Challenges and opportunities of distance learning and teaching

A.A.Y.Hansini

Undergraduate

University of Jaffna

THE BEST ARTICLE OF THE WEEK FROM 06TH APRIL TO 12TH APRIL, 2020

Graphene for a new era in the energy sector.

Ms. Lakshika Karunarathne, an Electrical Engineering undergraduate from University of Moratuwa shares her ideas about the IESL YMS Blog and invites you to join with. She is the author of the best article written to the YMS Blog for the week from 06th April to 12th April, 2020. In her article on "Graphene for a new era in the energy sector", she discusses how can we make the use of graphene to achieve the goals in the energy sector.

Watch the video

Ms. M.M.L.K Karunarathne
Department of Electrical Engineering
Faculty of Engineering
UOM
Author of "Graphene for a new era in the energy sector"

We give our heartiest congratulations on her achievement!

WHAT HAPPENED TO THE UNSINKABLE “TITANIC”?

RMS TITANIC leaving Southampton to start her maiden voyage on 10th of April 1912

On the 10^th of April 1912, ship “RMS TITANIC” started her maiden voyage from Southampton, England to New York, USA. At that time TITANIC was the largest passenger ship ever built in the world. It was owned by White Star Line Company. The ship was 230m long, 28m wide and weighed 46,000,000 kg which included a gym, swimming pool, rest rooms and other luxuries. With the reliable words of the builders’ she was called ‘the unsinkable ship’. They claimed that she cannot be sunk even under the worst conditions in the ocean. Therefore, no one out of 2200 people on board or on the ground never thought this famous girl would make 14^th of April night memorable forever with the loss of 1500 people. The ship was devastated by the collision into an iceberg. Everything but only sorrow, pity and terrified memories were remained.

What caused a vessel like this to fail when it crashed into an iceberg? What is the scientific explanation to this failure? Material failures and Designing defects played major role in this scenario. Even though officers gave their full strength to avoid the collision, it all ended up having a sideswipe at iceberg and the right side of the hull was damaged nearly 100m long due to crash. When designing this kind of vessel, material should have sufficient ductility .Simply ductility means the ability to deform without breaking when having applied load (examples of good ductile materials are gold, silver and copper).After the several explorations of the Titanic wreck in 1991, scientists were able to recover pieces of metal of the ship wreck which was belonged to ship hull.  These pieces of metal were faced charpy test (Impact Test) in laborites to analyze the material properties.

                                                                                                                

The Impact test is done by holding the metal specimen against steel pendulum and then release the steel pendulum from its starting position which allows it to swing freely and have an impact on the held specimen .Before the starting above procedure the scale reading should be set to 0 position. This reading indicates the energy absorption of the specimen.

Scientists also prepared a high quality steel piece which was kept  at -2°C alcohol mimicking the same ocean conditions on the night Titanic sank. Both steel pieces from Titanic hull and prepared on the same conditions were tested in laboratory. When prepared steel faced the test and when the steel pendulum gave a heavy impact on the prepared high-quality steel after swinging, it was not completely broken into two parts but gave only “V” shaped bend. However, when the metal piece of the ship hull was tested, due to the impact of the pendulum it was completely broken into two parts.

Figure 1. How the samples looked after the Impact Testing (a) the high quality modern steel which had been prepared for the test (b) Titanic ship hull steel from the wreck(Bassett 2000)

Therefore, this confirmed what happened to the hull steel when the ship collided into iceberg. When the ship was colliding, hull plates did not deform, which reveals that the ductility of the material is of poor condition. Unfortunately, because of the high brittleness ship hull plates shattered instead of deforming. What happened was similar to figure (b) instead of figure (a) in a much larger scale.

Simply brittleness means breaks with small elastic deformation without plastic deformation. Most of the time this breaking also emits a snapping sound. Also, brittle materials can absorb less amount of energy than ductile materials (examples of brittle materials are ceramic and glass).

Figure 2. Ductility vs Brittleness differences (Amgreen 2010)

On the other hand, the steel which had been used for making Titanic included high Sulphur content and Oxygen. Adding high Sulphur content into steel increases its brittleness. In steel when there is high level of Sulphur content, Sulphur bonds with the Magnesium in the steel which forms Magnesium Sulfide. Magnesium Sulfide causes cracks in steel. Adding Oxygen also produces similar results. This high level of Oxygen content increases the ductile to brittle transition temperature in steel. For the hull steel, this was about 25°C  to 35°C which was too high.  In the night that Titanic collided, temperature of the seawater was at -2°C . This low temperature also affected the ship hull to become more brittle. Therefore, due to all these reasons together resulted in ‘brittle fracture’ and above-mentioned Impact testing also proved this hypothesis.

There is also another theory to explain Titanic disaster. Irish journalist Senan Molony insisted that the Titanic ship hull was weakened before the voyage got started because of the coal fire inside the coal bunkers in the hull.

Figure 3.Titanic leaving Belfast on 2nd of April 1912. A black mark can be seen on the hull (Lewis 2017)

According to this ideology, because of the coal fire, temperature of the hull steel increased. The Titanic had only one hull same as most of the vessels in those days but nowadays ships have two hulls. In Titanic, place where coal was stored positioned right next to the hull. Therefore, heat of the engine may have been transferred to the hull through stored coal easily. , Molony’s conclusion was that, due to temperature changes in the hull, material structure of the hull was changed from that of the original form. Thereby nearly 30 feet long dark mark on the hull (above photograph) appeared. This area became more brittle. Iceberg crashed onto Titanic close to this area and the hull was broken easily. Although the conclusion was presented clearly, some of the scientists disagreed with this idea. They believed that this did not have an impact on brittle facture. The collision force of the iceberg would have penetrated even without having a heated hull.

Defects of the Titanic design also played a major role in this disaster. In the ship’s lower section there were sixteen watertight compartments which could easily seal off if there was a water leakage. However, these compartments were watertight only along horizontal direction but not vertically. The top of these compartments was opened. Therefore, if one compartment was overflowed, water flowed into the next compartment and likewise all the compartments could be filled with water. This is what exactly happened when Titanic collided with the iceberg. Because of the collision, six out of sixteen compartments were damaged and started to fill the sea water. Even though they sealed off the compartments, nothing could stop the water flow horizontally due to over flow.

Figure 4. This shows how the water flow happened in compartments after the collision (Harish 2019)

This water flow directly helped to push the ship towards the bottom of the ocean. In Scientists view, if those compartments were watertight in both horizontal and vertical directions the ship could have kept floating more than it did. This would bring sufficient time Carpathia (Carpathia was the ship which saved the survivors of Titanic) to reach the location and save everyone on board Titanic.

When water was rushing into the ship bow because of the weight of the water, front of the ship began to tilt down. The rear side of the ship started to lift from the water level. Titanic had three large and heavy propellers in its rear. When the rear of the ship was raised, due to the weight of the propellers, force acted in the downward direction on the board at rear. Thereby the board of the ship acted as a lever which hold two different masses in its two edges. When the lifting angle was rising and the moment it tried to pass the stress beyond the ship board metals’ maximum stress, ship board was broken into two parts from the expansion joint and both parts went down towards the bottom of the Atlantic Ocean.  

   

 Due to all these reasons and some other non-technical issues out of 2200 people only 705 survived.

Himalsha Dharmapala

Department of Manufacturing and Industrial Engineering

University of Peradeniya

References:

·         Amgreen, 2010, Graph comparing stress–strain curves for brittle and ductile materials,photograph,viewed 16 April 2020,<https://en.wikipedia.org/wiki/Brittleness#/media/File:Brittle_v_ductile_stress-strain_behaviour.png>.

·         Bassett,V 2000, Causes and effects of the rapid sinking of the Titanic,Explanatory thesis, University of Wisconsin,viewed 18 April 2020,<http://holms.faculty.writing.ucsb.edu/titanic2.pdf>.

·         Ewers,J 2008,'The secret of how the Titanic sank',U.S.News,25 September,viewed 16 April 2020,<https://www.usnews.com/news/national/articles/2008/09/25/the-secret-of-how-the-titanic-sunk>.

·         Harish, A 2019,'Why did the titanic sink? an engineer analysis', SIMSCALE Blog, blog post,4 November, viewed 18 April 2020,<https://www.simscale.com/blog/2018/01/why-did-titanic-sink-engineer/>.

·         Lewis,D 2017,'A coal fire may have helped sink the Titanic',Smithsonian MAGAZINE,smartnews,5 January,viewed 16 April 2020,<https://www.smithsonianmag.com/smart-news/coal-fire-may-have-helped-sink-titanic-180961699/>.

             

THE EVOLUTION OF LOCOMOTIVES IN SRI LANKA

Are you an enthusiast about trains and locomotives? It’s doesn’t matter whether you are zealous or not, most of us have to use train as our transportation mode. The railway network is spread over considerable terrain in Sri Lanka.

Figure : Railway network(www.Railway.gov.lk)

 With the extension of coastal line from Mathara to Beliatta total length railway network Is close to 1600km now. [1]

Train locomotives have served as the backbone of railway. Since the inaugural train dispatched from Colombo to Ambeypussa in 1864 large number of locomotives have been used to the date. They have been classified into several classes according to the type of locomotive. But majorly only two types of locomotives can be categorized with respect to the power source.

1.    Steam locomotives

2.    Diesel locomotives

STEAM LOCOMOTIVES

At the infant age of Sri Lanka railway (Ceylon Government railway(CGR)) steam locomotives were used. Most of them were imported from the United Kingdom. Even though Diesel engines were introduced in 1950 steam locomotives had been the heart of railway until 1970.Over 400 steam locomotives were imported within that period. They have been categorized under class A, B, C, D, E, F, J, H, K, L, V and R.

Steam Engines are external combustion engines where the fluid is separated from the combustion products. As coal was abundant and cheap fuel in that era, steam locomotives were highly utilized. But the environmental pollution due to coal was significantly high. They were subsequently replaced by the diesel locomotives. As a consequence of this, diesel locomotives were imported to Sri Lanka after 1940. [2]

DIESEL LOCOMOTIVES

When consider the diesel locomotives, there are two identifications. They are diesel locomotive engines and Diesel Multiple Unit(DMU). The uniqueness of DMU is that it is designed as one unit which train is powered by on-board engines and engines are incorporated into carriages, wherefore no separate engine is required.

 Class s12 DMU  

                                      

  Class M locomotives

                          

These diesel locomotives can be categorized in to three main types according to power transmission method.

1.    Diesel Electrical Locomotives

2.    Diesel Hydraulic Locomotives

3.    Diesel Mechanical Locomotives

Diesel Electrical Locomotives

Majority of diesel locomotives which are currently used in Sri Lanka are electrical. Class M locomotives and class S DMU after S8 have this transmission method. Main parts of this as follows.

   Figure : Parts of Diesel electric Locomotives 

 Figure : Simple chart of parts of Diesel electric locomotives

      

v Fuel tank -Store diesel

v Diesel engine

v Prime mover

v Radiator

v Alternator (those who have DC motors)

v Air compressor

v rectifier

v Inverter

v Traction motors

Figure: A Traction motor

 Figure : Types of axel  

  Figure : Lighting control system of DMU

    

First the diesel is injected from fuel tank to engine. Diesel engines work by compressing air. This increases the air temperature inside the cylinder to such a high degree that atomized diesel fuel injected into the combustion chamber ignites spontaneously. The crankshaft connected to engine is linked to a generator or alternator. It converts kinetic energy into electric energy while generating AC current and it goes through a rectifier, in order to convert AC current into DC current. The electric locomotives which have DC motors can directly use converted DC current. But modern locomotives require three phase AC Current as they consist of some AC motors. Therefore, inverter is required for that process. The axle of traction motors are connected to axle of the bogies. Diver can change both direction and speed of locomotive by changing the current. An air blower is located to cool down the traction motors. It also helps to cool down the alternator when applying the dynamic brakes to slow down the train. There are both pros and cons in these models.

v  Easy to maintain

v  Low wearing, tearing

v  Less lubrication

v  Smoothness in transmission

Are the main advantages

v  Less acceleration efficiency than other models

v  Power loss is higher than diesel hydraulic locos.

Are significant dis-advantages.

DIESEL ELECTRIC LOCOMOTIVES

1)      Class M1

v  Built in Britain

v  Imported in 1952

v  Engine type - mirlees JS12VT

v  Power output-1000hp

v  Axel arrangement-A1A-A1A

v  Weight-88tons

v  Total Imported- 25 [3]

2)      Class M2

v  Manufactured in Canada

v  Imported       -1954-1956

v  Sub classes      -M2,M2a,M2b,M2c.M2d

v  Power output    -1425hp and 1310hp(M2d)

v  Axel arrangement -A1A and Bo-Bo(M2c)

v  Weight 79 tons

v  Maximum speed -112kmph

Total imported -14 (1 was blasted by a bomb, another one was damaged by tsunami but now repaired and currently 13 in service) [3]

3)      Class M3

v  Built in Sri lanka-1956

v  Used the parts of S1 DMU

v   Power output 180hp

v  Maximum speed 89kmph

v  Axel -Bo-Bo

v  Weight -47 tons

v  Total produced -2 [3]

4)Class M4

v  Manufactured in Canada; imported in 1975

v  Engine type -Alco bombardier 251-c3- 4stroke 12Cylinders

v  Power output 1750 hp

v  Maximum speed-65kmph

v  Axel arrangement -Co-Co

v  Total imported -14 [3]

5)Class M5

v  Built in Japan

v  Built by Hitachi 

v  Imported in 1970

v  Sub classes -M5A ,M5B

v  Engine type -V12 diesel engine

v  Power Output-1640 hp (M5A and M5B-1150hp,M5B-1600 hp)

v  Maximum speed -97kmph

v  Axel arrangement -B0-Bo

v  Weight - 60-70tons

v  Total imported -16 [3]

6)Class M6

v  Built in Germany

v  Imported in 1979

v  Engine type -V12 two stroke diesel

v  Power output-1650 hp

v  Maximum speed -90kmph

v  Axel arrangement A1A-A1A

v  Weight-60-70tons

v  Total imported -16 [3]

7)Class M7

v  Built in Britain

v  Imported in 1981

v  Engine type -V8 two Strokes

v  Power output-994hp

v  Weight -66tons

v  Maximum speed -80kmph

v  Axel Arrangement -Bo-Bo

v  Total imported- 16 [3]

8)Class M8

v  Built in India

v  Sub classes -M8A

v  Imported in 1996 and 2001(m8a)

v  Engine type -M8(V16) ,M8A(V12)

v  Power output- 2800hp(M8)  ,2200hp(M8A)

v  Maximum speed- 120kmph

v  Axel arrangements -Co-Co

v  Weight -112 tons

v  Total imported -10 [3]

9)Class M9

v  Built in France

v  Imported in 2000

v  Engine type -V12 4 stroke

v  Power output -3200 hp

v  Maximum speed-110kmph

v  Axel arrangement -C0-C0

v  Weight -100 tons

v  Total imported- 10 [3]

10)Class M10

v  Built in India

v  Sub classes - M10A

v  Imported in 2012

v  Engine type- V12 four strokes

v  Power output -2300hp

v  Maximum speed -120kmph

v  Axel arrangement - Co-Co

v  Weight- 117tons

v  Total imported -9 [3]

11)Class M11

v  Built in India

v  Imported in in 2018-19

v  Engine type -EMD 12-710G 3C

v  Power output -3000hp

v  Maximum speed -120kmph

v  Axel arrangement- Co-Co

v  Weight -130tons

v  Total imported -10 [3]

DIESEL ELECTRIC DMUS

1. Class S9

v  Built in China

v  Imported in 2000.

v  Engine Type -V12

v  Power output -1580hp

v  Maximum speed -100kmph

v  Weight -73 tons

v  Axel Arrangement -B-B

v  Total imported -15sets [3]

2. Class S10

v  Built in China

v  Imported in 2008

v  Engine type MTU V12 4000R41

v  Power output-1950hp

v  Maximum speed 100kmph

v  Axel arrangement -Bo-Bo

v  Weight- 76tons

v  Total imported -15sets [3]

3. Class S11

v  Built in India

v  Imported in 2011

v  Engine type -KTA50L V16-EFI

v  Power output -1350-1800 hp

v  Maximum speed-110kmph

v  Axel arrangement -Bo-Bo

v  Weight- 100tons

v  Total imported-20sets [3]

4. Class S12

v   Built in China

v  Imported in 2012

v  Engine type -MTU V12 4000R1

v  Power output -1950hp

v  Maximum speed-100kmph

v  Axel arrangement -Bo-Bo

v  Weight- 76tons

v  Total imported-13sets [3]

5. Class S13

v  Built in India

v  Imported in 2018-19

v  Power output -1800hp

v  Maximum speed-120kmph

v  Axel arrangement -Bo-Bo

v  Weight- 76tons

v  Total imported - 5sets [3]

6.Class S14

v  Built in China

v  Imported in 2019

v  Power output -1950hp

v  Maximum speed-120kmph

v  Axel arrangement -Bo-Bo

v  Weight- 74tons

v  Total imported-4sets [3]

7.Class S14a

Imported to carry garbage from Colombo to Aruwakkaru.

DIESEL HYDRAULIC LOCOMOTIVES

There are only few diesel hydraulic locomotives in Sri Lanka. Class W and Class S1 to S8 DMU locomotives have this type transmission method. 

Figure: Parts & Flowchart of Diesel Hydraulic locomotives(http://ceylonrailway.com/technical-info)

The main parts are as follows.

v Fuel tank

v Diesel engine

v Radiator

v Torque converter

v Gear Box.

       

Usually RPM value of locomotive engines is lower than car engines. Accordingly, today the engine RPM varies from 60-100 RPM for large capacity engines to 20,000 RPM for racing car engines. The power to weight ratio in kg/kW varies from 0.4 to 55 kg/kW for slow speed engines. [4] If typical car engine gear system is applied, about 10-15 gears are required to operate a train. Therefore, typical car engines’ gear system is not applicable for locomotive engines. In order to solve this problem Torque converter is applied as a unique component. But when the torque is increased speed get decreased. As a solution, this type of locomotives uses higher RPM than other types and it is around 1500.Torque converter serves a vital component in the processes of engine.

As electric engine, diesel is injected to combustion chamber from fuel tank. During combustion, drive shaft begins to rotate. This shaft is connected to Gear box through Torque converter which is a modified fluid coupling system. This fluid couple consist of two components. [5]

Figure: Hydraulic torque converter (www.railmotorsociety.org.)

1.    An impeller or a pump connect to the engine and it rotates with the engine.

2.    A turbine connected to the gear box.

These two consist of two rotors which are placed close to each other and the space between fans is filled with special oil. When the engine rotates impeller also get rotated. But it’s not possible to transfer more power in this method because torque doesn’t rise over certain value and therefore output power is restricted. But a special component in torque converter which is called “stator” rectifies this error. stator is located between turbine and impeller ad main task of it is to change the direction of oil after hitting the turbine. In this process stator increases the torque while it is keeping stationarity. As a result the power output is increased. Usually there are two torque converters in diesel hydraulic locomotives. Then the resultant power is transmitted to gear box. The throttle of this locomotive has 8 notches. When the driver changes the notch gearbox work accordingly and rotates the wheel of locomotive with required power.

Figure: Control in a locomotive

                                

The dynamic breaks of these locomotives are also called as hydrodynamic brakes. The resistive force for the wheels is produced by the breaking energy heating the hydraulic fluid.

ADVANTAGES

v  Higher acceleration

v  Higher power efficiency

v  Less wheel slips

v  Possible to drive in the flooded conditions

DISADVANTAGES

v  Higher maintain cost

v  Wearing of parts is higher

v  Availability of spare parts is low

Diesel Hydraulic Locomotive Engines

1) Class W Engines

About 45 of Class w1 engines were imported in 1968 from Germany. And after serving about 20 years they were retired due to high wearing and less availability of spare parts.

In 1970 Class w2 Engines were imported and most of them are out of service now.

A new locomotive was built in Sri Lanka using the parts of w1 locomotives in 1977.and they were categorized as Class w3. Most of them are still in service.

Class w locomotives

                     

2) DMUs

Class s locomotives up to S8 is categorized in this group. But now only S8 DMU is in service.

Class S6

Class S7 

      

Class S5

  

    Class S8

v  Built in Japan (Hitachi +Hyundai (South Kore))

v  Imported in 1989

v  Engine type -MTU V12

v  Maximum Speed -88kmph

v  Axel arrangement - B-B

v  Weight -70 tons

v  Total imported -20 sets

DIESEL MECHANICAL LOCOMOTIVES

This transmission system is not used for high power locomotives. This transmission is used for small engines such as shunting locomotives. The main reason for them not being used in heavy locomotives is if the power supplied from the engine is directly connected to gear box, both engine and gear box can be severely damaged due to the large inertial force. Like other transmission methods, fuel combustion in chamber powers the shaft connected to gear box. This is done through a fluid coupling method which act as a hydraulic clutch. Then the mechanical energy output from the gear box is used to rotate the wheels. The power transmitted is quite smaller than other locomotives as they are in the range of 300 to 500 horsepower while on other locomotives it is in the range of 1000-3000.

                   

A shunter (class G and Y)

                         

FUTURE OF SRI LANKA RAILWAY AND LOCOMOTIVES

After initiating the railway service in 1864, gradually it has passed several milestones on the way. But we are still quite behind in railway technology and facilities compared to many developed countries. As young blooming engineers our prime task is to develop these technologies and facilities in order to make these transportation modes more upgraded. [6]

                                              

                                                       

S.G.S.S DE JAYATHUNGA

UNIVERTSITY OF SRI JAYAWARDENAPURA

DEPARTMENT OF CIVIL ENGINEERING

References

[1]	"Railway Network in Sri Lanka," February 2014. [Online]. Available: http://www.srilankatravelnotes.com. [Accessed 12 April 2020].
[2]	"Types of locomotives," May 2018. [Online]. Available: http://ceylonrailway.com. [Accessed 12 April 2020].
[3]	SLRF Staff, "Class M2 - Sri Lanka Railway Forum," 22 September 2019. [Online]. Available: https://slrailwayforum.com. [Accessed 12 April 2020].
[4]	S. D. Mane, "Technologies adopted in Diesel Locomotive Engines over Indian Railways," January 2016. [Online]. Available: https://www.researchgate.net. [Accessed 17 April 2020].
[5]	"The Hydraulic Torque Converter," [Online]. Available: http://www.railmotorsociety.. [Accessed 12 April 2020].
[6]	S. A. Jayasekera, "Megapolis Development Ministry's Light Railway System JICA to provide US$ 1.7 billion," Mirror Citizen, vol. 7, no. 3, p. 573, 2018.