CN-116504334-B - Fatigue failure mode prediction method for composite material and metal rivet bonding mixed connection structure

CN116504334BCN 116504334 BCN116504334 BCN 116504334BCN-116504334-B

Abstract

A fatigue failure mode prediction method for a composite material and metal rivet bonding mixed connection structure is characterized in that mechanical connection failure is preset for the composite material/metal rivet bonding mixed connection, a material parameter prediction model based on water absorption, a chemical structure and environmental temperature is constructed, the maximum strain of each material in a joint structure is calculated, an original material epsilon-N curve, namely a relation curve between fatigue loading maximum strain and fatigue cycle life is processed to meet the prediction requirements of different environmental influences, and failure corresponding preset specific types are judged according to the maximum strain and equal life curve curves of each material in the joint structure. The invention simplifies the test flow, simultaneously obviously shortens the test period, and can realize quick calculation based on the common personal notebook computer.

Inventors

ZHU PING
ZHANG HANYU
LIU ZHAO
ZHANG LEI
SONG ZHOUZHOU

Assignees

上海交通大学

Dates

Publication Date: 20260512
Application Date: 20221031

Claims (7)

1. The fatigue failure mode prediction method for the composite material and metal rivet bonding mixed connection structure is characterized by comprising the following steps of: firstly, presetting a fatigue failure mode comprising mechanical connection failure, namely type A failure and adhesive bonding failure, namely type B failure for composite material/metal rivet bonding mixed connection; Secondly, constructing a material parameter prediction model based on water absorption, chemical structure and environmental temperature, which specifically comprises the following steps: Wherein: is a predicted value of the mechanical property parameter of the material, Aging item M is the moisture absorption value, k is the number of functional groups sensitive to aging obtained by infrared spectrum analysis, a, b, c and lambda are fitting parameters, and the environmental temperature term , T is the real ambient temperature value, Alpha and beta represent fitting coefficients of each material to temperature items, and i represents the order of fitting curves; Thirdly, calculating the maximum strain of each material in the joint structure, namely, after endowing the material parameter prediction model obtained in the second step with material properties corresponding to connection, carrying out grid division, displacement boundary condition setting and contact setting, and extracting load peaks in fatigue cycles to be predicted, namely, force values corresponding to wave peaks in fatigue loading cycle curves as boundary conditions of forces; fourth, for the original material The curves, namely relation curves between the maximum strain of fatigue loading and the fatigue cycle life are processed to meet the prediction requirements of different environmental influences, namely the fatigue life of the material under the conditions of different stress ratios of tension and compression is described by improving life curves such as the construction of two S-N curves of tension, tension and compression and the like of a Kawai method; and fifthly, judging the specific type corresponding to the failure in the first step according to the maximum strain of each material in the joint structure obtained in the third step and the equal-life curve obtained in the fourth step.
2. The method for predicting fatigue failure mode of composite material and metal rivet bonding mixed connection structure according to claim 1, wherein the fatigue failure mode is that under the combined action of different damp-heat environment and fatigue load conditions, each material forming the mixed connection has different relative competitive advantages, so that multiple failure modes can occur, wherein mechanical connection failure, namely A-type failure and cementing failure, namely B-type failure exist together, and the connection is completely failed; The mechanical connection failure includes fastener failure, namely a type A1 failure and substrate failure, namely a type A2 failure; The cementing failure comprises composite material layering, namely B1 type failure and bonding layer failure, namely B2 type failure; In the fatigue failure mode, when any mechanical connection failure occurs, the hybrid joint is degraded into a cohesive joint, so that A1 type failure and A2 type failure cannot occur on one joint in the failure process, and likewise B1 type failure and B2 type failure cannot occur simultaneously in the failure process, and the sequence of the failure modes is changed due to different competitive advantages of various materials under different conditions, so that for the same hybrid connection, under different damp and hot conditions and fatigue load conditions, the failure modes specifically comprise A1-B1 type failure, A1-B2 type failure, A2-B1 type failure, B1-A2 type failure, B2-A1 type failure and B2-A2 type failure, wherein "_" represents the front and back sequence of the occurrence of the failure types, namely a first stage and a second stage; The fatigue failure mode refers to a specific form that a connecting structure is completely disconnected after fatigue loading or is partially damaged when reaching a fatigue limit; The failure mode sequence refers to that the mixed connection is divided into two sub-parts of gluing and riveting, wherein one part of the mixed connection fails without causing structural disconnection, which means that rivet bonding the complete failure of the mixed connection structure is accompanied with the complete failure of gluing and riveting, and the failure sequence is necessarily existed, wherein A1 and A2 cannot coexist in the failure, and B1 and B2 cannot coexist.
3. The method for predicting fatigue failure mode of composite material and metal rivet bonding mixed connection structure according to claim 1, wherein the material parameters are material elastic modulus, poisson ratio and strength used in finite element calculation; Analyzing the aged polymer material by using an infrared spectrometer to obtain a spectrogram, wherein the absorption peak value corresponding to the functional group; The functional groups sensitive to aging refer to functional groups with obvious spectral absorption peak changes after aging, and 2 functional groups with the most obvious changes are recommended to be selected as variables according to actual conditions.
4. The method for predicting fatigue failure mode of composite material and metal rivet bonding mixed connection structure according to claim 1, wherein said meshing means establishing a numerical model and meshing according to real structural geometry information; the displacement boundary condition setting refers to the displacement constraint setting of the connecting piece according to the actual external displacement constraint condition; The contact arrangement refers to the contact between the fastener and the base plate, and is of a rigid contact type.
5. The method for predicting fatigue failure mode of composite material and metal rivet bonding mixed connection structure according to claim 1, wherein the fifth step specifically includes: 5.1 Substitution of predicted maximum strain of the mixed-linked component materials under a specific environmental influence into the component materials under the specific environmental influence Curve to calculate fatigue life of each component material Wherein: the ratio of =1, 2, the number of the first and second embodiments of the present invention, respectively correspond to the composite material in the surface, the composite material interlayer, the adhesive layer, the metal plate and the rivet, and are the smallest I.e. The corresponding material is the first failure part, so that the failure type of the first stage is judged; 5.2 Considering the difference of fatigue competition advantages of different materials in the joint under different fatigue loading and environmental factors, predicting different failure types when environmental conditions are changed for the same joint, drawing a fatigue competition machine graph according to q-N curves of corresponding parts of different failure types, and drawing a fatigue type partition graph by extracting intersection points of the q-N curves under different environments; 5.3 Considering the problem of failure sequence, the structure is not completely disconnected after the first stage of failure occurs, returning to the third step, deleting the grid of the numerical model corresponding to the material of the failed part, degrading the rivet bonding hybrid connection structure into a pure cementing or riveting form, and recalculating the maximum strain When the damage reaches 100%, fatigue failure is considered to occur, namely the second stage is started, and the residual fatigue life percentage of the unbroken part is After grid deletion, the maximum strain is recalculated, again based on Curve acquisition of second stage pseudo fatigue life Further obtaining the actual fracture life of the rest part in the second stage as Wherein: the smallest corresponding material, namely the first failure part in the second stage, so that the failure type in the second stage is preset and judged according to the failure mode in the first stage; 5.4 The method comprises the steps of determining the fatigue type of a mixed connection, namely, the fatigue type of the mixed connection is determined by a first-stage fatigue type partitioning diagram, namely, the fatigue type of the mixed connection is determined by a second-stage fatigue type partitioning diagram, wherein the second-stage fatigue type is also influenced by a material fatigue competition mechanism, the fatigue competition mechanism diagram is drawn according to q-N curves of corresponding parts of different failure types, the intersection points of the q-N curves under different environments are extracted on the basis of the fatigue type partitioning diagram of the first-stage fatigue type, the second-stage fatigue type partitioning diagram is drawn, and the influence rule of different fatigue loading and environmental factors on the second-stage failure type is judged by the diagram, so that the fatigue failure type prediction of the mixed connection influenced by the environment is realized.
6. The method for predicting fatigue failure mode of composite material and metal rivet bonding mixed connection structure according to claim 5, wherein the fatigue damage is that in the fatigue loading process, even if no fracture occurs, microcrack initiation and expansion still exist in the interior of material, so that certain damage is accumulated in the position where no failure occurs in the first stage; the damage accumulation criterion is Miner fatigue damage linear accumulation criterion, which is used for meeting the calculation force requirement of quick prediction and ensuring the prediction accuracy; The pseudo fatigue life is calculated by assuming that the initial fatigue damage does not occur in each part at the beginning of the second stage.
7. A system for realizing the fatigue failure mode prediction method of the composite material and metal rivet bonding mixed connection structure according to any one of claims 1-6 is characterized by comprising a failure mode predefining module, a material rigidity and strength performance prediction module considering environmental factors, a maximum strain extraction module of each material in a joint structure and a processing original material The system comprises a curve module and a failure mode judging module, wherein the failure mode predefining module performs summarizing analysis according to a fracture mechanism of a connecting structure to obtain all possible failure modes in theory, the material rigidity and strength performance predicting module considering the influence of environmental factors constructs a material parameter predicting model based on water absorption, a chemical structure and environmental temperature according to experimental data of moisture absorption, infrared spectrum and material mechanical properties to obtain rigidity and strength performance of materials under different wet and hot working conditions, the maximum strain extracting module of each material in a joint structure builds a numerical model according to the actual connecting piece geometry and service loaded working condition, performs finite element simulation calculation, obtains the maximum strain of each material in connection through post-processing of finite element calculation results, and processes an original material The curve module describes the fatigue life of the composite material in the states of different stress ratios of pulling and pressing by improving the life curve graph of a Kawai method in the structure of a pulling-pulling curve and a pressing-pressing curve and the like according to material fatigue loading test data, and the failure mode judging module judges the failure types of the first stage and the second stage of the mixed connection in two steps according to the life curve of the maximum strain and the material and the like, so that the fatigue failure type of the mixed connection influenced by the environment is completely predicted.

Description

Fatigue failure mode prediction method for composite material and metal rivet bonding mixed connection structure Technical Field The invention relates to a technology in the field of composite material processing, in particular to a method for rapidly predicting a fatigue failure mode of a composite material and metal rivet bonding mixed connection structure under the influence of environmental factors. Background Hybrid (riveted/bonded) joints include joining advanced composite materials and high strength alloys together to form a complete structure, which differs from conventional joints in a relatively single failure type, and hybrid joint failure modes are diverse. And the failure mode of the mixed connection is difficult to predict because the mixed connection faces the common influence of the damp-heat aging effect and different fatigue loading in the service process. Aiming at the fatigue failure problem in the service environment of the composite material and metal rivet bonding mixed connection structure, how to analyze the influence of the damp-heat aging factors and how to analyze the relative strength of each part of the joint under different fatigue loading conditions is the key for realizing the rapid prediction of the fatigue failure mode. Disclosure of Invention Aiming at the defects that the prior art does not consider a complex connection structure with a glue layer and cannot calculate the fatigue life of connection under the influence of wet heat aging in the actual service process, the invention provides a fatigue failure mode prediction method for a composite material and metal rivet bonding mixed connection structure. Based on priori knowledge, preset failure categories, the relative advantages of materials under specific fatigue loading and environmental influence working conditions are compared by utilizing the proposed internal grouping competition fatigue mechanism of the hybrid joint, and the result is matched with the preset failure categories, so that the fatigue failure types are rapidly predicted. The invention is realized by the following technical scheme: The invention relates to a fatigue failure mode prediction method for a composite material and metal rivet bonding mixed connection structure, which comprises the following steps: First, the composite/metal rivet bonding hybrid bond presets include a fatigue failure mode of mechanical bond failure, i.e., type a failure, and glue failure, i.e., type B failure. The fatigue failure mode refers to that under the combined action of different damp and hot environments and fatigue load conditions, materials forming the mixed connection have different relative competitive advantages, so that multiple failure modes possibly occur, wherein mechanical connection failure, namely A-type failure and cementing failure, namely B-type failure exist simultaneously, and the connection is completely failed. The mechanical connection failure includes fastener failure, i.e., a type A1 failure, and substrate failure, i.e., a type A2 failure. The adhesive failure includes composite delamination, i.e., type B1 failure, and tie layer failure, i.e., type B2 failure. In the fatigue failure mode, when any type of mechanical connection failure occurs, the hybrid joint will degrade into a cohesive joint, and thus a type A1 failure and a type A2 failure cannot occur on a joint during the failure. Also, during the destruction process, B1 type failures and B2 type failures cannot occur at the same time. The order of failure modes may also vary due to the different competitive advantages of the various materials under different conditions. Thus, for the same hybrid connection, under different wet and hot conditions and fatigue loading conditions, failure modes specifically include A1_B1 type failure, A1_B2 type failure, A2_B1 type failure, A2_B2 type failure, B1_A1 type failure, B1_A2 type failure, B2_A1 type failure, and B2_A2 type failure, where "_" indicates the order in which the failure types occur, i.e., the first stage and the second stage. The preset failure mode already contains all failure possibilities for this type of connection. The fatigue failure mode refers to a specific form that the connecting structure is completely disconnected after fatigue loading or is partially destroyed when reaching the fatigue limit. The damp-heat environment refers to the temperature range of-40 to 80 ℃ and the humidity range of 0 to 100 percent relative humidity. The competitive advantage is that a certain material or structure shows more excellent performance than other materials or structures under specific damp-heat conditions and fatigue loading conditions. The mechanical connection failure refers to the release of the constraint effect of the rivet on the composite material substrate and the metal substrate. The cementing failure refers to the release of the binding action of the adhesive on the composite material substrate and the metal substrate. The fail