Wear Issues Research Articles

Realization of high efficiency and low damage machining of anisotropic KDP crystal by grinding

Potassium dihydrogen phosphate (KDP) is a non-linear material used in various opto-electronic applications including Q-switches, high-speed photography shutters, frequency harmonic generation lens and Pockels cells in the Inertial Confinement Fusion (ICF) devices. KDP belongs to the most difficult-to-cut material, due to its delicate and unique characteristics including the combination of softness with brittleness, anisotropic performances, tendency for deliquescence and sensitivity to temperature change. Single point diamond turning (SPDT) is considered to be the ideal method for machining KDP components. However, the process efficiency is rather low and often accompanied with severe tool wear issues. This paper studies the feasibility using grinding method to remove the surface material of KDP components with high process efficiency and low damage, fulfilling the task of re-aligning the surface orientation to the crystalline axis. The grinding tests were carried out on a common CNC grinder, using resin bonded diamond grinding wheel, whilst the diamond abrasives are coated with Ni-P alloy. The direction of precision grinding was determined by studying the anisotropy of KDP, including its elastic modulus E, Vickers hardness HV and fracture toughness KIC, to reduce the influence of material anisotropy on machining quality. The grinding process parameters were preliminarily determined based on the experimental results investigating the effects of peripheral speed of the grinding wheel, worktable feed rate and grinding depth on the ground surface roughness. The surface defects, surface morphology and sub-surface damage under different process parameters were investigated. Surface roughness Ra ≤ 0.3 μm and sub-surface damage depth SSD ≤ 6 μm were obtained. The machining efficiency can be improved by nearly ten times using the proposed precision grinding method, producing nearly the same surface quality (Ra ≤ 0.2 μm, SSD ≤ 6 μm) as that in the axis fixing phase in SPDT.

MAXIMIZING DRILLING PERFORMANCE THROUGH ENHANCED SOLID CONTROL SYSTEM

High solid content in drilling mud may affect its properties and result in uncertainties at downhole condition. It eventually contributes to poor rig operation performance and operating cost. This research focus on developing a solid control system that is suit for drilling 12.25-inch hole. The first part discussed on the effect of solid control system performance to mud properties Plastic Viscosity (PV), Yield Point (YP) and Low-Gravity Solid (LGS) while the second part of research discussed about the mud performance to Rate of Penetration (ROP), Equivalent Circulating Density (ECD) and drill string drag. The input parameters such PV, YP, LGS, ROP, LGS, ECD and drill string drag were gathered from two different set up of solid control systems that were used in Well A and Well B. The result was mainly based on the performance of old design and new design solid control system. Installation of mud flow distributor tank to channel the mud into respective shale shakers significantly enhanced the mud treatment capability and operational performance. Mud properties while drilling the 12.25-inch hole section; PV, YP and LGS values were improved by 14%, 17% and 25% respectively. The ROP improved by 25%, ECD margin by reducing additional pressure exerted using original mud from 4.9% to 2.9% and drill string drag friction factor (FF) concentrated within 0.2FF trend. Proper mud flow control and routing system at new develop design of solid control system effectively removed the solid in the drilling fluid. This improvement minimizes the tendency of frequent mud flow, screen mesh plugging and tool wear issue. Mud properties such PV, YP and LGS were maintained with an acceptable mud design envelope.
 Keywords: PlasticViscosity (PV), LowgravitySolid (LGS), Rateofpenetration (ROP), Equivalent circulatingdensity (ECD), drillstringdrag.

Sa1067 IMMEDIATE PRE-INSERTION ALCOHOL FLUSH AND FLEX PROTOCOL (AFFP) FOR ADDITIONAL DECONTAMINATION AT ERCP AND EUS: EXPERIENCE WITH 4671 CASES

Serious systemic infections due to carbapenem resistant enterobacteria (CRE) and other bacteria have been traced to inadequately disinfected elevator equipped endoscopies (EEE). The potential reason for residual microbes appear to be multifactorial including errors in mechanical or AER cleaning, endoscope wear or design issues, or post-cleaning contamination. 70% isopropyl alcohol has been proven to be an effective medical hand sanitizer due to its rapid bactericidal effect. Since 6/2015, we have been using a standard isopropyl alcohol based decontamination protocol just before endoscope insertion to reduce the risk of unexpected residual bacteria. All EEE are first cleaned by OEM guidelines supervised by a reprocessing specialist. In the endoscopy suite, just before insertion, ERCP and EUS endoscopes are flushed with 60cc of 70% isopropyl alcohol while flexing the elevators repeatedly. After suctioning back the alcohol, sterile water is suctioned to clear the channel of residual. Surveillance cultures are performed by CDC guidelines on two of our twelve elevator endoscopes weekly or biweekly after a minimum “hang time” of twelve hours. All cultured EEE are then held in quarantine pending results. Positive cultures are reprocessed and recultured. Effectiveness of this protocol is evaluated by hospital epidemiology case research and CRE point prevalence monitoring. From the onset of the AFFP in 6/2015 to 11/2017, 4671 cases (3277 ERCP and 1394 EUS) have been performed. Surveillance cultures were positive in 8/309 (2.6%) contaminants 5 (skin flora), non-pathogens 2 (Corynebacterium) and pathogens 1 (Enterococcus faecium (broth only)) or 1/309 (0.32%). Of note, this one pathogen was prior to improvements in CDC culture guidelines, and new OEM disinfection training. No EEE associated infections have been identified despite the presence of drug resistant organisms including CRE in our hospital. The source of occasional residual microbes after OEM cleaning documented by CDC culture techniques remains unclear.

Wear of Polycrystalline Boron Nitride Tool During the Friction Stir Welding of Steel

The wear issue of a polycrystalline boron nitride (PCBN) tools during the friction stir welding of two grades of steel, DH36 and EH46, was studied. Two welding traverse and tool rotational speeds were used when welding the DH36 steel. A low tool speed (200RPM, 100 mm/min) and a high tool speed (550RPM, 400 mm/min) were denoted by W1D and W2D, respectively. Nine welding conditions were applied to the welding of EH46 steel plate including seven plunge/dwell trials (W1E–W7E) and two steady-state trials (W8E and W9E). SEM–EDS and XRD tests were applied in order to reveal the boronitride (BN) particles inside the welded joints, and the percentage (%) of BN was calculated according to the standard quantitative metallographic technique. The findings showed that tool wear increases when the tool rotational speed increases as a result of binder softening which is a function of the peak temperature (exceeds 1250 °C) at the tool/workpiece interface. When considering the EH46 steel trials, it was found that an increase in the tool traverse speed in friction stir welding caused a significant tool wear with 4.4% of BN in the top of the stirred zone of W9E compared to 1.1% volume fraction of BN in W8E which was attributed to the higher thermomechanical action on the PCBN tool surface. Tool wear was also found to increase with an increase in tool plunge depth as a result of the higher contact between the surface of friction stir welding tool and the workpiece.

Issues of tool wear in excavation works

Issues of tool wear in excavation works

Tool wear in TBM hard rock drilling – backgrounds and special phenomena

AbstractIn hard rock TBM drilling, wear issues play a crucial role in the success of a tunnelling project. Thus, excavation tools must be selected carefully and be adapted to ground conditions. Wear‐related changes in the tools that occur over the course of the tools' operating lives must also be taken into account. This paper presents five basic types of macroscopic wear for cutter rings: (1) abrasive/normal wear, (2) tapering, (3) mushrooming, (4) brittle fracture of the cutter ring (special wear type 1) and (5) blockade of the roller bearing (special wear type 2). These basic wear types lead to distinct cutter ring shapes which allow deriving some fundamental characteristics of the interacting rock types. In addition, a microscopic analysis of the surfaces and associated metallographic sections from worn cutter tools has been performed. As a result, the tribological processes under the cutter, leading to tool wear, can be better understood. In summary, the investigations may contribute to a better understanding to make it easier to choose the proper TBM disc cutter for a distinct rock type in order to minimize the risk of tool‐related downtimes.

A Preliminary Study to Enhance the Tribological Performance of CoCrMo Alloy by Fibre Laser Remelting for Articular Joint Implant Applications

CoCrMo alloy has long been used as a pairing femoral head material for articular joint implant applications because of its biocompatibility and reliable tribological performance. However, friction and wear issues are still present for CoCrMo (metal)/CoCrMo (metal) or CoCrMo (metal)/ultrahigh molecular weight polyethylene (UHMWPE) (plastic) pairs in clinical observations. The particulate wear debris generated from the worn surfaces of CoCrMo or UHMWPE can pose a severe threat to human tissues, eventually resulting in the failure of implants and the need for revision surgeries. As a result, a further improvement in tribological properties of this alloy is still needed, and it is of great interest to both the implant manufacturers and clinical surgeons. In this study, the surface of CoCrMo alloy was laser-treated by a fibre laser system in an open-air condition (i.e., no gas chamber required). The CoCrMo surfaces before and after laser remelting were analysed and characterised by a range of mechanical tests (i.e., surface roughness measurement and Vickers micro-hardness test) and microstructural analysis (i.e., XRD phase detection). The tribological properties were assessed by pin-on-disk tribometry and dynamic light scattering (DLS). Our results indicate that the laser-treated surfaces demonstrated a friction-reducing effect for all the tribopairs (i.e., CoCrMo against CoCrMo and CoCrMo against UHHMWPE) and enhanced wear resistance for the CoCrMo/CoCrMo pair. Such beneficial effects are chiefly attributable to the presence of the laser-formed hard coating on the surface. Laser remelting possesses several competitive advantages of being a clean, non-contact, fast, highly accurate and automated process compared to other surface coating methods. The promising results of this study point to the possibility that laser remelting can be a practical and effective surface modification technique to further improve the tribological performance of CoCr-based orthopaedic implants.

The Mobile-bearing TKA: Is There Still a Place?

During the 1980s, fixed-bearing total knee arthroplasty (TKA) became a reliable, reproducible procedure with about 95% implant survival after 10 years. However, implant loosening and polyethylene wear became recognized as long-term causes of late failure. If loosening is related to abnormal strains at the bone-implant interface, polyethylene wear is mainly caused by the lack of congruency during implant motion, and thus surgeons tried to improve TKA’s kinematics by introducing a second degree of freedom in their implants. Mobile-bearing knee replacements are based on a mobile polyethylene insert that articulates with a metallic femoral component and a metallic tibial tray. Those TKA designs have sought to increase congruency without increasing the stresses on the implant fixation. In vitro kinematic studies have shown reduced polyethylene wear in mobile bearings because of increased implant conformity and reduced polyethylene contact. In vivo kinematic analysis tends to confirm that mobile-bearing implants allow more natural knee movement. Despite several prospective, randomized studies having been performed, there is no clinical evidence supporting mobile bearing superiority over fixed-bearing designs. Studies focusing on gait parameters, clinical scores, or implant survival failed to confirm in vitro substantial advantage of mobile-bearing implants. More, recent improvement in polyethylene materials might solve wear issues: the last generation of cross-linked polyethylene, associated with a more morphometric design will probably provide superior implant survivorship and more physiological knee biomechanics.

Effect of Abrasive Waterjet Machining Parameters on Hybrid AA6061-B4C- CNT Composites

In general, Metal Matrix Composites (MMC)are very hard to machine using conventional machining due to complexity towards elevated temperature and tool wear issues. Abrasive water jet machining is a very efficient machining process which overcomes tool wear issues and cutting temperature issues. In this research study,AA6061-B4C- CNT was machined using Abrasive Waterjet Machining under different process parameters such as mesh size, abrasive flow rate, pressure and traverse speed. Boron carbide was used as reinforcement and Carbon Nanotube (CNT) was used as a solid lubricant. Two different composition of boron carbide (5, 15 vol%) and CNT (5, 15vol%) with residual volume percentage of aluminium as a core material were fabricated using stir casting method. The Machining approach is based on the Taguchi L9 orthogonal array design to enhance the Abrasive waterjet process parameters effectively. Then the multiple responses were investigated such as kerf taper geometries (θ), surface roughness (Ra) and material removal rate (MRR). The features of different machined surface regions were studied using Scanning electron microscopy (SEM). The investigational results indicate that increasing reinforcement improves the kerf taper angle under the significant parameter of traverse speed and decreasing the reinforcement leads to the lower surface roughness under significant parameter of pressure and traverse speed. It was observed that increasing reinforcement increasing the Material Removal Rate under the significant contribution of reducing mesh size of abrasive particles and inclined velocity.

Drilling and Milling µEDM – A Comprehensive and Comparative Evaluation

This paper accentuates the inherently persistent tool wear issue and its consequences in variants of micro-electro discharge machining (µEDM). µEDM-drilling and µEDM-milling, two important variants of µEDM have been currently considered for the analysis as they have distinct feed directions for tool electrodes. The difference in feed directions of the processes provide distinct scope for debris removal and hence dissimilar machining time, material removal rate (MRR), tool wear etc. In order to quantify such effects, the processes are evaluated based on a scientific approach adopted in experimentation. On analysis, the effects of poor evacuation of debris on tool wear and dimensional inaccuracies in work piece was found dominating in case of µEDM-drilling.

EVALUATING THE INFLUENCE OF BENDING STRESS ON A 1H18N9 STEEL SHAFT WEAR PROCESS IN A WATER LUBRICATED SLIDING BEARING WITH A RUBBER BUSHING

The issue of excessive wear of shaft journals co-working with a rubber bearing has been unexplained so far. Premature and sometimes very intensive wear of ship sliding bearings in water conditions is the reason for carry out very expensive and more frequent than expected repairs. The authors (E. Piątkowska, W. Litwin) made an attempt to find a case that influences the value of this wear described in the paper “Attempt at Evaluating the Influence of Bending Stress on Shaft Wear Process in Water Lubricated Sliding Bearing with Rubber Bush” (TRIBOLOGY 1/2017). These studies, however, did not explain the dependency of the wear process but showed how to progress further to find the answer to the question about the effect of bending stress on shaft wear. The research is continued on a modified test stand, and their results are presented in this paper. The profilographometer was used to evaluate the wear of the journal shaft. To compare wear intensity, roughness profiles have been 'removed' from the journals both before and after co-operation. They were compared in terms of bending stresses and bending moments.

Study on Abrasive Wear of Brake Pad in the Large-megawatt Wind Turbine Brake Based on Deform Software

For the friction and wear issues of brake pads in the large-megawatt wind turbine brake during braking, this paper established the micro finite element model of abrasive wear by using Deform-2D software. Based on abrasive wear theory and considered the variation of the velocity and load in the micro friction and wear process, the Archard wear calculation model is developed. The influence rules of relative sliding velocity and friction coefficient in the brake pad and disc is analysed. The simulation results showed that as the relative sliding velocity increases, the wear will be more serious, while the larger friction coefficient lowered the contact pressure which released the wear of the brake pad.

Fuel economy in gasoline engines using Al2O3/TiO2 nanomaterials as nanolubricant additives

Energy resources are of strategic interest worldwide. Transportation sector is a principal consumer of different energy resources, therefore reducing the consumption of vital energy resources is critical in automobiles. The friction and wear issues impact the energy efficiency of engines, therefore it is an important development of the lubricant for saving energy. The current study supports that goal. This study deals contribution of Al2O3/TiO2 hybrid nanoparticles as nanolubricants to improve gasoline engine efficiency and fuel economy. The gasoline engine performance characteristics were evaluated experimentally using an AVL dynamometer under different operating conditions including the New European Driving Cycle (NEDC). Additionally, the engine was tested under critical operating conditions (warm-up phase). The results showed that using Al2O3/TiO2 nanolubricants increases the brake power, torque, and mechanical efficiency, while the brake specific fuel consumption (BSFC) reduced owing to the mechanical efficiency of the engine improved by 1.7–2.5%, as compared to the engine oil without nanoparticles. Hence, the vehicle fuel consumption during NEDC could be improved up to 4 L per 100 km in the urban. Furthermore, FESEM, EDS line scanning, XPS, and Raman spectroscopy were conducted to understand the major tribological reasons for improving the engine performance to link tribological tests in the laboratory with actual engine performance. Eventually, the results suggest that nanolubricants provide economical engines with high efficiency that it may be an appropriate direction for vehicle manufacturers and users to suppress the engine fuel cost with engine durability under different operating conditions.

Maximizing Drilling Performance through Enhanced Solid Control System

High solid content in drilling mud may affect its properties and result in uncertainties at downhole condition. It eventually contributes to poor rig operation performance and operating cost. This research focus on developing solid control system that is suit for drilling 12.25-inch hole. The first part discussed the performance of Rate of Penetration (ROP), Equivalent Circulating Density (ECD) and drill string drag while the second part of the research discussed about the effect of solid control system performance to mud properties Plastic Viscosity (PV), Yield Point (YP) and Low-Gravity Solid (LGS). The input parameters were gathered from two different set up of solid control systems that were used in Well A and Well B. The result is mainly based on the performance of original solid control system new design versus old design. Installation of distributor tank and channel the mud to respective shale shakers significantly enhanced the system and operational performance. The ROP at 12.25-inch drilling were improved by 20%. New design improved average the ECD margin by reducing additional pressure exerted using original mud from 4.9% to 2.9%. High ECD margin is not recommended because it can break the weak formation. Mud properties while drilling the 12.25-inch hole section; PV, YP and LGS values were improved by 14 %, 17 % and 25 % respectively. Proper mud flow control and routing system at new develop design of solid control system effectively removed the solid in the drilling fluid. This improvement minimizes the tendency of frequent mud flow, screen mesh plugging and tool wear issue. Mud properties such PV, YP and LGS were maintained with an acceptable mud design envelope.

Robust control of mode transition for a single-motor full hybrid electric vehicle

The single-motor full hybrid electric vehicle tends to suffer drivability and excessive clutch wear issues during the mode transition from electric driving to hybrid driving because the single motor must simultaneously propel the vehicle and divert torque via clutch engagement to start the engine. In this study, a novel four-phase compound robust control method consisting of the feedforward–feedback technology and the robust compensation approach is proposed to address these problems during the mode transition. The whole mode transition process was divided into four consecutive phases according to the operating status of engine and clutch. In each phase, a nominal controller based on the feedforward–linear quadratic regulator feedback technology is first designed for the nominal linear model to guarantee a desired control performance. And then, the nonlinear uncertain part of the engine/clutch torque and the vehicle resistant torque as well as the model parameter uncertainties are all considered as equivalent disturbances, and a robust compensator is introduced to suppress the effect of equivalent disturbances. Simulation is performed to validate the effectiveness of the proposed control method. The results show that the four-phase compound robust control method can achieve better vehicle drivability and minimize clutch wear during the mode transition from electric driving to hybrid driving even in the presence of various torque disturbances and parameter uncertainties.

Performance and wear mechanisms of novel superhard diamond and boron nitride based tools in machining Al-SiCp metal matrix composite

Metal matrix composites are the desired materials in aerospace and automotive industries since they possess high specific strength. However addition of reinforcement to the matrix material brings the adverse effects of high wear rate of tool materials used in their machining. The current study addresses the issues of wear and performance of superhard tools when high speed machining cast Al-Si alloy reinforced with particulate SiC (20% vol.). A wide range of developed superhard materials was compared to the commercial PCD tools. Nano grain sized wBN-cBN, binderless cBN; B6O-cBN, nano-diamond with WC binder; diamond/MAX-phase; and diamond/SiC tool materials were employed. Use of nano-diamond/WC and diamond/MAX-phase composites resulted in their rapid deterioration due to primarily adhesive pluck-out of diamond and binder phase. Diamond/SiC material exhibited slightly lower performance than the PCD, with the primary wear being the abrasive on the SiC binder phase. Machining with cBN-based tooling at lower speed lead to formation of stable build-up layer, frequently accompanied by severe seizure of tool and workpiece material. However at speed of 400m/min the absence of such build-up layer caused rapid tool wear. Presence of chemical and diffusional wear mechanisms for diamond tooling has been confirmed through scanning and transmission electron microscopy. Archard-type model of abrasive tool wear was developed for modelling of tool deterioration for all studied tool materials.

Investigation and Interpretation of Flooring Wear Development for Pedestrian Slip Resistance Assessments

ABSTRACTSurface conditions of pedestrian footpaths and walkways continually change throughout their services. Many causes may contribute to the variation of surface qualities, but a decline of slip resistance functioning is a critical problem for the pedestrian safety of walkway surfaces. Despite the importance of flooring wear issue, their ensured operations and influences on slip resistance performance against pedestrian falls have not been systematically investigated. The present study aims to understand wear progress of floor surfaces, investigate the mechanism of surface changes due to wear advances, and recognize their impacts on slip resistance operations. To measure traction properties and characterize wear behaviors of walkway surfaces, slip resistance tests were operated among three different types of floor specimens with a similar range of topographic characteristics and two dissimilar shoes. Wear formations and developments of the floor specimens were comprehensively assessed by a combination of numerical and microscopic investigations. The test outcomes evidently presented that the initial surface finishes of floor specimens were extensively modified by direct (straight move) and indirect wear processes (reverse and joint moves) and significantly affected slip resistance performance. The idea explored in this study may help to uncover valuable information for better understanding of the complex nature of slip resistance properties amongst the shoes, floors, and environments and have possible applications for the safety design improvements of pedestrian floors and floor coverings.

Intelligent clutch control with incremental encoder to improve wear issues of an intercept pendulum in real time

A pendulum impact tester is a technical device which is used to perform plasticity characterizations of metallic materials. Results are calculated based on fracture behavior under pendulum impact loadings according to DIN 50115, DIN 51222/EN 10045. The material is held at the two ends and gets struck in the middle. A mechanical Problem occurs when testing materials with a very high impact toughness. These specimen often do not break when hit by the pendulum. To return the pendulum to its initial position, the operator presses a service button. After a delay of approximately 2 seconds a clutch is activated which connects the arm of the pendulum with an electric motor to return it back upright in start position. At the moment of clutch activation, the pendulum can still swing or bounce with any speed in any direction at any different position. Due to the lack of synchronization between pendulum speed and constant engine speed, the clutch suffers heavy wear of friction. This disadvantage results in considerable service and repair costs for the customer. As a solution to this problem this article presents a customized technical device to significantly increase the lifetime of the clutch. It was accomplished by a precisely controlled activation of the clutch at a point of time when pendulum and motor are at synchronized speed and direction using incremental encoders.

Influence of particulate reinforcement on microstructure evolution and tensile properties of in-situ polymer derived MMC by friction stir processing

The authors recently reported a novel in-situ method of fabricating nano-polymer derived metal matrix composite (PD-MMC) by friction stir processing (FSP) and addressed the issues of tool wear and particle agglomeration. In the present work, the microstructural evolution and tensile properties of the processed composite are reported. The microstructure during FSP evolved by discontinuous dynamic recrystallization. In the composite, fine ceramic particles pin the grain boundaries, preventing grain growth resulting in a fine grain (2μm) structure being retained. FSPed Cu (processed with the same process parameters as that of the composite) exhibited a grain size of 100μm compared to 400μm in the base Cu. The composite microstructure was characterized by equiaxed grains with narrow grain size distribution and a high fraction (>80%) of high angle grain boundaries. The combined effect of grain refinement and ceramic particle incorporation lead to a twofold improvement in the proof stress of the composite (201MPa compared to 98MPa of base copper). The ultimate tensile strength improved by 33% and there was small drop in the ductility of the composite when compared to base Cu. Kocks-Mecking plot of the composite showed stage III of work hardening.

Exploring wear detection method for special drilling parts in liquid media

In special drilling projects conducted under arduous liquid conditions, wear-related failures of hardmetal moving parts can easily trigger accidents. The problem is that no acceptable method is available to detect such wear failures. This work endeavors to propose a novel wear detection method for preventing the hardmetal moving parts from the accidents: (i) designed and optimized an attachment device for a conventional ball-on-disc tester; (ii) used a part-screw downhole motor made of cemented carbide as a typical example to validate the detection method; and (iii) offered solutions to wear issues. The designed device consisted of top cover, sleeve, and working platform. The device strength is inspected through finite element static stress, and its structure is then optimized using the zero-order method. Wear experiments are performed on the screw downhole motor rotor under conditions of air, water, and mud showed that the main wear mechanisms in air is abrasive wear, whereas motors experienced fatigue abrasive and tribo-corrosion wears under water and mud conditions. As a result, the solutions are proposed based on the wear mechanisms to prevent the wear failures.