Quality and cost improvement in specific vehicles manufacturing.

Vartolomei-M, Mihael ; Jadaneant, Mihai ; Vartolomei, Mihaela 等

1. INTRODUCTION

In the activity of tank soldier, the main problem is to be insured some specific conditions in order to eliminate or reduce the vibrations and their effects (Krause, 1995). In this millennium the process of substitution the classic materials with superior technical-functioning and economic features is very necessary, especially in armored transporters engineering realm, in naval and aerospace industry, for reduce armored vehicles' vibrations and harmful effects. The response is simply: "new materials", "intelligent materials" (Vartolomei-M & Jadaneant, 2007b), composite based on boron filament, glass, asbestos, carbon and Kevlar, nano-materials, materials with form's memory, amorphous metallic materials (Popescu, 2004).

2. ON-TRACK VEHICULES AND HARMFUL EFFECTS

Caterpillar transporters, as any land motor, don't have surplus of suspension and own absorption, so the effects of the shocks and vibrations are more aggressive for tank man than other vehicle's driver. The experimental studies regarding the influence of the vibrations on human body have been made generally in environment of exciting with sinusoidal vibrations. But, during driving a tank in hilly land, the vibrations are certainly different than the lab experiences. The land where the tanks are used is so hilled that the multidirectional requesting leads to resultant forces much bigger than those who action in the lab experimental situations (Vartolomei-M & Jadaneant, 2007a). The research results emphasized a negative impact for the driver ability, especially regarding to maintain the human equilibrium and a constant pressure of the foot on the pedals (Darabont et al., 1983). In this study, the real model (figure 1 a) is replaced with its equivalent model (figure 1 b).

[FIGURE 1 OMITTED]

In the equivalent scheme, the body of the tank is drawn as a metal bar with two degree of freedom (it can make vibrations on vertical and balance in rocking). Six weights are coupled by this metal bar (from [m.sub.r1,] to [m.sub.r6,] figure. 1 b), representing the cobbles. The torsion metal bars and helical spring have the elastic constants [k.sub.1],...,[k.sub.6,] and the dumping constants [C.sub.1]...[C.sub.6]. The track and cobble rubber rim features are represented by the elastic constants [k.sub.r1],...,[k.sub.r6] and shock-absorber constants [C.sub.r1],...[C.sub.r6].

3. NOISES AMELIORATION IN ROMANIAN ON-TRACK VEHICULES TECHNIQUE

Noise reduction in a room treated with noises absorber materials can be obtained by reduction the reverberation time.

Starting with the work of Darabont et al. (1983), we calculated the reduction of noises level by covering noises sources with noises-absorber materials, using relation (1):

L = 10 1g [A.sub.1]/[A.sub.2][dB] (1)

Where: [A.sub.1] is the equivalent absorption surface of the room after noises-absorption treatment, in [m.sup.2] AU (squares meters acoustic unities),

[A.sub.2] is the equivalent absorption surface of the room before noises-absorption treatment, in [m.sup.2] AU.

In the case of rooms untreated with noises absorbers the value of the equivalent absorption surface, [A.sub.2], is determined with relation (2):

[A.sub.2] = 0.35 V [sup.3/2][[m.sup.2]AU], (2)

Where V is the volume of the room, in [m.sup.3]. The equivalent absorption surface [A.sub.1], is calculated with relation (3):

[A.sub.1] = 0,35 V [sup.3/2] + [m.summation over (i=1)] [A.sub.i][[m.sup.2] AU], (3)

where [A.sub.1]...[A.sub.i] are the equivalent absorption surfaces of some acoustic treatments, in [m.sup.2]AU.

Every surface is calculated with the relation (4):

[A.sub.i] = [a.sub.i] [S.sub.i] (i = 1,2,..., n) (4)

where [a.sub.i] is the acoustic absorption coefficient of some construction elements of the room.

[S.sub.i] is that surface with the acoustic absorption coefficient [a.sub.i], in [m.sup.2].

Absorption coefficient of noises isolation and absorber materials a (%) are given in special tables in Romania.

For reverberation time T we can use the relation (5):

T = 0,163V/S( --[a.sub.med]) [s] (5)

Where

[[alpha].sub.med] = [n.summation over i = 1] [a.sub.i][S.sub.i]/S (6)

As we can see in figure 2, the noise can be propagated by such elements: the room's walls (1), leaky spaces and inevitable orifices (2,3), elements for linking the frame and the machine (4), vehicles' components passing that are rigidly linked by the room's walls (5), elements of the machine, leaky passage of some elements of the machine through the room's walls (pipes, tubes, axles etc), neighboring elements of the construction rigidly linked by the room's walls (7,8), construction elements the room and the machine are neighbors (9,10). In order to determine the attenuation degree of the noise level achieved by using a room for a noisy source (if we consider that there is a diffuse field inside this room), we use relation (7):

[DELTA]L = R--10 1g [s.sub.C]/[A.sub.C] = R--10 1g [S.sub.C]/ [n.summation over (i=1)] [a.sub.i][s.sub.i][db] (7)

where R is the sonorous reduction of the room's wall, in dB;

[S.sub.C] is the surface of room's wall, in [m.sup.2];

[A.sub.C] is the equivalent noise absorption surface of the interior of the room's wall, in [m.sup.2]AU;

[a.sub.i] is the noises absorption coefficient of the elements from the room's interior;

[S.sub.i] is the corresponded inner surfaces, in [m.sup.2];

[FIGURE 2 OMITTED]

We noticed that from expression (7) results the attenuation achieved by the room is a function of sonorous reduction R, of the room's wall, respectively a function of wall's weight and of absorption coefficient. Using the weight law, sonorous reduction can be calculated with relation (8):

R = 20 1g pf - 47,5[dB], (8)

where p is the weight of a separating element on square meter ([m.sup.2]) in da N /[m.sup.2],

f is the frequency in Hz.

The value of frequency bands is [DELTA]f = 2,5 [f.sub.lim] [hz], where [f.sub.lim] represents the frequency when sonorous reduction R starts to decrease.

Furthermore, we stated that the room's wall must be covered with special materials (Popescu, 2004) and we first propose to replace the classic materials with modern ones with superior technical, functional and economic properties (cost reason), as a real necessity for military transporter production.

4. CONCLUSIONS

This working paper is a part of research in doctoral study, and it is in the experimental stage. Here we studied another possibility to increase the quality of military technology manufacturing through noises amelioration. The methods we presented in this paper (advanced material use in isolation the noisy sources) can be applied to all caterpillar transport vehicles, heavy technique "on track", fighting vehicles, but also for air or naval technique. The measures proposed are needed to be taken in order to prevent and combat the noises during the functioning of some equipments and vehicles in military technique, in order to ameliorate the conditions and the comfort of the soldiers. Thus we calculated the noise level reduction. Furthermore, we took into account the possibility to entirely lock the noises source in a noises-separator room, to ensure phonic isolation of these noises sources, using advanced materials. The great technological progress in advanced materials applied in military technique leads to a new perception of military interventions. This is possible only if the manufacturing system is well thought out and well worked. New solution in the management of specific transport manufacturing (Lean Manufacturing, cost reduction, quality management increase) is necessary as military endowment must be prepared to cope with third millennium challenges.

5. REFERENCES

Darabont,, A.; Costin, A.; Vaiteanu, D. (1983). Combaterea zgomotului si vibratiilor in tehnica militara (Noises and Vibrations Combating in Military Technique), Military Publishing House, Bucuresti

Krause, K. (1995). Arms and the State: Patterns of Military Production and Trade, Cambridge: Cambridge University Press, ISBN 0-521-55866-2

Popescu, M. (2004). Tehnici de imbinare a materialelor plastice (Techniques of Plastic Materials Joining), Politehnica Publishing, ISBN 973-625-165-9, Timisoara

Vartolomei-M, M.S; Jadaneant, M. (2007a). Aspects Regarding Quality Improvement in Romanian Military Technique in NATO Framework, AGIR Bulletin, No.2, (april-june 2007), p.86-90, ISSN 1224-7928

Vartolomei-M, M.S., Jadaneant, M. (2007b). The Management of Military Technical, Technological and Manufacturing Systems, 4-th International Conference on Economic Engineering and Manufacturing Systems, ICEEM--2007 Brasov, 25th-26th[degrees]Ctober 2007, p.371-374, ISSN 15820246, RECENT Journal, vol.8, nr.3a(21a), November 2007