scholarly journals Surface Degradation of Ductile Metal in Elevated Temperature Gas-Particle Streams

1985 ◽  
Author(s):  
Alan Levy ◽  
Yong-Fa Man
Keyword(s):  
Erosion Rate ◽  
Loss Rate ◽  
Elevated Temperatures ◽  
Negative Slope ◽  
Material Loss ◽  
Loss Mechanism ◽  
High Loss ◽  
Air Atmosphere ◽  
Continuous Scale ◽  
Erosion Corrosion

The mechanisms and rates of erosion and combined erosion-corrosion of 9CrlMo steel and 310SS at elevated temperatures were investigated to better understand the behavior of piping steels in fluidized bed combustor environments. Tests were performed in a partially inert gas atmosphere to study erosion behavior and in an air atmosphere to study combined erosion-corrosion behavior. It was determined that the erosion rate remained constant or decreased with temperature in nitrogen until a temperature was reached at which the tensile strength v.s. temperature curve of the alloy markedly changed its negative slope. Above this temperature the erosion rate increased rapidly with temperature. In an erosion-corrosion environment corrosion was the dominant mechanism at all test conditions. At higher temperatures and velocities the material loss mechanism changed from low loss rate chipping of the scale to high loss rate periodic spalling. The continuous scale formed on 9CrlMo steel in air appeared to protect the metal surface, decreasing its loss rate in α=30° tests compared to that of 310SS tested at the same conditions in nitrogen where a continuous scale did not form.

Corrosion Behavior of Aluminium-Boron Carbide-Graphite Composites

2014 ◽  
Vol 591 ◽  
pp. 51-54 ◽  
Author(s):  
Chinnasamy Muthazhagan ◽  
A. Gnanavelbabu ◽  
K. Rajkumar ◽  
G.B. Bhaskar
Keyword(s):  
Boron Carbide ◽  
Corrosion Behaviour ◽  
Stir Casting ◽  
Silica Sand ◽  
Nacl Solution ◽  
Material Loss ◽  
Loss Mechanism ◽  
Corrosion Tests ◽  
Sand Erosion ◽  
Erosion Corrosion

The corrosion behaviour of Al (6061)-B4C-Graphite was investigated. The Aluminium Metal Matrix Composites (AMMC) was fabricated through two step stir casting method. The composites were fabricated with various volume percentages of Boron Carbide (5, 10 &15%) and Graphite (5, 10& 15%). Corrosion studies of AMMC was investigated with 4%, 8%, 12% wt. % NaCl solution at room temperature. Also erosion-corrosion test were performed on the specimens in the NaCl solution with silica sand. Erosion-corrosion tests indicated that the rate of material loss mechanism is mechanical abrasion with enhanced corrosion. The material loss mechanism was significantly higher in the case of erosion-corrosion tests.

Trowelable Rubber Rocket Insulation for Use at 2800°C

1984 ◽  
Vol 57 (4) ◽  
pp. 843-854 ◽  
Author(s):  
J. G. Sommer
Keyword(s):  
Room Temperature ◽  
Loss Rate ◽  
Service Temperature ◽  
Material Loss ◽  
Blowing Agent ◽  
Unusual Combination ◽  
Novel Approaches ◽  
Glass Microballoons ◽  
Burning Propellant ◽  
Intense Heat

Abstract Ablative, trowelable rocket insulation was prepared; it crosslinks at room temperature and self-bonds to prevulcanized NBR insulation. The material loss rate (MLR) of this insulation is low when it is tested by an oxyacetylene torch at temperatures of about 2800°C. Boric acid in the insulation causes an effective char to form at service temperature. This char slows the loss rate of nondegraded insulation beneath it. Density of this nondegraded insulation is 1.3 g/cm3. Density is reduced sharply to 0.8 g/cm3 by incorporating glass microballoons. They cause only a slight increase in MLR of the insulation at service temperatures. MLR can be significantly reduced by incorporating a blowing agent which decomposes only after the insulation is exposed to service temperature. Hence, an unusual combination of requirements is met by several novel approaches. This insulation has protected rockets as large as 6.6 meters in diameter from the intense heat of burning propellant in service.

Experiment and Optimization of High-Efficiency Mechanical Separation of Peanut Seedlings and Residual Film Based on Suspension Velocity

2021 ◽  
Vol 64 (4) ◽  
pp. 1381-1389
Author(s):  
Fengwei Gu ◽  
Meng Yang ◽  
Zhichao Hu ◽  
Yanhua Zhang ◽  
Chong Zhang ◽  
...  
Keyword(s):  
Moisture Content ◽  
Rotational Speed ◽  
Loss Rate ◽  
Removal Rate ◽  
Performance Tests ◽  
Test Results ◽  
Material Loss ◽  
Validation Test ◽  
Residual Film ◽  
Forage Utilization

HighlightsAn efficient method for separating peanut seedlings and residual film harvested from film-mulched peanut was proposed, and the mechanism was optimized.The relationships between the suspension velocity and moisture content of different shredded materials were studied.Four-factor, three-level Box-Behnken experiments were carried out and analyzed, and the optimal parameter combination was determined.A validation test was carried out to verify the rationality and accuracy of the optimized regression model.Abstract. To address the problems of lower residual film removal and higher material loss in the forage utilization of peanut seedlings wrapped in residual film, this study explored the relationships between the suspension velocity and moisture content of different shredded materials derived from peanut seedlings and conducted performance tests and parameter optimization for a machine that uses peanut seedlings as forage material. Four-factor, three-level Box-Behnken experiments were designed using the rotational speeds of the shredding shaft, upper fans, and lower fans and the frequency of the vibrating sieve as test factors, and using the residual film removal rate and material loss rate as response values. The test results indicated that the suspension velocity of the shredded materials showed a quadratic relationship with moisture content. The performance tests showed that the significance sequence of the test factors for the residual film removal rate was: rotational speed of the lower fans, rotational speed of the upper fans, rotational speed of the shredding shaft, and frequency of the vibrating sieve. The significance sequence for the material loss rate was: rotational speed of the lower fans, rotational speed of the shredding shaft, frequency of the vibrating sieve, and rotational speed of the upper fans. The parameter optimization and validation test showed that the residual film removal rate was 92.71% and the material loss rate was 8.19% when the rotational speeds of the shredding shaft, upper fans, and lower fans were 1650, 770, and 665 rpm, respectively, and the frequency of the vibrating sieve was 4 Hz. The relative errors between the validation test results and the predicted values from the regression models were less than 3%, which suggests that the regression models are reliable. This study provides a reference for the forage utilization of peanut seedlings harvested from film-mulched peanut and provides a reference for determining the optimal working parameters of forage processing machines. Keywords: Agricultural machinery, Box-Behnken experiment, Optimization, Peanut film-seedling separation, Suspension velocity.

scholarly journals Potential distribution of the endangered endemic lizard Liolaemus lutzae Mertens, 1938 (Liolaemidae): are there other suitable areas for a geographically restricted species?

2014 ◽  
Vol 74 (2) ◽  
pp. 338-348 ◽  
Author(s):  
GR. Winck ◽  
P. Almeida-Santos ◽  
CFD. Rocha
Keyword(s):  
Geographic Distribution ◽  
Diurnal Temperature Range ◽  
Potential Distribution ◽  
Sand Dune ◽  
Loss Rate ◽  
Distribution Area ◽  
Environmental Matrices ◽  
High Loss ◽  
Original Distribution ◽  
High Loss Rate

In this study we attempted to access further information on the geographical distribution of the endangered lizard Liolaemus lutzae, estimating its potential distribution through the maximum entropy algorithm. For this purpose, we related its points of occurrence with matrices of environmental variables. After examining the correlation between environmental matrices, we selected 10 for model construction. The main variables influencing the current geographic distribution of L. lutzae were the diurnal temperature range and altitude. The species endemism seemed to be a consequence of a reduction of the original distribution area. Alternatively, the resulting model may reflect the geographic distribution of an ancestral lineage, since the model selected areas of occurrence of the two other species of Liolaemus from Brazil (L. arambarensis and L. occipitalis), all living in sand dune habitats and having psamophilic habits. Due to the high loss rate of habitat occupied by the species, the conservation and recovery of the remaining areas affected by human actions is essential.

A brief review on the erosion-corrosion behavior of engineering materials

2018 ◽  
Vol 36 (5) ◽  
pp. 435-447 ◽  
Author(s):  
Roshan Kuruvila ◽  
S. Thirumalai Kumaran ◽  
M. Adam Khan ◽  
M. Uthayakumar
Keyword(s):  
Adverse Effects ◽  
Industrial Process ◽  
Industrial Applications ◽  
Appropriate Technology ◽  
Material Loss ◽  
Adverse Conditions ◽  
Wide Range ◽  
Erosion Corrosion ◽  
The Cost ◽  
Selection Of

AbstractThe efficiency of industry depends upon the working conditions of the equipment and components used in the industrial process. The biggest problems faced by the industries are the problems of erosion and corrosion. The harmful effects of corrosion will lead to material loss, which results from the degradation of the equipment. The degradation of the equipment will cause the breakdown of the plant; moreover, it is a threat to the safety of people, and also from the point of conservation, it can cause the exploitation of available resources. The cost of replacing equipment increases the expense, and it can also result in the temporary shutdown of the plant. The protection of surfaces from the adverse effects of corrosion and erosion-corrosion is a matter of great concern in most industrial applications. Advancements in technology provides a wide range of techniques to overcome adverse conditions. The selection of appropriate technology must be from the viewpoint of their interaction with the environment. This review paper addresses the adverse effects of erosion-corrosion in the present scenario.

Erosion Evaluation of Gas-Turbine Grade CMC’s at Room and Elevated Temperatures

2021 ◽  
Author(s):  
Amirhossein Eftekharian ◽  
Ragav P. Panakarajupally ◽  
Gregory N. Morscher ◽  
Dade Huang ◽  
Frank Abdi ◽  
...  
Keyword(s):  
Erosion Rate ◽  
Elevated Temperatures ◽  
Solid Phase ◽  
Phase Particle ◽  
Crack Density ◽  
Smooth Particle Hydrodynamic ◽  
Ceramic Matrix Composites ◽  
Glass Beads ◽  
Erosion Process ◽  
Fiber Matrix

Abstract The objective of this study is to predict ceramic matrix composites (CMCs) erosion behavior and Retained Strength (RS) under environmental conditions using an Integrated Computational Material Engineering (ICME) physics-based approach. The state-of-the-art erosion analysis using phenomenological algorithms and Finite Element Models (FEM) models follows a test duplication methodology and is not able to capture the physics of erosion. In this effort, two CMC systems are chosen for Erosion evaluation: (a) Oxide/Oxide N720/alumina; and (b) MI SiC/SiC. Experiments are conducted at room and elevated temperatures (RT/ ET). Erosion testing considers: (i) a high velocity oxygen fuel (HVOF) burner rig for ET, and (ii) a pressurized helium impact gun for RT. Erodent particles are chosen as alumina and garnet. Experimental observations show that the type of erodent materials affects CMC erosion degradation at ET. Alumina exhibits to be an effective erodent for maintaining a solid phase particle erosion, while Garnet, experiences some degree of melting. Erosion of the oxide/oxide composite is more severe for the same erodent, temperature, mass, and velocity conditions than the MI SiC/SiC composite for all conditions tested. In general, increasing erosion temperature results in increasing erosion rate for the same erodent mass/velocity condition. In conjunction with experiments, a computational Multi-Scale Progressive Failure Analysis (MS-PFA) is also used to predict erosion of the above-mentioned material systems at RT/ET. The MS-PFA augments FEM by a de-homogenized material modeling that includes micro-crack density, fiber/matrix, interphase, and degrades both fiber and matrix simultaneously during the erosion process. Erodent particles are modeled by Smooth Particle Hydrodynamic (SPH) elements. Erosion evolution in CMCs considering strain rate effect predicts a) spallation, b) mass-loss, and c) damages in fiber, matrix, and their interphase. ICME modeling is capable of predicting the erosion process and reproducing the test observation for the MI SiC/SiC at RT, where: a) erodent particles break up the layer of matrix covering fiber due to interlaminar shear (delamination); b) fiber is fractured because of brittle behavior; c) the process (erosion tunneling) continues till it gets to the next thick matrix layer that slows down the tunneling; and d) Erosion tunnel widens as exposed fiber layers are removed (eroded). Simulations are also performed for erosion of the oxide/oxide due to glass beads at RT and ET. Predictions show that erosion rate is lower at ET because voids in the CMC vanish and the glass beads are less effective at ET. Finally, prediction of retained strength of eroded CMC test specimens is predicted by MS-PFA.

Arc-Sprayed Iron-Based Coatings for Erosion-Corrosion Protection of Boiler Tubes at Elevated Temperatures

2013 ◽  
Vol 22 (5) ◽  
pp. 808-819 ◽  
Author(s):  
Vasyl Pokhmurskii ◽  
Mykhailo Student ◽  
Volodymyr Gvozdeckii ◽  
Taras Stypnutskyy ◽  
Oleksandra Student ◽  
...  
Keyword(s):  
Corrosion Protection ◽  
Elevated Temperatures ◽  
Boiler Tubes ◽  
Erosion Corrosion ◽  
Iron Based

The Reason Statistics and Analysis of the Loss of Hotel Employees

2014 ◽  
Vol 926-930 ◽  
pp. 4138-4141
Author(s):  
Lei Lei Wang ◽  
Wen Su Xu
Keyword(s):  
Sustainable Development ◽  
Loss Rate ◽  
Rapid Development ◽  
Employment Opportunities ◽  
The Sustainable Development ◽  
High Loss ◽  
Hotel Employees ◽  
The Status ◽  
Face Threat ◽  
High Loss Rate

Hotels have offered a large number of employment opportunities for society as one of rapid development industries in our country. Whereas hotels face threat from the high loss rate of personnel' demission that even exceeds expected numerical value,as a result,loss directly influences the sustainable development of enterprises. This paper describes the status and characteristic of loss of hotels employees according to the investigation datum of personnel' demission interview in one hotel of Shenzhen,and dissects the main reason why employees leave their posts by adopting Maslow’s demand level theory.

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