<div><p>The article deals with analysis of causes of lorry piston combustion engine damage. For docummentation and analysis of causes was used macroscopical, microscopical and scanning electron microscopy. The analysis showed that the reason of fatal damage resides in production process of lorry combustion pistons which proved in implication of fatigue damage and subsequent burnout in two piston place.<em> </em></p> <p><em> </em></p></div

Karin Kocúrová

Mária Štefániková

Roman Moravčík

The article deals with analysis of causes of lorry piston combustion engine damage. For docummentation and analysis of causes was used macroscopical, microscopical and scanning electron microscopy. The analysis showed that the reason of fatal damage resides in production process of lorry combustion pistons which proved in implication of fatigue damage and subsequent burnout in two piston place

Štefániková, Mária

Moravčík, Roman

Kocúrová, Karin

Materials Engineering - Materiálové inžinierstvo (MEMI - E-Journal)

THE ANALYSIS OF CAUSES OF LORRY PISTON COMBUSTION ENGINE DAMAGE

Materials Engineering - Materiálové inžinierstvo (MEMI)

The article deals with analysis of causes of lorry piston combustion engine damage. For docummentation and analysis of causes was used macroscopical, microscopical and scanning electron microscopy. The analysis showed that the reason of fatal damage resides in production process of lorry combustion pistons which proved in implication of fatigue damage and subsequent burnout in two piston place.   </div

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M. Štefániková, R. Moravčík, K. Kocúrová: The analysis of causes of lorry piston combustion engine damage  Materials Engineering - Materiálové inžinierstvo 19 (2012) 47-51 47  THE ANALYSIS OF CAUSES OF LORRY PISTON COMBUSTION ENGINE DAMAGE  Mária Štefániková1*, Roman Moravčík1, Karin Kocúrová1  1Institute of Materials Science, Faculty of Materials Science and Technology, Slovak University of Technology in Bratislava, J. Bottu.25, 917 24 Trnava, Slovakia *corresponding author: Tel.: +421 918 646 038, Fax.: +421 33 5521 007, e-mail: maria.stefanikova@stuba.sk   Resume The  article  deals  with  analysis  of  causes  of  lorry  piston  combustion engine damage. For docummentation and analysis of causes was used macroscopical, microscopical and scanning electron microscopy. The analysis showed that the reason of fatal damage resides in production process  of  lorry  combustion  pistons  which  proved  in  implication  of fatigue damage and subsequent burnout in two piston place.      Available online: http://fstroj.uniza.sk/journal-mi/PDF/2012/08-2012.pdf Article info Article history: Received 12 July 2011 Accepted 25 January 2012 Online 17 February 2012  Keywords: Piston; Damage; Crack; SEM.  ISSN 1335-0803 (print version) ISSN 1337-6471 (online version)  1.  Introduction The  pistons  for  combustion  engines  are produced  of  aluminium  alloys  with  various silicon  contents  and  additional  elements  in different constructional version. The composition of aluminium alloy and application of production technology  differs  in  dependence  of  specific utilize [1,2]. Engine  pistons  are  one  of  the  most complex  components  among  all  automotive  or other  industry  ﬁeld  components  [3,4].  The pistons are directly exhibited to fuel explosions and product of fuel combustion. Such obtained energy  with  help  of  piston  is  transformed  into kinetic  energy  which  is  used  for  wheel  drives. Big part in material draft plays used type of fuel itself.  Petrol  engines  work  more  efficiently during higher turns as well as speeds from which follow  that  fatigue  strength  is  achieved  earlier and  it  also  comes  to  higher  friction  than  oil engines.  Compression  ignition  engines  work during distinctively higher pressures and higher temperatures.  The  decisive  influence  on  the activity  and  also  engine  lifetime  has  chemical composition  of  fuel  [5],  therefore  combustion products  itself  certain  fuel  compounds aggressively  influence  used  materials  in  active part  of  engine.  Damage  mechanisms  have diﬀerent  origins  and  are  mainly  wear, temperature,  and  fatigue  related.  Among  the fatigue damages, thermal fatigue and mechanical fatigue,  either  at  room  or  at  high  temperature, play a prominent role [6,7]. Also, analysis of the piston thermal behaviour is extremely crucial in designing more eﬃcient engine [8,9].The aim of the  article  is  to  determine  the  cause  of  lorry piston combustion engine damage.  2.  Damaged piston characterization and used experimental procedures  Two damaged pistons of lorry combustion engine  were  used  for  analysis.  The  damaged pistons  in  engine  were  changed  before automobile had done 10000 km. Both damaged pistons  were  burnt  out  same  in  active  and  the most  exposed  parts  of  piston  (Fig.  1)  and  in sideway  of  piston  (Fig.  2).  Crack  occurred closely  (red  arrows)  to  burnout  parts  which This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-nd/3.0/ or send a letter to Creative Commons, 444 Castro Street, Suite 900, Mountain View, California, 94041, USA. This copy of the article was downloaded from http://www.mateng.sk , online version of Materials Engineering - Materiálové inžinierstvo (MEMI) journal, ISSN 1335-0803  (print version), ISSN 1338-6174 (online version). Online version of the journal is supported by www.websupport.sk  .      M. Štefániková, R. Moravčík, K. Kocúrová: The analysis of causes of lorry piston combustion engine damage  Materials Engineering - Materiálové inžinierstvo 19 (2012) 47-51 48  spread  out  from  piston  pivot  up  to  the  central part of active piston area. The burnout places and also  shape  of  the  crack  were  identical  in  both cases of damaged pistons. The origin of damage was  determined  using  macroscopic  and microscopic  analysis  (optical  and  scanning electron microscopy) of damaged pistons.    Fig. 1 Burnout place and crack in active part of piston (full colour version available online)   Fig. 2 Place of burnout sideway of piston and crack propagation (full colour version available online) For microscopical analysis piston was cut into more parts which were subject to analysis. Parts  for  microscopical  analysis  were  prepared standard  metallographical  procedure  without etching.  For  scanning  electron  microscopy fracture surfaces and parts of piston joined with degradation  damage  were  cleaned  in  acetone using ultrasound. The analysis was carried out by means  of  TESLA  BS  300  scanning  electron microscope. 3.  Macroscopic analysis Two  base  features  of  piston  degradation (except  abrasion)  were  identified  by  visual investigation  of  damage  piston  combustion engine. At first the crack was created which rose up  to  the  hole  into  piston  pivot  (Fig.  2)  and stopped almost at the middle active piston part. The  second  feature  was  relatively  big  burnout holes in active and also sideway part of the gear piston. The seal ring was joined with piston in burnout place, distinctively abrasively worn and damaged. Due to the burnout localization close to the crack it can not be stated that burnout was initiator of piston damage but burnout was result of  crack  formation  and  its  propagation  in exhibition  process  of  piston.  In  that  case attention  was  focused  on  crack  which  had  the same shape in both damaged combustion engine pistons. External  cylindrical  surface  was  worked on  the  base  of  morphology  by  roughly  lathe-turning. Probably, cutting tool caused tearing out of  material  by  wrong  machining  parameters  in hole place for piston (Fig. 3) from hole edge for piston  pivot  (green  arrows)  in  consequence relatively sharp and large notches were created at that place. That way damaged hole edge had effect as the initiation place for formation of fatigue crack which  after  achieving  hole  for  leading  away excess oil from wipeable ring and subsequently propagated in its direction. That documents Fig. 4 where sudden change is seen in the orientation during  crack  propagation.  Material  is  in  the closeness of that hole weakened what enables its next propagation up to the active piston part. In this place high temperatures and pressure effect for material of piston. Fuel mixture was getting into material volume by the crack what caused also local melting down of fracture surface and by medium pressure caused its removal through crack  and  the  weakest  section  out  of  piston material.  M. Štefániková, R. Moravčík, K. Kocúrová:The analysis of causes of lorry piston combustion engine damage   Materials Engineering - Materiálové inžinierstvo 19 (2012) 47-51 49  Fig. 3 Split off piston edge of pivot after machining (full colour version available online)   Fig. 4 Direction of fatigue crack propagation (full colour version available online)  4.  Microscopic analysis Microstructure of piston cast was analysed in bottom, middle and active part of piston. In all three  areas  microstructure  was  formed  by  base matrix on the basis of aluminium solid solution, sharp-edge Si particles and interdendritic spaces were  filled  by  eutectics.  On  the  base  of microstructure  it  can  states  that  it  is  alloyed hypereutectic Al-Si alloy [10]. Microstructure of active  piston  part  is  documented  in  Fig.  5,  its middle part is given in Fig. 6 and bottom part of piston  is  shown  in  Fig. 7.  Microstructural heterogeneity  in  individual  piston  parts  is observed in photographs.  In Fig. 8 fracture surface in place of the fatigue  crack  initiation  can  be  seen.  Typical fatigue  (relaxation)  lines  were  observed  in fracture surface which proceeded from place of initiation fracture in this case from place where parts  of  material  were  torn  out  from  surface during  machining.  Groove  for  safety  ring  of piston  pivot  was  situated  in  left  upper  part  of image.   Fig. 5 Microstructure from active part of piston   Fig. 6 Microstructure from middle part of piston   Fig. 7 Microstructure from bottom part of piston      M. Štefániková, R. Moravčík, K. Kocúrová: The analysis of causes of lorry piston combustion engine damage  Materials Engineering - Materiálové inžinierstvo 19 (2012) 47-51 50  Fig  9  documents  micrograph  of  external machined surface which contains tracks caused by  cutting  tool.  Places  were  observed  in  edge (left)  where  material  was  torn  out  during machining of surface. Same damage (tearing out) was observed in opposite side of hole for piston pivot.   Fig. 8 Surface fracture in place of crack origin,  fatigue lines, split off material   Fig. 9 Machined piston surface, split off material  and fracture surface  5.  Discussion and conclusion On the base of carried out analyses it can be stated that the most probable cause of piston damage during exhibition process is caused by wrong  machining  parameters  of  external cylindrical  piston  surface.  Parts  of  material were  torn  out  in  hole  place  for  piston  pivot during machining. This place is cyclically also dynamically  strained  during  the  activity  of engine while role itself plays also temperature change of material of piston.  As  microscopic  analysis  showed  in  the microstructure  of  combustion  engine  piston relatively big particles of primary and eutectic origin occurred which support the material to tear out after impact of tool. The tearing out of small  material  particle  in  edge  hole  led  in consequence  of  cyclical  loading  to  initiation and subsequent fast fatigue crack propagation which  continued  in  direction  of  the  least material resistance of piston, i.e. in direction of channel  which  serves  for  conducting  away excess  oil  deflated  by  wipeable  ring  from combustion engine cylinder.  The  next  consequence  of  created  crack was formation of the burnout. The fuel which was  supplied  into  combustion  space  over piston penetrated by effect of pressure by crack into  material  piston  volume  and  during  its igniting  it  probably  causes  local  overheating and later melting down of surface fracture. In the  process  of  time  burning  out  of  piston happened  by  way  of  repeated  pressure  of burning fuel. Melted down material had effect as abrasive which wore piston rings in burnout place.  The conclusion states that during whole production  process  conditions  of  individual technological operations are needed to respect. Not respecting of define conditions can lead to damage  of  component  and  it  means  to distinctive decrease of lifetime and actually to complete  destruction  of  constructional  unit which part is component [11].  Acknowledgements This contribution/publication is the result of  the  project  implementation:  CE  for  the development  and  application  of  diagnostic methods in the processing of metallic and non-metallic  materials,  ITMS  code  26220120048, supported  by  the  Research  &  Development Operational Programme funded by the ERDF.  M. Štefániková, R. Moravčík, K. Kocúrová:The analysis of causes of lorry piston combustion engine damage   Materials Engineering - Materiálové inžinierstvo 19 (2012) 47-51 51   We support research activities in Slovakia / The project is co-financed by the European Union.  References [1]  E. Buyukkaya, M. 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THE ANALYSIS OF CAUSES OF LORRY PISTON COMBUSTION ENGINE DAMAGE

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