an evaluation method based on mechanical parts structural characteristics for proactive remanufacturing

Lien doi: 10.1016/j.procir.2014.06.095 ScienceDirect 21st CIRP Conference on Life Cycle Engineering An Evaluation Method Based on Mechanical Parts Structural Characteristics for Proact

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Procedia CIRP 15 ( 2014 ) 207 – 211

(http://creativecommons.org/licenses/by-nc-nd/3.0/)

Selection and peer-review under responsibility of the International Scientific Committee of the 21st CIRP Conference on Life Cycle

Engineering in the person of the Conference Chair Prof Terje K Lien

doi: 10.1016/j.procir.2014.06.095

ScienceDirect

21st CIRP Conference on Life Cycle Engineering

An Evaluation Method Based on Mechanical Parts Structural

Characteristics for Proactive Remanufacturing

Xuan Zhoua,*, Qingdi Kea, Shouxu Songa, Ming Liua

a School of Mechanical and Automotive Engineerin, Hefei University of Technology, No.193 Tunxi Road, Hefei, 230009, China

* Corresponding author Tel.: +86-15256028667; fax: +00-86-0551-62901775.E-mail address:1991zhouxuan@163.com

Abstract

Currently, due to the uncertainty of operation loading and service time, sometimes the mechanical parts are difficultly or hardly to be remanufactured On the otherwise, it is also wasteful to remanufacture these parts too early In remanufacturing, a large number of inspections and evaluations of failure condition in the parts have to be done, which are uneconomical and inefficient In this paper, the concept of proactive remanufacturing is given, with considering remanufacturability in the initial design stage of parts Analyzing the performance deteriorating law, one main characteristic of proactive remanufacturing is the best timing point to be remanufactured Informed by modular design theory, structural characteristics are extracted, and the mapping relationship of design parameters and remanufacturability of parts is established Moreover, the proactive remanufacturing factor is hierarchically and qualitatively expressed as a comprehensive index to measure parts overall remanufacturability, which can implement the design parameters feedback to adjust the best timing point to avoid one-sided optimization of design parameters Finally, an engine crankshaft is given as an instance to validate this method

Selection and peer-review under responsibility of the International Scientific Committee of the 21st CIRP Conference on Life Cycle

Engineering in the person of the Conference Chair Prof Terje K Lien

Keywords: Uncertainty; Remanufacturability; Proactive Remanufacturing; Structural Characteristic

1 Introduction

Remanufacturing engineering is a series of technical measures

or engineering activities made to restore the retired

electromechanical products, with considering the whole life

cycle design and management of electromechanical products,

aimed at achieving the performance improvement of

electromechanical products, taking high-quality, high

efficiency, energy-saving, material-saving and environmental

protection as principles, and taking advanced technology and

industrialization production as means[1] Domestic and

overseas engineering applications show that both performance

and quality of remanufacturing products can reach and even

above the originals’, meanwhile the cost is only one third of

the new one, with saving 60% energy, and 70% materials, and

decreasing the negative impacts on the environment [2]

However, not all of the retired electromechanical products

can be remanufactured The precondition of remanufacturing

is that the parts keep a good status of remanufacturability at the end of life cycle Zhang Guoqing et al developed an assessment model for remanufacturability based on the assimilability assessing model, consisting of two modular constructions: technological module and economical module [3] Zhang Zongxiang et al analyzed the influential factors of the remanufactureability on the basis of characteristics of product, and determine the hierarchical and structural relationships between each index and the calculation formula

of each index [4] Zeng Shoujin et al established a micro assessment model, a macro assessment model and a comprehensive assessment model of green remanufacturing for waste electromechanical products by analyzing TOERE, energy sources, time and service ability factors[5]

Due to the uncertainty of service time and performance of used products, it is usually to remanufacture the “over-used” product which means higher cost or even can't be remanufactured On the other hand, it will be “previous

(http://creativecommons.org/licenses/by-nc-nd/3.0/)

Selection and peer-review under responsibility of the International Scientifi c Committee of the 21st CIRP Conference on Life Cycle Engineering in the person of the Conference Chair Prof Terje K Lien

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remanufacturing” which means a huge waste [6] The current

main solution is to conduct inspection and testing, which is

uneconomical and inefficient Whether the product could be

remanufactured and the remanufacturing performance is good,

it depends deeply on the design stage [7-9]

To meet this issue, the concept of proactive

remanufacturing is presented in this paper It is to take

remanufacturability as an important product performance into

account in the initial design stage From the perspective of

modular design, structural characteristics are extracted to

represent the overall parts structures, based on which the

mapping relationship of design parameters and

remanufacturability of parts is established And then, through

the hierarchical and qualitative analysis, the proactive

remanufacturing factor is introduced as a comprehensive

index to measure parts overall remanufacturability As a

result, the proactive remanufacturing can be conducted in an

appropriate time to obtain the maximum economic benefit,

with ignoring the uncertainty of used products

2 The concept of proactive remanufacturing and the best

timing point

Nowadays, the process of products remanufacturing normally

consists of four key stages [10]: Disassembly/Cleaning,

Inspection/Grading, Reprocessing, and Reassembly/Testing,

as shown in Fig.1 Due to the uncertainty in performance

status of remanufacturing blank, inspection and grading of

every unit is an essential and massive work before

remanufacturing, which meanwhile limits the

remanufacturing industrialization

Inspection/Grading Disassembly/Cleaning

Reprocessing

Reassembly/Testing

Used products

Remanufactured products

Fig 1 Key process of products remanufacturing

2.1 Proactive remanufacturing

Proactive remanufacturing is a series of engineering activities

made to implement the remanufacture of products actively at

some point during the service time, aimed at guaranteeing

products’ function and performance of the original design,

and taking high-quality, high efficiency, energy and material

saving, environmental protection and the total service time

being longest as principles There are three important characteristics of proactive remanufacturing[11]:

x Proactive Instead of conducting remanufacturing after products being retired, the timing is determined in advance, through comprehensive decision method When reached the time, the product should be remanufactured actively

x Batched Proactive remanufacturing reduced the uncertainty of blanks As a result, the products can be remanufactured in batches, which made a great increase in efficiency

x Objective The performance of products with the same design scheme and batch will decrease Then the timing exists objectively

to achieve comprehensive optimum of indexes in product life cycle

2.2 The best timing point

Determined by the performance deteriorating law of parts,

there exists the best timing point, T 0, at which conducting remanufacturing is most appropriate in both technologically and economically, as shown in Fig.2

D

Remanufacture Performance

Fig 2 Performance deteriorating curve of parts (Before and after remanufacturing)

Illustrational, D refers to the design performance; D’(t)

refers to the generated performance damage after service time

t After conducting remanufacturing at time t, the performance recovery capacity is H(t), then figure out the total performance of new life cycle is D-D’(t)+H(t)

P i is selected as the index to measure the remanufacturability of some structural characteristic, and then

P i is defined by [12],

- ' ( ) ( ) ' ( )

i

D

P

t

(1)

where, i=1, 2, , n

When t=T 0, it is the most appropriate time to conduct remanufacturing in both technologically and economically

Assumed that the given service life of parts is T g, from the perspective of proactive remanufacturing and optimization,

there should be T 0 =T g The given service life, T g is determined

by the design requirements, which cannot be changed usually

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Thus, T 0 should be variable to get approach to T g By

changing design parameters, T 0 can be adjusted

3 Structural Characteristics and the proactive

remanufacturing factor

The remanufacturability, design information, service

performance and failure modes are interrelated In this paper,

from the perspective of modular design [13-15], the overall

parts structures can be represented by several structural

characteristics (S i ) Thus, the change of T 0, namely the change

of remanufacturability at the end of life cycle can be achieved

by changing design parameters of structural characteristics

3.1 Structural characteristics

According to the failure statistics, empirical evaluation and

theoretical analysis, S i can be selected from the weak or

unstable structures,which are prone to functional failure For

example, as to shaft components, since structural strength is

deeply affected by journal and fatigue failure are prone to

occur in shaft shoulder and transition fillet because of stress

concentration S i can be selected from the journal, shaft

shoulder and transition fillet

3.2 The proactive remanufacturing factor

Generally, according to theory of “Buckets effect”, the overall

performance is determined by the length of the shortest board

[16] In order to improve parts performance, the design

parameters of weak structures, namely the short board is the

object to be optimized However, from the overall

perspective, due to different structures being closely

interrelated, the interaction effects between different

structures may cover or distort the main effect of single

structure, resulting in that the one-sided pursuit of

optimization of each single structure may not achieve the

expected overall improvement of performance

Due to the influence degree of S i on overall performance

are different, directive comparison of P i is of no use By

reference to the fuzzy comprehensive evaluation, a

comprehensive index, the proactive remanufacturing factor

(f AR) is proposed in this paper to measure parts overall

remanufacturability Assumed that there are n structural

characteristics, then after t, the proactive remanufacturing

factor (f AR) is defined by:

(2) For achieving the quantitative comparison of

remanufacturability, the weighting factor (ω i)is introduced to

conduct the equalization processing of each structural

characteristic And then, the influence degree of part,ω i •P i

are equal and comparable Thus, f AR can be described by:

1 2

1

n

i n

f

Z Z

ª º

« »

¬ ¼

¦

(3) where, i=1, 2, , n

ω i can be figured out with the method, Fuzzy Analytical

Hierarchy Process (FAHP) [17] f AR is a comprehensive index

to measure parts overall remanufacturability When f AR>1, it refers to that the part has a good status of remanufacturability

at the end of life cycle, and can be remanufactured The larger

f AR is, the better the overall remanufacturability is

Apparently, the flow chart of evaluation method based on structural characteristics can be described, as shown in Fig.3

Parts

S1 S2 Sn

ω i P i ω i P i ω i P i

fAR

Characteristic Extraction

Parts Database, Design Database, Statistical Database, Failure Statistics, Empirical Analysis, Bench Test, Analog Simulation,

Ă Ă

Feedback

Functional Requirements

Design Parameters

Design Information Model

T0

Tg

Approach to

Modularization Model

Comprehensive Index

Fig 3 Flow chart of evaluation method based on structural characteristics

It's important to note that f AR is mostly aimed at single component For products with several components need to be remanufactured, the life time of different components should

be matched With the evaluation method proposed above, the

best timing point T 0 of different components should be adjusted in cooperative relationship, such as being equal or multiple, to achieve the overall optimization More researches will be done about this problem

4 Case study

The crankshaft is a core part of automobile engine; the crankshaft remanufacturing has great research significance and economic benefits In this paper, the crankshaft of a six-cylinder engine is taken as the research object to validate the effectiveness and feasibility of the method above

4.1 Determination of S i and ω i

The main failure modes of crankshaft are fatigue fracture, wear and bending-torsion deformation If the crankshaft is fatigue fractured or having potential cracks after testing, it cannot be remanufactured Then, the crankshaft will generally

be material recycled through melting treatment Besides, it is supposed that the wear on the crankshaft can be completely repaired under current technology

With the aid ofHeavy Engine Remanufacturing Company,

an abundant Statistic Database about crankshaft is obtained After failure statistics, empirical evaluation and theoretical analysis, eight structural characteristics as selected They are,

respectively, S 1 - Diameter of journals, S 2- Aperture of oil

hole, S 3 - Radius of transition fillet, S 4-Tortuosity of journals,

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S 5 -Cylindricity of journals, S 6 -Circular run-out of journals, S 7

-Parallelism between journals and S 8-Axial clearance

According to Fuzzy Analytical Hierarchy Process, after

multiple comparisons, listing the comparison matrix,

calculation, and then quantization of comparison, the original

weight (ω i o) of each structural characteristic is figured out

The relative weighting comparisons and ω i o of structural characteristics are shown in Table 1 And then, conducting

normalization processing of ω i o above, ω i is figured out, as shown in Table 1

Table 1 Relative weighting compositions and ωi of structural characteristics

4.2 Determination of P i

P i is an index used to measure the remanufacturability at the

end of life cycle, the selection of P i is universal According to

different requirements, the appropriate indexes are selected

As to engine crankshaft, since the main failure modes of

crankshaft are fatigue and wear, fatigue life and wear loss can

be chosen as the performance indexes It is supposed that the

wear on the crankshaft can be completely repaired under the

current technology Therefore, the fatigue failure of

crankshaft is considered merely in this paper; further,

selecting fatigue strength representing P i from the perspective

of structural strength

Combining fatigue analysis by FE-SAFE with the Statistic

Database provided by Heavy Engine Remanufacturing

Company, P i is obtained, as shown in Table 2

Table 2 P i of structural characteristics

Cylindricity 0.593

Circular run-out 0.352

Axial clearance 0.609

Calculating the proactive remanufacturing factor, f AR:

1 8 2

1 8

i

Z Z

ª º

« »

¬ ¼

¦

=0.1734×1.322+0.1960×1.618+0.2635×1.878+

0.0756×0.832+0.0583×0.593+0.0583×0.352+

0.0583×0.687+0.1166×0.609

=1.2703

Apparently, f AR>1, it refers to that this crankshaft has a good status of remanufacturability at the end of life, and can

be remanufactured Further, by changing the design parameters of structural characteristics, the best timing point,

T 0 gets approach to T g

5 Conclusions

(1)Through proactive remanufacturing, the uncertainty in performance status of retired electromechanical products can

be largely reduced, and it helps to avoid remanufacture the

“over-used” product and “previous remanufacturing” as well Based on structural characteristics of parts, the proactive

remanufacturing factor, f AR is presented to measure parts overall remanufacturability

(2)Through structural characteristics, the mapping relationships of design parameters and remanufacturability of

products is established, which provide a way to get T 0

approached to T g As a result, the proactive remanufacturing can be conducted in an appropriate time to obtain the maximum economic benefit

(3)This design method can be applied in different parts, and the selection of remanufacturability index is diverse according

to different requirements However, this design method still needs further improvement, especially on the extraction and

calculation of index, and the determination of P i (4)With this method proposed, retired products can keep similar remanufacturability at the end of life cycle, which avoids the inefficient inspection of blanks and provides feasibility to realize industrialization

(5) In this paper, f AR is mostly aimed at single component For products with several components need to be remanufactured, further researches on life matching of different components are required

Acknowledgements

This research is supported by National Basic Research Program of China (973 Program, 2011CB013406) and National Natural Science Foundation of China (51305119)

Si Journal Oil hole Fillet Tortuosity Cylindricity Circular run-out Parallelism Axial clearance ωi o

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