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With the development of microsatellite technology, the heat generated by onboard components is increasing, leading to a growing demand for improved thermal dissipation in small satellites. Metal powder additive manufacturing technology offers the possibility of customizing and miniaturizing heat pipes to meet the specific requirements of small satellites. This article introduces a small-scale heat pipe designed using selective laser melting (SLM) technology. The heat pipe's material, structure, and internal working fluid were determined based on mission requirements. Subsequently, the SolidWorks 2021 software was used for heat pipe modeling, and the ANSYS 2021R2 finite element analysis software was employed to simulate the heat transfer performance of the designed heat pipe, confirming its feasibility. The heat pipe's structure was optimized using multi-objective regression analysis, considering various structural parameters, such as the channel diameter, vapor chamber height, and narrow gap width. The simulation results demonstrate that the optimized heat pipe achieved a 10.5% reduction in thermal resistance and an 11.6% increase in equivalent thermal conductivity compared to the original heat pipe. Furthermore, compared to conventional metal heat-conducting rods, the optimized heat pipe showed a 38.5% decrease in thermal resistance and a 62.19% increase in equivalent thermal conductivity. The heat pipe was then fabricated using a 3D printer (EOS M280), and a vacuum experimental system was established to investigate its heat transfer characteristics. The experimental results show that the heat pipe operated most efficiently at a heating power of 20 W, reached its maximum heat transfer capacity at 22 W, and had an optimal fill ratio of 30%. These results highlight the excellent performance of the heat pipe and the promising application prospects for SLM technology in the field of small satellites. [ABSTRACT FROM AUTHOR]

Objectives. In the present study, we evaluated the mechanical outcome of different configurations of cannulated compression screws for the fixation of Pauwels type III femoral neck fracture and the stress distribution around the holes corresponding to fixation protocol after screws removal. Methods. The Pauwels type III of femoral neck fracture was created in 3-matic software and the models of cannulated compression screws were constructed using UG-NX software. Five fixation systems were assembled to the fracture models. Abaqus software was used to perform the process of finite element analysis. Values of stress distribution, maximum stress, model principal strains of proximal fragment, and stress distribution around the holes of femur model were recorded. Results. Stress of cannulated compression screws was intensely focused on the middle area of the screw near the fragment of each group. Inverted triangle model showed the highest peak stress on screws under different phases of load. Each screw dispersed some stresses, but at least one underwent the peak stress. Fracture model fixed by inverted triangle configuration showed the lowest volume of yielding strain in the proximal fragment. The area of higher stress around the holes was largest after triangle screws removal when compared with other four models. Conclusions. Our study indicated that different cannulated compression screws fixation configurations for the unstable femoral neck fractures showed the different mechanical efficiency. Inverted triangular configuration showed the mechanical advantage and being less likely to cutout. The fixation strategy of triangle configuration was least recommended if patients tended to remove the implants. [ABSTRACT FROM AUTHOR]

Objectives. We evaluated the biomechanical outcome of different plate fixation strategies (the single plate construct, 45° double-plate construct, 90° double-plate construct, 135° double-plate construct, and 180° double-plate construct) used for the fixation of the femoral shaft nonunion with no cortical support opposite the primary lateral plate. This may help surgeons choose the optimal therapy to the femoral shaft nonunion. Methods. The femoral shaft nonunion with no medial support and the models of lateral plate and medial plate was constructed in 3-matic software and UG-NX software, respectively. We then assembled the single plate and different double plates to the fracture model separately to form the fixation models. After meshing the models’ elements, we used the ABAQUS software to perform the finite element analysis. Values of the von Mises Stress (VMS) distribution of the implant, peak VMS, and model displacement and deformation were used to capture the mechanical factors in this study. Results. Our results indicated that the peak von Mises Stress (VMS) of the lateral plate was concentrated in middle surface of the lateral plate near the fragment of each group. The peak VMS was 5201.0 MPa (the single-plate construct), 3490.0 MPa (45° double-plate construct), 1754.0 MPa (90° double-plate construct), 1123.0 MPa (135° double-plate construct), and 816.5 MPa (180° double-plate construct). The additional short plate dispersed some stress leading to the decrease in the peak VMS of the lateral plate. As angle formed by the double plates increased, the dispersed function of the additional plate was becoming obvious. The bending angles of the lateral plate were 18° versus 12° versus 3° versus 2° versus 1° (the single-plate construct versus 45° double-plate construct versus 90° double-plate construct versus 135° double-plate construct versus 180° double-plate construct). Conclusions. Our study indicated that increasing the angle between the plates in a double-plate construct improves the stability of the construct over a single lateral plate when there is no cortical support opposite to the lateral plate. The strongest fixation occurred when the angle between the two plates was greater than ninety degrees. [ABSTRACT FROM AUTHOR]

The present study presents a novel procedure to assess the seismic slope stability, using the finite-element upper-bound method combined with the pseudo-dynamic approach. A pioneering work is performed to incorporate the pseudo-dynamic accelerations into the finite-element upper-bound analysis which combines the advantages of upper bound and finite element methods. The finite element method is principally used to discretize the domain of soil mass into finite elements, aiming to construct a kinematically admissible failure mechanism based on which the external and internal rates of work can be expressed. Based on the upper bound theorem, the upper bound formulations are derived from the virtual work rate equation, in the form of slope safety factor and limit surcharge acting on the slope crest. The problem of seeking the optimal upper bound solution is transformed to solve a linear programming problem within numerous kinematically admissible velocity fields, and this is achieved by using the interior-point algorithm implemented into the MATLAB. Pseudo-dynamic solutions are calculated and compared with the pseudo-static, limit equilibrium and FLAC results. The proposed procedure is versatile in considering the homogeneity and non-homogeneity of soil strength properties in seismic slope stability analysis. A benchmark problem with 0.5 m thick weak interlayer is discussed. [ABSTRACT FROM AUTHOR]

Objectives: In the present study, we evaluated the mechanical outcome of different configurations formed by partially threaded screws (PTS) alone or combined screws consisting of PTS and fully threaded screws (FTS) in the treatment of unstable femoral neck fracture.Methods: The Pauwels type III unstable femoral fracture and screw models of PTS and FTS were created in 3-matic software and UG-NX software respectively. We assembled the different screw fixation types to the fracture model separately to form the fixation models. We used Abaqus software to perform the finite element analysis.Results: Our results indicated that the peak von Mises stresses of screws increased when some PTSs changed into FTSs in all groups except for the inferior triangle group. FTS in each group underwent the most stress while PTS underwent a little bit of stress. The combined screws fixation types were less likely to be cut-out and was more stable than PTPs alone fixation strategy. Less yielding regions around the screw tunnels for the superior and inferior triangle configuration fixed by combined screws was indicated. Superior triangle fixation model underwent the largest area of stress concentration around the screw holes after screws removal.Conclusions: For unstable femoral neck fractures, superior results were obtained by stabilizing the fracture with superior or inferior triangle configuration consisting of one PTS and two FTSs. If screws removal was taken into account after fracture union, fixation type of inferior triangle configuration should be the recommended choice. [ABSTRACT FROM AUTHOR]

Objectives: Using finite element analysis and biomechanical tests, the biomechanical behaviors of Medial Sustainable Nail (MSN) and Proximal Femoral Nail Antirotation (PFNA) were compared for the fixation of fracture type of AO/OTA 31-A2.3.Methods: Finite element software Abaqus 6.14 was used to conduct axial loading of 2100 N and we analyzed the von Mises stress distribution and the model displacement of two implant models. Biomechanical tests were separately conducted in the axial stiffness test and axial cyclical loading test on a mechanical testing machine.Results: The results indicate that von Mises stress of MSN was lower than that of PFNA, and the model displacement in the MSN group was lower than that in the PFNA group. In the axial stiffness tests, MSN group was stiffer than PFNA construct. With respect to the axial load to ultimate failure, the PFNA construct exhibited higher loads exceeding 4000 N while the MSN construct withstood 3313.8 ± 92.8 N. Specifically, F10mm was 2178.6 ± 133.2 N of the MSN group and 1822.6 ± 93.1 N of the PFNA group (P = 0.001). Additionally, X2100N was 9.8 ± 0.5 mm of the MSN group and 11.7 ± 0.7 mm of the PFNA group (P = 0.002). The MSN group exhibited superior performances in terms of the mean value of the vertical displacement, frontal rotation angle, and lateral rotation angle.Conclusions: The results indicated that the MSN construct might exhibit a better biomechanical performance when compared with that of the PFNA in reducing displacement and anti-varus in fracture type of AO/OTA 31-A2.3. [ABSTRACT FROM AUTHOR]

Objectives: In the present study, we assessed the biomechanical advantage between the single LISS and double-plate used in AO type 33-C2 fractures with the method of finite element analysis, which will help surgeons choose the optimal therapy to the unstable distal femoral fracture.Methods: The AO type 33-C2 fractures and the models of LISS plate and medial plate was constructed in 3-matic software and UG-NX software respectively. We then assembled the single plate and the double-plate to the fracture model separately to form the fixation models. After meshing the models' elements, we used the Abaqus software to perform the finite element analysis. Values of peak Von Mises Stress (VMS) on the plate, maximum deformation of the models and the distance changes of the fracture gap were used to capture the mechanical factors in this study.Results: Our results indicated that the single LISS underwent 1.2 times higher amount of stress than the double-plate (316.0 MPa VS 281.6 MPa). And the medial plate dispersed some stresses (the maximum stress is 47.4 MPa). Single-plate generated 3 times greater bending angle than double-plate (0.6° VS 0.2°). The bending angles of the single and double-fixation-fracture models are 0.9° and 0.3° respectively. The maximum distance changes of the fracture gap in the single-plate model was 2 times higher than that of double-plate model (2.6 mm VS 1.3 mm). In the torsional load analysis, peak VMS of the single and double model was 1.0 MPa and 0.8 MPa respectively. And the bending angle was 0.8° in the single model and 0.4° in the double model.Conclusions: The double-plate is more effective scenario using in the distal femoral fractures, particular in unstable fractures with joint involvement. [ABSTRACT FROM AUTHOR]