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  • 1. DEVELOPMENT  OF  AN   INTELLIGENT  HEADREST  USING   SMART  MATERIALS   Ajmal  Abdu  Salam   M.Sc.  Mechanical  Engineering  with  Industrial  Management     Supervisor:     Dr.  Olga  Ganilova  
  • 2. AIMS  AND  OBJECTIVES   •  To  inves;gate  the  problem  of  whiplash  and   the  latest  achievements  in  the  field   •  To  study  the  area  of  smart  materials   •  To  develop  a  novel  design  for  an  intelligent   headrest  applying  smart  materials   •  Evolvement  of  an  analy;cal  model  of  the   smart  headrest   © The University of Sheffield
  • 3. Whiplash  Injuries  in  an  Accident   •  Whiplash  injury  results  from  an   rear  end  accident  in  which  the   driver  is  in  a  sta;onary  vehicle   that  is  struck  from  behind   •  The  movement  of  the  neck  is   followed  by  massive  rebound  in   the  opposite  direc;on,  causing   bone  and  soD  ;ssue  injuries   •  Around  570,000  whiplash  injury   claims  were  made  in  the  UK,  last   year  [ABI  2012]   © The University of Sheffield What is a Whiplash? Figure  2.  ‘S’  curve  during  Whiplash  [Chiroprac)c  Health  Blog]   Figure  1.  Mechanism  of  Whiplash  [IIHS]  
  • 4. Smart  Materials   •  “A    system  or  material  which  has  built-­‐in  or  intrinsic  sensor(s),   actuator(s)  and  control  mechanism(s)  whereby  it  is  capable  of   sensing  a  s;mulus,  responding  to  it  in  a  predetermined   manner  and  extent,  in  a  short/appropriate  ;me,  and  rever;ng   to  its  original  state  as  soon  as  the  s;mulus  is  removed.”     •  Examples  -­‐  Piezo-­‐ceramics,  Piezoelectric  polymers,   Magnetostric;ve  ceramics,  Shape  memory  alloys,  Electro-­‐ rheological  fluids  and  Magneto-­‐rheological  fields  etc.   © The University of Sheffield
  • 5. Comparison  of  Mechanical  Actuators           Actuator     Max.   ActuaPon   Strain     Max.   ActuaPon   Stress  (MPa)     Modulus   E  (GPa)     Maximum   Frequency  (s-­‐1)     Maximum   Power  Density   (Wm-­‐3)     Density   (kgm-­‐3)     Efficiency     Low  Strain   Piezoelectric     5  x  10-­‐6  –   3  x  10-­‐5     1-­‐3     90-­‐300     5  x  105  –   3  x  107     1  x  108  –   1  x  109     2600-­‐4700     >  0.999     High  Strain   Piezoelectric     5  x  10-­‐5  –   2  x  10-­‐4     4-­‐9     50-­‐80     5  x  105  –   2  x  107     9  x  107  –   5  x  108     7500-­‐7800     0.90  –  0.99     Piezoelectric   Polymer     2  x  10-­‐4  –   1  x  10-­‐3     0.5-­‐5     2-­‐10     1  x  105  –   1  x  107     ≈  3  x  108     1750-­‐1900     0.90  -­‐  0.95     SHAPE   MEMORY   ALLOY     7  x  10-­‐3  –   7  x  10-­‐2     100-­‐700     30-­‐90     2  x  10-­‐2  –   7  x  100     7  x  105  –   1  x  108     6400-­‐6600     0.01  -­‐  0.02 © The University of Sheffield Table  1.  Characteris;c  features  of  the  mechanical   actuators  [The  Selec)on  of  Mechanical  Actuators]  
  • 6. Shape  Memory  Alloys   •  Shape  Memory  Alloys  are  alloys  of   metals  that  have  the  ability  to   remember  their  original  shapes.   •  The  Two  Unique  Proper;es  –     1.  One-­‐way  Effect   2.  Two-­‐way  Effect   3.  Pseudo-­‐elas;city   •  The  Advantages  –     1.  Rela;vely  Light  Weight   2.  Easy  to  manufacture   3.  High  Force  to  Weight  Ra;o     © The University of Sheffield Figure  3.  One-­‐way  and  Two-­‐way  effect  of  SMA  [Issues  in   the  Design  of  Shape  Memory  Alloy  Actuators]   Figure  4.  Pseudo  elas;city  behavior  of  SMA  [h=p:// linkinghub.elsevier.com/retrieve/pii/S0045782596012327]  
  • 7. NiTi  -­‐  Flexinol®   •  The  NiTi  SMA  -­‐  developed  at  the   Naval  Ordnance  Laboratory   •  ADVANTAGES  –     1.  Large  Recoverable  Mo;on   2.  Great  Duc;lity,     3.  Excellent  Corrosion  Resistance,     4.  Stable  Transforma;on  Temperatures     5.  High  resis;vity,  resul;ng  in  Cheaper   costs  in  cyclic  applica;ons     Property Value Density,   6.45  g/cm3 Specific  Heat,  cA  =  cM 837.36  J/kg/K Latent  Heat  of  TransformaPon,  XAM 24,190.4  J/kg Electrical  ResisPvity   Austenite,   100  micro-­‐ohms*cm Martensite,   80  micro-­‐ohms*cm TransiPon  Temperatures 70  Wire 90  Wire As 70 90 Af 90 110 Ms 65 80 Mf 45 60 Modulus  of  ElasPcity   Martensite,  Em 28  GPa Austenite,  EA 83  GPa Poisson’s  raPo 0.3 Stress  Influence  Coefficients   CA 7MPa/℃ CM 7MPa/℃ CriPcal  Shear  Stress   Start  of  Martensite  De-­‐twinning  process  ,   114.0  MPa End  of  Martensite  De-­‐twinning  process  ,   72.4  MPa Upper  Plateau  Shear  Stress  ,   183  MPa Maximum  Recoverable  Shear  Strain,   0.05 © The University of Sheffield Table  2.  Technical  Characteris;cs  of  NiTi  Wire  [Technical   Characteris)cs  of  FLEXINOL  ®  ]   Figure  5.    NiTi  Shape  Memory  Alloy  [http:// www.pnk.com.cn/material/ shape_memory_alloy.htm]  
  • 8. ProtecPon  Systems  developed  by   Automobile  Companies   10/10/13 © The University of Sheffield •  Volvo  and  Jaguar  use  WhiPS  or  more  commonly  known  as   Whiplash  Protec;on  System.   •  Consists  of  a  recliner  along  with  a  modified  backrest  and  a   head  restraint.     •  Toyota  uses  WIL  or  Whiplash  Injury  Lessening  system,  which  has   no  ac;ve  parts  but  has  an  improved  geometry  and  a  soDer  seat   back   •  This  is  a  concept  idea  and  has  not  been  implemented  yet     •  Grammar  AG  and  BMW  jointly  developed  ac;ve   head  rest  systems.     •  The  forward  displacement  of  the  seat’s  head  rest   is  ini;ated  by  a  pyrotechnical  inflator  unit,   ac;vated  when  there  is  a  rear  end  collision.     Figure  8.  Headrest  designed  by  Grammar  AG  in  BMW   [Grammar  AG]     Figure  7.  WIL  and  RHR  Concept  [TOYOTA.  WIL  -­‐  Whiplash   Injury  Lessening]   Figure  6.  The  WhiPS  Seat  Mo;on  [WHIPS  –  Volvo’s   whiplash  protec)on  study]  
  • 9. Design  Methodology   •  Headrest  is  fiped  with  a  Smart  Material   Actuator   •  One-­‐way  Shape  Memory  Effect  NiTi  used  for   the  NiTi  Spring  Actuator   •  Actuator  will  have  a  fixed  part  and  a  movable   part   •  All  the  components  designed  in  Solidworks   © The University of Sheffield
  • 10. Design  of  the  NiTi  Spring  Actuator   •  NiTi  Spring  Actuator  was  designed  by   taking  the  NiTi  Wire  diameter  as   0.510mm,  keeping  a  Spring  Index  of   6.22.  The  Spring  diameter  was   calculated  to  be  3.175mm  .     •  A  bias  spring  of  low  s;ffness  made  of   Titanium  provided  on  the  opposite   side  to  provide  the  required  poten;al   energy.       © The University of Sheffield Figure  9.  Pre-­‐ac;vated  and  Post-­‐ac;vated  NiTi  Spring   Actuators  
  • 11. Pre-­‐acPvated  Smart  Headrest   •  Carefully  designed  aDer  a  study  of   the  male  and  female   anthropometry  data.   •  The  headrest  has  a  total  length  of   229.09mm  suitable  for  both  male   and  female.   •  The  Design  is  just  en;tled  to  show   the  headrest  and  it’s  working   mechanism   •  The  en;re  headrest  will  be  covered   with  foam  and  leather  when   installed  inside  the  vehicle.       © The University of Sheffield Figure  10.  Pre-­‐ac;vated  Smart  Headrest  
  • 12. Post-­‐acPvated  Smart  Headrest   •  Phase  transforma;on  of  the  NiTi   Spring  takes  place  when  the   sensor  detects  an  imminent   collision,  which  leads  to  the   contrac;on  of  the  spring  in  its   length.     •  Because  of  this,  the  top  part  of   the  headrest  apached  along  with   hinges  ;lts  for  an  angle  of  22   degrees.     © The University of Sheffield Figure  11.  Post-­‐ac;vated  Smart  Headrest  
  • 13. Flow-­‐chart  of  the  AcPvaPon   Mechanism   © The University of Sheffield
  • 14. ConvenPonal  Head  Rest   © The University of Sheffield •  During  a  rear  impact,  the   occupant’s  head  makes  a  point   contact  with  the  head  rest.   •  This  point  contact  is  not  sufficient   enough  for  the  headrest  to  prevent   the  whiplash.   •  The  head  thus,  rotates  to  more   than  45  degrees  leading  to  hyper-­‐ extension  causing  whiplash  injury.   Figure  12.  Contact  of  Driver  with  a  Conven;onal  Headrest   Figure  13.  Point  Contact  of  the  Driver’s  Head  in  a   Conven;onal  Headrest  
  • 15. Smart  Head  Restraint   •  In  this  case,  the  head  makes  a  contact  with  the   head  rest  and  the  area  was  calculated  to  be   1532.30  mm2     ​ 𝑚↓ℎ ∗  ​ 𝑣↓ℎ +  ​ 𝑚↓ℎ𝑟 ∗  ​ 𝑣↓ℎ𝑟 =  ​ 𝑚↓ℎ  ∗  ​​ 𝑣↑′ ↓ℎ +  ​ 𝑚↓ℎ𝑟 ∗  ​ 𝑣′↓ℎ𝑟      𝑒=  ​​​ 𝑣↑′ ↓ℎ −  ​ 𝑣′↓ℎ𝑟   /​ 𝑚↓ℎ         𝐹=  ​​ 𝑚↓ℎ ∗  ∆ 𝑣  /∆ 𝑡      •  From  the  above  equa;ons,  the  force  created   by  the  head  due  to  the  contact  with  the   headrest  was  calculated  to  be  101.546  Newton   at  an  impact  speed  of  35  km/hr.  and  the  stress   as  0.662  N/mm2.   © The University of Sheffield Figure  14.  Contact  of  Driver  with  the  Smart  Head  Restraint   Figure  15.  Contact  Area  of  the  Driver’s  Head   with  the  Smart  Headrest   EquaPons  –  [Engineering  Mechanics;  Dynamics  –  J.L.   Meriam,  6th  Edi)on]  
  • 16. CONCLUSIONS   •  Insight  about  whiplash  injuries  due  to  rear  impact  collisions  and  the  latest   achievements  by  the  automobile  companies  to  prevent  this  injury.   •  Insight  into  smart  materials  and  shape  memory  alloy  actuators  are   compara;vely  beper.   •  LimitaPon  was  observed  in  the  wire  diameter  as  it  was  limited  to  0.510mm.   •  Actua;on  Times  and  the  Force  generated  by  SMA  Spring  were  approximated   based  on  the  researches  done  in  the  par;cular  field   •  Smart  Head  Restraint  with  NiTi  Spring  Actuator  can  arrest  the  head  neck   moPon  before  it  goes  to  hyper-­‐extension,  thus  preven;ng  the  driver  from   suffering  the  whiplash  injury  when  compared  to  a  conven;onal  headrest.   © The University of Sheffield
  • 17. Further  Research   •  In-­‐depth  research  needs  to  be  done  on  the  ac;va;on  ;mes  of  the  phase   transforma;ons  of  the  Ni;nol.   •  Actua;on  force  needs  to  be  calculated  with  bundle  wires  and  larger  wire   diameters.   •  A  Locking  Mechanism  can  be  used  in  order  to  retain  the  head  restraint  in   its  ac;vated  state.  This  can  be  either  mechanically  or  electronically   actuated.   •  An  effec;ve  ANSYS  or  LS  –  DYNA  simula;on  of  the  head  impact  on  the   headrest  for  a  more  approximate  stress  calcula;on  on  the  driver’s  head.   •  Valida;on  of  the  Smart  head  rest  performance  in  terms  of  Whiplash  Injury   Criterion.       © The University of Sheffield
  • 18. Thank You !! Any Questions?