Behaviour of shotcrete supported rock wedges subjected to blast-induced vibrations

The static state of stress at the brow in a sub-level caving mine is, due to stress re-distribution, almost uniaxial (major principal stress perpendicular to the cross cut). Since large amounts of explosives are detonated in each production round, the impact of stress waves on the brow can be significant. An extensive failure mapping programme in the Kiirunavaara mine showed that many of the failures close to the brow were structurally controlled. Furthermore, the area of damaged shotcrete was extensive when plain shotcrete was used. At brows supported by fibre reinforced shotcrete, damage in the roof was observed within a horizontal distance of about 3 m from the drawpoint. To study the behaviour of roof wedges supported by shotcrete and subjected to blast-induced vibrations a single-degree-of-freedom (SDOF) model was developed. The model consists of a shotcrete layer and a rock wedge.Vibration measurements showed that maximum particle velocity was approximately 1.2 m/s. The acceleration record showing the largest magnitude was used as the load in the dynamic analyses.The analyses showed that a wedge can be ejected by a dynamic load even if the static safety factor was >10. Furthermore, the non-linear response of the wedges was in most of the cases greater when the wedge was supported both by the joints and the shotcrete layer compared to the case when the wedge was only supported by shotcrete. A conclusion from the analyses is that it is difficult to predict the dynamic response from static calculations.To provide a safe working environment close to the drawpoint, the rock support must sustain the impact of stress waves from production blasting. To support rock wedges subjected to dynamic load the support must be able to consume the energy imposed on the wedges from blasting. The non-linear numerical analyses showed that reinforced shotcrete has the necessary bearing capacity to support the wedges formed in the roof of the cross cut close to the brow. This was in fair agreement with the failure mapping.The single-degree-of-freedom (SDOF) model can be used to study the response of an arbitrarily shaped rock wedge supported by shotcrete as long as the movement of the wedge can be idealised by a pure translation and the dimensions of the wedge are small compared to the length of the incident wave. Analyses showed that 2D wedges can be used to judge whether symmetric or non-symmetric 3D wedges in a uniaxial stress field (which occurs close to the brow) are stable or not when they are subjected to waves induced by blasting.     

The Effect of Intensity Pulsed Ion Beam Irradiation on Wear Resistance of High-speed Steel

INTENSITY pulsed ion beam(IPIB)technology hasbeen developed over the last two decades primarily fornuclear fusion and high-energy density physicsresearch,which is also named as high-intensity pulsedion beam technology(HPIB)and becomes a newmodification technique of materials surface such as inthe fields of metal materials modification,functionalfilms and nano-powder synthesis[1-5].Directdeposition of a beam into a solid surface results in arapid melt and resolidification with heating and…     

高合金钢管穿孔顶头的失效分析

介绍了高合金钢管穿孔顶头的主要失效形式,对失效顶头断口进行了SEM和光学金相分析、X射线荧光光谱化学成分分析等测试,探讨了顶头开裂的主要原因。通过适当调整Nb、Co、W等元素的含量,提高顶头铸造质量等,使穿孔顶头的使用寿命有所提高。     

原位自生钢基复合材料耐磨性能的研究

用铸造的方法制备了原位自生复合碳化物[(Ti,W,Cr,V,Nb)C]增强钢基复合材料,并对该复合材料的磨粒磨损性能及磨损机理进行了研究。结果表明,采用该方法制备的钢基自生复合材料中,自生碳化物颗粒细小、圆整、且分布均匀,碳化物颗粒增强相体积分数达到42.8%;原位自生钢基复合材料的耐磨性能优良。在磨粒磨损条件下,其磨损机制主要是显微切削、颗粒脱落和脆性剥落;稀土和合金元素能够提高原位自生钢基复合材料的耐磨性能。     

国外TOFD检测标准分析和比较

概述了超声波衍射时差法（TOFD），对目前世界上主要的七个TOFD检测标准或规范进行了分析和比较，归纳了其中十二个方面的异同点。为我国TOFD检测标准的制订和TOFD技术的发展提供参考。     

铸件表面合金化层性能研究

针对采用水玻璃、树脂等作为粘结剂进行铸件表面合金化时，合金层中容易产生气孔、夹渣缺陷的问题，研究了一种铸件表面合金化新工艺，即加入一种YB成型剂将合金粉末压制成块的方法进行表面合金化，在铸钢ZG65Mn本体表面得到高含Cr、W等元素的合金化层。结果表明，通过消失模铸造工艺，使用YB成型剂较好地消除了水玻璃等粘结剂造成的气孔、夹渣，合金化层和本体之间实现了冶金结合；合金化层具有较好的耐磨性和耐热性能，加入WC后耐磨性可达本体材料的4．82倍，抗氧化性能提高50％左右，且合金化粉末压块放置操作简便、可靠。     

不同载荷下CuZnAl合金干滑动磨损性能研究

对CuZnAl（RE）形状记忆合金采用不同热处理工艺后,进行了干滑动磨损试验.在不同相变温度、不同载荷、不同磨损时间的条件下,做了CuZnAl（RE）形状记忆合金的干磨损试验,并与ZQSn5-5-5和ZQAl9-4做了对比,用电子扫描显微镜和X衍射仪对磨损表面和磨屑相组成进行了观察和检测.试验结果表明,晶粒细化与锻打能提高合金的耐磨性,合金的M相比β相耐磨,两级时效处理的合金耐磨性能优于分级淬火处理的合金.CuZnAL（RE）形状记忆合金的耐磨性优于ZQSn5-5-5和ZQAl9-4.CuZnAl（RE）形状记忆合金磨损机制主要为粘着磨损、剥离磨损和磨粒磨损.     

Wear behaviour of thermal flame sprayed FeCr coatings on plain carbon steel substrate

The principle aim of this study is to investigate the wear behaviour of FeCr coatings on Ni-based bond deposited plain carbon steel substrate for several applications in power generation plants. For this purpose, FeCr and Ni-based powders were sprayed on plain carbon steel substrates using a thermal flame spray technique. Fabricated layers were characterized by using a X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), microhardness and surface roughness testers. FeCr coatings were subjected to sliding wear against AISI 303 stainless steel counter bodies under dry and acidic environments. A pin-on-plate type of apparatus was used with normal loads of 49 and 101 N and sliding speed of 1 Hz. XRD results revealed that FeCr, Fe, Cr, Fe–Cr–Ni, γ-Fe₂O₃ and Fe₃O₄ phases are exist in the coating. In addition, some inhomogenities such as oxides, porosity, cracks, unmelted particles and inclusions were observed by SEM. The surface morphologies of FeCr samples after wear experiments were examined by SEM and EDS. It was found that friction coefficients of the coatings in dry condition are higher than that in acidic environment.     

论软件测试

本文论述了软件测试的重要性,简要介绍软件测试的基本过程,以及一些常用的技术手段、测试策略和准则。使读者在认识到软件测试重要性的同时,能够进一步了解应如何正确地选择和有效地运用各种各样的测试方法、技术和工具,来提高软件的质量和可靠性。     

ICP-AES法测定锰矿中多种组分

通过对试样溶解方法、分析元素谱线选择、基体背景干扰消除和仪器工作条件的研究,建立了一种碱熔、酸浸溶解试样,用电感耦合等离子体原子发射光谱仪对锰矿中TFe、SiO2、CaO、MgO、Al2O3、P、TiO2进行检测的方法。本方法准确、快速、成本低。