• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.9 s.240
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• pp.1161-1168
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• 2005

As a result of vehicle maintenance of rocker arm shaft for 4-cylinder SOHC engine, failure analysis of rocker arm shaft is needed. Because more than $30\%$ of vehicles investigated have been fractured. Failure analysis is classified into an naked eyes, microscope and X-ray fractography etc. It can predict applied load as well as load type. These methods are applicable to components with simple boundary condition but aren't applicable to components with complex boundary condition. The existing fractography don't catch hold of failure boundary condition quantitatively. Especially, in case that the components isn't fractured at same position. We must determine the most dangerous failure boundary condition to evaluate their operation mechanism. The effect of various factors on response should be estimated to solve this statical problem. This study presents the most dangerous failure boundary condition of rocker arm shaft using orthogonal array and ANOVA in order to assure its robustness.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.9
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• pp.35-41
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• 2021

A rotor is a crucial component in various mechanical assemblies. Additionally, high-speed and high-efficiency components are required in the automotive industry, manufacturing industry, and turbine systems. In particular, the failure of high-speed rotating bearings has catastrophic effects on auxiliary systems. Therefore, bearing reliability and fault diagnosis are essential for bearing maintenance. In this work, we performed failure mode and effect analysis on bearing rotors and determined that corrosion is the most critical failure type. Furthermore, we conducted experiments to extract vibration characteristic data and preprocess the vibration data through principle component analysis. Finally, we applied a machine learning algorithm called support vector machine to diagnose the failure and observed a classification performance of 98%.

• The Journal of Engineering Geology
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• v.27 no.3
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• pp.267-274
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• 2017

Behavior of rock mass depend on the mechanical properties of intact rock and geometrical property of discontinuity distributed in rock mass. In case of rock slope, particularly, location of slope failure surface and behavior after failure are changed due to discontinuities. In this study, two 3D slope stability analysis methods were developed for two different failure types which are circular failure and planar failure, considering that failure type of rock slope is dependent on scale of discontinuity which was then applied to real rock slope to review the applicability. In case of circular failure, stable condition was maintained in natural dry condition, which however became unstable when the moisture content of the surface was increased by rainfall. In case of planar failure, rock slope become more unstable comparing to dry condition which is attributable to decrease in friction angle of discontinuity surface due to rainfall. Viewing analysis result above, analysis method proved to have well incorporated the phenomenon occurred on real slope from the analysis result, demonstrating its applicability to reviewing the slope stability as well as to maintaining the slope.

• Structural Engineering and Mechanics
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• v.20 no.1
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• pp.123-141
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• 2005

Design details pertaining to the connection between some recently developed fiber reinforced polymer (FRP) composite deck systems and the supporting girders require openings through cells of the deck. This significantly changes the stress distribution in these components. As a result, the conventional assumptions that deck designs are controlled by their stiffness, and not strength, needs a closer examination. This paper proposes an analytical method to investigate the stress states and failure mechanisms using a type of "global-local" modeling perspective, incorporating classical lamination theory and first ply failure criterion with use of appropriate stress concentration factors around the cutouts. The use of a "smeared-stress" approach is presented as a potential means of simplifying certain FRP specific complexities, while still enabling prediction of overall failure.

• Transactions of Materials Processing
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• v.19 no.4
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• pp.217-223
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• 2010

The objective of this study is to propose the FE model for mechanical clinched joint using cohesive zone model to analyze its failure behavior under impact loading. Cohesive zone model (CZM) is two-parameter failure criteria approach, which could describe the failure behavior of joint using critical stress and fracture toughness. In this study, the relationship between failure behavior of mechanical clinched joint and fracture parameters is investigated by FE analysis with CZM. Using this relationship, the critical stress and fracture toughness for tensile and shear mode are determined by H-type tensile test and lap shear test, which were made of 5052 aluminum alloy. The fracture parameters were applied to the tophat impact test to evaluate the crashworthiness. Compared penetration depth and energy absorption at the point where 50% of total displacement in result of FE analysis and experiment test for impact test, those has shown similar crashworthiness.

• Journal of Periodontal and Implant Science
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• v.49 no.5
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• pp.287-298
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• 2019

Purpose: The aim of this retrospective study was to determine the prevalence of early implant failure using a single implant system and to identify the factors contributing to early implant failure. Methods: Patients who received implant treatment with a single implant system ($Luna^{(R)}$, Shinhung, Seoul, Korea) at Dankook University Dental Hospital from 2015 to 2017 were enrolled. The following data were collected for analysis: sex and age of the patient, seniority of the surgeon, diameter and length of the implant, position in the dental arch, access approach for sinus-floor elevation, and type of guided bone regeneration (GBR) procedure. The effect of each predictor was evaluated using the crude hazard ratio and the adjusted hazard ratio (aHR) in univariate and multivariate Cox regression analyses, respectively. Results: This study analyzed 1,031 implants in 409 patients, who comprised 169 females and 240 males with a median age of 54 years (interquartile range [IQR], 47-61 years) and were followed up for a median of 7.2 months (IQR, 5.6-9.9 months) after implant placement. Thirty-five implants were removed prior to final prosthesis delivery, and the cumulative survival rate in the early phase at the implant level was 95.6%. Multivariate regression analysis revealed that seniority of the surgeon (residents: aHR=2.86; 95% confidence interval [CI], 1.37-5.94) and the jaw in which the implant was placed (mandible: aHR=2.31; 95% CI, 1.12-4.76) exerted statistically significant effects on early implant failure after adjusting for sex, age, dimensions of the implant, and type of GBR procedure (preoperative and/or simultaneous) (P<0.05). Conclusions: Prospective studies are warranted to further elucidate the factors contributing to early implant failure. In the meantime, surgeons should receive appropriate training and carefully select the bone bed in order to minimize the risk of early implant failure.

• Knowledge Management Research
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• v.12 no.4
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• pp.121-132
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• 2011

Failure, the research object, means situations when goals and their results are different, which has developed presenting various aspects from ancient times and modern times. Failure is a complex concept which essentially requires judgement, and also a relative concept which can be changed depending on how you set up time base and standard. There are four stages for failure study to have been developed from studying failure through historical facts to the approach of organizational theory and it has been studied by looking at the failure of an organization according to different categories such as a developmental stage, a type of business, a period and a course. Compared with success science, failure study has not been studied sufficiently and also the level of its analysis is low. Thus, since lessons of failure tend to repeat themselves instead of being didactically accumulated, there need more studies on this. This thesis identified the main cause of the failure through various studies regarding failure which have been conducted at home and abroad. What the main cause of the failure that more than three studies mentioned have in common was that it occurred because organizations concentrated on the inside without communicating with external environment. The key point of failure study is to analyze failure, utilize it as assets, and create a frame of failure management. This thesis focused on delivering fragmentary knowledge on failure study, but case studies regarding this subject should be done in the future.

• Journal of Korea Society of Digital Industry and Information Management
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• v.8 no.2
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• pp.1-10
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• 2012

In this study, software products developed in the course of testing, software managers in the process of testing software test and test tools for effective learning effects perspective has been studied using the NHPP software. The finite failure nonhomogeneous Poisson process models presented and the life distribution applied exponential and log shaped type hazard function. Software error detection techniques known in advance, but influencing factors for considering the errors found automatically and learning factors, by prior experience, to find precisely the error factor setting up the testing manager are presented comparing the problem. As a result, the learning factor is greater than autonomous errors-detected factor that is generally efficient model could be confirmed. This paper, a failure data analysis of applying using time between failures and parameter estimation using maximum likelihood estimation method, after the efficiency of the data through trend analysis model selection were efficient using the mean square error and coefficient of determination.

• Structural Engineering and Mechanics
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• v.63 no.2
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• pp.195-206
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• 2017

This paper presents the parametric numerical analysis on the ultimate bearing capacity of the purlin-sheet roofs connected by standing seam clips. The effects of several factors on failure modes and ultimate bearing capacity of the purlins are studied, including setup of anti-sag bar, purlin type, sheet thickness and connection type et al. A simplified design formula is proposed for predicting the ultimate bearing capacity of purlins. Results show that setting the anti-sag bars can improve the ultimate bearing capacity and change the failure modes of C purlins significantly. The failure modes and ultimate bearing capacity of C purlins are significantly different from those of Z purlins, in the purlin-sheet roof connected by standing seam clips. Setting the anti-sag bars near the lower flange is more favorable for increasing the ultimate bearing capacity of purlins. The ultimate bearing capacity of C purlins increases slightly with sheet thickness increasing from 0.6 mm to 0.8 mm. The ultimate bearing capacity of the purlin-sheet roofs connected by standing seam clips is always higher than those by self-drilling screws. The predictions of the proposed design formulas are relatively in good agreement with those of EN 1993-1-3: 2006, compared with GB 50018-2002.

• Journal of Applied Reliability
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• v.18 no.2
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• pp.130-142
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• 2018

Purpose: The purpose of this study is to introduce regression method in the presence of competing risks and to show how you can use the method with hypothetical data. Methods: Survival analysis has been widely used in biostatistics division. But the same method has not been utilized in reliability division. Especially competing risks, where more than a couple of causes of failure occur and the occurrence of one event precludes the occurrence of the other events, are scattered in reliability field. But they are not utilized in the area of reliability or they are analysed in the wrong way. Specifically Kaplan-Meier method is used to calculate the probability of failure in the presence of competing risks, thereby overestimating the real probability of failure. Hence, cumulative incidence function is introduced. In addition, sample competing risks data are analysed using cumulative incidence function along with some graphs. Lastly we compare cumulative incidence functions with regression type analysis briefly. Results: We used cumulative incidence function to calculate the survival probability or failure probability in the presence of competing risks. We also drew some useful graphs depicting the failure trend over the lifetime. Conclusion: This research shows that Kaplan-Meier method is not appropriate for the evaluation of survival or failure over the course of lifetime in the presence of competing risks. Cumulative incidence function is shown to be useful in stead. Some graphs using the cumulative incidence functions are also shown to be informative.