scholarly journals Towards a Deeper Understanding of Creep and Physical Aging Behavior of the Emulsion Polymer Isocyanate

Polymers ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1425
Author(s):  
Shihao Zhou ◽  
Xuansheng Fang ◽  
Yaolong He ◽  
Hongjiu Hu
Keyword(s):  
Physical Aging ◽  
Diffusion Mechanism ◽  
Isothermal Condition ◽  
Mechanical Analysis ◽  
Tensile Creep ◽  
Creep Tests ◽  
Positron Annihilation Lifetime ◽  
Emulsion Polymer ◽  
Polymeric Isocyanate ◽  
Structural Adhesive

Information of the relaxation behaviors of polymer film is crucial to judge the durability of emulsion polymer isocyanate (EPI) as a structural adhesive for bonding timber-based products. A sequence of tensile creep tests and free volume evaluation of the cured EPI adhesive films during isothermal condition were carried out by dynamic mechanical analysis and positron annihilation lifetime spectroscopy, respectively. It is the first time to explore the creep response and physical aging of the EPI film, as well as associated microstructural evolution. The results indicate that the creep characteristics of the glassy EPI coating intimately depend upon the crosslinker and elapsed time, and the ideal momentary creep master curve can be constructed in terms of modified horizontal shifting method. Furthermore, the relaxation process is found to be dominated by vacancy diffusion mechanism. In addition, increasing the polymeric isocyanate content can significantly enhance the resistance to creep deformation of EPI films, but also accelerate the physical aging process. Due to a higher packing degree of pure polymer films, the EPI films with aqueous emulsified isocyanate exhibit much better relaxation resistance compared to that with general isocyanate crosslinker.

scholarly journals Analysis of Isothermal Physical Aging of Polycarbonate from Tensile Creep Tests

2014 ◽  
Vol 1 (2) ◽  
pp. 34-40
Author(s):  
Sudheer Kolisetty ◽  
◽  
Rajeswara Reddy Resapu
Keyword(s):  
Physical Aging ◽  
Tensile Creep ◽  
Creep Tests

scholarly journals Influence of Different Annealing Atmospheres on the Mechanical Properties of Freestanding MCrAlY Bond Coats Investigated by Micro-Tensile Creep Tests

Metals ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 692 ◽  
Author(s):  
Sven Giese ◽  
Steffen Neumeier ◽  
Jan Bergholz ◽  
Dmitry Naumenko ◽  
Willem J. Quadakkers ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Creep Strength ◽  
Bond Coat ◽  
Oxide Dispersion Strengthened ◽  
Tensile Creep ◽  
Creep Tests ◽  
Bond Coats ◽  
Nial Phase ◽  
Lower Strain ◽  
Plasma Sprayed

The mechanical properties of low-pressure plasma sprayed (LPPS) MCrAlY (M = Ni, Co) bond coats, Amdry 386, Amdry 9954 and oxide dispersion strengthened (ODS) Amdry 9954 (named Amdry 9954 + ODS) were investigated after annealing in three atmospheres: Ar–O2, Ar–H2O, and Ar–H2–H2O. Freestanding bond coats were investigated to avoid any influence from the substrate. Miniaturized cylindrical tensile specimens were produced by a special grinding process and then tested in a thermomechanical analyzer (TMA) within a temperature range of 900–950 °C. Grain size and phase fraction of all bond coats were investigated by EBSD before testing and no difference in microstructure was revealed due to annealing in various atmospheres. The influence of annealing in different atmospheres on the creep strength was not very pronounced for the Co-based bond coats Amdry 9954 and Amdry 9954 + ODS in the tested conditions. The ODS bond coats revealed significantly higher creep strength but a lower strain to failure than the ODS-free Amdry 9954. The Ni-based bond coat Amdry 386 showed higher creep strength than Amdry 9954 due to the higher fraction of the β-NiAl phase. Additionally, its creep properties at 900 °C were much more affected by annealing in different atmospheres. The bond coat Amdry 386 annealed in an Ar–H2O atmosphere showed a significantly lower creep rate than the bond coat annealed in Ar–O2 and Ar–H2–H2O atmospheres.

scholarly journals Study on creep performance of launch canister under long-term storage

2019 ◽  
Vol 43 (2) ◽  
pp. 199-208 ◽  
Author(s):  
Cun-Gui Yu ◽  
Tong-Sheng Sun ◽  
Guang-Yuan Xiao
Keyword(s):  
Residual Deformation ◽  
Bottom Layer ◽  
Tensile Creep ◽  
Creep Model ◽  
Model Parameters ◽  
Creep Tests ◽  
Software Environment ◽  
Long Term Storage ◽  
Term Storage

In this paper, the creep performance of a multi-barrel rocket launch canister under long-term stacking storage is studied. Based on the Bailey–Norton model, a creep model for the frame material of a launch canister was established. Constant stress tensile creep tests under different stress levels at room temperature were carried out on the frame materials of the launch canister and the creep model parameters were obtained by test data fitting. The three-dimensional finite element model of the launch canister was established in the ABAQUS software environment and the creep deformation of the launch canister after long-term stacking storage was studied. The results indicated that the bottom layer of the launch canister frame presented an extended residual deformation when the stacking storage solution with the original support pad was used. Therefore, a position adjustment program of the support pad was put forward. The residual deformation of the launch canister frame after long-term storage could be significantly reduced, thus the performance requirements for the launch canister are guaranteed.

scholarly journals The Mechanical Properties of Single Crystals of Pure Ice

1969 ◽  
Vol 8 (54) ◽  
pp. 463-473 ◽  
Author(s):  
S. J. Jones ◽  
J. W. Glen
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
Single Crystals ◽  
Fracture Stress ◽  
Constant Strain Rate ◽  
Tensile Creep ◽  
Stress Dependence ◽  
Creep Tests ◽  
Dislocation Multiplication ◽  
Compressive Tests

AbstractResults obtained from tensile and compressive tests on pure ice single crystals at various temperatures down to −90°C are reported. At −50°C tensile creep tests give a continually increasing creep rate until fracture, as observed at higher temperatures. The stress dependence of the strain-rate is discussed. Fracture stress increases with decreasing temperature. Results from constant strain-rate compressive tests are compared with theoretical curves computed from Johnston’s (1962) theory of dislocation multiplication. A dislocation velocity of the order of 0.5×10−8 m s−1 is deduced for ice at −50°C.

scholarly journals Dynamic Mechanical Relaxation in LaCe-Based Metallic Glasses: Influence of the Chemical Composition

Metals ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 1013 ◽  
Author(s):  
Minna Liu ◽  
Jichao Qiao ◽  
Qi Hao ◽  
Yinghong Chen ◽  
Yao Yao ◽  
...  
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Metallic Glasses ◽  
Physical Aging ◽  
Enthalpy Of Mixing ◽  
Mechanical Analysis ◽  
Mechanical Relaxation ◽  
Atomic Mobility ◽  
Dynamic Mechanical ◽  
Β Relaxation

The mechanical relaxation behavior of the (La0.5Ce0.5)65Al10(CoxCu1−x)25 at% (x = 0, 0.2, 0.4, 0.6, and 0.8) metallic glasses was probed by dynamic mechanical analysis. The intensity of the secondary β relaxation increases along with the Co/Cu ratio, as has been reported in metallic glasses where the enthalpy of mixing for all pairs of atoms is negative. Furthermore, the intensity of the secondary β relaxation decreases after physical aging below the glass transition temperature, which is probably due to the reduction of the atomic mobility induced by physical aging.

A Reference Stress Approach to Creep Bending of Straight Tubes

1974 ◽  
Vol 16 (3) ◽  
pp. 125-138 ◽  
Author(s):  
J. Fairbairn
Keyword(s):  
Entire Range ◽  
Creep Behaviour ◽  
Tensile Creep ◽  
Bending Moments ◽  
Stress Distributions ◽  
Creep Tests ◽  
Reference Stress ◽  
Hyperbolic Sine ◽  
Rotation Method ◽  
Reference Stress Approach

Reference-stress parameters, based on the Norton constitutive equation, are developed for creep bending of circular and elliptical tubes. The parameters are presented in the form of a design chart. The reference stress methods apply also to other simple constitutive equations of the power law, exponential and hyperbolic sine forms, and also to two complex equations describing creep behaviour over the entire range from primary to tertiary. In these equations the functions of stress and time are not separable and reference stress techniques provide a convenient method of evaluating stationary stress distributions and investigating the variation of these stresses with time. Aluminium alloy tubes were creep tested with cyclic uniform bending moments. Creep strains to fracture were measured by an end-rotation method. The creep behaviour of the tubes was well predicted by reference-stress cyclic tensile creep tests.

Tensile and Creep Properties of the Refractory Nb Base In-Situ Composite

2003 ◽  
Vol 17 (08n09) ◽  
pp. 1608-1614
Author(s):  
Jin Hak Kim ◽  
Tatsuo Tabaru ◽  
Hisatoshi Hirai
Keyword(s):  
Fracture Surface ◽  
Tensile Tests ◽  
Constant Load ◽  
Tensile Creep ◽  
Tensile Fracture ◽  
Creep Tests ◽  
Tensile Fracture Surface ◽  
In Situ Composite ◽  
Temperature Ranges

Niobium-base in-situ composite Nb-18Si-5Mo-5Hf-2C (in mol%) was prepared and heat-treated at 2070 K for 20 hour. The uni-axile tensile tests at high temperature ranges and the constant load tensile creep tests at 1570 K were performed. The specimen tensile-tested at 1470 K exhibited the excellent UTS of 450 MPa, and the brittle to ductile transition temperature is between 1470 and 1670 K. The specimens creep tested showed good creep strength; the stress exponent is about 5. The tensile fracture surface of the in-situ composite is complex and attributed to cleavage of the Nb 5 Si 3, Nb ss / Nb 5 Si 3 interface separation, ductile rupture of the Nb ss and correlations of these. On the otherhand, the fracture surface of creep tested consists of intergranular above 150 MPa and transgranular below 120 MPa with severely deformed Nb ss .

Effect of TiO2 nanoparticles on the viscoelastic and time-dependent behaviors of TiO2/epoxy particulate nanocomposite

2017 ◽  
Vol 37 (2) ◽  
pp. 185-196 ◽  
Author(s):  
Hamid Reza Salehi ◽  
Manouchehr Salehi
Keyword(s):  
Epoxy Resin ◽  
Storage Modulus ◽  
Creep Resistance ◽  
Epoxy Resins ◽  
Loss Modulus ◽  
Tensile Creep ◽  
Titania Nanoparticles ◽  
Test Machine ◽  
Creep Tests ◽  
Mechanical Creep

Abstract In this work, the effects of nano titania are investigated on mechanical, creep, and viscoelastic behaviors of epoxy resin. For this purpose, 0.25, 0.5, and 1 vol.% of TiO2 nanoparticles were mixed with thermoset epoxy resin by mechanical and ultrasonic homogenizers and then the tensile, creep, and DMTA test samples were fabricated. The results of tensile tests show that the addition of TiO2 nanopowder slightly increased the strength and Young’s modulus of epoxy resin. However, the ultimate tensile strain or the rupture strain of nanocomposites is decreased. In addition, to understand the viscoelastic behavior of nanocomposites, the DMTA and tensile creep tests have been done. Tensile creep test has been done by DMTA and universal test machine. Both results confirmed that the creep resistance of nanocomposites has extensively improved by adding the titania nanoparticles. Variations of storage modulus, loss modulus, and tan (δ) by adding TiO2 nanopowder were examined in two modes of bending and tension. Storage and loss moduli of nanocomposite are considerably increased in all the states, but the storage modulus was more sensitive to TiO2 loading intensity. Thus, test results showed that introduction of TiO2 in the epoxy resin leads to the improvement of mechanical, creep resistance, and viscoelastic properties of nanocomposites. Due to the wide applications of epoxy resins in engineering devices, this method of reinforcement can be practical and useful to overcome some limitations of epoxy resins.

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