Ti80合金巴东拘束试样拘束度有限元分析

Finite Element Analysis on Restraint Intensity of Ti80 Alloy Rigid Restraint Specimen

针对船用Ti80合金板材,基于弹塑性力学理论,使用ABAQUS软件对带加载块试样、简易试样和标准试样进行拘束度模拟,并对带加载块试样的拘束度进行实测。结果显示,带加载块试样拘束度模拟值与实测值误差在10%以内,有限元模拟方法较为准确。带加载块试样、简易试样的拘束度均明显高于标准试样,若使用带加载块试样和简易试样评价裂纹敏感性,结果偏保守。针对标准试样分别改变试板和底板厚度进行有限元模拟,结果表明,底板厚度为40 mm时,随着试板厚度(δ_(1))增加,拘束度(R)近似呈线性增加,拘束度拟合方程为R=23.63δ_(1)+1837.74。试板厚度为20 mm时,随着底板厚度增加,拘束度不断增加,但超过40 mm基本保持不变,对巴东拘束试样选择过厚的底板增加拘束度并无意义。

Many studies have shown that there is a clear positive correlation between welding cold crack sensitivity and joint con‐straint.However,there are few studies on restraint intensity of titanium alloy rigid restraint specimens,and it is not conducive to prep‐aration work of welding.The material studied in this paper was Ti80 alloy,which was a widely used marine titanium alloy.The theoreti‐cal basis used was metallic materials elastic-plastic mechanics,and method was finite element simulation,with the purpose of explor‐ing the impact of types and sizes on restraint intensity.Firstly,the accuracy of finite element simulation was verified.The self-made equipment was used to test restraint intensity of specimen with load blocks.Small hydraulic pump was selected as load source.The load was transmitted to specimen through the load blocks.The intensity of pressure obtained from hydraulic pump piezometer multiplied by hydraulic cylinder piston area was loading force.Before and after loading,the groove root was taken pictures using digital integrated microscope respectively.The groove root distance was gained through VISTAR that was an image processing software.Hence the lateral deformation of groove root could be achieved from difference of the two measurements.The restraint intensity was equal to total loading force divided by the product of lateral deformation and groove length.The results showed that restraint intensity in groove midpoint was3944 N·(mm·mm)^(-1).As a contrast,the same specimen was analyzed using ABAQUS finite element software,and the material proper‐ty parameters were gained from experimental measurement.The results showed that restraint intensity in groove both ends were higher than central part because of closer to restraint weld seam.The restraint intensity in midpoint was 3718 N·mm^(-1)·mm^(-1).Therefore,the deviation of values obtained from simulation and actual measurement was less than 10%,the finite element simulation should be trust‐ed.Next,the restraint intensities of standard and simple specimens were analyzed by finite element simulation.And the loading condi‐tion was the same as that of specimen with load blocks.The deformation color nephogram showed that all specimens deformation pre‐sented symmetry,which mainly because of the symmetry of specimen shape and loading situation.Due to the strong effect of restraint weld beam,the deformation in groove both ends closing to the weld beam were smaller than central part.The deformation of simple specimen was minimum because of the strictest restraint condition of test plate.Deformation occurred only in the location nearby groove root,and most regions were almost undeformed.The lateral deformation was extracted from elements of groove root,then re‐straint intensity could be calculated according to the definition.Results showed that,the restraint intensity distributions of the three specimens along grooves were similar,that was restraint intensity in groove both ends were higher than in central part,and that in cen‐tral part was relatively stable.The average value in central part of 100 to 200 mm was selected as observed value.The restraint intensi‐ty of standard,simple and load blocks specimens were 2310,4771 and 3729 N·(mm·mm)^(-1)respectively,it’s clearly that restraint in‐tensity of simple and load blocks specimens were obviously higher than that of the standard one.For load blocks specimen,the loading location kept away from groove root,so the deformation nearby groove root was smaller,consequently the restraint intensity was high‐er.For simple specimen,elements in the location of restraint weld beam were assumed as rigid fixing,that is the deformation of re‐straint weld beam and base plate were neglected.So that restraint intensity was also higher than that of the standard specimen.Natural‐ly,it was conservative to use load blocks and simple specimens to evaluate cold crack sensitivity.Finally,the influence of test and base plate thickness on restraint intensity was studied for the standard specimen.Firstly,the base plate thickness was kept as 40 mm,and test plate thickness marked asδ1 were changed as 16,26,30,36 and 40 mm respectively.According to the finite element simula‐tions results,the restraint intensity marked as R increased almost linearly with the increase of test plate thickness.The linear fitting was performed based on data of restraint intensity and thickness,and equation was R=23.63δ_(1)+1837.74,which could be used to pre‐dict restraint intensity with arbitrary test plate thickness.Secondly,the test plate thickness was kept as 20 mm,and base plate thick‐ness changed as 20,30,50,60 and 70 mm respectively.Results showed that,as the increase of base plate thickness,the restraint in‐tensity increased continuously.However,when the base plate thickness exceeded 40 mm,increment of restraint intensity was very small.So,it was meaningless to increase the base plate thickness for increasing restraint intensity.