金属材料激光相变硬化的三维数值模拟

给出了用有限差分法对金属材料激光相变硬化过程建立的三维数值模型。模型考虑了工件有限尺度、工件材料热物理性质的温度依赖关系、激光处理参数以及对流、辐射造成的表面热损失．根据模型可以得出工件表面和内部任意部位的三维温度分布像，可以预测激光处理的相变层深，并据此优化激光处理参数的选定．通过对一种锆合金的激光相变硬化实验，验证了所得结果与模型理论计算的一致．     

Iron nitride mask and reactive ion etching of GaN films

One of the major GaN processing challenges is useful pattern transfer. Serious photoresist mask erosion and hardening are often observed in reactive ion etching of GaN. Fine pattern transfer to GaN films using photoresist masks and complete removal of remaining photoresist after etching are very difficult. By replacing the etch mask from conventional photoresist to a sputtered iron nitride (Fe-8% N) film, which is easily patterned by wet chemical etching and is very resistive to Cl based plasmas, GaN films can be finely patterned with vertical etched sidewalls. Successful pattern transfer is realized by reactive ion etching using Cl (H) containing plasmas. CHF₃/Ar, C₂ClF₅/Ar, C₂ClF₅/Ar/O₂, SiCl₄, and CHCl₃ plasmas were used to etch GaN. The GaN etch rate is dependent on the crystalline quality of GaN. Higher crystalline quality GaN films exhibit slower etch rates than GaN films with higher dislocation and stacking fault density.     

激光入射角度对激光表面硬化效果的影响

研究不同激光入射角度对不同类型高功率ＣＯ_２激光表面硬化效果的影响。选定激光器后,在相同的输出功率,扫描速度,离焦量下,随着激光入射角度的变化,试样表面吸收的实际功率密度发生变化,因此引起激光硬化深度、硬化宽度、表面显微硬度变化。只有法线方向的能量被吸收,随着入射角度的增大。淬硬层的宽度逐渐增大,实际结果和理论计算基本相一致。     

Si-栅MOSFET抗总剂量加固技术

ＭＯＳＦＥＴ总剂量加固强烈依赖于工艺技术,对干氧方式下不同条件制备的ＮＭＯＳ,ＰＭＯＳ管,分析其辐照响应,并借用亚阈值Ｉ－Ｖ技术分离氧化物陷阱电荷和界面陷阱对阈值电压漂移的贡献,得出较佳的干氧抗总剂量加固工艺条件。     

A Lagrangian model for hardening behaviour of materials at finite deformation based on the right plastic stretch tensor

In this paper a modified multiplicative decomposition of the right stretch tensor is proposed and used for finite deformation elastoplastic analysis of hardening materials. The total symmetric right stretch tensor is decomposed into a symmetric elastic stretch tensor and a non-symmetric plastic deformation tensor. The plastic deformation tensor is further decomposed into an orthogonal transformation and a symmetric plastic stretch tensor. This plastic stretch tensor and its corresponding Hencky’s plastic strain measure are then used for the evolution of the plastic internal variables. Furthermore, a new evolution equation for the back stress tensor is introduced based on the Hencky plastic strain. The proposed constitutive model is integrated on the Lagrangian axis of the plastic stretch tensor and does not make reference to any objective rate of stress. The classic problem of simple shear is solved using the proposed model. Results obtained for the problem of simple shear are identical to those of the self-consistent Eulerian rate model based on the logarithmic rate of stress. Furthermore, extension of the proposed model to the mixed nonlinear isotropic/kinematic hardening behaviour is presented. The model is used to predict the nonlinear hardening behaviour of SUS 304 stainless steel under fixed end finite torsional loading. Results obtained are in good agreement with the available experimental results reported for this material under fixed end finite torsional loading.     

The variation of strain rate sensitivity exponent and strain hardening exponent in isothermal compression of Ti–6Al–4V alloy

The deformation behavior in isothermal compression of Ti–6Al–4V alloy is investigated in the deformation temperatures ranging from 1093 K to 1303 K, the strain rates ranging from 0.001 s⁻¹ to 10.0 s⁻¹ at an interval of an order magnitude and the height reductions ranging from 20% to 60% at an interval of 10%. Based on the experimental results in isothermal compression of Ti–6Al–4V alloy, the effect of processing parameters and grain size of primary α phase on the strain rate sensitivity exponent m and the strain hardening exponent n is in depth analyzed. The strain rate sensitivity exponent m at a strain of 0.7 and strain rate of 0.001 s⁻¹ firstly tends to increase with the increasing of deformation temperature, and maximum m value is obtained at deformation temperature close to the beta-transus temperature, while at higher deformation temperature it drops to the smaller values. Moreover, the strain rate sensitivity exponent m decreases with the increasing of strain rate at the deformation temperatures below 1253 K, but the m values become maximal at a strain rate of 0.01 s⁻¹ and the deformation temperature above 1253 K. The strain rate affects the variation of strain rate sensitivity exponent with strain. Those phenomena can be explained reasonably based on the microstructural evolution. On the other hand, the strain hardening exponent n depends strongly on the strain rate at the strains of 0.5 and 0.7. The strain affects significantly the strain hardening exponent n due to the variation of grain size of primary α phase with strain, and the competition between thermal softening and work hardening.     

不锈钢粉末冷等静压数值模拟与实验验证

通过冷等静压实验获得了不锈钢粉末的压力-密度关系,在模拟中用于表征材料的硬化特性。为了描述粉末的致密化行为,使用了ABAQUS有限元软件中的Cam-Clay模型,对粉末的冷等静压实验过程进行模拟,结果表明实验的尺寸与模拟的结果符合得较好,说明模拟中使用的参数设置是合理的。然后使用选择性激光烧结/冷等静压复合工艺制造球形制件,并对冷等静压过程进行模拟,结果表明制件变形比较均匀,实验的结果与模拟的结果符合得较好,密度的预测与实验结果比较吻合。通过模拟不仅为冷等静压工艺提供有益的指导,也为以后复杂试样的冷等静压尺寸设计提供了重要参考。     

直齿圆柱齿轮的激光热处理

本文提出了齿轮热处理的三项关键技术。在此基础上,获得了沿齿廓分布的均匀硬化层。检测结果表明：齿轮激光淬火变形很小,不影响齿轮的精度等级。     

Soft error estimation and mitigation of digital circuits by characterizing input patterns of logic gates

Soft errors caused by particles strike in combinational parts of digital circuits are a major concern in the design of reliable circuits. Several techniques have been presented to protect combinational logic and reduce the overall circuit Soft Error Rate (SER). Such techniques, however, typically come at the cost of significant area and performance overheads. This paper presents a low area and zero-delay overhead method to protect digital circuits’ combinational parts against particles strike. This method is made up of a combination of two sub-methods: (1) a SER estimation method based on signal probability, called Estimation by Characterizing Input Patterns (ECIP) and (2) a protection method based on gate sizing, called Weighted and Timing Aware Gate Sizing (WTAGS). Unlike the previous techniques that either overlook internal nodes signal probability or exploit fault injection, ECIP computes the sensitivity of each gate by analytical calculations of both the probability of transient pulse generation and the probability of transient pulse propagation; these calculations are based on signal probability of the whole circuit nodes which make ECIP much more accurate as well as practical for large circuits. Using the results of ECIP, WTAGS characterizes the most sensitive gates to efficiently allocate the redundancy budget. The simulation results show the SER reduction of about 40% by applying the proposed method to ISCAS’89 benchmark circuits while imposing no delay overhead and 5% area overhead.     

10 keV X射线在"加速实验"辐照中的优势

文章利用实验结果分析了54HC04的阀值电压在不同剂量率下随总剂量的变化关系，对若干种加速实验方法进行了比较，认为10 keV X射线源可以作为对MOS器件进行快速的加速实验性能测试的辐照源。从环境安全考虑，10 keV X射线源易于屏蔽，可以用于硅片级的参数测试，且花费远远小于封装后的器件在^60Co源上的性能测试，是一种可行的评估器件总剂量水平的手段。