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This article presents the results of research conducted to determine the influence of heating temperature on the structure of a dual-phase steel with low manganese content (0.53% Mn). The ferrite-martensite structures were obtained by intercritical quenching (heating to temperatures located between 750 and 850 ℃, followed by cooling in water), andthe metallographic analyses revealed the volume fraction of martensite in these structures; to evaluate the influence of the structure, and therefore of the heating temperature, on some mechanical properties, the carbon content of martensite was calculated and the Vickers hardness was measured. [ABSTRACT FROM AUTHOR]

The paper presents an analysis of the processing by cold bending of wide strips on double convex surfaces. The state of tension and deformation are plane states. The deformation state is defined by two real and opposite main deformations. It was established calculus formulas for the real principal deformations at a point on the workpiece, for thickness and for stretch force in the different piece sections, whose can be utilised in technological calculus. [ABSTRACT FROM AUTHOR]

This article presents the influence of research equipments used in studies conducted at the University "Stefan cel Mare" from Suceava to characterize a dual-phase steel with 0.094% C and 0.53% Mn (Si, Cr, Ni, Mo, Al, Cu, P and S below 0.1%). The research was conducted in two stages, namely: the study of the influence of intercritical quenching on the structure and mechanical properties (2014 - 2015) and the study of the influence of structural succession on the ferrite-martensite structure and mechanical characteristics (2019 - 2020). Spectrophotometric, metallographic analyses and mechanical tests were performed with different equipments from one research stage to another. [ABSTRACT FROM AUTHOR]

Most residential buildings in Romania have metal tiles roofs usually made in our country by profiling semi-manufactured products imported from European Union countries (steel sheets with a thickness of 0.40 ÷ 0.50 mm, coated with zinc, primer, polyester-polyamide paint and epoxy-polyurethane paint layers). Inappropriate (smaller) thickness of the layers deposited on the steel sheet causes defects of the final product (roof tile); when receiving the semi-manufactured products from the external partners, the Romanian metal roof tile manufacturers are performing a series of quick tests, which do not always lead to the identification of regions with inadequate thicknesses of the layers covering the steel sheet. In this article are presented the results of the study conducted at the University "Stefan cel Mare" for the identification and measurement of the paint (polyester polyamide and epoxy polyurethane), primer and zinc layers of some semi-manufactured products used for making metal roof tiles, with a laser microscope (Olympus LEXT OLS4100); 23.81% of the measurements made on the polyester-polyamide paint layer and 31.58% of those made on the primer layer had values below the lower limit of the thicknesses prescribed for these layers. [ABSTRACT FROM AUTHOR]

This article contains the results of the dilatometric analysis carried out on a steel with 0.087% C and 0.511% Mn (Si, Cr, Ni, Mo, Al, Cu, V and W, under 0.1%) to determine the coefficient of linear thermal expansion (CTE), depending on the heating rate. For such research, the authors have used a Fe-C alloy intended for obtaining dual-phase stees with lowmanganese (less than 1% Mn). The dilatometric analysis were performed with a dilatometer DIL Expedis-402 SUPREME on cylindrical specimens (5 x 25 mm), heated in a 30 ÷ 980°C, with heating rates of 1, 3, 5, 10 and 30°C/min, while the coefficient of linear thermal expansion was determined for temperatures between 30 and 700°C. [ABSTRACT FROM AUTHOR]

Continuous research in the field of metal additive manufacturing has led to the need for constant improvement of manufacturing parameters especially in the case of FDM (Fused Deposition Modeling) manufacturing. In recent years, the main directions outlined for productivity and quality improvement were related to higher printing speed and the use of ironing-type processes. This article aims to study the manufacturing parameters of the dimensional accuracy and surface quality of FDM-manufactured 316L stainless steel. The degree of novelty is given by the application of the ironing process for the green part. A full factorial 33 experimental design was designed for this study, in which the factors studied were ironing angle, ironing speed, and layer spacing during ironing. The dimensional accuracy and surface roughness were analyzed by means of deviation measurement from CAD to the green part and final part after the sintering process. Using the design of experiments offers the possibility of applying the analysis of variance (ANOVA) which provides information about the degree of influence of each of the studied factors. The results obtained for the dimensional accuracy showed that the ironing direction had the biggest influence on the Z-axis shrinkage. Overall, approximately 6% shrinkage in the Z and Y directions was obtained while in the X directions, the shrinkage percentage was around 20%. Surface roughness showed an improvement with higher ironing speeds for the green part while for the sintered part the most significant factor was ironing spacing. [ABSTRACT FROM AUTHOR]

The scientific literature regarding additive manufacturing, mainly the material extrusion method, suggests that the mechanical characteristics of the parts obtained by this technology depend on a number of the input factors specific to the printing process, such as printing temperature, printing trajectory, layer height, etc., and also on the post-process operations for parts, which, unfortunately, requires supplementary setups, equipment, and multiple steps that raise the overall costs. Therefore, this paper aims to investigate the influence of the printing direction, the thickness of the deposited material layer, and the temperature of the previously deposited material layer on the part tensile strength, hardness by means of Shore D and Martens hardness, and surface finish by using an in-process annealing method. A Taguchi L9 DOE plan was developed for this purpose, where the test specimens, with dimensions according to ISO 527-2 type B, were analysed. The results showed that the presented in-process treatment method is possible and could lead to sustainable and cost-effective manufacturing processes. The varied input factors influenced all the studied parameters. Tensile strength tended to increase, up to 12.5%, when the in-process heat treatment was applied, showed a positive linear variation with nozzle diameter, and presented considerable variations with the printing direction. Shore D and Martens hardness had similar variations, and it could be observed that by applying the mentioned in-process heat treatment, the overall values tended to decrease. Printing direction had a negligible impact on the additively manufactured parts' hardness. At the same time, the nozzle diameter presented considerable variations, up to 36% for Martens hardness and 4% for Shore D, when higher diameter nozzles were used. The ANOVA analysis highlighted that the statistically significant factors were the nozzle diameter for the part's hardness and the printing direction for the tensile strength. [ABSTRACT FROM AUTHOR]

The present paper aims to contribute to the methodology of 3D printing in-process colouring and study its implications and impact on the tensile strength and surface quality of the obtained parts. The proposed study was based on a Taguchi L27 DOE plan using standardised EN ISO 527-2 type 1B-shaped specimens, in which four factors on three levels were considered. The obtained results highlight the possibility of using the presented in-process colouring method. Different materials (PLA, PLA+, and PETG) with varying infill densities (15%, 30%, and 50%), colour distribution (33%, 66%, and 99%), and colour pigments (blue, green, and red) were studied and the results highlighted that the most influential parameter on the tensile strength of the parts was infill density, followed by the tested material, colour pigment, and colouring percentage; regarding surface roughness, the most influential parameter was infill density, followed by colouring percentage, colour pigment, and material. Moreover, the values resulting from the Taguchi DOE were compared to uncoloured parts, from which it could be concluded that the colouring of the parts had direct implications (negative for tensile strength and positive for surface roughness). [ABSTRACT FROM AUTHOR]

One of the main research areas in additive manufacturing (AM) no matter of the technology involved (MEX - Material Extrusion, VPP - Vat Photopolymerization, BJT - Binder Jetting etc.) are the mechanical proprieties of the machined parts, especially the tensile strength. The aim of this paper is to highlight the most frequent problems that may appear during the tensile strength testing of MEX 3D printed parts and also to purpose a new sample clamping device - grip able to overcome some of the possible testing errors. Samples of three different materials (PLA - Polylactic acid, PLA+ - Enhanced Polylactic acid and PETG - Polyethylene terephthalate glycol) dog bone shaped type 1B according to ISO 527 were printed on a Creality CR 6-Se 3D printer. The results highlighted the importance of proper clamping during tensile strength testing of 3D printed parts. [ABSTRACT FROM AUTHOR]

Continuous research in the field of 3D printing, and the study of the resulted parts from the FFF (Fused Filament Deposition) manufacture, demonstrated the possibility and usefulness of applying post-processing by heat treatment on parts from different materials. In most cases, it has been shown that both parts with semi-crystalline structure (PLA) and those with amorphous structure (ABS, ASA) can be subjected to heat treatment, ensuring enhanced mechanical properties. This article presents the influence of the heat treatment applied to ASA (acrylonitrile styrene acrylate) parts, especially in the layer change zone. The parts were in the form of standardized specimens (ISO 527-2 type 1B), which were subjected to tensile tests. The results showed that, under the right annealing temperature for minimum dimensional changes, the tensile strength of the parts was increased, even in the layer change zone. [ABSTRACT FROM AUTHOR]

This paper is focused on bolts failure analysis of a compression press. 8 bolts were used to attach the high speed cylinder cap to the upper ram cylinder of a hydraulic press used to produce forging parts. The bolts had been in service less than one year. Six (6) broken bolts out of eight (8) were submitted for failure analysis. One of the most common failure mechanism for bolts is fatigue. Fatigue cracks initiate and propagate in regions where the strain is most severe. Most fatigue cracks initiate and grow from structural defects. The manner through which the crack propagates through the material gives great insight into the mode of fracture. Incorrect placement of a component or incorrect assembly order can cause high residual stresses or failure to occur. Improper specifications or torque requirements can also cause premature bolts failure. [ABSTRACT FROM AUTHOR]