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Materials selection in the Life-Cycle Design process: a methodto integrate mechanical and environmental performances

in optimal choice

F. Giudice *, G. La Rosa, A. Risitano

DIIM Department of Industrial and Mechanical Engineering, Faculty of Engineering, University of Catania,

Viale Andrea Doria 6, 95125 Catania, Italy

Received 21 November 2003; accepted 26 April 2004

Available online 7 July 2004

Abstract

The choice of materials takes on strategic importance in design aimed at harmonising the performance characteristics and eco-

compatibility of products in line with the Life-Cycle Design approach. The objective of the present study is the development of a

systematic method which introduces environmental considerations in the selection of the materials used in components, meeting

functional and performance requirements while minimising the environmental impact associated with the products entire life-cycle.

The proposed selection procedure elaborates data on the conventional and environmental properties of materials and processes,

relates this data to the required performance of product components, and calculates the values assumed by functions which quantify

the environmental impact over the whole life-cycle and the cost resulting from the choice of materials. As shown in the case study

presented, the results can then be evaluated using multi-objective analysis techniques.

2004 Elsevier Ltd. All rights reserved.

Keywords: Selection for material properties (H); Performance indices (H); Environmental performance (E)

1. Introduction

In the last decade, awareness of environmental

problems has led to the development of strategies to

promote an industrial production as ecological as pos-

sible, integrating environmental demands with product

standards. In the context of the process of product de-

velopment, interpreting these new requirements calls for

a broader view of the problem, moving from a con-

ventional approach, where the sale of the product is

considered the final analytical step, to an innovative

approach which extends to the end of the products

useful life and to retirement. Thus environmental re-

quirements must become factors of innovation for a

successful, and therefore sustainable, product design.

This is possible through a systematic approach to inte-

gral and simultaneous design, in accordance with the

new principles of Life-Cycle Design (LCD) [13]. This is

a design approach which takes into consideration all the

phases of the products life-cycle, from concept devel-

opment to retirement, analysing and harmonising de-

termining factors such as quality, cost, production

feasibility, requirements of use, servicing and, indeed,

environmental aspects.

Products environmental impact is directly influenced

by the environmental properties of the materials used,

such as energy costs, emissions involved in production

and manufacturing phases, and recyclability. The choice

of materials therefore assumes strategic importance, and

requires an extension of the characterisation of materi-

als, integrating conventional characterisation aimed at

defining physicalmechanical properties, with a com-

plete characterisation of environmental performance.

For the designer to make an optimal choice of materials,

harmonising performance characteristics and properties

of eco-compatibility, the selection process must take

* Corresponding author. Tel.: +39-095-7382418; fax: +39-095-

330258.

E-mail address: [email protected] (F. Giudice).

0261-3069/$ - see front matter 2004 Elsevier Ltd. All rights reserved.

doi:10.1016/j.matdes.2004.04.006

Materials and Design 26 (2005) 920

www.elsevier.com/locate/matdes

Materials& Design
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account of a wide range of factors: constraints of shape

and dimension, required performance, technological and

economic constraints associated with the manufactura-

bility of materials, environmental impact of all the

phases of the life-cycle.

The enormous variety of materials available for en-

gineering applications and the complexity of the set ofrequirements conditioning the choice of the most ap-

propriate materials, leads to a taxing problem of mul-

tiple-criterion optimisation. In recent years, several

systematic methods have been proposed to help the

designer in the selection of materials and processes [4,5].

Of the more commonly used quantitative selection

methods, that of Ashby is based on the definition of

material indices, consisting of sets of physicalmechan-

ical properties which, when maximised, maximise some

performance aspects of the component under examina-

tion [6]. Defining these indices, it is possible to compile

selection charts summarising the relations between

properties of materials and engineering requirements [7].

Usually taking into consideration the physicalme-

chanical properties of materials, these selection charts

can be extended to introduce some environmental

properties [8]. From this standpoint, several important

studies have been based on the definition of indices able

to express the environmental performance of materials

by introducing the energy consumption and emissions

(into the atmosphere or water) associated with the ma-

terials [9], or eco-indicators developed on the basis of

life-cycle assessment methods [10]. An alternative ap-

proach is that of translating environmental impact in

terms of economic cost of production, introducingfunctions of environmental cost, such as energy con-

sumption and toxicity, which again depend on the

properties of the materials [11].

All the methods proposed are limited to quantifying

the environmental impact of the choice of materials on

the basis of their environmental properties associated

with the production phase. Only particular studies have

considered the influence of the choice of materials on the

impact associated with the working life of the compo-

nent [12]. To date, the problem of choice of materials

from the viewpoint of LCD (taking into account the

environmental impacts involved in all phases of the life-

cycle, from production to retirement) has been consid-

ered only in general terms, with the aim of defining

guidelines for a choice which integrates properties of

materials, manufacturing demands and end-of-life im-

pacts, suggesting a distinction of selection criteria be-

tween component design and assembled product design

[13].

In accordance with the life-cycle design approach, the

objective of the present study is to develop a systematic

method which includes environmental considerations in

the selection of materials used for components, satisfy-

ing functional and performance requirements while

minimising environmental impact over the products

entire life-cycle.

The proposed selection procedure elaborates data on

the conventional and environmental properties of ma-

terials and processes, relates this data to the perfor-

mance required of the product components, and

calculates the values assumed by functions whichquantify the environmental impact over the life-cycle,

and the cost resulting from the choice of materials. The

results can then be evaluated using multi-objective

analysis techniques.

2. Life-cycle analysis and environmental characterisation

of materials and processes

The optimal choice of materials, also in relation to

environmental demands, requires a complete environ-

mental characterisation, with particular regard to the

following aspects: environmental impact associated with production

processes (energy costs and overall impact);

environmental impact associated with phases of end-

of-life (recycling or disposal);

suitability for recycling (expressed by the recyclable

fraction).

Information on the energy costs and recyclable frac-

tions of more common materials can be obtained from

commercially available databases, such as that of the

CES materials selection software [14]. Overall environ-

mental impact can be evaluated using the techniques of

life-cycle assessment, an analysis method used to quan-

tify the environmental effects associated with a process or

product through the identification and quantification of

the resources used and the waste generated, evaluating

the impact of using these resources and of the emissions

produced [15,16]. Quantification of the impacts is based

on inventory data [17], subsequently translated into eco-

indicators such as those used here. These are evaluated

according to the Eco-Indicator 99 methodology [18],

calculated using SimaPro 5.0 software [19].

Environmental characterisation is also extended to

common manufacturing processes, primary (forming)

and secondary (machining), evaluating the indicators

which quantify the impacts of standard processes perunit of process parameter or of volume/weight of ma-

terial processed.

2.1. Data on materials and processes

For each material, it is necessary to integrate the in-

formation used in conventional design with that re-

garding environmental properties to obtain:

general properties (density, cost);

mechanical properties (modulus of elasticity, hard-

ness, fatigue limit, etc.);

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thermal and electrical properties (conductivity and

thermal expansion, operating temperature, electrical

resistance, etc.);

environmental properties (energy cost, environmental

impact, recyclability).

As an example, the datasheet of Fig. 1, relating to a

widely-used plastic material (polypropylene), shows the

data on the environmental properties. Eco-indicators

were evaluated with SimaPro 5 software, using the Eco-

Indicator 99 method and expressing impacts in mPt

(milliPoint). With this software it is possible to select the

inventory data to be used for impact evaluation, in this

specific case Buwal 250 data [20].Regarding the primary and secondary manufacturing

phases, the following information must be obtained:

physical attributes of the final product;

economic cost of standard process (fixed and variable

costs);

environmental properties (energy consumption, envi-

ronmental impact of standard process).

3. Method of selection

The reference method (Fig. 2) is based on calculation

models which quantify and interrelate the various per-

formances required of the material in order to identify

potential solutions, and a successive multi-objective

analysis aimed at harmonising the conventional perfor-

mance, costs and environmental performance of the

product.

The first phase consists of defining the set of design

requirements and parameters:

primary performance (Pf1), in relation to the specific

functionality of the component;

secondary performance (Pf2), which can impose fur-

ther restrictions to guide the selection;

geometric parameters, distinguishing between fixed

(Gf) and variable geometric parameters (Gv);

typology of shape and relative level of complexity

(Sh), which greatly effects the choice of forming

processes;

use of component (Us), which can influence an initial

selection of materials.

The set of design requirements constitute the input

for the procedure of selecting potential solutions. This

procedure is based on two different types of analysis

(Fig. 3). In the first stage, the production feasibility of

Fig. 1. Material datasheet: polypropylene.

Fig. 2. Summary of method.

F. Giudice et al. / Materials and Design 26 (2005) 920 11

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each hypothetical solution is evaluated, analysing some

of the information given in the set of design require-

ments (in particular the typology of shape required and

the intended use). The solutions identified in the analysis

of production feasibility must then be evaluated in terms

of the required performances (Pf1, Pf2). The potential

solutions obtained are then analysed in subsequent

phases of the selection method. Each potential solution

S is defined by pairs of material-primary forming pro-

cess (M, FPr), and by the performance volume (PfV),

representing the minimum volume needed to respect the

requirements of primary performance. If appropriate,

the definition of the generic solution S can also include

any processes of secondary machining required after the

initial forming.

In the second phase, the calculation models are ap-

plied to each potential solution in order to evaluate the

indicators of environmental impact and cost over the

entire life-cycle.

The final phase of the method regards analysing the

results and identifying the optimal choice.

4. Analysis of production feasibility

The first stage of the selection procedure must cor-

relate material, process, shape and function. The prob-

lem of the interaction between these factors is

considered central to the selection of materials and has

already been amply treated [7].In the method proposed, this problem is addressed by

considering shape (Sh) and use (Us) to be design re-

quirements, expressed using binary vectors VSh and VUs,

and is based on binary matrices correlating shape-

process, material-use and material-process

USP uSPsp

h ip1;...;nps1;...;ns

UUM uUMum m1;...;nm

u1;...;nuUPM uPMpm

h im1;...;nmp1;...;np

; 1

where nm, np, ns and nu are the numbers of, respectively,

possible materials, processes, shape typologies and uses.

Considering processes of primary manufacture only, onthe basis of the correlation matrices (1) and vectors VSh

and VUs, and following the calculation scheme sum-

marised in Fig. 4, it is possible to obtain first the vectors

VPr and VMt, indicating, respectively, the primary pro-

cesses able to produce the required typology of shape,

and the materials suitable for the intended use. The

subsequent application of the material-process correla-

tion matrix gives a matrix of producible solutions

X xpm m1;...;nm

p1;...;np; where

xpm xpm VSh

; VUs;USP;UUM;UPM

: 2

This matrix indicates all the pairs of material-primary

process Sj Mm FPrp which constitute the set ofproducible solutions.

The material-use correlation matrix constitutes a fil-

ter in the pre-selection of possible solutions in that it

limits the choice to those materials conventionally

employed for the intended use. For a more open pre-

selection, it is possible to by-pass this filter. In this case,

the terms of matrix (2) would depend solely on VSh,

USP and UPM.

Fig. 4. Summary of production feasibility analysis.

Fig. 3. Procedure for selection of potential solutions.


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Using the above approach in the analysis of pro-

duction feasibility, it is possible to:

operate an analytical and exhaustive selection of all

the possible solutions which can satisfy the intended

form and use;

separate the selection conditioned by production fea-

sibility from that conditioned by performance re-quirements, thereby evidencing the relationships

between choice of material and effect on life-cycle im-

pacts, relationships which, as shown below, de-

pend on the different performance capacities of the

materials.

This approach requires the prior compilation of the

correlation matrices (1). Given the ever greater variety

of engineering materials and related manufacturing

processes, it is reasonable to consider compiling these

matrices by typology of material.

Alternatively, for a first selection of material-process

pairs, it is possible to use pre-existing software tools,

such as CES, which implements Ashbys methodology

[7,14]. It must be remembered, however, that tools of

this type allow a selection that already takes account of

the performances required.

5. Analysis of performance

The second stage of the selection procedure allows

the identification of producible solutions that respect the

required performance characteristics. In this way a set of

potential solutions is obtained which are then analysed,

applying the calculation models to evaluate the envi-ronmental and economic impacts over the entire life-

cycle.

In general, the analysis of performance can be sim-

plified considering three different typologies of mathe-

matical relations.

5.1. Function of performance volume (PfV)

Expresses the minimum volume necessary to respect

the primary performance requirements. Generally it is a

function of Pf1, the geometric parameters (Gf, Gv) and

the properties of the material (MtPp)

PfV PfV Pf1; Gf; Gv; MtPp : 3

5.2. Geometric conditions of performance

If the variable geometric parameters Gv are directly

correlated with primary performance Pf1, the geometric

conditions of performance can be expressed by functions

constrained by a range of values (defined by the design

requirements)

Gv Gv Pf1; Gf; MtPp ; Gv 2 Gv1; Gv2 : 4

5.3. Secondary conditions of performance

Conditions of this type can be generally expressed

using functions dependent on the properties of the ma-

terials and the performance volume, to be compared

with assumable limit-values

Pf2 Pf2 PfV; MtPp ; Pf26 PPf2LIM: 5

5.4. Final considerations

In conclusion, if a producible solution Sj M FPr respects all the constraints and requirementsof performance, it then becomes a performing solution

and can be selected for final evaluation. The set of po-

tential solutions consists of all the performing material-

primary process pairs, integrated by the corresponding

performance volume Sj M FPr PfV . The latterparameter acquires particular relevance in the proposed

method because it directly conditions the values as-sumed by the life-cycle indicators which, defined below,

guide the optimal choice. Using this approach, it is

possible to correlate the search for environmentally and

economically convenient solutions with the performance

characteristics of the materials.

Only in the case of particularly simple design prob-

lems can the functions of type (3) be defined in analytical

form. More generally, the performance volume cannot

be explicitly ascribed to the factors effecting it, but ra-

ther is the result of design procedures employing modern

methods of engineering design, implemented in com-

monly used tools based on parametric CAD and FEMsoftwares for structural-performance analyses.

6. Life-cycle indicators

The final phases of the selection method consist of

applying the calculation models to the set of potential

solutions, evaluating the indicators of environmental

impact and cost (EILC, CLC) relative to the entire life-

cycle, and then of analysing the results and identifying

the optimal choice. The indicators are functions of the

quantities of material necessary to produce the compo-

nent, expressed by the performance volume.The environmental impact of the life-cycle is ex-

pressed by

EILC EIMat EIMfct EIUse EIEoL; 6

where EIMat is the environmental impact of the material

needed to produce the component; EIMfct the impact

associated with its manufacture; EIUse the impact related

to the entire phase of use (which can depend on the

choice of material); and EIEoL is the impact of the end-

of-life (recycling, disposal).

The first two terms of (6) constitute the Environmental

Impact of Production EIProd, which can be expressed by


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EIProd EIMat EIMfct

eiMat W eiPrss l

eiMchg g; 7

where eiMat is the eco-indicator per unit weight of ma-

terial (expressed by W); eiPcss the eco-indicator of the

primary forming process per unit of l, which can rep-

resent the characteristic parameter of the process orthe quantity of material processed; and eiMchg the eco-

indicator of the secondary machining process per unit of

characteristic parameter of process g. As mentioned

above, these eco-indicators can be evaluated using the

Eco-Indicator 99 method.

The environmental impact of end-of-life can be ex-

pressed by

EIEoL eiDsp 1 n W eiRcl n W ; 8

where eiDsp and eiRcl are, respectively, the environmental

impact of disposal and of recycling processes per unit of

weight of material (eiRcl generally includes a quota of

environmental impact recovered); n is the recyclable

fraction. So defined, (8) refers to the optimal condition

where, at the end-of-life, all of the recyclable fraction of

material is recovered. Considering a more realistic con-

dition, it is possible to introduce an appropriate coeffi-

cient of reduced recyclability to obtain the fraction

actually recycled.

Finally, the Environmental Impact of Use EIUsecannot be expressed in general terms and must be de-

fined each time, according to the specific case under

examination. In this study, this term was defined in re-

lation to the particular case discussed below.The second indicator quantifies the economic cost

related to the entire life-cycle. Hypothesising that both

production and disposal costs are paid by a single sub-

ject (the manufacturer), the cost of the life-cycle CLC can

be expressed as

CLC CProd CEoL: 9

The cost of production CProd can be expressed in form

analogous to (7), in function of the quantity of material

to be employed and of the more significant process pa-

rameters. Alternatively, it is possible to use a conven-

tional evaluation of the production costs of a

component, distinguishing between variable and fixed

costs, and dividing the latter by the size of the produc-

tion batch [21].

The cost of end-of-life can be expressed as

CEoL cDsp 1 n W cRcl rRcl n W 10

where cDsp, cRcl and rRcl are, respectively, the cost of

disposal, the cost of recycling processes and the proceeds

from the sale of recycled material per unit weight of the

material; n is the recyclable fraction.

7. Analysis of results and optimal choice

Applying the models introduced, the life-cycle indi-

cators (EILC, CLC) are calculated for each potential so-

lution Sj M FPr PfV . Various tools can be usedto evaluate the fitness of each solution in order to

identify the optimal choice. Two tools which are par-ticularly simple, but significant in terms of the proposed

method, are indicated below. More sophisticated tools

are treated in references on multi-objective optimisation

in general [22], and in relation to the specific case of

materials selection [23].

7.1. Graphic tools

Graphs of CLCEILC to visualise the different fitness

of each potential solution.

7.2. Multi-objective analysis

Analysis of a multi-objective function c, which in-

cludes the more significant product properties, suitably

normalised and weighted

c Xni1

ai Bi: 11

As already suggested for the comparison of alterna-

tive solutions in the problem of choice of materials [24],

the following expression can be used to calculate the

normalised values Bi of the properties (in the case wherethe multi-objective function and all properties are to be

minimised)

Bi Vi

Vmaxi; 12

where Vi is the value assumed by the i-th property for the

solution under examination, and Vmaxi is the maxi-

mum value assumed by the i-th property among all the

solutions to be compared.

A set of Bi coefficient is obtained for each of the

potential solutions to be evaluated. The optimal solution

is that with the minimum value of the function c.

8. Case study: selection of material for a automobile brake

disk

The following case study illustrates the application of

the method of selection and choice of materials and of

the supporting calculation models. The design problem

consists of the optimum choice for the material of an

automobile brake disk (Fig. 5).


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8.1. Definition of design requirements

The first phase of the method is the definition of the

set of design requirements:

primary performance required (Pf1) is that of guaran-

teeing, in relation to a reference condition of vehiclemovement, efficient braking within a given distance,

which in physicalmechanical terms translates into

the dissipation of energy through friction and struc-

tural performance correlated with the mechanical

and thermal loading conditions (stressstrain analy-

sis);

secondary performance (Pf2) is that of limiting the

weight W;

fixed geometric constraint (Gf) is the external radius

of the disk Re;

variable geometric parameters (Gv) are the thickness

s and internal radius of the disk Ri;

shape required (Sh) is a three-dimensional rotation

solid.

8.2. Analysis of production feasibility

On the basis of the form required (Sh) and of the

expected use (Us), the analysis of production feasibility

suggests some hypothetical solutions of which two were

considered (one conventional and one of recent intro-

duction):

S1 consists of grey cast iron BS 350 as material, and

green sand casting as primary forming process;

S2 consists of F3K20S Duralcan (aluminium matrix

compound) as material, and squeeze casting (liquid

metal forging) as primary forming process.

8.3. Analysis of performance

Defining the weight of the automobile, and imposing

the required braking capacity, it was possible to deter-

mine the braking moment required on each wheel, and

the pressures at the disk-pad contact necessary to pro-

duce this moment. The primary performance was

therefore translated into the following conditions of

correct functioning which must be guaranteed by the

thermal-mechanical characteristics of the material:

thermal peaks below the maximum operating temper-

ature of the materials;

global stress state, due to superimposition of mechan-

ical and thermal loading, below the mechanic resis-

tance limits of the materials;

global strain state, due to the superimposition of me-

chanical and thermal loading, within the elastic limit

of the materials.

Given the complexity of the problem, the perfor-

mance analysis was conducted with the aid of the finite

element software MSC Patran/Nastran [25], which al-

lowed the correlation of performance properties of the

materials, variable geometric parameters and the cor-

responding structural and thermal loading. As an ex-

ample, Fig. 5 shows some results of the stress and

thermal analyses on the disk. These FEM analyses were

Fig. 5. Case study: automobile brake disk.


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calibrated on the basis of experimental data available in

the literature [26,27]. Both of the producible solutions

under examination were found to function. Table 1

shows the values which the performance volume PfV

and the variable geometric parameters (thickness s and

internal radius Ri) must assume in order to guarantee the

performance, together with the corresponding weights.

Comparing the two solutions under examination,

that in Duralcan requires the greater performance vol-

ume PfV (and therefore the greater overall dimensions)

to guarantee primary performance. The conventional

solution in cast iron reduces the overall dimensions, but

results in a greater weight (+56% compared to Dural-

can).

8.4. Evaluation of life-cycle indicators and analysis of

results

Functions (6) and (9) were used to calculate the in-

dicators of environmental impact and cost for each

performing solution. The results of the calculation

models are reported in Table 2. The general models were

simplified as follows:

in the calculation of production impacts and costs,

only the primary manufacturing processes were con-sidered, ignoring secondary processes;

in the evaluation of (9), the end-of-life costs expressed

by (10) were ignored because of the difficulty of ob-

taining the relevant data. Thus only the cost of pro-

duction CPROD was considered as cost indicator;

in this first phase, (6) was evaluated ignoring the en-

vironmental impact related to the use.

From the values in Table 2, it is clear that the solution

in Duralcan leads to an impact (2272.2 mPt) two orders

of magnitude greater than that of the solution in cast

iron (43.5 mPt). The graph shown in Fig. 6 describes the

composition of the environmental indicator EILC and is

particularly interesting in that it evidences the different

distribution of the environmental impact over the life-

cycle for each potential solution. Comparing the two

solutions, it is evident that:

the overall impact of the solution in Duralcan is es-

sentially due to the impact of producing the material

itself, which also offers a negligible recycling fraction

(low recovery of impact);

the solution in cast iron has a much lower productionimpact and, further, its high recyclability allows a

substantial recovery of impact at end-of-life.

The values reported in Table 2 clearly highlight which

of the two solutions is more favourable, the conven-

tional solution in cast iron, since it results in the lowest

values of both CPROD and EILC.

In conclusion, it is evident that when the properties

considered most important for the final product are

those of reduced cost and environmental impact of the

life-cycle, the best solution is that in cast iron. The al-

ternative solution in Duralcan is favourable only when

lightness is chosen as the primary property. This is

confirmed by the application of the multi-objective

analysis method introduced in Section 7.

Considering EILC, CPROD, weight W and perfor-

mance volume PfV as objective functions, different val-

ues of the function to minimise c are obtained for the

two alternative solutions according to how the set of

weight coefficients ai is defined. Fig. 7 shows the results

for four different orientations of investigation, corre-

sponding to the different importance given to the ob-

jective functions in the evaluation of c : (1) maximum

importance to environmental impact, medium to cost,

low to Wand PfV reductions; (2) maximum importance

to W reduction, medium to cost, low to environmentalimpact and PfV reductions; (3) primary reduction of

cost; (4) primary reduction of environmental impact. It

can be seen that, compared to the solution in cast iron,

the solution in Duralcan is interesting only in the second

case.

9. Introduction of environmental impact of use: evaluation

of life-cycle indicators and analysis of results

As noted, the solution in Duralcan has the primary

advantage of reducing the weight of the disk. The con-

sequent lightening of the vehicle can result in a sufficient

reduction in the environmental impact of use to recover

Table 1

Performance volume, weight and variable geometric parameters

PfV (dm3) W (kg) s (mm) Ri (mm)

BS 350 0.82 6.00 25 110

F3K20S 1.36 3.83 30 90

Table 2

Results of evaluation of life-cycle indicators

Life-cycle indicators

EIPROD (mPt) EIEOL (mPt) CMAT (EURO) CPRSS (EURO) EILC (mPt) CPROD (EURO)

BS 350 208.9 )165.4 6.59 14.70 43.5 21.29

F3K20S 2293.3 )21.1 18.94 27.52 2272.2 46.46


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the increased impact in production. To evaluate whe-

ther, and under what conditions, this is true, it is nec-

essary to evaluate the term EIUse of Eq. (6), ignored

previously. Apart from this, all the other simplifications

introduced in Section 8.4 remain the same. Having fixed

an overall reference distance travelled (mission), the

environmental impact of use EIUse can be expressed as

EIUse EIFuel EIMission

eiFuel qFuel eiMission qMission; 13

where eiFuel is the eco-indicator per unit weight of fuel;

eiMission the eco-indicator associated with the use of the

vehicle powered with this kind of fuel per unit of dis-

tance travelled; qFuel the quantity of fuel needed for the

entire distance covered; and qMission is the total expected

distance.

To evaluate all the quantities in play, the following

assumptions were made:

weight of vehicle 1000 kg; mean fuel consumption 0.0850 l/km; reduction in consumption due to a 10% reduction in

total weight of vehicle 4.5% (source: IKP, Univer-sity of Stuttgart, Germany).

On the basis of these assumptions, and after having

evaluated the overall reduction in weight due to the

choice of 4 disks in Duralcan instead of cast iron ()8.7

kg), it was possible to evaluate the reduced weight of the

vehicle (991.3 kg) and the mean consumption of the

lightened vehicle (0.0847 l/kg).

Table 3 shows the environmental indicators of the

life-cycle, considering the environmental impact of use

for an expected travelling distance of 150,000 km.

From the values in Table 3, it is clear that the solution

in Duralcan results in a lower environmental impact

than that in cast iron, in terms of both the phase of use

alone ()0.4%) and the entire life-cycle ()0.3%). The

Fig. 6. Composition of indicator EILC in relation to phases of life-cycle.

Fig. 7. Study of multi-objective function c.


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percentage reduction in EILC also depends on the ex-

pected distance travelled. The graph in Fig. 8 shows, for

the two solutions, the Break-Even Point of EILC. This

represents the minimum distance which must be trav-

elled for the EILC corresponding to the solution in

Duralcan to be less than the EILC of the solution in cast

iron (about 31,300 km).

The graph in Fig. 9 describes the new composition

of the environmental indicator EILC, in relation to the

different phases of the life-cycle for each potential so-

lution (distance travelled 150,000 km). Because of thedifferent orders of magnitude, the components regard-

ing the phase of use are shown in Pt rather than in

mPt.

Table 3

Results of the evaluation of life-cycle indicators (including phase of use)

Life-cycle indicators

EIPROD (mPt) EIUSE (mPt) EIEOL (mPt) EILC (mPt)

BS 350 208.9 2729884 )165.4 2729927

F3K20S 2293.3 2719201 )21.1 2721479

Fig. 8. Break-even point of EILC for the two solutions.

Fig. 9. Composition of indicator EILC in relation to phases of life-cycle (including use).


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In conclusion, when the environmental impact relat-

ing to the phase of use, influenced by the vehicle weight,

is also taken into account, the alternative solution in

Duralcan is advantageous not only when lightness is

chosen as the primary property, but also when the en-

vironmental impact of the entire life-cycle is considered.

And this occurs from a minimum distance travelled of

around 31,000 km.

Again, this consideration is confirmed applying the

multi-objective analysis method. Considering EILC(which now also includes EIUSE, calculated for the ref-

erence distance of 150,000 km), CPROD, the weight W

and the performance volume PfV as objective functions,the results shown in Fig. 10 are obtained for the four

different investigation orientations described in Section

8.4. It can be seen that, again, the solution in cast iron is

better for the first (maximum importance to environ-

mental impact, medium to cost) and third (primary re-

duction of cost) investigation typologies, while that in

Duralcan is better for the second one (maximum im-

portance to weight reduction). For the last investigation

typology, directed at reducing primarily the environ-

mental impact, however, the two solutions are essen-

tially equivalent, while for distances over 150,000 km the

solution in Duralcan tends to be more advantageous

than that in cast iron (since the lower value of EILC due

to the reduced weight tends to increase with the distance

travelled).

10. Conclusions

The environmental impact of a product is directly

effected by the environmental properties of the materials

used, as impacts corresponding to production and

manufacturing phases, and recyclability. In accordance

with the life-cycle design approach, the present study

proposed a systematic method which introduces envi-

ronmental considerations in the selection of materials

used in components, and harmonises functional and

performance requirements with the minimisation of

the environmental impact over the products entire life-

cycle, from production to retirement.

The proposed selection procedure elaborates data,

both conventional and environmental, regarding the

properties of materials and processes. It relates this data

to the performance requirements demanded of the

product and calculates the values assumed by functions

which quantify the environmental impact over the entirelife-cycle, including the phases of use and retirement,

and the costs resulting from the choice of materials. A

complete application of the method in the design of an

automobile component, the brake disk, allowed a direct

comparison between the multi-objective optimal choice

and that obtained in a conventional design approach.

This evidenced the need to use new tools in order to

guarantee, in the design phase, environmental safeguard

in the development of industrial products, and the

possibility of their full integration with conventional

design tools.

References

[1] Alting L. Life-cycle design of products: a new opportunity for

manufacturing enterprises. In: Kusiak A, editor. Concurrent

engineering: automation, tools and techniques. New York: Wiley;

1993.

[2] Keoleian G, Menerey D. Life cycle design guidance manual. EPA

Risk Reduction Engineering Laboratory, Environment Protection

Agency; 1993.

[3] Ishii K. Life-cycle engineering design. ASME J Mech Des

1995;117:427.

[4] Charles J, Crane F. Selection and use of engineering materials.

London: Butterworth-Heinemann; 1996.

Fig. 10. Study of multi-objective function c (including use).


7/30/2019 1-s2.0-S0261306904000950-main_2

12/12

[5] Farag M. Materials selection for engineering design. Englewood

Cliffs, NJ: Prentice Hall; 1997.

[6] Ashby M, Cebon D. A compilation of material indices. Granta

Design Ltd.; 1995.

[7] Ashby M. Materials selection in mechanical design. New York:

Pergamon Press; 1992.

[8] Navin-Chandra D. Design for environmentability. In: ASME

design theory and methodology conference (Miami, FL); 1991.

[9] Holloway L. Materials selection for optimal environmental

impact in mechanical design. Mater Des 1998;19(4):13343.

[10] Wegst U, Ashby M. The development and use of a methodology

for the environmentally-conscious selection of materials. In: Third

Biennial World conference on integrated design and process

technology (IDPT) (Berlin, Germany); 1998.

[11] Chen R, Navin-Chandra D, Kurfess T, Prinz F. A systematic

methodology of material selection with environmental consider-

ations. In: IEEE international symposium on electronics and the

environment (San Francisco, CA); 1994.

[12] Kampe S. Incorporating green engineering in materials selec-

tion and design, In: Green engineering conference: sustainable

and environmentally conscious engineering (Roanoke, VA);

2001.

[13] Stuart J. Materials selection for life cycle design. In: IEEE

international symposium on electronics and the environment (Oak

Brook, IL); 1998.

[14] Cebon D, Ashby M, Lee-Shothaman L. Cambridge Engineering

Selector V3.1 users manual. Granta Design Ltd; 2000.

[15] Fava J, Consoli F, Denison R, Dickson K, Mohin T, Vigon B. A

technical framework for life-cycle assessment. SETAC Society of

Environmental Toxicology and Chemistry, Washington, DC;

1991.

[16] SETAC. Guidelines for life-cycle assessment: a code of practice.

SETAC Society of Environmental Toxicology and Chemistry,

Brussels, Belgium; 1993.

[17] EPA. life-cycle assessment: inventory guidelines and principles.

Office of Research and Development, EPA/600/R-92/245, Wash-

ington, DC; 1993.

[18] Goedkoop M, Spriensma R. The Eco-indicator 99: Methodology

report. Amersfoort, The Netherlands: Pre Consultants BV; 2000.

[19] Goedkoop M, Oele M. SimaPro 5 user manual. Amersfoort, The

Netherlands: Pre Consultants BV; 2001.

[20] Pre. SimaPro 5 database manual: The BUWAL 250 library.

Amersfoort, The Netherlands: Pre Consultants BV; 2003.

[21] Ulrich K, Eppinger S. Product design and development. New

York: McGraw-Hill; 2000.

[22] Sawaragi Y, Nakayama H. Theory of multi-objective optimisa-

tion. London: Academic Press; 1985.

[23] Ashby M. Multi-objective optimization in material design and

selection. Acta Materialia 2000;48(1):35969.

[24] Farag M. Quantitative methods of materials selection. In: Kutz M,

editor. Handbook of materials selection. New York: Wiley; 2002.

[25] MSC. MSC Patran 2001 r2. MSC Software Corporation, Santa

Ana, CA; 2001.

[26] BREMBO. Il manuale del disco freno. Giorgio Nada Editore;

1998.

[27] Bassignana P, Gavello E, Leonti S. Analisi termica, termoelastica

e meccanica di freni automobilistici. ATA Ingegneria Automoto-

ristica 1984;37(11):72740.


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