Asymmetric deformation of metal and front flexure of thick sheet in rolling. Part 1

In thick-sheet rolling, formulas are obtained for the kinematic parameters of the deformation source, the torques, and the front flexure of the sheet leaving the rollers. A criterion for front linearity of the sheet is developed. The basic parameters affecting sheet flexure are the temperature gradient over the slab cross section and the insertion angle of the sheet in the rollers.     

Damage to thick steel sheet in cyclic plastic flexure

The laminar development of damage in thick 10Г2С1 steel sheet during cold plastic deformation by cyclic flexure is investigated. The steel is subjected to pure flexure in a symmetric cycle, with strain of amplitude 5.5%. The variation in steel strength indicates the damage kinetics in the plastic deformation. In the region of reversible damage, the rate of change in the strength increases to a maximum and then declines. In the region of irreversible damage there is no further change in strength of steel before failure occurs. An upper limit is proposed for the damage of the steel: 20–30% of N_f, where N_f is the number of cycles to failure in cyclic extension–compression. In structural terms, the upper limit of reversible damage is assumed to correspond to the transformation of cellular dislocation structure to band structure.     

Asymmetric rolling of metal powders and granules

The paper examines asymmetric rolling of aluminum powder and granules on driving rolls of different diameters at the same angular velocity. The ratio of roll diameters is 1.1 to 1.4. It is established that asymmetric rolling of powder material allows removing drawbacks peculiar to traditional asymmetric rolling. These drawbacks are roll camber and destruction caused by nonuniform distribution of contact stresses across the roll width. Thereby it is possible to substantially reduce rolling defects and improve the quality of roll. __________ Translated from Poroshkovaya Metallurgiya, Vol. 46, No. 3–4 (454), pp. 115–121, 2007.     

Surface-crack formation in the two-phase region when rolling thick microalloyed-steel sheet

The formation of a surface defect (a lobed scab) in the final stage of large-diameter pipe production is analyzed. Surface microcracks are assumed to form in the rolling of thick sheet on account of problems in the two-phase region on rolling, with localization of the plastic strain, as well as the action of tensile stress in the surface layer and the attainment of limiting stress values. Physical modeling in the Gleeble system permits determination of the limiting stress (rupture strength) in rolling in the two-phase region, which depends on the temperature and is structure-sensitive. The limiting stress is determined by ferritic and bainitic transformation in the steel.     

Analyticoexperimental investigation of metal powder deformation in rolling

Conclusions Use of an analyticoexperimental method of investigation of metal powder deformation in rolling made it possible to obtain a mathematical model of the densification coefficient giving satisfactory agreement with experimental results and establish a geometric representation of the deformation of particulate solids. The results of this study may be utilized for developing elements of the theory of metal powder shaping in rolling and also for optimizing the roll compaction process and exercizing control over it.Translated from Poroshkovaya Metallurgiya, No. 9 (117), pp. 14–17, September. 1972.     

Strip deformation and densification in the forward slip zone in metal powder rolling

Conclusions In the rolling of powder materials, as in the working of nonporous metals, the strip thickness decreases in the forward slip zone. With increasing elastic roll compression, the relative deformation of strip in the forward slip zone grows. In the forward slip zone the intensity of densification of material is equal to or greater than the mean intensity of densification over the whole length of the region of deformation.Translated from Poroshkovaya Metallurgiya, No. 3(219), pp. 19–24, March, 1981.     

金属薄板面内压剪变形的损伤断裂行为

相变诱导塑性钢（TRansformation induced plasticity, TRIP）作为常用的先进高强钢在汽车等交通工具的轻量化方面有广泛的应用前景。而对于其复杂零件的成形过程,韧性断裂是不可忽视的问题之一。本文针对现有实验装置不易诱发薄板承受面内压剪时断裂失效,从而无法研究板料负应力三轴度区间断裂行为的问题,以高强钢TRIP800薄板为研究对象,设计了可在单向试验机完成压剪实验的试样和夹具。通过调整夹具旋转角度和试样装夹位置可以实现同一种试样在广泛的负应力三轴度范围内进行压剪断裂分析。基于ABAQUS/Explicit平台建立了三个典型加载方向20°、30°和45°对应的压剪过程有限元模型,分析表明:三种情况的试样局部变形区域的应力三轴度都小于0且断裂点的应力三轴度低至?0.485,验证了设计的装置可实现负应力三轴度区间的断裂失效分析,同时基于MMC断裂准则分析了不同应力状态的初始损伤情况及损伤扩展路径。      

冷轧窄带钢金属变形阻力的选择

分析了影响冷轧带钢金属变形阻力的变形程度,变形速度和变形温度等因素,并通过实例确定冷轧计算中变形阻力的选择。     

The effect of surface deformation on lubrication and oxide-scale fracture in cold metal rolling

Finite-element analysis is used to examine the surface deformation of a thin strip at the inlet to the bite in cold metal rolling. There is a “pre-entry” region ahead of the bite where there is significant elastic deformation of the strip and a very short transition region at the elastic-plastic boundary (which is not accurately modeled in this analysis). A suitable normalization allows the shape of the inlet profile and the surface extension of the strip ahead of the bite in the pre-entry region to be represented by a single master curve. The effect of strip deformation ahead of the bite on inlet lubrication and surface oxide fracture in aluminum rolling is investigated.     

Gel electrode imaging of metal fatigue: Part ii. deformation in 1100 Aluminum

During the early stages of metal fatigue, the accumulation of damage produces microcracks in the surface oxide film. This process was first measured quantitatively by the exoelectron method. This paper describes a new and much simpler electrochemical technique, which can also detect microcracks in surface oxide films and provide quantitative information on the distribution and severity of fatigue damage. In these experiments the specimens are coated initially with thin (14 nm) anodic oxide films. After fatigue cycling, a semisolid electrolyte is placed in contact with the specimen, and the flow of current to the microcracks in the anodic oxide is measured. The distribution of fatigue deformation which accumulates prior to the appearance of a fatigue crack is easily measured, and in this regard the sensitivity of the technique is shown to exceed that of a scanning electron microscope. Fatigue deformation in 1100 aluminum is detected as early as 1 pct of the fatigue life, and the electrochemical current flow increases systematically with fatigue cycling as the density of microcracks in the oxide increases. The charge flow can therefore be used to predict the remaining fatigue life.