7050高强铝合金断裂韧度KIC值试验结果有效性影响因素分析

平面应变断裂韧度KIC是表征材料抵抗裂纹扩展的能力,是度量材料韧性好坏的一个定量指标,因此断裂韧度KIC值测试数据的有效性和可靠性在实际生产检测中就显得尤其重要.针对日常检测工作中对KIC值有效性影响较大的几个主要因素,对7050厚板、锻件CT试样进行断裂韧度KIC测试,分析了不同试样厚度、试样方向及残余应力对断裂韧度...     

Ti-B-C体系复相陶瓷的制备及性能研究

以Ti、B和C粉末为原料,采用自蔓延高温合成工艺制备了不同组份的TiC-TiB2复相陶瓷.分析了不同TiB2含量材料的力学性能、断口形貌和裂纹扩展情况,研究表明:TiC-TiB2复相陶瓷比其单相陶瓷材料的断裂韧度有较大提高,当n(TiB2):n(TiC )= 56.4:43.6,该复相陶瓷的弯曲强度和断裂韧度达到最大值,且相对密度高达99.4%;长棒状TiB2颗粒能有效改善材料的断裂韧度和强度,其强化机理主要为裂纹偏转和拔出效应.     

06MnVAl断口分层及其对断裂行为的影响

采用电子显微镜,扫描电镜和X射线能谱分析等研究了出现在低温压力容器用06MnVAl钢板断口“分层”的本质。试验结果表明,这种宏观断口上的“分层”实际上是沿轧制方向拉长成片的硫化物夹杂在打断口时与基体发生分离的结果。测量了断裂韧度,评价片状夹杂对裂纹扩展的影响。试验结果指出,当轧制方向即片层夹杂物的拉长方向与预裂纹垂直时,材料的断裂韧度没有明显下降。换句话说,在压力容器中沿同心作环状分布的片状夹杂物对它与垂直方向上来的裂纹扩展没有明显影响。     

纳米/微米Al2O3-ZrO2内衬复相陶瓷的自蔓延高温合成

采用SHS重力分离技术制备出内衬Al2O3-ZrO2复相陶瓷.复相陶瓷基体主要由纤维状(Al2O3+ZrO2)共晶体组成,其中共晶体的ZrO2纤维直径达到纳米/微米尺度.经Vickers压痕法测试其断裂韧度为15.96MPa·m1/2,SEM观察和陶瓷材料断裂韧度测试得出裂纹的扩展主要受共晶体中Al2O3-ZrO2纳米/微米相增韧机制控制,迫使裂纹沿共晶体边界或层片共晶体Al2O3-ZrO2相界偏转,从而维持了该复相陶瓷较高的断裂韧度.     

层理结构板岩动态断裂特性

基于动力冲击试验和插入黏聚力单元数值模拟方法，对层理结构板岩中心直切槽半圆盘（NSCB）试样在不同冲击速度和层理面倾角下的断裂性能展开研究。讨论了含层理结构岩样中的裂纹路径及其断裂参数。结果表明：冲击速度和层理面倾角对层理结构板岩裂纹扩展影响明显，在冲击速度较小的条件下，裂纹倾向于沿薄弱层理面扩展；随着冲击速度的增加，裂纹沿薄弱层理面扩展的长度逐渐减小，裂纹扩展路径更倾向于忽略薄弱层理面的影响，直接向加载点扩展。在冲击速度一定的情况下，裂纹沿薄弱层理面扩展的长度随层理面倾角的增加亦减小。随着冲击速度的增加，层理结构板岩的断裂韧度也逐渐增加；在给定冲击速度的条件下，层理结构板岩的断裂韧度随着层理面倾角的增加而增大。     

低碳贝氏体钢低温CTOD试验断口分离分析

通过对低碳贝氏体钢在-20℃CTOD试验中出现的分离断口进行微观分析,研究了断口分离和失稳断裂的原因.结果表明,断口分离面均为脆性断裂,至主断面为韧性扩展,分离裂纹产生的主要因素不是夹杂物,而是材料内部的带状组织和成带状的硬相组织受三维应力作用的结果.拉伸材料的分离裂纹是在达到一定抗拉强度之后开始萌生和扩展,不影响材料的使用性能.在断裂韧度试验中,一方面分离裂纹能降低材料裂纹尖端的三维应力约束,提高材料的韧性;另一方面较大程度的分离裂纹,减小了裂纹形核功和扩展功,诱发主裂纹的失稳扩展.     

原位SiC颗粒增强MoSi_2基复合材料室温断裂韧度的效果与机制

以钼、硅、碳粉末为原料,采用湿法混合和原位反应热压一次复合工艺制备纯MoSi2及含原位SiC颗粒体积分数为40%的SiCP/MoSi2复合材料试样,并研究其显微结构和室温断裂韧度.结果表明,原位SiC使MoSi2基体晶粒得到明显细化,消除了脆性SiO2玻璃相,并阻碍SiCP/MoSi2复合材料断裂时的裂纹扩展而造成裂纹的偏转和桥接,最终使SiCP/MoSi2的室温断裂韧度比纯MoSi2有了大幅度的提高,达到4.91 MPa.m1/2.     

15MnNi锻钢的疲劳和断裂性能

本文研究了１５ＭｎＮｉ锻钢的低周疲劳，裂纹扩展速率（ｄａ／ｄＮ），动态和静态断裂韧度，结果表明，１５ＭｎＮｉ锻钢的低周疲劳和动、静态断裂韧度满足ＡＳＭＥ规范要求，该材料具有良好的综合力学性能。     

新型奥氏体耐热钢C-HRA-5原位拉伸断裂机理

 断裂机理是材料力学性能研究的主要方向之一。为了阐明C-HRA-5钢单轴拉伸断裂机理,通过原位SEM观察拉伸全过程,对该耐热钢内部微裂纹萌生—扩展—断裂进行了深入分析。结果表明,C-HRA-5钢在室温和700 ℃下都表现出典型的韧性断裂特征。材料断裂主要受到M₂₃C₆相和MX相的影响,微裂纹由M₂₃C₆相聚集的三叉晶界处萌生。室温时,微裂纹与晶内MX相处裂纹相连,形成穿晶裂纹;高温时,微裂纹在剪应力的作用下形成局部穿晶裂纹,导致材料最终失效。     

ZrO2强韧化MoSi2复合材料显微结构和性能

通过对热压合成制备的ZrO2 MoSi2复合材料显微组织及其断口形貌分析,结合硬度、抗弯强度、断裂韧度等力学性能和孔隙率、晶粒度的测试,初步探讨了ZrO2颗粒强韧化MoSi2复合材料的机制。结果表明,复合材料中ZrO2粒子沿着MoSi2晶界偏聚,抑制MoSi2晶粒长大;复合材料断口晶粒细小,裂纹扩展曲折,呈现出沿晶与穿晶的混合型断裂特性;ZrO2颗粒通过第二相强化和细化晶粒使复合材料强度得到提高,通过细化晶粒、裂纹偏转和分支、形成微裂纹等机制的综合作用增韧复合材料。     

转炉炉壳热应力分析

根据实际转炉建立实体模型。以有限元为手段,考虑了炉衬和炉壳材料的物性参数随温度变化的特点和炉衬与炉壳之间膨胀间隙,计算了转炉炉壳在温度载荷和炉衬膨胀压力同时作用下的热应力。所得结果可为转炉炉壳设计提供依据。     

Rehabilitation of disorders of the breaking of voice

The adolescent's breaking of the voice is the result of the substitution of the chest voice (or heavy mechanism) for the head voice (or light mechanism). In cases of late breaking, the voice is abnormally high-pitched and feeble, often with a distorted timbre, while the larynx is normal and pubescent. Such people are generally not fully aware of their voices' real nature. Therapy classically resorts to laryngeal manipulations, of which a new technique is put forward. Another therapeutic approach is based, on the one hand, on critical listening compared with a control male voice, thus enabling the subject to become aware of his own voice, and, on the other hand, on high intensity work which helps passing from head to chest voice.     

2008年中国电解金属锰发展态势浅析

对中国电解金属锰发展的市场态势、价格行情以及原材料供应情况作了初步分析,提出我国电解金属锰行业挑战与机遇并存,只要抓住机遇、迎接挑战、夯实基础、科技创新,电解金属锰行业前景将会更加光明。     

Replication of dimensions of locus of control.

Employed 120 male and 113 female undergraduates in a replication of H. L. Mirels's (see record 1970-10386-001) study which found 2 factors in analyzing responses to 23 items on Rotter's Internal-External Control Scale. The same polar dimensions of "luck" as the arbiter of life events as opposed to personal control were found as well as a 2nd dimension of degree of control over political and social institutions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

显微维氏硬度测量不确定度评定

对显微维氏硬度测量不确定度进行评定，建立了不确定度计算的数学模型，确定了影响实验结果的各项因素，计算出了各因素的标准不确定度，得出结果的扩展不确定度，并给出最终测量结果的表达式。     

Concept of freedom of infection of animal flocks

Totally negative results of epidemiological investigation of random samples do not prove the absence of the infection as the pathogen may be restricted to only a few animals in the herd for a long time. The statement "absence of infection" is critical for such situations. The question is raised, whether the statement "absence of infection" should be generally avoided. Classification of herds and flocks according to the prevalence of the pathogen would be more valid for the implementation of control measures.     

Change of the dynamic modulus of elasticity as criterion of the state of oxidation of boron fibers

Conclusions At 723 K, which obviously is the melting point of the oxide B₂O₃, the mechanism of growth of the oxide on BF changes. Below 723 K the activation energy of growth of oxide is equal to 1.0; above 723 K it is equal to 1.7 eV.The suggested method of investigating the oxidation of solids is based on the measurement of the normalized dynamic modulus of elasticity of the specimen in the process of oxidation. This method can be used for studying oxidation from the surface, not only of cylindrical specimens but also of specimens with other cross-sectional profile. It is also applicable in the investigation of intracrystalline corrosion because expression (9), determining the thickness of the oxide film, was obtained on the basis of the ratio of the volume fractions of the phases coexisting in the specimen, independently of the place in the specimen at which the new phase grows and what profile it has. Formula (9) describes some effective thickness of the phase which would grow from the surface if the specimen had cylindrical shape. The change of the effective thickness of the phase in annealing in dependence on time makes it possible to determine the true kinetic parameters of the process because this change corresponds to the change of the volume fraction of the growing phase.Translated from Poroshkovaya Metallurgiya, No. 11, pp. 91–95, November, 1990.