注塑模具毕业设计外文翻译--立体光照成型的注塑模具工艺的综合模拟(编辑修改稿)

注塑模具毕业设计外文翻译--立体光照成型的注塑模具工艺的综合模拟(编辑修改稿)内容摘要：

where subscripts I, II represent the parameters of Part I and Part II, respectively, and CmI and CmII indicate the moving free meltfronts of the surfaces of the divided two parts in the filling stage. It should be noted that, unlike conditions Eqs. 7 and 8, ensuring conditions Eqs. 9 and 10 are upheld in numerical implementations bees more difficult due to the following reasons: 1. The surfaces at the same section have been meshed respectively, which leads to a distinctive pattern of finite elements at the same section. Thus, an interpolation operation should be employed for u, v, T, P during the parison between the two parts at the juncture. 2. Because the two parts have respective flow fields with respect to the nodes at point A and point C (as shown in Fig. 2b) at the same section, it is possible to have either both filled or one filled (and one empty). These two cases should be handled separately, averaging the operation for the former, whereas assigning operation for the latter. 3. It follows that a small difference between the meltfronts is permissible. That allowance can be implemented by time allowance control or preferable location allowance control of the meltfront nodes. 4. The boundaries of the flow field expand by each meltfront advancement, so it is necessary to check the condition Eq. 10 after each change in the meltfront. 5. In view of abovementioned analysis, the physical parameters at the nodes of the same section should be pared and adjusted, so the information describing finite elements of the same section should be prepared before simulation, that is, the matching operation among the elements should be preformed. 7 Fig. 2a,b. Illustrative of boundary conditions in the gapwise direction a of the middleplane model b of the surface model Numerical implementation Pressure field. In modeling viscosity η, which is a function of shear rate, temperature and pressure of melt, the shearthinning behavior can be well represented by a crosstype model such as: where n corresponds to the powerlaw index, and τ∗ characterizes the shear stress level of the transition region between the Newtonian and powerlaw asymptotic limits. In terms of an Arrheniustype temperature sensitivity and exponential pressure dependence, η0(T, P) can be represented with reasonable accuracy as follows: Equations 11 and 12 constitute a fiveconstant (n, τ∗ , B, Tb, β) representation for viscosity. The shear rate for viscosity calculation is obtained by: Based on the above, we can infer the following filling pressure equation from the governing Eqs. 1–4: where S is calculated by S = b0/(b−z)2 η dz. Applying the Galerkin method, the pressure finiteelement equation is deduced as: 8 where l_ traverses all elements, including node N, and where I and j represent the local node number in element l_ corresponding to the node number N and N_ in the whole, respectively. The D(l_) ij is calculated as follows: where A(l_) represents triangular finite elements, and L(l_) i is the pressure trial function in finite elements. Temperature field. To determine the temperature profile across the gap, each triangular finite element at the surface is further divided into NZ layers for the finitedifference grid. The left item of the energy equation (Eq. 4) can be expressed as: where TN, j,t represents the temperature of the j layer of node N at time t. The heat conduction item is calculated by: where l traverses all elements, including node N, and i and j represent the local node number in element l corresponding to the node number N and N_ in the whole, respectively. The heat convection item is calculated by: For viscous heat, it follows that: Substituting Eqs. 17–20 into the energy equation (Eq. 4), the temperature equation 9 bees: Structural analysis of the mold The purpose of structural analysis is to predict the deformation occurring in the photopolymer mold due to the thermal and mechanical loads of the filling process. This model is based on a threedimensional thermoelastic boundary element method (BEM). The BEM is ideally suited for this application because only the deformation of the mold surfaces is of interest. Moreover, the BEM has an advantage over other techniques in that puting effort is not wasted on calculating deformation within the mold. The stresses resulting from the process loads are well within the elastic range of the mold material. Therefore, the mold deformation model is based on a thermoelastic formulation. The thermal and mechanical properties of the mold are assumed to be isotropic and temperature independent. Although the process is cyclic, timeaveraged values of temperature and heat flux are used for calculating the mold deformation. Typically, transient temperature variations within a mold have been restricted to regions local to the cavity surface and the nozzle tip [8]. The transients decay sharply with distance from the cavity surface and generally little variation is observed beyond distances as small as mm. This suggests that the contribution from the transients to the deformation at the mold block interface is small, and therefore it is reasonable to neglect the transient effects. The steady state temperature field satisfies Laplace’s equation 2T = 0 and the timeaveraged boundary conditions. The boundary conditions on the mold surfaces are described in detail by Tang et al. [9]. As for the mechanical boundary conditions, the cavity surface is subjected to the melt pressure, the surfaces of the mold connected to the worktable are fixed in space, and other external surfaces are assumed to be stress free. The derivation of the thermoelastic boundary integral formulation is well known [10]. It is given by: where uk, pk and T are the displacement。