Cone Cracks Research Articles

Understanding cone crack formation in cosmic dust aerogel collectors by low-velocity similitude impact test

Low-density silica aerogel is an ideal medium for capturing cosmic dust in space, as the perforated tracks provide valuable insights into the characteristics of interplanetary particles. However, the mechanism behind track formation remains unclear. This paper examines the skirt-shaped or cone-in-cone cracks commonly observed in both ground experiments and returned aerogel samples. Similitude impact tests using various techniques compare cone cracks formed at different velocities. Results show that cone cracks typically form at lower impact velocities. Additionally, impact tests with hard spherical projectiles at speeds below 50 m/s, conducted using an electromagnetic coilgun, produced multiple tracks with single cone cracks. The impact process is captured in real-time using a high-speed camera, and the formation mechanism is investigated. A theoretical model, based on contact mechanics and energy methods, is developed to quantify the relationship between cone crack morphology and projectile impact parameters. The model's accuracy is validated through experimental results. This study reveals the formation of cone cracks in penetration tracks within silica aerogel. The proposed model identifies the energy absorption mechanism during single cone crack formation, potentially improving the understanding of key parameters (initial size, composition, velocity distribution, astrophysical source) from the perforated tunnels in cosmic dust aerogel collectors.

Contact damage response of alumina-based layered architectures under different loading configurations

Hertzian contact damage upon spherical indentation is investigated in alumina-based ceramics designed with embedded textured compressive layers. The effect of the location of the embedded layer and the testing configuration (parallel or normal to the layer orientation) on the sub-surface damage evolution is explored. An acoustic emission system for crack detection and post-mortem cross sectioning are employed to evaluate the onset and extension of damage in the different samples. Distinct acoustic signals detected at different contact loads are correlated with the onset of the ring crack, cone crack propagation and quasi-plastic deformation within the textured layer. The distinct damage mechanisms are influenced by the location of the embedded textured compressive layer and the loading orientation with respect to the layers. The design of layered ceramics for contact applications should consider the loading orientation as well as the contact stress field with respect to the “protective” layer to enhance damage tolerance.

Ballistic impact wave and back bulge propagation mechanism and blunt trauma assessment of ceramic/UHMWPE composite body armor

With increasing local conflicts worldwide, studying the impact response of body armor is crucial for enhancing soldier survival rates. However, there is still insufficient understanding of the back bulge expansion patterns, the impact waves transmission features, and blunt injury assessing method of body armor. To investigate these problems deeply, the three-dimensional digital image correlation method and numerical models were employed to reveal the ballistic response mechanism of ceramic/ultra-high-molecular-weight polyethylene (UHMWPE) composite body armor impacted by 7.62 mm rifle bullet. This study built theoretical function for the bulge expansion, revealed the wave transmission mechanism and fractures in both materials and their interaction. Firstly, the experiment revealed that the back-face bulge transverse expansion velocity exhibits a double exponential decrease. Secondly, the contour of back-face bulges consistently demonstrated excellent hyperbolic characteristics at various moments. Thirdly, the average Viscous Criterion (VC) and Blunt Criterion (BC) values were 5.37 and 0.95, corresponding to Abbreviated Injury Scale (AIS) values of 6 and 4. Fourthly, the simulation revealed that the ceramics transverse and radial cracks seems primarily induced by shear stress xy; ceramics conical cracks occurring at the boundaries of equivalent stress seems primarily induced by stress in x and y directions. Fifthly, numerical results revealed that the velocity of compression waves within the laminate increases over time in the impact direction and consistent with ceramic velocity impacted on the laminate. These findings lead to experimental and theoretical advances in the impact response mechanism of composite body armor and provide index for improving the protective performance.

Experimental study on rock-breaking characteristics of advanced premixed abrasive water jet

ABSTRACT To investigate the rock-breaking characteristics of the advanced premixed abrasive water jet, experiments of abrasive water jet eroding granite were carried out. The micro-failure morphology of erosion pits was observed and analyzed by CT (Computerized Tomography) and SEM (Scanning Electron Microscope). The results show that the difference in erosion effect caused by different rock breaking pressures is due to the difference in impact kinetic energy. The higher the jet pressure, the higher the impact kinetic energy of abrasive particles, and the erosion effect is enhanced. The difference in erosion effect caused by abrasive types is that the harder abrasives produce greater cutting force on the rock and consume less fracture surface energy. The CT scanning results show that the conical crack at the bottom is caused by the stamping action of abrasive particles and expands rapidly under the action of a water wedge, the action of reflective particles makes the erosion holes appear spindle-shaped. The results of SEM show that the sidewalls of the erosion pit are dominated by the cutting and fatigue-crushing effects of reflected abrasives. The bottom of the erosion pit is mainly driven by the punching action of the incident abrasive.

Protection mechanism of B4C–TiB2–SiC composite ceramic under ultra-high velocity impact

As the penetration technology develops and the projectile velocity increases, it becomes imperative to investigate the protection mechanism of high-performance ceramic under hypervelocity impact. The impact process of tungsten alloy projectile penetrated into B4C–TiB2–SiC composite ceramic target using ballistic test and finite element simulation at an ultra-high velocity of 2154 m/s was researched in the present study. Additionally, the protection mechanisms were described in terms of the morphology of target damage, the behavior of projectile kinetic energy dissipation, and the temperature field cloud. The findings from the ballistic experiments highlighted that the formation of macro-damage areas (concentrated damage, cone crack, circumferential crack, and radial crack areas) and micro-fragmentation zones could consume a significant amount of impact energy. The mixed fracture mode and the typical inelastic deformation characteristics (dislocations and micro-twinning) contributed to the energy dissipation. Simulation results indicated that the surface dwell effect of the projectile exhibited the highest rate of energy consumption. Furthermore, the temperature field results indicated that the maximum temperature on composite ceramic surface could reach 2310 K, which was below the melting point of B4C ceramic (2723 K). However, this temperature could cause the melting of the majority of metal materials. Therefore, ceramic materials exhibited a significant advantage under conditions of ultra-high impact velocities.

Effects of kinetic energy and firearm-to-target distance on fracture behavior in flat bones.

This research implements a fractographic approach to investigate the relationships between kinetic energy, firearm-to-target distance, and various aspects of fracture behavior in gunshot trauma. Gunshot experiments were performed on pig scapulae (n = 30) using three firearms generating different muzzle (initial) kinetic energies, including a 0.32 pistol (103 J), 0.40 pistol (492 J), and 0.308 rifle (2275 J). Specimens were shot from two distances: 10 cm (n = 15) and 110 cm (n = 15). Features evaluated in fractographic analysis such as cone cracks, radiating cracks, crack branching points, and circumferential cracks could be easily identified and measured in flat bones and allowed for statistical comparison of crack propagation behavior under different impact conditions. Higher-energy bullets produced more radiating cracks, more crack branching points, and longer fracture lengths than lower-energy bullets. Distance had no significant effect on fracture morphology at the distances tested. That quantitative measures of crack propagation varied with energy affirms that kinetic energy transfer is important in determining the nature and extent of fracture in gunshot wounds and suggests it may be possible to infer relatively high- versus relatively low-energy transfer using these features. Ranges obtained with the three firearms exhibited considerable overlap, however, indicating that other variables such as bullet caliber, mass, and construction influence the efficiency of energy transfer from bullet to bone. Therefore, fracture morphology cannot be used to identify a specific firearm or to directly reconstruct the muzzle (initial) kinetic energy in forensic cases.

The impact-corrosion behavior of HVAF-sprayed monolayer and hierarchical Fe-based amorphous coatings

The impact-corrosion behavior of the monolayer and hierarchical Fe-based amorphous coatings (AMCs) fabricated by high velocity air fuel (HVAF) in 3.5 wt% NaCl solution were investigated in detail. The polarization results indicate with the impact energy increases, the monolayer coating exhibits a corrosion failure as evident by a distinct increment in passive current density, which is caused by the penetrated radial cracks. The radial cracks provide corrosion channels between the solution and the substrate. Differently, the hierarchical coating shows a gradual improvement in passive current density and metastable pitting frequency with the increase of impact energy. This is related to the IR drop, and the larger potential difference between inside and outside the crack results in the passive film being more susceptible to breakdown. Long-term electrochemical impedance spectroscopy results demonstrate that the hierarchical coating possess excellent resistance to impact-corrosion. Nevertheless, when the impact energy exceeds 21.6 J, a corrosion degradation occurs after 720 h. This failure is because that the cone cracks are extended with the energy increasing, causing pH drop and Cl− accumulation and oxygen deficiency inside the cracks. This work reveals the mechanism of impact-corrosion of Fe-based AMCs, and provides guidance for their engineering application.

Subsurface fracturing of sedimentary stones caused by bullet impacts.

The immovable nature of built heritage means that it is particularly vulnerable during times of armed conflict. Although impacts from small arms and shrapnel leave relatively inconspicuous impact scars, they elevate the risk of future stone deterioration. This study investigates the subsurface damage caused by bullet impacts, which is not apparent from surface inspection, in order to better understand the geometry and mechanics of this form of conflict damage to heritage. Controlled firearm experiments were conducted to simulate conflict damage to sandstone and limestone buildings. The bullet impacts created conical fractures or zones of increased fracture intensity below the impact, radial fractures, and spallation, in addition to a crater. Dynamic fracture distinguishes the formation of these features from quasi static cone crack experiments, while the lack of a shockwave differentiates these bullet impacts from hypervelocity experiments. Damage was created by momentum transfer from the bullet, so that differences in target properties had large effects on the nature of the damage. The crater in the limestone target was almost an order of magnitude deeper than the sandstone crater, and large open fractures formed in the limestone below the crater floor, compared with zones of increased fracture intensity in the sandstone target. Microstructural analysis of subsurface damage showed that fracture intensity decreased with increasing distance from the impact centre, suggesting that regions proximal to the impact are at increased risk of future deterioration. Conical subsurface fractures dipping away from the impact beneath multiple impact craters could link up, creating a continuous fracture network. By providing pathways for moisture and other weathering agents, fractures enlarge the region at increased risk of deterioration. Their lack of surface expression makes understanding their formation a vital part of future surveying and post conflict assessments.

Effects of input energy and impactor shape on cranial fracture patterns

This study documents relationships between input energy, impactor shape, and the formation of fractures in human crania. Parietal impact experiments (n = 12) were performed at 67% higher input energy compared to previously reported experiments. Fracture origins, characteristics, and locations were compared at two input energy levels with three impactor shapes (focal “hammer”, flat “brick”, and curved “bat”). Impacts with all three impactors at both energy levels produced fractures originating at and remote to the impact site, indicating both mechanisms are typical in temporoparietal blunt force impacts. Higher energy impacts generally produced more impact site fractures, depression, and comminution than lower energy impacts. A small, focal impactor produced cone cracks, depression, and fractures localized near the impact site. A broad, curved impactor produced circumferential fractures and linear fractures extending into adjacent bones. A broad, flat impactor produced fracture patterns ranging from linear fractures to large depressed and comminuted defects.

Fatigue behavior, failure mode, and stress distribution of occlusal veneers: influence of the prosthetic preparation cusp inclinations and the type of restorative material.

To evaluate the effects of cusp inclination of the prosthetic preparation's occlusal surface and type of restorative material on the fatigue behavior, failure mode, and stress distribution of occlusal veneers. Glass fiber-reinforced epoxy resin prosthetic preparations for occlusal veneers with three different occlusal surface cusp inclination degrees (0°, 15°, and 30°) were produced and assigned into six testing groups (n = 11) according to the cusp inclination (0°, 15°, or 30°) and type of restorative material (lithium disilicate-LD or resin composite-RC). Despite different substrate preparation cusp inclination degrees, the restorations were designed maintaining 30° inclination between the cusps at the occlusal surface and a thickness of 0.7mm at the central groove region of the restorations to be machined in a CAD/CAM system. After cementation, the specimens were stored for about 7days (under water at 37°C), and subsequently submitted to a load to failure test (n = 2) and an intermittent cyclic fatigue test (n = 9) (initial load: 100 N; step size: 50 N; cycles/step: 10,000; loading frequency: 20Hz; loading piston: 6-mm-diameter stainless steel) until observing cracks. The data were analyzed by two-way ANOVA, Kaplan-Meier, and Mantel-Cox post hoc tests. Finite element analysis (FEA) and fractographic analyses were performed. The fatigue performance of LD and RC occlusal veneers was evaluated based on different prosthetic preparation cusp inclinations. The 0° inclination showed the best fatigue performance for both materials (LD: 944N, RC: 861N), while the 15° and 30° inclinations had lower values (LD: 800N and 533N, RC: 739N and 717N, respectively). The study also found that for a 0° inclination, LD occlusal veneers performed better than RC ones (LD: 944 N > RC: 861N), while for a 30° inclination, RC occlusal veneers had better fatigue performance than LD ones (LD: 533N < RC: 717N). No significant difference was observed between the materials for a 15° inclination (LD: 800N = RC: 739N). The FEA results showed a higher tensile stress concentration on lithium disilicate than on resin composite occlusal veneers. All lithium disilicate occlusal veneers showed radial crack failures, while resin composite occlusal veneers showed Hertzian cone cracks and radial cracks combined. Considering mechanical perspective only, RC occlusal veneers should be indicated when prosthetic preparation cusps inclinations are 30°. When 0° prosthetic preparation cusps inclinations are observed, LD occlusal veneers will behave mechanically better. When a 15° cusp inclination is preserved, both restorative materials behave similarly.

Numerical analysis of glass edge chipping by impact loading

This study presents numerical analyses for edge chipping by impact loading. As a numerical analysis method, we extend Particle Discretization Scheme Finite Element Method (PDS-FEM) developed by the authors to be able to simulate fracture due to impact loading. We performed simulations targeting edge chipping of soda-lime glass by impact of rigid steel sphere and examined the crack morphology while varying the diameter of the impactor, the impact velocity, and the impact distance. The proposed method successfully simulates the 3D complex crack pattern on edge chipping such as Hertzian cone crack and conchoidal chip scar. The method also reproduces the change of crack morphologies depending on the impact force and the impact distance. Also, a series of numerical analyses is presented to reveal the effect of the impactor geometry on the chip dimensions. The height of chip is independent of the impactor geometry while the width of chip depends on it. According to the agreement with experimental results, it is confirmed that the proposed method is capable of realizing edge chipping due to impact loading.

Photographic studies of the normal impact of hard spheres on fused silica generating hertzian cones

Colour high-speed photographic framing sequences of the normal impact of 2 mm diameter tungsten carbide spheres on a block of fused silica at 150 m s−1 were taken at 1 × 106 frames per second. The initiation and growth of the resulting two coaxial cone cracks, which formed within 0.1 µs of the initial projectile contact, were followed. The innermost cone crack of a semi included angle of 32° travelled at a velocity of (2270± 100) m s−1 which is close to the theoretical maximum crack velocity of 2180 m s−1 in fused silica. Importantly, the semi included angle of the cone crack was about a half of the angle of the cone crack produced by quasi-static loading. A suggested explanation, based on the localized decrease of the target's Poisson's ratio due to the high impact loading rate, has been proposed and examples are given which support this suggestion.

Fatigue behavior of multilayer ceramic structures in traditional and reverse layering designs.

This study evaluated the fatigue failure load (FFL) and the number of cycles for fatigue failure (CFF) of traditional (porcelain layer up) and reversed (zirconia layer up) designs of porcelain-veneered zirconia samples prepared with heat-pressing or file-splitting techniques. Zirconia discs were prepared and veneered with heat-pressed or machined feldspathic ceramic. The bilayer discs were bonded onto a dentin-analog according to the bilayer technique and sample design: traditional heat-pressing (T-HP), reversed heat-pressing (R-HP), traditional file-splitting with fusion ceramic (T-FC), reversed file-splitting with fusion ceramic R-FC), traditional file-splitting with resin cement (T-RC), and reversed file-splitting with resin cement (R-RC). The fatigue tests were performed using the stepwise approach at 20Hz, 10,000 cycles/step, step-size of 200 N starting at 600 N, and proceeding until failure detection or up to 2600 N if enduring. The failure modes (from radial and/or cone cracks) were analyzed in a stereomicroscope. The reversed design decreased the FFL and CFF of bilayers prepared with heat-pressing and file-splitting with fusion ceramic. The T-HP and T-FC reached the highest results, which were statistically similar between them. The bilayers prepared by the file-splitting with resin cement (T-RC and R-RC) were similar to the R-FC and R-HP groups regarding FFL and CFF. Almost all reverse layering samples failed by radial cracks. The reverse layering design did not improve the fatigue behavior of porcelain veneered zirconia samples. The three bilayer techniques behaved similarly when used in the reversed design.

FEM-SPH adaptive method for analysis protection mechanism of B4C ceramics

To simulate the collision of a tungsten heavy alloy projectile with different velocities on the B4C ceramic target, an adaptive conversion model from Lagrangian elements to SPH particles is developed due to the limitations of the traditional finite element method (FEM) with the element erosion technique. By comparing the simulation results with experimental data and FEM simulation results, the accuracy and effectiveness of the model were validated. According to the damage morphological characteristics, the target damage was classified into the central crush area, cone cracks area, radial/circular area, and fragment falling area by analyzing the damage nephogram, and the formation causes of each area were discussed in detail. According to the simulation results, the impact process between the projectile and target is split into three stages: initial impact stage, erosion stage, and crack propagation stage, and the energy dissipation in each phase was computed and examined. Finally, the protection mechanism is summarized in detail. This study contributes to improve the protection mechanism system of B4C ceramic target.

Subsurface damage model in single and double scratching of fused silica with a blunt indenter

The subsurface damages (SSDs) generated during abrasive processes greatly impact the service performance and life of the devices or components made from brittle materials. The abrasive processes can be simplified as multi-scratching where the abrasive grits tend to be blunt. Consequently, the evaluation of SSDs in the scratching with a blunt indenter is worth of study. In this paper, by extending the blunt indenter-related indentation fracture mechanics and deriving the analytic equations for the contact areas between the indenter and the workpiece, a theoretical SSD depth model is first developed for the single and double scratching of brittle materials. The model correlates the depth of subsurface cone, median, and lateral cracks with the indenter nose radius, scratching depth, residual depth, normal load, tangential load, scratch spacing, and workpiece material properties. To validate the model, scratching experiments are carried out on polished fused silica under different scratch spacing, and the effects of scratch spacing on the surface/subsurface morphologies of scratch grooves, scratching load, and friction coefficient are investigated experimentally. The results show that the radial, cone, median, and lateral cracks are coexistent in fused silica. The second scratching leads to an increase in the fracture degree of the first one, while the SSD depth in double scratching approximates that in single scratching. A small scratch spacing leads to an increase in tangential load or friction coefficient while a decrease in normal load. It is proven that the theoretical model can accurately determine the upper/lower bounds of scratching normal load and subsurface crack depth considering the workpiece fracture degree. Moreover, it is revealed that the SSD depth increases slightly with an increased friction coefficient. This research contributes to the evaluation of SSDs in the abrasive-processed fused silica or similar brittle materials.

When Does a Light Sphere Break Ice Plate Most by Using Its Net Buoyance?

A free-rising buoyant sphere can break an ice plate floating above it. The problem is when the light sphere breaks the ice plate most, or the optimal relative density of the sphere which can break the ice plate the most severely. This experimental study was done to answer this problem. A set of experimental devices were designed, and a high-speed camera system was adopted to record the whole dynamic process, including the free-rising of the sphere, the collision between the sphere and the ice plate, the crack initiation and propagation, as well as the breakup of the ice plate. The failure mode of the ice plate under impact load was analyzed. It was found that conical cracks were formed under the reflected tensile wave at the top surface of the ice plate. On this basis, the influences of ice thickness, the initial submergence depth, and the relative density of the sphere on icebreaking were further investigated. An optimal relative density of the sphere was found when the sphere was released at a certain initial submergence depth, at which point the ice was damaged the most severely. For example, when the dimensionless initial submergence depth of the sphere was 2.31, the optimal relative density of the sphere was close to 0.4, with the probability of the ice plate breakup as high as 91.7%. It was also found from the experiments that the degree of damage to the ice plate correlated well with the kinetic energy of the sphere just before collision. Results showed that the optimal relative density can be estimated by theoretical analysis of the kinetic energy of the sphere, which will provide a reference for potential icebreaking applications in the future.

Weak adhesion between ceramic and resin cement impairs the load-bearing capacity under fatigue of lithium disilicate glass-ceramic crowns

ObjectiveTo evaluate the fatigue behavior of lithium disilicate crowns with a simplified anatomy against progressive cement/ceramic debonding scenarios. Materials and methodsLithium disilicate crowns were fabricated via CAD/CAM and luted onto a dentin analogue material using resin cement following the manufacturer's instructions. Then, the different crown regions were isolated with paraffin oil for the absence of chemical adhesion according to four experimental groups (n = 15): Shoulder; Shoulder + Axial; Fully isolated; and Control (no insulation/fully bonded). Load to failure tests (n = 3) were run to determine cyclic fatigue parameters, and the specimens were subsequently submitted to a cyclic fatigue test (n = 12) (initial load 200 N for 5000 cycles, step 100 N, 15,000 cycles/step, frequency 20 Hz) until cracks were observed, and later fracture. The data were analyzed by Kaplan-Meier + Mantel-Cox post-hoc tests for both outcomes (cracks and fracture). Fractographic, cross-sectional surface, and finite element (FEA) analyzes were performed. ResultsWhen it comes to crack occurrence when the chemical adhesion to the occlusal surface is compromised, there is worsening (p < 0.05) in fatigue behavior compared to groups where the occlusal portion of the crown is still bonded. Considering fracture occurrence, there was no difference (p > 0.05) among the tested groups. All cracks occurred in the occlusal portion, first as a radial crack at the ceramic intaglio surface, and posteriorly unleashing a Hertzian cone crack at the top surface, resulting in fractures on the frontal walls. The interface analysis showed no interference of the insulating agent. FEA showed that as the isolated areas increased, there was also an increase in both tensile and shear stresses concentration in the crown and in the cement layer. ConclusionThe chemical adhesion between cement and ceramic is essential for better fatigue behavior of lithium disilicate crowns with a simplified anatomy, especially in the occlusal portion, but the restoration performance is impaired when such adhesion is compromised. There is an increase in crown and cement stress concentration with the progressive loss of chemical bonding of the crown's walls.

Uniaxial tensile tests and refined finite element analyses of the grouted welded rib sleeve connections

AbstractAs the major connection of precast concrete structure, a novel Grouted Welded Rib Sleeve (GWRS) was proposed in this research. Six splice specimens were designed and tested under uniaxial tensile load to investigate the influence of anchorage length and inner cavity structures on their connection performance. To further investigate the failure mechanism of the specimens, a refined finite element (FE) modeling method was proposed, and the corresponding refined models were established, validated, and analyzed. This research shows that the rebar anchorage length is the key factor that controls the failure modes of the specimens. The failure loads of the specimens are mainly influenced by the failure modes. Distributing sleeve ribs close to the sleeve end with lower 25 mm spacing could enhance the confining effect of the sleeve and improve the interlocking effect between the bar and grout. The conical cracks in the grout are distributed at an angle between 35° and 45°, which is also the distributed angle of the compressive struts of the grout. The bond deterioration observed in the tests is caused by the cracking of the grout and the shearing‐off of the grout keys, resulting in the transfer of sleeve effective confining zone.

Cone cracking in human bone: A CT case review series

• Cone cracking is the mechanism responsible for the production of beveling in bone. • Beveling results from impacts, including projectile or blunt. • Case studies reveal and support the cone cracking mechanism of bevel formation. Skeletal trauma analysis often involves the assessment of the types and patterns of fractures, followed by categorizing the trauma into one of several broad “mechanisms.” Trauma analysis ideally also involves understanding the underlying mechanistic basis for the bone's failure. Beveling in bone is one example of a fracture pattern that is often cited as evidence of a high-velocity projectile impact, but appears to be poorly understood in terms of both the mechanism for bevel production as well as the loading conditions responsible for its formation. It has recently been demonstrated that bone beveling results from a failure mechanism called cone cracking, which is also associated with lower velocity impacts. Many case reviews and instructional texts include imagery of beveled bone in association with projectile impacts, but present various other explanations (or no explanation) for the fracture mechanism responsible. Five cases are presented here involving cone cracking in human forensic cases. For each case, the associated fracture patterns are discussed, photographic and micro-CT imagery are shown, and a review of the cone crack is presented in cross-section. The diagnostic utility of CT examination of ambiguous perforations is also highlighted.

Adhesion and wear of diamond: formation of nanocracks and adhesive craters of torn out material.

Mechanical transformation of rough diamonds into brilliant ones is usually achieved by polishing using microsized abrasive diamond particles. It is shown that in addition to formation of periodic pattern of 'partial' Hertzian cone cracks on the diamond surface, nano-sized domains (50-150 nm in diameter) of crumbled material are observed. Because these domains are located in the centres of the regions (250-500 nm in diameter) partially surrounded by the Hertzian cone cracks, where the stresses are close to the stress field of hydrostatic compression, the material removal cannot be explained by creation of tensile or shear cracks. It is argued that the creation of these domains of crumbled material is due to adhesive interactions between sliding diamond particles and the diamond surface. Employing a two-term law of friction, the scheme of ultimate equilibrium between the particle and the surface is presented. The distributions of contact stresses are calculated for two approaches: (i) the extended Johnson-Kendall-Roberts model and (ii) the 'soft' model of adhesive contact. Thus, adhesion between the sliding diamond particle and the surface leads to creation of periodic pattern of the crumbling domains with the steps 500-1000 nm and adhesive tearing out of the material from the domains. This article is part of the theme issue 'Nanocracks in nature and industry'.