Design method of dynamic creep-fatigue load for high temperature structure deformation accumulation under peak shaving condition

Abstract

The present application relates to the technical field of high-temperature component creep fatigue test and life assessment, and particularly relates to a high-temperature structure deformation accumulation dynamic creep fatigue load design method under a peak regulation working condition. High-temperature creep performance, cyclic deformation performance, a target test temperature, a typical start-stop number or equivalent cycle number, a main load level range during steady operation, and basic parameters of stress / strain control capability of a testing machine of a target high-temperature structure or a sample thereof are obtained. A stress / strain hybrid control mode is used to generate a dynamic creep fatigue load waveform of the high-temperature structure or the sample thereof. When a dynamic creep fatigue load is executed on a creep fatigue testing machine and a cycle feature meets preset stability and repeatability criteria, the load design is determined to be effective. The present application is easy to implement on existing equipment: the designed load waveform can be realized through software control on a creep fatigue testing machine with stress / strain double closed loop and program loading function, without the need to increase additional hardware, and the engineering operability is strong.

Description

Technical Field

[0001] This invention relates to the field of creep fatigue testing and life assessment technology for high-temperature components, and in particular to a design method for dynamic creep fatigue load of high-temperature structural deformation accumulation under peak-shaving conditions applicable to typical high-temperature power equipment such as gas turbines and high-temperature pipelines. Background Technology

[0002] High-temperature components such as gas turbine disks, turbine blades, and high-temperature pipes operate under high temperatures and high principal stress levels for extended periods during typical service. The constant or slowly changing stress caused by centrifugal force and internal pressure can lead to significant high-temperature creep deformation and related damage accumulation over a long period of time.

[0003] Meanwhile, during engine start-up, shutdown, and rapid switching of operating conditions, the temperature field and constraint conditions inside the components change, generating additional thermo-mechanical strain. These strain changes typically occur at low frequencies or intervals and can be considered as a strain-type fatigue process superimposed on long-term constant load creep. Overall, long-term constant load creep often occupies the majority of the time and dominates deformation accumulation, while strain fatigue caused by start-up and shutdown further weakens the structural safety margin on the basis of creep deformation.

[0004] To study this type of service characteristic characterized by "creep dominance and fatigue dependence," existing creep fatigue tests often employ cyclic loading with fixed strain or stress amplitudes, and set load-holding segments at the cyclic peaks or troughs. While traditional CCFI / HCFI loads can simulate the interaction between creep and fatigue to some extent, their cyclic peaks and troughs are usually set to fixed values ​​before the test, and fatigue cycles mostly revolve around fixed horizontal stresses or strains, making it difficult to accurately reflect the path-dependent behavior in actual service where "creep deformation first occurs under constant load, and then on the basis of this deformation, start-stop fatigue disturbances occur."

[0005] In existing dynamic creep fatigue load design, the common approach is to "update the reference for the next cycle with the strain at the end of the load holding period." This involves superimposing the fatigue strain path onto the new reference after creep deformation, allowing the fatigue cycle to migrate with the creep deformation, thus reflecting the creep-dominated and fatigue-dependent loading characteristics. However, this method does not constrain the geometric range of the cyclic strain path in the load construction. When the stress change is small during the load holding period and the strain difference before and after the load holding period is limited, the strain baseline may continuously shift in the unloading direction during the cycle, making it difficult to keep the cyclic trajectory within a reasonable range. This, in turn, affects the stable equivalent simulation of the load under long-term service conditions. Therefore, it is necessary to propose a dynamic creep fatigue load design method that constrains the cyclic strain path while maintaining the creep-dominated characteristics, to ensure the stability and controllability of the load path and more realistically characterize the deformation accumulation behavior of high-temperature components under frequent start-stop and long-term service conditions.

[0006] Therefore, there is an urgent need for a new dynamic creep fatigue load design method that, while maintaining the physical characteristics of "creep-dominated and fatigue-dependent", controls the strain stroke through geometric constraints and avoids unidirectional drift of the strain baseline, so as to improve the representativeness and controllability of test results for frequent start-stop and long-term service conditions. Summary of the Invention

[0007] The purpose of this invention is to provide a design method for dynamic creep fatigue load of high-temperature structure deformation accumulation under peak load conditions. By triggering constant stress holding in the strain control unloading section and applying geometric constraints on the unloading stroke, the unloading and loading strain strokes of each cycle remain fixed, while the constant stress holding position is adaptively adjusted along the unloading path. This not only reflects the load characteristics of constant load creep dominance and start-stop fatigue attached to it, but also avoids the distortion of test results caused by unidirectional drift of the cyclic reference.

[0008] The present invention adopts the following technical solution: The method for designing dynamic creep fatigue loads for high-temperature structures under peak-shaving conditions, as described in this invention, includes the following steps: S1. Obtain the basic parameters of the material's high-temperature creep properties, cyclic deformation properties, target test temperature, typical start-stop times or equivalent cycle times, main load-bearing capacity range during steady-state operation, and stress / strain control capability of the testing machine for the target high-temperature structure or its specimen. S2. Based on the aforementioned basic parameters, determine the following to be used during the experiment: Preset strain amplitude ε1; holding stress level σ_d; holding time t_h; strain loading and unloading rate; S3. Based on the preset strain amplitude ε1, holding stress level σ_d, holding time t_h and strain loading and unloading rate set in step S2, the dynamic creep fatigue load waveform of the high temperature structure or its specimen is generated by stress / strain hybrid control method. The dynamic creep fatigue loading process includes a strain-controlled loading stage, a strain-controlled unloading stage, and a strain-controlled unloading stage holding stage; the process continues until the strain-controlled loading cycle is completed, based on the number of cycles completed. S4. Execute the dynamic creep fatigue load on a creep fatigue testing machine with stress / strain hybrid control capability, record the strain-time curve, stress-time curve and stress-strain hysteresis curve, observe the stability of the stress plateau in the load holding section, the smoothness of control switching and the cyclic strain drift. When the cyclic characteristics meet the preset stability and repeatability criteria, the load design is determined to be effective.

[0009] The dynamic creep fatigue load design method for high-temperature structural deformation accumulation under peak-shaving conditions described in this invention includes, in S1, target high-temperature components such as gas turbine disks, turbine blades, high-temperature pipes, and standard specimens representing the local stress state of such components.

[0010] The dynamic creep fatigue load design method for high-temperature structures under peak-shaving conditions described in this invention, wherein step 3, which uses a stress / strain hybrid control method to generate the dynamic creep fatigue load of the high-temperature structure or its specimen, is a strain-controlled loading stage as follows: Starting from the current cycle's initial strain state, the strain is applied up to the peak strain using strain control; the increment of the peak strain relative to the cycle's initial strain is set to a preset strain amplitude ε1; The preset strain amplitude ε1 is selected by referring to the equivalent strain variation range at key locations under start-stop or temperature gradient conditions, and is determined comprehensively by combining the material's cyclic deformation characteristics and the testing machine's range. Generally, it is determined to be 0.25%-1.2% based on pure fatigue tests of the material at the same temperature. The unloading phase of strain control is as follows: after loading to the peak value during the loading phase, the strain control method is used for unloading. When the stress reaches the preset holding stress σ_d, the strain from the peak strain unloading to the trigger point is recorded as ε2, and the stress control is switched to hold for t_h at σ = σ_d. The strain control unloading phase is as follows: After the strain control is completed, switch back to strain control and continue unloading the strain ε3 from the strain state at the end of the strain control. The unloaded strain ε3 satisfies the following constraints:

[0011] Based on the constraint relationship of the unloading strain ε3, the total unloading strain expression from the peak strain to the valley strain is as follows: ε2 + ε3 = 2ε1 The cycle is completed by the above-mentioned strain control loading, unloading, and load holding stages; Starting from the valley strain of the dynamic creep fatigue load waveform of a high-temperature structure or its specimen generated by a stress / strain hybrid control method, the strain 2ε1 is applied using a strain control method to return the strain to near the peak strain region, thereby completing a dynamic creep fatigue cycle with an unloading amplitude of -2ε1 and an loading amplitude of +2ε1.

[0012] The dynamic creep fatigue load design method for high-temperature structural deformation accumulation under peak-shaving conditions described in this invention uses the load-bearing stress σ_d, which is selected based on the principal stress level at the target location under steady-state operating conditions, preferably the representative nominal stress or its equivalent value at that location during long-term service.

[0013] The dynamic creep fatigue load design method for high-temperature structural deformation accumulation under peak-shaving conditions described in this invention, wherein the stress trigger zone is set based on the oscillation caused by the switching of strain / stress control during the unloading stage, is expressed as follows:

[0014] Its minimum duration is Δt. Stress control load holding only switches to the mode when stress enters the trigger zone and the duration exceeds Δt. To maintain load stress, The allowable overshoot stress range when switching control.

[0015] The present invention describes a method for designing dynamic creep fatigue loads for high-temperature structures under peak load conditions. After the strain control cycle reaches its peak value, strain unloading is performed, and the strain variable is ε2. Then, load holding is performed, and after the load holding ends, the unloading dependent variable is ε3. ε2 and ε3 are allowed to vary in different cycles, but the total unloading strain variable ε2 + ε3 is constant at 2ε1 to ensure that the unloading geometric stroke is fixed in each cycle, while the load holding position is dynamically adjusted along the unloading path according to the material response.

[0016] The dynamic creep fatigue load design method for high-temperature structural deformation accumulation under peak-shaving conditions described in this invention, in the cyclic execution process of step S3, continuously records the peak strain, valley strain and strain at the end of the load holding period for each cycle, tracks the drift of the strain baseline and the center of the hysteresis loop, and divides the test process into a deformation overall downward shift stage, a basic stable stage and an overall upward shift stage, to correspond to the deformation accumulation behavior of different service stages.

[0017] The dynamic creep fatigue load design method for high-temperature structural deformation accumulation under frequent start-stop conditions described in this invention uses a creep fatigue testing machine in step S4 that has high-temperature environment control and stress / strain dual closed-loop control functions.

[0018] The method for designing dynamic creep fatigue loads for high-temperature structural deformation accumulation under frequent start-stop conditions, as described in this invention, is characterized in that: the time proportion of the constant stress holding period in the dynamic creep fatigue load is greater than the time proportion of the fixed strain stroke period, so as to reflect the working condition characteristics of constant load creep deformation dominating and start-stop strain fatigue intervals occurring during long-term service. Beneficial effects

[0019] The dynamic creep fatigue load design method for high-temperature structural deformation accumulation under frequent start-stop conditions provided by this invention is creep-dominated and fatigue-dependent: the load waveform includes a constant stress holding segment in each cycle, which corresponds to the long-term constant load creep process. Strain-type fatigue is superimposed on the constant load creep deformation by a fixed strain stroke, which conforms to the physical characteristics of frequent start-stop and long-term service conditions.

[0020] This invention employs controllable geometric stroke to avoid unidirectional drift: by introducing a geometric constraint of ε3 = 2ε1 − ε2, it ensures that the total unloading stroke and total loading stroke of each cycle are constant at 2ε1. This preserves the degree of freedom for the load-bearing trigger position to change with the cycle, while avoiding the phenomenon that the strain baseline will continue to drift in one direction, causing the sample to fail prematurely.

[0021] Under the dynamic creep fatigue load waveform of this invention, different deformation stages can be distinguished: by tracking the relationship between peak strain, valley strain and strain at the end of load holding, the test process can be divided into an overall downward shift stage, a basic stable stage and an overall upward shift stage, which makes it easy to correlate the test results with the deformation accumulation behavior of different stages of actual service.

[0022] This invention is easy to implement on existing equipment: the designed load waveform can be realized by software control on a creep fatigue testing machine with stress / strain dual closed loop and programmed loading functions, without the need for additional hardware, and is highly operable in engineering. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the control waveform of the dynamic creep fatigue load of the strain-time curve according to the present invention. Figure 2 This is a schematic diagram of the control waveform of the dynamic creep fatigue load of the stress-time curve according to the present invention. Figure 3 This is a schematic diagram illustrating the dynamic creep fatigue load of the present invention as an equivalent superposition of constant amplitude fatigue and constant stress creep. Detailed Implementation

[0024] To make the objectives and technical solutions of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0025] The present invention provides a method for designing dynamic creep fatigue loads for high-temperature structures under peak-shaving conditions, with the following steps for setting load parameters and implementing control logic: S1. On a creep fatigue testing machine (such as the 809 MTS creep fatigue testing machine) with high temperature environment control and stress / strain dual closed-loop control capabilities, a dynamic creep fatigue test is performed on a standard specimen of a certain high-temperature alloy material.

[0026] The target high-temperature components include gas turbine disks, turbine blades, high-temperature pipes, and standard specimens used to represent the local stress state of such components.

[0027] To obtain basic parameters of the material, such as high-temperature creep properties, cyclic deformation properties, target test temperature, typical start-stop cycles or equivalent cycles, main load-bearing capacity range during steady-state operation, and stress / strain control capability of the testing machine, for the target high-temperature structure or its specimens.

[0028] S2. Determine the parameters to be used during the test: preset strain amplitude ε1; holding stress level σ_d; holding time t_h; strain loading and unloading rate; S3. Based on the preset strain amplitude ε1, holding stress level σ_d, holding time t_h, and strain loading and unloading rates set in step S2, a dynamic creep fatigue load waveform of the high-temperature structure or its specimen is generated using a stress / strain hybrid control method. The dynamic creep fatigue load process includes a strain-controlled loading stage, a strain-controlled unloading stage, and a holding stage of the strain-controlled unloading stage. The process continues until the strain-controlled loading cycle is completed, based on the number of cycles. In step 3, the strain-controlled loading stage for generating dynamic creep fatigue loads on high-temperature structures or their specimens using a stress / strain hybrid control method is as follows: Starting from the current cycle initiation strain state, the strain is applied to the peak strain using strain control. The increment of the peak strain relative to the initiation strain of this cycle is set as the preset strain amplitude ε1. The preset strain amplitude ε1 is selected by referring to the equivalent strain variation range of key locations under start-stop or temperature gradient conditions, and is determined in combination with the material cyclic deformation characteristics and the testing machine range.

[0029] The load-bearing stress σ_d is selected based on the principal stress level at the target location under steady-state operating conditions, preferably the representative nominal stress or its equivalent value during long-term service at that location.

[0030] The unloading phase of strain control is as follows: after loading to the peak value during the loading phase, the strain control method is used for unloading. When the stress reaches the preset holding stress σ_d, the strain from the peak strain unloading to the trigger point is recorded as ε2, and the stress control is switched to hold for t_h at σ = σ_d. During the unloading phase of strain control, a stress trigger zone is set based on the oscillations caused by the switching between strain and stress control, as expressed in the following formula:

[0031] Its minimum duration is Δt. Stress control load holding only switches to the mode when stress enters the trigger zone and the duration exceeds Δt. To maintain load stress, This represents the allowable overshoot stress range during control switching.

[0032] The strain control unloading phase is as follows: After the strain control is completed, switch back to strain control and continue unloading the strain ε3 from the strain state at the end of the strain control. The unloaded strain ε3 satisfies the following constraints:

[0033] Based on the constraint relationship of the unloading strain ε3, the total unloading strain expression from the peak strain to the valley strain is as follows: ε2 + ε3 = 2ε1 The cycle is completed by the above-mentioned strain control loading, unloading, and load holding stages; After the strain control cycle reaches its peak value, strain unloading is performed, and the strain variable is ε2. Then, the load is held, and after the load holding ends, the unloading dependent variable is ε3. ε2 and ε3 are allowed to vary in different cycles, but the total unloading strain variable ε2 + ε3 is constant at 2ε1 to ensure that the unloading geometry of each cycle is fixed, while the load holding position is dynamically adjusted along the unloading path according to the material response.

[0034] Starting from the valley strain of the dynamic creep fatigue load waveform of a high-temperature structure or its specimen generated by a stress / strain hybrid control method, the strain 2ε1 is applied using a strain control method to return the strain to near the peak strain region, thereby completing a dynamic creep fatigue cycle with an unloading amplitude of -2ε1 and an loading amplitude of +2ε1.

[0035] In this step, the following control flow is programmed into the testing machine control program: (1) Loading from the initial strain 0 to the peak strain ε_p¹ = ε1 using strain control; (2) Starting from ε_p¹, unload using strain control. During the unloading process, the stress is collected in real time. When the stress decreases to within the trigger zone and is held for a time not less than Δt, the strain from ε_p¹ to the trigger point is recorded as ε2¹, and the stress control is switched to hold for a time t_h under σ = σ_d. (3) After the load holding period ends, switch to strain control and continue to unload the strain ε3¹ from the strain at the end of the load holding period. ε3¹ satisfies ε3¹ = 2ε1 − ε2¹, so that the total unloaded strain from the peak to the valley in this cycle is ε2¹ + ε3¹ = 2ε1. (4) Record the valley strain ε_v¹, and starting from the valley, load the strain variable 2ε1 in a strain control manner to bring the strain back to a level close to ε_p¹, thus completing the first cycle; (5) Repeat steps (2) to (4) in subsequent cycles. Only in the nth cycle, the corresponding ε2ⁿ and ε3ⁿ can change due to the change of material state, but always satisfy ε2ⁿ + ε3ⁿ = 2ε1.

[0036] In the aforementioned control process, constant stress load is always positioned on the strain unloading path, and its trigger position can automatically move back and forth as stress relaxation and material response evolve during the cycle. Simultaneously, geometric constraints ensure that the unloading and loading strokes are fixed for each cycle. This allows the dominant role of constant load creep and the additional effect of start-stop fatigue to be uniformly expressed at the load level.

[0037] S4. Execute the dynamic creep fatigue load on a creep fatigue testing machine with stress / strain hybrid control capability, record the strain-time curve, stress-time curve and stress-strain hysteresis curve, observe the stability of the stress plateau in the load holding section, the smoothness of control switching and the cyclic strain drift. When the cyclic characteristics meet the preset stability and repeatability criteria, the load design is determined to be effective.

[0038] like Figure 3 As shown: whether the hysteresis curve corresponds correctly to the load waveform, whether the stress corresponding to the strain peak is accurate, whether the stress can be accurately detected during the strain-controlled unloading process, and whether stress control is switched after the preset stress is reached. If effective, it means whether the peak strain curve is always in the rising stage.

[0039] Example 2: Load Equivalence and Stability Assessment

[0040] Based on Example 1, the strain-time curves and stress-strain hysteresis loops obtained during the experiment were analyzed. Furthermore, the deformation accumulation characteristics and load control stability were evaluated by combining the evolution of the number of cycles and characteristic strain parameters. Figure 2 As shown, this is used to characterize the process of material deformation gradually evolving and accumulating under the dynamic creep fatigue load of the present invention.

[0041] The load design method proposed in this invention can be equivalent to the superposition of constant amplitude fatigue and constant stress creep, which can faithfully reproduce the typical damage evolution process of raw materials under high-temperature service environment. This method breaks through the limitations of traditional control mode: it effectively overcomes the defect that deformation cannot accumulate under strain control, and successfully suppresses the uncontrolled ratcheting deformation that is inevitable in stress control. Thus, while maintaining a constant fatigue amplitude, it realizes a realistic, controllable creep-fatigue interaction simulation with staged characteristics, providing a more scientific experimental means for the mechanism study and life prediction of high-temperature materials.

[0042] Simultaneously, the stability of the stress plateau in the constant stress holding section of each cycle, the continuity of stress and strain response at the moment of control mode switching, and the repeatability of the stress-strain hysteresis loop shape are checked as the basis for evaluating the stability and feasibility of the load control method of the present invention. When the above indicators meet the requirements of engineering applications, it can be determined that the constructed dynamic creep fatigue load can be stably realized on the testing machine and can reasonably characterize the deformation accumulation behavior of high-temperature components under frequent start-stop and long-term service conditions.

[0043] It should be noted that, without departing from the spirit of this invention, those skilled in the art can adjust parameters such as test temperature, holding stress σ_d, holding time t_h, preset strain amplitude ε1, strain loading / unloading rate, and trigger bandwidth Δσ according to the service requirements of different materials and components, or form different parameter combinations under the same control logic framework, all of which should fall within the protection scope of this invention.

[0044] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for designing dynamic creep fatigue loads due to cumulative deformation of high-temperature structures under peak-shaving conditions, characterized in that, Includes the following steps: S1. Obtain the basic parameters of the material's high-temperature creep properties, cyclic deformation properties, target test temperature, typical start-stop times or equivalent cycle times, main load-bearing capacity range during steady-state operation, and stress / strain control capability of the testing machine for the target high-temperature structure or its specimen. S2. Based on the aforementioned basic parameters, determine the following to be used during the experiment: Preset strain amplitude ε1; Maintain the load stress level σ_d; Hold time t_h; Strain loading and unloading rates; S3. Based on the preset strain amplitude ε1, holding stress level σ_d, holding time t_h and strain loading and unloading rate set in step S2, the dynamic creep fatigue load waveform of the high temperature structure or its specimen is generated by stress / strain hybrid control method. The dynamic creep fatigue loading process includes a strain-controlled loading stage, a strain-controlled unloading stage, and a strain-controlled unloading stage holding stage; the process continues until the strain-controlled loading cycle is completed, based on the number of cycles completed. S4. Execute the dynamic creep fatigue load on a creep fatigue testing machine with stress / strain hybrid control capability, and record the strain-time curve, stress-time curve, and stress-strain hysteresis curve. When the cyclic characteristics of step S3 meet the preset stability and repeatability criteria, the load design is determined to be effective.

2. The method for designing dynamic creep fatigue loads for high-temperature structures under peak-shaving conditions as described in claim 1, characterized in that: The target high-temperature components in S1 include gas turbine disks, turbine blades, high-temperature pipes, and standard specimens used to represent the local stress state of such components.

3. The method for designing dynamic creep fatigue loads for high-temperature structures under peak-shaving conditions as described in claim 1, characterized in that: The strain-controlled loading stage for generating dynamic creep fatigue loads on high-temperature structures or their specimens using a stress / strain hybrid control method in step 3 is as follows: Starting from the current cycle's initial strain state, the strain is applied up to the peak strain using strain control; the increment of the peak strain relative to the cycle's initial strain is set to a preset strain amplitude ε1; The unloading phase of strain control is as follows: after loading to the peak value during the loading phase, the strain control method is used for unloading. When the stress reaches the preset holding stress σ_d, the strain from the peak strain unloading to the trigger point is recorded as ε2, and the stress control is switched to hold for t_h at σ = σ_d. The strain control unloading phase is as follows: After the strain control is completed, switch back to strain control and continue unloading the strain ε3 from the strain state at the end of the strain control. The unloaded strain ε3 satisfies the following constraints: ； Based on the constraint relationship of the unloading strain ε3, the total unloading strain expression from the peak strain to the valley strain is as follows: ； The cycle is completed by the above-mentioned strain control loading, unloading, and load holding stages; Starting from the valley strain of the dynamic creep fatigue load waveform of a high-temperature structure or its specimen generated by a stress / strain hybrid control method, the strain 2ε1 is applied using a strain control method to return the strain to near the peak strain region, thereby completing a dynamic creep fatigue cycle with an unloading amplitude of -2ε1 and an loading amplitude of +2ε1.

4. The method for designing dynamic creep fatigue loads for high-temperature structures under peak-shaving conditions as described in claim 3, characterized in that: The load-bearing stress σ_d is selected based on the principal stress level at the target location under steady-state operating conditions.

5. The method for designing dynamic creep fatigue loads for high-temperature structures under peak-shaving conditions as described in claim 3, characterized in that: The unloading phase of the strain control is based on the stress triggering zone set according to the oscillation caused by the switching of strain / stress control, as expressed in the following formula: ； Its minimum duration is Δt, and it switches to stress control load holding only when the stress enters the trigger zone and the duration is greater than Δt; To maintain load stress, This represents the allowable overshoot stress range during control switching.

6. The method for designing dynamic creep fatigue loads for high-temperature structures under peak-shaving conditions as described in claim 3, characterized in that: After the strain control cycle reaches its peak value, strain unloading is performed, and the strain variable is ε2. After the load holding period ends, the unloading dependent variable is ε3. Based on the total unloading strain ε2 + ε3 being constant at 2ε1, the unloading geometric stroke of each cycle is kept fixed, and the load holding position is dynamically adjusted along the unloading path according to the material response.

7. The method for designing dynamic creep fatigue loads for high-temperature structures under peak-shaving conditions as described in claim 1, characterized in that: The creep fatigue testing machine used in step S4 is a testing device with high-temperature environment control and stress / strain dual closed-loop control functions.

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