Papers by Keyword: Process

Abstract: The influence of the chemical mechanical planarization process on the 4o off-axis 4HN SiC removal rate for silicon carbide slurry produced by Cabot Microelectronics Corporation (CMC) has been studied. A detailed kinetic analysis was applied and the linearity of an Arrhenius-like activation energy plot suggests that the primary removal occurs from particles adhered to the pad surface.

Abstract: In this work a 50Ni50Ti at % powder mixture, commercially pure, prepared by mechanical alloying in an attritor with the following conditions: the milling speed and the ball charge were 1500 rpm and 15:1 respectively. The milling time was 1h under a nitrogen atmosphere at room temperature. After milling it was determined the particles size distribution, the phases by Xray diffractions (XRD) and the powder morphology by scanning electron microscopy (SEM). The powders after milling were compacted and hot extruded at 600 °C with an extrusion ratio of 3 to 1 and characterized by evaluation the density and microstructural determination by optical microscopy. The obtained results are discussed to show that this route could be an alternative route to prepare the shape memory alloy.

Abstract: Semi-solid metal forming (SSM) has been recognized as a new forming technology, which is different from the present metal forming methods. Basic research on SSM has been put into operation and a number of SSM techniques have been widely applied in industry. In the application of SSM technique, at present, it is mainly used to produce the low melting point alloys such as Al-base, Zn-base and Mg-base alloys, but the high melting point alloys, for example steels as the most widely useful metal are not extensively studied and applied. In the present work, the electromagnetic stirring method was used to prepare semi-solid slurry of spring steel–60Si2Mn and stainless steel–1Cr18Ni9Ti. At the same time, spring steel–60Si2Mn and stainless steel–1Cr18Ni9Ti were directly rolled into thick strips in the semi-solid state (Rheo-rolling). It is aimed at studying the microstructure and properties of the strips to establish the feasibility of rheo-rolling for the production of the steel strips. According to the present research work, it has been shown that rheo-rolling process combines the casting and hot rolling into a single step for near net-shape production, compared with the conventional hot-rolled metallurgical process. Besides being such a cost-effective process, rheo-rolling process possesses irregular crystal grains such as rosette-type primary crystals in the microstructures because of sufficient agitation during solidification. The overall homogenization of the macrostructures in the whole part of steel ingot can be achieved.

Abstract: In the present study, fire reaction improvement of an epoxy polymer mortar (PM) formulation, induced by polymer modification with three different flame retardant (FR) systems, was analyzed and quantified. For this purpose, several epoxy PM formulations, modified with different contents and/or types of phosphate, metal hydroxide and brominated based FR systems, were manufactured and tested for both, fire reaction and flexural strength. The results were compared with those of plain epoxy PMs. Fire reaction of PM formulations was assessed by means of the Oxygen Consumption Calorimeter test, also known as Cone Calorimeter test. This test allows the determination of the main parameters that assess fire reaction behaviour of combustible materials: heat release rate, smoke extinction area, carbon dioxide and monoxide release rates, and ignitability. Test results revealed that all FR systems, in particular the phosphate based one, are effective in improving fire reaction performance of epoxy PMs. Moreover, this improvement is attained without significant losses of bearing carrying capacity of PM materials.

Abstract: The improvements in the design of the HPT tools lead to a well defined torsion deformation and permits, therefore, a comparison with other SPD-techniques. The design of the tools, the advantages and disadvantages of HPT, as well as the limitation in the sample size are discussed.

Abstract: With the increasing demands of energy efficiency and environment protection, composite materials have become an important alternative for traditional materials. Composite materials offer many advantages over traditional materials including: low density, high strength, high stiffness to weight ratio, excellent durability, and design flexibility. Despite all these advantages, composite materials have not been as widely used as expected because of the complexity and cost of the manufacturing process. One of the main causes is associated with poor dimensional control. General curved composite parts are often used as the structural components in the composite industry. Due to the anisotropic material nature, process-induced dimensional variations make it difficult for tighttolerance control and limit the use of composites. This research aims to develop a practical approach for the design of general curved composite parts and assembly. First, the closed-form solution for the process-induced dimensional variations, which is commonly called spring-in, was derived. For a general curved composite part, a Structural Tree Method (STM) was developed to divide the curve into a number of pieces and calculate the dimensional variations sequentially. This method can be also applied to an assembly of composite parts. The approach was validated through a case study. The method presented in this paper provides a convenient and practical tool for the dimensional and tolerance analysis in the early design stage of general curved composite parts and assembly, which is extremely useful for the realization of affordable tight tolerance composites. It also provides the foundation of Integrated Product/Process Development (IPPD) and Design for Manufacturing/Assembly (DFM/DFA) for composites.

Abstract: The paper describes the manufacture of thin composite panels using high performance sheet moulding compound (SMC). Topics discussed within the paper include characterisation of curing and flow behaviour of SMC material, tooling design concept and determination of suitable processing conditions for compression moulding. A Full scale “Burst test” was carried out to evaluate the mechanical performance of SMC panels. The overall performance of the SMC panels was satisfactory with all panels failed beyond the specification value. The main failure mode was a through-thickness cracking. In addition, a geometrical non-linear numerical analysis was also carried out to investigate the stress distribution and deflection behaviour of SMC panel during “Burst testing”.

Abstract: Titanium and titanium alloys are the materials of choice for many industrial applications because of their attractive combination of low density, good mechanical properties, and high corrosion resistance, and titanium is the fourth most abundant metal in the earth crust (0.86 % by weight) behind aluminum, iron, and magnesium. However, titanium and titanium alloys are not widely. The reason for this is the high cost of titanium and titanium alloys! The cost gap for titanium and titanium alloys widens when they are used for fabricating components and structures. Consequently, much effort has been expended to reduce the cost of titanium and titanium alloys. In conjunction with the University of Waikato, Titanox Development Limited-New Zealand has been successful in creating a modified novel process to produce TiAl based alloy powders with different particle sizes and compositions at low cost. The process offers several benefits to the titanium industry the most significant one of which is that it displays the potential to significantly reduce the commercial production costs of Ti-Al based alloys. This paper describes the Titanox Development Limited technology in brief, and shows how it can economically produce titanium alloy powders for different industrial applications and making titanium alloys affordable. The process has been disclosed in a PCT (Patent Corporation Treaty) application which was approved in 2004 [1], and the related patent applications either have been approved or are being filed in different countries.

Abstract: The paper presents the mathematical model of abrasive waterjet milling process. Based on analysis of existing models the authors realize a new mathematical model, considering some simplifying hypothesis. This model uses output data from model [1] and determines the advance speed, the consumption of the abrasive and the productivity of the process. To establish the productivity of the process and the advance speed we’ll use the “energy preservation” model. This model takes in account the material characteristics. The mathematical model has been solved numerical and the results have been interpreted.

Abstract: A growing interest in nanostructured materials brought about development of their fabrication methods. A great interest has been paid in this context to the methods of grain refinement which can be induced by plastic deformation. Hydrostatic extrusion was recently proposed as an alternative method of grain size reduction down to nanometer scale in metallic materials. The aim of the present contribution is to describe, in a systematic way, advantages of this processing method, such as the possibility of processing hard-to-deform materials and obtaining large dimesions products. Special attention was given to the role of hydrostatic pressure and the effectiveness of the process in terms of grain refinement and high angle grain boundaries formation. Limitations of hydrostatic extrusion, such as restriction on strain in one pass and morphological texture are also discussed together with possibilities of their overcoming.