Failure Analysis of Radiant Tube Burners in Continuous Annealing Line (CAL) of an Integrated Steel Plant

Failure analysis of radiant tube burners (ACI HK 40 with composition ~25 wt.% Cr, ~20 wt.% Ni) removed from a continuous annealing line (CAL) of a cold rolling mill (CRM) of an integrated steel plant was performed using optical microscopy (OM), scanning electron microscopy (SEM), electron probe microanalysis (EPMA), and microhardness measurements. Studies revealed that the failures were mainly attributed to combined influences of creep and carburization-assisted localized oxidative attack. A suitable heat-resisting cast austenitic stainless steel was identified as a candidate alloy to replace the previously used ACI HK 40 alloy.     

Effect of component pressure drops in two-fluid pumpless continuous vapour absorption refrigerator

Miniaturisation of the vapour absorption refrigerator requires replacement of the solution pump by a heat operated bubble pump and air cooled condenser and absorber. The replacement necessitates the selection of working media restricted to vacuum operation, and the air cooling poses the problem of high pressure drops in the refrigerator. Thermodynamic analysis of the absorption refrigerator with such a suitable working medium is performed considering the pressure drops in the system as parameters. The analysis shows that the effect of the evaporator to absorber pressure drop on the system performance is more significant than that of the generator to condenser pressure drop, and it becomes more predominant at the low generator temperature normally encountered in solar operated systems.     

Double-Doping Approach to Enhancing the Thermoelectric Figure-of-Merit of n-Type Mg2Si Synthesized by Use of Spark Plasma Sintering

We report significant enhancement of the thermoelectric figure-of-merit of Mg₂Si by double-doping with a combination of Bi, Pb, and Sb as doping elements. Addition of any two of these three elements to Mg₂Si increases the electrical conductivity by more than three orders of magnitude at 323 K, irrespective of the doping elements used. However, a corresponding decrease in the Seebeck coefficient is observed in comparison with undoped Mg₂Si. Irrespective of the combination of the three elements used for double doping, a figure-of-merit of approximately 0.7 at 873 K is obtained for Mg₂Si; this is primarily because of enhancement of the electrical conductivity.     

Optimal geometric tolerance design framework for rigid parts with assembly function requirements using evolutionary algorithms

A new forming technology of car steering knuckle was presented, aiming at eliminating the defects in the existing steering knuckle forming process. Based on orthogonal experimental design to numerical simulation by using FEM, for steering knuckle closed extrusion of multi-objective optimal design problems in systematic research, the influences of extrusion temperature and speed, mold temperature, and lubrication of forming technology were discussed with comprehensive scoring method and integrated balance method, then the process parameters used in the forming were applied in the productive practice. Results show that the orthogonal test method combined with finite element simulation can be flexible and efficient in handling of multi-objective optimization problems. As for the forming of other types of long rod fork forging, the new process and the design method have important guiding significance.     

Influence of Silicon Carbide Reinforcements on Mechanical and Wear Behaviour AA7075/15% wt. Glass fiber Hybrid Composites

Silicon - Aluminium hybrid composites are a new generation of metal matrix composites that have the potential of satisfying the recent demands of advanced applications. Hence, Aluminum alloy AA7075...     

Application of Taguchi Method to the Optimization of Detonation Spraying Process

The present study deals with an application of the Taguchi method to the optimization of a detonation spray process for alumina coatings. Coating experiments were conducted using the TaguchUfractional factorial (L₈) design parametric study to optimize spray process parameters. The Taguchi design evaluated the effects of four detonation spray process parameters: acetylene to oxygen ratio, carrier gas flow rate, frequency of detonations and spray distance. The coating qualities evaluated were surface roughness, porosity, microhardness, and abrasion mass loss. The influence of process parameters on the as-sprayed coating qualities is discussed. The results of the study indicate that the higher fuel ratio and lower spray distance will result in higher hardness, lower porosity and lower abrasion mass loss. The Taguchi analysis employed in the present investigation led to optimized process parameters for the most abrasive wear resistant alumina coatings.     

果胶酶处理对各种棉的影响

果胶质存在于棉纤维的表层,由于其中85%的羧基被甲基化,故它的存在影响着原棉的吸湿性.棉纤维果胶酶处理是利用局部水解破坏表层连续性的原理.过去,棉纱通常由不同种类的棉混合加工而成.分析了果胶酶活性对棉纤维的影响以及酶处理对不同棉纤维、棉纤维重量损失以及棉纤维束纤维强度的影响.     

Mechanical properties and corrosion behaviour of developed high nitrogen high manganese stainless steels

Influence of composition, specifically manganese and nitrogen content, on the microstructure associated corrosion resistance property of newly developed stainless steel has been studied. The developed steels have been characterised for their microstructure, mechanical and electrochemical properties. The results indicate that the addition of manganese and nitrogen as a substitute for nickel favours the austenite microstructure, higher yield strength (>350 MPa), tensile strength (>700 MPa), elongation and superior Charpy V-notch impact toughness properties. The results obtained from electrochemical tests such as potentiodynamic polarisation and electrochemical impedance spectroscopy of manganese stainless steel show remarkable improvement (about 4 times) in corrosion resistance exhibiting passivity behaviour like that of commercial stainless steel (316L).     

Joint power allocation and channel assignment for device-to-device communication using the Hungarian model and enhanced hybrid Red Fox-Harris Hawks Optimization

Multihop device-to-device (D2D) communication is a promising advancement since it allows wireless users in close proximity to communicate directly with one another without using base stations (BSs). With two nearby users, this technology intends to keep up with the accelerating development of mobile devices and the rising demands of local traffic loads. High-data-rate short-range transmission is made possible by this paradigm, which also lowers network backhaul expenses while improving end-user experience, spectral efficiency (SE) and network coverage. In order to maximize the cell's overall sum rates, this article examines the problem of selecting the optimal M-D2D linkages and cellular users (CUs) to form spectrum-sharing partners while taking quality of service (QoS) and energy efficiency (EE) needs into consideration. This study examines the use of a channel assignment system and a power allocation technique to manage interference in D2D communication scenarios involving many hops (more than one hop). The suggested channel assignment approach is based on the Hungarian method, but the power allocation system is based on the time-efficient enhanced Harris hawks optimization (HHO) and red fox (RF) algorithms. A genetic algorithm (GA)-based methodology and various baseline approaches are used to compare the effectiveness of the suggested system. Because it combines exploitation and exploration using a memory-based local search methodology and a perturbation mechanism, the suggested approach outperforms the GA in simulations. The results clearly demonstrate that the suggested method increases EE by up to 13% by producing the appropriate channel and power assignment for CUs and M-D2D users.