Advanced Materials Research Vol. 445

Abstract: Spherical grains can be obtained by several semisolid processes in aluminium alloys. One of these methods is called Strain Induced Melt Activated (SIMA). In this work, commercially available 2024 and 7075 alloys were subjected SIMA process. First, optimised process parameters were investigated for the homogeneous spherical grain structure. This was followed by solution heat treatment of the parts. For the quenching medium, room temperature and 80°C boiling water was selected. The effect of different quenching temperatures over the mechanical properties was tested. Hardness, tensile and fatigue tests were applied. In addition, reduced pressure test was used to assess alloy quality and the results were compared with the mechanical tests.

Abstract: In this study, surrogate models are constructed to approximate the behavior of simulation models for springback angles, sidewall curl, and sheet thickness reduction in U-bending process. The surrogate-modeling techniques used here are: (i) polynomial response surface (PRS), (ii) Kriging (KR) and (iii) radial basis functions (RBF). While constructing surrogate models, the following procedure is pursued. First, a set of training points is generated using Latin hypercube sampling method, and finite element simulations are performed at these points. Then, surrogate models are constructed utilizing the training data. The accuracies of the surrogate models are evaluated by using the leave-one-out cross validation errors. First-order PRS is found to be most accurate surrogate model for prediction of the springback angles, side wall curl, and sheet thickness reduction.

Abstract: During chip formation, material is subjected to high deformations and high strain rates which generate high pressures and temperatures. Cutting fluids have an important role but produce many constraints: cleaning of parts, environment quality degradation, cost increase, diseases as identified by the European Agency for Safety and Health at Work. Dry machining is one of the future challenges although its implementation remains delicate, in particular for TiAl6V alloy. This paper aims at correlating the contact conditions at the tool/chip interface with the tool wear to understand the wear mechanisms of carbide tools in dry machining. Numerical simulations, experimentally validated, allow pointing out that the temperature distribution at the tool/chip interface depends on chip type (continuous, serrated). For continuous chips, the temperature is fairly uniform and stationary throughout the interface. For segmented chips, a cold zone between two temperature peaks is observed and moves along the tool rake face during the formation of a chip segment. The evolution of the normal stress at the interface is similar for both types of chips at the beginning of the localization phenomenon. These pressure and temperature fields allow the titanium to diffuse into the tungsten carbide and form the mixed carbide (Ti, W)C, which is very sensitive to oxidation above 500°C. This could explain the attrition of the tool, due to the brittleness of the oxycarbides. Contact conditions and tool wear are finally correlated.

Abstract: The study presents the need for instrumented testing to optimizing materials against impact forces. The objective of the study is how the impact behaviour of composite materials is investigated by slow and high speed impact tests. Instron Dynatup 9250HV and Instron Dynatup 8150 Impact test machines (Fig.1.) are used which are located in TUBITAK-MRC, Materials Institute , Impact Test Laboratory". The damage process in composite materials under low and high velocity impact loading and the impact energy-displacement properties of the composite materials were investigated. Composite samples were produced by woven fabrics. The results are given as graphs and tables. The Impulse Data Acquisition software is used to send the data to computer.

Abstract: The mechanical properties mainly tensile properties, impact toughness and high-cycle fatigue properties, of two-phase Al-20Zn alloy subjected to severe plastic deformation (SPD) via equal-channel angular extrusion (ECAE) using route A up to 2 passes were studied. The ECAE almost completely eliminated as-cast dendritic microstructure including casting defects such as micro porosities. A refined microstructure consisting of elongated micro constituents, α and α+η eutectic phases, formed after ECAE via route A. As a result of this microstructural change, mechanical properties mainly the impact toughness and fatigue performance of the as-cast Al-20Zn alloy increased significantly through the ECAE. The rates of increase in fatigue endurance limit are approximately 74 % after one pass and 89 % after two passes while the increase in impact toughness is 122 %. Also the yield and tensile strengths of the alloy increase with ECAE. However, no considerable change occurred in hardness and percentage elongation of the alloy. It was also observed that the ECAE changed the nature of the fatigue fracture characteristics of the as-cast Al-20Zn alloy.

Abstract: During the technological development, some equipments remain mostly the first days design besides most of others change repeatedly. CNC Milling machines spindle design is one of these which remains mostly the same. With the existing design, in order to obtain the desired torque for metal milling process, the body of the spindle is made huge and heavy which causes the whole machine body to be constructed huge and heavy. In this study a new approach to CNC Milling Machine Spindle Design is made. The design changes the hob to be held indirectly instead of to be held directly at the lower end of the spindle. The huge spindle motor is fixed to the ceiling over the machine and a flexible steel rope is used to transfer the rotational motion. At the end of the steel rope, a planetary gearbox is fixed which is also fixed to the mobile part of the CNC construction. By this way, the required torque is obtained just at the milling process takes place and the motion transmission parts can be made light in weight like the whole construction would be made.

Abstract: Blanking is one of the most widely used manufacturing technologies in sheet metalprocessing, because nearly each sheet must be trimmed out of a semi-finished part or has to beblanked after a forming process to get the precast part in the manufacturing chain. In general, a highquantity of blanked parts should be manufactured without reworking the tool. Therefore a capableprocess is indispensable to avoid inadequate part quality or premature failure of the tool because ofwear. The blanking process is affected by tool parameters, the press and the material properties ofthe blanked part.However, another important factor is the occurring temperature in the shearing zone of the sheetmetal due to the dissipation of nearly 95% of the plastic work during blanking and, in addition,frictional heating. This temperature impacts the blanking process features such as tool-wear andresulting cut edge quality. It has been presumed to be negligible by a lot of authors yet. In contrastsome publications with experimental and analytical research assume that the temperature reachesvalues up to 1000°C. Therefore, this report outlines a thermoelectric method to measure theresulting temperature distribution during the blanking process on the cutting edge of the blankingpunch. The feasibility of the investigated measurement concept is shown on a concrete example.

Abstract: The mechanical properties, among all the properties of plastic materials, are often the most important properties because virtually all service conditions and the majority of end-use applications involve some degree of mechanical loading [1]. In the present work three different commercial polyethylene materials are tensile tested at four or five different tensile rates and two or three temperatures. Tensile test results against tensile rate include stress at 0.5 % elongation, tensile strength, yield strength, modulus of elasticity, elongation at yield and % elongation are determined. It is concluded that the structure, chain lengths and branching rates of polymer matrix significantly effected tensile test curve characteristic.

Abstract: Wood chips and polymer composites are effectively used in the industrial products. It is important to establish a relationship between mechanical strength and processability in extruder of these composites. Especially, the most important factor is to determine the time-dependent strength. Although many short-term values were obtained via normal mechanical experiments, very little effort has been spent in order to estimate the long-term behavior of polymer. Composites were prepared with processed and unprocessed wood chips. Pretreatment of wood chips were carried out by using hydrochloric acid (HCl) and water. The products were prepared with different ratios of mixtures which contain wood chips and high density polyethylene (HDPE) grains. The long-term mechanical behavior and viscoelastic behavior of these composites were analyzed using Dynamic Mechanic Analyzer (DMA) test equipment. The effect of composite content and pretreatment method of wood chips on mechanical strength of wood plastic composites (WPCs) were determined. The relationship among the composite content, preparation method of wood chips, DMA and TG/DTA test results were tried to establish. FT-IR spectrums of the beginning materials and the composites are also examined in order to determine the chemical bonds of these materials.

Abstract: As the inkjet printers have two axes of movement, (one for scrolling of the paper and one for travelling of the cartridges) inkjets have closed loop stepper motor control cards for two axes which can be used in CNC routers. There are few studies in literature and internet about this method. The main difficulty while using these cards as motion control card is to send the motion data of the cutting process to the CNCs motor drivers. As programming ability is needed, this is the point where the projects are mostly left unfinished. In this study, a new method to help use of printer motherboards as CNC router motion control cards, with no need of programming skills and buying expensive software, is given. In this method, the third dimension of the picture is represented by colors. After drawing the two dimensional top view of the workpiece with any simple graphics painting software which can be found in every computer like Paint, is painted with the colors black to white, from the lowest level to highest respectively, like in the geographical maps which the oceans are painted darker to lighter according to the depth. As it is known that there are 16.7 millions of colors between black and white, the system is impressively precise in Z axis. The analogue signals of the colors which are sent from printers motherboard to the cartridges are captured with a PIC based circuit, which is designed for this project. Then the color codes are converted to Z axiss position data and PWM signals that are needed in Z axis motion. The X and Y axes stepper motor control PWM signals are generated by printer motherboard and used in the system just as is. While doing the cutting process on a printer motherboard attached CNC, the computer assumes as if a picture is being printed with the printer that is connected to USB or parallel port. This method is candidate to be one of the most common used home based or laboratory based CNC control methods in the near future.