共查询到18条相似文献,搜索用时 62 毫秒
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在加载速率为100~106MPam1/2/s的范围内,分别采用准静态、示波冲击、Hopkinson杆型试验装置对某船用钢进行了断裂韧性测试。试验结果表明,此钢的断裂韧性对加载速率敏感,即随着加载速率的升高,断裂韧性下降;应用位错动力学对实验现象作出了解释。 相似文献
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高加载率下Ⅱ型裂纹试样的动态应力强度因子及断裂行为 总被引:3,自引:1,他引:3
采用Hopkinson单压杆技术对单边平行双裂缝试样进行高速剪切加载,用实测的试样加载面上的载荷p(t)结合有限元计算确定其动态应力强度因子。同时还发展了一种用实测的裂尖动态应变,通过在准静态下标定的裂尖应变与应力强度因子间的关系来确定动态应力强度因子的近似方法。实验结果表明,对于稳定裂纹在无边界反射应力波干扰的情况下,两种方法获得的动态应力强度因子吻合得相当好。对40Cr钢和Ti6Al4V钛合金两种材料的动态Ⅱ型断裂实验结果显示出两种完全不同的剪切破坏模式和机理。 相似文献
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为了揭示国产超强钢18NiC250的强度、断裂韧性随加载速率的变化规律,利用电子万能试验机和Hopkinson压杆,测试其在0.001~2 000 s-1的塑性流动应力应变曲线及在10-1~106 MPam1/2/s的断裂韧性,同时对断裂破坏机理进行了微观分析。结果表明:该材料的强度对加载速率不敏感,即流动应力基本保持在1.9 GPa;而断裂韧性很敏感,当加载速率由10-1 MPam1/2/s增大到106 MPam1/2/s时,断裂韧性降低了38.2%,断裂模式由韧窝断裂转变为解理断裂。 相似文献
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节理岩体爆生裂纹扩展动态焦散线模型实验研究 总被引:5,自引:0,他引:5
应用动态焦散线测试系统,模拟含节理岩体断裂爆破过程,进行了PMMA模型透射式动态焦散线实验,着重研究了爆炸初始裂纹与节理面夹角不同的情况下,裂纹尖端动态强度因子的变化规律、裂纹穿过节理面的扩展规律、以及炮孔与节理距离不同时裂纹穿过节理扩展的规律。实验结果分析表明,爆生裂纹穿过节理面时,裂纹尖端的动态强度因子和裂纹扩展速度显著下降,穿过节理面后,强度因子又增强;裂纹穿过节理面时,裂纹会沿节理面偏离一段距离后沿原方向继续扩展。实验结果还表明,炮孔与节理间距适宜的情况下,裂纹才会穿过节理继续扩展,间距太小和过大都不利于裂纹的扩展。 相似文献
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运用岩石破裂过程分析软件RFPA-dynamic,就爆炸荷载的加载速率、炮孔到自由边界的距离以及两炮孔中间空孔的大小对动态裂纹扩展方式的影响进行了研究。结果表明:随着加载速率的减小,炮孔周围的破碎区逐渐减少;裂纹开始萌生的位置逐渐由破碎区外边缘向炮孔孔壁转移;萌生的分支小裂纹逐渐减少,主裂纹扩展长度逐渐增大。由于自由边界的影响,炮孔向下扩展的裂纹逐渐弯向水平方向,且炮孔到自由边界的距离越小,这种趋势越明显。由于空孔的导向作用,使靠近空孔的裂纹逐渐弯曲向空孔处扩展,同时在空孔孔壁两端产生一条向炮孔扩展的裂纹;空孔半径大小对裂纹的导向作用,并无明显的影响;材料的非均匀性,对裂纹的扩展方式有显著的影响。 相似文献
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The boundary and loading conditions in many dynamic fracture test methods are frequently not well defined and, therefore,
introduce a degree of uncertainty in the modeling of the experiment to extract the dynamic fracture resistance for a rapidly
propagating crack. A new dynamic fracture test method is presented that overcomes many of these difficulties. In this test,
a precracked, three-point bend specimen is loaded by a transmitter bar that is impacted by a striker bar fired from a gas
gun. Different levels of energy can be imparted to the specimen by varying the speed and length of the striker to induce different
crack growth rates in the material. The specimen is instrumented with a crack ladder gage, crack-opening displacement gage
and strain gages to develop requisite data to determine toughness. Typical data for AISI 4340 steel specimen are presented.
A simple quasi-dynamic analysis model for deducing the fracture toughness for a running crack from these data is presented,
and the results are compared with independent measurements. 相似文献
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介绍了设计的新型圆台式压头及配套的衬片加载部件,推导了采用新的加载部件进行冲击断裂实验时的断裂韧度计算公式。采用SHPB实验装置,用新加载部件对带有V形切口的无烟煤短棒试件的裂纹尖端施加拉伸载荷,测定了无烟煤的动态断裂韧度。结合准静态实验数据得到了无烟煤断裂韧度随加载率lg(dF/dt)的总体变化规律:当lg(dF/dt)6时,无烟煤的断裂韧度缓慢上升,但当lg(dF/dt)6以后,无烟煤的断裂韧度随加载率的增加快速增大。实验表明:圆台式加载比刀刃式加载更具优越性和适应性,是测试岩石类材料短棒试件动态断裂韧度较好的方法。 相似文献
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岩石动态断裂韧度的尺寸效应 总被引:1,自引:0,他引:1
采用两种圆孔裂缝平台巴西圆盘试件(一种为直径分别为42、80、122、155 mm的几何相似试件,另一种为直径80 mm、仅裂缝长度不同的单一尺寸试件)对岩石动态断裂韧度的尺寸效应进行了研究。给出了在霍普金森压杆系统上对试件进行径向撞击产生的应变波形和断裂模式。实验结果表明,对于几何相似试件,动态断裂韧度的测试值随着尺寸的增大而增大,而对于单一尺寸试件,其测试值随着中心裂缝长度的增加呈现先增大后减小的趋势。裂缝前端的断裂过程区长度和孕育时间是岩石动态断裂韧度测试值表现为尺寸效应的主要原因,为了减小尺寸效应,建立了考虑这两个参数在空间-时间域对动态应力强度因子的分布进行积分后再平均来确定岩石动态断裂韧度的方法。 相似文献
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A fracture criterion of the type of the Neuber-Novozhilov criterion is proposed to describe the fracture in the vicinity of the tip of a V-shaped notch under tensile and shear loading. In the proposed criterion, the limits of averaging of the stresses along the notch axis depend on the presence, location, and size of the initial defects in the material. The crystal lattice parameter of the initial material is chosen for the characteristic linear size. For a V-shaped notch subjected to tension and shear, simple equations are obtained that relate the stress intensity factors for the modified singularity coefficients, the singularity coefficients themselves, and the theoretical tensile and shear strengths of a single crystal of the material taking into account the damage to the material in the vicinity of the notch tip. The equations obtained allow a passage to the limit from a notch to a crack. It is shown that the classical critical stress intensity factor used in the strength analysis of cracked solids is not a material constant.Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 46, No. 1, pp. 106–115, January–February, 2005. 相似文献
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用裂纹张开位移计算三点弯曲试样的动态应力强度因子 总被引:4,自引:0,他引:4
给出了一种由裂纹的动态张开位移计算三点弯曲试样的动态应力强度因子的简单方法。对于两种不同几何尺寸的试样,在三类不同载荷作用下给出了数植算例,并与完全的动态有限元方法的计算结果进行了比较。结果表明:两种方法的计算结果相当一致。最后,还给出了由测定三点弯曲试样的裂纹张开位移确定试样的动态应力强度因子,最终确定材料动态起裂韧性的方法。 相似文献
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The Small-Scale Steady State (S4) test has been recently developed in order to assess the fracture behaviour of polyethylene
(PE) gas distribution pipe material during rapid axial crack propagation. Based on an investigation of the S4 test, a simulation
model of S4 test has been developed. This paper describes the use of the results obtained from the S4 test and program modified
from PFRAC (Pipeline Fracture Analysis Code) to evaluate the fracture toughness of the material,G, which could not be directly obtained from the test, and to predict critical pressure,p
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, for rapid crack propagation (RCP) in a full scale PE pipe. The algorithms for contact conditions are developed to consider
the opening pipe wall impact against a series containment rings and the capabilities of PFRAC are also extended. WhenG
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is evaluated, investigations are made on the effect of temperature, wall thickness and crack velocity. In addition, procedures
to evaluate the critical pressure for the S4 test pipe are also discussed. 相似文献