Finite Element Code MARC Research Articles

Preliminary Analysis of Long-Term Performance of a Piping: Aging and Creep Effects.

Combining global experience, comprehensive aging knowledge, and predictive methodologies provides ideal prerequisites for the long-term operation strategy (LTO) of a nuclear power plant (NPP). Applying management strategies with an understanding of the ways in which structures relevant for the plant safety perform and interact in their operating environments is of meaningful importance for operating the plant beyond its originally licensed service life. In performing aging studies on the nuclear systems, structure, and components (SSCs), the results are crucial for demonstrating the safety and reliability of the NPP beyond 30 years of nominal operation. In this study, the synergistic effect of a creep mechanism with the alteration suffered by piping material is analyzed by means of MSC©MARC finite element code. Nonlinear analyses were performed to calculate the effects of the long operational period on a primary pipe, assess its degradation, and determine its residual functionality. In these analyses, both homogeneous and inhomogeneous pipe wall thinning are considered, as well as the operating or expected thermal–mechanical loads. The obtained results indicate that thermo–mechanical loads are responsible for pipe deformation, which develops and increases as the transient progresses. Furthermore, an excessive (general or local) wall thinning may determine a dimensional change of the pipe, even causing bending or buckling.

Prediction of turn down warping during hot plate rolling based on a Gaussian function

Turn down warping is a shape defect observed at the front end of a plate during hot rolling. To produce a flat plate without warping, a precise prediction of turn down warping is essential to achieve optimal control. Therefore, we propose a model based on a Gaussian function to predict turn down warping. The model uses the results from numerical analyses of hot plate rolling. The finite element code MARC was used for the numerical analysis. Hot plate rolling processing parameters, such as roll diameter, plate dimension, rolling speed, and pass line were all considered in the model. To verify the accuracy of the prediction model, the numerical results obtained by FEM were confirmed with data measured during industrial hot plate rolling. For the actual measurements of turn down warping, image processed high speed camera data from the exit side of the rolling were used. The results show that the proposed Gaussian function model can successfully predict turn down warping of a plate’s front end under various hot plate rolling conditions.

Numerical Analysis of Three-Dimensional Semi-Elliptical Interfacial Cracks Subjected to Indentation Load

The aim of this study is to show elastic J-integral needed to evaluate the interfacial fracture toughness of bi-material in indentation test. Three dimensional J-integrals along the crack front tip in semi-elliptical crack lying on the interface were analyzed using domain integral technique installed in commercialized finite element code MARC. The J-integral was calculated under several kind of aspect ratio of semi-elliptical cracks. In order to have to evaluate the interfacial fracture toughness from interfacial crack length and indentation load obtained in indentation tests, the analytical formula for two dimensional interfacial crack J-integral under plane stress, which had been introduced by J. R. Rice and G. C. Sih, was modified in reflecting upon the three dimensional effect. Finally, the indentation test was conducted for Aluminum alloy/ PMMA combination sample, and the associated fracture toughness was evaluated.Fig.1 Schematic illustration of indentation testFig.2 Schematic illustration of analysis mode

Research on WALKER Constitutive Model Tangent Modulus

In elasto-plasticity computation on materials by sub-increase finite element method, in general, it is necessary to calculate the consistent tangent modulus of elements. In this paper, based on the backward Euler integration, for an unified viscoplasticity constitutive equations, a new expression of consistent tangent modulus is derived for rate-dependent plasticity. The constitutive equations and consistent tangent modulus expression are implemented into a commercial finite element code-MARC. Numerical examples are given to verify the finite element implementation.This template explains and demonstrates how to prepare your camera-ready paper for Trans Tech Publications. The best is to read these instructions and follow the outline of this text.

시일과 스틸면 사이에 구형 입자가 있는 미끄럼 접촉 해석

In this paper, a three elastic body sliding contact problem is modeled to investigate more precise wear mechanisms related with the sealing surface. A 3-D finite element contact model, a small spherical elastic particle, PTFE seal and steel surface, is solved using a nonlinear finite element code MARC. The deformed seal and steel surface shapes, von-Mises and principal stress distributions are obtained for different seal sliding distances. The entrapped small particle within PTFE seal results in very high stresses on the steel surface which exceeded its yield strength and produce plastic deformation such as groove and torus. The sealing surface could also be worn down by sub-surface fatigue due to intervening small particles together with the well-known abrasive wear. Therefore the proposed contact model adopted in this paper can be applied in design of various sealing systems, and further studies are required.

A Method of Improving Limiting Drawing Ratio：Differential Temperature Deep Drawing Based on Superplasticity

A thermal-mechanical coupled analysis of superplastic differential temperature deep drawing (SDTDD) with the MARC finite element code is performed in this paper. Initial drawing blank of an AA5083 bracket was calculated and adjusted according to the simulation result. During the SDTDD simulation, the power-law constitutive model of AA5083 was established as function of temperature and implanted in software MARC through new complied subroutine. Under the guide of the numerical simulation, the die was fabricated and the AA5083 bracket was successfully manufactured via superplastic differential temperature deep drawing. In forming practice, the temperature of female die was kept at 525°C, i.e. the optimal superplastic temperature of AA5083, and the punch was cooled by the flowing water throughout the forming process. The drawing velocity of punch was 0.1mm/s. Results revealed that the formed bracket had a sound uniform thickness distribution. Good agreement was obtained between the formed thickness profiles and the predicted ones.

Effects of thickness and surface roughness on mechanical properties of aluminum sheets

The effect of thickness on the mechanical properties of Al 6K21-T4 sheet specimens under uniaxial tension was investigated. In order to reduce the thickness of the specimens without changing the microstructure and grain size, chemical etching was carried out, resulting in Al sheets ranging from 0.40 mm to 1.58 mm in thickness. Additionally, the effect of surface roughness was determined by finite element (FE) calculations performed using FE code MARC 2007. Tensile specimens of varying surface roughness were modeled and simulated. An analysis of the combined effects of the thickness and surface roughness revealed that the yield and tensile strengths decreased when the number of grains over the thickness was decreased. The ductility also decreased when reducing the thickness. An FE simulation showed that both the surface roughness and thickness affected the flow-curve shape. Moreover, the effect of the surface roughness tended to increase when decreasing the sheet thickness of specimens having the same roughness.

Nd:YAG 레이저 맞대기 용접의 비드형상 예측에 관한 유한요소해석

Nd:YAG pulse laser welding of stainless steel plate was simulated to find welding condition by using commercial finite element code MARC. Due to geometric symmetry, a half model of AISI 304 stainless steel plate was considered and user subroutines were applied to boundary condition for the heat transfer. Material properties such as conductivity, specific heat, mass density and latent heat were given as a function of temperature. As results, Three dimensional heat source model for pulse laser beam conditions of butt welding has been designed by the comparison between the finite element analysis results and experimental data on AISI 304 stainless steel plate. Nd:YAG laser welding for AISI 304 stainless steel was successfully simulated and it should be useful to determine optimal welding condition.

1107 引張圧縮負荷を受ける鉛フリーはんだの粘塑性有限要素解析(J08-1 電子情報機器,電子デバイスの強度・信頼性評価と熱制御(1) はんだ接合部信頼性,ジョイントセッション,21世紀地球環境革命の機械工学:人・マイクロナノ・エネルギー・環境)

When we estimate the fatigue life of solder joints, we have to conduct FE analysis with a constitutive model which can exhibit dynamic property of Pb free solder. We proposed a creep-plasticity unified viscoplastic constitutive model with Armstrong-Frederick type nonlinear kinematic hardening rule which can describe temperature and rate dependent cyclic stress-strain relations. Then, we implemented the proposed model into finite element code MARC and analyzed tension tests and the tension-compression tests of Sn3.5Ag0.5Cu0.07Ni0.01Ge solder. We compared test data with analytical FE results of the proposed model, anand model and classical creep-prasticity decoupled model. It was confirmed that analytical results using the proposed model were in good agreements with the experimental results.

Nd:YAG 레이저 필렛 용접의 비드형상 예측에 관한 유한요소해석

Nd:YAG pulse laser fillet welding of stainless steel plate was simulated to find welding condition by using commercial finite element code MARC. Full model of AISI 304 stainless steel plate was considered and user subroutines were applied to boundary condition for the heat transfer. Material properties such as conductivity, specific heat, mass density and latent heat were given as a function of temperature. As results, Three dimensional heat source model for pulse laser beam conditions of fillet welding has been designed by the comparison between the finite element analysis results and experimental data on AISI 304 stainless steel plate. Nd:YAG laser welding for AISI 304 stainless steel was successfully simulated and it should be useful to determine optimal welding condition.

Comparative Study of Element Formulation on Simulation of Superplastic Forming

A comparative study of different element formulations in simulating superplastic forming with the MARC finite element code is performed in the paper. Simulations were accomplished with solid, shell, membrane elements to predict forming characteristics and pressure-time curves. Finite element analysis (FEA) predictions of SPF pressure-time curves were found to be greatly affected by the element type and the strain rate control algorithms. Two strain rate control algorithms were applied in the present study: an algorithm based on limiting the rate of deformation with the average strain rate of all the elements, i.e. the build-in method in MARC, and a second algorithm which limits the rate of deformation based on the average strain rate of the elements with the 20 highest strain rates. The resulting pressure-time curves for each of these formulations were compared with respect to each type of element. Under the guide of the analysis, the die was fabricated and the AA5083 bracket was successfully manufactured. Good agreement was obtained between predicted and measured thickness in the part.

ANALISIS SQUARE CUP DEEP DRAWING

The applications of sheet metal forming is very important in the automotiveindustries since most of the car components are produced by press formingprocesses. Survey shows that the role of numerical simulation and optimization toimprove performance and quality of their products are still very limited. Thispaper describes the use of MARC finite element code in a single stage sheet metalforming simulation on square cup deep drawing. The MARC’s results arevalidated with experimental results of benchmark problem square cup deepdrawing in Numisheet ’93. The paper also discusses the localized stress andstrain values of the formed part

AISI 304 스테인리스 강판의 Nd:YAG 펄스 레이저 용접에 관한 유한요소해석

Pulse laser welding of AISI 304 stainless steel plate was simulated to find optimal welding conditions by using commercial finite element code MARC. Due to geometric symmetry, a half model of AISI 304 stainless steel plate was considered and user subroutines were applied to boundary condition for the heat transfer. Material properties such as conductivity, specific heat, mass density and latent heat were given as a function of temperature. A moving heat source was designed on the basis of experimental data. As a result, Nd:YAG laser welding for AISI 304 stainless steel was successfully simulated and it should be useful to determine optimal welding condition.

Measurement and modeling of residual stress in a welded Haynes ® 25 cylinder

An experimental and simulation study of residual stresses was made in the vicinity of a gas tungsten arc weld, used to join a hemispherical end cap to a cylinder. The capped cylinder is used in a satellite application and was fabricated from a Co-based Haynes ® 25 alloy. The cylinder was 34.7 mm in outer diameter and 3.3 mm in thickness. The experimental measurements were made by neutron diffraction and the simulation used the implicit Marc finite element code. The experimental resolution was limited to approximately 3 mm parallel to the axis of the cylinder (the weld was 6 mm in the same direction) and comparison over the same volume of the finite element prediction showed general agreement. Subject to the limited spatial resolution, the largest experimentally measured tensile residual stress was 180 MPa, located at the middle of the weld. However, the predictions suggest that there are regions in the weld where average tensile residual stresses as much as 400 MPa exist. One qualitative disparity between the model and the experiments was that the measurement included a larger degree of asymmetry on either side of the weld than predicted by the model.

Model of laser-TIG hybrid welding heat source

The welding mechanism of laser-TIG hybrid welding process is analyzed. With the variation of arc current, the welding process is divided into two patterns: deep-penetration welding and heat conductive welding. The heat flow model of hybrid welding is presented. As to deep-penetration welding, the heat source includes a surface heat flux and a volume heat flux. The heat source of heat conductive welding is composed of two Gaussian distribute surface heat sources. With this heat source model, a temperature field is calculated. The finite element code MARC is employed for this purpose. The calculation results show a good agreement with the experimental data.

Thermal Modelling of Surface Grinding Using Implicit Finite Element Techniques

A finite element model is proposed to simulate the precision and ultraprecision grinding of steel and to describe the temperature fields developed during the process. The grinding is modelled using the commercial implicit finite element code MARC. In order to obtain the input data required for the model and to examine the heat damage induced to the workpiece, a series of experiments was performed with the same grinding conditions, but using different aluminium oxide grinding wheels of different bonding on the same work material. Comparison between numerical results obtained from the proposed model and experimental predictions, as well as numerical and analytical calculations reported in the literature, revealed a good agreement between theory and practice, indicating therefore that the model may be suitable for industrial applications.

Analysis of Tube Hydroforming by Means of an Inverse Approach1

This paper presents a computational tool for the analysis of freely hydroformed tubes by means of an inverse approach. The formulation of the inverse method developed by Guo et al. [1] is adopted and extended to the tube hydroforming problems in which the initial geometry is a round tube submitted to hydraulic pressure and axial feed at the tube ends (end-feed). A simple criterion based on a forming limit diagram is used to predict the necking regions in the deformed workpiece. Although the developed computational tool is a stand-alone code, it has been linked to the Marc finite element code for meshing and visualization of results. The application of the inverse approach to tube hydroforming is illustrated through the analyses of the aluminum alloy AA6061-T4 seamless tubes under free hydroforming conditions. The results obtained are in good agreement with those issued from a direct incremental approach. However, the computational time in the inverse procedure is much less than that in the incremental method.

Analysis of Tube Free Hydroforming Using an Inverse Approach With FLD-Based Adjustment of Process Parameters1

This paper describes an inverse approach (IA) formulation for the analysis of tubes under free hydroforming conditions. The IA formulation is derived from that of Guo et al. established for flat sheet hydroforming analysis using constant strain triangular membrane elements. First, an incremental analysis of free hydroforming for a hot-dip galvanized (HG/Z140) DP600 tube is performed using the Marc finite element code. The deformed geometry obtained at the last converged increment is then used as the final configuration in the inverse analysis. This comparative study allows an assessment of the predictive capability of the inverse analysis. The results are compared with the experimental values determined by Asnafi and Skogsga¨rdh. After that, a procedure based on a forming limit diagram (FLD) is described as a means to adjust the process parameters such as the axial feed and internal pressure. Finally, the adjustment process is illustrated through a re-analysis of the same tube using the inverse approach.

Static and dynamic axial collapse of fibreglass composite thin-walled tubes: finite element modelling of the crush zone

Explicit and implicit finite element codes have been developed for predicting the axial collapse of thin-walled structures with a reasonable amount of computer time, allowing, in this manner, such structural components to be designed and analyzed without having to build and test expensive prototypes. The present paper describes the implementation of the ȁimplicitȁ finite element code MARC in the simulation of the crush behaviour of cylindrical thin-wall composite tubes under static and dynamic axial compression, in accordance with the progressive mechanism of failure (Mode I of collapse). The predicted numerical results are validated by comparing with actual experimental data obtained from quasi-static and impact tests conducted in a tensile test machine and a drop hammer rig respectively. Furthermore, for ultimate validation, load and energy absorption values from the numerical results are also compared with those analytically calculated, thereof showing good agreement.

Assessment of crack growth in a space shuttle main engine first-stage high-pressure fuel turbopump blade

A two-dimensional finite element fracture mechanics analysis of a space shuttle main engine (SSME) turbine blade firtree was performed using the MARC finite element code. The analysis was conducted under combined effects of thermal and mechanical loads at steady-state conditions. Data from a typical engine stand cycle of the SSME engine were used to run a heat transfer analysis and, subsequently, a thermal structural fracture mechanics analysis. Temperature and stress contours for the firtree under these operating conditions were generated. High stresses were found at the firtree lobes where crack initiation was triggered. A life assessment of the firtree was done by assuming an initial and a final crack size.