Chapter Crashworthiness Injury Biomechanics from head to foot 6-7.pdf

Chapter Crashworthiness Injury Biomechanics from head to foot 6-7

1. Chapter 6
Injury Biomechanics from Head to Foot
INJURY MECHANISMS

2. Contents
•Introduction to Injury Biomechanics,
•Head injury mechanism,
•Injury Mechanisms,
•Head,
•Neck,
•Thoracic,
•Abdominal
•Pelvic etc.
•Mechanical response (reading assignment)
•Humanimpacttolerance(readingassignment)

3. IntroductionInjury Biomechanics
•The entire human body will be covered under the four main branches of
impact biomechanics.
•The branches are injury mechanisms, mechanical response, tolerance and
the biofidelity of surrogates.
•The development of surrogates or test dummies for automotive safety
testing depends on a clear understanding of the injury mechanisms
involved and of the mechanical response of various body regions to blunt
impact.
•To be able to interpret the measurements made on such a dummy,
knowledge of human tolerance to impact is needed.
•To ensure biofidelity of dummy response, it is necessary to incorporate
mechanical components that mimic human response.
•Dummy design is based on human response data that are obtained largely
from testing of human cadavers.

10. Injury Mechanisms
•In this branch of impact biomechanics, tests and analyses are conducted to
determine the mechanical parameters involved in causing a certain injury.
•Generally, several reasonable hypotheses are proposed and tested and the one
that most consistently produces the same injury emerges as the mechanism of
injury.
•Failure of a long bone occurs as the result of a tensile load being applied to it. In
most cases, the tension would come from bending of the bone and thus the
mechanism of bony fracture of a long bone is frequently due to the application of a
bending moment.
•In some cases, two different loads or motions can cause the same injury. For
example, in the brain, diffuse axonal injury (DAI) can result from angular as well as
linear acceleration of the head. In that sense, the injury mechanism for DAI is not
unique.
•However, both of these motions can cause shear stresses to develop in the brain
and thus the injury mechanism can very well be shear stress or strain. It is not clear
at this time if any injury has a unique mechanism.

11. Head Injury Mechanisms
•They are positive pressure, negative pressure and shear due to pressure
gradients or relative motion of the brain with respect to the skull.
•At the site of impact or the coup site, a positive pressure or compressive
stress is developed and a negative pressure occurs at the contrecoup site.
•These pressures are accentuated by the deformation of the skull; in-bending
at the coup site and out bending at the contrecoup site.
•Positive pressure can contuse the brain while the mechanism of injury for
negative pressure can be due to either tensile loading or cavitation, which is
compressive loading due to the collapse of vapor bubbles formed as a result
of negative pressure.
•Injuries due to relative motion of the brain inside the skull are based on
contusions seen on the surface of the brain and on a diffuse form of brain
injury called ‘diffuse axonal injury’.

21. Thoracic Injury Mechanisms
•The thorax houses organs essential to life.
•It is protected to a certain extent by the rib cage and the thoracic spine.
•The forces encountered in a severe automotive crash are frequently large
enough to fracture the ribs and sternum as well as tear the main arteries within
the thorax or injure the walls of the heart.
•At times, highspeed blunt impacts can cause the heart to go into ventricular
fibrillation.
•The lungs can be contused by impact with the chest wall or by the passage of
compression waves through the alveolar tissue.
•Lungs can also be lacerated by the ends of fractured ribs.
•The various injury types appear to be dependent on the rate of loading
because of the viscoelastic nature of the tissues involved.

38. NCAPtests and criteria

39. Con…

40. Con…

41. IIHS Rating Frontal Impact

42. Con…

44. Reading assignment (for final exam)
•Mechanical responses (pages 280 –304)
•Human impact tolerance (pages 304 –330)
•Discussion ontheinjurymechanisms,Mechanical response, human
impact tolerance and conclusion. (Pages 330 –335)

45. Chapter 7
Dummies
Text book from page 353

46. Dummies are ATDs
•Anthropomorphic test devices (ATDs), commonly referred to as dummies, are
mechanical surrogates of humans.
•Crashworthiness engineers use ATDs to evaluate the occupant protection
potential of various types of restraint systems in simulated collisions of new
vehicle designs.
•Current ATDs are designed to be biofidelic, meaning they mimic pertinent
human physical characteristics such as size, shape, mass, stiffness, and energy
absorption and dissipation.
•The dummies’ mechanical responses simulate corresponding human
responses of trajectory, velocity, acceleration, deformation, and articulation
when the dummies are exposed to prescribed simulated collision conditions.
•Engineers equip dummies with transducers that measure accelerations,
deformations and loading of various body parts.
•Analyses of these measurements are used to assess the efficacy of restraint
system designs.

47. Con…
•Transducers
everywhere
in the body
to capture
impact
information

49. Dummy family (classification)

51. Hybrid III 3-yearold, 6-year-old
and the CRABI 12-month
Hybrid III adult dummies
(small females, mid-size
male and large male)

53. Dummies for side impact
50th percentile adult male side impact
dummies (SID, EUROSID-1, BIOSID)

54. Key dimensions and weights for various sizes of dummies
•Chronology
of notable
dummies
used by the
United States
auto industry

55. Chronology of notable dummies used by the United States auto industry

56. Con…

57. Recent models

58. Dummy harmonization
•The Hybrid III mid-size adult male is the only dummy that is used by regulatory bodies
worldwide for restraint system evaluation.
•NHTSA is in the process of incorporating the Hybrid III dummy family and the CRABI infant
dummies into its safety standards. While there is a good possibility of other countries
adopting the use of the Hybrid III small female and large male dummies into their
regulations, there appears to be no worldwide acceptance of the child and infant dummies.
•TNO has been funded by the European Union (EU) to develop a new family of Q series child
dummies to replace the P-series which are currently specified in European regulations.
•For side impact regulations, SID is specified by NHTSA as the only dummy allowed for
FMVSS 214 compliance testing.
•Europe and Japan have specified EUROSID-1 for side impact compliance testing.
•Australia allows either dummy to be used. Recently, the ISO has taken on the task of
developing World SID, a side impact dummy acceptable to all regulatory bodies.
Development of World SID was completed in 2004.
•Clearly, to obtain dummy harmonization for safety regulation there must be an
international agreement on the need to improve an existing dummy design, an agreement
on the improvements, a cooperative development program to make the changes, and a
willingness to accept the upgraded dummy by all interested parties.

59. Big harmonies family

60. The End
Thank you

61. Remark
Schedule will be communicated for:
•Presentation of assignments
•Presentations of seminar paper
•Please study the test book
•Final exam will include the whole topic, but mainly the
portion after mid exam