Experimental study of cohesive strain prior to crack initiation in constant force single cantilever beam test

Retarded deformation at the bond line edge of a thick, viscoelastic adhesive layer is observed using digital image correlation. Such information is required for proposing physical crack onset/propagation parameters which take into account viscoelastic and viscous mechanisms in the evaluation of dissipated energy. A complex stress/strain redistribution is observed in the early stage after specimen loading. The results illustrate that viscoelasticity dissipates a considerable amount of energy prior to crack nucleation and the lack of predictive models to account for that phenomenon.     

浅谈光面预裂爆破在县乡山区公路中的应用

论述了光面爆破和预裂爆破的含义,归纳了光面预裂爆破的优点,通过具体工程实例,从所布置炮孔的孔径、孔距、孔深及装药等方面详细介绍了影响光面预裂爆破效果的主要参数,以积累光面预裂爆破施工经验.     

超前切顶卸压技术在沿空掘巷中的应用

为保证沿空掘巷巷道支护强度满足安全生产需要,避免因煤柱留设过大而造成资源浪费,在顺槽巷道走向沿工作面采用超前切顶卸压的方式进行超前爆破,巷道基本顶与采空区基本顶之间断出裂缝,使采空区加速稳定,以此减少顺槽顶板的矿压显现。     

对白云鄂博铁矿主采场不同岩性预裂爆破的探讨

本文对白云鄂博铁矿主采场不同岩性中的预裂爆破进行了探讨，通过计算给出了一些基本的爆破参数，并详细介绍了预裂爆破施工组织过程。     

谈白云铁矿主采场预裂爆破使用自制预裂药柱的效果

本文介绍了白云鄂博铁矿主采场预裂爆破使用自制预裂药柱的施工要求和效果，并针对采场不同岩性计算出基本的预裂爆破参数。     

含夹矸顶煤破碎机理及控制技术研究

为探究含夹矸顶煤冒放性机理及增大冒放程度措施,以天安煤矿20103综放面为研究对象,分析了顶煤上方顶板三种岩梁结构和夹矸形态影响,制定了深孔预裂爆破技术措施。工程实践表明,深孔预裂爆破能够有效降低顶煤冒放块度,提高资源回收率,产生可观的经济技术效益。     

6106综放工作面端头放顶煤工艺优化研究与应用

针对南阳坡矿综放工作面两端头区域顶煤损失严重的问题,通过分析煤岩层力学性质和工作面端头矿压显现规律,提出了弱支护深孔爆破耦合CO2分布式预裂松动综放工作面端头放煤工艺,实现综放面端头煤柱的安全高效回收,为其他类似工作面提供了一定的实际参考价值。     

Fracture-mechanics-based evaluation of failure limit on pre-cracked and hydrided Zircaloy-4 cladding tube under biaxial stress states

ABSTRACT

To better understand the failure limit of fuel cladding during the pellet-cladding mechanical interaction (PCMI) phase of a reactivity-initiated accident (RIA), pre-cracked and hydrided cladding samples with base metal final heat-treatment status of cold worked (CW) and recrystallized (RX) were tested under biaxial stress conditions (strain ratios (ε_z/ε_θ) of 0 and 0.5). Displacement-controlled biaxial-expansion-due-to-compression (biaxial-EDC) tests were performed to obtain the hoop strain at failure (failure strain) of the samples. The conversion of the failure strains to J-integrals at failure (J_IC) by finite-element analysis involving data of stress-relieved (SR) cladding specimens from our previous study revealed that the failure limit in the dimension of J_IC unifies the effects of pre-crack depth. About 30–50% reduction in the J_IC value was observed as the strain ratio increased from 0 to 0.5 irrespective of the annealing type, pre-crack depth, and hydrogen content. The rate of fractional decreases of J_IC with increase of hydrogen content is in the order of CW>SR>RX, which are essentially independent of strain ratio for the CW and SR samples. The results were incorporated into the failure prediction model of the JAEA’s fuel performance code in the form of a correction factor that considers the biaxial loading effect.     

自愈合对氯离子在开裂混凝土内侵蚀的影响

开裂及自愈合是混凝土不可避免的现象。对3种不同水灰比的预制多裂缝试件,进行40d和160 d在质量分数为6％的NaCl溶液中的完全浸泡试验,结果表明,裂缝面处出现了不同程度的自愈合,自愈合面积随水灰比减小而增大,随时间增长而逐渐增大,但增大的速度逐渐变小。相同深度处裂缝附近的自由氯离子质量分数随距裂缝距离的增大而减小,...     

带环形裂纹的微试样小冲杆试验法测试材料断裂韧性探讨

火电、核电、石油化工行业中有大量的在役压力容器、管道和构件,准确评价在役设备材料的脆化和结构完整性,对于保证装置的安全运行具有重要意义。为适应这一需求,小冲杆测试技术得到了发展,但对小冲杆试样评估在役容器材料的断裂韧性时,仍然只是依靠经验方法和标准的断裂韧性值进行关联,缺乏理论依据。该文提出了在小冲杆试样上开一环形裂纹,以反映裂纹体的断裂韧性测试要求。