Journal of Powder Metallurgy & Mining
Open Access

The inter-particle coefficient of friction as well as the normal and tangential force-displacement relationships at the contacts of soil grains are crucial input factors in DEM research. Even though there has been significant progress in the creation of contact models for unbonded and bonded grainsDEM researchers occasionally have to rely on assumptions for the input properties used in the numerical analysis. This is largely due to the lack of experimental data available that examines the behaviour of grains in contact with real soils (grain contact behaviour).According to Iverson.Due to the lack of reliable equations or parameter values, multiple numerical models may produce output that differs significantly. The significance of collecting grain contact parameters in the laboratory can advance the state-ofthe- art in the micromechanical-based analysis of complicated granular materials, according to Cheung's numerical investigation on the behaviour of sandstone reservoirs. In order to advance the state-of-theart in geomechanics and provide a platform for more realistic models to be developed for use as input in DEM studies, it is consequently emphasised that additional insights into the grain contact behaviour of real soils must be achieved in the laboratory.

For the purpose of simulating the force-displacement connection in the normal and tangential directions of the contacted grains, respectively, DEM analyses frequently use the Hertz and Mindlin and Deresiewicz models (after Researchers have demonstrated that the Hertz model can be used satisfactorily to fit the experimental normal force - displacement data in order to obtain useful information on the Young's modulus of the contacted surfaces. This is based on experiments on real soil grains and reference materials (such as chrome steel balls and glass beads However, it has been observed that this model has a flaw in that it is unable to reflect the soft behavior's initial regime that is attained for the majority of the timeresources .Different elastic-plastic models exist in the tangential direction.that primarily concentrate on the stick condition and are typically derived on the basis of a constrained range of material types. Olsson and Larsson's recent work for elastic-plastic materials accounted for slip behaviour by taking into consideration various plastic responses and variable hardness. It may be because there is a dearth of sophisticated experimental data for actual geological materials that many earlier studies or produced models are often restricted to manufactured materials. This is especially true for actual soil-grain interactions that adhere to configuration of the spheresphere (or grain-grain) kind According to investigations by Nardelli and Sandeep the Mindlin and Deresiewicz models did a poor job of fitting experimental tangential force - displacement data on Eglin sand and totally disintegrated volcanic granules, respectively, for genuine geological materials. These earlier investigations have emphasised the necessity of taking theoretical model alterations into account in order to better fit the force-displacement connection of soil grain interactions. This study focused on the slip (or microslip) displacement that resulted from laboratory testing in order to scientifically explore the link between inter-particle tangential force and displacement of various geological and reference grains. Modeling and describing energy dissipation, fretting, and damping both heavily rely on the calculation of the slip displacement of contacted surfacesThis slide behaviour is connected to the friction, surface morphology, elastic properties, and hardness of the investigated materials, among other parameters.

Subjective Heading

In the current work, the micromechanical behaviour of three naturally occurring geological materials—Leighton Buzzard sand grains (LBS), crushed limestone (LS), and totally decomposed granite (CDG)—as well as chrome steel balls (CSB) was examined. With an emphasis on the inter-particle coefficient of friction at a steady-state sliding and its relationship with the surface roughness and the Young's modulus of the contacted surfaces, these materials were looked at by Sandeep and Senetakis. The aim of the current work is the examination of the force-displacement connection of the various materials experimentally, focusing on how the choice of material affected the slip displacement that actually happened.

Summarises the fundamental characteristics of the materials whose attributes were investigated for the current investigation. Quartz makes up the LBS grains, which are rounded, spherical, and have a low degree of roughness. The LS grains are uneven in shape and made of crushed non-clastic rock. A weathered rock from Hong Kong called CDG is used extensively in the research of landslides as well as geotechnical and infrastructure engineering in tropical and sub-tropical areas. It is made up of very abrasive grains that are unevenly formed, and some of the original minerals, primarily feldspar and mica, have undergone chemical changes.

Discussion

According to the research, surface roughness has a substantial impact on how geological and manufactured material interfaces behave.The materials' roughness was assessed for the study at the City University of Hong Kong using the Veeco NT9300 optical surface profiler in order to qualitatively incorporate this parameter in the analysis of the micromechanical test findings. Because it can scan wide regions of heterogeneous materials, the vertical scanning interferometry (VSI) mode was chosen to measure the surface roughness. With a high resolution of 0.1 nm, this VSI mode in the current optical surface profiler enables non-destructive examination of the surface roughness. Sandeep and Senetakisdescription of how to quantify roughness for the in keeping with earlier studies a field of view of 20x20m was selected, and the influence of the curvature was eliminated. The root mean square (RMS) roughness is used to represent surface roughness.

The materials' micro-hardness and the force-displacement connection as well as the frictional behaviour of the grains at their contacts were both quantified using two main experimental approaches in this work. Three of the examined materials (CSB, LBS, and LS) had their micro-hardness evaluated using the Fischer-scope HM2000 micro-hardness tester. The indenter is a typical Vickers diamond pyramid with facets that are at an angle of 136 degrees. With a maximum indentation depth (h) of 150 m, the indenter can exert a maximum normal force (FN) of 2 N.

The City University of Hong Kong's specially constructed interparticle loading equipment, as described by Senetakis and Coop [61] and Nardelli [47], was employed for the normal and tangential forcedisplacement studies. Fig. 3 provides a visual representation of the existing inter-particle loading apparatus, showing all of its component pieces. Three loading arms and a stainless steel frame make up the device. A linear micro-stepping motor, a high-resolution load cell with a capacity of 100 N and an accuracy of 0.02 N, and an eddy-current displacement sensor with a resolution of 10-5 mm are all included in each arm. Three chrome steel balls and an extremely durable bearing system support the stainless steel sledpolished stainless-steel plate, which reduces friction as it moves over the horizontal plane. With the help of numerous mechanical connections and linear micro-bearing systems, the horizontal arms are attached to the sled. The stainless steel sled's vertical loading arm (upper particle) and brass wells with hollow cross sections are where the particles are mounted on brass mounts with cylindrical cross sections of 8 mm in diameter and 17 mm in height (lower particle). Laterally positioned screws are used to secure the mounts in the wells. Two digital micro-cameras positioned in two orthogonal horizontal directions, along with the observation of the response from the two horizontal load cells during the bringing the grains into contact, are used to determine the apex-to-apex location of the grains. A Perspex chamber that houses the entire apparatus aids in preserving humidity levels during the testing.

Conclusion

The micromechanical behaviour of various materials was examined in terms of normal/tangential contact behaviour and inter-particle friction, with a focus on the slip displacement and its relationship with material properties. The materials studied included reference chrome steel balls (CSB) as well as three natural-geological materials. To assess the Martens hardness of the geological and reference materials, microhardness experiments were also carried out. When the grains were characterised, it became clear that the fully disintegrated granite (CDG) particles had the highest values of roughness as The micromechanical behaviour of various materials was examined in terms of normal/ tangential contact behaviour and inter-particle friction, with a focus on the slip displacement and its relationship with material properties. The materials studied included reference chrome steel balls (CSB) as well as three natural-geological materials. To assess the Martens hardness of the geological and reference materials, micro-hardness experiments were also carried out. When the grains were characterised, it became clear that the fully disintegrated granite (CDG) particles had the highest values of roughness as

Acknowledgement

I would like to thank my Professor for his support and encouragement.

Conflict of Interest

The authors declare that they are no conflict of interest.

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