• Advances in Computational Design
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• 제4권3호
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• pp.239-250
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• 2019

The insertion of femoral implants is the most important phase for surgeons, given the characteristics of the cement during its mixing phase, generating residual stresses of thermal origin that increase the different stresses induced in the bone cement. The aim of our study is to determine the different stresses that affect the cement and more particularly at the cement-implant interface for different temperatures, and to make a comparison with the cement at ambient temperature. It was concluded that, there are a large concentration of stresses in the proximal part of the cement. For normal stresses, the bone cement is affected by stresses of tension and compression due to the effect of polymerization and the contraction of the cement.

• Steel and Composite Structures
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• 제18권3호
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• pp.583-601
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• 2015

In the present study, the combined effects of thermal and mechanical loadings on the interlaminar shear stresses of both moderately thin and thick composite laminated beams are numerically analyzed. The finite element modelling of laminated composite beams and analysis of interlaminar stresses are performed using the commercially available software package MSC NASTRAN/PATRAN. The validity of the finite element analysis (FEA) is demonstrated by comparing the experimental test results obtained due to mechanical loadings under the influence of thermal environment with those derived using the present FEA. Various parametric studies are also performed to investigate the effect of thermal loading on interlaminar stresses generated in symmetric, anti-symmetric, asymmetric, unidirectional, cross-ply, and balanced composite laminated beams of different stacking sequences with identical mechanical loadings and various boundary conditions. It is shown that the elevated thermal environment lead to higher interlaminar shear stresses varying with the stacking sequence, length to thickness ratio, ply orientations under identical mechanical loading and boundary conditions of the composite laminated beams. It is realized that the magnitude of the interlaminar stresses along xz plane is always much higher than those of along yz plane irrespective of the ply-orientation, length to thickness ratios and boundary conditions of the composite laminated beams. It is also observed that the effect of thermal environment on the interlaminar shear stresses in carbon-epoxy fiber reinforced composite laminated beams are increasing in the order of symmetric cross-ply laminate, unidirectional laminate, asymmetric cross-ply laminate and anti-symmetric laminate. The interlaminar shear stresses are higher in thinner composite laminated beams compared to that in thicker composite laminated beams under all environmental temperatures irrespective of the laminate stacking sequence, ply-orientation and boundary conditions.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 춘계학술대회 논문집
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• pp.872-877
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• 2004

Welding residual stresses are the main topics of welding research fields. The residual stresses and distortion of structures by welding exert negative effect on the safety of mechanical structures. That is, expansion of material by high temperature and distortion by cooling during welding process are caused by tensile and compressive residual stresses in welding material, and this residual stresses can induce fracture and fatigue problems of welding structures. The accurate prediction of residual stress and relaxation due to mechanical loading of weld zone is very important to improve the quality of weldment. In this study, a finite element modeling technique is developed to simulate the relaxation of residual stresses due to mechanical loading. The effects of load ratio for static and cyclic loading are evaluated based on analytical results.

• Structural Engineering and Mechanics
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• 제52권1호
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• pp.89-95
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• 2014

We analyze the buckling of a thin elastic plate due to intrinsic stresses in thin films attached to the surfaces of the plate. In the case of cylindrical buckling, it is shown that for a plate with clamped edges compressive intrinsic film stresses can cause flexural buckling of the plate, while tensile intrinsic film stresses cannot. For a plate with free edges, film intrinsic stresses, compressive or tensile, cannot cause buckling.

• 한국해양공학회지
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• 제10권2호
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• pp.88-97
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• 1996

The pupose of this study is to improve the mechanical properies and to evaluate the residual stresses of flame-sprayed Alumina ceramic coating layer. The first work in this study is to investigate the effects of strengthening heat treatments on the mechanical properties of coating layer. Strengthening heat treatments for sprayed specimens were carried out in vaccum furnace. The mechanical properties such as microhardness, thermal shock resistance, adhesive strength and erosion resistance were tested for the sprayed specimens after strengthening heat treatments. And it was clear that the mechanical properties of coating layer were much improved by strengthening heat treatments. The second work in this study is to evalute the residual stresses in coating lsyer by numerical analysis. FDM and FEM were used to analyze temperature distribution and residul stresses in coating layer. It was proved that are tensile stresses in coating layer and that residual stresses can be controlled by the appropriate selection of the spraying parameters such as preheat temperature, coating thickness and bond coat thickness.

• Journal of Mechanical Science and Technology
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• 제14권1호
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• pp.19-29
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• 2000

A viscoelastic finite element analysis is presented to investigate residual stresses occurred in a laminated cylindrical shell during cure. An incremental viscoelastic constitutive equation that can describe stress relaxation during the cure is derived as a recursive formula which can be used conveniently for a numerical analysis. The finite element analysis program is developed on the basis of a 3-D degenerated shell element and the first order shear deformation theory, and is verified by comparing with an one dimensional exact solution. Viscoelastic effect on the residual stresses in the laminated shell during the cure is investigated by performing both the viscoelastic and linear elastic analyses considering thermal deformation and chemical shrinkage simultaneously. The results show that there is big difference between viscoelastic stresses and linear elastic stresses. The effect of cooling rates and cooling paths on the residual stresses is also examined.

• Journal of Computational Design and Engineering
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• 제3권2호
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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.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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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.

• 대한기계학회논문집A
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• 제26권8호
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• pp.1653-1665
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• 2002

One of the most significant problems in the processing of composite materials is residual stresses. The residual stresses may be high enough to cause cracking in the matrix even before external loads are applied and can degrade the integrity of composite structures. In this study, thermo-viscoelastic residual stresses occurred in the polymeric composite cylinder are investigated. This type of structure is used for the launch vehicle fuselage. The time and degree of cure dependent thermo-viscoelastic constitutive equations are developed and coupled with a thermo-chemical process model. These equations are solved with the finite element method to predict the residual stresses in the composite structures during cure. A launch vehicle experiences high thermal loads during flight and re-entry due to aerodynamic heating or propulsion heat, and the thermal loads may cause thermal buckling on the structure. In this study the thermal buckling analysis of composite cylinders are performed. Two boundary conditions such as all clamped and all simply supported are used for the analysis. The effects of laminates stacking sequences, shapes and residual stresses on the critical buckling temperatures of composite cylinders are investigated. The thermal buckling analysis is performed using ABAQUS.

• 대한기계학회논문집A
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• 제32권3호
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• pp.250-257
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• 2008

We calculate the variation of the surface stresses according to uniaxial and biaxial strains in face-centered cubic (FCC) metals. In our study, three mainly observed free surfaces of seven representative FCC metals are considered. Employed method is molecular mechanics, in which the interaction of atoms is described by empirical interatomic potentials. As uniaxial strain increases to tensile direction, the surface stresses on {100} and {110} free surfaces decrease monotonously, while those on {111} surface increase. These tendencies are the same regardless of the species of metals and interatomic potentials employed. However, when the system is under biaxial strain, surface stresses change different according to the surface directions, the species of metals, and even interatomic potentials. On {100} and {111} surfaces, heavy metals (Pt, Au) show the opposite variation to light metals (Ni, Cu). In the cases of Pd and Ag, the surface stresses reveal the opposite tendency, depending on interatomic potentials used.