基于SHPB试验的岩石应变率效应分析

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。     

泡沫金属的研究与应用进展

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。     

AlSi/hBN可磨耗封严涂层的动态力学性能研究

AlSi/hBN是一种可磨耗性能优异的中低温封严涂层,在实际服役工况下,封严涂层承受叶片的高温高速对磨刮削,通过自身的高速塑性变形-断裂发生主动磨耗,进而起到封严及保护叶片的作用,该过程本质上是一种材料在冲击载荷下的动态力学行为.首先通过紫铜片波形整形技术、铝质分离式霍普金森压杆(SHPB)系统和半导体应变片等手段对H...     

泡沫金属的发展现状、研究与应用

详细论述了国内外泡沫金属的发展情况、研究现状与应用状况，从而为我国生产新型多功能材料提供可靠的工艺与理论参考依据。     

Mg-Y-Zn合金高应变率下LPSO结构的变形机制

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...     

泡沫金属LED灯散热器研究现状

概述了LED灯的散热机理及其研究现状.开孔泡沫金属的比表面积大、热导率高、流体混合能力强,这使其成为一种增强热交换的有效材料.将泡沫金属应用于LED散热器,LED将会越来越多地应用于公共照明和严酷环境下的照明.     

泡沫金属的制备、分类及展望

介绍了泡沫金属的制备并对各种制备方法按照不同的标准进行了分类.重点介绍了泡沫金属制备方法的最新进展.展望了泡沫金属制备方法的研究方向和发展趋势.     

真空热压烧结制备SiCp/2024Al复合材料动态力学性能北大核心

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。     

真空热压烧结制备SiCp/2024Al复合材料动态力学性能

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,...     

拜耳法种分槽内泡沫对分解率影响的研究

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。     

Effect of Microstructural Parameters on the Relative Densities of Metal Foams

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.     

应变速率的影响与带钢热轧模型预报精度改进

轧制力预报模型是带钢热轧模型的核心，而变形阻力模型作为轧制力预报模型的核心，直接决定轧制力预报精度。从解决调试生产中存在的实际问题出发，对变形阻力模型的结构以及自适应方法进行分析。指出应变速率的影响、存在的问题以及相应的改进措施，并进一步阐明在实践中应用所取得的良好效果。     

Bending Properties of Al-Steel and Steel-Steel Composite Metal Foams

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.     

Effect of Strain Rate on the Yield Stress of Ferritic Stainless Steels

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.

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应变速率对Fe-Mn-Si-Cr-Ni合金组织和力学性能的影响

目前的TRIP钢由于Mn、Si含量较低,室温条件下仅保留约10%的残余奥氏体,结果使变形过程中材料产生的相变诱发塑性量有限,不能满足一些要求产生更大相变诱发塑性场合的需要。研究表明：提高钢中Mn、Si含量并辅以适量其它合金元素（如铬和镍）是提高材料相变诱发塑性的有效途径。研究了Fe-17Mn-5Si-10Cr-4Ni合...     

Effect of Strain Rate on Deformation Behavior of Semi-Solid Dendritic Alloys

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.     

金属基复合材料研究进展

新材料的研究、发展与应用一直是当代高新技术的重要内容之一。其中复合材料，特别是金属基复合材料在新材料技术领域中占有重要的地位。金属基复合材料对促进世界各国军用和民用领域的高科技现代化，起到了至关重要的作用，因此倍受人们重视。文章简单综述了金属基复合材料的发展，分类，性能和应用；以及增强体的选取，制成品的成型工艺，性能，以及应用和展望。     

Influence of Strain Rate,Temperature, Plastic Strain,and Microstructure on the Strain Rate Sensitivity of Automotive Sheet Steels

This work identifies the influence of strain rate, temperature, plastic strain, and microstructure on the strain rate sensitivity of automotive sheet steel grades in crash conditions. The strain rate sensitivity m has been determined by means of dynamic tensile tests in the strain rate range 10^?3–200 s^?1 and in the temperature range 233–373 K. The dynamic flow curves have been tested by means of servohydraulic tensile testing. The strain rate sensitivity decreases with increasing plastic strain due to a gradual exhausting of work hardening potential combined with adiabatic softening effects. The strain rate sensitivity is improved with decreasing temperature and increasing strain rate, according to the thermally activated deformation mechanism. The m‐value is reduced with increasing strength level, this decrease being most pronounced for steels with a yield strength below 400 MPa. Solid solution alloying with manganese, silicon, and especially phosphorous elements lowers the strain rate sensitivity significantly. Second phase hardening with bainite and martensite as the second constituent in a ferritic matrix reduces the strain rate sensitivity of automotive sheet steels. A statistical modeling is proposed to correlate the m‐value with the corresponding quasistatic tensile flow stress.