共查询到20条相似文献，搜索用时 747 毫秒
1.
以某常减压装置含缺陷管道为研究对象,采用超声相控阵检测方法对管道焊接接头进行无损检测,确定管道缺陷类型和尺寸,根据GB/T 19624—2019推荐的安全评定方法对管道缺陷进行安全评定,通过改变缺陷的大小和间距,探究缺陷类型、尺寸和相互位置对管道安全评定的影响,结果表明：裂纹缺陷单独存在时,缺陷高度对安全评定影响最大;未焊透缺陷单独存在时,缺陷长度对安全评定影响最大;两条缺陷共存时,随着缺陷间距S的增大,缺陷处应力先缓慢增大后快速减小并逐步趋于稳定,但是由于管道中缺陷数量增加,导致两条单独存在时均安全的缺陷在共存时可能造成管道不安全。 相似文献
2.
This article explores the suitability of static analysis techniques based on the abstract syntax tree (AST) for the automated assessment of early/mid degree level programming. Focus is on fairness, timeliness and consistency of grades and feedback. Following investigation into manual marking practises, including a survey of markers, the assessment of 97 student Java programming submissions is automated using static analysis rules. Initially, no correlation between human provided marks and rule violations is found. This paper investigates why, and considers several improvements to the approaches used for applying static analysis rules. New methods for application are explored and the resulting technique is applied to a second exercise with 95 submissions. The results show a stronger positive correlation with manual assessment, whilst retaining advantages in terms of time cost, pedagogic advantages and instant feedback. This study provides insight into the differences between human assessment and static analysis approaches and highlights several potential pitfalls of simplistic implementations. Finally, this paper concludes that static analysis approaches are appropriate for automated assessment; however, these approaches should be used with care. 相似文献
3.
4.
Theresistanceofapipelinesteeltohydrogensulfidestresscorrosioncracking (SCC)andhydrogen inducedcrack ing (HIC)isveryimportantforsteeltobeusedinsouroil/gasapplications.ElongatedMnSinclusionsarethemostsus ceptiblesitesforHICinitiation[1] ashydrogenatomscaneasi lyaccumulateattheinterfacebetweenthesteelmatrixandnon metallicinclusions.ThesegregationofsuchelementsasP ,Mn ,Cinthesteelenhancestheformationofhardbandsoncooling[2 ] .Theexistenceofthebandingstructurenotonlydecreasestheresistanceofthe… 相似文献
5.
刘海侠 《河北软件职业技术学院学报》2007,9(3):63-65
本文在弹塑性断裂双参数分析方法的基础上,导出了预测压力容器等重要工程结构断裂韧度CTOD要求的理论表达式.只要在实际结构服役条件下,材料断裂韧度高于该表达式要求的韧度值,就可防止结构的弹塑性断裂失效.同时,在该表达式中考虑了应力集中及焊接残余应力的影响,并表明断裂韧度要求随作用应力及板厚的增加而增加.最后给出了两个实例,以考核该理论表达式的实用性. 相似文献
6.
7.
Louis Volante Christopher DeLuca Lenore Adie Eva Baker Heidi Harju-Luukkainen Margaret Heritage Christoph Schneider Gordon Stobart Kelvin Tan Claire Wyatt-Smith 《Educational Measurement》2020,39(4):21-29
The synergy, or lack thereof, between large-scale and classroom assessment has been fiercely debated in both academic and policy spheres for decades around the world. This paper seeks to explicate how different countries are utilizing large-scale testing and test results at the classroom level. Through country profiles, this paper analyzes contemporary developments on the tensions and synergies between large-scale assessment and classroom teaching, learning, and assessment observed across seven international jurisdictions: United States, Canada, Australia, England, Germany, Finland, and Singapore. The paper concludes with an analysis of international trends leading to a synthesis of root causes contributing to the current limited uptake of large-scale assessment results at classroom levels. 相似文献
8.
9.
提出了一种利用非对称三点弯曲加载下的单边垂直切槽深梁试件(SEVNDB)开展岩石Ⅰ-Ⅱ复合断裂韧度测试方法。通过有限元法对试件的无量纲应力强度因子进行了数值分析与标定,研究了无量纲应力强度因子YⅠ、YⅡ及无量纲T应力T*与裂纹长度a、支座间距S1、S2之间的关系,定量刻画了实现纯Ⅱ型加载对应的裂纹长度a、支座间距(S1和S2)数值。研究结果表明,该方法在不改变试样裂缝倾角的前提下,通过调整裂缝长度a和支座间距S1、S2,即可方便地实现从纯Ⅰ型到纯Ⅱ型任意复合度载荷作用下的岩石断裂韧度测试。 相似文献
10.
ZHOU Zhi-qiang YANG Qing-da CHEN Wel-qlu 《浙江大学学报(A卷英文版)》2006,7(8):1289-1295
INTRODUCTION Adhesive bonding technology has been widely applied in modern structures in industries such as automotive, aerospace and in microelectronic device. The core idea of this technology is to bond two similar or dissimilar structure members with a thin continuous interface layer which can provide far better stress transfer across the interface than those traditional point-wise joining technologies such as spot welding, riveting and bolting. Furthermore, the damage tolerance proper… 相似文献
11.
本文运用Rauh和Bullough及国内研究者提出的裂纹应力场中点缺陷的迁移规律 ,研究了球墨铸铁断裂韧性Kc随温度T变化的规律。结果表明 :球墨铸铁断裂韧性随温度的提高而降低 ;Kc 计算值和实测值吻合较好。 相似文献
12.
赋能型评价倡导创新性和先进性的教育实践观,体现以人为本的教育价值观,凸显可持续的教育发展观,是一种新时代中小学学业质量综合评价的区域评价范式。通过协同化赋能、项目化赋能和数据化赋能等方式,赋能型评价既可以全面评价区域内某一学校或班级的学生的学业表现与发展现状,也可以依据评价结果分析与反馈,实现精准帮扶与改进,全面优化教育质量。 相似文献
13.
The fracture processes of concrete were described by a cohesive crack model based on initial toughness criterion. The corresponding analytical method to predict the instability state was proposed. In this model, the initial toughness was adopted as the crack propagation criterion and the weight function method was used to calculate the stress intensity factor and the crack opening displacement caused by the cohesive stress. The unstable toughness can be easily obtained using the proposed method without measuring parameters at the critical state that was necessary in traditional methods. The proposed method was verified by existing experimental data of wedge splitting specimens with different grades of concrete and the sensitivity of the results on the tensile softening curve was discussed. The results demonstrate that the proposed method can well predict the peak load, the critical effective crack length, and the unstable toughness of concrete specimens. Moreover, the calculated unstable toughness is not sensitive to the tensile softening curve. 相似文献
14.
15.
《Emotional and Behavioural Difficulties》2013,18(4):255-268
Abstract A functional behavioral assessment was conducted to identify the maintaining function(s) of aberrant behaviors displayed by a 6-year-old diagnosed with multiple disabilities. The assessment included indirect measures such as interviews, rating scales, and direct observations such as antecedent, behavior, consequence (A‐B‐C) charting. These assessments allowed the teacher to develop a hypothesis about the maintaining function of the aberrant behaviors. A functional assessment was not conducted. Instead, treatment was initiated quickly based on an abbreviated analysis. The results showed decreased rates of aberrant behavior following the implementation of the functional assessment based intervention; however, occurrences of aberrant behavior were not eliminated. Additional analyses suggested that changes in routine may be analogous to high demand situations that act as setting events for aberrant behavior. The results are discussed in terms of developing strategies for identifying events at home and in the community that may influence the occurrence of aberrant behavior. 相似文献
16.
采用一种新型的离心喷射沉积(CSD)成形技术制备了Ti—48A1—2Mn—2Nb金属间化合物，较系统地研究了该合金的微观组织结构以及室温拉伸、压缩和断裂韧度等力学性能，探讨和研究了该合金制备过程中形成的孔隙、特殊层片状组织及对材料性能的影响规律。图像分析系统定量测试结果表明，CSD制备的金属间化合物的孔隙率在2％左右，热等静压(HIP)有效地消除了合金在喷射成形制备中产生的孔隙，致密度达99.6—99．9％。性能研究结果表明，CSD制备的Ti—48A1—2Mn—2Nb合金具有良好的室温拉伸、压缩和断裂韧度等性能，尤其是压缩性能和断裂韧度值，显示了很好的应用前景。 相似文献
17.
The joining of aluminum alloy sheets with thickness less than 2.0 mm is difficult via conventional frictionstir welding owing to the defects in the joint, such as root flaw, keyhole and lazy S. In the present research, a newlydesigned pinless tool with involute grooves on its shoulder surface was applied to weld 1.5 mm thick AA2024-T3. Theeffects of the rotating speed and welding speed on the microstructure and mechanical properties of the joints were analyzed.The experimental results showed that the root flaw and keyhole were successfully eliminated. The lazy S wasalso eliminated under the optimized welding parameters. The maximum tensile strength of the joints was 326 MPa,which is about 74.1% that of the base material. Moreover, all the tensile samples fractured from the retreating side.Two fracture modes were observed during the tensile tests, which are related with the lazy S. 相似文献
18.
分析了当代大学生心理健康现状,认为目前我国高校心理健康教育存在着教育系统性缺失,教育评价制度缺失,教育监管制度缺失,教育制度创新机制缺失等问题,提出了建立统一的大学生心理健康教育制度,制定当代大学生心理健康教育评价体系,完善高校校规制定程序,建立健全高校大学生心理健康教育监管制度等建构科学大学生心理健康教育体系的措施。 相似文献
19.
对13 mm厚E40船板钢进行焊接,测定了焊接接头不同位置的力学性能,并观察了焊接接头不同位置的显微组织,结果表明,在焊缝区域晶粒较为粗大,焊缝厚度中心为铁素体和珠光体,焊缝上表面为粗大的柱状晶,导致此处的韧性较差,硬度较低;在焊缝厚度方向的中心位置向一侧母材偏移4 mm后为热影响区的过热区,此位置的组织中存在大量的魏氏组织,故硬度较高,但不利于韧性的改善;偏移6~8 mm后进入热影响区的正火区,组织为细小的铁素体与珠光体,因此硬度大幅降低;偏移10 mm后由于受到热应变失效脆化影响该处的硬度达到最高值,此处组织为粗化的针状铁素体与准多边形铁素体;由焊缝中心偏移12 mm后进入母材区,其低温韧性基本等于母材。 相似文献
20.
本文按照“西气东输”管线钢焊接技术条件，对武钢开发研制的板厚为10．3mmX70管线钢进行了气体保护焊试验。焊接材料为高韧性气保焊丝WER60及富氩保护气体。研究结果表明，焊缝具有优良的强韧性匹配，焊接接头强度及冲击韧性均满足管线钢工程焊接技术条件。 相似文献