• DOMINANT TECHNOLOGIES IN “INDUSTRY 4.0”

    Tensile strength and dimensional variances in parts manufactured by sla 3D printing

    Industry 4.0, Vol. 6 (2021), Issue 4, pg(s) 143-149

    With the rise of additive manufacturing (AM) technologies, a numerous limitations in conventional manufacturing have been circumvented. Additive manufacturing uses layer-by-layer fabrication of three-dimensional physical models directly from a computeraided design (CAD) model. The CAD design is transformed into horizontal cross-section layers that are stacked together in physical space until the physical model is completed. This process can be used to directly manufacture tools for injection molding or for an y other technology that requires a specific cavity shape to produce a part. This is referred to as Rapid Tooling (RT) and one of the up and coming
    AM technologies is the resin based stereolithography (SLA).
    An increasing number of companies are starting to develop desktop machines that utilize this technology and their low cost an d high speed changes the design workflow. As a printing technology, SLA creates parts with a smooth surface finish which is ideal for applications such as investment casting for developing jewelry or rapid tooling for injection molding.
    The development of rapid tools using SLA usually requires more rigid materials which can withstand higher temperatures and stresses and part models that need to have more accurate dimensions in order for a precise part to be produced from that specific tool. Even though models created by SLA have more isotropic characteristics compared to other 3D printing technologies, there are still some variations linked to the process parameters. This paper covers how orientation of the model on the build plate impacts the pa rt accuracy and the tensile strength of the models. The effects of different post-processing procedures after SLA printing are also taken into consideration, since most resins need to be UV cured after 3D printing in order to achieve maximum mechanical strength.
    This paper gives designers and engineers better understanding on the final properties of the models and the tolerances that have to be taken into consideration when designing parts intended to be manufactured via SLA 3D printing.

  • MATERIALS

    Influence of the pressing force on the strength properties of sintered materials based on water-dispersed iron powders alloyed with copper

    Machines. Technologies. Materials., Vol. 15 (2021), Issue 1, pg(s) 34-37

    In this publication we study the influence of the pressing force on the strength characteristics of sintered materials based on water – dispersed iron powders alloyed with copper. Three brands of iron powders were studied – AHC 100.29, ASC 100.29 and ABC 100.30, to which 2 and 4% electrolytic copper were added. After pressing with a force of 300 ÷ 800 MPa, they were sintered at a temperature of 1150 ° C for 1 h. Experiments were performed to determine three strength characteristics – tensile strength, yield strength, elongation. In determining the mechanical characteristics in order to prevent the influence of porosity, five measurements were made for each type of samples, and in the graphical interpretation of the results the arithmetic mean values were used.

  • The mode of hardening heat treatment for deformable piston hypereutectic silumins

    Materials Science. Non-Equilibrium Phase Transformations., Vol. 5 (2019), Issue 3, pg(s) 74-77

    A series of piston hypereutectic silumin based on Al – (15÷20) % Si, alloyed with copper, magnesium, nickel, chromium is investigated. The mechanical characteristics of ingots from experimental alloys were determined: temporary tensile strength, hardness, relative elongation depending on the composition of the alloys, and temperature coefficient of linear expansion (TCLE). It is shown that the tensile strength of forged blanks is 1.5-2.4 times higher than ingots of hypereutectic silumins. The resulting structure of forgings ensures their high plasticity (relative elongation δ = 5.7÷7.5%; relative narrowing Ψ = 10.3÷14.2%). The optimal mode of heat treatment of deformed silumin is determined: quenching from step heating and aging, which allows increasing the strength of forgings up to 370-470 MPa. Moreover, the plasticity indicators remain at a high level, and the average thermal expansion coefficient of the alloys is (18.0 ÷ 19.2) · 10-6 K-1 in the range of 50 ÷ 200 ° C.

  • INFLUENCE OF THE TYPE OF IRON POWDER ON THE TENSILE STRENGTH OF Fe – C POWDER MATERIALS ALLOYED WITH COOPER

    Materials Science. Non-Equilibrium Phase Transformations., Vol. 3 (2017), Issue 1, pg(s) 18-21

    In the present study the influence of the monitored type iron powder, and the process of sintering in the presence of a liquid phase on the tensile strength of the powder metallurgical samples of the system Fe-C-Cu . Research samples are subjected made of three types of iron powders – ASC 100.29, SC 100.26 and NC 100.24. Thereto is added of 0,2 to 0,8% carbon and 2,5% copper. After sintering the measured density of the samples in the range of 6,20÷7,00g/cm3. Are presented graphics, amending the tensile strength of the samples depending on their density and the concentration of copper and carbon in the iron matrix.

  • MECHANICAL PROPERTIES OF DENTAL Co-Cr ALLOYS FABRICATED VIA CASTING AND SELECTIVE LASER MELTING

    Materials Science. Non-Equilibrium Phase Transformations., Vol. 2 (2016), Issue 3, pg(s) 3-7

    The aim of the present paper is to investigate the mechanical properties (hardness and tensile strength) of dental Co-Cr alloys fabricated via casting and selective laser melting (SLM). Two groups of metallic specimens (four-part dental bridges and standard tensile test specimens) made of Co–Cr dental alloys were produced by lost-wax casting and SLM processes. Vickers hardness distribution along the depth of the dental bridges as well as the Rockwell hardness and tensile strength of the samples were studied out. The hardness of Co–Cr dental alloys are dependent on the manufacturing technique employed. It was established that the average Vickers hardness of the samples, produced by SLM, was higher than that of the cast samples 382 HV and 335 HV respectively. The nearly even hardness distribution in the bridges, produced by SLM, and fluctuations of the hardness values along the depth of the cast bridges were observed. The Rockwell measurements confirmed the higher hardness of the SLM samples – 39 HRC in comparison with that of the cast ones – 33 HRC. The tensile strength is in good agreement with the hardness values. Due to the unique microstructure, the yield strength and tensile strength for the SLM samples were higher than those of the as-cast alloy.