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Biomechanics For Dummies


At once a basic and applied science, biomechanics focuses on the mechanical cause-effect relationships that determine the motions of living organisms. Biomechanics for Dummies examines the relationship between biological and mechanical worlds. It clarifies a vital topic for students of biomechanics who work in a variety of fields, including biological sciences, exercise and sports science, health sciences, ergonomics and human factors, and engineering and applied science. Following the path of a traditional introductory course, Biomechanics for Dummies covers the terminology and fundamentals of biomechanics, bone, joint, and muscle composition and function, motion analysis and control, kinematics and kinetics, fluid mechanics, stress and strain, applications of biomechanics, and black and white medical illustrations.




Biomechanics For Dummies



Steve McCaw PhD is a professor at Illinois State University. Dr. McCaw has taught Biomechanics of Human Movement Occupational Biomechanics and Quantitative Biomechanics and has vast experience presenting biomechanics concepts in easy-to-understand formats for use in criminal and civil cases.


The crash test dummy, an important tool for car crash safety tests, is of great significance to explore the injury biomechanics of the occupants and improve the safety performance of the vehicle. The article mainly consists of four parts: brief introduction of injury mechanism, early experiments for obtaining biomechanical response (animal tests, cadaver tests, and volunteer tests), and development and validation of mechanical dummies and computational models. This study finds that the current crash test dummies are generally designed based on European and American, so they have limitations on the damage prediction of other regions. Further research in the crash test dummy needs the participation of various countries in order to develop a crash test dummy that meets the national conditions of each country. Simultaneously, it is necessary to develop dummies of vulnerable groups, such as the elderly dummy and obese people dummy.


This paper reviews the development of dummies and is introduced from four aspects. The first is theoretical foundation of crash test dummy, named biomechanical injury mechanism. In order to study the injury mechanism, researchers conducted cadaver experiment, animal experiment, and volunteer test in early time, so the second aspect is about biomechanical test. The third and fourth aspects introduce the development and verification process of the mechanical dummies and computational models used in crash test.


In the abovementioned volunteer tests, animal tests, and cadaver tests, there are significant drawbacks such as experimental risks, physical differences, and violating ethics. Therefore, developing a new human substitute to apply to the research on vehicle impact injury biomechanics is important. The substitute model is supposed to have the same structure, size, mass distribution, and impact motion characteristics compared to human body. The crash test dummy is such a substitute for human body in crash tests. It is made of various materials such as steel, aluminum, rubber, and polymers and is equipped with multiple acceleration sensors, force sensors, torque sensors, and displacement sensors to record responses.


In 1949, the first dummy was used in the air force; after years of development, the dummies have been widely used as substitutes for human body in car crash tests. According to the type used for collision, the dummies can be categorized as frontal impact dummy, side impact dummy, and rear impact dummy. Table 3 lists crash test dummy types and their application conditions. In order to better understand the development of mechanical dummies, the following describes in detail the development process of each series of dummy.


As SID dummy developing, Europe also launched the development work of the side impact dummy. During 19781982, three dummies produced by APR, ONSER, and MIRA were released, respectively [18]. Although these dummies cannot obtain the desired lateral impact response, they provided prototypes for the new side impact dummy EuroSID. The EuroSID-I was developed according to the European male size in the mid-1980s.


In 1997, the ISO initiated the development of a more biofidelic side impact dummy: the WorldSID dummy. WorldSID dummy was based on the medium size of men worldwide. The reproducibility, the durability, and the sensitivity have been greatly improved compared to other dummies.


As the key equipment for vehicle collision safety inspection, the crash test dummy must not only be similar to the human structure in terms of external dimensions and mass distribution, but at the same time, the mechanical response of the major parts of the dummy should also be highly similar to the biological response of the same part of the human body. The higher the similarity is, the easier it is to get a more accurate injury assessment. Therefore, it is very important for the artificial simulation of dummy. In different collision conditions such as frontal impact, side impact, and rear impact, the major parts of the injured parts are not exactly the same, the forms of injury are different, and the method of verifying the biofidelity of the dummy is also different. According to the type of collision, the following introduces the validation of different dummies.


From these experimental results, the existing dummy model currently used anthropomorphic crash test dummies that can reflect the human response to a certain extent, but they are limited in their biofidelity and in their application type. Further improvement research on existing physical dummy is necessary.


Nowadays, commercial mechanical dummies are expensive and consume huge during crash tests. Only large corporations and research institutes have the financial resources to purchase physical dummies for research on car crash safety. With the continuous advancement of computer technology and digitization methods, visual model in computer is also widely used in automotive crash simulation. Currently, the models used for car crash studies mainly include multirigid models and finite element models. Multirigid body models are based on multibody dynamics theory. Engineers use simple planes and ellipsoids to simulate various structures of the human body and construct adult body model, using ADAMS, MADYMO, and other software to analyze. The finite element model uses the principle of finite element method to build the model. The essence of the finite element method is to discretize the entire study object. In contrast, the finite element model is more detailed so that it can investigate the local deformation and stress distribution. Therefore, the application of the finite element model is more extensive.


The study of finite element dummy for car crash originated in the late 1970s. Some companies have developed recognized FE dummy models, such as ERAB, ETA, FTSS, ARUP, and FAT [32]. Based on the mechanical dummies mentioned above, the FE model of dummies can be developed by five steps [33]. Firstly, capture the geometries of mechanical dummies by 3D scan. Secondly, translate the obtained geometries to CAD data. Thirdly, represent the model with 3D elements that means generating the FEM meshes. Fourthly, develop single components. Lastly, validate the model; the validation process is consistent with that of the mechanical dummy. Recent advancements in computer hardware technology and software developments have made it possible to develop detailed finite element models, by increasing the model structural details, refining mesh density, and improving material properties to improve the calculation accuracy of FE model. Nowadays, the commercial mechanical dummies all have a finite element dummy corresponding to them; the most recognized FE models are developed by FTSS.


Many scholars also have validated the finite element dummies by comparing with physical tests or regulations. In 2002, Noureddine et al. [34] illustrated the construction and validation of the Hybrid III dummy FE model in detail. The simulation results of chest model, head model, and neck model were compared with the mechanical dummy tests according to the Code of Federal Regulations. The time histories of the chest acceleration and head acceleration showed reasonable agreement with the results of physical test. In 2007, Friedman et al. [35] performed a head drop test using a Hybrid III finite element dummy to compare the upper neck force with the test in published mechanical dummy test. The results demonstrated that FE model shows good agreement with the test response in a rollover crash environment. In 2013, Tanaka et al. [36] studied the relationship between external force to shoulder and chest injury using WorldSID FE model. According to the seating posture and impact position of the manual to perform the CAE, there was a good agreement between CAE simulation results and physical test results. In 2017, the FE model of 5th percentile THOR had been compared with biofidelity corridors from head to toe [37]. The peak thorax probe impact response can be consistent with that of biofidelity corridors.


The Injury Biomechanics Research Center (IBRC) at The Ohio State University is a multi-disciplinary research center dedicated to investigating the relationships between human injury and physical mechanical properties. The IBRC has completed research in the field of automobile safety since 2004. The IBRC brings together an interdisciplinary team of engineers, anatomists, anthropologists, physicians, computer modelers and technicians who focus on both mechanisms of injury and injury thresholds of the human body. The IBRC has the capabilities to test biomechanical loading and impact scenarios with anthropomorphic test devices (crash test dummies), post-mortem human subjects, and non-injurious scenarios with research volunteers. The IBRC works closely with several Ohio State departments and many government and industry partners to offer one of the most diverse testing facilities in the country. 041b061a72


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