Laser powder bed fusion (L-PBF) technology offers significant advantages, such as lightweight and miniaturized product fabrication and short manufacturing cycles. Circular channels are widely ...utilized in hydraulic manifold blocks due to their favorable hydrodynamic properties. However, when manufactured using L-PBF, circular channels often exhibit shape deviations caused by residual stresses. In this study, Ti6Al4V (TC4) circular channels with various processing parameters were produced through L-PBF. The influence of scanning speed and laser power on the actual channel profile was investigated. A novel deformation prediction model for circular channels was established based on the Euler–Bernoulli theory. This model accurately predicts deformations resulting from residual stresses during horizontal manufacturing of circular channels using L-PBF, considering the interaction between forces and deformations across different manufactured layers. Furthermore, the model can be employed for channel shape compensation design. The results indicated excellent agreement between the proposed deformation prediction model and the profile of the experimentally manufactured samples. Using the channel shape compensation model for circular channels substantially can reduce the root mean square (RMS) deviation, thereby improving dimensional accuracy.
Low thermal conductivity and poor shape stability have significantly restricted the wide application of phase change materials (PCMs). In this work, a lightweight, mechanically strong, high-quality ...graphene aerogel was successfully prepared and used to encapsulate polyethylene glycol (PEG). After impregnating PEG into the porous graphene aerogel, a composite PCM was obtained. Owing to the preconstructed thermally conductive pathway of the graphene aerogel, the composite PCM obtained much higher thermal conductivity than neat PEG. The composite PCM also had a high latent heat of fusion and outstanding thermal cycling stability. Furthermore, the mechanically strong graphene aerogel also greatly benefited the shape stability of the composite PCM, making it capable of keeping the original shape and preventing leakage of PEG above the melting temperature. We also demonstrated that a composite PCM with such commendable comprehensive properties holds tremendous promise in fields of solar energy harvesting, thermal energy storage and thermal management.
In this work, form-stable phase change composites (PCCs) with high thermal conductivity and adjustable thermal management capacity are prepared based on phase change microcapsules (SiO2@SA) and ...surface-modified boron nitride (m-BN). The phase change properties are successfully infused into PCCs through the incorporation of microcapsules and the thermal conductivity can be elevated up to 0.506 Wm-1K-1. Furthermore, the phase change enthalpies of PCCs can be facilely tailored from 3.74 J/g to 18.52 J/g by changing the loading fraction of microcapsule, enabling adjustable thermal energy storage and thermal management ability. PCCs are proved to possess outstanding long-term stability even after 500 cycles of charging-discharging. Besides, practical application of PCCs as thermal regulating materials is explored through a self-designed temperature control system. Finally, the PCCs exhibit good leakage proof property at 100 °C due to the shielding effect of SiO2 shell. These results show that this work offers a promising strategy for the development of advanced form-stable PCCs with good comprehensive properties.
•Form-stable PCCs are developed based on a core-shell structural microcapsule and surface-modified boron nitride.•The PCCs possess high thermal conductivity up to 0.506 Wm-1K-1.•The phase change enthalpy can be easily tailored from 3.74 J/g to 18.52 J/g.•The PCCs are proved to have efficient thermal management ability in practical application.
In the present work, poly(vinyl formal) (PVF) foams were prepared using water as the pore‐forming agent and formaldehyde as the crosslinking agent. The acetalization process of poly(vinyl alcohol) ...was exploited in depth in order to obtain a precise guidance on the preparation of PVF foams with adjustable properties. With the increasing of formaldehyde, the crosslinking degree was gradually increased and the prepared PVF foams changed to be amorphous. Morphology observation showed that the porous structure of PVF foams was successfully created using water as the blowing agent and it was strongly affected by the crosslinking agent and polymer concentration, leading to an easily tuned pore size from hundreds of microns to few microns. The prepared foams were proved to have small apparent density below 0.27 g/cm−3 and excellent mechanical strength, with the largest specific compressive strength of 11.54 MPa·cm3·g−1. Based on the results, it is believed that this study can provide a scientific basis for the design and optimization of PVF foams with controllable structure and properties.
Based on the transmission theory of single roller enveloping end face meshing worm drive and isothermal elastohydrodynamic lubrication theory， and considering the influence of surface wavy roughness， ...a numerical analysis method is adopted to analyze the influence of different meshing positions， roughness amplitude， roller radius and throat diameter coefficient on the elastohydrodynamic lubrication performance of transmission pair. The results show that the lubrication performance is the worst at the top of the worm gear at the meshing position of the transmission pair， and the increase of roughness amplitude， roller radius and throat diameter coefficient has a positive effect on the lubrication performance， and makes the oil film thickness increase and the oil film pressure decrease.
