Wear Area Research Articles

Online Detection of Turning Tool Wear Based on Machine Vision

Abstract To identify the tool wear in real time, this article builds the online detection system and proposes an integrated image processing method to measure the wear width for flank face of turning tool. First, the images of flank face wear are collected by the image acquisition system. Second, the collected images are cropped near the flank face wear, and the wear area and background for the cropped images are separated by k-means clustering algorithm. Then, the wear edge is identified by the grayscale transformation and edge detection algorithm, and the wear width is calculated by Hough transformation. Finally, the cutting experiment is carried out on MAG HTC200 CNC lathe to verify the validity of the proposed method, and the results show that the identified wear width by the proposed method and actual measured wear width for flank face of turning tool are in good agreement and show the proposed method is effective and have micron scale calculation accuracy.

Study of the Two-Phase Flow and Wear of a Pump with Mixed-Size Particles

This paper used a combination of numerical simulations and experiments to study the hydraulic performance and the wear law of a centrifugal pump when conveying mixed particle sizes. The numerical simulation was based on the Discrete Phase Model (DPM). The model was used to complete the mutual coupling between the solid particles and the flow field as well as the calculation of wall wear. The results show that under the same mass concentration, the head and the efficiency of the centrifugal pump were significantly improved with an increase in the small particle composition. Compared with transporting single-sized large particles, the wear law of the mixed particle size on the flow parts changed greatly. The addition of a certain number of small-sized particles to large-sized particles aggravated the wear of the impeller, but when the small particles occupied a relatively high proportion, the wear area of the impeller was reduced even smaller than that for the transportation of single-sized large particles.

Prediction Model of Casing Wear Shape and Residual Strength under Compound Modes

Summary Casing wear is one important reason for wellbore integrity failure in deep and ultradeep wells. Field measurement data show that there are multiple wear areas on the casings in some well sections, and the wear shape is more complicated than a single crescent, which exceeds the scope of conventional casing wear theory. To solve this problem, prediction models of casing wear shape and residual strength under compound modes are built. First, the compound wear mode is divided into four categories according to field measurement results, and the prediction model of wear shape is built. Second, the failure mechanism of casing with the compound wear shape is revealed through experiment and numerical simulation. Next, the influences of various factors on casing strength are revealed, and an intelligent prediction model of casing strength is built. Last, a software platform of casing wear and strength prediction is developed and applied to an ultradeep well. The results show that casing wear shape is not only a single crescent but also has the modes of overlapping, separating, and crossing crescents. Different wear modes are caused by different reasons: overlapping is caused by the change of wear diameter, separating by a large deviation of wear position, and crossing by slight deviation of wear position. The failure mechanisms of worn casing under internal and external pressures are different: Internal pressure failure is one kind of strength failure while external pressure failure is one kind of stability failure. The critical internal pressure of the casing is mainly determined by the main wear area but irrelevant to the secondary wear area, yet the critical external pressure is closely related to both the main and secondary wear areas. Casing strength will be overestimated if casing wear is neglected, so casing wear should be sufficiently considered in ultradeep well design.

The Correlation Between Wear Evolution and Mechanical Property Degradation of Wire Rope in a Multilayer Winding System

Abstract Surface wear is one of the major causes of damage to wire ropes in multilayer winding systems. This damage leads to performance degradation and affects the service safety of wire rope. To reveal the wear evolution and the performance degradation of wire rope in service, the correlations between the wear characteristic parameters and the residual strength were investigated. The results show that the variation in the wear parameters is affected by the wear distribution and the structure of the wire rope. The main wear mechanisms between wire ropes are adhesion wear and abrasive wear. Different wear parameters should be combined to evaluate the wear state of the wire rope. The tensile temperature rise could accurately reflect the wear evolution of the in-service wire rope under the condition of a large wear degree. The negative correlation between the residual strength and the wear area of the damaged rope samples is the strongest.

Measuring the “Clothing Mountain”: Action Research and Sustainability Pedagogy to Reframe (Un)Sustainable Clothing Consumption in the Classroom

This study's purpose is to support the practice of transformative learning by reporting on a class project which examined unsustainable clothing consumption behaviors using action research and the holistic principles of the Burns Sustainability Pedagogy. The study has three objectives: to engage students in action research in which students were asked to measure the clothing volumes bought, used, and discarded during one school semester; to reflect on their unsustainable clothing consumption practices through facilitated peer discussion; and to use educational intervention as a pedagogical tool to expand students' awareness of unsustainable clothing consumption behaviors to cultivate learners capable of effecting holistic sustainable change. The “clothing mountain” was assessed among 755 students, who purchased 10,931 garments for a total of $754,239. The findings provide a baseline for improving the textile and apparel scholarship on sustainability teaching and learning, particularly in the areas of responsible clothing purchases, wear, and disposal.

Implementation of a Fatigue Fracture Approach to Grinding Wheel Wear Using Numerical Simulation

The paper proposes an approach to assessing the grinding wheel wear, which includes the wear of grains and pulling them out of the bond, based on fatigue failure under cyclic loads caused by cutting forces, with a period of the order of microseconds. This approach is implemented on the basis of stress life calculation in the ANSYS Fatigue module using loading data obtained from the numerical simulation of grain-workpiece interaction. The simulation results allows to obtain the grain wear area, the level of bond fatigue fracture and the possibility of self-sharpening of the grinding wheel for a given grain size and operation conditions.

Machine vision based adaptive online condition monitoring for milling cutter under spindle rotation

Tool condition monitoring (TCM) is an important guarantee for quality evaluation of products and parameter optimization of machining operations. The direct methods of TCM have made significant progress in condition recognition and wear measurement. However, these methods based on a single image that reflects the tool condition inevitably bring downtime to the machine tool. Moreover, a single image cannot reflect the tool wear characteristics integrity because the morphology of tool wear is complex. Regarding the issue above, the aim of this paper was to adaptively online monitoring for milling cutters. Firstly, tool condition image sequence (TCIS) is proposed in successive images to express and enhance tool wear characteristics from multiple angles. Secondly, the time-sequential gradient map between adjacent images is constructed based on histograms of oriented gradient. It is used to capture the initial frame of TCIS. Then, the subsequent images are encoded into the classification model. A logistic regression algorithm is applied to train the classification model to capture the end frame of TCIS. Finally, the tool wear area is located by balancing the rectangular box of wear area and benchmarks of wear measurement and is tracked based on the motion model and the local search. In the experiment of accelerating milling cutter life and three different failure phenomena, the recognition accuracy in the initial and end frame of TCIS is 100%. The average measurement accuracy of flank wear based on the proposed method in two experiments is up to 97.02% and 94.71%, respectively. These operations are automated online and provide complete data support for TCM.

Improvement of the lubrication performance of an ester base oil with coated ferrite nanoadditives for different material pairs

In the present work, lubrication properties (friction and wear) of a synthetic ester oil, tris(2-ethylhexyl) trimellitate (TOTM) containing ferrite nanoparticles coated with oleic acid (F3O4-OA) were investigated for two different material pairs: steel ball-steel disc and silicon nitride ball-steel disc. Thus, four TOTM nanolubricants were formulated: TOTM + 0.010 wt% Fe3O4-OA, TOTM + 0.015 wt% Fe3O4-OA, TOTM + 0.020 wt% Fe3O4-OA and TOTM + 0.025 wt% Fe3O4-OA showing all of them a moderate time stability due to the oleic acid coating. Wettability behaviour of the ferrite-based nanolubricants on steel surface was analysed, revealing that the addition of Fe3O4-OA nanoparticles in TOTM decreases the contact angle between the steel surface and TOTM lubricant surface. Friction sliding tests were performed with the neat TOTM and with the formulated nanolubricants under a 20 N of load. All nanolubricants showed lower coefficients of friction than those reached with TOTM base oil for both material pairs. Worn area was significantly reduced for all Fe3O4-OA concentrations in the steel-steel contact and for the highest concentrations in the silicon nitride-steel contact. Specifically, the largest achieved reductions were for the TOTM + 0.010 wt% F3O4-OA nanolubricant: 43% reduction in friction (silicon nitride-steel) and reductions of 17% in wear track width, 42% in wear track deep and 36% in area (steel-steel). In addition, roughness analysis and Raman microscopy of the tested discs showed that tribofilm formation and surface repairing mechanisms occur.

Study on the Non-Steady-State Wear Characteristics and Test of the Flow Passage Components of Deep-Sea Mining Pumps

In the process of conveying coarse-grained minerals, the internal flow-through passage components of mining pumps are subject to wear. The flow of coarse particles in such pumps is complex and changes constantly, making it necessary to study the non-steady-state wear characteristics and test the flow passage components. The evolution of the surface wear rate for the flow passage components during one third of a rotation cycle (120°) of a mining pump impeller with small, design, and large flow rates was analyzed in this study based on a discrete phase model (DPM). The flow that occurs during an entire rotation cycle of the impeller was investigated. The wear test was carried out with a small test pump with the same specific speed as and a similar structure to that of the deep-sea mining pump. The test results were compared with the numerical calculation results of the deep-sea mining pump obtained by using the same numerical calculation method and wear model, and the test wear area was found to be more consistent with the numerical calculation wear area. The results show that the numerical calculation method used in this article can more accurately predict the surface wear of the passage components of the mining pump and provides a suitable method for the prediction of the wear characteristics of the mining pump.

Investigation on the effect of powder size on the properties of cladding layer based on RSM

This paper aims to reveal the influence of different TiC powder particle sizes and process parameters on the cladding morphology of composite materials and realize the forming control of cladding layer. The center composite design of response surface method was adopted to analyze the effects of laser power, scanning speed and particle size on the cladding morphology of composite materials. The mathematical models between process parameters, TiC powder particle size and micro-hardness, wear volume of the composite cladding layer were established and confirmed by variance analysis and model verification. The results indicate that powder particle size has most significant effect on the micro-hardness, and it increase with the increase of scanning speed, laser power and powder particle size; the effect of powder particle size on the wear resistance of the clad layer is most significant, and it increases with the increase of powder particle size and decreases with the increase of scanning speed and laser power. The optimization of process parameters is carried out with the target of maximizing micro-hardness and minimizing wear area. The error rates between prediction and experiment for the micro-hardness and wear area are 0.1% and 2.0% respectively. The results of this paper provide a reference for the prediction and control of the cladding morphology of composite materials.

Геохімічні особливості нагромадження і міграції Стронцію в торфах Львівської області

The article is devoted to the study of geochemical characteristics of the distribution, accumulation and migration of Strontium in the lowland peats of the Lviv region, both laterally and vertically, and to identify the main factors influencing the formation of its concentrations. A significant uneven distribution of concentration, high dispersion and variability (coefficient of variation – 116.61, standard deviation – 564.11) of Sr in peats within deposits, districts and regions both with depth and area of distribution and high content indicators were established Sr relative to clarks of the lithosphere, soils, plant ash (CC relative to the lithosphere = 1.42; CC relative to soil clarks = 1.94; Сs relative to background values in the soils of Ukraine = 4.56; CK relative to clarks of terrestrial plants = 1.61). The content of Sr in the peat of the Lviv region ranges from 40–3190 mg/kg (average content 483.75 mg/kg, median content (background content) – 250 mg/kg), which is due to natural-climatic, geological, lithological, hydrogeochemical and anthropogenic factors. The features of the distribution and the degree of concentration of Sr in the peatlands of the Lvіv region are mainly influenced by the chemical-mineralogical-petrographic composition of the bedrocks of the wear area during their weathering; terrain, climatic, geomorphological, tectonic and hydrogeological conditions of the area, which determine the of the weathering processes of the rocks in the wear areas, the degree of transformation of terrigenous material in the weathering processes, the rate of accumulation of biomass and the rate of its decomposition; features of water and mineral nutrition of the peatland. High concentrations of Strontium in the peat of the Lviv region reflect the local regional processes of the concentration of the element in the mass of peat and may indicate the accumulation of Sr of both natural and anthropogenic origin in the upper layers of peat profiles.There is an enrichment of Sr in the upper intervals of deposits (0–1 m) of deposits in the northeastern part of the Lviv region (Malopoliska peat region) is observed.

ОСОБЕННОСТИ МИКРОМЕТРАЖА ГИЛЬЗ ЦИЛИНДРОВ ДВИГАТЕЛЕЙ ЯМЗ

The most important part that limits the engine life is the cylinder liner. Before fault finding in the cylinder liners, it is necessary to carry out the micrometry of their surface to identify the areas of greatest and least wear. For carrying out the micrometry and testing it on new and worn cylinder liners, 40 cylinder liners of YaMZ engines were used. The working surface of the cylinder liners was controlled by the inner diameter, which was measured in eight sections and two planes. The micrometry was carried out with an indicating hole gauge with a digital head of increased accuracy with a sensitivity of 0.001 mm; ten new cylinder liners met the technical requirements. The micrometry of thirty cylinder liners showed that the greatest wear was 253 μm in the connecting rod oscillation plane and 189 μm in the perpendicular plane. It was found that liner micrometry should be particularly thoroughly carried out at the top of the cylinder liners. The greatest wear occurs at the top piston ring stop at the start of the expansion stroke, with more intensive wear in the connecting rod oscillation plane due to the normal force. The uppermost part of the cylinder liners is the wear-free liner flange, the diameter of which indicates the original dimensions of the liner bore. However, it must also be measured due to the effects of high temperatures, changes in the crystal pattern of the material, oxidation and the presence of combustion products in the form of carbon deposits. The lower part of the cylinder liner is subject to wear due to the friction of the piston skirt against its surface. However, due to the lower temperature, the better lubrication, the much larger contact surface and the correspondingly lower pressure, increased wear here can only occur if there are misalignments in the crank mechanism: the misaligned crankshaft axle or the bent connecting rod.

73 - Wear of Orthodontic Aligners Through Simulated Bruxing

Studies to simulate bruxing on polymeric materials can provide clinicians with important information when selecting materials for fabricating orthodontic aligners/retainers. The aim of this study was to evaluate and compare the wear produced by one-year equivalent of simulated nighttime bruxing on clear aligners. A set of upper and lower first and second premolars and molars were milled out of a zirconia puck and then micro-CT scanned for manufacturing the aligners. The aligners (n=2 for each material) were made of six materials: Bioacryl (B) ComfortTrack (CT) Duran (D) Endure (E) Hard Cast (HC) and Invisacryl (I). 12k cycles, i.e. approximately one-year equivalent, of moderate nighttime bruxing at 75 N was applied to the samples using the chewing simulator at the Minnesota Dental Research Center for Biomaterials and Biomechanics (MDRCBB). The MDRCBBs contact profiling system and the corresponding software Ansur were used to measure the volume, surface area, and maximum and mean depths of wear. Furthermore, micro-CT images of the samples were taken for fracture analysis. The combined volume loss ranged from 0.056 mm (CT) to 0.502 mm (B), with CT < D < E < HC < I < B. The wear surface area for the maxillary ranged from 1.8 mm (D) to 10.9 mm (B), with D < CT < I < HC < E < B. That for the mandibular ranged from 2.7 mm (CT) to 20.15 mm (HC), with CT < D < B < E < I < HC. The maxillary maximum wear depth ranged from 32.83 m (D) to 137.61 m (B), with D < I < HC < E < CT < B. The mandibular maximum depth ranged from 60.11 m (CT) to 112.75 m (B), with CT < I < HD < D < E < B. Fractures were observed at the mandibular internal fitting surface of the buccal-lingual & mesial distal cross-sections of both samples of E and CT and on one of the HC samples. Only one maxillary of D had a fracture observed at the same area. The wear rate of orthodontic aligners under bruxing was highly material-dependent. Samples with higher wear rates did not fracture but those with the lower wear rates fractured.

Особливості зносу пар тертя канат-блок і канат-барабан за умов роботи підйомно-тягових пристроїв

The features of wear of rope-block and rope-drum friction pairs of lifting and traction devices operating in the conditions of a hot manufactory of the metallurgical plant and also the mining and beneficiation plant were studied. It is shown that the causes of wear of the elements of the rope-block and rope-drum friction pairs are the interaction in their contact zones, which occurs in the surface layers under the influence of high contact stresses, friction, cyclic loads, abrasive particles, active atmospheric and industrial environments. It was found that these actions lead to irreversible processes of accumulation of stresses and plastic shifts, which have a periodic and heterogeneous character. It is shown that the strength of the lifting or traction rope is determined by the degree of wear of the wires, primarily those in contact with the block and the drum. The structural changes in the surface layers of the wires and the mechanisms of the formation of wear particles were analyzed, which confirm the heterogeneous nature of the wear of the wires in the strands of the rope. Areas of abrasive wear were also observed on the worn surface of the wires, where under the action of solid foreign particles of contamination with sharp corners falling between the wires, the surface of the wires was undercut. It is shown that the presence of non-metallic inclusions leads to the formation of wear particles and fatigue cracks. It was established that the wear of friction pairs of rope-block and rope-drum of hoisting and traction devices has a fatigue-corrosive nature, and the main mechanism of the formation of wear particles is the development of plastic shifts in the surface layers of friction pairs and their separation by plastic exfoliation and abrasive and corrosive destruction. The shape of the wear particles depends on the type of material and the conditions of their formation. It is proposed to take measures regarding structural approaches to friction pairs, taking into account their working conditions, in order to reduce contact stresses and increase their wear resistance, reliability and durability.

Wear Characteristics of 22MnB5 Boron Steel under Friction Micro Pin-on-Disks Test

22MnB5 Boron Steel can be considered as emerged material for high strength and low weight application. This material potentially used in abrasive condition such as cutting tool or brake pad where high friction resistance applies. In this study, the wear characteristics of 22MnB5 was investigated under the frictional tests via micro pin-on-disk. 22MnB5 Boron Steel was prepared the form of round shape within the size of 2.6 mm thickness and 12 mm diameter by using laser cutting. 4 different samples were tested namely blank (sample A), self-hardening heat treatment (sample B), 60 HRC hot stamped (sample C) and 70 HRC hot stamped (sample D). The results show that Coefficient of Friction (COF) increased as the hardness of 22MnB5 decreased. Low COF of 0.2114 recorded for sample D with 70 HRC hardness. The COF increased to 0.24, 0.29 and 0.3 when sample C (60 HRC), sample B (52 HRC) and sample A (45.5 HRC) applied respectively. For pin-on disc test, worn area decreased as the hardness increased. 22MnB5 that prepared with the highest hardness of 70 HRC presented smallest wear area of 700 µm x 2400 µm. It is followed by 800 µm x 2400 µm, 1000 µm x 2400 µm, 1600 µm x 2800 µm, when sample C, B and A were scratched. Observation on the worn surface revealed delamination of 22MnB5 surface in the form of fragmented flaking debris.

Enhancing Wear Resistance and Cutting Performance of a Long-Life Micro-Groove Tool in Turning AISI 201

Tool-chip friction increases cutting temperature, aggravates tool wear, and shortens the service life of cutting tools. A micro-groove design of the rake face can improve the wear performance of the tool. In this study, we used the finite element simulation “Deform” to obtain the temperature field distribution of the tool rake face. The size of the micro-groove was determined by selecting a suitable temperature field combined with the characteristics of tool–chip flow in the cutting process, and the tool was prepared using powder metallurgy. The three-direction cutting forces and tool tip temperature were obtained by a cutting test. Compared with the original turning tool, the cutting force and cutting temperature of the micro-groove tool were reduced by more than 20%, the friction coefficient was reduced by more than 14%, the sliding energy was reduced and the shear energy was greatly decreased. According to the analysis of tool wear by SEM (scanning electron microscope) and EDS (energy dispersive X-ray spectroscopy), the crater wear, adhesive wear and oxidation wear of the micro-groove tool were lower than those of the original turning tool. In particular, the change in the crater wear area on the rake face of the original tool and the micro-groove tool was consistent with the cutting temperature and the wear width of the flank face. On the whole, the crater wear area and the change rate of the crater wear area of the micro-groove tool were smaller. Due to the proper microgroove structure of the rake face, the tool-chip contact area decreased, and the second rake angle of the tool became larger. Hence, the tool-chip friction, cutting forces, cutting energy consumption were reduced, tool wear was improved, and the service life of the micro-groove tool was five times longer than that of the original tool.

The Effect of Carbon Fiber Types on Tool Wear During Edge Trimming of 0 deg, 45 deg, 90 deg, and 135 deg Carbon Fiber-Reinforced Plastic Laminates

Abstract Carbon fiber-reinforced plastics (CFRP) composites are difficult-to-machine materials due to extensive tool wear. This article investigates the impact of carbon fiber types on tool wear in edge-trimming CFRPs, each with the ply angle of 0 deg, 45 deg, 90 deg, or 135 deg, using uncoated tungsten carbide endmills at the high spindle speed of 6000 rpm and the constant feed of 0.0508 mm/rev. Three distinct types of carbon fiber tows, including T300 as standard modulus (SM), IM-7 as intermediate modulus (IM), and K13312 as high modulus (HM), have been vacuum infused into CFRP laminates and edge trimmed to investigate wear characteristics. Three wear criteria measured are flank wear, edge rounding radii, and worn area. The results show that tool wear is influenced by carbon fiber properties, such as fiber tensile strength, tensile modulus, and fiber microstructure. Overall, IM carbon fibers with the highest tensile strength produced the most extensive tool wear due to the abrasive carbon fibers. Of four fiber directions, the largest tool wear was obtained from the 45 deg angle, while the lowest tool wear occurred in the 0 deg angle.

Study of Wear and Redistribution Dynamic Forces of Wheel Pairs Restored by a Wear-Resistant Coating 15Cr17Ni12V3F

The relevance of this study lies in the need to research the wear process of the elements of dynamic systems and to establish the dependence of the geometric and structural characteristics of wheels restored by plasma surfacing with a coating of 15Cr17Ni12V3F on dynamic, cyclically varying loads. The study was aimed to establish the dependencies between the deviation of the wear area, the formation of contact and fatigue stresses, and the change in the phase structure of the wheel defect. It is important to justify the permissible limits of wear of the transverse profile in the contact zone of a wheel and ridge. The object of the study was the dynamic interaction of the “wheel–ridge–rail contact surface” system. To achieve the goal, the following methodology was adopted: kinematic analysis, strength calculation, the use of mathematical analysis in dynamic system modelling, virtual modelling in the SOLIDWORKS software environment of the GearTrax application, experiment planning, and model correction through the results of metallographic studies. The results of the study are presented as reasonable prediction criteria that consider contact cycles during the formation of fatigue stresses at the stage of defect origin. The process of the dynamic interaction of the contact worn profile of a wheel with a railway rail is explored. Polynomial equations are proposed to substantiate the optimal design and technological parameters of designing a railway carriage wheel. The permissible limits of wear of the transverse profile in the contact zone of the wheel and the ridge are justified while taking the coefficient of the reduction of contact stresses in the metal into account. The dependences of the change in static load on the utilization factor of the railway carriage load capacity are established. The dependences of changes in fatigue stresses on the design deviation of the contact area of wheel wear are established. It is confirmed that the stress concentration under cyclic loads is formed in the ferritic layers of the material structure before the appearance of wear.

Life and Flaking Failure of 13Cr-2Ni-2Mo and SUS440C Stainless Steel Bearings in Water

The rolling contact fatigue (RCF) tests of 13Cr-2Ni-2Mo and SUS440C stainless steels were carried out in water. Their groove surfaces and the flaking failures were observed. Some hair cracks, wear and high roughness area were found. While the flaking depth of SUS440C was shallower than that of 13Cr-2Ni-2Mo stainless steel, the RCF life of the latter was longer than the former one. The flaking depth did not influence the RCF life.

Technical Considerations for an Anteromedializing Tibial Tubercle Osteotomy

Background: Tibial tubercle osteotomy and distal realignment allows for adjustment to the patellofemoral articulation in order to improve patellar tracking and redistribute patellar contract pressures. Indications: A healthy, active 39-year-old woman status post right knee tibial tubercle osteotomy presented with &gt;2 years of patellar instability symptoms in the left knee. Imaging revealed a tibial tubercle to trochlear groove (TT-TG) distance of 21 mm and patellar tendon lateral trochlear ridge (PT-LTR) distance of 14 mm. Technique Description: After knee arthroscopy is performed, an open incision is made along the inferomedial patellar tendon. Two pilot holes are created before a sagittal saw is used to make the tibial tubercle osteotomy, before completing it with an osteotome. Anteromedialization and/or distalization of the osteotomy is performed relative to templated values in order to improve patellar articulation. After correction, 3 bicortical screws are placed to achieve stable fixation. Results: There were no immediate complications following surgery. Surgical management led to improvement of the patient’s patellofemoral pain, which allowed return to prior baseline level of function. Discussion/Conclusion: The preferred technique for an anteromedialzing tibial tubercle osteotomy is presented. An anteromedializing tibial tubercle osteotomy is an effective surgical option for patients with evidence of patellar maltracking or central or lateral patellar chondromalacia whom have failed conservative management. This case demonstrates the efficacy of an anteromedializing tibial tubercle osteotomy to provide pain relief by improving patellar tracking and offloading patellar contact pressures on areas of prominent chondral wear.