About Silicone Pencil Case:
Hey,here is a Silicone Pencil Case wanna recommend you,it's made of silicone,and it won't harm our body.Compare with traditional pencil case,our silicone pencil case is washable,durable and do not break easily.If you are interested in our silicone pencil case,welcome to visit our other pencil case such as:Cute Pencil Case,Pencil Case Pen Bag,Pen Pencil Case,Pencil Case Kawaii,Silicone Pencil Case,Pencil Case Holder.
Product introduction:
1.Product name:Cute Pencil Case,Pencil Case Pen Bag,Pen Pencil Case,Pencil Case Kawaii,Silicone Pencil Case,Pencil Case Holder
2.Place of origin:Guangdong China
3.Color:any pantone color
4.Effect:Any effect according to customer's requirement
5.MOQ:500pcs.
6.Package:1 pcs/opp,customized design is available.
7.Design:Customized/stock
8.Certification:FDA,LFGB,SGS,ROHS,etc.
9.Usage:Use for pencil,pen and other stationery
10.Silicone Pencil Case photos for reference.
Cute Pencil Case,Pencil Case Pen Bag,Pen Pencil Case,Pencil Case Kawaii,Silicone Pencil Case,Pencil Case Holder Dongguan OK Silicone Gift Co., Ltd. , https://www.dgsiliconepettags.com
Solving the finite element equation, we can find various mechanical parameters of the deformation process. Since the radial return method has the characteristics of unconditional stability calculation, it is actually used for stress calculation in the large deformation elastoplastic finite element program design.
Boundary condition model of forming process Deformation mode In the gear precision forging, various shunting measures are often used to design three kinds of process schemes: the tube material is used for rough forging spur gears: closed die forging two-step forming; closed die forging pre-forging , hole split final forging; closed die forging pre-forging, constrained hole split final forging.
A schematic diagram of the tool (fixed tooth die and mandrel, moving upper die) and blank in the forming simulation is given. When the mandrel is fully inserted, as the upper mold moves downward, the blank is deformed and filled into the concave cavity, simulating the forming condition of the closed die forging; when the mandrel is inserted into a part, the deformed body is filled into the cavity of the concave die, and part of the blank is filled. The material flows to the bottom of the mandrel to simulate the forming conditions of the constrained split final forging. The constraint depth is controlled by the mandrel insertion depth; the mandrel is not inserted, and the deformed body is filled into the cavity of the cavity while the centripetal flow of the material, simulating the free hole shunting Forming conditions for forging.
When the interface friction model is analyzed by finite element simulation, how to correctly deal with the friction boundary conditions has a great influence on the success of the simulation process and the correctness of the simulation results. Using the most widely used Coulomb friction model, write the joint force form f=μfn{t}, where f is the friction force; fn is the normal reaction force; μ is the friction coefficient; {t} is opposite to the relative sliding speed Tangential unit vector.
Boundary Constraint Model When the boundary of the deformable body is in contact with the mold, the joint can only slide tangentially along the curved surface of the mold cavity, that is, a non-penetrating condition is applied at the contact interface. Let the mold move at the wp speed in the Z direction (for the fixed mold wp=0), the normal unit vector outside the surface of the mold that is in contact with the N node of a certain unit is {n}={n1, n2, n3}.
The relative sliding speed of the N-node in the Xi coordinate system is {dr}={dN,dN 1,dN 2-wp}, and the orthogonality between {d} and {n} is n1dN n2dN 1 n3(dN 2-wp) =0. When n3≠0, the surface equation can be expressed as X3=Z(X1, X2), and the normal outside the surface of the mold in contact with the N point is n1=-5Z5X1, n2=-5Z5X2, n3=1. There is a constraint equation dN 2=n1dN n2dN 1 wp of the node N. It is easy to know that the coefficient matrix of the single-rigid equation is no longer symmetric after introducing the interface sliding constraint.
To this end, matrix transformation is performed using meta-algebraic elimination techniques. After the N 2th equations of the equation are multiplied by n1 and n2 respectively, the Nth and N1 equations are added, and then the Nth equation is removed, which is equivalent to the corresponding row transformation, and the single rigid matrix does not change the property. When the node N is a common node of several units, each unit performs a similar transformation, and the configuration stiffness matrix is ​​reassembled, and the obtained correction matrix is ​​symmetric. The stiffness matrix after such constrained processing is symmetric, and the conventional symmetric solution method still works, reducing the solution scale. Similarly, when n3=0, and n1≠0 or n2≠0, it can be processed accordingly.
Numerical simulation simulation conditional final forging gear die parameters are: number of teeth z = 12, modulus m = 2, pressure angle α = 20 °, displacement coefficient x = 0. The pre-forging cavity is an equidistant curved surface of the final forging cavity, and the equidistance is δ = 0.2 mm. The initial blank outer diameter is Φ19mm, the inner diameter is Φ10mm, and the height H0=20mm.
For constrained splitting, the design has a skin thickness h = 4 mm, controlled by the mandrel insertion depth. The bottom corner radius of the mandrel bar is r = 1.5 mm. The industrial pure aluminum is used as the numerical simulation material. The flow stress model of the material under annealing state is σ=170ε0. 24(MP), the material elastic modulus E=69MPa, Poisson's ratio γ=0.31. The friction coefficient of the lubrication state is μ = 0.1, and the Coulomb friction model is followed.
Pre- and final-forging simulation analysis considers the symmetry of the gears, and only half of the tooth profiles are analyzed in the numerical simulation. The calculation starts from the pre-forging (closed die forging) and considers the characteristics of the outer edge deformation during the deformation filling process. The initial billet generates a sparsely meshed uneven mesh, and the block spline generation technique is used to perform the grid weight during the deformation process. Minute. The mesh deformation maps at different stages are given. When the height reduction ratio reaches 17.5 and 3 pre-forging different deformation stages of the mesh contour (non-uniform grid Δ=5, Δ=17.5, Δ=25, Δ=30Δ=34), Mesh distortion occurs separately and two points are re-divided. When the height reduction ratio reaches 34, the cavity is substantially full. The equivalent strain distribution at a height reduction ratio of 17.5 is given.
From pre-forging to final forging, the annealing process is generally required in the middle, so the loading history of the pre-forging is not reserved. Since most of the material distribution and transfer are completed in the pre-forging, the amount of deformation during the final forging process is small without the need for grid re-dividing. The load height reduction ratio curves in the three final forging processes of closed die forging, hole splitting and constrained hole splitting are given. It can be seen that due to the δ gap between the final forging blank and the final forging cavity, the free surface of the blank is more in the initial forging process, and the load rises slowly. In the deformation, since the radius of curvature of the involute region is large, the involute profile portion is in contact with the root and the crest region. This large-area contact causes the free surface of the blank to be suddenly reduced and the load to increase rapidly.
This trend is evident in all three process schemes, but the presence or absence of the diversion zone and the size of the diversion capacity make it behave differently. The problem of steep increase in closed die forging load is very significant. The load of the free hole splitting rises slowly, but the material splits more into the inner hole. Especially after the involute tooth profile contacts, the root root and the crest area form two closed areas. The material is mainly shunted into the inner hole, and the top filling is difficult. The initial forging load of the constrained hole splitting initial rise is slower, and the load at the final deformation moment increases. At this time, the restraining hole becomes smaller but the top of the tooth is full.
Conclusion In the cold precision forging of spur gears, the forging load is steeply increased, the cavity filling capacity is sharply reduced, the metal deformation flow is complicated, the influencing factors are many, and the product quality is difficult to control. Therefore, based on finite element numerical simulation to predict the forming Regularity, guiding processes and mold design are extremely necessary. According to the characteristics of cold forging, the three-dimensional large deformation elastoplastic finite element method is used to numerically simulate the gear forging forming process. For closed forging, forging, closed forging, hole diversion and constrained hole diversion The deformation flow of the final forging forming process was analyzed. The results of numerical simulation analysis show that the constrained diversion measures are very effective in improving the corner filling and reducing the working load. In addition, other deformation mechanics and formability analysis given by numerical simulation can provide effective information for practical process research and design, and will not be described here. The method described in this paper and the three-dimensional large deformation elastoplastic finite element simulation software with independent intellectual property rights can also be used for other complicated three-dimensional volume forming.
