Vertical injection molding machine shrinkage rate (3)

Date：2015-09-28 20:43:53

Study abroad before 1.3 molding shrinkage rate
        As mentioned earlier, the current engineering practice commonly used mold designers to calculate the average shrinkage molding size. Taking into account the shrinkage of the selection have large errors, in order to facilitate the repair mode after the tryout, generally calculated according to the maximum material condition radial cavity size and depth dimension, radial dimension and a height dimension of the core, according to the intermediate entity condition calculate the center distance category feet.
        On the other hand, engaged in research in the field of plastic molding researchers have been trying to reduce shrinkage prediction error, in order to shorten the mold manufacturing cycle and improve the success rate of the mold.
        1.3.1 shrinkage predicted experimental data fitting method
        At first, people focus on the impact of fluctuations in vertical injection molding machine injection molding process conditions on shrinkage generated by the large number of vertical injection molding machine injection experiment, trying to figure out vertical injection molding machine injection molding process conditions and shrinkage of the quantitative relationship between. In accumulated some experience, some scholars have proposed a method using experimental data to predict the vertical injection molding machine injection molding shrinkage rate under actual production conditions. The basic idea is: through a multi-factor orthogonal experiment, measuring some plastic in different cylinder temperature, injection pressure, injection time, packing pressure, systolic pressure retention time, mold temperature, mold cooling time and other parameters under rate, according to data sample test was fitted out as a function of shrinkage and the various process parameters; and in the application, the actual production of the vertical injection molding machine injection molding process parameters used in the generation of the corresponding function formula to give each corresponding shrinkage value, its weighted average, it will have the desired mold designers' actual shrinkage. " This approach to a variety of factors affect the shrinkage, taking into account the vertical injection molding machine injection molding material properties and vertical injection molding machine injection molding process conditions, for adjusting the process parameters during vertical injection molding machine injection molding production is instructive.
        But because there is no structure to consider the effect of molding shrinkage, so that the experimental data fitting method used to predict the vertical injection molding machine in a very limited shrinkage when injection molded article, a vertical injection molding machine is when the actual injection molding products When the distribution of the gate number, position and mold cooling circuit is different from the test case, vertical injection molding machine injection molded article inside the pressure distribution and temperature distribution are also different experiments, so that the actual vertical injection molding machine with the injection molding process conditions vertical injection molding machine are not comparable between the injection molding process conditions experiments; the second is not considered within the vertical injection molding machine injection molding mold shrinkage during limited effect.
        1.3.2 Shrinkage prediction numerical simulation
        In order to more accurately predict the shrinkage, must consider the impact of structure on the vertical injection molding machine injection molding shrinkage rate, and molding the structure is changing, we can not only rely on experimental data of several molding structure to fit out structure and quantitative relationship molding Vertical injection molding machine injection molding products throughout shrinkage between the various, so vertical injection molding machine with a computer on the injection molding process mathematical simulation research work is increasing, becoming polymer processing science development Soon the forefront of research. Mathematical modeling of various physical and mechanical problems, it must first establish equations describe its physical state and processes (mostly PDE) in the calculation of the range, according to definite conditions (including the boundary conditions and initial conditions) of the equations to solve it. Definite solution of the problem with the analytical method for solving equations of mathematical physics is no calculation error, but the analytical solution only in a few conditions to get the problem most engineering problems analytical solution is difficult to find, especially for complex geometries and boundary conditions, only Approximate numerical methods for solving. The emergence of high-speed digital computer, make the application of numerical methods possible.
        Computer-aided analysis of vertical injection molding machine injection molding (Computer a AidedEngineering, abbreviated as cAE) to polymer physics, fluid mechanics, heat transfer, the theoretical basis of viscoelastic mechanics, analysis of the vertical injection molding machine injection molding process basic in line with the objective law, and flow, pressure, cooling the various stages of the numerical simulation technology matures, it can flow to the vertical injection molding machine injection molding, packing, cooling the basis for an integrated analysis of the predicted vertical injection molding machine injection molding products forming quality, including the shape and size of vertical injection molding machine injection molding products, micro-structure and the use of performance. On the basis of the existing vertical injection molding machine injection molding simulation method of research results, there has been the commercialization of vertical injection molding machine injection molding CAE integration software, such as the US ACTech's C-Mold software, Australian MF MoldFlow software company, Toyota Central Research Institute of IMAP software 153] l541, the State Key Laboratory of Huazhong University of Science mold technology HSCAE software, Z rubber molds National Engineering Research Center of Zhengzhou University a Mold software and so on. Put the following prediction flow vertical injection molding machine injection molded article shape and size analysis to be carried out, pressure analysis, cooling analysis, residual stress analysis and research in warpage analysis introduced one by one:
        (1) flow analysis
        Simulated filling flow process, according to the forefront of the plastic melt flow determination method can be divided into the following categories:
        Distribution Principle 1. Press the branch pressure drop equal to the flow rate of each branch of the three-dimensional geometry of the vertical injection molding machine injection molding products flattened two-dimensional graphics, and then rely on the experience analyst or mold designers roughly divided into several flow branches, each branch and then flow into several one-dimensional flow cell in series (such as pipe, conical tubes, sector plate, rectangular plate, ring plate, etc. In the upstream flow distribution to the downstream of the branch, to make Each branch drop equal to the pressure from the gate at the forefront of its liquidity.
        Specific process: Press previous time allocated to the various branches of the traffic flow front advancing the current time of each branch, and solve the current temperature field time, and then calculate each branch descending from the gate to the forefront of pressure flow, if each branch pressure drop is not equal, modify the distribution of the various branches of traffic, recalculate the current time temperature field and pressure drop, until the pressure drop is equal to each branch. With this method of thinking has a branch flow method (BranchingFlowMcthed, abbreviated as BFM).
        11. melt front velocity field is determined according to the previous node at a time the flow front velocity, multiplied by the time step, to get the current time the flow front position (if the flow front boundary wall beyond the mold, then beyond part traffic recovered, according to the principles of flow front and the mold wall boundary orthogonal turn assigned to the interior of the mold wall boundary flow field at the present time is obtained melt pressure, speed, temperature distribution in the future, the speed of the previous value of the current time a time weighted average speed, and then multiplied by the time step, the position of the current time corrected flow front, and meshing the present time to increase the flow of new areas. This method is also known to predict a correction method (predieto two orreetorseheme), and it is mainly used for two-dimensional flow analysis when dealing with three-dimensional objects, which can be expanded into flat pattern on a plane to get some area adjacent, in the case of the melt flow across regional boundaries, to borrow optics Relationship between the incident and refraction of light, so that the flow lines in the area to determine the boundaries of refraction and changed the direction of the flow velocity and size.
        111. According to the previous time pressure field distribution of each mesh traffic, the first cavity geometry discrete computational grid is fixed and formed corresponding to each grid node control volume. In flow analysis, based on previous time pressure field is calculated for each flow into the forefront of the control volume and the time that the net flow volume control is completely filled with the need to take the shortest time to full time step is necessary at the current time There will be a cutting-edge control volume is filled with the melt, the adjacent control volume will become the new frontier; the forefront of the current time for each unfilled control volume, based upon the previous time pressure field to determine flow into the control volume The net flow and the extent of the control volume is filled, and the melt front as the current time position.
        Solving the current temperature field time, and then every principle has full control over the melt volume flow rate should be zero net, the establishment of the node to be pressure for quantity equation control the volume of each of its nodes had been filled, this nonlinear equations are solved at the present time pressure distribution obtained. With this thought in the network flow analysis method method (Flowing unharmed alysis a NetworkMethod, abbreviated as FAN) and control volume method (eontrol a volunleseheme).
        The above three methods, the Type I method can not be formed with the packing, cooling and other analysis modules consistent computing grid, and divide the flow branches without a unified, rational principle;
        N-type method in dealing with problems melt in contact with the mold wall requires manual intervention, high degree of automation, in addition to the cavity area is not the first discrete processing modules completed, and to be in flow analysis, an increase Flow analysis module contents;
        111th class of these problems do not exist, and therefore become the main method currently performing flow analysis used. The method of determining the flow front position after pressure control equations to solve the finite element method mainly, but also scholars attempt boundary element method, or the Ohm's law electrical network theory introduced flow analysis.
        Since the thickness of conventional thermoplastic injection molding machine vertical injection molding products is much smaller than the flow length, and a large plastic melt viscosity, it is usually the plastic melt filling flow of generalized Newtonian fluid viscosity deemed extended laminar flow, ignoring flexible plastic melt, and that there is no flow in the thickness direction. In the fiber reinforced plastic vertical injection molding machine injection molding simulation of flow and gas-assisted injection molding machine vertical injection molding simulation of flow often make such assumptions. From the extent consistent with the objective look at the situation in the upstream flow front velocity component in the thickness direction is indeed small to be ignored: but in the flow front, the plastic melt is "fountain" approach flow - that is, from a core melt steering mode wall direction, rather than a straight line forward. If you want more accurate analysis of high molecular orientation vertical injection molding machine injection molding products, processes, you should consider a fountain effect, and the polymer melt as the viscoelastic fluid to deal with, because the elastic polymer melt flow in the fountain area performance more obvious, in addition to the extrusion process of polymer melt elasticity can not be ignored.
        (2) Packing Analysis
        Packing phase of the mission is to rely on holding pressure to the mold cavity has been filled with pressed into the plastic melt, shrink to compensate for vertical injection molding machine injection molding products due to the temperature drop or crystallization generated. Vertical injection molding machine injection molding simulation of injection pressure and holding pressure, all referring to the plastic melt pressure at the nozzle injection machine. Holding pressure is usually slightly lower than the injection pressure of prison, but because they are filled at the packing stage cavity had, melt flow is blocked by the die wall, mainly due to a pressure drop from the melt flow into the filling stage packing stage of compaction, so the packing phase of the internal pressure of the cavity greatly increase over the filling phase, and the pressure distribution becomes relatively uniform, away from the melt pressure and melt pressure at the gate at the gate of the the gap is much smaller than the female mold filling stage. Increase the internal pressure of the cavity of the plastic melt and the solidified layer obvious compressive strain, so the plastic can not be regarded as a constant specific volume. For the calculation of hematocrit value in the early research work, SPeneer a single domain state equation what Gilmore s] once adopted, is now widely used to more accurately calculate the specific volume of plastic double domain Tait equation of state.
        In addition, since the melt flow rate is very low holding pressure phase, shear heating effect is reduced, as compared with the filling stage, the cooling rate products increased significantly, the temperature changed much, so not only to consider specific volume with temperature changes, and specific heat, thermal conductivity and other thermal parameters occur with a change in temperature should also be accounted for. In packing simulations, usually ignored flexible plastic melt, as a viscous fluid to handle its. However, if the choice of the viscoelastic model packing process, it is possible to obtain more comprehensive information flow stress, the study of polymer orientation and relaxation of great help. Generally considered packing process begins the moment the mold cavity is completely filled, in fact, pressure phenomenon also exists in the filling stage. When some part of the mold cavity has not yet been filled, those first to be filled full, substantially stop the flow of melt from the melt region has contacted its mold wall, since the flow reaches the end of the moment into the packing state. If you completely removed the plastic melt filling phase incompressible assumption would be artificially separated from the original mold filling phase and packing phase of the merger, the unified mathematical model to analyze the state of packing, although the charge can be calculated more accurately pressure and temperature molding stage in packing state of the region, thus affecting a prominent plastic products child geometry of the molding process, but also increases the complexity of the numerical simulation.
        For plastic melt flow state and Keiichi, incompressible assumption is appropriate, in filling state of the plastic melt Mach number (the ratio of the flow velocity and the fluid velocity of propagation of sound waves) is less than 0.4, can be it as an incompressible fluid. If we can state with packing filling state filling stage processed separately, then both consider the compaction phenomenon that occurs filling stage, the program will not run too complicated. After packing some time, operating cylinder injection engine is switched from the hold pressure to pre-plastic back pressure. When the holding pressure to withdraw the injection screw begins to rotate, so that vertical injection molding machine injection molding material is fed forward along the spiral groove and is plasticized melt in the dual role of the barrel and the screw shear heating frictional heat to prepare for the next injection while reaction material driven by a screw to move back to the specified location, this is called pre-plastic process.
        If the injection machine vertical injection molding machine injection molding products before closing the gate to enter the pre-plastic phase, then the vertical injection molding machine injection molding products packing terminates at packing pressure to withdraw in time; if the gate is small, in Bulgaria Undo-pressure long before completely solidified, cutting off the stream path, then the vertical injection molding machine injection molding products packing ending at the gate closure time condensate. One end of the packing stage, vertical injection molding machine injection molding products to enter the mold cooling stage.
        (3) Cooling Analysis
        The purpose within the setting mold cooling time, it is to make vertical injection molding machine injection molding products to be able to withstand the curing mold ejection systems ejection force applied without deformation. Vertical injection molding machine at all stages of the production cycle of injection molding, in-mold cooling stage takes the longest time. When removed injection cylinder injection screw holding pressure, the screw will force due to a sudden loss of balance and back, then the back vent resistance within the injection cylinder operating oil blocked, so the removal of holding pressure will be instantaneous flow plastic melt tract back into the nozzle of the reverse phenomenon, reverse flows back to the beginning of a very high speed, but quickly slowed down.
        If before the gate has solidified, the mold cavity will not melt back out the gate, the mold cavity pressure is not reduced; otherwise, melt a small part of the cavity will reverse out the gate, so mold cavity pressure decreased. In either case, a great gate solidification mold cavity pressure is called "closed pressure." After that the internal pressure of the mold cavity with plastic to reduce the temperature decreases, plastic hematocrit remained unchanged; when the internal pressure of the mold cavity down to a pressure equal to the atmospheric pressure no longer decreased, beginning with the plastic temperature plastic hematocrit The decrease shrink, shrink plastic products mold. For the calculation of the cooling phase in the mold temperature field of plastic products, usually assume is always a full contact between the plastic and the mold wall, consider the plastic surface temperature is equal to the mold wall temperature, and consider only the plastic in the thickness direction of the heat transfer, the use of a one-dimensional finite difference method to solve it. As for the plastic surface of the mold caused by shrinkage from the mold wall, the gap between both the objective situation, only a few scholars to be discussed with the contact thermal resistance of heat transfer in concept, but has not been used for in-mold cooling phase Numerical simulations.
        Mold wall temperature as a boundary condition of temperature field of plastic products, which is calculated to attract the attention of many scholars at home and abroad: the beginning of a continuous vertical injection molding machine injection molding, the temperature of the mold base increases as the number of vertical injection molding machine and gradually increased, experienced several vertical injection molding machine injection molding cycle later, the amount of vertical injection molding machine injection molding cooked material passed to the die mold heat dissipation basically balanced, the overall temperature of the mold tends to be stable, far away from the mold cavity One is no longer at a mold temperature changes near the mold cavity temperature is stable and unchanging cycle around the mean value fluctuate with the vertical injection molding machine injection molding production process. In each vertical injection molding machine injection molding cycle, mold wall temperature at first due to filling, packing phase of the plastic melt into a lot of heat and gradually rises to a peak, with the plastic in the mold cooling phase of the temperature drop, reduce heat to pass mold, mold wall temperature and slow decline, the next model, the top of the plastic products, the process of clamping the mold wall and the outside cold air heat exchange, after clamping the mold wall temperature is reduced to a minimum points.
        Vertical injection molding machine in the next cycle, mold wall temperature again experience such a change. Since the mold wall temperature does not change the average period, so in the early research work on behalf of more to cycle the average mold wall temperature, the mold wall as a steady temperature field to deal with. In recent years, mold wall temperature fluctuations began to be concerned about the emergence of the calculation method for solving mold wall transient temperature field. When solving the mold wall temperature, heat transfer coefficient around the cooling circuit between the cooling water and mold, and heat flux around plastic products and mold between the mold wall boundary conditions to calculate the temperature field.
        Usually the first to get the heat transfer coefficient between the die and the cooling water through a cooling pipe network analysis, and through co-iteration disaster plastics and mold wall temperature field calculation of temperature field calculations to determine the product temperature and mold wall temperature. Numerical Methods for Solving mold wall temperature field, mostly using the boundary element method, because it simply calculate the area of ​​border and solving discrete, finite element method than the entire calculation area are scattered to the computing unit to solve, and the resulting The number of linear algebraic equations significantly reduced, but also much easier to implement a discrete work. Calculated after the mold wall temperature distribution, in order to guide the mold designers to modify the design of the cooling system in order to obtain as uniform distribution of mold wall temperature, sensitivity analysis is introduced into the vertical injection molding machine injection mold cooling system optimization design. By calculating the mold wall temperature on the sensitivity of each point of the cooling duct at various locations, it can be provided to improve the mold wall temperature distribution of the most advantageous position, and change the direction of the cooling duct to mold designers, to avoid blindness and randomness modify the cooling system.
        (4) Analysis of Residual Stress
        The purpose of residual stress analysis is to obtain vertical injection molding machine injection molding products stress state at the time of release, the calculation of residual stress analysis, is the initial condition after release warpage analysis. Residual stress vertical injection molding machine injection molded article consists of two parts: the flow of residual stress and thermal residual stress. Residual stresses due to the polymer flow along the flow direction of orientation caused by freezing; thermal residual stress due Tears' contraction trend molded article can not fully occur caused. When the polymer melt flow polymer chains are arranged in the role of the flow stress of the direction of flow. After stopping the flow ratio, if the molecular orientation and flow stress due to excessive cooling rate can not achieve complete relaxation, it will form a frozen molecular orientation and mobility residual stress. Molecular orientation and flow stress generated in the filling stage and the plastic melt flow packing stage, frozen molecular orientation and residual stress depends on the flow of filling, packing, cooling various stages of molecular orientation and flow stress relaxation process.
        Constitutive model with viscous shear flow stress can only be obtained in using viscoelastic constitutive model in order to determine the flow stress of the normal stress. But if the pressure in the filling phase and packing phase equations directly using viscoelastic constitutive model, rapid growth make the program run time, for which the residual stress calculation proposed flow separation Some scholars: Let polymer melt Little impact elastic flow field to be negligible, still uses a viscous constitutive model equations to solve the pressure; then put pressure and temperature field coupled iterative calculation of the resulting pressure, speed and temperature substituting viscoelastic constitutive model to calculate the normal stress of the flow stress. Similar results with the direct method of separation, but also save a lot of computing time. Thermal residual stress generation began to shrink in the mold process.
        When there is shrinking trend between the vertical injection molding machine injection molding products uneven with some restraining effect, shrink or vertical injection molding machine injection molded articles by external constraints, make some shrinkage trend can not happen, then it will produce thermal residual stress. Uneven shrinkage trend vertical injection molding machine injection molding products, there are three: the thickness direction of the contraction of the layers are different; different shrinkage direction perpendicular to the molecular orientation in the direction of molecular orientation of contraction; vertical injection molding machine injection molding products shrinkage between parts different. In the thickness direction of the vertical injection molding machine injection molding products, mold near the outer wall of the inner layer is bound to occur before curing. In the same period of time, internal shrinkage tendency cured layer is greater than the melt, but is limited by the contraction of the melt can not be completely cured layer occurs, resulting in tensile stress inside vertical injection molding machine by injection molded article, and the outer layer compressive stress.
        If the vertical injection molding machine injection molding products, lower surface cooling due to different circumstances and different tendency to shrink, vertical injection molding machine injection molding products have a tendency to bending deformation. In the previous release, due to the mold wall limiting vertical injection molding machine injection molding products can not be bent, so the direction of the thickness of each layer are by the smallest contraction trend that layer, this layer of compressive stress, tension remaining layers Stress. After stripping, thermal residual stress to a certain degree of release, vertical injection molding machine injection molding products will generate corresponding bending. Contraction, differs from the direction of molecular orientation in the vertical direction of molecular orientation, primarily because the alignment direction of the alignment reply shrinkage leaving larger than the vertical direction. However, the contraction in both directions between each other there is no restraint, without disturbing each other, can be totally happen, so it will not cause thermal residual stress.
        Uneven mold wall temperature distribution, cavity or core to hinder the formation of weld lines and vertical injection molding machine injection molding shrinkage, will result in different portions of the contraction of vertical injection molding machine injection molding products, so some shrinkage not occur, the resulting thermal residual stress. For releasing previously calculated thermal residual stress, thermal elastic model results obtained with the use of hot sticky elastic model results obtained qualitatively. However, due to the temperature of the cooling phase in the mold cured layer remains high, viscoelastic properties of polymers obvious, so the curing process within the vertical injection molding machine injection molding products more suitable thermal viscoelastic model to analyze. Thermal residual stress values ​​higher than one to two orders of magnitude higher than the flow of residual stress, and therefore to predict vertical injection molding machine injection molding products for the warped shape and size analysis of general purpose flow excluding residual stresses. But the flow of residual stresses in the microstructure and performance of vertical injection molding machine injection molding products is very important in predicting the flow of residual stress as reflected in the orientation of the polymer freeze is to make vertical injection molding machine injection molding products thermal properties, mechanical properties root causes and produce anisotropic optical properties.
        (5) warpage analysis
        Warping deformation analysis is solved after stripping vertical injection molding machine injection molding products that occur at the beginning of the equivalent stress load and temperature loads, structural analysis module that is outside the curing process. Residual stress analysis of initial stress resulting release time vertical injection molding machine injection molding products internal stress; equivalent load by the die temperature during cooling vertical injection molding machine injection molding products temperature drops generated transformed from contraction trend.
        After the release of vertical injection molding machine injection molding products, generally assumed that the relaxation time of the polymer had increased to the polymer chain flexibility not reflect that the polymer strain independent of time, which can follow thermal elasticity calculation of stress-strain relationship deformation vertical injection molding machine injection molding products. Thermo-elastic structure warpage analysis, there are linear and nonlinear analysis of the points. If the vertical injection molding machine injection molding products not bending deformation, is considered to be in a small strain range, you can use the linear structural analysis; if the vertical injection molding machine injection molding products bending deformation, not meet the requirements of small linear strain conditions, nonlinear structural analysis should be used. When stripping vertical injection molding machine injection molding products are top of the mold cavity changes arising from vertical injection molding machine injection molding products spatial position of each point, they do not show up in the warp analysis. When warpage analysis module, the spatial position of the inner end of the initial cooling stage vertical injection molding machine injection molding products of the same points, but the walls of the vertical injection molding machine injection molding products each point displacement constraints are lifted. At the end of the warp analysis, the resulting spatial position of each grid node as well as its relative displacement occurring before molding after molding. According to the distance between nodes before and after the change in shape, you can calculate the corresponding size shrinkage.
        In addition to the above analysis module front, vertical injection molding machine injection molding CAE technology also includes post-processing module. Pre-processing module is responsible for the area to be analyzed to establish the geometry (including mold casting system, cavity and cooling systems), and auto-complete meshing; post-processing module put the value range of data analysis results obtained, as promote the process of filling the plastic melt flow front of the stage, in vertical injection molding machine injection molding temperature and pressure of each stage of plastic products each point, after the distribution of the residual stress when releasing the curing process and the die vertical injection molding machine deformation of molded articles, etc., on a computer screen visually displayed in contour maps in the form of colored shadows. Numerical simulation of vertical injection molding machine injection molding, the vertical injection molding machine injection molding material properties is viscosity, thermal conductivity of plastics, specific heat, specific volume and other physical properties data to representatives; molding structural factors, namely pouring shape and size of the system, the shape and size and shape of the cavity size of the cooling system is by the geometric model on a computer set up to describe; the impact of the vertical injection molding machine vertical injection molding process parameters on shrinkage of injection molding machine, places vertical injection molding machine injection molding process, vertical injection molding machine injection molding temperature changes and pressure changes throughout the article to reflect.
        Problems in the application of numerical simulation methods 1.3.3 stored fashion
        Mathematical model, numerical solution and program code to simulate the basic elements, the most important is the establishment of a mathematical model, it is necessary to be able to objectively reflect the essence of things, but also to facilitate problem solving, and taking into account the required data obtained The possibility, because if as a physical performance data based itself can not be very precise, then less precise on the basis of raw data to solve very precise is meaningless. The key question is relatively easy to obtain and given practical problems to adapt to the accuracy of the solution. Research on vertical injection molding machine injection molding simulation method is also based on how to better serve the practical applications for the development direction. On the one hand, from the perspective of the starting line with objective reality, to improve mathematical models gaps in; on the other hand, from the convenience of practical application point of view, to study how to improve the analysis methods to improve computing speed, shorten analysis time, because of the vertical injection molding machine injection molding simulation of the various stages of computation are large, vertical injection molding machine for plastic injection molding simulation time required for the entire process is longer, if only in the design of the mold on the vertical injection molding machine forming process simulation once or twice, you can not use this method for mold design modifications repeatedly in order to find the optimal design.
        In addition, vertical injection molding machine injection molding simulation method in the application of the various materials needed for the problem difficult to obtain a constant need to be addressed. Vertical injection molding machine at present description of the injection molding process to be improved mathematical model in the following areas:
        (1) the establishment of nonlinear viscoelastic constitutive relation polymers.
        Long-chain structure of the polymer of the mechanical properties of the polymer are beyond the scope of the theory of elasticity and viscosity type, in particular, when the curing process inside the vertical injection molding machine injection molding article analyzes vertical injection molding machine injection molding process, can not be Consider the unique viscoelastic properties of polymers. Study of nonlinear viscoelastic constitutive relation polymer materials is a very important but very difficult issue, through the efforts of many people, the mechanical properties of polymer materials, the gradual deepening of understanding, but the problem remains unresolved, is still in contending stage, various nonlinear viscoelastic theory also need to develop improvement. According to the mechanical properties, the material can be divided as follows rigid solid ~ linear elastic solid (Hooke body) a nonlinear elastic solid a solid stick a bomb a nonlinear viscoelastic fluid viscous fluid (non-Newtonian fluid) linear viscous fluid (Newtonian fluid) a non-viscous fluid.
        Wherein the elastic and viscoelastic fluid viscosity are all solid viscoelastic body. When applying a constant load, response Hook body is immediately deformed and maintain a constant deformed state, the energy stored, remove the external force and then recover its original shape, the energy stored in the release of all; in response Newtonian fluid occurs immediately irreversible flow and to maintain a stable flow state, all of the energy dissipation, not stored; in response to deformation of the viscoelastic body is immediately and then over time, resulting in a limited or unlimited amount of flow process, the gradual dissipation of the stored energy both show the instantaneous elastic effect, also show the creep characteristics. Show stress and strain there is a linear relationship between Hooke's law describes the behavior of linear elastic solids; indicate stress, strain rate there is a linear relationship between Newton's laws describe the behavior of linear viscous fluid; spring by Hooke and Newton dashpot in series or in parallel different combinations, can constitute different mechanical model of linear viscoelastic behavior, obtain differential form linear viscoelastic constitutive relation, when the number of units in the mechanical model tends to infinity, it is equivalent to the established principle of superposition integral by Boltzlnann in the form of linear viscoelastic constitutive relations viscoelastic behavior linear polymer materials rarely meet the conditions, but the geometric nonlinearity (nonlinearity caused by the large strain) and physical nonlinearity (nonlinear small strain caused by prolonged) .
        In a vertical injection molding machine injection molding cooling stage nonlinear viscoelastic behavior of polymers is a physical nonlinearity. Or quantitative theory of nonlinear viscoelastic approaching three ways: 1. the project approach. Nonlinear viscoelastic behavior under certain conditions, a series of experimental measurements, and then the experimental data are summarized into contact stress, strain, and the equation of time, this equation does not explain the physical sense. Various empirical equations roughly divided into the stress two categories utilization strain curves; the other uses the power function of the stress-strain relationship. H. molecular theory approximation. Nonlinear viscoelastic behavior is considered to be a result of polymer molecular motion mechanism. The large number of polymer movement unit and the time change of motion, so that only the use of molecular statistical mechanics to describe the movement of polymer, reveal the relationship between macroscopic and microscopic mechanical properties of molecular structures. People polymer sport a lot of experimental studies, but understanding the mechanism of intermolecular entanglement did not unify, simplify the structure of the model so diverse molecular theory, there are beads spring chain models, hunting model, transient network model , fuzzy random network model, and so on.
        Strict continuum mechanics approach. By the principle of superposition is Boltzmalm amend the description in the form of extended linear viscoelastic behavior of the nonlinear behavior go. There are two routes of its development, a development route is the use of multiple integral expression, in theory, an accurate description of the multiple integral expression of nonlinear viscoelastic behavior, but it leads to a lot of complexity in mathematics, even if only to get to the triple integral, constitutive relationship is still very complicated, not only caused tedious calculations, but also to determine the number of experiments required material constants contained therein is striking: Another development path is to establish the appropriate single integral type expression for a particular material, the names. an extensive single integral constitutive relation expression, limited linear viscoelastic theory and BKZ model more representative.
        At this stage there is not a treatment method is perfect, and therefore commonly used linear viscoelastic constitutive equations to numerical simulation of the vertical injection molding machine injection molding mold cooling process, including the direct application of Boltzmann superposition principle and based on the assumption of a single small deformation Integral nonlinear viscoelastic constitutive relation of linear. In order to avoid the linear viscoelastic constitutive relation error analysis theory of nonlinear viscoelastic behavior brought about, it was proposed neural network simulation of vertical injection molding machine injection molding: firstly plate-shaped plastic vertical injection molding machine injection experiment, and in accordance with vertical injection molding machine injection molding process conditions experiments of vertical injection molding machine injection molding products for flow, pressure, numerical simulation cooled, the pressure of each computing unit numerical simulation of temperature and density as nerve Enter the network will get the measured vertical injection molding machine injection molding products converted to calculate the amount of displacement plane strain unit and as an output neural network, in order to complete the self-training process; since the end of the training process, in predicting the same kind of plastic contraction of different shapes of products, to the neural network input on this vertical injection molding machine injection molding products for flow, pressure, cooling analysis of the calculation results, the neural network will output the strain of each computing unit, each computing unit

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