Study on Constitutive Model for Butt Fusion Welded Joint of High⁃density Polyethylene Pipe

doi:10.19491/j.issn.1001-9278.2021.04.012

Abstract

Abstract:

This paper reported an investigation on the material performance difference between the butt fusion welded joint and pipe body of high-density polyethylene （PE-HD） through an experimental method. With the formation of the butt fusion welded joint according to the ISO 21307 standard method， the inner and outer crimps were removed， and the joint sampling method was design to improve the tensile specimen. A new constitutive analysis and a Suleiman method were used to study the difference of constitutive models through the tensile testing of pipes and welded joints at different strain rates. The nonlinear relationship between model parameters and strain rate was obtained. Through comparing the model prediction and test results， the effectiveness and rationality of the nonlinear fitting constitutive model were verified. The model can predict the stress-strain curve under a low strain rate， providing a basis for engineering practice and finite element analysis. The results indicated that the elastic modulus and yield stress of the PE-HD welding area were better than the pipe， but the difference was not obvious.

Key words: high-density polyethylene, pipe, butt fusion welding, constitutive model, stress-strain

CLC Number:

TQ 323.1⁺2

ZHAO Xingmin, ZHAO Jianping, YAN Jizhong. Study on Constitutive Model for Butt Fusion Welded Joint of High⁃density Polyethylene Pipe[J]. China Plastics, 2021, 35(4): 65-71.

Figures/Tables 16

Fig.1. Welding samples taken from butt fusion joints

Fig.2. Tensile specimen after modification

Fig.3. Stress?strain curves of pipe tensile specimen

Fig.4. Stress?strain curves of welded tensile specimen

Fig.5. Results of linear fitting

类型	$应变率$ /s^?1	a	B	R
管材	0.1	0.000 482 1	0.000 311 8	0.998 30
	0.01	0.000 655 8	0.000 346 4	0.999 34
	0.001	0.000 693 6	0.000 351 9	0.999 45
	0.000 1	0.000 869 3	0.000 412 4	0.999 49
	0.000 01	0.001 260 0	0.000 463 6	0.999 17
接头	0.1	0.000 359 1	0.027 250 0	0.994 27
	0.01	0.000 452 2	0.028 980 0	0.998 99
	0.001	0.000 594 9	0.033 100 0	0.999 16
	0.00 01	0.000 740 6	0.037 410 0	0.999 00
	0.000 01	0.000 940 5	0.047 050 0	0.999 22

类型	$应变率$ /s^?1	a	B	R
管材	0.1	0.000 482 1	0.000 311 8	0.998 30
	0.01	0.000 655 8	0.000 346 4	0.999 34
	0.001	0.000 693 6	0.000 351 9	0.999 45
	0.000 1	0.000 869 3	0.000 412 4	0.999 49
	0.000 01	0.001 260 0	0.000 463 6	0.999 17
接头	0.1	0.000 359 1	0.027 250 0	0.994 27
	0.01	0.000 452 2	0.028 980 0	0.998 99
	0.001	0.000 594 9	0.033 100 0	0.999 16
	0.00 01	0.000 740 6	0.037 410 0	0.999 00
	0.000 01	0.000 940 5	0.047 050 0	0.999 22

Tab.1. Results of Suleiman linear regression

应变率/s^?1	E_t/MPa
应变率/s^?1	管材	接头
0.1	2 074.129	2 784.856
0.01	1 524.855	2 211.479
0.001	1 441.712	1 681.008
0.000 1	1 150.245	1 350.309
0.000 01	793.651	1 063.320

Tab.2. Initial modulus of pipe and the welded specimen

Fig.6. Elastic modulus of pipe and welding joint at different strain rates

参数	管材	接头
a	0.000 346 98 $ε ˙$ ^{-0.103 83}	0.000 284 19 $ε ˙$ ^{-0.104 14}
b	0.000 276 51 $ε ˙$ ^{-0.043 49}	0.022 076 14 $ε ˙$ ^{-0.062 64}

参数	管材	接头
a	0.000 346 98 $ε ˙$ ^{-0.103 83}	0.000 284 19 $ε ˙$ ^{-0.104 14}
b	0.000 276 51 $ε ˙$ ^{-0.043 49}	0.022 076 14 $ε ˙$ ^{-0.062 64}

Tab.3. Results of parameter fitting

Fig.7. Elastic modulus

Fig.8. Comparison between strain?stress from experiment and nonlinear models

$k i$	Base		Weld
$k i$	$α i$	$β i$	$α i$	$β i$
1	2 062.148 00	0.069 36	2 167.846 00	0.065 67
2	37.080 40	0.066 16	37.136 74	0.061 89
3	-0.672 01	0.049 89	-0.706 81	0.042 15

$k i$	Base		Weld
$k i$	$α i$	$β i$	$α i$	$β i$
1	2 062.148 00	0.069 36	2 167.846 00	0.065 67
2	37.080 40	0.066 16	37.136 74	0.061 89
3	-0.672 01	0.049 89	-0.706 81	0.042 15

Tab.4. Fitting constants of base and welded joints αi and βi

Fig.9. Fitting constitutive equation parameter ki of the weld and base

Fig.10. Relative error of yield stress in the weld

Fig.11. Yield stress at different strain rates

Fig.12. Stress?strain curves of nonlinear model predicts at different strain rates

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