1023 深絞り円筒容器の残留応力測定結果の FEM による検討

The residual stresses in the wall of a SUS304 stainless steel cylindrical drawing cup were evaluated by split-ring tests, and the influences of stamping die parameters on the residual stress were investigated. A new theoretical model of a split-ring test was developed to evaluate the residual stress in a ring, which was verified to be reasonable and reliable by numerical simulations with ABAQUS code and by nanoindentation tests. Seven groups of split-ring tests were completed, and the residual stresses were calculated according to the theoretical model. The split-ring test results showed that the circumferential residual stress in the wall of the SUS304 stainless steel cylindrical drawing cup was very large and did not change with the different die corner radius. The circumferential residual stress first increased with the increase of drawing punch–die clearance, then was almost unchanged when the clearance increased greater than blank thickness 1 mm. Thus, a smaller clearance was suggested to be chosen to reduce the residual stress in the wall of the SUS304 stainless steel drawing cup. Seven groups, three samples in each group, and a total of 21 qualified cylindrical drawing cups in Fig. 2 were made from a circular SUS304 stainless steel sheet about 72 mm in diameter and 0.94 mm in thickness by deep drawing with different processing parameters. After the rings were cut from the cup walls, each ring was split along the radial direction. Two ends of each split ring opened a distance to release the circumferential residual stress in the closed ring. After measuring the opening distance, the residual stresses in the drawing cup walls were calculated by Eq. (18) in the newly developed split-ring test theoretical model of this paper. Then reasonable technology measures were found to reduce the residual stress by analyzing the influence of the mold parameters on residual stresses.

In the deep drawing process, material of blank is transformed into the desired complicated shape by a punch. In this paper, a technique for increasing the drawability of AA1200 aluminium alloy cylindrical cups has been developed. Effects of die and punch geometry including die and punch fillet radius, on limiting drawing ratio (LDR), drawing load with respect to punch stroke and strain of the cup wall have been investigated numerically for optimal process design. A commercial finite element simulation package, ANSYS 14.0, is used in order to determine the optimum limiting drawing ratio. An experimental setup is built accordingly with a half cone angle of 18°. In the experimental and finite element analysis, AA 1200 alloy sheets are used. The effects of the original blank thickness (t = 2 mm) on the various LDR and punch load are numerically investigated. The present process successfully produces cylindrical cups with drawing ratio of 2.64.

Spent fuel pool and storage racks are important nuclear security structures and components. In order to prevent it from structural failure, which includes the loss of the structural integrity of the spent fuel pool and stability of the spent fuel storage racks, also includes the possibility of fallen down of storage racks under seismic loading. Besides the necessary static analysis of structures, the influence of seismic loading on the interaction between water and structure should be fully considered, Especially concerned the analysis of the shaking effect of water sloshing on the storage racks, the displacement and the possibility of fallen down of the storage racks. The present paper is concerned with the problem of modeling the fluid-structure interaction (FSI) in filled liquid and filled with spent fuel pool. The study focuses on the sloshing phenomena and on the coupling computational fluid dynamic (CFD) analysis with the finite element stress analysis (FEA) code LS-DYNA. By the results of the response of seismic, such as the displacement of the storage racks, pressure exerted on the plate of racks and the walls of the pool. This paper also evaluates the seismic performance of the structure and the safety margin. Various numerical methods can be used for analysis of liquid storage pools, among these we mention explicit finite element, implicit Lagrangian-Eulerian, hybrid finite element, Smoothed Particle Hydrodynamics volume of fluid. In this article the coupled sloshing dynamics in a rectangle pool were studied using a model developed in LS-DYNA environment. The main solution methodology is based on explicit time integration. In order to demonstrate the FSI results of the FEA models of the spent fuel pool on seismic analysis, a 3D FEA models were developed. The Finite element model composed of the spent fuel pool (steel plate concrete), spent fuel storage racks, cushion block, water and air. Solid element modeling is used in concrete, cushion block, water and air. Steel plate and storage racks employ the shell element. The constitutive model of solid element is linear elastic. And the constitutive model of fluid element is described by the Gruneisen equation. Arbitrary Lagrangian-Eulerian (ALE) formulation is thought of as algorithms that perform automatic rezoning. It realized the advection of water and air in the ALE multi-material group.

The residual stress in thin films composing metal oxide semiconductor field emitter transistors (MOSFETs) was quantified, and a finite element method (FEM) based on the residual stress was proposed to predict stress in a scaled-down MOSFET which consists of a variety of thin films. A numerical analysis of process-induced stress in 130-nm-technology node MOSFETs was also carried out. The strain in the Si area in an actual MOSFET was measured by convergent-beam electron diffraction (CBED) and was compared with the FEM results to verify the validity of the FEM methodology. The FEM analysis results showed that (1) the magnitude of the compressive strain in the channel area increases as the source/drain length is reduced, (2) salicide reduces the magnitude of the compressive strain in the channel area, and (3) depositing tensile-stress SiN film in the sidewall spacer effectively reduces the channel strain. From a comparison of the FEM and CBED results it was found that although differences in the strain values obtained by these two methods are recognized, the results for both methods are in good agreement with regard to the shape of the strain distribution.

Non-destructive testing was applied to an aircraft tow hook made of forged AISI 4130 alloy steels to evaluate its structural integrity under service conditions. Five inspection methods including magnetic particle, liquid penetrant, eddy current, ultrasonic, and radiographic testing were applied to the same component and correlated with finite element stress analysis. Eddy current, ultrasonic, and radiographic methods proved ineffective due to material ferromagnetism, complex geometry, and field equipment limitations, while liquid penetrant testing detected surface indications but suffered from a high level of non-relevant responses. In contrast, magnetic particle testing reliably identified a linear surface crack approximately 13 mm long at the inner curvature near the attachment region. Finite element analysis indicated a yield utilization of approximately 43%, corresponding to a safety factor of about 2.3 under nominal towing loads, and fracture-mechanics evaluation yielded a critical crack length of 19.6 mm, indicating that the observed defect had reached about 66% of the critical value. The strong agreement between experimental crack detection and numerical stress predictions demonstrates the value of integrating targeted NDT with finite element analysis and confirms magnetic particle testing as the most reliable inspection method for forged AISI 4130 aircraft tow hooks under realistic field conditions.

This paper describes a new user-friendly structural design system for pressure vessels which is based on finite element stress analyses. A basic concept of the developed system is to minimize the input data required for the finite element analyses and to perform the analysis quickly. To realize this, the system consists of the finite element modeling module based on fuzzy knowledge processing, the input data generation module, the finite element analyzer, the graphical user-interface module for analysis results and the stress evaluation module. Fundamental performances of the present system are clearly demonstrated through the analysis of a top nozzle.

A computer aided analysis method is described for durability assessment in the early design stages using multibody dynamic analysis, finite element stress analysis, and fatigue life prediction methods. From multibody dynamic analysis of a mechanical system, dynamic loads of a mechanical component were calculated. Finite element stress analysis with substructuring techniques produced accurate stress fields for the component. From the dynamic loads and the stress field of the component, a dynamic stress history at the critical location was produced using the superposition principle. Using Neuber’s rule, a local strain time history was produced from the dynamic stress history. The local strain based fatigue life prediction method was then used to predict “crack initiation” life of the critical component. The predicted fatigue crack initiation life was verified by experimental durability tests. This methodology can be combined with identification of weak links and optimization techniques such that the design optimization for an entire mechanical system based upon durability is possible during the early product development stage.

The aim of this study was to calculate the stress distribution of fiberglass post associated with resin composite crown restoration and fiberglass posts with zirconia restorations in mature and immature endodontically treated central maxillary incisor under various loading conditions. The study created six different study models in a virtual environment: healthy mature maxillary central teeth, intact immature maxillary central teeth, mature maxillary central teeth with fiberglass post associated with resin composite crown restoration, immature maxillary central teeth with fiberglass post associated with resin composite crown restoration, mature maxillary central teeth with fiberglass posts and zirconia restoration, and immature maxillary central teeth with fiberglass posts and zirconia restoration. Loading conditions simulating mastication, trauma, and bruxism were applied to each of the models at different angles and amounts. The von Mises and the maximum and minimum principal stress values in tooth structures (dentin) and support structures (bone, PDL) and materials were observed using finite element stress analysis. The highest stress values in the tissue and the restoration structure were observed for masticating force and crowns rehabilitated with zirconia restorations. None of the compared loading conditions and restorations showed destructive stress values on periodontal ligament or bone. The mature and immature endodontically treated central maxillary incisors can be better rehabilitated using fiberglass post associated with resin composite crown restoration and may be preferred to zirconia restorations in order to reduce the stresses on the surrounding tissues and teeth. However, further clinical studies are needed to fully explore this topic.

The usability of drones is largely related to their performance, and among them, lightening is a very important factor in increasing flight distance and flight time by mounting a larger battery as a flight object and enabling low power flight. In this paper, finite element analysis was used to optimize the design aimed at reducing the weight and improving the strength of a 1 kgf class drone arm with a leg-type landing gear. o this end, finite element stress analysis and optimization design were performed step by step, and a method of modifying design variables using a combination of methods such as element removal method was used to realize the optimal structure. As a result of the stepwise optimal design performed in this paper, the optimization of the drone arm was achieved, which reduces the maximum effective stress by 0.04% while reducing the mass by 12.38%.

Brittle break downs are typical failures of ceramic materials. Chipping problems associated with all-ceramic zirconia restorations are studied and discussed at the moment. Factorial analysis showed that material and thickness of prosthetic crowns are of primary importance in stress magnitude. Laboratory tests such as finite element analysis (FEA) may help to predict the behaviour of different restorations during biomechanical simulation. The aim of this study was to evaluate by FEA stresses in all-ceramic crowns in regard to different veneer thicknesses. For the experimental analysis a first upper premolar was chosen. A static structural analysis was performed to calculate the stress distribution from different coping designs. FEA may help to predict the behaviour of all-ceramic bilayer crowns during biomechanical simulation. FEA investigations show that a constant veneering thickness of 1-1.8 mm doesn't affect the stress distribution and maximal stress values in the teeth structures and restorations.

Zirconium alloy has been extensively used as a cladding material in nuclear power reactors due to its low neutron absorption cross section, excellent mechanical properties, and corrosion resistance. The influence of the swaging parameter, feed rate (0.7, 1.25, 2 m/min) on residual stress induced in Zr-4 alloy is investigated in the present work. A three-dimensional finite element model was implemented in the Deform 3D software to simulate the rotary swaging (RS) process over a circular rod of Zr-4 alloy. The simulation results based on the 3D framework provide a detailed insight of residual stress, true stress versus true strain and force applied over the rod during the multiple pass swaging process; the results are compared with experimental results. The experimental hole drilling method is used to determine the residual stresses on swaged zirconium alloy at different feed rates (0.7, 1.25, and 2 m/min). A similar trend of residual stress between experimental and numerical results from the surface to the center on the swaged rod samples is observed. The same magnitude of residual stress at the surface of the swaged Zr-4 rod is also observed. It is found to be compressive at the surface and tensile in the center of the samples, as observed in the present work.

With the development of petrochemical industry, the status of pressure vessel has become increasingly important, and higher requirements are introduced for the security of nozzle zone at the pressure bearing region of pressure vessel. In order to study the stress status of nozzle zone at the channel of pressure vessel, solid modeling for channel and straight pipe was performed with ANSYS software. Through finite element analysis and calculation, the stress concentration region of channel was determined and the reason was analyzed. In addition, the nozzle zones of the model before and after loading were compared. The result reveals that symmetrical stress concentration region lies at the junction of channel and pipe. The maximum stress is located at the inside of nozzle zone of channel and less than the yield stress of material.

Finite element analysis of stress and wear characterization in total ankle replacements

This study aimed to investigate the stress accumulation on the skull base caused by the forces applied to fracture the bone at the sinus floor during the closed trans-alveolar technique of sinus elevation. This study was based on three-dimensional finite element analysis. Study models were determined as follows: Model 1, Model 2, and Model 3 (bone thickness at the sinus floor 1, 2, and 3 mm, respectively). The forces required for fracture of the bone at the base of the sinus were found to be 89,04 N, 138,88 N, and 210 N for Models 1, 2, and 3, respectively. The von Mises (VM), maximum principal (Pmax), and minimum principal (Pmin) stress values were examined at three different locations in the petrous part of the temporal bone. The highest stress values during the fracture process were recorded. During fracture, VM, Pmax, and Pmin stress values were highest in Model 3 and lowest in Model 1. When the most critical levels were analyzed, it was seen that all stress values in Model 3 were more than twice the values in Model 1. In closed trans-alveolar sinus lifting, as the forces applied to break the bone at the sinus floor increase, the stress accumulation at the petrous part of the temporal bone increases in direct proportion. This increase in cranial base stress may lead to an increased risk of benign paroxysmal positional vertigo which is a major complication of closed sinus lifting.

Development of a process modeling for residual stress assessment of multilayer thin film structure