Stress, types compression

Generic Material Type Flexural Modulus, MPa Flexural Yield Stress, MPa Compressive Modulus, MPa Compressive Stress, MPa At... 

DIF values vary for different stress types in both concrete and steel for several reasons. Flexural response is ductile and DIF values are permitted which reflect actual strain rates. Shear stresses in concrete produce brittle failures and thus require a degree of conservatism to be applied to the selection of a DIF. Additionally, test data for dynamic shear response of concrete materials is not as well established as compressive strength. Strain rates for tension and compression in steel and concrete members are lower than for flexure and thus DIF values are necessarily lower. 

FIGURE 14.7 Major types of stress tests compressive (a) pulling stress or tensile strength (b) and shear stress (c). 

Fig. 8.12 Steady-state creep rates versus applied stress for compressive creep experiments performed in nitrogen and in air at 1200-1400°C for Al2Oj/SiC composites. The data conform to a power-law type constitutive relation.27...

Fig. 1. Specific yield strength (0.2 % proof stress in compression per unit weight density at 10 4s 1 strain rate in compression) as a function of temperature for the D022 phase Al3Nb [112, 113], the Heusler-type phase Co2TiAl [67], the Laves phasesTiCr15Si05 andTaFcAl [67,114], the two-phase alloy NbNiAl-NiAl with 15 vol.% NiAl in the Laves phase NbNiAl [67,114], and the hexagonal D8g phase Ti5Si3 [100] in comparison to the superalloy MA 6000 (in tension) [115] and the hot-pressed silicon nitride HPSN (upper limit of flexural strength) [116],...

Assessment of mechanical properties is made by addressing the three basic stress types. Because tensile and compressive loads produce stresses that act across a plane, in a direction perpendicular (normal) to the plane, tensile and compressive stresses are called normal stresses. The shorthand designations are as follows. 

Two types of stress can be present simultaneously in one plane, provided that one of the stresses is shear stress. Under certain conditions, different basic stress type combinations may be simultaneously present in the material. An example would be a reactor vessel during operation. The wall has tensile stress at various locations due to the temperature and pressure of the fluid acting on the wall. Compressive stress is applied from the outside at other locations on the wall due to outside pressure, temperature, and constriction of the supports associated with the vessel. In this situation, the tensile and compressive stresses are considered principal stresses. If present, shear stress will act at a 90° angle to the principal stress. 

The types of stress relaxation test standardized (for rubbers) split into the two intended purposes. Seals are commonly stressed in compression or in a complex mode of stressing that compression can represent. Hence, sealing force tests arc usually made in compression. The bulk of such test pieces slows oxidative aging and also the uptake of any fluid. but swelling and aging effects do have to be considered in long-term applications. 

Corresponding to the three main types of stress—tensile, compressive, and shear— three types of strain can be distinguished. Thus, tensile strain is expressed as elongation per unit length (Figure 3.1a),... 

Polished reference samples showed an average residual stress of ct = 12 N/mm. Both up and down milling induce residual stresses of compressive type. The compressive stresses measured in the direction orthogonal to the cutting velocity are generally higher than those determined in the direction of cutting. 

New domains of type 1 may also be generated through nucleation process to speed up the domain switching process. This domain switching may continue imtil the unfavored domains (type 2 as shown in Fig. 3.9b) are driven out of the system. If the applied stress is compressive as shown in Fig. 3.9d, some domains are annihilated. The presence of domain walls makes the shape deformation very easy in the martensite phase. Upon heating, all shapes in Fig. 3.9b-d go back to the same shape as in Fig. 3.9a. In other words, the shape in the high temperature phase is remembered . This shape memory... 

Many other polymer properties, such as stress, compressive set, strain, shear strength, friction coefficient, shrinkage, toughness, abrasion resistance, stress relation compressive creep, weatherability, and resistance to various types of radiation, can be of importance in polymers, whether or not they are reinforced. Methods for measuring these properties are discussed in Chapter 2. 

Figure 2.52. Illustration of various types of loads (stresses), which result in material strain. Shown are (a) tensile stress, (b) compressive stress, (c) shear stress, and (d) tortional stress. Reproduced with permission from Callister, W. D. Materials Science and Engineering An Introduction, 7th ed., Wiley New York, 2007. Copyright 2007 John Wiley Sons, Inc.

Interestingly, a nanocomposite of LiMnP04 nanoparticles and carbon is directly and rapidly prepared from the starting powder materials by a one-step mechanical method without extra heat assistance. This method is based on an attrition-type milling machine that repeatedly provides strong shear stress and compressive stress to the raw materials. 

Thermomechanical analysis (TMA) is a technique in which the deformation of a substance under a nonoscilla-tory load is measured as a function of temperature while the substance is subjected to a controlled temperature program. It is used extensively in polymer studies. The mode, as determined by the type of stress applied (compression, tension, flexture, or torsion), should always be noted. As already stated, dynamic mechanical analysis is a technique in which the viscoleastic response of a sample under an oscillatory stress is studied while the substance is subjected to a temperature regime. Torsional braid analysis is a particular case of dynamic thermomechanometry where the material is supported. 

In the hemi-spherical dent, the loading on the dent is largely hydrostatic the stress state is compressive in the immediate vicinity of the dent. This stress field is responsible for the bump at the top. Where as, in the trapezoidal dent, the loading is anisotropic. While the stress is compressive over the horizontal portion, significant shear stresses are also built in. This type of stress field will result in crater on the top. The loading conditions of these two cases are shown in Fig. 7a 7b. 

Flow behaviour of polymer melts is still difficult to predict in detail. Here, we only mention two aspects. The viscosity of a polymer melt decreases with increasing shear rate. This phenomenon is called shear thinning [48]. Another particularity of the flow of non-Newtonian liquids is the appearance of stress nonnal to the shear direction [48]. This type of stress is responsible for the expansion of a polymer melt at the exit of a tube that it was forced tlirough. Shear thinning and nonnal stress are both due to the change of the chain confonnation under large shear. On the one hand, the compressed coil cross section leads to a smaller viscosity. On the other hand, when the stress is released, as for example at the exit of a tube, the coils fold back to their isotropic confonnation and, thus, give rise to the lateral expansion of the melt. 

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