脉冲电流对45钢损伤的恢复作用

研究了脉冲电流对４５钢淬火裂纹的修复作用。结果表明,脉冲电流显著提高有裂纹的马氏体材料的强度和塑性,但硬度降低不多,脉冲电流处理后,裂纹周围的组织发生了显著变化。对裂纹钝化有利,探讨了裂纹在脉冲电流作用下的愈合效应,说明电流,热效应及热压应力可能是诱发该效应的主要因素。     

脉冲电流作用下40Cr钢淬火残余应力的消除

研究了脉冲电流作用下40Cr钢淬火残余应力的消除.结果表明,当脉冲电流密度达到一定数值后,材料中的残余应力开始部分弛豫;当电流密度达到6.3 kA/mm2时,残余应力可在700μs的脉冲电流处理时间内完全消除,而试样的瞬时温升仅约为360℃.在脉冲电流作用下残余应力弛豫的主要原因,可能是电流的电致塑性效应降低了材料的屈服强度,试样在由快速加热产生的瞬时热压应力和残余应力的共同作用下发生了微量的塑性变形.     

金属材料裂纹愈合的研究进展与展望

金属材料表面及内部的裂纹扩展是引起金属构件断裂失效的主要原因之一,裂纹研究一直是金属材料领域的一个重要方向。综述了近年来国内外对金属材料裂纹(表面裂纹、内部裂纹)愈合研究的进展,介绍了物质补给与能量补给的各类方法,物质补给方法主要包括钎焊法和表面筑膜法,能量补给方法主要包括加热法与施加脉冲电流法。总结了影响金属材料愈合的因素及愈合机制,并对未来金属材料的裂纹愈合研究作出了展望。     

12Cr超临界转子钢裂纹愈合研究

在研究超临界转子钢的内裂纹愈合过程中，用钻孔压缩法制备预制试样内裂纹，在一系列不同的加热温度下对裂纹进行修复，观察内裂纹的愈合情况，从而得出控制裂纹愈合的最佳温度范围。     

脉冲电流对疲劳后30CrMnSiA钢组织结构的影响

对在应力控制下预疲劳卸载的热轧态30CrMnSiA钢样品进行高密度脉冲电流处理后，得到了细小均匀的等轴晶组织，晶粒尺寸远小于热轧样品的晶粒尺寸．处理后样品的疲劳寿命显著提高．高密度脉冲电流使疲劳形成的位错产生运动，当刃型位错的距离达到临界距离时，位错发生湮灭，使局部的位错密度梯度增大，在位错密度低的地方发生再结晶形核，使钢发生再结晶．     

非金属材料裂纹愈合研究综述

对国外30多年以来在非金属材料裂纹愈合领域的研究结果进行了归纳总结,重点分析了对非金属材料裂纹愈合现象提出的各种解释机理及裂纹愈合过程中的形态变化,并进行了讨论。     

微观组织对贝氏体钢疲劳裂纹扩展行为的影响

为了研究组织对疲劳裂纹扩展行为的影响,对3种不同贝氏体组织钢进行了疲劳裂纹扩展实验,并采用SEM和EBSD等方法对裂纹进行了分析.结果表明,板条贝氏体组织在近门槛区和稳定扩展区阻碍裂纹扩展的能力最强,具有最小的裂纹扩展速率.板条贝氏体组织中的大角度晶界使裂纹更容易发生偏折,导致断口表面粗糙度增加,裂纹扩展受到较强的粗糙度诱导裂纹闭合效应的作用.随着ΔK的增大,塑性诱导裂纹闭合效应取代粗糙度诱导裂纹闭合效应开始占据主导作用,是板条贝氏体组织中裂纹扩展速率对ΔK的变化较敏感的原因.     

材料疲劳恢复新途径的探索Ⅱ：脉冲电流对Ti—6Al—4V合金裂纹扩 …

研究了大电流脉冲对Ｔｉ－６Ａｌ－４Ｖ合金疲劳裂纹扩展行为的影响。结果表明，在疲劳裂纹扩展后，试样经大电流脉冲处理，对疲劳裂纹的扩展有阻滞作用。并可以延长其疲劳扩展寿命。     

云母微晶玻璃的裂纹愈合研究

通过热处理对云母微晶玻璃预制裂纹的愈合进行了初步的探索与研究,分析认为其愈合过程可分为裂面内凹与裂尖钝化、裂腔分节与球化和球化孔洞的缩小愈合三个部分.在与外界无物质交换的条件下,材料内部裂纹与损伤的愈合靠内部物质迁移及结构变化完成.该系列微晶玻璃的裂纹愈合主要受愈合温度的影响.     

脉冲电流对金属材料的作用及其研究进展

综合评述了脉冲电流作用下的金属的凝固过程，金属的电致塑性效应，非晶结构变化和纳米晶化，金属材料的仿生恢复和愈合等方面的最近进展，着重介绍了脉冲电流在材料制备，加工和使用中的应用，同时提出了利用瞬态能量输入进行材料仿生复效处理这一新途径。     

Experimental evaluation of pulse electric current effect on residual stresses in composite-to-copper joints

Experimental method for evaluation of residual stress distribution in carbon fiber reinforced carbon composite jointed to copper is presented. Pulse electric current passed through composite-to-copper joint essentially reduces the level of residual stresses. __________ Translated from Problemy Prochnosti, No. 4, pp. 79–86, July–August, 2008.     

Improvement of pitting corrosion resistance of stainless steel by electric current pulse

ABSTRACT

The electric current pulse (ECP) was applied on the liquidus of 304 stainless steel during solidification and the pitting corrosion of the water-quenched specimens was explored in the present work. The results revealed that the utilisation of ECP can inhibit manganese sulphide from segregating around oxide inclusions during solidification and consequently, the pitting corrosion resistance of ECPed steel was significantly improved. Hence, the application of ECP during solidification might be an efficient way to improve the pitting corrosion resistance of the 304 stainless steel.

This paper is part of a themed issue on Materials in External Fields.     

Effect of electric current pulse on preparation of nano Y2O3

ABSTRACT

The effect of electric current pulse (ECP) on preparing nano Y₂O₃ powder was initially investigated in this paper. From the determination of thermogravimetric analysis, differential scanning calorimetry and X-ray diffraction, it was revealed that the composition of non-calcined precursor had changed due to the application of ECP. In addition, the scanning electron microscope results indicated that Y₂O₃ powders fabricated by ECP treatment had less aggregate and were in nano size. Therefore, the ECP treatment is a promising way to prepare nano Y₂O₃ powder.

This paper is part of a themed issue on Materials in External Fields.     

X90钢级高压气体管道爆炸裂纹起裂与止裂实验研究

开展X90钢级高压气体管道爆炸模型实验,初步探索并解决了管道爆炸实验的关键技术问题,为管道全尺寸爆破实验提供数据和方法支撑。结果表明:实验方法及测试仪器的选择可靠有效,解决了管道封堵、初始裂纹引入、传感器安装及密封、动态参量测试以及测试系统构建等关键技术问题;填充空气的运行压力为12.3MPa的X90钢管裂纹最大扩展速度约为248m/s,临界止裂压力约为4.5MPa,临界止裂速度约为100m/s;裂纹止裂器止裂效果明显,可进一步优化其安装位置并适当加宽加厚,进一步提高止裂效果。     

X90钢级高压气体管道爆炸裂纹起裂与止裂实验研究

开展X90钢级高压气体管道爆炸模型实验,初步探索并解决了管道爆炸实验的关键技术问题,为管道全尺寸爆破实验提供数据和方法支撑。结果表明:实验方法及测试仪器的选择可靠有效,解决了管道封堵、初始裂纹引入、传感器安装及密封、动态参量测试以及测试系统构建等关键技术问题;填充空气的运行压力为12.3MPa的X90钢管裂纹最大扩展速度约为248m/s,临界止裂压力约为4.5MPa,临界止裂速度约为100m/s;裂纹止裂器止裂效果明显,可进一步优化其安装位置并适当加宽加厚,进一步提高止裂效果。     

Research on solidification structure refinement of pure aluminum by electric current pulse with parallel electrodes

The influence of electric current pulse (ECP) with parallel electrodes on the solidification structure of pure aluminum has been investigated. The experimental results indicate that the solidification structure cannot be refined when the ECP is applied before the molten metal starts nucleating. However, significant refinement of the solidification structure can be achieved by applying ECP during the nucleation stage. In addition, under the same cooling conditions, ECP with parallel electrodes has better refinement effect than ECP with up–down electrodes. The refinement mechanism of ECP with parallel electrodes has also been proposed.     

Quantitative evaluation of the displacement distribution and stress intensity factor of fatigue cracks healed by a controlled high‐density electric current field

Fatigue cracks were healed by controlling a high‐density electric current. The changes in the displacement distribution around the crack tip and the stress intensity factor before and after crack healing were evaluated quantitatively with a digital image collation method. According to the results, it was determined that the cracks were closed by approximately 2 to 7 µm in this study. On the other hand, the stress intensity factor decreased or increased depending on the conditions of the crack and the current applied. The physical restriction between the crack surfaces, such as bridging, is important with respect to lowering the stress intensity factor after healing.     

电脉冲孕育处理对纯铝凝固组织的影响

金属熔体结构对液-固相变动力学及其凝固组织具有重要影响.本文通过对处于熔点以上的纯铝施加电脉冲,系统研究了其凝固组织及其力学性能的变化.结果表明:脉冲电场处理后,试样晶粒明显细化,表现为等轴晶区扩展,柱状晶长大受到抑制,同时力学性能亦有较大提升.另一方面,电脉冲孕育处理后的铝熔体具有较强的遗传性和抗衰退性,DSC测试揭示了采用电脉冲孕育处理的高纯铝试样在液相线以上存在物相改变.     

Experimental evaluation of the electric pulse effect on residual stresses in a Ti-Al-Si-Ag coating

Experimental results and stress-strain state simulation by the finite element method show that a thin oxidation-resistant coating sputtered onto a titanium alloy substrate develops high-level residual stresses. The electric pulse passed through a coated specimen significantly reduces an average level of residual stresses in the coating. __________ Translated from Problemy Prochnosti, No. 3, pp. 47–52, May–June, 2008.