3D printed laboratory equipment to measure bulk materials in extreme conditions

1 Vol.:(0123456789) Scientific Reports | (2022) 12:17331 | https://doi.org/10.1038/s41598-022-22114-2 www.nature.com/scientificreports 3D printed laboratory equipment to measure bulk materials in extreme conditions Jan Divis 1,2*, Jakub Hlosta1,2, David Zurovec2, Jiri Rozbroj2, Weronika Kruszelnicka3, Jan Necas1,2 & Jiri Zegzulka1,2 Due to relatively new solutions in the field of 3D printing, there are few studies on the possibility of using printed elements in measuring devices. The aim of this study was to investigate the possibility of using instruments made by material extrusion 3D printing method for measurement of selected mechanical-physical properties of bulk materials. Study explores the feasibility of measuring bulk material mechanical-physical properties when there are obstacles for printing original or modified measuring instruments in common practice. To achieve the goals a series of experiments such as Schulze’s ring shear tests, Freeman’s FT4 shear tests, compressibility tests, and Flow Rate and Stability tests were performed with use of original aluminium or steel made instruments and 3D printed instruments from polylactic acid and acrylic styrene acrylonitrile materials, using lunar regolith simulants LHS-1 and LMS-1 produced by CLASS Exolith Lab as a sample material. The results obtained from tests with original and printed instruments were then compared. The compared values of tests showed applicability of the 3D printed measuring instruments in a 5% range of measurement deviation. The biggest advantages of the 3D printed measuring instruments were the lower weight, the ability to print on the spot, to replace a damaged part with a new 3D printed part on-demand if extremely fast results are needed or due to the logistical unavailability, customization of the standardized tests for better understanding the behaviour of the particulate materials, and cheaper manufacturing costs. Scientists and engineers made significant development in the exploration missions of planets and celestial bodies in last few decades and gained knowledge about their resources and their properties. However, besides reaching the planets, to land safely in the universe still proves to be a difficult task. To change this, geology resources, atmosphere and radiation data are gathered by landers and rovers, which are required to verify measurements by probes from orbit. Landers and rovers provided with excavator booms extract rocks and dust for material properties analysis1. The aim is to gather data and prepare strategies to build landing sites and radiation shielding habitats, and to develop suitable constructions, such as infrastructure, factories, and laboratories, prior to the arrival of astronauts. To extend and facilitate such exploration missions, two insitu concepts are needed2,3. Firstly, it is insitu fabrication and repair (ISFR) equipment and infrastructures. Secondly, it is insitu resource utilization (ISRU). As a result, resources for insitu lunar fabrication have been studied intensely in the last decade and several technologies have been proposed4–7. To simulate materials on other planets, ceramic-based products are used, such as lunar regolith1, which is very fine sand8. In terrestrial environment lunar regolith simulants with similar mechanical-physical properties9 were developed, such as LHT-1 M3, NU-LHT7 or JSC-1A10. However, due to different physical environment, material properties and behaviour on other celestial bodies differ from Earth. Behaviour of real regoliths differs based on the linearized angle of internal friction (LAIF, ϕ), effective angle of internal friction (EAIF, δ), flow function (ffc), cohesion c, and compressibility, depending on environment which regoliths are measured in, place of regolith excavation, environment of regolith origin and environment of regolith transformation. Thecomposition of regoliths varies from place to place because of the variability in asteroid OPEN 1ENET Centre, Bulk Solids Centre, VSB-TU Ostrava, 17. listopadu 15/2172, 708 33 Ostrava-Poruba, Czech Republic. 2Department of Mining Engineering and Safety, Faculty of Mining and Geology, VSB-TU Ostrava, 17. listopadu 15/2172, 708 33 Ostrava-Poruba, Czech Republic. 3Department of Machines and Technical Systems, Faculty of Mechanical Engineering, Bydgoszcz University of Science and Technology, Al. Prof. S. Kaliskiego 7, 85-796 Bydgoszcz, Poland. *email: [email protected] 2 Vol:.(1234567890) Scientific Reports | (2022) 12:17331 | https://doi.org/10.1038/s41598-022-22114-2 www.nature.com/scientificreports/ collisions and the weathering by wind or water. Therefore, there will be a crucial need to be able to measure mechanical-physical properties of insitu regoliths and bulk material resources during the exploration missions11. Due to the fact that transportation of any equipment from Earth is very costly, currently it may take years to get spare parts to orbit. This problem has been partially overcome by fused deposit modelling (FDM, registered trademark by Stratatys) technology modified for microgravity12. FDM is a type of additive manufacturing (AM), where a3Dgeometry is built by superimposed layers of extruded thermoplastic filament13. FDM technology modified by Made in Space projects14,15 explore the possibility to create tools16 that astronauts currently need for repairs or work. FDM allows for the use of a broad range of thermoplastics13 which are light but durable and can withstand a certain extent of mechanical load when designed properly. FDM printing is also highly precise and most of its advantages are due to the enclosed printing chamber which allows the internal temperature to be maintained (nozzle-air-heated bed). It leads to better mechanical properties, where the adhesion between layers is strengthened and warping and curling of the printed parts are prevented16. However, the technology is very costly and is not widely available for research. Extending theability and options to print parts on demand in orbit or during exploration missions will reduce the time it takes to get parts to orbit, reduce the mission costs, reduce the need of having every tool and part on board, while increasing the reliability and safety of space missions. Despite the developments in the field of 3D printing, there is a lack in studies on the use of printed elements in measuring devices and/or devices intended to measure bulk materials. Traciak etal.17 developed a3D printed device to measure the surface tension of nanofluids and showed that the result of measurement is comparable with commercial devices. Bernard and Mendez18 presented a low-cost Polarimeter to be used by students during classes. The study19 described the dynamic behaviour of 3D-printed strain sensors embedded in structures and supported the statement that 3D printed sensors could be used for dynamic measurement. The study20 reported the design of a 3D printed compact interferometric system for cell phones to measure small angles. All these studies show a high potential of 3D printing devices and the lack of specific guidance for the manufacturing of measuring equipment. In order to fill the gap in this area, the aim of this study was to investigate the possibility of using measuring instruments made by material extrusion 3Dprinting method for the measurement of selected mechanicalphysical properties of bulk materials. Due to the unaffordability of FDM 3D printing technology and related problems such as testing the effects of high radiation environments on printed measurement tools, fused filament fabrication (FFF) 3D printing technology was used in this study. This article thus presents a feasibility study of measuring mechanical-physical properties of bulk materials using 3D printed instruments, should the reasons for doing so arise. Lu etal.21, Li etal.22, and Pelech etal.23 showed why is to measure important mechanicalphysical properties of lunar regolith simulants. Further, the use of 3D printed instruments to measure standardized mechanical-physical properties of particulate materials is not researched. These reasons for printing original or modified measuring instruments are also encountered on Earth, such as the need for a lower weight of the measuring instruments, the ability to pre-print a set of laboratory measuring instruments or to print the set on the spot, to replace a damaged part with a new 3D printed part on-demand, the logistical unavailability, customization of the standardized tests for better understanding of the behaviour of the particulate materials, and cheaper manufacturing cost. The 3D printed instruments are preferred when versatility of the instruments, light weight, and/or quick result in the extreme locations are needed. If the conditions are laboratory and the measured particulate material is without unusual properties which requires customized measuring tools, standardized tests should be made. Supposing the measuring instruments will be used for exploration mission, regolith simulant samples were also tested. The measurements of the mechanical-physical properties such as EAIF (δ), LAIF (ϕ), ffc, cohesion c, compressibility, basic flowability energy BFE, stability index SI, and flow rate index FRI for lunar regolith simulants: lunar mare simulant (LMS-1) and lunar highlands simulant (LHS-1) from the CLASS Exolith Lab in Orlando, USA, are presented. EAIF(δ), LAIF (ϕ), ffc, c, and compressibility are fundamental characteristics of bulk material flow, which is used to design storage, handling, and process equipment. Firstly, two lunar regolith powders were characterized by particle size distributions and their morphology. Secondly, comparison of results was carried out between standard measuring instruments and 3D printed instruments from polylactic acid and acrylic styrene acrylonitrile materials. Values of EAIF(δ), LAIF (ϕ), ffc, c, compressibility, SI, FRI, and BFE were compared. Results presented in this article showed repeatability and similar precision for the test methods of Schulze’s ring shear test, Freeman’s FT4 shear test, Freeman’s FT4 compressibility standard test, and Freeman’s FT4 flow rate and stability standard test. This showed applicability of 3D printed instruments for the test methods in hardly reachable, or extra-terrestrial environment. Materials and methods The materials and methods concern two areas. The first area is the materials and methods related to the printed measuring instruments made via Fused Filament Fabrication. The second area of interest is the bulk material (regolith) used to test the produced measuring instruments. The subsection of Bulk Material Tests describes all the tests related to examining theperformance of the 3D printed measuring instruments, of the 3D printed measuring instruments in combination with original stainless steel components, and of original stainless steel instruments. Fused filament fabrication printed equipment. The measuring instruments were printed by fused filament fabrication (FFF) 3D printing technology on a Prusa i3 MKS3 printer (Praha, Czech Republic), which is shown in Figure1a. PLA and ASA filaments manufactured by Prusament were used. ASA filament is the successor of ABS filament with superior properties, such as UV stability, high impact resistance, wear resistance, and easier printability for FFF printing method24. 3 Vol.:(0123456789) Scientific Reports | (2022) 12:17331 | https://doi.org/10.1038/s41598-022-22114-2 www.nature.com/scientificreports/ The Prusa i3 MKS3 printer uses G-code numerically controlled machines, which allows users to provide instructions telling the motors where to move, how fast to move, what path to follow and how fast to feed the filament. Before creating the G-code, a 3D CAD model of the original is created that could be 3D printed as shown in Figure1b. The G-codes for the prints were sliced in PrusaSlicer version 2.3.0 with the layer height of0.20mm as shown on Figure1c. The infill for all the parts had different infills that are shown in this section. The infill pattern was chosen as gyroid except for 100% infill, which is forced to be rectilinear. The PLA instruments were printed at an extrusion temperature of 210°C and bed temperature of 60°C. The ASA instruments were printed at an extrusion temperature of 260°C bed temperature of and 110°C. For the Schulze’s RST-01.pc (RST) tests, we used a set of shear cell and lid from different materials (original aluminium, PLA printed, ASA printed). RST tests are described in the following subsection Bulk Material Tests. For the Freeman’s Flow Tester 4 (FT4) tests, we used a 85ml measuringsample vessel as an assembly of parts that will contain the sample powder during measurements. The 3D printed sample vessels and instruments were printed from PLA and ASA filaments. These printed instruments required design modifications to withstand mechanical loads. The printed vessels were either all printed or were partly 3D printed and also comprised of original components, such as compression piston and blade manufactured from stainless steel. Overall, we used a set of specimens (original stainless steel, PLA printed, ASA printed) and their combinations (original vessel with a PLA blade, original vessel with an ASA blade, PLA vessel with an original blade, and ASA vessel with an original blade). FT4 tests are described in the following subsection Bulk Material Tests. Fused filament fabrication (FFF) 3D printing technology creates parts layer by layer. A consequence of layering is the presence of pores and heterogeneities that cause anisotropic behaviour and preferential crack orientation25. The resistance of parts to mechanical damage is dependent on the orientation of the deposited layers26–28. Thus, the orientation of the parts on the 3D printer bed is an important consideration when manufacturing components29–31. The orientation of the measuring instruments was chosen accordingly as shown on Figure2., and the design modifications have been made to the measuring instruments to prevent damage due to mechanical loading. The Figure2 is illustrative to show layering of the parts from the bottom up and the picture does not show support material, support material interface, skirt, bridge infill, and overhang perimeter. The layers are stacked from the bottom up. The Figure2a shows Schulze’s small ring cell, lid, and driving pins. The Figure2b shows layering of the FT4’s bottom part, upper part, and funnel. The Figure2c shows layering of the FT4’s shaft with the nut, shear head, blade, and vented piston. The Schulze’s small ring cell (S size)32 was printed with bottom plate as one piece. Three pins with interference fit were printed separately to rotate the cell by driving axle. The Schulze’s lid matching small ring cell was printed as a single piece. The shear bars32 were thickened from 1 to 2 mm and no screws were used. The design of the original, the 3D modelled, and the PLA fabricated shearing cell with lid are shown in Fig.1b. The weighed parts, the weighed printed parts with supports and their infill percentage used in printing are shown in Table1. The original aluminium shear cell weighed 728.4 g and the original aluminium lid with stainless steel shearing bars weighed 235.4 g. The PLA printed parts weighed 2.6times less, and the ASA printed cell weighed almost 3 times less than the original parts. Infill used for all Schulze’s printed parts was 100%. The differences in weight are due to different material densities. Aluminium has a density of 2.7 g.cm−3, PLA filament has a density of 1.24 g.cm-3, and ASA filament has a density of 1.07 g.cm−3. Figure1. (a) Prusa i3 MKS3 printer with FT4’s 3D printed blade and vessel; (b) Schulze’s S size shear cell with lid (from top to bottom–aluminium, 3D CAD by Autodesk Inventor 2021, 3D printed); (c) Schulze’s shear cell sliced in PrusaSlicer version 2.3.0. This figure was created in Gimp 2.10.32. 4 Vol:.(1234567890) Scientific Reports | (2022) 12:17331 | https://doi.org/10.1038/s41598-022-22114-2 www.nature.com/scientificreports/ The 3D printed FT4 measuring set and the original measuring set are shown in Figure3b and c. FT4’s sample vessel is originally made from five pieces, which were reduced to two parts. The3Dprinted bottom part has replaced 85 ml vessel with an inner diameter of 48 mm, its removable bottom, the holder that keeps it in place during measurement, and rotational holder for top part. The3D printed upper part replaced for the upper 85 ml vessel with an inner diameter of 48 mm and it is pivotally seated on the bottom part. The original vessel assembly of two 85ml vessels with a removable bottom, a holder that keeps the whole vessel in place during measurement, and rotational holder for the upper part weighed 291.8 g. The original vessel assembly for angle of internal friction measurement differed by having a removable bottom for internal friction and weighed 289.9 g. Vessel assemblies printed from PLA for compressibility and internal friction measurements weighed approximately 3times less than the original assemblies. The ASA printed vessel assemblies weighed more than 3.3 times less than original assemblies. The 3D printed funnel had a reduced height, which does not affect the measurement. The original funnel is made of plastic and weighed 30.7 g. The PLA printed funnel weighed 25.8 g, and theASA printed funnel weighed 22.2 g. The FT4 measuring instruments such as the shear head, blade, and vented piston, were 3D printed in two parts. The first part was the shaft with the nut, which was the same for all three measuring instruments. The shaft was connected to the second part by end of a square cross-section shaft (Figure3a). This shaped connection transmits torque without the two parts of the measuring tool rotating against each other. Themanufacturing precision of the FFF printing method created aslight overlap that allowed the two parts to be joined by hand but did not require protection against ejection. The shaft infill was chosen as 7% to overcome the warping during printing with ASA filament. The infill setup improves geometric dimensions and tolerances, such as radial runout and total run out of the shaft. The second parts of the blade, the vented piston, and the shear head were printed with 15% infill setup. Design modifications to the instruments were made to prevent damage due to mechanical loading, the shearing bars of the shear head were thickened from 0.1 to 0.8 mm, and the blade was thickened from 0.7 to 1.8 mm. The 3D printed shear head was printed as one piece, so the screws were not used Figure2. (a) The layering of the Schulze’s small ring cell (S size), lid, and driving pins; (b) the layering of the FT4’s bottom part, upper part, and funnel; (c) the layering of the FT4’s shaft with the nut, shear head, blade, and vented piston. Layering was generated by PrusaSlicer version 2.3.0. This figure was created in Gimp 2.10.32. Table 1. Original and 3D printed measuring instruments weight, 3D printed parts with supports weight and printed parts infill in percentage as used in PrusaSlicer. Measuring tool Original (g) PLA printed (g) PLA filament used (g) ASA printed (g) ASA filament used (g) Printed part infill (%) Schulze’s shear cell 728.4 283.1 347.8 244.4 300.1 100 Schulze’s lid 235.4 89.5 107.7 77.5 92.9 100 FT4’s compressibility vessel (two 85ml vessels, removable bottom, holder of the vessel, rotational holder for upper part) 291.8 92.8 134.9 80.2 123.3 10 FT4’s internal friction vessel (two 85ml vessels, removable bottom for internal friction, holder of the vessel, rotational holder for upper part) 289.9 109.8 159.0 94.9 137.2 10 FT4’s flow stability vessel (one 85ml vessel, one 165ml vessel, removable bottom, holder of the vessel, rotational holder for upper part) 345.7 110.2 190.8 95.0 164.7 10 FT4’s funnel 30.7 25.8 31.6 22.2 27.3 10 FT4’s blade 111.8 13.6 17.9 10.9 15.5 7 (shaft)/15 (head) FT4’s vented piston 184.0 30.6 36.5 26.3 31.5 7 (shaft)/15 (head) FT4’s shear head 240.9 25.7 35.0 21.5 30.2 7 (shaft)/15 (head) 5 Vol.:(0123456789) Scientific Reports | (2022) 12:17331 | https://doi.org/10.1038/s41598-022-22114-2 www.nature.com/scientificreports/ in the design. The blade was further modified to ensure similar forces and torques during conditioning of the measured samples. The curvature of the blade had less bending, resulting in a smaller angle at each end of the blade (Figure3a). The original blade had the end of the blade curved at an angle of 70 degrees, while the end of the 3D printed blade is only curved at anangle of 40 degrees. The price of 3D printing has its benefits. The material for 3D printing (PLA and ASA) is approximately 3 times more expensive compared to aluminium or stainless steel per kilogram. However, 3D printed instruments are 2.5 to 10 times lighter than the originals. After accounting for productional waste, the difference in material weight is even greater. The costs diversify depending on the cost of machining, complexity of machining, need to change machining tools. In contrast, 3D printing is more versatile, simpler, and with lower weight of the final product. The productional costs of the original instruments are at least 30 times higher than for 3D printed instruments. Bulk material. Regolith is a terrestrial term which is also used to refer to materials on other celestial bodies. Nowadays, it is used as a common expression for a layer of fragmental rock material. The formation and evolution of regolith is a complex process. In the formation of lunar regolith, two basic mechanisms have been determined. Firstly, destructive, which is the excavation of existing regolith by impact crater, and secondly, constructive, which is the addition of new layers. These processes cause very wide structural and stratigraphical differences in regolith, even between locations only few meters apart11. Lunar regolith simulant powders are terrestrial based on samples analysed by experiments carried out directly on the Moon, or remotely monitored from Earth11. As mentioned above, materials used in this study are two lunar regolith simulants. These two powders were made by the CLASS Exolith Lab. The simulants, shown on Fig.4a, are made from natural terrestrial materials in a terrestrial environment, and thus not all properties of lunar mare simulant (LMS-1) and lunar highlands simulant (LHS-1) may be copied. The producer guarantees properties such as mineralogy, bulk chemistry, and particle size distribution. However, particle shape, reactivity, oxidation, andweathering are poorly simulated properties in the simulants. Although the particle size is guaranteed by the manufacturer to be between 0 and 1mm, agranulometric analysis was carried out. Cilas 1190 laser analyzer (Cilas, Orleans, France) was used to measure the particle size distribution by the Fraunhofer diffraction method31. Water was used as the measurement medium because neither LHS-1 nor LMS-1 dissolved in water. Sonication was used during the measurements to ensure complete dispersion of the sample. The sample dispersed in medium was measured using a coherent light with a wavelength of 830nm from a low-power laser diode. The resulting values were evaluated directly in the Cilas device33,34. The interpretation was based on Fraunhofer’s theory35. Each sample was measured three times, so the resulting parameters are the average values of dmean, d10, d50 and d90. Particle shape is a property of a bulk material that affects its behaviour during extraction, processing, and storage. As mentioned above, lunar regolith simulant manufacturer does not attempt to simulate exact particle shapes. The lunar regolith is formed by various processes that are the constant impacts of small and large asteroids and that are unique to the airless conditions of the Moon11. Therefore, the assessment of particle shapes presented in this paper is only illustrative based on scanning electron microscope (SEM) photographs. Figure3. Design of FT4 instruments (a) FT4’s printed shaft, blade, vented piston, and shear head; (b) PLA printed FT4’s measuring set; (c) original FT4’s measuring set. This figure was created in Gimp 2.10.32. 6 Vol:.(1234567890) Scientific Reports | (2022) 12:17331 | https://doi.org/10.1038/s41598-022-22114-2 www.nature.com/scientificreports/ Bulk material tests. The following tests were used to test the performance of the printed measuring instruments. To verify the measurement stabilty of the printed instruments, we also used 3D printed instruments in combination with original stainless steel instruments, and original steel instruments. Shear test. Shear properties show how easily particulate material flows. For a particle material flow to occur, the yield point must be overcome. The yield point is greatly influenced bymechanical-physical properties of the particles such as surface properties, shape, and size. Other variables, like moisture content, Van der Waals forces, or level of flow additive also affect the flow of bulk material. The shear properties of bulk materials are used in the design of handling, storage, and process equipment. The flow properties of bulk materials are used in various applications36, usually quantified as linearized angle of internal friction (LAIF, ϕ), effective angle of internal friction (EAIF,δ), and flow function ffc to describe the bulk material behaviour37. The values of EAIF(δ), LAIF (ϕ), ffc, and cohesion c were measured on Schulze Ring Shear Tester RST-01.pc (Wolfenbuttel, Germany, Fig.4b and Freeman’s FT4 Powder Tester (Freeman Technology, Tewkesbury, Gloucestershire, UK, Fig.4c38. The main monitored parameters are EAIF(δ), LAIF (ϕ), cohesion c, and flow function ffc39,40. The measurements of AIF (δ, ϕ), ffc, and c had pre-shear normal stress of10000Pa, shear points with normal stresses values of 250Pa, 500Pa, 1 000Pa, 2 500Pa, 5 000Pa and 7 500Pa. The resulting values of AIF (δ, ϕ), ffc, and cohesion c were the average of ten measurements. Twelve combinations of measurements were performed for two measuring devices, two lunar regolith simulants (LHS-1 and LMS-1), and three measuring set materials (steel and additive plastic materials) giving a total of 120 measurements. The methods of measuring AIF(δ,ϕ), ffc, and c were rotational. However, there were different measurement procedures and characteristics in the shear cell. A recent comparison showed that in most cases, lower values of EAIF (δ), LAIF (ϕ) and ffc are obtained using FT436. Due to theincomparable geometry, area ratios, and cell sizes, the total sample volume differs. In general, this behaviour is derived from the property of bulk materials that the bulk material flows less easily through smaller cross-sections. Schulze’s ring shear cell and lid, and FT4’s sample vessel, funnel, blade, vented piston and shear head were 3D printed from PLA and ASA filaments. The printed instrument designs and their modifications are described in the section Fused Filament Fabrication printed equipment. All 3D printed parts were appropriately calibrated prior to measurement because they exerted less pressure due to their lower weight. Compressibility. Compressibility is a property of bulk materials that shows the change in the bulk density as a function of consolidation pressure. The compressibility measurement is neither a shear property nor a flow property of the bulk material but it is dependent on similar quantities. This property is affected by particle size distribution, cohesion, particle surface texture, particle shape, and particle stiffness. Compressibility is an important property for the design of process equipment such as silos, conveyors, mixers, compacting equipment, and tablet presses41. Compressibility was measured with Freeman Technology’s FT4 powder rheometer with standard compressibility test42. The standard test obtained data by expressing the percentage compressibility for a normal load from 0.5 to 15 kPa applied onto the sample. Samples of lunar regolith simulants were measured in the 85 ml sample Figure4. (a) Lunar regolith simulant LHS-1 (above) and LMS-1 (bottom); (b) Schulze’s shear test setup; (c) FT4’s shear test setup. This figure was created in Gimp 2.10.32. 7 Vol.:(0123456789) Scientific Reports | (2022) 12:17331 | https://doi.org/10.1038/s41598-022-22114-2 www.nature.com/scientificreports/ vessel with a diameter of 50 mm. Vented compression piston with diameter of 47.5 mm and blade with 48 mm were used. These design modifications were described in the section Fused Filament Fabrication printed equipment. For each set of instruments (original stainless steel, PLA printed, ASA printed), 10 measurements were performed. Stability index, flow rate index and basic flow energy. Stability Index (SI), Flow Rate Index (FRI) and Basic Flowability Energy (BFE) were analysed by using Freeman’s FT4 powder rheometer in a manner that previously described (Freeman Technology, Tewkesbury, Gloucestershire, UK)42. The SI, FRI and BFE measurements are performed using the standardized test preset in the FT4 powder rheometer. The SI and the FRI measurements were carried out in a 65 ml vessel. Five measurements were taken for each set of instrument materials (original stainless steel, PLA printed, ASA printed) and their combinations (original vessel with PLA blade, original vessel with ASA blade, PLA vessel with original blade, and ASA vessel with original blade). Stability Index (SI) of a powder42 shows the conditioned flow properties under the action of forces during flow, which may change due to the tendency of powder to agglomeration, caking, and attrition. TheSI program measures the particulate material by conditioning sequence followed by a test cycle. The test cycles are repeated seven times. The seven measurement points form a straight line, and the more stable the powder, the straighter the line. The SI is defined as the ratio of the energy consumed during test 7 to the energy consumed during test 143. The more the SI approaches 1, the more stable the measured powder is. If the SI > 1, the measured powder is affected by moisture absorption, segregation, agglomeration, de-aeration, and electrostatic charge. If the SI < 1, then the measured powder is affected by over-blending, de-agglomeration, attrition, and additive coating of the blade and of the vessel42. The variable FRI42 is measured as a decreasing flow in measuring points 8 to 11, where the Flow Rate of the blade decreases from 100 mm.s-1 to 10 mm.s-1. The FRI of the blade indicates thesensitivity of the measured powder, and it is expressed as Flow Rate Index (FRI). Non-cohesive powders show fewer sensitive changes for the FRI, which is defined as ratio of the energy test 11 to the energy test 842. The FRI < 1 has powders with extremely good flow. The FRI = 1 has powders with asurface coating or large particle size distribution, which makes them insensitive to changed flow rate. Most measured powders have Flow Rate sensitivity 3 > FRI > 1.5. If the FRI > 3, then the powder is overly sensitive to changed flow rate43. The Basic Flowability Energy (BFE)42 is a property defined by the energy consumed for point 7 during the standardized variable flow test, which corresponds to the flow energy43. The energy consumed by the specific flow is generated in the exact volume of the vessel as the blade moves downward. Results Particle characterization. The particle size distributions of the regolith simulants LHS-1 and LMS-1 are shown in Figure5 and the values of dmean, d10, d50, and d90 are given in Table2. For both simulants, all particles were smaller than 500 µm. LHS-1 had smaller particles than LMS-1, as shown in Table2. The parameters dmean, d10, d50, and d90 show that the difference in particle size is due to a greater representation of a larger fraction from 80 to 400 µm. The SEM photographs appropriately complement the characterization of LMS-1 and LHS-1 (Figure6). The photographs show the faceted angular shape of the lunar regolith simulant particles. Figure5. The particle size distribution (differential and cumulative) for LMS-1 and LHS-1 regolith simulants. 8 Vol:.(1234567890) Scientific Reports | (2022) 12:17331 | https://doi.org/10.1038/s41598-022-22114-2 www.nature.com/scientificreports/ Shear test. The values of EAIF (δ), LAIF (ϕ), flow function ffc, and cohesion c are averaged values from 10 measurements. Table3 shows EAIF (δ) with standard deviation (SDδ), its maximum value (δmax), and its minimum value (δmin), LAIF (ϕ) with standard deviation (SDϕ), maximum value (ϕmax), and its minimum value (ϕmin). Table4. shows flow function ffc with standard deviation (SDffc), its minimum value (ffcmin) and maximum value (ffcmax), cohesion c with standard deviation (SDc), its minimum value (cmin) and maximum value (cmax). As can be seen from the tables (below), the data were split into two parts, the top half with the LMS-1 specimen and the bottom half with the LHS-1 specimen. Each half of the tables is based on RST and FT4 measurements of the appropriate combination of regolith simulant and shear instrument set. Comparison between RST and FT4 measuring methods should not be taken unambiguously. The values of EAIF(δ), LAIF (ϕ), ffc, and c corresponded to the size of the shear surface, being larger for the RST (8482 mm2) and smaller for the FT4 (1879 mm2)44. However, a comparison of standard RST and FT4 shear test methods between LMS-1 and LHS-1 regolith simulants showed slightly better flowability of LHS-1 powder. The resulting flow properties of LHS-1 are due to the larger fraction of particles below 80µm in the powder. The smaller Figure6. Scanning electron microscope (SEM) photos of lunar regolith simulants (a) LMS-1, and (b) LHS-1. Table 3. Shear test results – effective angle of internal friction δ and linearized angle of internal frictionϕ. Measuring device Specimen and shear cell material combination δ(°) SDδ(°) δmin (°) δmax(°) ϕ(°) SDϕ (°) ϕmin (°) ϕmax (°) RST LMS-1, original 43.94 1.00 42.10 45.50 42.16 1.05 40.20 43.70 LMS-1, PLA 42.55 0.83 41.60 43.90 41.19 0.85 40.20 42.70 LMS-1, ASA 41.52 0.65 40.60 42.40 40.06 0.65 39.20 40.90 FT4 LMS-1, original 42.81 0.38 42.33 43.75 40.36 0.34 39.77 41.08 LMS-1, PLA 40.07 0.68 39.09 41.10 36.87 0.74 35.41 37.80 LMS-1, ASA 40.92 1.07 39.54 42.95 37.64 0.87 36.61 39.25 RST LHS-1, original 41.74 0.18 41.50 42.10 40.03 0.15 39.80 40.30 LHS-1, PLA 43.15 0.34 42.50 43.70 41.51 0.33 40.90 42.10 LHS-1, ASA 42.34 0.62 41.30 42.20 40.68 0.62 39.60 41.60 FT4 LHS-1, original 39.28 0.51 38.70 40.27 36.75 0.51 36.10 37.71 LHS-1, PLA 38.90 0.64 38.00 40.10 36.42 0.63 35.62 37.50 LHS-1, ASA 39.34 0.74 38.07 40.40 36.74 0.59 35.62 37.56 Table 2. Particle size distribution characterization values. lunar regolith simulant dmean (µm) d10 (µm) d50 (µm) d90 (µm) LMS-1 86.85 7.62 67.58 193.44 LHS-1 58.71 4.95 41.79 139.32 9 Vol.:(0123456789) Scientific Reports | (2022) 12:17331 | https://doi.org/10.1038/s41598-022-22114-2 www.nature.com/scientificreports/ particles act as a lubricant that allows the larger particles to rotate into a position with the possibility of movement. Cohesion c shows the macro-effect of the flow properties of the powders. The correlation between LMS-1 and LHS-1 is interesting, as the former powder had worse comparison results for different material instrument sets. The results obtained from measurements of the LMS-1 powder on RST with the original aluminium shear cell and lid had slightly worse flowability than the measurements with the PLA and ASA printed shear cells and lids. This is evident from the lower ffc values and higher EAIF (δ) and LAIF (ϕ) values measured with the original set compared to the 3D printed instrument measurements. The ASA printed shear cell and lid showed the smallest standard deviation for EAIF (δ) and LAIF (ϕ). Although the standard deviation value for ffc was the smallest for the original instrument set, the difference from other material sets was negligible. The most striking observation that emerged from the data comparison was the LMS-1 powder measured on FT4. The differences between AIF (δ, ϕ) were up to 3°, and the difference in ffc was up to 2°. However, the slightly worse EAIF (δ) and ffc of the LMS-1 measured on FT4 are due to the smaller shear vessel cross-section. Interestingly, for the LHS-1 powder, a good corelation of the results measured on the RST was observed between all three combinations of the shear cell and lid materials. The worst ffc was measured on the RST with original instruments for LHS-1 powder, but the difference from the other material instrument sets was negligible. Even in the case of LHS-1 powder measurements on FT4, a significant positive correlation was found between all three sets of measuring instruments. The ffc values measured on the FT4 showed the best correlation of all measurements when comparing between different material instrument sets. We now turn to the experimental results of cohesion c, which shows a correlation with the EAIF (δ), LAIF (ϕ) and ffc deviations. The LMS-1 powder shows significant differences in cohesion c results. The measured results of cohesion c are somewhat counterintuitive. It is due to the reduced values that measured on theRST with the PLA and ASA printed instruments, but increased values measured on the FT4 with the PLA and ASA printed instruments compared to the original instrument sets for both devices. Compressibility. The resulting values, shown in Fig.7, were averaged from ten measurements of thepercentage change in volume after compression. The presented compressibility curves show a high agreement when original and 3D printed instruments are compared. The LHS-1 powder with finer particles had a higher compressibility. For 15kPa of applied normal stress, its volume changed by more than 10%. The LMS-1 powder showed compressibility of over 6% for 15kPa of applied normal stress. The aim of the study was to investigate the effect of 3D printed instruments and vessels on the measured compressibility values. The values showed negligible deviations as shown in Fig.7. One unanticipated finding was that shearing of the powder after the initial conditioning had the greatest effect on the measured result. If this shearing of the powder did not take place almost perfectly in the plane, the subsequent result was noticeably different. This finding applies to both the original vessel and the 3D printed vessel. However, the 3D printed vessels had slightly poorer surface flatness in the shearing plane, which escalated the effect and the need for the perfect shear of the powder. Asignificant positive correlation between the diameter size of the 3D printed vented piston and thecompressibility results. Due to shrinkage during 3D printing, the diameter size in the CAD model was modified to match the original vented piston after 3D printing. Stability index and flow rate index. The results of the dependence of the energy consumed during the tests on the blade tip speed are shown in Fig.8. The results are the average of 5 measurements. Both powders showed very stable values of Stability Index (SI). However, the Flow Rate Index (FRI) values showed different behaviour for the two regoliths. The most significant difference was in the energy consumption during the tests, with the LMS-1 powder regolith showing a much higher BFE [mJ] than the LHS-1 powder regolith. The largest SI deviation for the LMS-1 measurement was in the original vessel with an ASA printed blade, where SI = 1.00 with standard deviation less than σSI = 0.024, the minimum value of SImin = 0.96 and the maximum Table 4. Shear test results—flow function ffc and cohesion c. Measuring device Specimen and shear cell material combination ffc (−) SDffc (−) ffcmin (−) ffcmax (−) c (MPa) SDc (MPa) cmin (MPa) cmax (MPa) RST LMS-1, original 12.30 0.77 11.02 13.44 414.70 33.82 356.00 463.00 LMS-1, PLA 15.91 0.73 14.69 16.86 308.20 17.07 289.00 337.00 LMS-1, ASA 15.51 0.89 14.24 16.65 312.60 17.81 291.00 341.00 FT4 LMS-1, original 9.33 0.79 7.99 10.43 483.18 51.73 412.23 591.27 LMS-1, PLA 7.54 0.54 6.64 8.28 561.37 46.96 500.66 643.17 LMS-1, ASA 7.34 0.71 6.33 8.48 576.01 58.63 494.81 665.34 RST LHS-1, original 13.17 0.71 11.90 14.51 363.10 20.90 330.00 400.00 LHS-1, PLA 13.40 0.79 12.08 14.54 375.30 22.82 344.00 408.00 LHS-1, ASA 13.63 0.54 12.57 14.30 361.90 14.48 336.00 390.00 FT4 LHS-1, original 9.44 0.46 8.40 10.16 472.00 27.79 427.75 531.84 LHS-1, PLA 9.70 0.44 8.73 10.30 448.36 21.55 421.10 497.11 LHS-1, ASA 9.24 0.70 8.20 10.00 473.98 38.08 435.40 534.40