HTPB复合固体推进剂含损伤和老化本构研究

通过热氧老化实验、声发射损伤检测实验和蠕变柔量测试实验确定HTPB复合固体推进剂非线性本构关系，并与Schapery非线性本构方程进行比较，结果表明，含损伤老化模型较好地解释了HTPB复合固体推进剂的非线性特征，可以应用分析HTPB复合固体推进剂的力学特性。     

Ni基单晶叶片粘塑性分析

从位错滑移机理出发，建立了一种适用于Ｎｉ基高温单晶结构分析用的晶体滑移粘塑性本构模型。该模型将八面体、十二面体及六面体滑移系作为潜在的开动滑移系，考虑阻应力和背应力两种内应力状态参量。利用某Ｎｉ基单晶叶片材料在７００℃和９５０℃的试验结果对模型进行了考核并标定了模型参数。进而将所建模型编入有限元结构分析软件中，对某型发动机单晶叶片进行了计算分析。     

A constitutive model coupling damage and material anisotropy for wide stress triaxiality

A constitutive model that can describe the damage evolution of anisotropic metal sheets during the complex forming processes which experience wide stress triaxiality history is essential to accurately predict the deformation and rupture behaviors of the processes. In this study, a modified Lemaitre damage criterion which couples with the anisotropic Barlat 89 yield function is established. The effects of stress triaxiality, Lode parameter and shear stress on damage accumulation are considered in the constitutive model. The model is numerically implemented and applied to fracture prediction in tensile tests with different stress triaxialities and a complex deformation process with wide stress triaxiality history. The good consistency of predictions and experiments indicates that the modified Lemaitre damage model has excellent fracture prediction ability. Finally, the accuracy of the model is analyzed and discussed.     

复杂结构试验中的应变应力转换

通过建立一种新的应力应变表述函数 ,在弹塑性范围内 ,应用双剪应力强度理论 ,对结构试验中检测到的应变进行转换 ,以求得结构测点的检测应力 ,进而为结构强度提供较为准确的数据 ,并通过实验数据验证了其正确性     

Inverse identification of constitutive parameters of Ti2AlNb intermetallic alloys based on cooperative particle swarm optimization

Ti₂AlNb intermetallic alloy is a relatively newly developed high-temperature-resistant structural material, which is expected to replace nickel-based super alloys for thermally and mechanically stressed components in aeronautic and automotive engines due to its excellent mechanical properties and high strength retention at elevated temperature. The aim of this work is to present a fast and reliable methodology of inverse identification of constitutive model parameters directly from cutting experiments. FE-machining simulations implemented with a modified Johnson-Cook (TANH) constitutive model are performed to establish the robust link between observables and constitutive parameters. A series of orthogonal cutting experiments with varied cutting parameters is carried out to allow an exact comparison to the 2D FE-simulations. A cooperative particle swarm optimization algorithm is developed and implemented into the Matlab programs to identify the enormous constitutive parameters. Results show that the simulation observables (i.e., cutting forces, chip morphologies, cutting temperature) implemented with the identified optimal material constants have high consistency with those obtained from experiments, which illustrates that the FE-machining models using the identified parameters obtained from the proposed methodology could be predicted in a close agreement to the experiments. Considering the wide range of the applied unknown parameters number, the proposed inverse methodology of identifying constitutive equations shows excellent prospect, and it can be used for other newly developed metal materials.     

基于路径相关本构模型的大型薄壁曲面复合材料零件固化变形分析

大型薄壁曲面复合材料零件多采用热压罐工艺成型,在固化过程以及脱模过程会产生变形,导致零件变形超差,部件装配困难。针对此问题,本文首先采用路径相关本构模型对其固化成型过程进行分析,然后进行热压罐成型试验验证理论分析结果,就此采用反向补偿法修正模具型面。仿真结果表明,某大型薄壁曲面复合材料零件成型后最大位移为11.121 mm,最小位移为0.171 mm,分别发生在对称轴方向短边的边角点和靠近对称轴方向短边的边角点;零件在变形较大的两侧边和短边处残余应力较大,与变形较小的长边相差7 MPa左右。仿真结果与试验结果吻合良好,固化变形平均误差为8.6%。使用补偿后的模具再次进行固化变形仿真,使该零件的最大固化变形降低了70.8%。     

基于改进Johnson-Cook模型的5083P-0铝合金动态本构关系研究

为研究5083P-0铝合金在高应变率下的力学行为及本构模型,通过RPL100材料试验机和分离结果显示随着应变率的增加,5083P-0铝合金的屈服强度、流动应力增加,应变硬化率减小,具有应变硬化效应,正应变率效应以及热软化效应。对其塑性变形原理进行分析发现,滑移系的作用导致材料发生较大的塑性变形,同时由于绝热温升的产生,材料表现出应变硬化与热软化机制相竞争的情况。在Johnson-Cook模型率效应并能准确地描述其流动应力。最后采用新的应变率进行补充实验,通过对比验证了模型的合理性。     

粘弹性材料的几个材料函数的测定

以一种粘弹材料（聚胺酯类高分子化合物）为对象，对其进行软化函数g(t），剪切松驰函数G(t)和粘性系数η的测定，为粘弹性本构关系在实际工程中的应用提供必要的数据和关系。     

A thermal activation based constitutive model for the dynamic deformation of AA5083 processed by large-scale equal-channel angular pressing

Aluminum alloy 5083 (AA5083) processed by large-scale Equal-channel angular pressing (ECAP) is an excellent engineering material with great prospects for industrial applications. An accurate assessment of the underlying constitutive relationships with easily determined material constants is critical for the predictive design and informed processing of such structural materials. To develop such a design framework, uniaxial dynamic compressive tests over a wide range of temperatures (293–573 K) were carried out for an ECAP-processed AA5083 alloy. Additionally, the microstructure before and after dynamic loading was characterized by SEM and TEM. Based on the experimental results, a new dynamic constitutive model, based on thermal activation theory, was established to describe the plastic flow behavior of the AA5083 alloy that incorporates the effects of plastic strain, temperature, and strain rate. The input parameters of the new model were determined using a particle swarm optimization (PSO) method. The model predictions show excellent agreement with experimental results, which suggests that the current predictive constitutive model is highly effective in reproducing the dynamic deformation behavior of the large-scale ECAP-processed AA5083.     

Out of phase thermal mechanical fatigue investigation of a directionally solidified superalloy DZ125

Out of phase(OP) thermal mechanical fatigue(TMF) behavior of a directionally solidified(DS) superalloy DZ125 was experimentally and numerically studied. Two different temperature conditions, which are 500–1000 °C and 400–900 °C, were considered in the present research.Stress and strain responses as well as fatigue life results were presented and discussed. Scanning electron microscope(SEM) and metallographic analysis were used to study the damage mechanism. An oxidation assisted crack initiation and propagation phenomenon were found to explain the shorted life under TMF cycles. In order to characterize the stress and strain deformations under TMF loadings, a modified Chaboche's constitutive model was applied. Additionally, the TMF life of the material was modeled and predicted by Neu–Sehitoglu damage law with high accuracy.