Average Penetration Depth Research Articles

Experiment study and numerical simulation on the dynamic rock-breaking process of rotary percussive drilling with different cyclic and stress-wave frequencies

The rotary percussive drilling tool was designed to improve rock-breaking efficiency, and the tool’s cyclic frequency and stress-wave frequency are the key influencing factors on the rate of penetration, but the correlative research reports are few. In view of this situation, the cyclic frequency of the rotary percussion drilling tool and the frequency of stress waves generated during impact were measured. A numerical model of polycrystalline diamond compact (PDC) cutter cutting hard rock was established, and the measured frequency parameters were imported into the numerical model. The effects of cyclic frequency and stress-wave frequency on the penetration depth, rock breaking volume, and rock debris size were studied. The finding demonstrated that the average penetration depth increased with the increase of cyclic frequency, and decreased with the rise in stress wave frequency. When the two parameters were simultaneously high, it was conducive to generating smaller rock cuttings and wellbore cleaning. When the cyclic frequency was high and the stress wave frequency was low, the effect on the drilling tooth penetration was the best. The research results can provide a practical reference for optimizing the structure of rotary impact drilling tools and improving the penetration rate.

Optical coherence tomography application for assessing variation in bone mineral content: a preclinical study.

Optical Coherence Tomography (OCT) is a non-invasive imaging technique that produces cross-sectional images through biological tissues, allowing three-dimensional reconstruction and analysis. Aim was to evaluate if OCT may discriminate among tissues with different bone density and composition, by measuring the depth of light penetration in porcine and rat bone samples. Two carpal bone samples (2 cm length) were harvested from the porcine forelimb and fixed overnight in 3.7% buffered formal saline. Following fixation, one sample was decalcified in a 1:1 mixture of 8% hydrochloric acid and 8% formic acid solution for three days, with solution changes each day. Samples were imaged using an OCT microscope. Furthermore, the calvaria, ulnar, alveolar and basal bone of the mandible of 6 male and 6 female rats were cleared of overlying soft tissues and scanned under OCT. The light penetration depth in each sample was measured using the software Image J, and Scattering Attenuation Microscopy. In the mineralized bone the average depth (µm) and standard deviation (SD) of light penetration were 790.1±18.05 and 410.4±21.7 for periosteal and endosteal surface, respectively, and 507.3±21.03 for cross-section surfaces, while it was 858.4±32.03 for periosteal surface, 1150±26.9 for endosteal, and 627.3±31.8 for cross-section bone surfaces in demineralized porcine bone. There was a significant difference (p<0.001) in depth of light penetration between normal and de-mineralized bone for all regions evaluated. No systematic significant difference in light penetration depth between-gender was found at any site evaluated, while there were variations between sites (p<0.001). The OCT detected differences in bone mineral and porosity among gender (p<0.0001) CONCLUSIONS: This study suggests that OCT may represent a valuable technique to estimate local variations in bone mineral content.

Effect of pressure impregnated of methyl silicate (TMOS) on pore structure and impermeability of cement mortar

The pressure-impregnation crystallization reaction of methyl silicate (TMOS) was investigated. Taking TMOS as impregnating agent and water absorption and compressive strength as evaluation indexes, the effects of impregnating pressure, impregnating time, and TMOS concentration were studied. The results showed that the best results were obtained at an impregnation pressure of 1.0–1.2 MPa, impregnation time of 1.0 h, and TMOS concentration of 100%. The water absorption of the samples treated with pressure impregnation decreased by 55.25%, and the compressive strength increased by 17.77% compared with the samples treated with atmospheric impregnation. The average penetration depth increased from 1.2 mm to 6.0 mm after 1.0 h of impregnation. Moreover, TMOS reacted with Ca(OH)2 can produce fibrous C–S–H and more C–S–H gels during pressure impregnation, which reduces porosity and optimize pore structure. It was demonstrated that pressure impregnation helps TMOS penetrate deeper into the mortar and improve its impermeability.

A computationally‐cost effective model for fluid flow in redox flow batteries

AbstractRedox flow batteries (RFBs) hold great potential for large‐scale, extended‐duration stationary energy storage. Here, a novel computationally cost‐effective hydraulic‐electrical analogous model (HEAM) for fluid flow in RFBs is developed. The HEAM demonstrated that lowering the electrode compression and enhancing the channel area lowers the pump power loss independent of the flow fields and electrodes. Additionally, the HEAM helped elucidate the deficiencies of flow distribution in interdigitated flow fields (IFFs) and suggested designing wider manifolds and/or shorter channels improve the flow distribution. Moreover, the HEAM suggested shallower and/or wider channels, and more permeable electrodes enhance the flow penetration rate above the channels. Finally, the HEAM showed that the average penetration depth in the electrode above the ribs (hpen) was the critical parameter in the fluid‐flow modeling of IFFs and was inversely proportional to the permeability. Hence, there is a trade‐off between the pump power loss and hpen when configuring electrode permeability.

Dependence of Lévy-flight transmission on the starting point for photons propagating in atomic vapors

The propagation of a photon in an atomic medium can be seen as a L\'evy-flight random walk where the probability distribution $P(z)$ for the photon step length $z$ scales with ${z}^{\ensuremath{-}(\ensuremath{\alpha}+1)}$, with $0&lt;\ensuremath{\alpha}&lt;2$. In atomic vapors, previous work reported the value of $\ensuremath{\alpha}$ obtained from direct measurement of $P(z)$ and also from the dependence of transmission on sample opacity, both for Doppler and Lorentz profiles. In this work, we report the measurement of $\ensuremath{\alpha}$ in a Cs cell from the scaling of transmission with starting point, i.e., the average penetration depth of the photon in the medium before the first scattering event. We show that the parameter $\ensuremath{\alpha}$ depends on the size of the system and on the probability that an atom suffers a collision before spontaneous emission. The measured $\ensuremath{\alpha}$ parameter corresponds to the expectation value for $P(z=L)$, with $L$ the size of the system, which is consistent with the so-called single-big-jump principle that states that a single jump rules the transport.

Effects of LED curing light on silver diamine fluoride penetration into dentin.

This ex-vivo study investigated the effect of a light-emitting diode (LED) curing light on the depth of penetration of Silver Diamine Fluoride (SDF) into carious lesions. Twenty-four primary teeth with untreated caries lesions were allocated into groups and treated within 5 min after extraction: (1) n = 6 treated for 1 min with one drop of SDF followed by 10 sec rinse with tap water, (2) n = 6 treated for 10 sec with one drop of SDF and exposed to LED light for 20 sec (30 sec total SDF exposure) followed by 10 sec rinse with tap water, (3) n = 6 treated for 10 sec with one drop of SDF followed by a 10 sec rinse with tap water, (4) n = 3 untreated, and (5) n = 3 untreated but exposed to LED light for 20 sec. Samples were prepared, embedded, sectioned and silver penetration was measured using backscattered electron imaging in the scanning electron microscope and energy-dispersive X-ray spectroscopy analysis. Results were expressed as the average relative depth of penetration (%) = Ag depth/lesion depth × 100 from 5 sites in each lesion. Group means were compared using mixed model analysis. Mean ± standard deviation (SD) penetration was: 86.4 ± 20.7% in Group 1, 94.3 ± 13.7% in Group 2, and 26.7 ± 13.9% in Group 3. Groups 1 and 2 were statistically similar and different from Group 3 (p < 0.001). Groups 4 and 5 had no silver present. Use of LED light for 20 sec after 10 sec SDF application appears to facilitate silver penetration, similar to a 1 min SDF application. Clinical studies are needed to define the role of silver penetration in sustained caries arrest.

Effect of vacuum sealing on corrosion resistance of high-velocity arc sprayed coating

Thermal spray coatings commonly have pores and micro cracks in their structure. Corrosive medium will pass through pores and micro cracks in corrosive conditions and damage the substrate, leading to coating failure and reduced service life. In this study, vacuum impregnation sealing (VIS) and conventional impregnation sealing (CIS) were used to seal high-velocity arc-sprayed NiCr-based coatings. The cross-sectional microstructure of the coating and its porosity are observed by optical microscopy. Energy spectrometry and scanning electron microscopy were used to measure the sealant’s penetration depth. corrosion behavior was studied by neutral salt spray testing and electrochemical methods. The results showed that the average depth of sealant penetration by VIS is 275 m, almost three times greater than that of CIS. Better corrosion resistance was indicated in the coating sealed by VIS, which had a smaller corrosion current density and a more noticeable passivation zone than the coating sealed by CIS. The coating sealed by VIS showed no rust stains after 432 hours in the salt spray corrosion environment, but the coating sealed by CIS showed corrosion rust spots after 96 hours. The coating sealed by VIS appeared to have greater corrosion resistance, providing experimental support for its use in engineering.

Laboratory investigation on performance of waste-oil cutback asphalt as prime coat on cement stabilized macadam base

The commonly used prime coat materials have shortages such as insufficient interlayer bonding performance, high cost, and serious environmental pollution. To solve the above problems, this study attempts to take waste-oil as the diluent and blend it with asphalt to prepare a new prime coat material: waste-oil cutback asphalt. And the feasibility of this prime coat material is studied on semi-rigid base. Through penetration test, direct shear test, and pull-out test, the optimum blending proportions and construction conditions of the waste-oil cutback asphalt are determined, and the feasibility of the waste-oil cutback asphalt was evaluated by comparing it with kerosene cutback asphalt and PC-2 emulsified asphalt. The results illustrate that the mass ratio of waste-oil to asphalt is 1:1, and the content of penetrant is 10 % of the asphalt mass (47.6 % waste-oil, 47.6 % asphalt, 4.8 % penetrant in the percentage of 100 %) can be used as the optimum blending proportion of waste-oil cutback asphalt. The average penetration depth of waste-oil cutback asphalt is 5.4 mm, which meet the standard requirements. The direct shear strength is 0.292 MPa, which is 23.7 % and 86.0 % higher than that of PC-2 emulsified asphalt and kerosene cutback asphalt. And the pull-out strength is 0.235Mpa, which is 11.4 % and 92.6 % higher than that of theirs. The optimum construction condition is 1.1 L/m2, and the best construction time is 1 day after the construction of the base course. It indicated the interlayer bonding performance of waste-oil cutback asphalt is significantly improved than traditional prime coat materials. Thus, the waste-oil cutback asphalt can be used as a new type of environmentally friendly and high-performance prime coat material on cement stabilized macadam base.

Aquifer characteristics and groundwater flow system in a typical basement complex and Gundumi formation northwest, Nigeria

Aquifer performance was tested in 280 locations of the study area to assess the hydraulic characteristics of the various aquifers, potential yield from the flowing boreholes of both hard rocks and sedimentary formation underlain Zamfara State Northwestern, Nigeria. Pumping test result were subjected to standard methods of Jacob’s and modified Theis equation for evaluation of aquifer parameters such as hydraulic conductivity (K), Transmissivity (T), Specific capacity and others. The results show that characteristic of areas underlain by crystalline rock units, especially migmatite, variably migmatized gneiss, schists and granites are characterized by thin/shallow overburden unit of usually less than 10m. In such settings the borehole depth varies from 38 to 78m while saturated thickness varies from 8 to 20m below ground level, with average yield of 44.1m3/day. Hydrogeological parameters obtained from pumping test analysis within the basement rock units revealed aquifer transmissivity (T) values which range from 0.14 to 141.23m2/day, with an average of 12.85m2/day. This implies aquifers of negligible to high potentials. The hydraulic conductivity (K) values vary from 5.0 x 10-2m/day and 8.8 x 10-1m/day with an average of 2.2 x 10-1m/day. The implication of these results is that the aquifers of the basement rock units cannot provide sufficient water for both domestic and agricultural needs of the area. However, Sixty-eight (68) analyzed borehole data set within Gundumi Formation, revealed the average discharge rate of 116.8m3/day. This formation shows the highest water discharge within the study area. The average penetration depth of 65m was achieved. The hydraulic conductivity of this aquifer revealed average value of 5.7 × 10-1m/day. This implies high permeability of aquifer system, which is typical of sedimentary formation of this nature. Transmissivity (T) revealed an average value of 38.89m2/day, which indicate high rate of water flow through the entire aquifer medium of this formation. The geospatial analysis of yield from the wells indicate excellent groundwater potential around the western part of the study area.

BACK-SCATTERING AND NEUTRALIZATION COEFFICIENTS OF NITROGEN IONS ON IRON SURFACE

The coefficients of back-scattering and neutralization of nitrogen ions (N+) on iron surface during ion bombardment at the processes of ion sputtering and niriding have been calculated using TRIM code. The pure iron target and two-element targets, Fe+Mo (1 and 5 %), Fe+W (1 and 5 %), were tested. The ion energy was from 0.1 to 70 keV. The ions N+ are considered to be back-scattering in the form of energetic N atoms. The calculations showed the back-scattering and neutralization coefficients are tens of percent for low energies N+ ions and several percent for energies of tens kiloelectron-volts. The average penetration depth of the ions into the Fe target and the ion sputtering coefficients are calculated, too.

Phytic acid-based hybrid complexes for improving the interfacial property and mildew-resistance of heat-treated bamboo

Thermally glue-laminated bamboo timber has become the most promising woody resource in the world. However, the poor glued bonding property and poor anti-mild property limit its practical applications. Current scholars focus on crack-free, flattened bamboo boards and its application. Herein, inspired by the natural phosphoric acid complexes, Phytic Acid-based hybrid complexes were fabricated on the bamboo surfaces for improving its interfacial property and mildew resistance. SEM-EDS mapping results showed that the phytic acid-based hybrid complexes were successfully coated on the bamboo surface. The average penetration depth values (AP) and effective penetration depth values (EP) of heat-treated bamboo increased from 10.55 µm and 79.32 to 15.69 µm and 98.12 µm. A large amount of phytic acid penetrates into the bamboo cell-matrix and a large number of hydrophilic groups attach to the bamboo inner tissue during the impregnation process. Thus, the grafted long-chain groups in phytic acid cross-link with the crown energy groups in phenolic resin, thus increasing the AP of phenolic resin and improving the interfacial property. Additionally, the modified bamboo samples exhibited better anti-mildew properties than those of the control.

Study on the Probability Distribution of Pitting for Naturally Corroded Prestressing Strands Accounting for Surface Defects

One of the most urgent scientific needs from a technical and economic engineering point of view is the assessment of concrete structures suffering corrosion deterioration. However, the pursuit of this target in the case of corroded prestressed concrete (PC) members is hindered by the lack of (i) consolidated simplified formulations to be used in the engineering daily practice and (ii) works investigating the uncertainties in the correlation between the damage induced by corrosion and the structural resistance. To this aim, the present study adopts a 3D-scanning technique for the pitting morphology evaluation of several corroded prestressing strands retrieved from 10-year-old PC beams. First, the probabilistic distributions of penetration depths have been investigated. Second, the pitting factors α and Ωi have been proposed and discussed to quantify the level of corrosion in longitudinal and transversal direction, respectively. Finally, correlations have been derived between the maximum and average penetration depth as a function of the level of corrosion and the surface defects mapping has been carried out on the corroded PC beams. The results show that the penetration depth of strands subjected to chloride-induced corrosion can be best fitted by a lognormal distribution function. Additionally, the simultaneous consideration of longitudinal and transversal pitting factor is found out to be essential for an exhaustive comprehension of pitting corrosion. Moreover, the outcomes highlight that the presence of longitudinal splitting cracks plays a fundamental role in the corrosion spatial variability of prestressing strands.

A pilot and ex-vivo study of examination of endometrium tissue by catheter based optical coherence tomography

ObjectiveThis study aimed to distinguish ex-vivo normal and abnormal endometrium tissue samples histologically by catheter based optical coherence tomography (OCT).MethodsA total of 72 ex-vivo endometrium specimens were obtained from June 2018 to March 2021 and were imaged fresh after hysterectomy. The scanned region of endometrium was excised for histological examination and endometrium OCT images were precisely compared to corresponding histological images. Meanwhile endometrium OCT images were analyzed quantitatively with intensity of backscattered light in region of interest (ROI) and maximum penetration depth of the OCT signal. Blinded qualitative analysis on endometrium OCT images was performed by 2 assessors to determine accuracy rate and inter-rating reliability on the histopathological diagnosis.ResultsOCT images were performed successfully in 72 endometrium specimens. Five endometrium specimens developed OCT interpretation criteria and the rest 67 endometrium specimens validated qualitatively and analyzed quantitatively. We defined an OCT criteria to distinguish normal endometrium and five different abnormal endometrium phases including proliferative endometrium, secretory phase endometrium, atrophic endometrium, endometrial hyperplasia with atypia and endometrial carcinoma based on OCT imaging features. The overall diagnosis accuracy achieved by the two assessors was 72.4% based on the OCT criteria. The inter-rater reliability between assessors on overall OCT images was substantial (Kendall τb of 0.720, p < 0.05). The changes in ROI minimum intensity, ROI maximum intensity, ROI average intensity and OCT signal maximum penetration depth of five different abnormal endometrium phases were significantly different (all p < 0.001). These parameters of endometrium carcinomas were significantly different from the other four endometrium phases (all p < 0.001).ConclusionOCT has the advantage of noninvasive and rapid diagnosis, which can contribute to the diagnosis of endometrial cancer and will be an indispensable complement to traditional biopsy. Future studies in vivo with larger samples are needed to confirm this conclusion.

The synergistic effect of mechanical vibration for skin puncturing using polymeric microneedles

The transdermal delivery effect of polymeric microneedles can be significantly improved with the aids of synergetic vibration. The finite element simulation software ANSYS was used to explore the skin puncturing results of microneedles under different vibration frequencies. The dynamic mechanical properties of polymeric microneedles and human skin were also investigated. Meanwhile, puncturing experiments were also performed under different vibration frequencies on abdomen of female mice using polymeric microneedles with different lengths. The results showed that the peak value of maximum equivalent stress and the plastic deformation of skin were the smallest at the vibrative frequency of 200 Hz. The maximum equivalent stresses presented 20%–50% decreases during the second puncturing cycle. Moreover, the puncturing result of longer microneedles (550 μm) is much better than that of shorter ones (350 μm) under the same vibration frequency. The average bottom diameter and penetration depth of the microchannel obtained under the conditions of 200 Hz vibration and 550 μm height microneedles were 671.03 and 367.55 μm, respectively. These results provided an experimental basis to verify the effectiveness of mechanical vibration for skin puncturing.

Evolution of geodetic mass balance over the largest lake-terminating glacier in the Tibetan Plateau with a revised radar penetration depth based on multi-source high-resolution satellite data

The southeast Tibetan Plateau has become the region with the fastest rate of mass loss within High Mountain Asia (HMA), and the mass loss from lake-terminating glaciers in the region is the most significant. However, the evolution of the mass change of lake-terminating glaciers is still unclear, and accurate penetration depth estimates of C-band and X-band radar in glacierized areas are unknown, which greatly hinders the monitoring and understanding of the glacier evolution. Hence, in this study, taking the largest lake-terminating glacier in HMA (the Yanong Glacier) as the study object, we first evaluated the X-band penetration depth using Pléiades and TanDEM-X data, and further combined the penetration depth difference between the C-band and X-band radar (1.14 ± 0.14 m) to estimate the C-band penetration depth based on a newly proposed area-weighted strategy, according to surface categories. The results indicate a region-wide average penetration depth of 1.84 ± 0.59 m and 2.98 ± 0.61 m for the X-band and C-band radar, respectively, demonstrating either an underestimation of 60% or an overestimation of 202% for the previous C-band penetration corrections. On this basis, we determined the multi-temporal glacier mass balance for the Yanong Glacier, using KH-9, SRTM DEM, SPOT-7, and multi-orbit TanDEM-X data. The results show that the Yanong Glacier has been in a state of serious mass loss (at a rate of −0.73 ± 0.13 m w.e./a) during 1974–2015, and the rate of mass loss has doubled since 2000 (i.e., −0.48 ± 0.20 (1974–2000), −0.95 ± 0.20 (2000−2012), and − 1.02 ± 0.53 m w.e./a (2012–2015)). Moreover, the inter-annual mass change has shown a highly volatile and accelerating trend during 2012–2015 (i.e., −0.47 ± 0.85 (2011−2012), −0.87 ± 0.66 (2012−2013), −1.26 ± 0.72 (2013–2014), and − 1.58 ± 0.44 m w.e./a (2014–2015)). By further analyzing the ERA5 reanalysis data and the changes in the proglacial lake and glacier dynamics, we can conclude that, qualitatively: 1) the long-term acceleration of mass loss at the Yanong Glacier has mainly been controlled by climate change, but has also been affected by the glacier dynamics to a limited extent; and 2) the inter-annual acceleration of mass loss has, to some extent, been affected by subglacial/englacial melting. The findings of this study will not only provide an accurate penetration depth correction for future relevant studies, but will also significantly improve the understanding of the evolution of lake-terminating glaciers in HMA and other high mountain areas of the world.

Effect of PF resin penetration on interphase microstructure and quantitative micromechanical properties of different grained-wood laminates

Abstract Wood, a natural anisotropic material, behaves differently in the radial (R) and tangential direction (T), which also gives rise to different penetration capacity of adhesive into wood tissues. The present study investigates the penetration behavior of adhesive in the interphase of three different wood laminates, namely R-R, T-R, and T-T combinations, and its effect on microstructure and micromechanical properties of the latewood bonding interphase using confocal laser scanning microscopy (CLSM) and nanoindentation (NI). The results showed that the average penetration depth (AP) of the radial surface (S R) was higher than that of the tangential surface (S T) and a significant improvement in the mechanics of cells compared with the control cell (C). the maximum reduced elastic modulus (E r ) and hardness (H) found at the fourth cell row were 21.7 GPa and 0.62 GPa for R-R laminate, respectively, which increased by 43% and 29% compared with C (15.1 GPa, 0.48 GPa), and the maximum E r and H found at the first cell row were 23.2 GPa and 0.65 GPa for T-T laminate, respectively, which increased by 52% and 44% compared with C (15.3 GPa, 0.45 GPa). The results provide an important platform for better understanding and predicting the properties of wood glue line and bonding interphase.

Radiocarbon in the Atmosphere and Seawater in the South China Sea: Flux, Inventory and Air‐Sea CO2 Exchange Rate Tracing

AbstractΔ14C values of the atmosphere and seawater dissolved inorganic carbon (DIC) were measured during a cruise in the South China Sea (SCS) in September 2015, in order to determine the 14C flux and bomb 14C‐based air‐sea CO2 exchange rates for this region. The background atmospheric Δ14C value (13.8 ± 5.0‰) for the SCS during that period was lower than that (35.4 ± 3.4‰) of surface seawater (5 m) DIC, and a net transfer of 14C from the sea to the atmosphere (7.4 ± 5.0 × 1011 atoms m−2 yr−1) was determined at the wind speed of 5.2 ± 1.7 m s−1. Seawater DIC Δ14C profiles showed the highest value (37.9 ± 3.7‰) at a depth of 100 m, a rapid decrease below that depth to −220.3 ± 3.2‰ at 1,500 m, and nearly constant values below 1,500 m. The average mean penetration depth of bomb 14C was 585.5 ± 99.2 m, and a value of 8.2 ± 1.0 × 109 atoms cm−2 was obtained for the bomb 14C inventory in this region. Based on this inventory, a long‐term (1954–2015) average air‐sea CO2 exchange rate of 20.2 ± 2.8 mol m−2 yr−1 was traced for the SCS. Combined with the pCO2 measurements in this region, a net CO2 flux rate of 0.54 ± 0.08 mol m−2 yr−1 was yielded for the SCS, which is comparable to the cruise measured flux (0.44 ± 0.62 mol m−2 yr−1) obtained from a synthesis study (Li et al., 2020, https://doi.org/10.1016/j.pocean.2020.102272). Our study highlights the importance of continued atmospheric and seawater 14C observations on determining the air‐sea flux in this region.

Effect of irradiation temperature on the nanoindentation behavior of P92 steel with thermomechanical treatment

The nanoindentation behavior of P92 steel with thermomechanical treatment under 3.5 MeV Fe13+ ion irradiation at room temperature, 400 and 700 °C was investigated. Pop-in behavior is observed for all the samples with and without irradiation at room temperature, while the temperature dependence of pop-in behavior is only observed in irradiated samples. The average load and penetration depth at the onset of pop-in increase as the irradiation temperature increases, in line with the results of the maximum shear stress. Irradiation induced hardening is exhibited for all irradiated samples, but there is a significant reduction in the hardness of sample irradiated at 700 °C in comparison to the samples irradiated at room temperature and 400 °C. The ratio of hardness to elastic modulus for all samples decreases with increasing penetration depth except for samples at 700 °C. With the increasing of irradiation temperature, the ratio of the irreversible work to the total work gradually decreases. In contrast, it increases for samples without irradiation.

Hysteresis friction modelling of BPT considering rubber penetration depth into road surface

ABSTRACT The British pendulum tester (BPT) provides a method to measure the skid resistance of pavement, which possesses both theoretical and practical engineering significance. This article aims to establish a numerical hysteresis friction model for BPT to reproduce the dynamic motion of the slider and estimate the pavement friction based on surface texture roughness, rubber viscoelasticity property and contact characteristics. The analytical hysteresis friction model was introduced based on one of the modern rubber friction theories. As an input parameter of this model, the average penetration depth of rubber was calculated based on the interfacial separation assumption. A numerical model was established by combining the geometric and motion characteristics of BPT. To validate the model, the self-affine characteristics of texture from four types of asphalt pavement were analysed; simultaneously, the storage and the loss modulus of rubber slider at various frequencies were obtained using the Zener constitutive model. As a result, the velocity of the slider decreases gradually with the dynamic fluctuation of the friction coefficient. A significant linear correlation was found between the predicted values and the measured data. This numerical friction model performs some potential for friction estimation. However, more conditions need considering for the improvement and practicability of the model.

Penetration Failure Mechanism of Multi-Diameter Tungsten Fiber Reinforced Zr-Based Bulk Metallic Glasses Matrix Composite Rod

In order to increase the penetration ability of tungsten fiber-reinforced Zr-based bulk metallic glasses matrix composite rod, two multi-diameter tungsten fiber-reinforced Zr-based bulk metallic glasses matrix composites (MD-WF/Zr-MG) are designed. In MD-WF/Zr-MG-I, the diameters of tungsten fiber (WF) increase gradually from the inside to outside, which is the opposite in MD-WF/Zr-MG-II. Penetration experiment of two kinds of MD-WF/Zr-MG rods into rolled homogeneous armor (RHA) steel target from 1470 m/s to 1630 m/s is conducted. The average penetration depth of the MD-WF/Zr-MG-II rod is higher than that of the MD-WF/Zr-MG-I rod. Penetration failure modes of MD-WF/Zr-MG-I and MD-WF/Zr-MG-II rods are bending, backflow of WFs and shear failure respectively. The failure mode of MD-WF/Zr-MG is affected by the bend spaces and the ultimate bending diameters of WFs. If the bend spaces of all WFs are equal or larger than their ultimate bending diameters, the penetration failure mode is the bending and backflow of WFs, oppositely the penetration failure mode is the shear failure. The MD-WF/Zr-MG rod with shear failure exhibits high penetration ability because of low penetration resistance and little residual material in the crater. When designing MD-WF/Zr-MG, bend spaces of a part of WFs should be smaller than their ultimate bending diameter to cause shear failure.