Journal of Materials Research
Specimens of 1045 steel with quenched crack were treated under electropulsing. Scanning electron microscopy was employed to examine the change of specimens before and after the treatment. The results showed that the crack can be healed under electropulsing without melting, and the healing could be produced within a very short time. The original microstructure of specimens was not changed during the healing. It is thought that the temperature and the transient thermal compressive stress caused by high-rate heating are the main factors causing the healing of the crack.
关键词:
transient
刘积厚
,
赵洪运
,
李卓霖
,
宋晓国
,
董红杰
,
赵一璇
,
冯吉才
金属学报
doi:10.11900/0412.1961.2016.00232
利用超声波辅助过渡液相(超声-TLP)软钎焊工艺方法对Cu/Sn/Cu结构进行了钎焊实验,在极短的时间内获得了全Cu-Sn金属间化合物接头,并研究了接头的显微组织和力学性能。结果表明,超声-TLP接头由15 μm厚的Cu6Sn5中间层和1 μm厚的Cu3Sn边界层构成。在超声波作用下,Cu6Sn5晶粒呈现小尺寸等轴状,80%的Cu6Sn5晶粒直径在5 μm以下。由细化的Cu6Sn5晶粒构成的接头表现出较均匀的力学性能,具有较稳定的弹性模量和硬度,分别为123 GPa和6.0 GPa;同时具有较高的互连强度,达到了60 MPa。
关键词:
过渡液相软钎焊,超声波,金属间化合物,纳米压痕,剪切强度
徐彩红
,
王优强
,
张同钢
,
王立梅
表面技术
doi:10.16490/j.cnki.issn.1001-3660.2017.06.012
目的 通过对传动过程中压力和膜厚的计算,提高齿轮齿条机构润滑性能,降低齿轮齿条传动过程中的磨损.方法 简化齿轮齿条传动过程载荷图谱,运用简化的实际载荷曲线,建立齿轮齿条啮合过程的弹流润滑计算模型,对齿轮齿条啮合过程中的瞬态弹流润滑问题进行研究.考虑啮合过程中单、双齿啮合时不同的载荷,计算一个啮合周期沿啮合线上的中心压力、中心膜厚、最大压力、最小膜厚以及啮入点、节点、啮出点压力和膜厚,还有双齿啮合区转换为单齿啮合区、单齿啮合区转换为双齿啮合区前后瞬时的压力和膜厚.压力求解采用多重网格法,弹性变形采用多重网格积分法,得到了齿轮齿条传动机构的瞬态弹流润滑完全数值解.结果 载荷突然升高引起中心压力突然升高,中心膜厚最大值出现在双齿啮合区与单齿啮合的临界点.啮合线上最小膜厚和最大压力出现了波动.计算得出啮入瞬时膜厚最薄,润滑状况较差.结论 沿啮合线各瞬时压力与膜厚不断变化,载荷突变引起的压力突变应通过提高轮齿强度等方式防止表面疲劳破坏的产生.整个啮合过程中,啮入点为危险点.
关键词:
齿轮齿条
,
瞬态
,
弹性流体动力润滑
,
压力
,
膜厚
,
单双齿啮合
S.B. Zhang
金属学报(英文版)
The decays of transient photoconductivity and their light-induced changes of polymor-phous silicon (pm-Si:H) films were investigated. The decays can be fit fairly well bya sum of two exponential decay functions, which indicates that there arc two kindsof traps contributing to the process. The light-induced changes of the concentrationand energy level of the traps were estimated. The results show that the light-inducedchanges in trap energy position Et, trap concentration Nt as well as photoconductivityare markedly less for pm-Si:H than that for a-Si:H.
关键词:
light-induced change
,
null
,
null
