Mark Depth Research Articles

Enhancement of machinability and surface tribological property of hardened bearing steel by electric pulse-assisted hard turning

Electric pulse-assisted cutting (EPAC) can reduce the hardness of the workpiece, improve the tribological state of the tool-workpiece/chip interfaces, and enhance the machinability of the workpiece material. Hardened bearing steel has a hardness higher than 60 HRC, so the hardened bearing steel has an extremely bad machinability. This paper carried out an experimental study on electric pulse assisted hard turning (EPAHT) of hardened bearing steel, and the tribological property of the turned hardened bearing steel was also explored. Results shown that compared to conventional hard turning, the EPAHT reduced the surface roughness of hardened bearing steel by 44.2 %. The workpiece surface work-hardening rate was reduced by 3.6 %, the thickness of the workpiece surface metamorphic layer was increased by 91.4 %, the friction coefficient of the workpiece surface was reduced by 20 %, the wear mark depth was decreased by 91 %, a uniform and clean wear morphology of the workpiece surface wear appeared. The surface friction and wear performance of hard-turning of hardened bearing steel were significantly enhanced by the EPAHT.

Impact of carbon injection in 4H-SiC on defect formation and minority carrier lifetime

Point defects in silicon carbide (SiC) can act as charge carrier traps and have a pronounced impact on material properties such as the mobility and carrier lifetime. Prominent among these traps is the carbon vacancy (VC) with a demonstrated detrimental effect on the minority carrier lifetime in 4H-SiC epitaxial layers. Hence, a variety of methods for VC removal have been proposed. Common to all is that they involve some sort of C-injection into the epi-layer that leads to annihilation of VC with C interstitials (Ci) via the reaction Ci＋ VC→0̸. However, many studies on injection of Ci for removal of VC do not take into account the potential effect of any additional defects that are formed as a result of excess C in the material, including electrically active defects that introduce energy levels in the SiC band gap. Herein, we study the formation and impact of carbon related defects that are introduced in 4H-SiC epi-layers by injection of excess carbon. C-injection is achieved by annealing 4H-SiC epi-layers covered by a graphitized photoresist known as a C-cap at 1250°C for different durations. The resulting appearance of defects in the samples is monitored using deep level transient spectroscopy (DLTS) and minority carrier transient spectroscopy (MCTS) measurements, which reveal the formation of both minority and majority carrier traps as a result of the C-injection. Intriguingly, the injected carbon is also found to interact with a perennially present impurity in 4H-SiC epi-layers and a potentially lifetime limiting defect, namely boron. Furthermore, we monitor the minority carrier lifetime as a function of C-injection time and depth from the surface using cross-sectional time-resolved photoluminescence (TRPL) measurements. Both the defect distributions and the minority carrier lifetime are found to depend strongly on the duration of the C-cap anneal, with a marked depth dependence being present for all samples studied. The moderate temperature C-cap annealing treatment is proposed as a method for enhancing the carrier lifetime in n-type 4H-SiC epi-layers for power device applications.

Ultimate bearing capacity analysis and structural optimization of packer slip

The packer's slips indent the inner wall of the casing, leaving a series of marks between the teeth of the slips and the inner wall of the casing. Excessive bite depth can result in damage to the inner wall of the casing, potentially leading to failure. To minimize damage to the inner wall of the casing and improve the ultimate bearing capacity of the slip, a three-dimensional finite element analysis model of the slips is developed and validated through laboratory experiments. The optimization objective is to minimize casing damage and maximize bearing capacity. This paper examines the correlation between the residual collapse strength of the casing and the maximum depth of slips penetrating the inner wall. It determines the critical depth value by calculating the extrusion force endured by the inner wall of the casing as an optimization evaluation index. At the same time, the optimal structural parameters of the slips were determined through numerical simulation and orthogonal experiments. These parameters include a 90° dental angle, a 21° inner cone angle, a 219 mm outer diameter, and a 6.5 mm tooth pitch. The research results indicate that the equivalent stress of the improved slip has decreased by 8.66 %. The equivalent stress on the inner wall of the casing has been reduced by 9.34 %, and the maximum tooth mark depth of the casing has decreased by 30.48 %. Furthermore, the ultimate bearing capacity of the slip has increased by 2.24 times. Research has shown that the improved slip not only reduces damage to the inner wall of the casing and minimizes stress concentration on the slip, but also increases the ultimate bearing capacity of the slip. The research results can serve as a reference for the study and application of packers.

Fatigue Fracture Behavior of TA15 Alloy after Laser Marking

In order to study the effect of laser marking on the fatigue properties of TA15 titanium alloy, the alloy was marked at two depths respectively, and the low-cycle fatigue properties and fracture mechanism of TA15 titanium alloy after marking were analyzed and discussed. The results show that different degrees of marking pits appear on the surface of the alloy after laser marking, which is easy to cause local stress concentration. With the increase of power, the cross section shape of the bottom end of laser marking changes from a semi-arc shape to a sharp cone shape, resulting in high stress concentration phenomenon. The low cycle fatigue life of laser shallow marking specimens decreases by 62.7%, and that of laser deep marking specimens decreases by 86.4%. With the increase of the marking depth, the fatigue source area gradually becomes rough from smooth at the beginning, the divergence degree of cracks increases, the spacing of each crack in the initiation area increases, and the morphology becomes rough. The deeper the marking area is, the more driving force is provided for the initiation of cracks, and finally the fatigue performance deteriorates significantly.

A Study on the Temperature Optimization of Mold and Melt Using Design of Experiments for Children's Chair

The quality of the finished product is affected by a number of factors during the plastic injection molding process. Two crucial process variables in the creation of products are melted and mold temperature. The study uses the Design of Experiments tool in Autodesk Moldflow to look at the impact of melt and mold temperatures on injection molding technology. Analytical items are specifically made of polypropylene (PP) using kids' chair mold. According to simulation analysis results, there is a remarkable effect of the melt temperature on both time at end of packing as well as deflection in the range of the analytical temperature at tmold of [40, 80]°C and tmelt of [180, 220]°C. Melt temperature also shows a notable influence not only on deflection but also on sink mark depth and volumetric shrinkage, along with the criteria to evaluate the expense of a product (time at end of packing, total part weight).

Multi response optimization of injection moulding process to reduce sink marks and cycle time

In the rapidly growing field of technology, there is a demand for consumer goods made of plastic. To meet needs of customer, plastic products are made in different ways. There are different plastic manufacturing process. Numerous plastic manufacturing process are thereInjection molding is involves injecting molten material into a mold and allowing it to take on the shape of the mold.There are wide ranges of products such as plastic chairs, Computer cabinet etc. are manufactured with the help of smaller and more complex profiles. Due to lack of dimensional accuracy these complex profile produces defects inside the mold. Current study provides insights into transparent thermoplastic Polypropylene products. Five plastic injection molding variable criteria are considered for reducing the depth of sink mark in injection molding for commercial grade transparent thermoplastic (Polypropylene). Melting temperature (8C), mold temperature (8C), packing time (seconds), ratio of ribs to walls (%) and rib to gate distance (mm). According to Taguchi's design L27 experiments are performed and factors are optimized using the Taguchi based utility concept for multi criteria problems. The sink mark's depth on the part's surfaceis considered as quality of product and cycle time is considered as the productivity of product. It is the one of the best techniques, which can maintain the equilibrium between two.

Forming Quality Research on the Variable-Diameter Section of the Hollow Axle in Three-Roll Skew Rolling.

The hollow axle is the key component of the high-speed train, and the realization of high-quality forming is the key to ensure the safety of train operation. In this paper, the specimen of the variable-diameter section of the hollow axle is taken as the research object, and the generation mechanism of surface spiral mark defects and the formula of spiral mark depth of variable-diameter section in the TRSR (three-roll skew rolling) process with variable roll spacing are explored. The external roundness error and the function C to measure the wall thickness uniformity of the cross-section were taken as the evaluation indexes and the single-factor simulation experiment was established and simulated in the software Simufact.forming16.0 to obtain the influence law of each process parameter on the external roundness error and wall thickness uniformity of the rolled piece. Orthogonal tests were designed and the order and optimal combination of process parameters on the forming quality were obtained by range analysis and ANOVA analysis. The research results provide theoretical guidance for improving the forming quality of the variable-diameter section of the hollow axle in three-roll skew rolling, and promote the transformation of the TRSR process to high performance and accurate forming.

The Effect of Temperature, Cooling Rate and Casting Speed on Quality of Continuous Cast Steel Billets

In continuous casting, the cooling rate, casting speed, and molten metal temperature significantly affect the quality of cast steel billets. Appropriate casting parameters can minimize quality problems such as surface, subsurface and interior crack, rhomboidity, oscillation mark depth, and central porosity. This research determines the relationship between defects and three significant factors temperature, cooling rate, and casting speed. The work has been performed on the two-strand continuous casting machine to investigate the billet (BS-4449 steel grade) cross-section of 150 x 150 cm2. The defects analysis through macro examination at different tundish temperatures (1510 °C to 1560 °C), varying cooling rates, and casting speeds (0.9 to 1.6 m/min). The present study provides detailed insight into the three parameters mentioned earlier, which directly affect the quality of cast steel billets.

Modelling the effect of catena position and hydrology on soil chemical weathering

Abstract. The sensitivity of chemical weathering to climatic and erosional forcing is well established at regional scales. However, soil formation is known to vary strongly along catenas where topography, hydrology, and vegetation cause differences in soil properties and, possibly, chemical weathering. This study applies the SoilGen model to evaluate the link between the topographic position and hydrology with the chemical weathering of soil profiles on a north–south catena in southern Spain. We simulated soil formation in seven selected locations over a 20 000-year period and compared it against field measurements. There was good agreement between simulated and measured chemical depletion fraction (CDF; R2=0.47). An important variation in CDF values along the catena was observed that is better explained by the hydrological variables than by the position along the catena alone or by the slope gradient. A positive trend between CDF data and soil moisture and infiltration and a negative trend with water residence time was found. This implies that these hydrological variables are good predictors of the variability in soil properties. The model sensitivity was evaluated with a large precipitation gradient (200–1200 mm yr−1). The model results show an increase in the chemical weathering of the profiles up to a mean annual precipitation value of 800 mm yr−1, after which it drops again. A marked depth gradient was obtained for CDF up to 800 mm yr−1, and a uniform depth distribution was obtained with precipitation above this threshold. This threshold reflects a change in behaviour, where the higher soil moisture and infiltration lead to shorter water transit times and decreased weathering. Interestingly, this corroborates similar findings on the relation of other soil properties to precipitation and should be explored in further research.

Variability and specificity of bone cutting mark properties in cases involving stabbing with knives.

Sharp force traumas are frequently encountered in stabbing crime victims. During an examination, the properties of cutting marks in bones are compared with the properties of suspect tools, particularly knives. Therefore, the variation and specificity of knife and cutting mark properties must be known. This article provides the variability and specificity of a set of knife blade and cutting mark properties. Plain and serrated knives are used to create experimental cutting marks in porcine ribs, knife properties are derived from surface acquisitions of the blades and mark properties from Micro-CT data. We consider two conditions, automated stabbing using a motorized stage and manual stabbing. In addition, we study the influence of maceration on marks. For knives, the blade edge angle, blade thickness, and bevel height, and for cutting marks, the shape, the wall angle, the width, and the bevel height are determined and compared. The results show that the relationship between corresponding properties of blades and marks depends on the knife type. For plain knives, the width and wall angle of the marks are dependent on the mark depth and are significantly smaller than the blade properties edge angle and width. For serrated knives, this is not the case. The mark shape only provides slight support for a knife type for marks deeper than the blade bevel height. In conclusion, mark properties are only specific for a particular knife brand and model if the blade properties differ significantly and assuming a specific knife type.

Incidence and risk factors of pneumothorax following pre-procedural ultrasound-guided thoracentesis.

BackgroundData regarding the incidence and risk factors of pneumothorax following pre-procedural ultrasound (US)-guided thoracentesis is scarce. We aimed to evaluate the incidence and risk factors of pneumothorax following pre-procedural US-guided thoracentesis in a tertiary medical center.MethodsRetrospective analysis of patients who underwent pre-procedural US-guided thoracentesis in Sheba Medical Center between January 2016 and December 2018. Data collected included incidence of pneumothorax following thoracentesis, baseline clinical and demographic characteristics, and thoracentesis-associated factors. Outcomes evaluated included length of hospital stay, mortality, chest tube insertion and intensive care unit admission.ResultsA total of 550 patients with pleural effusions underwent pre-procedural US-guided thoracentesis. Sixty-six (12%) of them developed pneumothorax. Compared to patients who did not develop pneumothorax, those who developed pneumothorax had a higher rate of congestive heart failure (32.2% vs. 47%, P=0.026), a smaller depth of pleural fluid marking (3.4 vs. 3.2 cm, P=0.024), a larger amount of pleural fluid drained (1,093 vs. 903.5 mL, P=0.01), and were more likely to undergo bilateral procedures (7.6% vs. 2.3%, P=0.044). In the multivariate regression analysis, volume of pleural fluid drained was significantly associated with the development of pneumothorax (OR, 1.001, 95% CI, 1–1.001; P=0.042).ConclusionsThe incidence of pneumothorax following pre-procedural US-guided thoracentesis was relatively high in the present study. The amount of pleural fluid drained was the main factor associated with the risk of developing pneumothorax in these cases.

Experimental Study on the Lubrication and Cooling Effect of Graphene in Base Oil for Si3N4/Si3N4 Sliding Pairs.

Recently, the engineering structural ceramics as friction and wear components in manufacturing technology and devices have attracted much attention due to their high strength and corrosion resistance. In this study, the tribological properties of Si3N4/Si3N4 sliding pairs were investigated by adding few-layer graphene to base lubricating oil on the lubrication and cooling under different experimental conditions. Test results showed that lubrication and cooling performance was obviously improved with the addition of graphene at high rotational speeds and low loads. For oil containing 0.1 wt% graphene at a rotational speed of 3000 r·min−1 and 40 N loads, the average friction coefficient was reduced by 76.33%. The cooling effect on Si3N4/Si3N4 sliding pairs, however, was optimal at low rotational speeds and high loads. For oil containing 0.05 wt% graphene at a lower rotational speed of 500 r·min−1 and a higher load of 140 N, the temperature rise was reduced by 19.76%. In addition, the wear mark depth would decrease when adding appropriate graphene. The mechanism behind the reduction in friction and anti-wear properties was related to the formation of a lubricating protective film.

Accuracy of different anatomic landmark methods in determining size of nasopharyngeal airway

Objective To evaluate the accuracy of different anatomic landmark methods in determining the size of nasopharyngeal airway. Methods Fifty-two patients of both sexes, aged 16-60 yr, of American Society of Anesthesiologists physical status Ⅰ to Ⅲ, with body mass index of 18-30 kg/m2, scheduled for elective awake craniotomy for supratentorial tumors under sedation-awake-sedation anesthesia, were included. For each patient, the distance from the apex of nose to the right tragus (NT), distance from apex of nose to the right mandibular angle (NM), and thyro-mental distance (TM) were measured and marked on a transnasal tube correspondingly. The patients were placed in supine position without pillow, topical anesthesia (nasal mucosal surface) was performed with 2% lidocaine, and patients were sedated with midazolam, propofol and dexmedetomidine. When Observer′s Assessment of Alertness/Sedation Scale score was 2 or 3 points, the tube was transnasally inserted to each marked depth. When the three marked depths mentioned above were reached, the positions of the tube′s tip were checked using a fiberoptic bronchoscope and recorded as: above epiglottis (the tip of the tube was placed between the epiglottis and the free edge of soft palate) or below epiglottis (the tip of the tube placed at or beyond the epiglottis). Results When the depth reached the NT mark, the tube′s tip was above epiglottis in 14 cases (27%), and the tube′s tip was below epiglottis in 38 cases (73%). When the depth reached the NM mark, the tube′s tip was above epiglottis in 31 cases (60%), and the tube′s tip was below epiglottis in 21 cases (40%). When the depth reached the TM mark, the tube′s tip was above epiglottis in 52 cases (100%). Compared with the NM and NT methods, the TM method had a higher probability with the tube′s tip above epiglottis when used to determine the depth of insertion (P<0.01). Conclusion TM anatomic landmark method provides higher accuracy in determining the size of nasopharyngeal airway. Key words: Anatomic landmarks; Airway management

Neural Network Modelling to Characterize Steel Continuous Casting Process Parameters and Prediction of Casting Defects

The current work outlines application of a data-driven multilayer perceptron-based artificial neural network (ANN) model to characterize the influence of melt compositions, tundish temperature, tundish superheat, casting speed and mould oscillation frequency on the important processing parameters such as mould powder consumption rate, oscillation mark depth and metallurgical length during continuous casting process. A two-layer feedforward back-propagation neural network model has been developed for predicting the probability of occurrence of defect in the cast product. The network training architecture has been optimized using a gradient-based algorithm, namely the back-propagation algorithm. The neural network predictions are found to be in good agreement with regard to oscillation mark depth, mould powder consumption rate, metallurgical length and probability of occurrence of defect using data obtained from an operating Indian steel plant (Rashtriya Ispat Nigam Limited, Visakhapatnam). The ANN model prediction has been validated successfully with multiple linear regression analysis carried out on each data set.

STUDY OF CUTTING AND LABELING OF POLYMETHYLMETHACRYLATE USING A CO2 LASER

Progress in direct laser marking when processing plastics with unmatched quality of markings, contrast and speed. This article presents the latest generation of laser materials and laser equipment systems. When properly applied, laser marking can provide quality for production and add value to the appearance and function of the product.Describe the parameters influencing the depth of the laser marking of polymethylmethacrylate (PMMA) products. Experimental results are presented for determining the quality of cuts on the polymer surface at specific parameters - power and speed.

STUDY OF LASER CUTTING AND MARKING ON THE FILT WITH THE HELP OF A CO2-LASER

Describe the parameters influencing the depth of the laser marking of textile products. Experimental results are presented to determine the quality of cuts on felt surfaces of different colors at specific parameters - power and speed. Approximately 100 extras were made on two materials with a change in laser power and speed. As a result, the optimal results for cutting and marking a felt are shown.

Procedure development for predicting the sink mark of injection molded thermoplastics by finite element method

The sink mark is one common defect of the injection-molded thermoplastics, which is harmful to the part appearance. A procedure for the sink mark prediction was proposed to build the finite element method (FEM) model in Abaqus. The temperature and pressure distributions were imported as boundary conditions at a different time from the injection molding simulation software Moldflow. The user subroutines UEXPAN and UMAT were coded and implemented in Abaqus to describe the pressure-volume-temperature (PVT) behaviors under actual cooling conditions and the polymer constitutive relationship. The PVT curves of the thermoplastic were obtained by the piston-die method at a cooling rate of 5 °C/min. The crystallizing behaviors were measured by a differential scanning calorimetry and adapted to modify the PVT curves at different cooling rates. The tension-compression tests at different temperatures were performed to obtain the stress-strain curves. The simulation of injection molding was conducted in the software Moldflow. The deflection tests were conducted on the coordinate measuring machine (CMM) to validate the predicted sink mark. It was found that the subroutines of UEXPAN described the volume variations under different cooling rates successfully. Furthermore, the subroutine UMAT predicted stress-strain curves successfully at different temperatures and strain rates. The predicted sink mark in Abaqus agreed well with the measured one. The sink mark depth from Abaqus reached one third of the experimental one and had obvious improvement than that from Moldflow.

Turbulence and Rotation in Solar-Type Stars

Stellar spectra with a high resolution of 115000 obtained with the HARPS spectrograph provide an opportunity to examine turbulence velocities and their depth distributions in the photosphere of stars. Fourier analysis was performed for 17 iron lines in the spectra of 13 stars with an effective temperature of 4900--6200 K and a logarithm of surface gravity of 3.9--5.0 as well as in the spectrum of the Sun as a star. Models of stellar atmospheres were taken from the MARCS database. The standard concept of isotropic Gaussian microturbulence was assumed in this study. A satisfactory fit between the synthesized profiles of spectral lines and observational data verified the reliability of the Fourier method. The most likely estimates of turbulence velocities, the rotation velocity, and the iron abundance and their photospheric depth distribution profiles were obtained as a result. Microturbulence does not vary to any significant degree with depth, while macroturbulence has a marked depth dependence. The macroturbulence velocity increases with depth in the stellar atmosphere. The higher the effective temperature of a star and the stronger the surface gravity, the steeper the expected macroturbulence gradient. The mean macroturbulence velocity increases for stars with higher temperatures, weaker gravity, and faster rotation. The mean macro- and microturbulence velocities are correlated with each other and with the rotation velocity in the examined stars. The ratio between the macroturbulence velocity and the rotation velocity in solar-type stars varies from 1 (the hottest stars) to 1.7 (the coolest stars). The age dependence of the rotation velocity is more pronounced than that of the velocity of macroturbulent motions.

Predictive model and parametric analysis of laser marking process on gallium nitride material using diode pumped Nd:YAG laser

Laser marking is one of the effective and efficient ways of permanent marking process in the different engineering materials like composites, ceramics and any other hard metals and alloys. The present investigation deals with the experimental analysis on laser marking process using diode pumped Nd:YAG laser considering several process parameters for example lamp current, pulse repetition rate and laser scanning speed. The Response Surface Methodology (RSM) based experimental design was adopted to study in-depth the influence of these parameters on marking performance criteria such as mark width, mark depth and mark intensity. Based on experimental results, the second order mathematical models were established. Multi performance optimized parametric combination was achieved to obtain high quality marking using developed models and desirability functions. Moreover, in order to determine the most influencing parameter on the responses, Sensitivity Analysis (SA) was performed on the test results obtained from experimentation as well as predictive models. SEM and optical microscopic images were also analyzed to examine the quality aspects of laser marking on gallium nitride.

Characterisation of automated part marking methods for use in helicopter component identification

Based on the results of a process assessment carried out on several automated part marking methods, namely laser, DOT peen, diamond engraving and milling, all the methods produced a high degree of legibility which would be acceptable for identifying aerospace components. In the case of the mechanical part marking methods, whilst the depth of marking has been shown to influence fatigue failures, ie the greater the depth the greater the likelihood of failures initiating from the part marking, this does not necessarily result in a reduction in fatigue endurance, as all the mechanical methods assessed produced high levels of compressive residual stresses from the part marking process, which largely counteract the effect of depth within the High Cycle Fatigue (HCF) regime. Nevertheless, depth of marking should always be kept to a minimum comensurate with legibility. Although tensile residual stresses were generated by the laser part marking, how this influenced fatigue endurance was a function of the substrate, e.g. fatigue failures of the steel samples were independent of applied stress, while with the aluminium samples failures occurred over the whole stressing regime and hence were responsible for lowering HCF. The reason for the different response between the different metallic materials was that the depth of marking was deeper and as a consequence the ratio between the depth of marking and thickness of the sample was higher and the level of heat damage was more severe. The importance of heat damage and in particular the presence of microcracking was considered to be far more deterimental to HCF than either the presence of tensile residual stresses or phase transformation. Hence, if a laser is to be used for part marking components then the processing parameters should be carefully selected in order to prevent the formation of microcracking and limit the depth of marking.