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A method for predicting the constitutive relation of any strain loading and unloading of a unidirectional ceramic matrix composite material
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A composite material and constitutive relation technology, applied in computer materials science, special data processing applications, instruments, etc., can solve the problems of calculating the stress-load process, unable to realize, and not providing analytical expressions for the stress-load process, etc.
Active Publication Date: 2019-05-28
NANJING UNIV OF AERONAUTICS & ASTRONAUTICS
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Song Yingdong et al. (Song Yingdong, Zhang Sheng, Gao Xiguang, Fang Guangwu, Stress-strain Behavior Prediction Method for Random Loading and Unloading of Unidirectional Ceramic Matrix Composites, Chinese Invention Patent, Authorization Number: CN104866690B) provided a kind of arbitrary loading and unloading of unidirectional ceramic matrix composites Stress-strain behavior prediction method, but this method only provides an analytical expression for calculating the strain load process based on the stress load process, but does not provide an analytical expression for calculating the stress load process from the strain load process, so it cannot be quickly calculated based on the strain load process stress loading process
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Embodiment a
[0091] Example a: There is already 1 forward slip area and 1 reverse slip area.
[0092] The main purpose of this example is to describe in detail the specific implementation of the present invention when there are n forward slip and n reverse slip zones, assuming that there is already a strain process ε 1 =0.005,ε 2 =0.001, and calculated the corresponding stress process σ 1 =490MPa, σ 2 =0MPa and length of slip zone Such as Figure 1a shown.
[0093] The following steps will be carried out on this basis.
[0094] Step 1: Judging the damage of composite materials. According to the existing loading process, it is obvious that the composite material has been damaged.
[0095] Step 2: Calculate the average spacing of matrix cracks.
[0096]
[0097] Step 3: Judging the distribution of the slip area.
[0098] Given a current strain of 0.004. Since the current strain is less than the strain ε corresponding to the first positive slip zone 1 , and greater than the stra...
Embodiment b
[0119] Example b: There are already 2 forward slip zones and 1 reverse slip zone.
[0120] The main purpose of this example is to describe in detail the specific implementation of the present invention when there are n forward slip and n-1 reverse slip regions, assuming that there is already a strain process ε 1 =0.005,ε 2 = 0.001, ε 3 =0.004, and calculated the corresponding stress process σ 1 =490MPa, σ 2 = 0MPa, σ 3 =377MPa and the length of the slip zone Such as Figure 1b shown.
[0121] The following steps will be carried out on this basis.
[0122] Step 1: Judging the damage of composite materials. According to the existing loading process, it is obvious that the composite material has been damaged.
[0123] Step 2: Calculate the average spacing of matrix cracks.
[0124]
[0125] Step 3: Assume the slip zone distribution.
[0126] Given a current strain of 0.002. Since the current strain is less than the strain ε corresponding to the second positive s...
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Abstract
The invention belongs to the technical field of composite material stress-strain behavior prediction methods, relates to a method for predicting the constitutive relation of any strain loading and unloading of a unidirectional ceramic matrix composite material, and aims to provide a prediction method capable of rapidly predicting the stress-strain behavior of any strain loading and unloading of the unidirectional ceramic matrix composite material. According to the method, the strain is expressed as the quadratic polynomial of the length of the forward slip region or the length of the reverse slip region, the analytic expression of the length of the forward slip region and the length of the reverse slip region is derived, and then the corresponding stress is calculated. According to the method, the rapid prediction of any strain loading and unloading stress-strain behavior of the unidirectional ceramic-based composite material can be realized without the repeated iterative computation.
Description
technical field [0001] The invention belongs to the technical field of prediction methods for stress-strain behavior of composite materials, and in particular relates to a method for predicting constitutive relations of arbitrary strain loading and unloading of unidirectional ceramic matrix composite materials. Background technique [0002] Ceramic matrix composites have many advantages such as high specific stiffness, high specific strength, high temperature resistance, corrosion resistance, low density, etc., and have broad application prospects in the hot end parts of aviation, aerospace, nuclear power and other industries. In order to apply ceramic matrix composites more efficiently and safely, it is necessary to predict their stress-strain behavior. In the actual application process, ceramic matrix composites have to bear the effect of variable amplitude cyclic load, and the load process has no obvious rules. In addition, in the process of displacement-type finite elem...
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