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Cutting forces play a significant role in machining because they directly affect the mechanics of machining, the energy requirements, and the tool stability required. In this study, the cutting forces occurring during the turning of AISI 4340 material with 30 Rockwell C hardness scale have been analyzed both experimentally and numerically. Many types of research have been conducted via 2-D simulation using the finite element analysis method. In other words, in most studies, the workpiece was modeled as a flat specimen. Therefore, this paper presents a real 3-D turning simulation model using cylindrical specimens. The cutting forces were measured using a Kistler 9129AA model piezoelectric dynamometer. The ABAQUS/Explicit finite element method was used, and a model by Johnson and Cook was assigned as a material model in the numerical analysis. A new PVD AlTiN coated carbide insert was incorporated to prevent wear. Experimental results obtained from cutting tests were compared with numerical results to establish the accuracy of the FEM. It was observed that experimental and numerical results overlapped each other. Thus, this method can be used directly in the industry to reduce high processing costs.

In this study, effects of cutting speed (V), feed rate (f), depth of cut (a) and tool tip radius (R) on surface roughness (Ra, Rz, and Rt) and cutting forces (radial force (Fx), tangential force (Fy), and feed force (Fz)) in hard finish turning processes of hardened 42CrMo4 (52 HRC) material was investigated experimentally. Taguchi’s mixed level parameter design (L18) is used for the experimental design (2x1,3x3). The signal-to-noise ratio (S/N) was used in the evaluation of test results. By using Taguchi method, cutting parameters giving optimum surface roughness and cutting forces were determined. Regression analyses are applied to predict surface roughness and cutting forces. Analysis of variance (ANOVA) is used to determine the effects of the machining parameters on surface roughness and cutting forces. According to ANOVA analysis, the most important cutting parameters were found to be feed rate for surface roughness and depth of cut among cutting forces. By conducting validation experiments, optimization was seen to be applied successfully.

In this study, cutting forces and chip shapes formed by turning cylindrical materials were researched experimentally and numerically. AISI 4340 steel alloy with a hardness of about 30 Rockwell C scale was chosen as workpiece material. Most of the turning simulations performed by finite element method (FEM) have been conducted 2D (two-dimensional) because 3D (three-dimensional) is very difficult and time-consuming and mechanics of more complex 3D cutting operations are usually evaluated by using geometrical and kinematic transformation models applied to the 2D cutting Process. In other words, the workpiece was modeled as a flat specimen. Nevertheless, 3D (three-dimensional) simulation using cylindrical models are more nearer to practical process. For this reason, to get the actual cutting process, this paper aims to present a real 3D (three-dimensional) turning simulation model using ABAQUS/ Explicit software using tube and bar specimens with a cylindrical shape. Cutting forces were measured utilizing the Kistler 9129AA model piezoelectric dynamometer. Cutting forces and chip shapes obtained by making FEM simulations were compared. Simulation results were determined to be in high proximity with experimental results. Also, realistic chip shapes were simulated by FEM. Therefore, this method could be used as reliable in the industry.

Significance In a popular parlor trick, plasma is created by irradiating grape hemispheres in a household microwave oven. This work ties the source of the plasma to microwave photonic hotspots at the junction of aqueous dielectric spherical dimers. We use a combination of thermal-imaging techniques and computer simulations to show that grape-sized fruit and hydrogel beads form resonant cavities that concentrate electromagnetic fields to extreme subwavelength regions. This is enabled by the large dielectric susceptibility of water at microwave frequencies. Furthermore, the absorptive properties of water are key to washing out complex internal modes and for allowing the evanescent hotspot build-up. Our approach to microwave resonances in high-dielectric materials opens a sandbox for nanocluster photonics research., The sparking of cut grape hemispheres in a household microwave oven has been a poorly explained Internet parlor trick for over two decades. By expanding this phenomenon to whole spherical dimers of various grape-sized fruit and hydrogel water beads, we demonstrate that the formation of plasma is due to electromagnetic hotspots arising from the cooperative interaction of Mie resonances in the individual spheres. The large dielectric constant of water at the relevant gigahertz frequencies can be used to form systems that mimic surface plasmon resonances that are typically reserved for nanoscale metallic objects. The absorptive properties of water furthermore act to homogenize higher-mode profiles and to preferentially select evanescent field concentrations such as the axial hotspot. Thus, beyond providing an explanation for a popular-science phenomenon, we outline a method to experimentally model subwavelength field patterns using thermal imaging in macroscopic dielectric systems.

When grape-sized aqueous dimers are irradiated in a microwave oven, an intense electromagnetic hotspot forms at their point of contact, often igniting a plasma. Here we show that this irradiation can result in the injection of mechanical energy. By examining irradiated hydrogel dimers through high-speed imaging, we find that they repeatedly bounce off of each other while irradiated. We determine that an average of 1 μJ of mechanical energy is injected into the pair during each collision. Furthermore, a characteristic high-pitched audio signal is found to accompany each collision. We show that both the audio signal and the energy injection arise via an interplay between vaporization and elastic deformations in the region of contact, the so-called 'elastic Liedenfrost effect'. Our results establish a novel, non-contact method of injecting mechanical energy into soft matter systems, suggesting application in fields such as soft robotics.

The design and analysis of GaN HEMT linear power amplifier to operate at 6 GHz frequency is presented in this work. The GaN HEMT with 800 nm gate length, was power matched at the frequency of 6 GHz. The linear model of the GaN HEMT was derived from the scattering parameter data for designing the power amplifier. The power amplifier displayed a power gain of 9 dB and noise figure of 2 dB at 6 GHz frequency. The Rollet’s Stability factor of the linear power amplifier at 6 GHz frequency is 1.4, hence the amplifier is stable. The scattering parameters of the GaN HEMT power amplifier were also obtained. At 6 GHz frequency the power amplifier exhibited an input return loss of -19 dB.

The DC and high frequency performance of AlGaN/GaN HEMT device with and without the AlGaN back barrier was studied and the performance of the devices are compared. Introducing the back barrier helps in lifting up the conduction band and thus minimizes the leakage path under the buffer layer and also helps in confining the 2DEG in the narrow channel. Also with the introduction of the back barrier, the drain leakage current in the subthreshold region is significantly minimized and the DC charecteristics of AlGaN/GaN HEMT is preserved. At the same time the RF performance is enhanced by reducing the short channel effects.

This paper presents the performance of a single effect absorption cooling system under three different climates in Saudi Arabia. The considered system capacity is 10.5[Formula: see text]kW and uses LiBr/water pair. The study results indicated that considering the dynamic response of the cooling cycle significantly increases (close to 30%) the time taken to reach steady-state operations and that the sensitivity of the system to form precipitation of LiBr also increases. Also, the dynamic performance was investigated under different heat inputs and resulted in shorter transient period with increasing the heat input. In addition, the performance of the solar absorption system was investigated for a representative summer day in different climatic regions in Saudi Arabia. The results indicated the requirement of different areas of collectors to meet the absorber heating demand from 09:00 a.m. to 04:00 p.m. if there is no auxiliary heating. Auxiliary heating is required from 04:00 p.m. to 09:00 a.m. Finally, the results indicated that the system performs better in Riyadh city than in Dhahran and Jeddah. This study emphasizes the importance of taking into consideration the thermal inertia of the system components when analyzing the performance of such systems.

The sparking of grapes in a household microwave oven is a popular yet largely unexplained phenomenon. Using FDTD simulations, high-speed videography, and thermal imaging, we tie this phenomenon to low-Q Mie resonances in aqueous dimers.

In this study, the effect of shot peening parameters on fatigue strength of steel manufactured by powder metallurgy (PM) was investigated. Steel material obtained from Hoganas ASC 100.29 in chemical composition of Fe–0.5% C–2% Cu was produced by using a single action press PM process. To determine the effect of shot peening parameters on fatigue performance, fatigue tests were performed on 20 unpeened and 80 shot-peened samples, which were machined from sintered steel. Furthermore, shot-peened samples were peened at different peening intensities, 100% and 200% saturation and full coverage conditions. Fatigue performance of steel, produced by PM process, was improved by surface peening process. For the studied PM steel, the best fatigue performance was obtained with the samples that were shot peened at 20 Almen intensity and 100% saturation. Fatigue strength and limit of the samples, however, were reduced after a certain cold work level. Higher intensity and saturation levels of peening process thus deteriorated the beneficial effect on fatigue strength and limit.

External thread cutting is a complex 3-D process in which the cutting conditions vary over the thread cutter profile. It is accepted as a mature; however, heavily experience based technology and there are few academic work published. Determining the cutting forces during machining is crucial to explain formation of the surface layer, residual stresses, selection of the most appropriate machine tool and optimizing the process. This investigation is an attempt to predict thread cutting forces by dividing the thread chip into three parts, one thread root and two side faces. Variation of the cutting parameters including the shear angle, mean cutting temperature and friction force on the flank face of the tool along the thread tool root and sides are determined. In the thread root and sides, chip compression ratios for the V-shaped single piece and separately cut chip zones are measured and cutting forces are calculated and compared for precision metric thread cutting on a SAE 4340 steel bar.

The strain hardening and the formation of the residual stresses at the roots of threaded joints produced by machining according to American Petroleum Institute (API) standards was investigated. Initially the problem is defined and then an experimental technique was developed for measuring the residual stresses at the roots of fine screw threads. The screw thread was cut on a tubular bar from chromium–nickel based alloyed steel. Residual stresses were measured by the electro-chemical layer removal technique. Experimental work showed that, sever strain hardening and the concentration of residual stresses at the roots of the screw threads took place depending on the machining conditions. Strain hardening in the range of 320–430 HV were found on the screw thread surfaces as compared to the base hardness of 260 HV. Residual stress ranging from 600 to 1450 MPa was developed as compared to the material tensile strength of 850 MPa. The depth for maximum residual stress is around 20 μm.

The effects of machining parameters on the fatigue strength of fine-machined threaded specimens were investigated by comparing with the endurance limits of circumferentially notched specimens with the same profile. A four-point rotary bending fatigue test machine was used to obtain constant bending moment and pure alternating stress along the thread. All specimens were machined from SAE 4340 steel, the typical material used for deep well oil drilling pipes. Notched specimens were fine-machined according to ASTM standards, while the threaded specimens were machined under the optimized cutting conditions, which maximize tool life and geometric precision, as well as under selected modified conditions. Endurance limits of all specimens after 2 × 10 6 cycles were experimentally determined and S – N curves were plotted for 90% reliability for all experiments. The effects of cutting force, radial feed, tool wear, and two thread cutting methods on the fatigue strengths of the threaded specimens were determined. Experimental results show that the fatigue strengths of threaded specimens lie within a large range, depending on machining conditions, as compared to circumferentially notched specimens. The most influential factors on the fatigue strength of threaded specimens are tool wear and cutting velocity, while the effects of cutting method and radial feed are less significant.

The aim of this study is to investigate the effects of drilling parameters such as friction angle, friction contact area ratio (FCAR), feed rate and spindle speed on workpiece surface temperature, thrust force and torque in friction drilling of ST12 material. The tool material is tungsten carbide coated with TiN treatment. Experimental results reveal that the thrust force and torque increases gradually with increasing friction angle, feed rate and FCAR. On the other hand, the thrust force and torque decreases with increasing drilling speed. It is found that drilling speed has an important effect on the workpiece surface temperature. As the drilling speed increases, the workpiece surface temperature increases. Increasing or decreasing the friction angle and FCAR has no significant effect on the workpiece surface temperature., Le but de l’étude est d’investiguer les effets des paramètres de friction, tels que l’angle de friction, le rapport de l’aire de contact de la friction (friction contact area ratio (FCAR) ; la vitesse d’avancement et la vitesse de la broche sur la température de la surface de la pièce, et la poussée force et torsion dans le perçage par friction d’un acier ST12. La composition de l’outil est faite de carbure et de tungstène recouvert d’étain. Les résultats des expériences révèlent que la poussée force et torsion augmente graduellement avec l’accroissement de l’angle de friction, la vitesse d’avancement et le FCAR. D’autre part, la poussée force et torsion diminue avec l’accroissement de la vitesse du perçage. On constate que la vitesse du perçage a un effet important sur la température de la surface de la pièce. Au fur et à mesure que la vitesse de perçage augmente, la température de la surface de la pièce s’accroît. L’augmentation ou la diminution de l’angle de friction et le FCAR n’a aucun effet significatif sur la température de la surface de la pièce., Turkish Academy of Sciences (TUBA)