Effect of Solute Segregation on Fracture Toughness in a Ni-Cr Steel

A study has been made of the influence of intergranular solute segregation on fracture toughness K_1c in a series of Ni-Cr steels individually doped with Sb, Sn, and P. By means of toughness measurements in steels having two different intergranular Sb distributions, of measurements of acoustic emissions and of scanning electron micrographs of a load-interrupted and post-test-fatigued specimen, the values of K_1c, computed from the “pop-in” load of the loadvs clip gauge displacement curves, are found to represent the formation of many patches of contiguous intergranular microcracks ahead of the precrack. The present experiments demonstrate that in the early stage of solute segregation, K_1c decreases more substantially than does the strength of grain boundaries σ* (measured in the notched bar tests), although the embrittlement effects of metalloid elements are the same order for both K_1c and σ*. A proposed model for the stress-gradient-control of brittle fracture supports the finding that the measurements of K_1c give a distorted view of the progress of intergranular embrittlement.     

双重退火制度对TC21钛合金断裂韧性的影响

利用光学显微镜和扫描电镜等手段研究了双重退火工艺对TC21钛合金断裂韧性的影响。结果表明：不同退火制度下TC21钛合金试样断裂韧性均在100MPa·m1/2以上;第一次退火温度相同的条件下,随着第一次退火温度的升高,TC21钛合金断裂韧性都略有升高,而在第二次退火温度相同的条件下,第一次退火温度对TC21钛合金断裂韧性影响较小;经950℃×2h／AC＋590℃×411／AC双重热处理的TC21钛合金具有较崎岖的裂纹扩展路径和较好的塑性,故其断裂韧性最高,可达109．7MPa·m1/2。     

跳过深冷处理对A100钢断裂韧性的影响

对A100钢进行了不同热处理后试样的力学性能的测试，跳过深冷处理的试样虽然获得了残余臭氏体。但经过时效处理后不仅断裂韧性降低，而且钢的屈服强度和其它各项力学性能均下降。     

Fracture Toughness of Wood Fiber Gypsum Panels from Size Effect Law

This paper addresses the size effect of inplane bending strength as well as Mode I fracture toughness and process zone length of wood fiber-reinforced gypsum panels. Wood fiber gypsum panels represent an incombustible short fiber composite material composed of recycled paper fibers embedded in a gypsum matrix. The material, which is used for sheathing and bracing of timber frame constructions, exhibits marked fracture softening supposedly resulting in a considerable size effect. In the paper presented, in a first step Ba?ant’s size effect law for quasi-brittle materials is derived. The parameters of this size effect law are then determined by means of nonlinear regression analysis applied to a test series with scaled single edge notched beam specimens. Detailed consideration is given to the adequacy of linear confidence intervals of the model parameters in comparison to nonlinear inferential results. Finally, the probability densities of fracture toughness and fracture process zone length are determined from the distributions of the size effect parameters by means of theory of random variables.     

F206钢断裂韧度研究

研究了Ｆ２０６钢的断裂韧度及其影响因素。试验结果表明，在钢中Ｓ≤０．００２％的情况下，Ｂ类氧化物夹杂的数量和形态是影响横向断裂韧度的重要因素。控制碳含量为０．１６％±０．０１％，可获得足够的强度和较高的断裂韧度。采用８６０℃加热，油淬，５１０℃时效５ｈ，钢的屈服强度为１５６０～１６２０ＭＰａ，１４０ｍｍ棒材纵向断裂韧度达到１７５～１８４ＭＰａｍ。     

Effect of Sulfur Contents on Fracture Toughness of Wheel Steels for High Speed Train

The effect of different contents of S on fracture toughness of railway wheel steels for high speed train has been researched.The results show that there are kinds of non-metallic inclusion when O content retaining at about 10×10-6,such as Al 2 O 3 inclusions and Al 2 O 3 +MnS complex inclusions and single MnS inclusions.This is connected with S content level in steel.Fracture toughness of railway steel increase obviously because of Al 2 O 3 covered by MnS around when S content is increase to about 70×10-6.It shows that,after Al 2 O 3 covering by MnS around,stresses around complex inclusion decrease rapidly till disappear when analyzed by tessellated stresses theory.That is the reason of fracture toughness rise.     

断裂韧性与断裂表面分形维数的相关性研究

建立了材料断裂韧性与断裂表面分形维数的相关关系模型。结果表明，断裂韧性是分形维数、材料屈服强度、微结构尺寸及夹杂物体积分数等多参数的函数，并非只取决于分形维数。     

稀土元素对T_（10）钢冲击韧性和断口形貌的影响

本文研究了添加稀土元素的Ｔ（１０）钢冲击性能和断口形貌的关系。试验表明，在Ｔ（１０）钢中添加稀土元素对硬度没有明显的影响，但能显著改善该钢的冲击韧性。对稀土改善Ｔ（１０）钢冲击韧性和断口形貌的原因进行了初步讨论。     

试样取向对15%SiCp/2009Al复合材料断裂韧性的影响

研究了粉末冶金法制备的15%SiCp/2009A1复合材料挤压棒材的断裂韧性,探讨了不同试样取向对复合材料断裂韧性的影响.结果表明:L-R取向的紧凑拉伸试样的KIC明显高于R-L取向和C-R取向.断口形貌观察表明:L-R取向的复合材料试样,断裂以SiC颗粒解理开裂为主.较少出现大面积的基体合金撕裂,没有出现SiCp/基体合金界面脱粘的现象.SiC颗粒的大量断裂以及高的界面结合强度会引起复合材料断裂韧性的提高.     

Effect of Temperature on the Fracture Toughness of Hot Isostatically Pressed 304L Stainless Steel

Herein, we have performed J-Resistance multi-specimen fracture toughness testing of hot isostatically pressed (HIP’d) and forged 304L austenitic stainless steel, tested at elevated (300 °C) and cryogenic (? 140 °C) temperatures. The work highlights that although both materials fail in a pure ductile fashion, stainless steel manufactured by HIP displays a marked reduction in fracture toughness, defined using J_0.2BL, when compared to equivalently graded forged 304L, which is relatively constant across the tested temperature range.     

X70管线钢的断裂韧性

对不同厚度和裂纹初始长度的X70管线钢三点弯曲试样进行了不同试验温度下的断裂韧性试验。试验和分析结果表明：随着试验温度降低，试样的破坏方式由韧性破坏向脆性破坏转换不同厚度试样的破坏断口均产生分层裂纹，分层裂纹的大小和数量与试样厚度有关，分层裂纹的位置与试验温度和裂纹初始长度有关；对于试验温度较低的脆性断裂，试样在破坏时产生的分层裂纹距主裂纹根部有一定距离，分层裂纹宽度较小且未充分张开，对厚度效应影响较小。对于试验温度较高时的韧性断裂，分层裂纹首先出现在主裂纹根部，试样破坏时分层裂纹宽度较大且充分张开，减小了试样的有效厚度。高强度、高韧性的X70管线钢由于分层裂纹的产生，其力学性能与具有普通强度和韧性的钢材的力学性能存在着明显的差异，普通金属材料的韧性试验方法和材料评价方法已不再适用，必须考虑管道壁厚、缺陷大小和环境温度的综合作用。     

β钛合金的强韧化机制分析

β钛合金的合金成分、热处理工艺和显微组织决定了合金的强韧性.β钛合金的β稳定元素和中型元素Zr可以提高合金的强度,降低断裂韧性.细小的β晶粒不能有效提高时效态β钛合金的强度,可以降低Ti-15-3合金的断裂韧性,对β-C和Ti-1023合金的断裂韧性无明显影响.时效态β钛合金的强度主要取决于时效析出的次生α相的含量和尺寸,在含有同样初生α相的情况下,细小的次生α相可以显著提高合金的强度.初生α相的粗化以及初生相从球状转变为片状会导致β钛合金塑性降低,断裂韧性提高.β钛合金的双态组织具有良好的强度、塑性和韧性的匹配.     

Effects and Mechanisms of RE on Impact Toughness and Fracture Toughness of Clean Heavy Rail Steel

 Clean high carbon heavy rail steel was prepared by the process of vacuum induction furnace smelting, forging and rolling. Mechanisms of RE on the impact toughness and fracture toughness for clean high carbon steel were investigated. In addition, the appropriate range of RE content for clean high carbon steel was determined. Both the austenite grain size and pearlite lamellar spacing decreased due to small amount of RE, consequently the impact toughness and fracture toughness were improved evidently. When the RE content exceeded a critical value, the pearlite lamellar spacing was increased, because RE was segregated on the austenite grain boundaries, damaged the orientation relationship of pearlite transformation, caused the disorder growth and morphology degenerating of pearlite. With the increasing of RE content, both the impact toughness and fracture toughness of clean high carbon steel were gradually increased at first and then decreased. It was found that when the RE content was between 00081% and 00088%, both the impact toughness and fracture toughness of clean high carbon heavy rail steel were the best. The maximum ballistic work was 212 J (20 ℃) and 122 J (-20 ℃), respectively. The maximum plane-strain fracture toughness was 4567 MPa·m1/2 (20 ℃) and 3704 MPa·m1/2 (-20 ℃), respectively.     

7B04铝合金断裂韧性研究

本文测定了7B04铝合金各时效工艺状态下的常规拉伸性能，通过标准三点弯试验方法测定了合金的断裂韧性，并对其断口进行了宏观分析，从而研究时效工艺对常规力学性能与断裂韧性的影响，结果得出一种强度和断裂韧性均比T73和T76高的过时效工艺。     

低碳低合金钢的静力韧度与断裂韧度

采取静拉伸和平面应变断裂韧性测试方法,测量了S355,S275,Q345D,Q345E4种低碳低合金钢自室温至-100℃的基本力学性能,包括屈服强度、抗拉强度、静力韧度、断裂韧度以及韧脆转变温度,试图寻找4种金属材料静力韧度和断裂韧度之间的关系;通过对200多组样品的试验结果进行分析,发现4种金属材料在其各自韧脆转变温度之上的静力韧度Uk和断裂韧度J0.2BL存在线性关系。     

Experimental Investigation of Fracture Toughness of Frozen Soils

This note presents an experimental study on the fracture toughness of frozen soil. Notched bend specimens were used in the test. Some preliminary results are given to describe the effects of temperature, water content, and loading rate on the fracture toughness of frozen soil.