Materials Science Forum Vols. 773-774

Abstract: A 1000MPa grade steel plate for coal mining machinery equipment was studied in this paper. The ultra-high strength steel plate is processed by direct quenching after hot rolling plus tempering (DQ-T) to obtain high toughness and ductility. It has found that the tempering temperature has an important influence on the steel microstructure, precipitation behavior and the plate mechanical properties. At the lower tempering temperatures from 400 °C to 450 °C, the steel plate has a low toughness. When the tempering temperature is higher than 450 °C, the higher mechanical properties can be obtained due to the carbides precipitation, dislocation dissolution and carbide decomposition from residual austenite after quenching. The steel microstructure is comprised of tempered sorbite and bainite, in which sorbite plays an important role in obtaining premium microstructure.

Abstract: The Friction lining is an essential part of braking system. Friction materials have their significant role for transmission in various machines. Their composition keeps on changing to keep pace with technological development and environmental requirements. Earlier asbestos has been used as a friction material because of its good physical and chemical properties. But later researchers eyed that there are many health hazards associated with asbestos handling. The average disk temperature and average stopping time for pass is increased and it has poor dimensional stability. Hence it has lost favor and several alternative materials are being replaced these days. In this work a non-asbestos bio-friction material is enlighten which is developed using an Agro-waste material palm kernel shell (PKS) along with other Ingredients. Among the agro-waste shells investigated the PKS exhibited more favorable properties. The developed friction material is used to produce automobile disk brake pads. The developed brake pads were tested for functional performance on a specially designed experimental test rig. Physical properties of this new material along with wear properties have been determined and reported in this paper. When compared with premium asbestos based commercial brake pad PKS pads were found to have performed satisfactorily in terms of amount of wear and stopping time.

Abstract: Two major drivers for the use of advanced steels in the automotive industry are 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 automobile manufacturers 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 complex-phase or multi-phase steel which has a complex microstructure consisting of various phase constituents and a high yield to tensile strength ratio. Transformation Induced Plasticity (TRIP) steels is another 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. A relatively new class of AHSS is the Quenching and Partitioning (Q&P) steels. These steels seem to offer higher ductility than the dual-phase steels of similar strengths or similar ductility as the TRIP steels at higher strengths. Finally, martensitic steels with very high strengths are also in use for certain parts. The most recent initiative in the area of AHSS is the so-called 3^rd Generation AHSS. These steels are designed to fill the region between the dual-phase/TRIP and the Twin Induced Plasticity (TWIP) steels with very high ductility at strength levels comparable to the conventional AHSS. Enhanced Q&P steels may be one method to achieve this target. Other ideas include TRIP assisted dual phase steels, high manganese steels and higher carbon TRIP type steels. In this paper, some of the above families of advanced high strength steels for the automotive industry will be discussed with particular emphasis on the role of niobium.

Abstract: With increasing quantities of applications of Metal Matrix Composites (MMCs), the machinablity of these materials has become important for investigation. This paper presents an investigation of surface roughness and tool wear in dry machining of aluminium LM6-TiC composite using uncoated carbide tool. The experiments carried out consisted of different cutting models based on combination of cutting speed, feed rate and depth of cut as the parameters of cutting process. The cutting models designed based on the Design of Experiment Response Surface Methodology. The objective of this research is finding the optimum cutting parameters based on workpiece surface roughness and cutting tool wear. The results indicated that the optimum workpiece surface roughness was found at high cutting speed of 250 m min^-1 with various feed rate within range of 0.05 to 0.2 mm rev^-1, and depth of cut within range of 0.5 to 1.5 mm. Turning operation at high cutting speed of 250 m min^-1 produced faster tool wear as compared to low cutting speed of 175 m min^-1 and 100 m min^-1. The wear minimum (VB = 42 μm ) was found at cutting speed of 100 m min^-1, feet rate of 0.2 mm rev^-1, and depth of cut of 1.0 mm until the length of cut reached 4050 mm. Based on the results of the workpiece surface roughness and the tool flank wear, recommended that turning of LM6 aluminium with 2 wt % TiC composite using uncoated carbide tool should be carried out at cutting speed higher than 175 m min^-1 but at feed rate of less than 0.05 mm rev^-1 and depth of cut less than 1.0 mm.

Abstract: The work of manufacturing engineers is to utilize the minimum amount of energy or resources in bringing out a product without compromising on quality. Hence, to achieve this, the engineers must figure out the optimum or the best possible method to fabricate a product. This paper uses a multi criteria decision making (MCDM) model namely Analytical Hierarchical Process (AHP) to determine the best possible machining process to achieve the optimum results for an engraving operation on gear face in an automobile industry which uses five nontraditional machining processes viz; Laser Beam Machining (LBM), Ultrasonic Machining (USM), Electric Discharge Machining (EDM), Electrochemical Machining (ECM) and Electron Beam Machining (EBM). The five criteria considered in this paper are Material Removal Rate (MRR), Surface Finish, Depth Damage, Tolerance and Toxicity. The AHP result shows that ECM is the most suitable machining process as compared to others.

Abstract: In this paper, a data acquisition system was constructed for examining grinding performance of a plunge grinding machine. The system is capable of simultaneously recording power assumption of main spindle, grinding normal force, and material removal of a workpiece. Through grinding experiments for cylindrical workpieces, parameters of grinding process including normal force, power consumption, and time history of diametric error were obtained. With the obtained parameters, the stiffness and time constant of the grinding system were being derived such that the performance of the grinding machine was well evaluated. The configured system described in this paper can be applied to improve grinding performance through further online compensation process.

Abstract: The preparation of AlB₁₂ powder by SHS has been investigated. Mg, Al₂O₃ and B₂O₃ powders were mixed as staring materials. SHS products were treated by acid pickling. Adiabatic temperatures were calculated by HSC software. XRD, SEM, TEM analyses were used products after acid picking treatment. The reason caused AlB₁₂ low purity is the formation of Mg_0.4Al_2.4O₄ and insoluble matter

Abstract: Titanium is difficult-to-cut materials due to its poor machinability and thermal conductivity when machining at high cutting speed. To overcome this machining titanium alloy problem, this study in interaction between machining structural system and the cutting process are very important. One of the main problems in the cutting process is chatter vibration. Due to chatter problem, the mechanism to suppress chatter named, process damping is a useful method can be manipulated to improve the limited productivity of titanium machining at low speed machining in milling process. In the present study, experiment are conducted to evaluate and study the process damping mechanism in milling using different types of variable tools geometries. These tools are variable he-lix/uniform pitch, variable pitch/uniform helix and variable helix and pitch and uniform helix/pitch. The result showed that the variable helix and pitch tools is very significantly improve process damping performance in machining titanium alloy compare to traditional of regular tools and other irregular tools.

Abstract: This paper presents an experimental study to analyze the surface roughness reached in pieces of UNS M11917 magnesium alloy obtained by intermittent turning. A design of experiments (DOE) was established to carry out the study. Namely, factors identified as posible sources of variation of the surface roughness and their levels, written between parentheses, are the following: depth of cut (1), feed rate (2), spindle speed (2), type of tool (2), quantity of lubrication (3), type of interruption (3), measurement length (3) and measurement generatrice (3). Due to the high number of possible combinations that can be generated with the set of factors and levels identified a combined design of experiments L₄x3² was performed. Data are was analyzed by means of the analysis of variance (ANOVA) method. The main results of the statistical analysis highlight the great influence of the feed rate on surface roughness among the set of factors and their interactions considered. In addition, focusing on the intermittent cutting, type of interruption and its interaction with the type of tool used are also important sources of variation, but at a lower level than feed rate.

Abstract: This paper describes design of a prototype of a wire-sawing machine and some machining demonstrations. Slicing the rock samples is preferable to observe their interior for in-situ analysis in lunar and planetary explorations. The requirements for the wire-sawing machine were clarified as follows: using a long saw wire to extend the duty cycle, and winding and unwinding the saw wire with two reels. After building a prototype of the wire-sawing machine, the cutting performance in vacuum was compared with that in air. The cutting depth in vacuum leveled off and was smaller than that in air.