The partial upsetting of the end of the shackle blank is called the top sill. It can be carried out on the free forging hammer friction press flat forging machine, etc. It is especially suitable for the production of forgings with large heads or flanges at the end of the slender rod; Among the equipments, the top boring process on the flat forging machine is the most typical, so the analysis of the forming of the bolt on the flat forging machine is carried out here. If the length or aspect ratio of the deformed portion of the bolt is too large, it will bend due to instability. Then developed into a folding, the previous flat forging process design is based on the top sill rules for step design, but for the dry high-strength bolts 3 also fully consider the material, the impact of the aspect 0, such as the forming limit deformation resistance and thermal effects. The forging temperature range of high alloy is very narrow, and the deformation of one step can not be too 7. According to the specific conditions of a high alloy long bolt, the bolt process is divided into one step, and each worker is analyzed by finite element method.
Before the start of the simulation, it is necessary to carry out the work of simulating the modeling of various models of motion parameters and boundary conditions. The mold structure design process should be fully considered and guaranteed.
The spatial geometry of each step mold is modeled by weekly computer graphics software. The space modeling of the parts can use many existing dimensional modeling software, such as 31. Before modeling. First, we need to determine the type of zero cattle, that is, the analytical mode of the analytical part of the experimental modal substructure, the finite element unit, the rigid body total matrix, etc., which are the basis of the part information and the matrix form, and then, based on the part Simplification of the geometry = after the end of the part modeling, it is also necessary to determine the mechanical properties and the finite element material properties. Since only the interaction between the mold cavity and the blank is considered in the simulation process, the mold can be simplified, for example, the dovetail lifting hole can be ignored. All the mold models are made of 3 holes and 1 oil, and the file format is input +. The mold cavity of this format has the characteristics of smooth interface and simple flow line, which can fully meet the requirements of the geometric structure of the foot mold. They are the structural meaning of the work step of the bolt flat forging process.
During the simulation, it is generally considered that the mold itself does not undergo plastic deformation. Therefore, the mold can be regarded as a rigid body treatment, thereby avoiding the gridding and the like, and the movement and loading mode of each mold are consistent with the actual process, such as. , 1 mold loading arrangement step 1 mold step 2 mold step 3 touch tool left clamping mold right clamping mold plus ash plus loading, loading loading plus loading, the movement speed of the mold 23 is the direction of motion is axial The moving speed of the left and right clamping dies is set to 0. The initial temperature of each mold is set to 20, and the top boring mold of step 23 is loaded according to the position of the stroke, and the left and right clamping dies are always loaded, where the left and right clamping dies are mainly The positional displacement from the position of the deformation zone of the control blank and the end face of the non-deformation zone of the blanking platform is defined as zero to ensure that the blank is not ejected during the deformation process. In the pressure processing of a ship using a lubricant, the friction on the contact surface can be considered to obey the Ameng Coulomb law. That is, the coefficient of friction is considered to be constant. The value varies with the nature of the metal, the surface condition of the surface condition in contact with the metal, and the type and nature of the lubricant used. 5. The coefficient of friction between the mold and the blank is taken as 2. It is worth noting that The step size setting during the simulation is neither. Big, too, can be too small. Too large is easy to cause calculation errors, too small is easy to cause too much calculation, usually can take the length of the blank grid, which is taken 36.
The drip selection uses a root diameter of 26 paws. The length is 427. The shed tree. The material is a high alloy, the forging temperature range is 95, and the material has a flow stress-strain curve 2 of 925, wherein curves 3 and 1 respectively represent strain flow curves of material flow rates of 2.5 and 26.8, respectively. The moving speed of the blank is, the initial deformation temperature is 2, and the blank is defined as a rigid plastic material. In the general shape forming problem, the strain value of some parts in the plastic deformation zone is large, and some strain children more than 2 are also common. In addition, the relative speed of the workpiece and the contact surface is also large. In the calculation process, such large deformation children and relative displacement will produce the following relative displacements of the workpiece and the mold contact surface. The grid of the workpiece boundary and the chessboard surface misalignment grid system are difficult to adapt to the plastic deformation zone. Change; large deformation of the circumference causes large distortion of the unit.
To overcome these difficulties, the computational process requires constant re-meshing of the grid system. First create a new grid system, which is exactly the same as the initial grid system, and then convert the information calculated by the old grid system to the new grid system. When converting information, first interpolate the effective strain and other fields in the old grid system to the node, and then interpolate the information into the new grid system.
Nowadays, many finite element softwares provide the automatic re-weighting function of the grid, which provides convenience for simulating the smooth calculation of the juice calculation. However, in actual use, the user often needs to artificially define the grid according to his own requirements, such as specifying a specific Part division is finer or meshing is controlled by an interface program.
The output format of the blank is 1; format. This format is suitable for plastomers, which can ensure that the deformed body is not distorted, and has the disadvantage that the surface finish of the blank is poor.
3. The results analyze the line meaning, from the stress field analysis results can be seen the distribution of stress on the unit area of ​​the deformed material. It can be seen from 7 that the stress value of the contact end face between the blank and the mold is the largest, and the change of the stress value near the root of the deformation zone is the most complicated and severe. The metal flow in some parts is hindered by the clamping die and the outer end of the blank, forming a so-called death. Zone, this must be given enough attention in the mold design, as far as possible to avoid this phenomenon, notice that the stress value of the rounded corner of the bolt is far greater than the core stress value, this stress field distribution progresses the bolt root The concentration of the metal streamline at the rounded transition, the greater the deviation of the stress value outside the deformation zone, the more uneven the distribution of the metal streamline. 4. Conclusion The metal flow velocity outside the deformation zone is related to the metal metal flow velocity. The formed metal flow line of the bolt is densely packed on the outside of the bolt, and the core is sparse. When machining, a large amount of metal flow lines are cut off, thereby reducing the strength of the bolt portion and the neck, which is in the mold design. Attention should be paid to; the stress value at the end face of the blank and the die is the largest, and the change in the stress value near the root of the deformation zone is the most complicated and intense. The greater the deviation of the stress value in the deformation zone of the dead zone bolt, the distribution of the metal streamline will go to the uneven step 1 and the step 5 is the speed field equivalent of a specific time in the bolt forging step. Idle. Conducive to the formation of the head of the tamper. Comprehensive analysis of this step, we can find that the flow velocity of the 佥1 outside the bolt head root is greater than the flow velocity of the metal at the core, so that the formed metal flow line of the bolt is dense on the outside of the bolt, and the heart is sparse, especially at the end. For each step, this velocity field will cause the metal streamline density at the transition between the head and neck of the bolt to be much greater than the metal streamline density at the core. 6 is the distribution of the velocity field in the deformation zone of the tamponade. From 6th, the flow trend of the various mass points inside the deformation body can be more clearly seen. The moving direction of the particle point points to the outside, and the more the outer side of the deformed body is encrypted, this phenomenon can be The interpretation of the law of least resistance. When the machine is twisted, the streamline of the neck is severely cut, resulting in a decrease in the strength of the head and neck of the bolt. This should be noted when designing the mold. Appropriately increase the mold fillet to improve the stress state, reduce the machining allowance will help the gold, streamline improvement, solid 5 violation field distribution
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