Abstract: The constitutive modeling of aluminum alloy under warm forming conditions generally considers the influence of temperature and strain rate. It has been shown by published flow stress curves of Al-Mg alloy that there is nearly no effect of strain rate on initial yield stress at various temperatures. However, most constitutive models ignored this phenomenon and may lead to inaccurate description. In order to capture the rate-independent initial yield stress, Peric model is modified via introducing plastic strain to multiply the strain rate, for eliminating the effect of strain rate when the plastic strain is zero. Other constitutive models including the Wagoner, modified Hockett–Sherby and Peric are also considered and compared. The results show that the modified Peric model could not only describe the temperature-and rate-dependent flow stress, but also capture the rate-independent initial yield stress, while the Wagoner, modified Hockett–Sherby and Peric model can only describe the temperature-and rate-dependent flow stress. Moreover, the modified Peric model could obtain proper static yield stress more naturally, and this property may have potential applications in rate-dependent simulations.
Abstract: This work is based on making a comparison of different inspection methods of non-destructive testing (NDT), to detect porosity, bite, undercut, splash, overlap, slag, concavity, lack of fusion and damage to base material, in welds of shielded metal arc welding (SMAW) and flux-cored arc welding (FCAW), made on a steel bridge ASTM-A-588. The main application of non-destructive tests is to evaluate the final state of a welded joint in critical points, in addition the fundamental objective is to ensure that the established acceptance and rejection criteria are met rigorously. For which non-destructive techniques are analyzed, such as the visual testing of welding on the beams of a bridge of length 35000 mm, subsequently, tests of inspection by liquid penetrant were used, based on the AWS D1.5 standard to confirm the failures in welded joints in ABA webs, an ultrasonic is also carried out using an SIUI CTS 602 equipment, finally to issue an acceptance and rejection criterion as determined by ASTM E165 and ASTM E2544-09.
Abstract: This experimental investigation evaluates the adherence of metal chromium plating on SAE-1026 cold-formed carbon steel surfaces for bus rims, the test-pieces were prepared in compliance with the ASTM-B456 standard regarding their size and surface. The study involves varying the parameters of the coating process, such as time, temperature and voltage, with the selection of critical tests that influence the adhesion of chromium plating such as: adhesion test where the strength with which the metallic coating is bonded to another surface was obtained based on ASTM D 3359-09, Vicker hardness test with the resistance that the material exhibits against permanent deformation established by ASTM B578-87, thickness test in the coating of metal substrates applying ASTM B456 and corrosion test by subjecting the surface to acetic salt mist (AASS) under strict preparation, cleaning and evaluation of ASTM G46-94. The optimal results discovered are 60 min. 40 °C and 7V in the nickel bath and 2min. 15 °C and 6V in chrome. In order to improve the results obtained from the experiments, the proposal is to cover with a layer of alkaline copper coating, reducing the anti-corrosion and adhesion properties.
Abstract: The mechanical properties of Al-Si alloys are affected by several microstructural features such as secondary dendrite arm spacing (SDAS), size and shape of eutectic Si-particles, presence of intermetallics as well as by porosity. In the current study, Al-Si-Cu alloy A380 was prepared by a unique directional solidification method to produce samples with two different SDAS of 9 μm and 27 μm. The lower solidification rate resulted in larger SDAS, larger grain size, larger eutectic Si and larger intermetallics including Fe-rich β phase. The microstructure with higher solidification rate was found to be finer and more homogeneous with smaller eutectic Si and intermetallics. The specimen with larger SDAS exhibited stronger texture than the one with smaller SDAS. The specimen with smaller SDAS showed improved mechanical properties including YS, UTS and ductility.
Abstract: Morphology of graphite affects the mechanical and physical properties of cast irons. It is known that the spheroidal shape of graphite promotes both tensile strength and ductility. The morphology of graphite is generally quantified by the percent nodularity and/or graphite shape factors (e.g. roundness, sphericity, compactness, aspect ratio). From the quality control aspect, the nodularity is controlled by the residual magnesium content determined by the Optical Emission Spectrometry (OES). However, the nodularity is also affected by the cooling rate and the sulfur level. Therefore, the percent nodularity alone cannot be precisely predicted by the residual magnesium. In this study, the Thermal Analysis (TA) was used to predict the residual magnesium and the nodularity of ductile iron. The newly created TA demonstrated the reliable prediction as the effect of the residual magnesium, sulfur level and the cooling rate were combined in forms of cooling curves. The correlations of the residual magnesium, the Maximum Cooling Rate (MCR) and the angle of the cooling rate curve (θ) at the end of solidification were shown in this work. Finally, the relationships were used to encode in the software for the on-site prediction.
Abstract: In the globally competitive environment, surface roughness and finer tolerances are becoming stringent and certainly most critical for optical components. The aim of this study is to determine the effects of diamond turning process parameters on surface finish when diamond turning RSA 443 alloy having high silicon content. This alloy is a new grade of aluminum that has a potential to be used for production of various optical components. The experiments were conducted based on the Box-Behnken design with three diamond-turning parameters varied at three levels. A mathematical regression model was developed for predicting surface roughness. Further, the analysis of variance was used to analyze the influence of cutting parameters and their interaction in machining. The developed prediction model reveals that cutting speed and feed rate are the most dominant diamond turning factors influencing surface roughness.
Abstract: This paper explains and demonstrates how miniature gears of excellent surface quality can be manufactured by modern machining methods. Necessity of gear finishing by post processes such as grinding, lapping, honing etc. is the major limitation of all conventional methods of miniature gear manufacturing. To overcome this limitation, modern machining methods such as wire-EDM, abrasive waterjet machining, and laser beam machining etc. have been explored. It resulted in significant achievements in geometric accuracy, surface finish, and integrity of miniature gears. Using modern machining methods, it is possible to manufacture gears equipped with precision finish (average roughness 1 μm), high geometric accuracy (DIN quality 5), and defect-free tooth surfaces at significantly low cost. This paper aims to facilitate researchers by providing information on important aspects as regards to the manufacturing of miniature gears by modern machining methods and hopes research and development in this area to establish the field further.
Abstract: Aiming at the issue of undercutting and machining difficulties caused by gear with a few teeth, the geometric modeling method and processing method of bi-directional displacement less tooth number were studied. Based on the calculation formula of the involute cylindrical gear and the characteristics of the bi-directional gear, the calculation formula of the diameter of the variable tooth top circle is derived, and the modeling of the gear pair with bi-directional variable bit number is carried out. The research shows that the bidirectional displacement can solve the root cutting problem well and improve the transmission quality. In view of the problem that machining efficiency is not high at present, a method of machining with tangent and radial gear is proposed, and the same gear cutter is used to process different cutting and radial gears, and the feasibility of the above method is verified by the processing test. The research work laid a foundation for further promotion and application of small tooth number gear transmission.
Abstract: Ballistic qualities of the material are important for the military defence barrier application for protection of military persons, their vehicles and equipment. In the present investigation ballistic performance of Kevlar29 fibre reinforced polyester composite (KPC) is analysed. A definite parametric study, taking into account various shape of projectiles (Flat-F, Spherical-S and Conical-C) impact on the composite target of different thicknesses (12, 16 and 20 mm). Impact velocity of the projectile considered for analysis 100-400 m / s. Ballistic parameters such as residual velocity, deformation and penetration behaviour are predicted. Conical projectile has more effect on the composite target compared to other projectiles. Composite thickness influenced the energy absorption. The thickness increase from 12 mm to 20 mm which leads to increase in energy absorption by almost 20%.