• Proceedings of the KWS Conference
• /
• v.43
• /
• pp.150-152
• /
• 2004

This study was aimed at evaluation of residual stress of steel pipe structures. The production process of pipes was complex (at first bending was done by roll forming or press forming and welding was final process of making of steel pipes). So there could be effected high residual stresses in steel pipes. In order to evaluate the changes of residual stress the locations of measurement were selected carefully. Measurements of residual stress were done for various kinds of pipes (shapes in circular and square). For the evaluation of residual stress, hole-drilling method (ASTM E837 was applied. The results showed that along the weld Eine high tensile stress were measured as effected, and high tensile stresses were measured where large plastic deformation developed. Through these efforts, experimental results could be more effectively assisted by numerical method.

• Journal of the Society of Naval Architects of Korea
• /
• v.48 no.5
• /
• pp.473-478
• /
• 2011

Welding process generates distortion and residual stress in the weldment due to rapid heating and cooling. Welding distortion and residual stress in the welded structure result in many troubles such as dimensional inaccuracies in assembling and safety problem during service. The accurate prediction of welding residual stress is thus very important to improve the quality of weldment and find the way to reduce itself. This paper presents the simulation of welding-induced residual stress analysis to examine the cause of cracking in the SUS-overlay welding specimen at FPSO Moon Pool structure.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.30 no.5 s.248
• /
• pp.602-608
• /
• 2006

Vehicle components such as lower control arm are usually affected by heat during the welding process. As a result, residual stress is generated, which has much effect on mechanical performances such as crashworthiness and durability. In this study, the residual stress in lower control arm has been measured by the x-ray diffraction method and been analyzed by finite element methods. Heat transfer during seam weld process has been calculated and used in calculating thermal deformation with temperature dependent material properties. High residual stress has been found at vertical wall both by measurement and simulation. The simulation also showed the residual stress re-distribution when the component is subjected to cyclic loading condition.

• Journal of the Korean Society for Precision Engineering
• /
• v.23 no.9 s.186
• /
• pp.127-133
• /
• 2006

Cold expansion method is used to protect a fatigue fracture from fastener hole in the structure and aerospace industry. Cold expansion is that an oversized tapered mandrel goes through the hole and produces a compressive residual stress as well as plastic deformation around the hole. Here, mandrel shapes are one of the factors which are influenced on the residual stress distribution by cold expansion method. This paper, according to mandrel shapes (diameter of mandrel, length of mandrel and length of taper), we are performed a finite element analysis of residual stress distribution by cold expansion method. From this study, it has been found that diameter of mandrel and length of taper are an important factor which was generated a low compressive residual stress surround of fastener hole by cold expansion method.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 1999.03b
• /
• pp.102-106
• /
• 1999

One of the main causes of unwanted dimensional changes in precision metal mold casting parts is excessive and irregular residual stresses induced by temperature gradients and plastic deformation in the solidifying shell. Residual stresses can also cause stress cracking and lower the fatigue life and fracture strength of the casting parts,. In the present study aluminum alloy casting system with metal mold equipped with electrical heating elements and water cooling units was designed and the casting specimens were produced to quantify the effects of different cooling conditions on the development of residual stresses. the layer removal method was used to measure the biaxial residual stresses in casting specimens produced from the experiments. The experimental results agreed with Tien-Richmond's theoretical model for thermal stress development for the solidifying metal plate

• Proceedings of the KSME Conference
• /
• 2000.11a
• /
• pp.470-474
• /
• 2000

Cold expansion of fastener holes is a mechanical process widely used in the aerospace industry. This treatment leads to an improvement of fatigue behavior due to the developed compressive residual stresses on the hole surface. The residual stress profile depends on the parameters of cold expansion, which are, expanding rate, inserting direction of mandrel, material properties etc. and the method to confirm this profile is only measurement by X-ray diffractometer. Despite its importance to aerospace industries, little attention has been devoted to the accurate modelling of the process. In this paper, Two-dimensional axisymmetric finite element simulations have been conducted for the cold expansion in an aluminium plate in order to predict the magnitude and distribution of the residual stress and plastic deformation. Maximum compressive residual stress could be increase about 7 percent using the 2-step cold expansion method.

• Journal of Powder Materials
• /
• v.1 no.1
• /
• pp.52-59
• /
• 1994

Since the coefficient of thermal expansion (CTE) of matrix phase is larger about 4 times than that of W particle in tungsten heavy alloy, the thermal stresses due to the CTE difference between the two phases are induced in the alloy during heating and cooling processes. In the present study, a series of W heavy alloy containing various W particle volumes of 0 to 90% is made to investigate the residual stress taking place during cooling process. The CTE and residual stress of the series of alloy are measured by dilatometer and X-ray diffractometer. The residual stress of W particle is in compressive stress irrespective of W particle vol% and tends to increase with decreasing W particle vol% while that of the matrix phase is in tensile stress. The measured residual stress of W particle is about a third of calculated thermal stress. The influence of W particle vol% on the residual stress of W heavy alloy is discussed in terms of the deformation behaviors of W particle and matrix phase.

• Transactions of Materials Processing
• /
• v.19 no.4
• /
• pp.224-229
• /
• 2010

During the multi-pass wire drawing process, wires suffer a great amount of plastic deformation that is through the cross-section. This generates tensile residual stress at surface of drawn wires. The generated residual stress on surface is one of the problems for quality of wires so that prediction and reduction of residual stresses is important to avoid unexpected fracture. Therefore, in this study, the effect of process variables such as semi-die angle, bearing length and reduction ratio on the residual stress was evaluated through Finite Element Analysis. Based on the results of the Analysis, a prediction model was established for predicting residual stress on the surface of high carbon steel(AISI1072, AISI1082). To identify the effectiveness of the proposed model, X-ray diffraction is used to measure the residual stresses on the surface. As the result of the comparison between calculated residual stresses and measured residual stresses, the model could be used to predict residual stresses in cold drawn wire.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2000.11a
• /
• pp.195-198
• /
• 2000

It can be acquired the high effective productivity through of high speed, precision of machine tools, and then, machine tools will be got a competitive power. Industrially advanced countries already developed that the high speed feed is 60m/min using the high speed ball screw. Also, a lot of problems have happened the feed drive system. It is necessary to study about the characteristics of thermal deformation played a more critical role than static stiffness and dynamic rigidity in controlling the level of machining accuracy. In spite of the improving the thermal deformation characteristics of machine tools at the design stage, there are always some residual errors that have to be compensated for during machining. In this study, thermal deformation error automated compensation device with multiple linear regression is proposed that thermal deformation error can be eliminated at the machining stage. The developed device has been practically applied to the feed drive unit.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
• /
• 2006.11a
• /
• pp.201-204
• /
• 2006

A three-dimensional finite element (FEM) model has been developed to simulate the deformation due to bead on plate welding of curved plates with curvature in the weld direction. By using traditional method such as thermal-elastic-plastic FEM, the weld-induced deformation can be predicted accurately. However, this method is not practical approach to analyze the deformation of large and complex structures such as ship hull structures in view of time and cost. This study is classified from the aspect of equivalent load based on inherent strain near the weld line. Therefore, the residual deformation can be simply computed by elastic analysis. Further more, a practical solution is proposed to consider the contact between the plate and the positioning jig by judging the reaction forces of the jig at calculation step and the effect of the longitudinal curvature is closely considered.