To enhance the overall performance of the manifold microchannel system, this study proposes a novel array column configuration based on the design of array manifold microchannels, numerical simulation methods are adopted herein, with HFE-7100 employed as the coolant and silicon as the solid material. The effects of rectangular, trapezoidal, and circular column microchannel structures on heat dissipation, pressure drop, flow characteristics, and comprehensive performance are investigated under both in-line (parallel) and staggered (cross) array arrangements. Additionally, the relationship between pressure drop and viscous/inertial resistance within the structure is analyzed using the porous medium model. The results indicate that, compared to the rectangular column array, the circular column array achieves an 11.2% increase in flow velocity, although with a corresponding rise in pressure drop. When the array arrangement is changed from in-line to staggered, fluid disturbance is enhanced and the thermal boundary layer is effectively suppressed, resulting in an average improvement of 13% in heat dissipation capacity. Although the staggered array improves thermal performance, it also leads to an average pressure drop increase of 6.6%. The comprehensive performance of the staggered array column structure is significantly higher than that of the in-line array, with an average improvement of 7.7%. Considering both heat dissipation and pressure loss, the circular staggered array exhibits the highest comprehensive performance index η due to its elevated viscous and inertial resistance. Furthermore, compared to the rectangular column structure, the circular column structure shows a 38.8% increase in inertial resistance and a 110.2% increase in viscous resistance. 

Biodegradable poly-lactic acid (PLA) stents reduce the risk of restenosis and late thrombosis, but their clinical adoption is limited by the trade-off between radial strength and deliverability. To address this, a novel auxetic-structured PLA (ASP) coronary stent is proposed. Finite element analysis was conducted to evaluate its performance against commercial Absorb and Fantom stents. The ASP stent achieved a 12.6% higher radial strength than the Fantom stent, along with -31.3% axial foreshortening, as well as reduced radial recoil and plastic strain. This improvements are attributed to the synergistic combination of PLA's properties and auxetic structure, which balances stability with deliverability.

This work presents four sets of welded multi-wires on Cu sheet (e.g., A-(95/95mm2), B-(35, 35, 25/35, 35, 25 mm2), C-(50, 35, 10/50, 35, 10 mm2), D-(35, 35, 25/50, 35, 10 mm2)) using ultrasonic wire harness welding (USWW). Forming quality of multi-wire joint, examination of microstructures, root gaps influence, fractographic analysis and surface micro-topography were investigated and clarified. Tensile strength and microhardness of samples in B-(35, 35, 25/35, 35, 25 mm2) increases up to peak load (6527.7 N and 484.5 HV) under welding energy of 1000 J. Tensile strength of B-(35, 35, 25/35, 35, 25 mm2/(6527.7 N)) is 29.2 % higher than A-(95/95mm2/(3681 N)) under effect of root gap. Maximum hardness of Cu plate in group B was obtained 484.5HV and maximum hardness of sample reached 363.2HV and 251HV in group C and A respectively. Stability of sample in group B is generally increased by 20.5 % compared to A3, C5 and D2. Failure displacement of joint A3 is 35 % higher than joint B1. Failure displacement of joint C5 is 15 % higher than joint D2. EDS analysis experienced Cu content at welded interface is higher compared to rest of locations which generates more fine grains structures to increase strength and weldability of joints. Kathmatic microscope investigated microtopographical features in group B sample wherein regular surface size was measured to be approximately 10μm. A standard root gap allows welded sheet to penetrate amid multi-wires being joined tightly and ensures a strong bond in group B. 

By the finite element analysis software ABAQUS, utilizing General Contact and Contact damping algorithm, the brush seal hysteresis numerical model with pressure differential considered was established. The hysteresis was quantified by the hysteresis energy, and the hysteresis energy and maximum stress are obtained by numerical calculations. An orthogonal test was conducted to study the effects of bristle diameter, bristle cant angle, fence height, bristle length, upstream and downstream differential pressure, and rotor radial displacement on the hysteresis and maximum stress of the brush seal. Results show that the primary and secondary orders of parameters affecting hysteresis are: rotor radial displacement, bristle diameter, upstream and down-stream differential pressure, bristle cant angle, bristle length, and fence height. The primary and secondary orders of parameters affecting maximum stress are: upstream and downstream differential pressure, fence height, bristle cant angle, bristle diameter, bristle length, and rotor radial displacement. Finally, based on the numerical results, a fitted correlation was developed. Comprehensive effects of the six parameters on both performances were analyzed, and structural design optimization methods focusing on single performance and comprehensive performance were proposed, providing references for the design of brush seals in practical engineering applications.

The microchannel heat sink is a commonly used structure in mechanical cooling systems for microelectronics. Based on bionics, a simplified heat sink with a spider-web design is proposed in this paper. Under the condition of bottom heat flux q = 100 W/cm2 and Reynolds number (Re) = 442-884, the influence of three parameters (main channel width, branch width and rib width) on the performance of a spider web microchannel heat sink (SW-MCHS) under different Re conditions was numerically analyzed by computational fluid dynamics. The results showed that the main channel had the greatest influence on the Nusselt number (Nu) and the Euler number (Eu); With the increase of main channel width, Nu increased by 46.97%, and Eu decreased by 31.74%. Rib width had the smallest influence on Nu and Eu; AWith the increase of rib width, Nu decreased by 7.18%, and Eu decreased by 12.00%. Based on the research results, the correlations for predicting Nu and Eu of the SW-MCHS were fitted; the Radj2 values for the two correlations were 0.9523 and 0.9246, respectively. These fitting correlations could be used to predict Nu and Eu for the SW-MCHS. The present study has contributed to advancing the applications of microchannel heat sinks and enhancing the cooling efficiency of mechanical microelectronics cooling systems.

With the rapid development of new energy vehicles and power electronics industry, the stability and durability of automotive wiring harness connections have become key technical issues. In this paper, a thermal shock test is designed for aging phenomenon caused by extreme temperature conditions of 25 square copper wire harness-terminal connectors in actual use of vehicles. The results show that after 72 thermal shock cycles, the grain organization of copper wire inside connector is significantly refined and the percentage of large-angle grain boundaries is increased. In addition, the distribution of cubic texture orientation {100} <001> weakens and transforms towards the shear texture {111} <111> parallel to the Z direction of common grain organization. In tensile test, the average tensile strength of joints after thermal shock increased by 6.08 %. The resistance of aged joints increased by 14.75 %, but still met the electrical safety standards. The temperature rise of joint resistance increased by 3.81 degrees C after being connected to a constant current of 100A and lasting for 2.5 h. In terms of corrosion resistance, the improvement of joints after thermal shock test is related to microstructural changes in joint material. Grain refinement introduced a high fraction of grain boundaries and more grain boundaries were able to act as barriers to prevent the penetration and diffusion of corrosive media.

The ultrasonic welding technology is widely promoted as a new connection approach in the field of current energy vehicle wiring harness connection. In this paper, three kinds of 25mm2 copper wire harnesses with different wire diameters and T2 copper terminals with different surface roughness were welded by ultrasonic welding. The mechanical properties of the joints were investigated by tensile experiments and the microstructure of joints was characterised using SEM and EBSD techniques. Excessive roughness increases plastic deformation at the weld interface during ultrasonic welding. This increases the dislocation density at the weld interface and refines the grain size. However, at the same time it inhibits recrystallisation to a certain extent. The lower roughness facilitates recrystallisation, but the low density of HAGBs makes the interface susceptible to slip in extended crystallographic plane and direction. Appropriate roughness allows the weld interface to generate fine equiaxed grains and a high density of HAGBs. This facilitates the obstruction of dislocation movement and improves the strength of joint. In addition, the high porosity of a longitudinal cross-section of the conductor with its small diameter was investigated. This results in a large number of wires remaining on the terminals when force is applied. It was determined that the larger a diameter of wire, the higher a cross-sectional porosity. The copper wire breaks at a weak point in cross-section when the force is applied, resulting in the entire wire being left on terminal. At a wire diameter of 0.2 mm, the porosity of a cross-section reaches an equilibrium and the strength of joint is even higher than the strength of material itself, resulting in the joint pulling off. The maximum strength reaches 4703.77 N. © 2024

In this paper, we present an investigation of ultrasonic welding performance for 25 mm2 copper wire and T2 copper plate across various welding parameters using orthogonal experimentation. The objective of this work was to explore the influence of operational parameters on the resulting welds. A comprehensive study of the mechanical properties and microstructure of the copper wire-to-copper plate joint was carried out using a series of sophisticated instruments. It includes a universal tensile machine, resistance measuring equipment, SEM, EDS and temperature measuring tool. This multifaceted approach enabled a detailed analysis of the joint's integral features and properties. This provides further insight into its performance and durability. Findings indicate that welding pressure has the most significant effect on welded joints. The optimal combination of parameters is achieved with the welding energy set at 6000 J, the welding amplitude at 85% and the welding pressure at 260 kPa. In different sets of welding parameters, joint strength is positively related to welding parameters and increases with increasing welding parameters. Joint resistance decreases with increasing joint tensile load and conductivity can be used to evaluate ultrasonic welding. It has been found that the development of the welded joint is achieved gradually in a direction moving inwards from the welding tool head, exhibiting a methodical forming process. Three distinct failure modes are observed in welded joints such as joint pullout, joint tearing and busbar breakage. The peak temperature during the welding process was recorded at 373 °C which indicates that the ultrasonic welding is a solid state connection. © The Author(s), under exclusive licence to Korean Society for Precision Engineering 2024.

An experimental characterization of the mechanical properties in a low-density polyethylene (LDPE) film is performed in this article. Anisotropy in LDPE at different in-plane material orientations is measured from the stress–strain response and digital image correlation observations of the specimens under uniaxial tension. Finite element simulation of in-plane anisotropy of the material is carried out in Abaqus R2020 using available models like von Mises, Hill 48, Barlat Yld91, and Barlat Yld2004-18P. To express the mechanical behavior at larger strain, a suitable hardening extrapolation model is selected from a trial of several extrapolation models. To validate the simulation methods and the material characterization process, finite element simulation results such as force displacement and strain distribution are compared with the experimental data showing good agreement. Finally, a calibrated anisotropic yield model together with ductile failure criterion is shown to successfully simulate the response of precracked LDPE film under tension. Overall, this study provides valuable insights into the modeling of LDPE polymer films with and without cracks using different anisotropic yield functions and largely simplifies material characterization with some tradeoffs. Copyright © 2024 by ASTM International

Injection-molded polyethylene plates exhibit highly anisotropic mechanical behavior due to, e.g., the uneven orientation of the polymer chains during the molding process and the differential cooling, especially in the thickness direction. Elastoplastic finite element modeling of these plates in particular is used with isotropic yield criteria like von Mises, trading off accuracy in favor of simpler constitutive characterization and faster solution. This article studies three different anisotropic yield criteria, namely, Hill 1948, Barlat Yld91, and Barlat Yld2004-18P, for the finite element modeling of low-density polyethylene (LDPE) at large uniaxial tensile deformation and compares the accuracy and computation time with von Mises. A simplified calibration technique is investigated to identify the constitutive parameters of the studied Barlat group yield criteria. The calibration process is simplified in the sense that only uniaxial tensile tests with digital image correlation measurements are used for the calibration of all the yield criteria studied in this article, although a standard calibration procedure for the Barlat group yield criteria requires additional material testing using more demanding test setups. It is concluded that both Barlat Yld91 and Barlat Yld2004-18P yield criteria can be calibrated with only a few tensile tests and still capture anisotropy in deformation–stress–strain at different levels of accuracy. © 2023 by the authors.