Noor Zaman Khan

Investigations on the effect of wire EDM process parameters on surface integrity of HSLA: a multi-performance characteristics optimization

Surface roughness (Ra) and micro-hardness (μh) are two important constituents of the surface integrity (SI) of the machined component. In Wire Electric Discharge Machining (WEDM), the machining factors that affect SI are generally the pulse on-time, pulse off-time, current, etc. This paper presents a study that investigates the effect of the WEDM parameters on the surface roughness average and the micro-hardness of the High Strength Low Alloy steel (ASTM A572-grade 50). Nine experimental runs based on an orthogonal array of Taguchi method are performed and grey relational analysis (GRA) method is subsequently applied to determine an optimal WEDM parameter setting. The SI parameters i.e. surface roughness and micro-hardness are selected as the quality targets. An optimal parameter combination of the WEDM process is obtained using GRA. By analyzing the grey relational grade matrix, the degree of influence for each controllable process factor onto individual quality targets can be found. The pulse off-time is found to be the most influential factor for both the surface roughness and the micro-hardness. Further, the results of the analysis of variance reveals that the pulse off-time is the most significantly controlled factor for affecting the SI in the WEDM, according to the weighted sum grade of the surface roughness and the micro-hardness.

Analysis of defects in clean fabrication process of friction stir welding

Abstract Striving for cleaner production is a sought-after manufacturing philosophy. Friction stir welding (FSW) is a joining technique with par excellence and far less invasive to the environment than even best conventional welding processes. It is energy efficient and free from consumables, affluent and radiations. It is, thus, accepted as a clean welding process that can produce acceptable quality joints. It suffers from some major challenges of defects of its own kind that subject the process open to improvements so as to prove itself a reliable production process. This study presents a holistic characterization of defects commonly found in FSW joints. The finding of the present study reveals that most defects are caused by inadequate heat generation, improper material movement around the pin and inadequate material consolidation behind the pin. The amount of heat generation and material stirring depends on several FSW parameters which may lead to the defect formation, if not selected properly. The results reported in this work are derived from sound literature support and experimentation. Prescriptions are made in the form of characteristics of defects such as likelihood of their location, main responsible parameters along with the recommendations for minimizing them.

Surface treatments of plant fibers and their effects on mechanical properties of fiber-reinforced composites: A review

The need of natural fiber-reinforced composites is increasing at very fast rate because of their ecofriendly production, decomposition, high specific strength, abundance, good physical and mechanical properties. Available literature reveals that past researchers have done a lot of work for the preparation and characterization of fiber-reinforced composites. While developing natural fiber composites, researchers encountered various problems like hydrophilic nature of natural fibers, incompatibility of natural fibers with matrix materials, thermal instability of natural fibers, and poor interfacial bonding between reinforcing phase and matrix phase. However, some of these problems can be solved to a greater extent by considering surface treatment of natural fibers before they are used in the preparation of fiber-reinforced composites. Thus, there is a need for understanding the effect of several surface treatments on the mechanical properties of fiber-reinforced composites. The aim of this paper is to put forth a comprehensive review on the effects of different surface treatments on the mechanical properties such as tensile strength, flexural strength, and impact strength and also interfacial shear strength of the fiber-reinforced composites.

Investigation on the effect of tool pin profile on the joint quality of Friction Stir Welded aerospace grade Aluminium Alloy

Abstract Present paper explores the effect of the various tool pin profiles viz. cylindrical, threaded cylindrical, threaded cam and threaded triflute on the joint quality of Friction stir welded aerospace grade aluminium alloy (AA7475). 2.5 mm thick plates of AA7475-T761 are welded using Friction stir welding (FSW) and subsequently, the welds are characterized using optical microscopy (OM) and mechanical testing. Microstructural examinations reveal that the tools with threaded cylindrical, threaded cam, and threaded triflute pin profile lead to the formation of tunneling defect and joint line remnant (JLR) in the welds probably due to imbalance in material movement caused by insufficient plunge and sticking of base material around and on the bottom of the pin. Further, it is also found that cylindrical pin profile results in the maximum tensile strength (291.8 MPa) and threaded cam pin profile gives minimum tensile strength (247.5 MPa). Low tensile strength is observed due to sticking of 0.1 mm thick layer of aluminium on the bottom of the pin leading to reduction in the active plunge causing defects formation and deteriorating the joint quality.