JP2016148888A - Calculation method of adhesive characteristics and calculator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for preparing an adhesive analysis model capable of reducing a computation time by combining analysis models of adhesive in the strength analysis of an adhesion junction.SOLUTION: A method for calculating adhesive characteristics includes a pre-analysis process for modeling adhesive with at least one element of a beam element and a solid element to identify a stress concentration zone and a model creation process for modeling a stress concentration domain in the periphery of an adhesive section with a cohesive element and an adhesive section of an elastic domain other than that with at least one element of the beam element and the solid element.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a method and an apparatus for calculating adhesive properties of a finite element analysis model in an adhesive joint structure using an adhesive.

  Mechanical joints using bolts and nuts, welding, etc. are used for the joints of members, but CFRP is generally adhesively bonded due to its characteristics such as strength reduction due to fiber breakage and high temperature heat resistance. Is used.

  Adhesive bonding that uses adhesive element or adherend element obtained by dividing an adhesive or adherend into elements, or a portion where the adhesive element and adherend element are joined, using the Finite Element Method (FEM) In the strength analysis of the part, an adhesive model creation method using a beam element has been proposed so far, and the stress of each mode I (peeling) and mode II (in-plane shear) mode depends on the strength of the adhesive. When it reaches, it has been determined to be broken (see, for example, Patent Document 1).

JP 2009-99132 A

  However, it is known that the actual fracture mainly occurs in these mixed modes, and the adhesive fracture phenomenon reaches the fracture after softening due to the occurrence of fine damage, etc. There was a problem that could not be considered. In rigorous analysis, it has been proposed to model with a cohesive element (cohesive element, cohesive element) in consideration of these failure modes.

  In addition, when the area of the joint is relatively small, such as spot welding, and it can be considered that there is no stress distribution in the bonding surface, it is possible to determine the fracture by comparing the generated stress of the beam element with the joint strength. When the bonding area is large as in the case of adhesive bonding, the stress distribution at the bonded end and inside cannot be ignored, and accurate calculation of the stress at the bonded end that often starts fracture is a beam element. It was difficult.

  However, when all the bonded joints are modeled with bonding force elements (cohesive elements, cohesive elements), the time required for model creation and calculation becomes enormous, and the adhesive thickness needs to be constant. For this reason, it has been difficult to accurately model an adhesive joint.

  The present invention can reduce the cost of model creation / calculation when calculating the adhesive properties of the fracture strength analysis model at the adhesive joint, especially modeling even when the adhesive thickness differs at the adhesive joint It is an object of the present invention to provide a method and an apparatus for calculating adhesive properties.

(1) An adhesive structure in which two adherends are bonded with an adhesive is divided into a plurality of elements, and the adherend element of the adherend is used as a shell element, and as an adhesive element of the adhesive, This is a method for calculating adhesive properties using a finite element analysis model that combines at least one of beam elements and solid elements in addition to coherent elements, and cohesive adhesive elements that are thought to break due to softening of the adhesive. Set as an element, other adhesive elements are set as either beam elements or solid elements, and the strength of the adhesive joint where the adherend element and the adhesive element are joined by the destruction of the coherent element A method for calculating adhesive properties.
(2) When setting the coherent element, the adhesive element is set in advance as either a beam element or a solid element, and the normal stress and shear stress of the adhesive element at the time of load deformation are set in the respective adhesive elements. Pre-analysis is performed to identify an adhesive element that is 80% or more of the damage initiation stress in the deformation mode. Based on the result of the pre-analysis, the adhesive is peeled off, and the stress state in the shear direction is determined after the material yield. The method for calculating adhesive properties according to (1), wherein the adhesive element in a state is set as a coherent element.
(3) The method for calculating adhesive properties according to (2), wherein, in the preliminary analysis, the material physical properties of the adhesive element are set so that the stress decreases after the material yield.
(4) Splitting means for splitting an adhesive structure in which two adherends are bonded with an adhesive into a plurality of elements, the adherend element of the adherend as a shell element, and an adhesive element of the adhesive As an apparatus for calculating adhesive properties, including at least a finite element model forming means for forming a finite element analysis model combining at least one of a beam element and a solid element in addition to a coherent element, the adhesive softens The adhesive element that is considered to cause fracture is a coherent element, and the model of the other adhesive joint is set to either a beam element or a solid element, and by the destruction of the coherent element, the adherend element and the adhesive element An apparatus for calculating adhesive properties, comprising: a determination unit that determines the strength of an adhesive bonding portion to which an adhesive element is bonded.
(5) When setting the coherent element, the adhesive element is set in advance as either a beam element or a solid element, and the normal stress and shear stress of the adhesive element at the time of load deformation are set in the respective adhesive elements. Pre-analysis is performed to identify an adhesive element that is 80% or more of the damage initiation stress in the deformation mode. Based on the result of the pre-analysis, the adhesive is peeled off, and the stress state in the shear direction is determined after the material yield. The apparatus for calculating adhesive properties according to (4), wherein the adhesive element in a state is set as a coherent element.
(6) The adhesive property calculation apparatus according to (5), wherein in the preliminary analysis, the material physical property of the adhesive element is set so that the stress decreases after the material yield.

  The terms are defined below.

  In the present invention, the “adhesive” refers to a base material bonded by an adhesive, and the shape does not need to be flat on the bonding surface, and a curved surface may be formed. Further, the two adherends facing each other at the bonding portion need not have a uniform thickness.

  In the present invention, an “adhesive” is a substance composed of a material different from the adherend that forms the joint together, and unlike rivet joining or welded joining, , A material for bonding adherends together by adhering along the surface of the adherend as an amorphous object having a Young's modulus lower than that of the adherend, and then curing by heating or drying . Typically, it is a liquid or gel-like object before curing. From the viewpoint of improving the bonding strength, the adhesive may be pretreated on the adherend or may be composed of a plurality of components. Moreover, not only liquid but solid and powder may be sufficient.

  In the present invention, the “adhesive property” refers to an item to be analyzed and evaluated at the bonded portion. Specific examples include fracture strength, stress, strain, temperature, and the like.

  According to the present invention, in calculating the adhesive property of the fracture strength analysis model in the adhesive joint, it is possible to reduce the model creation and calculation costs, and more strictly even when the adhesive thickness is different in the adhesive joint. It becomes possible to model.

It is a schematic diagram of the adhesion structure in this embodiment. It is the figure which showed the flow regarding the calculation method of the adhesive agent property in this invention. It is the figure which showed an example of the stress-displacement diagram of a coherent element. It is a schematic diagram which shows an example at the time of modeling the adhesion part of FIG. 1 in a prior analysis by a solid element. It is a schematic diagram which shows an example at the time of converting into a cohesive element the adhesive agent element of a stress concentration part after a prior analysis, and modeling.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

  In the present invention, a structural analysis for the purpose of determining whether or not the bonded portion is broken will be described with respect to the structure having the bonded portion.

  FIG. 1 shows a schematic diagram of an adhesive structure 100 having an adhesive portion in the present embodiment. Specifically, the adherend 1 and the adherend 2 have a configuration in which they are adhered by an adhesive 3 between them.

  FIG. 2 is a diagram showing a flow relating to a method for determining the type of element of the bonded portion in the present invention.

  First, in the pre-analysis step (procedure 1), in order to determine by calculation the stress concentration portion that can be a fracture starting point in the bonding structure 100 shown in FIG. 1, the adhesive element is set in advance as either a beam element or a solid element. . At this time, the entire adhesive may be composed of only the beam element or the solid element, or may be composed of a combination of both the beam element and the solid element. A pre-analysis is performed to identify an adhesive element in which the normal stress and shear stress of each adhesive element are 80% or more of the damage initiation stress of each deformation mode in each adhesive element during load deformation. Here, FIG. 4 shows an enlarged schematic perspective view of a part of the finite element model when the adhesive 3 in the part X of the adhesive structure 100 shown in FIG. 1 is modeled as a solid element. Solid elements 11 to 20 represent finite elements of the adhesive 3. The upper nodes of the solid elements 11 to 20 are shared with the adherend 1 and the lower nodes are shared with the adherend 2. As a material characteristic of the adhesive element, it is preferable to use a linear elastic body.

  Subsequently, in the adhesive stress determination step (procedure 2), the tensile / compressive stress and shear stress in the mode I and II directions generated in the adhesive element in the pre-analysis are 80% of the damage initiation stress in each adhesive element. The above adhesive element can also be regarded as a stress concentration part. In all adhesive elements, if the tensile / compressive stress in mode I, II direction and the shear stress are less than 80% of the damage initiation stress in the coherent element, it is determined that the adhesive does not break, End the analysis.

  In the stress concentration part element conversion step (procedure 3) of the adhesive, the adhesive element regarded as the stress concentration part by the above procedure 2 is converted into a coherent element. In addition, since it is necessary for the coherent element to have a constant adhesion thickness, when the type of the element is converted, the model shape may be modified at a location where the adhesion thickness is different. Here, FIG. 5 shows a schematic perspective view showing an example of a finite element model obtained by element conversion from FIG. Elements 11 ′ and 16 ′ to 20 ′ are cohesive elements in which the stress of the adhesive element is equal to or greater than the damage initiation stress, and elements 12 ′ and 15 ′ are 80% of the damage initiation stress. It is less than 100% and indicates a coherent element that is regarded as a stress concentration part and has been subjected to element conversion.

  As shown in the stress-displacement diagram of the coherent element in FIG. 3, the coherent element shows elastic behavior at the initial stage of deformation, but the deformation becomes large, and softening starts when the stress reaches the yield start point (viscoelastic behavior). ) When the stress finally reaches zero, the fracture occurs. In the present invention, only the linear type softening behavior of the coherent element is shown, but the present invention can also be applied to a coherent element that exhibits other behavior.

  In the re-analysis step (procedure 4), the analysis is performed again on the model of the bonded structural member converted by the above-described procedure, and the destruction of the adhesive is determined by determining the destruction of the coherent element. That is, by determining the analysis result of the coherent element, it is possible to determine the strength of the adhesive joint where the adherend element and the adhesive element are joined, and to calculate the strength of the adhesive structure.

  As described above, the coherent element exhibits an elastic behavior until yielding, but it is preferable to determine that a fracture phenomenon occurs when the stress decreases with deformation after the yielding and finally reaches zero.

1: Adhering material 2: Adhering material 3: Adhesives 11 to 20: Solid elements 11 ′, 12 ′, and 15 ′ to 20 ′ representing the adhesive 3 Cohesive element

Claims (6)

  An adhesive structure in which two adherends are bonded with an adhesive is divided into a plurality of elements, and the adherend element of the adherend is used as a shell element, and an adhesive element of the adhesive is used as a coherent element. In addition, it is a calculation method of adhesive properties by a finite element analysis model that combines at least one of beam element and solid element, and the adhesive element that is considered to break due to softening of the adhesive is set as a coherent element The other adhesive element is set to either a beam element or a solid element, and the strength of the adhesive joint where the adherend element and the adhesive element are bonded is determined by the destruction of the coherent element. , Calculation method of adhesive properties.   When setting the coherent element, the adhesive element is set in advance as either a beam element or a solid element, and the normal stress and shear stress of the adhesive element at the time of load deformation depend on each deformation mode in the adhesive element. Pre-analysis is performed to identify an adhesive element that is 80% or more of the damage initiation stress. Based on the result of the pre-analysis, the adhesive is peeled off, and the stress state in the shear direction is the state after material yielding. The method of calculating adhesive properties according to claim 1, wherein the adhesive element is set as a coherent element.   The calculation method of the adhesive characteristic of Claim 2 which sets the material physical property of an adhesive element in the said prior analysis so that stress may fall after a material yield.   Splitting means for splitting an adhesive structure in which two adherends are bonded with an adhesive into a plurality of elements, the adherend element of the adherend as a shell element, and a coherent as an adhesive element of the adhesive In addition to the element, a calculation device for adhesive properties including at least a finite element model forming means for forming a finite element analysis model combining at least one of a beam element and a solid element, the adhesive softens and breaks down The adhesive element that is considered to be generated is a coherent element, and the model of the other adhesive joint is set to either a beam element or a solid element, and the adherend element and the adhesive element are caused by the destruction of the coherent element. An apparatus for calculating adhesive properties, comprising: a determination unit that determines the strength of an adhesive joint portion to which the two are joined.   When setting the coherent element, the adhesive element is set in advance as either a beam element or a solid element, and the normal stress and shear stress of the adhesive element at the time of load deformation depend on each deformation mode in the adhesive element. Pre-analysis is performed to identify an adhesive element that is 80% or more of the damage initiation stress. Based on the result of the pre-analysis, the adhesive is peeled off, and the stress state in the shear direction is the state after material yielding. 5. The adhesive property calculation device according to claim 4, wherein the adhesive element is set as a coherent element. 6. The adhesive property calculation apparatus according to claim 5, wherein, in the preliminary analysis, the material property of the adhesive element is set so that the stress decreases after the material yields.

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