical steel sheets. This paper focuses on the residual stresses induced by punching with different shear cutting conditions using finite element analysis. Influence of cutting clearance of the shear cutting tool on were observed. [ABSTRACT FROM AUTHOR]

The bending is one of the most frequently processing techniques applied to the metallic tubes. During the tube bending process different defects, such as cross-section distortion and excessive wall thinning may occur. Over the time, various techniques were developed as an attempt to reduce these defects. In this study, an experimental validated finite element model of rotary draw tube bending process with internal fluid pressure was used to investigate the effect of internal fluid pressure on the stress distribution, cross-section distortion and wall thickness change of bent tubes. The results show that the cross-section distortion can be considerably decreased by increasing in internal pressure, while the wall thinning increases and the wall thickening decreases with the increase of internal fluid pressure. A direct relationship between the tangential stress and the tube wall thickness changes was observed. [ABSTRACT FROM AUTHOR]