Influences of specimen size and heating mode on the ignitability of polymeric materials in typical small-scale fire test conditions

2011 ◽  
Vol 36 (3) ◽  
pp. 231-240 ◽  
Author(s):  
Yong Wang ◽  
Jun Zhang
Keyword(s):  
Fire Test ◽  
Polymeric Materials ◽  
Specimen Size ◽  
Small Scale ◽  
Test Conditions ◽  
Heating Mode

scholarly journals Thermal Contact Conductance-Based Thermal Behavior Analytical Model for a Hybrid Floor at Elevated Temperatures

Materials ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 4257 ◽  
Author(s):  
Min Jae Park ◽  
Jeong Ki Min ◽  
Jaehoon Bae ◽  
Young K. Ju
Keyword(s):  
Thermal Behavior ◽  
Elevated Temperatures ◽  
Heated Surface ◽  
Thermal Contact ◽  
Polymeric Materials ◽  
Steel Plates ◽  
Thermal Contact Conductance ◽  
Small Scale ◽  
Element Analysis ◽  
Contact Conductance

Hybrid floors infilled with polymeric materials between two steel plates were developed as a prefabricated floor system in the construction industry. However, the floor’s fire resistance performance has not been investigated. To evaluate this, fire tests suggested by the Korean Standards should be performed. As these tests are costly and time consuming, the number of variables were limited. However, many variables can be investigated in other ways such as furnace tests and finite element analysis (FEA) with less cost and time. In this study, furnace tests on heated surface areas smaller than 1 m2 were conducted to investigate the thermal behavior of the hybrid floor at elevated temperatures. To obtain the reliability of the proposed thermal behavior analytical (TBA) model, verifications were conducted by FEAs. Thermal contact conductance including interfacial thermal properties between two materials was adopted in the TBA model, and the values at elevated temperatures were suggested based on thermo-gravimetric analyses results and verified by FEA. Errors between the tests and TBA model indicated that the model was adequate in predicting the temperature distribution in small-scale hybrids. Furthermore, larger furnace tests and analysis results were compared to verify the TBA model’s application to different sized hybrid floors.

Scaling of Pop-Ins During Brittle Fracture Testing

2019 ◽  
Author(s):  
O. J. Coppejans ◽  
C. L. Walters
Keyword(s):  
Fracture Toughness ◽  
Analytical Method ◽  
Offshore Structures ◽  
Specimen Size ◽  
Small Scale ◽  
Unstable Fracture ◽  
Displacement Curve ◽  
Fracture Toughness Test ◽  
Key Factor

Abstract Measurement of the fracture toughness of steel is important for the assurance of the safety of ships and offshore structures, especially when these structures are made of thick sections and/or applied in cold environments. One key factor that will affect the determination of the fracture toughness is a pop-in, which is a short event in which unstable fracture is initiated and then self-arrests. If the pop-in is large enough, it will be used to calculate the fracture toughness. Pop-ins are believed to be the products of local brittle zones, which occur randomly at crack tips and have finite sizes. Fracture toughness testing codes have ways of determining whether a pop-in is critical (thus, identifying the maximum force and displacement to be used in the determination of the toughness of the material) or not important (thus, allowing for the test to proceed). In an ongoing project on the use of small-scale fracture specimens to predict standard fracture toughness test results, we would like to know how pop-in acceptance criteria should be scaled for specimen size. It is expected that the physical size of the brittle zones that cause pop-ins is invariant of specimen size, meaning that the contribution of the pop-in will be proportionally more important for smaller specimens. An analytical method for relating the pop-ins on one specimen size to another specimen size is developed. This method is partially verified by observations on the size of a local brittle zone observed on a fracture surface and the effect of that pop-in on the force-displacement curve during a CTOD test. The analytical method showed that an equivalent pop-in for a small-scale specimen is indeed larger, but that the effect was subtle.

Small-scale plasticity critically needs a new mechanics description

2013 ◽  
Vol 22 (1-2) ◽  
pp. 3-10
Author(s):  
Alfonso H.W. Ngan
Keyword(s):  
Plastic Deformation ◽  
Specimen Size ◽  
Constitutive Laws ◽  
Small Scale ◽  
Discrete Events ◽  
Satisfactory Description ◽  
Continuum Description ◽  
Micrometer Scale ◽  
The Continuum

AbstractContinuum constitutive laws describe the plastic deformation of materials as a smooth, continuously differentiable process. However, provided that the measurement is done with a fine enough resolution, the plastic deformation of real materials is often found to comprise discrete events usually nanometric in size. For bulk-sized specimens, such nanoscale events are minute compared with the specimen size, and so their associated strain changes are negligibly small, and this is why the continuum laws work well. However, when the specimen size is in the micrometer scale or smaller, the strain changes due to the discrete events could be significant, and the continuum description would be highly unsatisfactory. Yet, because of the advent of microtechnology and nanotechnolgy, small-sized materials will be increasingly used, and so there is a strong need to develop suitable replacement descriptions for plasticity of small materials. As the occurrence of the discrete plastic events is also strongly stochastic, their satisfactory description should also be one of a probabilistic, rather than deterministic, nature.

scholarly journals CROSS-SHORE TRANSPORT ON GRAVEL BEACHES

2011 ◽  
Vol 1 (32) ◽  
pp. 43
Author(s):  
Betsy S. Hicks ◽  
Nobuhisa Kobayashi ◽  
Jack A. Puleo ◽  
Ali Farhadzadeh
Keyword(s):  
Experimental Investigation ◽  
Numerical Model ◽  
Incident Wave ◽  
Small Scale ◽  
Quasi Equilibrium ◽  
Wave Flume ◽  
Test Conditions ◽  
Equilibrium Profiles ◽  
Hydrodynamic Data ◽  
Gravel Beach

A numerical and experimental investigation of profile evolution was completed on a laboratory gravel beach. A total of four tests were completed on a gravel beach constructed in a small-scale wave flume, with different incident wave conditions and initial beach slopes. The tests allowed for an examination of erosional, accretional, and migratory bar conditions as well as how the differences affected the final quasi-equilibrium profiles. Profile evolution and hydrodynamic data were collected for comparison with the time- and depth- averaged numerical model CSHORE. The numerical formulations developed for damage progression on a stone armor layer were found to predict the profile evolution on the steeper test conditions but required modifications to the bedload formula to better predict the accretional and bar migration tests.

scholarly journals Fire Spread of Thermal Insulation Materials in the Ceiling of Piloti-Type Structure: Comparison of Numerical Simulation and Experimental Fire Tests Using Small- and Real-Scale Models

2019 ◽  
Vol 11 (12) ◽  
pp. 3389
Author(s):  
Heong-Won Suh ◽  
Su-Min Im ◽  
Tae-Hoon Park ◽  
Hyung-Jun Kim ◽  
Hong-Sik Kim ◽  
...  
Keyword(s):  
Thermal Insulation ◽  
Fire Test ◽  
Fire Spread ◽  
Scale Model ◽  
Fire Intensity ◽  
Small Scale ◽  
Insulation Material ◽  
Fire Tests ◽  
Insulation Materials ◽  
Real Scale

Large-scale fires mainly due to the ignition of thermal insulation materials in the ceiling of piloti-type structures are becoming frequent. However, the fire spread in these cases is not well understood. Herein we performed small-scale and real-scale model tests, and numerical simulations using a fire dynamics simulator (FDS). The experimental and FDS results were compared to elucidate fire spread and effects of thermal insulation materials on it. Comparison of real-scale fire test and FDS results revealed that extruded polystyrene (XPS) thermal insulation material generated additional ignition sources above the ceiling materials upon melting and propagated and sustained the fire. Deformation of these materials during fire test generated gaps, and combustible gases leaked out to cause fire spread. When the ceiling materials collapsed, air flew in through the gaps, leading to flashover that rapidly increased fire intensity and degree of spread. Although the variations of temperatures in real-scale fire test and FDS analysis were approximately similar, melting of XPS and generation of ignition sources could not be reproduced using FDS. Thus, artificial settings that increase the size and intensity of ignition sources at the appropriate moment in FDS were needed to achieve results comparable to those recorded by heat detectors in real-scale fire tests.

Influence of Test Conditions and Couple Materials on Frictional Characteristic of Polymeric Materials

2011 ◽  
Vol 306-307 ◽  
pp. 684-687
Author(s):  
Li Xiao Jia ◽  
Yong Zhen Zhang ◽  
Yong Ping Niu ◽  
San Ming Du ◽  
Jian Li
Keyword(s):  
Friction Coefficient ◽  
Polymeric Material ◽  
Polymeric Materials ◽  
Friction Characteristic ◽  
Test Conditions ◽  
Frictional Characteristic

Frictional characteristic of three kinds of polymeric material was studied by Mark II slipmeter under the condition of different couple materials and test conditions in order to understand the frictional mechanism of people’s walking deeply and decrease the probability of accidents caused by slips and falls. The results indicate that test conditions and couple materials influent friction characteristic of polymeric materials but the influence of test conditions is more significant. In the three test conditions, the friction coefficient of dry condition is highest and that of oil condition is lowest. The friction coefficient of polymeric materials on different floor samples had different trend indicated that there was interaction between shoe sole samples and floor samples.

A Simple Method for Evaluating Flaw Distributions Responsible for Size Effects in the Strength of Small-Scale Silicon Specimens

2006 ◽  
Vol 312 ◽  
pp. 77-82 ◽  
Author(s):  
Kai Duan ◽  
Xiao Zhi Hu
Keyword(s):  
Size Effects ◽  
Single Crystal Silicon ◽  
Specimen Size ◽  
Small Scale ◽  
Size Distributions ◽  
Power Law Distribution ◽  
Crystal Silicon ◽  
Simple Method ◽  
Self Consistent ◽  
Two Parameter

A simple means of deconvoluting the size distributions of fracture-controlling flaws from Weibull strength plots for small-scale specimens is proposed. The method makes use a power-law distribution function, empirical in form but self-consistent with a conventional two-parameter Weibull probability distribution. Literature data for single-crystal silicon beam specimens covering a range of widths from mm to nm are analyzed according to this procedure. The analysis indicates a reduction in scatter in addition to increase in strength with diminishing specimen size, and quantifies a systematic tightening in flaw distribution associated with refinement in fabrication method.

scholarly journals Bearing Capacities of Different-Diameter Concrete-Filled Steel Tubes under Axial Compression

2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
Wenjing Wang ◽  
Zhenyun Tang ◽  
Zhenbao Li ◽  
Hua Ma
Keyword(s):  
Bearing Capacity ◽  
Axial Compression ◽  
Peak Load ◽  
Steel Tube ◽  
Specimen Size ◽  
Small Scale ◽  
Strengthening Effect ◽  
Steel Tubes ◽  
Specimen Diameter ◽  
Concrete Filled Steel Tubes

The bearing capacities of concrete-filled steel tubes are normally derived through experiments with small-scale specimens, but it is uncertain whether such derivations are appropriate for the much larger components used in practical engineering. This study therefore investigates the effect of different diameters (219, 426, 630, and 820 mm) on the axial compression of short concrete columns in steel (Q235) tubes. It is found that the peak nominal stress decreases with increasing specimen size and that the axial bearing capacity is determined by three separate components: the cylinder compressive strength of the concrete, the improvement in strength due to the confining effect of the steel tube, and the longitudinal strength of the steel tube. At peak load, increases in the specimen diameter reduce the hoop stresses in the steel tube, thereby reducing the strengthening effect of confinement. Vertical stress in the steel tube is increased with diameter; therefore, the axial bearing capacity of the steel tube is directly related to the specimen size. Size effect coefficients for these three aspects of bearing capacity are defined and used to develop a size-dependent model for predicting the axial bearing capacity of large, concrete-filled steel tubes. The model is then validated against experimental data.

scholarly journals Screening of plenum cables using a small-scale fire test protocol

2006 ◽  
Vol 30 (1) ◽  
pp. 65-76 ◽  
Author(s):  
Mohammed M. Khan ◽  
Robert G. Bill ◽  
Ronald L. Alpert
Keyword(s):  
Fire Test ◽  
Small Scale ◽  
Test Protocol
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