Mechanics and FEM estimation of gaps generated in star-ring active contacts of ORBIT motor during operation

International Journal of Mechanics and Materials in Design - We estimate deformations or gaps occurring at all the ideally form-closed contacts, that separate the chambers, in epitrochoid...     

Role of Niobium in Advanced High Strength Steels for Automotive Applications

Two major drivers for the use of newer steels in the automotive industry is fuel efficiency and increased safety performance.Fuel efficiency is mainly a function of weight of steel parts,which in turn,is controlled by gauge and design.Safety is determined by the energy absorbing capacity of the steel used to make the part.All of these factors are incentives for the U.S.automakers to use Advanced High Strength Steels (AHSS) to replace the conventional steels used to manufacture automotive parts in the past.AHSS is a general term used to describe various families of steels.The most common AHSS is the dual-phase steel that consists of a ferrite-martensite microstructure.These steels are characterized by high strength,good ductility,low tensile to yield strength ratio and high bake-hardenability.Another class of AHSS is the multi-phase steel which have a complex microstructure consisting of various phase constituents and a high yield to tensile strength ratio.Transformation Induced Plasticity (TRIP) steels is the latest class of AHSS steels finding interest among the U.S.automakers.These steels consist of a ferrite-bainite microstructure with significant amount of retained austenite phase and show the highest combination of strength and elongation,so far,among the AHSS in use.High level of energy absorbing capacity combined with a sustained level of high n value up to the limit of uniform elongation as well as high bake hardenability make these steels particularly attractive for safety critical parts and parts needing complex forming.Finally,martensitic steels with very high strengths are also in use for certain parts.The role of Niobium in all of the above families of advanced steels for the automotive industry will be discussed in this paper.     

Thermodynamics of nozzle blockage in continuous casting of calcium-containing steels

Calcium-bearing material is added commercially to remove sulfur and to control sulfide shape. Few steelmakers, however, have used calcium additions to cast aluminum-killed steels successfully through metering nozzles. In a development program to cast aluminum-killed steels at Inland's No. 1 Electric Furnace and Billet Caster Shop, calcium-silicide injection at first resulted in nozzle blockage in both aluminum-killed and silicon-killed steels. This paper discusses the thermodynamics of iron containing silicon, aluminum, calcium, oxygen, and sulfur, as well as analyses of the nozzle deposits. The thermodynamic calculations show that, in iron containing aluminum, the calcium content can be too high, so that solid calcium sulfides form. In iron containing silicon without aluminum, with similar calcium contents, solid calcium silicates and calcium sulfides can form. The results of the analyses from plugged nozzles were in agreement with these thermodynamic predictions.     

Mechanism of hot-shortness in leaded and tellurized free-machining steels

This investigation was aimed at understanding the mechanism of hot-shortness in AISI 12L14 + Te steels, which might lead to a hot-rolling practice to minimize the high yield losses in this grade. High temperature tensile tests showed a pronounced loss in ductility between 810 and 1150 °C, the embrittlement being most severe at about 980 °C. Electron microprobe studies confirmed thermodynamic stability data which indicated that tellurium occurs primarily as PbTe in this steel composition. SEM fractography revealed increasingly brittle, partially intergranular tensile fracture with a loss of ductility. Auger Electron Spectroscopy of samples quenched from the embrittlement temperature range indicated the formation of a thin film of PbTe on the grain boundary surfaces. All these results are consistent with a mechanism of liquid metal embrittlement by PbTe which has a melting point of 923 °C. Some theoretical considerations of this mechanism are discussed. The characteristic return to ductility above the embrittlement range suggests that rolling at temperatures above 1150 °C might minimize the hot-shortness problem. Results of limited hot-rolling experiments to study the incidence of surface cracking as a function of temperature support the above suggestion. Formerly with the Inland Steel Research Laboratories.     

Effect of Sulfur and Zirconium on the Machinability and Mechanical Properties of AISI 1045 Steels

The effects of small increases of sulfur and addition of zirconium in conjunction with sulfur on the machinability and mechanical properties of laboratory-produced AISI 1045 steels have been investigated. Machinability was measured in terms of cutting energy per unit volume of metal machined. With increasing sulfur, there is a linear increase in sulfide volume fraction and improvement in machinability. Ductility parameters such as tensile reduction in area and impact shelf energy, however, significantly decrease with sulfur, particularly in the transverse direction. Addition of zirconium causes formation of manganese-zirconium sulfides and increased globularity. Although further improvement in machinability by zirconium addition is not evident, there is a significant improvement in transverse impact properties by zirconium addition for steels containing high sulfur. The study suggests that an optimum combination of higher sulfur for improved machinability and zironium for better impact properties yields a steel with acceptable machining and ductility criteria.     

An investigation of factors controlling part growth and surface finish of form tools in the automatic screw machine test

In order to investigate factors controlling part growth and surface finish in the automatic screw machine test, a set of eight separate experiments was carried out. It was observed that flank wear is the major factor in controlling rough-form part growth, but does not account for all of it. Other possible factors were reviewed. The elastic deflection of the workpiece estimated from the increase of the taper of rough-formed part with machine time appears to account for most of the difference between the observed part growth and the estimated values from flank wear. BUE overhang and thermal expansion of the workpiece could also contribute to rough-form part growth. The contribution of BUE overhang could be either positive or negative depending on how overhang size changes with machine time. Thermal expansion of the workpiece would give rise to negative part growth. Interestingly, during the initial 30 min of machining, negative part growth for rough-form tool and rapid positive part growth for finish-form tool were observed. Thermal expansion for the rough-form tool and the change in the size of BUE overhang for both tools are believed to be at least partially responsible for these effects. A procedure to start measuring part growth after approximately 30 minutes of machining is thus recommended. For finish-formed surface finish in this investigation, uneven BUE is believed to be the dominant factor in determining surface roughness.     

GAN for synthesizing CT from T2-weighted MRI data towards MR-guided radiation treatment

Magnetic Resonance Materials in Physics, Biology and Medicine - In medical domain, cross-modality image synthesis suffers from multiple issues , such as context-misalignment, image distortion,...     

Machinability of Steel

Free-machining steels are an important component of the U.S. steel industry—over two million tons per year have been consumed during peak periods. From an economic perspective, the total cost of machining alone is estimated at $125 billion.¹ Thus, any improvement in a steel’s machinability will significantly impact the cost of manufacture. Not surprisingly, free-machining steels and machinability are areas to which recent insights are being applied for the development of a better product. This article reviews the characteristics of machinability, measurement and analytical techniques, methods for improving machinability, and ways of improving free-machining steels.