Deformation-softening behaviors of high-strength and high-toughness steels used for rock bolts

In deep ground engineering,the use of high-strength and high-toughness steels for rock bolt can significantly improve its energy absorption capacity.However,the mechanisms and effects of rock loading conditions on this kind of high energy-absorbing steel for rock bolt remain immature.In this study,taking Muzhailing highway tunnel as the background,physically based crystal plasticity simulations were performed to understand the effect of rock loading rate and pretension on the deformation behaviors of twinning induced plasticity(TWIP)steel used for rock bolt.The material physical connecting to the underlying microscopic mechanisms of dislocation glide and deformation twinning were incorporated in numerical modeling.The rock loading conditions were mimicked by the real-time field monitoring data of the NPR bolt/cable equipment installed on the tunnel surrounding rock surface.The results indicate that the bolt rod exhibits pronounced deformation-softening behavior with decrease of the loading rate.There is also a sound deformation-relaxation phenomenon induced by the dramatic decrease of loading rate after pre-tensioning.The high pretension(>600 MPa or 224 k N)can help bolt rod steel resist deformation-softening behavior,especially at low loading rate(<10~(-1)MPa/s or 10~(-2)kN/s).The loading rate was found to be a significant factor affecting deformation-softening behavior while the pretension was found to be the major parameter accounting for the deformation-relaxation scenario.The results provide the theoretical basis and technical support for practical applications.

Numerical Model Research on Rotational Performance of Beam-Column High-Strength Bolt Extension End-Plate Connection Node

The high-strength bolted end plate connection is widely used in the construction industry with its green environmental protection and excellent seismic performance. The joints of the joints are semi-rigid, the force performance is extremely complicated, and the experimental research cost is relatively high, and the cycle is very long. Therefore, the establishment of an efficient numerical model is of great significance for evaluating the force performance of high-strength bolt end plates. In this paper, the influence of different material models on the rotation performance of the joint is studied by numerical simulation, and the bending moment-rotation curve is obtained. The numerical simulation and the experimental results are in good agreement, so as to provide a reference for the design and application of this kind of joint.

运载火箭段间连接螺栓组设计方法

运载火箭形体非常大,为了制造、存储和运输的方便,往往需要将火箭箭体沿特定的面分割开来,分段制造,然后安装使用。各段之间的连接采用螺栓组,但现有螺栓组设计方法大多考虑机器底座的安装和法兰连接,对运载火箭段间连接设计并不方便。文中详细推导了火箭箭体在受弯和轴向拉/压载荷作用时,螺栓最大拉力计算公式和预紧力计算公式,并详细分析了压溃条件,最后,通过实例对文中提出的设计方法进行了验证。

提高PDMS项目法兰连接用螺栓长度的准确性

给出了如何提高三维设计软件PDMS螺栓长度的解决方案,主要通过螺栓连接元件建模标准化、对夹元件建模标准化、螺栓集标准化、螺栓长度标准化、螺栓等级标准化,从而确保PDMS项目螺栓长度的准确。

快掘成套装备研究与探讨

快掘成套装备由加长运输系统横轴掘进机、门式支架预支护系统、跨骑式锚杆钻车、桥式转载机和自移机尾等组成,系统分工明确,掘支并行作业,减人、提效效果明显,能够有效解决煤矿巷道“掘快支慢”难题,实现巷道快速掘进。

大型混流式机组水发联轴螺栓拆卸研究

大型混流式水轮发电机大修主要任务完成水轮机和发电机拆卸检查回装,而其中各联轴螺栓和过盈配合部位的拆卸过程尤为重要,一旦发生螺栓卡死的情况将大大影响检修工期。从某电站大型混流式机组检修时大轴螺栓卡死原因上深入分析,提出了多条改善措施,经过实施后大大降低了螺栓卡死发生的概率。

Influence of anchorage length and pretension on the working resistance of rock bolt based on its tensile characteristics

In coal mining roadway support design,the working resistance of the rock bolt is the key factor affecting its maximum support load.Effective improvement of the working resistance is of great significance to roadway support.Based on the rock bolt’s tensile characteristics and the mining roadway surrounding rock deformation,a mechanical model for calculating the working resistance of the rock bolt was established and solved.Taking the mining roadway of the 17102(3)working face at the Panji No.3 Coal Mine of China as a research site,with a quadrilateral section roadway,the influence of pretension and anchorage length on the working resistance of high-strength and ordinary rock bolts in the middle and corner of the roadway is studied.The results show that when the bolt is in the elastic stage,increasing the pretension and anchorage length can effectively improve the working resistance.When the bolt is in the yield and strain-strengthening stages,increasing the pretension and anchorage length cannot effectively improve the working resistance.The influence of pretension and anchorage length on the ordinary and high-strength bolts is similar.The ordinary bolt’s working resistance is approximately 25 kN less than that of the high-strength bolt.When pretension and anchorage length are considered separately,the best pretensions of the high-strength bolt in the middle of the roadway side and the roadway corner are 41.55 and 104.26 kN,respectively,and the best anchorage lengths are 1.54 and 2.12 m,respectively.The best anchorage length of the ordinary bolt is the same as that of the high-strength bolt,and the best pretension for the ordinary bolt in the middle of the roadway side and at the roadway corner is 33.51 and 85.12 kN,respectively.The research results can provide a theoretical basis for supporting the design of quadrilateral mining roadways.

Hydrogen-induced delayed fracture of Cu-containing high-strength bolt steel

The hydrogen-induced delayed fracture(HIDF)behavior of a 1300-MPa-grade high-strength bolt steel 42CrMoV containing 0.42 wt.%Cu was investigated by constant load tensile test in a pH 3.5 Walpole solution.It is shown that the addition of Cu is beneficial to enhance the HIDF resistance by~13%.The observation of the fracture surface revealed that the area fraction of brittle crack initiation zone decreased remarkably for the Cu-added steel.Both the corrosion pit depth and the corrosion rate of the Cu-added steel in the Walpole solution are notably decreased,which is primarily because of the formation of a Cu-rich protective compact rust layer and slightly higher corrosion potential.As a result,the absorbed hydrogen content in that solution was also decreased by~21%.It is concluded that the improvement in the HIDF resistance of the tested steel is primarily due to the increase in corrosion resistance and resultant decrease in the absorbed diffusible hydrogen content in the acidic condition.

基于滚压轮自动对刀和螺纹动态测量的研究

高强度螺栓的疲劳寿命决定了飞机飞行的安全系数,滚压强化是提高螺栓疲劳寿命的重要方法。传统的滚压方式一般是采用手动操作机床滚压,存在加工一致性差、精度低、表面粗糙度不好等问题。为了解决此类问题,提出采用高精度接触式测头通过编程的方式实现滚压轮微米级对刀以及螺纹牙底的动态测量。结果表明,通过程序控制滚压轮的重复对刀精度可保证在0.01 mm以内;螺纹滚压动态测量程序能够有效地控制滚压路径及滚压量,保证滚压误差不超过0.01 mm,当滚压深度为0.05 mm时,螺纹滚压后表面粗糙度较滚压前减小了55.8%。

汽轮发电机组联轴器螺栓紧力不足故障诊断

通过分析某型汽轮发电机组振动异常数据,总结故障特征,对机组振动异常进行了故障诊断。结果表明:汽轮发电机组联轴器螺栓孔绞孔不合适,使机组运行过程中联轴器发生相对位移而导致联轴器螺栓不能有效传递扭矩,引起转子平衡状况发生变化,造成机组异常振动。该故障可通过复紧螺栓紧力和现场动平衡试验进行消除。此故障诊断经可为同类故障诊断分析提供参考。

不同杆体外形树脂锚杆锚固与安设性能对比试验研究

采用实验室试验的方法研究了目前煤矿巷道支护常用的5种不同杆体外形树脂锚杆的锚固性能、树脂锚固剂搅拌均匀性、搅拌扭矩和搅拌推力。研究结果表明：5种锚杆在125 mm锚固长度下抗拔力均在170 k N以上;精轧右旋全螺纹锚杆搅拌效果差,锚固段中多处出现空洞或杆体与锚固剂分离现象;搅拌扭矩阻力最小的为细肋左旋无纵肋螺纹钢锚杆,精轧右旋全螺纹粗牙锚杆、新型低宽肋左旋锚杆、精轧右旋全螺纹细牙锚杆、普通左旋无纵肋螺纹钢锚杆分别是它的1.16倍、1.18倍、1.24倍和1.65倍;锚杆安装推力最小的为精轧右旋全螺纹粗牙锚杆,新型低宽肋左旋锚杆、精轧右旋全螺纹细牙锚杆、细肋左旋无纵肋螺纹钢锚杆、普通左旋无纵肋螺纹钢锚杆分别是它的1.75倍、1.85倍、2.7倍和2.5倍;在全长锚固情况下,精轧右旋全螺纹粗牙锚杆和精轧右旋全螺纹细牙锚杆在安装时需要1~2个工人才能完成安装,新型低宽肋左旋锚杆需要2~3个工人才能完成安装,细肋左旋无纵肋螺纹钢锚杆和普通左旋无纵肋螺纹钢锚杆需要3~4个工人才能完成安装。虽然新型低宽肋左旋锚杆在锚固性能和安装性能上明显优于目前常用的左旋无纵肋螺纹钢锚杆,但还存在一定的优化空间,特别是在横肋宽度和高度方面。

桥梁钢结构高强度螺栓组连接设计

分析了桥梁钢结构中高强度螺栓的机械性能、拧紧力矩、摩擦面间传递的作用力及摩擦系数,针对高强度螺栓受力参数进行了分析计算,分别以结构件材料的屈服极限σs和结构件所受轴向力P作为高强度螺栓组设计和计算的依据,在保证高强度螺栓联接所能产生的强度与钢板母材的屈服极限σs强度相当,即连接结构的强度匹配的前提下,对高强度螺栓联接进行设计计算。采用此方法进行的高强度螺栓组联接设计更为合理,在实际生产运行中稳定可靠。

地下巷道支护锚杆腐蚀状况调查及力学性能测试

调查了河南焦作煤矿地下巷道腐蚀环境和现场10a期管缝式锚杆腐蚀状况,对地下水腐蚀物含量、锚杆宏观质量损失和局部坑蚀情况实施了测量,并对锚杆杆体极限承载力和塑性性能进行测试。结果显示:未加任何保护措施的管缝式锚杆腐蚀较为严重,调查样本中的大多数锚杆寿命接近终结;锚杆外表面腐蚀状况以坑蚀为主,而内表面则以近似均匀腐蚀为主;锚杆表面的坑蚀数目、面积和深度等数据均遵循一定的散布规律,且坑蚀口部面积与深度间有内在关联;锚杆表面的坑蚀和穿孔对锚杆杆体力学性能有严重损害,而且锚杆延伸率损失率远大于极限承载力损失率,亦即腐蚀对锚杆塑性的损害程度远大于对其承载力的损害程度,这使得锚杆在发生破坏前难以监测到明显的变形,极易造成突发性事故。

基于多色集合理论的螺栓装配工艺建模方法

为提高螺栓装配工艺的设计和装配质量的一致性,便于工艺设计人员充分考虑影响螺栓装配质量的各个工艺因素,提出将工艺过程和质量检测得到的数据信息反馈到工艺设计各个阶段的方法;构建了工艺因素、因素属性和装配质量的层次关系模型,运用多色集合理论对其进行数字化建模;提出根据工艺因素的多色集合模型、映射模型和多色图,对螺栓装配进行工艺设计的基本方法。通过发动机缸体连接螺栓组的应用实例,对所提模型和方法进行了验证。

螺栓孔裂纹的漏磁检测

介绍了飞机机翼大梁螺栓孔漏磁检测方法,提出对工件进行脉冲式磁化,增强漏磁检测信号;对Hall检测传感装置进行优化设计,提高漏磁检测的灵敏度;采用圆光栅与驱动装置联动,消除探头运动速度不均匀对采样的影响,实现空域等距采样,并据此研制了螺栓孔裂纹漏磁检测系统,该系统能够在不解体或少量简单拆装条件下,对螺栓孔裂纹进行无损裂纹定量检测,取得了满意的效果。

破碎带工程围岩超前锚杆加固外插角研究

为了研究超前锚杆加固与破碎带工程围岩的相互作用机理及其参数选择,以福建武平紫金矿业有限公司230斜坡道在破碎带中超前锚杆加固为工程背景,在考虑隧洞工程的不可预见性和围岩压力模糊性的基础上,建立了相应的破碎带斜坡道(隧洞)大比例相似材料模型.通过对隧洞超前锚杆不同加固方式的开挖模拟试验研究和对超前锚杆加固各参数之间关系的理论推导,分析得出了超前锚杆加固外插角参数的选择原则与范围.

基于FLAC^(3D)的管缝锚杆与玻璃钢锚杆支护效果对比

高峰矿大部分巷道采用管缝锚杆支护,但受巷道支护环境以及防腐措施不当影响,支护的管缝锚杆常因腐蚀而失效,需要进行二次支护,大大增加了支护成本和劳动强度。玻璃钢锚杆具有高强、轻质、耐腐蚀和抗疲劳的优点,能有效克服锚杆易腐蚀的问题。通过采用FLAC3D有限差分软件对高峰矿管缝锚杆和玻璃钢锚杆支护进行数值分析,对比了2种锚杆在相同支护条件下的巷道变形、岩体应力场、塑性区以及安全度,充分分析了2种锚杆在高峰矿巷道的支护效果。研究表明高峰矿采用玻璃钢锚杆取代管缝锚杆进行支护具有可行性。

深部大跨度切眼顶板分区控制技术

针对深部大跨度切眼顶板自稳能力差、变形剧烈、支护困难等问题,以赵固二矿1105大采高工作面切眼支护为工程背景,综合现场调研、理论分析、顶板探测等方法,分析了深部大跨度切眼冒顶机理和不同顶板的控制关键,提出了以接长锚杆支护为主导的顶板分区控制技术,阐明了不同顶板分区的控制原理。据此,对赵固二矿1105切眼二次成巷进行了支护设计,并进行了顶板下沉量和顶板失稳垮落规律监测,结果表明:接长锚杆与中部层位顶板共同形成的"锚固体岩梁"呈现出较好的稳定性,各层位顶板均得到了有效控制,保证了切眼顶板安全与正常服务。

多层涡轮机匣内螺栓对换热特性影响的试验研究

针对叶尖间隙主动控制系统的高压涡轮多层机匣,研究了机匣内部斜向冲击高肋结构中,定位螺栓对机匣换热特性的影响规律。试验中改变孔平均雷诺数-Re(2543~7121)、螺栓直径与冲击孔直径比D d(2.67,4.13,5.33)、螺栓间距与冲击孔直径比S d(23.2,30.7,45.2)等参数,获得了不同工况下螺栓安装面局部和平均Nu数变化规律,并整理出对应的经验关系式。研究中发现,安装螺栓的存在,显著增强了机匣表面的局部换热效果,但是平均换热系数的提升幅度有限。研究结果表明,在本文试验参数范围内,当保持螺栓间距比不变时,增加螺栓直径可以有效强化机匣表面的换热系数,如当螺栓直径比D d由2.67增加到5.33时,螺栓周围机匣表面平均Nu数增加幅度达20%~30%。当螺栓直径比保持不变的工况中,螺栓间距比S d为30.7时机匣表面平均Nu数达到最大值,但是螺栓间距比参数对机匣表面换热系数影响相对较小,平均Nu数的变化幅度在10%以内。

基于结合面密封性的螺栓组连接工艺研究

主要研究了影响结合面密封性的两个因素,即螺栓预紧力和螺栓预紧顺序。建立了结合面任意易泄漏处压应力与螺栓残余预紧力的关联模型,通过工况载荷下的结合面分离应力反求各螺栓的初始预紧力,保证了零部件在装配过程中产生较高的密封性,为工程实践提供了有力的参考价值。提出了确定最优螺栓预紧顺序的工艺方案,并通过接触面上正压力与摩擦力的最大平均值和最小标准差确定了装配过程中的最优螺栓预紧顺序,保证了结合面的密封性。