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World Coal
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June 2015
(equivalent to the weight of more than
210 minivans), it is 8.3 m high and 15.7 m
long, runs on a set of six 4 m tyres and is
powered by a 3750 hp diesel engine.
“It’s like driving a two-story house,”
according to Dr Vladimir Pokras,
manager of Liebherr mining equipment
analysis and simulation.
One of the primary requirements
when designing these giant machines is
that total vehicle weight cannot exceed
tyre capacity. Every kilogram shaved
from the vehicle structure can be added
to the payload.
Tyre wear is also minimised by the
kinematics of the Liebherr dual-parallel
control-arm arrangement and by a
differential-wheel control system that
automatically adjusts the torque and
speed of the traction motors when
turning.
The engineering challenge is
integrating advanced features, such as
the differential-wheel control system,
into a lightweight truck strong enough to
withstand the mining operating
conditions. As one could imagine, this is
no easy feat.
For example, the
PT Kaltim Prima Coal mine in Indonesia
is situated one degree north of the
equator in a remote rainforest, where
hip-deep mud is common. This mine
relies on more than 30 Liebherr trucks to
get the job done. Likewise, Liebherr
trucks are being used to mine gold in
Nevada, copper in Chile, coal in
Australia and iron ore in South Africa
and Brazil.
Trucks are also put to work traversing
layers of clay and waterlogged peat – a
cushioned terrain that is described as
“like driving on a mattress” – to mine
oilsands in northern Canada. At least
1.7 trillion bbl of petroleum are estimated
to be in the Canadian Athabasca
oilsands, where Liebherr trucks are in
increasingly heavy demand.
The critical role of
multibody dynamics
Considering the millions of dollars and
months of work that would go into just
one round of physical testing, Liebherr
relied heavily on engineering analysis to
design the T 282 C to operate efficiently
under such heavy-duty conditions. In
particular, LMS Virtual.Lab™ software
from product lifecycle management
(PLM) specialist Siemens was used to
conduct full-vehicle simulations to study
the truck’s behaviour on various terrain
with a variety of load examples,
including acceleration, braking, turns,
bumps, holes, wash boarding and up
and down steep grades.
To refine the design as early as
possible, multibody simulation models
were created in the conceptual stage by
the analysis and simulation group, and
modified as more information became
available. The initial geometries of major
truck parts and assemblies were
estimated from preliminary solid
models and pieced together as rigid
bodies into a first-pass, full-vehicle
multibody model. Then, loads from a
multibody simulation were generated
for the structural group to perform finite
element analysis (FEA) for computing
stresses on the frame and other
structural components. The mechanical
group re-used these same loads to
design the vehicle hydraulics,
suspensions, the powertrain and other
systems.
A central point for unified
full-vehicle model design
“In this way, LMS Virtual.Lab serves as a
central point, where all the designs of
individual major components and
subsystems come together into a single
unified full-vehicle model,” explained
Pokras.
As component and subsystem
designs proceed, these engineering
groups update their individual-solid
and finite element models. The new
information is imported into the
multibody model, where the analysis
and simulation group can also add
greater detail such as stiffness, damping
and mass properties.
“Links with finite element codes
streamline the iterative process of
updating LMS models,” continued
Pokras. “With the ability to quickly enter
additional details, we can generate new
multibody models much more quickly
and with fewer errors than building
them from scratch each time. The
capability to import finite element
models as flexible bodies in the LMS
multibody solution is critical to accurate
full-vehicle simulation.”
Major structural components
throughout the vehicle, such as the
frame and dump body, are modelled as
flexible bodies to represent crucial
Siemens PLM Software solution enables Liebherr to explore design alternatives with
full vehicle simulation.
