济钢中板厂预防精轧机支承辊端部剥落的方法探讨

济钢中板厂精轧机支承辊在使用过程中经常出现端部剥落现象,影响生产的稳定顺行。结合中板厂的现场工作条件,有针对性地采取了几种方法,有效地控制了精轧机支承辊端部剥落现象的发生,大大缓解了由于精轧机支承辊端部剥落给生产造成的被动局面。     

6209轴承内套滚道剥落原因分析

通过常规金相检验方法分析了6209轴承内套滚道剥落的原因。结果表明：由于材料原始带状组织较为严重,引起带上与带间的碳、铬浓度的偏析,造成淬火组织和残余应力的分布不均匀并增加了基体脆性,导致了剥落。     

大采高综采煤壁片帮冒顶机理与控制技术

通过三维数值模拟分析认为,大采高综采工作面加长、采高加大易于发生片帮,其机理：在采动应力作用下,煤壁先发生较小的挠曲变形,达到极值时,将在煤壁上部0.35倍采高处产生破裂,之后煤壁全部片落;防治片帮可采取特种支架与合理的回采工艺.特种支架为提高支架工作阻力、缩小端面距、二级护帮机构.回采工艺:电液控制系统实现擦顶移架、及时移架,移架速度在8 s以内.     

Rolling contact fatigue mechanism of a plasma‐sprayed and laser‐remelted Ni alloy coating

The rolling contact fatigue behaviour of the plasma‐sprayed and laser‐remelted Ni‐Cr‐B‐Si alloy coatings under two different tribological conditions of contact pressure was investigated. Two sets of fatigue‐life data of coatings were characterized by Weibull distributions. The failure mode of the coatings was identified on the basis of worn morphologies as observed at the surfaces of the failed coatings. The tribological mechanism leading to the formation of the fatigue spall was discussed on the basis of the subsurface morphologies observed in the failed coating. Experimental results showed that, the mean life and characteristic life of the coating decreased with increasing the contact pressure. The failure of the coatings can be termed as spalling‐type failure. A refined ‘ring‐crack model' was proposed to explain the formation of the fatigue spall. In the refined model, it was postulated that the joining of the ring‐type cracks and subsurface branched cracks was directly responsible for the spall formation.     

马钢CSP高铬铁工作辊表面氧化膜控制研究

热轧工作辊的在线氧化膜对带钢表面质量影响很大,轧辊表面氧化膜剥落直接导致带钢表面产生二次压氧缺陷。通过大量的现场试验及相关理论,本文分析了高铬铁轧辊氧化膜的动态变化过程、轧辊氧化膜形成及剥落的原因,并提出相应控制措施,取得了较大成效。     

综放面煤壁片帮的理论分析和防治

综放面前方煤体出现应力重新分布．产生支承压力．导致煤壁片帮。研究根据煤壁前方煤体的变形特点,将其划分为破碎区、塑性区及弹性区．其变形过程划分为塑性流动（残余变形阶段）、塑性变形、弹性变形3个阶段。并给出了各阶段煤体强度的本构关系。在此基础上运用极限平衡理论,推导出煤壁破碎区宽度的理论计算公式,理论分析了煤壁片帮的机理,结合工作面实际情况,提出预防和治理煤壁片帮的措施。理论指导实践．取得了良好的控制效果．减少了片帮量。     

大采高综采工作面煤壁片帮机理及控制技术

为控制大采高综采工作面煤壁片帮,通过理论分析、数值模拟、现场实测等研究方法,研究了大采高综采工作面煤壁片帮机理,在此研究基础上,根据淮南张集矿1215(3)大采高综采工作面具体条件,提出了俯斜开采、采用高阻力结构合理的液压支架、加快工作面推进速度、加固煤壁和及时带压移架等控制煤壁片帮技术,应用实践表明,控制煤壁片帮效果良好.     

大采高综采面煤壁片帮特征分析与应用

片帮问题是制约大采高综采面安全高效开采的主要因素之一,为了弄清大采高工作面煤壁片帮特征,采用压杆理论分析完整性较好的煤壁的挠度特征,得到了煤壁容易发生片帮的位置在煤壁的中上部,并与现场实测结果对比分析,得到了大采高综采面两种典型的片帮形式:半煤壁片帮和整个煤壁片帮.现场采取了提高护帮板的使用率,增加支架的实际初撑力和工作阻力,及时移架等片帮综合治理措施,减少了工作面煤壁的大块煤片帮现象.     

注浆加固技术在大采高工作面片帮治理中的应用

文章以大采高3505综采工作面煤壁片帮治理为背景,通过片帮原因分析及现场观测得出了该工作面片帮特征范围广、强度强的结论,并已经影响到了工作面的安全生产,结合现场地质条件决定采用注浆加固技术来对片帮进行治理,并对注浆材料选择、钻孔布置、注浆工艺流程等进行详细阐述,实践证明,对3505工作面进行注浆加固后,周期来压及非周期来压期间,片帮现象均得到了有效的控制,因此充分证明了煤壁注浆可以有效防治工作面煤壁片帮。     

Failure process and characteristics of three-dimensional high-stress circular tunnel under saturated water content

True-triaxial compression tests were carried out on cubic granite samples with a circular through hole using a true-triaxial testing system to investigate the influence of saturated water content (SWC) on the failure process and characteristics of a circular tunnel of surrounding rocks. The spalling failure under SWC can be divided into four periods: calm period, buckling deformation period, period of rock fragment gradual buckling and exfoliation, and period of formation of symmetrical V-shaped notches. When the horizontal axial and vertical stresses were constant, the spalling failure severity was reduced with the increase in lateral stress. Under natural water content, a strong rockburst with dynamic failure characteristics occurred on the circular hole sidewall. Under SWC, the failure severity was reduced and the circular hole sidewall experienced spalling failure, exhibiting progressive static failure characteristics. Therefore, water can reduce the failure severity of surrounding rocks in deep underground engineering, which has a certain guiding significance for the prevention and control of rockbursts.