Thermal Damage, Cracking and Rapid Erosion of Cannon Bore Coatings

2003 ◽  
Vol 125 (3) ◽  
pp. 299-304 ◽  
Author(s):  
John H. Underwood ◽  
Anthony P. Parker ◽  
Gregory N. Vigilante ◽  
Paul J. Cote
Keyword(s):  
Thermal Damage ◽  
Shear Failure ◽  
Low Cycle Fatigue ◽  
Steel Substrate ◽  
Zone Model ◽  
Open Crack ◽  
Failure Strength ◽  
Closed Crack ◽  
Cyclic Shear ◽  
Coating Failure

Thermal damage observed at the bore of fired cannons has increased noticeably in the past decade, due to the use of higher combustion gas temperatures for improved cannon performance. Current authors and coworkers recently have described cannon firing damage and proposed new thermo-mechanical models to gain understanding of its causes, with emphasis on the severe damage that occurs in the steel beneath the chromium plating used to protect the cannon bore. Recent refinements in the models will be used here to characterize some additional damage observations in the area beneath the protective coating of fired cannons. Model results validated by microstructural observations give predictions of near-bore temperature and stress distributions and good agreement with observed depths of hydrogen cracking in the high strength steel substrate. Interest in damage and failure within a coating is also of concern for cannons, since coating failure leads to extremely rapid erosion of coating and substrate. The slip zone model of Evans and Hutchinson is adapted here to predict failure strength of cannon coatings based on observed crack spacing and microhardness of thermally damaged areas. Results are described for electroplated chromium coatings from fired cannons and for sputtered chromium and tantalum coatings with laser-heating damage to simulate firing. Coating mechanics analysis of fired and laser-heated samples provides an insitu measurement of coating failure strength, showing that sputtered chromium has more than twice the failure strength of electroplated chromium. An analysis of cyclic shear failure of a coating interface at an open crack shows a six-fold decrease in low cycle fatigue life compared to the life of a closed crack. Recommendations are given for preventing rapid coating failure and catastrophic erosion of fired cannon, with emphasis on methods to prevent deep, open cracks in coating and substrate.

Interlaminar Damage Behavior of CFRP Composite Laminates under Cyclic Shear Loading Conditions

2015 ◽  
Vol 1125 ◽  
pp. 121-125 ◽  
Author(s):  
Muhammad A'imullah Abdullah ◽  
Mohammad Reza Arjmandi ◽  
Seyed Saeid Rahimian Koloor ◽  
King Jye Wong ◽  
Mohd Nasir Tamin
Keyword(s):  
Composite Laminates ◽  
Quantitative Description ◽  
Shear Loading ◽  
Zone Model ◽  
Fe Model ◽  
Critical Energy Release Rate ◽  
Cyclic Shear ◽  
Load Amplitude ◽  
Cfrp Composite ◽  
Interlaminar Damage

This paper provides quantitative description of interlaminar damage process in CFRP composite laminates under cyclic shear loading. Quasi-static end-notched flexural (ENF) test on 16-ply CFRP composite laminate beam, [0]16 and its complementary validated FE model provide the reference “no-interlaminar damage” condition. Two identical ENF samples were fatigue to 50000 cycles, but at different load amplitude of 90 and 180 N, respectively (Load ratio, R = 0.1) to induce selectively property degradation at the interface crack front region. Subsequent quasi-static ENF tests establish the characteristic of the interlaminar damage degradation. The residual peak load for the fatigued ENF samples is measured at 1048 and 914 N for the load amplitude of 90 and 180 N, respectively. Cyclic interlaminar shear damage is represented by a linear degradation of the residual critical energy release rate, GIIC with the accumulated damage. Reasonably close comparisons of the predicted residual load-displacement responses with measured curves serve to verify the suitability of the assumed bilinear traction-separation law for the cyclic cohesive zone model (CCZM) used.

scholarly journals Study on Shear Mechanism of Bolted Jointed Rocks: Experiments and CZM-Based FEM Simulations

2019 ◽  
Vol 10 (1) ◽  
pp. 62 ◽  
Author(s):  
Shubo Zhang ◽  
Gang Wang ◽  
Yujing Jiang ◽  
Xianlong WU ◽  
Genxiao Li ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Failure Mechanism ◽  
Laboratory Experiments ◽  
Shear Failure ◽  
Cohesive Zone Model ◽  
Rock Fracture ◽  
High Strength ◽  
Simulation Method ◽  
Jointed Rock ◽  
Zone Model

Based on the underground jointed rock of the Huangdao water sealed oil depot in China, the shear failure mechanism of bolted jointed rock is studied through laboratory experiments and numerical simulation. Laboratory experiments are performed to explore the shear behavior of bolted jointed rock with different joint roughness. Our results show that using high strength bolts is beneficial to improving the shear strength of the jointed rock, but the high strength of bolts can also lead to the rock fracture, which should be avoided. For this particular project site, experimental results indicate that 15% elongation is the best. In addition, a new numerical simulation method with CZM (cohesive zone model) used for modeling the shearing process of bolted jointed rock is proposed. It can reasonably describe the characteristics of jointed rock as a discontinuous medium, and bolt as a continuous medium, that replicate well the shearing process. The numerical model is then verified by comparing the experiment results, and it can be effectively be applied to the simulation of joint shearing process. Finally, we use this simulation method to explore the shear failure mechanism of bolted joints, and find that the root cause of rock failure is the deformation mismatch between the bolt and the surrounding rock. The tensile stress between them eventually causes the rock to fracture near the bolt hole.

Spectral indicators in structural damage identification: A case study

1999 ◽  
Vol 213 (4) ◽  
pp. 411-415 ◽  
Author(s):  
J. A. Brandon ◽  
A. E. Stephens ◽  
E. M. O. Lopes ◽  
A. S. K. Kwan
Keyword(s):  
Structural Damage ◽  
Damage Identification ◽  
Vibration Signal ◽  
Open Crack ◽  
Severe Damage ◽  
Closed Crack ◽  
Spectral Signatures ◽  
Linear Behaviour ◽  
Systematic Effects

A pre-loaded cracked cantilever beam was excited vising a random vibration signal. Excitation levels were within the range of amplitudes that caused no suspicion of non-linear behaviour in an undamaged specimen of identical dimensions and material. Spectral signatures were acquired which made it possible to discriminate between open crack, closed crack and breathing conditions. Systematic effects relating to variations in resonant frequency were largely consistent with the literature for a lightly damaged beam but were unsupported for a beam with more severe damage.

scholarly journals Experimental and numerical evaluations of composite concrete-to-concrete interfacial shear strength under horizontal and normal stresses

PLoS ONE ◽  
2021 ◽  
Vol 16 (5) ◽  
pp. e0252050
Author(s):  
M. Yahya Al-Fasih ◽  
M. E. Mohamad ◽  
I. S. Ibrahim ◽  
Y. Ahmad ◽  
M. A. Mohd Ariffin ◽  
...  
Keyword(s):  
Shear Strength ◽  
Failure Mode ◽  
Failure Modes ◽  
Shear Failure ◽  
Zone Model ◽  
Normal Stresses ◽  
Interface Shear Strength ◽  
Interface Shear ◽  
Surface Textures ◽  
Roughened Surface

Effects of different surface textures on the interface shear strength, interface slip, and failure modes of the concrete-to-concrete bond are examined through finite element numerical model and experimental methods in the presence of the horizontal load with ‘push-off’ technique under different normal stresses. Three different surface textures are considered; smooth, indented, and transversely roughened to finish the top surfaces of the concrete bases. In the three-dimensional modeling via the ABAQUS solver, the Cohesive Zone Model (CZM) is used to simulate the interface shear failure. It is observed that the interface shear strength increases with the applied normal stress. The transversely roughened surface achieves the highest interface shear strength compared with those finished with the indented and smooth approaches. The smooth and indented surfaces are controlled by the adhesive failure mode while the transversely roughened surface is dominated by the cohesive failure mode. Also, it is observed that the CZM approach can accurately model the interface shear failure with 3–29% differences between the modeled and the experimental test findings.

scholarly journals Failure modes of coatings on steel substrate

2016 ◽  
Vol 64 (1) ◽  
pp. 249-256
Author(s):  
K.P. Mróz ◽  
S. Kucharski ◽  
K. Doliński ◽  
A. Bigos ◽  
G. Mikułowski ◽  
...  
Keyword(s):  
Failure Modes ◽  
Surface Defects ◽  
Steel Substrate ◽  
Sample Surface ◽  
Bending Test ◽  
Axisymmetric Stress State ◽  
Coating Failure ◽  
Stress Components ◽  
Axisymmetric Bending ◽  
Steel Substrates

Abstract The critical monotonic strain of Ni-W and MoS2(Ti,W) coatings on steel substrates was studied. The idea of axisymmetric bending test (called here as coin bending test) limited to monitoring of the coating failure was used. Experiments revealed mechanism of the coating failure, as cracking initiated from coating surface defects and/or substrate was demonstrated using indentation technique. By pushing the center of the uncoated side of a circular plate, the axisymmetric stress state was generated in the coating. The stress components varied gradually from the greatest value in the center to the smallest value at the edge of the specimen. The changes of the sample surface as a result of loading were monitored step by step via optical microscopy.

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