DESCRIPTION OF THE FAILURE

As always our approach is to propose solution found through understanding the mechanics of failure. A railway vehicle antennae raft is cantilevered the bogie transom by 4 M16 bolts. The bolts had repeatedly failed in service and was considered a severe hazard as a detached raft could in a worst case scenario derail a train and result in loss of life. MoreVision were invited to investigate the failure. The bolt samples were sent to a metallurgical laboratory and examination of the bolt fracture surfaces showed all the characteristics of a fatigue failure. The bolts were renewed every month as a risk mitigation action until the investigation reported its conclusions. MoreVision initially performed bolt fatigue calculations using the loading assumed in the design case. The calculations did not predict a bolt failure so it was suspected that the actual service loads were greater than that assumed for design purposes. Another possibility was that some element in the bolted joint was relaxing giving rise to loss of bolt pretension and a premature fatigue failure.

DESIGN AND CALIBRATION OF STRAIN GAUGE BOLTS

After disappointing performance with commercially available bolt sensors MoreVision devised and produced special test bolts by introducing flats on the shank of the bolts and attaching standard linear gauges (photo on the left). The bolts were calibrated in a laboratory load cell shown in the photo on the right.

BOLT RELAXATION TEST The test bolts were installed on a stationary vehicle in a depot. During installation the load in the bolt was measured as the bolts were torqued up. The bolt force was measured for a number of hours to see if any element in the joint would relax resulting in a significant loss of bolt pretension and premature fatigue failure. The test concluded that relaxation of the joint was within normal acceptable levels and the threat of bolt pretension loss was ruled out.

DYNAMIC 'HAMMER' TEST Whilst the the vehicle was stationary in the depot the antennae raft was struck with a rubber hammer allowing the raft to vibrate. The response was also seen by the bolt sensors. A spectrum analysis of the bolt test signals illuminated the frequencies associated with the natural modes of vibration. Closer examination of the phasing of the time signals showed the fundamental 'springboard' mode directly (see plot on left).

ON-TRACK TESTING

The data acquisition equipment and computer were installed in the drivers cab. A test route of over 200miles was considered representative of normal service. It was even possible for the train to remain in service as the data was acquired which helped the client maintain his train availability and service levels.

POST-PROCESSING OF TEST SIGNALS
1) FILTERING NOISE
When all the train systems were started up in the depot it was noticed that some noise was picked up by the strain gauges. The characteristic of this noise was very high frequency (greater than 500Hz). The hammer test has shown that the predominant structural frequency was less than 50Hz so frequencies of over 200Hz were taken out using software filters.
2) DAMAGE CALCULATION
The filtered signals were the assessed using rainflow counting techniques to reduce the signals to stress histograms. The fatigue life could be calculated from the stress histograms.

CONCLUSION
Local vibrations due to the resonant response of the raft resulted in higher levels of load than was assumed in the design loadcase. This gave rise to a premature bolt fatigue failure.

SOLUTION
MoreVision working together with the depot mechanical engineering team devised an end support bracket for the antennae. MoreVision prepared a finite element analysis justification for the new end support bracket together with revised bolt calculations and the solution was also proven by further on track testing.

MoreVision supply analysis services to the gas industry and have undertaken structural analysis to validate the of design of liquid natural gas (LNG) storage facilities.

Structural Analysis:

The lining of a vast concrete tank is required to provide a vapour barrier for the entire life of the LNG storage facility. Unfortunately concrete shrinks with age and a special cruciform joint was designed by MoreVision so that the lining could accommodate this movement. The analysis required a complex large deflection plastic analysis.

Pipework Stress Analysis:

Stresses in pipes and pipe attachment points are assessed against the requirements of ASME.

Thermal Analysis:

Components are exposed to liquid natural at temperatures down to  -160°C. It was necessary to build thermal models to check the effectiveness of the heat break designs and determine the temperature distribution throughout the tank roof equipment. This was required to ensure that the operational temperature limits of constituent parts are not exceeded or to determine the need for safety guards to protect personnel from extreme heat (or cold).

Typically model includes boundary temperatures, heat fluxes, the relevant conduction properties, convection surface details and radiation surface details.

ANSYS Script Generators

Often a large number of items require assessment and Morevision have developed ANSYS script generators to speed up the process of assessment. Most of the finite element models could be reduced in size by taking benefit of axi-symmetry and the time to complete an analysis was remarkably fast.

Fatigue assessment of rollercoasters.

Bruce's articulated head at Disneyland Paris.

Pinned articulated joint in wagon at Disneyland Paris.

Pinned joints on the London Eye dummy pods.

Building and managing a theme park is clearly focused on visitor safety. MoreVision are often called to assess the strength, fatigue strength and safety of new attractions.

The Hong Kong Disneyland Railroad Vehicles

The Hong Kong Disneyland Railroad vehicles carry guests between attractions on the resort and requires extensive analysis to satisfy the local regulatory bodies. The train comprises a loco, tender vehicle and coaches. Each vehicle has its own bogie and wheelsets and all items of equipment required assessment. Finite element analysis and calculations considered the static strength and the fatigue strength of the railroad vehicles. Analysis covered many combinations of vertical loads (tare to crush), longitudinal loads (braking, vehicle recovery) and transverse loads (curving, wind and slope). MoreVision worked closely with the vehicle manufacturers transferring data via the internet. MoreVision gave further support by assisting in the client design scrutiny process.

Static strength and fatigue strength analysis was required for the Main Street Vintage Vehicles in Disneyland's new Hong Kong Resort. These included a paddy wagon and a double deck omnibus vehicle.

MoreVision have done a great deal of railway bodyshell analysis but analysis for the Theme Park industry is actually more like crane design than railway design. MoreVision prepared calculations for TUV approval using German DIN standards. MoreVision were also required to take the calculations through the client scrutiny process.

      

The picture above shows Disneyland's 'Catastrophe Canyon' ride. A burning petroleum tanker about to falls onto a crowd of onlookers... a job for Superman? No MoreVision! We undertook a loading analysis and a stress and fatigue assessment of the wagon kingpin joint to ensure spectator safety.

Remember when Indiana Jones escaped a band of marauding natives by swimming to his bi-plane floating of a river.  Disney wanted to recreate the feel of the film and bought a identical plane for use in their  'Indiana Jones and the Eye of the Temple' attraction. These planes have a take off speed of 30 miles per hour so the problem given to MoreVision was to stop the plane from taking off in strong winds. We undertook some aerodynamics calculations and designed an anchorage system for the plane.
Pinned hold down connection for Indiana Jones's bi-plane at Tokyo DisneySea.

A market stall cart conceals a giant airbag to break the fall of a stunt man. It was particularly difficult to design a light weight but rigid frame.

Consultancy Projects... Pinned joints in Volvo loader arm. Pinned joints in Claas Tele-handler. Bruce's articulated head at Disneyland Paris. Pinned articulated joint in wagon at Disneyland Paris. Railway rod end investigation. Pinned joints on the London Eye dummy pods. Pinned hold down connection for Indiana Jones's bi-plane at Tokyo DisneySea.

Consultancy Projects - Fatigue Analysis Of Welded structures Finite element stress analysis. Understand fatigue classification of welds. Understand how to select appropriate stress from finite element model for fatigue assessment. Software developed by MoreVision to take benefit from fatigue enhancement methods (like toe grinding, TIG dressing and stress relieving). View fatigue classification directly on finite element model. View damage directly on finite element model. Export results to spreadsheet for detailed analysis and verification. Fatigue assessment of rollercoasters. Fatigue assessment of railway bodyshells and running gear.

Our Consultancy Projects - Random Vibration Analysis Shock loads to meet IEC61373 (category 1 class A). Vibration levels to meet IEC61373 (category 1 class A). Finite element model. Frequency assessment. Calculation of Acceleration Spectral Densities (ASD) Bolt assessment. Eurocode 3 fatigue assessment. View fatigue classification directly on finite element model. Shake table testing and analysis verification.

Related Consultancy Work Strength of composite railway vehicle partitions. Testing of composite panels (see video). Tram way composite floor study. Composite panel construction for toilet module. Dynamic analysis of composite structure. Rod end investigation. Thread SCF study Key slot fatigue study

Assessment of the interior of a railway vehicle is required to ensure the safety of passengers, particularly in a crash situation. MoreVision have extensive experience in supplying these calculations in particular for the refurbishment of London Underground's 73 tube stock (shown opposite) and the refurbishment of the Stansted Express. In addition MoreVision supports equipment suppliers in the preparation of calculations for new vehicles.

MoreVision has expertise in the analysis of composite honeycomb panel structures. These lightweight materials are commonly used for galley areas, toilet modules, doors and partitions.

The animation opposite shows the first mode of vibration of a ceiling hung steam oven unit made from honeycomb panels (shown transparently to view mounting brackets and body structure). The steam ovens were very heavy and our client was not only concerned about the strength of the honeycomb panels but also the strength of the body structure. Resilient mounting brackets were included to isolate the unit from high frequency vibrations to reduce noise levels in the galley.

Interior Doors, Partitions and Luggage Stacks. The picture opposite shows a finite element model of a full wall partition with a central door and two luggage stacks. It is constructed from composite honeycomb material, glass, aluminium and steel. The assembly included a number of bolted and riveted joints. The model was used for a static strength and fatigue strength check.

Another relatively simple analysis but the strength of the table could be very important in a crash situation

Toilet modules will contain walls, doors and various pieces of equipment that each require assessment.

Given our experience in structural calculations for the railway industry the class 222 project team asked MoreVision to head up the structural design validation process and support them through the Vehicle Acceptance Body design scrutiny process. The whole project involved the co-ordination of project engineers and subcontractor organisations to produce 75 document packages covering the vehicle interior and externally mounted equipment. Initially a guidance document was written and sample documents circulated so that subcontractor has a clear idea of what was required. As documents were supplied an audit process was established which raised over 500 scrutiny comments. Each comment was closed out individually and the document package was submitted to the Vehicle Acceptance Body. The activity was controlled using a database system and reported to the project director on a month by month basis until all documents had been accepted. Typically we would spend one day every fortnight at the clients premises in Belgium to report progress and discuss issues with each system engineer.

It is always late on Friday afternoons when something fails, or something is manufactured incorrectly, or some accident happens. We can't tell you why it is always Friday afternoon but at MoreVision we are well practised at working into the weekend to ensure that a situation is made safe in the short term and if necessary devise plans to ensure that a long term solution. Some cracks were found in the corner of a cross tube which the materials lab had said were formed during the manufacturing process. The cross tubes had been used in a whole fleet of bodyshells and it was necessary to demonstrate to the client that crack growth could not take place when the bodyshells were in service. MoreVision determined the stress levels in the cross tube from the global bodyshell finite element model, then used sub-modelling techniques to determine a detailed stress analysis of the cross tubes. MoreVision's Fracture Mechanics Software was then used to show that there was no danger of the cracks growing in the structure.