Stress concentration coefficient

This equation indicates that under isothermal conditions in instances where AHa < U0, w < y, and the polymer will experience ductile failure. Recognizing that the brittle stress concentration coefficient y is nearly constant (4), the requirements for brittle amorphous polymers, whose Affa > UQ and w > y, to fail in a ductile fashion are to minimize (AH — U0)/[Pg.130]

Coefficient a is related to stress concentration. Coefficients c and d are related to the adhesion of the polymer matrix to filler. In an experiment involving different sizes of calcium carbonate in poly(vinyl acetate), small and medium particles had a much larger values of coefficients c and d than did large particles. This is in agreement with an experiment which shows that large particles decrease the mechanical properties of composites. 

As shown in figure 10, the effect of coal 2 adopting face overlapping each other completely without coal pillar on protective layer of coal 1 was in area of 75 m away outside the face. And the maximum compression ratio was 0.15%, the maximum stress concentration coefficient was approximately 1.2 Protected layer was released by expansion within the range 5 75 m of inner side of the protective layer face the expansion ratio was approximately 0.8%, the stress was about 9% of stress in virgin rock mass. Expansion releasing state of the protected layer in the middle of the two... 

Where, Oy is vertical stress K is stress concentration coefficient y is average bulk density of overlying strata H is occurrence depth t is attenuation coefficient M is roof thickness y, is roof bulk density x is width of limit equilibrium. 

The stress concentration coefficient and the tensile stress area are two important indexes of surrounding rock stress field for tunnel stability... 

According to the theory of elasticity, the stress concentration coefficient near circular hole is equal to 3 in fact the real stress near the hole is approximately one. So, the circular hole might be considered as the standard stress concentrator. 

MPa the elastic modulus of the SiC whisker E = 400 GPa, and Poisson s ratio Vf = 0.16 the interfacial layer of the material is isotropic, Poisson s ratio is 0.2, and interfacial elastic modulus is E. The elastic-plastic modulus is calculated by using a different interfacial modulus E value. The exterior stress Oq is set at 0.85 MPa, and the influence of different interfacial bonding states on stress concentration coefficient, interfacial shear stress, and axial stress of whisker end face is simulated. Figure 4.12 is the stress concentration coefficient... 

Figure 4.12 Stress concentration coefficient distribution of the whisker end face with different interface elastic moduli.

The stress concentration coefficient of sharp triangle crack is expressed as follows [30] ... 

It is well-known [31], that stress concentration at notch tip intensification results to HDPE samples strength decrease in impact tests. The stress concentration coefficient for the notch of length a can be estimated according to the Noiber formula [4], which is similar to the Eq. (5.10) ... 

Let us consider in conclusion the physical significance of stable crack fractal dimension in PASF samples. As it has been shown in Ref [12], the stress concentration coefficient Kg of triangular crack is given by the Eq. (5.10). In Fig. 8.6 the relation between parameters and for PASF sample (solvent - chloroform) is adduced, fi om which linear reduction follows at growth. Thus, the dimension for stable crack has the simple physical significance - it is the value, reciprocal to stress concentration level at crack tip. 

FIGURE 8.6 The dependence of stress concentration coefficient of stable crack on its fractal dimension D for PAST [8],... 

For the considered polymer films two sources of decrease can be distinguished mechanical stress concentration at stable crack tip and an-harmonicity local splash owing to material structure modification in pre-fracture zone - ZD. The first factor can be taken into account by stress concentration coefficient A" introduction (see the Eq. (5.10)) [7] ... 

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