On  possible  amendments  to  the  equation  Griffiths
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Protect the surface of the concrete floor
To protect the concrete floor, which is operated in the normal mode, or is subject to wear in areas with high traffic, there are several ways to protect the surface.
   Comparable ways: their cost, appearance and ability to perform the task to protect.
   In this article, we consider three ways to finish and protect the floor. Each of them has its advantages and disadvantages.
  
   Thin fil...

Finishing compositions based on water glass. Part 3
When used as part of exhaustion moderator comes coagulation and solidification of liquid glass. However, due to the presence in the composition of Portland cement with a finishing time is an increase strength of the coating due to hydration of cement minerals. Thus from colloids formed during the coagulation liquid glass are actively assigned to the water for hydration of cement, a porous media formed tumors filled Portland cement, which leads to...

Finishing compositions based on water glass. Part 2
Studies in Berlin Institute Federal institute for Materials Research and Testing, show that the average density of 1730 kg/m3 brick large proportion of pores having a size in excess of 1 micron is more than 90% [3] and they are responsible for the increased migration of fluids through brickwork.
   Most fully meet these requirements structure obtained by coagulation and water-soluble potassium silicate forming silica with a high sp...

Modernization and repair of self-propelled machines. (3)
Hardening electrolysis BORATING hinge pins and bushings mates working equipment hydraulic excavators EO-4121 (EA-4321) gives an increase in wear resistance 4-6 times compared to the bulk quenching details.
   Taking into account the high wear resistance of brazed blades, hardened sintered alloys (see Table 1), are recommended for carbide knives dumps graders DZ-122 and RS-98, combined machine E-405 based on KAMAZ, for front dumps a t...

Specialized exhibition Architecture. Construction (END)
Mari-lime brick and gas silicate blocks
   JSC "MZSK" produces silicate brick and a half, color (white, yellow, black, red, blue, green, brown).
   For the production of silica brick used quartz sand from quarries near the plant. Limestone enters the factory with Dobryatinskogo deposit Vladimir region. Silicate brick (Table 1) is used for masonry exterior and interior walls of buildings and structures, as well as ...

Geophysical processes primers and security. Part 5
In the center of Moscow can distinguish vertical structure comprising a crashing into the Earth`s crust magma elongated cylinder (Fig. 2) [5]. In the center section marked lack of extensive vertical zone converted waves ("blind spot"), going from the depths of 70-80 km to 7.5 km. Such "blind spots" are characteristic of the earth`s crust with the introduction of monolithic dense mantle rocks such as gabbro, diabase, etc. In such a zone Tashkent e...

Finishing compositions based on water glass. Part 1
The quality of the decoration of buildings for new construction and reconstruction depend not only on their aesthetic, but also the operational parameters, as good-quality finish - a guarantee of durable service basic designs, long maintenance-free operation, the costs for maintenance and care. Traditional binders used for the production of finishing compositions, liquid glass is widely used, but it has some drawback: coatings based on it gaining...

On possible amendments to the equation Griffiths
Griffith presented a picture of destruction allowed to formulate the problem of determining conditions of the beginning of crack propagation and find its general solution.
   As seen from the above schemes, in the process of crack propagation material directly adjacent to it "coasts" unloaded relaxes. This means that the stress and strain it decreases, and the elastic energy stored earlier in this area of ​​the body is re...

Construction skyscrapers - the requirements of modernity. Part 4
The program is a high-rise building in Moscow
   The project is now a high-rise building in Moscow is implemented in two main areas: the construction of business center "Moscow City" and implementation of the program of the Government of Moscow "New Ring of Russia."
   1. Moscow international business center "Moscow - City"
   The project includes the construction of buildings on the territory of abou...

Degree project - beginning of the road. (3)
Given the great diversity of subject matter and content of diplomas in various specialties, the jury is faced with great difficulties in determining the winners - "Who better violinist or a dancer?". Nevertheless, often based on emotional perception and can estimate the relevance and novelty, and the author`s contribution to the thesis project or job. Absolute winners in recent years have been graduates of Rostov CSO GASU St. Petersburg, Nizhny N...

 

 
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 On  possible  amendments  to  the  equation  Griffiths

Griffith presented a picture of destruction allowed to formulate the problem of determining conditions of the beginning of crack propagation and find its general solution.
   As seen from the above schemes, in the process of crack propagation material directly adjacent to it "coasts" unloaded relaxes. This means that the stress and strain it decreases, and the elastic energy stored earlier in this area of ​​the body is released, while at the beginning of the destruction of all the released elastic energy is transferred to the surface energy of the newly formed sections "shores" crack. To simplify the calculation of the amount of elastic strain energy relations, passing under the surface energy relaxation "shores" the rising generation of the crack, it is assumed that the relaxation area is circular, circumscribed around a closed crack in thicker material. It follows from the theory of elasticity is known that the release of strain energy U is equal to half the product of three variables: stress σ, the strain ε = σ / E and the volume of the relaxed material π l2 1 (unit thickness of the material). Crack of a given length 2 l at less than the critical load (σ <σC) does not apply. If the actual stress will be more critical (σ> σS), the crack develops unceasingly at accelerating the release of elastic energy accumulated in the body. This is called an unstable crack growth.
   It can be assumed that materials having different stiffness structure of the stress relaxation region near the crack is also different. This assumption is confirmed, in particular, research IA Rokhlin [1], according to which, with increasing strength ceramics significantly increase the coefficient of internal friction and shear limiting angles. Specific values ​​are presented in the IA Rokhlin table of coefficients of internal friction f and limit shear angles α for ceramics of various strength grades from 35 to 600.
   Certain IA Rokhlin theoretical formulas of the angle α for the indicated shear strength values ​​are in the range 44-69 , which is confirmed by the results of numerous experiments. Upon saturation with water of normal ceramics and high temperature coefficients of the internal friction angle and the offset below on 5-15% respectively.
   As a result, an analysis of the IA Rokhlin data was plotted changes in the area of ​​the relaxation zone near the crack depending on the strength of ceramics and calculated correction factor k:
  
   k = 0,3028 ln (R) - 0,3454, (1)
  
   where R - compressive strength of ceramics.
   Analysis of formulas shows that the formula (1) is true only for the relatively low strength ceramics having 75 brand. For less durable ceramic brand M35 actual amount of elastic energy released from the relaxation area near the crack, is only 60% of the values ​​obtained using the formula (1), whereas for the high-strength ceramics brand M600 actual amount of elastic energy released from the relaxation area in 1.6 times the values ​​obtained by the formula (1).
   Because concrete can also be attributed to the ceramics, it is obvious that the proposed amendments are valid for it.
   If the proposed amendments do reflect the real state of things, they should be taken into account in all the dependencies of fracture mechanics, based on the energy concept.
  
   Source:
   1. Rokhlin IA On the physical basis of the strength of structural ceramics. - Glass and Ceramics, 1970, 7, p. 22-26
  

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