Y. Zhang
,
D.J. Wen
,
null
,
null
金属学报(英文版)
Ni3+ and Cr3+ doped Fe-Mn-Co-Cu-O spinels were prepared by solid phase sintering. The valence states and distribution of transition ions in the spinel crystals are being inferred from the consideration of thermodynamic principle and crystalline field theory. The microstructure and performance of those are studied by XRD, FT-IR and IRE-2 infrared radiant instrument. Ni3+ and Cr3+ occupy the vacancies or substitute the other ions in the spinel structure and formed diverse spinel structure, which exhibits infrared integral emissivities of 0.93 in the whole bands, and 0.94 in the bands within 14~25μm too. The content of Fe2O3 and MnO2 in the spinel crystals changes maybe induces infrared radiativity of spinels differently.
关键词:
Crystal structure
,
null
,
null
王昂
,
公茂琼
,
吴剑峰
工程热物理学报
微微型节流制冷器在微小元件和制冷应用中有广阔的前景.本文通过对搭建一微型压缩机驱动的微型混合工质节流制冷器系统,取得初步结果.该微微型J-T节流制冷器采用3D打印技术,通道特征尺寸为0.1 mm,突破了传统机械加工的极限.通道深宽比达到8:1.初步实验表明,微微型J-T节流制冷器达到了230 K温区.由于采用微型压缩机驱动,系统结构紧凑,可在便携生物储存设备、低温医疗以及电子器件冷却等领域应用并能长期运行.
关键词:
微微型节流制冷器
,
混合工质
,
3D打印
朱杰武
,
柳永宁
,
许雁
,
冯耀荣
机械工程材料
doi:10.3969/j.issn.1000-3738.2005.06.007
在不同温度下测试了X70管线钢动态断裂韧度K1d、J1d和止裂韧度K1a以及夏氏V型缺口冲击韧度Ak,对三者的关系进行了分析.结果表明:温度和加载速率都对断裂韧度产生影响;加载速率变化引起的韧-脆断裂转变具有热激活特征,在热激活分析基础上,在应力强度因子速率K=15 MPa·m1/2s-1条件下,得出断裂韧度、止裂韧度和冲击韧度三者的关系:Ak=4.84×106T-2.8K1d(或K1a).可以用小试样Ak数据计算得到K1d和K1a.
关键词:
管线钢
,
断裂韧度
,
止裂韧度
,
韧-脆断裂转变
Physical Review B
The Hamiltonian for a four-sublattice Heisenberg ferrimagnet or ferromagnet with different exchange constants (J(ab) = J(cd) not equal J(bc) = J(da)) was established. An extended Bogoliubov transformation was developed by solving an equation group, consisting of 20 equations and 20 unknowns. The procedure for solving the equation group was carried out by introducing a simple way of reducing the numbers of the equations and the unknowns. The spin-wave spectra in the present system have been determined by performing the standard Holstein-Primakoff transformation and the Bogoliubov one. It has been found that the spin-wave spectra of the present system depend on the exchange constants and that the degeneracy of the spin-wave spectra remains. The results for a special case (J(ab) = J(bc)) i.e., an antiferromagnet are discussed briefly. The spin-wave spectra of the four-sublattice Heisenberg antiferromagnet are found to be degenerative also and they are linear in k for small k.
关键词:
model
沙江波
,
孙军
,
邓增杰
,
周惠久
材料研究学报
应用大应变有限元方法和断裂实验研究了铝合金LY12在(Ⅰ+Ⅱ)型载荷下弹塑性断裂参量J积分与COD随外载荷变化规律及相互关系,结果表明:1)(Ⅰ+Ⅱ)型下LY12的J积分和COD关系为:J=dn·σ0·DⅠ+ds·T0·DⅡ;J=d·σ0.2·D.其中dn、ds、d为系数,随复合比而变,σ0、T0为裂尖屈服带上正应力和切应力、DⅠ和DⅡ为COD(D)的Ⅰ型和Ⅱ型分量;2)随Ⅱ型分量增加,LY12的起裂J积分和D值增加
关键词:
复合型
,
J-integral
,
COD
代巧
,
周昌玉
,
彭剑
,
贺小华
稀有金属材料与工程
通过断裂实验、二维有限元分析(2-D FEA)、三维有限元分析(3-D)以及EPRI解等4种方法获得了工业纯钛(CP Ti)紧凑拉伸试验(CT)的J积分.结果表明,EPRI解获得的J积分与2-D FEA结果吻合,但是它们明显低于实验结果,而3-D FEA获得的J积分更接近于实验值.为了提高J积分的估算精度,提出了基于3-D FEA改进的EPRI解,并用实验结果进行了验证.此外,将由原EPRI解和改进的EPRI解获得的J积分建立的CP Ti失效评定曲线(FAC)与实验结果进行比较,发现EPRI解的改进不仅提高了J积分的估算精度,而且提高了FAC的可靠性.
关键词:
J积分
,
CP Ti
,
FEA
,
EPRI
Y.G. Cao
,
X.Y. Sun
金属学报(英文版)
J-integral and crack opening displacement δ(COD) were important parameters for characterization of fractures in engineering materials. The relationship between J-integral and COD has been investigated for a long time and was enerally represented as J = m σyδ, where σy is the yield strength and m is a function of specimen geometry and material properties. To determine the value of m, extensive studies and experiments have been performed. The method that used the fracture-surface topography analysis (FRASTA) for determining J-integral from fracture surfaces of materials was introduced. On the basis of the relationship between COD and fracture surface average profile, the relationship between J-integral and COD was deduced and compared with the generally used equation. The method was experimentally confirmed to be able to provide a new way to determine the relationship between J-integral and COD.
关键词:
FRASTA
,
null
,
null
