Xz Plane Research Articles

Nanoindentation creep response of Ti–6Al–4V ELI alloy manufactured via laser powder bed fusion

The anisotropic creep response in both the XY and XZ planes of Ti–6Al–4V ELI manufactured by powder bed fusion (PBF) was examined under nanoindentation creep loading at room temperature, ranging from nm to μm scales. The stress exponent values of 4.06–4.30, rationalised through threshold stress, indicate that the creep behaviour is primarily dominated by dislocation gliding. Creep displacement results show that the anisotropic creep behaviour in the XY and XZ planes of the as-built, and heat treatment enhances the creep resistance of the XZ plane, while there is no significant difference in creep displacement between the as-built and heat-treated XY planes. Due to the higher dislocation density and compressive residual stress in the XY plane compared to the XZ plane, the creep resistance is higher in the XY plane for the as-built. It is highlighted that compressive residual stress is more relieved in the XY plane than in the XZ plane through heat treatment. The heat treatment results in improved creep resistance due to the formation of the Widmanstätten structure and β precipitates, which can impede dislocation movement under creep loading. The combination of residual stress and microstructural effects leads to anisotropic creep behaviour, suggesting that the anisotropy is inherited from the additive manufacturing process at micron scales.

A comprehensive study of the effect of scanning strategy on IN939 fabricated by powder bed fusion-laser beam

This study provides a comprehensive investigation into the effects of different scanning strategies on the material properties of IN939 fabricated using the PBF-LB process. The scanning strategies examined included alternating bi-directional scanning with rotation angles of 0°, 45°, 67°, and 90° between adjacent layers (named as shown), as well as alternating chessboard scanning with rotation angles of 67° and 90° (named as Q67° and Q90°). The results revealed that the 45° and 67° samples had the highest relative density, while the 0° and Q67° samples showed the highest average porosity. Moreover, various types of cracks, including solidification, solid-state, and oxide-induced cracks, were observed. Among the bi-directional scan samples, the 0° sample displayed the most extensive cracking and the highest σmax residual stress values in both XZ and XY planes. Conversely, the 45° and 67° samples exhibited fewer cracks. Notably, the lowest σmax residual stress in the XZ planes among the bi-directional scan samples was observed in the 67° sample. Additionally, microstructural analyses indicated differences in grain size and morphology, among the samples. Texture analysis indicated that the 0° and 90° samples exhibited strong cube textures, whereas the texture intensity weakened for the 45° and 67° samples. Moreover, the alternating chessboard scanning strategy led to rougher surfaces (higher Sa and Sz values) compared to the alternating bi-directional scanning strategy, regardless of the rotation angles. Furthermore, the microhardness values among the samples showed minimal variance, ranging between 321 ± 14 HV and 356± 7 HV.

Scan accuracy of wireless intraoral scanners while digitizing a combined scan body-healing abutment system: Scan accuracy of wireless scanners

To investigate the accuracy (trueness and precision) of wireless and wired intraoral scanners (IOSs) when scanning an implant with the combined healing abutment-scan body (CHA-SB) system. A partially edentulous mandibular model with a CHA-SB at the right first molar site was digitized with 2 wireless (NeoScan 2000 (NW) and TRIOS 4 wireless (T4W)) and 2 wired (NeoScan 1000 (N) and TRIOS 4 wired (T4)) IOSs 44 times in total (n=11). The reference scan file was generated by digitizing the same master model and CHA-SB with an industrial-grade optical scanner. All files were imported into a metrology-grade analysis software program to evaluate the surface (root mean square, RMS), linear, and angular deviations of the top part of the SB. The average deviation values defined the precision of the scans. The data were statistically analyzed (α = 0.05). IOS type affected the surface and angular deviations and the precision (linear deviations on the x-axis) of the scans (p ≤ 0.043). T4W had lower RMS than N and T4 (p ≤ 0.031). T4 had higher angular deviations than N on the XZ plane and had the lowest angular deviations on the YZ plane (p ≤ 0.011). T4W scans had higher precision than N scans (p = 0.024). Despite some differences in the trueness or precision of scans, tested IOSs mostly enabled similar scan accuracy. Regardless of the IOS, the implant scans had a tendency to tilt mesiobuccally, which can be considered clinically small. Tested wireless intraoral scanners may be suitable alternatives to their wired counterparts while digitizing an implant with a combined healing abutment-scan body system in the posterior region. However, the crowns fabricated from tested scans might require buccal, mesial, and occlusal surface veneering and distal surface adjustments.

Analysis of the mechanical behavior of asphalt pavement under multiple coupling effects

To reveal the damage mechanism of asphalt pavement caused by the spatial rotation of the stress principal axis, and the influence range of excess pore water pressure on the pavement under the coupling action of multiple fields, the finite element software was used to build the three-dimensional highway asphalt pavement models. Under the consideration of gravity's impact on dynamic computation results, the study investigated the variation patterns of the direction cosines of the principal stress axes of asphalt structural pavement elements under the action of moving loads, as well as the distribution laws of excess pore water pressure. The results indicate that the influence of gravity on dynamic computation results increases gradually with the depth of the pavement, reaching an error of first principal stress of 40.1 % at the bottom of the lower layer. During the movement of loads, the pavement elements directly under the load undergo rotation of the principal stress axes in the xy, xz, and yz planes under different physical fields. With increasing pavement depth, the angle between the first principal stress and the z-axis primarily fluctuates between −90° to 0° and 90° to 180°. The cosine of the angle between the first principal stress and the x-axis and z-axis undergoes instantaneous positive and negative conversion, which can easily lead to transverse and longitudinal cracks on the road surface. The influence widths of excess pore water pressure along the longitudinal and transverse directions of the pavement increase with the pavement depth, with maximum widths of 5.426 m and 2.075 m, respectively. These findings offer new insights into the mechanisms behind the formation of transverse and longitudinal cracks on asphalt pavement and hold significant implications for the improvement of asphalt design methods.

Microstructure-induced anisotropic biocorrosion response of laser additive manufactured WE43 alloy

The microstructure and corrosion of laser-processed WE43 was studied. Results suggest that multi-factors like grain structure, crystallographic defect, and precipitate distribution result in an anisotropic corrosion response. XY plane with high crystal defect densities offers more sites for pitting corrosion. Filiform corrosion is detected on both XY plane and XZ plane, where Zr-rich and RE-rich precipitate distribution plays an essential role in corrosion initiation and propagation. The enrichment of Zr around filament corrosion promotes local micro-galvanic corrosion. Notably, the XY-plane, with continuous distribution and extended scanning trajectory edge, is particularly susceptible to filiform corrosion as compared with XZ-plane.

Laser powder bed fusion of Mg–Zn–Zr alloy: Formability, microstructure evolution and biodegradation behavior

Laser powder bed fusion (LPBF) was used to fabricate Mg–Zn–Zr (ZK60) parts, with a thorough investigation of processability by varying laser power and scanning rate. The combined effect of these parameters, which determines laser energy density, significantly impacted the forming quality of LPBF ZK60. Dense parts (over 99%) free of visible defects such as pores and cracks were achieved at a laser energy density of 74.1 J/mm2. The formation mechanisms of pores and cracks were extensively analyzed concerning the characteristics of the molten pool and subsequent cooling behavior. The LPBF ZK60 parts exhibited extremely fine grains, with an average grain size of 3.2 μm. Both equiaxed and columnar grains were observed, with a central equiaxed zone in the melt pool and a perpendicular lamellar zone along its boundary. Additionally, the Mg7Zn3 eutectic phase precipitated within the α-Mg matrix of ZK60. Immersion and electrochemical tests indicated that the XZ plane displayed superior corrosion resistance, attributed to fewer deformation regions and lower dislocation density. Furthermore, in vitro cell experiments confirmed that the ZK60 alloy possesses good biocompatibility.

Research on positioning accuracy of the swivel head of milling and turning complex machining center

Abstract This article focuses on the swivel head of a milling-turning complex machining center and establishes a geometric error model between the rotary axes based on the multi-body system theory and the homogeneous coordinate transformation method. The double ball bar (DBB) is used to identify the geometric errors of the machine tool swivel head position-independent by measuring circular trajectories. The impact of PIGEs on the measurement trajectory is simulated. The swivel head is rotated at four angles (B0°, B45°, B90°, B-15°), and the laser tracker is used to analyze and study the linear axis straightness, perpendicularity, and the center coordinates and plane errors of the swivel head movement along the XZ plane. A swivel head rotation accuracy test fixture is designed to correct the positioning accuracy of a swivel head with a 45° inclination of the rotation axis. The research results show that the fluctuation of the center plane degree of freedom of the swivel head moving along the XZ plane is small, and the maximum value is 0.0086mm. Under the 45° angle posture of the swivel head, both the center coordinate error value and the plane error value are the largest. The simulation results of the swivel head position error are fairly consistent with the center coordinate error of the swivel head plane movement. A backward tilt displacement of 0.01mm~0.015mm of the machine column during assembly can reduce the influence of the weight of the swivel head on the perpendicularity and straightness of the vertical reciprocating motion, and adding auxiliary support near the base of the swivel head zero position can reduce machine straightness error.

Polarized Raman Study of First-Order Phonons in Self-Flux Grown Single-Crystalline WTe2.

Bulk single crystals of WTe2 were grown by the self-flux method and characterized by X-ray diffraction, polarized micro-Raman spectroscopy, and optical microscopy. All methods revealed a high crystalline quality, thus demonstrating the advantages of the growth method used as a starting base for the synthesis of high-quality 2D materials. In each main scattering configuration, we recorded a series of Raman spectra in different sample orientations achieved by rotating the sample around the incident laser beam. In addition to the well-established case of excitation along the c crystal axis, we also applied laser excitation along the a and b axes. Thus, scattering configurations were also realized in the XZ and YZ polarization planes, for which no comparative literature data have yet been established. In these experiments, two new Raman-active phonons with B2 symmetry and frequencies of 89 cm-1 and 122 cm-1 were identified. The obtained experimental data enabled us to derive the magnitude ratios of all three tensor elements of the A1 modes and to find their phase differences.

Numerical and Experimental Modal Analysis of a Gyroid Inconel 718 Structure for Stiffness Specification in the Design of Load-Bearing Components.

The study aims to investigate the modal properties of a 60 × 70 × 80 mm gyroid structure made of Inconel 718 with 67.5% porosity. The geometry model for sample production was created using the software PTC Creo, whereas the geometry model for numerical analysis was created using the Python application ScaffoldStructures. FE analysis was performed using ANSYS 2024 R1 software. Free boundary conditions were used in experimental modal analysis to ensure feasibility. The analysis identified the first four natural frequencies ranging from 10 to 16 kHz. The results revealed that the first natural frequency corresponds to the first torsional frequency about the Z axis, the second to the first flexural mode in the XZ plane, the third to the first bending mode in the YZ plane, and the fourth to the first torsional mode about the X axis. Small differences between the results of numerical and experimental modal analysis can be attributed to geometric errors in the manufactured sample, careless removal from the platform, and due to reduction in the complexity of the numerical FE model. Employing modal analysis of a component, the stiffness of a lightweight component can be revealed. In the case of the sample with the cellular structure of gyroid type, relatively high stiffness regarding the material savings was identified, which can be advantageously used in many applications.

Powder Bed Fusion-Laser Beam of IN939: The Effect of Process Parameters on the Relative Density, Defect Formation, Surface Roughness and Microstructure.

This study investigates the effects of process parameters in the powder bed fusion-laser beam (PBF-LB) process on IN939 samples. The parameters examined include laser power (160, 180, and 200 W), laser scanning speed (400, 800, and 1200 mm/s), and hatch distance (50, 80, and 110 μm). The study focuses on how these parameters affect surface roughness, relative density, defect formation, and the microstructure of the samples. Surface roughness analysis revealed that the average surface roughness (Sa) values of the sample ranged from 4.6 μm to 9.5 μm, while the average height difference (Sz) varied from 78.7 μm to 176.7 μm. Furthermore, increasing the hatch distance from 50 μm to 110 μm while maintaining constant laser power and scanning speed led to a decrease in surface roughness. Relative density analysis indicated that the highest relative density was 99.35%, and the lowest was 93.56%. Additionally, the average porosity values were calculated, with the lowest being 0.06% and the highest reaching 9.18%. Although some samples had identical average porosity values, they differed in porosity/mm2 and average Feret size. Variations in relative density and average porosity were noted in samples with the same volumetric energy density (VED) due to different process parameters. High VED led to large, irregular pores in several samples. Microcracks, less than 50 μm in length, were present, indicating solidification cracks. The microstructural analysis of the XZ planes revealed arc-shaped melt pools, columnar elongated grains aligned with the build direction, and cellular structures with columnar dendrites. This study provides insights for optimizing PBF-LB process parameters to enhance the quality of IN939 components.

Pressure induced impact on mechanical, electrical, optical, and thermal properties of Li4OX2 (X = Cl, Br and I): DFT study

We investigate the pressure effect on Li4OX2 (X = Cl, Br, and I) for the first time using DFT simulation. Li4OCl2 shows mechanical stability up to 8 GPa, whereas Li4OBr2 has stability up to 30 GPa pressure according to the Born stability criteria. In contrast, Li4Ol2 becomes unstable above 3.0 GPa pressure. Hence, anomalies were observed for Li4OX2 (X = Cl, Br, and I) solid electrolyte for elastic parameters, Cij under pressure study. The elastic moduli are isotropic in the xy plane, conversely, along the xz and yz plane anisotropic behavior is observed. There is a band gap that exists at zero temperature and pressure. The contribution at the fermi level mainly comes from the O 2p states. The highest reflectivity (∼98 %) was observed for Li4OCl2 at ∼ 17 eV in the IR-visible-UV region showing that this material under study may be considered as a potential coating material to avoid solar heating. The smaller value of the volume thermal expansion coefficient for Li4OCl2 indicates stronger atomic bonding exists, which was also observed from the elastic parameter analysis.

Multilayer focal plane metalens based on all-dielectric materials in the ultraviolet band

Metalens can expand optical imaging capabilities due to the ability of metasurfaces to manipulate light propagation. Multi-focal metalens have been widely used in multi-imaging systems, detectors, and laser printing. This study presents the design of a UV metalens composed of alumina nanopillars. We investigate the focusing properties of representative UVA (343 nm) at multiple focal points on the in-plane axis, off-axis, and within a single plane. In addition, we extend the focusing ability of the metalens with multiple focal planes. We design the metalens with multiple imaging capabilities and produce focuses with different shapes in four focal planes. Simulation results show that the focal points of the planes have different shapes, the location of the maximum light intensity in the xz plane is in good agreement with our designed focal length, and the average focusing efficiency is greater than 60% in each plane. To evaluate the feasibility of planar spacing detection, we calculate the error-tolerant rate (Etr) of the device to be more than 90%. This work has important implications for the integrated miniaturization of UV photonic devices and the study of optical tomography.

Comparison between 2D and 3D microstructures and implications for metamorphic constraints using a chloritoid–garnet-bearing mica schist

Abstract. Despite the fact that rock textures depend on the 3D spatial distribution of minerals, our tectono-metamorphic reconstructions are mostly based on a 2D visualisation (i.e. thin sections). This work compares 2D and 3D investigations of petrography and microstructures, modal abundances, and local bulk rock composition and their implication for P–T estimates, showing the pros and cons and reliability of 2D analysis. For this purpose, a chloritoid–garnet-bearing mica schist from the Dora-Maira Massif in the Western Alps has been chosen. In particular, for 2D a thin section scan has been combined with chemical X-ray maps, whereas for 3D the X-ray computerised axial microtomography (µCT) has been applied. Two-dimensional investigations are readily accessible and straightforward but do not consider the entire rock volume features. Conversely, the rise of 3D techniques offers a more comprehensive and realistic representation of metamorphic features in the 3D space. However, they are computationally intensive, requiring specialised tools and expertise. The choice between these approaches should be based on the research aims, available resources, and the level of detail needed to address specific scientific questions. Nevertheless, despite differences in the modal distribution, the estimated bulk rock compositions and relative thermodynamic modelled phase fields show similarities when comparing the 2D and 3D results. Also, since different thin section cut orientations may influence the results and consequent interpretations, three different cuts from the 3D model have been extrapolated and discussed (i.e. XZ, YZ, and XY planes of the finite-strain ellipsoid). This study quantitatively corroborates the reliability of the thin section approach for tectono-metamorphic reconstructions, still emphasising that 3D visualisation can help understand rock textures.

Broadband CP corner-truncated microstrip antenna with irregularly hexagonal AMC for 2.45 GHz applications

This research proposes a compact broadband circularly polarized (CP) corner-truncated microstrip antenna with irregularly hexagonal artificial magnetic conductor (AMC) for 2.45 GHz WLAN applications. The corners of the radiating patch are diagonally truncated to realize circular polarization and improve axial ratio. A 5▪5 irregularly hexagonal AMC array is employed to enhance the axial ratio bandwidth (ARBW) and antenna gain. In addition, a tri-section meandering feedline is used to realize impedance matching and improve the impedance bandwidth (IBW). The AMC array is used to manipulate electromagnetic waves by suppressing surface currents and back lobe, resulting in reduced back radiation and enhanced front-to-back ratio. The simulated IBW and ARBW are 50.9% (1.86 – 3.13 GHz) and 19.3% (2.24 – 2.72 GHz) respectively, with a maximum gain of 8.9 dBic at 2.45 GHz. The measured IBW and ARBW are 42.42% (1.95 – 3.0 GHz) and 29.4% (2.03 – 2.73 GHz), with a maximum gain of 8.6 dBic. The simulated half power beamwidth (HPBW) of the proposed antenna scheme in the xz plane at 2.24 GHz, 2.45 GHz, and 2.72 GHz are 67°, 62°, and 51°, respectively. The corresponding HPBW in the yz plane are 60°, 55°, and 62°. The simulated AR beamwidth in the xz plane at 2.24 GHz, 2.45 GHz, and 2.72 GHz are 177°, 164°, and 88°, respectively. The corresponding AR beamwidth in the yz plane are 148°, 106°, and 124°. The simulated cross polarized (XP) levels at 2.45 GHz are below -19.35 dB for both planes. The measured HPBW in the xz plane at 2.24 GHz, 2.45 GHz, and 2.72 GHz are 69°, 64°, and 50°, respectively. The corresponding HPBW in the yz plane are 65°, 54°, and 37°. The measured AR beamwidth in the xz plane at 2.24 GHz, 2.45 GHz, and 2.72 GHz are 161°, 200°, and 104°, respectively. The corresponding AR beamwidth in the yz plane are 162°, 85°, and 90°. The measured XP levels at 2.45 GHz are below -15.62 dB for both planes. The radiation pattern is unidirectional. Essentially, the proposed broadband CP antenna scheme is suitable for the WLAN frequency band and other 2.45 GHz wireless communication technologies. The novelty of this research lies in the use of the tri-section meandering feedline and the irregularly hexagonal AMC array to enhance IBW and ARBW.

Finite element method analysis of bone stress for variants of locking plate placement

This study investigates the optimal placement of locking plate screws for bone fracture stabilization in the humerus, a crucial factor for enhancing healing outcomes and patient comfort. Utilizing Finite Element Method (FEM) modeling, the research aimed to determine the most effective screw configuration for achieving optimal stress distribution in the humerus bone. A computer tomography (CT) scan of the humerus was performed, and the resulting images were used to create a detailed model in SOLIDWORKS 2012. This model was then analyzed using ANSYS Workbench V13 to develop a finite element model of the bone. Four different screw configurations were examined: 4 × 0°, 4 × 10°, 4 × 20°, 2 × 20°; 2 × 0°. These configurations were subjected to bending in the XZ and YZ planes, as well as tension and compression along the Z axis. The research identified the 2 × 20°+2 × 0° configuration as the most beneficial, with average stress values below 30 MPa and peak stress values below 50 MPa in 3-point bending at the first screw. This configuration consistently showed the lowest stress values across all loading scenarios. Specifically, stress levels ranged from 20 MPa to 50 MPa for bending in the XZ plane, 20 MPa–35 MPa for bending in the YZ plane, 20 MPa–30 MPa for extension in the Z-axis, and 18 MPa–25 MPa for compression in the Z-axis. The 4 × 10° and 4 × 20° configurations also produced satisfactory results, with stress levels not exceeding 70 MPa. However, the 4 × 0° configuration presented considerable stress during bending and compression in the Z-axis, with stress values exceeding 100 MPa, potentially leading to mechanical damage. In conclusion, the 2 × 20°; 2 × 0° screw configuration was identified as the most effective in minimizing stress on the treated bone. Future work will involve a more detailed analysis of this methodology and its potential integration into clinical practice, with a focus on enhancing patient outcomes in bone fracture treatment.

Laser powder bed fusion of high-strength low-alloy steels with post-heat treatment design for enhanced mechanical performance

A commonly used structural steel, namely high-strength low-alloy (HSLA) steel, HSLA-100, was fabricated using the laser powder bed fusion process in this work. Critical processing parameters such as laser power and scanning speed for achieving the least porosity were identified. The designed post-heat treatment differs from the traditionally manufactured HSLA steels. The optimum homogenization time was 80 min at 950 °C with the lowest prior austenite grain size. The peak hardness was achieved after tempering at 550 °C for 5 h, and atom probe tomography showed that the fraction of Cu and M2C (M: Mo, Cr) was the highest along with the co-precipitation of these strengthening phases at this condition. The yield strength (YS) and elongation (%El) of the builds printed with optimized parameters (porosity∼0.5%, YS = 875 MPa, and %El = 23%) were superior to those printed with factory-default parameters (porosity∼3%, YS = 772 MPa, and %El = 15%) after applying the designed post-heat treatment. Despite the anisotropy observed in the low-temperature toughness, the ductile-to-brittle transition temperature is below −40 °C for samples with a notch in the XZ plane and between −20 and −40 °C for samples with a notch in the XY plane. This work demonstrates the successful adaptation of HSLA-100 steel in additive manufacturing, and thus is critical for scaling up engineering applications at a higher technology readiness level.

High acoustic velocity x-cut lithium niobate sub-terahertz electromechanics

Micromechanical resonators operating above 100 GHz are favorable candidates for quantum physics studies due to their stronger ability to withstand thermal fluctuations, allowing them to remain in the quantum ground state even at kelvin temperatures. Furthermore, electromechanical resonators at sub-terahertz frequencies enable high-speed data transfer in modern communication technologies, making them attractive for communication industries. Recently, sub-terahertz electromechanics has been demonstrated on z-cut thin-film lithium niobate. Yet, the x-cut thin-film lithium niobate is more advantageous for scaling above 100 GHz due to its faster acoustic velocity. Here, we report sub-terahertz electromechanics on x-cut thin-film lithium niobate utilizing the thickness-longitudinal mode. In addition, we study the orientation dependence of these mechanical resonators due to the anisotropy of lithium niobate. We find that devices with a cross section close to the xy plane can be more efficiently excited, in contrast to those near the xz plane. This difference stems from the orientation-dependent nature of the e12 piezoelectric coupling element of the x-cut lithium niobate film. This investigation could assist in optimizing resonator designs by choosing the crystallographic direction that offers the best performance for specific functionalities.

A comparative study on Al-Mg-Sc-Zr alloy fabricated by wire arc additive manufacturing with controlling interlayer temperature and continuous printing: Porosity, microstructure, and mechanical properties

Wire arc additive manufacturing (WAAM) technique is a promising approach to producing large-scale metal components due to high deposition efficiency and low production cost. However, fundamental research about WAAM-processed Al-Mg-Sc-Zr alloy was still fewer. In this study, Al-6.54Mg-0.36Sc-0.11Zr (wt%) components were successfully manufactured by WAAM with an interlayer temperature at 100 °C (named IW) and continuous printing (named CP), and the corresponding porosity, microstructure, and mechanical properties of components were studied in detail. The porosity of components as-deposited was relatively low, about 0.385% and 0.116%, respectively. The microstructures of the two components exhibited the same distribution characteristics in XZ and YZ planes: fine equiaxed grains (FEG) at remelted zone + FEG and coarse equiaxed grain (CEG) alternative distribution at middle zone + FEG at the top zone of the molten pool. The average grain size of component IW was about 10.51 ± 6.01 μm, and that of component CP significantly increased, to about 11.85 ± 5.86 μm. The short-circuit transition mode of cold metal transfer technology and the heterogeneous nucleation effect of primary Al3(Sc, Zr) and Al3(Sc, Zr, Ti) phases together promoted the formation of equiaxed grains and refined the microstructures. After heat treatment at 325 °C and 6 h, nano-Al3Sc precipitated with a size of about 15–50 nm. The yield strength (YS) of components IW and CP increased from 171 ± 3 to 261 ± 1 MPa and 168 ± 7 to 240 ± 17 MPa, respectively. Component IW had the highest ultimate tensile strength, about 400 ± 1 MPa. For WAAM-processed Al-Mg-Sc-Zr alloys, the contribution of the strengthening mechanism to YS was solid solution strengthening > precipitation strengthening > fine grain strengthening > dislocation strengthening.

3D printed sequence-controlled copolyimides with high thermal and mechanical performance

Inadequate heat resistance and mechanical property limited the application of 3D printed polymer parts in aerospace industry. To address this restriction, a kind of sequence-controlled copolyimides with both amorphous segment and crystalline segment, suitable for fused deposition modeling 3D printing technique were designed and synthesized. The effect of content and distribution of crystalline segment on melt fluidity and crystallization behavior was disclosed. It was found that copolyimide with crystalline segment only distributed in the end of backbone exhibited good melt fluidity and slow crystallization rate. Microstructure change of the corresponding copolyimide during 3D printing and thermal annealing was revealed. Due to slow crystallization rate of copolyimide, no crystals formed during 3D printing. Thus, the diffusion and entanglement of polymer chain at interface were guaranteed. Thermal annealing at 350 °C facilitated diffusion and arrangement of polymer chain, leading to the enhancement of interfacial bonding and crystallization of copolyimide at interface and in filament. Therefore, the printed copolyimide specimens exhibited high heat resistance, high mechanical property and excellent interfacial bonding performance. The tensile strength of specimens printed in XY plane with 0° infill direction (XY-0), XY plane with 90° infill direction (XY-90) and XZ plane with 90° infill direction (XZ-90) were 110 MPa, 96 MPa and 57 MPa, respectively. The tensile strength of XY-0 printed specimen at 200 °C was 186 % higher than that of XY-0 printed amorphous polyimide specimen, reaching 40 MPa. This study expanded the kinds of polymeric materials suitable for fused deposition modeling, and provided the possibility of printing high performance engineering parts.

Reflection of quasi plasma wave in photo-piezo semiconductor medium with distinct higher order fractional derivative two temperature models

This article investigates the reflection of thermo-photo-piezo-elastic plane waves from a homogeneous, orthotropic, and piezo semiconductor medium during the photo-thermal process. A novel higher-order fractional dual-phase lag hyperbolic two-temperature model is employed to tackle this study. The analytical solution to the problem in the xz plane reveals the existence of five interconnected waves. The derivation of formulas for reflection coefficients and their corresponding energy ratios is performed for an incident quasi-plasma wave. Numerical computations determine the energy ratios for different angles of incidence. These energy ratios are visually represented in graphs, demonstrating the influence of higher-order parameters, two-temperature effects, fractional order derivatives, and various heat conduction models.