A structural integrity assessment
of the bolting on a sprocket of a military vehicle. In-service
reports of a loosening problem on the bolting were investigated
and an explanation was provided, based upon a joint analysis,
of the root cause of the problem. Based upon the analysis,
proposals were made on how the loosening could be resolved.
Fatigue failures had been experienced on fasteners that secure
vibrator motor drives in an asphalt mixing plant. The vibrator
motors have balance weights attached to them that generate
motion to drive a screen that segregates stones. The vibration
is extreme and the fasteners have to hold the motors in place.
Based upon a joint analysis the root cause of the fatigue
problem was established and proposals submitted so that the
issue could be resolved.
An investigation was completed on the effect of the tapping
drill diameter and thread engagement length on machine tools.
There are manufacturing advantages in having a large tapping
hole in that the holes can be tapped faster with a reduced
risk of tap breakage. For the particular application the tapping
hole diameter was optimised so that the required thread stripping
strength was achieved.
An investigation was completed on the root cause of a loosening
problem on bolts securing rail track to a bridge structure.
Based upon reference to published research and joint calculations
that were completed, proposals were submitted on how the problem
could be resolved.
A structural integrity assessment was completed on a high
volume medical trolley in which bolt fatigue failures sporadically
occurred. The work involved the completion of a joint analysis
coupled with torque-tension tests to establish the appropriate
tightening torque and investigate joint relaxation (which
was found to be a significant contributory factor). Proposals
were made in ways the joint could be improved to be more fatigue
and relaxation resistant.
Thread stripping strength calculations on tapped holes in
an axle to investigate occasional problems experienced in
this regard. Recommendations were made on how the problem
could be resolved.
A structural integrity assessment of bolting on a magnetic
relay. Preload loss of the fixing screws it was found was
caused by differing thermal expansion rates of the materials
comprising the joint and embedding loss within the laminations.
A series of proposals were made to resolve the problem that
included optimising the tightening torque and changes to the
design so that it was more resilient to the forces that it
A manufacturing process specification was completed for a
major aerospace manufacturer on the installation and inspection
of fasteners. The work included written details of how fasteners
should be installed, tightened and inspected. This included
torque recommendations and how residual torque measurements
should be completed.
A structural integrity assessment was completed on a joint
that secured a winch to a ship’s deck. Forces acting
on the individual bolts were computed and a detailed joint
analysis completed. Recommendations as to the number, size
and strength of bolts that were needed were provided together
with details of how they should be tightened.
A root cause investigation was completed on why securing
bolts were occasionally failing on the brake disk of a locomotive.
An assessment was completed of previous investigations and
potential flaws in the previous analyses. Based on an analysis
recommendations were made on how the failures could be eliminated.
A structural assessment was completed on a cable protector
assembly. A number of concerns with the design were revealed
that included a thread stripping issue. Recommendations were
made on how design changes could be implemented that would
structurally improve the product.
A joint analysis was completed on a piston rod of a hydraulic
cylinder. The purpose of the calculations was to check if
the thread size used was capable of sustaining the applied
forces and providing an adequate fatigue life. Based upon
the calculations, it was determined that the fatigue would
occur in the thread prior to the required life being achieved.
Design changes were proposed to allow an improvement in fatigue
life to be achieved.
An investigation was completed into the cause of the detachment
of the hook from a 25 tonne crane. The root cause of the incident
was established and recommendations made on how the occurrence
could be prevented in the future.
An investigation was completed into the cause of nuts self-loosening
in the roofing structure of a building. The root cause was
investigated and solutions proposed.
A structural integrity assessment was completed on the key
joints comprising a piling hammer. The joints sustain extreme
shock loading. Proposals were made that included the fastener
design that was more resilient to shock loading together with
tightening procedures and maintenance recommendations.
An investigation into the cause of a joint failure of a control
arm to the hub and sub frame of a passenger car. A joint analysis
and examination of the failed parts allowed the root cause
to be established.
An investigation into why preload loss was occurring on used
to secure brackets to the primary lining bolts in the tunnel.
The investigation involved inspection and torque audit measurements
completed on the bolts installed in the tunnel. Laboratory
tests were also completed to determine the torque-tension
relationship and longer term tests to investigate the relaxation
A stud that secures a punch head to the punch on an aluminium
can extrusion machine was occasionally failing resulting in
damage to parts and a loss of production. An investigation
into the problem was completed to establish the probable cause
of the failures and potential solutions.
Problems were being experienced with the seizure of nuts
onto bolts having a polyamide coating on the thread. The seizures
appeared to be from galling but a detailed examination and
measurements revealed that the root cause was a thread tolerance
An investigation was completed into the structural integrity
of M20 bolts used in a critical joint on a train. The work
involved laboratory test measurements to establish the torque-tension
relationship for the bolts and an assessment of the required
torque required to meet service loadings.
An investigation was completed into the causes of loose nuts
on the wheels of buses. Based upon this the likely causes
were established and recommendations made on how the problem
could be eradicated.
An analysis was completed of the failure of a M140 bolt due
to thread stripping. The investigation involved the determination
of the theoretical thread stripping force and recommendations
on how the design could be improved to prevent further failures.
An investigation was completed to determine the torque value
for a M64 studbolt. Based upon an investigation a bolt had
failed on an installation by what is thought to be due to
hydrogen embrittlement. The optimum torque value was established
and recommendations made on how the scatter in the preload
could be minimised.
An investigation was completed into the cause of a bolt loosening
problem on a turbocharger. The particular turbocharger application
was subject to high levels of vibration and thermal cycling.
Stress relaxation and embedding loss were factors in the problem.
Based upon the investigation changes to the bolt material,
specifying a tightening procedure and the introduction of
other design changes were proposed to overcome the problem.
A large sleeve and capnut with a M100 x 2 thread experienced
a stripping failure. Calculations were completed to determine
theoretically the failure load. Recommendations were submitted
on how the problem could be prevented from occurring in the
A review was completed into work that was proposed to prevent
further instances of a leak on a large bolted flange at a
nuclear power station. The proposals made involved how residual
torque measurements should be completed to allow a more accurate
preload assessment to be completed.
investigation was completed into the causes of the loosening
and failure of a bolted joint on a turbocharger. The root
cause of the loosening was established and appropriate recommendations
made on how the problem could be resolved.