Pit Area Research Articles

Histopathological features of glandular atrophy of the lamina propria of the gastric mucosa during its occurrence and development

ObjectiveTo explore the histopathological features of glandular atrophy of the lamina propria of gastric mucosa during its occurrence and development.MethodWe performed detailed histological observation and immunohistochemical examination on the endoscopic biopsy and ESD endoscopic resection specimens of 896 patients with glandular atrophy of the lamina propria of gastric mucosa. The EnVision two-step method was used for immunohistochemical staining, and the slices were incubated with primary antibody CK7, CK20, villin, CDX2, MUC5AC, MUC6, p53 and ki-67. Hematoxylin staining was performed and observed under the microscope and statistically analyzed.ResultsIn the initial stage of glandular atrophy of the lamina propria, the proliferation area of the deep gastric pits, and the isthmus and neck of the gastric glands are characterized by roughly normal structure of the glandular structure, increased mesenchyme, and widened space between glands. Subsequently, the gland becomes smaller in volume and less in number, especially at the base, in the gastric glandular part of the gastric unit. The disease at this stage has higher incidence, and occurs more often in the elderly who account for 64.0% (573/896) of our study group. The disease in this stage may exhibit some lesions that are physiologic (age-related degeneration) while others are pathological. Therefore, this condition is called simple glandular atrophy of the lamina propria of the gastric mucosa. When the gastric mucosal epithelium is subjected to infection or repeated infections, chemical stimuli, immune factors, and genetic factors, it can lead to the proliferation and transformation of stem cells in the proliferation area of the deep gastric pits, and the isthmus and neck of the gastric glands, forming single ducts, multiple ducts, or a proliferation of patchy cells. Then, atypical hyperplasia (intraepithelial neoplasia) presents, finally leading to gastric adenocarcinoma.ConclusionUnderstanding the histopathological characteristics of glandular atrophy of the lamina propria of gastric mucosa is of great significance in controlling the occurrence and development of gastric cancer.

Dissimilar welding of AISI 201 and 202 low nickel stainless steels by GTA and PA welding processes

This paper presents the results of dissimilar joining techniques for AISI 201 and 202 low nickel austenitic stainless steels. These were welded by Gas Tungsten Arc Welding (GTAW) and Plasma Arc Welding (PAW). The tests were performed to examine the weld bead shapes, microstructure, mechanical properties and corrosive behavior of the weld metals with different welding processes. The weld bead shape by GTAW was larger than that performed by PAW. The microstructure of the weld metal produced by GTAW contained more delta ferrite in the austenite matrix than the weld metal produced by PAW. The volume of hardness in welds produced by PAW higher than the GTAW process same with the ultimate tensile strength and percentage elongation welds produced by PAW higher than the GTAW process. According to the potentiodynamic polarization test results, pitting corrosion resistance of the weld produced by PAW was higher than the weld produced by GTAW. Both weld metals showed the pitted area adjacent to the phase boundary between austenite and delta ferrite in the mixed microstructure. Based on the present work, it was concluded that PAW was the more suitable welding procedure for joining dissimilar 201 and 202 austenitic stainless steels.

On the concrete breakage by pulsed water jet impact: Fracture characteristic, stress and damage evolution laws

To reveal the dynamic response characteristic and damage-fracture evolution laws of concrete under pulse water jet impact, the numerical simulations on pulse water jets impinging concrete for different operating parameters were established based on SPH-FEM coupling algorithm and verified in this paper. The concrete-breaking effects of pulse water jet and continuous water jet were compared, and the effects of key jet parameters and concrete strength on the damage-fracture characteristics of concrete were investigated. And the damage and stress evolution laws inner concrete were revealed. The results show that there is a better concrete-breaking effect for pulse water jet by repeatedly utilizing the extremely high water-hammer pressure and effectively weakening the water-cushion effect, compared with continuous water jet. The broken pit area and the total length of main cracks decrease with the increase of pulse length, and there is an optimal pulse spacing for pulse water jet to improve the concrete-breaking effect. The broken pit area and the total length of main cracks both linearly increase with the increasing jet velocity and exponentially increase with the increasing jet diameter. As the concrete strength increases, the broken pit area shows an S-shaped curve decreasing trend and the total length of main cracks exponentially decreases. The broken pit width first rapidly increases and tends to stabilize with the increase of jet velocity and concrete strength, and changes linearly with jet diameter and is less affected by pulse length and spacing. The farther away from the jet impact center, the longer the damage cumulative period of concrete due to the jet impact energy attenuation. In horizontal direction, concrete breakage range is approximately 4–5 times of jet diameter; in vertical direction, the previous pulses will cause concrete to be destroyed or damaged, and the subsequent pulses will make the damaged concrete suffer greater stress, causing more serve damage. And the induced stress peak decreases in form of Power function with the increasing distance. The research results could provide theoretical guidance for the parameters selection of pulse water jet efficiently breaking concrete.

Binding-induced fibrillogenesis peptide inhibits RANKL-mediated osteoclast activation against osteoporosis

Osteoporosis is primarily driven by an imbalance between bone resorption and formation, stemming from enhanced osteoclast activity during bone remodeling. At the crux of this mechanism lies the pivotal RANK-RANKL-OPG axis. In our study, we designed two binding-induced fibrillogenesis (BIF) peptides, namely BIFP and BIFY, targeting RANK and RANKL, respectively. These BIF peptides, with distinct hydrophilic and hydrophobic characteristics, assemble into nanoparticles (NPs) in aqueous solution. Through specific ligand-receptor interactions, these NPs efficiently target and bind to specific proteins, resulting in the formation of fibrous networks that effectively inhibit the RANK-RANKL associations. Experiments have confirmed the potent inhibitory effects of peptides on both osteoclast differentiation and function. Compared with the +RANKL controls, BIFP and BIFY demonstrated a more remarkable reduction in tartrate resistant acid phosphatase (TRAP)-positive cells, achieving an impressive decline of 82.8% and 70.7%, respectively. Remarkably, the administration of BIFP led to a substantial reduction in bone resorption pit area by 17.4%, compared to a significant increase of 92.4% in the +RANKL groups. In vivo experiments on an ovariectomized mouse model demonstrated that the BIFP treated group exhibited an impressive 2.6-fold elevation in bone mineral density and an astounding 4.0-fold enhancement in bone volume/total volume as against those of the PBS-treated group. Overall, BIF peptides demonstrate remarkable abilities to impede osteoclast differentiation, presenting promising prospects for the treatment of osteoporosis.

Angiosperms follow a convex trade-off to optimize hydraulic safety and efficiency.

Intervessel pits are considered to function as valves that avoid embolism spreading and optimize efficient transport of xylem sap across neighbouring vessels. Hydraulic transport between vessels would therefore follow a safety-efficiency trade-off, which is directly related to the total intervessel pit area (Ap ), inversely related to the pit membrane thickness (TPM ) and driven by a pressure difference. To test this hypothesis, we modelled the relative transport rate of gas (ka ) and water (Q) at the intervessel pit level for 23 angiosperm species and correlated these parameters with the water potential at which 50% of embolism occurs (Ψ50 ). We also measured ka for 10 species using pneumatic measurements. The pressure difference across adjacent vessels and estimated values of ka and Q were related to Ψ50 , following a convex safety-efficiency trade-off based on modelled and experimental data. Minor changes in TPM and Ap exponentially affected the pressure difference and flow, respectively. Our results provide clear evidence that a xylem safety-efficiency trade-off is not linear, but convex due to flow across intervessel pit membranes, which represent mesoporous media within microporous conduits. Moreover, the convex nature of long-distance xylem transport may contribute to an adjustable fluid balance of plants, depending on environmental conditions.

Research on rock breaking mechanism of composite cone single cone bit

Composite cone single cone bit is a new type of single cone bit based on spherical single cone bit. Its unique structure changes the rock breaking method of traditional single cone bit, and the rock breaking efficiency and service life of the bit are improved in hard rock formation. One of the most influential is the shape of cone, which changes the trajectory and the cutter loads of the bit at the bottom of well, affecting the drilling efficiency and service life of bit. Based on experimental and numerical analysis methods, the rock breaking mechanism of two kinds of bits with different structural shapes was analyzed, and the following conclusions were obtained. 1) Rock breaking of composite single cone bit can be divided into three areas: long-distance scratch area, dense short distance scratch area and crushing pit area. 2) The direction of cutter load is determined by structure and motion mode of the cone. 3) Impact and scraping proportion of cutter with different bits structures is different, resulting in different rock breaking modes of cutter with different cutter row. This research has a profound understanding of the influence of cone shape on cutter load and cutter failure of bit, and it is of great significance for the study of composite cone single cone bit with long service life and high rock breaking efficiency.

Tribological and dynamic performance analysis of rolling bearings with varied surface textures operating under lubricant contamination

This study aimed to evaluate the ability of textured rolling bearings to capture and store contaminants in a lubricant-contaminated state. Cylindrical thrust roller bearings (CTRBs) were selected for investigation, and circular textures were prepared on the bearing raceway surface using laser etching. The effects of pit location, diameter, depth, and area density on the tribological and dynamic performance of rolling bearings operating in a contaminated environment were examined. Results showed that adding texture only to the shaft washer raceway improved friction reduction and dynamic performance. Additionally, carefully designed textures could suppress vibration energy in the medium and high frequency bands of the bearing. Notably, the ability of the texture to capture contaminants was directly influenced by the diameter and area density of the pits. Furthermore, the relationship between the pits' depth and wear reduction capacity was closely linked to their diameter.

Identification of Vegetation on 3 Types of Post-Operation Land in Oil and Gas Mining, Riau Province

PT. Pertamina Hulu Rokan (PHR) is conducting activities to restore unproductive lands by revegetating in 3 types of areas. They are (1) areas of ex-well pad facilities where well plug & abandon (P&A) activities have been carried out, including the dismantling of related surface facilities, (2) areas of ex-production facilities that have been dismantled and (3) areas of ex-borrow pits. This research was conducted in PHR’s post-operation land area in 5 revegetation sites representing three types of post-operation areas, in Riau Province. The purpose of this study is to identify the types of vegetation found on post-operation land of oil and gas mining and to determine the types of vegetation that grow well on post-operation land based on the revegetation achievement target in each post-operation location in the document of Environmental Impact Analysis. Field research was conducted through the observation method. Observations were made by observing the type of plant, plant height, and plant mortality rate. The results showed that there were ten species of plants found in the 3 types of post-operation land in PHR, namely Cempedak (Artocarpus integer), Durian (Durio zibethinus), Jelutung (Dyera lowii), Jengkol (Pithecellobium jiringa), Mahoni (Swietenia macrophylla), Mangga (Mangifera indica), Matoa (Pometia pinnata), Medang (Litsea sp), Petai (Parkia speciosa), and Pulai (Alstonia scholaris). In total, the percentage of living plants was 88.2%. Furthermore, the average plant height in the five post-operation land areas was 169.8 cm. These values also indicate that the percentage of living plants and the height average of each type of plant in location is categorized as good, according to the achievement of the revegetation target in the document of Environmental Impact Analysis

Vessel, intervessel pits and vessel-to-fiber pits have significant impact on hydraulic function under different drought conditions and re-irrigation

Although xylem embolism is a key process during drought-induced tree mortality, its relationship to xylem anatomy remains debated. We subjected Syzygium aromaticum to different degrees of drought treatments for three years, followed by short-term and high-intensity drought stress, and then re-irrigation to explore the influence of anatomical structures on hydraulic function. We found that vessel area, vessel diameter, and pit membrane area (APM) of intervessel pits significantly reduced after long-duration severe drought stress, while the APM of vessel-to-fiber pits increased. These variations had a strong effect on hydraulic conductivity and embolism. Drought-adapted plants had higher embolism resistance when exposed to short-term and high-intensity drought stress. Unexpectedly, under extreme drought stress, some exudations presented on the vessel-to-fiber pit membrane, and the aperture area of intervessel pits and vessel-to-fiber pits in each organ decreased by 29–44% and 0.7–30%, respectively. Pit membrane and aperture, especially the intervessel pits, were associated with hydraulic efficiency and embolism resistance under different drought conditions and re-irrigation. These findings suggest that the intervessel pits have a substantial impact on hydraulic function, and the fibers around vessels also play an essential role in embolism resistance. Our study makes an addition to the developing knowledge on xylem plasticity, vessel traits, and their effect on hydraulic function.

Gleditsiaefructus regulates osteoclastogenesis by inhibiting the c‑Fos/NFATc1 pathway and alleviating bone loss in an ovariectomy model.

Medical and economic developments have allowed the human lifespan to extend and, as a result, the elderly population has increased worldwide. Osteoporosis is a common geriatric disease that has no symptoms and even a small impact can cause fractures in patients, leading to a serious deterioration in the quality of life. Osteoporosis treatment typically involves bisphosphonates and selective estrogen receptor modulators. However, these treatments are known to cause severe side effects, such as mandibular osteonecrosis and breast cancer, if used for an extended period of time. Therefore, it is essential to develop therapeutic agents from natural products that have fewer side effects. Gleditsiaefructus (GF) is a dried or immature fruit of Gleditsiasinensis Lam. and is composed of various triterpenoid saponins. The anti‑inflammatory effect of GF has been confirmed in various diseases, and since the anti‑inflammatory effect plays a major role in inhibiting osteoclast differentiation, GF was expected to be effective in osteoclast differentiation and menopausal osteoporosis; however, to the best of our knowledge, it has not yet been studied. Therefore, the present study was designed to examine the effect of GF on osteoclastogenesis and to investigate the mechanism underlying inhibition of osteoclast differentiation. The effects of GF on osteoclastogenesis were determined invitro by tartrate‑resistant acid phosphatase (TRAP) staining, pit formation assays, filamentous actin (F‑actin) ring formation assays, western blotting and reverse transcription‑quantitative PCR analyses. Furthermore, the administration of GF to an animal model exhibiting menopausal osteoporosis allowed for the analysis of alterations in the bone microstructure of the femur using micro‑CT. Additionally, assessments of femoral tissue and serum were conducted. The present study revealed that the administration of GF resulted in a reduction in osteoclast levels, F‑actin rings, TRAP activity and pit area. Furthermore, GF showed a dose‑dependent suppression of nuclear factor of activated T‑cells cytoplasmic, c‑Fos and other osteoclastogenesis‑related markers.

Structural and optical characterization of thin AlInN films on c-plane GaN substrates

The structure and optical characteristics of thin (∼30 nm) wurtzite AlInN films grown pseudomorphic on free-standing, c-plane GaN substrates are presented. The Al1−xInxN layers are grown by metalorganic chemical vapor deposition, resulting in films with varying In content from x = 0.142 to 0.225. They are measured using atomic force microscopy, x-ray diffraction, reciprocal space mapping, and spectroscopic ellipsometry (SE). The pseudomorphic AlInN layers provide a set where optical properties can be determined without additional variability caused by lattice relaxation, a crucial need for designing devices. They have smooth surfaces (rms < 0.29 nm) with minimum pit areas when the In content is near lattice-matched to GaN. As expected, SE shows that the refractive index increases and the bandgap energy decreases with increased In-content. Plots of bandgap energy vs In content are fitted with a single bowing parameter of 3.19 eV when using bandgap energies for AlN and InN pseudomorphic to GaN, which is lower than previous measurements and closer to theoretical predictions.

Inferring the lifestyles of extinct Crocodyliformes using osteoderm ornamentation.

Osteoderms are bony plates formed within the dermis of diverse vertebrate groups. They are present in all crocodylomorphs but Metriorhynchidae. Most of them show typical bone ornamentation consisting of pits and ridges on their outer surface. The most widely discussed functional hypothesis suggests that the ornamentation of osteoderms influences heat exchange with the environment through the adjacent vascular network, facilitating the absorption of solar radiation. This process allows semiaquatic crocodiles to compensate for heat loss resulting from the high thermal conductivity of surrounding water. In order to test this assertion, we conducted a phylogenetic logistic regression analysis to evaluate the relationship between osteoderm relative area of pits (RAP) and lifestyle (terrestrial versus aquatic) in a sample of crocodyliforms. Our results revealed that lifestyle is significantly explained by RAP: the lower the degree of ornamentation (RAP), the higher the probability of a terrestrial lifestyle. We used this model to infer the lifestyle of two extinct taxa, Peirosaurus torminni and Microsuchus schilleri. We concluded that terrestrial notosuchians may have lost osteoderm ornamentation due to the lower thermal conductivity of air and reduced heat loss in a terrestrial environment compared to what happens in water. Among these notosuchians, we hypothesize that large terrestrial baurusuchids maintained a stable body temperature due to thermal inertia, whereas small notosuchians took advantage of the early morning sun exposure to warm up and stayed in terrestrial burrows during periods of intense solar radiation. Finally, unlike the almost motionless behavior of freshwater crocodiles, fully marine Metriorhynchidae probably lost osteoderms because they constantly swim, generating heat by muscular contraction, so osteoderms with a thermoregulatory function for heat absorption were no longer positively selected.

Achieving superior burn resistant and mechanical properties of Ti40 alloy by laser solid forming

Laser solid forming (LSF) technology had a great influence on the manufacturing of aeronautical burn resistant titanium alloy Ti40, which was related to the comparison and competition between additive manufacturing and traditional forging parts. The Ti40 deposition blocks were fabricated using the LSF technique and tested for microstructure, mechanical properties and burn resistance. The results showed that, compared with the forged sample, the grain of LSFed sample was refined to a certain extent, and α phase and Ti5Si3 phase were precipitated. The tensile and yield strengths of the LSFed Ti40 alloy were 965 MPa and 962 MPa, respectively, which were higher than those of the forgings, and the elongation was close to that of the forgings. The fracture mechanism was a mixture of ductile and brittle fractures. The area and depth of the ablation pit and the area of the thermal zone of influence in the LSFed sample were smaller than in the bifurcated state. The Ti5Si3 precipitated in the LSFed sample not only improved the oxidation efficiency of the V and Cr elements by retaining the pores, but also slowed down the spallation of the oxide layer by strengthening the binding of the matrix to the oxide layer and improved the burn resistance of Ti40. Overall, the tensile strength and elongation of the LSFed Ti40 alloy were up to the forging standard, and the burn resistance was better than that of the forged Ti40 alloys.

Investigation of heat transfer and damage characteristics of high pressure abrasive water jet impacting high temperature sandstone

ABSTRACT Efficient breaking of hard mineral rocks is an important prerequisite for deep metal mining. In order to study the rock breaking mechanism of abrasive water jet erosion of high-temperature hard rock in deep ground, the temperature deformation evolution law during the process of jet impact on rocks was simulated and experimentally studied. The results show that the distribution of jet pressure, jet velocity, and jet turbulent kinetic energy near the residence point of the jet impingement wall is generally high in the middle and low in the outside. The heat transfer distance r on the rock surface is approximately (1.5–2.0) times the nozzle diameter, and the heat transfer distance inside the rock is (1.0–1.5) times the nozzle diameter. The maximum heat flux density at the jet cooling wetting boundary can reach 450 W/mm2. Within 0–3 seconds of the erosion process, the average surface temperature sharply decreases and exhibits a downward trend of jet stagnation point radiating outward. The radius of jet cooling influence gradually increases. Due to the impact cooling effect, tensile stress is generated at the top of the rock sample, and the tensile stress in the lower part of the rock is converted into compressive stress. With the increase of jet pressure and treatment temperature, the area and range of erosion pits significantly increase, and there is a significant phenomenon of thermal cracking around the erosion pits. The research conclusion can provide new ideas and basis for hydraulic breaking of high-temperature hard rocks in deep ground.

Adsorption of Sodium in an Aqueous Solution in Activated Date Pits

The use of acid-activated local date pits from Algeria's Oued Souf region for reducing water salinity by removing sodium. The raw and activated date pits were characterized using XRD, FTIR, SEM, and BET. The study used these materials to adsorb sodium from aqueous water, with the effects of activation time, initial sodium concentration, adsorption time, and pH of the solution on sodium removal being investigated. The specific surface area of natural date pits was found to be 645.46 m2/g, while activated date pits had a maximum of 825.03 m2/g. The maximum sodium adsorption capacity was observed at an adsorption time of 90 min, Na+ concentration of 600 mg/L, solution pH of 9.0, and adsorbent dosage of 0.1 g. The equilibrium data obtained from the experiment were analyzed using Langmuir and Freundlich isotherm models. The findings revealed that among the isotherm models examined, the Freundlich isotherm model demonstrated the strongest fit, exhibiting a high correlation coefficient of 0.999. Furthermore, the adsorption kinetics were investigated through the analysis of the pseudo-first-order and pseudo-second-order models, and the results indicated that the pseudo-second-order model provided the most suitable fit, with a correlation coefficient of 0.996.

EFFECT OF MICROSTRUCTURE AND RELATIVE HUMIDITY ON ATMOSPHERIC PITTING CORROSION OF DUPLEX STAINLESS STEEL BENEATH MGCL2 DROPS

One of the main issues for intermediate-level nuclear waste (ILW) is atmospheric corrosion in stainless steel. The impact of microstructure on the pit shapes on three orientations of the duplex stainless steel DSS 2205 plate and the relative humidity impact on the atmospheric corrosion pits of DSS beneath MgCl2 drops is determined through the use of four characterization tools: X-ray diffraction (XRD), Energy dispersive X-ray (EDX) analyses, Scanning electron microscopy (SEM), and optical microscopy. The pits on the top surface (LT) appears layered like an attack and mostly hemispherical, while the long transverse (LS) and short transverse (ST) planes reveal elongated strings. The map scan of EDX indicates mixed oxide inclusions and MnS inclusion existing in the steel alloy and the XRD analyses present the existence of two-phase both austenite γ and ferrite α peaks. The pit shape and area were influenced by relative humidity (RH) change. At RH 35% the trend of pits in 1-week exposure revealed a larger area of pit mouth than in RH 45%. For the same exposure time and in both RHs, the area seemed to be greater at the droplet’s center than in the edge of the droplet.

Coordination of intertracheid pit traits and climate effects among cycads.

Interconduit pit membranes, which are permeable regions in the primary cell wall that connect to adjacent conduits, play a crucial role in water relations and the movement of nutrients between xylem conduits. However, how pit membrane characteristics might influence water-carbon coupling remains poorly investigated in cycads. We examined pit characteristics, the anatomical and photosynthetic traits of 13 cycads from a common garden, to determine if pit traits and their coordination are related to water relations and carbon economy. We found that the pit traits of cycads were highly variable and that cycads exhibited a similar tradeoff between pit density and pit area as other plant lineages. Unlike other plant lineages (1) pit membranes, pit apertures, and pit shapes of cycads were not coordinated as in angiosperms; (2) cycads exhibited larger pit membrane areas but lower pit densities relative to ferns and angiosperms, but smaller and similar pit membrane densities to non-cycad gymnosperms; (3) cycad pit membrane areas and densities were partially coordinated with anatomical traits, with hydraulic supply of the rachis positively coordinated with photosynthesis, whereas pit aperture areas and fractions were negatively coordinated with photosynthetic traits; (4) cycad pit traits reflected adaptation to wetter habitats for Cycadaceae and drier habitats for Zamiaceae. The large variation in pit traits, the unique pit membrane size and density, and the partial coordination of pit traits with anatomical and physiological traits of the rachis and pinna among cycads may have facilitated their dominance in a variety of ecosystems from the Mesozoic to modern times.

A variation of foveal morphology in a group of children with hypermetropia.

During routine eye examinations, we noticed widened and flattened foveal pits with loss of normal V-shaped foveal profile and a pseudohole-like appearance in some otherwise healthy hypermetropic children. Our purpose was to describe clinical significance and multimodal imaging features of this incidental finding. Prospectively, 25 eyes of 13 hypermetropic children with these foveal changes and 36 eyes of 19 hypermetropic children with normal foveal appearance were enrolled. The macular thickness measurements and foveal parameters including pit diameter, depth, base, and area obtained by optical coherence tomography (OCT) (Heidelberg Spectralis, Heidelberg Engineering, Heidelberg, Germany), macular superficial and deep vessel density (VD) and foveal avascular zone values obtained by optical coherence tomography angiography (Avanti RTVue‑XR; Optovue, Fremont, CA, USA) were noted. The correlations of these parameters with visual function were evaluated. In the study group, significantly widened and flattened pit contours with decreased central foveal thickness (p = 0.01), and increased distance between foveal edges (p < 0.001) were observed. While the whole image superficial macular VD was similar between the groups (p = 0.74), a significant decrease in deep macular VD was observed in the study group (p = 0.01). None of these changes were correlated with visual acuity. Wider and flattened foveal pits described here represent a newly defined variation in healthy hypermetropic children. Although a correlation with visual acuity was not evident, these changes in foveal profile are shown to be related with macular microvascular changes in deep capillary plexus. Awareness of these morphologic changes will help clinicians in the differential diagnosis of macular pseudohole.

Study on Joint Damage of Double Prefabricated Fragments Penetrating Finite Thickness Concrete

In order to study the joint damage mechanism of multiple prefabricated fragments to finite thickness concrete targets, experiments on the damaging effect of a single fragment on a 300 × 300 × 100 mm concrete target were carried out, and the reliability of the simulation calculation model of single fragment damage to concrete was verified. On this basis, according to the trajectory of two fragments penetrating concrete, the double fragment penetration is divided into two penetration situations, that is, coplanar and heterogeneous. The orthogonal optimization method is used to carry out the joint damage simulation calculation of the double fragments to the concrete target by changing the fragment velocity, penetration angle, fragment spacing, and other factors. The simulation results show that the relationship between joint damage and fragment spacing is the largest when the fragment trajectories are coplanar, and the partial least squares regression coefficients affecting the joint damage time and surface joint length are 0.70 and 0.68 respectively. When the trajectory is different, the joint damage mode is relatively complex. Based on this, the joint damage degree analysis method between fragments is established, and each variable can explain 73.8% of the joint damage degree. It is found that the joint damage of the front pit area is the largest when the fragment is in different planes, and the PLS regression coefficient is −0.44. The hypothesis that joint damage is easy to occur in the area of the intersection line on the back of the target is analyzed and verified.

Effect of compound pit textures on the friction and wear of thrust cylindrical roller bearings under starved lubrication

PurposeThis study aims to investigate the effect of compound pit textures on the tribological properties of thrust cylindrical roller bearings (TCRBs) using several parameters, such as compound type, pit diameter, pit depth and pit area density.Design/methodology/approachThe surface texture parameters of the shaft washer (WS) raceway include pit diameter (D; 100, 300 and 500 µm), pit depth (H; 10 and 20 µm) and pit area density (S; 10%, 13% and 18%). Pits were produced on the WS of the TCRBs using laser marking equipment. The friction and wear performances of compound pit-textured TCRBs under starved lubrication conditions are studied using a friction and wear test rig. The influence mechanisms of the compound pit texture on the friction and wear properties of TCRBs are discussed through real tests and discussions.FindingsCompared with nontextured bearings, the average coefficient of friction (ACOFs) and wear loss of TCRBs with single/compound pit textures are reduced when rotating under starved lubrication. D has the greatest effect on the COFs curve. When D = 300 µm, H = 10 µm and S = 10%, the ACOF and wear loss are the lowest, that is, 0.0207 and 3.38 mg, respectively. Under the same lubrication conditions, compared with the nontextured bearing group, the COF and wear loss are reduced by 41.4 and 59.6%, respectively.Originality/valueThis study provides a useful reference for the raceways of textured TCRBs.