Method for characterizing the settlement of a (super) heavy machine tool foundation under the influence of concrete creep

Abstract

The application discloses a kind of (super) heavy machine tool foundation settlement characterization method under concrete creep induction, belong to high-end numerical control machine tool precision maintainability technical field.It is shown in research that concrete foundation is (super) heavy machine tool weak position, aiming at the problem that uneven settlement of foundation is caused by creep, leading to machine tool precision degradation, the application introduces the effective modulus method of age adjustment to characterize concrete creep, uses time hardening correction model, completes concrete foundation settlement analysis by finite element technology, proposes a kind of general (super) heavy machine tool foundation settlement characterization method, analyzes (super) heavy bed foundation settlement change rule, realizes foundation settlement prediction and evaluation in the service process of machine tool, strengthens the precision maintaining ability of domestic high-end numerical control machine tool.

Description

Technical Field

[0001] This invention belongs to the field of high-end CNC machine tool precision maintenance technology, and relates to the characterization of creep and settlement of concrete foundations. Combining the effective modulus method of concrete age adjustment and finite element technology, a general method for characterizing the settlement of (ultra) heavy machine tool foundations is proposed. Background Technology

[0002] For (ultra)heavy-duty machine tools, as the service life of the machine tool increases, the concrete foundation undergoes irreversible creep under the long-term action of the weight of the workpiece (hundred-ton level) and the machine tool itself, leading to uneven foundation settlement. The microscopic settlement deformation of the foundation is amplified and transmitted step-by-step through the bed, column, etc., to the tool tip, resulting in significant loss of spatial geometric accuracy. This invention introduces the effective elastic modulus of concrete over time, employs a time-hardening correction model, and combines finite element technology to complete the concrete foundation settlement analysis, proposing a general method for characterizing the foundation settlement of (ultra)heavy-duty machine tools, enabling the prediction and assessment of foundation settlement during machine tool service. This invention provides a theoretical basis and technical guidance for improving the accuracy retention of high-end CNC machine tools, achieving the long-term working requirements of high-precision machining. Summary of the Invention

[0003] The key to this invention is the introduction of the age-adjusted effective modulus method, the use of a time-hardening correction model, and the combination of finite element technology to complete the settlement analysis of concrete foundations. This invention proposes a general method for characterizing the settlement of (ultra) heavy-duty machine tool foundations, thereby achieving a quantitative characterization of machine tool foundation settlement.

[0004] To achieve the above objectives, the technical solution adopted by this invention is a method for characterizing the settlement of (ultra) heavy machine tool foundations under concrete creep-induced conditions, comprising the following steps performed sequentially:

[0005] Step 1: Based on the age-adjusted effective modulus method, establish a calculation model for the effective elastic modulus of concrete as it changes over time, providing a material constitutive basis for subsequent creep analysis;

[0006] Step 2: Based on the effective elastic modulus obtained in Step 1, establish the creep equation for the concrete foundation, and determine the creep model parameters by fitting experimental data to achieve a mathematical description of the creep behavior;

[0007] Step 3: Embed the creep equation obtained in Step 2 into the finite element analysis, divide the machine tool foundation area, fit the foundation settlement function of different areas, and finally realize the quantitative characterization of foundation settlement.

[0008] Further, in step 1, a calculation model for the change of the effective elastic modulus of concrete over time is established based on the age-adjusted effective modulus method. Specifically, under constant temperature conditions, the instantaneous elastic strain, basic creep flexibility, and drying creep flexibility are first calculated based on the concrete's age at the calculation time, loading time, and drying start age. Based on this, the aging coefficient and creep coefficient are introduced, and the influence of non-stress factors is ignored. The age-adjusted effective modulus method is then used to calculate the effective elastic modulus of concrete at any loading time. This effective elastic modulus reflects the stiffness reduction characteristics of concrete under long-term load due to creep.

[0009] Further, in step 2, based on the effective elastic modulus output in step 1, a creep equation for the concrete foundation is established, and the model parameters are determined by fitting experimental data. Specifically, this step uses the effective elastic modulus calculated in step 1 as input. First, based on the physical similarity between metal creep and concrete creep, a basic form of the creep equation containing multiple dimensionless parameters is established. Then, time dependence is introduced, and the effective elastic modulus output in step 1 is substituted into the creep equation to construct a complete creep equation considering time effects. The stress range is constrained to ensure that it does not exceed a specified proportion of the characteristic value of the concrete compressive strength. Finally, a nonlinear function fitting method is used to fit the constructed creep equation with the experimental data, identify the specific values ​​of the dimensionless parameters in the equation, and thus obtain a mathematical expression that can accurately describe the creep behavior of the concrete foundation.

[0010] Further, in step 3, the creep equation output from step 2 is embedded into the finite element analysis, and the quantitative characterization of foundation settlement is achieved through region division and function fitting. This step uses the complete creep equation identified in step 2 as the core input. First, based on the actual load-bearing characteristics of the (ultra) heavy-duty gantry milling machine foundation, the foundation is divided into at least two different regions, corresponding to parts with different load-bearing conditions and settlement characteristics. Then, the creep equation output from step 2 is embedded into the finite element simulation software as the material constitutive model of the concrete foundation, and the settlement behavior of the foundation under long-term load is numerically simulated to calculate the settlement data of each region over time. Next, based on the settlement data obtained from the finite element simulation, the least squares method is used to fit the foundation settlement function of each region, obtaining a mathematical expression for the settlement amount of each region over time. Finally, the fitted settlement function is used to predict and evaluate the foundation settlement during the machine tool's service life, achieving a quantitative characterization of uneven settlement in different regions.

[0011] Furthermore, step 1 further includes the following sub-steps:

[0012] Step 1.1: Under constant temperature conditions, calculate the instantaneous elastic strain, basic creep flexibility, and drying creep flexibility of the concrete based on the calculation time age, loading time age, and drying start age, and solve them according to industry design standards.

[0013] Step 1.2: Based on the age-adjusted effective modulus method, ignoring the influence of non-stress factors, the aging coefficient and creep coefficient are introduced to calculate the effective elastic modulus of concrete as a function of time;

[0014] The connection between step 1.1 and step 1.2 is as follows: the total strain composition provided in step 1.1 is the basic input for the effective modulus calculation in step 1.2.

[0015] Furthermore, step 2 further includes the following sub-steps:

[0016] Step 2.1: Based on the physical similarity between metal creep and concrete creep, establish the basic form of the creep equation containing multiple dimensionless parameters;

[0017] Step 2.2: Introduce time dependence, combine the effective elastic modulus obtained in Step 1.2, construct a creep equation that considers the time effect, and limit the stress to not exceed a specified proportion of the characteristic value of the concrete compressive strength;

[0018] Step 2.3: Using the nonlinear function fitting method, the creep equation in Step 2.2 is fitted with the experimental data to identify the specific values ​​of the dimensionless parameters in Step 2.1;

[0019] The connection between steps 2.1 and 2.2 is as follows: Step 2.1 provides the basic form of the creep equation, and Step 2.2 introduces time dependence and effective modulus constraints on this basis; The connection between steps 2.2 and 2.3 is as follows: The equation form given in Step 2.2 is used as the fitting model, and Step 2.3 completes parameter identification through experimental data.

[0020] Furthermore, step 3 further includes the following sub-steps:

[0021] Step 3.1: Based on the actual load-bearing characteristics of the (ultra) heavy-duty gantry milling machine foundation, divide the foundation into at least two different areas, including the first area and the second area;

[0022] Step 3.2: Input the creep equation identified in Step 2.3 into the finite element simulation software to calculate the settlement data of each region under long-term load;

[0023] Step 3.3: Based on the finite element simulation data obtained in Step 3.2, the basic settlement functions of the first and second regions are fitted using the least squares method to achieve zonal quantitative characterization.

[0024] Step 3.4: Use the settlement function obtained in Step 3.3 to predict and assess foundation settlement during machine tool service;

[0025] The connection between steps 3.1 and 3.2 is as follows: the region division in step 3.1 provides geometric and boundary conditions for the finite element modeling in step 3.2; the connection between steps 3.2 and 3.3 is as follows: the finite element simulation results provide data for the function fitting in step 3.3; the connection between steps 3.3 and 3.4 is as follows: the settlement function obtained by fitting is directly used for actual settlement prediction.

[0026] Furthermore, the settlement functions of the first and second regions are obtained by least squares fitting, respectively, to describe the settlement patterns of their respective regions over time.

[0027] Furthermore, the method is applicable to the characterization, prediction, and evaluation of uneven settlement of foundations induced by concrete creep during the service of (ultra) heavy-duty machine tools, and can be used to guide the design and maintenance of machine tool accuracy retention.

[0028] Furthermore, the method combines finite element technology with a time-hardening correction model to form a general method for characterizing the settlement of (ultra) heavy machine tool foundations, which is applicable to the settlement analysis of (ultra) heavy machine tool foundations of different tonnages and structural forms.

[0029] The present invention has the following advantages and positive effects: 1. It introduces the age-adjusted effective modulus method to characterize the creep of concrete foundations, revealing the creep law of heavy machine tool foundations under the cumulative effect of time; 2. It proposes a general (ultra) heavy machine tool foundation settlement characterization method, and for the first time realizes the quantitative characterization of foundation settlement of this gantry boring and milling machine. Attached Figure Description

[0030] Figure 1 A schematic diagram of the foundation of a heavy machine tool.

[0031] Figure 2 Quantitative characterization of foundation settlement in different regions. Detailed Implementation

[0032] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0033] A method for characterizing the settlement of (ultra)heavy-duty machine tool foundations induced by concrete creep is presented, belonging to the technical field of precision maintenance for high-end CNC machine tools. Research indicates that concrete foundations are weak points in (ultra)heavy-duty machine tools. Addressing the problem of uneven foundation settlement caused by creep, leading to machine tool precision degradation, this invention introduces the age-adjusted effective modulus method to characterize concrete creep. A time-hardening correction model is employed, and finite element method is used to analyze concrete foundation settlement. This proposes a general method for characterizing the settlement of (ultra)heavy-duty machine tool foundations, analyzing the settlement variation law of (ultra)heavy-duty machine tool foundations, enabling the prediction and assessment of foundation settlement during machine tool service, and enhancing the precision maintenance capability of domestically produced high-end CNC machine tools. Specifically, it includes:

[0034] Step 1: Based on the age-adjusted effective modulus method, establish a calculation model for the effective elastic modulus of concrete as it changes over time, providing a material constitutive basis for subsequent creep analysis;

[0035] Step 2: Based on the effective elastic modulus obtained in Step 1, establish the creep equation for the concrete foundation, and determine the creep model parameters by fitting experimental data to achieve a mathematical description of the creep behavior;

[0036] Step 3: Embed the creep equation obtained in Step 2 into the finite element analysis, divide the machine tool foundation area, fit the foundation settlement function of different areas, and finally realize the quantitative characterization of foundation settlement.

[0037] Step 1 calculates the effective elastic modulus of concrete as it decays over time and passes this modulus to Step 2. Step 2 uses the received effective elastic modulus as a core parameter to construct and identify the complete creep equation, which is then passed to Step 3. Step 3 embeds the received creep equation into a finite element simulation, obtains the settlement function through partitioned fitting, and finally completes the quantitative characterization of foundation settlement. These three steps are sequential and interconnected; the output of one step becomes the input of the next, together forming a complete method for characterizing the settlement of heavy machine tool foundations induced by concrete creep.

[0038] Specifically, the technical solution is as follows:

[0039] Step 1: Age-Adjusted Effective Modulus Method

[0040] Step 1.1 Under constant temperature and any loading time t, the total strain of the concrete at a certain moment is: Its core expression is as follows:

[0041]

[0042]

[0043] The concrete age (in days) at the time of calculation; The concrete age (in days) at the time of loading; The drying start age (days). It is an instantaneous elastic strain. For basic creep flexibility, This represents the drying creep flexibility. It can be calculated and solved according to the industry design standards issued by the Ministry of Transport of China.

[0044] Step 1.2: Temporarily ignoring the influence of non-stress factors, the effective elastic modulus of concrete as a function of age-adjusted effective modulus can be obtained. :

[0045]

[0046] The aging factor is... The creep coefficient is .

[0047] Step 2: Creep Equation for Concrete Foundation

[0048] Step 2.1 From the perspective of macroscopic physical phenomena, metal creep and concrete creep have a high degree of similarity in their mechanisms, and their creep equations are expressed as follows:

[0049]

[0050] In the formula , , , All are dimensionless parameter fitting values.

[0051] Step 2.2 considers the time-dependent creep equation:

[0052]

[0053] In the formula It is the effective elastic modulus. It is stress, and it should not exceed 0.45. (Characteristic value of compressive strength of concrete).

[0054] Step 2.3 Combining equations (3) and (4), the lsqcurvefit nonlinear function is used for fitting to identify... , , , The value of .

[0055] Step 3 Characterization of settlement of heavy machine tool foundation

[0056] Step 3.1 Based on the foundation bearing characteristics of a certain gantry milling machine, the foundation area is divided, such as... Figure 1 As shown.

[0057] Step 3.2 Combine the finite element simulation data and use least squares to fit the settlement function of different areas of the foundation to realize the characterization of the foundation settlement of different areas of the heavy machine tool.

[0058] Area 1:

[0059]

[0060]

[0061] Area 2:

[0062]

[0063] (6)

[0064] The above function realizes the quantitative characterization of foundation settlement in different areas of a gantry milling machine.

[0065] The present invention provides a method for characterizing the settlement of (ultra) heavy machine tool foundations under concrete creep-induced conditions, which has the following advantages compared with the prior art:

[0066] This invention introduces the age-adjusted effective modulus method, combining key parameters such as concrete age, loading age, and initial drying age to establish a decay model of the effective elastic modulus of concrete over time. This method can accurately describe the creep behavior of concrete foundations under long-term loads, breaking through the traditional simplistic approach of treating concrete as a time-invariant material, and revealing the intrinsic mechanism of the gradual degradation of foundation stiffness and continuous settlement during the service of (ultra)heavy machine tools.

[0067] This invention establishes a time-dependent creep equation and uses a nonlinear function fitting method to identify model parameters, transforming the abstract behavior of concrete creep into a calculable and predictable mathematical expression. Based on this, and combining finite element simulation technology and the least squares fitting method, a function for the change of foundation settlement over time is constructed for different regions. This function can quantitatively describe the uneven settlement in different areas, changing the previous reliance on empirical estimation or rough measurement, and achieving a leap from qualitative analysis to quantitative characterization of machine tool foundation settlement.

[0068] The method proposed in this invention is independent of specific machine tool models or foundation structures. By adjusting loading conditions, geometric partitioning, and finite element parameters, it can be applied to the settlement analysis of (ultra) heavy-duty machine tool foundations of different tonnages and structural forms. This method has good portability and promotional value, providing a unified technical framework for the precision-maintaining design, service-life maintenance, and settlement prediction and assessment of high-end CNC machine tools.

[0069] This invention clarifies the mechanism by which minute foundation settlement induced by concrete creep is progressively transmitted to the machine bed, column, and ultimately amplified to the tool tip during machine tool service, resulting in a loss of spatial geometric accuracy. By enabling early prediction and quantitative assessment of foundation settlement, it can guide pre-adjustment schemes during machine tool installation, settlement monitoring strategies during service, and foundation reinforcement measures when necessary. This effectively extends the high-precision machining life of (ultra-)heavy-duty machine tools, meeting the urgent needs of the manufacturing industry for long-term stable machining of large and complex components.

[0070] This invention follows a main process of "effective modulus calculation—creep equation construction—finite element simulation—partition function fitting," with a logically arranged sequence, clear connections, and well-defined input-output relationships between each step. Engineers can independently analyze and characterize machine tool foundation settlement using the provided process, combined with conventional concrete material parameters and finite element software, demonstrating strong engineering operability and practical value.

[0071]

Claims

1. A method for characterizing the settlement of (ultra)heavy machine tool foundations induced by concrete creep, characterized in that, The following steps are performed sequentially: Step 1: Based on the age-adjusted effective modulus method, establish a calculation model for the effective elastic modulus of concrete as it changes over time, providing a material constitutive basis for subsequent creep analysis; Step 2: Based on the effective elastic modulus obtained in Step 1, establish the creep equation for concrete foundations, and determine the creep model parameters by fitting experimental data to achieve a mathematical description of creep behavior; Step 3: Embed the creep equation obtained in Step 2 into the finite element analysis, divide the machine tool foundation area, fit the foundation settlement function of different areas, and finally realize the quantitative characterization of foundation settlement.

2. The method for characterizing settlement of (ultra) heavy machine tool foundations under concrete creep-induced conditions according to claim 1, characterized in that, Step 1 further includes the following sub-steps: Step 1.1: Under constant temperature conditions, calculate the instantaneous elastic strain, basic creep flexibility, and drying creep flexibility of the concrete based on the calculation time age, loading time age, and drying start age, and solve them according to industry design standards. Step 1.2: Based on the age-adjusted effective modulus method, ignoring the influence of non-stress factors, the aging coefficient and creep coefficient are introduced to calculate the effective elastic modulus of concrete as a function of time; The connection between step 1.1 and step 1.2 is as follows: the total strain composition provided in step 1.1 is the basic input for the effective modulus calculation in step 1.

2.

3. The method for characterizing settlement of (ultra) heavy machine tool foundations under concrete creep-induced conditions according to claim 1, characterized in that, Step 2 further includes the following sub-steps: Step 2.1: Based on the physical similarity between metal creep and concrete creep, establish the basic form of the creep equation containing multiple dimensionless parameters; Step 2.2: Introduce time dependence, combine the effective elastic modulus obtained in Step 1.2, construct a creep equation that considers the time effect, and limit the stress to not exceed a specified proportion of the characteristic value of the concrete compressive strength; Step 2.3: Using the nonlinear function fitting method, the creep equation in Step 2.2 is fitted with the experimental data to identify the specific values ​​of the dimensionless parameters in Step 2.1; The connection between steps 2.1 and 2.2 is as follows: Step 2.1 provides the basic form of the creep equation, and Step 2.2 introduces time dependence and effective modulus constraints on this basis; The connection between steps 2.2 and 2.3 is as follows: The equation form given in Step 2.2 is used as the fitting model, and Step 2.3 completes parameter identification through experimental data.

4. The method for characterizing settlement of (ultra) heavy machine tool foundations under concrete creep-induced conditions according to claim 1, characterized in that, Step 3 further includes the following sub-steps: Step 3.1: Based on the actual load-bearing characteristics of the (ultra) heavy-duty gantry milling machine foundation, divide the foundation into at least two different areas, including the first area and the second area; Step 3.2: Input the creep equation identified in Step 2.3 into the finite element simulation software to calculate the settlement data of each region under long-term load; Step 3.3: Based on the finite element simulation data obtained in Step 3.2, the basic settlement functions of the first and second regions are fitted using the least squares method to achieve zonal quantitative characterization. Step 3.4: Use the settlement function obtained in Step 3.3 to predict and assess foundation settlement during machine tool service; The connection between steps 3.1 and 3.2 is as follows: the region division in step 3.1 provides geometric and boundary conditions for the finite element modeling in step 3.2; the connection between steps 3.2 and 3.3 is as follows: the finite element simulation results provide data for the function fitting in step 3.3; the connection between steps 3.3 and 3.4 is as follows: the settlement function obtained by fitting is directly used for actual settlement prediction.

5. The method for characterizing settlement of (ultra) heavy machine tool foundations under concrete creep-induced conditions according to claim 4, characterized in that, The settlement functions of the first and second regions were obtained by least squares fitting, respectively, to describe the settlement patterns of their respective regions over time.

6. The method for characterizing settlement of (ultra) heavy machine tool foundations under concrete creep-induced conditions according to claim 1, characterized in that, The method is applicable to the characterization, prediction and evaluation of uneven settlement of foundations induced by concrete creep during the service of (ultra) heavy machine tools, and can be used to guide the design and maintenance of machine tool accuracy maintenance.

7. The method for characterizing settlement of (ultra) heavy machine tool foundations under concrete creep-induced conditions according to claim 1, characterized in that, The method combines finite element technology with a time-hardening correction model to form a general method for characterizing the settlement of (ultra) heavy machine tool foundations, which is applicable to the settlement analysis of (ultra) heavy machine tool foundations of different tonnages and structural forms.

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