Visit to NASA Langley Research Center - participation in the second World Wide Failure Exercise

在这次访问期间进行的工作将为第二次全球故障演习(WWFE II)*的几个测试案例提供一套完整的预测。练习的不同测试用例具有不同的难度级别，将涉及我们失败理论的不同领域，并且可能需要不同的实现。由于这个原因，到7月（在访问之前）的任何初步预测的准备水平将在测试用例到测试用例之间有很大的不同。访问将从根据准备程度组织初步预测开始。从预测被理解为更接近于完成的测试用例开始（更高的准备水平），每个预测将被详细地审查，并且最终的预测将被定义。具有最低准备水平的测试用例很可能在访问开始时对应于没有可用的初步预测。对于这些情况，在确定和商定最终预测之前，将需要更多的努力和时间。最后，表格和图表将按照世界二次世界经济论坛组织者要求的格式生成，以及相应的研究论文，其中包括所采用的理论及其在世界二次世界经济论坛测试用例中的应用。在访问期间，在WWFE II工作的同时，将讨论如何加强帝国理工学院与美国宇航局之间的未来合作。将采用的两条途径是：(i)联合研究项目的资金来源，以及（ii）包括美国宇航局的研究人员作为英国和欧洲资助的顾问/合作者。至于后者，我们已在近期向EPSRC提交的拨款中考虑。* WWFE II是一项基准测试，旨在建立在一般三维（3D）应力状态下用UD层增强复合材料失效的现有知识和预测能力。只有选定的公认的失效理论的提出者才被邀请参加演习，其中包括我们的团队，包括伦敦帝国理工学院，美国宇航局和波尔图大学。这次选择是对我们小组发表的失效理论的重要认可。遵循第一次练习（WWFE I）的传统，第二次练习将使参与者对失效理论有更高的认识，并提高复合材料失效的知识。该练习包括两个部分：在第一部分中，参与者被要求对涉及三维应力状态的失效包络进行盲预测，并公布他们的结果；在第二部分，参与者得到了实验结果，并被要求评论他们的预测与实验结果的相关性，并在适当的情况下对他们的理论提出任何修正。第一部分的截止日期是2007年11月底，我们的团队已经开始为一些测试用例生成失败包。

The work to be carried out during this visit will result in a complete set of predictions for the several test cases of the second World Wide Failure Exercise (WWFE II)*. The different test cases of the exercise have different levels of difficulty, will involve different areas of our failure theories, and might require different implementations of it. For this reasons, the readiness level of any preliminary predictions by July (before the visit) will vary substantially from test case to test case. The visit will start by organising the preliminary predictions according to readiness level. Starting from the test cases for which the predictions are understood to be closer to be finalised (higher readiness level), each prediction will be reviewed in detail, and the final predictions will be defined. It is likely that the test cases with lowest readiness level will correspond to no preliminary predictions available at the start of the visit. For these cases, a much greater amount of effort and time will be required before a final prediction is defined and agreed. Finally, tables and graphs will be generated in the format required by the organisers of the WWFE II, as well as the corresponding research paper with the theory employed and its application to the test cases of the WWFE II.During the visit, and in parallel with the work on the WWFE II, there will be discussions on strengthening future collaborations between Imperial College London and NASA. The two routes which will be exploited are (i) funding sources for joint research projects, and (ii) including NASA researchers as consultants/ collaborators in British and European grants. Regarding the latter, it is already being considered in a grant to be submitted to EPSRC in the near future.*The WWFE II is a benchmarking exercise aimed at establishing the current knowledge and predictive capability in failure of composites reinforced with UD plies under a generic three-dimensional (3D) state of stress. Only selected proposers of recognised failure theories were invited to participate in the exercise, and amongst them is our team, comprising Imperial College London, NASA and the University of Porto. This selection is an important recognition of the failure theories published by our group. Following with the tradition of the first exercise (WWFE I), this second exercise will give a high visibility to the failure theories of the participants, and advance the knowledge on failure of composites. The exercise comprises two parts: in a first part, the participants are asked to carry out blind predictions for failure envelopes involving a 3D stress state, and publish their results; in the second part, the participants are given the experimental results, and are asked to comment on the correlation of their predictions with the experimental results, and propose any amendments to their theories if appropriate. The deadline for the first part is end of November 2007, and our team is already working on generating failure envelopes for some of the test cases.