Ultrasonic pulsating water jet for non-thermal and selective removal of acrylic bone cement is studied. Variation of acoustic chamber length is used for tuning of the ultrasonic system into the ...resonance regime to gain maximum power transmission. The study investigates the minimal technological conditions such as nozzle traverse speed and supply water pressure required to generate disintegration grooves in bone cement mantle. It also proposes the safe standoff distance range, which is essential for its potential application during the extraction of bone cement without compromising host bone. Palacos R+G bone cement was used for the experiments. Generated groove depths were measured using MicroProf FRT and analyzed using SPIP software. Depth values showed an increasing trend with an increase in acoustic chamber length, decrease in traverse speed, and increase in supply pressure values. From the entire experimental domain, a maximum depth of 615 μm was obtained at 22-mm chamber length, 0.5-mm/s traverse speed, 10-MPa pressure, and a standoff distance of 4 mm. Brittle fractured surface features like material chipping, micro-pits, cracks, and sheared material layers were observed in the SEM images. Disintegrated debris, diameter 21–37 μm, conceived from pit diameters can be used to design a suction unit. Real-time control of the disintegration process using accelerometer sensors was shown. The results support the idea of using pulsating water jet for bone cement removal in a single blind hole. Minimal technological parameters reduce reaction force of the hand tool, allowing bone cement removal without bone fracture or perforation.
Maraging steel is one of the exotic materials showing the potential for application in the field of the aerospace industry. However, machining these materials with high surface quality and material ...removal rate is problematic. The micro-electro chemical discharge (MECDM) process is capable of resolving this problem to some extent, however, due to the spark action, it fails to attain a high surface finish. In the current investigation, micro-hole drilling is performed on maraging steel with powder-mixed alumina (1% wt. of Al2O3) using the micro-electro chemical discharge machining (PMECDM) process. The effect of different input process factors, for example, voltage (V), duty cycle (D), the electrolyte concentration (C), are considered for investigating the machining performance, i.e., rate of material removal (MRR) and roughness of surface (SR) of the machined substrate. Further, a comparative analysis is established between micro-ECDM (MECDM) and mixed powder ECDM (PMECDM). The Box–Behnken design is used to conduct all the experiments and analysis of variance (ANOVA) is used to optimize the results. The outcomes reveal that MRR in PMECDM is enhanced by 34%, and the average surface roughness is reduced by 21% over the MECDM process. The maximum MRR was observed to be 2.44 mg/min and the hole machined by the PMECDM results in a cleaner hole wall surface than the MECDM process due to the grinding action by the powder particles. The residual stress measurement indicates that the PMECDM (−128.3 ± 3.85 MPa) has the lowest equivalent stress as compared to the parent material (−341.04 ± 10.24 MPa) and MECDM (−200.7 ± 6.02 MPa) surfaces. The applied voltage is the most significant parameter, followed by the duty factor and electrolyte concentration for enhancing the MRR and surface finish. The addition of powder improves the surface integrity of the machined surface as compared to the surfaces produced by the MECDM processes.
The water hammer effect is the basis of technologies which is artificially responsible for the decay of continuous jets. A recently developed technique enhances the pressure fluctuations using an ...acoustic chamber, leading to enhanced erosion effects for various water volume flow rates. The optimum standoff distance for an ultrasonic enhanced water jet is not appropriately estimated using an inclined trajectory. The objective of this study is to comprehend the true nature of the interaction of the standoff distance following the stair trajectory and traverse speed of the nozzle on the erosion depth. Additionally, it also critically compares the new method (staircase trajectory) that obeys the variation in frequency of the impingements for defined volume flow rates with the inclined trajectory. In this study, at constant pressure (
= 70 MPa), the role of impingement distribution with the variation of traverse speed (
= 5-35 mm/s) along the centerline of the footprint was investigated. The maximum erosion depth corresponding to each traverse speed is observed at approximately same standoff distance (65 ± 5 mm) and decreases with the increment in traverse speed (
= 1042 and 47 µm at
= 5 and 35 mm/s, respectively). The results are attributed to the variation in the number of impingements per unit length. The surface and morphology analysis of the cross-section using SEM manifested the presence of erosion characteristics (micro-cracks, cavities, voids, and upheaved surface). By varying the water cluster, different impingement densities can be achieved that are suitable for technological operations such as surface peening, material disintegration, or surface roughening.
•Effect of ultrasonic pulsed water jet peening on AISI 304 welded joints was investigated.•Significant improvement in surface residual stresses was observed after the peening process.•Improvement in ...surface and sub-surface hardness was also recorded.•Results shows the process as potential method for the surface treatment application.
The residual stress and subsurface hardness of welded joints treated by peening using an ultrasonic pulsed water jet at pressures of 20–60 MPa with various traverse speeds and standoff distances were measured. The effect of the treatment was quantified by measuring the residual stress using X-ray diffraction in three regions (the welded zone, heat-affected zone, and base metal). To analyse the depth of the plastic deformation induced by the pulsating water jet, microstructural analyses and micro-hardness measurements were conducted. The surface topography of the treated samples was examined by measuring the surface roughness using a contact surface roughness profilometer. After pulsating water jet treatment, the samples showed both increased residual stress and surface roughness at pressures of 20–60 MPa. Increased subsurface hardness of the treated region was observed up to a depth of 200–250 µm at pressures of 40 and 60 MPa, deeper than that of the sample prepared at 20 MPa. The microstructural analysis identified the involved plastic deformation phenomenon occurred during the treatment process. This method of surface treatment, where the efficiency of the jet is enhanced by the generation of pulses using an acoustic generator, showed promising results for its practical application as a post-weld treatment method.
The local residual stresses (tensile) generated on the surface of a component during its manufacturing (machining, welding) cause deterioration of its service life. To eliminate the negative effect ...of the stresses, the surface is treated using different methods (shot peening, laser shock peening, heat treatment, water jet peening). The application of ultrasonic technology to modify the continuous jet has been intensively researched for treating advanced stages of erosion. In this work, the modifications in the mechanical properties (tensile strength, micro-hardness and residual stress measurements) of AISI 304 Tungsten inert gas welded joints were investigated after ultrasonic pulsating water jet treatment in the incubation stage of erosion. This revealed that the initial tensile residual stress in the welded joints was converted to compressive stress after the treatment. The micro-hardness of the joints after the treatment increased about 40% in the heat affected zone in the near-surface region. Also, the tensile properties increased by about 37.8% and 34.6% in yield strength and ultimate strength, respectively. The microstructural examination of the near-surface region showed the grain reformation mechanism.
Wire electrical discharge machining (WEDM) process provides a cost effective solution to generate complicated shapes in various exotic materials, irrespective of their hardness. However, WEDM process ...removes the material by thermal erosion mechanism which in term affects the topography and mechanical characteristics of the material. In view of this, an effort is needed to eliminate the adverse effect of WEDM process on the final product surface. Therefore, the present work evaluates surface morphology, surface roughness, elemental composition, micro-hardness and residual stress of the machined surface produced by various WEDM strategies such as, rough cut and finish cut. Two post-processing techniques namely, grinding and etching-grinding are proposed to remove recast layer and also to improve the surface integrity of the machined surface. The proposed strategy found to be an efficient post-processing technique for complete removal of recast layer and generation of surface with an average surface roughness as low as 0.024 μm, high compressive residual stress as high as 500 MPa and basic elemental composition. The basic mechanism of these process are also explained in details.
The paper deals with interlaminar fracture toughness testing of three different types of specimens from unidirectional aerospace laminate M21/T800S (autoclaved and hot pressed) and the woven fabric ...ECG Carbon 12k with respect to the ASTM Standard D5582. Simultaneously the materials were monitored by acoustic emission to evaluate the results via burst analysis. CFRP-specimens were mounted in a CNC-machining center by a chopper wire. The lower wire was fixed at a load cell (KISTLER 9257 B) to measure the force development. Standard specification the movement speed in z-direction was set to 5 mm/min. The acoustic emission sensor iMPact XS with accuracy is ±5% with a reference sensitivity of >1200 pC/N was fixed on the DCB-specimens with a two-sided adhesive tape with thickness of 0,5 mm. The sensor iMPact XS has a frequency range from 1 mHz up to 1 MHz limited to a maximum of 500 kHz. It has been found that the material properties correlate well with the results of the acoustic emission analysis. The burst rate reflects the manufacturing processes as it is influenced directly by the fibre bridging which occurs particularly for autoclaved composites. In contrast, the burst energy is not affected by the manufacturing process. It is only depending from the matrix properties.
This article deals with the effect of periodically acting liquid droplets on the polished surfaces of AISI 316L stainless steel and Ti6Al4V titanium alloy. These materials were exposed to a pulsating ...water jet produced using an ultrasonic sonotrode with an oscillation frequency of 21 kHz placed in a pressure chamber. The only variable in the experiments was the time for which the materials were exposed to water droplets, i.e., the number of impingements; the other parameters were kept constant. We chose a low number of impingements to study the incubation stages of the deformation caused by the pulsating water jet. The surfaces of the specimens were studied using (1) confocal microscopy for characterizing the surface profile induced by the water jet, (2) scanning electron microscopy for detailed surface observation, and (3) transmission electron microscopy for detecting the changes in the near-surface microstructure. The surface described by the height of the primary profile of the surface increased with the number of impingements, and was substantially more intense in the austenitic steel than in the Ti alloy. Irregular surface depressions, slip lines, and short cracks were observed in the Ti alloy, whereas pronounced straight slip bands formed in the austenitic steel. The dislocation density near the surface was measured quantitatively, reaching high values of the order of 1014 m−2 in the austenitic steel and even higher values (up to 3 × 1015 m−2) in the Ti alloy. The origins of the mentioned surface features differed in the two materials: an intense dislocation slip on parallel slip planes for the Ti alloy and mechanical twinning combined with dislocation slip for the austenitic steel.
Peening techniques are nowadays attracting more research attention due to their association with the extending of the service life and improving surface texture of engineering components. Ultrasonic ...pulsating water jet peening represents a new way of mechanical surface treatment. Accelerated water droplets via hammer effect cause small elastic-plastic deformations on the surface. This work deals with peening of aluminum alloy using an ultrasonic pulsating water jet, where periodically acting water droplets were used as the peening medium. The aim of the work was the feasibility study of the peening process and to observe the effects of pressure (p = 10, 20 and 30 MPa) and pattern trajectory (linear hatch and cross hatch). The peened surfaces were analyzed by the surface roughness profile parameters Ra and Rz and the microhardness along the peening axis into the material. Graphically processed results show a clear increase of measured values with increasing pressure (p = 10, 20 and 30 MPa), where the roughness values ranged from 1.89 µm to 4.11 µm, and the microhardness values ranged from 43.3 HV0.005 to 47 HV0.005, as compared to 40.3 HV0.005 obtained for the untreated sample. The achieved results indicate potential using of an ultrasonic pulsating water jet as a new method of surface treatment of metals. By controlled distribution of water droplets, it is possible to achieve a local distribution of surface roughness, and at the same time, strengthening of the subsurface layers in the material without thermal influence on the material.
Non-thermally affected surfaces created by abrasive water jet, among many other advantages, are manufactured with geometric inaccuracies. These geometric inaccuracies are mainly related to waviness, ...especially in the lower parts of thick engineering components. Therefore, the study establishes a link between the surface quality and abrasive water jet material disintegration parameters related to striation mark displacement. The materials used for the experiments (aluminum, steel, and polyethylene plastic) are selected to cover a wide range of hardness values. These materials are often machined, which enables to draw practical reference values from the results obtained. Experiments are used for determination of the surface quality to assign a range of surface roughness profile parameters
R
z
and
R
a
, as soon as no clear striation marks are recordable on the surface for particular materials with specific mechanical properties.
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