METHOD FOR CALCULATING FLUID-STRUCTURE INTERACTION RESPONSE OF CERAMIC MATRIX COMPOSITES
20220245313 · 2022-08-04
Inventors
- Yingdong Song (Nanjing, CN)
- Xiguang GAO (Nanjing, CN)
- Guoqiang YU (Nanjing, CN)
- Dong HAN (Nanjing, CN)
- Sheng Zhang (Nanjing, CN)
- Lu ZHANG (Nanjing, CN)
- Chao YOU (Nanjing, CN)
Cpc classification
G06F17/00
PHYSICS
G06F30/23
PHYSICS
International classification
Abstract
Disclosed is a method for calculating a fluid-structure interaction response of ceramic matrix composites (CMCs). The method includes: calculating a stress-strain hysteresis curve under loading and unloading of a CMC unit cell model through a multi-scale method; performing an interpolation to calculate a hysteresis loop response under arbitrary loading and unloading through a hysteresis loop under loading and unloading calculated through the unit cell model, and using the hysteresis loop response as a proxy model for a dynamics calculation of a solid domain of a fluid-structure interaction; and calculating a fluid load on a fluid-structure interaction interface through CFD, writing a program to read the fluid load and map the same to a solid node, reading a displacement of the solid node and mapping the same onto the fluid node, where a fluid domain and the solid domain use the same time step.
Claims
1. A method for calculating a fluid-structure interaction response of ceramic matrix composites (CMCs), comprising: establishing a finite element model of a representative volume element of woven CMCs, and assigning an appropriate meso-mechanical model for a fiber bundle; calculating a hysteresis loop under loading and unloading of the finite element model of the representative volume element of the woven CMCs, and performing an interpolation to calculate a hysteresis loop response under arbitrary loading and unloading, to obtain a method for calculating a stress-strain under arbitrary loading and unloading; calculating a fluid load on a fluid-structure interaction interface through computational fluid dynamics (CFD), reading the fluid load, mapping the same onto a solid node, and performing a calculation to obtain a solid node load; obtaining a fluid-structure interaction dynamic response of a CMC structure of a current time step based on the method for calculating the stress-strain under arbitrary loading and unloading and in combination with an explicit dynamic integration and the solid node load; reading a displacement result of the solid node in the fluid-structure interaction dynamic response and mapping the same onto a fluid node, to obtain a displacement result of the fluid node on the interaction interface, wherein a fluid domain and a solid domain use the same time step; and updating a position of the fluid node according to the displacement result of the fluid node on the interaction interface, proceeding to the step of “calculating a fluid load on a fluid-structure interaction interface through computational fluid dynamics (CFD), reading the fluid load, mapping the same onto a solid node, and performing a calculation to obtain a solid node load”, and calculating a fluid-structure interaction dynamic response of the CMC structure in the next time step.
2. The method for calculating a fluid-structure interaction response of ceramic matrix composites according to claim 1, wherein the calculating a hysteresis loop under loading and unloading of the finite element model of the representative volume element of the woven CMCs, and performing an interpolation to calculate a hysteresis loop response under arbitrary loading and unloading, to obtain a method for calculating a stress-strain under arbitrary loading and unloading comprise: assigning a series of loading and unloading paths for the finite element model of the representative volume element of the woven CMCs, wherein a maximum strain is gradually increased in a loading and unloading process, to obtain hysteresis loops corresponding to different maximum strains.
3. The method for calculating a fluid-structure interaction response of ceramic matrix composites according to claim 1, wherein the calculating a hysteresis loop under loading and unloading of the finite element model of the representative volume element of the woven CMCs, and performing an interpolation to calculate a hysteresis loop response under arbitrary loading and unloading, to obtain a method for calculating a stress-strain under arbitrary loading and unloading comprise: fitting the hysteresis loop by utilizing a cubic polynomial, to obtain a polynomial coefficient a.sub.n,b.sub.n(n=1 ˜4) corresponding to different ε.sub.i through fitting:
4. The method for calculating a fluid-structure interaction response of ceramic matrix composites according to claim 1, wherein the calculating a fluid load on a fluid-structure interaction interface through computational fluid dynamics (CFD), reading the fluid load, mapping the same onto a solid node, and performing a calculation to obtain a solid node load comprise: solving the fluid domain through the CFD, to obtain geometric information and load information of a fluid element on the fluid-structure interaction interface.
5. The method for calculating a fluid-structure interaction response of ceramic matrix composites according to claim 1, wherein the calculating a fluid load on a fluid-structure interaction interface through computational fluid dynamics (CFD), reading the fluid load, mapping the same onto a solid node, and performing a calculation to obtain a solid node load comprise: pairing solid elements and fluid elements, wherein each solid element corresponds to n fluid nodes; and determining mapping of the fluid load onto the solid node through the following equation:
6. The method for calculating a fluid-structure interaction response of ceramic matrix composites according to claim 1, wherein the reading a displacement result of the solid node in the fluid-structure interaction dynamic response and mapping the same onto a fluid node, to obtain a displacement result of the fluid node on the interaction interface comprise: matching any surface of each solid element with n fluid nodes in the surface; and determining mapping of a displacement of the solid node onto the fluid node through the following equation:
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0035] The present disclosure will be further described below with reference to the accompanying drawings:
[0036]
[0037]
[0038]
[0039]
[0040]
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0041] The present disclosure is described in more detail below with reference to the accompanying drawings.
[0042] As shown in
[0043] Firstly, a finite element model of a representative volume element (RVE) of woven CMCs is established, a self-defined meso-mechanical model may be added in the RVE model, and a strain under loading and unloading is assigned, to obtain a constitutive response curve under loading and unloading. In the dynamic calculation, it is very time-consuming to directly use the RVE model for a calculation. Therefore, a series of hysteresis loops under loading and unloading are calculated through the RVE model first, and in the dynamic calculation, an interpolation calculation is carried out among a series of hysteresis loops calculated before. As shown in
[0044] where σ denotes a stress, ε denotes the strain, ε.sub.i denotes a maximum strain of the i-th hysteresis loop, + and − denote loading and unloading respectively, and a polynomial coefficient may be expressed in the following form:
[0045] where f(ε.sub.i) denotes a function related to ε.sub.i.
[0046] In a dynamic calculation process, a current maximum hysteresis loop is calculated first, and if a maximum strain of the current hysteresis loop is ε.sub.t, which is between and maximum strains ε.sub.i and ε.sub.i+1 corresponding to the hysteresis loops calculated through the RVE model, the polynomial coefficient of the current hysteresis loop may be expressed as:
[0047] When an amplitude changes from large to small, it is necessary to perform an interpolation in the hysteresis loop, as shown in
[0048] where A and B denote upper and lower vertices of the hysteresis loop respectively.
[0049] A stress-strain response of the woven CMCs under arbitrary loading and unloading can be calculated through the above process, and is applied to a nonlinear dynamic calculation of the CMCs.
[0050] In a fluid-structure interaction calculation, if a dynamic solution method requiring an iteration such as Newmark is used in the solid domain, variable stiffness and a hysteresis behavior of the CMCs will cause a stiffness discontinuity during loading and unloading, which will bring a difficulty to the dynamic solution. In the present patent, an explicit integration method such as a central difference method is used to calculate a vibration response, so as to avoid iterating a constitutive model under loading and unloading, and avoid a divergence of a solution result.
[0051] Interface mapping of the fluid-structure interaction includes load mapping and displacement mapping. Load mapping is to map a fluid acting force onto a solid finite element node prior to a dynamic calculation of each time step. After a displacement is obtained through the dynamic calculation, displacement mapping is to map the displacement onto the fluid node.
[0052] As shown in
[0053] where S denotes a solid, f denotes a fluid, F.sub.si, denotes an equivalent fluid load acting on the i-th node of certain solid element, N.sub.i.sup.kdenotes a corresponding isoparametric interpolation coefficient during mapping an acting force of the k-th fluid element onto the i-th solid node, and F.sub.f.sup.k denotes an acting force, on a current solid element, of the k-th fluid element.
[0054] For the isoparametric interpolation coefficient, it is necessary to calculate parameter coordinates of the fluid node in the solid element, and the isoparametric interpolation coefficient can be calculated through a numerical method such as the Newton iteration method.
[0055] As shown in
[0056] where u.sub.fj, denotes a displacement of the j-th fluid node on any fluid element, N.sub.i.sup.j denotes a corresponding isoparametric interpolation coefficient during mapping a displacement of the i-th solid node of the solid element onto the j-th fluid node, the isoparametric interpolation coefficient is calculated through the Newton iteration method, and u.sub.si denotes a displacement of the i-th solid node.
[0057] Next, the method for calculating the fluid-structure interaction response of the ceramic matrix composites is specifically described in combination with a specific embodiment, and the method includes the following steps.
[0058] S1: establishing a finite element model of a representative volume element of woven CMCs, and assigning an appropriate meso-mechanical model for a fiber bundle.
[0059] S2: assigning a series of loading and unloading paths for the finite element model of the representative volume element, where a maximum strain shall be gradually increased during loading and unloading, to obtain hysteresis loops corresponding to different maximum strains, and the more hysteresis loops are obtained, the more accurate a calculation result will be. It should be noted that during unloading, unloading shall be carried out until a crack is closed. In other words, if unloading is continued, the stress-strain relationship becomes linear.
[0060] S3: fitting these hysteresis loops by utilizing a cubic polynomial to obtain sufficient accuracy, since convexity and concavity of each hysteresis loop usually change at most once, where a polynomial coefficient a.sub.n,b.sub.n(n=1-4) corresponding to different ε.sub.i obtained through fitting is as follows:
[0061] S4: when any maximum strain E.sub.t is between maximum strains calculated through certain two RVE models, that is, (ε.sub.i<ε.sub.t<ε.sub.i+t), performing an interpolation on a polynomial coefficient of a current hysteresis loop as follows:
[0062] S5: when an amplitude changes from large to small, and loading and unloading occur inside a maximum hysteresis loop, on the basis of knowing a current stress-strain, obtaining a stress at the next moment through the following equation:
[0063] S7: pairing solid elements and fluid elements, where fluid grids are usually much denser than solid grids, and each solid element corresponds to n fluid nodes; and mapping a fluid load onto a solid node through the following equation, where an isoparametric interpolation coefficient can be calculated through the Newton iteration method on the basis of knowing interface center coordinates of a fluid and four solid node coordinates:
[0064] S8: solving a fluid-structure interaction dynamic response of a CMC structure at a current time step based on the above-mentioned method for calculating the stress-strain under arbitrary loading and unloading, and in combination with the explicit dynamic integration, where a solid node load is calculated in S7.
[0065] S9: mapping a displacement of the solid node onto the fluid node of an interaction interface according to a displacement result of the solid node calculated in S8, where displacement mapping of the solid node also matches certain surface of each solid element and n fluid nodes in the surface, and the displacement of the solid node is mapped to the fluid node through the following equation, where similar to the previous step, an isoparametric interpolation coefficient is calculated through the Newton iteration method;
[0066] S10, updating a flow field node position according to a displacement result of the fluid node of the interaction interface calculated in S9, and performing a calculation of the next interaction step, that is, proceeding to S6.
[0067] It should be noted that, as used herein, terms such as “upper”, “lower”, “left”, “right”, “front” and “back” are merely employed for ease of a description, and not intended to limit the implementable scope of the present disclosure, and a change or adjustment of its relative relation shall also be deemed as falling within the implementable scope of the present disclosure without a substantial alteration of a technical content.
[0068] The above embodiments are provided merely for an objective of describing the present disclosure and are not intended to limit the scope of the present disclosure. The scope of the present disclosure is defined by the appended claims. Various equivalent replacements and modifications made without departing from the spirit and scope of the present disclosure should all fall within the scope of the present disclosure.