TC21钛合金锻件淬火过程温度场及热应力场数值模拟

通过利用ANSYS有限元分析软件对TC21钛合金锻件淬火过程进行数值模拟,获得TC21钛合金锻件淬火不同时刻温度场分布及热应力场分布,以及锻件上所选节点温度、热应力随淬火时间的变化关系,并观察从锻件心部至边部的组织变化,研究冷却速率对组织变化的影响规律。结果表明,当淬火3600 s时,锻件表面已冷却至室温,而心部仍然保持较高温度;从锻件心部至表面冷却速度逐渐增加,并且越靠近表面,组织越细小。 淬火开始阶段,锻件各点热应力迅速升至最大值,随着淬火时间延长,锻件表面及心部热应力均逐渐减小,至淬火结束时,锻件最大残余应力仅为77 MPa。     

AP1000核电主管道淬火过程温度和应力场数值模拟

根据有限元模拟软件ANSYS原理,对AP1000核电主管道锻件进行淬火过程数值模拟,以获得主管道淬火不同时刻温度场分布及应力场的情况。结果表明,当淬火结束时（t=600 s）,锻件表面已冷却至室温,而管接口心部仍然保持较高温度;淬火开始阶段,锻件中最大的热应力点,会相应急速上升至最大值;随着淬火结束,锻件中热应力会逐渐变小;淬火阶段,主管道大部分区域的畸变都很小,最大的畸变区域主要集中在管接口与主管道接口之间。     

板热应力弯曲的试验研究

板的弯曲变形是热应力成形的主要变形方式之一。为了控制热应力成形的尺寸精度,研究热应力板弯曲变形的基本规律具有重要意义。本文通过试验对火焰局部加热所产生的板热应力弯曲问题进行了研究,研究内容包括：工艺参数影响、板坯几何尺寸影响和板的材料性能影响等。     

调质大锻件高温回火冷却时的温度场与应力场分析

测量了调质大锻件高温回火冷却时的表面及心部冷却曲线、室温及低温冲击韧性，并且计算了400℃以后冷却时最大瞬时弹性热应力。结果表明：调质大锻件高温回火冷却到心部达400℃出炉空冷，不仅对残余热应力无明显影响，而且对室温冲击韧性略有改善，同时最大瞬时弹性热应力也构不成开裂的危险。     

液压管道在不同弯曲角度下流固耦合特性仿真研究

管道的弯曲角度影响流体流动特性与管道应力分布。利用有限元方法对不同曲率情况下管道的流固耦合特性进行了分析,研究了流固耦合作用下不同曲率管道的等效应力、位移变形和流体流动特性规律。结果表明:弯曲角度大于135°时对管道的固有频率影响较大;流体对弯曲管道壁面产生的作用力导致管道发生变形,管道的最大位移变形和管道内流体的最大流速随着弯曲角度的增加均先增加后减小。     

板热应力弯曲的若干变形规律的数值模拟研究

板的弯曲变形是热应力成形的主要变形方式之一, 为了了解其变形机理并进而控制热应力成形工件的尺寸精度, 本文通过数值模拟方法对多种工况下的矩形板的热应力弯曲变形的问题进行了研究。研究内容包括: 板坯几何尺寸、加热工艺参数对热应力弯曲的变形量、变形模式以及翘曲的影响。     

汽车高强钢锻件淬火开裂分析与有限元模拟北大核心CSCD

某汽车高强钢锻件在生产中面临淬火开裂问题,急需从生产工艺上回溯开裂原因。对淬火后的某汽车高强钢锻件进行解剖,观察了裂纹形貌、金属流线、微观组织和元素分布,发现断裂处材料流动极不均匀,锻造变形时剧烈的滑移和剪切是导致开裂的主要原因。模拟了某SAE5137H汽车高强钢锻件在浓度为9%的PAG淬火液(聚烷撑乙二醇质量分数为9%的水性淬火介质)中淬火的过程,发现淬火开裂位置的最大等效应力远低于材料的抗拉强度,淬火应力较小。综合裂纹分析的试验结果和有限元分析结果可知,该锻件锻造过程中材料流动不均匀,局部产生剧烈滑移,使材料塑性下降,虽然在锻造后未直接开裂,但在淬火热应力的作用下因塑性不足而导致开裂。根据开裂原因,将位置A开裂处预锻模膛局部凹模圆角半径减小至R8 mm,并对锻件位置B处局部加热,锻件淬火开裂比例显著下降,解决了开裂问题。     

铝合金汽车轮毂淬火过程温度场有限元分析

在对A356铝合金汽车轮毂热处理工艺分析的基础上,采用ANSYS有限元软件对铝合金汽车轮毂淬火过程中温度场及热应力场的分布进行数值模拟与分析。研究表明:在淬火过程中,轮毂在47 s时完全冷却到70℃,与实际较为吻合。轮毂受到的最大热应力为180.507 MPa,小于A356铝合金的强度极限。轮毂在淬火过程中会发生微量的变形,距离轮辐最远处的变形量最大,其值为0.127341 mm,建议在热处理后对汽车轮毂进行精密校核。     

板料弯曲减薄系数的计算

通过对板料弹塑性弯曲变形分析，利用材料力学中的平面曲杆理论，提出了大曲率弹性变形应变中性层向内移动的观点，并推导出了板弯弯曲减薄系数的计算公式。     

7075铝合金汽车支撑摆臂锻件固溶处理温度场模拟

利用ABAQUS有限元软件对7075铝合金汽车支撑摆臂锻件固溶处理过程温度场进行数值模拟,得到了锻件在不同升温方式、不同转运时间以及不同水温淬火下的温度场分布情况。结果表明,锻件随炉升温时,达到预定温度所需时间为112.1 min,最大温差为4.8 ℃;炉子到温后放入锻件升温时仅需71.2 min,最大温差为10.4 ℃。转运时间为3、3.5和4 min时,锻件中冷却最快部位的温度分别下降到384.0、375.9和367.8 ℃,最终确定转运时间不能超过3.5 min。采用25 ℃水淬时,冷却时间为95 s,冷却最快和最慢部位通过淬火温度敏感区的平均冷却速度分别为782.8和19.1 ℃/s,最大温差为237.6 ℃;80 ℃水淬时,冷却时间为56 s,锻件中冷却最快和最慢部分通过淬火温度敏感区的平均冷却速度则分别为587.4和16.8 ℃/s,最大温差为216.0 ℃。     

板料弹塑性弯曲应力应变中性层位置关系探讨

通过对板料弹塑性弯曲应力应变分析 ,利用材料力学中的平面曲杆理论 ,提出了板料大曲率弹塑性弯曲塑性应力应变中性层和弹性应力应变中性层均向内移动并重合的观点     

大型锻件热处理过程的数值模拟研究

在对大型锻件传热分析的基础上 ,建立了大型锻件的物理模型 ,对其温度场的变化规律进行了模拟计算 ,同时将模拟结果和实验结果进行对比分析 ,最后利用模拟计算对材料为 2 6Cr2Ni4MoV的某一电机转子的调质处理进行了模拟计算 ,从而说明了热处理过程的数值模拟方法的准确性和优越性。为进一步分析此类工件的组织转变和应力应变等奠定了基础。     

四辊连续滚弯侧辊位移计算与数值模拟

在四辊卷板过程中,卷制工件的曲率主要取决于侧辊的位移量。以塑性弯曲理论为基础,对四辊连续滚弯过程中板材各阶段的变形情况进行了理论分析。根据卸载定理推导出双线性硬化模型板材的回弹曲率计算公式,建立了四辊连续滚弯侧辊位移的数学模型。利用ABAQUS有限元软件对四辊连续滚弯过程进行三维动态模拟,对仿真值和理论值进行了比较,分析了不同板厚下侧辊进给量、相对弯曲半径与成形曲率半径之间的关系。结果表明:有限元仿真误差较小,可以用来指导实践;随着侧辊进给量的增加,板厚对成形曲率半径的影响逐渐减小;成形曲率半径随着相对弯曲半径的增加基本呈线性关系变化。     

Ductile fracture behavior of 5052 aluminum alloy sheet under cyclic plastic deformation at room temperature

Ductile fracture behavior of a 5052 aluminum alloy sheet undergoing cyclic plastic deformation is investigated in order to clarify the effect of cyclic plastic deformation on formability enhancement in incremental stretch sheet forming at room temperature. In the incremental forming, formability markedly increases owing to strain distribution and accumulation effects. The former effect is activated when the deformation region expands along tool paths. Thus, localization of deformation, which leads to necking or fracturing, can be prevented. On the other hand, local strain is accumulated without fracturing when a blank sheet is repeatedly subjected to out-of-plane deformation at the same position. In this paper, the effect of the strain accumulation due to cyclic deformation generated by bending and unbending is primarily focused on to discuss the effect on deformability. To apply cyclic plastic straining to the specimen, a cyclic stretch-bending test was adopted. A cyclic tensile test was also conducted for larger bending curvature. The experimental results show that cyclic bending–unbending affects the ductility of sheet metals. The fractography obtained by scanning electric microscopy also indicates that fewer and smaller voids are observed particularly on bending the inner side than on the outer side.     

单曲率板材激光弯曲成形过程的有限元模拟

利用有限元软件MSC.Marc建立了单曲率板激光弯曲成形过程的热力耦合有限元模型。计算并分析了激光弯曲成形过程中板材内部的温度场、应力场和位移场。此外,还研究了扫描线的长度和单曲率板的初始形状对激光弯曲成形的影响。结果表明:随着扫描线长度的增加,板材的弯曲变形量增大;随着单曲率板曲率的增加,板材的弯曲变形量减小。实验结果验证了模型的可靠性。     

Phase change flattening process for axial grooved heat pipe

A novel processing technique named phase change flattening process has been developed to fabricate the flattened grooved heat pipes, which are in high demand for electronics cooling. The phase change vapor pressure in the flattened heat pipe is analyzed on the basis of its operating principle. An elasto-plastic FEM simulation is proposed to analyze stress and strain distribution for the flattening process. An experiment is also set up to verify this elasto-plastic deformation of axial grooved heat pipe (AGHP). Results show that the vapor pressure is determined by the saturated vapor pressure equation of heat pipe. Punch load of the upper plate greatly increases due to its higher vapor pressure and the buckling phenomenon can be well eliminated when the vapor pressure reaches 1.002 MPa at vapor temperature 453 K. The maximum equivalent plastic stress and strain distribute on the maximum bend points at the bending wall of heat pipe when the punch stroke is over 3 mm. The width, vapor area and grooves of flattened heat pipe change greatly as the flattening proceeds.     

Effect of prestressed ultrasonic peen forming parameters on bending curvature and spherical deformation of plate

The elastic prestressed ultrasonic peen forming (UPF) was adopted in order to solve problems of insufficient bending deformation and large spherical deformation of plate during free UPF. The theoretical analysis of prestressed UPF and the influence of elastic prebending moment on deformation were analyzed. Spherical deformation coefficient was defined to quantificationally describe the spherical deformation. Experiments were conducted to compare the differences between free UPF and prestressed UPF processes and the effects of processing parameters on bending curvature and spherical deformation coefficient were studied. The results show that peening trajectory in chordwise direction is beneficial to enlarging spanwise bending deformation and decreasing spherical deformation coefficient. Large prebending curvature is helpful to increase spanwise bending deformation and decrease chordwise deformation, thereby obviously decreasing spherical deformation coefficient. Large spanwise deformation can be obtained under large firing pin velocity, small plate thickness and small offset distance. Large firing pin velocity plays a positive role in decreasing spherical deformation, while plate thickness and offset distance have little effect on it. Above all, prebending curvature and peening trajectory are the most important factors during prestressed UPF process. This study provides guidance for parameters optimization of prestressed UPF for wing plate with large thickness.     

铝合金模锻件热处理过程的热力耦合分析

采用有限元法对一个铝合金模锻件的沸水淬火和时效处理过程进行了热力耦合分析 ,研究了淬火过程中锻件与沸水之间的换热系数对淬火变形的影响、淬火过程中工件内应力的变化和水温对锻件残余应力的影响。对于铝合金锻件热处理过程的有关材料和工艺参数以及热处理结果进行了实验检测 ,并采用数值方法进行了处理。本文的研究对于控制和改进铝合金锻件热处理工艺具有一定的指导意义。     

Study on inhomogeneous cooling behavior of extruded profile with unequal and large thicknesses during quenching using thermo-mechanical coupling model

The interfacial heat transfer coefficient between hot profile surface and cooling water was determined by using inverse heat conduction model combined with end quenching experiment. Then, a Deform-3D thermo-mechanical coupling model for simulating the on-line water quenching of extruded profile with unequal and large thicknesses was developed. The temperature field, residual stress field and distortion of profile during quenching were investigated systematically. The results show that heat transfer coefficient increases as water flow rate increases. The peak heat transfer coefficient with higher water flow rates appears at lower interface temperatures. The temperature distribution across the cross-section of profile during quenching is severe nonuniform and the maximum temperature difference is 300 °C at quenching time of 3.49 s. The temperature difference through the thickness of different parts of profile first increases sharply to a maximum value, and then gradually decreases. The temperature gradient increases obviously with the increase of thickness of parts. After quenching, there exist large residual stresses on the inner side of joints of profile and the two ends of part with thickness of 10 mm. The profile presents a twisting-type distortion across the cross-section under non-uniform cooling and the maximum twisting angle during quenching is 2.78°.