Hydro-abrasive Erosion Research Articles

Wear of rocks by water flow

The paper summarises recent results obtained from wear and erosion tests performed on rocks and cementitious composites. A definition of relevant wear types is given. Experimental facilities, failure modes, threshold conditions, parameter influence, and resistance parameters are discussed for jet fluid erosion, hydro-abrasive erosion, drop impact erosion, and cavitation erosion. No single failure mode determines the response of the materials to any of the investigated wear types. The individual failure mode depends on certain process parameters, on material structure, and in some cases on the testing facilities. Threshold conditions for failure introduction are discussed. All wear types are characterised by selective material removal. It seems that non-linear fracture effects (such as tension-softening) play a notable role in certain impact situations.

Hydro-abrasive erosion of refractory ceramics

The paper discusses the material removal process in refractory ceramics eroded by hydro-abrasive jets. In particular, bauxite, sintered magnesia, and magnesia chromite are eroded. The influence of abrasive particle velocity, local exposure time, abrasive mass-flow rate, and abrasive type is investigated. Erosion depth, specific erosion rate, and geometry of the generated cavities are measured and analysed. For particle velocity as well as for local exposure time, threshold conditions are identified. At low erosion intensity, target material properties and abrasive type do not affect the material removal process notably. From optical and SEM-microscopy it is further found that the material removal mode changes with the progression of the erosion process. In the upper region of the eroded kerf, the dominating material removal mode is the simultaneous cutting of matrix and inclusion grains (transgranular). In the lower range, the erosion process is characterised by the removal of the binding matrix followed by washing off the inclusion grains (intergranular). The balance between both modes depends on the energy delivered to the erosion site. These observations are explained by assuming a continuous loss in kinetic energy of the abrasive particles during HAE. Some features of non-linear fracture are noticed and suggestions are made how to use non-linear fracture parameters to evaluate erosion resistance.

Fracture range detection in hydro-abrasive erosion of concrete

The paper discusses fast Fourier transform (FFT) parameters of acoustic emission signals acquired during the hydro-abrasive erosion (HAE) of five different concrete mixtures. The FFT-peak amplitude as well as the FFT-peak frequency shows some pronounced relationships to the depth of penetration and to the fracture behavior of the investigated materials. Correlation statistics is used to separate three distinguished fracture ranges during HAE: intergranular erosion, mixed-mode fracture, and transgranular fracture. It is concluded that FFT-peak amplitude and FFT-peak frequency of the acoustic emission signals can be used for the on-line control of HAE-processes.

Hydro-abrasive erosion of steel-fibre reinforced hydraulic concrete

In this paper, hydro-abrasive erosion tests on plain concrete (PC) and on steel-fibre reinforced concrete (FRC) are performed, and the erosion behaviour of the materials for different erosion conditions is investigated. Effects of suspension velocity, impact angle and solid content have been studied in detail. Two major erosion modes are identified. When the impact angle is shallow (15°), the damage is caused mainly by cutting the cement matrix and exposing the aggregates. However, at orthogonal impact, the formation and development of fatigue cracks in the concrete is the main cause of erosion. The addition of steel fibres provides a reinforcement to improve the erosion resistance of hydraulic concrete at shallow impact angles (15°) only. For low suspension velocities (ca. 60 m/s), fibre reinforcement and solid abrasive content do not influence the erosion rate favourably. For higher suspension velocities, abrasive content becomes important.

On-line analysis of hydro-abrasive erosion of pre-cracked materials by acoustic emission

Acoustic Emission (AE) sensing technique is used as a tool for on-line monitoring of hydro-abrasive erosion (HAE) of pre-cracked multiphase materials. As reference materials, five types of concrete materials were used for the experimental study. Compression tests were performed to determine the mechanical properties and the failure behavior of these materials. Erosion parameters, such as abrasive particle velocity, local exposure time, and abrasive mass flow rate were varied during the experiments and AE-signals were acquired. The trends exhibited by the time domain and frequency domain AE-signals with change in process parameters and material properties were analyzed. The results indicate that acoustic emission signal is capable of revealing the different material removal mechanisms occurring in pre-cracked multiphase materials when subjected to hydro-abrasive erosion. Visualization studies performed on the erosion site provide more insight into the physics of the process and verify the observations made from the AE-signals. Finally, it is concluded that due to its capability to quantify the amount of material removed, AE RMS could be considered as a parameter for monitoring the material removal process.

Hydro-abrasive erosion characteristics of 30vol.%SiCp/6061-T6 Al composite at shallow impact angles

Hydro-abrasive erosion characteristics were investigated for 30vol.%SiCp/6061-T6 Al composite material and 6061-T6 aluminium alloy at steady-state conditions using abrasive waterjets. The erosion rates were measured for shallow impact angles (< 20°) and the influence of the abrasive size, flow rate and the impact angle on the erosion process was studied. Scanning electron microscopy (SEM) was used to characterize the eroded surface and the results showed that erosion in the composite occurred due to microcutting of the aluminium matrix material, with the SiC particulates being removed subsequently by the shovelling action of the oncoming jet. The experiments also revealed that the erosive wear rates for the 30vol.%SiCp/6061-T6 Al composite were less than the erosive wear rates of the 6061-T6 aluminium alloy by a factor of two.