Mathematical Modeling of Flow Behaviour of API-X70 during Hot Torsion Testing

2011 ◽  
Vol 264-265 ◽  
pp. 60-65 ◽  
Author(s):  
Bahman Mirzakhani

The flow behaviour of material is strongly influenced by the microstructure evolution during hot deformation processes. In this work, a comprehensive mathematical modelling of heat transfer and plastic deformation was carried out employing finite element analysis based on rigidviscoplastic formulation. Semi-empirical models of dynamic recovery and recrystallization were utilized to develop the microstructure dependent constitutive equations. They were then integrated into the finite element code to simulate stress-strain curve of API-X70 steel during hot deformation process. Hot torsion tests were carried out at various deformation conditions for characterization of microstructure equations and model validation. The good agreement between experimental data and simulation results were achieved. The model predicts work hardening, dynamic recovery and recrystallization simultaneously and it considers their effects on the flow stress of the material during hot deformation.

2010 ◽  
Vol 2 (2) ◽  
pp. 3231-3236 ◽  
Author(s):  
A.W. Pugh ◽  
R. Hamilton ◽  
D.H. Nash ◽  
S.R. Otto

2016 ◽  
Vol 78 (11) ◽  
Author(s):  
Mariam Md Ghazaly ◽  
Tawfik Ahmed Yahya ◽  
Aliza Che Amran ◽  
Zulkeflee Abdullah ◽  
Mohd Amran Md Ali ◽  
...  

This paper presents an extensive characterising study of two novel electromagnetic actuators, each with different constructions and characteristics aiming to analyse the behaviour and output characteristics of the two designs. The two actuators are Tubular Linear Reluctance Actuator (TLRA) and Tubular Linear Permanent magnet (TLPM) with Halbach array actuator. The study covered the variation of three parameters, which are the actuator air gap, number of turns and actuator size. A comparative section was also presented for the purpose of comparison. The study concentrated extensively on the two characteristics of both actuators known as output thrust force and working range as they are considered as two main concerns of any actuator design. The simulation was used to show the differences between the two designs in many design aspects such as force, displacement and effects of parameters variations. The applied simulation was performed using 3D Finite-element Ansys software, which is capable of showing the magnetic field distribution in the whole actuator and predicting the strength and length of the output stroke.


Author(s):  
Toshiyuki Sawa ◽  
Naofumi Ogata

This paper deals with the stress analysis of a pipe flange connection with a spiral wound gasket using the elasto-plastic finite element method taking account the hysteresis and the non-linearity in the stress-strain curve of the spiral wound gasket, when an intemal pressure is applied to the pipe flange connections with the different nominal diameters from 2″ to 20″. The effects of the nominal diameter of the pipe flange on the contact stress distributions at the interfaces are examined. Leakage tests of the pipe flange connections with 3″ and 20″ nominal diameters were conducted and measurement of the axial bolt force was also performed. The results by the finite element analysis are fairly consistent with the experimental results concerning the variation in the axial bolt force. By using the contact stress distributions and the results of the leakage test, the new gasket constants are evaluated. As a result, it is found that the variations in the contact stress distributions are substantial due to the flange rotation in the pipe flange connections with the larger nominal diameter. In addition, a method to determine the bolt preload for a given tightness parameter is demonstrated.


Author(s):  
Cameron Ewing

Abstract Stress Intensification Factors or SIFs allow piping to be analyzed using beam theory, with a SIF representing local effects of specific piping geometry. However, the current piping codes do not explicitly provide SIFs for collared type piping joints for use in pipe stress calculations. The objective of this paper is to describe the methodology on how a finite element analysis (FEA) was to model the behavior of collared joints, and to ultimately develop appropriate SIFs that can be used in pipe stress analyses. This paper describes a real-life analysis example on collared joints installed on a set of existing fuel transfer lines. The lines, which ranged in size from DN200 to DN350, were concrete lined carbon steel with the collars fillet welded to the carbon steel section of the piping. Test coupons cut from existing pipe-collar sections were tested in a laboratory to determine the forces required to break the collar welds. Using FEA, the same test coupons were modelled to replicate the failure tests. Multiple iterations were undertaken to determine an appropriate bi-linear stress-strain curve fit for the weld material. The curves of different weld electrode materials were considered. The curve which lead to results similar to those observed in physical testing was selected. From this, a failure stress across the weld could be determined. This stress, 435MPa was then used in subsequent models to determine the point at which the weld fails under bending loads. Multiple tests were analyzed to allow for possible effects of inclusions and voids. Finite element models of the collar geometries were constructed and non-linear analyses were undertaken using the weld strengths determined from the coupon testing data. A simple cantilever type arrangement with a point load at one end was analyzed, inducing a bending moment across the collar. The peak stress resulting from the bending moment across the collar weld at the center of the cantilevered pipe arrangement, was investigated across various pipe diameters, wall thicknesses, weld sizes and collar geometries. Based on the results, a relationship between the pipe geometry and SIF was developed. Hence a pipe stress model of the transfer lines could ultimately be developed using these SIFs to predict the behavior of the piping.


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