Bond Strength of Pressed Composites

1993 ◽  
Vol 318 ◽  
Author(s):  
Donald A. Wiegand
Keyword(s):  
Compressive Strength ◽  
Transition Temperature ◽  
Low Temperature ◽  
Thin Layer ◽  
Strain Rate ◽  
General Study ◽  
Rate Dependent ◽  
Fracture Patterns ◽  
Graphite Coating ◽  
Temperature Strain

ABSTRACTComposites samples containing 80% and 85% organic filler in a polymer-plastizer binder were produced by mixing, extruding, cutting, drying and pressing. Before pressing the extruded material was in some cases coated with a thin layer of graphite (= one micron) for ease in pressing. As part of a general study of these composites the compressive strength, σm, was determined as a function of temperature, strain rate and the thickness of the graphite coating. Without graphite σm increases with decreasing temperature and increasing strain rate. With graphite σm has the same behavior above approximately −10 C, but is independent of both temperature and strain rate below −10 C for a strain rate of 1.0/Sec. In addition, the low temperature value of Om decreases with increasing graphite thickness. The cracking and fracture patterns are temperature and strain rate dependent and are different with and without graphite. These results indicate that the bond produced by pressing the graphite containing material is stronger than the composite above −10 C and weaker below −10 C so that failure initiates in the composite above −10 C and in the bond below −10 C. With decreasing strain rate this transition temperature decreases. The bonding is discussed.

A Theory of the Yield Point and the Transition Temperature of Mild Steel

1956 ◽  
Vol 23 (2) ◽  
pp. 219-224
Author(s):  
F. Forscher
Keyword(s):  
Transition Temperature ◽  
Mild Steel ◽  
Strain Rate ◽  
Yield Point ◽  
Structural Model ◽  
Yield Criterion ◽  
State Of Stress ◽  
Yield Point Phenomenon ◽  
Stress And Strain Rate ◽  
Temperature Strain

Abstract Experimental results indicate the dependence of the yield-point phenomenon of mild steel on temperature, strain rate, duration of stress, and stress state. This paper proposes a yield criterion which can account for these variables. The theory is developed on the basis of a “structural” model, by which the behavior of microscopic and submicroscopic elements is idealized. The theory postulates as yield criterion a critical number of relaxation centers (active Frank-Read sources) or, equivalently, a critical size of relaxation centers. The transition-temperature phenomenon is considered to be the result of an inhibition of yielding (upper yield point) by means of geometry, temperature and/or strain rate. A relation is given which expresses its dependence on the state of stress and strain rate.

Temperature and strain rate dependent constitutive model of TRIP steels for low-temperature applications

2011 ◽  
Vol 50 (7) ◽  
pp. 2014-2027 ◽  
Author(s):  
Seong-Won Yoo ◽  
Chi-Seung Lee ◽  
Woong-Sup Park ◽  
Myung-Hyun Kim ◽  
Jae-Myung Lee
Keyword(s):  
Low Temperature ◽  
Constitutive Model ◽  
Strain Rate ◽  
Trip Steels ◽  
Rate Dependent ◽  
Temperature Applications

Dynamic Mechanical Behavior of Two Fiber-Reinforced Composites

2012 ◽  
Vol 525-526 ◽  
pp. 261-264
Author(s):  
Y.Z. Guo ◽  
X. Chen ◽  
Xi Yun Wang ◽  
S.G. Tan ◽  
Z. Zeng ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Strain Rate ◽  
Mechanical Behavior ◽  
High Speed ◽  
Split Hopkinson Pressure Bar ◽  
Hopkinson Pressure Bar ◽  
Stress Strain ◽  
Rate Dependent ◽  
Dynamic Loadings ◽  
Axial Splitting

The mechanical behavior of two composites, i.e., CF3031/QY8911 (CQ, hereafter in this paper) and EW100A/BA9916 (EB, hereafter in this paper), under dynamic loadings were carefully studied by using split Hopkinson pressure bar (SHPB) system. The results show that compressive strength of CQ increases with increasing strain-rates, while for EB the compressive strength at strain-rate 1500/s is lower then that at 800/s or 400/s. More interestingly, most of the stress strain curves of both of the two composites are not monotonous but exhibit double-peak shape. To identify this unusual phenominon, a high speed photographic system is introduced. The deformation as well as fracture characteristics of the composites under dynamic loadings were captured. The photoes indicate that two different failure mechanisms work during dynamic fracture process. The first one is axial splitting between the fiber and the matrix and the second one is overall shear. The interficial strength between the fiber and matrix, which is also strain rate dependent, determines the fracture modes and the shape of the stress/strain curves.

Strain-Rate Dependence of the Brittle-to-Ductile Transition Temperature in TiAl

2000 ◽  
Vol 646 ◽  
Author(s):  
M. Khantha ◽  
V. Vitek ◽  
D. P. Pope
Keyword(s):  
Activation Energy ◽  
Transition Temperature ◽  
Strain Rate ◽  
Dislocation Motion ◽  
Rate Dependence ◽  
Strain Rate Dependence ◽  
Dislocation Generation ◽  
Thermally Activated ◽  
Brittle To Ductile Transition ◽  
Rate Dependent

ABSTRACTThe brittle-to-ductile transition (BDT) and the strain-rate dependence of the brittle-to-ductile transition temperature (BDTT) have been recently investigated in single crystals of TiAl [1]. It was found that the activation energy associated with the BDTT is 1.4 eV when the slip is dominated by ordinary dislocations and 4.9 eV when it is dominated by superdislocations. Despite this difference in the activation energies, the BDTT, while varying with the strain-rate, remains in the same temperature range, viz., between 516–750C and 635–685C for ordinary and superdislocations, respectively. In this paper, we examine how the activation energy of the BDTT can vary with the type of dislocation activity and explain why it can attain values which are clearly much larger than the activation energy for dislocation motion. We describe a strain-rate dependent mechanism of cooperative dislocation generation in loaded solids above a critical temperature and use it to explain the characteristics of the BDT in TiAl. We show that the activation energy associated with the BDTT is a composite value determined by two or more inter-dependent thermally activated processes and its magnitude can be much larger than the activation energy for dislocation motion in certain materials. The predictions of the model are in good agreement with observations in TiAl.

scholarly journals Experimental Study and Application of a Novel Foamed Concrete to Yield Airtight Walls in Coal Mines

2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Hu Wen ◽  
Shixing Fan ◽  
Duo Zhang ◽  
Weifeng Wang ◽  
Jun Guo ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Strain Rate ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Mechanical Tests ◽  
Air Leakage ◽  
Rate Dependent ◽  
Foamed Concrete ◽  
Residual Coal ◽  
The Impact

Airtight walls are vital to prevent spontaneous combustion of residual coal as caused by air leakage. A new type of foamed concrete (FC) was developed to control air leakage. FC specimens of four densities (250, 450, 650, and 850 kg/m3) were prepared for use in a series of physical and mechanical tests. A thickener was used to control the FC shrinkage and collapse. The permeability of the FC decreased approximately exponentially with an increasing density. On the contrary, the compressive strength (σ) and elastic modulus (E) increased in exponential and linear relationship separately with the increase in density, under uniaxial compression conditions. Under triaxial compression, the compressive strength of the FC increased with an increase in confining pressure and appeared slight plastic. The impact experiment showed that the dynamic compressive strength of the FC appeared to be strain-rate dependent, and it increased with an increase in the strain rate and pressure under a confining pressure. Without a confining pressure, the variation in compressive strength exhibited a slow decrease. Applied FC resulted in a 5 MPa 28-day compressive strength of the airtight wall with no remaining fissures and with air leakage suppression to the gob.

Sign in / Sign up

Export Citation Format

Share Document