Uniaxial compression tests

Darvell, B. W. (1990). Uniaxial compression tests and the validity of indirect tensile strength. Journal of Materials Science, 25, 757-80. 

Kwade, A., Schulze, D., and Schwedes, ]., Determination of the Stress Ratio in Uniaxial Compression Tests - Part 2, Powder Handl. Process., 6, 2, 199 (1994)... 

PP bead foams were subjected to oblique impacts (167), in which the material was compressed and sheared. This strain combination could occur when a cycle helmet hit a road surface. The results were compared with simple shear tests at low strain rates and to uniaxial compressive tests at impact strain rates. The observed shear hardening was greatest when there was no imposed density increase and practically zero when the angle of impact was less than 15 degrees. The shear hardening appeared to be a unique function of the main tensile extension ratio and was a polymer contribution, whereas the volumetric hardening was due to the isothermal compression of the cell gas. Eoam material models for FEA needed to be reformulated to consider the physics of the hardening mechanisms, so their... 

Figure 2 illustrates the temperature dependence of the swelling degree as a function of precursor polymer type. Methylcellulose (MC), hydroxypropyl-methylcellulose, type E (HPMC-E) and hydroxypropylmethylcellulose, type K (HPMC-K) gels have comparable effective crosslink densities of about 2 x 10 5 mol/cm3 (as determined from uniaxial compression testing), while the crosslink density of the hydroxypropylcellulose (HPC) gel is about half this [52]. The transition temperature for each gel is within several degrees of the precursor polymer lower critical solution temperature (LCST), except for the MC gel, which has a transition temperature 9 °C higher than the LCST. The sharpness of the transition was about 3%/°C, except for the HPC gel transition, which was much sharper - about 8%/°C. 

Figure 12.1 Typical stress-strain curves for thermosets at a temperature below Tg (a) uniaxial tensile test (b) uniaxial compression test. 

Figure 14.5b represents the uniaxial compression test, which uses samples with cylindrical or rectangular cross section. The stress and strain are defined in an analogous way to that of the tensile test. This test overcomes the disadvantages mentioned in relation to a tensile test. The stress is compressive, and consequently there is no possibility of the brittle fracture observed in tensile deformation. Plastic yield can even be seen in thermostable materials, which, under other conditions, can be brittle. In addition, the determination of the yield stress is made under conditions of stable deformation since there is no geometrical reason for the formation of a neck such as occurs in tension. A problem that can arise in this test concerns the diameter/height ratio of the sample. If this ratio is too large friction between plates and sample will introduce a constraint, and if it is very small... 

Using these two types of samples, we performed uniaxial compression tests under constant strain rates from 2.8x10 to 2.9x1 O s in a cold room at -10°C. The experimental conditions used in this study are summarized in Table 1. Nine series of the deformation tests were performed so as to study the dependencies on each physical parameter. 

The failure function can be measured directly in a number of ways. Some are rather complex and still under development, like the new plane strain biaxial tester with flexible boundaries30, but the simplest method so far is the uniaxial compression test. Only the version developed by Williams et al,24 gives results close to those obtained indirectly with the Jenike shear cell, the other versions yield relative measurements only. 

This is a simple version of the uniaxial compression test, first developed by Colgate-Palmolive25 but now used by other industries. The procedure described below is based on an article by Monick25 but with slight modifications, as practised at one large chemical company. 

FIG. 4 Confined uniaxial compression test. Bed compression of rigid and deformable particles (adapted from Lu et al., 2001). 

Yan et al. (2001), studied how bulk density of instant nonfat milk, spray-dried coffee, and freeze-dried coffee was affected by HHP processing times, particle size, and water activity. The experimental curves for each powder in Figure 10 show that the powder bulk density increased as the pressure increased but remained constant after the pressure reached a critical value of 207 MPa for spray-dried coffee and 276 MPa for freeze-dried coffee at different water activities. The final compressed densities were not significantly different. When the pressure is higher than the critical value, there are no void spaces between the agglomerates or primary particles even the primary particles are crushed, leaving no open or closed pores within. Bear in mind, it is assumed that the compression mechanisms are the same as those in the confined uniaxial compression tests. 

FLOW FUNCTION QUANTITY (ffc) (SCHUBERT, 1987) AND COMPRESSIBILITY (C2) USING THE MODIFIED UNIAXIAL COMPRESSION TEST METHOD (EHLERMANN AND SCHUBERT, 1987) CAN BE USED TO CHARACTERIZE FLOW ABILITY... 

Adams, M.J., Mullier, M.A., and Seville, J.P.K. 1994. Agglomerate strength measurement using uniaxial compression test. Powder Technol. 78, 5-13. 

From a set of uniaxial compression tests, the chanee in the Young s moduius as a function of... 

The probability of fracture propagation is plotted in Figure l.The probability curve has a shape similar to that of a typical AE account curve obtained during uniaxial compression tests of rock samples from Aspo (Li, 1993). 

Elastic modulus and Poisson s ratio were determined by uniaxial compression test. Young s modulus was 31.9 GPa, Poisson s ratio was 0.27, and shear modulus was 12.6 GPa. 

Krv relations obtained in this study show that the crack growth behavior in andesite is promoted by water vapor under air condition. These are consistent with the results of uniaxial compression tests and Brazilian tests by Jeong et al. (2003), in which the strengths of Kumamoto andesite decreased with increasing water vapor pressure. Therefore, stress corrosion can be considered as a primary process of subcritical crack growth in andesite, and it is important to consider the effect of water vapor on the crack growth behavior. 

For a uniaxial compression test, determine the plane on which the maximum shear stress will occur for a material that obeys the Mohr-Coulomb yield criterion. Suggest an approach for measuring the material parameters (d>, Tq) in the Mohr-Coulomb yield criterion. (Hint construct the Mohr s circle (see Fig. 2.23) for various values of the normal stress.)... 

Programming by Isothermal Flat-wise Uniaxial Compression Test... 

The SMP system is considered to be macroscopicaUy isotropic and homogeneous. A uniform stress field assumption is held. This assumption suggests that when comparing with experimental results, uniaxial compression test results are preferred because specimens under uniaxial loading create a uniform stress distribution within the gauge length of the specimens. 

The simplest test used to study the deformation behaviour of asphalts was the static unconfined uniaxial compression test, termed the creep test, developed in the 1970s by Shell Bitumen (Hill 1973). The specimen was subjected to static axial compressive load over a long period (1 h). The test procedure was very simple and required low-cost equipment. In addition. Shell Bitumen developed a rut prediction procedure based on results of the creep test but soon realised that it underestimated rut depths measured in trial pavements (Hill et al. 1974). This was attributed to the effects of dynamic loading producing higher deformation in the wheel-tracking test (Van de Loo 1974). 

Several techniques are available for the mechanical characterization of cryogels in swollen and dried states. Uniaxial compression tests are conducted on cylindrical cryogel samples to determine the Young s modulus E or shear modulus G from the slope of stress-strain curves at low compressions, while the stress at 3 or 5 % compression is reported as the compressive stress uniaxial compression of a cylindrical gel sample, the statistical theories of rubber elasticity yield for Gaussian chains an equation of the form [77, 78] ... 

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