Shear Blade Research Articles

Unsteady vane-rotor secondary flow interaction of the endwall region in a 1.5-stage variable-geometry turbine

Variable-geometry turbines present significant improvements in both off-design cycle efficiency and enhanced engine responsiveness for future adaptive cycle engines. The adjustable vanes regulate the through-flow capacity by varying the installation angle and thus unavoidably require endwall clearance, resulting in profound implications for vane and downstream blade rows. Unsteady numerical simulations are carried out to investigate the vane-rotor flow interaction under the zero and partial clearance type of the adjustable vane in a 1.5-stage variable-geometry turbine. First, specific vortical structures and loss characteristics of upstream adjustable vane leakage flow at turning angles of −5°, 0°, and +5° are described. Then, the basic mechanisms of vane-rotor secondary flow interaction between acquired upstream leakage flow and downstream blade rows secondary flow is explored by the time-resolved method and quantitative detailed analysis method. The results show that adjustable vane vortex core area is the primary cause of internal loss within the vortex, and the mixing and interaction between the leakage vortex and other vortex systems contribute to secondary loss in the vane. Due to the downstream blade shear action caused by different flow velocity on the suction and pressure surfaces, the vane leakage flow fragments upon entering the R1 blade passage and develops downstream of the endwall region. Compared to the vane with zero clearance case at same turning angle, the intensity of the R1 tip leakage vortex at the design turning angle and open turning angle is reduced by 47.4 % and 23.66 % with the upstream partial clearance, respectively. The unsteady vane-rotor secondary flow interaction under different turning angles has large influence on the flow structure and loss characteristics of the downstream blade rows, and results in significant differences in the variation pattern and trend direction of the turbine performance.

The effect of swirling shear blade on gas-liquid flow pattern and mass transfer performance in Venturi injector

To address the challenge of low mass transfer efficiency of gas-liquid reaction in traditional reactors, this study proposes a new method to improve the gas-liquid mass transfer efficiency by integrating swirl shear blades (SSB) into Venturi injectors. The gas-liquid flow patterns in the mixing and diffusion sections between the Swirl Venturi Injector (SVI) and the Traditional Venturi Injector (TVI) was compared, and it was found that the SSB significantly reduced the proportion of annular flow while increased the proportion of mist flow. The enhancement factor αE and the acceleration factor αA are applied to evaluate the mass transfer performance. Compared to TVI, the maximum αA of SVI was 29%, and the maximum αE was 43%. This work shows great potential in efficiently capturing gas components with low solubility in the liquid phase, thereby helping to achieve the goal of green chemical engineering.

Geometrically exact aeroelastic stability analysis of helicopter composite rotor blades in forward flight

In this paper, a sophisticated method for analyzing the geometrically exact aeroelastic stability of composite rotor blades in forward flight has been proposed. The unique advantage of the proposed method is to use the geometrically exact beam model with the updated Variational Asymptotic Beam Sectional analysis (VABS) for structural modeling to not only calculate the blade cross-sectional properties and blade spanwise deformations more accurately, but also take into account the effect of transverse shear deformation and blade initial twist and curvatures sophisticatedly. The Peters finite state airloads theory and the Peters-He finite state dynamic inflow model are coupled to calculate the three-dimensional unsteady airloads applied on the blade. The auto-pilot trim scheme is adopted to determine the blade pitch controls. The finite element spatial discretization method, the Newmark numerical integration method, the Newton-Raphson method and the moving-block analysis method are combined to solve the established geometrically exact aeroelastic equations and obtain the geometrically exact aeroelastic stability of composite rotor blades. The proposed method is validated by correlation with existing analytical results. The investigations show that the effect of transverse shear deformation on the aeroelastic stability of composite hingeless rotors in forward flight is non-negligible. Blade initial curvatures have significant effect on the aeroelastic stability of composite hingeless rotors in forward flight, which is not only related to the blade elastic couplings, but also to the advance ratio.

Automobile rear axle housing design and production process improvement using Failure Mode and Effects Analysis (FMEA)

The safety of automobile design is crucial to protect drivers, passengers, and other road users, ensuring reliable performance, accident prevention, and regulatory compliance.The rear axle housing in automobiles serves as a protective enclosure for the rear axle assembly, providing support, protection, and structural integrity for the drivetrain components. This research paper employs Failure Modes and Effects Analysis (FMEA) to comprehensively identify and assess common failures in the design and manufacturing process of rear axle housings in automobiles. The study highlights five critical failure modes, namely less durability, faulty blank, hole position out, burred edges, and bore position out. Through the application of recommended solutions, including design optimization, maintenance of shear blades, and the use of jigs, substantial reductions in Risk Priority Number (RPN) values were achieved. Specifically, the RPN values for the aforementioned failure modes were significantly decreased from 280 to 40, 256 to 48, 378 to 21, 378 to 45, and 392 to 56, respectively. Implementation of these solutions promises several benefits, such as enhanced customer satisfaction, reduced failure rates, elevated product/process quality and reliability, streamlined processes, and optimized resource utilization. This study emphasizes the significance of continuous improvement efforts in the automotive industry and demonstrates the pivotal role of FMEA as an invaluable tool for achieving and sustaining these improvements.

Metallurgical Investigation of Flying Shear Blades at Hot Rolling Rebar Mills

Metallurgical Investigation of Flying Shear Blades at Hot Rolling Rebar Mills

Recent Advances in Optimization Design and Performance Analysis of Vortex Pumps

Background: The vortex pump is a type of sewage pump renowned for its non-clogging performance. As the vortex pump has a special structure type, there are many vortex structures in the volute and impeller flow channel, which reduce the efficiency of the vortex pump. Reducing the energy loss and improving the efficiency of the vortex pump has been one of the main research objectives of designers. In this paper, the research progress of vortex pumps is summarized from the two aspects of transporting solid medium and low efficiency, which can provide a reference for future research. Methods: The latest patents and papers on vortex pumps were collected. The solid-liquid flow characteristics from the experimental and numerical perspectives, the influence of geometric parameters on external characteristics, and optimization design methods of the vortex pump were studied. Results: The particles, fibers, and cloth in the vortex pump will become trapped and blocked in the cavity. And the geometric parameters have an obvious effect on the pump. By using the intelligent optimization algorithm to optimize the impeller parameters, the pump efficiency can be increased by 10.25% under large flow conditions and the effective blade shear stress. Conclusion: The concentration and diameter of particles could change the performance of the pump. The retention and plugging of the solid medium in the vortex pump are related to flow structure and backflow. Appropriate geometric parameters should be selected when designing a vortex pump. Too large or too small a structure design will lead to poor performance of the vortex pump. This can be combined with intelligent optimization algorithms for pump design, which is a very effective method.

Metallurgical Characterization of Two 11th–12th Century Single-Bow Shears from Sigtuna, Sweden

Abstract Shears, being everyday objects, have received significantly less attention by archaeometallurgists than other edged tools or weapons. Yet, shear blades were forged with the same techniques as blades of, e.g. knives and swords. The most common shear type in ancient times was the bow shears, where the bow had to be flexible so it could be repeatedly bent without cracking or breaking. The shear-maker, therefore, faced the challenge of combining hard steel (the blades) with soft/flexible steel (the bow). In fact, bow shears are one of the first tools to be invented, where metal acts as a spring. Thus, ancient bow shears can be used for investigating the history and development of spring steel technology, which is currently unclear. Here, we present the metallurgical characterization of two 11th–12th c. single-bow shears from Sigtuna, Sweden. Both the blades and the bows of the two shears were found to be of decent quality and much better than in older shears from the Roman period. Although the steel qualities are not quite up to modern standards, this does not in itself prove that the Sigtuna blacksmiths lacked the technological knowledge to make ideal spring steel. Shears are relatively cheap everyday objects intended to be used until they break, at which point they are discarded. Therefore, it might not have been worth the Medieval blacksmiths’ time and effort to perfect the material properties of steel used in shears. The shears’ blades are on par with Medieval-period knife blades, and future studies on ancient shear-making should preferably involve comparisons of shears and knives from the same origins.

High-fidelity computational study of roughness effects on high pressure turbine performance and heat transfer

While blade surface roughness arising from in-service wear and/or the manufacturing process greatly affects aero-thermal performance, the detailed underlying physical mechanisms remain far from fully understood. In this study, a series of highly-resolved Large-Eddy Simulations of compressible flow past a high-pressure turbine vane with systematically varied levels of blade surface roughness have been performed, along with a smooth-blade simulation at matched flow conditions for comparison. Three non-dimensional roughness amplitudes have been investigated, namely, ks/c={1.0,2.0,3.0}×10−3, where ks is an equivalent value of Nikuradse’s sandgrain roughness for an irregular, multi-scale near-Gaussian height distribution, and c is the axial blade chord. All simulations have been performed at an axial chord Reynolds number of 0.59 ×106 and a Mach number of 0.9, based on the exit conditions of the reference smooth vane, and with synthetic inflow turbulence to mimic unsteady, three-dimensional disturbances from an upstream combustion chamber. The present investigation highlights the profound impact that blade surface roughness can have upon boundary-layer transition mechanisms, wall shear stress and blade surface heat flux, as well as the levels of turbulence kinetic energy and total pressure losses incurred in the wake. While blade surface roughness leads to major aero-thermal differences between the suction-side of the smooth and rough vanes, the pressure-side surface remains relatively unaffected — even for the largest roughness amplitude investigated here.

Temporal and spatial characterisation of tidal blade load variation for structural fatigue testing

To achieve the full potential of tidal stream energy, developers are incentivised to use larger blades on tidal turbines. This requires validation of blade structural designs through full-scale blade fatigue tests to de-risk the engineering process. However, the loading scenarios encountered in testing facilities and those in reality could be significantly different, which induces errors in blade loads and fatigue damage. Here we characterise the unsteady tidal blade load variation through model-scale experiment. It was found that the standard deviations of thrust load range between 200% and 637% of condition without waves. This results in an increase of predicted fatigue damage between 6% and 18%. It was observed that the centre of effort shifts towards the blade root when encountering wave crests of opposing waves, which has not been reported in the literature to date. To reduce errors in fatigue test while the centre of effort is fixed, matching blade shear forces should be sacrificed to match target bending moment at the root. Matching blade shear forces leads to a reduction of predicted fatigue damage ranges from 17% to 25%, which can induce errors in fatigue testing. We anticipate our findings would facilitate the development of fatigue testing of tidal turbine blades.

Parametric optimization and wear analysis of AISI D2 steel components

AISI D2 steel is widely used for forming die or cold stamping, chipper knives, shear blade, trimming cutter threading dies, punches and stamping tools etc. Hence, the current investigation aim is to determine the effects of sliding parameters on the wear performance of AISI D2 steel. The experiments were conducted on AISI D2 steel pin and disk of mild steel using the pin-on-disk apparatus. After that, relationships for forecasting weight loss of pins due to rubbing action have been developed using the design of experiment (DOE), which is based on response surface methodology (RSM) and has three independent parameters (slide duration, normal load, and sliding speed). ANOVA was used to perform the model adequacy tests, and the results of various parameters were computed and displayed in 3D surface graphs and contour plots. To reduce the weight loss, numerical optimization has been done while keeping all of the input parameters within range (wear volume). The manufacturing sector that uses AISI D2 steel for deforming dies would benefit from the study's findings.

Experimental investigation and optimization of WEDM process for AISI 420 stainless steel

AISI 420 Stainless steel is martensitic steel having sufficient corrosive resistance and outstanding hardness used for making knife blades, shear blades, hand tools, and surgical instruments for the medical industry. For the machining of this kind of high-strength material, WEDM is a popular advanced machining technique for creating items with complex forms and profiles. WEDM of AISI420 stainless steel is accomplished utilizing Zn coated copper wire as an electrode in this study. Machine input control parameters include pulse on time (Ton), pulse off time (Toff), peak current (Ip), and wire feed rate (Wf), whereas measured output response parameters include material removal rate (MRR), Kerf width (KW), and surface roughness (SR). Experiments were constructed using Taguchi L16 orthogonal arrays, and control parameters were optimized using Taguchi-based grey relational analysis (TGRA). Parametric analyses are done for multi-response optimization by obtaining grey relational grade (GRG). It has been found from the ANOVA table that Ton, Toff, Ip, and Wf are having % contributions of 85.67%, 4.38%, 8.47%, and 0.26% respectively. The optimal level of input parameters obtained by Taguchi-based GRA is Ton 125µs, Toff 40µs, Ip 220A, and Wf 8m/min. To validate the results confirmation tests are performed on optimal input parameters.

Strain self-sensing capability of a tidal turbine blade fabricated of PU-foam/glass fiber/epoxy composites using MWCNTs

A novel marine composite structure (experimental tidal turbine blade) made up of a polyurethane (PU) foam/glass fiber/epoxy resin composite with multiwall carbon nanotubes (MWCNTs) is proposed herein to self-sense its strain under a structural test scenario. To achieve this, MWCNTs were deposited onto glass fiber fabric by spray-coating technique in order to form an effective electrical percolation network onto the external skin surface of the tidal turbine blade which enables piezoresistive capability. After MWCNT deposition, the blade was manufactured by means of one-shot resin transfer molding (RTM) in a closed and heated metallic mold specially designed with a blade geometry of 67 cm length. The results confirm that the spray coating technique is a viable method to deposit MWCNTs onto glass fiber surface and form electrical networks into the blade at a relatively low MWCNT concentration. Finite element analysis (FEA) predicted a suitable structural blade design with a maximum failure index value of 0.9 attained in the blade shear web. The measured longitudinal strains of the tidal turbine blade were in good agreement with the numerical strain values predicted with FEA. Electromechanical tests carried out on a structural test rig designed and instrumented for tidal turbine blades showed that the electrical resistance change response of carbon nanotube (CNT) network integrated into the blade was capable of following the mechanical curve response up to the blade limit load, confirming its ability to self-sense its strain in real time.

Finite Element Model Construction and Cutting Parameter Calibration of Wild Chrysanthemum Stem

Due to a lack of an accurate model in finite element simulation of mechanized harvesting of wild chrysanthemum, the stem of wild chrysanthemum in the harvesting period is taken as the research object. ANSYS Workbench 19.0 software and LS-DYNA software (LS-PrePOST-4.3-X64) are used to calibrate the finite element simulation model of wild chrysanthemum stem cutting. The stem diameter distribution at the cutting height of the chrysanthemum is obtained. The maximum shear forces at different diameters (7 mm, 8 mm, 9 mm, 10 mm, and 11 mm) within the cutting range are determined as 120.0 N, 159.2 N, 213.8 N, 300.0 N, and 378.2 N, respectively, by using a biomechanical testing machine and a custom-made shear blade. The Plastic_Kinematic failure model is used to simulate the cutting process by the finite element method. The Plackett–Burman test is employed to screen out the test factors that significantly affect the results, namely, the yield stress, failure strain, and strain rate parameter C. The regression model between the shear force and significant parameters is obtained by central composite design experiments. To obtain the model parameters, the measured values are substituted into the regression equation as the simulation target values. In other words, the yield stress is 17.96 MPa, the strain rate parameter C is 87.27, and the failure strain is 0.0387. The maximum shear force simulation test is carried out with the determined parameters. The results showed that the maximum error between the simulated and the actual value of the maximum shear force of wild chrysanthemum stems with different diameters is 7.8%. This indicates that the calibrated parameters of the relevant stem failure model can be used in the finite element method simulation and provide a basis for subsequent simulations.

Near-infrared fluorescence clip guided robot-assisted wedge resection of a gastric submucosal tumour: A case report

BackgroundThe conventional near-infrared fluorescence clip (NIRFC): ZEOCLIP FS®, was difficult to observe using the Firefly on da Vinci. We improved the ZEOCLIP FS® and produced the da Vinci compatible NIRFC. In this report, we describe a robot-assisted wedge resection of a submucosal tumour (SMT) of the stomach using the da Vinci compatible NIRFC.Presentation of caseSurgery was performed for an enlarging SMT (from 18 to 22 mm with an intragastric growth type). Through endoscopy, four da Vinci-compatible NIRFCs were placed at the tumour edge two days prior to the surgery. The location of the NIRFC was confirmed when observed with the Firefly. The distal NIRFC site was incised with a monopolar shear blade to identify the NIRFCs and tumour base. The open area was sutured in two layers using a 3-0 V-Loc. The operation time was 83 min, and the amount of blood loss was 2 g. There were no complications or clip dropout.DiscussionThis method could be performed without intraoperative endoscopist.ConclusionIn this case, we were able to observe the position of the da Vinci-compatible NIRFC with Firefly on da Vinci. This technique may be an option as a simple procedure to minimize the resection area of the stomach.

Development and Evaluation of Self-propelled Cabbage/Cauliflower Harvester

In the present study, self-propelled cabbage/cauliflower harvester was designed, developed and evaluated. The machine consisted of different components like engine, frame, shearing (cutting) unit and power transmission unit. The power transmission unit consisted of main clutch, shearing blade operating clutch, belt drive unit, chain and sprocket drive, universal joint and cutter blade assembly. The main working principle of harvester is based on shearing of crop stem against high-speed rotating blade. The power from the engine is transmitted by belt-pulley drive unit to transmission shaft on which chain and sprocket is mounted on one side and then power is transmitted to shearing blade coupling with the help of a stationary pulley and fixed socket. Average mean head diameter of the selected cabbage and cauliflower was 89.5 ± 15.24 mm and 107.5 ± 15.24 mm, respectively. Average mean stem (plant) diameter of the selected cabbage and cauliflower was 18 ± 4.85 mm and 21.5 ± 3.08 mm, respectively. The shearing force increased with increase in diameter of stem. The optimum performance of the machine was achieved when it was operated at 1.5 km/h forward speed and the shearing blade moving at speed of 147 rpm. The mean field capacity for developed prototype was observed as 0.063 ha/h and 0.053 in case of cabbage and cauliflower, respectively with field efficiency of 91.97 and 90.48 %. The average head damage was negligible (0.15 %) for both the crops. The average untrimmed percentage with developed harvester was 3.2 and 3.0% in case of cabbage and cauliflower crop, respectively. The developed machine helps to increase the field capacity in cabbage/cauliflower harvesting due to 7-times more capacity and 50% cheaper compared to traditional method of cabbage/cauliflower harvesting. At the operating condition of forward speed (1.5 km/h) and shearing blade speed (147 rpm), the machine could harvest 0.5 ha of cabbage and 0.42 ha of cauliflower farm per day of 8-h. This same task would have required between 15 labour per day if entirely done manually.

Modeling and multiple optimization in face milling of hardfacing welding applied steel: Force, roughness, power

The coating performance for indexable inserts is very important for the main machinability indicators such as energy consumption, cutting force, and surface quality, especially in milling operations. The present study intend to the comprehensive analysis of machining conditions for above mentioned machinability indicators that can be considered most important for sustainability in hard milling of a worn machine part. First, the worn zone of the shearing blade made of X40CrMoV5-1 hot work tool steel was filled with electric arc welding. Then, hard milling experiments were carried out to analyze the performance of different coated carbide inserts in the machining of the hardfacing welded part. Experiments were performed by applying L18 experimental design for invariable cutting depth, three different cutting speed, and feed rate with PVD-AlTiCrN and CVD-TiCN/Al2O3/TiN coated inserts. Machining parameters for the responses namely the resultant force (Fr), surface roughness (Ra), and cutting power (Pc) were simultaneously optimized via applying Taguchi-based grey relationship analysis. Finally, predictive models for the responses were developed by RSM. The results obtained by both coatings shown that the Fr and Ra are mainly influenced by the feed rate, while cutting speed is the parameter that most influenced the Pc. The optimum results with regards to the responses were obtained with the PVD-AlTiCrN coated tool. In the current study, the developed quadratic models and probability graphs indicated that the responses were highly predictable.

Development of secondary vortex structures in rotor wakes

The blade tip vortex system is a crucial feature in the wake of helicopter rotors, and its correct prediction represents a major challenge in the numerical simulation of rotor flows. A common phenomenon in modern high-fidelity CFD simulations is the breakdown of the primary vortex system in hover due to secondary vortex braids. Since they are strongly influenced by the numerical settings, the degree to which these secondary vortex structures actually physically occur is still discussed and needs experimental validation. In the current work, the development of secondary vortex structures in the wake of a two-bladed rotor in hover conditions was investigated by combining stereoscopic particle image velocimetry measurements in different measurement planes and high-fidelity simulations. Secondary vortex structures were detected and quantified at different axial locations in the wake by applying an identical scheme to the measured and simulated velocity data. In agreement, it was found that the number of secondary vortices is maximum at a distance of 0.8,R below the rotor. The more intense secondary vortex structures were quantitatively well captured in the simulation, whereas in the experiment a larger number of weaker vortices were detected. No distinct preferential direction of rotation was found for the secondary vortices, but they tended to develop in vortex pairs with alternating sense of rotation. A clustered occurrence of secondary vortices was observed close to the primary tip vortices, where the rolled-up blade shear layer breaks down into coherent vortex structures.Graphical abstract

Gastrophysical and chemical characterization of structural changes in cooked squid mantle.

Squid (Loligo forbesii and Loligo vulgaris) mantles were cooked by sous vide cooking using different temperatures (46°C, 55°C, 77°C) and times (30 s, 2min, 15min, 1 h, 5h, 24h), including samples of raw tissue. Macroscopic textural properties were characterized by texture analysis (TA) conducted with Meullenet-Owens razor shear blade and compared to analysis results from differential scanning calorimetry. The collagen content of raw tissues of squid was quantified as amount of total hydroxyproline using ultra-high-performance liquid chromatography. Structural changes were monitored by Raman spectroscopy and small-angle X-ray scattering and visualized by second harmonic generation microscopy. Collagen in the squid tissue was found to be highest in arms (4.3% of total protein), then fins (3.0%), and lowest in the mantle (1.5%), the content of the mantle being very low compared to that of other species of squid. Collagen was found to be the major protein responsible for cooking loss, whereas both collagen and actin were found to be key to mechanical textural changes. A significant decreased amount of cooking loss was obtained using a lower cooking temperature of 55°C compared to 77°C, without yielding significant textural changes in most TA parameters, except for TA hardness which was significantly less reduced. An optimized sous vide cooking time and temperature around 55-77°C and 0.5-5h deserves further investigation, preferably coupled to sensory consumer evaluation. PRACTICAL APPLICATION: The study provides knowledge about structural changes during sous vide cooking of squid mantle. The results may be translated into gastronomic use, promoting the use of an underutilized resource of delicious and nutritious protein (Loligo vulgaris and Loligo forbesii).

Comparison of Ceramic and Coated Carbide Inserts Performance in Finish Turning of Hardened AISI 420 Stainless Steel

Martensitic stainless steels have a high carbon amount that can be heat treated to increase their hardness. There are widely used in cutlery, needle valves, shear blades, dental and surgical equipment. In this study finish hard turning was performed on the AISI 420 stainless steel using ceramic and coated carbide inserts under dry cutting conditions. Depth of cut, feed rate, and cutting speed were selected as machining parameters, while surface roughness was chosen as machinability criterion. Taguchi L9 orthogonal array was selected for the design of the experiment to decrease the number of trials for reducing time and cost of manufacturing. The response surface methodology was utilized for determining a relationship among process parameters and output parameter. The analysis of variance results indicates that feed rate is the utmost factor on the surface roughness for both ceramic and carbide inserts with 86.56% and 80.57% contribution, respectively. The developed mathematical models for ceramic and coated carbide inserts are capable to predict surface roughness with 97.07% and 96.13% accuracy, respectively. Based on the desirability function and response optimizer of the RSM, 0.2 mm depth of cut, 250 m/min cutting speed, and 0.05 mm/rev feed rate were selected as optimum machining factors. Finally, the mean surface roughness for ceramic and coated carbide inserts calculated as 0.57 µm and 0.71 µm, respectively. Therefore, the ceramic insert exhibited better performance compared to the coated carbide insert.

Low-Force Shear Blades Developed for High-Strength Coiled Tubing

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 204403, “Development of Low-Force Shear Blades for High-Strength Coiled Tubing,” by Scott Sherman, Nexus Energy Technologies, prepared for the 2021 SPE/ICoTA Virtual Well Intervention Conference, 22–25 March. The paper has not been peer reviewed. As coiled tubing (CT) grades have evolved during the past 20 years and wall thicknesses have increased, the resulting force required to shear coil has more than doubled. An industry need existed to develop a shear blade for blowout preventers (BOPs) that could cut high-strength CT using legacy pressure-control equipment already in use. The paper describes the iterative process of development of a novel shear blade able to cut high-strength CT with 50% of the normal shear force. Objective The objective of the work detailed in the complete paper was to develop a novel CT-shearing system capable of cutting high-strength heavy-wall CT with reduced hydraulic pressures. Considering that CT will continue to evolve in terms of yield strength, the goal of the study was to future-proof BOPs wherever possible to protect customers from the liability of obsolete equipment. The authors write that, ultimately, BOPs will need to cut 175-grade CT strings with a 7-mm wall thickness with 103 MPa of wellbore pressure and less than 17.2 MPa hydraulic pressure. Development Process Initially, the following five options were considered: - Larger-diameter cylinders. This seemingly simple option, which would generate more shear force, was ruled out because the implementation would not be backward-compatible with existing well-control equipment and the larger cylinder volume would result in slower cycle times. - Boosted actuators. These could double shear force while maintaining piston diameter. While this solution is simple, theoretically, these actuators require twice as much hydraulic fluid from the accumulator to function. This results in a closing time that is nearly double that of a nonboosted actuator. - Pressure-balanced actuators. With this option, hydraulic forces would not need to overcome the forces related to wellbore pressure in addition to providing sufficient force to shear CT. These actuators do increase the amount of shear force available to cut CT when used on high-pressure wells. However, they increase complexity, cost, and weight and could result in trapped wellbore fluids within the actuator that could lead to corrosion-related issues. - Increasing hydraulic pressure to a given set of rams using a pressure multiplier for the shear rams or a similar system. This solution was deemed unsuitable because the hydraulics of most BOPs are designed for 150% of their rated pressure. Doubling the hydraulic pressure available to the BOP could damage the hydraulic cylinders and associated actuators, resulting in a catastrophic well-control situation. - Modifying shear blade geometry to reduce the shear force needed to cut CT using existing equipment. This was selected as the most-logical approach because the modified shear blades could be retrofitted into existing BOPs. Furthermore, this solution would not require modification to existing wellsite equipment such as accumulator skids and would not increase the weight or size of the BOP stack.