In Hopkinson bar theory, stress, strain, and strain rate can be determined by analyzing the dimensions of the specimen. When conducting Split-Hopkinson Pressure Bar (SHPB) experiments, the stress-strain curve is obtained by considering the entire length and width of the specimen. However, in Split-Hopkinson Tensile Bar (SHTB) experiments, it is important to only consider the regions where deformation occurs in order to accurately determine the dynamic material properties. This study introduces a method for selecting the dimensions of the deformed region (LD and WD) in plate specimens for SHTB experiments using Finite Element Analysis (FEA). The analysis involved varying the length and width of a 1 mm thick SUS430 specimen, and the deformed region was determined using the proposed method. The stress-strain curves obtained from this region were then compared with the input Cowper-Symonds model. The validity of the proposed approach was confirmed, as the percentage error between them ranged from 2.54 to 6.62%.
This paper proposes a high-fidelity finite element model of a permanent synchronous motor (PMSM) to predict electromagnetic responses. The proposed method aims to generate electromagnetic responses from the PMSM under various operational conditions-including normal and faulty conditions-by coupling several partial differential equations governing the electromagnetics of a PMSM. The rotor eccentricity is considered to be a representative fault of a PMSM, which has electromagnetic characteristics that differ from the healthy state of a PMSM. Note that eccentricity is the most frequent fault during PMSM operation. Therefore, the proposed model could replicate the defected torque responses of an actual motor system. The effectiveness of the proposed model is validated using measurements from a PMSM test bench. Quantitative comparison reveals that the proposed model could replicate both the transient- and steady-state torque responses of the PMSM of interest at a variety of operational conditions, including a faulty status. The proposed model could be used to generate virtual electromagnetic responses of a PMSM, which could be used for data-driven fault detection methods of electric motor systems.
Ground drilling technology for drilling has an environment where the major parts are prone to damage due to high stress, torque, and harsh operating conditions that can occur in the rotary power transfer structure. Research for preventing this damage is very important, as it can be coupled with the nature of drilling operations that take a long time in operation, which can lead to enormous cost and time consumption. Previous work investigated the cause of damage by analyzing the working environment and breakage of drilling holes for connecting rods, and a power transfer component of directional mud motors used in ground drilling systems. The material properties by heat treatment conditions for applied materials were analyzed. Based on prior work, we evaluated whether the stress concentration part shown in the analysis results matched the actual damage occurring point by conducting a structural analysis of the connecting rod, a damaged part, using the finite element analysis. We also analyzed how to reduce the stress concentration phenomenon that occurs during the mud motor operation by conducting part shape and design changes between the connecting rod and key parts.
Research on the application of additively manufactured polymer (AMP) to the conventional manufacturing process is underway. In this study, an additively manufactured die-set (AMDS) was used and applied to the warm forming of the magnesium alloy. Heat transfer and coupled temperature-displacement analysis were conducted in the V-Bending and UBending processes to study the applicability of the AMDS to the warm-forming process of the magnesium alloy sheet (AZ31B). A heat transfer experiment was conducted to determine the thermal contact conductance between the AZ31B material and two types of die-set, the metal and AMP. V-Bending and U-Bending experiments were conducted at 373 and 423 K; reduction in temperature between metal die-set and the additively manufactured polymer die-set were compared. The springback after the bending process with different initial temperatures and die materials was investigated. The simulation model showed good agreement. The springback of AZ31B was more decreased with the additively manufactured polymer die-set than with the metal die-set. The stress of the additively manufactured polymer die-set in the bending process was very small. It was confirmed that in the AZ31B material, the additively manufactured polymer die set helps increase the formability and decrease springback by keeping the temperature of AZ31B better.
Elastomeric O-ring seals are widely used in static and dynamic applications due to their excellent sealing capacity, and availability in various costs and sizes. One of the critical applications of O-ring seals is solid rocket motor joint seal. In this, the operating hot gas must be sealed during the combustion time. In this study, we analyzed the behavior of O-ring compressed and highly pressurized by using the finite element method. The numerical analysis technique was verified through the comparison of analytical model and FE results. By using the verified FE method, the contact stress profiles at the sealing surfaces were investigated. It was found out that the contact stress profiles and deformation behaviors of the Oring are affected by friction coefficient, extrusion gap and stress relaxation considerably.
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In recent years, machinery industries such as aerospace and automotive industries have adopted high-precision machining. Cutting fluids increase the tool life and productivity through cooling and lubricating the machinery during processing. However, the cutting oil causes environmental pollution while the reuse of waste fluids negatively affects the tool life and machining quality. Therefore, it is important to study cutting oil environmental reuse methods and develop eco-friendly equipment such as a DC (Dust cake) filter system. In this study, the structural analysis was done using finite element method (FEM) to verify the stability and a study of the DC filter frame design improvementdone. Based on the damage on the DC filter system, the cause of the damage was assessed and an improvement to the structure suggested. Finally, the structural stability of the improved design was verified through analysis. The results of this analysis could be applied in order to further research.
Linear roller bearings are often used for linear positioning systems due to high load-carrying capacity, precision, and durability. In this paper, guide rail deformation of linear roller bearings under vertical and horizontal loads, has been experimentally investigated. An experimental system was made to measure displacement of the carriage and guide rail deformation of a bearing with varying load. Guide rail deformation inaccessible inside the carriage, was estimated by measured carriage displacement subtracted from calculated carriage displacement from a commercial program, that does not consider flexibility of guide rail and base. In addition to estimated deformation, guide rail deformation outside the bearing carriage was measured to make a complete guide rail deformation curve due to external loads. Results revealed deformations occurring in guide rail and base are significant, as to affect bearing accuracy. Thus, deformations in guide rail and base should be considered, to estimate stiffness and motion accuracy of linear roller bearing under external loading conditions.
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For 3D printing of high-strength polymers, such as PC (Polycarbonate) and PEI (Polyetheimide), the temperature of the nozzle should exceed the melting temperature of the high-strength materials. At the same time, the temperature of the transfer part, composed of the shaft extruder and the Teflon hose, should be cooled below the glass transition temperature and below the limit temperature of the transfer part. In this study, we analyzed the effect of the flow rate of the cooling fan when the extruder nozzle is heated to 300oC. We compare the natural convection environment, in which the cooling fan is not operated, and the forced convection condition, in which the cooling fan is operated, and analyze the effect on the cooling fan flow rate. The simulation considered the heat transfer in the air and the nozzle, as well as the flow characteristics of the air.
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This study aims at developing a high temperature extruder for an FDM (Fused Deposition Modeling) type 3D printer that uses engineering thermoplastic filaments. An extruder is a key part of an FDM type printer, in which a filament moves to a heating block and is extruded through a nozzle with a specific diameter. For an appropriate extrusion, the filament should be heated above its softening temperature. Specifically, the filament should not be melted nor softened before it reaches the heating block for appropriate delivery. Hence, the extruder temperature should be carefully controlled to ensure its heating capability as well as its proper delivery. To meet these requirements, thermal-structural finite element (FE) analyses were performed for the prediction of the distributions of temperature and thermal stress. Various extruder designs were then considered to maximize the temperature difference between the nozzle and delivery parts, as well as to ensure structural safety.
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A Study on the Improving Extrusion Defects in FDM 3D Printers Jun-Seok Do Journal of the Korean Society of Manufacturing Process Engineers.2024; 23(4): 80. CrossRef
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Recent use of mobile phones as a multimedia device has increased the development of micro-speaker modules having high quality and a compact size. Micro-speakers use polymer diaphragms fabricated by the thermoforming process. To improve the sound quality, micro-speaker diaphragms are usually designed to contain a number of micro-corrugations. This study investigated the effects of the corrugation depth on the acoustic characteristics of the diaphragm, using finite element (FE) analysis. Structural FE analysis was performed to investigate the stiffness change according to the corrugation depth. Modal FE analysis was used to compare the change in natural frequencies for each case. Harmonic response analysis further investigated the resulting variation in acoustic power. The effects of the corrugation depth on the acoustic characteristics of the diaphragm were discussed by reviewing all the FE analysis results synthetically.
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Design and Analysis of a Novel Microspeaker with Enhanced Low-Frequency SPL and Size Reduction Ki-Hong Park, Zhi-Xiong Jiang, Sang-Moon Hwang Applied Sciences.2020; 10(24): 8902. CrossRef
This paper describes the design of the beam of a gantry robot for Computer numerical control (CNC) lathe that can automatically attach and detach a workpiece. The gantry robot takes the unprocessed workpiece from the stoker and mounts it on the chuck of a CNC lathe. The robot then removes the processed workpiece fixed to the chuck and places it in the processed workpiece stoker. The workpiece consists of a body, x-axis beam, x-axis driving device, y-axis beam, yaxis driving device, z-axis beam and z-axis driving device. Finite element analysis was performed to design the x-axis beam, the y-axis beam, and the z-axis beam. Based on the results, the optimal size of the x-axis beam was designed to have a size of 150 mm × 150 mm × 4681 mm with a thickness of 9 mm. The x-axis beam is less eccentric in the position of the chuck of the CNC lathe.
Precise installation of a seam clamp is crucial as failure to do so will lead to defects, compromising the quality of paper containers. Even experts spend 90-120 minutes, which comprises 4.7 percent -6.25 percent of the replacement and adjustment process on a paper container manufacturing machine. To overcome an undesirable replacement procedure, a composite seam clamp was devised. The objective of this paper is to enhance the quality of a seam of a paper container and reduce time replacing seam clamps. The composite seam clamp was designed based on the Guerin process. Silicon rubber, which can be used in the temperature range of the paper container manufacturing process (110-130℃), was selected. To validate performance of the steel and composite seam clamp, 13 error situations resulted from translation and rotating misalignment of seam clamps were set and simulated. Through FEM (Finite Element Method) simulation, this paper confirms that the composite seam clamp shows higher transmission of clamping pressure compared to steel seam clamps in error situations. The feasibility of the composite seam clamp was validated in reducing replacement time of seam clamps through on-site tests.
Recently, a high-precision ball screw is an essential part of high-speed machines. However, producing high-precision ball screws has been costly and time-consuming. Nowadays, a whirling machine is used to produce high-precision ball screws efficiently. Rotating multi-tips are used to turn the ball screw in the whirling machine. In this study, a structural analysis was performed by a finite-element method to develop a whirling machine. An improved model of the whirling machine was proposed by the analysis. In addition, a thermal analysis was performed to confirm the thermal stability. The results of the analysis can be applied in order to further develop the whirling machine.
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