A method for calculating fatigue life of automobile rubber suspension under random load

Abstract

This invention discloses a method for calculating the fatigue life of automotive rubber suspensions under random loads, comprising the following steps: acquiring the suspension force load spectrum; obtaining the force-displacement relationship and strain results of the suspension under different displacement loads through finite element analysis; converting the force load spectrum of the suspension reinforced pavement into the suspension displacement load spectrum; dividing the suspension displacement load spectrum into 2n displacement load component spectra according to stiffness; conducting fatigue tests under different R-ratio conditions to obtain fatigue life; obtaining the effective tensile strain of the dumbbell-shaped test column under different R-ratio conditions through finite element analysis; establishing a uniform R-ratio condition SN curve based on the effective tensile strain and measured fatigue life; converting the suspension displacement load spectrum into the strain load spectrum at each point of the suspension finite element model, and calculating the fatigue life by rainflow counting and combining it with the uniform R-ratio condition SN curve. This invention can obtain the SN curve of the rubber material under a uniform R-ratio condition, which can be used to predict rubber fatigue under random loads.

Description

Technical Field

[0001] This invention relates to the field of fatigue analysis of automotive parts, and in particular to a calculation method based on the displacement load spectrum and fatigue damage of automotive rubber mounts. Background Technology

[0002] During vehicle operation, the rubber vibration isolators are subjected to two loads: low-frequency, high-amplitude road load spectra and periodic, high-frequency, low-amplitude vibrations caused by engine crankshaft torsion. Automotive rubber vibration isolators operate under random load conditions. Therefore, the fatigue life prediction of automotive rubber vibration isolators should consider the influence of random loads. Random loads generate dynamic stresses, leading to fatigue damage and ultimately fatigue fracture. Therefore, the acquisition and processing of road load spectra provides engineers with reliable data support for laboratory and multibody dynamics simulation analyses, enabling them to predict and assess the fatigue life of automotive components.

[0003] Generally, collected road spectrum data needs to be processed before it can be applied to simulation analysis and laboratory tests. Therefore, how to scientifically and realistically process road spectrum data directly affects the consistency between experimental results and actual effects. There are typically two methods for processing road spectrum data: the first is the load amplitude method, which involves selecting a constant load value based on the load information in the road spectrum and the engineer's personal experience for fatigue testing of the part; the second is the road spectrum iterative simulation method, which involves performing fatigue tests in the laboratory using an iterative method after simple screening of the collected road spectrum data. While the first method can quickly identify fatigue failure areas, its accuracy is low, it is heavily influenced by personal experience, and is too subjective. The second method can realistically reflect the actual load conditions of the part, but the testing cycle is long, generally requiring more than a month per cycle, resulting in high costs and low resource utilization. Summary of the Invention

[0004] To accurately determine the fatigue damage of automotive rubber suspensions, this invention provides a method for calculating the fatigue life of automotive rubber suspensions under random loads. Finite element analysis is used to obtain the strain results of the suspension and the S / N curves of the suspension material under a unified R-ratio condition. By analyzing the force-displacement relationship of the suspension, the load spectrum of the suspension reinforced by the road surface obtained in the experimental field is transformed into a displacement load spectrum. Considering the nonlinearity of the suspension stiffness, the displacement load spectrum is segmented, and the strain load spectrum at each node in the finite element model of the suspension is fitted using the strain results of different displacement loads. Rainflow counting is performed on the fitted strain load spectrum, and the fatigue damage of the suspension under the road surface load spectrum is calculated using the S / N curves of the suspension material.

[0005] To achieve the objective of this invention, a method for calculating the fatigue life of automotive rubber suspension under random loads is provided, comprising the following steps:

[0006] (1) By conducting vehicle durability tests on reinforced road surfaces at the test track, the suspension force load time history (load spectrum) suitable for bench testing and simulation analysis was collected.

[0007] (2) Establish a finite element model of the suspension and analyze it to obtain the force-displacement relationship and displacement-strain relationship of the suspension.

[0008] (3) Based on the force-displacement relationship obtained in step (2), the suspension force load spectrum is transformed into the suspension displacement load spectrum.

[0009] (4) Considering the nonlinearity of the suspension stiffness, the displacement load spectrum of the suspension is divided into 2n displacement load component spectra according to stiffness.

[0010] (5) Conduct fatigue tests under working conditions of R>0, R=0 and R<0 to obtain fatigue life under working conditions with different R ratios.

[0011] (6) The effective tensile strain of the dumbbell-shaped test column under different R ratio conditions was obtained through finite element analysis. The effective tensile strain and the measured fatigue life were fitted by the least squares method to establish the SN curve of the rubber material under a unified R ratio condition.

[0012] (7) Based on the strain results of the suspension displacement loading in step (2), transform the suspension displacement load component spectrum in step (4) into the suspension strain load spectrum.

[0013] (8) By rain flow counting, the suspended strain load spectrum is converted into multiple Block load blocks.

[0014] (9) Calculate the fatigue damage of the under-mounted Block load block based on the SN curve in step (6).

[0015] In step (3), the displacement load spectrum of the suspension needs to be transformed based on the geometry of the suspension. The force load spectrum of the reinforced pavement is collected by an accelerometer. The displacement load obtained by transforming the force-displacement relationship is not the actual displacement of the inner tube relative to the outer tube. Due to the limitations of the suspension structure, the displacement of the center point of the inner tube should be within a certain range (e.g., between -10mm and +15mm). When the load exceeds this range, the force load is approximately rigidly transmitted to the outer tube. The transformed displacement load is corrected according to this limit to obtain the displacement load spectrum of the suspension.

[0016] The basis for dividing the displacement load spectrum in step (4) is the inflection point between the linear segment and the nonlinear segment, as well as the midpoint of the tube impact limit block in the nonlinear segment.

[0017] The step (6) of obtaining the effective tensile strain of the dumbbell-shaped test column under different R ratio conditions is divided into the following three steps.

[0018] Step 1: Establish a finite element model of the dumbbell-shaped test column and apply displacement loads with different R-ratios to it. During a complete loading process, a point on the dumbbell-shaped test column reaches the reference strain ε. f and current strain ε f Cyclic loading is applied between ', with a strain range of Δε = ε f '-ε f Effective tensile strain ε t The criterion assumes that the damage is caused only by tension. Through secondary finite element analysis, the strain result at the valley of the displacement load is saved as the reference strain ε for calculating the effective tensile strain. f The strain during the displacement loading process is denoted as the current strain ε. f The difference between the current strain and the reference strain is denoted as the strain range Δε. To be applicable to multiaxial stress conditions, the effective tensile strain ε... t Composed of three equally weighted principal strains ε tm definition

[0019] ε t =ε t1 +ε t2 +ε t3 ,ε tm >0, m=1,2,3

[0020] In the global coordinate system, this can be represented as:

[0021]

[0022] Where [ε ti ε tj ε tk For effective tensile strain ε t Coordinates in the global coordinate system.

[0023] Step 2: By comparing the strain range components Δε m and the current strain component ε fm Determine the effective tensile strain components ε tm The size of the strain. According to the definition of effective tensile strain, only deformation within the tensile range will cause damage. Therefore, the strain range component ε tm and the current strain component ε fm All should be within the tensile range, and the strain range component ε tm It should also be subject to the limitations of the current strain components.

[0024]

[0025] Step 3: Effective tensile strain ε t The direction of the strain range Δε is consistent with the direction of the strain range Δε. Projecting the strain range Δε along the coordinate system direction yields the strain range components Δε. mThen, normalize it to obtain the direction matrix θ of the strain range Δε, which is the direction matrix of the effective tensile strain. The strain range is a 3×3 tensor, calculated using the following formula:

[0026] Δε=ε fm 'e m '-ε fm e m (1)

[0027] Its component expression form is:

[0028]

[0029] Where, ε fm The principal logarithmic strain components are m = 1, 2, 3. m ε is the direction cosine matrix. fm ' represents the principal logarithmic strain component during displacement loading, e m ' is the direction cosine corresponding to the principal logarithmic strain component during displacement loading.

[0030] Direction matrix of strain range Δε

[0031]

[0032] Its component form is:

[0033]

[0034] in Let Δε be the modulus of the strain range. 1i The strain range component Δε1 is projected along the x-direction in the global coordinate system. Strain range component

[0035] Δε1=ε' f1 -ε f1 (7)

[0036] Its component form is:

[0037] Δε1=[||ε' f1 ||cosα′1-||ε f1 ||cosα1||ε' f1 ||cosβ′1-||ε f1 ||cosβ1||ε' f1 ||cosγ′1-||ε f1 ||cosγ1] (8)

[0038] Step (7) establishes a load mapping channel by mapping the 2n displacement load component spectra from step (4) to the 2n displacement load strain results obtained in step (2). A piecewise linear method is used to fit the strain load spectrum at each point on the suspended finite element model, while considering the influence of pre-strain. The strain load spectrum calculation formula is as follows:

[0039]

[0040] Among them, U k (t) is the strain load component spectrum, ε k,FEResult The displacement load is U k,FE The strain result of the suspension, ε Base This is the pre-strain result after the diameter is reduced and the suspension is in place.

[0041] Compared with the prior art, the present invention has at least the following positive effects:

[0042] 1) Through secondary development of finite element method, the SN curve of rubber material under uniform R ratio working condition was obtained, which can be used to predict rubber fatigue under random load.

[0043] 2) By using a piecewise fitting method, the strain load spectrum at each node of the suspension is fitted, and the fitted strain load spectrum is used for fatigue life analysis. The load division is based on the suspension stiffness curve, which is universal and can calculate the random load fatigue life of rear tie rod suspensions of different sizes and shapes, providing a reference for the design of suspension systems.

[0044] 3) This invention can retain the strain ratio information of random loads, making the calculated fatigue life more accurate.

[0045] 4) This invention uses effective tensile strain as a damage parameter, which can simultaneously consider the effects of normal strain and tangential strain. It is an accurate critical plane method, and the calculation process is simple, which helps to improve calculation efficiency and reduce calculation time. Attached Figure Description

[0046] Figure 1 This is a flowchart of a method for calculating the fatigue life of automotive rubber suspension under random load, provided by an embodiment of the present invention.

[0047] Figure 2 This is the effective tensile strain contour map of the dumbbell-shaped test column in this embodiment of the invention.

[0048] Figure 3 This is a schematic diagram of the effective tensile strain SN curve in an embodiment of the present invention.

[0049] Figure 4 This is a uniaxial fatigue damage cloud map of the Ncode rubber suspension under random load in an embodiment of the present invention. Detailed Implementation

[0050] To make the objectives, technical solutions, and advantages of the present invention clearer and more explicit, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0051] Please see Figure 1 The present invention provides a method for calculating the fatigue life of automotive rubber suspension under random loads, comprising the following steps:

[0052] (1) Conduct vehicle durability tests on reinforced road surfaces at the test track and collect suspension force load time history (load spectrum) suitable for bench tests and simulation analysis;

[0053] (2) Establish a finite element model of the suspension and analyze it to obtain the force-displacement relationship and displacement-strain relationship of the suspension.

[0054] (3) Based on the force-displacement relationship obtained in step (2), the suspension force load spectrum is transformed into the suspension displacement load spectrum.

[0055] (4) Considering the nonlinearity of the suspension stiffness, the displacement load spectrum of the suspension is divided into 2n displacement load component spectra according to stiffness.

[0056] To fit a nonlinear curve using multiple linear segments, theoretically, the force-displacement relationship curve needs to be divided into sufficiently fine segments, meaning the displacement load spectrum needs to be segmented a sufficiently large number of times. Considering engineering feasibility, the segmentation should be determined by the inflection points where stiffness changes abruptly. One or two points are selected in the linear segments, and two or more points are selected in the nonlinear segments. To ensure symmetry, the same number of segmentation points are used for both the positive and negative strokes, resulting in a total of 2n segments. In some embodiments of this invention, the displacement load spectrum is divided into six components.

[0057] (5) Fatigue tests were conducted under different strain ratio conditions to obtain the fatigue life under different strain ratio conditions (R>0, R=0 and R<0), where the strain ratio

[0058] (6) The effective tensile strain of the dumbbell-shaped test column under different R ratio conditions was obtained through finite element analysis. The effective tensile strain and the measured fatigue life were fitted by the least squares method to establish the SN curve of the rubber material under a unified R ratio condition.

[0059] In some embodiments of the present invention, the obtained SN curves are as follows: Figure 3 As shown.

[0060] (7) Based on the strain results of the suspension displacement loading in step (2), the suspension displacement load component spectrum in step (4) is transformed into the suspension strain load spectrum.

[0061] The 2n displacement load component spectra in step (4) are matched one-to-one with the 2n displacement load strain results obtained in step (2), and a load mapping channel is established. The piecewise linear method is used to fit the strain load spectrum at each point on the suspended finite element model, while considering the influence of pre-strain.

[0062] (8) The suspended strain load spectrum is transformed into multiple Block load blocks by rain flow counting method.

[0063] (9) Calculate the fatigue damage of the Block load block under suspension based on the SN curve in step (6).

[0064] In some embodiments of the present invention, since road profiles are generally collected by professional engineers arranged by the OEM at the test track, and the road profiles collected by different OEMs are somewhat different, it is necessary to first check the collected road profiles to determine whether the input road profiles are suitable for laboratory and simulation analysis.

[0065] In some embodiments of the present invention, step (3) involves transforming the suspension displacement load spectrum based on the suspension geometry. The force load spectrum of the reinforced road surface is acquired by an accelerometer. The displacement load obtained through the force-displacement relationship transformation is not the relative displacement between the inner and outer suspension tubes. Due to the limitations of the suspension structure, the displacement of the center point of the inner suspension tube should be between -10mm and +15mm. When the load exceeds this range, the force load is approximately rigidly transmitted to the outer suspension tube. The transformed displacement load is corrected according to this limit to obtain the suspension displacement load spectrum.

[0066] In some embodiments of the present invention, step (4) is based on the inflection point between the linear segment and the nonlinear segment and the midpoint of the tube impact limiting block in the nonlinear segment.

[0067] In some embodiments of the present invention, step (6) of obtaining the effective tensile strain of the dumbbell-shaped test column under different R ratio conditions includes the following three steps:

[0068] Step 1: Establish a finite element model of the dumbbell-shaped test column and apply displacement loads with different R-ratios to it. During a complete loading process, a point on the dumbbell-shaped test column reaches the reference strain ε. f and current strain ε f Cyclic loading is applied between ', with a strain range of Δε = ε f '-ε f Effective tensile strain ε t The criterion assumes that the damage is caused only by tension. Through secondary finite element analysis, the strain result at the valley of the displacement load is saved as the reference strain ε for calculating the effective tensile strain. f The strain during the displacement loading process is denoted as the current strain ε.f The difference between the current strain and the reference strain is denoted as the strain range Δε. To be applicable to multiaxial stress conditions, the effective tensile strain ε... t Composed of three equally weighted principal strains ε tm definition

[0069] ε t =ε t1 +ε t2 +ε t3 ,ε tm >0, m=1,2,3

[0070] In the global coordinate system, this can be represented as:

[0071]

[0072] Where [ε ti ε tj ε tk For effective tensile strain ε t The coordinates in the global coordinate system. i represents the x-direction basis vector of the global coordinate system [1 0 0]. T , j represents the y-direction basis vector of the global coordinate system [0 1 0] T , where k represents the z-direction basis vector of the global coordinate system [0 0 1] T .

[0073] Step 2: By comparing the strain range components Δε m and the current strain component ε fm Determine the effective tensile strain components ε tm The magnitude of the effective tensile strain. According to the definition of effective tensile strain, only deformation within the tensile range will cause damage. Therefore, the variable range component ε tm and the current strain component ε fm All should be within the tensile range, and the strain range component ε tm It should also be subject to the limitations of the current strain components.

[0074]

[0075] Step 3: Effective tensile strain ε t The direction of the strain range Δε is consistent with the direction of the strain range Δε. Projecting the strain range Δε along the coordinate system direction yields the strain range components Δε. m Then, normalize it to obtain the direction matrix θ of the strain range Δε, which is the direction matrix of the effective tensile strain. The strain range is a 3×3 tensor, calculated using the following formula:

[0076] Δε=ε fm 'e m '-ε fm e m(1)

[0077] Its component expression form is:

[0078]

[0079] Where, ε fm Principal logarithmic strain component, e m =[cosα m cosβ m cosγ m ], m=1,2,3 are the direction cosines corresponding to the principal logarithmic strain components. ε fm ' represents the principal logarithmic strain component during displacement loading, e m '=[cosα m 'cosβ m 'cosγ m '] is the direction cosine corresponding to the principal logarithmic strain component during displacement loading.

[0080] Direction matrix of strain range Δε

[0081]

[0082] Its component form is:

[0083]

[0084] in Let Δε be the modulus of the strain range. 1i The strain range component Δε1 is projected along the x-direction in the global coordinate system. Strain range component

[0085] Δε1=ε' f1 -ε f1 (7)

[0086] Its component form is:

[0087] Δε1=[||ε' f1 ||cosα′1-||ε f1 ||cosα1||ε' f1 ||cosβ′1-||ε f1 ||cosβ1||ε' f1 ||cosγ′1-||ε f1 ||cosγ1] (8)

[0088] β′1 represents the current strain ε' f The first principal component ε' f1 The angle between the coordinate system and the Y-axis of the global coordinate system.

[0089] In an embodiment of the present invention, step (7) establishes a load mapping channel by mapping the 2n displacement load component spectra from step (4) to the 2n displacement load strain results obtained in step (2). A piecewise linear method is used to fit the strain load spectrum at each point on the suspended finite element model, while considering the influence of pre-strain. The strain load spectrum calculation formula is:

[0090]

[0091] Among them, U k (t) is the strain load component spectrum, ε k,FEResult The displacement load is U k,FE The strain result of the suspension, ε Base This is the pre-strain result after the diameter is reduced and the suspension is in place.

[0092] In some embodiments of the present invention, the radial indentation is -1.17 mm, and the displacement load U k,FE Some of the values ​​are shown in Table 1. The final fatigue damage is as follows: Figure 4 As shown, the larger fatigue damage is distributed near the rubber main spring, which is consistent with the fatigue failure location measured in the suspension, demonstrating the effectiveness of the method of the present invention.

[0093] Table 1 Displacement Load U k,FE Value

[0094]

[0095]

[0096] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for calculating the fatigue life of automotive rubber suspension under random loads, characterized in that, Includes the following steps: (1) Conduct vehicle durability tests on reinforced road surfaces at the test track and collect suspension force load spectra suitable for bench tests and simulation analysis; (2) Establish a finite element model of the suspension and analyze it to obtain the force-displacement relationship and displacement-strain relationship of the suspension; (3) Based on the force-displacement relationship obtained in step (2), the suspension force load spectrum is transformed into a suspension displacement load spectrum; (4) Considering the nonlinearity of the suspension stiffness, the displacement load spectrum of the suspension is divided into 2n displacement load component spectra according to stiffness. (5) Conduct fatigue tests under working conditions of R>0, R=0 and R<0 to obtain fatigue life under working conditions with different R ratios; (6) By using finite element analysis, the effective tensile strain of dumbbell-shaped test columns under different R ratio conditions is obtained, and the effective tensile strain and measured fatigue life are fitted to establish the SN curve of rubber materials under a unified R ratio condition. (7) Based on the displacement-strain relationship in step (2), the suspended displacement load component spectrum in step (4) is transformed into the suspended strain load spectrum by piecewise fitting. (8) Convert the suspended strain load spectrum into multiple Block load blocks; (9) Calculate the fatigue damage of the Block load block under suspension based on the SN curve in step (6).

2. The method for calculating the fatigue life of automotive rubber suspension under random load according to claim 1, characterized in that, The suspension force load spectrum is collected by an accelerometer.

3. The method for calculating the fatigue life of automotive rubber suspension under random load according to claim 1, characterized in that, In step (3), the transformation of the suspension displacement load spectrum is completed by combining the suspension geometry.

4. The method for calculating the fatigue life of automotive rubber suspension under random load according to claim 1, characterized in that, In step (3), the displacement load is obtained by transforming the force-displacement relationship; the displacement load obtained by transforming is corrected according to the displacement stroke range of the suspension to obtain the displacement load spectrum of the suspension.

5. The method for calculating the fatigue life of automotive rubber suspension under random load according to claim 1, characterized in that, In step (4), the basis for dividing the displacement load spectrum is the inflection point between the linear segment and the nonlinear segment, as well as the midpoint of the tube impact limit block in the nonlinear segment.

6. The method for calculating the fatigue life of automotive rubber suspension under random load according to claim 1, characterized in that, In step (6), the least squares method is used to fit the effective tensile strain and the measured fatigue life.

7. The method for calculating the fatigue life of automotive rubber suspension under random load according to claim 1, characterized in that, Step (6) to obtain the effective tensile strain of the dumbbell-shaped test column under different R-ratio conditions includes the following three steps: Step 1: Establish a finite element model of the dumbbell-shaped test column and apply displacement loads with different R-ratios to it: During a complete loading process, a point on the dumbbell-shaped test column reaches the reference strain ε. f and current strain ε f Cyclic loading is applied between ', with a strain range of Δε = ε f '-ε f Effective tensile strain ε t The criterion assumes that the damage is caused only by tension. Through secondary finite element analysis, the strain result at the valley of the displacement load is saved as the reference strain ε for calculating the effective tensile strain. f The strain during the displacement loading process is denoted as the current strain ε. f The difference between the current strain and the reference strain is denoted as the strain range Δε. To be applicable to multiaxial stress conditions, the effective tensile strain ε t Composed of three equally weighted principal strains ε tm definition e t =e t1 +e t2 +e t3 ,he tm >0,m=1,2,3 In the global coordinate system, this can be represented as: Where [ε ti ε tj ε tk For effective tensile strain ε t The coordinates in the global coordinate system, where i represents the x-direction basis vector of the global coordinate system [1 0 0]. T , j represents the y-direction basis vector of the global coordinate system [0 1 0] T , where k represents the z-direction basis vector of the global coordinate system [0 0 1] T ; Step 2: By comparing the strain range components Δε m and the current strain component ε fm Determine the effective tensile strain components ε tm Magnitude, strain range component ε tm and the current strain component ε fm All should be within the tensile range, and the strain range component ε tm It should also be subject to the limitations of the current strain components: Step 3: Effective tensile strain ε t The direction is consistent with the direction of the strain range Δε. Projecting the strain range Δε along the coordinate system direction yields the strain range components Δε. m Then, normalize it to obtain the direction matrix θ of the strain range Δε, which is the direction matrix of the effective tensile strain. The formula for calculating the strain range is: No = yes fm 'e m '-e fm e m (1) Its component expression form is: Where, ε fm Principal logarithmic strain component, e m =[cosα m cosβ m cosγ m ], m=1,2,3 are the direction cosines corresponding to the principal logarithmic strain components, ε fm ' represents the principal logarithmic strain component during displacement loading, e m '=[cosα m 'cosβ m ' cosγ m '] is the direction cosine corresponding to the principal logarithmic strain component during displacement loading; Direction matrix of strain range Δε Its component form is: in Let Δε be the modulus of the strain range. 1i The strain range component Δε1 is projected along the x-direction in the global coordinate system. De1=e' f1 -e f1 (7) Its component form is: δε1=[||ε' f1 ||cosα′1-||ε f1 ||cosα1 ||ε' f1 ||cosβ′1-||ε f1 ||cosβ1 ||ε' f1 ||cosγ′1-||ε f1 ||cosγ1] (8) β′1 represents the current strain ε' f The first principal component ε' f1 The angle between the coordinate system and the Y-axis of the global coordinate system.

8. The method for calculating the fatigue life of automotive rubber suspension under random load according to claim 1, characterized in that, In step (8), the suspended strain load spectrum is transformed into multiple Block load blocks by rainflow counting method.

9. A method for calculating the fatigue life of automotive rubber suspension under random load according to any one of claims 1-8, characterized in that, Step (7) matches the 2n displacement load component spectra in step (4) with the 2n displacement load strain results obtained in step (2) to establish a load mapping channel. The piecewise linear method is used to fit the strain load spectrum at each point on the suspended finite element model, while considering the influence of pre-strain.

10. The method for calculating the fatigue life of automotive rubber suspension under random load according to claim 9, characterized in that, The formula for calculating the strain load spectrum is: Among them, U k (t) is the strain load component spectrum, ε k,FEResult The displacement load is U k,FE The strain result of the suspension, ε Base This is the pre-strain result after the diameter is reduced and the suspension is in place.

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