共查询到16条相似文献,搜索用时 187 毫秒
1.
为探究X80管线钢不同缺陷类型的力磁耦合特性,设计了平板试件与穿孔、边缘切槽3种不同试件,通过金属磁记忆检测方法对X80管线钢试件不同缺陷类型的磁记忆信号特征进行了试验研究.采用材料试验机对试件导入不同程度的塑性损伤与应力集中,通过光学应变测量系统获取试件表面的实时应变情况,同时采用磁记忆检测仪对试件表面诱发磁场的法向分量与切向分量进行卸载离线检测.结果表明:随着塑性损伤程度的增加,无缺陷试件的磁记忆信号法向分量与切向分量从平缓趋向波动,但未出现明显的峰值;含穿孔与切槽试件磁记忆信号法向分量在缺陷处出现过零点与反对称双峰,切向分量出现单峰值,并且渐趋明显.初步探究了X80管线钢塑性损伤与磁记忆信号之间的关联性,为油气管道塑性损伤程度的无损定量评价奠定了基础. 相似文献
2.
3.
4.
建筑钢结构磁记忆检测技术的关键问题是确定磁记忆信号与内应力之间的关系。由于应力与应变是一一对应关系,故本文通过研究磁记忆信号与应变的关系,得到其与应力之间的关系。分析表明:钢梁下翼缘表面法向漏磁场强度与拉应变有着一定的关系,不论是处于弹性阶段,还是塑性阶段,磁记忆信号曲线变化与其应变变化趋势表现一致,磁记忆信号曲线可以反映应变的变化状态。钢梁腹板表面磁记忆信号与其水平压应力之间呈线性关系,无明显的拐点;但不同钢梁试件在相同应变下磁记忆信号强度存在差值,目前仅能作出定性评判。 相似文献
5.
拉伸载荷作用下中碳钢磁记忆信号的机理 总被引:3,自引:0,他引:3
测量了中碳钢试件表面各点的磁记忆信号,并观察断口的组织,研究了外载荷对磁记忆信号的影响和金属磁记忆的微观机理.结果表明:在弹性变形阶段内,随着载荷的增加中碳钢试件表面各点磁信号值由初始无规律分布逐渐向磁有序状态转变;进入塑性变形阶段后,位错对磁畴运动的钉扎使磁有序转变过程停止,磁信号几乎不再随载荷而变化.对于在弹性和塑性加载范围内卸载的两个试件,表面磁信号均具有不同程度的时效现象,试件的断口呈现韧窝及准解理混合断裂形式. 相似文献
6.
7.
通过对经退磁处理和未消磁的U75V钢光滑试件进行静载拉伸试验研究了初始磁状态对试件表面磁信号的影响。结果表明:消磁试件长度范围内的表面磁场在弹性阶段呈现很好的线性分布。进入塑性后,切向磁场出现局部弯曲。利用切向磁场均值和法向磁场斜率变化可以区分弹塑性阶段以及确定弹性阶段的应力幅值;未消磁试件随着载荷增加其表面磁场波动幅度减小,由初始无规律分布逐渐转向磁有序状态。利用未消磁试件长度范围外的磁记忆信号曲线的磁场均值及斜率变化可以有效表征不同的变形阶段。 相似文献
8.
9.
10.
11.
基于sablik-jiles-atherton模型和材料的自发磁化规律,在理论上探讨了更为简洁的力磁关系模型,分析了铁磁性材料在外应力和地磁场作用下的漏磁测量机理,获得了试件表面漏磁场信号切向最大、法向过零的特点.结合试件的弹塑性分析,得到在出现应力集中的缺陷位置漏磁信号变化剧烈,即梯度突然变大.利用Q235A钢材为实例,测量了试件在不同应力状态下的漏磁信号,得出在弹性范围内漏磁信号随拉力增大而增大,实验结果与理论有较好的符合,该工作为深入探讨铁磁性材料的力磁关系奠定了一定的理论基础,为检测铁磁试件的潜在缺陷提供了实验依据. 相似文献
12.
Variation of the stress‐induced magnetic field of the U75V rail steel under tension was investigated in this research. Various magnetic responses were registered by a magnetometer in the elastic and plastic deformation stages, which can be explained by the microstructural changes in magnetic domains. Two types of defective specimens were also tested to correlate the stress concentration with the magnetic field. It is found that the tangential component of the magnetic field Bx is much more sensitive to local stress concentration than the normal component Bz. The tangential component Bx reaches a peak value at the rupture position, and the peak magnitude is proportional to the concentrated stress caused by the defect. This observation is different from the Q235 steel, whose tangential component Bx and the normal component Bz are equally effective. Such discrepancy might be due to that U75V fails in a more brittle pattern than the Q235 steel. The average value of the Bx along the loading axis can determine the overall stress state of the structure, while the peaks in the Bx curve tell the local stress concentration caused by cracks and dislocation. 相似文献
13.
W. Sharatchandra Singh R. Stegemann M. Kreutzbruck C. K. Mukhopadhyay B. Purnachandra Rao 《Journal of Nondestructive Evaluation》2018,37(2):21
Giant magneto-resistive (GMR) sensor based metal magnetic memory (MMM) technique is proposed for mapping of deformation-induced self-magnetic leakage fields (SMLFs) in carbon steel. The specimens were subjected to different amounts of tensile deformation and the deformation-induced SMLFs were measured using a GMR sensor after unloading the specimens. 3D-nonlinear finite element modeling was performed to predict stress–strain state in a steel specimen under tensile load. The experimentally obtained SMLF images were correlated with the finite element model predicted stress–strain states. Studies reveal that the MMM technique can detect the plastic deformation with signal-to-noise ratio better than 20 dB. The technique enables the mapping of plastic deformation in carbon steels for the evaluation of the severity of deformation. The study also reveals that deformation-induced SMLF is influenced by the presence of initial surface residual stress, introduced by shot peening. The intensity of SMLF signal is found to increase with increase in tensile load and decrease with shot peening. 相似文献
14.
金属磁记忆检测是无损检测领域的新技术,而某些形状构件的应力集中和缺陷不能用该方法检测.为了研究构件形状对磁记检测的影响,计算了处于地磁场中的管道壁内的磁场.结果表明,管道和压力容器等适宜用磁记忆检测. 相似文献
15.
16.
De-Guang Shang Da-Kang Wang Ming Li Wei-Xing Yao 《International Journal of Fatigue》2001,23(10):903-910
According to the characteristic of the local behavior of fatigue damage, on the basis of stress field intensity approach, a theory of local stress–strain field intensity for fatigue damage at the notch is developed in this paper, which can take account of the effects of the local stress–strain gradient on fatigue damage at the notch. In order to calculate the local stress–strain field intensity parameters, an incremental elastic-plastic finite element analysis under random cyclic loading is used to determine the local stress–strain response. A local stress–strain field intensity approach to fatigue life prediction is proposed by means of elastic-plastic finite element method for notched specimens. This approach is used to predict fatigue crack initiation life, and good correlation was observed with U-shape notched specimens for normalized 45 steel. 相似文献