•The efficiency enhancement method of abrasive water jet slit-assisted shield cutter cutting reinforced concrete was investigated.•Revealed the efficiency enhancement mechanism of abrasive water jet ...slit-assisted shield cutters.•The main influencing factors affecting the effectiveness of abrasive water jet slit-assisted shield cutters were discussed.
To improve the efficiency and safety of shield machines cutting reinforced concrete (RC) obstacles, using an abrasive waterjet (AWJ)-assisted shield cutter to cut RC is considered a feasible solution. To explore the effect of an AWJ on a shell cutter cutting RC, laboratory experiments and numerical simulation methods were used to compare the breaking performance and damage mechanism of a shell cutter cutting RC with and without a slit. The results showed that the waterjet pre-cutting slit could effectively reduce the cutter force of the shell cutter and promote the cutting of steel bars. The reduction rate of the cutter force by the waterjet slit increased and then decreased with an increase in the penetration degree. When the penetration degree was 1.5 mm, the waterjet cutting slit had the best reduction effect on the cutting force. An optimal critical value was found for the waterjet cutting slit of the steel bar; when the waterjet slit was larger than ½ of the diameter of the steel bar, the steel bar was prone to tensile fracture under the cutting action. The waterjet pre-cutting slit reduced the residual cross-sectional area and stress distribution of the steel bar, which promoted the bending and tensile fracture of the steel bar and thus improved the cutting efficiency. Furthermore, construction recommendations for the AWJ-assisted shield cutting of RC obstacles were identified. The findings presented in this paper can provide useful reference information for the design and construction of AWJ shield machines.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Machinability of stacked Titanium (Ti6Al4V) and CFRP was evaluated using Abrasive Water Jet (AWJ) machining process. The experimental study was conducted using three pressure levels – 200, 275 and ...350 MPa. Traverse speed was varied between 1 and 10 mm/s for two stacking configurations (Ti/CFRP, and CFRP/Ti). The erosion characteristics, kerf width and surface roughness was studied as a function of process parameters. Surface roughness and kerf width variation was high at low jet power conditions, as described by lumped parameters (E˙/u and E˙/hu). The minimum average roughness Ra for Ti and CFRP was less than 3.5 μm and 4.5 μm respectively for both the stacking sequence. The kerf width increased significantly, especially when Ti6Al4V is at top in which case low-energy, turbulent jet diverges at the exit from Ti6Al4V. Mathematical regression models were developed to predict kerf width. An energy based, semi-analytical model was proposed to predict the kerf geometry with R2=92.26%.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
An abrasive water jet (AWJ) is commonly used to develop deep geothermal resources, such as drilling in hot dry rock (HDR). The influence of rock mineral properties, such as mineral types, mineral ...contents, and grain size, on the formation of perforation by AWJ is unclear yet. In this study, we investigate AWJ impacts on three types of granite samples with different mineral fractions using a polarizing microscope and scanning electron microscope (SEM). The results show that when the grain size is doubled, the perforation depth increases by 16.22% under the same type of structure and properties. In general, fractures are more likely to be created at the position of rough surfaces caused by abrasive impact, and the form of fractures is determined by the mineral type. In addition, microstructure analysis shows that transgranular fractures typically pass through large feldspar particles and quartz removal occurs along mineral boundaries. The longitudinal extension of perforation depends mainly on the strong kinetic energy of the jet, while the lateral extension is controlled by the backflow. The results contribute to a better understanding of the process involved in the breaking of hard rock by abrasive jets during deep geothermal drilling.
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•A doubling of grain size results in a 16.22% increase in perforation depth.•Fractures are more likely to be created at the position of rough surfaces.•The form of fractures is determined by the mineral type.•Clarifies the mechanism of perforation lateral and vertical expansion.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Validated CFD model was used to determine the temperatures of the water jet•The water jet cools down when passing the water nozzle•Main heating occurs in the region adjacent to the jet occupied by ...the carrier gas•Ice particles with d ≥ 0.5 mm should be used if water jet is not cooled•Ice particles with d ≥ 0.3 mm can be used if water jet is cooled
Ice abrasive water jet (IAWJ) technology uses ice particles instead of the mineral abrasives used in abrasive water jet (AWJ) technology. Since the thermal conditions are extremely important for the survival of the ice particles and their mechanical properties, the temperatures of the water jet and the adjacent air are analysed for different pressures and temperatures of the water upstream of the water nozzle and different nozzle orifice diameters. The temperature fields are calculated with a fully validated Computational Fluid Dynamic (CFD) model. The results show that the temperature of the jet core does not change significantly, but the adjacent air heats up considerably due to viscous heating; both are influenced by the water temperature and pressure upstream of the water nozzle. A low water temperature upstream of the water nozzle could significantly reduce the expected temperature of the ice particles exiting the cutting head. However, the use of a cold carrier gas such as nitrogen with a temperature of -196°C should not have a significant effect on the temperature of the ice particles inside the cutting head. It is recommended to optimise the geometry of the cutting head to reduce the travel time of the ice inside. If water cooling is not used, the ice particles should have a diameter of more than 0.5 mm. However, if cooling is used, particles as small as 0.3 mm in diameter can be used. The observed temperature conditions play a key role in the further development of IAWJ technology.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Abrasive Water-Jet Cutting (AWJC) is an unique technique and has found wide applications in the glass cutting industry due to high performance and cost-effective properties. There are several ...interconnected parameters of great importance in this method. In this experimental study, the selected AWJC parameters are working distances (3, 4 and 5 mm) and feed rates (1000, 1250 and 1500 mm/min) at constant water pressure (140 bar), abrasive grain size (120 mesh) and nozzle diameter (0,76 mm). This study will be concerned with investigating the effects of these parameters on the surface quality of flat glasses. AWJC can improve the surface quality of flat glass, if the cutting parameters are chosen appropriately. It was observed that; the optimum working distance and feed rate parameters should be selected as 3 mm and 1250 mm/min respectively, if minimum grit defect is required. Additionally, 4 mm of working distance and 1000 mm/min of feed rate cutting parameters would generate minimum burr defect.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Improve the performance of TBM in hard rock and extremely hard rock environments.•The method of rock breaking with pre-grooving assisted disc cutter is studied.•As the pre-groove depth increases, ...the cutting performance of the cutter increases.
To improve the tunnelling performance of tunnel boring machines in hard rock and extremely hard rock environments, abrasive water jet assisted rock breaking is a possible solution that has currently attracted considerable attention. In this approach, the depth of the pre-cut groove is a key factor affecting the performance of assisted rock breaking. To study the influence of the pre-groove depth on assisted rock breaking performance, a full-scale linear cutting test of pre-grooved rock was conducted with a disc cutter. The influence of the pre-groove depth on the rock breaking effect under the same-trajectory mode (SM) and different-trajectory mode (DM) of assisted cutting was explored, and the mechanism of assisted rock breaking with different groove depths was revealed. Compared with the complete cutting mode (CM), the results showed that the normal force (FN), rolling force (FR), side force (Fs), and specific energy (SE) under SM decrease as the groove depth increase. Under DM, the FN, FR, and SE decrease as the average groove depth on both sides increase, and the Fs decreases as the minimum groove depth increases. In SM and DM, the cutting SE first decreased rapidly and then tended to decrease slowly as the groove depth increased, indicating the existence of an optimal groove depth. The rock fracture patterns under SM and DM are more prone to tensile failure, which significantly reduces the rock cutting force and SE of the disc cutter. These results can provide inspiration for the design and construction of new types of tunnel boring machines that are assisted by abrasive water jet pre-grooving.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The paper presents possibility of Whale Optimization Algorithm application into abrasive waterjet (AWJ) machining of tool steel. Based on the control parameters of the process of cutting tool steel ...with AWJ, the objective function was determined using the Response Surface Methodology (RSM). Then the process of optimization and established the set of control parameters which the value of the objective function reaches the extremum value was carried out. Also, the effectiveness of this algorithm for optimizing the parameters of the studied process was determined. The calculated on the basis WOA value of optimum was comparison with value of the best effect determined experimentally.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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