莱钢特钢棒材冷剪的技术改造

针对莱芜钢铁集团公司特殊钢厂小型车间原有的4000kN冷剪存在的铸造框架多处开裂、箱体刚度低、剪切能力低等问题,通过将壳体“C”型结构改为龙门框架结构,采用40Cr铸造;用定位销取代方键;将剪头提升销直径由φ35mm增大到φ50mm,并对滑架加装碟簧缓冲装置;曲轴装配采用膨胀套无键连接,降低了设备故障率,提高了剪切质量和剪切效率.     

普通低碳钢剪切试验

一、引言万能材料试验机一般都附有剪切试验装置,我们可以通过剪切试验测得材料的剪切性能,从而对受剪零件的设计计算或强度校核,提供可靠的依据。工程中受剪切的零件是很多的,例如螺栓、铆钉、锲子、键、销以及焊缝等等,因此材料的剪切性能有着不容忽视的意义。我们还应注意到零件在工作时,受纯剪切是极少的,往往在受剪的同时,伴随着弯曲和挤压。当我们用试验机所附之剪切装置进行试     

降低和消除滚切剪剪切力峰值的研究

分析了滚切剪剪切力峰值产生的原因。提出了以下措施用于降低和消除该峰值：将导向装置向钢板剪切侧平移；将滚切机中心线与被剪钢板中心错开；适当加大曲柄相位夹角和曲柄半径；采用新型导向装置；采用液压滚切剪。     

履带板销轴选材及强化热处理工艺

履带板销轴 (图 1)是工程机械的关键零件之一 ,它在服役中承受强烈剪切、冲击、弯曲和扭转作用 ,同时受到摩擦。因此 ,销轴应具有高的抗剪、抗屈服和抗断裂强度 ,同时要有较好的抗冲击、抗疲劳和抗磨损综合力学性能。销轴通常用 45钢制造 ,经高频表面淬火 ,淬硬层深度 2～ 3 mm,硬度 42～ 5 0 HRC。在使用中常发生早期剪断失效。对失效销轴进行金相分析和力学性能测试 ,结果表明 ,在距销轴表面 1mm处为细针状马氏体 ,2～ 3 mm处为隐晶马氏体 ,硬度 45～ 5 0 HRC;过渡区为马氏体、珠光体与铁素体混合组织 ,硬度 3 0～3 5 HRC;心部为原始…     

辊轮导槽导向式滚切剪剪切机构优化设计系统

分析了滚切剪剪切力峰值的产生原因,对辊轮导槽导向式滚切剪进行了介绍,并对剪切力公式的选取进行了分析,在此基础上构建了集成剪切机构优化设计与设计验证于一体的剪切机构优化设计系统.并对该软件系统进行了可行性验证,通过验证结果,证明了辊轮导槽导向式装置在克服剪切力峰值和提高剪切质量等方面的优越性.该系统为实现滚切剪的优化设计提供了方便快捷的设计手段.     

岩石Ⅱ型断裂韧度的实验方法

针对纯剪断裂试件存在的问题,提出了采用压剪试件实现岩石Ⅱ型裂纹剪切断裂并测试岩石剪切断裂韧度的实验方法,并通过对压剪试件的应力分布和测试结果的分析讨论,提出了岩石Ⅱ型断裂韧度实验的最佳方案,并进而讨论了Ⅱ型裂纹的两种不同断裂型式和断裂判据。     

国内外中厚板滚切剪装备技术现状

阐述了国内外滚切剪技术的发展过程及现状,分析了滚切剪在滚切导向技术、结构设计、定尺装置、电控技术、自动优化剪切等方面的技术进展。为了提高国内滚切剪装备的技术水平,提出应尽快研发与中厚板滚切剪技术及自动剪切控制模型相关的核心理论技术。     

铸造铝合金镦粗挤压铆接接头失效形式和强度的分析

镦粗挤压铆接是针对铸造件的连接提出的一种铆接技术,从失效形式和强度两个方面对镦粗挤压铆接得到的接头性能进行分析,通过改变冲头直径和深度,采用正交试验,得到不同的试验组合。基于体积不变原理,计算出各个试验组合下需要的铆钉高度,进行镦粗挤压铆接试验,对铆接得到的试件进行剪切和拉伸试验。根据试验结果,分析接头的失效形式,并且绘制出接头的失效极限图,最后分析了冲头尺寸对接头抗剪强度和抗拉强度的影响。研究结果表明：采用镦粗挤压铆接方法得到的接头,其抗剪强度高于抗拉强度;剪切载荷下,接头只发生根部剪断失效;拉伸载荷下,接头发生头部剥离、头部剪断和铆钉根部拉断失效。     

滚筒飞剪机剪刃侧隙自动调节装置

滚筒机构飞剪机是高速连轧机组中的关键设备,其剪刃侧隙对剪切断面的质量、调节精度起着重要的作用.本文介绍了滚筒机构飞剪机剪刃侧隙自动调节装置的结构设计、计算方法,并给出了相关数据.该装置用于梅钢1420 mm飞剪机.     

板料剪切变形应力的试验分析研究

本文由基本假设出发 ,通过分析剪切区的受力情况 ,由平衡微分方程和塑性条件联解的方法 ,推出三向应力的计算式 ,由该式确定剪断面的应力分布和塑性功 ,根据所得应力和塑性功的大小和分布 ,分析了压紧装置的作用 ,解决了剪切变形中的若干力学问题。     

芳纶/聚合物基复合材料层间剪切性能研究

按照国内外现行试验方法进行芳纶复合材料层间剪切性能测试,发现试样仅出现大弯曲变形,没有出现层间分层失效模式,推断现有方法无法正确表征和测试芳纶纤维增强聚合物基复合材料的层间剪切强度。通过基于界面元原理的复合材料层合板试验数值仿真,优化了试样的厚度和试验跨厚比。按照优化参数试验,试样出现了层间分层的正确失效模式,获得了真实的层间剪切强度,并与仿真结果吻合较好。由此,建议修订现有试验方法或建立专门的芳纶复合材料层合板层间剪切强度标准试验方法。     

机场压实填土抗剪强度的试验研究

采用原位直剪试验、室内中型直剪试验等测试手段,运用优定斜率法等数理统计方法,对机场高填方压实土的强度特性进行了分类研究,为场区设计方案的优化、稳定性评价与治理,提供了参数。该试验成果可供类似工程借鉴、参考。     

抗剪强度直剪仪的机制分析和测控系统开发

抗剪强度直剪仪可用于检测岩体结构面抗剪强度并可获得稳定的抗剪强度力学参数。针对现有直剪仪存在的缺陷,提出一种改进的抗剪强度直剪仪工作方式,在此基础上开发出抗剪强度直剪仪的测控系统,经过高、低荷载下的准静态和动态保压过程测试后满足多尺度岩体试样的测试精度和可靠性,这为岩石试样抗剪强度的研究提供了参考。     

Shear behavior of AZ80 Mg alloy using experimental,theoretical and numerical techniques

The shear punch test (SPT) is a suitable experiment for characterizing the shear behavior of various materials, especially where there are volume limitations. In the present investigation, the relations among various parameters such as clearance, die diameter and sample thickness, and the yield and ultimate shear strengths of AZ80 Mg alloy were studied. Moreover, based on the Mohr?Coulomb theory, relatively optimum conditions were introduced for the shear punch test. With this regard, a range of 2%?10% is found to be suitable for the clearance/sheet thickness ratio. To provide a simple shear stress state during a shear punch test, it is also necessary to select the die diameter/sheet thickness ratio between 2:1 and 10:1. Based on the predictions of the Mohr?Coulomb theory, it is better to conduct a room-temperature shear punch test with a sample thickness of 0.5 mm, a clearance of 25 µm and a die diameter of 2 mm. Finally, the mean conversion factors to gain the tensile and compressive yield strengths of the cast AZ80 from its shear one are found to be 1.70 and 3.09, respectively.     

Shear Localization and Damage in AA5754 Aluminum Alloy Sheets

In this article, we study the Portevin-Le Chatelier (PLC) bands and their influences on strain localization and fracture in continuous cast (CC) AA5754 aluminum sheets. Three types of tensile tests are conducted: (1) tensile samples are pulled directly to fracture at 223 K, (2) tensile samples are pulled at 223 K to initiate diffuse necking followed by unloading and reloading to fracture at room temperature, and (3) tensile samples are pulled at 223 K to localized necking and unloaded followed by reloading to fracture at room temperature. Furthermore, in situ V-bending test coupled with deformation mapping using digital image correlation is used to study damage at large strains. The results show that PLC bands detect favorable geometrical sites for shear band initiation. The formation of shear bands precedes damage and damage is a consequence of shear band formation. This article was presented at Materials Science & Technology 2007, Automotive and Ground Vehicles symposium held September 16-20, 2007, in Detroit, MI.     

枝叉管形锻件的剪—挤变形规律模拟实验研究

给出枝叉管形锻件剪－挤变形工艺的理论基础及其工艺性要求。通过物理模拟实验得出一种枝叉管形件－－截止阀体锻件的剪－挤变形关键工艺参数（即成形条件）;通过网格试验研究分析了枝叉管形件剪－挤工艺过程的金属流动情况及其变形规律;由剪－挤和镦－挤成形枝叉管形件的挤压力对比模拟实验,得出剪－挤成形过程挤压力降低规律,并验证了该工艺节能省力的特点。结果表明,利用剪－挤成形新技术可以在千吨级中型锻造设备上开发大型枝叉管形锻件的成形工艺。     

基于结构应力方法的正面角焊缝抗剪强度分析

建立了基于结构应力定义的正面角焊缝抗剪强度理论,给出了新的焊缝抗剪强度计算公式,并基于该理论对焊缝抗剪强度相关问题进行了分析.结果表明,单向受剪等焊脚正面角焊缝的断裂角度理论值为22.5°,焊趾角度和受力状态均会影响断裂角度.另外焊趾角度为30°的单向受剪焊缝具有最大的承载能力,而双向受剪焊缝的承载能力比单向受力时的承载能力也明显提高.试验数据证明了该理论的正确性,该理论也为焊缝尺寸设计提供了理论基础.     

氢对锆基块体非晶合金形变和开裂的影响

通过充氢和未充氢缺口拉伸试样和三点弯曲试样在SEM下的原位加载,研究了氢对Zr65Al7．5Ni10Cu17．5块体非晶合金形变和开裂过程的影响,结果表明,无论是否有氢,块体非晶的剪切带发展到临界尺寸,剪切裂纹就沿剪切带形核、扩展,它一旦张开就导致快速的断裂,断口边缘观察到的无特征区是剪切带,而不是剪切裂纹断口;剪切断口形貌和拉伸断口形貌没有本质区别,只有当长时间充氢才能形成氢鼓泡,如鼓泡很小或尚未形成,则氢对剪切带以及裂纹的形核、扩展没有明显影响;如存在较大的氢鼓泡,则当剪切带尚未充分发展时微裂纹就形核,导致低应力脆断。     

基于实测剪切应力及局部应变的Ti-6Al-4V绝热剪切带的峰值温度估算

认为试样表面的变形场出现不连续性不是绝热剪切带出现的标志,而是形变绝热剪切带进一步发展的结果;在计算绝热剪切带内部的峰值温度时应从局部剪切应变中扣除弹性应变,因为弹性应变不会对塑性功有所贡献。以动态扭转的Ti-6Al-4V试样（TA-50）为例,计算了绝热剪切带内部的峰值温度,其被划分为3部分：环境温度、均匀和非均匀变形引起的温度。在两种条件下（从局部剪切应变中扣除弹性应变与否）,计算出的峰值温度分别为669和665 ℃,其在热回复和再结晶的温度范围之内,未达到相变的温度,比Liao及Duffy的理论计算值（630 ℃）要高。如果剪切应力-局部塑性剪切应变的关系不能完全确定,适当的近似是必要的。     

A study of the strain rate microstructural response and wear of metals

Titanium (Ti) and copper (Cu) pins were slid against alumina in a pin-on-disk machine at a load of 50 N and sliding speeds varying from 0.1 to 4 ms⁻¹. The evolution of the microstructure in the subsurface of the material and the wear rate was co-related to the strain rate microstructural response of the material in uniaxial compression, at different strain rates (0.1–100 s⁻¹) and temperatures (298–673 K). The strain rates and temperatures in the plastically deforming zone near the surface of the pins were determined using noniterative methods. The strain rates were found to be in the region of 100 s⁻¹ near the surface and decreases as one moves into the sub-surface of the pin. The temperatures increased as the speed increased. These estimated strain rates and temperatures were superimposed on the strain rate microstructural response maps of these materials. The uniaxial compression test results of Ti showed adiabatic shear banding as a microstructural mechanism that evolves at high strain rates (≥10 s⁻¹) and lower temperatures (<575 K). Adiabatic shear bands are sites of easy crack nucleation and propagation. When Ti is slid at low speeds the near surface region of the pins deform in the adiabatic shear banding regions in the strain rate microstructural response map. At such speeds the wear rate is found to be high and reduces as the sliding speed is increased, when the material undergoes a more homogeneous deformation. The microstructural response of Cu under uniaxial compression showed that the material undergoes flow banding at intermediate strain rates (1 s⁻¹) and temperatures of up to 473 K. The subsurface microstructure of the pins slid at low speeds showed subsurface cracking and sheet like debris formation. This happen at lower speeds because the flow banding and crack nucleation is expected in the subsurface where the strain rates and temperatures are lower. The present test results show a clear relation to exist between the strain rate response of the material in uniaxial compression and its subsurface microstructural evolution and wear rate.