DEVELOPMENT OF RECOMMENDATIONS FOR EXTENDING THE USEFUL LIFE OF PASSENGER CARS

Dep. «Cars and Cars Facilities», Dnipropetrovsk National University of Railway Transport named after Academician V. Lasaryan, Lasaryan St., 2, Dnipropetrovsk, Ukraine, 49010, tel. +38 (056) 776 84 98, e-mail sergeymyamlin@gmail.com, ORCID 0000-0002-7383-9304 Dep. «Cars and Cars Facilities», Dnipropetrovsk National University of Railway Transport named after Academician V. Lasaryan, Lasaryan St., 2, Dnipropetrovsk, Ukraine, 49010, tel./fax +38 (056) 793 19 16, e-mail reidemeister@mail.ru, ORCID 0000-0001-7490-7180 Dep. «Cars and Cars Facilities», Dnipropetrovsk National University of Railway Transport named after Academician V. Lasaryan, Lasaryan St., 2, Dnipropetrovsk, Ukraine, 49010, tel./fax +38 (056) 793 19 16, e-mail pularija@mail.ru, ORCID 0000-0003-1144-4179 Dep. «Cars and Cars Facilities», Dnipropetrovsk National University of Railway Transport named after Academician V. Lasaryan, Lasaryan St., 2, Dnipropetrovsk, Ukraine, 49010, tel./fax +38 (056) 793 19 16, e-mail kv47@i.ua, ORCID 0000-0002-8073-4631


Introduction
Total passenger car fleet of «Ukrzaliznytsia» consists mainly of cars built in the eighties with the designed: normative service life -28 years and maximum service life -41 years.The research of passenger car fleet is considered in [1], [5].
The car fleet has about 86% of passenger cars with outlasted service life (over 28 years), about 500 cars with normative service life of 20 years, only 343 of which have the service life of 10 years.During the period 1991 -end 2013 3 298 passen-ger cars were scraped (written off at the end of service life), 421 cars were to be written off in 2014.Thus, the intensity of passenger car fleet aging is increasing every year.
While the new cars are purchased in small amounts -«Ukrzaliznytsia» in the period 1991 -end 2013 at their own expense purchased 561 passenger cars, as well as 10 nine-car trains and 2 double-decker six-car trains.So every year the deficit of passenger cars is becoming tangible and may reach 2,364 cars in 2017, which is detrimental to the industry.Because of the above objective reasons it became necessary to extend the service life of cars that have exhausted their primary resource.This makes it possible to slow down the growing deficit of passenger cars due to reasonable extension of their service life.The prerequisites of the above said extension are as follows: -Designed service life was set at substantially excessive strength coefficients; -Detailed analysis of technical condition of the cars to be written off shows that some cars are scrapped because of the malfunction incompatible with their further safe operation, but many of cars are written off from the inventory park when they reach the normative service life.However, a certain number of the latter still remain in good condition.
The possibility of extending the life of car supporting structures should be grounded by experimental and calculation-theoretical methods that include: inspection of their technical condition; experimental determination of load level and stress state of structural members; numerical calculations based on modern software systems to determine the stress-strain state by simulating the most adverse operating modes; residual life assessment (determination of the extended service life) with the numerical calculations of fatigue damage or by experimental life length testing.In addition, it should be noted that cars require an individual approach to the definition of the next service life (life length).This range of activities must be supported by repair technologies, which go beyond the scope of this study.
Problems of need statement for adjustment of cars useful service life extension in a particular way was considered both in Ukraine [3,7,8,9,12], and in near [17] and far abroad [18,19].The works [7,9,12] studied the problems and peculiarities of passenger car technical diagnosis.And the works [3,8,17,18,19] performed numerical calculations based on the finite-element model with strength assessment by І and III design modes.Further, considering the preliminary results, the calculations of structural memberss fatigue damage were performed to assess the remaining service life.In addition, the work [3] provides calculations for new cars and cars with minimum thickness of members (due to corrosion), as well as calculated significant impact of mechanical or welded damage (undercuts), depending on the size of the latter, on the car service life.
However, only theoretical studies cannot fully take into account all the factors affecting the car during operation and possible deficiencies incorporated in the construction at the stages of design and production.It implies permissible size tolerances, replacement of materials during the manufacture, specific possible mechanical damage during repairs and corrosive damage in operation.Thus, the car physical condition for each batch of individual manufacturer will differ.
Therefore there is a need for implementing relevant tests conducted once every five years according to TSL-0070 [6].Effectiveness of field tests and their impact on rolling stock traffic safety is proved in [10].

Purpose
In order to determine the feasibility of extending the useful life of passenger cars the car testing laboratory of Dnipropetrovsk National University of Railway Transport named after Academician V. Lazaryan by order of «Ukrzaliznytsia» conducted a set of field tests in 2013.The tests included static strength, impact strength (determining) and impact life length testing of cars.

Methodology
The cars for testing were randomly selected from the operating park, which exhausted the set service life or underwent the required scheduled types of repair.Some cars had damages allowed under [6].As the sample cars there were selected two SOC cars (steel open-type sleeping cars) after 29 and 33 years of service, and two SSC cars (steel close-type sleeping cars) after 30 and 33 years of service.
Before testing the condition of cars underwent technical diagnosis to detect the level of corrosion and mechanical damage while metering the member thickness.All tests were performed according to the «Standards…» [11] and «Programme and methods …» [15].
Static strength tests were performed to determine the stresses in car parts caused by structure and passenger weight.Vertical static load on the car body members caused by passenger weight was carried out by the car shed employees, who were evenly distributed along the train, and that caused by own structure weight was determined as the total stress with the help of the factor that takes into account body weight, water and coal weight, etc.While carrying out the static tests the equipment readings were registered and the loading-unloading cycle repeated provided the sensor indication stability.
The impact strength tests were carried out to assess the stress state of the car structural members affected by the determined longitudinal forces in the range of 0,.5 MN…2.5 MN [11,15].Herewith the car structural member stress values and impact force values were recorded.
The impact life length tests were performed to calculate the life length of bearing members of car body for impact endurance affected by longitudinal force.Car impact was performed by run-up of a hammer car with the help of locomotive onto a test car, which was located in the head of a retaining wall.The tests were carried out at speeds of 3 km/h to 13 km/h [11,15] with a gradual impact velocity increase by 1…2 km/h.The impacts were carried out by series, corresponding to one year of operation.The condition for the test completion was to obtain the full amount of experimental data or the car bearing structure integrity damage, which would threaten the safety of further testing.
The tests determined the impact force and selectively tensions in some structural members (at impact force over 2 MN).
All kinds of tests were carried out on the territory of a car shed.To do this, after the removal of technically diagnosed car body damages, the strain-gage sensors were attached to the cars to determine the stresses, and the serial couplers were replaced with the strain-gage ones to determine the impact force.
According to obtained results of mathematical processing of the recorded processes (structural members tension and impact force) each type of the test determined the following: -The results of static tests defined the tension in the structural members caused by passenger weight and own body weight; -The impact strength tests allowed to build the dependency diagrams of impact force -speed (Fig. 1), of car part stresses -impact force (Fig. 2), to define tensions in some body members and to assess the structure stress state by design mode І [11].

Findings
State of SSC car bodywork after 30 and 33 years of service differed little and is typical for vehicles operating for 30 … 33 years.Local thinning of main bearing members (span bolster, crossbearer and underframe end, except diagonals) due to corrosion did not exceed 10%, there were no cracks, deformations, post breakages and other damages.The largest local corrosion damages were recorded in underframe sill diagonals (about 20%).
State of SOC car bodywork after 29 and 33 years of service is even worse in general, but is typical for this class of vehicles operating for 29…33 years.The span bolster thinning due to local corrosion reached 30% for 29-year service car and 35% for 33-year service car.The largest local corrosion damages in the side sill are recorded in the car after 29 years of service -33%, the longitudinal tie rod thinning is about the same for both cars -up to 24%.There are deformations and corrosion damage of side sill Z-shape of both cars, single corner post breakages, damage to the joints of longitudinal tie rod and span bolsters.
The above damages can be removed during the scheduled repair in accordance with the instructions of TSL-0026 [4], TSL-0036 [14], TSL-0041 [2] -so all the cars listed above have been taken for testing.
Static and impact strength tests showed: − Total static stress caused by passenger weight with luggage is insignificant.Herewith the stress in the sleeping car body members did not exceed 10.4 MPa.In the open-type cars the maximum stress was recorded in span bolster (20 MPa), cross-bearer (23.8 MPa) and side sill (30.3 MPa); − The obtained mathematically processed results of car impact strength tests provided the stress value and dependence in the structural members and the hammer car run-up velocity caused by impact force (Fig. 2).
The diagrams show the strict linear relationship of parameters.This dependency of stress on impact force is peculiar for the structural members of all tested cars: − The sleeping cars constructed in 1980 and 1983 take the impact load with the draft sill (105 MPa) and the span bolster (118 MPa), as well as the side wall panel bottom (230 MPa).Other  It should be noted that the stress level in some parts of the car built in 1984 is by 20% lower than that of the car built in 1980.In general, total stress of both cars does not exceed the allowable values.
As a result of impact endurance tests the entire range of longitudinal forces was distributed at intervals followed by calculation of impact endurance intervals, and then by total life length for each car.Fig. 3 shows an example of impact distribution in each force range (MN) for sleeping cars.
The figure shows the lighter tone for the number of efforts received by the car in the wall, the dark one -as a hammer.The largest impact number, 202, is recorded in the operating load range (0.5 … 1.5 MN).In total each car received 257 impacts from 0.5 to 2.94 MN.The results of experimental tests are correlated well with the results of theoretical studies [3].In both cases, the sleeping car design has a larger strength margin than that of the open-type car.

Originality and practical value
The results of experimental static and impact endurance tests prove that passenger cars after 28 … 30 and 33… 35 years of operation meet the requirements of regulatory documents relating to strength and safety of operation.The conducted life length tests have shown that provided the impact endurance the car service life can be extended for the next 5 years.The results can be used to extend the service life of above mentioned cars.The conducted research allowed justifying the possibility to continue the operation of passenger cars without additional measures after 28…30 and 33…35 years of service in the amount of 1,766 units.

Conclusions
The conducted studies determined that the passenger sleeping cars and open-type cars constructed before the year 1989 with specific corrosion damage level have the life length sufficient for their subsequent operation over the next 5 years.After the term exhaustion it is recommended to carry out the life length tests for assessment of the remaining life, which will depend on general and operation conditions of the cars.
In relation to open-type cars after 28 years of operation, when conducting the scheduled repairs, special attention should be paid to the state of side sill and corner posts.In case of suspected breakage in corner posts and side sill (visual subsidence of side wall) it is necessary to conduct a survey with removed outer skin and appropriate repairs.And in case of OR-1 these measures are mandatory.

Fig. 2 .
Fig. 2. Dependency of span bolster stress (MPa) on impact force (MN) − The open-type cars constructed in 1980 and 1984 take the impact load with longitudinal tie rod (187 MPa), span bolster (164 MPa) and side wall sill (228 MPa).Other structural members have much lower impact stress.The largest total stress in the structural members is marked in the longitudinal tie rod (127 MPa), span bolster (164 MPa), cross-bearer (214 MPa) and side sill

Fig. 3 .
Fig. 3. Number of impacts (vertical) in the force range (horizontal, MN) The impact endurance tests showed: − Sleeping cars were not damaged during the test − Open-type cars constructed in 1980 and 1984 after the tests had damages common to both cars: deformation of side sill Z-shape (Fig. 4), cracks and breakages of the corner posts from side sill, cracks in span bolster bottom sheet welds.Besides the car built in 1980 got a crack in the joint of longitudinal tie rod and span bolster (Fig. 5); − All cars passed the endurance tests without damage which would prevent from testing and could not be removed during the next depot repair or overhaul; − All cars have life length that allows them to extend the useful life for the next 5 years.