Finite element analysis and experiments of saw chip formation for bearing steel GCr15 in hard cutting process

The major characteristic is easy to produce saw chip in hard cutting process; the deformation process of chip has a huge impact on machining. Aimed at the generation of saw chip for the hardened bearing steel GCr15 in hard cutting process, the finite element model of 2D orthogonal cutting was built based on DEFORM, which made the simulation analysis on the distribution change the rule of stress field, strain field, temperature field and dynamic cutting force. Based on the method of hard cutting experiment combined with the 2D cutting finite element simulation and the chip cross-sectional microscopic analysis, this paper researched the deformation mechanism of saw chip forming process. When shear instability happened, the cutting tool squeezed the cut layer, and made the deformation and temperature higher on the tip of the cutting tool, which was easy to form the heat softening area. It appeared overload by reducing the loaded area of the chip root sliding area due to the heat softening area exist, the primary cause of saw chip formation is periodic adiabatic shear fracture for the hardened bearing steel GCr15. The deformation process of saw chip can be divided into the follow three stages: the cutting material changed trapezoid, adiabatic sheared slip, continued to slip formed chip unit

Experimental Study of Thin Wall Milling Chatter Stability Nonlinear Criterion

AbstractThe nonlinear dynamic behavior of milling process has been accompanied by the entire cutting process. In order to accurately determine and predict chatter stability of machining process, this article studied at both ends of the fixed thin part nonlinear criterion of milling chatter stability with experimental method. The experiment takes the vibration signal of thin part as the study object. And it analyses the vibration signal of different processing parameters based on the phase plane method, Poincare method and spectral analysis. Then, the relationship between the maximum Lyapunov exponent and the spindle speed and milling depth changes is discussed. Finally, taking the largest Lyapunov exponent as the criterion, the study determines the chatter stability domain of milling by using contour method. The comparative analysis is based on the milling chatter stability domain which obtained from the full discrete method. The experiments obtained the nonlinear stability criterion of aviation aluminium alloy 7075-T6 thin part

Thermal conduction simulation based on reconstruction digital rocks with respect to fractures

Effective thermal conductivity (ETC), as a necessary parameter in the thermal properties of rock, is affected by the pore structure and the thermal conduction conditions. To evaluate the effect of fractures and saturated fluids on sandstone’s thermal conductivity, we simulated thermal conduction along three orthogonal (X, Y, and Z) directions under air- and water-saturated conditions on reconstructed digital rocks with different fractures. The results show that the temperature distribution is separated by the fracture. The significant difference between the thermal conductivities of solid and fluid is the primary factor influencing the temperature distribution, and the thermal conduction mainly depends on the solid phase. A nonlinear reduction of ETC is observed with increasing fracture length and angle. Only when the values of the fracture length and angle are large, a negative effect of fracture aperture on the ETC is apparent. Based on the partial least squares (PLS) regression method, the fluid thermal conductivity shows the greatest positive influence on the ETC value. The fracture length and angle are two other factors significantly influencing the ETC, while the impact of fracture aperture may be ignored. We obtained a predictive equation of ETC which considers the related parameters of digital rocks, including the fracture length, fracture aperture, angle between the fracture and the heat flux direction, porosity, and the thermal conductivity of saturated fluid

Flexible Micro-Nano Fiber Sensors for Tactile Sensing

Flexible tactile sensors play an important role in wearable devices, human–computer interaction devices, and advanced robotics. We propose a novel structure of bionic flexible tactile sensor. The micro-nano fibers (MNFs) are packed in a 10-μm film on a polydimethylsiloxane (PDMS) base, forming a thin film-MNF-PDMS structure. A ridge-shaped sensing region is formed on the surface of the PDMS substrate. The MNF is so close to the sensor surface that vibration and pressure signals can act directly on the MNF. Compared to existing MNF flexible sensors, this sensor has higher sensitivity and faster response time. We tested the response of the flexible sensor to vibration and temperature. This sensor can measure vibration signals from 0.1 Hz to2 kHz. The sensitivity of this sensor to temperature can reach 1.43 nm/◦C. Surfaces with different roughness or texture can be distinguished by sliding on the sensor surface. The structural and functional characteristics of this sensor are desirable in flexible bionic devices and advanced robots

The metacognitive experience of time passing in Chinese college students: scale development, structure verification, and influencing factors

The experience of time passing (ETP) is also the consciousness of the progress of life. ETP contributes to time regulation and life management, which basically conforms to the metacognitive theory. Also, the traditional Chinese cultural approach to time emphasizes ETP. It is an indispensable part of Chinese education and culture to strengthen one’s appreciation of time by emphasizing the passage of time. In combination with the above two points, ETP equals metacognitive experience of time passing (METP) to a certain extent. However, we currently know little about the connotations of METP. To better understand traditional Chinese time culture, and referring to the concept of metacognition and model of time experience as proposed by Western scholars, the current study combined the results of open and semi-structured interviews, to explore the structure of METP in Chinese college students and developed a questionnaire with which to measure it. Using convenience sampling, 2,876 college students were recruited, the interview, and the reliability and validity tests were carried out. Five hundred and seventy-nine college students were tested a second time to investigate the correlation validity between METP and Ruminative Responses, time attitude, and meaning in life. The results led to the development of the METP Scale which contains 15 items and assesses two factors: ruminative and emotional experience of time passing. The two-factor model was well fitted, and invariable in measurements across gender, grade, and major. The internal consistency coefficients of the scale and its two factors ranged from 0.82 to 0.89, the half-point reliability between 0.76 and 0.88, and the retest reliability ranged from 0.77 to 0.78. METP Scale has good correlation validity, meanwhile, the results of regression analysis showed that symptom rumination, positive past, negative present, positive future, and searching for meaning in life significantly predict the intensity of METP

Up-down asymmetry measurement of tungsten distribution in large helical device using two extreme ultraviolet (EUV) spectrometers

Two space-resolved extreme ultraviolet spectrometers working in wavelength ranges of 10-130 Å and 30-500 Å have been utilized to observe the full vertical profile of tungsten line emissions by simultaneously measuring upper- and lower-half plasmas of LHD, respectively. The radial profile of local emissivity is reconstructed from the measured vertical profile in the overlapped wavelength range of 30-130 Å and the up-down asymmetry is examined against the local emissivity profiles of WXXVIII in the unresolved transition array spectrum. The result shows a nearly symmetric profile, suggesting a good availability in the present diagnostic method for the impurity asymmetry study

Density evaluation of tungsten W24+, W25+, and W26+ ions using unresolved transition array at 27–34 Å in Large Helical Device

The extreme ultraviolet (EUV) spectra of a tungsten unresolved transition array (UTA) at 15–70 Å have been studied in Large Helical Device (LHD) by injecting a tungsten pellet. Vertical profiles of the UTA line are measured with a space-resolved EUV spectrometer. In our previous study, it has been found that the UTA line at wavelength intervals of 32.16–33.32, 30.69–31.71, and 29.47–30.47 Å is composed of a single ionization stage of W24+, W25+, and W26+, respectively. In this report, therefore, the densities of W24+, W25+, and W26+ ions are evaluated from the radial profile measured at the above-mentioned wavelength intervals. To evaluate ion density, the photon emission coefficients of W24+, W25+, and W26+ ions are calculated using a collisional-radiative (CR) model. The chord-integrated radial profile of UTA lines is converted to a local emissivity profile using the Abel inversion technique. The density profiles of W24+, W25+, and W26+ ions are thus obtained from the local emissivity profile and the photon emission coefficient in addition to the temperature and density profiles. The obtained density profile of the W24+ ion is analyzed in detail by investigating the dependences of the electron density and the number of tungsten particles injected by the tungsten pellet. The total tungsten ion density nW near ρ = 0.7 where the W24+ ion locates is also estimated from the W24+ ion density with fractional abundance in ionization equilibrium calculated with the Atomic Data and Analysis Structure (ADAS) code. The nW evaluated from the present CR model seems to be larger than that estimated from the number of tungsten particles injected by the pellet. Discussions are made with the nW evaluated from the photon emission coefficient in the CL version of the ADAS code

Multi-functional groups decorated composite nanofiber separator with excellent chemical stability in ester-based electrolyte for enhancing the lithium-ion transport

As various heat-resistant polymer separators come out, although they possess better thermal stability and superior affinity to liquid electrolyte than commercial polyolefin separator, the porous structure and chemical stability of these novel separators should be paid more attention. In this work, we prepare a thin polyacrylonitrile/cellulose acetate (PAN/CA) composite nanofiber separator and discuss the importance of chemical stability in the ester-based electrolyte. The addition of CA decreases the PAN/CA fiber diameter from 310 nm to 210 nm. However, CA containing a lot of ester groups is easy to be dissolved by liquid electrolyte for the property of similarity and compatibility. Hence, the obtained PAN/CA composite nanofiber separator is treated via alkaline hydrolysis process, and some ester groups are transformed to be hydroxyl groups. Noteworthily, hydroxyl-rich PAN/CA composite nanofiber separator not only remains stable in electrolyte, but also possesses an improved lithium-ion transport property for reducing concentration polarization effect. As a result, the LiCoO2/Li half cells employing the hydroxyl-rich composite nanofiber separator exhibits better capacity retention (118.5 mAh g -1 after 300 cycles) and superior rate performance (143.1 mAh g -1 at 3C). Therefore, this multi-functional groups decorated composite nanofiber separator with excellent chemical stability is a candidate for next-generation lithium-based battery

The LncRNA signature associated with cuproptosis as a novel biomarker of prognosis in immunotherapy and drug screening for clear cell renal cell carcinoma

Cuproptosis is a new form of cell death, the second form of metal ion-induced cell death defined after ferroptosis. Recently, cuproptosis has been suggested to be associated with tumorigenesis. However, the relationship between cuproptosis and patient prognosis in clear cell renal cell carcinoma (ccRCC) in the context of immunotherapy remains unknown. The aim of this study was to investigate the correlation between cuproptosis-related long non-coding RNA (lncRNA) and ccRCC in terms of immunity as well as prognosis. Clinical information on lncRNAs associated with differences in cuproptosis genes in ccRCC and normal tissues was collected from The Cancer Genome Atlas (TCGA) dataset. Univariate Cox regression was used to screen lncRNAs. A total of 11 lncRNAs closely associated with cuproptosis were further screened and established using the least absolute shrinkage and selection operator (LASSO) algorithm and multivariate Cox regression, and the samples were randomly divided into training and test groups. A risk prognostic model was constructed using the training group, and the model was validated using the test group. We investigated the predictive ability of the prognostic risk model in terms of clinical prognosis, tumor mutation, immune escape, immunotherapy, tumor microenvironment, immune infiltration levels, and tumor drug treatment of ccRCC. Using the median risk score, patients were divided into low and high-risk groups. Kaplan-Meier curves showed that the overall survival (OS) of patients in the high-risk group was significantly worse than low-risk group (p < 0.001). Receiver operating characteristic (ROC) curves further validated the reliability of our model. The model consistently and accurately predicted prognosis at 1, 3, and 5 years, with an AUC above 0.7. Tumor cell genes generally precede morphological abnormalities; therefore, the model we constructed can effectively compensate for the traditional method of evaluating the prognosis of patients with renal cancer, and our model was also clinically meaningful in predicting ccRCC staging. In addition, lower model risk scores determined by mutational load indicated a good chance of survival. The high-risk group had greater recruitment of immune cells, while the anti-immune checkpoint immunotherapy was less efficacious overall than that of the low-risk group. Tumor and immune-related pathways were enriched, and anti-tumor agents were selected to improve the survival of ccRCC. This prognostic risk model is based on the levels of cuproptosis-associated lncRNAs and provides a new perspective in the clinical assessment and precise treatment of ccRCC