selection of material in automotive sector. Normally cost includes major components such as cost to design, cost of raw materials, manufacturing cost and cost of ...
International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 6, Issue 7, July 2016)
Application of Steel in Automotive Industry Mayank Kumar Singh Student, B.Tech (Automobile Engineering), Manipal Institute of Technology, Manipal In the recent past, there has been increasingly use of high-strength steels (HSS), which may also be referred to as high-strength, low-alloy (HSLA) steels. Series of studies conducted by American Iron and Steel Institute (AISI) Ultralight Steel Auto Body (ULSAB) demonstrated improved design and 19% mass reduction in a body structure that had superior strength and structural performance (including crashworthiness) along with a reduced parts count and net manufacturing cost savings compared to a conventional steel body [2]. Similar benefits in terms of mass reductions were achieved for doors, hoods, deck lids, and hatchbacks [3]. These materials further led to improved application and better forming processes allowing a significant optimization of vehicle body structures and components [1]. Iron and steel industry has embedded their research activity to address new designs and redesigns requirements of automotive manufacturers. The steel industry and component suppliers are investing heavily in innovation.
Abstract— Over the years, steel has remained the key materials in the automotive industry. Steel has wide range of yield strength with high modulus of elasticity. Steel is also considered as most preferable material in automotive application due to low cost. Other benefits of steel include light weighting opportunities using new generation high strength steel leading to fuel efficiency, enhanced safety, good recyclability, and formability characteristics. This paper discusses the current trend, application and recent progress in usage of various types of steel in automobile sector. Recent development of next generation steel such as Advanced High Strength Steel (AHSS) has also been elaborated. Keywords—Steel, Automotive, Industry, Advanced High Strength Steel, Material
I. INTRODUCTION Over the years, steel has remained the key materials in the automotive industry. Steel has also established as reasonable in cost, longer life and variability in strength levels while meeting the increasingly stringent engineering needs. Steel is also very adaptable to corrective rework. Moreover, this material has exceptional versatility in terms of formability and the industry has also responded quickly to recognize the changing due to legislative and environmental requirements. Some of the other advantages of steel with respect to be used in automotive sector are ease of forming, consistency of supply, corrosion resistance with zinc coatings, ease of joining, recyclability and good crash energy absorption. Some of the disadvantages are that steel is considered as heavier than its competitive materials and gets corroded very easily if uncoated. There have been significant developments in producing wide range of steel using various additives and deploying technological interventions during steel production. Steel is considered as vital material in the majority of vehicles. There has been development of new formulation of steel chemistry producing high-strength steels. This requires further attention on giving focus on new design, fabrication, and assembly techniques by automotive companies. As applications of steel is not only in vehicle bodies, but also engine, chassis, wheels and many other parts and components aiming further to demonstrate weight reduction, enhanced fuel efficiency and simultaneous improvements in strength, stiffness, and other structural performance characteristics [1].
II. DRIVERS OF STEEL APPLICATION Recent drivers of steel application in automotive sector include cost, fuel efficiency, regulatory requirements, safety, recyclability, light weighting, formability and specific customer requirements. Automotive companies consider all these factors in their design and maintain an optimized and balanced solution. A. Cost Cost is one of the most important driving factors for selection of material in automotive sector. Normally cost includes major components such as cost to design, cost of raw materials, manufacturing cost and cost of testing the product. Other key variables include manufacturing cycle times, better machinability, ability to have thinner and more variable wall dimensions, closer dimensional tolerances, reduced number of assemblies, more easily produced to near net shape(thus decreasing finishing costs, and less costly melting/metal-forming processes) [4]. B. Lightweight Weight reduction is considered a key criterion for reducing fuel consumption and greenhouse gases from the transportation sector. 246
International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 6, Issue 7, July 2016) It has been estimated that for every 10% of weight eliminated from a vehicle's total weight, fuel economy improves by 7% and reduction of 5% GHG emission achieved [10]. All automotive manufacturers along with their suppliers are investing significantly in development of lightweight materials. The major challenge associated with lightweight materials is their high cost. Priority is given to activities to reduce costs through development of new materials, forming technologies, and manufacturing processes while maintaining the same rigidity [4].
Steel is considered to be most recycled material in the world with high level of recycling efficiency. Polymers mixed with composites have major challenges recycling and recoverability. Considerable R&D efforts are now focused on developing materials with greater potential of recycling and re-use or developing ways of recycling and re-use of the current materials. III. MATERIAL PROPERTIES AND PERFORMANCE Before choosing a material for design there are three main factors to be looked upon. Material performance (density, tensile strength, modulus, corrosion resistance, elongation, cost, availability, environment considerations, performance, manufacturability), Government regulations (fuel efficiency, light weighting, crash performance, emissions), Customer requirements (cost, quality features). The basic criteria a material should also satisfy are structural dynamics, static stiffness, weight optimization, crashworthiness. Steel is having excellent performance in terms of yield and tensile strength, elongation to fracture, anisotropy and Young’s modulus. The strength of a component that should be under axial loading is related to the mechanical properties of the material [7].In bending and torsion, both material and shape are important parameters for the efficiency of the component to carry the applied load [8]. For bending, the elastic-plastic transition is a combination of shape and material properties. The following key characteristics should be considered for proper material selection:
C. Safety, crashworthiness There are two key safety concepts to consider viz. crashworthiness and penetration resistance. Crashworthiness is defined as the potential of absorption of energy through controlled failure modes and mechanisms that provides a gradual decay in the load profile during absorption while penetration resistance is concerned with the total absorption without allowing projectile or fragment penetration [4]. Steel is considered to be one of the best energy absorbent materials. The absorption energy is calculated based on the area covered under the stress-strain curves. High strength steel provides better performance in crash due to higher work hardening rate and high flow stress. This will result in more uniform strain distribution in steel material in the crash event. Some of the important aspects are considered in design for better crashworthiness include geometrical and dimensional aspects, materials deformation, progressive failure behaviour in terms of stiffness, yield, strain hardening, elongation and strain at break of the vehicle. [5].
A. Stiffness Modulus of elasticity (E) and geometry of material have direct linkage with stiffness of a component. As E value has been constant for all steel grades, so geometry can only be changed to improve stiffness. Steel provides excellent flexibility due to its higher formability for optimizing the stiffness. For high strength steel reduction in gauge can be counterbalanced by changes in geometry or by using continuous joining techniques such as laser welding or adhesive bonding [4].
D. Recycling and End of vehicle life considerations There have been key trends about developing the environment friendly vehicles with focus on conservation of resources, reduction of CO2 emissions, increasing the fuel efficiency during vehicle usage life time and subsequently enhanced recycling and recovery of materials at the end of vehicle life [6]. For achieving higher recoverability and recyclability of vehicle at its end of life, there are already regulations existing in EU, Japan, South Korea etc. India has also come up with draft standards on the same. The End of Life Vehicles (ELV) Directive aims to reduce the amount of waste produced from vehicles when they are scrapped. It also sets higher reuse, recycling and recovery targets and limits the use of hazardous substances in both new vehicles and replacement vehicle parts [6].
B. Strength Strength of a component is primarily dependent on yield strength, tensile strength and geometry of component. Steel offers design flexibility over other materials due to their higher formability and work hardening characteristics. High strength steel grades also have good bake hardening ability [9].
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International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 6, Issue 7, July 2016) C. Fatigue Fatigue properties of automotive components depend on geometry, thickness, applied loads and material endurance limit. The endurance limit of a material increases with tensile strength. Thus, high strength combined with superior work hardening and bake hardening, resulting in a significant increase in the as-manufactured strength of high strength steel components, also results in a better fatigue resistance [9].
Another classification method is based on yield strength range as all the steel grades are having same density and elastic modulus. Steel having yield strength less than 210 MPa are considered as conventional steel. High-Strength Steels (HSS) has yield strengths from 210 to 550 MPa and tensile strengths from 270–700 MPa, while Ultra/Advanced High Strength Steels (UHSS or AHSS) steels have yield strengths greater than 550 MPa and tensile strengths greater than 700 MPa [9]. In addition, many steel types have a wide range of grades covering two or more strength ranges. Third type of classification is based on the mechanical properties or forming parameters of different steels, such as total elongation, work hardening exponent (n-value), or hole expansion ratio (λ). As an example total elongation (a steel property related to formability) is compared to the tensile strength for the current types of steel, as shown in Fig 2 [9].
D. Formability Steel has many advantageous characteristics connected to formability coupled with high strength and good work hardening ability to stretch and distribute the strain more [9]. Fig. 1 indicates the typical comparison of various materials with respect to their key parameters such as stiffness, density and cost [9].
Fig 1 Relative Materials Properties and Costs [15]
Mild: Mild Steel; BH: Bake Hardenable; CP: Complex Phase; DP: Dual phase; FB: Ferritic Bainitic; HF: Hot Formed and Quenched; HSLA: High- Strength Low Alloy; IF: Interstitial Free; MS: Martensitic (MART); TRIP: Transformation Induced Plasticity; TWIP: Twinning Induced Plasticity
IV. CLASSIFICATION OF AUTOMOTIVE STEEL
Fig 2 Relative Materials Properties and Costs [9]
Automotive steels can be classified in several different ways. Common designations include low-strength steels (interstitial-free and mild steels); conventional HSS (carbon-manganese, bake hardenable and high-strength, low-alloy steels); and the new Advanced High Strength Steel (AHSS) (dual phase, transformation-induced plasticity, twinning-induced plasticity, ferritic-bainitic, complex phase and martensitic steels) [9]. Other types of steel include hot-formed, post-forming heat-treated steels, and steels designed for unique applications.
The principal difference between conventional HSS and AHSS is their microstructure. Conventional HSS are single-phase ferritic steels with a potential for some pearlite in C-Mn steels. AHSS are primarily steels with a microstructure containing a phase other than ferrite, pearlite, or cementite – for example martensite, bainite, austenite, and/or retained austenite in quantities sufficient to produce unique mechanical properties [9]. Conventional high strength steels are manufactured by adding the alloying elements such as Nb, Ti, V, and/or P in low carbon or IF (interstitial free) steels [11]. 248
International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 6, Issue 7, July 2016) High-strength steels can be little costlier but it provides opportunity to use thinner and lighter components. With HSS, there can be a tradeoff between strength and formability; in other words, the stronger a steel is, e.g., in resisting stretching (tension), the more difficult it can be to forge into shapes, particularly the stylistically and aerodynamically optimized shapes needed for new vehicles. Steel suppliers are therefore developing steels with a range of properties that give engineers more flexibility in selecting an ideal grade of steel for any given application [11]. Conventional high strength steels (HS) in order of increasing strength together with advanced high strength steels (AHS) and high manganese steels (HM) are shown in Table I [11]. AHS steels are multiphase which contain phases like martensite, bainite, and retained austenite in sufficient quantities to produce unique mechanical properties [11].Recently, new group of austenitic steels with high manganese contents has been developed for automotive use. These are high manganese steels (HMS) which combine and provide excellent combination of mechanical properties with an alloying concept less expensive than conventional or new high strength austenitic stainless steels. This group is divided into transformation induced plasticity steels (HMS-TRIP) and twinning induced plasticity steels (HMS-TWIP) due to the characteristic phenomena occurring during plastic deformation [11].
A. Conventional Low- and High-Strength Automotive Sheet Steels Cold-rolled sheet steel with a thickness ranging from 0.5 to 1.5mm is mostly used for body in white. Earlier, soft unalloyed materials were preferred because they offer a high degree of formability and freedom of design. In addition to deep drawing and stretch forming, the suitability for welding, joining, and painting are significant criteria of processing. These requirements are also met by the higher-strength thin sheets (with a minimum yield point of >180 MPa [12]. At present, there is a tendency toward Dual-phase (DP) steels, partially martensitic, and transformation induced plasticity (TRIP) steels or multiphase (MP) steels [12]. The basic problem with increasing strength is a natural decline in the forming capability leading to development of new generation steel known as Multi-Phase (MP steels) [12]. The raising of the strength is based on structural hardening. Early HSLA metallurgy are based on fine ferrite grain size, precipitation hardening, micro-alloy additions of columbium, vanadium, titanium and low sulfur and inclusion shape control. 1) Mild Steel: Mild steel has having ferritic microstructure and provide essentially Drawing Quality (DQ) and Aluminium Killed (AKDQ) steels which are predominantly used in automotive application over the years [9]. 2) Interstitial-Free (IF) Steels (Low Strength and High Strength): IF steels have been developed by achieving ultra-low carbon levels for lower yield strengths and higher work hardening exponents (n-values) [9]. These steels have more stretchability than Mild steels. The IF-HS grades utilize a combination of elements for solid solution strengthening, precipitation of carbides and/or nitrides, and grain refinement [9]. Phosphorus is added to increase the strength and are widely used for both structural and closure applications. 3) Bake Hardenable (BH) Steels: BH steels have a basic ferritic microstructure and solid solution strengthening. A unique feature of these steels is the chemistry and processing designed to keep carbon in solution during steelmaking and then allowing this carbon to come out of solution during paint baking or several weeks at room temperature which results in increase in yield strength of the component for increased dent resistance without reduction in formability [9].
Table I Conventional HS, MS and HMS Steels [11]
BH IFHS P IS Cmn HSLA DP TRIP CP PM
HMS HMS
HS Steels Bake hardening High strength IF Rephosphorised Isotropic Carbon/manganese High Strength Low Alloyed AHS steels Dual Phase Transformation Induced plasticity Complex Phase Partly Martensite HM steels TRIP high MN transformation induced plasticity TWIP high MN twinning induced plasticity 249
International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 6, Issue 7, July 2016) 4) High-Strength Low-Alloy (HSLA) Steels: HSLA steels increase strength primarily by micro-alloying elements contributing to fine carbide precipitation, substitutional and interstitial strengthening, and grain-size refinement [9]. HSLA steels are used in body-in-white and increased inservice load application components. 5) Micro alloyed Steel: A small amount i.e. 0.01% of titanium, vanadium, and niobium added for alloy formation resulting in increase of the yield point to 260–540N/mm2 and the tensile strength to 350–620 Mpa. Age hardening of finely distributed carbon nitrides results in an increase in the strength and higher-strength drawing properties of the conventional micro alloyed steel [12]. 6) Isotropic Steel: These steels possess unidirectional flow characteristics leading to better deep-drawing property and at the same time an increase in their strength. The minimum yield point in the delivery status of these sheet metals ranges between 210 and 280 MPa. These steels too, show a bake-hardening effect after preforming [12].
In comparison to DP steels, CP steels show significantly higher yield strengths at equal tensile strengths of 800 MPa and greater [9]. CP steels are also characterized by high energy absorption, high residual deformation capacity and good hole expansion. They are used for frame rails, chassis components, transverse beams, B-pillar reinforcements, tunnel stiffener, Rear suspension brackets, fender beam, rear frame rail reinforcements, rocker outer, rocker panels, bumper beams. 3) TRIP steels: TRIP steels are known as transformation induced plasticity effect, having high strength, good elongation, high energy absorption and high bake hardening. TRIP steels display high n-value strengthening coefficient up to the limit of uniform elongation. The microstructure of TRIP steels is retained austenite embedded in a primary matrix of ferrite with some amount of martensite and bainite [9]. TRIP steels use higher quantities of carbon than DP steels to obtain sufficient carbon content for stabilizing the retained austenite phase to below ambient temperature. Higher contents of silicon and/or aluminium accelerate the ferrite/bainite formation. Silicon and aluminium are used to avoid carbide precipitation in the bainite region. This steel is used for Frame rails, rail reinforcements, Side rail, crash box, Dash panel, roof rails, B-pillar upper, roof rail, engine cradle, front and rear rails. 4) Martensitic Steels: The MS steels are characterized by a martensitic matrix containing small amounts of ferrite and/or Bainite showing high ultimate tensile strength level up to 1700 MPa. MS steels are produced from the austenite phase by rapid quenching to transform most of the austenite to martensite. Using water quenching in a continuous annealing line, steels with 100 % martensite can be produced [9],[11]. This structure also can be developed with post forming heat treatment. MS steels are often subjected to postquench tempering to improve ductility, and can provide adequate formability even at extremely high strengths [11]. Adding carbon to MS steels increases hardenability and strengthens the martensite. Manganese, silicon, chromium, molybdenum, boron, vanadium, and nickel are also used in various combinations to increase hardenability. They are used in Cross-members, side intrusion beams, bumper beams, bumper reinforcements, rocker outer, side intrusion beams, bumper beams, and bumper reinforcements. Ferritic-Bainitic (FB) Steel: FB steels have a microstructure of fine ferrite and bainite. Strengthening is obtained by both grain refinement and second phase hardening with bainite [9].
B. AHS Steels Advanced high strength steels are already discussed earlier which is primarily distinguished based on their microstructural features. They offer extraordinary strengthductility relationship. 1) Dual phase steels: DP steels consist of a ferritic matrix containing a hard martensitic second phase in the form of islands. It is produced by controlled cooling from the austenite phase (in hot-rolled products) or from the twophase ferrite plus austenite phase (for continuously annealed cold-rolled and hot-dip coated products) to transform some austenite to ferrite before a rapid cooling transforms the remaining austenite to martensite [9],[11]. This steel is used in roof outer, door outer, body side outer, package tray, floor panel, hood outer, body side outer, cowl, fender, floor reinforcements, Body side inner, quarter panel inner, rear rails, rear shock Reinforcements, Safety cage components (B-pillar, floor panel tunnel, engine cradle, front sub-frame package tray, shotgun, seat), Roof rails, B-pillar upper etc. 2) Multiphase (MP) steels or Complex Phase (CP) steels: Multiphase steels, also referred to as complex phase steels, provide higher level of yield strength at the same comparable tensile strength levels of dual phase steels [9]. The microstructure of CP steels contains small amounts of martensite, retained austenite and pearlite within the ferrite/bainite matrix. An extreme grain refinement is created by retarded recrystallization or precipitation of micro alloying elements like Ti or Nb. 250
International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 6, Issue 7, July 2016) FB steels sometimes are primarily utilized to meet specific customer application requirements that require Stretch Flangeable (SF) or High Hole Expansion (HHE) capabilities for improved edge stretch capability [9]. Compared to HSLA steels with the same level of strength, FB steels also have a higher strain hardening exponent (nvalue) and increased total elongation. They are used in Rim, brake pedal arm, seat cross member, suspension arm, FB Lower control arm, rim, bumper beam, chassis parts, and rear twist beam. 5) Twinning-Induced Plasticity (TWIP) Steel: TWIP steels offers extremely high strength (>1000 MPa) with extremely high stretchability. It is developed by adding high manganese content (17-24%) which causes the steel to be fully austenitic at room temperatures. A large amount of deformation is driven by the formation of deformation twins. The twinning causes a high value of the instantaneous hardening rate (n value) as the microstructure becomes finer and finer [9]. It is used in A-Pillar, wheelhouse, front side member, wheel, lower control arm, front and rear bumper beams, B-pillar, wheel rim, floor cross-member, wheelhouse, door impact beam. 6) Hot-Formed (HF) Steel: Boron-based hot forming steels (between 0.001% and 0.005% boron) have been in use since quite long for body-in-white construction. A typical minimum temperature of 850°C must be maintained during the forming process (austenitization) followed by a cooling rate greater than 50°C/s to ensure that the desired mechanical properties are achieved [9]. These steel are used in A-pillar, B-pillar, cross beam. 7) Manganese–Boron Steels: Manganese–boron steels are considered for complex geometries with high strength requirements. For hot forming and hardening, the manganese–boron steels offer the highest strengths of up to 1650N/mm2 in the hardened condition [12]. High strength is achieved after heating the steel to the austenitization temperature followed by controlled cooling results in martensitic structure.
Fig. 3 and 4 depict the current percentage distribution of various materials for light vehicle in Europe and North America Table II North American Light Vehicle Material Content [13]
Material
1975
2005
2007
2015
Mild Steel
2180
1751
1748
1314
HSS AHSS Other Steels
140 65
324 111 76
334 149 76
315 403 77
Iron
585
290
284
244
Aluminium Magnesium Other metals Plastics/ Composites Other Materials Total Pounds
84 -
307 9
327 9
374 22
Change from 1975 to 2015(lbs) Down 866 Up 175 Up 403 Up 12 Down 341 Up 290 Up 22
120
150
149
145
Up 25
180
335
340
364
Up 184
546
629
634
650
Up 104
3900
3982
4050
3908
Up 8
V. APPLICATION OF AUTOMOTIVE STEEL Table II shows the trend of usage of various materials in light vehicle in North America. The trends in the recent years show decrease in the use of traditional mild steel, while newer materials like HSS, advanced HSS are beings used significantly more. With the advancement in technologies of production newer alloys of aluminium and magnesium are also being used more. Plastics and composite with their lightweight and recyclable properties are also liked by the automotive companies.
Fig 3: Light Vehicle Metallic Material Trends , North America [13]
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Fig 6: Light Vehicle Metallic Material Trends Europe [14]
Table III indicates typical mechanical properties of various steel materials and its application in various components of vehicle [9] Table III Mechanical Properties of Various Steel Materials and its Application Fig 4: Light Vehicle Metallic Material Trends Europe [13]
YS
The progressive material concept for steel has been represented for future steel vehicle project in Fig 5.
UTS
Steel grade Mild 140/270 BH 210/340
Fig 5: Light Vehicle Metallic Material Trends Europe [14]
Future opportunity of next generation advanced high strength steel development has been shown in Fig 6.
Total EL
nvalue (515%)
r-bar
App.
MPa
MPa
(%)
Code
140
270
38-44
0.23
1.8
A,C,F
210
340
34-39
0.18
1.8
B
BH 260/370
260
370
29-34
0.13
1.6
B
IF 260/410
260
410
34-38
0.2
1.7
C
DP 280/600
280
600
30-34
0.21
1
B
IF 300/420 DP300/500 HSLA 350/450
300 300
420 500
29-36 30-34
0.2 0.16
1.6 1
B B
350
450
23-27
0.22
1
A,B,S
DP 350/600
350
600
24-30
0.14
1.1
DP 400/700 TRIP 450/800 HSLA 490/600
400
700
19-25
0.14
1
A,B,C, W,S A,B
450
800
26-32
0.24
0.9
A,B
490
600
21-26
0.13
1
W
DP 500/800
500
800
14-20
0.14
1
A,B,C, W
SF 570/640
570
640
20-24
0.08
1
S
CP 700/800 DP 700/1000 Mart 950/1200 MnB Mart 1250/1520
700 700
800 1000
10-15 12-17
0.13 0.09
1 0.9
B B
950
1200
05-07
0.07
0.9
A,B
1200
1600
04-05
n/a
n/a
S
1250
1520
04-06
0.07
0.9
A
Application Code A-ancillary parts, B- Body Structure, C-Closures, FFuel tank, S-suspension/chassis, W-Wheels
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VI. CONCLUSION Steel is considered as vital material in the majority of vehicles. Steel will continue to play a dominant role in future due to its excellent mechanical properties. Steel fulfils the key criteria of material selection viz. stiffness, strength, fatigue, formability, crashworthiness, costeffectiveness, recyclability and light weighting. Steel has continued to excel in their easy availability and economic price-performance ratios. There has been significant development in producing various types of advanced high strength steel. Steel makers are collaborating with automotive companies to develop next generation of steel having high strength, reduced thickness, better formability and ease in joining. There has also been increasing trend in the automotive sector to embrace AHSS for their various components while developing new suppliers across the world for supply of low cost solution.
[5]
[6] [7] [8] [9] [10] [11] [12]
REFERENCES [1] [2] [3]
DeCicco J.M. 2005. Steel and Iron Technologies for Automotive Lightweighting. Environmental Defense. Ultralight Steel Auto Body. 1998 Final Report. Southfield, MI: American Iron and Stee Institute, March. Opbroek, E. and Weissert U. 1998, Ultralight steel auto closures project, SAE Paper No.982308.
[13] [14] [15]
253
Ghassemieh, E. 2011 Materials in Automotive Application. State of the Art and Prospects. New Trends and Developments in Automotive Industry. Prof. Marcello Chiaberge (Ed.), ISBN: 978953-307-999-8, InTech. Available from: http://www.intechopen.com/books/new-trends-and-developments-inautomotiveindustry/materials-in-automotive-application-state-of-theart-and-prospects Witteman, W. J. 1999 Improved Vehicle Crashworthiness Design by Control of the Energy Absorption for Different Collision Situations, Thesis. Eindhoven University of Technology. ISBN 90-386-0880-2 Environment-agency, 2010 http://www.environment-agency.gov.uk. Meyers, M. A. and Chawla, K. K. 1999 Mechanical Behaviour of Materials Upper Saddle River, Prentice-Hall. ISBN 0-13-262817-1 Ashby, M. F. 2000 Materials Selection in Mechanical Design Butterworth-Heinemann ISBN 0-7506-4357-9 Keeler, S. and Kimchi, M. 2014 Advanced High Strength Steel Application Guidelines Version 5.0. WorldAutosteel. WorldAutoSteel. http://www.worldautosteel.org/ [Web resources]. Zmik, J. et al: 2006 Recent progress in high strength low carbon steels. ISSN 0543-5846. METABK 45 (4) 323-331. Materials for automobiles. https;// ed.iitm.ac.in/~shankar_sj/Courses/ED5312/Materials_for_Automobi les11.pdf Hall, J. 2008 50 year Perspective of Automotive Engineering Body Materials and an Analysis of the Future.Great Designs in Steel. Hoffman, O. 2012 Steel lightweight materials and design for environmental friendly mobility. Thyssenkrupp Europe.Aarhus. Danny Codd, P.E. 2008 Advanced, Lightweight Materials Development and Technology for Increasing Vehicle Efficiency. KVA Incorporated. USA.
