Influence of microstructure on the premature failure of a second-intermediate sendzimir mill drive roll

In the article, the electrical and thermal processes in the LED lamp with varied parameters are investigated. Voltage and current measurements on all LEDs of the luminaire are carried out in the nominal operating mode. The power allocated to each LED is determined. The calculation of the LED crystal temperature was carried out using the developed thermal LED model based on the results of the measurements and by using “Multisim” program. It has been established that the temperature of the crystals of individual LEDs in the luminaire differ significantly, which leads to unfavourable thermal conditions for them and an increased likelihood of premature failure.

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Rubber Fracture Characterization Using J-Integral

Tire Science and Technology ◽

10.2346/1.2148797 ◽

1988 ◽

Vol 16 (1) ◽

pp. 44-60 ◽

Cited By ~ 14

Author(s):

C. L. Chow ◽

J. Wang ◽

P. N. Tse

Keyword(s):

Crack Initiation ◽

Carbon Black ◽

Natural Rubber ◽

Fracture Parameter ◽

J Integral ◽

Specimen Length ◽

Fracture Characterization ◽

Premature Failure ◽

Testing Procedures ◽

Material Evaluation

Abstract The use of the J-integral to investigate fracture characterization in a carbon black reinforced natural rubber is described. Three applications to crack initiation are included: two based on the use of a hypothetical zero specimen length and one on conventional testing procedures for metals. While the validity of the zero-length methods is questionable, the conventional method yielded a consistent Jc value of 1.01 N/mm for a typical tire compound. This value was obtained from 24 combinations of varying specimen geometries and pre-crack lengths. The J-integral is revealed as a valid fracture parameter that is applicable not only for material evaluation but also for designing tire structures to resist premature failure. These conclusions disagree with those from an earlier investigation, so the causes for the discrepancies are examined and discussed.

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Modelling of Corrosion-Induced Concrete Cover Cracking Due to Chloride Attacking

Materials ◽

10.3390/ma14061440 ◽

2021 ◽

Vol 14 (6) ◽

pp. 1440

Author(s):

Pei-Yuan Lun ◽

Xiao-Gang Zhang ◽

Ce Jiang ◽

Yi-Fei Ma ◽

Lei Fu

Keyword(s):

Service Life ◽

Corrosion Current ◽

Practical Experience ◽

Concrete Cover ◽

Premature Failure ◽

Rc Structures ◽

Structural Capacity ◽

Cover Cracking ◽

Deterioration Process ◽

Cracking Process

The premature failure of reinforced concrete (RC) structures is significantly affected by chloride-induced corrosion of reinforcing steel. Although researchers have achieved many outstanding results in the structural capacity of RC structures in the past few decades, the topic of service life has gradually attracted researchers’ attention. In this work, based on the stress intensity, two models are developed to predict the threshold expansive pressure, corrosion rate and cover cracking time of the corrosion-induced cracking process for RC structures. Specifically, in the proposed models, both the influence of initial defects and modified corrosion current density are taken into account. The results given by these models are in a good agreement with practical experience and laboratory studies, and the influence of each parameter on cover cracking is analyzed. In addition, considering the uncertainty existing in the deterioration process of RC structures, a methodology based on the third-moment method in regard to the stochastic process is proposed, which is able to evaluate the cracking risk of RC structures quantitatively and predict their service life. This method provides a good means to solve relevant problems and can prolong the service life of concrete infrastructures subjected to corrosion by applying timely inspection and repairs.

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Comparative Analysis of Different Mobile LiDAR Mapping Systems for Ditch Line Characterization

Remote Sensing ◽

10.3390/rs13132485 ◽

2021 ◽

Vol 13 (13) ◽

pp. 2485

Author(s):

Yi-Chun Lin ◽

Raja Manish ◽

Darcy Bullock ◽

Ayman Habib

Keyword(s):

Flow Direction ◽

Sediment Accumulation ◽

Digital Terrain Model ◽

Vertical Direction ◽

Point Clouds ◽

Lidar Data ◽

Cross Sectional ◽

Premature Failure ◽

3D Point Clouds ◽

Mapping Systems

Maintenance of roadside ditches is important to avoid localized flooding and premature failure of pavements. Scheduling effective preventative maintenance requires a reasonably detailed mapping of the ditch profile to identify areas in need of excavation to remove long-term sediment accumulation. This study utilizes high-resolution, high-quality point clouds collected by mobile LiDAR mapping systems (MLMS) for mapping roadside ditches and performing hydrological analyses. The performance of alternative MLMS units, including an unmanned aerial vehicle, an unmanned ground vehicle, a portable backpack system along with its vehicle-mounted version, a medium-grade wheel-based system, and a high-grade wheel-based system, is evaluated. Point clouds from all the MLMS units are in agreement within the ±3 cm range for solid surfaces and ±7 cm range for vegetated areas along the vertical direction. The portable backpack system that could be carried by a surveyor or mounted on a vehicle is found to be the most cost-effective method for mapping roadside ditches, followed by the medium-grade wheel-based system. Furthermore, a framework for ditch line characterization is proposed and tested using datasets acquired by the medium-grade wheel-based and vehicle-mounted portable systems over a state highway. An existing ground-filtering approach—cloth simulation—is modified to handle variations in point density of mobile LiDAR data. Hydrological analyses, including flow direction and flow accumulation, are applied to extract the drainage network from the digital terrain model (DTM). Cross-sectional/longitudinal profiles of the ditch are automatically extracted from the LiDAR data and visualized in 3D point clouds and 2D images. The slope derived from the LiDAR data turned out to be very close to the highway cross slope design standards of 2% on driving lanes, 4% on shoulders, and a 6-by-1 slope for ditch lines.

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Post-Processing of Cold Sprayed Ti-6Al-4V Coatings by Mechanical Peening

Metals ◽

10.3390/met11071038 ◽

2021 ◽

Vol 11 (7) ◽

pp. 1038

Author(s):

Niroj Maharjan ◽

Ayan Bhowmik ◽

Chunwai Kum ◽

Jiakun Hu ◽

Yongjing Yang ◽

...

Keyword(s):

Surface Integrity ◽

Volume Fraction ◽

Aerospace Industry ◽

Metal Alloys ◽

High Porosity ◽

Post Processing ◽

Premature Failure ◽

Additive Manufacturing Technology ◽

Hammer Peening ◽

Compressive Residual Stresses

Cold spray is an emerging additive manufacturing technology used in the aerospace industry to repair damaged components made of expensive metal alloys. The cold sprayed layer is prone to surface integrity issues such as high porosity and inadequate bonding at the substrate-coating interface, which may cause premature failure of the repaired component. This study explored the use of mechanical peening as a post-processing method to improve the surface integrity of the cold sprayed component by modifying mechanical properties near the surface. Two mechanical peening processes, deep cold rolling (DCR) and controlled hammer peening (CHP), were utilized to improve cold sprayed Ti-6Al-4V coating on the Ti-6Al-4V substrate. Experimental results indicate that DCR and CHP increase the strength of the bond between the coating and substrate due to introduction of compressive residual stresses. In addition, porosity is also reduced by as much as 71%. The improvement is attributed to both the compacting effect of peening processes and the increment in the volume fraction of deformed regions.

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Interfacial Delamination in Plastic Encapsulated Integrated Circuits (Pics)

MRS Proceedings ◽

10.1557/proc-445-239 ◽

1996 ◽

Vol 445 ◽

Author(s):

Nickolaos Strifas ◽

Aris Christou

Keyword(s):

Integrated Circuits ◽

Failure Analysis ◽

Stress Corrosion ◽

Integrated Circuit ◽

Point Of View ◽

Acoustic Microscopy ◽

Electrical Performance ◽

Premature Failure ◽

Interfacial Delamination ◽

Die Surface

AbstractThe reliability of plastic packaged integrated circuits was assessed from the point of view of interfacial mechanical integrity. It is shown that the effect of structural weaknesses caused by poor bonding, voids, microcracks or delamination may not be evident in the electrical performance characteristics, but may cause premature failure. Acoustic microscopy (C-SAM) was selected for nondestructive failure analysis of the plastic integrated circuit (IC) packages. Integrated circuits in plastic dual in line packages were initially subjected to temperature (25 °C to 85 °C) and humidity cycling (50 to 85 %) where each cycle was of one hour duration and for over 100 cycles and then analyzed. Delamination at the interfaces between the different materials within the package, which is a major cause of moisture ingress and subsequent premature package failure, was measured. The principal areas of delamination were found along the leads extending from the chip to the edge of the molded body and along the die surface itself. Images of the 3-D internal structure were produced that were used to determine the mechanism for a package failure. The evidence of corrosion and stress corrosion cracks in the regions of delamination was identified.

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Inclusion of CFRP-Epoxy Composite for End Anchorage in NSM-Epoxy Strengthened Beams

Advances in Materials Science and Engineering ◽

10.1155/2015/812797 ◽

2015 ◽

Vol 2015 ◽

pp. 1-10 ◽

Cited By ~ 5

Author(s):

Md. Akter Hosen ◽

Mohd Zamin Jumaat ◽

A. B. M. Saiful Islam

Keyword(s):

Reinforced Concrete ◽

Failure Modes ◽

Concrete Cover ◽

Structural Members ◽

Premature Failure ◽

Near Surface ◽

Steel Bars ◽

Near Surface Mounted ◽

Separation Failure ◽

Concrete Cover Separation

Nowadays, the use of near surface mounted (NSM) technique strengthening reinforced concrete (RC) structural members is going very popular. The failure modes of NSM strengthened reinforced concrete (RC) beams have been shown to be largely due to premature failure such as concrete cover separation. In this study, CFRP U-wrap end anchorage with CFRP fabrics was used to eliminate the concrete cover separation failure. A total of eight RC rectangular beam specimens of 125 mm width, 250 mm depth, and 2300 mm length were tested. One specimen was kept unstrengthened as a reference; three specimens were strengthened with NSM steel bars and the remaining four specimens were strengthened with NSM steel bars together with the U-wrap end anchorage. The experimental results showed that wrapped strengthened beams had higher flexural strength and superior ductility performance. The results also show that these beams had less deflection, strain, crack width, and spacing.

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