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Featured Application: A database of damage patterns for 5 mm-thick glass plates was established. The damage limit velocity of glass impacted by 8 mm and 10 mm steel balls launched by a slingshot was determined. The damage patterns of cone cracks and perforated holes based on velocity were evaluated. Slingshots, traditionally viewed as children's toys, have recently been modified for malicious purposes, including firing steel balls at building windows, causing significant damage. This misuse necessitates the development of methods to estimate impact velocity and launch point based on glass damage patterns at incident scenes. To achieve this, a comprehensive database correlating glass damage shapes with steel ball diameters is essential. This study conducted experiments to investigate the damage patterns of 5 mm thick glass upon impact with 8 mm and 10 mm steel balls. The damage limit velocities for 8 mm and 10 mm steel balls to cause damage to 5 mm glass were approximately 40 m/s and 21 m/s, respectively. Glass damage was categorized into two types: cone cracks and perforated holes. While cone crack patterns were similar for both 8 mm and 10 mm steel balls, perforation patterns exhibited distinct tendencies. Consequently, the impact velocity of each steel ball can be estimated based on the size of the perforated hole. However, determining the steel ball diameter solely from the size of the cone crack and perforated hole remains challenging. [ABSTRACT FROM AUTHOR]

Copyright of Nonferrous Metals (Mineral Processing Section) is the property of Beijing Research Institute of Mining & Metallurgy Technology Group and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Bearing is the property of Bearing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Slingshots, traditionally viewed as children’s toys, have recently been modified for malicious purposes, including firing steel balls at building windows, causing significant damage. This misuse necessitates the development of methods to estimate impact velocity and launch point based on glass damage patterns at incident scenes. To achieve this, a comprehensive database correlating glass damage shapes with steel ball diameters is essential. This study conducted experiments to investigate the damage patterns of 5 mm thick glass upon impact with 8 mm and 10 mm steel balls. The damage limit velocities for 8 mm and 10 mm steel balls to cause damage to 5 mm glass were approximately 40 m/s and 21 m/s, respectively. Glass damage was categorized into two types: cone cracks and perforated holes. While cone crack patterns were similar for both 8 mm and 10 mm steel balls, perforation patterns exhibited distinct tendencies. Consequently, the impact velocity of each steel ball can be estimated based on the size of the perforated hole. However, determining the steel ball diameter solely from the size of the cone crack and perforated hole remains challenging.

Copyright of Journal of Ordnance Equipment Engineering is the property of Chongqing University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Bearing is the property of Bearing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Bearing is the property of Bearing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Bearing is the property of Bearing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A finite element analysis of the stress-strain state of a steel ball stamping process from a cylindrical billet was performed under the conditions of a non-isothermal process in an axisymmetric formulation. Three options for stamping a ball from blanks with different height-to-diameter ratios are considered. Distribution of temperature, degree and deformation rate, average stress and stress intensity are given. It has been found that with an increase in the relative workpiece height, the degree of deformation over the ball volume increases. In this case, the temperature value in the ball volume increases. A metal cooldown zone on the periphery of billet ends was revealed. Stress state index assessment at the last stage of stamping made it possible to identify the workpiece dangerous zones from the point of failure. When considering the metal plasticity indicators, this makes it possible to predict the defectiveness of products. [ABSTRACT FROM AUTHOR]

The wear resistance and hardness of stainless steel (SS) balls formed by cold skew rolling are effectively improved due to the change in internal microstructure. In this study, based on the deformation mechanism of 316L stainless steel, a physical mechanism-based constitutive model was established and implemented in a subroutine of Simufact to investigate the microstructure evolution of 316L SS balls during the cold skew rolling process. The evolution of equivalent strain, stress, dislocation density, grain size, and martensite content was studied via simulation during the steel balls' cold skew rolling process. The corresponding skew rolling experiments of steel balls were carried out to verify the accuracy of the finite element (FE) model results. The results showed that the macro dimensional deviation of steel balls fluctuates less, and the microstructure evolution agrees well with the simulation results, which proves that the established FE model has high credibility. It shows that the FE model, coupled with multiple deformation mechanisms, provides a good prediction of the macro dimensions and internal microstructure evolution of small-diameter steel balls during cold skew rolling. [ABSTRACT FROM AUTHOR]

Copyright of Bearing is the property of Bearing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A population balance model is applied to a steel ball mill. Experimental data were obtained for two types of balls with different chemical compositions using a marked ball test in an industrial mill of a recognized cement producer company. The balls were marked since their manufacture by an international ball supplier who guided the entire experimental process. The mill was monitored for about eight months in 12 time cycles. It is found that the law of wear of balls was of zeroth order. The wear law is introduced to the model to predict and analyze the steel consumption due to the wear of the balls, the mass density function, the distribution function of balls, and the mill ball charge at steady state. Experimental data and theoretical predictions match in excellent agreement. [ABSTRACT FROM AUTHOR]

The effect of soot contamination on the tribological performance of engine oil was investigated. Carbon black is introduced to simplify diesel engine soot contamination. Besides, the tribological performance issue is verified by a four-ball tribometer. The steel ball worn surfaces were studied by Scanning Electron Microscopy (SEM), Optical Microscope (OM) and Energy Dispersive X-ray spectroscopy (EDX). In addition, Transmission Electron Microscopy (TEM) was used to investigate the morphology and nanostructure of soot and carbon black. According to the four ball test results, the average wear scar diameter of steel ball tested with engine oil blended with N220, N330, N550 and N660 by 1% by weight is larger than that of pure engine oil by 26%, 38%, 41%, and 39%, respectively. The wear scar diameter tends to increase after blended larger size of carbon black particle. The steel balls tested with formulated engine oil without soot contamination and with soot contamination by 0.5 wt%, 1 wt%, and 2 wt% have average wear scar diameters of 621, 567, 784 and 894 nm, respectively. On the other hand, wear scar roughness of steel balls tested with formulated engine oil without soot contamination and with soot contamination by 0.5 wt%, 1 wt%, and 2 wt% were 2.28, 0.25, 1.49 and 1.76 μm, respectively.Consequently, quantity of the soot nanoparticle approximately 0.5% by mass in engine oil significantly plays an important role in steel ball wear scar diameter and surface roughness reduction. Moreover, the agglomerated soot which is larger than the oil film thickness might block the lubricant from entering the contact. It leads to the breakdown of the oil film thickness resulting in increasing adhesive wear on the worn surface.

Peculiarities of the formation of secondary structures on the surface of a diamond-like coating are studied on the example of a friction contact between a steel ball and a diamond-like coating. The friction surface was examined in various areas; the zone of wear products (the boundary of the friction track) and the original surface outside the friction area. It is shown that secondary structures with a high content of iron, nickel, manganese, chromium, and oxygen are characteristic of areas with the highest wear resistance. Such secondary structures are formed because of the intense interaction of the diamond-like coating with the steel of the ball during dry friction. [ABSTRACT FROM AUTHOR]

• Conducted simulation studies on different density media in a tumbling mill. • Analyzed the efficiency patterns of mechanical energy conversion of media. • Examined the impact of media density on collision energy characteristics and liner wear. This study investigates why ceramic balls achieve superior grinding performance compared to steel balls at lower densities and lower energy consumption. Particle motion analysis shows that increasing the filling level significantly improves the velocity distribution of the grinding media. The energy input from the mill is mainly converted into the kinetic and potential energy of the media, with potential energy being dominant. As the filling level increases, the efficiency of kinetic energy conversion improves. Collisions between media and mineral particles dominate energy transfer, and lower media density enhances collision energy distribution uniformity. Reducing media density decreases grinding energy consumption while maintaining the same grinding effect. [ABSTRACT FROM AUTHOR]

Copyright of Bearing is the property of Bearing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Microstructure grain refinement is an effective way to improve the quality of 42CrMo steel ball. A three-dimensional thermal-mechanical-microstructure coupled Finite element model (FEM) of steel ball skew rolling is established in the finite element simulation software. Simufact software was used to simulate the effects of process parameters on the microstructure of steel balls, and the effects of roll Angle, roll temperature and roll speed on the average grain size of rolled pieces were analyzed by single factor variable method. The research results provide some reference for the improvement of 42CrMo steel ball quality. [ABSTRACT FROM AUTHOR]

Pack carburizing or solid media aims to increase the carbon value of steel, especially in low carbon steel so that with increasing carbon value in steel, the hardness value also increases. This study used a steel ball (cycle agel) as the object of pack carburizing treatment and Buffalo Bone Charcoal (ATK) as a carbon source and Barium carbonate (BaCO3) as a catalyst. Method, composition ratio 60% ATK: 40% BaCO3, 70% ATK: 30% BaCO3, 80% ATK: 20% BaCO3, heating temperature 8500C and 950° C, holding time 2 hours and fast cooling with plain water. As a result, the best steel ball hardness value at a heating temperature of 850° C is in the composition of the pack carburizing ratio of 80% ATK: 20% BaCO3 of 212.77 HB, while at the heating temperature of 9500 the composition of the pack carburizing ratio of 80% ATK: 20% BaCO3 is equal to 219.84 HB. [ABSTRACT FROM AUTHOR]

Copyright of Bearing is the property of Bearing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Grinding media have significant influence on the flotation of chalcopyrite and pyrite. This effect is mainly related to the change in the surface properties of chalcopyrite and pyrite. This paper investigates the influence of steel ball and nano-ceramic ball grinding on the floatability of chalcopyrite and pyrite. Flotation results, as well-scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), ultraviolet spectrophotometer, and zeta potential measurement results indicate that nano-ceramic ball grinding is beneficial to the flotation of chalcopyrite. Flotation results also indicate that chalcopyrite has better floatability after nano-ceramic ball grinding compared with steel ball grinding. Results of adsorption experiments show that nano-ceramic ball grinding contributes to the adsorption of isobutyl xanthate to chalcopyrite. XPS and SEM techniques demonstrated that steel ball grinding easily produces oxidation species at the surface of chalcopyrite, thereby reducing its floatability. Results from this study also confirmed that steel ball grinding is beneficial to the flotation of pyrite. Therefore, nano-ceramic media grinding produces better selective flotation in chalcopyrite than steel media grinding.

AISI 316L is a type of 316 austenitic stainless steel with characteristic very low carbon content. This material contains several elements such as molybdenum-chromium-nickel which are aimed to improve the corrosion and oxidation resistances at high temperature applications. The low carbon content and the high level of corrosion resistance of AISI 316L allow this material to be applied to the surgical implant applications in the human body as well as on the welding applications. Several methods of surface treatment applied in AISI 316L are aimed to improve the mechanical properties and corrosion resistance. Dry shot peening is one of cold deformation processes which is conducted on the material surface to improve the mechanical strength. The process was performed by firing balls of steel with particular sizes of 0.5 mm, 1 mm, 2 mm, and 3 mm on specimens with a certain speed that comes from the pressure of the air compressor. The results show that parameter of shot angle at the dry shoot peening process has an influence on microstructure and hardness of the AISI 316L austenitic stainless steel. The highest value of hardness was achieved using 3 mm diameter of steel ball with the value of hardness reached 560 VHN on metal surface then gradually decreased as the depth increased.

Copyright of Journal of Harbin University of Science & Technology is the property of Journal of Harbin University of Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The objective of this study was to find the effect of cooling rate on microstructure and hardness of steel ball. Steel samples of φ3 mm × 10 mm have been used under the different cooling experiments to study microstructure evolution. The microstructure is observed with optical microscopy and scanning electron microscope, respectively. The transformation temperature is determined by dilatometric curves. The results show that faster the cooling rate is, the lower is the starting and finishing temperatures of austenite-to-pearlite transformation. However, faster cooling rate has no effect on the starting temperature of martensite transformation. The prior austenite grain size increases rapidly with a higher temperature and almost remains invariant with a longer austenitization time. The hardness y of steel and cooling rates x accord with a relationship: y = 11.885x4 − 131.06x3 + 443.75x2 − 320.21x + 387.45. [ABSTRACT FROM AUTHOR]

The paper reports experimental results on the intensive (fast) cooling of 20 mm steel ball heated to 1000 K when immersing in different coolants in 0.003 m3 glass vessel: tap water, seawater with salt concentration y of about 18 g/l, water solution of NaCl with y~27 g/l. By using the high-speed video recording, we study heat and mass transfer on a surface of the heated ball during the cooling. Experiments allow us to conclude that the film boiling on a surface of the metallic ball is almost excluded when using water solutions of salt as coolants. As a result, a cooling time decreases by 2-4 s as compared to the tap water. In addition, when using water solutions of salt, the temperature balance between steel ball and coolant is reached during a minimum time versus the tap water and seawater.

According to cold heading process with overloaded craft, high-impact dynamic real-time measurement requirements, this paper presents researches on dynamic characteristics and optimization of PVDF piezoelectric film force sensor for steel ball cold heading forming quality monitoring, through the combination method of mechanism analysis, mathematical modeling, numerical simulation and experimental validation. The motivation and strategic objectives are to breakthrough dynamic time-varying impacting load measuring fundamental technologies in steel ball forging process. The structure of piezoelectric film force sensor is proposed. The theoretical calculation formula of natural frequency is deduced and calculated by using MATLAB software. The mechanical performance analysis on dynamic model and structural optimization simulation by FEM is carried out. In order to study the validity of the proposed method, a prototype of the sensor is fabricated. The static and dynamic calibration devices are designed to realize calibration experiments on the fabricated PVDF piezoelectric film force sensor. The differences among experimental value, simulation value and the theoretical value are given. The nonlinear error of the fabricated sensor is 0.197%. The sensor's first order natural frequency value is 5238 Hz. It is proved that the PVDF piezoelectric film force sensor has superior dynamic performance and high accuracy for measuring deformation in steel ball. The paper will provide important scientific basis and technical foundation to achieve superior performance steel ball. • Dynamic characteristics and optimization of PVDF force sensor is researched. • Mechanical behavior upsetting and dynamic response law of cold heading machine is revealed. • Time-varying impact load dynamic measuring key technologies are breakthrough. • A novel PVDF piezoelectric film force sensor on cold heading force is designed. • The PVDF piezoelectric film force sensor has good dynamic performance and high accuracy. [ABSTRACT FROM AUTHOR]

• Development of EC for an automatic on-line inspection of steel balls surface. • A FAECS is proposed to inspect the whole ball surface and sub-surface with high accuracy. • Simplify the mechanism of steel ball surface unfolding. In order to perform the rapid and efficient automatic on-line inspection of the surface quality of steel ball, a new spherical deployment method based on flexible array eddy current sensor (FAECS) is proposed. Full unfolding of the steel ball surface can be performed by combining the flexible array eddy current sensor with the one-dimensional orbital deployment. The inspection coil of array eddy current sensor is fabricated on flexible printed circuit board (FPCB), which is bent into a semicircle to fix on the top of one-dimensional track. When the steel ball rolls on the one-dimensional track, complete inspection of steel ball surface can be performed by the flexible array eddy current sensor. In this method, one-dimensional mechanical motion is used instead of the traditional two-dimensional deployment motion, which reduces the complexity and cost of deployment structure. Three typical defects include linear cracks (0.12 mm width × 0.5 mm depth), cross cracks (0.06 mm width × 0.9 mm depth) and arc cracks (0.05 mm width × 0.1 mm depth) are measured in the experiment to verify the effectiveness of the inspection system. Subsequently, same batch of steel balls are tested at speed of 4 pcs/s, results show that the inspection accuracy of surface defect of steel balls is 95.52%, and the false inspection rate is less than 0.7%, which proves this method efficiency. [ABSTRACT FROM AUTHOR]

Copyright of China Mechanical Engineering is the property of Editorial Board of China Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Bearing is the property of Bearing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Bearing is the property of Bearing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Bearing is the property of Bearing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Based on the principle of steel ball forming by skew rolling, a finite element model of steel ball forming by skew rolling was established by using software DEFORM-3D. This FEM model was proved to be reliable by contrast with laboratory experiment results. Using the data of FEM results, the metal flow laws in both the radial and axial directions were studied. It is found that metal deformation accumulates in a periodic oscillation way. In the axial direction, deformation at the connecting neck is the most severe, both the radial and axial deformation are larger at the location closer to the connecting neck. In the cross sections, smaller radial compression and larger axial elongation were found at the location closer to the center in the front semi-sphere. Differently, there are smaller axial deformation and radial compression at the location closer to the center in the back semi-sphere.

To understand and describe the behavior of charge dynamics in mills, a series of dry and wet grinding tests were performed on a laboratory-scale ball mill. The comparisons between experimental results and grinding media trajectory simulations were addressed. Results show that the grinding media trajectory simulations exhibit a good agreement with the experimental results. The shoulder angle was proportional to mill speed and ball filling. The toe angle was inversely proportional to ball filling, but the impact point angle was appeared to invariant to ball filling and inversely proportional to mill speed. By means of motion analysis of the charge, a good grinding efficiency can be obtained when the ball filling ranging from 20% to 40% and the mill speed ranging from 70% to 80%. For dry tests, the orthogonal analysis indicates that the influence order of four factors on power-mass ratio is ball filling, mill speed, powder-grinding media ratio and lifter profile and the influence order of four factors on −0.074 mm yield is mill speed, ball filling, powder-grinding media ratio and lifter profile. The best dry tests are a combination of 70% of critical speed, 20% of ball filling, 0.8 of powder-grinding media ratio and waveform lifter. Correspondingly, the power-mass ratio can increase by 28.27% and the production of −0.074 mm can increase by 50.38%. For wet tests, the variations of −0.074 mm yield on mill speed and moisture content increase up to a maximum and then decrease rapidly. The −0.074 mm yield can reach a maximum at the 80% of mill speed and 50% of moisture content. [ABSTRACT FROM AUTHOR]

In this study, foreign object damage on aircraft high pressure compressor blades made of Inconel718 nickel-based superalloy was experimentally simulated at the working temperatures of the blades. Steel balls (as a foreign objects) with velocities of 292, 208, 133 m/s were impacted on the surface of Inconel718 flat specimens at various temperatures (400, 475, 550, and 625℃). In order to characterize induced craters, impact sites were studied by scanning electron microscopy to identify mechanical features such as microcracks and notches. Then, the specimens were 3D scanned to measure the depth of each crater. It was found that variation of stress concentration factors and induced damages (including microcracks and notches, loss of material, and shear bands) could occur as a result of steel ball impact with velocities of 292 and 133 m/s at temperatures of 625 and 400℃, respectively. [ABSTRACT FROM AUTHOR]

Superhydrophobic surfaces have shown utility applications in drag reduction field. A novel method based on simulation analysis and test experiments is proposed to fabricate a superhydrophobic surface with 3D flower-like micro and nano-structures on a steel ball under an O _2 rich environment. The superhydrophobic steel surface has water CA of 166 ± 1.5°. The sliding angle is less than 2°. The experiment and the simulation of the superhydrophobic and the untreated steel ball fall under water are built to prove the validity of the method of reducing water resistance. The drag reduction ratio of the superhydrophobic steel ball is beyond 53% opposed to the untreated surface under water. A model simulation is built to simulate and analyze the solid-liquid interface drag reduction mechanism of superhydrophobic surface based on theoretical analysis. The result testifies the rationality of the drag reduction experiment.

Copyright of Bearing is the property of Bearing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Steel ball surface-defect inspection was performed by using a new saddle-type eddy current sensor (SECS), which included a saddle coil and a signal conditioning circuit. The saddle coil was directly wound on the steel ball's outer bracket in a semi-circumferential direction. Driven by a friction wheel, the test steel ball rotated in a one-dimensional direction, such that the steel ball surface was fully scanned by the SECS. There were two purposes for using the SECS in the steel ball inspection system: one was to reduce the complexity of the unfolding wheel of the surface deployment mechanism, and the other was to reduce the difficulty of sensor processing and installation. Experiments were carried out on bearing steel balls in diameter of 8 mm with three types of representative and typical defects by using the SECS, and the results showed that the inspection system can detect surface defects as small as 0.05 mm in width and 0.1 mm in depth with high-repetition detection accuracy, and the detection efficiency of 5 pcs/s, which meet the requirement for inspecting ISO grade 10 bearing steel balls. The feasibility of detecting steel ball surface defects by SECS was verified. [ABSTRACT FROM AUTHOR]

Ill this paper, the damage of common objects such as steel ball and sand on the aeroengine blader is studied. One level rotor-blade is considered as a research object on the basis of the Kinematic hardening plastic constitutive model, using the ANSYS / LS- DYNA software to simulate the shock from each one of ten balls and sands of different sizes and speed respectively. The impact of the relative kinetic energy, size of steel ball and sand shock on the size and shape of shock gap are analyzed carefully A detailed comparison on the impact of the gap is made to or ball and its rough size that may be initially determined by characteristic of shock gap. The gap can be used to determine whether the external material is steel or gravel and the approximate size range. [ABSTRACT FROM AUTHOR]