scholarly journals Prediction of Material Failure Time for a Bucket Wheel Excavator Boom Using Computer Simulation

Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7897
Author(s):  
Andrei Andraș ◽  
Sorin Mihai Radu ◽  
Ildiko Brînaș ◽  
Florin Dumitru Popescu ◽  
Daniela Ioana Budilică ◽  
...  
Keyword(s):  
Failure Time ◽  
Surface Mining ◽  
Time To Failure ◽  
Maximum Displacement ◽  
Excavation Process ◽  
Strength Tests ◽  
Opencast Mines ◽  
Response Determination ◽  
Industrial Machine ◽  
Financial Losses

Breakdown of stackers and excavators in opencast mines is possible because of operating, manufacturing and structural causes, and it produces high financial losses. These can be prevented by using various measures, including analyses and strength tests, with computerized modeling and simulation using FEA or other techniques being implemented in the recent years. In this paper a fatigue study is conducted on the boom of a BWE. Based on a computer model of the boom previously developed in SOLIDWORKS by our author team, first the modal analysis is conducted for three positions of the boom by studying the frequency response during the excavation process. This is followed by the time response determination corresponding to the maximum displacement frequency, in order to assess the stress during the excavation process, which causes the material fatigue in the boom structure. It was found that the maximum displacements appear when the BWE boom operates in a horizontal position. The aim was to estimate the period of time to failure in order to prevent unwanted accidents, and to develop a method that is applicable to any surface mining or industrial machine with similar structure.

Dependability Analysis of Homogeneous Distributed Software/Hardware Systems

2015 ◽  
Vol 22 (02) ◽  
pp. 1550007
Author(s):  
G. Vijayalakshmi
Keyword(s):  
Reliability Analysis ◽  
Distributed System ◽  
Failure Time ◽  
Load Sharing ◽  
Accelerated Failure Time Model ◽  
Time To Failure ◽  
Critical Systems ◽  
Time Model ◽  
Distributed Software ◽  
Dependability Analysis

With the increasing demand for high availability in safety-critical systems such as banking systems, military systems, nuclear systems, aircraft systems to mention a few, reliability analysis of distributed software/hardware systems continue to be the focus of most researchers. The reliability analysis of a homogeneous distributed software/hardware system (HDSHS) with k-out-of-n : G configuration and no load-sharing nodes is analyzed. However, in practice the system load is shared among the working nodes in a distributed system. In this paper, the dependability analysis of a HDSHS with load-sharing nodes is presented. This distributed system has a load-sharing k-out-of-(n + m) : G configuration. A Markov model for HDSHS is developed. The failure time distribution of the hardware is represented by the accelerated failure time model. The software faults are detected during software testing and removed upon failure. The Jelinski–Moranda software reliability model is used. The maintenance personal can repair the system up on both software and hardware failure. The dependability measures such as reliability, availability and mean time to failure are obtained. The effect of load-sharing hosts on system hazard function and system reliability is presented. Furthermore, an availability comparison of our results and the results in the literature is presented.

scholarly journals Heat Transfer Behavior of Green Roof Systems Under Fire Condition: A Numerical Study

Buildings ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 206
Author(s):  
Gerzhova ◽  
Blanchet ◽  
Dagenais ◽  
Côté ◽  
Ménard
Keyword(s):  
Heat Transfer ◽  
Failure Time ◽  
Numerical Study ◽  
Fire Hazard ◽  
Green Roof ◽  
Green Roofs ◽  
Heat Transfer Process ◽  
Heat Fluxes ◽  
Substrate Thickness ◽  
Time To Failure

Currently, green roof fire risks are not clearly defined. This is because the problem is still not well understood, which raises concerns. The possibility of plants catching fire, especially during drought periods, is one of the reasons for necessary protection measures. The potential fire hazard for roof decks covered with vegetation has not yet been fully explored. The present study analyzes the performance of green roofs in extreme heat conditions by simulating a heat transfer process through the assembly. The main objective of this study was to determine the conditions and time required for the roof deck to reach a critical temperature. The effects of growing medium layer thickness (between 3 and 10 cm), porosity (0.5 to 0.7), and heating intensity (50, 100, 150, and 200 kW/m²) were examined. It was found that a green roof can protect a wooden roof deck from igniting with only 3 cm of soil coverage when exposed to severe heat fluxes for at least 25 minutes. The dependency of failure time on substrate thickness decreases with increasing heating load. It was also found that substrate porosity has a low impact on time to failure, and only at high heating loads.

scholarly journals A Dynamic Failure Time Degradation-Based Model

Symmetry ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 1532
Author(s):  
Abdulhakim A. Albabtain ◽  
Mansour Shrahili ◽  
Lolwa Alshagrawi ◽  
Mohamed Kayid
Keyword(s):  
Hazard Rate ◽  
Failure Time ◽  
Degradation Process ◽  
Residual Lifetime ◽  
Time To Failure ◽  
Lifetime Distributions ◽  
Mean Residual Lifetime ◽  
Aging Properties ◽  
Degradation Models ◽  
Characterization Property

A novel methodology for modelling time to failure of systems under a degradation process is proposed. Considering the method degradation may have influenced the failure of the system under the setup of the model several implied lifetime distributions are outlined. Hazard rate and mean residual lifetime of the model are obtained and a numerical situation is delineated to calculate their amounts. The problem of modelling the amount of degradation at the failure time is also considered. Two monotonic aging properties of the model is secured and a characterization property of the symmetric degradation models is established.

Analysis of HDPE Failure Data in Support of Development of Flaw Acceptance Criteria for Butt Fusion Joints

2020 ◽  
Author(s):  
Cheng Liu ◽  
Douglas Scarth ◽  
Douglas P. Munson ◽  
Ryan Wolfe
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Failure Time ◽  
Slow Crack Growth ◽  
Time To Failure ◽  
Acceptance Criteria ◽  
Failure Data ◽  
Criteria For Evaluation ◽  
Hdpe Pipes

Abstract There is a need for ASME B&PV Code procedures and acceptance criteria for evaluation of flaws detected by inspection of high density polyethylene (HDPE) piping items in safety Class 3 systems. To support the development of flaw acceptance criteria for butt fusion joints in HDPE pipes, a series of coupon tests have been completed for specimens cut from butt fused HDPE pipes with surface or subsurface flaws placed in the joints prior to fusion process. Specimens containing known flaw sizes were tested under axial load at accelerated stresses and temperatures until failure; or until a prescribed number of test hours was reached. The failure time from the tests has been correlated to the net section stress and the stress intensity factor, and the results showed that the failure time can be better represented by the stress intensity factor. The test results were then used to fit the Brown and Lu formula that predicts the time to failure due to the slow crack growth of flaws as a function of stress intensity factor and temperature. With the developed Brown and Lu equation, the allowable stress intensity factors for a piping lifetime of 50 years at the maximum code allowable temperature of 60°C have been proposed for both surface and subsurface flaws in HDPE butt fusion joints. Examples of what might be corresponding allowable flaw sizes in the butt fusion joints of piping are also provided.

The time to failure of fiber bundles subjected to random loads

1979 ◽  
Vol 11 (03) ◽  
pp. 527-541 ◽  
Author(s):  
Howard M. Taylor
Keyword(s):  
Simple Model ◽  
Power Law ◽  
Failure Time ◽  
Constant Load ◽  
Asymptotic Distributions ◽  
Asymptotic Independence ◽  
Time To Failure ◽  
Random Load ◽  
The Mean ◽  
Wave Induced

The effect on cable reliability of random cyclic loading such as that generated by the wave-induced rocking of ocean vessels deploying these cables is examined. A simple model yielding exact formulas is first explored. In this model, the failure time of a single fiber under a constant load is assumed to be exponentially distributed, and the random loadings are a two-state stationary Markov process. The effect of load on failure time is assumed to follow a power law breakdown rule. In this setting, exact results concerning the distribution of bundle or cable failure time, and especially the mean failure time, are obtained. Where the fluctuations in load are frequent relative to bundle life, such as may occur in long-lived cables, it is shown that randomness in load tends to decrease mean bundle life, but it is suggested that the reduction in mean life often can be restored by modestly reducing the base load on the structure or by modestly increasing the number of elements in the bundle. In later pages this simple model is extended to cover a broader range of materials and random loadings. Asymptotic distributions and mean failure times are given where fibers follow a Weibull distribution of failure time under constant load, and loads that are general non-negative stationary processes subject only to some mild condition of asymptotic independence. When the power law breakdown exponent is large, the mean time to bundle failure depends heavily on the exact form of the marginal probability distribution for the random load process and cannot be summarized by the first two moments of this distribution alone.

Simulation Research for the Excavation Stability of IV Brittle Rock Based on Vault Settlement Effect

2014 ◽  
Vol 681 ◽  
pp. 209-213
Author(s):  
Ke Ling Liu ◽  
Long Guo
Keyword(s):  
Brittle Rock ◽  
Analysis Tool ◽  
Underground Engineering ◽  
Maximum Displacement ◽  
Element Analysis ◽  
Simulation Research ◽  
Engineering Construction ◽  
Excavation Process ◽  
The Finite Element Analysis ◽  
The Stability

Due to the brittle rock deformation is not obvious, and the destruction process has the features of sudden and concealment, it is often neglected in the field during construction. In this paper, Brittle rock was selected as the research object. Using the vault subsidence as monitoring parameters, the excavation process was simulated in single line tunnel by the finite element analysis tool of ANSYS, we obtain the maximum displacement of brittle rock and stress variation with time. Then the subsidence effect of different buried condition were analyzed, to determine the stability period of IV Brittle surrounding rock. The research results can be used to guide the development of the monitoring standard, in underground engineering construction of the brittle rock.

scholarly journals Estimation of the average time to failure of the turning steps according to the operation data

2019 ◽  
Vol 78 (1) ◽  
pp. 54-58
Author(s):  
M. V. Belousova ◽  
V. V. Bulatov
Keyword(s):  
Weibull Distribution ◽  
Failure Time ◽  
Operational Reliability ◽  
Likelihood Method ◽  
Point Estimate ◽  
Statistical Criterion ◽  
Time To Failure ◽  
Distribution Law ◽  
Software Environment ◽  
Technical Product

The purpose of this study is to determine the empirical law of the distribution of developments to the failure of the turning steps installed on passenger cars of locomotive traction. The correct choice of the distribution law for each technical product allows for the current calculation of reliability indicators, predicting them, as well as developing preventive measures for a specific technical product and leveling costs both during production and during operation.The article presents well-founded arguments that the failure time for turning steps is characterized by the Weibull distribution law. For confirmation, a statistical criterion for checking the deviation of the distribution from the normal one was applied.On the basis of carried statistic analysis a histogram of frequencies and a line of the density function of samples of failure time in the data fixation period from 2010 to 2017 were built. Results of applying the 2 agreement criterion in the same software environment revealed that the failure time of the closed turning step comply with the law of Weibull distribution. Authors suggest using the maximum likelihood method to identify Weibull distribution parameters, on the basis of which the value of the point estimate of the mean time to failure is calculated.Based on the research, it is concluded that this type of distribution law and the process of finding its parameters should be introduced into the program and methodology for assessing the operational reliability of the turning steps, when calculating the average time to failure of the steps, and consider the possibility of applying this law for analogous products.In conclusion, calculation of the pointed estimation of the average time to failure of the closed turning step was made on the basis of operational tests for one year in accordance with the adopted distribution law.

Members of the glutathione (GSH) and ABC-transporter families are associated with clinical outcomes in patients with diffuse large B-cell lymphoma (DLCL)

2006 ◽  
Vol 24 (18_suppl) ◽  
pp. 10035-10035
Author(s):  
C. Andreadis ◽  
P. A. Gimotty ◽  
P. Wahl ◽  
R. Hammond ◽  
J. Houldsworth ◽  
...  
Keyword(s):  
Drug Resistance ◽  
High Risk ◽  
Abc Transporter ◽  
Failure Time ◽  
Risk Group ◽  
Risk Groups ◽  
Time To Failure ◽  
Key Genes ◽  
Probe Set ◽  
Disease Free

10035 Background: Chemotherapy only cures 60–70% of DLCL patients (pts). While genes in both the GSH and ABC-transporter families have been implicated in drug resistance in other malignancies, their role in DLCL remains controversial. Methods: This study includes 94 DLCL pts with tissue expression data obtained prior to anthracycline-based chemotherapy from 2 oligonucleotide microarray datasets (Affymetrix) with annotated clinical information. Patient-level expression was derived for 10 key genes utilizing probe set matching and levels were adjusted for a common probe set signal. Freedom-from-progression (FFP) was analyzed using an accelerated failure-time regression model, stratified by the international prognostic index (IPI). CART software was used to develop a classification tree for the 2-year disease-free rate. Results: Based on IPI, 48% of pts were low risk, 23% were low-intermediate (int) risk, 24% high-int risk, and 12% were high risk. After therapy, 30 pts (32%) had disease relapse or progression within 2 yrs and 58 pts (62%) were disease-free; 6 (6%) had shorter follow-up. Expression of multi-drug resistance 1 (MDR1; ABCB1) was favorably associated with FFP (β=1.89, p=0.004), with a 100-point change in the expression signal resulting in a near-doubling of the time to failure (time ratio (TR) = 2.2, 95%CI: 1.3–3.6). Expression of GSH S-transferase μ, classes 1/2/4 (GSTM124) was also favorably associated with FFP (β=0.14, p=0.001); a 1000-point signal change resulted in a near-doubling of the time to failure (TR=1.8, 1.3–2.4). Based on our tree, 2 risk groups were identified using IPI and 3 genes: ABCB1, GSTM124, and GSH cysteine ligase modifier (GCLM). Thus, 89% (78%-96%) pts in the low-risk group (N=56) were disease-free at 2 yrs vs. 25% (11%-43%) pts in the high-risk group (p<0.001). Conclusions: We observed a significant favorable association between expression of genes in the GSH and ABC-transporter families, and FFP in pts treated for DLCL. Moreover, we generated 2 risk groups based on the IPI and the expression of 3 key genes, which we plan to validate in an independent dataset. Our findings suggest an additional role for these genes that are classically associated with drug resistance. No significant financial relationships to disclose.

Mechanics performance of three-degree-of-freedom excavating mechanism of an electric shovel

2011 ◽  
Vol 225 (6) ◽  
pp. 1443-1457 ◽  
Author(s):  
B Wei ◽  
F Gao ◽  
J Chen ◽  
J He ◽  
S Wu ◽  
...  
Keyword(s):  
Interaction Mechanism ◽  
Interaction Model ◽  
Surface Mining ◽  
Degree Of Freedom ◽  
Resistance Force ◽  
Mining Operations ◽  
Excavation Process ◽  
Mechanics Performance ◽  
Full Scale Tests ◽  
Three Degree Of Freedom

Electric shovel is one of the most important equipment in surface-mining operations. The medium–tool interaction model is an essential basis in the process of machine design. Therefore, it is important to make the model accurate compared to the actual situation. This article proposes a new medium–tool interaction model based on the analysis of medium–tool interaction mechanism taking into account the actual excavating process. The result of the new model is quite in agreement with the full-scale tests. In order to make the excavating process more efficient, the traditional two-degree-of-freedom (DOF) excavating mechanism is redesigned and a new three-DOF excavating mechanism is obtained. A new electric shovel with three-DOF excavating mechanism is more flexible in that it will perform the excavation process with a favourable excavating angle that can reduce the resistance force involved in medium–tool interaction. Based on the new medium–tool interaction model, the dynamic model of the three-DOF excavating mechanism is established for the mechanics performance analysis. The numeric validation shows that the new excavating mechanism is more efficient in the excavating process.

scholarly journals Fatigue-induced adjustment in antagonist coactivation by old adults during a steadiness task

2016 ◽  
Vol 120 (9) ◽  
pp. 1039-1046 ◽  
Author(s):  
Christopher J. Arellano ◽  
David Caha ◽  
Joseph E. Hennessey ◽  
Ioannis G. Amiridis ◽  
Stéphane Baudry ◽  
...  
Keyword(s):  
Maximal Voluntary Contraction ◽  
Failure Time ◽  
Voluntary Contraction ◽  
Matching Task ◽  
Electromyographic Activity ◽  
Time To Failure ◽  
Old Adults ◽  
Before And After ◽  
Wrist Flexors ◽  
Maximal Voluntary Contraction Torque

The purpose of this study was to determine the adjustments in the level of coactivation during a steadiness task performed by young and old adults after the torque-generating capacity of the antagonist muscles was reduced by a fatiguing contraction. Torque steadiness (coefficient of variation) and electromyographic activity of the extensor and flexor carpi radialis muscles were measured as participants matched a wrist extensor target torque (10% maximum) before and after sustaining an isometric contraction (30% maximum) with wrist flexors to task failure. Time to failure was similar ( P = 0.631) for young (417 ± 121 s) and old (452 ± 174 s) adults. The reduction in maximal voluntary contraction torque (%initial) for the wrist flexors after the fatiguing contraction was greater ( P = 0.006) for young (32.5 ± 13.7%) than old (21.8 ± 6.6%) adults. Moreover, maximal voluntary contraction torque for the wrist extensors declined for old (−13.7 ± 12.7%; P = 0.030), but not young (−5.4 ± 13.8%; P = 0.167), adults. Torque steadiness during the matching task with the wrist extensors was similar before and after the fatiguing contraction for both groups, but the level of coactivation increased after the fatiguing contraction for old ( P = 0.049) but not young ( P = 0.137) adults and was twice the amplitude for old adults ( P = 0.002). These data reveal that old adults are able to adjust the amount of antagonist muscle activity independent of the agonist muscle during steady submaximal contractions.

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