International Journal of Advanced Engineering and Management Research Vol. 2 Issue 5, ISSN:

Transcription

1 Internationa Journa of Advanced Engineering and Management Reearch Vo. 2 Iue 5, ISSN: STUDY ON TEMPERATURE FIELD DISTRIBUTION OF HOT MELT WELDING OF PE100 ZHANG Ao-peng MA Ting-xia LV Ya-feng (Schoo of Mechatronic Engineering,Southwet Petroeum Univerity,Chengdu, Sichuan, China, ) ABSTRACT In thi paper, ANSYS oftware wa ued to imuate the hot met weding proce of PE100, and the ditribution of temperature fied wa obtained. The reut of ANSYS imuation were compared with the experimenta reut in the iterature to verify the correctne of the finite eement weding proce. By comparing the above two apect, it i verified that the finite eement of PE pipe weding temperature fied imuate the accuracy of the whoe proce and obtain the ditribution aw of temperature fied during weding. It ha important guiding ignificance for practica engineering. Key Word: PE pipe; numerica imuation; finite eement method; hot met weding 0. Introduction HDPE pipe ha the advantage of good corroion reitance, tightne, ong ife and arge circuation capacity [1]. It ha become the word' bet choice for the ga pipeine. Weding technoogy i the main connection method of engineering patic pipe, and it i the key ink that directy affect the afety appication of high denity engineering patic pipe [2]. However, the pipeine tructure in the weding proce, due to uneven heating, cooing, materia change, contraint condition and fied operation and other reaon, and wi produce the deformation force and reidua tre in weding joint tranient interna to the production, ife and ocia ecurity wi bring huge oe [3]. Through conuting and retrieving, it i reported that the imuation anayi of weding temperature imuation of finite eement patic vicoeaticity i e. Wu Jian-jun et a. Have appied one dimeniona thermo vicoeatic finite eement method;the reidua tre and bending deformation of fat injection moded part with impe geometry are obtained and atifactory reut are obtained[4];li Hai-mei et a. Ued the two-dimeniona thermo vicoeatic finite eement method to mode the reidua therma tre of pate injection moded part The reut i reaonabe [5-6] Page 1619

2 Under thi background, thi thei propoe HDPE hot met weding method around the tube, according to the principe and effect of externa force fied on the poymer met mechanim of hot met weding, hot met weding temperature fied i imuated, and the anayi of weding parameter on the temperature fied and tre fied. Thi tudy wi provide important engineering vaue for improving the reiabiity and ife of HDPE ga pipe hot met weding joint and reducing the occurrence of ga pipe network accident. 1 The etabihment of finite eement mode 1.1 baic equation of weding temperature fied Baed on the conideration of pipe hape and mode etabihment in therma fuion weding, thi paper i a three-dimeniona heat conduction probem [7] : T T T T c ( ) ( ) ( ) Q t x x y y z z In the equation, Q( x, y, x ) The interna heat ource in the oution domain; c The pecific heat capacity of materia; Denity of materia;t The ditribution function of weding temperature fied; temperature. t Heat tranfer time Among thee parameter, c, 1.2 Etabihment and aumption of geometric mode Both vary with The imuated pipe for high denity poyethyene pipe PE100, pipe pecification for 160mm, SDR11 tandard dimenion ratio (the ratio of diameter and thickne), which i widey ued in dometic PE pipe pecification for ga deivery ytem. Conidering the ymmetry, began to take the ide a the reearch object from the wed center, the hape of weding and weding characteritic determine the finite eement mode of joint circuar, o take the outide diameter 160mm, diameter 130.8mm, thickne 14.6mm, ength 100mm cyinder to imuate. A hown in figure 1. Fig1. The geometry mode Page 1620

3 Hot met weding can be ummarized into 3 tage: heating, witching and weding cooing. In the proce of weding, the mode can make the foowing hypothei: (1) the tube i ubjected to iotropic heat tranfer; (2) the thermo phyica propertie of materia are ony a function of temperature; (3) the temperature ditribution of the heating pate i even; (4) ignore the heat radiation of the heating pate. 1.3Eement type and meh Thi paper ue the SOLID70 three-dimeniona therma oid eement, which ha 8 node, each node with a temperature degree of freedom, which can be ued for three-dimeniona teady-tate or tranient therma anayi probem. If the mode containing the therma entity eement need to be anayzed, it can be repaced by an equivaent tructura unit. In the finite eement anayi, in genera, increaing the denity of the meh can improve the accuracy of the cacuation reut, but the increae of the meh denity mean that the computationa compexity wi increae and the computationa cot wi increae. At the ame time, the denity of the grid can not be unimited rie, generay in order to enure the accuracy of the cacuation reut in the cope of uer contro. The accuracy and the cacuation reut conidering the time cot, the meh refinement in the weding end, unit grid contro in 1mm, the unit grid contro in 5mm, a tota of node, unit. Finite eement mode after meh generationa hown in figure The oution of temperature fied Fig2. mehing the geometric mode After entering the ANSYS over, you houd firt define the type of anayi and anayi option that cannot be changed after the firt oad tep (that i, after the firt SOLVE command i iued). The anayi of the weding temperature fied i a typica noninear tranient heat conduction probem. If the anayi option i not et propery, it uuay ead to the difficut convergence of cacuation. To do thi, the foowing etting need to be made: Page 1621

4 (1) the anayi type of the three-dimeniona temperature fied i et up a tranient anayi, that i, ANTYPE, 4. Activation time integration effect in noninear tranient anayi; (2) by Fu Newton-Raphon (Newton Raphon) method, for every iteration, i a reviion of the tiffne matrix and activation of adaptive function decine; (3) turn on the automatic time tep; (4) open time tep prediction; In addition, it i worth noting that due to the therma anayi of the ubject, it i neceary to et the ambient temperature. In thi project, the ambient temperature i et at room temperature, or 28 degree centigrade. 2 The reut of temperature fied anayi of PE pipe In thi paper, the program i written in APDL anguage of ANSYS oftware. After the cacuation i competed, the temperature fied ditribution of each oad tep i obtained by reading the oad tep of each time through the POST1 genera potproceor. Can ao ue ANSYS oftware to generate the animation dipay function, change in the whoe proce of weding temperature fied, can be ceary found aong with the weding proce forward, weding point on the temperature varie with time. The tranient temperature ditribution of 2.9, 30, 90, 145 and X are repectivey hown in the heating tage. (a)at 2.9 moment (b)at 30 moment ( c)at 90 moment (d)at 145 moment Page 1622

5 Fig3. tranient temperature ditribution nephogram at heating tage From the above figure 3, we can ceary ee the dynamic proce of the whoe temperature fied during the weding heating tage, and the hape of the iotherm profie change owy, that i, under the infuence of heat conduction, it move owy to the non weding urface. In the heating proce, the end face of the pipe i in contact with the heating pate, and the temperature of the heating pate i away tabe at 210, o the highet temperature of the wedment i away 210 on the weding urface. The temperature of each point on the wedment varie with time, and the temperature i tranmitted to the non weded urface, where the temperature ha begun to appear on the wedment. With the deveopment of weding proce, the temperature ditribution of wedment i more and more obviou temperature(c) Ditance from pate(mm) Fig4.axia temperature ditribution of outer wa of pipe at different heating time temperature(c) Ditance from pate(mm) Fig5.axia temperature ditribution of pipe wa at different heating time Figure 4 and 5 repectivey. The axia temperature ditribution of different heating time of pipe wa, can be een from the figure, the heating tage of heat affected zone i about 20mm aong the axia direction within the range aong the axia direction i greater than the temperature Page 1623

6 change at 20mm i ow, and coe to ambient temperature. The thickne of the moten ayer increae with the heating proce, and the thickne of the meting ayer i about 3mm-4mm (the temperature i greater than the axia ditance of meting point 135) at 145, which i coe to the vaue of the anaytic oution of the ection. 3 Comparion of anaytica oution and finite eement reut of temperature fied At thi tage, the temperature of the heating pate i over 210 and the meting point of the uper materia i very common. The object ytem not ony ha more than two kind of media, but ao ha the boundary movement probem, that i, the interface between the two media i not tatic, but moving, which make the probem more compicated. Athough the finite eement method and the finite difference method can be ued to ove the compex boundary condition, it i advantageou to etabih an appropriate mathematica anaytic mode for quaitative anayi [8]. The anayi method i impe and can predict the temperature variation at the weded joint and the thickne of the moten ayer at different heating temperature. Therefore, to impify the probem and etabih an appropriate mathematica mode i of great ignificance to optimize the weding proce parameter and guide the practice of production. 3.1 heating tage phyica mode Simpify the probem and make the foowing baic aumption: (a) the probem i impified a one-dimeniona heat tranfer, which i ony carried out aong the axia direction of the pipe; (b) aume that the meting proce i an idea proce, that i, meting occur at the point of meting rather than the meting; (c) it i aumed that the average vaue of the phae denity of the oid phae and the moten phae i the denity of the phae tranition interface; (d) therma convection caued by the expanion of the phae of the met irrepective of the decreae in denity; (E) ignore the therma effect of the outide urface and the environment; (f) uniform temperature of the initia pipe. 3.2 The mathematica mode of the heating phae Baed on above aumption, the probem can be impified a: haf infinite object (the meting point i contant, the initia temperature (135 C ), a contant, thi i 28 C ), from the time =0 began appying contant temperature at =0 (urface i contant, thi i 210 C ), for body temperature repone. Page 1624

7 Conidering the infuence of fuion heat, the meting phae (pin repreentation) and oid phae (foot marker) are decribed by two governing equation, and couped at the oid-iquid interface. The met phae: 2 T 1 T 2 x t x 0: T Tg The oid phae: 2 T 1 T 2 x t x : T T ; t 0 : T T 0 0 The couping condition of oid-iquid interface: x ( t) : T ( X, t) T ( X t) T, m ( ) : ( ) x ( ) X x X T T d() t x t k k L x x dt 2 X X Set the error function for the oution of the equation: x T( x, t) Tg Aerf ( ) 2 t x T ( x, t) T0 Berfc( ) 2 t Among them, A B i contant.the above two formua can be proved to be the oution of the equation. In the mode k - Soid therma conductivity, k - Therma conductivity of moten phae, L - Latent heat of fuion, c - Met phae pecific heat at contant preure, - Therma diffuivity of moten phae, - Soid phae therma diffuivity, - Meting phae denity, - Soid denity. Page 1625

8 3.3 Soving the mode High denity poyethyene pipe (HDPE) 160SDR11at ambient temperature 28, the ue of 210 heating pate heating 145, to find the pipe aong the axia temperature ditribution: Uing Matab oftware programming oution: ,The temperature ditribution aong the axia direction of the moten phae and the oid phae i a foow: 7 (, ) 210 erf x / ( t ) T x t erf (0.4575) erfc x 7 (, ) 28 / ( ) t erfc( / (2.610 )) T x t That i : x T ( x, t) erf ( ) t x T ( x, t) erfc( ) t 3.3 Comparion of anaytica oution and finite eement reut Thee vaue are brought into the formua t=90,120,145,x=0.001m,0.002m,0.003m, Cacuated The temperature ditribution aong the axia direction under heating time 90, 120 and 145 i expreed in oid ine in Fig.8. Then extract the finite eement imuation reut 90, 120, 145 and the correponding poition of the pipe node temperature, in figure 6 expreed in dotted ine temperature( C) Finite eement oution 145 Anaytic oution 120 Finite eement oution 120 Anaytic oution 90 Finite eement oution 90 Anaytic oution Ditance from pate(mm) Page 1626

9 Fig6. Comparion of temperature ditribution between finite eement oution and anaytic oution at different heating time The reut of the heating tage are compared with thoe of the finite eement reut, a hown in tabe 1. Tabe 1 Comparion between the anaytica reut and the finite eement reut heating time () The axia ditance from the center of the wed(mm) Mathematica mode for cacuating temperature( C ) Numerica imuation temperature( C ) The error % % % % % % % % % % % % See from figure 6 and tabe 1, the weding temperature ditribution near the joint finite eement cacuated with the anaytica mode cacuated vaue are broady conitent, but the finite eement cacuation vaue i away ower than the anaytica oution, the error baicay at 10 degree or e. The main reaon i the error on the aumption that the anaytica oution wa ignored in the therma effect of the tube urface and the environment, and in fact in the proce of weding pipe wi heat and air convection, preciey the finite eement cacuation i Page 1627

10 conidered in thi, o the finite eement cacuation vaue i ower than the anaytica oution i reaonabe. Concuion From the above figure 8 and tabe 1 how that both the weding or weding temperature fied ditribution of the overa critica poition temperature, hot met weding imuation experiment of temperature fied ditribution and temperature fied ditribution i conitent, which verifie the correctne of the anayi of weding heating tage finite eement imuation of hot met poyethyene pipe. The reaon of individua poition deviation i: (1) due to the actua weding environment, change of convection tube wa heat tranfer coefficient with poition and time change, whie imuated convective heat tranfer coefficient by uing the ame etting; (2) cacuating the atent heat need to determine and maintain a temperature range for the phae tranformation the temperature range i very ma, it i difficut to accuratey cacuate the atent heat. Reference [1] Sun Zengyin. Characteritic of poyethyene pipe and their appication in the fied of water uppy [J]. Fie, 2013 (9): [2] Song Hongmei. Technica meaure for contruction of poyethyene ga pipeine in municipa engineering [J]. Theoretica reearch on urban contruction, 2015 (3): [3] Zhang Jun. Rik aement and management of urban natura ga tranmiion and ditribution network and appication ytem [D]. Shanghai: Tongji Univerity, [4] Wu Jianjun, Ma Zeen. Patic injection of CAD/CAE/CAM (IV) cacuation and anayi of bending deformation of reidua tre. Mechanica cience and technoogy.1996, 15 (3): 468~472 [5] Li Haimei, GuYuanxian, ShenChangyu. Numerica cacuation of therma reidua tre of injection moded part. Journa of chemica.2000, 51 (3), 308 ~ 312 [6] Li Haimei, ShenChangyu, GuYuanxian. Uneven cooing on reidua tre. China patic.1999, 13 (6): 106 ~ 111 [7] Yu Ning. Fuid mechanic and therma engineering [M]. Beijing: China Architecture and Buiding Pre, 2005: [8] Li Wenping. HDPE tube hot pate weding and it faiure mode [J]. patic cience and technoogy, 1989,6:8-12 Author:ZHANG Ao-peng, mae, born in 1994, Geermu City Qinghai Prov. China, aitant engineer, mater' degree, reearch direction: Safety Management of Oi and Ga Pipeine Tranportation. Page 1628