Validity assessment of ductile fracture criteria in cold forming

This paper describes the assessment of various empirical and semiempirical ductile fracture criteria to determine their ability to predict the occurrence of fracture in metalforming processes. The criteria assessed are reformulated such that each is expressed in terms of mostly nondimensional material-dependent quantities and constants. The constants in each criterion are determined using data from published experimental results on cold upsetting of aluminum and steel specimens. The limit strain or the forming limit corresponding to each criterion is then determined and compared with the experimental data. There is clearly good agreement between theory and experiment for several criteria, but the predictions of other criteria fall far from experimental results.     

Online adaption of milling parameters for a stable and productive process

On the way to fully autonomous machine tools it is essential to independently select suitable process parameters and adapt them on-the-fly to the appropriate process conditions in a self-controlled manner. Such systems require complex physical process models and are usually limited to feed and spindle speed adaption during the milling process. This paper introduces a new approach enabling machines during the milling process to learn which parameters lead to a stable process with maximum productivity and to adjust them autonomously. It is shown that this approach enables the machine tool to independently find stable process parameters with maximum productivity.     

Structure of white cast iron and its conformity with the Charpy rule

Conclusions It was shown that it is possible to obtain a structure of white cast iron conforming with Charpy's rule by means of hot working.Ural Scientific-Research Institute of Ferrous Metals. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 5, p. 48, May, 1975.     

Ternary rare-earth aluminum systems with copper: A review and a contribution to their assessment

Constitutional data of the R-Cu-Al systems, with R = rare earth, are summarized and discussed. Crystal structures of the phases formed in the binary boundary systems and in the ternary systems are assessed, and the phase equilibria observed in the reported ternary systems are reviewed with special attention given to the isothermal and polythermal sections of the phase diagrams. Some regularities observed in the trends of the constitutional properties of the ternary R-Cu-Al alloys are briefly described.     

Ternary rare earth germanium systems with Cu and Ag—A review and a contribution to their assessment

Constitutional data of the R-(Ag, Cu)-Ge systems, with R=rare earth, are summarized and discussed. Crystal structures of the phases formed in the binary boundary systems and in the ternary systems are assessed, and the phase equilibria observed in the reported ternary systems are reviewed with special attention to the isothermal sections (generally at 400 or 600 °C) of the phase diagrams. Some regularities observed in the trends of the constitutional properties of the ternary R-(Ag, Cu)-Ge alloys are briefly described.     

Ternary rare earth germanium systems with Cu and Ag—A review and a contribution to their assessment

Constitutional data of the R-(Ag, Cu)-Ge systems, with R=rare earth, are summarized and discussed. Crystal structures of the phases formed in the binary boundary systems and in the ternary systems are assessed, and the phase equilibria observed in the reported ternary systems are reviewed with special attention to the isothermal sections (generally at 400 or 600 °C) of the phase diagrams. Some regularities observed in the trends of the constitutional properties of the ternary R-(Ag, Cu)-Ge alloys are briefly described.     

An evaluation of switching criteria for ferroelectrics under stress and electric field

The multi-axial responses of barium titanate (BaTiO₃) and hard lead zirconate titanate (PZT-4D) are measured for stress and electric field loadings, and are compared to the response of soft lead zirconate titanate (PZT-5H) taken from a previous study. First, poled ferroelectric specimens are subjected to an electric field at an angle to the original poling direction. Second, unpoled ferroelectric specimens are loaded by a uniaxial compressive stress and a parallel, proportional electric field. The switching surfaces of BaTiO₃ and PZT-4D are constructed from the experimental measurements, and compared with existing data for PZT-5H. The measured responses are then used to evaluate the accuracy of existing micromechanical and phenomenological models of ferroelectric switching.     

Generating mechanism and formation criteria of kinked surface in peripheral end milling

A kinked surface is commonly generated in a peripheral end milling process. In this paper, the generating mechanism of a kinked surface in end milling is systematically analyzed and revealed under the convolution framework through the establishment of a surface generation and form error model. It is found that the shape and kink positions of a form error profile can be determined by the three angular parameters: the axial and radial immersion angles and the flute spacing angle. From these angular parameters, four types of flute/work engagement conditions are defined to serve as the kink formation criteria with each type generating its own distinctive surface error profile in both down and up milling configurations. These form error profiles are characterized by either a kink-free form or by a single or a combination of three types of kink forms, which are defined based on changes in the flute/work engagement conditions and the resulting slope discontinuity in the force profile. Based on the kink formation criteria, kink charts scaled in normalized axial and radial depths of cut are devised to identify the types of kinked surface generated at any given depths of cut. An algebraic closed-form expression for the positions of kink points is also derived. The proposed kink formation criteria, the kink chart and the kink height prediction are validated through experiments and by comparison with data extracted from previously published results.     

安徽池州灌口锌多金属矿矿床成因及找矿标志

安徽池州灌口锌多金属矿属长江中下游成矿带之贵池—青阳铜、钼、金银、铅锌成矿亚带,具有明显的成矿系统.为在研究区进一步寻找更多的矿产资源,文章通过分析矿区地质特征,总结矿床成因,提出找矿标志,同时圈定找矿远景区,以期为今后研究区找矿提供支撑.     

A simple approach for assessment of the corrosion inhibition efficiency of triazole,oxadiazole and thiadiazole derivatives as a function of their concentrations without using complex computer codes

Protection of Metals and Physical Chemistry of Surfaces - A new approach is introduced to predict the corrosion inhibition efficiency of triazole, oxadiazole and thiadiazole derivatives. In...     

The art and science of thermochemical data assessment

Profound knowledge of experimental techniques and a large circle of friends around the world made Dr. O. Kubaschewski a leader in data assessment for high-temperature thermochemistry. He was a master of the use of data in graphical form, which served him better than highly-sophisticated programs. Considerable insight into the level of accuracy in the original studies gave Dr. Kubaschewski an unusual ability to foresee and evaluate the data without compromising the measured values. He understood how to use thermodynamic rules to optimize experimental data. New data are constantly being accumulated and the values recommended by Dr. Kubaschewski require changes, but his approach will always be invaluable.     

Experimental and numerical assessment of Tailor-Welded Blanks formability

A Tailor-Welded Blank (TWB) consists of steels of different thicknesses, strength types welded together to produce a single blank prior to the forming process. TWBs offer several notable benefits including decreased part weight, reduced manufacturing costs, increased environmental friendliness, and improved dimensional consistency. In order to take advantage of these benefits, however, designers need to overcome the formability of TWBs and be able to accurately predict unique characteristics related to TWB forming early in the design process. In this paper, a numerical model to predict the forming height dome and a specific forming curve of TWBs is presented. Finite element analyses of standard TWB forming tests (Nakazima) were performed in Arcelor Mittal Auto Application Research Center to determine the interaction between the weaker and the stronger materials. One of the most important aspects in the instability analysis is the problem of the measurement of the critical strain at necking. A new method is presented in this paper based on the analysis of the major strain rate using the discrete Gaussian convolution. A comparison of numerical and experimental results highlights a good agreement. The numerical approach offers a considerable gain to obtain specific FLC for all configurations.     

Process related assessment and supervision of surface textures

The surface texture of a finished geometrically defined body is the fingerprint of all process stages of the manufacturing process. With machining processes like forming, cutting and abrasive processes including etching and laser texturing macro- and micromechanical deviations from the nominal geometry at the individual geometrical features are caused by machine, process, tool and workpiece dependent influences.The effect of these causes on the deviations from the nominal geometry with different processes will be demonstrated.For functional reasons more and more the nominal geometry includes defined deviations from simple form features like straight line, circle, flat and cylinder but also defined microgeometrical form features having dimensions in the micro- and submicrometer range and which are part of so called engineered surfaces.Par examples it will be shown by which metrological means and by which 2-D and 3-D parameters the individual process stage for producing different defined surface textures can be assessed and supervised.Concerning engineered surfaces with defined microgeometrical surface geometry it must be decided which geometrical parameters like size (diameter, length, curvature, depth), distance, position and orientation of the texture element e.g. of the pits of a compact disc or of craters of a laser beam etched part should be used for assessing the results of the process and how the roughness of the texture element and the surrounding area should be evaluated.The discussion of the measuring procedures includes the effect of the properties of the probing systems (e.g. the tip radius), of the electrical filtering and the statistical character of the surface roughness.