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Study on the Time-Aging Temperature Equivalence of Creep Behavior of Polyethylene
DOI: 10.12677/IJM.2021.104026, PDF, HTML, XML, 下载: 127  浏览: 231  国家科技经费支持

Abstract: Polyethylene (PE) material is widely used in oil and gas transmission pipeline engineering. Its me-chanical behavior exhibits significant viscoelasticity. The viscoelasticity of the material reveals the existence of material’s characteristic relaxation time. This characteristic relaxation time is usually affected by temperature, stress level and aging. In the process of discussing this problem, the time- temperature superposition principle, the time-temperature-stress superposition principle, the time- temperature-aging time superposition principle and some others were proposed. Based on these equivalence theories, a shift factor expression similar to WLF equation for time-aging temperature equivalence is proposed in this paper. Through a series of uniaxial tensile tests on PE samples aged at different temperatures, the influence of aging temperature on the viscoelastic properties of PE is analyzed. A smooth creep master curve is constructed, which shows the time-aging temperature equivalence of PE material.

1. 引言

2. 等效理论

2.1. 时间–温度等效原理

$\mathrm{ln}\eta =\mathrm{ln}A+B\left(1/f+1\right)$ (1)

$f={f}_{0}+{\alpha }_{T}\left(T-{T}_{0}\right)$ (2)

$\mathrm{log}{\phi }_{T}=-\frac{B}{2.303{f}_{0}}\frac{T-{T}_{0}}{{f}_{0}/{\alpha }_{T}+T-{T}_{0}}=-\frac{{C}_{1}\left(T-{T}_{0}\right)}{{C}_{2}+\left(T-{T}_{0}\right)}$ (3)

$f={f}_{0}+{\alpha }_{T}\left(T-{T}_{0}\right)+{\alpha }_{\sigma }\left(\sigma -{\sigma }_{0}\right)$ (4)

$\eta \left(T,\sigma \right)=\eta \left({T}_{0},{\sigma }_{0}\right){\phi }_{T\sigma }$ (5)

$\mathrm{log}{\phi }_{T\sigma }=-{C}_{1}\left[\frac{{C}_{3}\left(T-{T}_{0}\right)+{C}_{2}\left(\sigma -{\sigma }_{0}\right)}{{C}_{2}{C}_{3}+{C}_{3}\left(T-{T}_{0}\right)+{C}_{2}\left(\sigma -{\sigma }_{0}\right)}\right]$ (6)

2.2. 时间–温度–老化时间等效原理

$f={f}_{0}+{\alpha }_{T}\left(T-{T}_{0}\right)+{\alpha }_{H}\left(h-{h}_{0}\right)$ (7)

$\mathrm{log}{\phi }_{TH}=-{C}_{1}\left[\frac{{C}_{4}\left(T-{T}_{0}\right)+{C}_{2}\left(h-{h}_{0}\right)}{{C}_{2}{C}_{4}+{C}_{4}\left(T-{T}_{0}\right)+{C}_{2}\left(h-{h}_{0}\right)}\right]$ (8)

2.3. 时间–老化温度等效原理

$f={f}_{0}+{\alpha }_{T}\left(T-{T}_{0}\right)+{\alpha }_{K}\left(k-{k}_{0}\right)$ (9)

$\mathrm{log}{\phi }_{TK}=-{C}_{1}\left[\frac{{C}_{5}\left(T-{T}_{0}\right)+{C}_{2}\left(k-{k}_{0}\right)}{{C}_{2}{C}_{5}+{C}_{5}\left(T-{T}_{0}\right)+{C}_{2}\left(k-{k}_{0}\right)}\right]$ (10)

$\mathrm{log}{\phi }_{K}=-\frac{{C}_{1}\left(k-{k}_{0}\right)}{{C}_{5}+\left(k-{k}_{0}\right)}$ (11)

${\phi }_{K}$ 为老化温度移位因子。上式表明了时间与老化温度之间的等效关系，以蠕变柔量D为例，可具体表示为：

$D\left(k,t\right)=D\left({k}_{0},\frac{t}{{\phi }_{K}}\right)$ (12)

3. 试验设置

Figure 1. Schematic diagram of PE material sample

4. 试验结果与分析

4.1. 简单拉伸试验结果与讨论

Figure 2. Stress-strain curves of simple tensile tests of sample aged for 36 hours at different temperatures

4.2. 拉伸蠕变试验结果与讨论

Figure 3. Creep curves of PE sample aged for 36 hours at different temperatures

Figure 4. Creep compliance curves of sample aged for 36 hours at different temperatures. (a) Linear coordinates; (b) Double logarithmic coordinates

Figure 5. Master creep compliance curve of sample aged for 36 hours at different temperatures

Table 1. Shift factors for master creep compliance curve of PE samples aged for 36 hours at different temperatures

$-\frac{1}{\mathrm{log}{\phi }_{K}}=\frac{{C}_{5}}{{C}_{1}}\cdot \frac{1}{k-{k}_{0}}+\frac{1}{{C}_{1}}$ (13)

Figure 6. Variation of shift factor with ageing temperature

5. 结论

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