Primena optičke DIC merne metode na projektu A_MADAM

Aditivne tehnologije sve više se koriste u izradi funkcionalnih proizvoda koji su za vreme eksploatacije podložni dinamičkim opterećenjima. Cilj projekta AMADAM je utvrditi pravila dizajna, tako da s obzirom na način proizvodnje proizvodi aditivnih tehnologija imaju optimalna dinamička svojstva. Primenili smo optičku mernu metodu baziranu na digitalnoj korelacijli slike (DIC) za potrebe ispitivanja materijala, merenja pomaka i deformacija kod propagacije naprslina i verifikaciju i kalibraciju numeričkih simulacija. Eksperimente u prvoj fazi projekta provodimo na uzorcima od poliamida (PA) proizvedenim na SLS 3D printeru. Dosadašnja iskustva pokazala su da se odabrana DIC metoda pokazala jednostavnom za korišćenje a rezultati koje daje pružaju detaljni uvid u stvarno ponašanje konstrukcija.The authors wish to acknowledge the support of European Commission through the project “Advanced design rules for optimal dynamic properties of additive manufacturing products – A_MADAM”, which has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 734455.Publishe

Advantages and Drawbacks of Additive Manufacturing

- This paper presents some various imperfections that can occur during Direct Metal Laser Sintering (DMLS) and their effects on part quality. Direct Metal Laser Sintering is one of the Additive Manufacturing (AM) technologies that enables fast production of an accurate, functional, complex shape parts and tools, without additional tooling, directly from 3D CAD model. This process is based on layer by layer manufacturing, where the fusion of the metal powder is performed by selective melting with laser beam. The laser beam moves and scans area that correspond to section of the part for the specific layer. In the DMLS the part is built layer by layer, where the process of the melting and solidification occur in small volume in relatively short time. Thanks to this kind of approach, the DMLS has much less limitations than the subtractive methods of part production. However, the production in the layers has some drawbacks, which can have a significantly influence on the part geometry, structural errors and part imperfections. Some of the advantages as well and drawback of the DMLS of metal parts has been presented in this paper.The authors wish to acknowledge the support of European Commission through the project “Advanced design rules for optimal dynamic properties of additive manufacturing products – A_MADAM”, which has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 734455.Publishe

Knoop hardness optimal loading in measuring microhardness of maraging steel obtained by selective laser melting

© IMechE 2019. Knoop microhardness method possesses several advantages over Vickers testing: lower penetration depth, higher accuracy in indentation measurement, and a better suitability to measuring thin and elongated morphological features. This study explores the optimal loading and load independent hardness of selective laser melted specimens in non-heat-treated and heat-treated conditions, by using different Knoop test loads. The obtained results were used to plot load to indentation size charts, which, in turn, were used to obtain prediction curves in accordance to Meyer, proportional specimen resistance, and modified proportional specimen resistance models. The fitting of fitting curves to the measured values was used to calculate appropriate correlation factors. The results indicate that indentation size effect occurs in all measured specimens. This suggests that there is material true microhardness. Also, the most adequate model was modified proportional specimen resistance, with correlation factors just under one.The authors wish to acknowledge the support of European Commission through the project “Advanced design rules for optimal dynamic properties of additive manufacturing products – A_MADAM”, which has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 734455

Effects of Machining on the Fatigue Strength of Steel Components Produced by DMLS

Direct metal laser sintering (DMLS) is the additive manufacturing (AM) technology that allows production of metal machine components with complex geometry. Due to the layer-wise production principle, its products usually require post-processing, predominantly machining, to achieve uniform or requested surface quality. Given the increasing application of DMLS technology in industry and insufficient published data about the effects of machining on the fatigue properties of steel, the focus of this research is put to investigation of the influence of thickness of allowance for machining to fatigue strength of DMLS products. Previous studies revealed significant differences in the mechanical behaviour of samples made of different kinds of steels, both during production and testing. Unlike the samples made from maraging steel, the samples made from stainless steel often deformed during cooling due to the strong residual stresses, and revealed dependence of mechanical properties on orientation during production process. To improve the understanding of the differences, fatigue testing according to ISO 1143 was performed on samples manufactured from two kinds of steel, maraging steel 1.2709 and stainless steel 15-5. Twelve sets of samples were tested with the aim to investigate the effects of machining allowance and build orientation according to an extensive DoE experimental plan.The authors wish to acknowledge the support of European Commission through the project “Advanced design rules for optimal dynamic properties of additive manufacturing products – A_MADAM”, which has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 734455.Publishe

Multivariate Interaction Analysis of Winter Wheat Grown in Environment of Limited Soil Conditions

The less productive soils present one of the major problems in wheat production. Because of unfavorable conditions, halomorphic soils could be intensively utilized using ameliorative measures and by selecting suitable stress tolerant wheat genotypes. This study examined the responses of ten winter wheat cultivars on stressful conditions of halomorphic soil, solonetz type in Banat, Serbia. The wheat genotypes were grown in field trails of control and treatments with two soil amelioration levels using phosphor gypsum, in amounts of 25 and 50 tha(-1). Across two vegetation seasons, phenotypic variability and genotype by environment interaction (GEI) for yield traits of wheat were studied. The additive main effects and multiplicative interaction (AMMI) models were used to study the GEI. AMMI analyses revealed significant genotype and environmental effects, as well as GEI effect. Analysis of GEI using the IPCA (Interaction Principal Components) analysis showed a statistical significance of the first two main components, IPCA1 and IPCA2 for yield, which jointly explained 70% of GEI variation. First source of variation IPCA1 explained 41.15% of the GEI for the grain weight per plant and 78.54% for the harvest index. The results revealed that wheat genotypes responded differently to stressful conditions and ameliorative measures

Effects of build orientation and thickness of allowance on the fatigue behaviour of 15–5 PH stainless steel manufactured by DMLS

The present study is focused on the fatigue strength of 15–5 PH stainless steel, built by Direct Metal Laser Sintering. Six-specimen sets were manufactured, mechanically and thermally treated and tested under rotating bending fatigue. The study investigates the effects of the build orientation (parallel, perpendicular, or 45° inclined with respect to the vertical stacking direction) and of allowance for machining (1 mm or 3 mm at gage). The results, processed by an ANOVA methodology, indicate that allowance for machining has a beneficial effect on the fatigue response. Removing the surface irregularities, averagely leads to a 19% enhancement of the fatigue limit. The build orientation also becomes beneficial, when the slanted samples are included in the experiment. In this case, a fatigue strength increase up to 20% can be achieved. Further developments will include the investigation of the effects of heat and surface treatments, involving also further materials in the study.The authors wish to acknowledge the support of European Commission through the project “Advanced design rules for optimal dynamic properties of additive manufacturing products – A_MADAM”, which has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 734455.Publishe

Investigation of mixed mode I and II fracture mechanical behaviour of SLS printed IASCB specimens by digital image correlation

This work focuses on the fracture mechanics properties of polyamide (PA) for selective laser sintering (SLS) and investigates the capability of additive manufacturing process to build 3D artificial cracks, otherwise impossible to create by classic methods. IASCB semi-circular specimen with tilted crack subjected to asymmetric three-point bend loading were tested in order to cover a wide range of stress intensity factors (KI, KII and mixed modes) and T-stress. Moreover, Digital Image correlation (DIC) technique was used by full strain field analysis with the purpose of evaluating the fracture behaviourThe authors wish to acknowledge the support of European Commission through the project “Advanced design rules for optimal dynamic properties of additive manufacturing products – A_MADAM”, which has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 734455.Publishe

Additively manufactured tensile ring-shaped specimens for pipeline material fracture examination - influence of geometry

Plane-strain fracture toughness is one of the main parameters in linear elastic fracture mechanics and its purpose is to show the material capability to withstand load while having a defect. Main validity aspect for such an assessment is to provide a wide enough crack front to enable plane-strain condition. Nonetheless, in FDM (Fused Deposition Modeling) polymers, due to structural anisotropy caused by material properties and Additive Manufacturing (AM) process parameters, more validity aspects must be met. During the planestrain fracture toughness test a crack must follow a straight line from initiation cite up to the point of structural failure. For such a purpose a DIC (Digital Image Correlation) device can be used for crack path direction analysis. Plane-strain fracture toughness assessment is conducted according to the ASTM D5045-14 standard for testing of polymer materials. Tests are performed on SENB (Single Edge Notched Bend) specimens, made from two similar polymer materials: quasi-brittle PLA and ductile PLA-X composite. Specimens are manufactured with four different AM process parameters, i.e., layer height, infill density, printing orientation and one batch was dried before testing. Testing is conducted using 3-point bending test fixture on universal testing machine, with DIC dual-camera device placed ahead of the machine in order to capture full-field deformations of front SENB specimen surface (Fig. 1)

CAVITATION RESISTANCE OF THE MATERIAL PA 3200 GF PRODUCED BY SELECTIVE LASER SINTERING

The present study focuses on the results of cavitation resistance research of samples obtained by the Selective Laser Sintering technology. The material used was Polyamide powder PA 3200 GF reinforced with glass fibers. The laser-sintered samples were produced from 100% new and recycled powder mixed with 70% of new powder. The samples were tested under cavitation conditions using an ultrasonic vibration method with a stationary sample according to the ASTM G-32 standard. Examination of the morphology of cavitation damage was investigated by scanning electron microscopy. The change in mass loss during different cavitation times was measured on the tested samples. The main objective of the research was to determine the validity application of the tested material in cavitation condition

EFFECT OF SECTION THICKNESS ON CAVITATION BEHAVIOUR OF SELECTIVE LASER SINTERED POLYAMIDE 12

The present study focuses the cavitation resistance results of samples obtained by the Selective Laser Sintering technology. All samples were made from Nylon 12 – Polyamide 12 powder, also known as PA2200 in the industry, produced by EOS GmbH. The powder used for building the samples represented a mixture of 50% new powder and 50% recycled powder. Samples with different section thicknesses (0.4mm; 0.8mm and 1.0mm) were subjected to the ultrasonically induced cavitation test method to investigate the effect of geometry on their cavitation behaviour. The change in mass loss during different cavitation times was measured on the tested samples. The morphology of cavitation damage was characterized using Scanning Electron Microscopy (SEM). The results obtained in this paper have shown that section thickness of the samples has a significant influence on the cavitation resistance, with the highest cavitation resistance obtained for the samples a thickness of 0.4mm