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Centrotecnica

Thermal Barriers

December 10, 2014DevUncategorized

OVERVIEW
Many vibration tests have to be performed with a shaker combined with a climatic chamber that performs at the same time thermal and humidity cycles on the items.
During these tests the shaker must be protected against moisture and the item should be thermally thermally from the shaker armature.
In order to achieve this aim, a thermal barrier between items and shaker has to be used.

APPLICATION
Apart from the thermal insulation capability, the thermal barrier should be rigid and stiff to allow vibration transmission to the items. To achieve this target thermal barriers are usually made out of fibreglass materials.
Centrotecnica supplies a wide range of thermal barriers both for horizontal and vertical axis with the possibility to fix a sealing flexible textile to the thermal barrier.

Fixtures

December 10, 2014DevUncategorized

WHAT IS?
The items to be tested should be held during the test in the same position and configuration present on their standard installation. Vibration should be transmitted to the item in the same quantity from any fixation point of the item.

The structures that connect the item held in the proper test position and the shaker armature are called Fixtures.

APPLICATION
The fixture is usually customized on the item dimension and shape, but a custom fixture can also be mounted on a standard fixture like and expander or a prism.
Standard fixtures are general purpose items that are part of the facilities of a vibration test laboratory. The most common one is the expander.

The fixture should be studied to be as light as possible to use less force as possible from the shaker to be vibrated, but must be as rigid as possible in the test frequency range.
Any resonance of the fixture present in the frequency range can alter the test results and cause non reproducible tests.

Extenders

December 10, 2014Andrea CambiaghiUncategorized

OVERVIEW
Many vibration tests have to be performed with a shaker combined with a climatic chamber that in the same time performs thermal and humidity cycles on the items.
The items should be mounted inside the chamber while the shaker remains outside. Sometimes the floor of the chamber is very thick and, in order to achieve this target, the armature should be reproduced inside the chamber by way of an extender.
The extender is a cylindrical fixture mounted on the shaker armature that reproduces the shaker armature inside the chamber.

APPLICATION
The height is the main feature or the extender and is required by chamber manufacturer to match shaker and chamber heights.
The extender should be studied to be as light as possible because the mass of the extender reduces the force of the shaker that can be used to vibrate items.
The extender should also be rigid enough to not alter vibration in shaker frequency range.

MAIN ADVANTAGES
The extender represents an optimal protection for the shaker from moisture compared to the use of the thermal barrier alone, but the weight of the extender usually is considered just an un-useful mass to be carried during vibration test.

Expanders

December 10, 2014Andrea CambiaghiUncategorized

OVERVIEW
An expander is a standard accessory for a shaker studied to enlarge the useful dimensions of the armature.

APPLICATION
The shaker armature has a limited round dimension that do not allow vibration test of large items. To install large items on the shaker a round or square expander is needed. The expander is similar to a pyramid or cone and is studied and optimized to be light and rigid.
When the item to be tested is very large and heavy maximum static load and momentum of the shaker can be overrun. In this case the expander can have an additional load support and guidance system to prevent damages to the shaker.

MAIN ADVANTAGES
Centrotecnica’s Expanders are optimized by FEM analysis and tested before delivery. The expanders are supplied with a complete technical report and operating manual that explains the best method to control the expander during vibration.
All our expanders have a very effective damping treatment aimed at reducing unwanted resonances effects at high frequency.

Fixtures

January 20, 2014DevUncategorized

WHAT IS?
The items to be tested should be held during the test in the same position and configuration present on their standard installation. Vibration should be transmitted to the item in the same quantity from any fixation point of the item.

The structures that connect the item held in the proper test position and the shaker armature are called Fixtures.

APPLICATION
The fixture is usually customized on the item dimension and shape, but a custom fixture can also be mounted on a standard fixture like and expander or a prism.
Standard fixtures are general purpose items that are part of the facilities of a vibration test laboratory. The most common one is the expander.

The fixture should be studied to be as light as possible to use less force as possible from the shaker to be vibrated, but must be as rigid as possible in the test frequency range.
Any resonance of the fixture present in the frequency range can alter the test results and cause non reproducible tests.

Resonant Fixtures

October 11, 2012Andrea CambiaghiUncategorized

 

OVERVIEW
A fixture studied with an intentional resonance between shaker and item is called “resonance fixture” and it is usually designed in order to achieve a very high vibration level.

APPLICATION
When the test to be performed presents a very high level in a restricted frequency range the only factual method to achieve the required level may be represented by the use of a resonant firxture.
The item is mounted in a resonant part of the fixture tuned to resonate at the frequency of interest. The amplification factor of the resonance fixture allows to achieve easily vibration level of hundreds of g.

MAIN ADVANTAGES
The use of a resonant fixture can save a lot of energy and prevents shaker damages. Many times it is the only way to achieve the required test level.

Triaxial Fixtures

October 11, 2012Andrea CambiaghiUncategorized

OVERVIEW
A three-axial fixture rotates the item in a particular direction to obtain the vibration components to be present along the three orthogonal axes of the items.

APPLICATION
When the test to be performed is of sinusoidal type and has to be repeated along the three axis, it is possible to apply the three vibrations at the same time.
The addition of the three vibration vectors together will lead to an higher vibration in one direction.
This allows the test to be executed on the three axis at the same time by increasing the vibration level and orienting the item along the resultant vector.

MAIN ADVANTAGES
The use of a triaxial fixture speeds up the test reducing to 1/3 the total test time. With many items the vibration applied at the same time along different axis better highlights weakness of the item to vibration.

Custom Fixtures

October 11, 2012Andrea CambiaghiUncategorized

OVERVIEW
The items to be tested should be held during the test in the same position and configuration of their standard installation. Vibration should be transmitted to the item in the same quantity from any fixation point of the item.
The structures that connect the item held in the proper test position and the shaker armature are called Fixtures.
When the fixture is studied for a particular item, it is called custom fixture.

APPLICATION
Automotive and aerospace field, where the fixation of the item is critical and usually complicated, are among those fileds where a custom fixture is necessary to perform vibration tests.
Usually the custom fixture can be used along the three mutual axes by rotating it or by the use of a slip-table.
It is designed starting from item fixation points and optimized by FEM analysis to achieve the minimum weight and maximum frequency range. Before delivery, the fixture is checked on dimensions and mechanical behavior.
Any custom fixture is supplied with technical report and user manual that describes the dynamical behavior and the use of the fixture.

MAIN ADVANTAGES
A customized fixture could appear as a very expensive solution, but the assurance to perform the test correctly from the fixture point of view usually could be a great saving of time, problems and money.
Also the possibility to study the fixture to mount many items at the same time will save a lot of testing time and cost.

Thermal Barriers

October 11, 2012Andrea CambiaghiUncategorized

OVERVIEW
Many vibration tests have to be performed with a shaker combined with a climatic chamber that performs at the same time thermal and humidity cycles on the items.
During these tests the shaker must be protected against moisture and the item should be thermally thermally from the shaker armature.
In order to achieve this aim, a thermal barrier between items and shaker has to be used.

APPLICATION
Apart from the thermal insulation capability, the thermal barrier should be rigid and stiff to allow vibration transmission to the items. To achieve this target thermal barriers are usually made out of fibreglass materials.
Centrotecnica supplies a wide range of thermal barriers both for horizontal and vertical axis with the possibility to fix a sealing flexible textile to the thermal barrier.

Extenders

October 11, 2012Andrea CambiaghiUncategorized

OVERVIEW
Many vibration tests have to be performed with a shaker combined with a climatic chamber that in the same time performs thermal and humidity cycles on the items.
The items should be mounted inside the chamber while the shaker remains outside. Sometimes the floor of the chamber is very thick and, in order to achieve this target, the armature should be reproduced inside the chamber by way of an extender.
The extender is a cylindrical fixture mounted on the shaker armature that reproduces the shaker armature inside the chamber.

APPLICATION
The height is the main feature or the extender and is required by chamber manufacturer to match shaker and chamber heights.
The extender should be studied to be as light as possible because the mass of the extender reduces the force of the shaker that can be used to vibrate items.
The extender should also be rigid enough to not alter vibration in shaker frequency range.

MAIN ADVANTAGES
The extender represents an optimal protection for the shaker from moisture compared to the use of the thermal barrier alone, but the weight of the extender usually is considered just an un-useful mass to be carried during vibration test.

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