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THE TESTING OF DAMPERS ON COMPACT PLATFORM (CPDT) FOR .... measurement of angles and harmonic rates (relating to fundamental value or relating ...
THE TESTING OF DAMPERS ON COMPACT PLATFORM (CPDT) FOR REDUCTION OF ELECTRICITY CONSUMPTION Voicea I.1), Matache M.1), Mihai M.1), VlăduŃ V.1), Iordache S.2) 1) INMA Bucharest; 2)University from Craiova

Abstract: One of the priority items of the energetic strategy is to improve energy efficiency. Increase energy efficiency has a major contribution in the achievement of security of supply, sustainability and competitiveness. Reduction of energy demand through increasing energy efficiency is a winning policy which, besides the saving of primary energy resources leads and to the reduction of greenhouse emissions. The Directive no. 2006/32/EC on energy efficiency at the final end-users which is compulsory for Romania in 2008, provides that the UE Member States undertakes to carry out the reduction of final energy consumption by at least 9% in a period of nine years (2008-2016) compared with the average consumption in the last five years for which data are available (2001-2005). The role of dampers in the whole geometry of a car is very important, because the damper is a vital element for the security and performances of a technical equipment. The tests that should be performed on a damper are of static and dynamic nature. The Compact Platform For Testing Of Dampers – CPTD can be used to perform both types of tests. The platform offers the possibility of simultaneous dynamic test at endurance of multiple dampers, thus reducing both the time and the cost of a one test, it could be used in the future and for testing of other machine parts. Keywords: dampers, electricity consumption, testing

INTRODUCTION In accordance with the New Energy Policy of the European Union (EU) elaborated in 2007, the energy is an essential element of development of the Union. But equally it is a challenge in front of EU countries in terms of the impact of energetic sector on climate change, of growth of the dependence on energy resources import as well the energy price increases. To overcome these challenges, European Commission (EC) considers absolutely necessary that the EU should promote a common energy policy, based on energy security, sustainable development and competitiveness. Regarding sustainable development, it should be noted that in 2007 the energy sector is, at EU level, one of the principal producers of greenhouse gases. If not taking drastic measures at EU level, at the present rate and at the existing technologies in 2007, the emissions of greenhouse gases at EU level will increase by about 5% and with around 55% at globally level, by 2030. One of the priorities of the energetic strategy is the improvement of energy efficiency. Increasing the energy efficiency has a major contribution to achieve the security of supply, the sustainability and competitiveness. Reducing energy demand through improvement of energy efficiency is a winning policy which, in addition to saving of primary energy resources, leads and to reduction of greenhouse emissions. The representative synthetic indicator on the efficiency of energy use at national level is energy intensity, respectively the energy consumption to produce one unit of Gross Domestic Product. In 2003 was elaborated the National Energy Efficiency Strategy which highlighted, among other things, the economic potential of energy efficiency improvement in various sectors. Following this strategy, it was established as a strategic objective the improvement of energy efficiency on the whole chain in Romania: natural resources, manufacturing, transport, distribution and end use, through optimal use of specific mechanisms of market economy, with an estimated 3% per year reduction in energy intensity over the whole national economy, until 2020, compared to 2001. The role of dampers in the whole geometry of a car is very important because the damper is vital for the safety and the performance of a technical equipment. It is proved that the use of dampers which do not comply with the norms in force have often led the production of certain accidents with tragic consequences. In addition, because it is designed by the originating designer of the vehicle as an integral part of the suspension system, any change of this has unexpected effects on the general characteristics of the machine [5].

The main function of the damper consists in controlling the ratio between the static masses of the technical equipment (chassis, bodywork, engine, passengers, cargo, etc.) and those in motion (wheels, tires, brakes, etc.) during its running. In running, these mass produce through the irregularities of the land or changes of direction, continuous mechanical shocks which are transmitted to the rolling system, passengers, steering, etc. The role of damper is just to absorb this mechanical energy caused by the vertical launches of the technical equipment and to dissipate it around in the form of thermal energy, thus making the vehicle trajectory stabilization [2]. The tests to be performed on a damper are static and dynamic nature. The compact platform for testing of dampers – CPTD can be used to make both types of tests that are suitable for such an equipment. The platform enables of simultaneous dynamic testing at endurance of several dampers, thus reducing both time and cost of a test, this could be used in the future and for the test of other machine parts. It also can perform both static strength tests of dampers and the dynamic tests for rising of elastic characteristics [2, 3]. The testing platform is equipped with quick coupling systems that will simulate the fastening systems on the technical equipment of the dampers. The equipment can reproduce different reference signals for operating of the dampers, in various forms and with different frequencies and amplitudes, and can thus reproduce the entire range of vibrations and loads that dampers are subjected by their daily use as well as the mechanical stresses at which must be submitted for testing, stipulated in standards and other regulations.

2. MATERIAL AND METHOD The experimental model of the Compact Platform for Testing of the Dampers (CPTD) is shown in Figure 1.

Fig. 1 - The compact dampers testing platform (stand) 1 – Mechanical system; 2 – Hydraulic system; 3 – Command and control system

Constructive description of the experimental model The Compact Platform for Testing of the Dampers (CPTD), consists of the following systems: 1. mechanical system (fig. 2) 2. hydraulic system (fig. 3) 3. command and control system (fig. 4)

Fig. 2 – Mechanical system 1 – holster; 2 – guiding column; 3 – superior chassis ; 4 – driving screw

Fig. 3 – Hydraulic system 1 – oil tank; 2 – pump engine ; 3 – hydraulic hose

Fig. 4 – Command and control system 1 – control panel; 2 – data acquisition system with oscilloscope; 3 – signal generator; 4 – data processing laptop

The Compact Platform for Testing of Dampers (CPTD) has the role of realize running-in and to determine the elastic characteristics of all types of dampers, by the following steps: 1. Through command and control system of hydraulic group and damper positioning system is running the following operations:  it is acting the hydraulic group in order to obtain the necessary pressure to hydraulic cylinder;  it is acting the damper positioning system in order to adjust the working distance to its dimensions; 2. The damper assembly on stand is done via the mechanical system. 3. Through the control and measurement system of parameters of the tested damper, the following operations can be performed:  determination of testing frequency and of damper stroke by commissioning the signal generator; visualization in real time of the elastic characteristic on the oscilloscope display and the checkout of its framing in the limits required by the manufacturer;  performing of data acquisition (force, displacement) necessary to achieve the elastic characteristic of the damper. Specific electricity consumption for each type of damper on the two installations for dampers testing was donne with the three phase energy analyzer type C.A. 8332 and C.A. 8334 (fig.5). These measure instruments allow not only to obtain current images of the main characteristics of a network but also monitoring of variations in a particular period. The multi-task measuring system

simultaneously handles all the measurement functions for different amplitudes, detection, continuous recording and displaying them without any coercion. Measurements that can be performed are:  RMS measurement up to 480V AC voltage (between phase and neutral) or up to 830 V (between phases) for 2, 3 or 4 conductors;  measuring the effective value of alternating current up to 3000 A rms;  measuring the frequency for the 50 Hz, 60 Hz networks (from 10 Hz up to 70 Hz);  calculation of amplitude coefficients for voltage and current;  calculation of short-term voltage fluctuations;  calculation of disbalance between phases for voltage and current;  measurement of angles and harmonic rates (relating to fundamental value or relating to the actual value) for voltage, current or power, up to order 50;  measurement of active, reactive and apparent power for each phase separately and their sum. Calculation of power factor, deviation factor and tangent factor. The amount of electric power from a time individually chosen by the user;  monitoring of the average value of any parameter, calculated for a period from one second to two hours;  registration, labeling and characterization of disturbances in time: thresholds, power lines arrows and interruptions, exceeding of thresholds of power and harmonics; Detection of transitory processes and recording of the associated waveforms. [2, 3]

Fig. 5 - Three phase energy analyzer

Calculation of electrical power required for each test on the two types of installations was carried out in sinusoidal regime. Thus, given that we are dealing with a three-phase balanced voltage and current, the consumed active power or real is calculated by the formula: P = 3 × U l × I × cosφ where: φ – phase angle between phase voltage phase current; I – current intensity; Ul – voltage line or between phases. 3. RESULTS The testing regime of the damper must meet company standard: the test temperature +60÷+80°C; to maintain this temperature will be built outer shirts of cooling water; vertical damper position; duration of test 3 x 106 cycles. Amortization characteristic is checked after every 106 cycles, comparing with the original amortization characteristic. Parts damaged or which present important characteristic wear shall be made photographs in order to determine the causes which determined the wear.

Testing of dampers on the Compact Platform for Testing of Dampers – CPTD, was carried out for a commercial damper, used to equip motor vehicles. For these dampers have risen the control characteristics (F-s) and were performed the tensile test. Experimental data obtained were processed and entered in a testing bulletin. Were performed more repetitions (minimum 10), aiming at reproducible parameters monitored in order to check the stability and reliability of the platform for dampers test - CPTD. In Figure 6 is shown the fixing system that testing a road vehicle for the mass damper max. 2t test platform dampers.

Fig. 6 – Bitubular damper testing designed to road vehicles on theplatform for testing of dampers - CPTD

A. Testing the maximum stroke and operation of damper Maximum stroke: 250 mm Testing ofn operation of damper was made according to STAS 9381-88 and consisted of : - number of courses of running-in: 8 to 10 complete cycles; - damper rod stroke: 200 mm - speed of the rod: 0,1 m/s - electrical control signal of movement (provided by the functions generator of the platform) - with amplitude of ± 10 V, triangular;

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B. Raising of the elastic characteristic F-s Raising of the elastic characteristic F-s of the damper was done in the following conditions: The effective stroke (displacement) of piston rod during the test with sinusoidal reference signal:  163.08 mm - at the test frequency of 0.3 Hz;  171.92 mm - at the frequency test of 0.4 Hz;  182.9 mm - at the frequency test of 0.5 Hz;  141.55 mm - at the frequency test of 1 Hz;  94.09 mm - at the frequency test of 1.5 Hz. The effective stroke (displacement) of piston rod during the test with triangular reference signal:  156.98 mm - at the frequency test of 0.3 Hz;  158.83 mm - at the frequency test of 0.4 Hz;  162.1 mm - at the frequency test of 0.5 Hz;  135,05 mm – at the frequency test of 1 Hz;  87,15 mm – at the frequency test of 1.5 Hz; electrical control signal with an amplitude of ± 10 V, sinusoidal / triangular; signal frequency:  0.3 Hz , 0.4 Hz, 0.5 Hz, 1 Hz, 1.5 Hz; body damper temperature : 23 ±5°C.

Electrical control signal of the displacement was provided by the function generator of the electrical control cabinet of the hydraulic cylinder. During testing there were no abnormal noises, tendency to jam the rod, oil leaks. The values of forces in the characteristic points of the diagram (FmaxD - relaxation, FmaxC - compression) is presented Table 1. The processing data from Table 1 is shown in Figure 7 for the test frequency of 0.3 Hz, triangular and sinusoidal signal form. [1] Table 1

Reference signal Sine wave Triangle wave

Testing force FmaxD FmaxC FmaxD FmaxC

(daN) (daN) (daN) (daN)

Testing frequency [0.3 Hz] 57 116 28 72

Testing frequency [0.4 Hz] 70 131 56 77

Testing frequency [0.5 Hz] 72 150 57 93

Testing frequency [1 Hz] 92 160 57 130

Testing frequency [1.5 Hz] 82 150 53 126

Fig. 7 – Raising of the elastic characteristic F-s of the damper

Determination of specific electricity consumption (fig. 8) for bitubular damper for road vehicles - type 1 was performed with three-phase energy analyzer for installation HIDROPULS, and for CPTD the energy was determined directly from the frequency converter display with which the control panel is fitted. The energy consumption values recorded for the two types of installations are presented in Table 2.

Fig. 8 - Determination of specific energy consumption Table 2

Energy consumption HIDROPULS installation [kWh] 50.45 50.75 52.50 53.80 54.65

Bitubular damper Frequency testing 0.3 Hz Frequency testing 0.4 Hz Frequency testing 0.5 Hz Frequency testing 1 Hz Frequency testing 1.5 Hz

Energy consumption CPTD [kWh] 9.30 9.45 9.65 10.05 10.35

By means of dates from Table 2 was performed the compared energy consumption chart between the two types of installations: the experimental stand of Compact Platform for Testing of Dampers CPTD - and respectively the old testing stand for a bitubular damper type for road vehicles purchased from trade [4]. Consumul comparativ pentru amortizor bitubular 60

Putere consumatat(Kw)

50 instalatia HIDROPULS

40 30 20 10

PCIA

0 0

0.5

1

1.5

2

Frecventa de incercare (Hz)

CONCLUSIONS Following the tests carried out it was found that the CPTD platform can reproduce various reference signals to drive the dampers in different forms, with different frequencies and amplitudes, being able thus simulate the full range of vibration and tasks l that dampers are subjected by their daily use, but also the mechanical stresses to which must be subjected for testing, stipulated in standards and other regulations. For dampers designed to road vehicles were carried out the tests to check the the functioning, of measuring the maximum stroke, respectively of rising of control elastic characteristic F-S of the dampers, at different frequencies test, the reference signal form being different: sine respectively triangle. The tests performed were aimed to check the capacity of compact platform fot testing of dampers - CPTD to carry out on the dampers the tests stipulated in the documentation for the execution of dampers and in the standards in force. The results were recorded and confirmed the ability of CPTD for testing of any type of damper under simulated and accelerated regime.

Also, on the Compact Platform for Testing of Dampers - CPTD can be performed s simultaneously testing at endurance of several dampers, depending on their type and size.

In the regard to determination of electricity energy consumption necessary for putting into service of hydraulic systems specific to each installation, this was determined by means of three-phase energy analyzer. Following the measurements was found a significant decrease in electric energy consumption necessary for any type of damper testing using the Compact Platform for Testing of Dampers - CPTD. The tests performed aimed to check the capacity of the Compact Platform for Testing of Dampers - CPTD, to carry out tests in accordance with the standards in force, achieving a significant reduction in electric energy consumption per test damper (of approximately 5 times). REFERENCES [1]. Matache M., Mihai M., VlăduŃ V., Voicea I. - Process automation of shock absorbing systems dynamic testing, specific to technical equipment construction, INMATEH - AGRICULTURAL ENGINEERING, vol.30, no. 1/2010, pg. 95-106; [2]. Mihai M. and others - Automating the dynamic testing process of damping systems specific to construction of technical equipment, Project: PN 09-15 01 03, Stage 2 / 2009: Design and execution of Compact Platform (stand), Research Report, INMA Bucharest; [3]. Mihai M. and others - Automating the dynamic testing process of damping systems specific to construction of technical equipment, Project: PN 09-15 01 03, Stage 3 / 2010: Dampers testing on stand, Research Report, INMA Bucharest; [4]. Mihai M. and others - Automating the dynamic testing process of damping systems specific to construction of technical equipment, Project: PN 09-15 01 03, Stage 4 / 2011: Demonstration of reducing energy consumption (by comparison). Possibilities for energy recovery; widespread dissemination, Research Report, INMA Bucharest; [5]. ENERGETIC STRATEGY OF ROMANIA IN THE PERIOD 2007 - 2020.