A Method for Predicting the Behavior of Plastics at Different Temperatures

2014 ◽  
Vol 1039 ◽  
pp. 107-111
Author(s):  
Yang Chen ◽  
Gui Qin Li ◽  
Bin Ruan ◽  
Xiao Yuan ◽  
Hong Bo Li
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Constitutive Model ◽  
Research And Development ◽  
Mechanical Behavior ◽  
Plastic Material ◽  
Different Temperatures ◽  
Plastic Parts

The mechanical behavior of plastic material is dramatically sensitive to temperature. An method is proposed to predict the mechanical behavior of plastics for cars, ranging from low-temperature low temperature ≤-40°C to high temperature ≥80°C. It dominates the behavior of plastic material based on improved constitutive model in which the parameters adjusted by a series of tests under different temperatures. The method is validated with test and establishes the basis for research and development of plastic parts for automobile as well.

scholarly journals GERMINATION AND VIGOUR IN SEEDS OF THE COWPEA IN RESPONSE TO SALT AND HEAT STRESS

2019 ◽  
Vol 32 (1) ◽  
pp. 143-151 ◽  
Author(s):  
Luma Rayane de Lima Nunes ◽  
Paloma Rayane Pinheiro ◽  
Charles Lobo Pinheiro ◽  
Kelly Andressa Peres Lima ◽  
Alek Sandro Dutra
Keyword(s):  
Salt Stress ◽  
Heat Stress ◽  
High Temperature ◽  
Low Temperature ◽  
Vigna Unguiculata ◽  
Salt Concentration ◽  
Dry Weight ◽  
Germination Percentage ◽  
Different Types ◽  
Different Temperatures

ABSTRACT Salinity is prejudicial to plant development, causing different types of damage to species, or even between genotypes of the same species, with the effects being aggravated when combined with other types of stress, such as heat stress. The aim of this study was to evaluate the tolerance of cowpea genotypes (Vigna unguiculata L. Walp.) to salt stress at different temperatures. Seeds of the Pujante, Epace 10 and Marataoã genotypes were placed on paper rolls (Germitest®) moistened with different salt concentrations of 0.0 (control), 1.5, 3.0, 4.5 and 6.0 dS m-1, and placed in a germination chamber (BOD) at temperatures of 20, 25, 30 and 35°C. The experiment was conducted in a completely randomised design, in a 3 × 4 × 5 scheme of subdivided plots, with four replications per treatment. The variables under analysis were germination percentage, first germination count, shoot and root length, and total seedling dry weight. At temperatures of 30 and 35°C, increases in the salt concentration were more damaging to germination in the Epace 10 and Pujante genotypes, while for the Marataoã genotype, damage occurred at the temperature of 20°C. At 25°C, germination and vigour in the genotypes were higher, with the Pujante genotype proving to be more tolerant to salt stress, whereas Epace 10 and Marataoã were more tolerant to high temperatures. Germination in the cowpea genotypes was more sensitive to salt stress when subjected to heat stress caused by the low temperature of 20°C or high temperature of 35°C.

Understanding the Effects of Processing on the Mechanical Behavior of a SI3N4 Ceramic Through Microstructural Investigations

2001 ◽  
Author(s):  
Q. Wei ◽  
J. Sankar
Keyword(s):  
High Temperature ◽  
Mechanical Behavior ◽  
Triple Junctions ◽  
Sintering Aids ◽  
Si3n4 Ceramic ◽  
Creep Tests ◽  
Furnace Annealing ◽  
Conventional Furnace ◽  
Different Temperatures ◽  
Si3n4 Ceramics

Abstract The mechanical properties of silicon nitride (Si3N4) ceramics are determined by their microstructure, which in turn depends on processing routes adopted to fabricate the material. To obtain dense Si3N4, sintering aids are almost always added during the densification process. The sintering aids remain in the ceramics as amorphous residues which adversely affect the high temperature mechanical behavior of the material. In this paper, we have investigated the effects of processing on the mechanical behavior of a sintered Si3N4 ceramic through detailed microstructural observations. A commercial Si3N4 was annealed using conventional furnace annealing and microwave annealing at different temperatures. Creep tests were performed to compare the high temperature mechanical behavior of the as-sintered and annealed ceramics. It was found that microwave and furnace annealing heat-treatments improve the creep resistance of the ceramic through devitrification of the triple junctions phases.

scholarly journals Experimental results and constitutive model of the mechanical behavior of Ti6Al4V alloy at high temperature

2019 ◽  
Vol 41 ◽  
pp. 723-730
Author(s):  
Jorge Ayllón Perez ◽  
Valentín Miguel Eguía ◽  
Juana Coello Sobrino ◽  
Alberto Martínez Martínez
Keyword(s):  
High Temperature ◽  
Constitutive Model ◽  
Mechanical Behavior ◽  
Ti6al4v Alloy ◽  
Experimental Results

scholarly journals A Constitutive Model for the Mechanical Behavior of Single Crystal Silicon at Elevated Temperature

2001 ◽  
Vol 687 ◽  
Author(s):  
H.-S. Moon ◽  
L. Anand ◽  
S. M. Spearing
Keyword(s):  
High Temperature ◽  
Constitutive Model ◽  
Single Crystal ◽  
Mechanical Behavior ◽  
Elevated Temperatures ◽  
Single Crystal Silicon ◽  
Operational Environment ◽  
Localized Deformation ◽  
Creep Tests ◽  
Crystal Silicon

AbstractSilicon in single crystal form has been the material of choice for the first demonstration of the MIT microengine project. However, because it has a relatively low melting temperature, silicon is not an ideal material for the intended operational environment of high temperature and stress. In addition, preliminary work indicates that single crystal silicon has a tendency to undergo localized deformation by slip band formation. Thus it is critical to obtain a better understanding of the mechanical behavior of this material at elevated temperatures in order to properly exploit its capabilities as a structural material. Creep tests in simple compression with n-type single crystal silicon, with low initial dislocation density, were conducted over a temperature range of 900 K to 1200 K and a stress range of 10 MPa to 120 MPa. The compression specimens were machined such that the multi-slip <100> or <111> orientations were coincident with the compression axis. The creep tests reveal that response can be delineated into two broad regimes: (a) in the first regime rapid dislocation multiplication is responsible for accelerating creep rates, and (b) in the second regime an increasing resistance to dislocation motion is responsible for the decelerating creep rates, as is typically observed for creep in metals. An isotropic elasto-viscoplastic constitutive model that accounts for these two mechanisms has been developed in support of the design of the high temperature turbine structure of the MIT microengine.

scholarly journals A Thermal Damage Constitutive Model for Oil Shale Based on Weibull Statistical Theory

2019 ◽  
Vol 2019 ◽  
pp. 1-11 ◽  
Author(s):  
Guijie Zhao ◽  
Chen Chen ◽  
Huan Yan
Keyword(s):  
High Temperature ◽  
Constitutive Model ◽  
Oil Shale ◽  
Thermal Damage ◽  
Triaxial Compression ◽  
Strain Curve ◽  
Practical Significance ◽  
Compression Tests ◽  
Different Temperatures ◽  
Damage Constitutive Model

In this work, we first studied the thermal damage to typical rocks, assuming that the strength of thermally damaged rock microelements obeys a Weibull distribution and considering the influence of temperature on rock mechanical parameters; under the condition that microelement failure conforms to the Drucker–Prager criterion, the statistical thermal damage constitutive model of rocks after high-temperature exposure was established. On this basis, conventional triaxial compression tests were carried out on oil shale specimens heated to different temperatures, and according to the results of these tests, the relationship between the temperature and parameters in the statistical thermal damage constitutive model was determined, and the thermal damage constitutive model for oil shale was established. The results show that the thermal damage in oil shale increases with the increase of temperature; the damage variable is largest at 700°C, reaching 0.636; from room temperature to 700°C, the elastic modulus and Poisson’s ratio decrease by 62.66% and 64.57%, respectively; the theoretical stress-strain curve obtained from the model is in good agreement with the measured curves; the maximum difference between the two curves before peak strength is only 5 × 10−4; the model accurately reflects the deformation characteristics of oil shale at high temperature. The research results are of practical significance to the underground in situ thermal processing of oil shale.

scholarly journals Dynamic Constitutive Model of Ultra-High Molecular Weight Polyethylene (UHMWPE): Considering the Temperature and Strain Rate Effects

Polymers ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 1561 ◽  
Author(s):  
Kebin Zhang ◽  
Wenbin Li ◽  
Yu Zheng ◽  
Wenjin Yao ◽  
Changfang Zhao
Keyword(s):  
Mechanical Properties ◽  
Constitutive Model ◽  
Strain Rate ◽  
Split Hopkinson Pressure Bar ◽  
Plastic Material ◽  
Strain Rates ◽  
Hopkinson Pressure Bar ◽  
Ballistic Performance ◽  
Stress Strain ◽  
Different Temperatures

The temperature and strain rate significantly affect the ballistic performance of UHMWPE, but the deformation of UHMWPE under thermo-mechanical coupling has been rarely studied. To investigate the influences of the temperature and the strain rate on the mechanical properties of UHMWPE, a Split Hopkinson Pressure Bar (SHPB) apparatus was used to conduct uniaxial compression experiments on UHMWPE. The stress–strain curves of UHMWPE were obtained at temperatures of 20–100 °C and strain rates of 1300–4300 s−1. Based on the experimental results, the UHMWPE belongs to viscoelastic–plastic material, and a hardening effect occurs once UHMWPE enters the plastic zone. By comparing the stress–strain curves at different temperatures and strain rates, it was found that UHMWPE exhibits strain rate strengthening and temperature softening effects. By modifying the Sherwood–Frost model, a constitutive model was established to describe the dynamic mechanical properties of UHMWPE at different temperatures. The results calculated using the constitutive model were in good agreement with the experimental data. This study provides a reference for the design of UHMWPE as a ballistic-resistant material.

Mechanical Behavior and Constitutive Equation of Concrete under High-Temperature Dynamical Conditions

2011 ◽  
Vol 228-229 ◽  
pp. 303-308
Author(s):  
Bin Jia ◽  
Zheng Liang Li ◽  
Jun Lin Tao ◽  
Chun Tao Zhang
Keyword(s):  
High Temperature ◽  
Constitutive Equation ◽  
Strain Rate ◽  
Mechanical Behavior ◽  
Test Data ◽  
Dynamical Behavior ◽  
Hardening Effect ◽  
Failure Evolution ◽  
Different Temperatures ◽  
Strain Rate Hardening

SPHB tests of concrete under different temperatures and various loading conditions are completed, and high-temperature dynamical behavior of concrete is obtained. Dynamical mechanical behavior of concrete with high temperature is affected by not only the strain rate effect, but also the high temperature weakening effect, and the strain rate hardening effect is coupled with high temperature weakening effect, but the latter has greater influence. Concrete failure evolution is described on basis of the damage factor, the intercoupling strain rate hardening effect and temperature weakening effect are simply set as mutually independent factors, each parameter is respectively fitted with test data, finally, concrete constitutive equation under high-temperature dynamical conditions is established, and comparative analysis with test data are conducted, indicating good coincidence with test results.

scholarly journals Isolation and Characterization of Vibrio kanaloae as a Major Pathogen Associated with Mass Mortalities of Ark Clam, Scapharca broughtonii, in Cold Season

2021 ◽  
Vol 9 (10) ◽  
pp. 2161
Author(s):  
Bowen Huang ◽  
Xiang Zhang ◽  
Chongming Wang ◽  
Changming Bai ◽  
Chen Li ◽  
...  
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Optimal Growth ◽  
Cold Season ◽  
Opportunistic Pathogens ◽  
Growth Ratio ◽  
Isolation And Characterization ◽  
Scapharca Broughtonii ◽  
Different Temperatures

High temperature is a risk factor for vibriosis outbreaks. Most vibrios are opportunistic pathogens that cause the mortality of aquatic animals at the vibrio optimal growth temperature (~25 °C), whereas a dominant Vibrio kanaloae strain SbA1-1 is isolated from natural diseased ark clams (Scapharca broughtonii) during cold seasons in this study. Consistent symptoms and histopathological features reappeared under an immersion infection with SbA1-1 performed at 15 °C. The pathogenicity difference of SbA1-1 was assessed under different temperatures (15 °C and 25 °C). The cumulative mortality rates of ark clams were significantly higher at the low temperature (15 °C) than at the high temperature (25 °C); up to 98% on 16th day post SbA1-1 infection. While the growth ratio of SbA1-1 was retarded at the low temperature, the hemolytic activity and siderophores productivity of SbA1-1 were increased. This study constitutes the first isolation of V. kanaloae from the natural diseased ark clams (S. broughtonii) in cold seasons and the exposition of the dissimilar pathogenicity of SbA1-1 at a different temperature. All the above indicates that V. kanaloae constitutes a threat to ark clam culture, especially in cold seasons.

Mechanical Behavior of Quasicrystals

MRS Bulletin ◽  
1997 ◽  
Vol 22 (11) ◽  
pp. 65-68 ◽  
Author(s):  
Knut Urban ◽  
Michael Feuerbacher ◽  
Markus Wollgarten
Keyword(s):  
Mechanical Properties ◽  
Wear Resistance ◽  
High Temperature ◽  
Low Temperature ◽  
Mechanical Behavior ◽  
Melting Temperature ◽  
Sliding Friction ◽  
Great Promise ◽  
Brittle To Ductile Transition ◽  
Physical Reasons

Scientists have studied the mechanical properties of quasicrystalline materials for quite some time. However the difficulty in obtaining material of reasonable quality hampered systematic investigations. The progress in materials preparation in recent years has triggered new activity in this field. Furthermore the new ternary and multicomponent alloys have demonstrated great promise for use as coatings with good wear resistance and low coefficients of sliding friction. However the physical reasons for these properties and their correlation with the particular structure of quasicrystals are still not understood. As in conventional alloys, experiments under well-defined conditions are required that can serve as a basis for understanding the intrinsic mechanical properties of quasicrystals. Such studies are now increasingly possible after the development of techniques to grow larger single quasicrystals up to a few centimeters in size directly from the melt.Since the mechanical behavior of quasicrystalline alloys is to a great extent determined by a brittle-to-ductile transition at about 70% of the absolute melting temperature, it is useful to discuss the mechanical properties with reference to appropriately defined low-temperature and high-temperature regions.

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