A New Regression Model for the Prediction of the Stress-Strain Relations of Different Materials.

Experimental flow stress-strain data under different stress states are often used to calibrate the plastic constitutive model of anisotropic metal materials or identify the appropriate model that is able to reproduce their plastic deformation behavior. Since the experimental stress-strain data are discrete, they need to be mathematically returned to a continuous function to be used to describe an equivalent hardening increment. However, the regression results obtained using existing regression models are not always accurate, especially for stress-strain curves under biaxial stress loading conditions. Therefore, a new regression model is proposed in this paper. The highest-order term in the recommended form of the new model is quadratic, so the functional relationships between stress-strain components can be organized into explicit expressions. All the experimental data of the uniform deformation stage can be substituted into the new model to reasonably reproduce the biaxial experimental stress-strain data. The regression results of experimental data show that the regression accuracy of the new model is greatly improved, and the residual square sum SSE of the regression curves of the new model reduced to less than 50% of the existing three models. The regression results of stress-strain curves show significant differences in describing the yield and plastic flow characteristics of anisotropic metal materials, indicating that accurate regression results are crucial for accurately describing the anisotropic yielding and plastic flow behaviors of anisotropic metal materials.

Identification of Anisotropic Coefficients in the Non-Principal Axis Directions of Tubular Materials Using Hole Bulging Test.

We propose an experimental method to identify anisotropic coefficients in non-principal axis directions of thin-walled tubes. The method involves extracting specimens from the parent tubes and machining a hole in the axial center. The specimens are then inserted into a tube without a hole. The inner diameter of the specimen is theoretically equal to the outer diameter of the inner tube. The double-layer tube undergoes free bulging under internal pressure in our self-developed experimental equipment, with the hole on the specimen expanding simultaneously. The stress states around the hole are uniaxial, and the hole deformation can reflect the anisotropic plastic flow characteristics of the tube. Furthermore, based on the information obtained from the proposed experimental method, a hybrid numerical-experimental method was used to identify the anisotropic coefficients of tubes. Through FE simulations, the relationships between the thickness, stress, and strain states around the hole, the hole shape, and anisotropic coefficients of non-principal axis directions are revealed, and the factors that affect the hole deformation are analyzed. Finally, the hole bulging experiments and FE simulations of AA6061-O extruded tube were conducted, and modeled with Hill48 and calibrated by uniaxial tensile and hoop tensile tests. Its in-plane anisotropy coefficients in any direction are given for the first time which first increase and then decrease from 0° to 90°, reaching a maximum of 1.13 in 60° and a minimum of 0.69 in 0°. This work can provide the key experimental data for establishing an accurate anisotropic plastic constitutive model of thin-walled tubes.

Nanosecond Laser Cleaning Method to Reduce the Surface Inert Layer and Activate the Garnet Electrolyte for a Solid-State Li Metal Battery.

The garnet-type electrolyte Li6.4La3Zr1.4Ta0.6O12 (LLZTO) has been widely researched for its high ionic conductivity and excellent stability against the Li anode. However, the garnet electrolyte is susceptible to CO2 and H2O in air to form a Li2CO3 insulating layer leading to poor wettability with the Li anode, which hinders its practical application. Herein, we introduced a simple method to effectively reduce the Li2CO3 layer on the garnet electrolyte surface by laser cleaning and made the garnet surface back with lithiophilicity. The resulting Li/garnet interfacial resistance decreased to 76.4 Ω·cm2 at 30 °C and 3.1 Ω·cm2 at 80 °C. The assembled Li symmetric cell with the as-laser-treated electrolyte steadily cycled for 300 h under 0.1 and 0.2 mA·cm-2 at 80 °C. The solid-state battery coupled with the composite LiFePO4 cathode and the Li anode exhibited stable long-term cycling performance for over 100 cycles with a capacity retention of 84.8%. This work provided a novel method to reduce the surface inert layer and make the garnet electrolyte reveal the intrinsic lithiophilicity by laser cleaning process with high efficiency, which helped address the challenges for the application of garnet-based solid-state batteries.

Energy-dependent photochromism at room temperature for visually detecting and distinguishing X-rays.

A radiochromic material with energy-dependent X-ray-induced photochromism was obtained by incorporating a radiosensitive glycolate ligand into an electron-transfer photochromic metalloviologen system. It is highly promising for detecting soft X-rays with energies less than 2 keV and may find application in qualitatively and visually distinguishing the energy range of X-rays.

Pairing of Luminescent Switch with Electrochromism for Quasi-Solid-State Dual-Function Smart Windows.

Smart window is a promising green technology with feature of tunable transparency under external stimuli to manage light transmission and solar energy. However, more functions based on the intelligent management of the solar spectrum need to be integrated into present smart windows. In this work, a dual-function smart window is fabricated by pairing the luminescent switch with the electrochromic window. The dual function is based on a single fluorine doped tin oxide coated glass functionalized with tungsten oxide and copper nanocluster, among which tungsten oxide serves as an electrochromic material and copper nanocluster provides photoinduced luminescence. Along with the regulation of the visible light based on the electrochromism of the window, the luminescence can be finely switched on and off, which establishes a pair of reversible states ("on" and "off") for the dual-function smart window. The contrast between two states reaches 88%. Furthermore, the manipulation of dual-function smart window is highly reversible with a short response time of 12.6 s. This prototype of dual-function smart window paves the way for developing multifunctional smart windows by integrating different functional materials into one smart window based on the rational management of the solar spectrum.

Influence of suture size on the frictional performance of surgical suture evaluated by a penetration friction measurement approach.

The frictional performances of surgical sutures have been found to play a vital role in their functionality. The purpose of this paper is to understand the frictional performance of multifilament surgical sutures interacting with skin substitute, by means of a penetration friction apparatus (PFA). The influence of the size of the surgical suture was investigated. The relationship between the friction force and normal force was considered, in order to evaluate the friction performance of a surgical suture penetrating a skin substitute. The friction force was measured by PFA. The normal force applied to the surgical suture was estimated based on a Hertzian contact model, a finite element model (FEM), and a uniaxial deformation model (UDM). The results indicated that the penetration friction force increased as the size of the multifilament surgical suture increased. In addition, when the normal force was predicted by UDM, it was found that the ratio between the friction force and normal force decreased as the normal force increased. A comparison of the results suggested that the UDM was appropriate in predicting the frictional behavior of surgical suturing.