Determination of linear and nonlinear viscoelastic material properties

对军事和人道主义人员和结构的一个重大威胁是爆炸的压力波。随着加拿大越来越多地参与和平行动，迫切需要发展爆炸防护系统。泡沫型粘弹性材料因其优越的吸能和耗能能力以及独特的应力-应变关系，在航空航天、军事、海洋、汽车、医疗等领域被广泛应用于减振、降噪、减应力等领域。最近的研究表明，如果系统设计得当，它们也可以用于提高结构的抗爆能力。为了设计最有效和最有效的防爆系统，必须知道每个部件的材料特性，并且必须很好地了解其动态行为。对现有文献的回顾表明，由于它们的形式多种多样，机械行为也多种多样，需要更多的探索来确定它们的动态特性以及用于识别它们的技术。一般而言，表征其爆炸或冲击应用性能的技术是改进的分离式霍普金森压杆(SHPB)试验和振动试验。修正的SHPB试验是基于线粘弹性杆的波传播理论。在这项研究中，将使用半解析有限元(SAFE)方法来研究线性粘弹性杆中的波传播。在进行实际改进的SHPB试验之前，将建立一个实验来验证安全方法的结果。对于振动试验，在进行振动试验之前，将使用非线性大变形有限元软件LS-DYNA来研究泡沫型粘弹性试件的行为。这项研究的短期和中期目标是彻底调查和适当修改用于识别泡沫型粘弹性固体的动态特性的技术，并开发这些材料的适当数学模型。该项目的长期目标是利用这些数学模型开发一种有效的爆炸防护系统。

A significant threat to military and humanitarian personnel and structures is blast's pressure wave. With Canada increased involvement in peace operations, there is an urgent need for developing blast protection systems. Foam-type viscoelastic materials have been widely used to reduce vibration, noise, and stresses in aerospace, military, marine, automobile, and medical industries due to their superior ability to absorb and dissipate energy in different forms, as well as their unique stress-strain relation. Recent studies showed that they can also be used to enhance the blast resisting capacity of structures if the system is properly designed. To design the most efficient and effective blast protection systems, the material properties of each component must be known and its dynamic behaviour must be well understood. A review of existing literature reveals that, due to the wide variety of their forms and the broad range of their mechanical behaviours, more exploration is needed to determine their dynamic properties as well as the techniques used to identify them. In general, the techniques to characterize their properties for blast or impact applications are the modified split Hopkinson pressure bar (SHPB) test and the vibration tests. The modified SHPB test is based on wave propagation theory of linear viscoelastic bars. In this research, a semi-analytical finite element (SAFE) method will be used in the study of wave propagation in linear viscoelastic bars. An experiment will be set up to validate the results of the SAFE method before the actual modified SHPB test is conducted. For vibration tests, LS-Dyna, a finite element software for nonlinear large deformations, will be used to investigate the behaviour of foam-type viscoelastic samples before the vibration tests are carried out. The short- to medium-term objectives of this study are to thoroughly investigate and appropriately modify the techniques used to identify dynamic properties of foam-type viscoelastic solids and to develop appropriate mathematical models of these materials. The long-term objective of this project is the development of an effective blast protection system using these mathematical models.