STF interlayer energy dissipation component with damping changing along with frequency and characteristic analysis method of STF interlayer energy dissipation component

Abstract

The invention aims at providing an STF interlayer energy dissipation component with damping changing along with frequency and a characteristic analysis method thereof, and the STF interlayer energy dissipation component comprises an upper restraint layer which is made of a metal material and has a first thickness; a lower restraint layer made of a metal material and having a second thickness; the damping layer is arranged between the upper restraint layer and the lower restraint layer, the damping layer is composed of shear thickening liquid, the shear thickening liquid comprises a dispersion phase and a dispersion medium, the dispersion phase is nano silicon dioxide particles, and the dispersion medium is polyethylene glycol; the packaging layer surrounds the damping layer and is used for sealing the damping layer; wherein the ratio of the thickness of the damping layer to the reference value of the thickness of the damping layer is defined as the thickness ratio, the thickness ratio is larger than 2, and the thickness of the damping layer is matched with the mass fraction of the nano silicon dioxide particles in the damping layer. And the damping ratio of the component is in a change trend of decreasing, increasing and decreasing along with the increase of the vibration frequency.

Description

Technical Field

[0001] The present invention relates to the technical field of engineering vibration reduction, in particular to an STF sandwich energy-absorbing component whose damping varies with frequency and a characteristic analysis method thereof. Background Art

[0002] Energy dissipation and vibration reduction of engineering structures has always been a research focus in the engineering field. Traditional damping and vibration reduction devices such as viscous dampers, friction dampers and tuned mass dampers have disadvantages such as heavy weight, large size and complex installation during use, and their damping characteristics cannot be adjusted accordingly according to changes in external vibration frequency.

[0003] Shear-thickening fluid (STF) is a highly concentrated colloidal suspension based on nanomaterials and is a non-Newtonian fluid. The viscosity of STF is related to the shear rate. When the external vibration reaches the STF critical shear rate, the viscosity of the system increases exponentially; after the external load is removed, the viscosity returns to its initial state within a relatively short period of time. Therefore, STF shows great potential in applications such as dampers, flexible protective clothing, and structural vibration reduction and energy dissipation.

[0004] At present, some studies have applied STF to sandwich structures. Fischer et al. (FISCHER C, BRAUN SA, BOURBAN PE, et al. Dynamic properties of sandwich structures with integrated shear-thickening fluids [J]. Smart Materials and Structures, 2006, 15 (5): 1467.) applied STF to sandwich beams and applied various dynamic loads to the sandwich beams through a dynamic test system to explore their dynamic response characteristics. Minghai Wei (WEI M, HU G, JIN L, et al. Forced vibration of a shear thickening fluid sandwich beam [J]. Smart Materials and Structures, 2016, 25 (5): 055041) et al. studied the effects of excitation frequency, excitation amplitude and excitation position on the natural frequency of STF sandwich beams. Selim Gürgen ( NS, M A.Vibration attenuation of sandwich structures filled with shear thickening fluids[J].Composites Part B:Engineering,2020,186:107831.) et al. filled STF into polystyrene foam to study the effect of STF on the vibration of sandwich structures.

[0005] However, existing research has yet to identify key metrics for measuring the damping performance of STF sandwich structures, making it difficult to assess their effectiveness in vibration reduction and energy dissipation in practical applications. In particular, how the damping of STF sandwich structures varies with frequency, and the factors influencing this variation, have not been systematically investigated. Summary of the Invention

[0006] The purpose of the present invention is to provide an STF sandwich energy-absorbing component whose damping varies with frequency and a characteristic analysis method thereof, aiming to overcome the problem in the prior art that the damping characteristics of the STF sandwich structure are difficult to quantify and evaluate, and to realize a systematic study of the law of variation of the damping of the STF sandwich structure with frequency.

[0007] The present invention discloses an STF sandwich energy-absorbing component with frequency-dependent damping, comprising:

[0008] an upper constraining layer made of a metal material and having a first thickness;

[0009] a lower constraining layer made of a metal material and having a second thickness;

[0010] a damping layer disposed between the upper constrained layer and the lower constrained layer, the damping layer being composed of a shear thickening fluid comprising a dispersed phase and a dispersion medium, wherein the dispersed phase is nano-silica particles and the dispersion medium is polyethylene glycol; and

[0011] an encapsulation layer surrounding the damping layer and used for sealing the damping layer;

[0012] Among them, the ratio of the thickness of the damping layer to the reference value of the thickness of the damping layer is defined as the thickness ratio, the thickness ratio is greater than 2, the thickness of the damping layer is adapted to the mass fraction of nano-silica particles in the damping layer, so that the damping ratio of the component shows a trend of first decreasing, then increasing, and then decreasing as the vibration frequency increases.

[0013] Preferably, the particle size of the nano-silicon dioxide particles is 12 nm, and the mass fraction of the nano-silicon dioxide particles is between 16% and 24%.

[0014] Preferably, the particle size of the nano-silicon dioxide particles is 50 nm, and the mass fraction of the nano-silicon dioxide particles is between 36% and 40%.

[0015] Preferably, the reference value is 1 mm, and the thickness ratio is between 2 and 10.

[0016] Preferably, the upper constraint layer and the lower constraint layer are both aluminum plates, and the packaging layer is EVA foam.

[0017] Preferably, the thickening ratio of the shear thickening fluid increases with the increase in the mass fraction of the nano-silica particles, wherein the thickening ratio is defined as the ratio of the peak viscosity of the shear thickening fluid after thickening to the viscosity at the critical shear rate.

[0018] The characteristic analysis method of STF sandwich energy dissipation components with frequency-dependent damping includes:

[0019] Establishing a constrained damping model of the STF sandwich energy-absorbing component, wherein the STF sandwich energy-absorbing component includes an upper constrained layer, a lower constrained layer, and a damping layer disposed between the upper constrained layer and the lower constrained layer, wherein the damping layer is composed of a shear thickening fluid;

[0020] Obtaining the storage modulus and loss modulus of the shear thickening fluid through rheological testing;

[0021] Based on the constrained damping model and the energy method analysis principle, a deformation analysis equation group of the STF sandwich energy-absorbing component is established, wherein the deformation analysis equation group includes an equation for the relationship between angular displacement and axial displacement, an equation for calculating shear deformation, and an equation for stress analysis;

[0022] Solving the deformation analysis equations to obtain the total vibration energy and total loss energy of the STF sandwich energy-absorbing component;

[0023] Calculating a damping ratio of the STF sandwich energy-absorbing component, where the damping ratio is defined as a ratio of the total loss energy to the total vibration energy;

[0024] The variation law of the damping ratio of the STF sandwich energy-absorbing component with frequency under different parameter combinations is analyzed.

[0025] Preferably, the rheological test comprises:

[0026] Steady-state rheological test, setting the shear rate range to 0.01s -1 to 1000s -1 , obtaining the relationship between the viscosity of the shear thickening fluid and the shear rate;

[0027] In the dynamic rheological test, the shear strain amplitude was set to 40%, 80%, 120% and 160%, the frequency sweep range was 1 rad·s-1 to 1000 rad·s-1, the frequency was set to 1 rad·s-1, 5 rad·s-1, 10 rad·s-1 and 20 rad·s-1, the strain sweep range was 1 to 1000, and the relationship between the storage modulus and the loss modulus of the shear thickening fluid and the angular frequency was obtained.

[0028] Preferably, in the deformation analysis equation group, the shear deformation calculation equation is:

[0029]

[0030] Where γ is the shear strain of the STF damping layer, δ B and δ C are the displacements on both sides of the STF damping layer, H2 is the thickness of the STF damping layer, θ is the angular displacement, δ1 and δ3 are the axial displacements of the upper and lower constrained layers, respectively, H 31 is the distance between the neutral surface of the lower constrained layer and the neutral surface of the upper constrained layer.

[0031] As an advantage, the method further comprises the following steps:

[0032] Analyze the effect of the mass fraction of nano-silica particles in the shear thickening fluid on the damping ratio of the STF sandwich energy-absorbing component;

[0033] Analyze the effect of the damping layer thickness ratio on the damping ratio of the STF sandwich energy dissipation component;

[0034] Based on the analysis results, an optimal parameter combination suitable for a specific frequency range is determined.

[0035] The beneficial effects of the present invention include:

[0036] 1. Designed an STF sandwich energy dissipation component with frequency-dependent damping. This component can automatically adjust its damping characteristics according to the external vibration frequency, achieving adaptive vibration reduction and energy dissipation.

[0037] 2. A constrained damping model for STF sandwich energy-absorbing components was established, and a calculation formula for the component damping ratio was derived based on the energy method, providing a theoretical basis for quantitatively evaluating the damping performance of STF sandwich components.

[0038] 3. The effects of nano-silica particle mass fraction and damping layer thickness ratio on the damping characteristics of STF sandwich components were systematically studied, providing guidance for optimizing component parameters and improving vibration reduction effects.

[0039] 4. We discovered that there is a critical thickness ratio for STF sandwich components. When the thickness ratio is greater than 2, the maximum damping ratio of the component increases significantly with the increase of the thickness ratio, providing an important reference for practical applications.

[0040] 5. The law of how the damping of STF sandwich components changes with frequency is revealed, that is, the damping ratio shows a trend of first decreasing, then increasing, and then decreasing as the frequency increases. This characteristic enables the component to provide the best vibration reduction effect for vibrations in a specific frequency range. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0042] Figure 1a Schematic diagram of the STF sandwich structure of the present invention;

[0043] Figure 1b is a cross-sectional view of the STF interlayer of the present invention;

[0044] Figure 2a and 2b Rheological test results of STF materials with 12nm and 50nm SiO2 respectively;

[0045] Figure 3a and 3b The STF energy consumption characteristic curves of 12nm and 50nm SiO2 respectively;

[0046] Figure 4 Schematic diagram of the theoretical model of STF sandwich structure;

[0047] Figure 5 Schematic diagram of the geometric relationship of the STF sandwich structure;

[0048] Figure 6 Schematic diagram of the stress relationship of the STF damping layer;

[0049] Figure 7a and 7b Damping ratio curves of STF sandwich structures with different mass fractions of 12nm and 50nm SiO2;

[0050] Figure 8 This is the shear thickening mechanism diagram of the "particle cluster" theory;

[0051] Figure 9 The maximum damping ratio of STF with different mass fractions of 12 nm;

[0052] Figure 10a 、 10b , 10c and 10d are the damping ratio curves of the STF sandwich structure at different thickness ratios;

[0053] Figure 11 is the relationship between the STF thickness ratio and the maximum damping ratio of the sandwich structure;

[0054] Figure 12 It is the STF-50-40% frequency scanning curve;

[0055] Figure 13 This is the STF-50-40% strain scanning curve. DETAILED DESCRIPTION

[0056] The preferred embodiments of the present invention are described in detail below with reference to Figures 1-13 to make the advantages and features of the present invention easier for those skilled in the art to understand, thereby making a clearer and more precise definition of the protection scope of the present invention.

[0057] Referring to Figure 1, the STF sandwich energy dissipation component designed in this invention primarily consists of three parts: an upper constraining layer 1, a damping layer 2, and a lower constraining layer 3, each with thicknesses of H1, H2, and H3, respectively. The constraining layer is constructed of aluminum sheet, while the damping layer is constructed of STF material containing varying mass fractions of silicon dioxide (SiO2). The surrounding EVA foam encapsulation layer seals the STF damping layer.

[0058] In a preferred embodiment of the present invention, the dispersed phase of the STF material is 12nm and 50nm SiO2 nanoparticles, and the dispersion medium is polyethylene glycol (PEG) with a molecular weight of 200. The upper and lower constrained layers are made of a density of 2700kg / m 3 , aluminum plate with elastic modulus of 72GPa and thickness H1=H3=1mm.

[0059] The present invention defines the ratio of the thickness H2 of the STF damping layer to the reference value H0 (1 mm) as thickness ratio C = H2 / H0. Experimental research shows that when the thickness ratio C is greater than 2, the maximum damping ratio of the STF sandwich energy dissipation component increases significantly as the thickness ratio increases. Therefore, the present invention preferably designs the thickness ratio C between 2 and 10 to achieve optimal vibration damping.

[0060] For STF materials, the present invention designs different combinations of particle size and mass fraction: when 12nm SiO2 is selected, its mass fraction is preferably between 16% and 24%; when 50nm SiO2 is selected, its mass fraction is preferably between 36% and 40%. The specific parameter combinations are shown in Table 1:

[0061] Table 1 STF material composition and components

[0062]

[0063] The STF sandwich energy-absorbing component of the present invention can be installed on the structural part that needs vibration reduction by pasting. When the structure vibrates, the STF damping layer is subjected to shearing. When the shear rate reaches a critical value, the STF thickens and the viscosity increases rapidly, increasing the structural damping, thereby achieving the effect of vibration reduction and energy dissipation.

[0064] The damping characteristics of STF sandwich energy-absorbing components mainly depend on the properties of STF materials. The present invention prepares STF by mechanical stirring and ultrasonic dispersion, and then conducts steady-state rheological performance test on the experimentally prepared STF. The shear rate setting range is 0.01s -1 ~1000s -1 , the relationship between STF viscosity and shear rate is obtained, which is used to judge the shear thickening performance of STF materials.

[0065] Referring to Figure 2, Figure 2(a) shows the relationship between the viscosity and shear rate of the STF material prepared with 12nm SiO2. When the shear rate is less than the critical shear rate, the STF exhibits shear-thinning characteristics, and the viscosity gradually decreases. After reaching the critical shear rate, the viscosity increases in a step-like manner, reaching a maximum value. As the shear rate continues to increase, the STF exhibits shear-thinning characteristics again, and the viscosity begins to gradually decrease. This indicates that the 12nm SiO2 STF material is a discontinuous shear-thickening fluid.

[0066] Figure 2(b) shows the relationship between viscosity and shear rate for the STF material prepared with 50nm SiO2. Unlike 12nm SiO2, the viscosity of the 50nm SiO2 STF increases continuously with increasing shear rate, reaching a maximum value and then decreasing. There is no shear-thinning followed by a step-like increase, indicating that the 50nm SiO2 STF material is a continuously shear-thickening fluid.

[0067] The thickening ratio is an important indicator for measuring the thickening effect of STF. It is defined as the ratio of the peak viscosity after STF thickening to the viscosity at the critical shear rate. In the present invention, as the SiO2 mass fraction increases, the thickening ratios of STF prepared with 12nm SiO2 are 26.62, 71.55, 81.53, 88.12, and 119.20, respectively; and the thickening ratios of STF prepared with 50nm SiO2 are 25.72, 28.45, and 33.64, respectively. A larger thickening ratio indicates a better thickening effect of the STF and a stronger vibration reduction and energy dissipation capability.

[0068] Please refer to Figure 12-13The vibration reduction and energy dissipation characteristics of the STF material mainly depend on the storage modulus G' and the dissipation modulus G". The present invention conducts dynamic tests on the experimentally prepared STF, sets the shear strain amplitude to 40%, 80%, 120% and 160%, the frequency scanning range to 1rad·s-1 to 1000rad·s-1, sets the frequency to 1rad·s-1, 5rad·s-1, 10rad·s-1 and 20rad·s-1, and the strain scanning range to 1 to 1000, and obtains the relationship between the storage modulus G' and the dissipation modulus G" of the shear thickening fluid and the angular frequency.

[0069] Referring to Figure 3, Figures 3(a) and 3(b) show the curves of the storage modulus and dissipation modulus of STF materials prepared with 50nm and 12nm SiO2, respectively, as a function of angular frequency. As can be seen from the figure, when the angular frequency is low in the early stage, the SiO2 particles form layers, the order between particles increases, the collisions between particles decrease, and the system does not form particle clusters. Due to the lubrication effect of the dispersion medium, the storage and dissipation moduli of the STF decrease. When the critical angular frequency is reached, as the angular frequency increases, both moduli show an increasing trend, the solvent layer is destroyed, the contact between particles increases, and particle clusters are formed. The dissipation modulus is always greater than the storage modulus, showing good energy dissipation characteristics.

[0070] The basic principle of material damping is energy dissipation, converting the vibration energy generated by the structural system when it is excited into other types of energy, allowing the structural system to return to a static and stable state. The vibration reduction and energy dissipation characteristics of STF materials mainly depend on the storage modulus G' and the energy dissipation modulus G". The storage modulus G' represents the magnitude of the elastic capacity, and the energy dissipation modulus G" represents the quality of the system's viscous energy dissipation capacity. When the energy dissipation modulus G" is greater than the storage modulus G', the system is mainly energy-consuming. As can be seen from Figure 3, whether the STF is prepared with 12nm or 50nm SiO2, its energy dissipation modulus is greater than the storage modulus. In addition, during the thickening process, as the viscosity of the STF increases, the material changes from a liquid-like state to a solid-like state, resulting in an increase in energy consumption. Therefore, STF can be used as a damping material for vibration reduction and energy dissipation.

[0071] The energy consumption of STF sandwich components is caused by shear thickening of STF materials when the vibration reaches the critical shear rate of STF materials, which increases the damping of the structure. In order to study the damping characteristics of STF sandwich components, the present invention establishes a cantilever beam in the form of Figure 4 In the theoretical model shown, the left end of the cantilever beam is fixed, and a simple harmonic concentrated load F is applied to the free end of the right end. The length of the free section of the cantilever beam is L and the width is b.

[0072] In order to facilitate the study of the relationship between stress, strain and displacement per unit length of the STF sandwich structure, the following assumptions are made when modeling the present invention:

[0073] (1) The constraint layer conforms to the Euler-Bernoulli beam theory, ignoring the shear and torsional deformation of constraint layer 1 and constraint layer 3. The damping layer 2 is a liquid-like STF that cannot produce stretching and bending. Affected by the particle clusters, combined with the Timoshenko beam theory, the STF only produces shear deformation.

[0074] (2) The lateral displacement of each layer is equal;

[0075] (3) The layers are well bonded and there is no relative sliding between the layers;

[0076] (4) Ignore the influence of packaging materials.

[0077] Reference Figure 5 When the STF sandwich structure is subjected to a simple harmonic load, the constraint layer 1 and the constraint layer 3 produce axial tension and transverse bending within the elastic range, and the STF damping layer produces shear deformation. When the cantilever beam is subjected to a simple harmonic load F, the angular displacement caused by the cross-section bending is θ(x) = θ0cosωx. The displacements of any point on the cross section of the constraint layer 1, STF damping layer 2, and constraint layer 3 in the x direction are δ1, δ2, and δ3 respectively, and the shear strain of the STF damping layer is Y. The relationship between the axial displacement θ and the shear strain γ and the angular displacement θ is δ n =Y n θ′,γ n =P n θ′,

[0078] Among them, γ n is the tensile effect coefficient, P n is the shear effect coefficient (n = 1, 2, 3). The distance from point B of the STF damping layer to the mass center of the constrained layer 1 is y1, and the distance from point C of the STF damping layer to the mass center of the constrained layer 3 is y3. According to the geometric relationship, the displacement δ2 of the STF damping layer in the x direction is:

[0079]

[0080] When the sandwich structure is subjected to simple harmonic load, the shear strain γ of the STF damping layer is composed of the shear angle φ around the y-axis and the cross-sectional bending angular displacement θ, that is, γ = φ + θ. The distance between the neutral surface of the constraint layer 3 and the neutral surface of the constraint layer 1 is H. 31 =H2+(H1+H3) / 2, the shear strain γ of the STF damping layer is:

[0081]

[0082] The rheological test shows that the shear modulus of the prepared STF is G2, and the shear stress τ can be obtained from Hooke's law of shear τ=G2γ:

[0083]

[0084] A micro segment of length dx is cut along the STF sandwich structure, such as Figure 6 As shown in the figure, the axial force on the BC side of the STF unit is f2. After a length of dx, the increment generated on the EF side of the STF unit is df2. On the CF side, the constraint layer 3 acts on the STF layer df3. From the balance of the STF unit force, the force on the BE side is df3 + df2. Therefore, the shear stress τ acting on the STF damping layer with a width of b is:

[0085]

[0086] It is known that the Young's modulus of the constraint layer 1 and the constraint layer 3 are E1 and E3, and the Young's modulus of the STF material is E2; from the knowledge of mechanics, we know that From the equality of formulas (3) and (4), and integration over the cross-section width b, we can obtain:

[0087]

[0088] The change in the resultant normal stress of each layer in the sandwich structure is dF n (n = 1, 2, 3) For a sandwich structure subjected to lateral vibration, due to the balance of forces, the resultant longitudinal force in the cross section is zero:

[0089]

[0090] δ n =θY n Substituting into the independent equations (5) and (6), we can get the structural tensile effect coefficient Y n , and then γ n =θP n Substitute into formula (2) to obtain the shear effect coefficient P n .

[0091] Based on the analysis of the bending angular displacement θ of the STF sandwich structure, the axial displacement δ of each layer, and the shear strain γ of the STF damping layer, the energy method is used to further solve the damping ratio η of the STF sandwich structure. Taking the STF sandwich structure of unit length as the research object, the cross-sectional area of the constraint layer 1 and the constraint layer 3 is A, the centroid radius of the cross section is r, and the elastic modulus is E, so the tensile stiffness K = EA and the bending stiffness B = r of the constraint layer 1 and the constraint layer 3 2 K, the longitudinal strain is ε=dδ / dx, then the tensile deformation energy W of the constraint layer 1 and the constraint layer 3 is e and bending deformation energy w f ,STF shear deformation energy per unit length w s They are:

[0092]

[0093] By integrating the above formula over a period T = 2π / ω, we can obtain the tensile deformation of the sandwich structure when it is subjected to a simple harmonic wave: for:

[0094]

[0095] Similarly, the bending deformation energy of the constraint layer 1 and the constraint layer 3 in one period T can be obtained as and the shear deformation energy of the STF damping layer They are:

[0096]

[0097] The tensile stiffness K1 and bending stiffness B1 of the constrained layer 1, the tensile stiffness K3 and bending stiffness B3 of the constrained layer 3, the loss modulus G2 of the STF damping layer, and δ n =Y n θ,γ n =P n Substituting θ(n=1,2,3) into the above formula, the total vibration energy of the structure can be obtained as follows:

[0098]

[0099] The tensile loss factor of the constrained layer 3 and the constrained layer 1 is α1 = α2 = α, and the loss factor β2 of the STF damping layer is the ratio of the loss modulus G″ to the storage modulus G′, that is, β2 = G″ / G′. The energy of the tensile and bending loss of the constrained layer 3 and the constrained layer 1 is ΔW ef , the energy consumed by shear ΔW s for:

[0100]

[0101] Therefore, the total energy loss is as follows:

[0102]

[0103] Therefore, the damping ratio η of the STF sandwich structure is the ratio of the total loss energy ΔW to the total vibration energy W [28-29]:

[0104]

[0105] When the STF sandwich structure is subjected to simple harmonic load, the total energy loss ΔW is mainly generated by the shear of the STF damping layer, and the energy consumed by the constrained layers 1 and 3 due to tension and bending can be ignored, so α1 = α2 = α = 0. The relationship between the angular frequency ω and the bending stiffness K and mass m is: The width of the cross section is b, and the height of each layer of the sandwich structure is Hn. Then the moment of inertia of each layer is The tensile stiffness K of the constrained layer 3 and the constrained layer 1 n =E n A n , bending stiffness B n =r 2 K n (n=1, 2, 3), the loss factor of the STF damping layer is β2, and the damping ratio of the STF sandwich structure after sorting is as follows:

[0106]

[0107] Where f is the vibration frequency, E1 and E3 are the elastic moduli of the constraint layer 1 and constraint layer 3 respectively, H1 and H3 are the thickness of the constraint layer 1 and constraint layer 3 respectively, H2 is the thickness of the STF damping layer, G2 is the loss modulus of the STF damping layer, β2 is the loss factor of the STF damping layer, and H 31 is the distance between the neutral surface of constrained layer 3 and the neutral surface of constrained layer 1.

[0108] Referring to Figure 7, Figures 7(a) and 7(b) show the damping ratio curves of STF sandwich structures with different mass fractions of SiO2, prepared with 12nm and 50nm SiO2, respectively, as a function of frequency. As can be seen from the figures, the mass fraction of the STF has a direct impact on the damping ratio of the STF sandwich structure. As the mass fraction of SiO2 in the STF increases, the initial and maximum damping ratios of the STF sandwich structures prepared with 12nm and 50nm SiO2 increase, while the structural frequency corresponding to the maximum damping ratio ηmax decreases.

[0109] In addition, with the increase of frequency, the damping ratio of the STF sandwich structure prepared with 50nm SiO2 continuously increases from the initial value to the maximum value, showing a continuous damping characteristic; while the STF sandwich structure prepared with 12nm SiO2 shows a discontinuous damping characteristic, and the damping ratio first decreases and then increases stepwise to the maximum value.

[0110] This phenomenon is closely related to the rheological properties of STF. At low shear rates, SiO2 particles form layers. Due to the lubrication effect, the particles flow easily, the STF shear thins, the viscosity decreases, the vibration reduction and energy dissipation capacity deteriorates, and thus the damping ratio decreases. As the frequency increases, the adsorption force between the particles increases, forming particle clusters (such as Figure 8 As shown in the figure, the viscosity increases, the vibration reduction and energy dissipation capacity is enhanced, and the damping ratio increases.

[0111] Reference Figure 9As the SiO2 mass fraction in the STF increases, the maximum damping ratio ηmax of the STF sandwich structure increases significantly. STF sandwich structures fabricated with 12nm SiO2 mass fractions of 16%, 18%, 20%, 22%, and 24% have maximum damping ratios ηmax of 0.027, 0.064, 0.14, 0.29, and 0.56, respectively. The maximum damping ratio of the STF sandwich structure with a mass fraction of 24% is 20.7 times that of the STF sandwich structure with a mass fraction of 16%.

[0112] In addition, as the mass fraction of SiO2 in STF increases, the frequency at which the sandwich structure produces the maximum damping ratio ηmax decreases significantly. The STF sandwich structures prepared with 12nm SiO2 mass fractions of 16%, 18%, 20%, 22% and 24% have the corresponding frequencies when the maximum damping ratio is 13.23s -1 , 6.60s -1 , 5.23s -1 , 4.15s -1 and 3.29s -1 The frequency corresponding to the maximum damping ratio of the STF sandwich structure with a mass fraction of 24% is 4.02 times lower than that with a mass fraction of 16%.

[0113] This is because as the mass fraction of particles in STF increases, the interaction force between particles increases, the collision and friction between particles increase, the shear rate required for the formation of particle clusters decreases, and the shear rate at which STF produces maximum viscosity and energy modulus decreases, resulting in a decrease in the frequency at which the maximum damping ratio is produced.

[0114] Referring to Figure 10, Figures 10(a)-(d) show the damping ratio versus frequency curves for STF sandwich structures fabricated with 12nm SiO2 at different thickness ratios of 18%, 20%, 22%, and 24%, respectively. As can be seen from the figure, when the STF thickness ratio C varies from 1 to 10, as the frequency increases, each damping ratio curve exhibits a trend of first decreasing to a minimum damping ratio ηmin, then increasing in a stepwise manner to a maximum damping ratio ηmax, and then continuing to decrease.

[0115] At a constant frequency, the damping ratio of the sandwich structure increases with the increase in the STF thickness ratio. This is because as the STF thickness increases, more particle clusters are formed in the system, the strength and density of the particle arrangement structure within the STF increase, the friction between the particle clusters increases, the flow resistance increases, the viscosity and loss modulus of the STF increase, and the vibration reduction and energy dissipation capacity of the sandwich structure increases, thus increasing the damping ratio of the sandwich structure.

[0116] Reference Figure 11The present invention discovered that STF sandwich structures exhibit a critical thickness ratio phenomenon. When the thickness ratio is less than 2, the number of SiO2 particles in the sandwich structure is insufficient to form effective particle clusters, and the maximum damping ratio ηmax is low. When the thickness ratio is greater than 2, the maximum damping ratio ηmax of the STF sandwich structure increases significantly as the thickness ratio increases.

[0117] Taking a 24% mass fraction of STF as an example, when the thickness ratio C = 2, the maximum damping ratio of the sandwich structure is ηmax = 0.38; when the thickness ratio C = 10, the maximum damping ratio of the sandwich structure is ηmax = 0.72, an increase of 1.89 times. Furthermore, under the same thickness ratio conditions, the higher the mass fraction, the greater the maximum damping ratio of the sandwich structure. When the thickness ratio C = 10, the maximum damping ratio of the sandwich structure with an 18% mass fraction of STF is ηmax = 0.22, while the maximum damping ratio of the sandwich structure with a 24% mass fraction of STF is ηmax = 0.72, which is 3.27 times the former.

[0118] The reason why the STF sandwich energy-absorbing component of the present invention exhibits the characteristic of damping changing with frequency is mainly due to the shear thickening mechanism of the STF material. During low-frequency vibration, the nano-silica particles in the STF are in a stratified state. The lubrication effect between the particles makes the system viscosity low and the damping effect is not obvious. As the vibration frequency increases, when the critical frequency is reached, particle clusters (such as Figure 8 As shown in the figure, the viscosity of the system increases sharply and the damping effect is significantly enhanced; when the frequency increases further, the particle cluster structure may be destroyed, causing the damping effect to begin to decrease again.

[0119] The STF fabricated with 12nm SiO2 exhibits discontinuous damping characteristics, primarily because smaller particles have a larger specific surface area, resulting in stronger inter-particle interactions and denser particle clusters. This results in a step-like change in the damping ratio near the critical frequency. In contrast, the STF fabricated with 50nm SiO2 exhibits continuous damping characteristics because larger particles have a relatively smaller specific surface area, weaker inter-particle interactions, and a more gradual cluster formation process.

[0120] The influence of mass fraction on damping characteristics is mainly reflected in two aspects: first, the higher the mass fraction, the smaller the interparticle spacing, which makes it easier for particle clusters to form, resulting in an increase in the maximum damping ratio; second, the higher the mass fraction, the lower the critical shear rate required to form particle clusters, and therefore the smaller the frequency corresponding to the maximum damping ratio. This provides a design basis for vibration reduction applications for vibrations of different frequencies.

[0121] The thickness ratio affects the damping properties primarily by changing the space within the STF layer for the formation and growth of particle clusters. When the thickness ratio is less than 2, the STF layer is too thin, restricting the formation and growth of particle clusters. When the thickness ratio is greater than 2, the STF layer has sufficient space to form a complete particle cluster network. As the thickness ratio increases, more particle clusters can form, enhancing the energy dissipation effect.

[0122] When the STF sandwich structure is used for energy dissipation and vibration reduction, the damping characteristics mainly depend on the middle STF layer. Therefore, combined with formula (14), the influence of STF mass fraction and thickness on the damping ratio of the STF sandwich structure is analyzed under the action of simple harmonic loads of different frequencies. The sandwich structure used in this study is 1500mm long and 40mm wide. The constraint layer is selected as an aluminum plate with a density of 2700kg / m3 and an elastic modulus of 72GPa. The storage modulus G′ and the dissipation modulus G″ of the middle STF are obtained from the above rheological test. For the convenience of research, the thickness ratio of STF is defined as C=H2 / H0, where H0=1mm and H2 is the variable thickness of the STF layer. The sandwich structure is named STF-JL-DMC, D is the particle diameter of SiO2, M is the STF mass fraction, and C is the thickness ratio. The parameters of the STF sandwich structure are shown in Table 2.

[0123] Table 2 STF sandwich structure parameters

[0124]

[0125] The present invention also provides a method for analyzing the characteristics of an STF sandwich energy-absorbing component whose damping varies with frequency, comprising the following steps:

[0126] Establish the constrained damping model of STF sandwich energy dissipation components, such as Figure 4 The model consists of an upper constrained layer, a lower constrained layer, and an STF damping layer disposed between the two constrained layers. The model assumes that the constrained layer conforms to the Euler-Bernoulli beam theory, and the STF damping layer conforms to the Timoshenko beam theory, producing only shear deformation.

[0127] The storage modulus G' and loss modulus G" of the STF material are obtained through rheological testing. The rheological testing includes:

[0128] (1) Steady-state rheological test: Set the shear rate range to 0.01s -1 to 1000s -1 , obtain the relationship between STF viscosity and shear rate;

[0129] (2) Dynamic rheological test: set the shear strain amplitude to 120% and the frequency sweep range to 0.01ra d·s -1 to 1000 rad·s -1 , obtain the relationship between STF storage modulus and loss modulus and angular frequency.

[0130] Based on the constrained damping model and the energy method analysis principle, the deformation analysis equations of the STF sandwich energy-absorbing component are established, including:

[0131] Based on the constrained damping model and the energy method analysis principle, the deformation analysis equations of the STF sandwich energy-absorbing component are established, including: (1) the relationship equation between angular displacement and axial displacement: δ n =Y n θ′, where Y n is the tensile effect coefficient; (2) Shear deformation calculation equation:

[0132]

[0133] Where γ is the shear strain of the STF damping layer, δ B and δ C are the displacements on both sides of the STF damping layer, H2 is the thickness of the STF damping layer, θ is the angular displacement, δ1 and δ3 are the axial displacements of the upper and lower constrained layers, respectively, H 31 is the distance between the neutral plane of the lower constraint layer and the neutral plane of the upper constraint layer; (3) stress analysis equation: τ = G2γ, where τ is the shear stress and G2 is the STF shear modulus.

[0134] Solving the deformation analysis equations yields the total vibration energy W and total loss energy ΔW of the STF sandwich energy-absorbing component. The total vibration energy includes the tensile and bending deformation energies of the constraining layer and the shear deformation energy of the STF damping layer; the total loss energy is primarily due to the shear deformation of the STF damping layer.

[0135] Calculate the damping ratio η of the STF sandwich energy-absorbing component, which is defined as the ratio of the total loss energy ΔW to the total vibration energy W:

[0136] The variation of damping ratio of STF sandwich energy dissipation components with frequency under different parameter combinations is analyzed, mainly including:

[0137] (1) Analyze the effect of the mass fraction of STF nano-silica particles on the damping ratio;

[0138] (2) Analyze the effect of STF damping layer thickness ratio on damping ratio;

[0139] (3) Based on the analysis results, determine the optimal parameter combination applicable to a specific frequency range.

[0140] The analysis method of the present invention can systematically study the damping characteristics of STF sandwich energy-absorbing components, providing theoretical guidance for optimizing component parameters and improving vibration reduction effects. In practical applications, STF sandwich energy-absorbing components with different parameter combinations can be selected for vibrations in different frequency ranges:

[0141] For low-frequency vibration (0.1-5 Hz): select STF sandwich components with high mass fraction (22%-24%) and large thickness ratio (C=8-10);

[0142] For medium frequency vibration (5-50 Hz): select STF sandwich components with medium mass fraction (18%-22%) and medium thickness ratio (C=4-6);

[0143] For high frequency vibration (>50Hz): select STF sandwich components with lower mass fraction (16%-18%) and small thickness ratio (C=2-4).

[0144] This paper designs an STF sandwich energy-dissipating component whose damping varies with frequency, establishes its theoretical model, and proposes a characteristic analysis method. Through systematic research, the following conclusions are drawn:

[0145] 1. The STF sandwich energy-absorbing component has the characteristic that damping changes with frequency. The damping ratio shows a trend of first decreasing, then increasing, and then decreasing as the frequency increases, showing adaptive vibration reduction capability;

[0146] 2. As the mass fraction of nano-silica in the STF increases, the maximum damping ratio of the sandwich component increases significantly, while the frequency corresponding to the maximum damping ratio decreases;

[0147] 3. There is a critical thickness ratio for STF sandwich components. When the thickness ratio is greater than 2, the maximum damping ratio of the component increases significantly with the increase of the thickness ratio.

[0148] The STF sandwich components prepared with 4.12nm SiO2 exhibit discontinuous damping characteristics, while the STF sandwich components prepared with 50nm SiO2 exhibit continuous damping characteristics, which is closely related to the shear thickening mechanism of STF.

[0149] The STF sandwich energy-absorbing component of the present invention has the advantages of light weight, small size, easy installation, and adaptive vibration reduction. It can be widely used in vibration reduction and energy consumption in the fields of building structures, mechanical equipment, and transportation, providing a new solution for vibration reduction of engineering structures.

[0150] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be included within the scope of protection of the present invention.

Claims

1. An STF sandwich energy dissipation component with frequency-dependent damping, characterized in that: include: an upper constraining layer made of a metal material and having a first thickness; a lower constraining layer made of a metal material and having a second thickness; a damping layer disposed between the upper constrained layer and the lower constrained layer, the damping layer being composed of a shear thickening fluid comprising a dispersed phase and a dispersion medium, wherein the dispersed phase is nano-silica particles and the dispersion medium is polyethylene glycol; and an encapsulation layer surrounding the damping layer and used for sealing the damping layer; Among them, the ratio of the thickness of the damping layer to the reference value of the thickness of the damping layer is defined as the thickness ratio, the thickness ratio is greater than 2, the thickness of the damping layer is adapted to the mass fraction of nano-silica particles in the damping layer, so that the damping ratio of the component shows a trend of first decreasing, then increasing, and then decreasing as the vibration frequency increases.

2. The STF sandwich energy dissipation component with frequency-dependent damping according to claim 1, characterized in that: The particle size of the nano-silicon dioxide particles is 12 nm, and the mass fraction of the nano-silicon dioxide particles is between 16% and 24%.

3. The STF sandwich energy dissipation component with frequency-dependent damping according to claim 1, characterized in that: The particle size of the nano-silicon dioxide particles is 50 nm, and the mass fraction of the nano-silicon dioxide particles is between 36% and 40%.

4. The STF sandwich energy dissipation component with frequency-dependent damping according to claim 1, characterized in that: The reference value is 1 mm, and the thickness ratio is between 2 and 10.

5. The STF sandwich energy dissipation component with frequency-dependent damping according to claim 1, characterized in that: The upper constraint layer and the lower constraint layer are both aluminum plates, and the packaging layer is EVA foam.

6. The STF sandwich energy dissipation component with frequency-dependent damping according to claim 1, characterized in that: The thickening ratio of the shear thickening fluid increases with the increase in the mass fraction of the nano-silicon dioxide particles, wherein the thickening ratio is defined as the ratio of the peak viscosity of the shear thickening fluid after thickening to the viscosity at the critical shear rate.

7. The characteristic analysis method of STF sandwich energy dissipation component with damping varying with frequency is characterized by: include: Establishing a constrained damping model of the STF sandwich energy-absorbing component, wherein the STF sandwich energy-absorbing component includes an upper constrained layer, a lower constrained layer, and a damping layer disposed between the upper constrained layer and the lower constrained layer, wherein the damping layer is composed of a shear thickening fluid; Obtaining the storage modulus and loss modulus of the shear thickening fluid through rheological testing; Based on the constrained damping model and the energy method analysis principle, a deformation analysis equation group of the STF sandwich energy-absorbing component is established, wherein the deformation analysis equation group includes an equation for the relationship between angular displacement and axial displacement, an equation for calculating shear deformation, and an equation for stress analysis; Solving the deformation analysis equations to obtain the total vibration energy and total loss energy of the STF sandwich energy-absorbing component; Calculating a damping ratio of the STF sandwich energy-absorbing component, where the damping ratio is defined as a ratio of the total loss energy to the total vibration energy; The variation law of the damping ratio of the STF sandwich energy-absorbing component with frequency under different parameter combinations is analyzed.

8. The method for analyzing the characteristics of STF sandwich energy-absorbing components with damping varying with frequency according to claim 7, characterized in that: The rheological tests include: Steady-state rheological test, setting the shear rate range to 0.01s -1 to 1000s -1 , obtaining the relationship between the viscosity of the shear thickening fluid and the shear rate; In the dynamic rheological test, the shear strain amplitude was set to 40%, 80%, 120% and 160%, the frequency sweep range was 1 rad·s-1 to 1000 rad·s-1, the frequency was set to 1 rad·s-1, 5 rad·s-1, 10 rad·s-1 and 20 rad·s-1, the strain sweep range was 1 to 1000, and the relationship between the storage modulus and the loss modulus of the shear thickening fluid and the angular frequency was obtained.

9. The method for analyzing the characteristics of STF sandwich energy-absorbing components with damping varying with frequency according to claim 7, characterized in that: In the deformation analysis equation group, the shear deformation calculation equation is: Where γ is the shear strain of the STF damping layer, δ B and δ C are the displacements on both sides of the STF damping layer, H2 is the thickness of the STF damping layer, θ is the angular displacement, δ1 and δ3 are the axial displacements of the upper and lower constrained layers, respectively, H 31 is the distance between the neutral surface of the lower constrained layer and the neutral surface of the upper constrained layer.

10. The method for analyzing characteristics of STF sandwich energy-absorbing components with damping varying with frequency according to claim 7, characterized in that: The following steps are also included: Analyze the effect of the mass fraction of nano-silica particles in the shear thickening fluid on the damping ratio of the STF sandwich energy-absorbing component; Analyze the effect of the damping layer thickness ratio on the damping ratio of the STF sandwich energy dissipation component; Based on the analysis results, an optimal parameter combination suitable for a specific frequency range is determined.

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