A Finite Element Procedure for Three-dimensional Analyses of Thermopiezoelectric Structures in Static Applications

The development and application ofsmart structures and smart composite materials require eflicient numerical tools to evaluate the thermopiezoelectric behavior and stress state. In this paper, finite element techniques are suggested for three-dimensional coupled thermo-electromechanical static analyses. The actual thermopiezoelectric responses subjected to thermal loadings can be determined by adopting a procedure TPESAP. The detailed implementation is presented with emphasis on the integration with software ABAQUS. Several verification example problems are discussed, including the benchmark problem ofafive-layer hybrid plate

Fabricating a novel HLC-hBMP2 fusion protein for the treatment of bone defects

Treating serious bone trauma with an osteo-inductive agent such as bone morphogenetic proteins (BMPs) has been considered as an optimized option when delivered via a collagen sponge (CS). Previous work has shown that the BMP concentration and release rate from approved CS carriers is difficult to control with precision. Here we presented the fabrication of a recombinant fusion protein from recombinant human-like collagen (HLC) and human BMP-2 (hBMP2). The fusion protein preserved the characteristic of HLC allowing the recombinant protein to be expressed in Yeast (such as Pichia pastoris GS115) and purified rapidly and easily with mass production after methanol induction. It also kept the stable properties of HLC and hBMP2 in the body fluid environment with good biocompatibility and no cytotoxicity. Moreover, the recombinant fusion protein fabricated a vertical through-hole structure with improved mechanical properties, and thus facilitated migration of bone marrow mesenchymal stem cells (MSCs) into the fusion materials. Furthermore, the fusion protein degraded and released hBMP-2 in vivo allowing osteoinductive activity and the enhancement of utilization rate and the precise control of the hBMP2 release. This fusion protein when applied to cranial defects in rats was osteoinductively active and improved bone repairing enhancing the repairing rate 3.5- fold and 4.2- fold when compared to the HLC alone and the control, respectively. There were no visible inflammatory reactions, infections or extrusions around the implantation sites observed. Our data strongly suggests that this novel recombinant fusion protein could be more beneficial in the treatment of bone defects than the simple superposition of the hBMP2/collagen sponge

Cohesive zone criterion for cracking along the Cu/Si interface in nanoscale components

Crack initiation and propagation along the Cu/Si interface in multilayered films (Si/Cu/SiN) with different thicknesses of the Cu layer (20 and 200 nm) are experimentally investigated using a nano-cantilever and millimeter-sized four-point bending specimens. To examine the cohesive zone model (CZM) criterion for interfacial delamination along the Cu/Si interface in nanoscale stress concentration, an exponential type of CZM is utilized to simulate the observed delamination processes using the finite element method. After the CZM parameters for the Cu/Si interface are calibrated by experiment, interface cracking in other experiments is predicted. This indicates that the CZM criterion is universally applicable for describing cracking along the interface regardless of specimen dimensions and film thickness which include the differences in plastic behavior and residual stress. The CZM criterion can also predict interfacial cracking along Cu/Si interfaces with different stress singularities

First-Principles Investigation of the Shear Properties and Sliding Characteristics of c-ZrO2(001)/α-Al2O3(11¯02) Interfaces

The ideal mechanical shear properties and sliding characteristics of c-ZrO2(001)/α-Al2O3(11¯02) interfaces are examined through simulated shear deformations using first-principles calculations. We investigate three types of interface models, abbreviated as O-, 2O-, and Zr- models, when shear displacements are applied along the <11¯01> and <112¯0> directions of their Al2O3 lattice. The theoretical shear strength and unstable stacking energy of the ZrO2/Al2O3 interfaces are discussed. In the process of the ZrO2/Al2O3 interfacial shear deformation, we find that the sliding of the ZrO2 atomic layers, accompanied by the shifting of Zr atoms and Al atoms near the interface, plays a dominant role; in addition, the ZrO2/Al2O3 interfaces fail within the ZrO2 atomic layer. Among the three models, the O- model exhibits the strongest shear resistance; whereas the Zr- model is the most prone to slip. Furthermore, their tensile and shear strengths are compared; moreover, their potential applications are provided

First-Principles Investigation of the Shear Properties and Sliding Characteristics of c-ZrO₂(001)/α-Al₂O₃(<inline-formula><math display="inline"><semantics><mrow><mn mathvariant="bold">1</mn><mover><mn mathvariant="bold">1</mn><mo mathvariant="bold">¯</mo></mover><mn mathvariant="bold">02</mn></mrow></semantics></math></inline-formula>) Interfaces

The ideal mechanical shear properties and sliding characteristics of c-ZrO2(001)/α-Al2O3(11¯02) interfaces are examined through simulated shear deformations using first-principles calculations. We investigate three types of interface models, abbreviated as O-, 2O-, and Zr- models, when shear displacements are applied along the 11¯01> and 112¯0> directions of their Al2O3 lattice. The theoretical shear strength and unstable stacking energy of the ZrO2/Al2O3 interfaces are discussed. In the process of the ZrO2/Al2O3 interfacial shear deformation, we find that the sliding of the ZrO2 atomic layers, accompanied by the shifting of Zr atoms and Al atoms near the interface, plays a dominant role; in addition, the ZrO2/Al2O3 interfaces fail within the ZrO2 atomic layer. Among the three models, the O- model exhibits the strongest shear resistance; whereas the Zr- model is the most prone to slip. Furthermore, their tensile and shear strengths are compared; moreover, their potential applications are provided

STUDY ON THE EFFECT OF PREPREG PLACEMENT TIME ON THE INTERLAMINAR SHEAR STRENGTH OF ARAMID COMPOSITE MATERIAL (MT)

The performance of the aramid III composite product is affected by the molding process parameters. Through the analysis of the prepreg molding process, it is found that the prepreg placement time is the main parameter that affects the interlaminar shear strength（ILSS） of the aramid III composite. In order to study the influence and sensitivity of the prepreg placement time on the ILSS of the aramid III composite material, the short beam method interlaminar shear experiment method was used to obtain the corresponding strength values of the prepreg under different placement time. According to the experimental data, the regression model of the process parameters on the ILSS was established, and the reliability and validity of the regression model were verified by the residual error, the comparison between the predicted value and the actual value. Using this regression model can accurately give the ILSS of the aramid III composite under different storage time of the prepreg, and obtain a single parameter sensitivity curve. Through the analysis of the sensitivity curve, the stability and instability range of the parameters can be determined. The experimental results show that as the placement time increases, the ILSS of the aramid III composite material increases first and then decreases. The optimal prepreg placement time corresponding to 0°/0°, 0°/90°, ±45° layup is within the range of 10～22 h. Within this range of process parameters, the aramid III composite material can be guaranteed to have the maximum ILSS

Scale-free behavior of displacement bursts: Lower limit and scaling exponent

Plastic flow of micro-samples proceeds in an intermittent displacement bursts, showing a scale-free power-law distribution. Using maximum likelihood estimator and the Kolmogorov-Smirnov statistic, we investigate the statistics of displacement bursts such as lower limit and scaling exponent, for selected micro-samples from previous researches. The results of lower limit indicate that all the crystals considered share a common lower limit, the magnitude of which is found to be comparable to the largest burst size governed by short-range interactions (i.e., junctions). Additionally, the calculated results of the scaling exponents challenge those observed in many previous studies where other statistical techniques are employed. We demonstrate that our results are consistently manifested in the experimental data