Electromechanical cracking in ferroelectrics driven by large scale domain switching

Experimental results indicate three regimes for cracking in a ferroelectric double cantilever beam (DCB) under combined electromechanical loading. In the loading, the maximum amplitude of the applied electric field reaches almost twice the coercive field of ferroelectrics. Thus, the model of small scale domain switching is not applicable any more, which is dictated only by the singular term of the crack tip field. In the DCB test, a large or global scale domain switching takes place instead, which is driven...     

Correlation between microstructure and property of electroless deposited Pt counter electrodes on plastic substrate for dye-sensitized solar cells

Flexible Pt counter electrodes (CEs) were prepared on indium-doped tin oxide coated polyethylene naphthalate (ITO-PEN) substrate by electroless deposition. The correlation between the microstructure and the property of the Pt CEs was investigated. Results showed that isolated Pt nanoparticles were uniformly distributed on the ITO surface at a short deposition duration, and then grew with the deposition duration, leading to the interconnection of adjacent Pt nanoparticles. The interconnection of Pt nanoparticles was beneficial to the electrical property of the Pt CEs, while it was unfavorable to the electrocatalytic property of the Pt CEs. A microstructure model was proposed to explain the correlation between the microstructure and the property of the Pt CEs. In addition, the Pt CEs showed low charge transfer resistance (1.66-0.58 Ω cm²), which was comparable to that (1.16 Ω cm²) of the conventional sputtered Pt CE. The high electrocatalytic property of the electroless deposited Pt CEs makes the assembled DSCs present comparable energy conversion efficiency of the DSCs using sputtered Pt CE.     

Affine Springer fibers of type A and combinatorics of diagonal coinvariants

We calculate the Borel–Moore homology of affine Springer fibers of type A   associated with some regular semisimple nil elliptic elements. As a result, we obtain bigraded _Sn${\mathfrak{S}}_n$-modules whose bigraded Frobenius series are a generalization of the symmetric functions introduced by Haglund, Haiman, Loehr, Remmel, and Ulyanov.     

Toughness and failure of heat resistant steel before and after hydrogenation

Fracture toughness of heat-resistant steel can be increased by a preliminary thermomechanical loading called warm pre-stressing (WPS). The procedure creates a plastic deformed area around the crack tip and hence allows larger service loads to be tolerated by the cracked specimen. It is shown that a hydrogenation in the preloading stage decreases the fracture toughness of material.Investigations are also presented of the applicability of physical and mechanical approaches for the prediction of cleavage stress of materials after preliminary plastic deformation (PPD) effects and hydrogenation. Different schemes of the plastic deformation and influence of hydrogenation are considered in the preloading stage to provide different levels cleavage stress of steel 15Kh2MFA.     

Computing stable loads for pallets

This paper describes an Integer Programming model for generating stable loading patterns for the Pallet Loading Problem under several stability criteria. The results obtained during evaluation show great improvement in the number of stable patterns in comparison with results reported earlier. Moreover, most of the solved cases also ensure optimality in terms of utilization of a pallet.     

Elastodynamic analysis of a thin layer bonded on a visco-elastic medium under combined in-plane and lateral pulse loads

An analytic solution of a thin layer bonded on a visco-elastic medium under the action of in-plane and lateral pulse loads is presented. The analysis is based on double integral transforms with respect to space and time. Representative examples are studied and discussed to determine the influence of the (a) damping and elastic coefficients of visco-elastic medium, and (b) in-plane compression and stretching of the thin layer on wave propagation.     

Coupled fluid–solid interaction under shock wave loading

This paper considers the treatment of fluid–solid interaction problems under shock wave loading, where the solid experiences large bulk Lagrangian displacements. This work addresses the issues associated with using a level set as a generalized interface for fluid–solid coupling where the fluid–solid interface is embedded in an unstructured fluid grid. We outline the formulation used for the edge‐based unstructured‐grid Euler solver. The identification of the fluid–solid interface on the unstructured fluid mesh uses a super‐sampled ??² projection technique, which in conjunction with a Lagrangian interface position, permits fast identification of the interface and the concomitant imposition of boundary conditions. The use of a narrow‐band approach for the identification of the wetted interface is presented with the details of the construction of interface conditions. A series of two and three‐dimensional shock‐body computations are presented to demonstrate the validity of the current approach on problems with static and dynamic interfaces, including projectile/shock interaction simulations. Copyright © 2010 John Wiley & Sons, Ltd.     

The onset of mixed-mode intralaminar cracking in a cross-ply composite laminate

The intralaminar fracture toughness of a unidirectionally reinforced glass/epoxy composite is determined experimentally at several mode I and mode II loading ratios. The crack propagation criterion, expressed as a quadratic form in terms of single-mode stress intensity factors (alternatively, linear in terms of energy release rates), approximates the test results reasonably well. The mixed-mode cracking criterion obtained is used to predict the intralaminar crack on set in a cross-ply glass/epoxy composite under off-axis tensile loading. Translated from Mekhanika Kompozitnykh Materialov, Vol. 44, No. 6, pp. 785–794, November–December, 2008.     

端头带有质量块的悬臂梁在冲击载荷下的两种剪切失效模型

剪切失效是强动载荷作用下结构失效的重要模式。本文给出了计及梁的转动惯量时端头带有质量块的悬臂梁结构受到冲击载荷作用后发生剪切失效的无量纲判据。分析表明，在初始速度间断面上是否发生剪切失效取决于质量块初始动能和质量块尺寸与梁厚之比，而与梁的长度无关。梁的转动惯量对于剪切失效具有不可忽略的影响。     

Diagonally compensated reduction and related preconditioning methods

When solving linear algebraic equations with large and sparse coefficient matrices, arising, for instance, from the discretization of partial differential equations, it is quite common to use preconditioning to accelerate the convergence of a basic iterative scheme. Incomplete factorizations and sparse approximate inverses can provide efficient preconditioning methods but their existence and convergence theory is based mostly on M-matrices (H-matrices). In some application areas, however, the arising coefficient matrices are not H-matrices. This is the case, for instance, when higher-order finite element approximations are used, which is typical for structural mechanics problems. We show that modification of a symmetric, positive definite matrix by reduction of positive offdiagonal entries and diagonal compensation of them leads to an M-matrix. This diagonally compensated reduction can take place in the whole matrix or only at the current pivot block in a recursive incomplete factorization method. Applications for constructing preconditioning matrices for finite element matrices are described.