• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.4
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• pp.467-474
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• 2010

Stainless steel sheets are widely used as the structural material for railroad cars and commercial vehicles. Structures made of stainless steel sheets are commonly fabricated by gas welding, For the fatigue design of gas welded joints such as fillet joints, it is necessary to obtain design information of the stress distribution at the weldment as well as the fatigue strength of the gas-welded joints. Further, the influence of the geometrical parameters of gas-welded joints on stress distribution and fatigue strength must be evaluated. in this study, ${\Delta}P-N_f$ curves were obtained by fatigue tests. and, the ${\Delta}P-N_f$ curves were rearranged on the basis of the ${\Delta}{\sigma}-N_f$ relation for the hot-spot stresses at the gas-welded joints. These results, were used for conducting an accelerated life test(ALT) From the experiment results, an acceleration model was derived and factors were estimated. The objective is to obtain the information required for the analysis of the fatigue lifetime of fillet welded joints and for data analysis by the statistic reliability method to save time and cost and to develop optimum accelerated life prediction plans.

• Journal of the Korea Concrete Institute
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• v.28 no.4
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• pp.419-426
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• 2016

This study examined the effect of transverse reinforcement and compressive stress on the shear friction performance at the shear interface intersecting two structural elements with various concrete types. From the prepared 12 push-off test specimens, various characteristics at the interface were measured as follows: crack propagation, shear load-relative slip relationship, initial shear cracking strength, ultimate shear friction strength, and shear transfer capacity of transverse reinforcement. The configuration of transverse reinforcement and compressive strength of concrete insignificantly influenced the amount of relative slippage at the shear friction plane. With the increase of applied compressive stress, the shear friction capacity of concrete tended to increase proportionally, whereas the shear transfer capacity of transverse reinforcement decreased, which was insignificantly affected by the configuration type of transverse reinforcement. The empirical equations of AASHTO-LRFD and Mattock underestimate the shear friction strength of concrete, whereas Hwang and Yang model provides better reliability, indicating that the mean and standard deviation of the ratios between measured shear strengths and predictions are 1.02 and 0.23, respectively.

• Journal of the Korean Ceramic Society
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• v.26 no.1
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• pp.116-122
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• 1989

MOR test and concentric ring test were performed to evaluate the failure probability of sin/hip Si3N4 under uniaxial and biaxial stress state, respectively. Their failure probabilities were analized with KARA program based on Weibull PIA model and Batdorf model with 5 criteria, and they were compared with experiments. PIA model is in best accordance with experiments in higher fracture strength regions, especially for Pf 0.3. But in lower fracture strength region, none of the models predicts the failure probabilities appropriately.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.2
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• pp.382-390
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• 1995

Failure of connecting rod in automotive engine may cause catastrophic situation. The corner radius at small end has an effect on stress raising. To investigate the stress distribution in connecting rod during operation, the finite element analysis was used by giving possible maximum tension and compression. Excessive sizing after forging connecting rod may result in the tensile residual stress which lower the fatigue life and cause premature failures. It was shown that when the sizing amount is too large, the location of high tensile residual stress coincide with that of high stress amplitude during operation through the elastic-plastic finite element analysis. The endurance limit moves down due to the surface finish and decarburization, which combines with the movement of resultant stress points to dangerous range. It was concluded that the precise control of sizing and enough corner radius are necessary to a reliability of connecting rod.

• Journal of Welding and Joining
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• v.21 no.5
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• pp.547-554
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• 2003

Apparent mechanical properties in structural components can be different from the initially designed values due to the formation of the residual stress in metal forming and welding. Therefore, the evaluation of residual stress has great importance in the reliability diagnosis of structural components. A nondestructive instrumented indentation technique has been proposed to evaluate various strength concerning mechanical properties from the analysis of load-depth curve. In this study, quantitative residual stress estimation on API X65 welded joints for natural gas pipeline was performed by analyzing the variation of indentation loading curve by residual stress through a new proposed theoretical model. The residual stress from the indentation method was compared with that from the saw-cutting method.

• Transactions of Materials Processing
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• v.14 no.6 s.78
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• pp.541-546
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• 2005

Apparent mechanical properties in structural components can be different from the initially designed values due to the formation of the residual stress in metal forming and welding. Therefore, the evaluation of residual stress has great importance in the reliability diagnosis of structural components. A nondestructive continuous indentation technique has been proposed to evaluate various strength concerning mechanical properties from the analysis of load-depth curve. In this study, quantitative residual stress estimation on API X65 welded joints for natural gas pipeline was performed by analyzing the variation of indentation loading curve by residual stress through a new proposed theoretical model. The residual stress from the indentation method was compared with that from the saw-cutting method.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.126-129
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• 2005

Apparent mechanical properties in structural components can be different from the initially designed values due to the formation of the residual stress in metal forming and welding. Therefore, the evaluation of residual stress has great importance in the reliability diagnosis of structural components. A nondestructive continuous indentation technique has been proposed to evaluate various strength concerning mechanical properties from the analysis of load-depth curve. In this study, quantitative residual stress estimation on API X65 welded joints for natural gas pipeline was performed by analyzing the variation of indentation loading curve by residual stress through a new proposed theoretical model. The residual stress from the indentation method was compared with that from the saw-cutting method.

• Structural Engineering and Mechanics
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• v.47 no.2
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• pp.167-183
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• 2013

Methods for estimating structural reliability using probability ideas are well established. When the residual ultimate strength of a buried pipeline is exceeded the limit, breakage becomes imminent and the overall reliability of the pipe distribution network is reduced. This paper is concerned with estimating structural failure of underground flexible pipes due to corrosion induced excessive deflection, buckling, wall thrust and bending stress subject to externally applied loading. With changes of pipe wall thickness due to corrosion, the moment of inertia and the cross-sectional area of pipe wall are directly changed with time. Consequently, the chance of survival or the reliability of the pipe material is decreased over time. One numerical example has been presented for a buried steel pipe to predict the probability of failure using Hasofer-Lind and Rackwitz-Fiessler algorithm and Monte Carlo simulation. Then the parametric study and sensitivity analysis have been conducted on the reliability of pipeline with different influencing factors, e.g. pipe thickness, diameter, backfill height etc.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.30 no.1
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• pp.45-52
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• 1994

The study was conducted to evaluate reliability of the longitudinal tensile properties of unidirectional carbon fiber reinforced composites. Two kinds of carbon fiber reinforced composites laminates were tested in order to examine the factors of variability and have the information concerning reliability improvement. Temperature dependence of the strength and its variability were investigated by means of testing at two kinds of temperatures. Statistical distributions of the respective mechanical properties were obtained from the tensile tests. As a result, strength of composites was directly proportional to the ultimate strain and was not proportional to the elastic modulus. The fracture behavior in bending of notched plate was studied for a composite material. The uniform bending tests of notched plates have been carried out for a wide range of notch radii. The experiment shows that the nominal stress at failure decreased with decreasing notch radius and it approaches a constant value when the notch radius is less than about 0.3mm. The critical maximum stress is governed by notch root radius alone in the case of a constant thickness of specimen.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.12
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• pp.1-7
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• 2020

An experimental evaluation of bending fatigue strength for austempered ductile iron (ADI) spur gears was performed using a Zwick fatigue tester. The gear material was manufactured using vertical continuous casting, resulting in the radius of the graphite grains being smaller. The stress-number of cycles curve (S-N curve) for the bending fatigue strength of the ADI spur gears thus manufactured, without any specific surface treatments, was obtained using post-processing software. It was observed that when the reliability was 50%, the allowable root stress was 610 MPa. was calculated using an analytical method as well as the finite element method, and the difference between the values calculated using the two methods is only 7%. This study provides a reliable basis to rate the reliability design of small gearboxes in automation in the future.