Study on Fe-Based Metallic Glass Micro Hole Machining by Using Micro-EDM Combined with Electrophoretic Deposition Polishing

Fe-based metallic glass possesses high hardness and brittleness. It is a hard-to-cut metal material and difficult to machine by conventional methods. Although electrical discharge machining (EDM) has advantages in machining hard-to-cut metal materials, recast layer, pores, and micro cracks will form on the machined surface after machining. The study used a helical tool for the micro electrical discharge drilling (µ-EDD) process on Fe-based metallic glass. The influence of processing parameters, including the pulse on time, gap voltage, duty factor, and spindle rotational speed on the micro hole machining quality characteristics was investigated. The helical tool with SiC electrophoretic deposited (EPD) film was used to polish the inner surface of the electrical discharged micro hole. The findings show that the best micro hole accuracy, tool wear length, and inner surface were obtained at the spindle rotation speed of 1150 rpm, pulse on time of 5 μs, gap voltage of 30 V, and duty factor of 40%. The inner surface roughness can be reduced to 0.018 µm by using EPD tool. The inner surface was polished up to form a mirror surface.

The science case for LIGO-India

The global network of gravitational-wave detectors has completed three observing runs with ∼50 detections of merging compact binaries. A third LIGO detector, with comparable astrophysical reach, is to be built in India (LIGO-Aundha) and expected to be operational during the latter part of this decade. Such additions to the network increase the number of baselines and the network SNR of GW events. These enhancements help improve the sky-localization of those events. Multiple detectors simultaneously in operation will also increase the baseline duty factor, thereby, leading to an improvement in the detection rates and, hence, the completeness of surveys. In this paper, we quantify the improvements due to the expansion of the LIGO Global Network (LGN) in the precision with which source properties will be measured. We also present examples of how this expansion will give a boost to tests of fundamental physics.

Effect of Various Process Parameters of EDC on Mild Steel Substrate and their Properties

In the present study, A layer of the modified composite coated surface is made using Copper, molybdenum disulfide, and hexagonal boron nitride. For this process, Electrical discharge machine (EDM) is used but in reverse polarity. Various factors of the machine influenced the thickness of the deposited layer like the amplitude of peak current, duty factor, powder mixing ratio, used etc. For the deposition process, green compacted electrodes which was made after mixing the powder material in mortar for approximately 2.5 hour and post processing in Hot mount press moulding machine. After that the mixture powder was put in the Hot mounting press machine to made green compact electrode with specific parameters. Experiment was performed on EDM and many analysis were carried out to study the morphology of the coated surface. To get the morphology of the coated layer, FESEM images were examined and found the satisfying uniform distribution of deposited layer constituents with material powder mixing ratio of (Cu/HBN/MoS2) at (20/40/40) got with 50% duty factor and 10 Ampere peak current amplitude. Also done XRD, for the evidence of Cu, MoS2 and HBN.

Thermal Simulation of the Continuous Pulse Discharge for Electro-spark Deposition Diamond Wire Saw

Due to their excellent physical and mechanical properties, third-generation super-hard semiconductor materials (such as SiC, GaN) are widely used in the field of microelectronics. However, due to its ultra-high hardness, the machining is very difficult, which has become the bottleneck of its development. The electro-spark deposition (ESD) process can deposit electrode materials on the substrate under the condition of low heat input to achieve metallurgical bonding between metal materials. And it can improve the wear resistance, corrosion resistance, and repair the size of the workpiece. It has been widely used in the field of surface modification engineering. It can effectively improve the bonding strength of the abrasive grains, and the sawing ability of the wire saw to make the consolidated diamond wire saw by the ESD process. Due to its thin matrix and poor thermal properties, the saw wire is easy to burning or even breaking in the manufacturing process. At present, the selection of pulse interval time in the ESD process is generally determined by the duty factor. However, the pulse interval time selected according to duty factor is difficult to meet the heat dissipation requirements of electro-spark deposition diamond wire saw (ESDDWS). In this paper, two kinds of motion modes of ESDDWS manufacturing are put forward, according to the manufacturing characteristics of ESDDWS. The boundary conditions of the continuous pulse discharge of ESDDWS are established. The thermal simulations of continuous pulse discharge of ESDDWS under two motion modes are analyzed. According to the simulation results, the basis of the value of pulse interval in the ESDDWS process is put forward. The effect of pulse interval time on the mechanical performance of the wire saw is analyzed experimentally. The results show that the discharge interval time selected base on the simulation results can ensure the continuous production of the ESDDWS.

Straight Gait Research of a Small Electric Hexapod Robot

Gait is an important research content of hexapod robots. To better improve the motion performance of hexapod robots, many researchers have adopted some high-cost sensors or complex gait control algorithms. This paper studies the straight gait of a small electric hexapod robot with a low cost, which can be used in daily life. The strategy of “increasing duty factor” is put forward in the gait planning, which aims to reduce foot sliding and attitude fluctuation in robot motion. The straight gaits of the robot include tripod gait, quadrangular gait, and pentagonal gait, which can be described conveniently by discretization and a time sequence diagram. In order to facilitate the user to control the robot to achieve all kinds of motion, an online gait transformation algorithm based on the adjustment of foot positions is proposed. In addition, according to the feedback of the actual attitude information, a yaw angle correction algorithm based on kinematics analysis and PD controller is designed to reduce the motion error of the robot. The experiments show that the designed gait planning scheme and control algorithm are effective, and the robot can achieve the expected motion. The RMSE of the row, pitch, and yaw angle was reduced by 35%, 25%, and 12%, respectively, using the “increasing duty factor” strategy, and the yaw angle was limited in the range −3°~3° using the yaw angle correction algorithm. Finally, the comparison with related works and the limitations are discussed.

Relationship between duty factor and external forces in slow recreational runners

ObjectivesRecreational runners show a large interindividual variation in spatiotemporal characteristics. This research focused on slow runners and intended: (1) to document the variance in duty factor (DF) between runners in a real-life running setting and (2) examine whether the interindividual variation in DF and stride frequency (SF) relates to differences in external loading parameters between runners.MethodsSpatiotemporal characteristics of 23 slow runners (ie, <2.6 m/s) were determined during a 5.2 km running event. To relate the interindividual variation in DF and SF to differences in external forces between runners (maximal vertical ground reaction force (FzMax), peak braking force (PBF) and vertical instantaneous loading rate (VILR)), 14 of them were invited to the lab. They ran at 1.9 m/s on a treadmill while ground reaction forces were recorded. A multiple linear regression analysis was conducted to investigate the effect of DF and SF on external force measures.ResultsDF between slow runners varied from 42.50% to 56.49% in a recreational running event. DF was found to be a significant predictor of FzMax (R²=0.755) and PBF (R²=0.430). SF only improved the model for PBF, but to a smaller extent than DF (R² change=0.191). For VILR, neither DF nor SF were significant predictors.ConclusionExternal forces are lower in recreational runners that run with higher DFs and slightly lower SFs. These findings may be important for injury prevention purposes, especially directed to recreational runners that are more prone to overuse injuries.

The scaling of ground reaction forces and duty factor in monitor lizards: implications for locomotion in sprawling tetrapods

Geometric scaling predicts a major challenge for legged, terrestrial locomotion. Locomotor support requirements scale identically with body mass ( α M 1 ), while force-generation capacity should scale α M 2/3 as it depends on muscle cross-sectional area. Mammals compensate with more upright limb postures at larger sizes, but it remains unknown how sprawling tetrapods deal with this challenge. Varanid lizards are an ideal group to address this question because they cover an enormous body size range while maintaining a similar bent-limb posture and body proportions. This study reports the scaling of ground reaction forces and duty factor for varanid lizards ranging from 7 g to 37 kg. Impulses (force×time) ( α M 0.99−1.34 ) and peak forces ( α M 0.73−1.00 ) scaled higher than expected. Duty factor scaled α M 0.04 and was higher for the hindlimb than the forelimb. The proportion of vertical impulse to total impulse increased with body size, and impulses decreased while peak forces increased with speed.

There Is No Global Running Pattern More Economic Than Another at Endurance Running Speeds

Purpose: The subjective Volodalen® score (V®score) and the objective duty factor metric can both assess global running patterns. The authors aimed to investigate the relation between running economy (RE) at endurance running speeds and the global running pattern quantified using both subjective and objective measures. Methods: RE and 3-dimensional whole-body kinematics were acquired by indirect calorimetry and an optoelectronic system, respectively, for 52 trained runners during treadmill runs at 10, 12, and 14 km/h. Results: Correlations between RE and V®score and RE and duty factor were negligible and nonsignificant across speeds tested (P ≥ .20), except for a low and significant correlation between RE and V®score at 10 km/h. Conclusions: These findings suggest there is no global running pattern more economic than another at endurance running speeds. Therefore, there is no advantage of choosing, favoring, or prescribing one specific global running pattern along a continuum based on V®score or duty factor metrics, and coaches should not try to modify the spontaneous running pattern of runners at endurance running speed to improve RE.