Maximum Deformation Research Articles

The Behaviour of Thin-Walled Cylinders with Reinforcing Inner Walls Subjected to High-Velocity Impact

Thin cylindrical tubes as impact energy absorbers have been widely used in various fields. Previous researchers have proposed many methods to increase the ability to absorb energy by modifying the geometry or using different materials. This study discusses using reinforcing walls in the cylinder to increase energy absorption capability. We make thin cylindrical specimens made of aluminium alloy with a length of 150 mm, a diameter of 50 mm, and a thickness of 1 mm. Reinforcing walls are fitted in the cylinder with a vertical position of 1, 2, 3, and without supporting walls. An impactor moving at high velocity hits the up-end cylinder in the axial direction. The finite element method modelling results show that installing reinforcing walls in thin-walled cylinders increase the maximum impact force, decreases the maximum deformation, changes the deformation mode, and increases the energy absorption capability. The amount of wall added to the thin wall will affect the impact behaviour of the specimen. However, in this study, the presence of a wall will have an effect when the deformation reaches the location of the wall. Nevertheless, using this reinforcing wall also makes the manufacturing process more complex. Therefore, this study’s results are recommendations for the design of the impact energy absorption structural system.

Deformations and Wave Forces in the Motion of a Load on an Ice Cover in the Presence of a Current with Velocity Shear

The deformations of an ice cover on the surface of an ideal incompressible fluid of finite depth under the action of a pressure domain that moves rectilinearly at a constant velocity in the presence of a current with velocity shift, as well as the wave forces exerted on a moving body, are studied. Fluid flow is not potential. The ice cover is modeled by a thin elastic plate with account for uniform compression. The motion of the load can occur at an arbitrary angle to the direction of current. It is assumed that the ice deflection is steady in the coordinate system moving with the load. The Fourier transform method is used within the framework of the linear wave theory. The maximum deformations of ice cover and the wave forces are studied depending on the current velocity gradient, the direction of motion, and the compression ratio.

Segment Thickness Design and Bearing Performance Analysis of Large Inner-Diameter Shield Tunnel under Lateral Unloading

In order to accommodate more transportation-supporting facilities, the expansion of structures’ inner diameter has become the development trend of metro shield tunnels. But for large inner-diameter shield tunnels, the segment thickness design and bearing performance characteristics of tunnels under lateral unloading are still unclear. The purpose of the research was to select the optimal segment thickness and clarify the bearing performance of large inner-diameter shield tunnels. Therefore, in this study, a 3D refined numerical model was established to analyze and determine the optimal segment thickness for a shield tunnel with an inner diameter of 5.9 m. Furthermore, a full-scale test was carried out to study the bearing performance of the shield tunnel under lateral unloading. The results showed that the maximum tunnel horizontal deformation difference between the calculation and the test did not exceed 5%, and the maximum difference in the overall structure deformation between the calculation and the test did not exceed 7%. Increasing the segment thickness can reduce the convergence deformation of the shield tunnel nonlinearly; the deformation reduction was no longer significant when the segment thickness increased to 400 mm with an inner diameter of 5.9 m. Under the lateral unloading condition, the internal force of the tunnel structure increased significantly at sections of 0°, 55°, 125°, and 190°. Compared with the normal design load stage, the maximum bending moment and axial force increased by 36% and 74.1%, respectively, in the final failure stage. There was no bolt yield during the entire unloading process, indicating that the excessive strength of the bolt could not fully play a role in the entire life cycle of the large inner-diameter tunnel structure. The failure mechanism of the shield tunnel can be described as follows: in the early stage of a load, a shield tunnel will appear with joints open and dislocated. As the load increases, cracks in different directions gradually appear near the tunnel joint. In the ultimate load stage, the shield tunnel loses load-bearing capacity, and large areas of falling blocks appear at the top and bottom of the tunnel.

Investigation and measurement of old building response to the overlapped shield tunnel of multiple schemes in the sandy cobble stratum

Ground movements due to tunneling are becoming increasingly critical as buildings are located around construction sites. This study proposes a new combined reinforcement method using a foundation grouting oblique pipe roof. The former improves the bearing capacity of the subsoil, and the latter blocks the transmission of soil deformation, which weakens the influence of construction during overlapped tunnel under-crossing. Based on this new method, a case study of the shield tunneling response to an old building in Line 6 of China’s Chengdu Metro is presented. Additionally, three-dimensional numerical models without reinforcement, traditional foundation grouting reinforcement, and the new combined reinforcement schemes were compared. The numerical simulation performance was verified using a set of field instrumentation data, which demonstrated that the old building response to the overlapped tunnels was under control, and the maximum deformation, angular distortion, and principal tensile strain of the building were 5.25 mm, 5.10 × 10–6 rad/m, and 0.0081%, respectively. Compared with the traditional reinforcement scheme, the deformation, angular distortion, and principal tensile strain in the combined reinforcement scheme were reduced by 54.78%, 71.02%, and 70.22%, respectively. These results have important implications for the design and construction of shield tunnels and their response to old buildings.

A hybrid GRA-FIS based genetic algorithm and simulated annealing approach for camshaft material optimization using finite element analysis

Failures in the camshaft drive can allow the valves to contact the piston crowns, which can result in significant internal damage. Most of the researchers have reported that aluminium–silicon carbide composite has not only proven to be lightweight but also resulted in lower deformation and better fatigue strength when compared to other alloys or steel. No predictive approach has been taken to predict more durable materials and the optimum working condition of camshafts using optimization methods. As a result, in order to fill such gaps, this study focuses on the design of camshafts made of various materials. In order to reduce the maximum stress, maximum deformation, and maximum strain obtained, this study focuses on optimising the camshaft by choosing the best material and loading conditions. The Taguchi L16 orthogonal array design and ANSYS 17.2's were used for the analysis. Finite element analysis was used for static structural analysis, and the findings produced by cast iron camshafts were compared to aluminium–silicon carbide composite composites. Later on, multi-objective optimization was tested using grey relational analysis in conjunction with a fuzzy inference system. The simulated annealing and genetic algorithm approaches were also used to forecast optimized results. It resulted that aluminium–silicon carbide composite 40% composite is the most suitable material. The most important factor was determined using an analysis of variance, followed by confirmatory tests. It showed that loading condition was the most significant factor.

Development of a composite based on polylactic acid and lignocellulosic waste: new packaging for meat food storage

Pursuing new packaging that contributes to the safety of meat products, that can also be from renewable sources and that has adequate mechanical properties is a challenge. Therefore, this study attempted to incorporate a layer of polylactic acid (PLA) containing nisin and oregano oil extract (OEO) into biocomposites of cassava bran (CB) and coffee husk (CH) to improve their mechanical properties and enhance their antimicrobial properties. A compression molding process is carried out, the operating conditions for the preparation of the biocomposite were pressure: 40 bar, temperature: 170°C, and time: 2.5 min. The composition of the biocomposite was 80, 18, and 2% of CB, CH, and glycerol respectively, with 30% moisture. The polylactic acid (PLA) layer was added by immersion and contained nisaplin and OEO. PLA layer was evaporated in forced convection oven. Once the active packaging was obtained, inhibition in vitro against Listeria monocytogenes was performed. The packing containing OEO and nisin that showed the highest inhibition on the pathogen was used for stability analysis in pork. In order to measure changes in pork meat quality, the biocomposite with and without coating and with commercial polystyrene packaging were compared. Raw meat muscle was kept at 4° C and was tested for color, pH, moisture, and texture profile analysis (TPA) for 0, 7, 14, and 21 days. The values of the flexural test of the biocomposite were: 11.08 MPa of maximum flexural strength (σF), 1.81% of maximum deformation (εF), and 842.22 MPa of elastic modulus (EM). According to the results of in vitro inhibition, the packaging can contribute to reduce the proliferation of gram-positive microorganisms, such as L. monocytogenes. During storage, the hardness and gumminess of the meat showed significant changes, mainly in the PLA-free biocomposite. Results on pork meat showed that packaging with antimicrobials and PLA can maintain color, texture, moisture, and pH similar to commercial packaging.

Analysis of rigid-flexible coupled torsional vibration and vibration suppression of crankshaft system under multiple working conditions

With the rapid development of shale gas resources in China, there is an increasing demand for large and multiple column compressors. However, this development has brought to light the issue of torsional vibration in compressor crankshaft systems, particularly under variable loads and multiple working conditions. In order to reduce the torsional vibration of the compressor crankshaft and ensure the safe and stable operation of the compressor unit, this study proposes a method for calculating and suppressing torsional vibration in the crankshaft system of a shale gas compressor, which takes into account the flexibility effect of various parts and considers multiple working conditions. The analysis focused on the rigid-flexible coupling torsional vibration characteristics of the crankshaft system under multiple working conditions, considering the flexible deformation of the main bearing, connecting rod, and crankshaft. The study successfully determined the torsional vibration response of the crankshaft system under seven typical working conditions. Furthermore, for the worst conditions, a detailed analysis of the vibration response of the crankshaft system was conducted and carried out a study on suppressing crankshaft torsional vibration through response surface optimization design. The study findings indicate that the compressor system exhibits low-frequency vibrations during operation. The maximum torsional angular deformation at the crank pin of the fourth column is measured to be 0.052°. Following structural optimization, the relative torsional angular deformation of the crank pin is reduced by 25.61% under the worst operating conditions. Moreover, the peak angular velocity of the center of mass is reduced by 22.17%. These results demonstrate a significant suppression effect on torsional vibrations in the compressor crankshaft system, leading to improved working safety.

An adaptive clamp system for deformation control of aerospace thin-walled parts

The assembly and service of thin-walled parts are usually threatened by machining deformation. In this study, phase change material (Sn-Bi-Pb-Cd alloy with a melting point of 70 °C) was used to develop an adaptive clamp system, which could adjust the clamping position when the material was liquid to follow the stress-releasing deformation after rough machining. The material's solidification could re-clamp the workpiece, whose internal stress had been minimized. Afterwards, the workpiece deformation could be removed in finishing machining. Comparing to the counterpart using traditional vacuum fixture, the maximum deformation and the flatness tolerance of the web using the adaptive clamp system reduced by 82.0 % and 72.9 %, respectively, thus effectively improving the accuracy of thin-walled parts manufacturing.

Explicit and Computational Fluid Dynamics Analysis of a Novel Polo Helmet Design: A Parametric Study

Abstract Polo is a popular sport in New Zealand, Australia, the United Kingdom, and many other countries. Polo is a vigorous sport involving players and horses moving at speed and can result in head injuries caused by falls. Helmets play a vital role in the safety and protection of Polo players. This study investigates different hemispheric bumper shapes of the helmet to improve the impact resistance performance using finite element analysis (FEA) and explicit dynamics analysis (EDA). The aerodynamic performance of the proposed helmet is investigated using computational fluid dynamics (CFD) to account for drag impact on the Polo player's speed. These are investigated for impact resistance and the drag coefficient under different speeds. The EDA results show that the new proposed bumper will absorb the impact and reduce the energy transferred to the inside foam at a relative impact speed of 6.2 m/s, as recommended by the U.S. Consumer Product Safety Commission (CPSC), with a maximum total deformation of 4.42 mm compared to 4.19 mm and 3.85 mm for impact speeds of 5.9 m/s by the European standard PAS015:2011 helmets for equestrian use and 5.42 m/s BS EN 1078 helmets for bicyclists' use, respectively. Additionally, under speeds ranging from 15 km/h to 65 km/h, the new helmet demonstrated a drag coefficient of 0.454, similar to that of the national team helmet, at 0.423.

Working process and opening characteristics of soft insulator of pulse motor

AbstractIn this paper, a simulation test system for the working process of soft insulation is designed, using equivalent simulated ablation test methods combined with a CCD measuring system and micro electron microscope scanning technology, which can better describe the thermal properties and state of insulation after ablation. At the same time, a test plan for the opening characteristics of the insulator based on different ablation times and different opening structure sizes as the main influencing factors are designed. The experimental results show that the ablation test can well simulate the state of an actual pulse engine compartment after the ablation and the maximum relative error of the ablation rate can be controlled within 5 %. From the influence of ablation time on the opening characteristics of the insulator, it can be seen that the maximum axial deformation of the insulator is different from the relative value of the opening pressure. The radial deformation of the insulator is larger than that of the non‐ablated insulator and larger than the inner diameter of the insulator shell after ablation. From the influence of the size of the opening structure of the insulator (depth of weakening grooves) on the opening characteristics of the insulator, it can be seen that as the weakening groove depth of the compartment deepens, the original pressure change pattern disappears, and the opening pressure and opening time of the insulator decrease significantly.

Research on Bionic Hierarchical Optimization of Wing Based on PLSR and PSO

The layout of the wing's internal structure not only dramatically influences the wing's strength stiffness but also directly affects the aerodynamic characteristics of the aircraft. Based on the original wing structure, a more flexible spatial design layout to achieve improved overall structural load-bearing performance, and a reasonable structural lightweight design are the research priorities to be considered for the development of future aircraft. Therefore, this paper attempted to design and analyze a lightweight airfoil that meets the performance requirements. Combining the strategy of hierarchical optimization design with the advantages of engineering bionics, the diatom Arachnoidiscus bionic structure, topological optimization, partial least squares regression (PLSR), and multi-objective particle swarm algorithm (PSO) are applied to optimize the placement and size of wing’s internal components. The simulation results show that the weight of the optimized wing structure is reduced by 6% while satisfying the requirements of maximum stress and maximum deformation.

А particle model of interaction between weakly non-spherical bubbles

A mathematical model of interaction of weakly non-spherical gas bubbles in liquid is proposed. It is a system оf the second order ODEs in the radii of bubbles, the position vectors of their centers and the amplitudes of their small deformations in the form of spherical harmonics. Compared to the available analogs, the proposed model equations are more accurate in terms of the ratio of the radii of bubbles to the distance between their centers. This allows one to study bubble-bubble interaction at smaller distances between the bubbles. The model equations are quite compact, which simplifies their theoretical analysis and construction of algorithms of their solution. Five problems (dynamics of a single bubble under harmonic excitation, bubble collapse near a plane rigid wall, interaction of three synchronized and nonsynchronized bubbles located in line, and interaction between sixteen bubbles with the centers located on a plane surface) are considered for validation. It is shown that in all cases the proposed model results well agree with the corresponding available experimental data and numerical solutions. For demonstration of the applicability, the proposed model is used to analyze radial oscillations, spatial movements and surface deformations of the bubbles in rectilinear, planar and spatial clusters under harmonic forcing. Initially 125, 121 and 125 bubbles of the clusters are located at the nodes of 1D, 2D and 3D uniform grids, respectively. It is found that the monotonically decaying radial oscillations of the 1D cluster bubbles during one period of forcing are quite similar to those of a single bubble. Unlike this, the attenuation of the radial oscillations of the central bubbles in the 2D and 3D clusters is essentially non-monotonic. The maximum pressures in the central bubbles of the 2D and 3D clusters are significantly higher than in the single and 1D cluster bubbles. In all clusters the maximum deformations of bubbles are in the form of the second spherical harmonics, except for the central bubble of the 3D cluster, the maximum deformations of which are in the form of the fourth harmonics.

Design and analysis of multi-material structures of 3D printed implants of mandible

Significant advances in 3D printing technology have paved the way for improvements in the integrity and biological characteristics of polymer implants. The principal objective of this research is the construction of a heterogeneous implant structure using a multi-material approach and 3D printing. Due to their advantageous strength-to-weight ratio, biocompatible polymers have an increasing application in the field of medicine. The osteo-integration process, in which implants bind to the bone over time, can be made more effective by incorporating these materials into implants. In this work, we focused especially on analyzing the strength and integrity of polymer material implants that were created using a combination of different materials, and their stress distribution, and the deformation of these multi-material structures when they were subjected to physiological loading through finite element analysis. The evidence from the frontal bite condition has led to some fascinating conclusions. The variations in stress were observed in homogenous structures, with values ranging from 37.42 MPa for the TPU to 41.07 MPa for the PETG. In contrast, stress distributions in multi-material constructions ranged from 52.31 MPa (in the case of TPU +TPU) to 73.55 MPa (in the case of PLA+ PCL). Similarly, the maximum deformation in homogeneous constructions ranged from 0.81mm (PLA) to 6.85mm (PCL). The deformation of multi-material structures composed of several different materials ranged from 0.68mm (PLA+ PLA) to 5.74 mm (PCL+PCL).These findings provide conclusive evidence that multi-material architectures have a considerable impact on known stress and strain levels. Particularly noteworthy is the fact that the combination of PLA+PLA and PLA+PETG displayed deformation that was equivalent to that of the intact bone model while having lower stress levels. The results of this study provide useful information that can be used to select optimal multi-material combinations that can be 3D printed for implants.

Largely deformable torsional soft morphing actuator created by twisted shape memory alloy wire and its application to a soft morphing wing

We present a new type of torsional soft morphing actuator designed and fabricated by twisted shape memory alloy (SMA) wires embedded in polydimethylsiloxane matrix. The design and fabrication process of the proposed soft morphing actuator are presented with investigations of its working mechanism. Actuation performance was evaluated with respect to the temporal response, the maximum torsional deformation under an applied electric current, and various design parameters including the twist direction, wire diameter, helical pitch of the SMA wire, and the actuator’s thickness and length. We demonstrate potential applications of the proposed soft morphing actuator as a soft morphing wing and airfoil. The proposed actuator will aid in the development of soft actuators, soft robotics, and other relevant scientific and engineering applications.

Heat transfer-deformation analysis and optimization of air-cooled reciprocating compressor cylinders under heat-flow-solid coupling

Heat transfer deterioration and deformation can jeopardize the operating safety of compressor-air-cooled cylinders. To comprehend the heat transfer-deformation mechanism, enhance the heat dissipation and cooling effects, and reduce the deformation effect, a study on the control and optimization of heat transfer-deformation of compressor cylinders under the influence of multi-field coupling was conducted. The orthogonal experiment method is used to examine the effects of rib height, air chamber width, and working wall thickness on the cylinder's heat transfer properties and deformation effect. The results show that the average temperatures of the exhaust chamber and the working chamber of the air-cooled cylinder are higher, at 99.2 °C and 96 °C, respectively, and the proportion of the hot zone is as high as 44.1 %. The maximum radial deformation of each section of the working chamber and the maximum deformation of the cylinder are 0.223 mm and 0.451 mm, respectively. Through orthogonal experimentation and range analysis, it was found that the height of the cylinder rib plate has the greatest influence on the deformation. Besides, the cylinder structure is optimized, and the average temperatures of the exhaust chamber and the working chamber of the optimized cylinder are reduced to 98.4 °C and 95.5 °C, respectively. The maximum radial deformation is suppressed to 0.193 mm and 0.440 mm, respectively, preventing the sealing failure of the cylinder's working chamber and guaranteeing the compressor's operation efficiency. This study provides theoretical guidance for the optimization of heat transfer, deformation control, and the standardized design of reciprocating compressor cylinders.

Computational modelling and analysis of hard tissue behavior around 0.5 mm and 0.85 mm platform switched abutment using 3D finite element analysis

Permanent tooth avulsion is a common but extremely serious dental injury that can negatively affect both economic output and lifestyle. Even though it is not a disease, no one is ever completely safe from the possibility of suffering from these disastrous injuries. Dental implants play a vital role in the treatment of such injuries (tooth loss). This work was focused on to find the effects of two different platform switched abutment-implant assembly on hard tissues (Cortical and cancellous) bone. Materialized Mimics Medical Software was used for processing clinical imaging (CBCT) data of mandibular bone and micro-CT data of implant (5.5 × 9.5 mm), Abutments (Pt. sw. I and Pt. sw. II) and final 3D model of all parts were obtained by Fusion 360 CAD software and implanted into a right mandible bone block. Implant-Abutment with different switching assembly as platform switched-I (Pt. Sw. I) Ø5.5-mm implant and Ø3.8-mm abutment and the platform switched-II (Pt. Sw. II) Ø5.5-mm implant and Ø4.5-mm abutment were compared. Each model was subjected to 50 N, 100 N and 150 N longitudinal and lateral loads at occlusal surface of the abutment to evaluate the mechanical parameters. ANSYS 2020R1 was used to conduct the computational analysis. Mechanical characteristics such as von-Mises stresses and total deformation were measured in the hard tissues using finite element modelling. Under the application of different loads the cancellous bone experiences maximum von misses stress 4.7 MPa and 5.4 MPa for Pt. Sw. I and Pt. Sw. II respectively under longitudinal load and 7.4 MPa and 8.7 MPa for Pt. Sw. I and Pt. Sw. II respectively under lateral load. Similar trends were observed for cortical bone. While maximum total deformation of 2.1 µm (Pt. Sw. I) and 2.2 µm (Pt. Sw. II) under longitudinal load and 4.4 µm and 4.6 µm in cancellous bone and cortical bone under longitudinal load and 4.4 µm (Pt. Sw. I) and 4.6 µm (Pt. Sw. II) under lateral load in cancellous and 7.5 µm (Pt. Sw. I) and 8 µm (Pt. Sw. II) in cortical bone were recorded. The analysis may help to prevent the progression of marginal bone loss (MBL) because lower results for these variables indicated for higher platform switching in marginal bone. The findings of computational frameworks can help clinicians and other medical professionals make more informed decisions when selecting a treatment strategy from the many options available.

Experiment and Numerical Study on the Dynamic Response of Foam Sandwich Panels under the Near-Field Blast Loading

Aiming at the problem that the blast load, generated by the explosion of the tandem-shaped-charge warhead, may cause damage to the warhead structure, material failure and even phase change, the material damage and structural protective capacity of the near-field blast load on the sandwich structure with foam-aluminum core were investigated by experimental test and numerical simulation. Firstly, the near-field blast test was performed to observe the deformation of sandwich structure and to collect the acceleration signals of fuze. Then, the mechanical properties of foam materials were tested, and a numerical model of blast load environment was established in the explicit dynamics software ANSYS/LS–DYNA 2020 R2. Finally, the experimental test data and simulation results were compared and analyzed. The strong agreement between the experiment and the simulation results indicates that the calculation method and simulation model are reasonable. Furthermore, the damage mode of foam-aluminum core materials with different densities and cell diameters under near-field blast load were carefully analyzed by simulation method. The simulation results show that, with the decrease of the density of foam-aluminum material and the increase of the cell chamber diameter, the deformation of the foam-aluminum panel gradually increases; the acceleration peak value of the fuze gradually decreases, and the pulse width barely changes and remains basically constant; the start and end times of the peak stress of the fuze cover gradually lag behind, and the peak stress hold-up time increases gradually; the maximum displacement deformation of the fuze cover decreases firstly and then increases. This work is expected to provide basic data and design guidelines for the graded foam sandwich panels of the blasting warhead fuze against the near-field blast load.

Performance of a Corrugated Metal Pipe with Shallow Burial Depth in Loosely Compacted Sand: Soil Box Test and 3D Finite Element Modeling

There have been many studies that have investigated the behavior of buried corrugated metal pipes (CMPs) in culvert applications. However, full-scale testing of buried culverts is a major undertaking since performing numerous large-scale tests is not always possible. A large-scale physical test was done on a corrugated metal pipe with a 1.52 m diameter under a monotonic loading test. The finite element modeling (FEM) tool (ABAQUS) was employed to verify and simulate different behaviors of a pipe-soil system. The finite element model showed a suitable match with the laboratory test results and properly identified local buckling as the failure mode for testing conditions, a CMP buried under shallow cover. The FE model indicated satisfactory performance in predicting the strains, bending moments, thrusts, and pressure distribution in the CMP. Subsequently, the behavior of CMP pipes was examined by increasing 25% and 100% in the burial depth and loading pad area, respectively. Results indicated that with an increase in the burial depth by 25%, the maximum deformation of the pipe at the crown decreased by approximately 31%. An increase in loading pad size by 100% led to a decrease in minimum factor safety at the crown by approximately 93%.

A Study on the Evaluation of the Compression Behavior of PLA Lattice Structures Manufactured by FDM

The paper brings forward the results of a study on the compression test of 28 lattice structures made of PLA by FDM, with the height of the deposited layer at a pass of Hs = 0.20 mm and 50% filling percentage Pu. The 28 samples were made on Anycubic 4 Max Pro 2.0 the 3D printer, considering 7 filling patterns: Grid, Tri-hexagon, Octet, Triangles, Cubic subdivision, Gyroid, and Cross 3D for each type of lattice structure. The dimensions of the specimens, before and after the compression test, were determined using the DeMeet 3D coordinate measuring machine. In this context, a minimum printing accuracy value of 98.98% and a maximum deformation value of 57.70% were recorded for the lattice structure corresponding to the Triangles fill pattern. For the same Triangles type lattice structure, the highest average maximum compressive force of 87.32 kN was obtained. The maximization of the ratio between the use value and the production cost, one of the fundamental technical-economic principles of value analysis, was obtained for the lattice structure corresponding to the Cubic subdivision filling model.

Numerical Study on the Flow and Structural Characteristics of a Large High Head Prototype Pump-Turbine under Different Operating Conditions

During the operation of pumped storage power stations, complex operating conditions can lead to different internal flow characteristics, which can cause different vibration characteristics or even damage to the structural components of the pump-turbine units. The time–frequency characteristics of the structural components’ response are of great significance for the safe operation of the unit. In this study, a three-dimensional flow field and structural field model of a large high head prototype pump-turbine is built in order to study the flow and the flow-induced dynamic response characteristics in different turbine operating conditions. The analyzed results show that the maximum deformation occurs at the inner head cover, and the maximum value of stress is located at the fillets on the outlet side of the stay vanes. Under the 50% load condition, the vortices in the runner caused by changes in the opening of the guide vanes result in the main response frequency of 4 fn of the stationary components. The research results can provide references for the structural optimization design of other pump-turbine units.