Search

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This article deals with the manifestations of erosion of statically acting concentrated multiple droplet impingements on materials over different lengths of time in order to assess the erosion evolution when the materials are submerged, as compared with the action of droplets on the materials under atmospheric conditions. The study aims to determine the extent of the erosive effects of droplets in underwater conditions. Experiments were conducted in a plastic pool in which the water level was varied from h = 80 to h = 120 mm to identify the effect of hydrostatic pressure at p 120 = 0.1025 MPa and p 80 = 0.1021 MPa. The results were compared with that of a control group of samples obtained under atmospheric air conditions. To observe the erosive damage evolution, 15 (n = 5) sites on the ductile materials EN AW-Al 99.5 and CW004A were exposed to high-intensity droplet impingement at defined exposure times. The exposure time varied from 0.125 s to 1.875 s, with increments of 0.125 s. As a droplet generator, an ultrasonic pulsating water jet with a frequency f = 20 kHz, a pressure p = 30 MPa and a nozzle diameter d = 0.4 mm was used to achieve the theoretical subsonic speed of the droplets. The results exceeded the assumptions regarding the possible attenuation of water pulses. It was found that under the theoretical speed of the jet v w = 225 m/s, the submerged condition causes attenuation in its erosive action. The incident area in the case of submerged treatment was more symmetrical. The erosion shift in term of prolonging incubation erosion stage was found to be a result of the increasing hydrostatic pressure. The results suggest that this method can also be used under submerged conditions for treatment or material drilling. • A low-pressure pulsating water jet under submerged conditions causes erosion. • Hydrostatic pressure influences the erosion shift. • The incident area is symmetrical under submerged conditions. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

• Pulsating water jet (PWJ) induces local deformation on AISI 304 surface. • PWJ at 20 kHz induces stresses ranging between 287 MPa – 540 MPa. • Inhomogeneous plastic deformation is responsible for enhancing the surface integrity. Enhancement of the life of the engineering components is essential from the perspective of its performance, therefore, it is necessary to eliminate the negative effects that attenuates the life of these components. Numerous surface treatment methods are used at present out of which water jet peening process have been stated to overcome the shortcoming reported in other surface treatment methods like surface defects caused by the embedment of particles during shot peening, thermal effects caused by laser shock peening. It has been reported in studies that the technological modification of water jet technology, ultrasonically generated pulsed water jet (PWJ) can be used for the peening application but still the detailed study of parametric variations for the peening process is not clearly explained. The present work aims at reporting the effect of variation of parameters: jet pressure (40 MPa to 100 MPa), traverse speed of the nozzle (5 mm/s to 25 mm/s) and standoff distance (15 mm to 31 mm) during the ultrasonically generated PWJ peening process. The peened surface was quantified in terms of surface residual stress measurements, micro hardness and surface roughness measurements. The results indicate that the variations in the parameters shows significant changes in the surface residual stress enhancement and strengthening process. The lower pressure (40 MPa), lower traverse speed (5 mm/s) and higher standoff distance (31 mm) showed the maximum improvement in the surface residual stress (up to 540 MPa) and micro-hardness (up to 570 HV). The impact of the repeated pulses causes plastic deformation on the surface and sub-surface layers which results into the change in the microstructures of the affected area. The microstructural examination through field emission scanning electron microscopy showed variations in these deformations under different parametric conditions. This study can give better understanding for the proper selection of the peening parameters for practical applications using ultrasonically generated pulsed water jet technology. [ABSTRACT FROM AUTHOR]

This study addresses the erosion transition of an aluminium surface arising from the periodic impact of a tangentially acting pulsating water jet (PWJ) with a spatial frequency of f = 20 kHz. The erosion effect was observed as a function of the standoff distance z (mm) along an incline (from 5 mm to 90 mm) and constant trajectory (at standoff distances of z = 25 mm, 75 mm and 125 mm) at a jet pressure of 100 MPa and traverse speed v = 10 mm/s. The aim of this study is to assess the manner in which the erosion along the PWJ pathway changes the measured dynamic signal (by means of acoustic emission measurements). The effects of hydrodynamic erosion, such as elastic and plastic deformation, were observed with the aid of a scanning electron microscope and compared with time records in terms of acoustic emission (AE) recorded during impact. Moving the PWJ head and gradually changing the standoff distance along the inclined trajectory resulted in different erosion regimes. With a gradual increase in the standoff distance (from 5 mm–90 mm), the observed erosion regimes were observed in terms of micro-pitting action, crack and crater formation and material folding/upheaving. The erosion effects of a PWJ compared with those of a continuous water jet were investigated at constant standoff distances of z = 25 mm, z = 75 mm and z = 125 mm. The differences in the erosion phenomenon under different conditions were observed in terms of the material damage, crater dimensions and surface and sub-surface features. The AE recorded during the impact of the PWJ demonstrates a correlation between the ongoing erosion phenomenon and the AE signals. This relation for the encoded complex waveform (PWJ) confirms the significant information about the ongoing process in terms of material deformation and dislocation movement. • Standoff distance generates different erosion regions. • Isolated sub-surface voids were observed. • The time records clearly exhibit an increase in amplitudes whenever material disintegration-separation-tearing occurs (load above the strength limit). • The correlation between the depth profile and AW reveals the effective interaction between the dynamic signal. [ABSTRACT FROM AUTHOR]

• New device for hydroabrasive disintegration of rotating workpieces was tested. • This study uses acoustic emission for on-line control in the form of an adaptive connection. • Increasing in traverse speed, the signal intensities decrease due to shorter interaction time. • Focuses on the acquisition of theoretical knowledge about the technology with the aid of SEM surface analysis. The paper deals with the potential of employing accompanying physical phenomena, acoustic emissions, during monitoring of abrasive water jet disintegration of rotating workpiece. It focuses on the acquisition of theoretical knowledge about this technology with the aid of SEM surface analysis. Variation in traverse speed of the cutting head is used during the experiments. All values were obtained during experimental materials turning by AWJ method. The surfaces were scanned using optical profilometer MicroProf FRT to obtain surface roughness parameters such as Ra (10.75 µm–22.5 µm), Rq (13.75 µm–28.25 µm) and Rz (88 µm–166 µm). The result includes the possibility of on-line control in the form of an adaptive connection, which applies information gathered by an array of sensors and its transformation into a digital form. The acquired signals represent that with increase in traverse speed, the signal intensities decrease due to shorter interaction time. SEM images provide characteristics of surfaces created by HADRO process such as craters, peaks and valleys, micro-cracks and striations marks. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The erosion of 25CrMo4 (EA4T) steel was studied to determine the surface and subsurface damage due to the high-frequency impingement of water droplets using an ultrasonic droplet generator. The material under investigation is railway axle steel, where the pulsating water jet can be used as a surface treatment method to increase the fatigue resistance. The surface processing is related mainly to standoff-distance which was changed to explore the effect of pulsating water jet while the other parameters were kept constant. Surface and subsurface conditions of the material were analyzed by means of light microscopy, scanning electron microscopy and transmission electron microscopy. By altering the standoff distance, it is possible to investigate droplet impingement from the point of view of the pulsating water jet process for different purposes, such as for maximal erosion or for an increase of fatigue resistance by introduction of severe plastic deformation to the surface. The maximum erosion state was reached for a standoff distance of 35 mm when a crater depth of 750 μm and a width of 1500 μm was observed. The mild conditions, when only plastic deformation is reached occurred at a standoff distance of 21 mm. The occurrence of subsurface cavities in materials with higher hardness indicates a significant penetration ability of the periodic high-density action of water droplets at subsonic speeds. • Surface and subsurface erosion manifestations on EA4T steel were analyzed. • Microchannels due to penetration ability under the visible groove were observed. • The subsurface hardening on the sides of the groove is stochastic. [ABSTRACT FROM AUTHOR]

This paper addresses the hydroabrasive disintegration of the difficult-to-machine material, Monel K-500. An experiment was performed using a hydroabrasive cutting system with an additional rotating module. The objective of the preliminary experiments was to identify significant technological factors and investigate their impact on the machined surface quality of difficult-to-machine materials. To describe the impact of parameters, experiments were carried out according to the design of experiment. Surface roughness parameters were measured, and surface topography visualisation and analysis were conducted. The results concluded that the abrasive mass flow rate and traverse speed significantly influence the surface roughness and material removal rate. From a practical point of view, the technology can prepare semi-finished workpiece shapes; however, surface finishing is necessary. [ABSTRACT FROM AUTHOR]

The paper deals with the tangential abrasive water jet turning of hybrid aluminium matrix composite fabricated by electromagnetic stir casting technology, consisting A359 aluminium alloy as base matrix and 2% BC and 2% AlO as reinforcing particles with final workpiece diameter of 14.5 mm. The influence of abrasive mass flow rate within 100-400 g/min using two different abrasive grains-olivine and Barton garnet-was studied. Abrasive grains were fed to the water stream created by water orifice of diameter 0.33 mm at pressure level of 300 MPa and a stand-off distance 8 mm. Abrasive type and abrasive mass flow rate, as important technological factors, are evaluated, and topography of created surfaces is analysed using optical profilometry and microscopy methods. A diameter reduction of 25-30% was observed during the experiments. The lowest average roughness value of 6.64 μm was obtained using olivine grains at an abrasive mass flow rate of 400 g/min. The topographical detail of the machined surface revealed several cutting traces, grooves and furrows which show the ploughing nature. [ABSTRACT FROM AUTHOR]

The paper deals with tangential abrasive water jet (AWJ) turning of Incoloy alloy 925. The aim of the experiment was to analyze the impact of the AWJ traverse speed (1.5-9 mm/min) on the surface quality in terms of micro-structure formed on the created surface. The water pressure was set to 400 MPa and the spindle revolution to 34 rpm. Australian garnet ( MESH 80) was used as an abrasive component. The surfaces were visualized and qualitatively described using a laser confocal microscope. Basic roughness parameters of the surfaces ( Ra, Rq, Rz) were measured using an optical profilometer. The presented experimental results demonstrate that the technology of abrasive water jet turning is an appropriate tool for rough machining of difficult-to-machine materials. [ABSTRACT FROM AUTHOR]

This article deals with the analysis of the subsurface deformation effects of materials due to the periodic action of liquid droplets, each with a constant volume of approximately 36 mm3 distributed with a spatial frequency of 20,000 i/mm. Sample grooves were analyzed within standoff distances where the prevailing mechanism is acceleration culmination depletion using the stair trajectory to avoid a possible Doppler effect. Using X-ray μ-CT, a network of cavities corresponding to a fractal shape was identified below the surface. It is apparent that the ability to erode does not end with the formation of a groove but continues into the core of the material in the form of microjetting, tunneling, or piercing. From that perspective, two types of these cavities have been identified, blind and transient, with diameters of a few micrometers. The topological changes in the subsurface region of the sample were analyzed using X-ray μ-CT progressive sectioning. The anticipated subsurface deformation was further explored and analyzed using SEM analysis. The integrity of the material around the cavities was assessed according to microhardness to explain the microjetting, tunneling, and piercing propagation. The results suggest that the effect of the lateral jetting after droplet collapsing causes extensive hydrodynamic tunneling in the material that is much higher during the intense periodic action of water droplets, even at subsonic speeds. [Display omitted] • The origin of subsurface voids is clarified. • Subsurface network microcavities are identified. • Blind and transient subsurface cavities are observed. • Relative and real erosion depths are identified. • Residual water microjetting is observed to be multidirectional. [ABSTRACT FROM AUTHOR]

Improving of bone cements properties is possible by research of variables influencing exothermal behaviour and mechanical properties. Paper deals with exothermal behaviour experimental evaluation of bone cements used for medical purposes. Specimens were prepared by a conventional manual mixing technique. The work addresses primary risk factor associated with application of bone cement to femoral canal. Different size samples of bone cement has been created with diameter d = 2; 5;12,5 mm fixed in dentacryl. As an experimental material, Palacos R+G high viscosity, radiopaque bone cement containing Gentamicin and Radiopaque bone cement Antibiotic Simplex with Tobramycin, was used. Thermal effect during exothermic polymerisation was measured with period 1 minute. Evaluated factors were mass and thickness of bone cement. Significant influence of bone cement mass on temperature has been found. [ABSTRACT FROM AUTHOR]

The paper discusses connections of acoustic emission in abrasive water jet cutting. Introduction focuses on theoretical knowledge on this technology and offers analysis related to current state of the art of the problem research. Further description of performed experiments is presented in case in which acoustic emission behaviour was observed with the exactly scheduled change of cutting conditions or rather cutting head traverse speed v. The beginning of the initial part contains FFT spectral analyses and comparison of the examined sections of the experimental samples. Consequently a graphical representation and comparison of peak-to-peak values (maximal amplitudes) and values of AE at the time of experimental cutting follow. At the close of the work, the analyses are expressed as dependence on the cutting head traverse speed v with expressed regulation equations applicable in the close-loop control process with minimum human intervention and in case of fault conditions-broken focusing tube, fractured water nozzle. [ABSTRACT FROM AUTHOR]

Ultrasonic stress measurement is based on the acoustoelasticity law which presents the relationship between the stress and acoustic wave velocity in engineering materials. The technique uses longitudinal critically refracted (LCR) waves that travel parallel to the material surface. The LCR wave is a bulk longitudinal wave that propagates within an effective depth underneath the surface while the penetration depth of a LCR wave depends on its frequency. It is possible to measure the residual stress in different depths by employing different frequencies of the LCR waves. This paper evaluates welding residual stresses in different depths of a plate made of austenitic stainless steel (304L). The penetration depths are accurately measured for the LCR waves produced by 1MHz, 2MHz, 4MHz, and 5MHz transducers. Residual stresses through the thickness of the plate are then evaluated by employing four different series of transducers. It has been concluded that the LCR method is nondestructive, easy and fast, portable, readily available, and low cost and bulk measuring technique which can be accurately employed in through-thickness stress measurement of austenitic stainless steels. [ABSTRACT FROM AUTHOR]

In the present study, real topographic function and maximal depth of neglected initial zone were analytically developed to predict surface roughness on the top region of surfaces created by abrasive waterjet. An upper area of workpieces was analysed in details. Experimentally created surfaces were measured by HOMMEL TESTER T8000 and non-contact profilometer Micro Prof FRT. As an experimental material, stainless steel AISI 304, AISI 309 and aluminium with a thickness of 10 mm have been used. On the basis of analysis and interpretation of data obtained from the surface, a topography function Ra, which is necessary to be known for the subsequent prediction and control of abrasive waterjet cutting technology, is derived. In the framework of interpretation of measured values, relations among these parameters are systematically analysed and physico-mechanical and distributional principles governing these parameter are formulated newly. Results are very important for further estimation of analytical expression of the real topographic function for any surface created by abrasive waterjet cutting. [ABSTRACT FROM AUTHOR]

The paper deals with an innovative way of cutting materials by abrasive waterjet with a view to increase its quality. In the research work, we were concerned with the search for a relationship between surface roughness and noise in the abrasive waterjet cutting process. Innovation lies in the use of negative characteristic of the technology—noise, which is a carrier of information about the quality of cutting process. In this way, the noise can be positively used in the on-line control of the technological process. The final result is a project for control of the process of abrasive waterjet cutting of materials by means of feedback according to the on-line measurement of acoustic pressure level L aeq (dB). Instantaneous information about the state of cut according to the instantaneous value of L aeq amplitude allows the automatic regulation of traverse speed of cutting head v p (mm.min−1), which is, together with the pressure p (MPa), one of the most important technological factors of control of production technology from the point of view of economic indicators and qualitative indicators of a semiproduct. The proposed model has been experimentally verified and was simulated in Matlab. [ABSTRACT FROM AUTHOR]

The paper deals with a proposal for surface geometric parameters for advanced quality control of abrasive waterjet technology according to the results obtained by means of non-contact optical shadow method. The main emphasis is put on the analysis of results for defining the process for prediction of new surface creation generated by the set of the abrasive waterjet factors stream of abrasive waterjet, including its geometric parameters. By means of decomposition of measured surface profile according to the root mean square parameter, in four topographical different zones the initial zone, the smooth zone, the transition zone and the rough zone new possibilities for evaluation of the surface quality and optimizing the selected technological factors of the cutting process and their control through the proposed databank conceptual structure are presented. This report deals with the problems of selecting and proposing an acceptable method for surface quality control which is available for continuous measurement and production. [ABSTRACT FROM AUTHOR]

The objective of the study is to investigate the erosion effects of periodic water clusters interacting with flat AISI 304 surface to evaluate erosion regimes, surface morphology and variation in the subsurface microhardness below the disintegrated grooves. Stairs trajectory within the standoff distance 5–101 mm with step height 2 mm and length 20 mm was used. The pulsating water jet was changed by varying the supply pressure of the liquid from 40 MPa–100 MPa, at a traverse speed of 5 mm/s which is equivalent to constant impingement distribution of 4000 impingements per mm. Morphology of the PWJ defines different erosion regimes based on specific value of supply pressure and standoff distance. Increasing of supply pressure shifts prevalence of both impact pressure and stagnation pressure at higher standoff distances leading to the delay in formation of incubation, acceleration, culmination, depletion, and termination regime. Impinged surface features such as micro-pits, craters, upheaved surface and isolated voids near the periphery of the trace were observed along with PWJ footprint. The values of the micro-hardness showed strengthening of material subsurface at selected standoff distances. At certain standoff distance effect of supply pressure is inverse to micro-hardness values. Determination of studied technological parameters can be used for effective surface peening operation at v > 5 mm and surface activation of the metals. Results opens a new avenue for determination of erosion resistance of material. • Erosion effects of pulsating water jet as function of standoff distance and flow rate was investigated. • Linear offset of erosion stages and erosion intervals due to interaction of water flow rate and standoff distance was found. • Different erosion stages were observed due to non-uniform plastic deformation with the variation of standoff distance. [ABSTRACT FROM AUTHOR]

This research article aims at comparing the erosion performance of continuous and ultrasonically generated pulsating water jet technologies on granite samples at three pressure levels of 20 MPa, 40 MPa and 60 MPa. The granite surface was eroded using the circular nozzle of diameter d = 1.9 mm with the variation of traverse speed at each pressure levels. The depth, width and volume erosion of the grooves generated by both the technologies were evaluated using surface profilometer. It was evident from the results, that the variations in the process parameters show the influential behaviour on the erosion performance of granite by pulsating water jet in comparison to the continuous water jet. The optical microscopy and scanning electron microscopy (SEM) of the generated grooves were analysed to observe the surface morphology and plastic deformation phenomenon during the erosion of the granite samples. The above study shows that the pulsating water jet technology is the preferable approach over continuous water jet that can be utilised for different manufacturing applications. Also, the technology is economically more beneficial than the presently used cleaner technologies (non-abrasive and abrasive) as it reduces the extra cost invested in high-pressure pumps. [ABSTRACT FROM AUTHOR]

• Using 0.9% physiological saline instead of pure water increases cutting depth. • Lower fluid flow rate is required for saline than water to obtain similar disintegration. • Condition monitoring can be used for controlling bone cement extraction. • The results open avenues for a minimally invasive and non-thermal technique. This paper deals with performance analysis of disintegration of polymethylmethacrylate using pulsating liquids jet with different density with frequency 20 kHz using condition monitoring. The influence of the liquid on the cutting depth was studied by using contactless measurement device MicroProf, FRT. The cutting depths were compared to studies that used a continuous water jet to assess the volume flow reduction. On-line condition measurement was used for controlling the disintegration process without compromising the structural integrity of neighbouring materials. With a flow rate of 0.54 l/min, a maximum disintegration depth of 1.3 mm and material removal of 0.4 mm3 was obtained using physiological saline and 1.1 mm and 0.2 mm3 for water. Continuous jets required approximately 1.0 l/min to reach similar cutting depths. Hence, a pulsating liquid jet enhances the cutting capacity with reduced flow rate. Signal strength for individual pressures 7–10 MPa is not significant, but signal increases during significant bone cement removal. The results open new avenues for research a minimally invasive and non-thermal technique for on-line controlled processes for medical purposes. [ABSTRACT FROM AUTHOR]

Erosion caused by water droplets is constantly in flux for practical and fundamental reasons. Due to the high accumulation of knowledge in this area, it is already possible to predict erosion development in practical scenarios. Therefore, the purpose of this study is to use machine learning models to predict the erosion action caused by the multiple impacts of water droplets on ductile materials. The droplets were generated by using an ultrasonically excited pulsating water jet at pressures of 20 and 30 MPa for individual erosion time intervals from 1 to 20 s. The study was performed on two materials, i.e. AW-6060 aluminium alloy and AISI 304 stainless steel, to understand the role of different materials in droplet erosion. Erosion depth, width and volume removal were considered as responses with which to characterise the erosion evolution. The actual experimental response data were measured using a non-contact optical method, which was then used to train the prediction models. A high prediction accuracy between the predicted and observed data was obtained. With this approach, the erosion resistance of the material can be predicted, and, furthermore, the prediction of the progress from the incubation erosion stage to the terminal erosion stage can also be obtained. [ABSTRACT FROM AUTHOR]

Recently, the demand for lightweight multilayered parts in electronics and biomedical fields has been accelerated and shown great interest in understanding the combined effect of multilayered materials. However, these industries are still facing the challenge of developing dissimilar multilayered materials that can be suitable for biomedical applications. In this context, magnesium emerges as a promising biocompatible material used for several biomedical applications. However, the issues related to joining magnesium alloys with other similar materials still need to be solved. Moreover, friction stir additive manufacturing (FSAM) occupies a niche domain for developing or joining biocompatible materials such as magnesium alloys with low weight and high strength. Therefore, the present work highlights the development of a multipurpose three-layered multifunctional laminated composite plate of magnesium-based AZ31B–Zn–Al 1100 through the FSAM route. Microstructural and morphological examinations were carried out by light microscopy and FESEM equipped with EDS analysis and line mapping. Moreover, the grain refinement at the interfaces during the FSAM was also addressed using the electron backscattered diffraction (EBSD) study. Further, investigation on mechanical properties such as tensile test with fractography analysis and microhardness variation at the cross-section of the built-up section has been investigated. Furthermore, the corrosion and tribological analysis was also performed, and a 3D profilometer was used to visualize the corroded and worn-out surfaces. The microstructural results revealed that the average grain size of 6.29 μm at interface AZ31B–Zn and 1.21 μm at interface Zn–Al 1100 occurred, improving the bonding strength and overall properties. The tensile strength has occurred as 171.5 MPa at 15.5% elongation, whereas maximum microhardness is reported as 105 HV at the interface of AZ31B–Zn and 84.6 HV at the interface of Zn–Al 1100. The corrosion rate was calculated as 0.00244 mm/day, and the average coefficients of friction (COF) for both the interfaces, such as AZ31B–Zn and Zn–Al 1100, are 0.309 and 0.212, respectively. [ABSTRACT FROM AUTHOR]

Lightweight composite materials for potential thermal applications are the contemporary demand for manufacturing and aircraft industries where the possibility to improve and tailor the desired properties is based on the application. Carbonized eggshell powder is a solid lubricant with absorbent capability and has proven as a reinforcement for metallic base composites. In the present work, an attempt is made to investigate the effect of carbonized chicken eggshell powder (3 to 9% by weight) on the microstructural and thermal properties of Al7075 alloy processed by solid-state friction stir processing. An infrared thermography and three K-type thermocouples equipped with the base plate at three equal distances are used to measure the temperature with respect to time. The comparative study of microstructure and grain structure analysis has been done by light microscopy, scanning electron microscopy, and electron backscattered diffraction methods. The findings explored the dynamic recrystallization and grain recovery with a reduced grain size of 6.2 to 10.3 µm at a varying percentage of eggshell powder (3 to 9%) in the stir zone. The thermal conductivity and coefficient of thermal expansion (CTE) were measured for the temperature range of 50 to 400 °C. In addition to it, differential thermal analysis (DTA), thermo-gravimetric analysis (TGA), and derivative thermo-gravimetric analysis (DTG) are conducted for the temperature range of 25 to 900 °C to discuss the endothermic, exothermic nature, and degradation characteristics. The result revealed the decreasing trend of thermal conductivity, and CTE values were found in the range of 97 to 53 W/mK and 26.6 to 24 × 10−6 K−1 (heating cycle), 27.2 to 23.8 × 10−6 K−1(cooling cycle), respectively. Furthermore, the higher and lower thermal conductivity of 108 W/mK and 62 W/mK is observed at higher and lower terminal voltages, 250 V and 100 V, respectively. The DTA, TGA, and DTG curves explored the maximum weight loss, which varies up to 5.25% with exothermic peaks and decomposition steps for each surface composite. [ABSTRACT FROM AUTHOR]

There are many technological ways to activate biocompatible surfaces, but in some cases, there are not reliable for elderly patients. It has been found that surfaces created using pulsating water jets have a structure similar to trabecular bone structures. Such a similar shape to the endoprosthesis stems would enable faster fixation. The paper presents a novel way of utilizing the water hammer effect caused by forced multiple droplet impingement with a spatial frequency of 40,000 i/s on Ti6Al4V titanium alloy surface under different technological conditions. The objective was to create a structured surface with desired values of surface profile parameters Ra and Rz to increase the possible potential for implant osseointegration, fixation and stability. Pulsating water jet was generated at pressures from 20 to 100 MPa using a circular nozzle with a diameter of 1.32 mm. Two different strategies of the jet trajectory, namely linear and cross-hatch strategy, were investigated. Results were compared with grit blasted followed by plasma spray-coated femoral stem for cementless total hip arthroplasty. It has been found that variation in the input parameters results in significant changes in the surface generated. Samples whose surfaces were generated using energy intensity lower than 5 KJ/mm2 and have surface roughness in the range Ra = 4 – 8 μm were selected for surface topography and morphology analysis along with the commercial femoral stem. SEM analysis revealed the absence of foreign contamination and steeper surface heights on pulsating water jet treated samples compared to standard femoral prosthetic. The cross-section images showed the presence of sub-surface voids and craters of different sizes due to the jet's action. Surface topology is similar to trabecular shape. This indicates that roughening the surface increases the surface area and thus has potential bone tissue ingrowth during osseointegration. [ABSTRACT FROM AUTHOR]

More efficient ways to process materials are constantly being sought, even in the case of continuous water flow technology, which acts on materials mainly by stagnant pressure. An alternative method is an ultrasound-stimulated pulsating water jet, the basis of which is the repeated use of impact pressure, which reduces the time interval for mechanical relaxation. This article focuses on a comparative study from the point of view of water mass flow rate on material penetration and its integrity. Relatively low pressures (p = 20, 30, and 40 MPa) with varying nozzle diameters (d = 0.4 and 0.6 mm) were used to identify the effectiveness of the pulsating water jet. The time exposure of the jet at a fixed place was varied from t = 0.5 to 5 s for each experimental condition. The results showed that with an increase in the pressure and diameter values, the disintegration depth increased. In addition, the surface topography and morphology images showed signs of ductile erosion in the form of erosion pits, upheaved surfaces, and crater formation. The microhardness study showed an increase of 10% subsurface microhardness after the action of the pulsating water jet as compared to the original material. [ABSTRACT FROM AUTHOR]

Paper deals with dynamic measurement of performance parameters for selected vehicles engines using incremental sensor attached to the rest bed roller. Data collection was performed with an eight-channel collector. The moment of the inertia is the result of the measurement, which can also be used in the measurement of performance parameters. The external speed characteristics of the engine primarily resulting from the dynamic measurement is the absolute result of the measurement. It can be concluded on the technical conditions of the motor vehicle based on the evaluation of external speed characteristics of the engine. It is possible to maintain consistently good technical state of the motor engine with an appropriate maintenance and contribute to the ecology and the economy of the vehicle operation. [ABSTRACT FROM AUTHOR]

The paper deals with the verification of suitability of water jet and abrasive water jet application for the disintegration of rotating samples of wood plastic composites (WPCs) with diameter d = 36 mm. The influence of selected technological factors (traverse speed of cutting head v [mm/min] and size of abrasive particles [MESH]) on the topography of resulting surfaces has in particular been studied. Surface topography and quality have been assessed using the methods of optical and confocal microscopy and optical profilometry. The presented procedures and results of experiments demonstrate the technology of abrasive water jet as an appropriate tool for the rough machining of WPCs and similar composite materials. In addition, the application of this technology can effectively solve the problem of the melting of the polymer matrix and its subsequent sticking to the functional parts of a cutting tool resulting from conventional turning. [ABSTRACT FROM AUTHOR]

The article focuses on the turning of sandstone through the use of abrasive waterjet (AWJ). Topics discussed include the importance of technological innovations, the machining management, and the sandstone surface analysis. Also mentioned are the mechanical and physical properties of rock materials, the rock fabrication, and the importance of AWJ technology.

Conical pick is a widely used tool for cutting coal in mines. It has a cemented carbide tip inserted in a steel body. Cemented carbide has been in use for many years for coal/rock cutting because it has the optimum combination of hardness, toughness and resistance against abrasive wear. As coal/rock is a heterogeneous substance, the cutting tool has to undergo various obstructions at the time of excavation that cause the tool to wear out. The cracks and fractures developing in the cemented carbide limit the life of the tool. For a long time, different wear mechanisms have been studied to develop improved grades of cemented carbide with high wear resistance properties. The research is still continuing. Moreover, due to the highly unpredictable nature of coal/rock, it is not easy to understand the wear mechanisms. In the present work, an attempt has been made to understand the wear mechanisms in four conical picks, which were used in a continuous miner machine for underground mining of coal. The wearing pattern of the conical pick indicates damage in its cemented carbide tip as well as the steel body. The worn out parts of the tools have been critically examined using scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) point analysis. Mainly four types of wear mechanisms, namely, coal/rock intermixing, plastic deformation, rock channel formation and crushing and cracking, have been detected. The presence of coal/rock material and their respective concentrations in the selected area of worn out surface were observed using the spectra generated by EDX analysis. [ABSTRACT FROM AUTHOR]

This work explores the possibility of repairing damaged pressure piping systems using composite repair bandaging technology. Loctite technology from Henkel was selected from several existing methods and applied at the weld joint. To assess the performance of the bandage, a bore was made at the weld joint to simulate a replacement defect of the composite bandage. The bandage, along with the welded joints, was subjected to microstructural and macrostructural analysis, and mechanical and fire resistance tests were also performed. Based on the obtained results, it is concluded that the properties of the Loctite composite system are suitable for repairing pressure piping in the power industry. However, it is not always possible to use this repair method due to certain boundary conditions for its application, such as maximum pipe overpressure, the temperature of the internal medium and the environment, degradation of the repair system due to the medium being transferred and the environment, reduction of the pipe wall at the repair site, possible surface treatment before application of the system, etc. For these reasons, the repair system may be used for a temporary period (approved by the power plant operator), and the spot will then be repaired in the standard way by replacing parts of the pipeline during a planned equipment shutdown. • Possible extented service life of pipelines by bandaging. • Composite bandage application in energetic industry. • Bandage application on welded joints in pipelines to postpone the shutdown of the power plant. • Testing of composite bandages on pressurized pipeline during conditions simulating earthquake and against fire. [ABSTRACT FROM AUTHOR]

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 Rz and Ra, as soon as no clear striation marks are recordable on the surface for particular materials with specific mechanical properties. [ABSTRACT FROM AUTHOR]

WC-Co based tools are widely used in the field of coal and rock excavation because of their unique combination of strength, hardness, and resistance to abrasive wear. Conical pick is one of the coal cutting tools. The tip of the pick is made of WC-Co material. As coal and rock are heterogeneous elements, they pose various constraints during excavation. As a result the tools wear out during the process. Other parameters like cutting techniques, tool orientation, and environmental conditions also affect the tool significantly. The wearing phenomenon greatly reduces the service life of the tools and thereby cuts down the production rate. To prevent such wearing process, it is important to investigate the different wear mechanisms in WC-Co. Simultaneously, there has to be an ongoing endeavour for the development of better quality WC-Co. This paper focuses on different wear mechanisms in a conical pick which has been used in a continuous miner machine for coal cutting. The worn out surface has been observed by using FE-SEM (field emission scanning electron microscopy) and EDS (energy dispersive X-ray spectroscopy). The mechanisms, namely, coal/rock intermixing, cracking and crushing of WC grains, and adhesion of rock particles, have been predominantly investigated in this study. A little indication of corrosive decay in the WC grain has also been reported. The EDS has detected material concentration in a selected area or point of the worn-out surface. The spectrograph confirms the presence of coal/rock materials. Elements such as W, C, Ca, K, O, and Co have been mainly found in different concentrations at different positions. [ABSTRACT FROM AUTHOR]

The paper deals with the determination of vibration emission frequency depending on the impact of abrasive particles during cutting of materials. In order to verify the investigated hypothesis, the factor of the abrasive mass flow rate m = 250 and 400 g min at the traverse speed of cutting head v = 50, 75, 100 and 150 mm min was determined. The Barton Garnet with MESH 80 and focusing tube with diameter of 0.8 and 1.4 mm were used in the experiment. Vibrations were recorded during experimental cutting by sensors PCB IMI type 607A11 placed on the stainless steel AISI 309. During the experimental sample cutting, vibrations were monitored and consequently processed by the LabVIEW 8.5 software. Research results are useful for improving the quality of surface created by abrasive water jet, and they can encourage the on-line process control of abrasive water jet cutting with the minimum human intervention in case of a fault or error during the supply of abrasives to cutting head. [ABSTRACT FROM AUTHOR]

Surfaces exposed to natural forces in the form of water droplets are structurally deformed over time through changes in their surface morphology. Plastic deformation in thin subsurface layers where compressive stress prevails is typical for this stage of erosion. The stress accumulation does not exceed the fatigue limit, so the structural integrity is not broken. Information about this stage has been obtained by post-experimental assessments using various observation techniques. This article considers the changes to a surface using techniques to assess a specific site before and after exposure to the erosive action of water droplets. An electron backscatter diffraction analysis was conducted pre-exposure of water droplets for detection on an electrochemically polished surface of stainless steel AISI 316 L. Specific areas that were exposed to the effects of water droplets at subsonic speed were marked with indents. The droplets were generated by an ultrasonic pulsating water jet (PWJ) with a nominal frequency of 40 kHz and supply pressure of p = 50 MPa. To assess the development in the very early stages of erosion, individual runs were performed with a time range of 1–3 s. The erosion development was compared with control runs, where a continuous water jet (CWJ) with a frequency of 1 Hz was used with a time range of 3–6 s. A post-exposure electron backscatter diffraction analysis showed a real change in the grain orientation using kernel average misorientation. It was found that multiple droplet impingement changes the grain geometry and results in an increase in misorientation inside the grains. The misorientation distribution in the zone treated by the water jet was not homogeneous over the entire cross-section of the sample; the CWJ required double or even triple the time to achieve a similar level of plastic deformation when compared to the PWJ. • An EBSD-based procedure for observation of the incubation stages was applied. • The misorientation inside the grains was numerically evaluated. • The misorientations around 1° form walls resulting in subgrain-like structures. • Grain tilting was established as the main surface deformation mechanism. [ABSTRACT FROM AUTHOR]

Mining and petroleum drill bits are subjected to highly abrasive rock and high-velocity fluids that cause severe wear and erosion in service. To augment the rate of penetration and minimize the cost per foot, such drill bits are subjected to increasing rotary speeds and weight. A rotary/percussive drill typically hits the rock 50 times per second with hydraulic impact pressure of about 170-200 bar and feed pressure of about 90-100 bar, while rotating at 75-200 rpm. The drill rig delivers a high-velocity flow of drilling fluid onto the rock surface to dislodge cuttings and cool the bit. The impingement of high-velocity drilling fluid with entrained cuttings accelerates the erosion rate of the bit. Also, high service temperature contributes to softening of the rock for increased penetration. Hence, there is a need to optimize the drilling process and balance the wear rate and penetration rate simultaneously. This paper presents an experimental scanning electron microscopy (SEM) study of electroplated (nickel-bonded) diamond drills for different wear modes. [ABSTRACT FROM AUTHOR]

The paper deals with basic research of vibration generated at abrasive waterjet cutting of materials and their analysis of frequency spectrum in the plane cut. As an experimental material, stainless steel AISI 309 has been used. Experimentally controlled factor involved in the experiment was abrasive mass flow rate with values m = 250 and 400 g min at a constant traverse speed v = 100 mm min. The vibrations were recorded during experimental cutting by sensors PCB IMI type 607A11 placed on experimental material along the cut at a distance of 50 mm from the cutting plane. Data collection was carried by NI PXI measurement system and frequency analyzer Microlog GX-S. Signal was evaluated by virtual instrument created in the object-programming environment LabView 8.5. Various sizes of amplitudes were observed depending on the distance of abrasive waterjet cutting process from the beginning of the cut. Two peaks of frequency bands have been also found: the first between 500 and 600 Hz and the other at approximately 12.5 kHz. Using this method is possible to ensure the determination of technology efficiency of the material removal process. [ABSTRACT FROM AUTHOR]

The process of material cutting and fracture by high velocity water jets is a complex series of phenomena which may involve compression, tension, shear, erosion, wears, cracking, wave propagation, and cavitations damage. This makes the exact analysis of the jet cutting process to be very complicated. The problem of water jet coal cutting is a multiresponse problem. There are two output variables, depth of cut and cutting width whose optimization will result in the increase in the productivity of coal cutting. In this paper, a Taguchi-Fuzzy decision method has been used to determine the effective process parameters for improving the productivity of coal mines. The Taguchi method of experimental design is a widely accepted technique used for producing high quality products at low cost. The optimization of multiple responses in complex processes is common; therefore, to reduce the degree of uncertainty during the decision making, fuzzy rule-based reasoning was integrated with the Taguchi loss function. [ABSTRACT FROM AUTHOR]

Abstract: Experimental study of the surface quality produced by abrasive waterjet (AWJ) on metallic materials has been performed. The surface roughness/waviness was quantitatively evaluated by using the contactless optical measurement. In order to characterize the cut surface qualities, a single-parameter criterion has been proposed. Based on root mean square (RMS) roughness evaluation of the worst cut surface zone, the dimensionless statistical parameter C can be calculated as a basic quantity for AWJ surface cut characterization. As it was approved, besides its dependency on depth of AWJ trace, the value of C-parameter for the specific material is noticeably related also to the traverse speed of the cutting head. Such a relationship can be potentially used for adjusting the cutting speed of the machining process. [Copyright &y& Elsevier]

This study investigates the erosion performances of a high-speed modulated jet (MWJ) and continuous water jet (CWJ). Two sets of hydrodynamic nozzles (HDNs) and two circular water nozzles (CWNs) were compared for two levels of hydraulic power (26 and 62 kW), representing middle- and high-power energetic water jets. The HDNs and CWNs were selected based on their size equivalence factor. The erosion effects of modulated and continuous jets were compared using the aluminum alloy EN AW-6060. Owing to the anisotropy of the modulated jet, two orientation angles (0° and 90°) were used in the experiment with a traverse speed of v = 1 mm/s at an optimal standoff distance z (mm). The hydraulic power of the generated water jets was monitored online using a flowmeter and pressure sensor. Overall, 36 runs were performed for mutual comparison. Optical and scanning electron microscopy were employed to investigate the grooves created using these techniques. Achieving a sharper interface in a deeper groove is possible under certain conditions, thereby inducing the effect of the liquid saw blade. In addition, this phenomenon reduces the effect of lateral flow action, which causes significant extrusion of the material above the original plane of the surface when using a pulsating water jet. • The modulated water jets show better erosive actions compared to the continuous water jets. • Erosion ability of modulated water jets depends on the hydraulic power, nozzle type, and orientation. • U and V-shaped grooves were achieved with 90° and 0° orientation using of the modulated water jets. [ABSTRACT FROM AUTHOR]

• Al-Cu joint of dissimilar thickness is successfully obtained using FSW method. • Joint tensile strength of dissimilar metals is examined at different tool offsets. • The joint quality is improved by 1 mm of tool offset along aluminum side. • Joint properties are influenced by the varying intermetallic thickness. Friction stir welding has been successfully employed to fabricate dissimilar thickness AA1050 and oxygen free copper (Cu-OF). The highest value of the joint tensile strength obtained was 91% of the AA1050 alloy strength with the tensile fracture path on the aluminum side. At the Al-Cu interfacial microstructure, a layer of Al 4 Cu 9 and Al 2 Cu intermetallic compounds (IMCs) with thickness of 2.2 μm–0.26 μm was developed at different welding speeds. The voluminous IMCs have an adverse impact on the tensile characteristics of the joint. The IMCs (0.26 μm−0.77 μm) at welding speeds of 160 mm/min and 213 mm/min with 1 mm tool offset, has trivial effect on the tensile property. The mechanical property of the joint was significantly affected by the tool offset and welding speed. Image processing techniques such as Gaussian blur, histogram normalization and binarisation were utilized to understand the distribution of copper in the weld stir zone. [ABSTRACT FROM AUTHOR]

Abstract The paper deals with microhardness measurement up to a depth of 3 μm on hybrid metal matrix composite A359/Al 2 O 3 /B 4 C from the surface created by wire electric discharge turning and abrasive waterjet turning at the same of a range of rotational speed. The study also includes the topographical and morphological aspects of measurements to compare the surface quality. The microhardness was measured by Vickers indentation test at a load of 100 g for 10 s. Surface roughness profile parameters (Ra, Rq and Rz), and 3D surface visualisation were measured by an optical profilometry. Laser confocal microscope was used to characterize the topographical details. FE-SEM analysis was used to discuss the morphological observations and to explore the quality and defects of the machined surfaces. The sub-surface element like residual stresses is also investigated through the depth profile for both types of turning process by means of XRD machine. The results showed that a lower value of microhardness (165 HV) as compared to cast sample (200 HV) has been observed in the recast layer of wire electrical discharge turning along with induction of tensile residual stress (340 MPa). During abrasive water jet turning a nominal change in microhardness (204 HV) along with compressive residual stress (−285 MPa) was observed. [ABSTRACT FROM AUTHOR]

This study focused on the development of an AZ31B/Si 3 N 4 /Eggshell surface composite via solid-state multi-pass friction stir processing. The study aimed to characterize the developed surface composite based on its structural, microstructural, mechanical, and tribological performance at one, two and three successive tool-passes. The structural and compound analysis was conducted using an XRD pattern. Microstructural characterization and grain refinement studies were conducted using FESEM images and EBSD analysis. Furthermore, the mechanical properties were investigated through tensile tests equipped with digital image correlation (DIC) images and fractography analysis via FESEM images. In addition, tribological characteristics, such as COF, friction forces, and volumetric wear losses, were examined using a universal tribometer, and the 3D profile of the wear track was analyzed through surface profilometry. The results revealed the formation of structural compounds such as Mg 2 Al 4 , Mg 2 SiO 4 , Mg 2 Ca, and Ca 2 Mg 4 Zn 13 in the stir zone. The morphological study revealed plenty of white-grey (ESP) and dark grey (Si 3 N 4) sub-micron precipitates uniformly dispersed into the AZ31B matrix alloy. The EBSD map exhibited an average grain size of 2.95 ± 1.83 μm. The ultimate tensile stress at one, two and three successive tool-passes were found to be 357 MPa, 366.5 MPa and 375.4 MPa, respectively, which was comparatively 20–25% higher than the base alloy. The FESEM images of the fractured surface exhibited ductile striations and tear ridges with flat shear bands mixed with brittle fracture. The lowest COF obtained in this study was 0.29 for three too-passes at an average frictional force (Fx) of 2.17 N with a volumetric wear loss of 0.0769 mm3. • Multi-pass FSP of AZ31B alloy to overcome the challenges associated with the less hexagonal structure. • Utilization of waste chicken eggshell in a useful reinforcement to enhance the mechanical and tribological properties. • Microstructural changes and grain refinement analysis has been done through FESEM and EBSD analysis. • Tensile behavior with (DIC) images and fractographic analysis. • Tribological characteristics supported with 2D and 3D wear track analysis through surface profilometry. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This article deals with measurement of the thermal gradient on material during abrasive water jet cutting. The temperature was measured by thermocamera before the technological process started, during the abrasive water jet cutting process technology, and just after the cutting process. We performed measurements on several types of materials. We calculated the approximate amount of energy during the abrasive water jet cutting process technology that changes into thermoenergy, which is the current water pressure drained in a catcher tank. [ABSTRACT FROM AUTHOR]