High-Speed Machining of Malleable Cast Iron by Various Cutting Tools Coated by Physical Vapor Deposition

The coating material of a tool directly affects the efficiency and cost of machining malleable cast iron.However,the machining adaptability of various coating materials to malleable cast iron has been insufficiently researched.In this paper,turning tests were conducted on cemented carbide tools with different coatings(a thick TiN/TiAlN coating,a thin TiN/TiAlN coating,and a nanocomposite(nc)TiAlSiN coating).All coatings were applied by physical vapor deposition.In a comparative study of chip morphology,cutting force,cutting temperature,specific cutting energy,tool wear,and surface roughness,this study analyzed the cutting characteristics of the tools coated with various materials,and established the relationship between the cutting parameters and machining objectives.The results showed that in malleable cast iron machining,the coating material significantly affects the cutting performance of the tool.Among the three tools,the nc-TiAlSiN-coated carbide tool achieved the minimum cutting force,the lowest cutting temperature,least tool wear,longest tool life,and best surface quality.Moreover,in comparisons between cemented-carbide and compacted-graphite cast iron machined under the same conditions,the wear mechanism of the coated tools was found to depend on the cast iron being machined.Therefore,the performance requirements of a tool depend on multiple factors,and selecting an appropriately coated tool for a particular cast iron material is essential.

Role of RE and Mg on Graphitization of Spheroidal Graphite Malleable Cast Iron

Spheroidal graphite malleable cast iron is a new structural material developed in the recent years. This paper studies the influence of the residual content of rare earth and magnesium on the nodule counts, the time of first stage graphitization and the rate of ferritization of it. Moreover, the role of sulfides of rare earth and magnesium in the process of graphitization has been analyzed. The results show that the residual content of rare earth and magnesium has a notable influence on the graphitic nodule counts and the time of the first stage graphitization of spheroidal graphite, but has unremarkable influence on the time of the second stage graphitization. There are a large number of spherical sulfides of rare earth and magnesium in as-cast structure, which will act as the nucleus of graphite in the process of first stage graphitization.

EFFECT OF STRUCTURE ON GRAPHITIZATION OF WHITE MALLEABLE CAST IRON

The structure of white iron treated with Si-Bi-AI complex inoculant has been observed by SEM and TEM. The results show that, in comparison with the samples treated with ordinary inoculants, disorder, overlapping and inflexion of the pearlitic lamella appear, besides, the dis- location density increases apparently. The graphitization can be quickly realized at the tem- perature lower than that of austenitic transition (720℃).

Locating Malleable Bulk Metallic Glasses in Zr-Ti-Cu-Al Alloys with Calorimetric Glass Transition Temperature as an Indicator

We defined the plastic deformability under constrained loading conditions as malleability for bulk metallic glass （BMG） materials. Quaternary Zr-Ti-Cu-Al alloys in the Zr-rich composition range are selected to investigate the compositional dependence of malleability assessed by bending testing and glass transition temperature （Tg ）. As indicated, increasing the Al or Cu concentration in the alloys leads to the rise of T g . The Zr（61）Ti2Cu（25）Al（12） （ZT1） and Zr（61.6）Ti（4.4）Cu（24）Al（10） （ZT3） alloys exhibit an optimal combination of lower T g and higher glass-forming ability. The malleable BMGs such as ZT1 manifests two characters during deformation, the stable propagation of a single shear band indicated by large shear offsets and easy proliferation of shear bands. With increasing the T g of BMG, the yield strength σy,Young＇s modulus and shear modulus simultaneously increase as well, while the Poisson s ratio decreases. The σy of ZT1 BMG is about 1680 MPa in compression and 1600 MPa in tension. In tensile loading, no any visible plasticity appears even when the strain rate increases up to the order of magnitude of 10（-1）s（-1）. In consistent with the T g , malleability of Zr-Ti-Cu-Al BMGs manifests significant compositional dependence. The malleable BMG is associated with lower Tg , as well as lower shear modulus or higher Poisson s ratio, which can be understood on the basis of the correlation of Tg with shear energy barrier in metallic glass. Thus, the calorimetric Tg can be used as an indicator to screen malleable BMG-forming composition, with advantage of experimental accessibility.

A Nonprecedence－based Query Schedule Algorithm on Heterogeneous Multiprocessor System

There has been a number of algorithms designed to handle intra-query or inter-query scheduling in multiprocessor-based parallel database system. They all have the assumption that the processorsare identical. But in some cases, such as shared nothing environment, this assumption would not be fullyvalid. In this paper we devise and evaluate a scheduling algorithm ELLIST to handle nonprecedence-basedheterogeneous malleable scheduling problem. It uses LLIST-NM as subroutine that handles nonmalleablescheduling without precedence and assuming the processors are identical. Even though the problem we considered is NP-hard in the strong sense, the schedule generated by our algorithm is seen experimentally toachieve results that are close to optimum when there are enough tasks to be scheduled.

Infrapubic versus Penoscrotal Approaches for Implantation of Semi-Rigid Penile Prosthesis

Background: Modification of surgical techniques to minimize wound infections in penile implant surgery using malleable prosthesis which is easy to use, of very low risk of mechanical failure and is financially suitable to improve outcome and ensures less complications. The aim of the study is to compare infrapubic approach and Penoscrotal approach in penile semi-rigid prosthesis implantation surgery. Patients and methods: Fifty patients were randomly divided into two groups and each group underwent one approach. Results: No statically significant differences were found between both groups in terms of operative time. Corporeal cross over was the most common intraoperative complications, 3 cases in IP approach and 6 cases in PS but not statistically significant. Peyronie’s disease patients underwent penile implant through infrapubic approach in 3 cases and PS in 4 cases with one recorded complication of keloid formations with IP. Urethral false passage reported only in one case with PS approach without affecting the procedure. Only minor complications including superficial wound infection which was significantly more with PS, 6/25 (24%) and IP 1/25 (4%), p value = 0.041. Penile and scrotal edema was common with IP approach (92%) in comparison with PS approach (60%). The urethral catheter can be abandoned with IP to avoid the risk of catheterizations. No significant relation between diabetes and infections and no erosions were encountered. Conclusion: Through this research work, infrapubic approach is better than Penoscrotal approach even if it is not commonly used by surgeon.

An Innovative Cerclage Wire Passer

The cerclage wire is an important adjuvant in the management of Orthopaedic and trauma cases and is particularly useful in long bone fractures. It is especially useful for addressing the fractures, especially the comminuted ones with a butterfly fragment. Orthopaedic cerclage Wiring is used as an adjunct to maintain fracture reduction (either temporarily or permanently), while the bone is primarily stabilised by either a plate intramedullary nail or external fixation frame. Multiple cerclage wires provide adjunctive fixation against compressive shear, bending & rotational forces and have been used in traumatology since many years. The aim of this article is to introduce a new year simple low cost instrument named as “Suyash cerclage wire passer”, with excellent outcomes without any major complications to the Orthopaedic community.

Deformation and failure behavior of heterogeneous Mg/SiC nanocomposite under compression

The heterogeneous magnesium(Mg) matrix nanocomposite with dispersed soft phase exhibits high strength and toughness. Herein, the deformation behavior and failure process were investigated to reveal the unique mechanical behavior of the heterogeneous microstructure under compression. The extensive plastic deformation is accompanied by the flattening and tilting of the soft phase, inhibiting strain localization and leading to strain hardening. Moreover, a stable crack multiplication process is activated, which endows high damage tolerance to the heterogeneous Mg matrix nanocomposites. The final failure of the composite is caused by crack coalescence in the shear plane along a tortuous path. The presence of dispersed soft phases within the hard matrix induces a noticeable change in mechanical response. Especially,the malleability of the heterogeneous Mg matrix nanocomposite is two and ten times higher than that of pure Mg and the homogeneous Mg matrix nanocomposite, respectively. The current study provides a novel strategy to break the trade-off between strength and toughness in metal matrix nanocomposites.

二维蜂窝状单层中的超高应变铁弹性:从共价键到金属键

本文提出了二维蜂窝状晶格的一种可能的铁弹翻转路径,可以实现其扶手形方向和之字形方向的转换,其可逆应变达到73.2%.第一性原理计算结果表明,该铁弹翻转路径不适用于石墨烯和BN等共价体系.然而,对于具有金属键的单层材料(如锡烯、锡烷、单层InBi等),其铁弹翻转势垒(小于0.15 eV)和应力(小于石墨烯在1%拉伸应变下的应力)较小,并且铁弹翻转过程中的最高能量/应力点仍在其弹性区,因而能够在室温环境下实现铁弹翻转.这种不同的行为可以归结为共价键和金属键的不同特性:前者具有定向性和刚性,而后者具有韧性和延展性.文章进一步揭示了同族化合物的铁弹翻转势垒随金属性的增强呈线性下降的趋势.类似的铁弹特性可以推广到闪锌矿或纤锌矿结构中,这两种结构可视为褶皱状单层结构的多层叠加.单层InBi类二元化合物同时具有面内铁电性、垂直铁电性以及非平庸拓扑性,因而也是一类多铁材料.