Shot Velocity Research Articles

Study of Impact Velocity on Residual Stress and Surface Hardness of SKD11 in Shot Peening Process

Shot peening process could create compressive residual stress and increase surface hardness and hence also used to improve material surface properties in case thermal effect is to be avoided. The shot peening process parameters such as pressure which result in different shot impact velocity could affect the compressive residual stress distribution which results in different post-process material properties. The ability to understand and predict the effect of process parameters on stress distribution could be very useful to control and obtain material properties as required. In this work, a shot peening process commercially available locally was investigated. The residual stress distribution after shot peening of SKD11 was studied using the finite element (FE) technique. A single shot impact was simulated. A maximum velocity with a miximum impact angle was assumed. The computational predictions showed higher compressive residual stress developed with increasing shot velocity as expected due to higher impact energy. However, experimental results suggested that the process arrangement and machine control highly affect the properties of the material after process. The compressive residual stress and surface hardness obtained experimentally was almost unchanged with an increase in pressure from 0.35MPa to 0.6MPa. It was found that, due to machine arrangement, an increase in impact velocity at higher pressure was relatively small and did not observed in all effected area due to fixed arrangement of nozzle and samples. Hence, research results suggested that a detail computational methodology including the effect of unevent impact velocity and impact angle should be employed to increase the predictive ability of the FE model. The current work could be extended to include such effects with no major difficulty to develop useful information for the design of shot peening process for any specific machine and arrangement.

Numerical investigation of surface topography and residual stress after abrasive water jet sequential peening (AWJSP)

This article reveals the formation mechanism of surface topography and the formation and coupling mechanism of residual stress field (RSF) after abrasive water jet sequential peening (AWJSP) that can sequential peening on the material surface at a certain distance interval, and proposes a mathematical model of surface dimple characteristic verified by simulation results. In addition, the influences of shot velocity v0, shot radius R and the distance between the center of adjacent shots DC on surface topography and RSF were also investigated. Results show the surface dimple forms resulting from the material plastic strain, and the residual stress (RS) is mainly induced by the unrecovered elastic strain resulting from the hindering of plastic strain. Decreasing v0, R or DC can decrease the surface roughness Rt, while increasing v0 and R is beneficial to induce a large and deep compressive RS layer. DC influences the whole distribution of compressive RS layer directly.

Experimental investigation of shot peening: correlation of pressure and shot velocity to Almen intensity

Shot peening is a mechanical surface enhancement process that is extensively used in various industries to increase fatigue life of components. This process relies heavily on post-processing quantification such as Almen strip system. With the main objective of replacing the Almen strip system with suitable sensors, this study is performed with the intent of achieving real-time monitoring for the process and finding an alternative means to quantify it by correlating sensor signals to Almen intensity. The pressure drop across a typical shot peening nozzle using pressure sensors and its correlation to shot velocities using a high-speed camera and a ShotMeter™ obtained at different operating conditions was evaluated. The information from the pressure sensors and shot velocity was analyzed to ascertain the presence of any correlation with process inputs (pressure and mass flow rate) and process output (Almen intensity). By deploying pressure sensors at the inlet of the system and the nozzle, the study demonstrates the capability for a real-time monitoring and control of the shot peening process without using Almen strip system.

Residual Stress Field of High-Strength Steel After Shot Peening by Numerical Simulation

The high-strength steel (40CrMnsiMoVA) used in aviation industry was taken in this work. The residual stress field of the steel after shot peening was determined by x-ray stress instrument. Meanwhile, the finite element model of the shot peening was established, and the residual stress field of the steel after shot peening was numerically simulated by ANSYS software. Then, the simulated result was compared with the measured one to verify the validity of the model. Based on this model, the residual stress fields of the steel with different shot velocities and shot diameters were simulated. The results show that, with the increase in the shot velocity, maximum residual stress (σmrs), maximum residual stress depth (ξ0) and strengthen depth (ξm) are increased gradually. When the shot velocity is 280 m/s, the σmrs reaches − 696 MPa, and the ξ0 and ξm increase to 0.43 and 0.70 mm, respectively. With the increase in the shot diameter, the σmrs, ξ0 and ξm are increased gradually. When the shot diameter is 1.5 mm, the σmrs, ξ0 and ξm increase to − 800 MPa, 0.56 and 0.78 mm, respectively.

Measurement of shot velocity using particle image velocimetry and numerical analysis of residual stress at two shot peening conditions

Measurement of shot velocity using particle image velocimetry and numerical analysis of residual stress at two shot peening conditions

Combining the finite element method and response surface methodology for optimization of shot peening parameters

In this study, a finite element shot peening model was employed in order to obtain the values of maximum compressive residual stress (σmaxRS), the depth of compressive residual stress field (δ0) and the stress concentration factor (K) in specimens treated by shot peeing process. Based on the finite element simulation results, Response Surface Methodology was conducted to optimize the response variables of σmaxRS, δ0 and K. The effects of three shot peening parameters (shot velocity, shot diameter and coverage ratio) on the values of σmaxRS, δ0 and K were investigated. The influence of the values of σmaxRS, δ0 and K on the fatigue property was discussed via giving different weights to these response variables in the optimization approach. The results showed that the proposed shot peening finite element model could give a reasonable prediction of compressive residual stress field and dimple size. Meanwhile, response surface methodology could be used to optimize these response variables (σmaxRS, δ0 and K) well. The priority should be given to the values of σmaxRS, δ0, and K in sequence when shot peening parameter optimization was conducted within a reasonable shot peening parameters range without microcrack appearing on treated surface. The optimal shot peening parameters were the shot velocity of 88 m/s, the shot diameter of 0.8 mm, and the coverage ratio of 170% for 42CrMo specimens. The fatigue life of 42CrMo specimens treated by shot peening with optimal parameters was improved by 104% in experiments.

Direct Observation of Filling Process and Porosity Prediction in High Pressure Die Casting.

Although numerical simulation accuracy makes progress rapidly, it is in an insufficient phase because of complicated phenomena of the filling process and difficulty of experimental verification in high pressure die casting (HPDC), especially in thin-wall complex die-castings. Therefore, in this paper, a flow visualization experiment is conducted, and the porosity at different locations is predicted under three different fast shot velocities. The differences in flow pattern between the actual filling process and the numerical simulation are compared. It shows that the flow visualization experiment can directly observe the actual and real-time filling process and could be an effective experimental verification method for the accuracy of the flow simulation model in HPDC. Moreover, significant differences start to appear in the flow pattern between the actual experiment and the Anycasting solution after the fragment or atomization formation. Finally, the fast shot velocity would determine the position at which the back flow meets the incoming flow. The junction of two streams of fluid would create more porosity than the other location. There is a transition in flow patterns due to drag crisis under high fast shot velocity around two staggered cylinders, which resulted in the porosity relationship also changing from R1 < R3 < R2 (0.88 m/s) to R1 < R2 < R3 (1.59 and 2.34 m/s).

The relationship between shot velocity and physical characteristics of lacrosse players.

This study was designed to quantify the relationship between the velocity at which lacrosse players can shoot a lacrosse ball (shot velocity) with a lacrosse stick and a variety of physical strength attributes. Twenty lacrosse athletes were recruited to participate in the study. We measured shot velocity with a microwave, speed-measuring apparatus. Shot velocity showed significant and moderate correlations with the distance a player can throw a medicine ball (r=0.58-0.66), the height at which a player could jump vertically from a crouching position (r=0.44-0.46), a player's hand grip strength (r=0.33-0.46), and the isokinetic concentric strength of player knees (r=0.20-0.45). The thrown distance of a medicine ball was significantly and moderately correlated with vertical jump height (r=0.32-0.47) and hand grip strength (r=0.33-0.53), respectively. Strength and conditioning coaches should train lacrosse players in strengthening their core, lower extremities and in movements that link their arms with the lower part of the body. The muscular strength of trunk rotation, which relies on the strength of the arms and lower limbs, greatly enhances a player's ability to shoot a lacrosse ball at high velocities.

Numerical Analysis of Shot Peening with Incident Angle

Shot peening has been used to improve the fatigue strength of metal structural components because it can produce large compressive residual stress near the surface. The distribution of compressive residual stress is strongly dependent on shot peening conditions such as the material of the shot, the shot diameter, the shot velocity, the incident angle, and the peening time (coverage). In this study, a finite element model including multiple shots and the specimen was developed in order to investigate the influence of the incident angle on the compressive residual stress and the depth of its location from the surface in high-strength aluminum alloy. The residual stress and its distribution were analyzed when multiple shots were randomly impacted on the surface of the specimen. The analyzed residual stress distribution using the kinematic material model agreed very well with experimental ones at the incident angles of 90° and 30°. It can be concluded that the depth of the compressive residual stress is proportional to the velocity component perpendicular to the surface.

Assessment of Resisted Trunk Rotation Exercise With and Without Kiai Double-Pulse Breathing Technique on Hockey Shot Velocity: A Pilot Study

ObjectiveThe purpose of this study was to assess the feasibility of a study to measure the effect of resisted band antirotation exercises with the use of a double-pulse (DP) breathing kiai exercise on slapshot and snap shot velocity and subjective assessment of performance. MethodsTen participants between 20 and 30 years of age who play ice hockey were recruited. The study was conducted over 3 weeks, and participants were randomized into 2 groups; group 1: resisted band antirotations with DP kiai (a shout used in martial arts) exercises, and group 2: resisted band antirotations alone. After week 1, there was a 1-week washout period, after which group 1 performed resisted band antirotations alone, and group 2 performed resisted band antirotations with DP kiai exercises. ResultsData were successfully collected on all 10 participants. There appeared to be no difference between groups regarding slapshot and snap shot velocity. ConclusionThe design for this study appears to be feasible. Preliminary data show that the average shot velocity before and after the intervention did not show a positive relationship between DP kiai breathing and hockey shot (slapshot and snap shot) velocity.

Numerical simulation study of steel plate anti-penetrating features

With the high strength and high impact resistance, the steel structure has been widely applied in the military field of protective armor, weapon shelter and other military fields, and the impact resistance of steel structure has become the focus and hotspot of research. The smoothed particle hydrodynamics method was used to simulate the process of the hemispherical head impact on the multi-layer steel plate. Compared with the experiment, the failure mode of the steel plate after the impact of the hemispherical head was analyzed, and the plate uplift at the impact point was obtained, and the process of butterfly failure, the Von Mises stress distribution of the steel plate and the remaining velocity of the hemispherical head shot were obtained, which verified the effectiveness of the SPH method in simulating the steel plate's penetration deformation problem. Through numerical simulations, the effects of steel body layers and the thickness of the steel body on the anti-penetration properties was studied. The results show that the single-layer steel plate is more resistant than the multi-layer steel plate at 3 mm, and the multi-layer steel plate is more than single-layer steel plate at 9 mm. 12mm multi-layer steel plate and single-layer steel plate protection is same.

Numerical analysis of hydrogen transport into a steel after shot peening

Abstract Surface peening is a potential method of suppressing hydrogen embrittlement (HE). But experimental observations in literatures have shown that it can suppress HE of steels exposed to a mild hydrogen-containing environment, but in a severe hydrogen-containing environment it enhances HE. To explain this from the perspective of hydrogen transport and concentration, this paper gives a numerical analysis of hydrogen transport into a PSB1080 high strength steel after shot peening (SP) focusing on the combined effect of residual compressive stress and SP plastic deformation on diffusion. The diffusion model established by Oriani and Sofronis et al. is used, which considers the effect of the increase of trap sites due to plastic strain and assumes that the populations of hydrogen in trap sites and in normal lattice sites are in equilibrium. The results were related to experimental observations. In mild hydrogen-containing environment, the increase of trap sites due to SP can significantly reduce the apparent hydrogen diffusivity, thus suppress the transport and resulting hydrogen concentration level in normal lattice sites. As a result, hydrogen trapped at grain boundaries is reduced, and HE mechanism changes from HEDE to simultaneous HELP and HEDE. Intergranular fracture is suppressed thus reducing HE. And the suppression of hydrogen transport increases with increasing shot velocity, as a faster shot gives rise to more severe plastic deformation. In severe hydrogen-containing environment, SP deformation has little influence on diffusivity but significantly increases trapped hydrogen, leading to irreversible hydrogen blisters hence enhancing HE.

FE analysis of shot-peening-induced residual stresses of AISI 304 stainless steel by considering mesh density and friction coefficient

ABSTRACT In order to investigate the effect of shot peening (SP) on residual stress distribution of AISI 304 stainless steel, a 3D dynamic model for describing single and multiple shot impact phenomenon was built via ABAQUS/Explicit 6.10 by considering the mesh density of treated component as well as the friction coefficient between shot and treated component and validated via X-ray residual stress measurement. The results show that an optimal surface element size about 1/18th of the dimple diameter and reasonable friction coefficient of μ > 0.2 are the key factors for the accuracy of residual stress estimation and the computational efficiency. The error of simulated residual stresses indicates the effect of the deformation-induced martensitic transformation phenomenon should be considered in AISI 304 stainless steel SP model. The effects of shot hardness, impact angle, velocity, diameter and coverage ratio on residual stress distribution were examined and discussed via the optimised SP model.

Dynamic finite element analysis of shot peening process of 2618-T61 aluminium alloy

Shot peening is one of the surface treatment processes usually used for the improvement of fatigue strength of metallic parts by inducing residual stress field in them. The evaluation of shot peening parameters experimentally is not only very complex but costly as well. An attractive alternative is the explicit dynamics finite element (FE) analysis having the capability of accurately envisaging the shot peening process parameters using a suitable material’s constitutive model and numerical technique. In this study, ANSYS/LS-DYNA software was used to simulate the impact of steel shots of various sizes on 2618-T61 aluminium alloy plate described with strain rate dependent elasto-plastic material model. The impacts were carried out at various incident velocities. The effect of shot velocity and size on the induced compressive residual stress and plastic deformation were investigated. The results demonstrated that increasing the shot velocity and size yielded in an increase in plastic deformation of the aluminium target. However, as observed, the effect of shot velocity and size was small in magnitude on the target's subsurface compressive residual stress.

INFLUENCE OF BALL RESIN TO SHOT ACCURACY IN HANDBALL

Opinions of handball experts differ in terms of importance of individual elements of handball technique, but they are all in agreement that shot is relevant and important factor. Shot velocity and accuracy gain importance in terms of score outcome of the game. We may draw a conclusion that they are two basic factors and that they are extremely significant for shot efficiency. In this paper, research will be aimed answering whether and to what extent ball resin influences shot accuracy. The sample consists of 20 male handball players, members of handball clubs which play in Serbian Super league aged 17 to 36, systematically training for at least two years without longer brakes. For the purpose of accuracy assessment, the participants shot equilateral triangles positioned between the goal posts in upper and lower corners. Shot was performed with size 3 handball with and without resin as follows: jump shot from 9-meter distance (SMP9M), 7-meter throw from standing position (SMP7M) and shots by positions (SMPP). For the purpose of determining the statistical significance all the data was processed at univariant level, the descriptive parameters were calculated and after that the Student’s t-test for paired samples was applied at the multi-variant level and relevant parameters were defined. Results of the Student’s t-test for paired sampled provided confirmation for identification of statistically significant differences between mean values: (SMP9ML – SMP9MBL .001, SMP7ML – SMP7MBL .006 and SMPPL – SMPPBL .024) at the statistical significance level p < .05. Article visualizations:

Biomechanical Analysis of the Back Sliding Techniques of Li-jiao GONG

The main technical factors affecting the shot-putter’s performance are studied from the biomechanical perspective with emphasis on the speed rhythm. Li-Jiao GONG, the silver medal winner of the women's shot put at 2015 World Championships in Athletics, is chosen as the research object. The results show that the sliding initiation technique of GONG is good with a desirable angle between the leg and the ground (ALG); in the transitional stage, the shot velocity increases but the barycentric velocity decreases owing to too long a supporting time caused by her poor concession capability and the ability to quickly transfer to the forward acceleration; in the last exertion, GONG’s distinct acceleration point (exerting point) leads to significant increase of shot velocity.

Explicit dynamics simulation of shot peening process induced by various types of shots impacts

Shot peening is a cold-working process that induces a small indentation on a metallic surface by impacting shots onto it causing residual compressive stresses which delays the initiation of fatigue cracking. The experimental assessment of shot-peening process parameters is not only very complex but costly as well. The most promising technique is the explicit dynamics finite-element (FE) analysis capable of determining the shot-peening process parameters subject to the selection of a suitable material’s constitutive model and numerical technique. In this work, Ansys/LS-Dyna code was employed to simulate the impact of shots of various sizes made of steel and glass on an aluminium alloy plate defined with strain-rate-sensitive elasto-plastic material model. The impacts were carried out at various incident velocities. The effects of velocity, size, and material of the shots on the compressive residual stress, indentation, and force–time response were investigated. The results showed that impact with the steel shots caused more indentation and larger area of plastic deformation in target material than the glass shots due to higher kinetic energy. Furthermore, increasing the shot velocity and size resulted in an increase in indentation. However, a negligible effect of the shot velocity, size, and material was observed on target’s surface and subsurface residual stress. The obtained results demonstrated that the proposed FE models simulated the shot-peening process in a realistic way. The study can be used to determine and optimise the shot-peening parameters such as shot size, material and velocity, and amount indentation and residual stresses in the aluminium alloy plate.

Fluidized bed classification of particles of different size and density

The main objectives of this study were to quantify the classification efficiency of a binary mixture of two different particle types and to demonstrate that CPFD can be used to simulate the main features of the classification process. A lab-scale cylindrical fluidized bed (8.4 cm inner diameter, 150 cm height), equipped with pressure sensors and a video camera for recordings, was applied in the experiments. The particles used in the study were ceramic beads (median diameter 70 µm, skeletal density 3830 kg/m3) and steel shot (290 µm, 7790 kg/m3). Ambient air was used as the fluidization medium.The minimum fluidization velocities of pure ceramic beads and steel shot were found to be 0.015 m/s and 0.240 m/s, respectively. In the experiments with a binary mixture of the two materials, the fluidization column was filled by alternating layers of ceramic beads and steel shot. In principle, segregation of the two particle types can be obtained by applying a suitable gas velocity within the interval defined by the two minimum fluidization velocities, resulting in a top layer of mainly lighter and smaller particles (flotsam) and a bottom layer of mainly heavier and larger particles (jetsam). In the experiments, the air velocity was gradually increased until the entire bed was fluidized. A gradual rearrangement of the multi-layer structure into a two-layer structure was observed. The rearrangement started at the top and then progressed downwards until most of the steel particles were collected at the bottom of the bed and practically all the ceramic beads were gathered at the top. The velocity at which the flotsam and jetsam layers were clearly segregated was found to be 0.180 m/s. The jetsam layer contained less than 0.3 wt% ceramic beads indicating that an almost pure steel shot fraction could be produced through fluidized bed classification. The flotsam layer was, however, less pure, with a steel shot content up to 24 wt%, suggesting that this layer may need a second classification stage for improved purity.Computational particle-fluid dynamics (CPFD) simulations of the same setup were performed using the commercial software Barracuda. The simulated minimum fluidization velocity of steel shot, applying the Ergun drag model, perfectly matched the experimental value. For the ceramic beads, however, the simulations, applying the Wen-Yu drag model, gave a value lower than the experimental value. Still, the simulations were able to capture the general behavior of the particles in the bed observed in the classification experiments, i.e. the rearrangement of the layers, even if a higher gas velocity was required for complete classification of the particles. The formation of air pockets was also observed in the simulations, as in some of the experiments. The results suggest that Barracuda CPFD simulations can be a useful tool in design and evaluation of fluidized bed classifiers.

Shot peening in a novel centrifugal air blast reactor

ABSTRACTA novel reactor to synthesise a thick nanocrystalline (NC) layer on metallic surface by shot peening is presented. In this cylindrical reactor, air enters inside the reactor tangentially and propels shots on specimen surface for peening. The air then leaves the reactor after multiple rotations. Air vortex and very high turbulence inside the reactor dissipate the heat generated during shot peening and thus avoids dynamic recovery. Experiments were conducted on samples of austenitic stainless steel with different shot velocities. Characterisation of shot peened surfaces showed that thick layers with NC/nano-twinned structure were developed under all peening conditions used in the experiments. Microstrain in the lattice, dislocation density and volume fraction of strain-induced martensite observed to increase with rise in shot velocity. Consistent reduction in grain size and enhancement in dislocation density with increase in strain, indicate that no dynamic recovery occurred during the shot peening process in the reactor.

New approach to estimate coverage parameter in 3D FEM shot peening simulation

ABSTRACTShot peening is a surface cold working process used to enhance the fatigue life of metallic parts or members. Coverage is a major parameter of shot peening process, which is defined as the percentage of the sum of peened area over the total area on the surface of the specimen. In this paper, a new method is proposed to estimate the full coverage for simulation of the shot peening process. A dynamic plastic model of the shot peening process with the aid of MatlabTM code is also presented using the finite element method (FEM). The numerical results show that the coverage, shot velocity and radius significantly affect the residual stress distribution of the target material, AISI 4340 steel. In addition, a double-shot peening process is also studied in simulation to consider its effect on compressive residual stress distribution.