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.

Optimized DISA system parameters of a thin-wall malleable iron pipe casting by numerical simulation

The filling and solidification of a malleable iron pipe casting manufactured by DISA casting mold line with different design parameters were calculated by using software MAGMASOFT. Then the shrinkage porosity was predicted by thermal criterion. Based on the simulation results, the influences of the runner ratio and feeder position on the porosity were discussed. The results show that synchronization of injection can be significantly influenced by the size of downsprue section, and an de-sign structure of DISA gating system was used to solve the problem of flow imbalance in the filling procegs. At the same time, the riser was designed on the hotspot for feeding shrinkage. At last, the optimizated gating system and feeding system were ac-complished to eliminate shrinkage porosity.

Oil quenched malleable iron,the strength of an old material in a “green cast” development and a new future

Malleable iron lost the interest and the development stopped in the turbulent seventies of tremendous developments of new technologies. The personal computer, emission spectrometer, thermal analysis, cold-box core system and automatic vertical moulding were introduced into the foundry industry. Experience shows that these new technologies do not always match up with malleable iron. Solidifciation and mould filling simulation programs are not always capable to handle a low carbon equivalent iron like malleable iron. Recent developments show however by using these new technologies and combined with practical experience, it is possible to increase the casting yield of malleable iron to the same level as ductile iron. The mechanical properties, especially the yield strength of malleable iron according to the standard are equivalent to those of ductile iron, however the yield strength of oil quenched malleable iron is signifciantly higher than that of ductile iron. An extensive investigation is made between ductile iron, air quenched and oil quenched malleable irons based on the properties of more than 350 test bars produced under the same conditions. The results are compared with the existing international standards and discussed. Other properties like fatigue strength and response to surface treatments as induction hardening are also discussed. The costs of malleable iron are reviewed and compared with other ferro alloys. These recent developments in increasing the casting yield, the understanding of the strength, makes malleable iron competitive with ductile iron and cheaper than the first grade of ausferritic ductile iron, or steel qualities. It is possible to design lighter and save weight which is essential in the automotive industry. An example of "green cast" development for typical applications, used in automotive transmissions and engines are shown.

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.

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℃).

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.

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.

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.

Ultrahigh-strain ferroelasticity in two-dimensional honeycomb monolayers:from covalent to metallic bonding

We propose a possible ferroelastic switching pathway of two-dimensional(2 D)honeycomb lattice(including graphene,BN,stanene,etc.)that may swap its armchair and zigzag direction,reversing an unprecedented strain of 73.2%.Our ab initio calculations reveal that such pathway cannot work in covalent systems like graphene and BN;for monolayer with metallic bonds like stanene,stanane and In Bi that have all been synthesized,however,such pathway can be feasible with a low switching barrier(<0.15 eV)and stress(<graphene upon 1%tensile strain),also with the highest energy/stress point in the elastic region.Their distinct behaviors are attributed to the different feature of covalent bonds and metallic bonds:the former is rigid with directionality,while the latter is malleable with ductility.A general trend of linear decrease in switching barrier with uprising metallicity for the same group compounds is revealed.Similar behaviors can be extended to bulk zinc-blended or wurtzite structure that can be deemed as multilayer stacking of buckled monolayer.Binary compounds like In Bi monolayer are even multiferroics with both in-plane and vertical ferroelectricity as well as nontrivial topological properties.