FVPM simulation of scratching induced by a spherical indenter

International audienceThis article presents a single particle scratching simulation using the Finite Volume Particle Method (FVPM). FVPM is a variant of the well-known Smooth Particles Hydrodynamics method (SPH) which is locally conservative and consistent, what's more it features advantages of mesh-free methods for handling moving interfaces and multi-scale interpolation. The test material is represented by overlapping particles and data exchanges occur through the interfaces. The indenter is modeled as a rigid sphere whose path is a straight horizontal line. The resulting surface topography as well as constraints and scratching efforts have been numerically studied. The FVPM simulation code assessed in this article has been found suitable for the scratching simulation based on a comparison with other results from the literature. The presented results suggest the possibility to simulate more complex surface finishing operations. Manufacturing processes based on abrasion material removal, such as the grinding process, will be considered in the future

Surface Integrity Study For FC300 Cast Iron Using TiAIN Ball End Mill

Finishing of FC300 gray cast iron predominantly done by manual polishing. Study the surface integrity of FC300 after machining is crucial to investigate the surface characteristics before polishing. This work aims to investigate the surface profiles and subsurface alterations induced by milling of FC300 gray cast iron using TiAlN Ball end mill. Machining trials were performed using CNC variaxis machine in dry condition at the cutting speeds of 66-99 m/min, feed rates of 0.27-0.42 mm/tooth and constant depth of cut of 0.1 mm. The results shows that the surface roughness decreased as the cutting speed increased from 66 m/min to 88 m/min. Smooth and shiny surface profiles appeared at the lower cutting speed of 66 m/min due to effect of lubrication layer that formed from the small fragmented graphite flakes. When the cutting speed increased to 99 m/min, surface profiles appeared with smeared and large graphite flakes probably due to higher rotational impact from the cutting tool. Analysis of subsurface microstructure observed bending effects at the region where worn cutting tool applied. Severe crack nucleation’s were evidence to reflect severe rubbing action from worn cutting tool

Simulation FVPM de rayage mono-grain

International audienceLa réalisation des pièces mécaniques à forte valeur ajoutée implique des temps d'usi-nage conséquents et nécessite parfois une finition des surfaces fonctionnelles par abrasion pour atteindre les spécifications requises. La maîtrise du procédé de fabrication pendant la phase de pré industrialisation des pièces peut encore être améliorée par l'apport d'outils de simulation adaptés. L'article présenté étudie la pertinence de la méthode Finite Volume Particle Method (FVPM) quant à simuler le processus d'abrasion. Cette technique particulaire sans maillage utilisée pour simuler le comportement mécanique de la matière est une variante de la méthode Smoothed Particle Hydrodynamics (SPH). Une étude a été menée pour la comparaison des ré-sultats de simulation avec des données expérimentales. Un essai de dureté Brinell et un essai de rayage ont été simulés. Les résultats de simulations sont encourageants. La prise en compte de la matière repoussée par la sphère d'indentation est cohérente avec les mesures. La démarche d'implémentation des essais numériques et les résultats observés correspondent avec l'analyse de la littérature à ce sujet. Ces corrélations satisfaisantes entre les essais numériques et réels laissent espérer des résultats pour de futurs scénarios intégrant une complexité mécanique et cinématique plus importante et plus pertinente

Effect of mechanical and thermochemical tool steel substrate pre-treatment on diamond-like carbon (DLC) coating durability

Diamond-like carbon (DLC) coatings are becoming well established across many industrial sectors including aerospace, automotive, oil and gas, and cold-forming tools. While DLC coatings exhibit good mechanical properties and a low coefficient of friction, the coating–substrate systems may suffer from insufficient wear resistance. This paper describes the effect of mechanical and thermochemical tool steel substrate pre-treatment on DLC coating durability. We have investigated two tool steel substrates, Sverker 21 (AISI D2) and an advanced powder metallurgy alloyed steel Vanadis 8. Initially, the substrates were heat treated in a vacuum furnace and gas quenched resulting in hardness of 59 ± 1 and 64 ± 1 Hardness Rockwell C (HRC) respectively. Subsequently, the samples were subjected to mechanical turning and burnishing with 130 N and 160 N forces, using diamond composite tools with a ceramic bonding phase. Afterwards, a plasma-assisted vacuum nitriding process in a physical vapour deposition (PVD) coating chamber, as a pre-treatment for subsequent DLC coating deposition, was carried out. Coated samples were subjected to a series of ball-on-disc wear tests against Al2O3 and Si3N4 counterparts. X-ray diffraction, instrumented indentation and scanning electron microscopy were employed to examine the mechanical and chemical properties of the wear scars. Selected variable factors, including the type of steel, the burnishing force and the type of counterbody material, were analysed in order to correlate them with the durability of DLC coating deposited on a pre-treated steel substrate. The effect of sequential processes used as pre-treatment on DLC coating durability was demonstrated. The wear resistance was over 180 (Sverker 21 substrate) and 10 (Vanadis 8 substrate) times greater against the Al2O3 counterbody for samples subjected to the following treatment: turning + burnishing with 160 N force + vacuum nitriding + DLC coating, comparing with the sample after grinding. The results are discussed in light of improving the cold-forming tools' tribological performance

Análise de reparação por soldadura de moldes de injeção para termoplásticos

A crescente demanda de termoplásticos tem exercido pressão na indústria de moldes, exigindo cada vez mais ferramentas com melhores acabamentos, em espaços de tempo mais reduzidos. Durante a produção do molde ou no funcionamento do mesmo, a geometria das zonas moldantes pode ficar comprometida por diversas razões, pelo que é preciso a sua reparação ou substituição. A substituição é uma opção mais demorada e dispendiosa, visto que implica novamente a realização de todas as operações, como maquinação, tratamentos térmicos (se aplicável) e acabamentos. Assim a opção mais comum é a reparação da ferramenta já existente por processos de soldadura, por se tratar de um processo rápido e económico, comparado com a outra solução apresentada. O processo de soldadura utiliza uma fonte de calor para fundir o material localmente, que seguido da solidificação do banho de fusão, origina a ligação da peça com o material de adição. No entanto, apesar de ser uma solução rápida e com custos associados relativamente baixos, a introdução de calor na ferramenta origina uma zona termicamente afetada, com propriedades diferentes do material base. Estas diferenças podem complicar o processo de polimento, deixando marcas visíveis nas peças plásticas. Neste trabalho será examinada a influência dos tratamentos térmicos, antes e após a soldadura, em três tipos de aços utilizados na indústria de moldes. O objetivo do presente trabalho reside na identificação da melhor sequência de operações, que resultem numa zona soldada o mais impercetível possível. No decorrer do trabalho serão analisados: um aço pré-tratado, um aço de trabalho a quente, e um aço inoxidável martensítico, soldados a TIG e Laser Nd:YAG. A análise das amostras preparadas compreende a avaliação visual, seguido da medição de rugosidade, elaboração de perfis de dureza e por fim, após o seccionamento, análise metalográfica. Os resultados obtidos permitem determinar a melhor solução para cada material base