• Title/Summary/Keyword: types of failure

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Development of Local Failure Criteria for Well Thinning Defect by Simulated Specimen Tests (모사시편 시험을 통한 감육결함 국부손상기준 개발)

  • Kim, Jin-Weon;Kim, Do-Hyung;Park, Chi-Yong;Lee, Sung-Ho
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.31 no.3 s.258
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    • pp.304-312
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    • 2007
  • The objective of this study is to develop a local failure criterion for a wall thinning defect of piping components. For this purpose, a series of tensile tests was performed using several types of simulated specimens with different stress states, including smooth round bar, notched round bar (five different notch radii), and grooved plate (three different groove radii). In addition, finite element (FE) simulations were performed on the simulated specimen tests and the results were compared with the test results. From the comparisons, the equivalent stress and strain corresponding to maximum load and final failure of notched specimens were proposed as failure criteria under tensile load. The criteria were verified by employing them to the estimation of failure of grooved plate specimens that simulate the wall thinning defect. It showed that the proposed criteria accurately estimate the maximum load and final failure of grooved plate specimen tests.

Wind Fragility for Urban Street Tree in Korea (강풍 발생 시 국내 가로수의 취약성 분석)

  • Sim, Viriyavudh;Jung, WooYoung
    • Journal of Wetlands Research
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    • v.21 no.4
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    • pp.298-304
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    • 2019
  • In this paper, the analytical method to derive wind fragility for urban street tree in Korea was shown. Monte Carlo Simulation method was used to determine the probability of failure for urban street tree. This probability result was used to determine wind fragility parameters for four types of tree based on the study of street tree species in urban area in Daegu, Korea. Wind fragility for street tree was presented in terms of median capacity and standard deviation of the natural logarithm of the capacity. Results showed that the dominant factor affecting the probability of failure of tree under wind load was their diameter. Moreover, amongst the four types of tree chosen, the tree with height 7m and diameter 35cm had the lowest probability of failure under wind loading, whereas the tree with height 8m and diameter 30cm could resist the least wind loading. The median failure wind speed for urban street tree with height 7m were 43.8m/s and 50.6m/s for diameter 30cm and 35cm, respectively. Also, for tree with height 8m, their median failure wind speeds were 38.7m/s and 45.4m/s for tree with diameter 30cm and 35cm, respectively.

A Proposal for Damage Index of Steel Members under Cyclic Loading (반복하중하에서의 강부재에 대한 손상지수 제안)

  • Park, Yeon Soo;Kang, Dae Hung;Oh, Jung Tae;Choi, Dong Ho;Oh, Back Man
    • Journal of Korean Society of Steel Construction
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    • v.14 no.5 s.60
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    • pp.613-625
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    • 2002
  • This paper aimed to investigate the damage process of steel parts experiencing failure under strong repeated loading. Likewise, a damage index using various factors related to the damage was proposed. An analysis method for evaluating the damage state was also developed. The damage assessment method focused on the local strain history at the cross-section of the heaviest concentration of deformation. Cantilever-type steel parts were analyzed under uniaxial load combined with a constant axial load, considering horizontal displacement history, Loading patterns and steel types were considered as the main parameters in analyzing the models. The effects of the parameters on the failure modes, deformation capacity, and damage process as seen from the analysis results were also discussed. Each failure process was compared as steel types. In addition, the failure of steel parts under strong repeated loading was determined according to loading. Results revealed that the state of the failure is closely related to the local plastic strain.

Differential Effects of Recovery Efforts on Products Attitudes (제품태도에 대한 회복노력의 차별적 효과)

  • Kim, Cheon-GIl;Choi, Jung-Mi
    • Journal of Global Scholars of Marketing Science
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    • v.18 no.1
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    • pp.33-58
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    • 2008
  • Previous research has presupposed that the evaluation of consumer who received any recovery after experiencing product failure should be better than the evaluation of consumer who did not receive any recovery. The major purposes of this article are to examine impacts of product defect failures rather than service failures, and to explore effects of recovery on postrecovery product attitudes. First, this article deals with the occurrence of severe and unsevere failure and corresponding service recovery toward tangible products rather than intangible services. Contrary to intangible services, purchase and usage are separable for tangible products. This difference makes it clear that executing an recovery strategy toward tangible products is not plausible right after consumers find out product failures. The consumers may think about backgrounds and causes for the unpleasant events during the time gap between product failure and recovery. The deliberation may dilutes positive effects of recovery efforts. The recovery strategies which are provided to consumers experiencing product failures can be classified into three types. A recovery strategy can be implemented to provide consumers with a new product replacing the old defective product, a complimentary product for free, a discount at the time of the failure incident, or a coupon that can be used on the next visit. This strategy is defined as "a rewarding effort." Meanwhile a product failure may arise in exchange for its benefit. Then the product provider can suggest a detail explanation that the defect is hard to escape since it relates highly to the specific advantage to the product. The strategy may be called as "a strengthening effort." Another possible strategy is to recover negative attitude toward own brand by giving prominence to the disadvantages of a competing brand rather than the advantages of its own brand. The strategy is reflected as "a weakening effort." This paper emphasizes that, in order to confirm its effectiveness, a recovery strategy should be compared to being nothing done in response to the product failure. So the three types of recovery efforts is discussed in comparison to the situation involving no recovery effort. The strengthening strategy is to claim high relatedness of the product failure with another advantage, and expects the two-sidedness to ease consumers' complaints. The weakening strategy is to emphasize non-aversiveness of product failure, even if consumers choose another competitive brand. The two strategies can be effective in restoring to the original state, by providing plausible motives to accept the condition of product failure or by informing consumers of non-responsibility in the failure case. However the two may be less effective strategies than the rewarding strategy, since it tries to take care of the rehabilitation needs of consumers. Especially, the relative effect between the strengthening effort and the weakening effort may differ in terms of the severity of the product failure. A consumer who realizes a highly severe failure is likely to attach importance to the property which caused the failure. This implies that the strengthening effort would be less effective under the condition of high product severity. Meanwhile, the failing property is not diagnostic information in the condition of low failure severity. Consumers would not pay attention to non-diagnostic information, and with which they are not likely to change their attitudes. This implies that the strengthening effort would be more effective under the condition of low product severity. A 2 (product failure severity: high or low) X 4 (recovery strategies: rewarding, strengthening, weakening, or doing nothing) between-subjects design was employed. The particular levels of product failure severity and the types of recovery strategies were determined after a series of expert interviews. The dependent variable was product attitude after the recovery effort was provided. Subjects were 284 consumers who had an experience of cosmetics. Subjects were first given a product failure scenario and were asked to rate the comprehensibility of the failure scenario, the probability of raising complaints against the failure, and the subjective severity of the failure. After a recovery scenario was presented, its comprehensibility and overall evaluation were measured. The subjects assigned to the condition of no recovery effort were exposed to a short news article on the cosmetic industry. Next, subjects answered filler questions: 42 items of the need for cognitive closure and 16 items of need-to-evaluate. In the succeeding page a subject's product attitude was measured on an five-item, six-point scale, and a subject's repurchase intention on an three-item, six-point scale. After demographic variables of age and sex were asked, ten items of the subject's objective knowledge was checked. The results showed that the subjects formed more favorable evaluations after receiving rewarding efforts than after receiving either strengthening or weakening efforts. This is consistent with Hoffman, Kelley, and Rotalsky (1995) in that a tangible service recovery could be more effective that intangible efforts. Strengthening and weakening efforts also were effective compared to no recovery effort. So we found that generally any recovery increased products attitudes. The results hint us that a recovery strategy such as strengthening or weakening efforts, although it does not contain a specific reward, may have an effect on consumers experiencing severe unsatisfaction and strong complaint. Meanwhile, strengthening and weakening efforts were not expected to increase product attitudes under the condition of low severity of product failure. We can conclude that only a physical recovery effort may be recognized favorably as a firm's willingness to recover its fault by consumers experiencing low involvements. Results of the present experiment are explained in terms of the attribution theory. This article has a limitation that it utilized fictitious scenarios. Future research deserves to test a realistic effect of recovery for actual consumers. Recovery involves a direct, firsthand experience of ex-users. Recovery does not apply to non-users. The experience of receiving recovery efforts can be relatively more salient and accessible for the ex-users than for non-users. A recovery effort might be more likely to improve product attitude for the ex-users than for non-users. Also the present experiment did not include consumers who did not have an experience of the products and who did not perceive the occurrence of product failure. For the non-users and the ignorant consumers, the recovery efforts might lead to decreased product attitude and purchase intention. This is because the recovery trials may give an opportunity for them to notice the product failure.

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Behaviors of novel sandwich composite beams with normal weight concrete

  • Yan, Jia-Bao;Dong, Xin;Wang, Tao
    • Steel and Composite Structures
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    • v.38 no.5
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    • pp.599-615
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    • 2021
  • The ultimate strength behaviour of sandwich composite beams with J-hooks and normal weight concrete (SCSSBJNs) are studied through two-point loading tests on ten full-scale SCSSBJNs. The test results show that the SCSSBJN with different parameters under two-point loads exhibits three types of failure modes, i.e., flexure, shear, and combined shear and flexure mode. SCSSBJN failed in different failure modes exhibits different load-deflection behaviours, and the main difference of these three types of behaviours exist in their last working stages. The influences of thickness of steel faceplate, shear span ratio, concrete core strength, and spacing of J-hooks on structural behaviours of SCSSBJN are discussed and analysed. These test results show that the failure mode of SCSSBJN was sensitive to the thickness of steel faceplate, shear span ratio, and concrete core strength. Theoretical models are developed to estimate the cracking, yielding, and ultimate bending resistance of SCSSBJN as well as its transverse cross-sectional shear resistance. The validations of predictions by these theoretical models proved that they are capable of estimating strengths of novel SCSSBJNs.

Identification of failure mechanisms for CFRP-confined circular concrete-filled steel tubular columns through acoustic emission signals

  • Li, Dongsheng;Du, Fangzhu;Chen, Zhi;Wang, Yanlei
    • Smart Structures and Systems
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    • v.18 no.3
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    • pp.525-540
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    • 2016
  • The CFRP-confined circular concrete-filled steel tubular column is composed of concrete, steel, and CFRP. Its failure mechanics are complex. The most important difficulties are lack of an available method to establish a relationship between a specific damage mechanism and its acoustic emission (AE) characteristic parameter. In this study, AE technique was used to monitor the evolution of damage in CFRP-confined circular concrete-filled steel tubular columns. A fuzzy c-means method was developed to determine the relationship between the AE signal and failure mechanisms. Cluster analysis results indicate that the main AE sources include five types: matrix cracking, debonding, fiber fracture, steel buckling, and concrete crushing. This technology can not only totally separate five types of damage sources, but also make it easier to judge the damage evolution process. Furthermore, typical damage waveforms were analyzed through wavelet analysis based on the cluster results, and the damage modes were determined according to the frequency distribution of AE signals.

Estimating Failure Rate Using Warranty Claim Data with Delayed Report of Customers (고객의 지연보고를 고려한 보증수리내역자료에서의 고장률 추정)

  • Park, J.H.;Kim, Y.H.;Baek, J.H.;Lie, C.H.
    • IE interfaces
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    • v.23 no.2
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    • pp.176-181
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    • 2010
  • Warranty claim data analysis is a useful tool for the manufacturer because it contains many useful informations regarding reliability of the product in the real-world environments. Because of the nature of uncertainty and the incompleteness of data, some bias patterns are observed on warranty claim rate known as 'spikes'. Two types of spikes are considered. One is due to manufacturing-related failures. The other is caused by customer's behavior. This paper proposes a model by considering two types of spikes. Warranty claim data is analyzed with the proposed model. To represent spikes observed on the early warranty period, we classify failures into manufacturing-related failures and usage-related failures. Uniform distribution is assumed for the time delayed to diagnose and report by customers. By reducing maximum value of the delayed time by customers, the proposed model characterizes customer's rush in the vicinity of the warranty expiration limit. Experimental results by using the real warranty claim data show that the proposed model is better than the existing one in respect to MSE(Mean Squared Error). Moreover it is expected to estimate the failure rate more realistically with proposed model because it considers the delayed time to diagnose and report by customers.

Performance Analysis of Scheduling Rules in Semiconductor Wafer Fabrication (반도체 웨이퍼 제조공정에서의 스케줄링 규칙들의 성능 분석)

  • 정봉주
    • Journal of the Korea Society for Simulation
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    • v.8 no.3
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    • pp.49-66
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    • 1999
  • Semiconductor wafer fabrication is known to be one of the most complex manufacturing processes due to process intricacy, random yields, product diversity, and rapid changing technologies. In this study we are concerned with the impact of lot release and dispatching policies on the performance of semiconductor wafer fabrication facilities. We consider several semiconductor wafer fabrication environments according to the machine failure types such as no failure, normal MTBF, bottleneck with low MTBF, high randomness, and high MTBF cases. Lot release rules to be considered are Deterministic, Poisson process, WR(Workload Regulation), SA(Starvation Avoidance), and Multi-SA. These rules are combined with several dispatching rules such as FIFO (First In First Out), SRPT (Shortest Remaining Processing Time), and NING/M(smallest Number In Next Queue per Machine). We applied the combined policies to each of semiconductor wafer fabrication environments. These policies are assessed in terms of throughput and flow time. Basically Weins fabrication setup was used to make the simulation models. The simulation parameters were obtained through the preliminary simulation experiments. The key results throughout the simulation experiments is that Multi-SA and SA are the most robust rules, which give mostly good performance for any wafer fabrication environments when used with any dispatching rules. The more important result is that for each of wafer fabrication environments there exist the best and worst choices of lot release and dispatching policies. For example, the Poisson release rule results in the least throughput and largest flow time without regard to failure types and dispatching rules.

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Acoustic Emmision Characteristics according to Failure Modes of Pipes with Local Wall Thinning (감육배관의 손상모드에 따른 음향방출 특성)

  • 안석환;남기우;김선진;김진환;김현수;박인덕
    • Journal of Ocean Engineering and Technology
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    • v.16 no.5
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    • pp.66-72
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    • 2002
  • Fracture behaviors of pipes with local wall thinning are very important for the integrity of nuclear power plant. However, effects of local wall thinning on strength and fracture behaviors of piping system were not well studied. Acoustic emission(AE) has been widely used in various fields because of its extreme sensitivity, dynamic detection ability and location of growing defects. In this study, we investigated failure modes of locally wall thinned pipes and AE signals by bending test. From test results, we could be divided four types of failure modes of ovalization, crack initiation after ovalization, local buckling and crack initiation after local buckling. And fracture behaviors such as elastic region, yielding region, plastic deformation region and crack progress region could be evaluated by AE counts, accumulative counts and time-frequency analysis during bending test. The result of the frequency range is expected to be basic data that can inspect plants in real-time.

Analysis of Failure Reduction Properties Cementitious Composites with Reinforced Fiber by Impact of High Velocity Projectile (비상체의 고속 충격을 받는 시멘트복합체의 혼입 단섬유에 따른 파괴저감특성 분석)

  • Jeon, In-Woo;Kim, Gyu-Yong;Cheo, Gyeong-Cheol;Kim, Hong-Seop;Kim, Jung-Hyun;Han, Sang-Hyu
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2014.11a
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    • pp.186-187
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    • 2014
  • Flexural stress and fracture energy of fiber reinforced cementitious composites is increased by bridge effect of reinforced fiber, scabbing failure is restrained. Shape, properties of fiber were SF(steel fiber), PA(polyamide), NY(nylon) have effects on flexural stress and fracture energy, impact resistance improve of fiber reinforced cementitious composites. In this study, local failure properties by impact of high velocity projectile was analyzed by mixing 3 types of fiber which have different shape and properties respectively.

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