XY Direction Research Articles

Ultra-high strength and flame retardant carbon aerogel composites with efficient electromagnetic interference shielding and superior thermal insulation via nano-repairing route

Carbon aerogel composites (CAs) have received numerous attention for protection of aircraft due to their unique properties. However, the shrinkage mismatch between rigid fibers and carbon sources during carbonization dramatically weakens the performance of CAs, and no significant breakthroughs have been made. We propose a vacuum impregnation assisted nano-repairing (VINR) strategy to fabricate crack-free carbon fiber reinforced carbon aerogel (Cf/CA) composites with high strength, electromagnetic interference shielding and thermal insulation. The cross-confined, overlapping nano-CA particles greatly limits the shrinkage of the carbon source, conferring excellent mechanical properties to Cf/CA, and its compressive strength and modulus reaches 3.93 MPa and 69.96 MPa in XY direction and 2.03 MPa and 40.67 MPa in Z direction, respectively, at 5 % strain. In addition, Cf/CA exhibits significant thermal insulation (0.054 W/(m·K) at 25 °C under air condition) and superior electromagnetic interference shielding properties (EMI SE is ∼48.52 dB at a thickness of ∼2 mm). Herein, the structurally optimized Cf/CA provides a promising solution for multi-effect protection for critical electronic devices of aircraft in special service environments.

Study on Measurement Method of Three-dimensional Position of Unlabeled Microspheres under Bright Background

Abstract: Using computer vision technology to obtain the position and trajectory data of particle probe microspheres from microscope images has significance and value in the molecular field. However, most of the existing microsphere measurement methods are based on transmission, which can only be measured under transparent samples and substrates and are not suitable for the application scenario of living cell measurement. In this paper, a method based on reflectivity imaging is proposed to measure the three-dimensional position of the dark microspheres in the bright field. Based on the outermost ring radius method, the relationship between the inner ring radius of the microsphere spot and the out-of-focus distance was explored to measure the coordinates in the Z direction. Cardiomyocytes were combined with 10um size silica microspheres. Experiments show that in a bright field with a high perturbation environment, it can achieve high precision measurement of dark microspheres and achieve three-dimensional position measurement with an accuracy of 50nm in XY direction and 100nm in Z direction.

Facile Synthesis and Properties of Highly Porous Quartz Fiber-Reinforced Phenolic Resin Composites with High Strength.

Lightweight and high-strength insulation materials have important application prospects in the aerospace, metallurgical, and nuclear industries. In this study, a highly porous silica fiber reinforced phenolic resin matrix composite was prepared by vacuum impregnation and atmospheric drying using quartz fiber needled felt as reinforcement and anhydrous ethanol as a pore-making agent. The effects of curing agent content on the structure, composition, density, and thermal conductivity of the composite were studied. The mechanical properties of the composite in the xy direction and z direction were analyzed. The results showed that this process can also produce porous phenolic resin (PR) with a density as low as 0.291 g/cm3, where spherical phenolic resin particles are interconnected to form a porous network structure with a particle size of about 5.43 μm. The fiber-reinforced porous PR had low density (0.372~0.397 g/cm3) and low thermal conductivity (0.085~0.095 W/m·K). The spherical phenolic resin particles inside the composite were well combined with the fiber at the interface and uniformly distributed in the fiber lap network. The composite possessed enhanced mechanical properties with compressive strength of 3.5-5.1 MPa in the xy direction and appeared as gradual compaction rather than destruction as the strain reached 30% in the z direction. This research provides a lightweight and high-strength insulation material with a simple preparation process and excellent performance.

Influence of anisotropy and walls thickness on the mechanical behavior of 3D printed onyx parts

Predicting the behavior and mechanical properties of 3D-printed parts is crucial for 3D printer users. This study conducted experimental investigations on Onyx 3D-printed parts to identify the most important printing parameters. These parameters were specimen positioning and the number of specimen walls. The experimental results indicated that specimens oriented in the XZ direction were 48% stiffer than those oriented in the XY direction and 54% stiffer than those oriented in the ZX direction. Additionally, the results demonstrated that walls significantly influenced the mechanical properties of specimens in the XY and XZ orientations but had no effect on those in the ZX orientation. The Young's modulus increased by 60% between a specimen with one wall and another with eight walls. This paper presents an analytical model for predicting mechanical properties based on the number of walls, with a prediction error ranging from 1% to 15%. Additionally, a numerical simulation approach was proposed to predict the mechanical behavior of parts. The numerical and experimental results comparison showed a 1% to 9% prediction error and a good correlation between numerical and experimental curves. These findings can be a valuable aid to engineers in the design of 3D printed mechanical concepts.

Development of a human-size magnetic particle imaging device for sentinel lymph node biopsy of breast cancer.

In this study, a novel human-size handheld magnetic particle imaging (MPI) system was developed for the high-precision detection of sentinel lymph nodes for breast cancer. The system consisted of a highly sensitive home-made MPI detection probe, a set of concentric coils pair for spatialization, a solenoid coil for uniform excitation at 8kHz@1.5mT, and a full mirrored coil set positioned far away from the scanning area. The mirrored coils formed an extremely effective differential pickup structure which suppressed the system noise as high as 100dB. The different combination of the inner and outer gradient current made the field free point (FFP) move in the Z direction with a uniform intensity of 0.54T/m, while the scanning in the XY direction was implemented mechanically. The third-harmonic signal of the Superparamagnetic Iron Oxide Nanoparticles (SPIONs) at the FFP was detected and then reconstructed synchronously with the current changes. Experiment results showed that the tomographic detection limit was 30mm in the Z direction, and the sensitivity was about 10μg Fe SPIONs at 40mm distance with a spatial resolution of about 5mm. In the rat experiment, 54μg intramuscular injected SPIONs were detected successfully in the sentinel lymph node, in which the tracer content was about 1.2% total injected Fe. Additionally, the effective detection time window was confirmed from 4 to 6min after injection. Relevant clinical ethics are already in the application process. Large mammalian SLNB MPI experiments and 3D preoperative SLNB imaging will be performed in the future.

Cu@Co with Dilatation Strain for High-Performance Electrocatalytic Reduction of Low-Concentration Nitric Oxide.

Electrocatalytic reduction of nitric oxide (NO) to ammonia (NH3 ) is a clean and sustainable strategy to simultaneously remove NO and synthesize NH3 . However, the conversion of low concentration NO to NH3 is still a huge challenge. In this work, the dilatation strain between Cu and Co interface over Cu@Co catalyst is built up and investigated for electroreduction of low concentration NO (volume ratio of 1%) to NH3 . The catalyst shows a high NH3 yield of 627.20µg h-1 cm-2 and a Faradaic efficiency of 76.54%. Through the combination of spherical aberration-corrected transmission electron microscopy and geometric phase analyses, it shows that Co atoms occupy Cu lattice sites to form dilatation strain in the xy direction within Co region. Further density functional theory calculations and NO temperature-programmed desorption (NO-TPD) results show that the surface dilatation strain on Cu@Co is helpful to enhance the NO adsorption and reduce energy barrier of the rate-determining step (*NO to *NOH), thereby accelerating the catalytic reaction. To simultaneously realize NO exhaust gas removal, NH3 green synthesis, and electricity output, a Zn-NO battery with Cu@Co cathode is assembled with a power density of 3.08mW cm-2 and an NH3 yield of 273.37µg h-1 cm-2 .

Cost-effective fabrication of customized LTCC devices with multilayer using multi-material 3D printing

Low-temperature co-fired ceramic (LTCC) devices have been widely used in the defense, automotive, medical, and aerospace industries. However, the traditional manufacturing process of LTCC devices is hardly suitable for cost-effective, fast design and customization requirements. In this work, we propose a multi-material integrated 3D printing technology for LTCC. LTCC slurry was configured using homemade borosilicate glass powder and Al2O3 powder, and the influence of printing parameters on the printed effect was investigated. The shrinkage of the ceramics sintered at 850 °C for 15 min was 14.82 ± 0.47 % in the XY direction and 13.7 ± 0.26 % in the Z direction, comparable to that of commercial LTCC. Wireless sensing multilayer LED circuit and passive humidity sensor were fabricated, where the sensor with a sensitivity of 0.132 MHz/%RH. These cases demonstrate that the proposed technology can rapidly produce LTCC devices and meet the demand for custom LTCC devices in high-end manufacturing.

Photoinduced Ultrafast Phase Transition in Bilayer CrI3.

In two-dimensional magnets, the ultrafast photoexcited method represents a low-power and high-speed method of switching magnetic states. Bilayer CrI3 (BLC) is an ideal platform for studying ultrafast photoinduced magnetic phase transitions due to its stacking-dependent magnetic properties. Here, by using time-dependent density functional theory, we explore the photoexcitation phase transition in BLC from the R- to M-stacked phase. This process is found to be induced by electron-phonon interactions. The activated Ag and Bg phonon modes in the xy direction drive the horizontal relative displacements between the layers. The activated Ag mode in the z direction leads to a transition potential reduction. Furthermore, this phase transition can invert the sign of the interlayer spin interaction, indicating a photoinduced transition from ferromagnet to antiferromagnet. This investigation has profound implications for magnetic phase engineering strategies.

Microstructure, crack formation and improvement on Nickel-based superalloy fabricated by powder bed fusion

Nickel-based superalloy (Haynes 230) parts were fabricated by powder bed fusion using a laser - based system. Crack defects were unavoidable. In order to solve the cracking problem, it was necessary to understand the crack formation mechanism, and the hot isostatic pressing method was used to eliminate the crack defects. The results indicated that the microstructure displayed cellular crystal structure in XY direction and columnar crystal structure with {001} < 001 > cubic texture in XZ direction. Under the thermal stress and micro-segregation, M23C6 carbides and NiSi eutectic phases were precipitated at high angle grain boundaries, which promoted the formation of solidification and liquation cracks. Because the direction of the internal cracks in the horizontal tensile sample was perpendicular to the tensile direction and the microstructure was {001} < 001 > cubic texture, the tensile properties were anisotropic. After hot isostatic pressing treatment, the cracks were obviously eliminated, the ultimate tensile strength and elongation were significantly improved. The carbides transformed from Cr-rich M23C6 to W-rich M6C.

Accuracy of radiographic techniques in detection of the calcaneofibular ligament calcaneal insertion for lateral ankle ligament complex surgery.

Grade III ankle sprains that fail conservative treatment can require surgical management. Anatomic procedures have been shown to properly restore joint mechanics, and precise localization of insertion sites of the lateral ankle complex ligaments can be determined through radiographic techniques. Ideally, radiographic techniques that are easily reproducible intraoperatively will lead to a consistently well-placed CFL reconstruction in lateral ankle ligament surgery. To determine the most accurate method to locate the calcaneofibular ligament (CFL) insertion radiographically. MRIs of 25 ankles were utilized to identify the "true" insertion of the CFL. Distances between the true insertion and three bony landmarks were measured. Three proposed methods (Best, Lopes, and Taser) for determining the CFL insertion were applied to lateral ankle radiographs. X and Y coordinate distances were measured from the insertion found on each proposed method to the three bony landmarks: the most superior point of the postero-superior surface of the calcaneus, the posterior most aspect of the sinus tarsi, and the distal tip of the fibula. X and Y distances were compared to the true insertion found on MRI. All measurements were made using a picture archiving and communication system. The average, standard deviation, minimum, and maximum were obtained. Statistical analysis was performed using repeated measures ANOVA, and a post hoc analysis was performed with the Bonferroni test. The Best and Taser techniques were found to be closest to the true CFL insertion when combining X and Y distances. For distance in the X direction, there was no significant difference between techniques (P = 0.264). For distance in the Y direction, there was a significant difference between techniques (P = 0.015). For distance in the combined XY direction, there was a significant difference between techniques (P = 0.001). The CFL insertion as determined by the Best method was significantly closer to the true insertion compared to the Lopes method in the Y (P = 0.042) and XY (P = 0.004) directions. The CFL insertion as determined by the Taser method was significantly closer to the true insertion compared to the Lopes method in the XY direction (P = 0.017). There was no significant difference between the Best and Taser methods. If the Best and Taser techniques can be readily used in the operating room, they would likely prove the most reliable for finding the true CFL insertion.

Design, development and application of a compact robotic transplanter with automatic seedling picking mechanism for plug-type seedlings

Automation of agricultural operation such as seedling transplanting is needed to ensure efficient as well as timely operation. Robotics is the area that needs to be focused for the future of automatic seedling transplanter. This paper presents the design, development as well as working of the robotic transplanter (RT) for plug seedlings. The developed RT consists of three systems: (1) robot initiation; (2) seedling picking mechanism (SPM); and (3) vehicle movement system (VMS). The SPM consists of a main frame, manipulator, end-effector and control unit. Whereas, the VMS is having photoelectric sensor, robot controller and DC motor. The stepper motors were mounted on the main frame for movement in XY direction. The manipulator was on the crossbar that used to move the end-effector in Z-axis. The pick-up mechanism consists of an end-effector having jaw-type gripper controlled by servo motor. The control unit consists of microchip 16F877 and the system is controlled with computer programming. The gripper moves to each seedling in the pro-tray, grasp and pick-up the seedling, moves to the delivery point and then release the seedling. The manipulator was tested and analyzed for pickup and releasing of 96 seedlings with soil base from pro-tray. The initial experimental result showed that the seedling success rate, leakage rate and successful transplanting of 30 days old chilli seedling was 95.1%, 7.6% and 90.3%, respectively. Robotic technology seems to be expensive but the scope lies in the non-availability or high cost of manual labour and to ensure timeliness of repetitive field operations.

Influence of binder jet 3D printing process parameters from irregular feedstock powder on final properties of Al parts

• The possibility of using irregular particles of aluminum in the Binder Jet 3D printing technology has been demonstrated. • The influence of the printing parameters on the properties and quality of the final parts was determined. • Vacuum sintered parts obtained a higher density than those sintered in argon or hydrogen. • The printed parts showed a linear shrinkage of up to 2% and 43–50% of the theoretical density. • Increased porosity of the samples leads to a rougher surface. This work for the first time presents the results of optimization of printing parameters in the Binder Jetting technology in terms of the possibility of using an irregular aluminum powder which is much cheaper and more common than spheroidal. The influence of binder saturation (15–100 %), roller traverse speed (10–110 mm/ sec ), layer thickness (30–90 µm), and sintering atmosphere (vacuum, argon, hydrogen) on the quality of aluminum printed parts has been investigated. The study included the density, shrinkage, porosity, surface topography, and roughness of printed, and sintered aluminum parts. An anisotropy of linear contraction in the X, Y, and Z directions was observed, with the largest linear shrinkage occurring in the Z direction. In terms of roughness, the top surfaces (XY direction) turned out to be the smoothest and the side surfaces (YZ direction) were the roughest. Samples that were sintered under vacuum resulted in higher density, lower shrinkage, and lower porosity compared to those sintered in argon or hydrogen. On the basis of results, it was found that generally, increasing the saturation level and layer thickness causes a decrease in density and increases the shrinkage and the porosity of additive manufactured parts.

A study on the compressive mechanical properties of 316L diamond lattice structures manufactured by laser powder bed fusion based on actual relative density

Lattice structure design is a novel structural lightweight method and has many advantages, but some researches ignored the effects of the factors studied on actual relative density and skipped actual relative density to discuss the effects on mechanical properties. In this paper, the effects of process parameters and geometrical parameters on the compressive mechanical properties of 316L diamond lattice structures manufactured by laser powder bed fusion were investigated on the basis of actual relative density. The results show that the actual relative density (28.0 % → 25.4 %) and the compressive strength in the building direction (55.7 ± 1.3 MPa → 42.0 ± 1.5 MPa) decrease as the hatch spacing (0.05 mm → 0.09 mm) increases, and they conform to the parabolic function relationship better than the Gibson-Ashby relationship, but the opposite in the XY direction. The actual relative densities and compressive strength inevitably conform to the Gibson-Ashby relationship regardless of the nominal relative densities and cell sizes, and the modulus (857 ± 54 MPa → 1019 ± 51 MPa) increases with the increasing of strut diameter (0.54 mm → 3.21 mm). The compressive strength could decrease slightly with the increasing of contour size (10 mm → 30 mm), while the modulus (964 MPa → 682 MPa) decreases rapidly. To sum up, the process parameters and geometrical parameters could affect the actual relative density significantly, and the actual relative density is the key to correctly analyze the effects of various parameters. The conclusions of this work are helpful to optimize the manufacturing process of lattice structures and design geometrical parameters according to the required performance.

Microstructures and mechanical behaviors of additive manufactured Inconel 625 alloys via selective laser melting and laser engineered net shaping

The microstructure and mechanical behaviors of as-built Inconel 625 prepared by selective laser melting (SLM) and laser engineered net shaping (LENS) technologies were investigated in this study. The results show that the microstructure of Inconel 625 alloy prepared by SLM process is composed of obvious columnar and cellular grains. Inconel 625 fabricated by LENS also has columnar and cellular structures, but the grain size is relatively large. Significant anisotropy of mechanical properties is observed in SLM and LENS printed Inconel 625. The mechanical properties in XY direction are higher than those in XZ direction, and the maximum tensile strength of SLM-XY sample is 1241.5 MPa. SLM printed Inconel 625 has a relatively higher dislocation density of 2.8 ± 1.2 × 10 14 m −2 . The difference in yield strength between SLM and LENS printed Inconel 625 is mainly caused by the different dislocation strengthening effects. • The microstructure and mechanical properties of Inconel 625 printed by SLM and LENS are systematically compared. • The anisotropy of mechanical properties is affected by grain morphology due to different printing directions. • Dislocation strengthening effects play a major role in mechanical properties.

Method to maximize the productivity of laser powder bed fusion systems through dimensionless parameters

Productivity in laser powder bed fusion systems can be increased by using high layer thickness (&amp;gt;40 μm). The process parameters for high layer thickness are typically found by one-factor-at-a-time, design of experiments, or computationally intensive numerical simulations. In this paper, a method to scale-up the process parameters from low to high layer thickness is proposed. The method is based on dimensionless parameters from the analytical model. Through the proposed scale-up method, the build rate increase was proportional to an increase in layer thickness. The scale-up method was demonstrated for laser powder bed fusion of stainless steel 316L from 30 to 50 μm layer thickness and from 50 to 70 μm layer thickness. For both cases, no detriment to part density was observed—measured densities before and after the scale-up were above 99.6%. The density results obtained were within high density windows with variation of parameters resulting in the same respective volumetric energy densities and one-factor-at-a-time parameter studies. There was no significant change in tensile properties after the scale-up except reduction in elongation at break in the XY direction. The comparable mechanical properties before and after the scale-up method were attributed to the observed similarities in microstructure features such as the crystal orientation, cell sizes, and proportions of low and high angle grain boundaries.

Nonlinear Numerical and Analytical Assessment of the Shear Strength of RC and SFRC Beams Externally Strengthened with CFRP Sheets

This study investigates numerically utilizing nonlinear finite element (ANSYS software) and analytically the shear response of the Reinforced Concrete (RC) beams. Different beams are considered in the current study, such as RC, steel fibre reinforced concrete (SFRC) without web reinforcement, and RC externally reinforced in the shear zone with carbon fibre reinforced polymer (CFRP) sheets. Nonlinear finite element model (FEM) is designed to simulate the performance of the designed beams. The results of FEM are compared to experimental measurements and standard design codes (ACI 440.2R‐17, FIB 14, CNR‐DT200, and ACI 318‐19). According to the experimental approach and nonlinear finite element, the enhancement in the load carrying capacity of SFRC beam due to CFRP strengthening decreases with a volume fraction of steel fibres of 2%. However, the effect of CFRP strengthening on the shear behaviour of RC beams was observed in increased load carrying and ultimate deflection capacities as a result of the CFRP strengthening. The results show that CFRP has a significant contribution to shear strength. At each load increment, the created model accurately reproduced the initial and progressive crack patterns. A comparison of nonlinear finite element and analytical models was conducted using the codes ACI 440.2R‐17, FIB 14, CNR‐DT200, and ACI 318‐19. Numerically, the FEM results showed a high agreement with ACI 440.2R‐17 standard code, with correlation approach to 99%. The comparison experimental load capacity of beams to FEM and ACI 440.2R‐17 shows that the FEM can be significantly used to estimate the shear strength of beams in the X‐Y directions with simulating different scenarios of CFRP and SFRC characteristics. The discrepancy between the nonlinear FEA and the theoretical predictions from the ACI 440.2R‐17 code is less than 1%, from the FIB14 code is less than 2%, from the CNR‐DT200 code is less than 15%, and from the ACI 318‐19 code is less than 30%. The ultimate load capacity evaluated based on ACI 440.2R‐17 code provision shows a good agreement with the experimental data as compared to the others’ code provision. The results of the finite element analysis and analytical models were in good agreement with the experimental results. The most significant advantage of finite element analysis over experimental approaches was that it can aid in the investigation of different output results that cannot be measured experimentally, such as shear stress in the XY direction throughout the beam strengthened in shear with different CFRP properties and steel fibre reinforced concrete (SFRC).

Stress field analysis of an infinite plate with a central closed inclined crack under uniaxial compression

In view of the shortcomings of existing studies, the mechanical behavior of the closed crack under uniaxial compression is studied. Based on the far-field and the crack surface stress boundary conditions, Kolossoff-Muskhelishvili stress function of an infinite plate with a central closed inclined crack is derived with Muskhelishvili complex theory. Then the calculation methods of the stress components, stress intensity factors and T-stress at the crack tip are proposed. The mainly findings are as follows. First of all, the crack surface stress boundary conditions vary with variation of the far-field stress condition from tension to compression, so it’s false to directly introduce the theory for the crack under tension to that for the closed crack under compression. Next, it is found that there is no KI singular term at the crack tip and meanwhile KII and T-stress are influenced by the effective shear stress on the crack surface. When the effective shear stress is zero, there are two T-stress components (i.e. Tx and Ty, which are parallel and perpendicular to the crack surface respectively). While the effective shear stress is greater than zero, the third T-stress component (namely Txy which is along the xy direction) also exists. Finally, the theoretical predictions with the proposed method are verified with the isochromatic fringe patterns of photoelasticity experiment near the crack tip under uniaxial compression. Meanwhile the distribution of each stress component around the crack is effected obviously by the friction coefficient of the crack surface and the dip angle of crack, but the distribution tendency of these stress components is similar.

Study on the maximum tangential strain criterion for the initiation of the wing-crack under uniaxial compression

The global stress field function of an infinite plate with a closed inclined crack under uniaxial compression is presented, then the stress field at the crack tip is obtained, namely the formulae of KI, KII and T-stress are obtained. A new maximum tangential strain (MTSN) criterion is proposed to predict the initiation of the crack under compression by considering singular and non-singular terms based on the classical MTSN criterion. The influence factors on KII are analyzed and the effects of T-stress on the tangential strain at the crack tip under different critical plastic zones (rc), dip angel of crack (β), friction coefficients of crack surface (f) and Poisson’s ratio (ν) are studied. The comparison of the wing-crack initiation angle measured from the experimental results and predicted by the proposed criterion and other researchers’ models are made. The following findings are obtained. First of all, the proposed global stress field function satisfies the far-field and crack surface stress boundary conditions. The singular term of KII and non-singular term of T-stress vary with the effective shear stress along the crack surface. When the effective shear stress is zero, there is still singularity at the crack tip, which is completely opposite to the classical theory, and there are two components of T-stress (i.e. Tx and Ty, which is parallel and perpendicular to the crack surface respectively). While there is a third component of T-stress (i.e. Txy, which along the xy direction) when the effective shear stress is greater than zero. Next, the comparison of the wing-crack initiation angle measured from the experimental results and predicted by the proposed criterion and other researchers’ models are made. The results of the proposed method are consistent with the experiments very well, especially when the effective shear stress decreases to zero with the increase of friction coefficient (f). Finally, the tangential strain field at the crack tip are effected significantly by the critical plastic zones (rc), dip angel of crack (β), friction coefficients of crack surface (f) and Poisson’s ratio (ν).

Evaluating Directional Dependency of Selective Laser Sintered Patient Specific Biodegradable Devices to Improve Predictive Modeling and Design Verification.

Additive manufacturing, or 3D printing, of the bioresorbable polymer [Formula: see text]-polycaprolactone (PCL) is an emerging tissue engineering solution addressing patient specific anatomies. Predictively modeling the mechanical behavior of 3D printed parts comprised of PCL improves the ability to develop patient specific devices that meet design requirements while reducing the testing of extraneous design variants and development time for emergency devices. Predicting mechanical behavior of 3D-printed devices is limited by the variability of effective material moduli that are determined in part by the 3D printing manufacturing process. Powder fusion methods, specifically laser sintering, are known to produce parts with internal porosity ultimately impacting the mechanical performance of printed devices. This study investigates the role of print direction and part size on the material and structural properties of laser sintered PCL parts. Solid PCL cylinders were printed in the XY (perpendicular to laser) and Z direction (parallel to laser), scanned using microcomputed tomography, and mechanically tested under compression. Compositional, structural, and functional properties of the printed parts were evaluated with differential scanning calorimetry, gel permeation chromatography, microcomputed tomography, and mechanical testing. Computational models of printed and scanned cylinders were fit to experimental data to derive effective moduli. Effective moduli were used to predict the mechanical behavior of splints used for emergency repair of severe tracheobronchomalacia. Laser sintering did not cause significant differences in polymer material properties compared to unmanufactured powder. Effective moduli (Eeff) were greater for larger part sizes (p < 0.01) and for parts oriented in the XY direction compared to the Z direction (p < 0.001). These dependencies were congruent with the differences in void volumes associated with the print direction (p < 0.01) and part size (p < 0.01). Finite element models of splint parallel compression tests utilizing the Eeff dependent on print direction and size agreed with experimental closed compression tests of splints. Evaluating the microstructural properties of printed parts and selecting effective moduli for finite element models based on manufacturing parameters allows accurate prediction of device performance. These findings allow testing of a greater number of device design variants in silico to accomodate patient specific anatomies towards providing higher quality parts while lowering overall time and costs of manufacturing and testing.

Microstructure and Mechanical Property of High Strength and High Toughness Titanium Alloy by Laser Deposition Manufacturing

In this study, the high strength and high toughness Ti-6Al-3Mo-2Sn-2Zr-2Cr alloy was fabricated by the laser deposition manufacturing (LDM) technology. The effect of process parameters on the forming quality of LDMed alloy was studied. The microstructure and mechanical properties of LDMed Ti-6Al-3Mo-2Sn-2Zr-2Cr alloy was deeply analysed by the optical microscope, scanning electron microscope, tensile tester and impact tester. The results show that the optimized process parameters are as follows: laser power is 2.4 kW, scanning speed is 10 mm/s and scanning interval is 2.4 mm. Due to the temperature gradient, the LDMed titanium alloy shows obvious microstructure anisotropy exhibiting fine β equiaxed grain in scanning direction (XY direction), but shows coarse β columnar grain in deposition direction (Z direction). The micro-morphology exhibits classic dual-phase microstructure with basket appearance composing of equally distributed α phase and metastable β-transformed phase. Due to the grain boundary strengthening effect, obvious mechanical anisotropy can also be observed in LDMed titanium alloy showing a higher tensile strength, lower plasticity and impact toughness in XY direction, but reverses in Z direction.