• Title, Summary, Keyword: residual stresses

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Experimental investigation of residual stresses in cold formed steel sections

  • Besevic, Miroslav
    • Steel and Composite Structures
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    • v.12 no.6
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    • pp.465-489
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    • 2012
  • Residual stresses play important role for design of steel structural members. Cold formed sections usually have residual stresses caused by roll forming. When compared to stresses caused by the working load, especially for compressed members, the effects of residual stresses can be favorable or unfavorable depending on magnitude, orientation and distribution of these stresses. The research presented in this paper includes experimental investigations of residual stresses, initial imperfections and material properties on cold formed carbon steel open cross sections. Experimental results have been compared to results obtained in similar tests with stainless and high strength steel cross sections. Theoretical and experimental research, conducted for cold formed open cross sections, are important for design of axially compressed members. This paper presents two methods of residual stresses investigation: magnetic method and method of pre-drilled holes and obtained results have been compared with results of residual stresses from other authors.

The Distribution of Residual Stresses in Quenched Plastic Parts including Fee Volume Theory (자유체적이론을 고려한 플라스틱의 급냉시 잔류응력의 분포)

  • 김종선
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.106-111
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    • 2000
  • The residual stresses in molded plastic parts can be divided into the flow induced residual stresses produced in flowing stages and the thermally induced residual stresses produced in cooling state. Reducing residual stresses in the final parts is one of the goals in recent study. The present study focused on comparing the predicted values for thermal residual stresses in freely and constrained quenched plastic plates with and without free volume theory. As a result the final residual stresses showed the opposite pattern in thickness direction. furthermore by applying free volume theory the predicted residual stress at the center showed about 50% of the values without free volume theory for constrained quenched case.

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Effect of Heat Treatment Conditions and Densities on Residual Stresses at Hybrid (FLN2-4405) P/M Steels

  • Kafkas, Firat;Karatas, Cetin;Saritas, Suleyman
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • pp.566-567
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    • 2006
  • The characteristics of residual stresses occurring in PM steel based nickel (FLN2-4405) was investigated. The measurements of residual stresses were carried out by electrochemical layer removal technique. The values and distributions of residual stresses occurring in PM steel processed under various densities and heat treatment conditions were determined. In most of the experiments, tensile residual stresses were recorded in surface of samples. The residual stress distribution on the surface of the PM steels is affected by the heat treatment conditions and density. Maximum values of residual stresses on the surface were observed sinter hardened condition and $7.4\;g/cm^3$ density. Minimum level of recorded tensile residual stresses are150 MPa and its maximum level is 370 MPa.

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Design optimization of precision casting for residual stress reduction

  • Keste, Appasaheb Adappa;Gawanden, Shravan Haribhau;Sarkar, Chandrani
    • Journal of Computational Design and Engineering
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    • v.3 no.2
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    • pp.140-150
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    • 2016
  • Normally all manufacturing and fabrication processes introduce residual stresses in a component. These stresses exist even after all service or external loads have been removed. Residual stresses have been studied elaborately in the past and even in depth research have been done to determine their magnitude and distribution during different manufacturing processes. But very few works have dealt with the study of residual stresses formation during the casting process. Even though these stresses are less in magnitude, they still result in crack formation and subsequent failure in later phases of the component usage. In this work, the residual stresses developed in a shifter during casting process are first determined by finite element analysis using ANSYS(R) Mechanical APDL, Release 12.0 software. Initially the analysis was done on a simple block to determine the optimum element size and boundary conditions. With these values, the actual shifter component was analyzed. All these simulations are done in an uncoupled thermal and structural environment. The results showed the areas of maximum residual stress. This was followed by the geometrical optimization of the cast part for minimum residual stresses. The resulting shape gave lesser and more evenly distributed residual stresses. Crack compliance method was used to experimentally determine the residual stresses in the modified cast part. The results obtained from the measurements are verified by finite element analysis findings.

A Study on the Production Mechanisms of Residual Stress in Welded T-joint of Steel Pipe Member (T형 강관 용접 이음부의 잔류응력 생성기구에 관한 연구)

  • 장경호;장갑철;경장현;이은택
    • Journal of Welding and Joining
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    • v.21 no.6
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    • pp.40-45
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    • 2003
  • Steel members have advantages of resisting torsion and axial compression. In design, residual stresses at the welded joint of T-shape steel pipes are one of the most important points to be considered. In this paper, characteristics of residual stresses of welded joints are clarified by carrying out 3D non-steady heat conduction analysis and 3D thermal elastic-plastic FE-analysis. According to the results, the production mechanism of residual stresses at the welded joint of T-shape steel pipe is clarified. In this paper, circumferential stresses depended on thermal histories but axial and radial stresses were more dependent on geometrical shape than thermal histories. Residual stresses in the axial direction on the lower part of pipe member were tensile, controlled by geometrical shape. However, in case of middle part, residual stresses in all the directions were controlled by thermal histories.

The Formation of Residual Stresses and the Surface Fracture by the Break-in Process (길들이기에 의한 잔류응력의 형성과 표면파괴)

  • 김진욱;이영제
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • pp.159-165
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    • 2000
  • In this paper the residual stresses on lubricated sliding surfaces were measured during break-in procedure and up to scuffing by the X-ray diffraction method. The cylinder-on-disk type tribometer was used with the line-contact geometry. Scuffing tests were done using a constant load. In the break-in procedure the loads were increased from very low values in several steps. It was found that the sliding surfaces with break-in represented relatively higher values of residual compressive stresses than those without break-in. The residual stresses below the surfaces showed the small amount of stress increases. The results of scuffing tests with and without break-in showed the same trends as break-in tests did. However, in case of tests with break-in procedure the stresses below the surfaces showed very large increases in the residual compressive stresses. From the tests of break-in and scuffing, it was found that the increases in scuffing lives were related with the increases of residual stresses on the lubricated sliding surfaces with break-in.

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Measurement Method of Residual Stresses in Thick Composite Cylinders (두꺼운 복합재 원통의 잔류응력 측정방법)

  • Kim, Jong-Woon;Park, Dong-Chang;Lee, Dai-Gil
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.245-248
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    • 2005
  • During manufacturing thick composite cylinders, large thermal residual stresses are developed and induce catastrophic interlaminar failures. Since the residual stresses are dependent on many process parameters, such as temperature distribution during cure, cure shrinkage, winding tension, and migration of fibers, calculation of the residual stresses is very difficult. Therefore a radial-cut method have been used to measure the residual stresses in the composite cylinders. But the conventional radial-cut method needs to know numerous material properties which are not only troublesome to obtain but also vary with change of fiber arrangement during consolidation. In this paper, a new radial-cut method with cut-cylinder-bending test was proposed and the measured residual stresses were compared with calculated thermal residual stresses. It was found that the new radial-cut method which does not need to know any of material properties gave better estimation of residual stresses regardless of radial variation of material properties. Additionally, interlaminar tensile strength could be obtained by the cut-cylinder-bending test.

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Analysis of Chemically and Thermally Induced Residual Stresses in Polymeric Thin Film

  • Lee, Sang Soon
    • Journal of the Semiconductor & Display Technology
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    • v.14 no.1
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    • pp.1-5
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    • 2015
  • This paper deals with the residual stresses developed in an epoxy film deposited on Si wafer. First, chemically induced residual stresses due to the volumetric shrinkage in cross-linking resins during polymerization are treated. The curvature measurement method is employed to investigate the residual stresses. Then, thermally induced stresses are investigated along the interface between the epoxy film and Si wafer. The boundary element method is employed to investigate the whole stresses in the film. The singular stress is observed near the interface corner. Such residual stresses are large enough to initiate interface delamination to relieve the residual stresses.

Residual Stress Measurement in Hard Turned Workpiece (SKD11의 하드터닝 가공 열처리 시편의 표면잔류응력 측정에 관한 연구)

  • 김종혁;이태홍;장동영;한동철
    • Journal of the Korean Society for Precision Engineering
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    • v.20 no.5
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    • pp.148-155
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    • 2003
  • Most manufacturing processes such as welding, cutting and molding generate residual stresses on the surface of manufactured parts. Between compressive and tensile residual stresses, the tensile residual stress is harmful to the surface integrity, which results in reduced fatigue life and causes other structural failures when the service stresses are superimposed on the residual stresses. In the research, the residual stresses in the hardened tool steel (SKD11) were measured using hole-drilling method. The specimens were prepared through hard turning. Most of residual stresses in the machined surface were compressive.

The relationship between residual stresses and transverse weld cracks in the plate (후판용접부의 잔류응력과 횡균열의 상관관계)

  • 이해우;강성원;박종진
    • Proceedings of the KWS Conference
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    • pp.263-265
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    • 2003
  • The transverse crack, a type of cold crack, occurs perpendicular to the axis of the weld interface, longitudinal residual stresses ($\sigma$k direction) are more important in transverse crack occurrence from my own experience. Specimens were fabricated and welded under actual construction conditions, and then residual stresses of longitudinal stresses were measured for different welding conditions with SAW and FCAW process. The residual stress values for the specimen welded Interpass temperature below 30$^{\circ}C$ was higher than the specimen welded interpass temperature of 100~120$^{\circ}C$. And also the residual stress values for a specimen measured at weld surface, as welded condition, was higher than that of longitudinal residual stresses that was measured from a small test piece, due to the residual stress was relieved in the process of the cutting and machining. Transverse weld cracks were detected in the area of the maximum residual stresses both SAW and FCAW process.

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