Introduction & Injury Tolerance Limit

Introduction

·         Application of mechanical principles to all living things

·         Bio mechanics is studied on the behavior of humans under internal and external forces, as well as applied engineering work.

·     For mechanical engineers, biomechanics is important because to develop vehicles by understanding injury mechanisms.

Injury Tolerance Limit

• Describe as fractures, injuries of organs, and other injuries. A classification is done via Abbreviated Injury Scale (AIS) or Overall Abbreviated Injury Scale (OAIS).
• AIS is an anatomically based, consensus derived, global severity scoring system that classifies each injury in every body region according to its relative importance on a six point ordinal scale.

·         The data span a range from 0 to 6.

©     The purposes of AIS are:

ü  to describe injuries anatomically,

ü  to standardize injury terminology,

ü  to rank injuries by severity

©     Table 2 shows the relationship between injury description and AIS.

Prepared by Arif Shafiq B M Sohaimi 54268111089

PERFORMANCE CRITERIA FOR THE RULE-MAKING PROCESS

PERFORMANCE CRITERIA FOR THE RULE-MAKING PROCESS

CHEST

 

Resultant chest acceleration <60g (>msec)

TTI = Thoracic Trauma Index          <85g (four-doors)

                                                         <90g (two-doors)

TTI = 0.5 x (RIBY + T12Y)

RIBY = Maximum absolute value of lateral acceleration in g’s of the

             fourth and eighth rib in the struck side.

T12Y = Maximum absolute value of lateral acceleration in g’s of the

             twelfth thoracic vertebra after filtering of the acceleration

             signal

Force < 8000 kN

PELVIC

Resultant acceleration <130g

Force abdomen <2.5 kN

Force symphysis <10kN

LEG AND KNEE 

Upper Leg:

Force limit in frontal impacts<10000 N (requirement FMVSS 208)

Shear load in the knee joint <5000 N

Knee dislocation <15mm (requirement for Europe)

Force in the femur in the longitudinal direction (requirement for  Europe), Flong < (7.6 – 9 kN) as f(t) (as shown in Figure 4.10) 

 

Figure 4.10 Upper leg force as a function of time

Lower leg:

  Force in the tibia (compression force criteria)(requirement for

                Europe)

   Flong < 8 kN

                Tibia index Ti measured at the top and bottom of each tibia must

                not exceed 1.3 at either location (requirement for Europe)

The tibia index is calculated on the basis of the bending moments (Mx and My) by the following expression:

Mx        = Bending moment about the x-axis

 

My        = Bending moment about the y-axis

 

(Mc)R  = Critical bending moment and shall be taken to be 225 Nm

 

Fz         = Compressive axial force in the z direction

 

(Fc)z   = Critical compressive force in the z direction and shall be taken to

             be 35.9 kN

 

The tibia index is calculated for the top and bottom of each tibia; however, Fz may be measured at either location. The value obtained is used for the top and bottom TI calculations. Moments Mx and My are measured separately at both locations.

Due to the requirements already defined and because of improved restraint systems, especially the combination of seat belts and airbags, the degree of protection of the human body has increased. This means that the knee and the lower leg area have become a relatively high priority. For the feet of the front occupant, it is important to prevent too high a bending-flexion around the y-axis.

Pedestrian Protection 

  

Figure 4.11 Test requirements for pedestrian protection

a) Limitation of the headform acceleration for two different head forms,
     child and adult simulation,
               
b)A simulation of a leg impacting the bumper of the vehicle front, where the leg angle should not exceed 15º, the shear distance of the knee should be below 6 mm (0.23 in.), and the acceleration of the tibia is less than 150g.

c)The simulation of the upper leg against the bonnet of the front hood with the requirement that the shear force should be lower than 4 kN and bending moment of the impactor less than 200Nm.

Prepared by Kalaivaani a/p Ramachawolran

54268111124