Single Impact Experiments Research Articles

Dynamic mechanical response and fracture mechanism of rock-like materials with concealed structural planes of different filling thicknesses

Structural planes are the primary variables determining the stability of rock masses. Numerous non-penetrating structural planes exist in nature and are concealed inside the slopes or underground rock formations. The concealed structural planes (CSP) pose a possible hazard to the construction safety of rock mass engineering, particularly for the rock mass subjected to dynamic load. Using rock-like materials, intact specimens and specimens with CSP of varying filling thicknesses are constructed in order to examine the dynamic mechanical response and fracture mechanism of rock masses with CSP. Single impact experiments and cyclic impact experiments are carried out at various speeds using the Split Hopkinson Pressure Bar experimental system (SHPB). The results demonstrate that the specimens' peak stress is negatively correlated with the filling thickness, and that as the reflection coefficient increases and the transmission coefficient decreases, the filling thickness increases. Also, the energy dissipation rate of the specimens is positively correlated with the increase in thickness of filling at impact velocities of 3.7 m/s and 4.5 m/s, with the rate showing an increasing trend followed by a decreasing trend at impact velocities of 5.5 m/s and 6.5 m/s. The main surface and internal cracks of specimens can be categorized into seven types, which are combined into three failure modes. As the filling thickness increases, the failure mode changes from transverse tensile failure to combined tensile and shear failure to bi-directional tensile failure under combined transverse and axial tensile action. The crack propagation behavior and the fracture mechanism from the interior to the exterior of the CSP specimens are investigated using the impact test results, finite element model, and mechanical theory analysis, which can be used as a reference to reveal the destabilization process of the rock mass with CSP.

Machining performance evaluation under recently developed sustainable HAJM process of zirconia ceramic using hot SiC abrasives: An experimental and simulation approach

The proposed research work accomplishes the experimental study and computational fluid dynamics (CFD) technique for erosive footprint prediction extent in hot abrasive jet machining (HAJMing) constraints on target surface erosion rate, surface roughness of intricately shaped tapered holes generation. The CFD-obtained footprints were in superior agreement with experimentally measured data. HAJMing process uses a relatively high speed air-hot abrasive stream to produce both high accuracy micro-channels and tapered holes. HAJM also defines itself phenomenal competence over all advanced manufacturing techniques due to its growing demands for better surface reliability with defects (mostly stress, heat) free surfaces. Zirconia is widely accepted and associated in the non-conventional machining processes and industries with the years of track on record of proven performance in a vast number of brittle materials. Most perceptible act in this research is the selection of abrasive particle to achieve the appropriate intricate shaped holes on zirconia ceramic with hot silicon carbide (SiC) abrasives. Machining of these features are done with varying the abrasive temperature. Optical microscopic view was considered for the generation of machined holes during HAJMing. All the experimental data were presented to study the effect of machining constraints on target surface erosion rate and surface roughness using HAJMing. Single impact experiments were executed to measure the target surface erosion due to impact of individual hot silicon carbide abrasive particles. An experimental setup has been designed to conduct the machining trials using Box-Behnken design of experiments. It is also shown that the generated workpiece surface contour and erosion rate are the function of machining constraints which have a negligible influence on air-abrasive flow characteristics. This research work also deals with the sustainability assessment under environmental-friendly hot abrasive-assisted machining conditions.

G0300905 高温エロージョン摩耗における衝突角度依存性の有限要素法解析

Erosion is a phenomenon that damage the surface of material is removed by the particles impact. Erosive wear becomes a problem in pulverized coal injection system and rotating chute. In order to reach an aim of high safety and low cost, it's important to develop wear resistant material and to estimate of life service during erosion. According to research pertaining to erosion, three types of conditions are known to affect. Particle's condition is hardness and particle shape. Impact condition is angle and velocity. Target material's condition is mechanical properties and structure. This study investigated that impact angle dependently on erosive wear by Finite-element-method (FEM). LS-DYNA suitable for contact problems was used in this study. Analysis conditions are shown below of specimens. Impact velocity of the particles was 20m/s. The contact time of the collision is 0.01ms. The dimensions of the impact material are 10 x 10 x 10mm. Test specimen was SUS630 stainless steel. The erodent particle used in this study was a 1mm alumina ball. Impact angle was analyzed from lOdeg. to 90deg. The particle was assumed to be rigid. The elastic constants of SUS stainless steel were used to define the particle material. For verification of the analysis result, a single impact experiments were conducted. The Correlation was obtained in result of experiment and analysis. As a result of focused on equivalent plastic strain and Mises stress. It's possible to test the efficacy of FEM analysis of impact angle dependency for high temperature erosive wear.

Surface roughness and erosion rate of abrasive jet micro-machined channels: Experiments and analytical model

Abrasive jet micro-machining (AJM) uses a high velocity particle jet to erode features in target substrates for a variety of applications, including micro-electro-mechanical and micro-fluidic device fabrication. The roughness of micro-channels for micro-fluidic applications made using AJM can affect fluid flow phenomena such as separation efficiency, electro-osmotic mobility and solute dispersion. Moreover, surface roughness plays a major role in micro-scale adhesion contact in MEMS and light scattering in optoelectronics devices.This paper presents experimental data on the effect of particle size, velocity, and angle of attack on the roughness of unmasked channels machined in borosilicate glass using AJM. Single impact experiments were conducted to quantify the damage due to the individual alumina particles. Based on these observations, the assumed location of lateral crack initiation in a relatively simple analytical model from the literature was modified, and used to predict the roughness and erosion rate. The previous model, which calculated an areal roughness, was also modified to yield a 2D linear value of Ra so that it could be compared with linear profilometer scans. This modified model predicted the steady-state roughness and erosion rate of unmasked channels with average errors of 36% and 73%, respectively.

Ion-beam damage and non-radiative exciton decay in LiNbO 3

A model to account for the defects generated by ion irradiation in the electronic loss regime, and based on non-radiative decay of self-trapped excitons, is discussed and compared to experiments. It takes into account the competing role of the light-emission (radiative) and defect-creation (non-radiative) decay channels. Calculations are applied to LiNbO 3, a useful electro-optic crystal, where a large number of relevant experimental data are available. The model explains the strong nonlinear dependence of the defect creation rates as a function of electronic stopping power ( thresholding behavior). It also satisfactorily accounts for the formation and growth of amorphous layers by ion-beam irradiation at moderate fluences, φ>10 13 cm −2. Moreover, it also provides the right trend and reasonable quantitative accordance to data showing the dependence of the track radius on stopping power in single-impact experiments. Finally, the model determines the light emission yield during irradiation. In particular, it predicts that the number of photons emitted by ion impact first increases and then decreases monotonically with increasing electronic stopping power.

Erosion and Damage by Hard Spherical Particles on Glass

Solid particle impact of hard spherical particles on glass is of fundamental interest because of the presence of a number of different impact regimes. Understanding the impact of spherical particles is also a step toward modeling the behavior of rounded particles. This paper verifies theoretical models for the transitions between the different impact regimes and process parameters like erosion rate and surface roughness. The work also includes rounded particles. The transitions plotted in a so-called erosion map are validated with single-impact experiments. Data from erosion experiments are used to test the relations for the erosion rate and resulting surface roughness following from the models. Although the theoretical transitions compare reasonably with experiments, the models for erosion rate and surface roughness do not describe the experimentally found behavior. The models not incorporating the interaction between an impact and the damage remaining from earlier impacts might cause this deviation.

Production of Narrow Size Distributions in Classifier Mills

ABSTRACT In various technical processes particles with well-defined, narrow size distributions are required. These powders can be produced in impact mills with internal classifier. The top size and size distribution of particles are controlled by variation of impact speed, and by the circumferential velocity of the impeller wheel classifier. Possibilities for minimization of the amount of fines are discussed. However, the production of a certain amount of fines is unavoidable. The physical limit of produced fines depends on the material properties and the parameters governing the impact of particles. The amount of unavoidable fines can be evaluated by means of single impact experiments, in which the particles are stressed with well-defined impact speed and angle of impact.

An analysis of the localization of deformation and weight loss during single-particle normal impact

Localized lip formation and subsequent lip fracture is the dominant mechanism by which material is removed during the normal incidence of single spherical particles on ductile targets. A theoretical model which predicts the extent of lip formation as well as the weight loss during these single impact experiments is presented. The model postulates that the lip formation is the result of localization of deformation in the near-surface regions of the target and that the lip is removed either by inertial-stress-induced tensile fracture or by separation across adiabatic shear bands formed at the base of the lip. The single-impact data for copper, brass, thoria dispersed (TD) Nickel and nickel targets are shown to compare very well with the predictions of the model.