How the risk of failure in lifetime of tempered glass depends on the size of NiS inclusions and heat soak test duration

The probability of breakage in service lifetime of heat-tempered glass panes contaminated by nickel sulfide inclusions is estimated with a multiscale micromechanically motivated statistical theory, which considers the effects of the heat soak test (HST). Short and long HSTs differently affect the phase transformation of NiS of diverse chemical composition, whose increase in volume can break the glass. The main hypothesis, corroborated by experiments, is that there is a lower limit for the size of NiS stones below which no crack can be initiated from the volumetric expansion. The catastrophic propagation of nucleated fractures in the long term is modeled through a rescaled critical stress intensity factor, which accounts for the subcritical crack propagation and the slow phase transformation of NiS. A parametric analysis evidences how the failure probability is strongly affected by these parameters, depending on the holding time in the HST. Tailored experimental activity is suggested for the proper calibration of the model.     

Air impingement and intermittent drying: Application to apple and to mango

An original drying process combining air impingement and intermittent drying was studied on apple slices and mango cubes. The influence of four operating parameters (air velocity, drying/tempering periods, upper height, and air temperature) on the drying time and on the drying rate was evaluated. Continuous and intermittent drying were compared. The intermittency α = 1/7 (τ_on = 10 seconds and τ_off = 60 seconds) gave the best results. A time savings of 54% for apple and 67% for mango was reached. In continuous drying, a time savings of 4620 seconds was observed by increasing the air velocity from 6 to 40 m s^?1 for apple. Air temperatures of 328 K for apple and of 328 K or 338 K for mango were determined as optimum to prevent case‐hardening. Experimental results were fitted with the analytical solution of Fick's second law and the modified Page equation (average values R² = 0.985 and 0.961, for apple and mango, respectively). For both products, the apparent moisture diffusivity D_app, the drying constant k, the drying coefficient n, and the activation energy E_a, were identified. Activation energies calculated from the analytical solution were 30.3 and 36.8 kJ mol^?1 and were 25.4 and 30.0 kJ mol^?1 using the modified Page equation for apple and mango, respectively. Mango has an increased temperature sensitivity and thus will need less energy for drying than apple.     

测试性能估算的测试集重排序方法

目前在集成电路测试中,测试时间长、测试效率低是影响测试成本的关键问题之一,针对此问题提出了一种基于测试性能估算的测试集重排序方法。首先针对不同的故障类型进行分类建模,然后对每种故障类型进行仿真,通过在每个逻辑门注入故障,统计测试向量命中故障门的面积之和来估算测试向量的测试性能,最后根据测试性能的优劣对测试集进行重新排序。实验表明,对于单固定故障使用排序后的测试集测试可以减少5329%的故障检测时间。该方法是通过对电路的逻辑结构进行分析和统计然后对测试集进行优化,对ISCAS 89标准电路进行试验,与其他测试集重排序对比,有着明显的优化。算法运行完全是基于软件的,不需要增加任何硬件开销,可以直接相容于传统的集成电路测试流程。     

宽频段雷达天线罩电厚度反射测试探头设计

在雷达天线罩电厚度反射测试中,针对测试探头与被测天线罩的失配反射限制测量范围,以及传统校准方法只适用于 特定单一工作频率的问题,采用波导魔 T 和半星形截面的介质柱相结合,设计了一种消除波导探头与天线罩外壁失配影响的贴 合式探头,优化提升了测试信号相位与天线罩插入相位变化的映射线性度,无需校准即可实现宽频段测量。 在 X 波段方波导 8~12 GHz 全频段范围内,探头对测试端口失配抑制可达 30 dB。 利用该探头,可以方便地将反射测试信号转化为传输信号,而 且仅通过简单的相位比对,即可获取天线罩电厚度信息,并可以直接实现不同工作频率下的测试。     

Combined damaged elasticity and creep modeling of ceramics with wedge splitting tests

During the crack propagation in common refractory ceramics at high temperatures, creep may occur in the wake of a process zone and in front of a crack tip. To account for this phenomenon, an integrated material constitutive model was developed by combining the mechanical behavior following isotropic damaged elasticity concept and Norton-Bailey creep. The post peak fracture behavior followed the bilinear softening law and a simple criterion was defined to consider the creep asymmetricity in uniaxial tension and compression. The material constitutive model was applied to inversely identify mode I fracture parameters with wedge splitting tests of an alumina spinel material at 1200 °C. It showed that the mean ratio of the nominal notch tensile strength to the actual tensile strength was 1.93 and the mean pure fracture energy was 297.6 N/m. In addition, the creep contributed 12.9% on average into the total fracture energy.     

On the calibration of cohesive parameters for refractories from notch opening displacements in wedge splitting tests

Cohesive elements are commonly used to describe crack propagation in heterogeneous materials with toughening mechanisms. This work aims to provide a guideline on how these fracture parameters can be calibrated using notch opening displacements (NODs) measured via digital image correlation and force data from wedge splitting tests (WSTs). Weighted finite element model updating was applied to calibrate material and boundary condition parameters in the same framework. The influence of each parameter on force and NOD data are given together with uncertainties for the calibrated parameters. Numerical results were in very good agreement in terms of splitting force, NOD, displacement and gray level residual fields. It is shown that images obtained during WSTs focusing on the crack path (i.e., hiding the loading region) can be used to drive numerical simulations and obtain cohesive parameters.     

轰运飞机气动元件综合测试台的设计

本文较系统地介绍了测试台气动系统和CAT系统的设计。该测试台一方面功能齐全、可靠性高、操作方便，另一方面软件部分较为完善优越，运行速度较快，使得数据的采集、处理实现了计算机自动化，是航空气动元件比较理想的测试设备。     

Novel accelerated corrosion test for LY 12CZ and LC4CS aluminum alloys

A new accelerated corrosion test--comprehensive environmental test （CET） was developed in order to estimate the outdoor corrosion of aluminum alloys in marine environment. The environmental characteristics in CET were studied by atmospheric corrosion monitor （ACM）, and the morphology of corrosion product was observed by SEM. The correlation between the accelerated corrosion tests and outdoor exposure was discussed. The results show that the anti-corrosion ranking for LY12CZ, LC4CS, clad LY12CZ, and clad LC4CS in CET is the same as that of the alloys exposed outdoor, and ACM study shows that CET demonstrates the .same environmental characteristics as that exposed outdoor. CET is a more accurate accelerated corrosion test, and a mathematical relation was obtained to describe the relation between CET and outdoor test.     

Effects of molten aluminum on H13 dies and coatings

The effects of molten aluminum casting alloy A390 on a commercially heat treated H13 die steel and two wear-resistant coatings, Cr₂₃C₆ and TiN, were investigated by an accelerated corrosion test. The H13 steel suffered severe corrosion due to the rapid formation of intermetallic compounds. The formation of multilayer intermetallic compounds and the simultaneous dissociation of the intermetallic compound τ6 (Al₄FeSi) were attributed to the fast dissolution of H13 steels into the melt. This dissolution of the H13 steel was accelerated dramatically by turbulence and an increase in melt temperature. Significant improvement in corrosion resistance was achieved for the H13 steel coated by Cr₂₃C₆ via a pack cementation process.     

Hot dip fine Zn and Zn-Al alloy double coating for corrosion resistance at coastal area

A new hot dip Zn-7Al alloy coating was performed on a structural steel by double coating of fine Zn and Zn-7 wt.% Al alloy, to prevent severe corrosion in coastal area. The alloy-coated steels were exposed to seaside, quasi-industrial, and rural districts to compare with conventional Zn coating. Double coating was significantly effective in preventing corrosion, particularly in a seaside. It was estimated from the exposure test for 10 years that the life of the Zn-7Al alloy-coated steel would be almost four times that of the Zn-coated steel in the seaside. A bending test showed that no exfoliation occurred at the interface between the coated alloy and substrate steel. TEM observation revealed that the excellent adhesiveness of the doubly coated fine Zn and Zn-7Al alloy to the steel substrate was due to formation of the interface region consisting of heterogeneous fine phase mixture of zinc, aluminium and iron.