共查询到20条相似文献,搜索用时 62 毫秒
1.
岩石材料在静荷载和动荷载作用下,其力学特性差异很大。采用直径100 mm分离式Hopkinson压杆试验装置和波形整形技术对岩石进行动态冲击压缩试验,研究应变率范围为10~100 s~(-1)岩石的动态抗压强度、峰值应变及破坏形态的应变率效应。试验结果表明:试件动态抗压强度和峰值应变均随应变率增加而增大,最大动态抗压强度约为静态强度的2倍。试件动态破坏形态从低应变率下径向劈裂破坏到高应变率下粉碎破坏,随着应变率增加碎块数量明显增多而粒径变小,碎块粒径和块度分布变化显示出试件破坏形态具有明显的应变率效应。 相似文献
2.
本文通过对泡沫金属国内外发展的概况的介绍,主要内容包括泡沫金属基本概念,制备方法,泡沫铝、泡沫镁、泡沫钛、泡沫铜、泡沫铁的制备与应用研究,泡沫金属的特征及应用等,以对泡沫金属的发展现状、研究与应用有一个较全面的认识。 相似文献
3.
4.
5.
长周期堆垛有序(long period stacking ordered,LPSO)结构是广泛存在于Mg-Y-Zn系镁合金中一种强化相.本文利用分离式霍普金森压杆(SHPB)和万能试验机测试了Mg-Y-Zn变形镁合金的动态压缩力学性能和准静态压缩力学性能,结果显示,Mg-Y-Zn变形镁合金存在一定的应变率强化效应;利用... 相似文献
6.
7.
8.
通过真空热压烧结制备30%(体积分数)SiCp/2024Al复合材料,采用分离式霍普金森压杆(SHPB)对其进行动态压缩实验,得到应变速率为1600~3800 s-1的动态应力-应变曲线。结果表明:在一定的高应变率范围内承受动态载荷时,30%SiCp/2024Al复合材料在不同应变率下,应力-应变曲线趋势变化不大,基本表现为应变率不敏感材料。试样在动态冲击下均未出现宏观剪切破坏,采用扫描电镜(SEM)对压缩试样微观组织进行表征,高应变率试样内部出现孔洞和微裂纹等损伤,试样边界出现增强体颗粒脱粘现象,材料表现出良好的塑韧性。还讨论了动态载荷压缩变形机制。 相似文献
9.
通过真空热压烧结制备30%(体积分数)SiCp/2024Al复合材料,采用分离式霍普金森压杆(SHPB)对其进行动态压缩实验,得到应变速率为1 600~3 800 s-1的动态应力-应变曲线.结果表明:在一定的高应变率范围内承受动态载荷时,30%SiCp/2024Al复合材料在不同应变率下,应力-应变曲线趋势变化不大,... 相似文献
10.
本文研究了在拜耳法氧化铝生产上种分槽内泡沫的去除方法。种分槽内存在的大量泡沫对种子分解有相当的危害。通过添加消泡剂,能够消除泡沫.可以优化种子分解过程,并使种子分解效率提高1%左右。 相似文献
11.
A detailed quantitative microstructural analyses of primarily open cell FeCrAlY and 314 stainless steel metal foams with different relative densities and pores per inch (p.p.i.) were undertaken in the present investigation to determine the effect of microstructural parameters on the relative densities of metal foams. Several elements of the microstructure, such as major and minor cell sizes, cell areas and perimeters, ligament dimensions, cell shapes, and area fractions of closed and open cells, were measured. The cross-sections of the foam ligaments showed numerous pores, and their circularity factors and average sizes were determined. The area fractions of the open cells and ligaments decreased, whereas that of the closed cells increased linearly with increasing relative density. The relative densities and p.p.i. were not significantly dependent on cell size, cell perimeter, and ligament dimensions within the limits of experimental scatter. A phenomenological model is proposed to rationalize the present microstructural observations. 相似文献
12.
13.
14.
Metal foams are usually used as light structural/functional materials.The nucleation,evolution and the solidification behavior of the metal foams can be influenced by the stirring mode and the foaming parameters.In this paper,the effects of electromagnetic stirring on metal foaming process were investigated.Comparative tests were carried out and the optimized parameters of the stirring modes were discussed.The stirring effects of the spiral electromagnetic field are better than the travelling wave electromagnetic field.The effects of the spiral electromagnetic-mechanical combined stirring are better than the situations of the single electromagnetic stirring or the single mechanical stirring. 相似文献
15.
16.
Judith A. Brown Lakshmi J. Vendra Afsaneh Rabiei 《Metallurgical and Materials Transactions A》2010,41(11):2784-2793
The performance of new composite metal foams (CMFs) under bending was evaluated with simultaneous acoustic emission (AE) monitoring
on samples processed by cast and powder metallurgy (PM) techniques. The results showed high maximum strength in all samples
up to 86 MPa with more ductile failure in PM samples. Acoustic emission behavior confirmed that the dominating failure mechanism
of cast CMF is the brittle fracture of intermetallic phases that mostly exist at the interface of the steel spheres with the
aluminum matrix, whereas in PM samples (100 pct steel), the failure is governed by the propagation of preexisting microporosities
in the matrix resulting in a complete ductile failure. SEM imaging of the fracture surfaces supported these findings. 相似文献
17.
Kester D. Clarke Robert J. ComstockJr. Martin C. Mataya Chester J. van Tyne David K. Matlock 《Metallurgical and Materials Transactions A》2008,39(4):752-762
The effect of strain rate on the yield stress of ferritic stainless steel sheet was experimentally determined and a previously
developed model was applied to the data. Five ferritic stainless steel alloys, including one in two thicknesses, were mechanically
tested at room temperature in uniaxial tension at strain rates ranging from 0.001 to 300 s−1, and low-strain-rate tests were selectively performed at nonambient temperatures. The hypothesis that ferritic stainless
steels react similarly to strain rate as mild steels was investigated by the application of a widely accepted strengthening
model, based on body-centered-cubic (bcc) crystal lattice deformation mechanisms, to the experimental data.[1] Yield stresses were compared to model predictions and good agreement was found. The results allow for the prediction of
yield stresses for these materials over strain rate ranges of 0.001 to 300 s−1, and as a function of test temperature. Model parameters for the ferritic stainless steels were reasonable relative to those
previously reported for pure bcc ferritic iron.[1] A correlation between the effect of alloying additions on solid solution strengthening and the athermal component of shear
stress is also suggested. The results allow prediction of yield stress of ferritic stainless steels over a wide range of strain
rates and temperatures.
This article is based on a presentation made in the symposium entitled “Dynamic Behavior of Materials,” which occurred during
the TMS Annual Meeting and Exhibition, February 25–March 1, 2007 in Orlando, Florida, under the auspices of The Minerals,
Metals and Materials Society, TMS Structural Materials Division, and TMS/ASM Mechanical Behavior of Materials Committee.
相似文献
Kester D. Clarke (Graduate Research Assistant)Email: |
18.
19.
The behavior of semi-solid Sn-Pb alloys was studied in compression between two parallel plates. Small dendritic samples were
deformed at cross-head speeds leading to initial strain rates ranging from 1.3 × 10-3 s-1 to 1.2 × 103 s-1 in the semi-solid state at a temperature just above the eutectic. At the lower rates of deformation, breakdown of the dendrite
structure occurs, at strains of 0.2 to 0.4, and a high degree of segregation of the liquid phase occurs. For higher rates
the segregation no longer occurs to such a great extent and the alloy deforms more homogeneously. Some related experiments
involving compression over a filter are presented to obtain stress-strain relations in bulk compression for later analysis.
The behavior in compression of alloys in the semi-solid state may be used as a refining process in the low strain-rate range
where segregation of the liquid is large. It may also prove useful in the high strain-rate range as a forming method.
M. SUERY, formerly Visiting Scientist, Materials Processing Center, Massachusetts Institute of Technology. 相似文献