# On Influence Of Design Parameters Of Mining Rail Transport On Safety Indicators

Kirill Ziborov, Volodimir Protsiv, Serhii Fedoriachenko, Illya Verner

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Kirill Ziborov, Volodimir Protsiv, Serhii Fedoriachenko, Illya Verner. On Influence Of Design Parameters Of Mining Rail Transport On Safety Indicators. Mechanics, Materials Science & Engineering Journal, 2016, 10.13140/RG.2.1.2548.5841. hal-01297434

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# On Influence Of Design Parameters Of Mining Rail Transport On Safety Indicators

Ziborov Kirill¹, Protsiv Volodimir², Fedoriachenko Serhii³, a, Verner Illya⁴

1 – Associated professor, Head of the Machinery Design Fundamentals Department, National Mining University, Ukraine.

2 – Professor, Head of the Mining Engineering Department, National Mining University, Ukraine.

3 – Associated professor, Machinery Design Fundamentals Department, National Mining University, Ukraine.

4 – Head of the Computational Engineering Laboratory, Machinery Design Fundamentals Department, National Mining University, Ukraine.

a – [serg.fedoryachenko@gmail.com](mailto:serg.fedoryachenko@gmail.com)

**Keywords:** tractive effort, safety, mining locomotive, rolling stock, hard rock, mathematical simulation, principal scheme

**ABSTRACT.** The influence of design parameters of mining rail transport on safety indicators is defined in the paper. The mining locomotive ЭШК-10 is studied. Substantiated, that during constant locomotive speed V, variation of the tangential component $Q_x$ occurs when the increment speed of the boundary layers of friction pair materials $\delta V$ leads to energy loss in the contact area. This provokes unstable state of the electromechanical system. To increase stability and safety, reduce the load on the bogie, as well as on the rail track, additional movability of the kinematic connection of its links can be used. Basing on the thrust forces equations subject to adhesion and permissible power for definite conditions, we can determine the values of engine voltage $U_c$ as a function of the locomotive speed.

**Introduction.** The large tonnage hard rock mines, either coal or copper etc., use underground rail. South and Central America, Canada, China, South Africa, Ukraine these are may be the biggest regions using mining rail transport [0]. Almost each region has its own suppliers of mining locomotives and rolling stock. There is a tendency, that mining rolling stock suppliers focusing on the locomotive rebuilds and refurbishment of old locomotives and rolling stock [0]. However, the economical conditions of the mining regions are different and the development of a new locomotive has its own strategy from region to region.

The Ukrainian locomotive ЭШК-10, that has been developed by the team of scientists from National Mining University, has a lot of specific features, which allows using this loco worldwide from mine to mine.

This happens due to comprehensive mathematical models and usage of sophisticated 3D simulation.

**Research results.** During the rock mass and coal transportation by the mining rail transport along the mining shafts, the rail's functions are not only carrying static loads, but to transmit the dynamical stress and bogie mass to the rail track structure as well. The interaction area between wheel and rail facilitates transmitting braking and tractive forces. In order to increase the productivity of the mining rolling stock, an adhesion weight of the modern mining locomotives increases either and now achieves 10-28 tons. This mass allows hauling heavier mining tub with significantly increased static loads on the rail track on the steeper slopes. Due to the fact, that existing mining rail tracks have been designed for much lower locomotives' weight, increased axial loading on the rail track elements rocketed up to 1,5-2,5 times and for mining tub 7 times more.

However, increased adhesive weight did not solve the problem insufficient friction properties of rolling stock that caused unreasonable energy loss, reduction of its exploitation characteristics. Exploitation indexes of railway transport show, that to overcome friction up to 30 % of all consuming energy is necessary, and loss of material of friction pair amounts 15 % of producing metal [0].
Each of mining drifts has its own climate environment, rail track profile and plan, bending radii, track incline, admissible haulage speed and braking distance etc. All these factors dependence on both economic and exploitation indexes, and on transport system reliability in general. Thus, study of the rail, wheel and their interaction surface as a standalone system elements, wheel-rail interaction control, allow optimizing their work during difficult motion regime.

Modern design methods [0], which base on the scientific simulation and research approaches, facilitate definition of the location and character of arising dynamical loading and prevent their growth during forming within the mining vehicle chassis.

This prevents the following dynamical load transfer on the bolster structure. Thus, the structure selection and selection of mining machines parameters, which bases on the detailed analysis of running processes, might be an essential part of energy-mechanical system and its scheme development during development [0].

The purpose of the paper is to define the influence of design parameters of mining rolling stock on the rational tractive regimes with high exploitation indexes and low energy loss.

As it is known, the frictional surfaces move across the interaction area with tangential velocities $V_1$ and $V_2$. The bodies have the components of angular rotation velocity relatively to the base tangent to the surface. Different relations of the wheel set line speed $V_1$ and speed of rotational motion $V_2$ is characterized by the sliding velocity $\delta V$.

After each wheel's turn on the interaction area resilient and plastic deformations arise. As a result, the friction elements wheel-rail start negotiate through the finite size area. Taking into account existing rail track imperfections and imperfections of contact area, let assume nominal and real contact areas. All force interactions of frictional pair wheel-rail are carrying within the real contact area. Therefore, the tangent reaction $Q_{xy}$ is formed with elementary forces $Q_{xyi}$, which act on each ith point of the real contact area (fig. 1). Thus, during analytical research we need to proceed from the elementary contacting area of the interacting bodies.

The wheel, moving along the rail, can be either in free ($Q_{xy}= 0$), tractive ($Q_{xy}> 0$) or braking ($Q_{xy}< 0$) regimes (fig. 2, b).

<figure><img src="image_3.png" /><figcaption>Fig. 1. Real contact areas of interacting bodies</figcaption></figure>

These forces are directed opposite to the sliding velocity of i-th point $\delta V_i$ in the contact area (fig. 2) in dependence on motion regime. The total force, in the case when $\mu$ doesn't independent on $\delta V_i$ direction, acts in the direction opposite to the wheel's slipping velocity, and their scalar product $Q_{xy}\delta V$ defines the power of dissipative forces in the contact area.

Thus:
$$Q_{xy} = \mu \sum_{i=1}^{k} Q_{zi} \cos \alpha_{i} \quad (1)$$

where k – amount of the contact points in the slipping area;

$\mu$ – coefficient of friction limit.

During mining locomotive motion along the mining drifts, the wheel contacts rolls both on the inner and outer rails, which have different curvature and gage width. This fact induces the lateral displacement of the contact area though its width. The worn wheel tread profile represents the total envelope profile of all rails that are contacting with tread [0]. The tread areas, which contact with rails most often, expose to intensive sliding, high contact stress and significant wear in comparison to other tread areas. Mine drifts with big amount of straight track segments lead to wear concentration on the rolling area at the center of the wheel tread. In this case the wear of the flange is minimal. Otherwise, motion on the curvilinear rail track segments (most often case for coalmines) causes significant flange wear.

<figure><img src="image_4.png" /><figcaption>Fig. 2. The calculation scheme of forces and velocities. a) tractive regime ($Q_{xy} > 0$); b) braking regime ($Q_{xy} < 0$)</figcaption></figure>

As a result, of frictional interaction of the wheel and rail, a clearance between contact surfaces forms. Uncontrollable growth of the clearances provokes additional dynamical forces, acting on the bogie and track, that reduce the exploitation characteristics of the machine.

However, there is possible to revise the machine design and additional kinematical movability either to reduce the duration of nonstationary motion regime. This is essential for mining conditions, which is marked by lots of unfavorable factors [4]. To provide the smooth wear of coupled kinematical members a coupling with local movability can be applied [4].

For example, locomotive of the module scheme, that includes a few sections. It allows for development of the vehicle with different trailing weight, energy supply system and necessary exploitation indexes. The distinguish feature of such locomotives is kinematical coupling between bogie and tractive section (Fig. 3).

Such connection provides necessary relative movability and transmits vertical loading from frame to bogie, horizontal lateral forces – centrifugal force, reaction of overrunning rail, which has geometrical imperfections in all surfaces. Movability around the vertical axis is necessary for tractive
bogie turn and in order to avoid odd couplings, because the pin does not carry the chassis weight; around lateral axis – for correct weight distribution between locomotive axles and reduction influence on the rail track; longitudinal movability is absent because the tractive effort transmits in this direction.

<figure><img src="image_5.png" /><figcaption>Fig. 3. Pin joint locomotive (a); Locomotive joint (b)</figcaption></figure>

In order to define relations between kinematical and dynamical characteristics of mine rollingstock we need to provide the analysis of rail and wheel interaction, and to evaluate locomotives tractive and safety properties.

The obtained data allows for assessment of the safety index, which is used to describe by safety co-efficient [0]:

$$SF = \frac{\operatorname{tg} \chi - \mu}{1 + \mu \cdot \operatorname{tg} \chi} \left( \frac{Q_z}{Q_y} \right) > 1 \qquad (2)$$

where $\chi$ – angle of wheel flange;

$\mu$ – friction coefficient;

$Q_z$ – normal rail reaction under ongoing wheel, $N$;

$Q_y$ – guiding force on the ongoing wheel, $N$.

Local and regular rail imperfections lead to additional growth of guiding force $Q_y$ that can cause the derailment at some certain critical value (Fig. 4, 5, b). Reduction of guiding force can improve stability and predict derailment (Fig. 4, 5, a).

The most complex motion regime is driving through curvilinear rail track with wheel flange climbing by both rear and front axles. This induces the rotation of tractive bogie in relation to mass center (Fig. 4, 5). Simultaneously, the middle section rotates around pin joint. At axial displacement of the wheels, a reaction force arises at the point of flange contact, which acts flatwise to motion direction. A sudden growth of these forces appears while wheel misalignment. To reduce reactive forces an additional local movability of kinematical pair coupling is necessary.
<figure><img src="image_6.png" /><figcaption>Fig. 4. The forces on the wheel flange while straight motion (a) and along bend rail segment (b)</figcaption></figure>

<figure><img src="image_7.png" /><figcaption>Fig. 5. The creep forces between rail and wheel during straight motion (a) and in the bend rail segment (b)</figcaption></figure>
The usage of mathematical simulation facilitates the designing and dynamical interconnection of mine rolling stock. The study of mining vehicle dynamics is provided via developed system of differential equations.

Thus, we have obtained several relations of dynamic forces and safety factor (SF) indexes (Fig. 7).

As mentioned above, the characteristics of contact surfaces, and the pressing force define friction properties at the contact point. When the position of the wheel set in the rail track cannot be achieved through the friction forces, there is a two-point contact appears and lateral forces on the flange, which protects the wheel set from derailment (Fig. 4 a, b). At the same time, an additional resistance force arises. However, the forces on the flange are connected with frictional components, which may lead to force reduction in the contact area. Thereby it facilitates the wheel climbing on the rail, especially on curved track sections of small radius.

<figure><img src="image_8.png" /><figcaption>Fig. 6. General scheme of tractive bogie rotation in relation to mass center during wheel climbing (1- tractive bogie; 2 – middle section; 3 – pin joint)</figcaption></figure>

To enhance the stability and safety, reduce load on the vehicle’s chassis and the track and to reduce motion resistance become possible while the usage of a new kinematical design where the kinematical pairs will have an additional local movability. Thus, it will reduce the number of redundant links with shortage of the unnecessary weight. To determine the appropriate value of mobility, providing the necessary performance, we can use modern means of computer simulation interoperability of mine transport and track.

<figure><img src="image_9.png" /><figcaption>Fig.7. Safety factor relation to track curvature subject to structural scheme. V=4 m/s - - - - sectional pin-joint locomotive; —conventional locomotive</figcaption></figure>

Taking into account the denoted above approach of wheel and rail interaction evaluation, the motor torque, reduced to the wheel set with rigid connection between the wheels, as a function of absolute motion veloc-
ity $v$ and relative velocity of the boundary layers $\delta V_i$ of the frictional pair wheel-rail, defines as

$M_{\text{δε}} = \sum_{i=1}^{N} Q_{xyi} R_i$. The value $Q_{xyi}$ for each wheel calculates according to [4]. Each point of the grip charac-
teristics is corresponded by its distinguish energy state of interaction process of the pair wheel-rail. Thus,
alteration of the grip accompanies by a change of the state. At a constant locomotive speed $v$ alteration of
the tangent component $Q_{xy}$ takes place during increase of the boundary layer displacement of frictional
pair material $\delta V_i$, which leads to energy loss in the contact area and unstable state of the eletromechani-
cal system. Such combination of adverse factors can evoke skidding (during tractive regime) or blocking
wheels (during braking).

The critical velocity can be determined by equating the limit values for traction grip and power to each
other. The maximum permissible torque, at which there will be no grip disruption, can be defined from the
expression of $M_{\text{δε}}$ after substitution the relative velocity $\delta V$ [4]. Using the relation between torque and
angular velocity of tractive motor, we can determine the voltage $U_C$ as a function of the speed $v$ for these
conditions and formulate requirements for tractive motor (braking) control algorithm.

However, the operator of the loco can lose the driving control in hard mining environment. As a result the
wheels can be slipping or skidding, which will significantly increase the braking distance (especially on
the 50‰ slopes). As a result, the necessity of automated control ABS (anti-block system) system ap-
peared.

The main purpose of the ABS is to predict the wheel blocking and skidding adjusting tractive and braking
characteristics of the locomotive [7]. The ABS must connect to different systems: electromechanical pow-
er-train and braking hydraulic systems. The principal electrical-hydraulic ABS system has been developed
subject to [8] and is depicted on the fig. 8.

<figure><img src="image_10.png" /><figcaption>Fig. 8. The general electric-hydraulic scheme of automated control system against skidding and wheel blocking of mining pin-joint loco.</figcaption></figure>
**Summary.** While constant locomotive speed V variation of the tangential component $Qx$ occurs when the increment speed of the boundary layers of friction pair materials $\delta V$ leads to energy loss in the contact area and the unstable state of the electromechanical system. To increase stability and safety, reduce the load on the vehicle and chassis, as well as on the rail track, additional movability of the kinematic connection of its members can be used. Basing on the thrust forces equations subject to adhesion and permissible power for definite conditions we can determine the values of engine voltage $Uc$ as a function of the locomotive speed. To improve tractive and braking characteristics of mining pin-joint locomotive a special ABS system has been developed and described in the paper.

**References**

[1] Moore P. (2012), Mine locomotion, International Mining, Vol. 3, pp. 88-96.

[2] Isaev I.P., Lujhnov Ju., (1985), Problems of locomotive's traction grip, Mashinostroenije, 238 P.

[3] Ziborov K.A., Protsiv V.V., Fedoriachenko S.A. (2013), Application of computer simulation while designing mechanical systems of mining rolling stock, Scientific Bulletin of NMU, №6, pp. 55-59.

[4] Ziborov K.A., Fedoriachenko S.A. (2014), The frictional work in pair wheel-rail in case of different structural scheme of mining rolling stock, Progressive technologies of coal, coalbed methane and ores mining, Netherlands, pp. 517 - 521., doi: 10.1201/b17547-87

[5] Ziborov K.A. (2014), Characteristics of Friction Pair "Wheel—Rail" of Mining Locomotive with Kinematical and Power Imperfections, mining Equipment and Electromechanics, №3 (100), pp.26-32.

[6] Garg V.K., Dukkipaty R.V. (1988), Dynamics of rail transport, New-York, 391 P.

[7] Protsiv V.V., Gonchar O.Ye. (2010), *Проців В. В.* On the usage of automated system, prevented wheel blocking and skidding of mining pin-joint locomotive, Mining electro-mechanics and automatics, Vol. 84, pp. 116 – 125.

[8] Protsiv V.V. Indicators of arising skid during braking with limited frictional force on the wheel, Scientific bulletin of NMU, Vol. 5, pp.106 – 112.