电梯导轨矫直压弯挠度理论计算与数值模拟

为使导轨的平直度达到高速电梯的要求,通过应用弹塑性理论,建立了电梯导轨在矫直过程中的数学模型,模型给出了电梯导轨在反弯矫直过程中挠度、弯矩、曲率以及中性层之间的关系,并获得了矫直压下量的取值范围.通过有限元软件ANSYS分析验证了理论计算得到的矫直压下量取值的可靠性,并证明能够使矫直后的导轨符合使用要求.     

辊式矫直过程弯辊量对边浪影响的仿真分析

针对辊式矫直过程建立具有边浪特征的带钢有限元仿真模型,通过对比现场工况实测矫直力与有限元模型计算所得的矫直力,得到二者误差在10%以内,验证了有限元模型的精度。分别采用原始曲率补偿法和塑性变形层增加法确定了4种弯辊量设定方案。采用上述方案对浪高为20 mm的带钢进行矫直,对比矫直后带钢平直度情况,得出按最高浪采用原始曲率补偿法计算得到的弯辊量矫直效果最优。同时随着弯辊量的加大,矫直力也随之增加,为现场边浪矫直过程提供了依据。     

Residual stresses in ground steels

A new X-ray method for the evaluation of three dimensional (residual) stress states is demonstrated by studies of the effect of grinding on Armco iron and a medium carbon steel. Although the penetration depth of the Cr-radiation employed in this study is only 5 μm, there is evidence of residual stresses normal to the surface (normal and shear components). In the past it has been assumed that these stress components can be neglected. Shear stresses normal to the surface are small in Armco iron, but significant (± 60 MPa) in steel. From the sign of the shears, the direction of final grinding can be determined. Cooling decreases the tensile stresses parallel to the surface in steel; surprisingly, the opposite result is found in Armco iron.     

Residual stresses in alumina-SiC nanocomposites

Residual stresses in an alumina-SiC particulate composite were studied as a function of SiC content by X-ray diffraction. The average microstresses in each phase and the stress fluctuations in the matrix were evaluated from a combination of X-ray reflection shift and line broadening analysis. The measured average microstresses show good agreement with those calculated theoretically from a simple model. The average microstresses in the matrix increases with the SiC content while the fluctuations of the stress field decrease. In effect, the mean dislocation density in the alumina matrix increases with the SiC volume fraction with more dislocations forming networks and subboundaries, as was confirmed by transmission electron microscopy.     

六斜辊管材矫直过程精度解析

以管材六斜辊矫直过程为研究对象,推导了管材经一次反弯后,弹复曲率及残余曲率的演变过程。根据管材旋转一圈弯曲2次,计算了管材全流程矫直微元段的反弯次数;借助三次样条函数,以管材与矫直辊接触点为特征点,拟合出了管材在辊系中的弯曲形态。基于所获得的函数,可以获得任意位置处的弯曲曲率;对某一微梁段的反弯弹复过程进行循环迭代,计算出管材微梁段的最终残余曲率,进而得到最终的管材矫后的直线度精度。通过与现场矫直数据对比,证明该模型能够可靠地预测六斜辊矫直精度,为科学合理的设定矫直参数奠定了理论基础。     

Residual grain-interaction stresses in zirconium alloys

Residual grain-interaction stresses develop during the thermomechanical treatment of Zr alloys due to the anisotropy of the mechanical and thermal properties of the hep lattice. The origin and characteristics of this type of residual stress are described in conjunction with underlying physical principles employed to measure grain-interaction strains by means of neutron diffraction. The effect of thermal treatments, deformation, and irradiation on the evolution of residual grain-interaction strains are reviewed, and the most up-to-date experimental results are presented. The effects of grain-interaction stresses on the plasticity and in-reactor deformation of ZIRCALOY-2 will be discussed. This paper is based on a presentation made in the symposium “Irradiation-Enhanced Materials Science and Engineering” presented as part of the ASM INTERNATIONAL 75th Anniversary celebration at the 1988 World Materials Congress in Chicago, IL, September 25–29, 1988, under the auspices of the Nuclear Materials Committee of TMS-AIME and ASM-MSD.     

Residual grain-interaction stresses in zirconium alloys

Residual grain-interaction stresses develop during the thermomechanical treatment of Zr alloys due to the anisotropy of the mechanical and thermal properties of the hep lattice. The origin and characteristics of this type of residual stress are described in conjunction with underlying physical principles employed to measure grain-interaction strains by means of neutron diffraction. The effect of thermal treatments, deformation, and irradiation on the evolution of residual grain-interaction strains are reviewed, and the most up-to-date experimental results are presented. The effects of grain-interaction stresses on the plasticity and in-reactor deformation of ZIRCALOY-2 will be discussed. This paper is based on a presentation made in the symposium “Irradiation-Enhanced Materials Science and Engineering” presented as part of the ASM INTERNATIONAL 75th Anniversary celebration at the 1988 World Materials Congress in Chicago, IL, September 25–29, 1988, under the auspices of the Nuclear Materials Committee of TMS-AIME and ASM-MSD.     

Residual stresses in high-velocity oxy-fuel metallic coatings

X-ray based residual stress measurements were made on type 316 stainless steel and Fe₃Al coatings that were high-velocity oxy-fuel (HVOF) sprayed onto low-carbon and stainless steel substrates. Nominal coating thicknesses varied from 250 to 1500 μm. The effect of HVOF spray particle velocity on residual stress and deposition efficiency was assessed by preparing coatings at three different torch chamber pressures. The effect of substrate thickness on residual stress was determined by spraying coatings onto thick (6.4 mm) and thin (1.4 mm) substrates. Residual stresses were compressive for both coating materials and increased in magnitude with spray velocity. For coatings applied to thick substrates, near-surface residual stresses were essentially constant with increasing coating thickness. Differences in thermal expansion coefficient between low-carbon and stainless steels led to a 180 MPa difference in residual stress for Fe₃Al coatings. Deposition efficiency for both materials is maximized at an intermediate (∼600 m/s) velocity. Considerations for X-ray measurement of residual stresses in HVOF coatings are also presented.     

Residual stresses and their effects on deformation

Residual stresses induced by thermal expansion mismatch in metal-matrix composites are studied by three-dimensional (3-D) elastic-plastic finite element analyses. Typically, the stress-free state is 150 to 300 K above room temperature. The coefficient of thermal expansion of the matrix is 3 to 5 times larger than that of the ceramic inclusion, resulting in compressive stresses of order 200 MPa in the inclusions. Both compressive and tensile stresses can be found in the matrix. Since the stress may exceed the matrix yield strength near the particles, plastic flow occurs. The authors find a significant influence of this flow on the elastic and plastic properties of the composite. The calculated residual strains in TiC particles due to thermal expansion mismatch and external loads compare well with recent neutron diffraction experiments (Bourkeet al.) The present work is the first reported three-dimensional analysis of spherical inclusions in different arrays (simple cubic (sc) and face-centered cubic (fcc)) that permit a study of particle interactions.     

Residual stresses in silicon carbide particulate reinforced aluminum composites

In metal matrix composites (MMCs) residual stresses are unavoidable during cooling from high temperature in fabrication or heat treatment because of the difference in the thermal expansion coefficients between the matrix and the reinforcement. In particle reinforced MMC the residual stresses have been proved to be hydrostatic in this study by both experiments and mathematical analysis. A very slight surface effect on the measured stresses was predicted in the case Cu Kα radiation was used. The residual stresses were determined to be tensile in the Al matrix and compressive in the reinforcement. A reduction in residual stress magnitudes of both the matrix and reinforcement was observed after the sample was cooled into liquid nitrogen and heated back to room temperature, which is believed to be caused by plastic deformation of the matrix in low temperature treatment.     

CM01冷轧拉矫机上工作辊断辊的失效分析

通过对失效工作辊材料的理化检测，高、低倍分析、断口形貌的观察分析，确定了引起工作辊失效的原因是拉矫机在工作中受到折叠钢板造成卡钢，瞬间冲击截荷过大导致断辊。     

Internal stresses due to dislocation walls around second phase particles

Nickel base superalloys with large γ′ volume fractions exhibit a high threshold stress during a tensile test, and a large internal stress when tested in high temperature creep. Arrays of regularly spaced edge dislocations which develop during the first stages of creep have been observed. They lie in the γ-γ′ interfaces and form dipolar arrangements on opposite sides of the γ′ cuboids. The various components of the stress tensor are calculated for such a dipolar wall configuration and mapped by drawing equistress lines. The stress field resulting from such dislocation configurations has a very strong component along the tensile axis and opposes the applied stress. The shear component in the glide plane of similar dislocations is also very large between the precipitates and would tend to repel any new dislocation, in the absence of an external stress. The structural instability of these alloys under creep strain is also interpreted by this model.     

高速重轨矫直辊使用中破损原因分析及预防

武汉钢铁股份有限公司轨梁生产线引进德国西马克公司的平立复合矫直机矫直辊在生产中常发生破损事故,从矫直辊材质选择、孔型设计、矫直受力、来料要求等方面分析了矫直辊破损的原因,并针对这些原因提出了改进措施。通过这些措施的实施,矫直辊破损现象明显减少,提高了矫直辊的使用寿命,降低了重轨的生产成本。     

钢管斜辊矫直机辊形的一种空间算法及应用

矫直辊是斜辊矫直机上用于矫直钢管的工模具,辊形为特殊曲面,辊形设计直接决定了矫直效果。介绍了钢管斜辊矫直的工作原理及对矫直辊辊形的理论要求,选取了研究对象并建立坐标系,以矫直辊和基准钢管的空间接触曲线几何特性分析为基础,通过一系列数学路径,推导出空间接触曲线、辊形曲面、辊形母线的方程式,对辊形曲面的几何性质进行了描述。将所描述方法推导出的空间接触曲线方程式和基于共轭运动啮合原理算法推导出的空间接触曲线方程式进行了统一,实现了算法间的理论印证。利用推导出的方程式,对某一规格矫直机的辊形母线进行了数据计算和数值处理,介绍了数值处理的方法及效果。将该算法在某新建工程的3台矫直机辊形设计中进行应用,现场检测表明,在基准条件下,设计的辊形和样管的接触度良好,生产中矫直效果良好。