44 research outputs found
Laser welding of polypropylene using two different sources
No full textIn this paper, laser weldability of neutral polypropylene has been investigated using fibre and carbon dioxide lasers. A design of experiment (DoE) was conducted in order to establish the influence of the main working parameters on the welding strength of the two types of laser. The welded samples were characterized by carrying out visual and microscopic inspection for the welding morphology and cross-section, and by distinguishing the tensile strength. The resulting weld quality was investigated by means of optical microscopy at weld cross-sections. The tensile strength of butt-welded materials was measured and compared to that of a corresponding bulk material
Development of a numerical methodology for flowforming process simulation of complex geometry tubes
No full textPublisher Copyright: © 2017 Author(s).Nowadays, the incremental flowforming process is widely explored because of the usage of complex tubular products is increasing due to the light-weighting trend and the use of expensive materials. The enhanced mechanical properties of finished parts combined with the process efficiency in terms of raw material and energy consumption are the key factors for its competitiveness and sustainability, which is consistent with EU industry policy. As a promising technology, additional steps for extending the existing flowforming limits in the production of tubular products are required. The objective of the present research is to further expand the current state of the art regarding limitations on tube thickness and diameter, exploring the feasibility to flowform complex geometries as tubes of elevated thickness of up to 60 mm. In this study, the analysis of the backward flowforming process of 7075 aluminum tubular preform is carried out to define the optimum process parameters, machine requirements and tooling geometry as demonstration case. Numerical simulation studies on flowforming of thin walled tubular components have been considered to increase the knowledge of the technology. The calculation of the rotational movement of the mesh preform, the high ratio thickness/length and the thermomechanical condition increase significantly the computation time of the numerical simulation model. This means that efficient and reliable tools able to predict the forming loads and the quality of flowformed thick tubes are not available. This paper aims to overcome this situation by developing a simulation methodology based on FEM simulation code including new strategies. Material characterization has also been performed through tensile test to able to design the process. Finally, to check the reliability of the model, flowforming tests at industrial environment have been developed.Peer reviewe
Material saving by means of CWR technology using optimization techniques
No full textPublisher Copyright: © 2017 Author(s).Material saving is currently a must for the forging companies, as material costs sum up to 50% for parts made of steel and up to 90% in other materials like titanium. For long products, cross wedge rolling (CWR) technology can be used to obtain forging preforms with a suitable distribution of the material along its own axis. However, defining the correct preform dimensions is not an easy task and it could need an intensive trial-and-error campaign. To speed up the preform definition, it is necessary to apply optimization techniques on Finite Element Models (FEM) able to reproduce the material behaviour when being rolled. Meta-models Assisted Evolution Strategies (MAES), that combine evolutionary algorithms with Kriging meta-models, are implemented in FORGE® software and they allow reducing optimization computation costs in a relevant way. The paper shows the application of these optimization techniques to the definition of the right preform for a shaft from a vehicle of the agricultural sector. First, the current forging process, based on obtaining the forging preform by means of an open die forging operation, is showed. Then, the CWR preform optimization is developed by using the above mentioned optimization techniques. The objective is to reduce, as much as possible, the initial billet weight, so that a calculation of flash weight reduction due to the use of the proposed preform is stated. Finally, a simulation of CWR process for the defined preform is carried out to check that most common failures (necking, spirals,.) in CWR do not appear in this case.The research leading to these results received funding from the European Union´s Seventh Framework Program, managed by REA-Research Executive Agency (FP7/2007-2013) under grant agreement No. 606171 FP7-SME-2013-1 (CoVaForm). The research leading to these results received funding from the European Union's Seventh Framework Program, managed by REA-Research Executive Agency (FP7/2007-2013) under grant agreement No. 606171 FP7-SME-2013-1 (CoVaForm).Peer reviewe
Bacterial Appraisal in Expired and Unexpired Pharmaceutical Products
No full textThe microbial quality of expired and unexpired Pharmaceutical products like Metronidazole, Acetylsalicylic acid, Chloramphenicol, Silver sulphadiazine, combination of Polymyxin B Sulphate, Propylene Glycol, Lignocaine, combination of Betamethasone and Neomycinand the combination of Lignocaine, Ethanol and Cetylpyridiniumwere examined by the microbial growth on culture plates. Isolation was performed by serial dilution method and bacterial recovered by streak plate technique on Blood Agar, Chocolate Agar and MacConkey’s Agar. Isolates were characterized morphologically by gram staining and biochemical analysis. Microorganisms isolated from expired product are S.epidermidis (33.3%), B. subtilis (4.7%), Streptococcus (28.5%), Pseudomonas (9.5%), Listeria (4.7%) and B.cereus (19%) while B. subtilis(9.5%), Enterococcus (9.5%), E. coli (9.09%), S. epidermidis (27.2%), Listeria (9.5%) and Streptococcus (9.09%) are isolated from unexpired products. The isolated organism is mostly normal flora but opportunistic and pathogenic bacteria are also isolated which can cause disease especially in immune-compromised person or infants. The isolation of organisms may be due to improper hygiene maintenance or poor packaging techniques as the risk of contamination is higher while processing rather than during use. It revealed that quality of unexpired products have to be improved by producers to minimize the bio-liability so pharmaceutical companies should adopt good manufacturing practice to avoid microbial contamination in unexpired pharmaceuticals as well as the consumer should be educated and are aware of hazardous effect of using expired products
Point, surface and volumetric heat sources in the thermal modelling of selective laser melting
No full textSelective laser melting (SLM) is a powder based additive manufacturing technique suitable for producing high precision metal parts. However, distortions and residual stresses within products arise during SLM because of the high temperature gradients created by the laser heating. Residual stresses limit the load resistance of the product and may even lead to fracture during the built process. It is therefore of paramount importance to predict the level of part distortion and residual stress as a function of SLM process parameters which requires a reliable thermal modelling of the SLM process. Consequently, a key question arises which is how to describe the laser source appropriately. Reasonable simplification of the laser representation is crucial for the computational efficiency of the thermal model of the SLM process. In this paper, first a semi-analytical thermal modelling approach is described. Subsequently, the laser heating is modelled using point, surface and volumetric sources, in order to compare the influence of different laser source geometries on the thermal history prediction of the thermal model. The present work provides guidelines on appropriate representation of the laser source in the thermal modelling of the SLM process.Computational Design and Mechanic
Computationally efficient thermal-mechanical modelling of selective laser melting
No full textThe Selective laser melting (SLM) is a powder based additive manufacturing (AM) method to produce high density metal parts with complex topology. However, part distortions and accompanying residual stresses deteriorates the mechanical reliability of SLM products. Modelling of the SLM process is anticipated to be instrumental for understanding and predicting the development of residual stress field during the build process. However, SLM process modelling requires determination of the heat transients within the part being built which is coupled to a mechanical boundary value problem to calculate displacement and residual stress fields. Thermal models associated with SLM are typically complex and computationally demanding. In this paper, we present a simple semi-analytical thermal-mechanical model, developed for SLM that represents the effect of laser scanning vectors with line heat sources. The temperature field within the part being build is attained by superposition of temperature field associated with line heat sources in a semi-infinite medium and a complimentary temperature field which accounts for the actual boundary conditions. An analytical solution of a line heat source in a semi-infinite medium is first described followed by the numerical procedure used for finding the complimentary temperature field. This analytical description of the line heat sources is able to capture the steep temperature gradients in the vicinity of the laser spot which is typically tens of micrometers. In turn, semi-analytical thermal model allows for having a relatively coarse discretisation of the complimentary temperature field. The temperature history determined is used to calculate the thermal strain induced on the SLM part. Finally, a mechanical model governed by elastic-plastic constitutive rule having isotropic hardening is used to predict the residual stresses.Computational Design and Mechanic
Designing new practices of transformative urbanism: an experiment in Toronto
No full textThe increasing complexity, rapid change, and often unpredictable outcomes of city-design-and-building processes demand new modes of practice that are responsive and adaptive to the specifics of such changing contexts in the twenty-first century. These include open-ended outcomes, rather than rigid and predictable products, that emerge out of interactions with a specific context, specific communities and specific interactive processes. This article describes how we can design such new practices of transformative urbanism, derived largely—but not exclusively—from the innovation, resourcefulness and collective creativeness of informal urbanisms. To illustrate such new practices of transformative urbanism, the author describes an experiment in the city of Toronto undertaken as a partnership between the residents of the Thorncliffe Park neighborhood and urbanists from the University of Toronto. The article concludes by describing several promising results of the experiment
آئینہ ماہ و سال کے تخصیصی پہلو
No full textThe diverse experiences of life and the emotions related to it have been a central theme in literary works. Urdu literature is adorned with a variety of genres, among which autobiography holds significant prominence. The core and main focus of an autobiography centers on self-expression, allowing the author to shape his own portrait through his writings. Inam ul Haq Javed is a renowned scholar, literary critic, and linguist. He has written extensively on various aspects of Urdu literature, including poetry, fiction, autobiography and criticism. His works are known for his depth, insight, and thorough analysis, and have been widely acclaimed by scholars and literary circles.
As an autobiographer Inam-ul-Haq Javed enhances the charm of autobiography through detailed descriptions, vivid imagery, and the use of metaphors. His work "Aaina-e-Mah-o-Saal" fully adheres to the principles of autobiography. Undoubtedly, it holds a significant position in the tradition of autobiographical writing. In this article, we will explore the intellectual and artistic elements of "Aaina-e-Mah-o-Saal" within the context of the tradition of autobiography
