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- Improving Preventive Maintenance Management in an Energy Solutions CompanyPublication . Martins, L.; Silva, Francisco J. G; Pimentel, C.; Casais, Rafaela B.; Campilho, R.D.S.G.In industry, production processes and assets are constantly evolving, Thus, continually improving and updating them is essential to their sustainability. This work intended to apply a set of methods and philosophies to improve the Preventive Maintenance Management process in a case study company dedicated to the development, production and maintenance of power and distribution transformers. Thus, a Action – Research methodology was used. After identifying the main problems, a mixed maintenance strategy based on Reliability Centered Maintenance (RCM) and Total Productive Maintenance (TPM) was applied. The following achievements were obtained by this work: (a) method of grading equipment critically based on its importance to the production process was developed and implemented;(b) a new flowchart of decisions and actions was developed for Preventive Maintenance Plan Management; (c) a reduction of the waste time in Preventive Maintenance (PM) was obtained; (d) the implementation of Autonomous Maintenance (AM) resulted in a reduction of 66% in equipment failures; (e) a set of new Key Performance Indicators (KPI´s) were introduced; (f) maintenance plans compliance rates increased by 12%. At the end of the work a reduction of € 120 060 could be achieved. Thus, the main contribution of this work was to show that bringing to the action different tool together in an organized way and share the information and responsibilities with the workers can result in important savings to the company, becoming the maintenance function more effective.
- Comparative Study of the Wear Behavior of B4C Monolayered and CrN/CrCN/DLC Multilayered Physical Vapor Deposition Coatings Under High Contact Loads: An Experimental AnalysisPublication . Silva, Francisco J. G.; Casais, Rafaela C. B.; Baptista, Andresa P. M.; Marques, M. J.; Sousa, V. M. C.; Alexandre, R.There are several ways to characterize the wear resistance of coatings in the laboratory, almost all of them applying relatively low contact pressure, both punctually and over surface contact. Pin-on-disc, reciprocal sliding, and micro-abrasion wear tests are quite common configurations for this purpose. Thus, a gap was identified in terms of characterization of hard physical vapor deposition (PVD) coatings subject to higher levels of contact pressure. This study aims to study and compare the wear behavior of two different coatings made by PVD, a B4C (Boron Carbide) monolayer, less used, and another following a multilayer structure of CrN/CrCN/DLC, to identify the wear mechanisms involved in quite different coatings. Both coatings were initially characterized in terms of chemical composition, thickness, morphology, structure, hardness, and adhesion to the substrate, being subsequently tested in laboratory equipment for wear tests following the block-on-ring configuration and relatively high levels of contact pressure, with a view to study the failure mechanisms of the coatings and their wearrate. CrN/CrCN/DLC multilayered coatings presented a better overall wear behavior, whereas B4C coating showed a good wear behavior regarding the load and configuration used, but in line with the behavior already observed when other wear testing configurations had been used. Thus, under the conditions imposed, CrN/CrCN/DLC coating is the best option when high contact pressure is applied to the coated surfaces.
- Experimental study on the wear behavior of B4C and TiB2 monolayered PVD coatings under high contact loadsPublication . Casais, Rafaela B.; Baptista, António Monteiro; Silva, Francisco J. G.; Andrade, Fátima; Sousa, Vitor; Marques, Maria JoséThere are several ways to characterize the wear resistance of coatings in the laboratory, almost all of them applying relatively low loads, both punctually and more widely. Pin-on-disc, reciprocal sliding, and micro-abrasion wear tests are quite common configurations for this purpose. Thus, a gap was identified in terms of characterization of hard PVD coatings subject to higher loads. This work aims to study and compare the wear behavior of two different coatings obtained by PVD, both monolayer, B4C (boron carbide) and TiB2 (titanium diboride), focused on identifying the wear mechanisms present in different coatings provided with high hardness. Both coatings were initially characterized in terms of chemical composition, thickness, morphology, structure, hardness, and adhesion to the substrate, being subsequently tested in laboratory equipment for wear tests following the block-on-ring configuration and relatively high loads; with a view to study the failure mechanisms of the coatings and their wear rate, it was found that the main wear mechanism, sustained by the analyzed coatings, was abrasive wear in the contact area. In the craters left by the tests, it was determined that the main wear mechanism was two-body abrasion. The B4C and TiB2 coatings performed well in relation to the load and configuration used, in line with the behavior already observed in other used wear test configurations. However, under the imposed conditions, and comparing the two coatings, TiB2 is the best option when high loads need to be applied to the coated surfaces, as these coatings did not suffer perforation during testing and the amount of removed volume was inferior to that of the B4C coated samples.
- Cutting Forces Assessment in CNC Machining Processes: A Critical ReviewPublication . Sousa, Vitor F. C.; Silva, Francisco José Gomes da; Fecheira, José S.; Lopes, Hernâni M. L; Martinho, Rui Pedro; Casais, Rafaela B.; Ferreira, Luís PintoMachining processes remain an unavoidable technique in the production of high-precision parts. Tool behavior is of the utmost importance in machining productivity and costs. Tool performance can be assessed by the roughness left on the machined surfaces, as well as of the forces developed during the process. There are various techniques to determine these cutting forces, such as cutting force prediction or measurement, using dynamometers and other sensor systems. This technique has often been used by numerous researchers in this area. This paper aims to give a review of the different techniques and devices for measuring the forces developed for machining processes, allowing a quick perception of the advantages and limitations of each technique, through the literature research carried out, using recently published works