Papers by Keyword: Compression Test

Abstract: AlCoCrFeNi high entropy alloys (HEA) have superior strength and corrosion resistance at both room and high temperatures and are expected to application in elevated temperature environments. However, it is not clear the relationship between the harmonic structure and the mechanical properties of these HEAs at elevated temperatures. The harmonic structure is composed of dispersed coarse grains and fine grains that are networked around them. In this study, the harmonic structure AlCoCrFeNi HEA was fabricated by mechanical milling (MM) / spark plasma sintering (SPS) process and the microstructure and elevated temperature mechanical properties of AlCoCrFeNi HEA are investigated in detail. AlCoCrFeNi mixed powders with average particle sizes of 14.6 and 82.4 μm were treated with MM. The MM powders were consolidated by SPS at 1173 to 1373 K. Mechanical properties were evaluated by compression tests at room temperature to 1073 K. Microstructural observation was performed using a scanning electron microscope, electron back scattered diffraction and energy dispersive X-ray spectrometer. The conventional SPS compacts have modulated structure with BCC and B2 phase and grain boundary precipitates with FCC phase. While the MM-SPS compacts have a similar structure of the conventional compacts at dispersed region and an equiaxed nanograins including a σ phase at network region. MM compacts with harmonic microstructure demonstrate high compression strength compared to conventional compacts at room temperature to 673 K. However, conventional microstructure compacts have higher strength than harmonic structure above 873 K. These results suggest that the harmonic structure has unique deformation behavior at elevated temperatures.

Abstract: In response to the urgent need for more sustainable and environment friendly construction materials, this work explores the viability of partially or fully substituting the traditional glass fibers with date palm leaf fibers in bulk molding compounds (BMC) for infrastructure applications, specifically pedestrian network elements. To achieve this, assessment of mechanical properties across three composite groups was carried out: pure date palm fiber, hybrid (date palm and glass fiber), and pure glass fiber. The compression and flexural strengths of each composite were quantitatively assessed and compared. Results demonstrated that composites solely comprising glass fibers exhibited superior compressive and flexural. Conversely, pure date palm fiber composites showed the lowest strength values. So as expected, significant improvements were observed with glass fiber hybridization, up to 88.59% in compression and 349.21% in flexural strength in comparison to the pure date palm fiber composites. These findings underline the potential of date palm fiber hybrid composites which offers a balance between performance and environmental sustainability. The research also supports Sustainable Development Goals by encouraging low-carbon industrial materials, responsible production, and sustainable resource management.

Abstract: Laser Powder Bed Fusion (L-PBF) is turning out to be very promising for biomedical components production and stents are among the devices that would be suitable for tailor-made production. One of the most common stent types are the self-expandable, manufactured with Nitinol (NiTi). The use of NiTi alloy with L-PBF needs to be well controlled, as Ni evaporation during the process leads to significant variations in the final component properties. In the present work, prototype NiTi stents were produced via L-PBF and heat treated to examine the possibility of employing this technology for their application, also considering the Ni evaporation resulting from the layer-by-layer deposition. Samples were characterized through differential scanning calorimetry (DSC), microstructural observations, and compression tests in plate-to-plate configuration according to the standard. In parallel, a commercially available stent manufactured with traditional technology was tested for comparison.

Abstract: The lattice structures are a particular type of structures made by the multiply of a unit cell. In addition, their structure is close to some physiological tissues and bone structure, which can allow their use to develop prostheses needed to the rehabilitation or replacement of a body part. Lattice structures are widely used in various engineering applications due to their high weight-to-strength ratio and exceptional energy absorbing performance. The feasibility of using different base materials to fabricate these cellular structures with complex geometries has been significantly widen with the development of additive manufacturing (AM) technology. Additive manufacturing in particular metal selective laser melting (SLM) processes are rapidly being industrialized. In this work, samples with different lattice structures were manufactured by SLM technique using CoCr powder alloy. Compression tests were carried out to characterize their mechanical behavior. Starting from a BCC lattice cell measuring 5x5x5mm and 1mm diameter of the strut, were designed using Catia V5 R19 software. The BCC lattice unit cell consists of 4 solid struts with circular cross-section by which they intersected at 45°angle and modify by adding radius at the intersection of all four struts, furthermore the empty space is filled with BCC cell to increase the stiffens of the structure. The BCC cell was duplicate in three directions (X, Y, Z) measuring 20mm in each direction. To obtain the final part the BCC structure ware intersected with a cylindrical part measuring 20mm in Z direction, 15mm diameter and 1mm wall thickness, resulting a cylindrical part with three different BCC lattice structure inside.

Abstract: Additive manufacturing is considered an important alternative way for the fabrication of high quality polymer parts for various applications. Especially, Acrylonitrile styrene acrylate (ASA) is a promising thermoplastic polymer, exhibiting favorable mechanical properties and is also resistant to environmental conditions and various chemical substances. Given that it is possible to process this material through Fused Filament Fabrication (FFF) technology, it is required that optimal conditions are determined based on various criteria. Especially, as manufactured parts are expected to withstand various types of loads, the fabrication process should ensure adequate mechanical behavior under different conditions. For that reason, it is important both to determine the appropriate printing settings and investigate the mechanical behavior of additively manufactured ASA parts. In the present study, compression tests are conducted and statistical analysis is performed on the obtained results, in order to determine the mechanical properties of ASA parts with different infill densities for two different infill patterns. The results indicated that the reduced mechanical properties, in respect to the infill density are inversely correlated with the infill density and that honeycomb infill pattern is superior to gyroid in every case for the same infill density.

Abstract: This work emphasize on utilization of fly ash in to novel aluminium alloy (Al-2024). The Al-2024 alloy and composites (≈10%flyash) prepared by stir casting technique. The composites is cold forged and identified properties (mechanical, structural and stress distribution in component). Upset tests at room temperature, during the deformation process, provide representative behaviour. The metallographic structure of alloy revelled dendritic and composites shows fine spherical prime segment split and regularly dispersed intermetallic compounds. The stress intensity and distribution of temperature were examined in depth at different input combinations. Compression tests were conducted on Ø 12 mm cylindrical specimens at an H/D ratio of 1.0 and 1.5 for alloy and fly ash composites (2, 6 and 10 wt %). In determining the forging load, the upset ratio defined as the mainly important factor. The strain in composites increased with increasing % of reduction in size and decreased with % of fly ash.

Abstract: For the evaluation of final component properties under consideration of production-induced material characteristics, it is necessary to determine the mechanical parameters of parts and structures. Thus, there is a need of new test methods for the material characterization and quality control of produced goods. The miniaturization of the test specimens offers the potential for the local testing of the material properties at almost any position on the component. However, due to the reduction in size of the test specimens, size effects can occur which may affect the material behavior. For this reason, this contribution analyses the influence of size effects on the derived material parameters in dependence of the specimen size and material by using upsetting tests according to DIN 50106:2016 standard. The materials Cu-OFE (copper), X5CrNi18-10 (stainless steel) and AA7075-T6 (aluminum) are investigated to ensure a broad transferability of the findings. The specimens are cut from a bar stock by using a high precision 3D micro electrical discharge milling machining. Due to the small size, every specimen is measured with an optical 3D coordinate measuring system to determine the exact size. Through these investigations, the reproducibility and scatter in the determination of material properties for scaled cylindrical upsetting specimens are evaluated. Furthermore, limits of geometric dimensions at constant aspect ratios are derived. The results of this investigation enable an estimation of the geometrical influence of the specimen size in regard to the mechanical properties.

Abstract: Mortar is another construction medium made of cement, which is mixed with sands and water, and lime is applied to increase the product's longevity. The gypsum renders workability to make mortar or concrete by keeping the cement in plastic state at early age of hydration. The gypsum is called the retarding agent of cement because the gypsum which is mainly used for regulating the setting time of cement. To get the optimal setting time for optimum compressive strength, gypsum in the cement needs to be control. Cement setting time when it hydrates and renders cement paste when combined with water. The objective of this research is to analyze the effect of different amount in Ordinary Portland Cement (OPC). Vicat apparatus was used to analyze the initial setting time of cement paste. Gypsum and clinker were used in production of mortar with the size 50 mm x 50 mm x 50 mm. This research deals with observation of the cement setting time to point out some differences that would effect to strength of mortar. The results reveal that control gypsum with 4% of gypsum has the highest strength as compared to 0% of gypsum and 8% of gypsum. The setting time of cement paste are discussed with respect to their influence on the strength of mortar.

Abstract: Polyurethane (PU) foam were produced from polyol (PolyGreen R3110) and 4,4- diphenylmethane diisocyanate (Maskiminate 80) with distilled water as a blowing agent. Natural fibers have received more attention from researchers due to their ability to increase the properties of the polymer composites. In this work, PU/Henna foam composites were prepared by used Henna fibers at different loading of 5, 10, 15 and 20 wt. %. The effect of different Henna loading on PU foam were investigated by density, compression test, morphology and water absorption. Core density of PU/Henna foam composites increased with addition Henna compared to control PU and showed highest core density of 85.10 kgm^-3. Compressive strength decreased to 0.53 MPa after Henna addition at 5 % PU/Henna foam composites. Henna addition to 20 % PU/Henna foam composites were reduced the compressive strength to 0.97 MPa due to stiffness effect of Henna that contributed to embrittlement of the cell wall. The distorted cell wall and less uniform of cell structure were proved by SEM due to Henna addition as compared to control PU. Water absorption percentage of PU/Henna foam composites were increased with Henna addition as compared to control PU. It is because hydrophilic properties of Henna tendency to absorb moisture.

Abstract: It is convenient for designers to get the buckling loads of sparse stiffened panels quickly by using engineering calculation method to analyze the stability of composite stiffened panels, but it is still unable to meet the accuracy requirements of analysis of dense stiffened panels. The buckling loads of stiffened panels are closely related to the buckling modes. Based on capturing and analyzing the Compressive Buckling waveforms of T-shaped densely stiffened panels, this paper presents a formula for calculating the buckling loads according to the geometric coefficients. The results are very similar to those of finite element simulation, and can be used to calculate the buckling loads of sparse and dense stiffened panels with different stiffeners.