Erstes Design und Einsatz 3D‐gedruckter Strukturen in Blasensäulenreaktoren

A new method is described, in which 3D‐printed structures are implemented in bubble column reactors to dissolve the macroscopic and the microscopic influences. The effect of these structuring method on the fluid dynamic behavior, the gas distribution, mass transfer, and fluid velocity inside bubble columns is shown in this contribution.     

Processing of AlSi9Cu3 alloy by selective laser melting

ABSTRACT

Additive manufacturing of Al-alloys allows the production of components with a complicated structured shape, geometry composed by lattice structures, internal cooling, etc. The portfolio of Al-alloys for metal additive manufacturing is still under development and is strongly limited, compared to the conventional technology. The alloy AlSi9Cu3 is used in many applications, but its processing details are still missing. The main aim of this paper is to describe the laser process parameters for AlSi9Cu3, processed by SLM technology and manufactured from two powders of different shapes and particle sizes. The tested process parameters were laser power, laser speed, and hatch distance in the range of 100–400?W, 200–1500?mm?·?s^?1 and 90–150?µm. These were tested using a single-track and cube test. Microstructure, mechanical properties and the fatigue of SLM samples were analysed and compared with as-casted material.     

Optimal cost design of flow lines with reconfigurable machines for batch production

Modular reconfigurable machines offer the possibility to efficiently produce a family of different parts. This paper formalises a cost optimisation problem for flow lines equipped with reconfigurable machines which carry turrets, machining modules and single spindles. The proposed models take into account constraints related to: (i) design of machining modules, turrets, and machines, (ii) part locations, and (iii) precedence relations among operations. The goal is to minimise equipment cost while reaching a given output and satisfying all the constraints. A mixed integer programming model is developed for the considered optimisation problem. The approach is validated through an industrial case study and extensive numerical experiments.     

3D打印连续纤维复合材料丝材的成形规律

针对3D打印连续纤维增强热塑性树脂复合材料,研究了热塑性树脂在螺杆挤出过程中的流动机理和在纤维界面的浸渍行为,揭示了螺杆转速和牵引速度对复合丝材成形直径和纤维含量的影响规律。提出使用实际浸渍时间和理论完全浸渍时间来共同表征树脂对纤维的浸渍程度,观察复合丝材断面的形貌可知,高浸渍程度的丝材内部空隙较少,树脂和纤维结合更紧密。进行3D打印成形测试,当丝材的浸渍程度从17.25%提高到40.02%,样件的拉伸强度可从132 MPa提高到160 MPa,提高约21%。对样件进行动态力学性能分析(DMA)测试,试验结果表明浸渍程度高的复合材料成形件具有高的存储模量和损耗模量,表明其纤维和基体间的界面结合程度得到了提高和改善。     

Comparative investigations into microstructural and mechanical properties of as-cast and laser powder bed fusion (LPBF) fabricated duplex steel (1.4517)

A methodology is presented that compares the microstructural and mechanical properties of as-cast and additive-made ferritic-austenitic duplex steel 1.4517. Microstructure of approximately equal amounts of ferrite and austenite measured in as-cast material could not be replicated in post heat-treated laser powder bed fusion samples after 30 min and 60 min of post heat treatment. This is attributed to nitrogen loss during powder atomization which left fewer austenite formers. Post-heat treated laser powder bed fusion samples of duplex structure had its austenite content repeatedly adjusted between 38 % and 40 %. As-built laser powder bed fusion tensile specimens which had a ferritic microstructure recorded high tensile and yield strength but had very poor elongation. Post heat-treated duplex laser powder bed fusion tensile specimen built in both horizontal and vertical orientations had good tensile and yield strength comparable to conventional casting processes; Tensile strength – 739 MPa (horizontal), 759 MPa (vertical); Yield strength (R_p0.2) – 489 MPa (horizontal), 525 MPa (vertical). The horizontally built duplex specimen had a very high elongation of 32 % than the vertical (11 %) or conventionally reported (22 %). This work establishes the 1.4517 duplex steel as a good candidate with good mechanical properties when processed by additive manufacturing.     

Novel Flexible Electrochemical Microreactor and its Validation by Three Model Electrosyntheses

A novel flexible electrochemical microreactor has been developed. Flexibility is reached by a modular design, suitability for a broad process parameter range including high pressure operation, and accessibility of production scale. Selected reactor aspects have been validated by applying the reactor to three different electrosyntheses: synthesis of tailor-made mixtures of paraffins by Kolbe electrolysis, cation flow method, and synthesis of peroxodicarbonate. High conversion rates, yields, selectivities, and Faraday efficiency levels have been observed, showing precise process control.     

间隙填充电弧增材制造对表面质量的影响

针对单层多道增材制造,提出一种新的搭接模型——间隙填充模型。研究间隙填充模型对多道焊缝表面质量的影响,发现基体中心间距和接触角对成形件表面质量有重大影响。通过计算平均高度、总熔宽、方差和极差定量比较间隙填充模型和传统搭接模型的表面质量。结果表明:间隙填充模型沉积的多道焊缝表面质量明显优于传统搭接模型,提升了表面质量,节约了材料和时间成本。     

Drivers and enablers of supplier sustainability practices: a survey-based analysis

A rich research stream investigates the drivers and enablers of supplier sustainability practices, usually classified into suppliers’ monitoring and collaboration with suppliers. Differently from previous works analysing relationships between supplier sustainability practices and drivers or enablers, this research investigates how well-defined configurations of monitoring and collaboration can be characterised in terms of drivers and enablers. In this way, it intends to advance knowledge by identifying what drivers and enablers are important and distinctive for the different configurations of supplier sustainability practices. A first result is that moving from configurations of plants which less adopt supplier sustainability practices (i.e. non-adopters) to those which invest on monitoring and/or collaboration to a limited extent (i.e. partial adopters) up to the most advanced ones (i.e. full-adopters), the pressure due to cost reduction lessens its relative importance as a driver, while the pressure due to regulations remains essential. Other relevant results are that plant size acts as a barrier for non-adopters, and the alignment between the sustainability project and plant goals results determinant especially for full-adopters. This research also enriches the debate on the opportunity of differentiating between supplier monitoring and collaboration when investigating drivers/enablers, providing evidence of the risk of oversimplifications for some enablers/drivers.     

Additive manufacturing of Sm-Fe-N magnets

Isotropic Sm-Fe-N bonded magnets were obtained by additive manufacturing(AM). The technique used was the so-called powder bed fusion(PBF) and the feedstock was composed of a polymeric binder(PA-12) and Sm-Fe-N flake particles(Nitroquench-P). The AM set-up equipment uses a computer-controlled CO_2 laser beam to melt the binder and constructs magnets layer-by-layer. In order to develop this study, a cylinder with 10 mm of both height and diameter was selected as the shape of samples. Specimens were analyzed by scanning electron microscopy(SEM) and X-ray diffraction(XRD). Magnetic properties were measured in a hysteresis graph. XRD results indicate that there is no degradation of the main magnetic phase(SmFe_7 N_x). In the AM component, porous regions were identified on SEM micrographs, as well as magnetic particles and polymeric binder. Remanence values(B_r) as great as 0.3 T are achieved, while intrinsic coercivities remain in the range from 616 up to 642 kA/m. An additional isostatic compression of the parts results in greater remanence, which is directly proportional to the density increase. Coercivity is also sensitive to the porosity decrease, probably due to a better interlocking of particles. Current results indicate AM as a promising route for near net-shape manufacturing of Sm-Fe-N permanent magnets, a market niche yet to be widely explored.