A Numerical-Experimental Study on Orthogonal Cutting of AISI 1045 Steel and Ti6Al4V Alloy: SPH and FEM Modeling with Newly Identified Friction Coefficients

Numerical simulation of metal cutting with rigorous experimental validation is a profitable approach that facilitates process optimization and better productivity. In this work, we apply the Smoothed Particle Hydrodynamics (SPH) and Finite Element Method (FEM) to simulate the chip formation process within a thermo-mechanically coupled framework. A series of cutting experiments on two widely-used workpiece materials, i.e., AISI 1045 steel and Ti6Al4V titanium alloy, is conducted for validation purposes. Furthermore, we present a novel technique to measure the rake face temperature without manipulating the chip flow within the experimental framework, which offers a new quality of the experimental validation of thermal loads in orthogonal metal cutting. All material parameters and friction coefficients are identified in-situ, proposing new values for temperature-dependent and velocity-dependent friction coefficients of AISI 1045 and Ti6Al4V under the cutting conditions. Simulation results show that the choice of friction coefficient has a higher impact on SPH forces than FEM. Average errors of force prediction for SPH and FEM were in the range of 33% and 23%, respectively. Except for the rake face temperature of Ti6Al4V, both SPH and FEM provide accurate predictions of thermal loads with 5–20% error.

Quantifying Face Mask Comfort

Face mask usage is one of the most effective ways to limit SARS-CoV-2 transmission, but a mask is only useful if user compliance is high. Through anonymous surveys, we show that mask discomfort is the primary source of noncompliance in mask wearing. Further, through these surveys, we identify three critical parameters that dictate mask comfort: air resistance, water vapor permeability, and face temperature change. To validate these parameters in a physiological context, we performed experiments to measure the respiratory rate and change in face temperature while wearing different types of commonly used masks. Finally, using values of these parameters from experiments and the literature, and surveys asking users to rate the comfort of various masks, three machine learning algorithms were trained and tested to generate overall comfort scores for those masks. Although all three models tested performed with an accuracy of approximately 70%, the multiple linear regression model also provides a simple analytical expression to predict the comfort scores for any face mask provided the input parameters. As face mask usage is crucial during the COVID-19 pandemic, the ability of this quantitative framework to predict mask comfort is likely to improve user experience and prevent discomfort-induced noncompliance.

Real-time Face Mask-Wearing Detection and Temperature Measurement based on a Deep Learning Model

In the context of the COVID-19 outbreak in a global scenario, mandatory mask-wearing and temperature control can effectively prevent its spread and realize self-protection. Therefore, real-time face-mask wearing and temperature measurement technology is of greater importance against the background of infectious disease prevention and control. The present study adopted MobileNet as the backbone of the single-stage RetinaFace framework for real-time face detection and mask-wearing detection. Moreover, the focal loss function of α dynamic value was adopted to avoid the class imbalance problem and improve the classification accuracy in the training stage. Regarding face temperature measurement technology, non-contact and uncooled temperature-sensitive elements were used for temperature measurement, but it was easily affected by environmental variables. Therefore, an SVR model was employed for temperature calibration with the constant temperature blackbody as reference. The alignment errors for the accuracy of face detection, mask wearing detection and temperature correction were 89.58%, 97.84% and 4.85%, respectively. The parameter quantity of the face mask wearing detection model reached 0.42 M, while the computation quantity arrived at 2.039 GFLOPs. The detection model proposed in this study combines real-time mask-wearing detection with face temperature measurement, which can help to quickly measure the body temperature and detect whether one wears face masks properly in the context of COVID-19, so as to reduce the risk of epidemic spread.

Thermal mixing effect and heat transfer in U-shaped notch on the mechanical seal face

A three-dimensional thermohydrodynamic (THD) model of a notched mechanical seal is developed based on the commercial software ANSYS Fluent. The flow behavior of hot and cold fluid in and around the notch, namely, the thermal mixing effect, is detailly analyzed. The heat transfer between the notch fluid and the seal rings as well as the cooling effect mechanism of the notch are discussed. Finally, a parametric analysis is conducted to study the effect of notch size, rotational speed and seal gap on heat transport. The results show that the notch fluid locally decreases the notched stator face temperature around the notch boundaries. The reflux occurs between the sealing chamber and notch, which brings the most cooling effect to the notch. The notch depth and width have a significant effect on the heat transfer between the fluid and sealing rings. Because of the non-simplified THD model, the proposed research provides increased reliability of understanding the flow and temperature behavior in the notch.

Experimental Study of The Insulating Effectiveness of Silicone Rubber Composites by Oxyacetylene Ablation Testing

The objective of this study was to characterize the thermal insulation efficiency of the silicone rubber reinforced composites by oxyacetylene torch. These composites reinforced by glass, carbon, ceramics and silica fibers were intended to be used as ablators in a low-thrust hybrid propulsion motor. The back-face temperature measurements were used as a criterion for insulation efficiency of the specimens, whose frontal face is subjected to the oxyacetylene flame for 40 s. The paper includes the results of the ablation rate measurements and the influence of orientation of glass and carbon fibers relatively to the flame direction on the back-face temperature of the specimens.

Measurement of Rake Face Temperature in Cryogenic Machining of Titanium Alloy

Titanium alloys are widely used as mechanical components, since they have superior properties such as high strength-to-weight ratio. They are regarded as difficult-to-cut materials. Their low thermal conductivity increases the temperature near the cutting edge, which causes excessive tool wear during cutting. Recently, many studies on cryogenic machining have been conducted. Cryogenic machining has emerged as an environmentally friendly alternative to traditional emulsion coolants. In this study, the rake face temperatures of cutting tool in the turning of titanium alloy under dry, soluble coolant, cryogenic carbon dioxide coolant and liquid nitrogen coolant conditions were measured to clarify the effect of coolant on cutting temperature. Turning tests were performed using a precision lathe. Tool insert was made by a translucent alumina. A small hole was drilled into the tool insert. An infrared radiation pyrometer with an optical fiber was used. The optical fiber was inserted into the hole. During chip formation, the infrared rays, radiated from the tool-chip interface and transmitted through the cutting tool, were accepted and transmitted by the optical fiber. The effects of cryogenic coolant on the rake face temperature were investigated. The rake face temperatures under carbon dioxide cooling and liquid nitrogen cooling were approximately 60 °C and 90 °C lower than that in dry cutting, respectively.

Face Temperature as an Indicator of Thermal Stress in Outdoor Work Environments

The frequency and duration of heatwaves are steadily increasing as climate change becomes more serious. These changes particularly endanger the health of those who must work outdoors in hot environments. This study introduces a novel approach to monitor the heat-health of airport outdoor workers using infrared thermography. The faces of airport workers who were refueling airplanes in extreme heat conditions were monitored using a thermal infrared thermometer during their work cycle throughout the day. Changes in temperature on their exposed faces (e.g., the ear, cheek, chin) were monitored throughout the day over a two-month period. In every test, the subject’s face temperature increased, then suddenly dropped for a short time, and then continued increasing. Subjects were also asked to assess their thermal perception of the work each time they were tested throughout the study. They reported that they felt discomfort in terms of thermal comfort when the facial skin temperature went down temporarily before the temperature rose. These results show that the physical measurement criteria when outdoor workers’ thermal health is in jeopardy can be based on the results of facial skin temperature measurements.

Improving Quality Control of Operating Room Environment by Computational Fluid Dynamics

In Vietnam, the operating room (OR) is used with max productivity. So, how to maintain comfort environment level, which is one of the assignments in designing and installing the operating room. In this study, the OR model is designed based on ASHRAE 170 – 2013 standard [1], and dimensions are referred to as “Comparison of Operating Room Ventilation System in the Protection of the Surgical Site” [2]. ANSYS CFX is used for calculating and simulating velocity and temperature of surveyed air points inside the room by many cases. A face temperature between 20,3 and 20,6 °C and a velocity of around 0,15 to 0,18 m/s is provided from the same laminar diffuser array. From the results, the OR comfort level is reviewed through the ADPI index.

Ablation Behavior of Silicone Rubber-Benzoxazine-Based Composites for Ultra-High Temperature Applications

A novel type of silicon rubber composite with benzoxazine resins (BZs) and ZrO2 was prepared. The ablative response of the composites was investigated. The results showed that the composites with BZs had superior thermal stability and higher resides compared to the pristine composites. The linear ablation rate of the composites decreased significantly with the increase in ZrO2 content. The maximum back-face temperature of the burnt samples was no more than 100 °C for the obtained composites. Three major ablation processes were carried out simultaneously during the ablation processing. These mainly involved the carbonization of the composite, and the formation of ceramic compounds such as SiC and ZrC, as well as the shielding effect of the ablated layer, which subsequently enhanced the ablation resistance of the composites.