《低温延性断裂韧度J_(IC)测试技术》J=J_(IC)的理论基础

论述了J_(IC)测试技术的理论基础,主要概括了三点:1、在定常裂纹中,当HRR场大到足够包围断裂过程区时,J积分就是断裂参量,其临界值J_(IC)就是材料的一种断裂韧度;2、在扩展裂纹中,只要满足J控制裂纹扩展条件,J积分仍然是断裂参量,J_R曲线就表示材料的一种性能,而J_(IC)就是J_R曲线上的一个点;3、根据上述二点,利用J_R曲线就可以测定材料的断裂韧度J_(IC),而且J_(IC)可以是J_R曲线上的条件值。     

“低温下金属材料延性断裂韧度测试技术”获局一等奖

<正> “低温下金属材料延性断裂韧度测试技术”,是由我院机械系研究室断裂力学组完成的,巳于1989年12月通过大庆科委技术鉴定,并获大庆市优秀科技成果一等奖。此项技术适用于中、低强度钢在低温环境下确定延性断裂韧度J_(IC)值,成果中提出了低温下确定金属材料裂纹稳态扩展的I积分阻力(J—R)曲线和低温下确定裂纹尖端钝变形规     

《低温延性断裂韧度J_(IC)测试技术》J=J_(IC)的工程应用

简要说明了断裂力学在工程中,特别是在石油工业中应用的重要性。主要通过3个实际工程例子,详细体现了《低温延性断裂韧度J_(IC)测试技术》 J=J_(IC)的应用。     

表征聚合物材料韧性的一种新方法—J积分法

介绍了 J 积分的概念及其理论,并选用该理论建立了一套较完整的测试方法。整个数值计算过程采用自编 BASIC 程序由 PB—700微型计算机完成。结果表明,实验方法可行,J_(IC)值符合一般规律。     

关于阻力曲线法测定J_(1c)在低温下如何标定钝化线方程的探讨

本文就J积分测试标准GB2038—80所推荐的钝化线公式进行了讨论,在对共所表达的意义予以理论征明的同时,并着重指出了在低温条件下它的不适用性(根据试验证明)。 研究在低温条件下如何标定钝化线过程中,我们认识到:应在不同低温下具体标定转动因子γ来计算COD,由此确定具体材料试验温度下的J—δ关系,并根据不同材料在钝化阶段的δ—△α关系,以确定饨化阶段的J—△α关系,即得相应低温下的钝化线方程。 由此得到的钝化线方程,具有J—α_0+β△α的形式,它和J_R阻力曲线交点所确定的J值,与利用多试件法结合声发射监测技术确定的裂纹尖端全面启裂时的J_(1c)值颇为接近。     

《低温延性断裂韧度J_(IC)测试技术》编制说明

详细说明了编制《低温延性断裂韧度J_(IC)测试技木》的背景,以及实验的和理论的根据。     

低温延性断裂韧度J_(IC)测试技术

根据低温环境下对石油天然气设备及机器中常用的几种金属材料的实验研究结果编制的一项规范,用于油田低温断裂工程进行安全分析.用裂纹小试样,按本《测试技术》测定金属材料低温延性断裂韧度J_(IC)值,以及换算成低温K_(IC)值,此外,矿山、铁路、桥梁等露天作业的机械设备,在冬季作业时,对可能发生的低温断裂进行分析,也可参考使用。     

关于复合型J准则的讨论

J积分作为弹塑性断裂准则已为大多数人接受,而能否作为复合型断裂准则仍在讨论之中,本文指出: 当K_1>K_Ⅱ时,tgθ_0=J_2/J_1 当K_Ⅰ>K_1时 ctgθ_0=J_2/J_1当J_1与J_2的合成量达到J_(1c)时,裂纹开始扩展。理论计算值与本院实验值符合很好。     

关于断裂过程中钝化直线的初步研究

在本试验过程中,作者通过三点弯曲试件的试验,得到了一些有用的结果,并与其它J_(IC)试验中确定钝化直线的各种方法进行了比较。结果发现本试验由裂纹尖端伸张区宽度(SZW)方法所测得钝化直线的斜率比美国ASTM标准所介绍的钝化直线大。因此,与ASTM方法相比,SZW方法所得到的J_(IC)和(△a)c值都偏小,因而就更偏安全些。所以尽管采用SZW方法来确定J_(IC)值比ASTM方法略为多花点功夫和费用,然而事实证明是很有必要的。     

关于二个Bessel函数乘积的广义积分∫((x~2-α~2)~(1/2)-x)J_0(xη)J_0(xζ)dx from x=0 to ∞的注记

采用复变函数方法,把形如integral from 0=1 to ∞ ((x~2-α~2)~(1/2)-x)J_0(xη)J_0(xζ)dx的积分转换成有限区间内的积分,构造成交错级数,然后利用Euler变换得到上述积分值。计算结果,大大优于其他方法,类似方法还可用于其他形式的Bessel函数乘积积分。     

High temperature strength and ductility of the （C＋N） strengthening Fe-Cr-Mn（W, V） steels

Fe-Cr-Mn(W, V) austenite steels used as low radioactive structural materials in fusion reactor have been investigated. The resuits show that the high temperature strength and the creep fracture life of Fe-Cr-Mn(W, V) steels can be effectively improved through (C N) complex-strengthening, so can be the high temperature ductility. The strength and ductility of the steels are superior to that of SUS316 steels and JPCAS below 673 K. The relationship between strength, ductility and the formation temperature is related to the evolution of deformation microstructure. The fracture and microstructure observation above 673 K indicates that the main way to further improve ductility at high temperature is the control of carbide coarsening at the grain boundaries.     

不锈钢在NaCl溶液和海水中的腐蚀行为

用动电位扫描法测定了几种不锈钢在３．５％ＮａＣｌ溶液和海水中的阳极极化曲线。研究了Ａ７２５Ｍ０２Ｔｉ及Ｒ１系列的不锈钢在二种腐蚀介质中的电化学腐蚀行为，并与含Ｃｌ－的Ｈ３ＰＯ４溶液中几种不锈钢的腐蚀特征进行了比较。结果表明，在不同的腐蚀介质中，各种不锈铜的腐蚀行为不同，铬、铂、镍等合金元素对不锈钢的耐蚀性能有很大影响。几种不锈钢在含Ｃｌ－的Ｈ３ＰＯ４溶液中其极化曲线具有典型的活化—钝化极化曲线的特征，而在３．５％ＮａＣｌ溶液和海水中，除了Ａ７２５外，其它几种不锈钢极化曲线上的钝化区很小或没有钝化区．Ａ７２５，Ｒ（１０）及Ｍ０２Ｔｉ等三种不锈铜均出现点蚀的情况．     

Effect of Nb on the transformation kinetics of low carbon （manganese） steel during deformation of undercooled austenite

The hot compression tests using Gleeble 1500 were performed by varying the true strain up to 1.6 （80% reduction） in Nbfree and Nb-microalloyed steels. The effect of Nb addition on the transformation kinetics during deformation of undercooled austenite was investigated. It was found that as compared with Nb-free steel, the transformation incubation period of Nb-bearing steel was prolonged and the transformation kinetics curves parallelly moved to higher strain because of the solute Nb drag effect. Studies on kinetics also showed that the deformation-enhanced ferrite transformation （DEFT） of the two steels were composed of three stages, which can be expressed by the J-M-A equations individually. However, the parameter n related to the mode of nucleation and growth is somewhat different in the first and second stages of the two steels, and the same in the third stage for both the steels corresponding to the nucleation Of retained austenite.     

Corrosion behavior of tempered dual-phase steel embedded in concrete

Dual-phase(DP) steels with different martensite contents were obtained by appropriate heat treatment of an SAE1010 structural carbon steel,which was cheap and widely used in the construction industry. The corrosion behavior of DP steels in con-crete was investigated under various tempering conditions. Intercritical annealing heat treatment was applied to the reinforcing steel to obtain DP steels with different contents of martensite. These DP steels were tempered at 200,300,and 400°C for 45 min and then coo...     

Characteristics of retained austenite in TRIP steels with bainitic ferrite matrix

Heat treatment process for producing cold rolled transformation induced plasticity-aided (TRIP-aided) steels with bainitic ferrite matrix was adopted. Characteristics of retained austenite (RA) in such TRIP steels were investigated. SEM and OM determination results showed that the stable austenite retained at room temperature were mainly located between laths and some of them inside the coarse ferrite. The grains were uniformly distributed in heat treated steel matrix and the regularly dispersed RA represented to be triangular morphology. XRD analysis indicated that RA content in matrix was not less than 10%, and TEM testified that RA inside the matrix were formed at the prior austenite boundaries and represented to be single or twin crystals. The ductile fracture originated from the boundaries of martensite islands from RA and ferrite. The cracks propagated along grain boundaries and some passed through the large ferrite grains and induced transgranular fracture.     

1Cr13不锈钢焊接接头组织及力学性能的研究

采用钨极氩弧焊的方法,对3 mm厚的1Cr13马氏体型不锈钢板实施焊接,通过LOM,SEM方法对焊接接头组织及断口形貌进行观察及分析;利用显微硬度计、电子万能拉伸机测量了焊接接头的力学性能.结果表明,通过手工钨极氩弧焊,采用直流正接接法(焊接电流为80 A,焊接速度为110 mm/min)能够获得外观平整、组织均匀、力学性能满足要求的焊接接头.     

Effects of warm compaction on mechanical properties of sintered P/M steels

The green and sintered densities,and tensile strength of sintered P/M steels produced by cold compaction,warm compaction,warm compaction combined with die wall lubrication(DWL)were measured under various compaction pressures using polytetrafluoroethylene(PTFE)emulsion as the die wall lubricant.The effects of warm compaction on the mechanical properties were studied.The tensile fracture behaviors of cold compaction and warm compaction were studied using scanning electron microscope(SEM).The results show that the density of sintered P/M steel prepared by warm compaction or warm compaction with DWL is higher than that by cold compaction under all compaction pressures.Meanwhile,the highest tensile strength is obtained by combination of warm compaction and die wall lubrication under all compaction pressures.The SEM results show that the fracture modes of the sintered samples prepared by cold compaction and warm compaction at 700 MPa are the mixed mode of ductile fracture and brittle fracture,and obvious dimples can be found in some regions.The fracture of sample prepared by cold compaction is uneven and has irregular and big pores,but that by warm compaction is relatively even and the pores are round mostly,and the samples have many obvious dimples on the whole fracture surface.     

应力状态对 16Mn 钢焊接接头断裂行为的影响

利用光滑、缺口试件拉伸试验及电子显微技术研究了１６Ｍｎ钢焊接接头在不同应力状态下的强度、塑性特征,裂纹起始、扩展特性及各特征区的断裂韧性ＶＧＣ,讨论了应力状态对接头断裂行为的影响．结果表明：随着应力三轴度的增加,接头由韧性向脆性断裂方式转变,断口形貌则由韧窝向准解理、解理转化,断裂应变急剧下降．母材的ＶＧＣ值最高,熔合区、焊缝次之,过热区的ＶＧＣ值最低．     

SBR的疲劳断裂特性

以断裂力学为基础，研究了SBR胶料从高应变到低应变较宽广区域的S－N曲线及断裂参数β和Co，从定性和定量角度解析了SBR胶料的疲劳破坏和断裂特性，认为SBR胶料在动态疲劳过程中抗裂纹扩展性较差，加入NR可以显著改善这一性能。     

MnS+TiN夹杂物对超高强度钢韧性的影响

超高强度钢中常见的两类夹杂物为MnS和TiN,它们共同对韧性的影响迄今尚未系统研究过。本文以D_6AC钢为基体,分别改变硫和氮的含量,使钢中含有8种不同含量的MnS+TiN夹杂物。通过板状试样拉伸实验,观察裂纹在夹杂物上形核和扩展的准动态过程,并测定了试样的常规机械性能和断型韧性。试验结果表明,夹杂物总体积分数fv和平均间距dT是影响K_1c和a_K值的两个重要参数。结果还表明,随着夹杂物尺寸的增加,裂纹临界形核应变降低。在相同尺寸情况下,裂纹在TiN上形核的临界应变比在MnS上形核小,因而MnS对韧性的影响低于TiN。