Papers by Keyword: SPD

Abstract: Severe plastic deformation (SPD) has been known as a method for materials grain refining. Among its numerous techniques, equal channel angular pressing (ECAP) is the representative model for the theoretical analysis in the view of equipment design challenge. By rigid block model of plastic deformation zone, technological parameters such as high accumulative strain, hydrostatic stress, punch pressure and distribution of stress and strain state are estimated. A compressive hydrostatic pressure created by a friction force in a contact surface between a die and a workpiece, which is directly proportional to the strength of the treated material, prevents its fracture and increases punch pressure significantly. The paper presents a method used in metalworking for determining the main parameters. The solution can be used for the die design in comparing with other conventional technologies to overcome the difficulty.

Abstract: The integration of photovoltaic systems into energy grids has been very common in recent times since more renewable forms of energy are sought after. Reliability and safety are among the most essential concerns that have to be considered for the deployment and operation of such systems. There have been some very conspicuous failures of protective devices in recent installations, leading to huge damage to solar equipment and an estimation of millions of Naira in repair and maintenance costs. The said incidents further underscore the need for technical competency in PV system installations as well as good-quality protective component acquisition. This study examines the critical role of protective devices in photovoltaic (PV) systems, focusing on their impact on system reliability, operational safety, and financial implications. A survey of industry professionals revealed that the major causes of device failures are overvoltage and poor-quality devices. Similarly, Circuit Breakers and Surge Protectors top the list of devices affected by failures. Critical system shutdowns take up 50% of the resultant consequences of failures, deteriorated performance, and safety hazards. Surprisingly, 65% of those who responded reported financial losses due to the failures, estimated at 45% between N100,000 and N500,000, while 15% had losses above N500,000. The study recommends high-quality protective devices be installed, installation and maintenance be standardized, and predictive maintenance/remote monitoring technologies be adopted to improve reliability and early fault detection. The long-term performance of devices in varying environmental conditions and the economic benefit of using durable, high-quality components are to be focused on further for research. These findings also put forward actionable suggestions to better ensure the PV system resilience for all stakeholders, thereby reducing their financial risks and ensuring the continued growth of the solar energy infrastructure in a reliable manner.

Abstract: Titanium is a hard metal with good mechanical properties, corrosion resistant and biocompatibility which makes it have a wide range of applications (biomedical and aerospace). Severe plastic deformation (SPD) is employed to produce Ultrafine Grained (UFG) structures. UFG structures have better mechanical properties due to their compaction. Equal Channel Angular Pressing (ECAP) is adapted to produce a UFG structure in Titanium. In this process, titanium sponge powder is filled in the aluminium shell by intermediate tapping to fill the volume of the shell. The shell is then closed with an Al cap and ECAP is done with continuous back pressure at 300°C. The test specimen has undergone four passes in route B_C at different back pressure (50, 100 and 150 MPa) where titanium is consolidated without any crack. Titanium showed decreased grain size and porosity with increasing backpressure. In particular, it is seen that the sample ECAPed by 100 MPa backpressure showed a relative density of about 98% with a hardness of 37 HRC. It is seen that ECAP is more economical and the product obtained by the ECAP process has better properties.

Abstract: AA6061 alloy was selected as starting material, as this alloy play vital role in aerospace, automotive and naval applications. To enhance mechanical properties and study the structural correlation of AA6061 using one of the promising SPD (Severe Plastic Deformation) technique. In RCS (Repetitive Corrugation and Straightening), repetitive bending and shearing stresses act alternatively on the specimen. The die models and work piece were designed using Creo parametric 2.0 and imported to AFDEX-2014 (Adviser metal Forming Design Expert) for simulation studies. AA6061 was subjected to four passes (8 stages) of RCS. Effective strain observed in AA6061 alloy was 2.389 and strain rate increased during corrugation and less during straightening stages. The theoretical effective strain was 2.65.The experimental effective strain was validated and found to be nearly approximately 92% of the theoretical result. Further, mechanical properties like tensile strength and microhardness increased to 1.5 to 2 times in AA6061 alloy after eight passes of RCS. Keywords: AA6061, RCS, SPD, Microhardness, Tensile strength

Abstract: In this paper an experimental investigation of mechanical behavior of a thermoplastic polymer (polyamide PA 66) processed by constrained groove pressing (CGP) using several passes is presented. To this end, corrugating and straightening tools are designed and manufactured. The effects of the number of passes and the hold time on the mechanical behavior of the polyamide have been highlighted. The obtained results show that the material properties and the microstructure are significantly altered under CGP process. It has been found that the microhardness and the tensile properties have been progressed accordingly to the number of cycles, especially when the samples are processed using a hold time of five minutes. Hence, it can be concluded that this latter plays a very important role on the reorientation and stabilization of the microstructure when the processed material is a polymer.

Abstract: This paper focuses on the effect of rolling with cyclic movement of rolls (RCMR) on microstructure refinement, mechanical properties and electrical conductivity of CuCr0.6 alloy after applying different heat treatments (quenching and aging). It was found that the presence of second phase particles obtained during aging treatment has a significant effect on the formation of ultrafine grain (UFG) structure during the RCMR processing. The presence of high dislocation density inside subgrains and presence microshear bands are the marked features of the microstructure after aging at 500^°C/2h and RCMR deformation. Whereas after aging at 700^°C/24h and RCMR processing, fine precipitates were effective in inhibiting the grain/subgrain boundary motion. The RCMR processed alloy after aging at 500^°C/2h shows high mechanical strength attributed to the high density of coherent precipitates and ultrafine grained structure. The RCMR processing induces a significant reduction of the electrical conductivity for samples at quenching state but for samples at aging state electrical conductivity was restored thanks to precipitation process.

Abstract: Investigation of the mechanical behaviour of multilayered metallic materials obtained during novel joining technique called Constrained Compression (CC) is presented. 316L stainless steel material was used in CC to achieve multi-layered structure. Microstructural study based on light microscopy was performed focused presumably on the joining areas of the deformed metallic laminate. The qualitative and quantitative assessment of the processing conditions, microstructure development and microhardness distributions showed the possibility of achievement good bonding quality. Experimental study was supported by numerical stress and strain analysis. It has been shown that determination of the optimum processing parameters allowed for improvement of the joining process, which in turn will enable to produce multilayered metallic materials on a larger scale.

Abstract: This paper describes selected capabilities of unconventional processing of steels in semi-solid state under various process conditions and with the use of various steel chemistries for obtaining unusual structures formed by rapid solidification in combination with other procedures. This investigation involves the use of severe plastic deformation techniques (SPD) and in-situ observation of the transformation of microstructure from solid state to semi-solid state at temperatures above 1200°C using a high-temperature microscope.

Abstract: In this article, the results of microstructure and hardness investigation performed on CuFe2 alloy processed by rolling with cyclic movement of rolls (RCMR) were presented. The investigations were focused on cross section planes of deformed samples. This results were compared with the ones obtained for samples after conventional rolling. It was shown that in the initial passes, the additional movement of rolls in RCMR method generate in material heterogeneous microstructure and hardness. With increase of deformation the microstructure and hardness distribution is more homogeneous.

Abstract: In this present study Al-5083 alloy powders were prepared from elemental powders using high energy ball milling under optimized milling parameters. Various properties such as crystalline size, particle size and morphology have been studied using X-Ray diffraction analysis and Scanning Electron Microscopy. It was found that Al-5083 alloy was formed and nanocrystalline size particles were achieved. These nanocrystalline Al-5083 alloy powders were consolidated using equal channel angular pressing with and without application of back pressure. Physical and mechanical properties such as density and hardness are studied.