CAE Analysis Of One Child Restraint System And The Preliminary Study On The Design Requirements

1. PrefaceIn recent years, the number of domestic cars in China has increased year by year, occupant safety of child is increasingly prominent. According to the Chinese Ministry of Public Security Traffic Management Bureau statistics show that in 2006, the death toll of children under the age of 12 in a traffic accident is 4167, and 4.67% for the proportion. 683 children died in the car, accounting for the death number of children in traffic accidents 16.4%. In the first half of 2007, mortality rate of children under the age of 12 which died in the car reached 6.8%.Restrained systems such as car seats, seat belts and airbags, these should match the occupant's the height, weight and tolerance characteristics. The child's physical structure and characteristics are quite different from adults, which makes children need to be higher protection compared with the conditions of adult. Therefore, the child restraint situation is very special. At present, the vehicle restraint system is mainly designed for adults, so for other special populations such as children can not play the best protection. If direct use these may cause serious injury to children.Many foreign countries have laws specifically require that: child must use the child restraint system. Mandatory use of child car safety seat countries and regions are: England, the United States, France, Germany, Japan, Singapore, China Taiwan, Italy, the Netherlands, Australia, South Africa, Sweden and so on. The United States is the first country which set up the children occupant safety regulations. The earliest occupant safety regulations FMVSS 213 was promulgated in 1971.Europe promulgated child occupant safety regulations ECE R44 in 1981In China, child occupant safety has just aroused the attention. Child restraint of publicity and regulations are just starting. For the universal use of child safety seats have a lot of remains to be done. National Automotive Standardization Technical Committee Started researching the standards and test methods of child restraint system in 2003. In October 2007, China's first "motor vehicle child occupant restraint system" standards began to open for comments. June 2008, the end stage for comment, finalized by the end of 2008, the standards is expected to effect in early 2009.Child restraint system is one of the main studies in children passive safety area. Child restraint system studies including: child restraint system performance studies, together with the vehicle matching studies, relevant regulations studies, testing methods studies and so on. Computer simulation is the most common means of study, it can reduce the number of real vehicle collisions, save development costs, but also provide guidance on the concept design phase and shorten the development cycle.This paper is centered on "CAE Analysis of One Child Restraint System and the Preliminary Study on the Design Requirements". Form a complete study methods and processes of child restraint systems, as a child restraint system research reference.2. Main content of this paper2.1 Child Restraint System Test-Related and DesignThe test in this paper comprises three parts: child restraint system frontal impact test, child seat belts stiffness test and data collection of child seat.Child restraint system frontal impact test is mainly for the purpose of confirming simulation model. As a reference to the ECE R44 regulations and taking into account the actual situation, design and implement of the programs. Access to the child dummy injury data as the basis for model validation. Child seat belt stiffness test, the purpose of which is to access to the belt load characteristics, which is the basis data for modeling. And this is the key of whether the belts simulation reflects a true or not. Child Seat Dimension Data Acquisition was aimed at getting the three-dimensional data of the child seat. The above tests are the basis of establishing child occupant restraint system simulation model. Reasonable and accurate tests ensure the smooth progress of modeling work.2.2 Simulation and Validation of Children Restraint SystemIn this paper, set up three different forms of child restraint system simulation models by using the collision simulation software version MADYMO6.2 which is researched by the Dutch TNO. MADYMO software based on the multi-rigid-body and finite element coupling theory, simulates the collision process and occupant injuriesChild restraint system model consists of four main parts: sled module, seat module, children seat belts module and dummy module. The establishment of the first three modules based on the actual system, dummy is extracted from MADYMO dummy database.Set up three different forms of child restraint system simulation models (multi-rigid-body model, finite element models and multi-rigid-body combination with the finite element model) based on actual data. According to their different characteristics, determine their use methods. This comprehends multi-rigid-body model and finite element model of the different features. Combine the simulation accuracy and computational efficiency and improve the computational efficiency greatly. As a result of the test conditions, model simplifies and other reasons, the simulation models need further debugging. For general engineering studies, the credibility of the model reaches 85% meaning effective. Based on child restraint system collision tests, use of qualitative and quantitative evaluation conduct a comprehensive verification of child restraint system models and dummy. Test and simulation results of the comparative analysis showed that the models are effective. We can carry out to further study on the practical engineering problems on the basis of these models.2.3 Child Restraint System Parameters Analysis and OptimizationDiscuss protection of child restraint system for children in frontal crash and come to the conclusion: cushion friction coefficient, seat back stiffness, seat belts stiffness, seat belts slot position and so on parameters in collision are relatively sensitive, which are needed to improve design. Determine the appropriate parameters area for the next optimization.Understand that the relationship between the system parameters and the child occupant injury is not simple linearity. It is necessary to improve the system performance constraints that must be considered from the whole of the child restraint system performance analysis. Application of the analysis results, using of orthogonal experiment method, improve the optimization program for a child restraint system.Optimizing results are the "point" design. This is very easy to achieve in theory simulation. However, it is very difficult to achieve a single point design requirements in the actual production, and therefore need to change the optimizing results from the "point" to the range. In the following work we will consider the actual restrictions on the scope of the design requirements, so that make the simulation a more realistic significance.2.4 Reverse to the design requirementsFrom the view of protecting the occupant Maximum and child restraint system practical design considering, optimization of a single point program has little value of application in practice. Based on research results of the relationship between the occupant injuries and the child restraint system parameters, get the optimum range of each system parameter,guide the scope of the design with optimum range, get simulation and practical application so that together.Survey results show that 70-80% of children seats do not match with cars, and about 30% of the children seats does not match problems are more serious. Similarly, the same CRS in the different types of vehicles, the collision results are marked difference. This means that the occupant protection of children should take full account of the compatibility problems with the vehicle. Therefore, the child restraint system and vehicle matching the design is reasonable or not, directly impacting on the protection performance of the child restraint system and the security of children. In this paper, look at children between the restraint system and vehicle matching relationship. In this paper, study on the matching relationship between the vehicle and child restraint systems. Make the actual design requirements for child restraint system and the vehicle body of the child restraint system-related components respectively to guide design. According to the design requirements, equip with the appropriate child restraint system for one car. And carry out score in accordance with the European NCAP, to test the reasonableness of the design requirements. Complete set of more comprehensive methods of child restraint system research,which can be used as future reference for the actual design.3. Significance of PaperFirst of all, the first propose a more comprehensive methods and processes of child restraint systems study. Master the process of child restraint system performance study, after which the researchers sum up the experience;Secondly, through the establishment of different forms of simulation models, master a method of combining simulation accuracy and with computational efficiency. Analysis the role of various parameters of the child restraint system in the collision and put forward the conclusions of the sensitive parameters to reduce the workload of the optimization phase; Thirdly, propose approach to the effective application of the simulation to practice. Reverse to the use of simulation can guide the actual design requirements and propose design requirements for the child restraint system and vehicle body, respectively, the corresponding matching;Fourthly, combining the issue of the child restraint system and the vehicle body matching, under the front of the design requirements, equip with the child restraint system to adapt for one car. And in accordance with European NCAP standards, carry out the assessment scores to verify the reliability of research methods of the full set of child restraint system study.