圆盘剪传统控制方式的缺陷及优化方法

以韶钢热轧宽板厂用于切边的圆盘剪为例,分析了圆盘剪在传统恒速控制剪切模式下存在的各种缺陷,结合韶钢对圆盘剪控制模式的优化实践,详细介绍了圆盘剪变速控制剪切模式的优点和具体的实现方法,为同类型生产线减少圆盘剪设备故障、提高有效作业率提供一种新思路.     

圆盘剪水平剪刃间隙调整

通过分析圆盘剪剪切时钢板受力状态与圆盘剪水平剪刃间隙之间的关系,以及水平剪刃间隙在钢板剪切过程中变化的原因,制定了圆盘剪水平剪刃间隙的调整规程;通过生产实践摸索出的圆盘剪剪切工艺数据,推导出了剪刃水平间隙设置的经验公式,为实际生产提供了技术保证.     

圆盘剪传统控制方式的缺陷及优化方法

本文以韶钢热轧宽板厂用于切边的圆盘剪为例，分析了圆盘剪在传统恒速控制剪切模式下存在的各种缺陷，结合韶钢对圆盘剪控制模式的优化实践，详细介绍了圆盘剪变速控制剪切模式的优点和具体的实现方法，为同类型生产线减少圆盘剪设备故障、提高有效作业率提供一种新思路。     

酸洗冷轧联合轧机组中圆盘剪结构分析与设计

分析了酸洗冷轧联合轧机组中圆盘剪的结构,对圆盘剪咬入角、剪切力、剪切力矩、带钢后拉力产生的力矩进行了计算验证,介绍了圆盘剪侧隙、重叠量选择标准.介绍了无驱动型圆盘剪的工作原理和结构特点,并对冷轧圆盘剪侧隙和重叠量调整装置、机架旋转装置及自动调宽装置等进行了分析和设计.     

一种圆盘剪剪切力测试的模拟实验装置研究

根据圆盘剪剪切钢板的基本原理,设计了一种圆盘剪剪切力测试的模拟实验装置,通过现场测试,其结果与理论公式计算所得剪切力一致,证明了理论公式在圆盘剪剪切力计算上的准确性,同时为圆盘剪剪切力的测试提供了一种简便易行的新方法。     

圆盘剪卡钢的因素分析及措施

介绍了圆盘剪的生产情况,对剪切中板时圆盘剪卡钢的各种因素进行分析,提出了相应的改进措施,改善了剪切质量,提高了圆盘剪的生产效率。     

热轧带钢生产横切机组圆盘剪的改进与应用

介绍了迁钢开平机组的圆盘剪机组中的圆盘剪、碎边剪、废边卷取机等的结构及主要技术参数,分析了影响圆盘剪与碎边剪剪刃侧隙的因素,为了消除剪刃侧隙的影响,提出调整与控制措施.     

圆盘纵剪机力能参数的实验及剪刃的调整方法

本文主要研究动力圆盘剪和拉力圆盘剪的剪切力与力矩的关系,同时也研究了拉力圆盘剪拉力的计算方法以及剪刃重叠量的变化关系,找出了最佳剪刃重叠量和侧间隙量,避开在尖峰负荷处剪切,以便减少设备负荷,提高产品的产量和质量。实验证明,如果剪刃重叠量调整适当,剪切力就可减少很多,同时又证明了动力圆盘剪的剪切力和拉剪剪切力的垂直分量是相等的。在计算拉剪的剪切力时,完全可以按照动力圆盘剪的计算方法来计算。     

浅谈圆盘剪在带钢连续酸洗机组中的应用

近几年,双机架塔式旋转圆盘剪(简称圆盘剪)在连续卧式酸洗机组中得到广泛应用。在介绍这种圆盘剪结构、原理及参数计算的基础上,重点阐述剪刃侧隙和重叠量的确定及其对剪切质量的影响。此种形式的圆盘剪已投入到多个酸洗生产线上,钢带的剪切质量等各项指标均达到了预期效果,机组运行良好。     

圆盘剪在带材生产设备中的设计和应用

本文主要介绍圆盘剪的主要组成部分,以及圆盘剪的应用与设计改进。     

Critical Shear Offset of Fracture in a Zr-based Metallic Glass

The nanoscale shear band operation process of Zr_(55)Pd_(10)Cu_(20)Ni_5Al_(10) metallic glass(MG)was reined in by constant force during well-designed loading-holding-unloading cyclic microcompression test.Through the test,it is revealed that the whole shear banding process involves three stages:shear band initiation,shear sliding and shear band arrest.Based on the energy balance principle,the size-affected speed of shear sliding is interpreted.The energy originated from the shear sliding leads to heat-up of the shear plane;therefore,the temperature in shear band increases with the size of shear offset caused by the energy accumulation during shear sliding.Taking the glass transition temperature as the critical temperature of fracture for the Zr-based MG,the critical shear offset is predicted to be approximately 190μm,fully in line with the experimental observation.This directly proved that the fracture of the MG is caused by the temperature rise during shear sliding.     

Development of adiabatic shear bands in annealed 316L stainless steel: Part I. Correlation between evolving microstructure and mechanical behavior

Adiabatic shear localization in an annealed AISI 316L stainless steel was examined through a forced shear technique using a split Hopkinson pressure bar and hat-shaped specimens. A well-controlled forced shear technique provided the possibility of correlating the microstructural evolution of adiabatic shear localization to its transient mechanical behavior. The initiation of adiabatic shear bands occurred when the shear stress peaked after substantial work hardening. The work-hardening rate was found to play a dominant role in the formation of adiabatic shear localization. The stress drop presupposed the development of the localized deformation. A core structure of shear bands was generated within the shear band, which characterized a narrow-down process in the early stage of the shear band evolution. The continuous expansion of the shear band core to the entire width of the band was seen to correlate with the full development of shear localization.     

宝钢宽厚板定尺剪主传动控制系统

主要介绍了宝钢5 m宽厚板剪切线中最后一台剪切装置一定尺剪的电气主传动控制方法.通过使用西门子交流调速系统,使得剪切位置控制准确,实现了最优化剪切.     

飞剪剪切力计算模型及影响因素分析

针对连退机组飞剪设备由于刀刃钝化而导致剪切力计算值与实际并不相符的问题,充分考虑到飞剪的设备与工艺特点,通过分析刀刃钝化规律,建立了飞剪刀刃钝化模型。在此基础上,首次提出了刀刃钝化系数新概念,并根据斜刃剪切理论建立了针对连退机组飞剪剪切力计算模型,实现了对实际所需剪切力的精确表达。随后,分析了飞剪所需剪切力大小的影响因素,并编制了剪切力预报分析软件,可推广应用到某钢厂连退机组生产线,为飞剪设备电机功率与刀刃硬度的选择以及工艺参数的设定起到了指导作用。     

Shear Band Formation Observed in Ring Shear Tests on Sandy Soils

Shear band formation is an important factor in understanding failures in soil. In this paper, shear localization and shear band formation and evolution are examined using ring shear tests performed on three sands prepared by air pluviation. A transparent outer confining ring was used to visualize formation and evolution of the entire shear band. By comparing the ring shear stress paths with visual observations made during shearing, the writers show that the specimen shears uniformly over its entire height prior to shear localization. Bifurcation under constant volume and drained conditions occurs as the soil fully mobilizes its effective friction angle, and subsequent shear displacements occur only within the shear band. Consistent with previous studies, the final thickness of the observed shear band ranged from 10 to 14 times the median particle diameter. Substantial particle damage occurred within the shear band after large displacements, particularly for dilative specimens, causing additional strain-softening in contractive specimens and a second phase transformation and considerable strain-softening in dilative specimens.     

Prediction of hemolysis in turbulent shear orifice flow

This study proposes a method of predicting hemolysis induced by turbulent shear stress (Reynolds stress) in a simplified orifice pipe flow. In developing centrifugal blood pumps, there has been a serious problem with hemolysis at the impeller or casing edge; because of flow separation and turbulence in these regions. In the present study, hemolysis caused by turbulent shear stress must occur at high shear stress levels in regions near the edge of an orifice pipe flow. We have computed turbulent shear flow using the low-Reynolds number k-epsilon model. We found that the computed turbulent shear stress near the edge was several hundreds times that of the laminar shear stress (molecular shear stress). The peak turbulent shear stress is much greater than that obtained in conventional hemolysis testing using a viscometer apparatus. Thus, these high turbulent shear stresses should not be ignored in estimating hemolysis in this blood flow. Using an integrated power by shear force, it is optimal to determine the threshold of the turbulent shear stress by comparing computed stress levels with those of hemolysis experiments or pipe orifice blood flow.     

Objective Oriented Multistage Ring Shear Test for Shear Strength of Landslide Soil

Ring shear tests were conducted on five samples of different nature with a modified Imperial College type ring shear machine. The three different testing methods used, (1) individual sample testing for each normal stress, (2) increasing load multistage ring shear test, and (3) reducing load multistage ring shear test, all showed similar effective residual internal friction angle for the samples, irrespective of testing method. However, effective residual shear intercept was different according to the testing methodology. The internal friction angle did not vary, particularly after the first minimum point in the stress displacement curve, although the residual shear intercept decreased with increase in the displacement. The thickness of the shearing zone increased along with the displacement. The remolded peak shear strength for saturated conditions at field dry density varied with the consolidation history. Measurement of remolded peak shear strength was possible in a single sample using the increasing load multistage ring shear test at normal consolidation. The equilibrium water content of the sample after the ring shear test was nearly equal to the plastic limit.     

Influence of Shear Rate on Undrained Vane Shear Strength of Organic Harbor Mud

Dredging operations in European harbors for maintenance of navigable water depth produce vast amounts of harbor mud. Between 2005 and 2007, the second largest harbor construction project in Germany was designed as a pilot study to use dredged harbor mud as backfill material to avoid expensive disposal or ex situ treatment. During this project, a partial collapse of the backfill highlighted the need for an improved assessment of undrained shear strength of naturally occurring liquid harbor mud. Using vane shear testing, this study evaluates the effect of shear rate on the undrained shear strength of harbor mud. It is shown that measured values for both peak and residual shear strength are significantly influenced by shear rate effects. Furthermore, the influence of shear rate on the peak shear strength is found to be independent of water content while the influence of the shear rate on the residual shear strength strongly depends on water content. New shear rate dependent correction factors μ are proposed using the test results and the observed time to failure in the harbor basin. The proposed correction leads to significant lower design undrained shear strengths than the classical Bjerrum correction and would have predicted the failure during the construction.     

Interaction between Steel Stirrups and Shear-Strengthening FRP Strips in RC Beams

RC beams shear strengthened with either fiber-reinforced polymer (FRP) U-jackets/U-strips or side strips commonly fail due to debonding of the bonded FRP shear reinforcement. As such debonding occurs in a brittle manner at relatively small shear crack widths, some of the internal steel stirrups may not have reached yielding. Consequently, the yield strength of internal steel stirrups in such a strengthened RC beam cannot be fully used. In this paper, a computational model for shear interaction between FRP strips and steel stirrups is first presented, in which a general parabolic crack shape function is employed to represent the widening process of a single major shear crack in an RC beam. In addition, appropriate bond-slip relationships are adopted to accurately depict the bond behavior of FRP strips and steel stirrups. Numerical results obtained using this computational model show that a substantial adverse effect of shear interaction generally exists between steel stirrups and FRP strips for RC beams shear strengthened with FRP side strips. For RC beams shear strengthened with FRP U-strips, shear interaction can still have a significant adverse effect when FRP strips with a high axial stiffness are used. Therefore, for accurate evaluation of the shear resistance of RC beams shear strengthened with FRP strips, this adverse effect of shear interaction should be properly considered in design.     

Experimental Study on the Shearing Behavior of Saturated Silty Soils Based on Ring-Shear Tests

The shearing behavior of saturated silty soils has been examined extensively by performing undrained and partially drained (the upper drainage valve of the shear box was open during shearing) ring-shear tests on mixtures of a sandy silt with different loess contents. By performing tests at different initial void ratios, the shear behavior of these silty soils at different initial void ratios is presented and discussed. Undrained-shear-test results showed that the liquefaction phenomena in ring-shear tests were limited within the shear zone; for a given void ratio or interfine void ratio, both the peak and steady-state shear strengths decreased with increase of loess content. The partially drained shear tests revealed that a great reduction in the shear strength could result after the shear failure, due to the buildup of excess pore-water pressure within the shear zone; the magnitude of reduction in shear strength after failure was affected by the initial void ratio, the shear speed after failure, as well as the loess content in the sample. For a given void ratio or interfine void ratio, with increase of loess content, the drained peak shear strength became smaller, while the brittleness index became greater. It was also found that due to localized shearing, the permeability of the soil within the shear box after drained shearing could be three orders of magnitude smaller than before shearing.