| The groove fracture controlled blasting method which uses machinery and high water jet to carve groove along predictable direction of crack expanding on hole side and control the position and direction of cracking in specimens cut with loose blasting and static split drug is one of fracture controlled blasting methods.Lath sections with more smooth face and less destructive object cut and easy application to production are this way's advantages. Nowadays, two carving groove with machinery methods(carving V-shaped groove and carving rectangular groove method) have been patented. They are important measures of raising raw material ratio of masonry materials mining in our country.The paper discuss the principle of the groove fracture controlled blasting, and sums up the results of some research and results as simulating the groove fracture controlled blasting. The results of V-shaped groove and rectangular groove and half circularity are solved by finite element numerical simulation. And the results can show that the equivalent stress around wedge tip of them are expanding excess other position's by equivalent stress graphic.In this paper, firstly, the linear elastic plane strain model with even internal pressure in infinite elasticity is set up and the equivalent stress distribution around the groove and wedge tip is calculated by the numerically simulated finite element method. It is used during the studying groove, and prove the regulations of V-shaped groove and rectangular groove and half circularity groove that wedge tip is the first forming position of crack.Equivalent stress calculating data of V-shaped groove show that the relation of groove angle, groove depth and groove tip's curvature radius effecting equivalent stress around groove, and gain how they effect equivalent stress around groove. Equivalent stress calculating data of rectangular groove show that the relation of groove depth and groove width effecting equivalent stress around groove, and gain how they effect equivalent stress around groove. Equivalent stress calculating data of half circularity groove show that the relation of groove radius effecting equivalent stress around groove, and gain how they effect equivalent stress around groove. The fact is proved by mechanics that groove can control initial position and direction of crack expanding effectively, the groove fracture controlled blasting is an effective method in mining masonry materials.The numerically simulated finite element method is used during the studying several different parameters of V-shaped groove and rectangular groove and half circularity groove hole. The equivalent stress distribution around the groove and wedge tip is calculated and found those rules such as follow:(1) the values of equivalent stress around wedge tip and predictable surface ofcrack(on x- axis) expanding excess other position's greatly, therefore initial position of crack expanding comes out on wedge tip and crack expands along predictable axis of crack expanding when the loads increase on the v-shape hole inside.(2) the increase of groove depth of V-shaped groove and rectangular groove raise the values of equivalent stress around wedge tip; It had better choose the groove depth in 4~6mm to fit the ask of project of machine.(3) It had better choose the groove angle in 60 掳~90 掳 on the basis of the relation of groove angle effecting equivalent stress around groove.(4) The decrease of wedge tip's curvature radius enhance the values of equivalent stress around wedge tip. In the fact of project, the decrease of wedge tip's curvature radius raise resistance which rock nips blade and diminish the efficiency of machine working and raise blade damage. It had better choose wedge tip's curvature radius in 0.6 ~2.0mm and can choose less.(5) the increase of rectangular groove tip's width decrease the values of equivalent stress around wedge tip, the groove tip's width had better choose in 3mm~4mm and can't choose bigger..(6) V-shaped groove and rectangular groove all can...
|
PDF Full Text Request