AU2020101415A4

AU2020101415A4 - Method for quickly selecting three-dimensional (3D) micro-scale cutting simulation of carbon fiber reinforced polymer

Info

Publication number: AU2020101415A4
Application number: AU2020101415A
Authority: AU
Inventors: Tianyu Gu; Zhenyuan JIA; Fuji WANG; Xiaonan WANG; Boyu Zhang; Xiang Zhao
Original assignee: Dalian University of Technology
Current assignee: Dalian University of Technology
Priority date: 2019-07-19
Filing date: 2020-07-20
Publication date: 2020-08-20
Anticipated expiration: 2028-07-20
Also published as: CN110427668B; CN110427668A

Abstract

METHOD FOR QUICKLY SELECTING THREE-DIMENSIONAL (3D) MICRO-SCALE CUTTING SIMULATION OF CARBON FIBER REINFORCED POLYMER ABSTRACT A method for selecting a mass scaling factor for three-dimensional (3D) micro-scale cutting simulation of carbon fiber reinforced polymer (CFRP) in the present invention relates to the field of composite material cutting simulation. In particular, the present invention relates to a method for selecting a mass scaling factor for 3D micro-scale cutting simulation of CFRP based on finite element simulation. The method includes: creating a micro geometric model of a composite material and meshing the model; assigning a corresponding material property to each mesh part, and defining a material direction; importing each mesh part into an assembly module, and setting a relative position between the parts through translation, rotation and other operations and constraints; using a dynamic explicit analysis step; setting contact and boundary conditions; and submitting for analysis. The method is applicable to different cutting velocities. With the method, a mass scaling factor can be efficiently selected in CFRP 3D micro-scale cutting at different cutting velocities, and calculation efficiency can be improved while calculation accuracy is ensured, thereby facilitating development and improvement of a CFRP 3D micro-scale cutting model and research of a CFRP cutting mechanism. ?54130 i 1/3 A B C D E FIG. 1 25480130

Description

1/3

A B C

D E FIG. 1

METHOD FOR QUICKLY SELECTING THREE-DIMENSIONAL (3D) MICRO-SCALE CUTTING SIMULATION OF CARBON FIBER REINFORCED POLYMER

Technical Field

[0001] The present invention relates to the field of cutting simulation of composite materials, and in particular, to a method for quickly selecting a mass scaling factor for three-dimensional (3D) micro-scale cutting simulation of carbon fiber reinforced polymer (CFRP) based on finite element simulation.

Background

[0002] CFRPs are widely used in aerospace and other high-end equipment fields due to their excellent mechanical properties. However, CFRPs are frequently damaged during processing because of their heterogeneity and anisotropy, which seriously affects the performance and reliability of parts. Therefore, to fundamentally suppress the processing damage, it is necessary to delve into a processing mechanism of CFRPs and analyze a formation mechanism of the processing damage. Finite element simulation, especially 3D micro-scale cutting simulation, is the most effective way to study the processing mechanism of composite materials. It can well simulate the interaction between multiple fibers and the resin and cutting tools, and allows easy observation of a material removal process. However, 3D micro-scale cutting simulation of CFRP is usually inefficient in calculation, often taking days or even weeks to calculate. In addition, most of the existing models are based on many simplifications and assumptions, and more complex factors need to be considered for subsequently improved models, further reducing the calculation efficiency and seriously hindering the research of CFRP processing. Therefore, it is necessary to improve the calculation efficiency as much as possible while ensuring the calculation accuracy, to advance the research of CFRP cutting.

[0003] Generally, the calculation efficiency is mainly improved by improving meshing quality and mass scaling. However, due to the presence of extremely small geometric dimensions in a CFRP 3D micro model, which limits the size of elements, the calculation efficiency cannot be significantly improved by improving meshing quality. There is no such limitation in improving mass scaling, which is a better approach in this case. However, since the essence of mass

? 4R130 i scaling is to artificially modify the unit density, this will undoubtedly affect the calculation accuracy. Therefore, mass scaling needs to be used properly while the calculation accuracy is ensured. Analysis of cutting simulation of composite materials with a very low cutting velocity (less than 10 mm/s) is usually considered to meet the quasi-static assumption, and quasi-static criteria are used to determine whether mass scaling is properly selected.

[0004] The selection is proper when kinetic energy accounts for less than 10% of internal energy during the analysis. In "Machining of UD-GFRP Composites Chip Formation Mechanism" published in 2007 in the journal "COMPOSITES SCIENCE AND TECHNOLOGY", Rao et al. used the quasi-static evaluation criteria and used different mass scaling factors for different phases in two-dimensional (2D) micro-scale cutting simulation of GFRP. Agarwal et al. also used this evaluation method in "MODELLING OF ORTHOGONAL CUTTING OF IDEALIZED FRP COMPOSITES" published in 2014 at the International Mechanical Engineering Congress and Exposition. However, cutting velocities used in both the papers are very low, much less than milling and drilling velocities commonly used in practical machining. As the model is further improved, higher cutting velocities need to be simulated while more complex factors need to be considered, and dynamic effects in the simulation analysis become increasingly apparent, making it difficult to meet the quasi-static premise. In this case, an appropriate mass scaling factor needs to be redetermined, and the appropriate mass scaling factor can be selected only by calculating a set of models with different mass scaling factors. This requires a lot of calculations and seriously affects the development and improvement of the CFRP 3D micro model. Therefore, a method for quickly selecting a mass scaling factor for 3D micro-scale cutting simulation of CFRP is urgently required, to greatly reduce the amount of calculation during a test.

Summary

[0005] It is an object of the present invention to substantially overcome, or at least ameliorate, one or more disadvantages of existing arrangements. Some aspects of the present disclosure are intended to provide a method for quickly selecting a mass scaling factor for 3D micro-scale cutting simulation of CFRP, to overcome the disadvantage of the prior art. In the method, based on a relationship between kinetic energy and internal energy of a workpiece at an initial stage of calculation, whether the factor is appropriate can be learned only by comparing and analyzing the kinetic energy and the internal energy in a short period of time after the

? 4R130 i calculation starts, thereby greatly reducing the amount of calculation during a test and efficiently determining an appropriate mass scaling factor. In addition, since a direct relationship between a velocity and kinetic energy is considered in the method, unlike a requirement in a quasi-static standard that the kinetic energy can be ignored compared to the internal energy, the method is applicable to different cutting velocities. In the method, based on a ratio of kinetic energy to internal energy at an initial stage of calculation, whether the factor is appropriate or needs to be adjusted can be learned without a need to fully calculate a model, thereby greatly reducing the amount of calculation during a test. The method is simple and practical, and can be used to efficiently select a mass scaling factor in CFRP 3D micro-scale cutting at different cutting velocities, thereby improving the calculation efficiency.

[0006] One aspect of the present disclosure provides a method for quickly selecting a mass scaling factor for 3D micro-scale cutting simulation of CFRP. The method is based on ABAQUS finite element simulation calculation software. For a specific CFRP 3D micro-scale cutting model, a set of models with different mass scaling factors are calculated separately at a given velocity to obtain kinetic energy and internal energy of a workpiece at an initial stage of the calculation, and a ratio of the kinetic energy to the internal energy is analyzed. Apparent fluctuations caused by numerical instability are ignored, and a mass scaling factor obtained in a case that the ratio of the kinetic energy to the internal energy at the initial stage of the calculation is close to 1 satisfies a goal of improving calculation efficiency while ensuring calculation accuracy. The method specifically includes the following steps:

step 1: creating a micro geometric model of a composite material and meshing the model, including a fiber, resin, an interface and an equivalent homogeneous material that serves as a support part, where a diameter of the fiber is D, a thickness of the interface is h, and a length of each of the fiber and the interface is L; creating a geometric model of a cutting tool and setting a reference point, where a rake angle of the cutting tool is a, a relief angle of the cutting tool is P, and a radius of a blade circle is r; and setting each component as a 3D deformable body, dividing the 3D deformable body into hexahedral elements, where an element type is first order reduced integration, and generating a mesh part for each component for subsequent assembly; step 2: assigning a corresponding material property to each mesh part, and defining a material direction, where because the fiber is a transversely isotropic brittle material, a linear elasticity assumption and a maximum stress failure criterion are used: it is assumed that when a tensile stress or a shear stress of a unit integration point reaches a failure strength, that is, fails, there is no damage evolution; and the material direction is defined as follows: a direction 1 is along the fiber, and directions 2 and 3 are perpendicular to the fiber; and the resin uses an elastoplastic constitutive and shear failure criterion, and it is considered that when an equivalent plastic strain reaches a failure strain, the damage starts, and linear damage evolution is used; the interface is modeled on a resin-like material, slightly weaker than the resin; and the equivalent homogeneous material provides only a support function, regardless of its failure and deletion, and therefore, only density and an elastic modulus are set; and to improve a calculation velocities, cutting tool wear is not considered, and therefore, in the next step, cutting tool parts are constrained to be rigid bodies; step 3: importing each mesh part into an assembly module, and setting a relative position between the parts through translation, rotation and other operations and constraints; step 4: setting an analysis step and an output variable, where due to complex nonlinearities for the 3D micro-scale cutting simulation of CFRP, a dynamic explicit analysis step is used to set a mass scaling factor f; as the cutting velocity increases, a dynamic effect becomes apparent, and the premise of a quasi-static assumption is not met; to quickly select an appropriate mass scaling factor, an easily distinguishable and quickly-responding variable is required, and considering that the ratio of the kinetic energy to the internal energy is characterized by quick response and fewer fluctuations, the selection method is still based on the variable of the ratio of the kinetic energy to the internal energy, but in order to reduce an amount of calculation during a test, only the ratio of the kinetic energy to the internal energy at an initial stage needs to be calculated; and in order to obtain the ratio, an energy output needs to be set separately for the workpiece part in a history output manager; step 5: setting contact and boundary conditions, where constituent phases are connected by Tie constraints; surface-to-surface contact based on nodes and a penalty contact method is set between the cutting tool and the workpiece, and to avoid mutual intrusion of the phases, general contact is set, where to avoid double calculations, contact between all faces and a cutting tool face is removed; and in a load module, the bottom and back of the workpiece are fixed by using ENCASTER, and the cutting velocity is set at the reference point of the cutting tool by using velocity/angular velocity; and step 6: submitting for analysis, to obtain the kinetic energy and the internal energy at an initial stage of the calculation; analyzing the ratio of the kinetic energy to the internal energy of the workpiece, to determine whether the selected mass scaling factor is appropriate; and

? S4RO I in obtaining the internal energy and the kinetic energy based on history variable outputs in a result file, to obtain the ratio of the kinetic energy to the internal energy of the workpiece, where the kinetic energy and the internal energy are calculated according to the following formulas:

EK = -pv.vdV (1)

EU = pUdV = -fL :cdV 7r-Uo (2) V 0 V where EKis the kinetic energy, Eu is the internal energy, p is current density, v is a velocity field vector, V is a volume, a is the stress, e is the strain, and Uo is energy at a moment ; and the apparent fluctuations caused by numerical instability are ignored, and if a peak value of the ratio is close to 1, the factor is an appropriate mass scaling factor, or if the peak value of the ratio is not close to 1, the mass scaling factor is increased or decreased according to a relationship between the peak value of the ratio and 1, and the steps 4 to 6 are repeated, until the foregoing condition is met.

[0007] The beneficial effect of the present invention is to provide a method for quickly selecting a mass scaling factor, to resolve the problem of difficulty in selecting a mass scaling factor when a cutting velocity is high for 3D micro-scale cutting simulation of CFRP. The method focuses on calculation of a ratio of kinetic energy to internal energy at an initial stage, and whether the factor is appropriate or needs to be adjusted can be learned without a need to fully calculate a model, thereby greatly reducing the amount of calculation during a test. In addition, because the kinetic energy is directly related to mass and a velocity, the method is applicable to different cutting velocities. With the method, an appropriate mass scaling factor can be quickly selected, and calculation efficiency can be improved while calculation accuracy is ensured, thereby facilitating development and improvement of a CFRP 3D micro-scale cutting model and research of a CFRP cutting mechanism. The method provided in the present invention is simple and practical, and can be used to efficiently select a mass scaling factor in CFRP 3D micro-scale cutting at different cutting velocities, thereby improving the calculation efficiency and having a wide application prospect.

Brief Description Of The Drawings

[0008] Preferred embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which

[0009] FIG. 1 is a schematic diagram of a CFRP 3D micro-scale cutting model, where A is a resin phase, B is an interface phase, C is afiber phase, D is an equivalent homogeneous phase, and E is a cutting tool.

[0010] FIG. 2 is change curves of a ratio of kinetic energy to internal energy of a workpiece over time with different mass scaling factors at an initial stage of calculation performed by using ABAQUS finite element simulation calculation software at a cutting velocity of 1 m/s. FIG. 2(a) to FIG. 2(d) are change curves of a ratio of kinetic energy to internal energy of a workpiece over time with mass scaling factors of 10000, 6000, 4000 and 2000, respectively.

[0011] FIG. 3 is a flowchart of a selection method.

Detailed Description

[0012] The following describes specific implementations of the present invention in detail with reference to technical solutions and the accompanying drawings.

[0013] The present invention is based on ABAQUS finite element simulation calculation software, with a cutting velocity of 1 m/s as an example. FIG. 3 is a flowchart of a method. The method specifically includes the following steps.

Step 1: separately create micro geometric models of composite material micro parts, including a single fiber, resin, an interface, an equivalent homogeneous material, and a cutting tool. A diameter D of the fiber is 5.6 m, a thickness h of the interface is 0.2 m, a length L of each of the fiber and the interface is 300 m, a rake angle a of the cutting tool is 250, a relief angle P of the cutting tool is 5, and a radius r of a blade circle is 10 m. Each component is set as a 3D deformable body, and divided into hexahedral elements by using a sweeping method, and an element size of a cutting area is set to about 0.7 m, so that an aspect ratio of the element is 1 as much as possible to ensure calculation accuracy. Elements away from the cutting area have gradually increasing sizes, to improve calculation efficiency. Each element type is first-order reduced integration, and a mesh part is generated for each component for subsequent assembly.

? S4RO I in

Step 2: assign a corresponding material property to each mesh part, and define a material direction.

Transverse isotropy of the fiber and a maximum stress failure criterion are implemented by using a VUMAT subroutine. In addition, the material direction is defined as follows: a direction 1 is along the fiber, and directions 2 and 3 are perpendicular to the fiber. The resin uses an elastoplastic constitutive and shear failure criterion, and linear damage evolution is used. The interface is modeled on a resin-like material, only slightly weaker than the resin, and both materials are isotropic materials, with no direction set. The equivalent homogeneous material provides only a support function, and therefore, only density and an elastic modulus are set. Material properties of each phase are shown in Table 1:

Table 1 Material properties of each constituent phase Fiber Ei (GPa) 295 E2=E 3 (GPa) 14 V12-V13 0.2 V23 0.07 XT (MPa) 5880 S23 (MPa) 380 p (T/cm 3) 1.7x10-9 Resin E (GPa) 3.4 v 0.34 p (T/cm 3) 9.8x10-10 ao (Mpa) 85 Cf 0.02 Equivalent homogeneous material p (T/cm 3) 1.5x10-9 E (GPa) 175 v 0.25

E is the elastic modulus, v is a Poisson's ratio, subscript i (i=1, 2, 3) is the material direction, p is the material density, XT is the tensile failure strength along the fiber direction, S23 is the shear strength in the direction 23, ao is a yield strength, and ef is an equivalent plastic strain at the beginning of failure. Step 3: import each mesh part into an assembly module, and set a relative position between the parts through translation, rotation and other operations and constraints, as shown in FIG. 1. Step 4: set an analysis step and an output variable, where due to complex nonlinearities for the 3D micro-scale cutting simulation of CFRP, a dynamic explicit analysis step is used, and a mass scaling factor f=10000 is tried for a cutting velocity of 1 m/s. In the method,

? S4RO I in because a mass scaling factor is selected according to a ratio of kinetic energy to internal energy of a workpiece at an initial stage of calculation, in order to obtain the ratio, an energy output needs to be set separately for the workpiece part in a history output manager. Step 5: set contact and boundary conditions; and connect constituent phases by Tie constraints. Surface-to-surface contact based on nodes and a penalty contact method is set between the cutting tool and the workpiece, and to avoid mutual intrusion of the phases, general contact is set. To avoid double calculations, contact between all faces and a cutting tool face is removed. In a load module, the bottom and back of the workpiece are fixed by using ENCASTER, and the cutting velocity is set at the reference point of the cutting tool by using velocity/angular velocity. Step 6: submit for analysis. In step 4, the mass scaling factor f is set to 10000, and calculation is performed according to the formulas (1) and (2), to obtain the kinetic and the internal energy at an initial stage of the calculation. The ratio of the kinetic energy to the internal energy of the workpiece is analyzed, and a result is shown in FIG. 2(a). It can be found that a part of the curve of the ratio of the kinetic energy to the internal energy apparently exceeds 1. Therefore, the mass scaling factor of 10000 is too large, and steps 4 to 6 are repeated. To reduce the mass scaling factor, the mass scaling factor is set to 6000, 4000, and 2000, respectively. Results are shown in FIG. 2(b) to FIG. 2(d). It can be seen from the figures that the method is satisfied only when the mass scaling factor is 2000. Therefore, the appropriate mass scaling factor for this velocity is 2000.

[0014] In the method, calculation needs to be performed for only a short period of time, and whether the coefficient is appropriate or needs to be adjusted can be learned, thereby greatly reducing the amount of calculation during a test. Due to a direct relationship between the kinetic energy and mass and a velocity, the method is applicable to different cutting velocities. With the method, a mass scaling factor can be efficiently selected in CFRP 3D micro-scale cutting at different cutting velocities, and calculation efficiency can be improved while calculation accuracy is ensured, thereby facilitating development and improvement of a CFRP 3D micro-scale cutting model and research of a CFRP cutting mechanism.

? 4R130 i

Claims

1. A method for selecting a mass scaling factor for three-dimensional (3D) micro-scale cutting simulation of carbon fiber reinforced polymer (CFRP), wherein the method is based on ABAQUS finite element simulation calculation software, and for a specific CFRP 3D micro scale cutting model, a set of models with different mass scaling factors are calculated separately at a given velocity to obtain kinetic energy and internal energy of a workpiece at an initial stage of the calculation, and a ratio of the kinetic energy to the internal energy is analyzed; and apparent fluctuations caused by numerical instability are ignored, and a mass scaling factor obtained in a case that the ratio of the kinetic energy to the internal energy at the initial stage is close to 1 satisfies a goal of improving calculation efficiency while ensuring calculation accuracy; and the method specifically comprises the following steps: step 1: creating a micro geometric model of a composite material and meshing the model, comprising a fiber, resin, an interface and an equivalent homogeneous material that serves as a support part, wherein a diameter of the fiber is D, a thickness of the interface is h, and a length of each of the fiber and the interface is L; creating a geometric model of a cutting tool and setting a reference point, wherein a rake angle of the cutting tool is a, a relief angle of the cutting tool is P, and a radius of a blade circle is r; and setting each component as a 3D deformable body, dividing the 3D deformable body into hexahedral elements, wherein an element type is first-order reduced integration, and generating a mesh part for each component for subsequent assembly; step 2: assigning a corresponding material property to each mesh part, and defining a corresponding material direction, wherein because the fiber is a transversely isotropic brittle material, a linear elasticity assumption and a maximum stress failure criterion are used: it is assumed that when a tensile stress or a shear stress of a unit integration point reaches a failure strength, that is, fails, there is no damage evolution; and the material direction of the fiber is defined as follows: a direction 1 is along the fiber, and directions 2 and 3 are perpendicular to the fiber; the resin uses an elastoplastic constitutive and shear failure criterion, and when an equivalent plastic strain reaches a failure strain, the damage starts, and linear damage evolution is used; the interface is modeled on a resin-like material, slightly weaker than the resin; and the equivalent homogeneous material provides only a support function, regardless of its failure and deletion, and therefore, only density and an elastic modulus are set; and

?254R01I3i to improve a calculation velocity, cutting tool wear is not considered, and therefore, in the next step, cutting tool parts are constrained to be rigid bodies; step 3: importing each mesh part into an assembly module, and setting a relative position between the parts through translation, rotation and other operations and constraints; step 4: setting an analysis step and an output variable, wherein due to complex nonlinearities for the 3D micro-scale cutting simulation of CFRP, a dynamic explicit analysis step is used to set a mass scaling factor f; as the cutting velocity increases, a dynamic effect becomes apparent, and the premise of a quasi-static assumption is not met; to quickly and properly select a mass scaling factor, an easily distinguishable and quickly-responding variable is required, and considering that the ratio of the kinetic energy to the internal energy is characterized by quick response and fewer fluctuations, the selection method is still based on the variable of the ratio of the kinetic energy to the internal energy, but in order to reduce an amount of calculation during a test, only the ratio of the kinetic energy to the internal energy at an initial stage needs to be calculated; and in order to obtain the ratio, an energy output needs to be set separately for the workpiece part in a history output manager; step 5: setting contact and boundary conditions; and connect constituent phases by Tie constraints, wherein surface-to-surface contact based on nodes and a penalty contact method is set between the cutting tool and the workpiece, and to avoid mutual intrusion of the phases, general contact is set; to avoid double calculations, contact between all faces and a cutting tool face is removed; and in a load module, the bottom and back of the workpiece are fixed by using ENCASTER, and the cutting velocity is set at the reference point of the cutting tool by using velocity/angular velocity; and step 6: submitting for analysis; to obtain the kinetic energy and the internal energy at an initial stage of the calculation, analyzing the ratio of the kinetic energy to the internal energy of the workpiece, to determine whether the selected mass scaling factor is appropriate; and obtaining the internal energy and the kinetic energy based on history variable outputs in a result file, to obtain the ratio of the kinetic energy to the internal energy of the workpiece, wherein the kinetic energy and the internal energy are calculated according to the following formulas:

EK =f -pv.vdV (1) V

?S4Rfl130

EU = pUdV = f -a: idV Ir-UO (2)

wherein EKis the kinetic energy, Eu is the internal energy, p is current density, v is a velocity field vector, Vis a volume, a is the stress, c is the strain, and Uo is energy at a moment ; and the apparent fluctuations caused by numerical instability are ignored, and if a peak value of the ratio is close to 1, the factor is an appropriate mass scaling factor, or if the peak value of the ratio is not close to 1, the mass scaling factor is increased or decreased according to a relationship between the peak value of the ratio and 1, and the steps 4 to 6 are repeated, until the foregoing condition is met.

Dalian University of Technology

Patent Attorneys for the Applicant/Nominated Person

SPRUSON&FERGUSON

FIG. 1 1/3

Ratio of kinetic energy to internal Ratio of kinetic energy to internal energy of workpiece energy of workpiece

25480130 (c) (a) Time (s)

Time (s) Mass scaling factor 10000

Mass scaling factor 4000 Ratio of kinetic energy to internal

FIG. 2 2/3

Ratio of kinetic energy to internal energy of workpiece energy of workpiece

(d) (b) Time (s)

Time (s) Mass scaling factor 6000

Mass scaling factor 2000