Testing Machines and Systemsfor the Aerospace Industry

Intelligent Testing

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Testing Systems

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Fig. 1: Zwick Roell AG and Zwick GmbH & Co. KG: Administration Building, Ulm, Germany

These companies have comprisedthe Zwick Roell Group since 1992.July 2001 saw the group become acorporation under the name ofZwick Roell AG, incorporating Zwick,Toni Technik and Indentec Ltd.Between them these companiesprovide a comprehensive materials,construction materials and functiontesting program – from manuallyoperated hardness testing instru-ments to complex systems forprocess-parallel applications. AcmelLabo, the French manufacturer oflaboratory instruments for thecement, lime and plaster industry,has been part of the group sinceMay 2002.

Zwick Roell AG’s expertise in sensortechnology for load and extensionmeasurement was enhanced andconsolidated by the acquisition ofGerman company GTM in 2007 andMessphysik of Austria in 2006.

Zwick’s years of accumulatedexperience are reinforced by a policyof maintaining regular contact withour many customers. This provides asolid platform from which thecompany supplies a wide range ofproducts – from economicalstandard machines to customizedversions for specialized testingsituations. State-of-the-art engi-neering, powerful electronics andapplication-orientated software arethe keynote of these modern, versa-tile, highly intelligent testingmachines and systems.

Zwick Roell AG is far more than justa manufacturer, however. As longago as 1994 the company receivedDIN EN ISO 9001 certification - aguarantee of consistently high prod-uct and service quality. In addition,accredited calibration laboratoriesallow companies in the Group toinspect and calibrate test equipmentand provide internationally recog-nized certification.

1 Zwick Roell AG – Over aCentury of Experience inMaterials Testing

Mechanical testing is one of theoldest forms of materials testing. DaVinci and Galileo were alreadyturning their attention to bendingstrain and the elastic properties ofmaterials in the 15th and 16th cen-turies. Time brought new insights,culminating in the appearance of thefirst testing machines in 18th-centuryFrance.

Roell & Korthaus have been involvedin materials testing since 1920, whileZwick began building machines andinstruments for mechanical materialstesting in 1937. Many years earlier,in 1876, Professor Seger hadestablished a chemical laboratoryproviding scientific advice on acommercial basis to the stoneindustry. During the 20th century thisevolved into the present-dayconcern Toni Technik, leadingspecialists in the field of constructionmaterials testing systems.

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2 Faster and moreReliable Test Results forthe Aerospace Industry

Don't take Chances with Safetyand Reliability

With few exceptions no otherindustry focuses more on quality andsafety than the aerospace industry.Dramatic improvements in airplaneconstruction, including new materialsand components, are pushing thetechnical boundaries in order toachieve greater fuel efficiency andmeet environmental challenges.

This is why companies turn to Zwickfor materials and component testingproducts. Together with the industryin general, Zwick’s focus on safety,and reliability of testing equipmenthelps to make sure that productsare safe. Whether at the forefront ofmaterials research within universitiesand institutes or integrated into thequality assurance / productioncontrol process you will always findZwick products in organizations thatare serious about the quality andsafety of their products.

Allround-Line SupportsMaterials Development

Around the world great effort is beingapplied to research and develop-ment of new material technologiesespecially lightweight, or intelligentmaterials. Allround-Line testing sys-tems use state-of-the-art standardcomponents in a highly flexiblemodular concept and enable Zwickto work closely with Academiaaddressing growing demands espe-cially in relation to new develop-ments in materials and componentdesign, testing and associated dataanalysis. Precision load frames andmeasurement and control

electronics testControl are designedand manufactured in Germany. Allour product development teams areon the same campus resulting inefficient communication across thecomplete product portfolio andresulting in fast response to custom-ers’ specific support requirements.

Zwick’s testXpert® software withmore than 15,000 copies in useworldwide is the global benchmarkfor materials testing, and operateswith virtually all Zwick products.This improves operator safety andreduces training and support costs inthe long term.

Quality First with ProLine

For quality assurance testing acomplete range of ProLine testingsystems offer superb value formoney for laboratories carrying outroutine testing, but still using coreZwick technology for high accuracymeasurement and control.

High Productivity, Perfomance,and Cost Savings

The roboTest robotic range of testingsystems are ideal for testing appli-cations where speed, low cost oftesting per specimen, and very highaccuracy and reproducibility is impor-tant. Unattended testing systemsallow you to deploy staff on moreimportant tasks thereby adding valueto your testing process.

Fig. 1: Materials testing machine Allround-Line Z250

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3 Varied Applications forAerospace Industry

Zwick is active in more than 20 dif-ferent industry sectors, and offers awide variety of testing systems tosuit them all. With its own applica-

Testing of Metals

Tensile test Sheet metal testing High-temperature testing Hardness testing

Pendulum impact test Biaxial testing High-speed testing Fracture mechanics

Components• Fasteners (bolted, bonded)• Structures (external, internal)• Interiors• Electronics/Mechatronics• Springs• Landing gear (wheels, brakes)• Engine Parts

Materials• Composites• Metals (alloys, titanium, steel)• Ceramics (exhaust, bearings)• Acrylic, Polycabonate• Polymers

Typical Materials Testing inthe Aerospace Industry

Types of Mechanical Tests• Static Testing*• Fatigue Testing (LCF, HCF)*• Fracture Mechanics (J1C, K1C)• Creep Tests

* Ambient, elevated and low temperature

• Shear Tests• Multi-Axis Testing• High-Speed Testing• Impact Testing (pendulum and drop-weight)• Hardness Testing

Industry Overview

tions laboratory and trained special-ists in all relevant fields, Zwick canprovide sophisticated solutions forany application. Many of the testingapplications used in these sectorswere developed as a result of Zwick’srelationship and collaboration with

Academia and Research organiza-tions. This close cooperation ensuresthat Zwick is actively involved in thelatest developments and is also inpossession of many patents coveringtesting machines, grips, tools andfixtures.

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Testing of Plastics

Tensile test 3-point flexure test Fatigue testing Hardness testing

Impact testing

3-point flexure test Inter laminar shear test

Testing of Component Parts

Spring testing

Drop-weight test High temperature testingFatigue testing

Testing of Composites

Shear test on rivet joint Tensile test on screws Fatigue test onT-specimen

Fatigue testing of chains

Testing of solenoidactuators

Fatigue test on screws Fatigue test onH-specimen

Compression testTensile test

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3.1 Focus on Composites

Mechanical tests on compositematerials and structures are often atime consuming and difficult process.Test results are often operatordependant due to difficulties inhandling, measuring, and aligningthe specimen at temperaturesabove and below ambient. Thetraditional way to measure strainunder these conditions is to attachstrain gages or a clip-on extenso-meter to the specimen which canalso introduce measurement errors.

Robots Improve Consistencyand Increase Throughput

Robotic technology removes manyof these problems. Handling be-comes consistent, test throughput isincreased especially for environmen-tal testing because the specimencan be fed through a small shutterrather than opening the chamberdoor. Automated extensometers canbe used to measure strain, and toeliminate the time needed to attachcontact devices. By using intelligentsoftware the cost per specimen canbe reduced significantly and at thesame time staff can be betteremployed on more important tasks.

Automatic Control ofEnvironmental Conditions

A typical system configuration in-cludes tensile tests at temperaturesranging from -80 ºC to +300 ºC usinga macro sensor arm extensometer.The temperature chamber is con-nected to the computer system andthe temperature can be set inde-pendantly for each specimen orbatch. The test temperature can berecorded and stored with the stressand strain data offering unbeatableease of use and data tracability.

For flexure testing a similarly config-ured system features a flexure testkit with motorized lower supportscontrolled by the test software. Thetemperature chamber operating inthe range from 23 ºC to +300 ºC isalso software controlled.

Fig. 1: Temeperature chamber forcomposite tensile tests

Fig.2: Robotic testing system for automatic flexure tests on composites

Fig. 3: Automatic specimen handling

Fig. 4: Flexure test device

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Drop Weight Test

Drop weight testers are used todetermine the dynamic behavior ofmaterials within a limited speedrange from about 3 m/s. Thefollowing tests can be performedwith the instrumented drop weighttester HIT230F:

• Multiaxial impact tests accordingtoISO 6603-2, ISO 7765-2, andASTM D 3763 at ambient andnonambient conditions.

• Airbus AITM 1- 0010 /6- 2005,Boeing 7260, DIN6556-1, ASTMD7136 / D7136 M, DIN EN 6038

The drop height of 1m allows impactspeeds of up to 4.43 m/s. The plate-type specimens to be tested areheld with a pneumatic clampingdevice and then impacted by aninstrumented tup of standardizeddiameter with hemispherical tupinsert. Depending on the standard,different tups and clamping fixturesare available. During the test theload-time signal is measured. The“forcetravel” signal as well as theenergy consumed during impact canbe calculated from this data by thesoftware.

Compression after Impact

The aerospace industry carries outcompression after impact (CAI) teststo different standards (common onesinclude Airbus Standard AITM 1.0010and Boeing BS 7260) The CAI test,carried out after the impact testdescribed above, is based on arectangular plate in which the ver-tical sides of the specimen aresupported, and a compression loadis applied to the horizontal edges.The compressive strength is reducedas an effect of the delaminationcaused by the impact test.

Compression Tests onComposites

Hydraulic composites compressiontest fixture, HCCF Zwick offers anew and innovative hydraulic com-pression test fixture for testing oflarge numbers of specimen.

Advantages are:• Time saving, resulting from the

improved specimen handlingcompared to traditional Celaneseor ITTRI test fixtures.

• The bending influences during theclamping process are virtuallyeliminated.

• This test fixture complies withvarious test standards as well asdifferent specimen geometries.The test is carried out with refer-ence to the procedures in ISO14126, prEN 2850, DIN 65380 andQVA-Z10-46-38, with the advan-tage that the following specimendimensions can be tested:

Specimen width: 6.35 to 35 mmSpecimen thickness: up to 6.6 mmMax. clamping length: 65 mm eachMax. grip-to-grip separation: up to35 mm

The compression fixture can be usedin shear loading mode, in end loadingmode or in a mixed mode combiningboth.

Fig. 1: Drop-weight tester HIT230F

Fig. 2: Compression after impact test device Fig. 3: Hydraulic composites compressiontest fixture (HCCF)

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Fig. 2: High-temperature flexure test infurnace

3.2 Focus on EnvironmentalTesting

High-Temperature Tests onMetals

In applications such as enginemanufacture, material behavior atelevated temperatures (up to approx.1600 °C) is of vital importance,calling for high-temperature tensiletesting and, to a lesser extent,flexure testing. Zwick’s solutions forthese tests comprise temperature-controlled furnaces, specimenpullrods, high-temperature strainmeasurement and other essentialaccessories for integration into Zwicktesting machines.

Creep Test

There is currently a great deal ofinterest in saving energy and reduc-ing environmentally harmful emis-sions. This is particularly the casewith aircraft turbine blades. Oneapproach to increasing efficiency isto raise operating pressure andtemperature, for which the develop-ment of new, high-temperature-resistant materials is vital. The creeptest is one of the most importantexperiments for describing the high-temperature behavior of materials(standardized in others ASTM E 139and ISO 204 and elsewhere), asproven material properties obtainedover an extended period are essen-tial for the design and operation of“high-temperature” components.

Testing in Hot and ColdConditions

Many types of plastic and compositematerials significantly change theirmechanical properties depending onthe temperature. For some thermo-plastic materials it is known that themodulus value can change about 3to 4 % for 1°K. According to thelongterm use of materials, especiallyin automotive and aerospaceindustries, it is very important toknow the behavior of materials in dif-ferent environmental conditions.

Temperature Chambers

Zwick temperature chambers exhibitthe following characteristics:• Aperture for extensometer sensor

arms on the rear left side (exceptfor chambers without cooling)

• Digital temperature control unitwith display for actual value andset value.

• Illumination inside the chamber• Front door with insulated window• Removable segments for moving

the chamber back withoutremoving the grips

• Insulating and electrical designmeet the CE requirements forsafety

Fig. 1: High-temperature tensile test up to1600° C

Fig. 3: Creep testing machine

Fig. 4: Tensile test in temperature chamberup to -70 °C

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Fig. 3: Biaxial testing machine for metals

3.3 High Capacity Testing

High Capacity Fatigue Tests

Large components and aerostruc-tures for aircraft such as the AirbusA380 can be tested using highcapacity testing systems with ca-pacities up to 2000 kN.

These systems are designed to per-form both quasi-static and fatiguetests on components up to 5 mlong, and typically carry out fatiguetests up to a frequency of 15 Hz.

In order to accommodate a multi-tude of different specimen sizes theupper crosshead can be positionedat any intermediate point and thespecimens can be clamped in paral-lel acting fatigue rated hydraulicgrips.

Mounting of complete assemblies orcomponents is simplified by incorpo-rating a T-slot base crosshead.

Biaxial Tensile Test

The biaxial tensile test is used todetermine the deformationcharacteristics of materials. This testis used primarily for research anddevelopment as it allows definedstress values in the intersection areaof the specimen to be set up andinvestigated.

These testing machines are pro-duced to customers’ requirements.Strain measurement is performedusing non-contact extensometry inmost cases and Zwick providesseveral solutions for this. The mea-surement of strain distribution isavailable via collaboration with Zwick’sspecialist partners

Fig. 1: High capacity fatigue testingmachine HB2000

Fig. 2: Strain gaged specimen undergoing atensile test

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3.4 Focus on Dynamic andFatigue Testing

Fatigue Test on Screws/Bolts

In addition to static loading, fas-teners are generally subjected to fre-quent cyclic loadings, includingvibrations. Fatigue tests on screwsand bolts (and other items) are mostquickly and efficiently performed in aVibrophore, which can apply cyclicloads up to 600 kN in a frequencyrange up to approx. 300 Hz, usinggrips tailor-made for screws/boltsand other fasteners. The magneticdrive which generates controlledresonance in the system (and in thespecimen) requires minimal electricalpower, resulting in highly cost-effective testing.

Fracture Mechanics KIc Deter-mination

Fracture toughness KIc is an impor-tant material property for metallicmaterials in safety-related applica-tions such as aircraft construction,and is determined using a specimeninto which an artificial crack hasbeen introduced. The specimen isloaded until failure and the fracturetoughness KIc is determined from theload-deformation curve and thecrack length. Details of the testprocedure are contained in the rele-vant standard (ASTM E 399) and thetwo-stage test can be performedvery efficiently using ZwickVibrophores (HFP).

Crack formation in the specimen isinstigated by the mechanicallyproduced notch followed by cyclicloading. The high frequency usedallows rapid generation of a definedcrack (‘precracking’) and theprocess is highly reproducible,thanks to the high sensitivity of theresonant frequency to crackformation. The specimen geometrymost frequently used is illustrated inFig. 3; the specimen is known as aCT (Compact Tension) specimen.The load is applied through pinsinserted into holes in the specimen,giving a mixed tensile and flexureloading.

Fatigue Tests with Servo-hydraulic Testing Machines

Material properties for fatiguestrength and fatigue limit as deter-mined in fatigue tests often have asafety-relevant significance in thechoice of material and design ofparts. Specimens are tested undercyclic load conditions and through-zero loading. Zwick can supply, asstandard, fatigue testing machinesup to 600 kN, depending on drivemethod. The largest Zwick servo-hydraulic testing machine currently inuse handles loads up to 5000 kN.

Fig. 2: Fatigue test on bolts/screws

Fig. 1: Vibrophore with high-temperaturefurnace

Fig. 3: CT specimen in Vibrophore (HFP)

Fig. 4: Servo-hydraulic testing machineAmsler HA

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Fig. 2: RKP 450 pendulum impact tester (Inset: anvil)

3.5 Focus on ImpactStrength Testing

Charpy Impact Test

Notched impact strength is animportant characteristic for manyapplications and can be determinedwith Charpy specimens in pendulumimpact testers. EN10045-1 / ISO148 / ASTM E23 specifies the testrequirements, and notched Charpyspecimens can be inserted by hand,simple feeding devices, or fullyrobotic systems and impacted withenergies up to 750 J. If requiredZwick can also supply temperatureconditioning baths for specimen.Under the Machinery Directive,pendulum impact tester operation issubject to very strict safety require-ments, which are met by Zwick’ssafety housing and safety technology.

Charpy specimens are standardizedaccording to EN10045-1 or ASTME23. The Notch Vision systemmeasures the complete specimendimension in 3 to 12 secondswithout touching it offering muchbetter accuracy and reproducibilitythan more traditional systems.Calibration can be performed veryeasily by using a reference speci-mens traceable to InternationalStandards though our DKD, UKAS,COFRAC, A2LA accreditedlaboratories.

High Speed Testing

High-speed testing machines areused especially for high-ratepuncture impact and other materialstests requiring high testing speeds.

Examples of applications:• Instrumented multiaxial impact

tests according to ISO 6603-2 andASTM D 3763

• Determination of tensile propertiesat high strain rates, ISO/DIS 18872

• Instrumented impact tests onsemifinished products andcomponents

Fig. 1: Optical measurement system notchvision

Fig. 3: High-speed testing machineAmsler HTM

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4 Zwick Modular System for Individual Testing Requirements

Materials testingmachines

Sheet metaltesting machines

Torsion testingmachines

Static Testing Machines

Servo-hydraulictesting machines

Vibrophores

Pedulum impacttesters

Drop weighttesters

Dynamic and Fatigue TestingMachines

Hardness testers Vicat testers

Extrusionplastometers

Testing Instruments

Load Cells, Specimen Grips and Extensometers

Load cells Non-contactmeasuring systems

Specimen grips Contact measuringsystems

Temperaturechambers

AutomationHigh-temperaturefurnaces

Specimenpreparation

Individual Testing Solutions

testXpert® testControl

Testing Software / Measurement and Control Electronics

Materials testingmachines with lineardrive

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4.1 Quasi-Static TestingMachines

Quasi-static Allround-LineTesting Systems

The Allround-Line products arespecifically targeted at organizationscarrying out complex testing applica-tions such as in Research andDevelopment on new materials, andcomponents.

As the flagship of the Zwick productrange these systems offer power,flexibility, and virtually limitless pos-sibilities to measure, collect, processand store multichannel test datawith very high accuracy and repro-ducibility. Some of the advantages ofthese products include:

Patented Measurement Tech-nology with Wide MeasuringRanges

• Very wide measuring range forload and extension (which farexceeds the requirements of theInternational Standards) typically0.2 % to 150 % of load cellcapacity and from 25 Hm forhighest accuracy extensometers

• Patented range of ultra high accu-racy – side load resistant load cells

Smart Sensors with Fast DataAcquisition

• Smart sensor technology to recog-nize and calibrate load cell,extensometers and otherconnected sensors. Exceeds therequirements of TEDS (IEEE 1541)

• Automatic logging of sensor data(serial number etc.) for completesensor data traceability

• Digital extensometer strain data isacquired at 10MHz so no testcharacteristics are missed.

Operator Safety

• Zwick’s unique machine environ-ment (limit switches, crossheadposition, grip separation, test area /sensor load limits) are all stored aspart of the test specification – evenwhen the machine is switched off.

• All products fully comply with CEand EMC regulations and haveintegrated safety electronics fordouble interlocked safety shields.

Fig. 1: Allround-Line floor-standing machine Z600

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4.2 Dynamic and FatigueTesting Machines

Servo-hydraulic TestingMachines

Zwick's servo¬hydraulic testingmachines are universally applicablefor materials and component testingunder pulsating or alternating load,with periodic or random signals.Quasistatic and continuous loadingare also easily achieved.

Special Features• Precisely aligned load frames

featuring extremely high stiffness

• Hydrostatic bearings, making theactuators virtually frictionless – andalso wear-free

• Linear variable differential trans-ducer extensometer (LVDT) withhigh resolution and linearity inte-grated centrally in the actuator rod

• Precision strain-gage load-cell formounting on actuator rod or fixingto crosshead as required

• Wide range of hydraulic powerpacks

• Comprehensive range of accesso-ries (specimen grips, extensome-ters, temperature chambers etc.)

Vibrophore with Electro-Magnetic Resonance Drive

Zwick are suppliers of the world-famous Amsler HFP Vibrophore, thefirst version being introduced byAmsler in 1945. It is valued by testlaboratories in the automotive sectorfor its high-level performance andlow operating costs.

Special Features• Minimal energy consumption due

to resonance principle• No hydraulic power pack or other

installation outlay required• Maintenance-free operation• High testing frequencies, short test

times.

Applications• Dynamic tests to define the fatigue

strength of materials, e.g. fatiguetests in accordance with DIN50100 (S/N curve), in tensile, com-pressive, pulsating and alternatingload ranges

• Fatigue strength and durabilitytests on components

• Fracture mechanics tests• Testing under various environ-

mental conditions (temperature,aggressive media)

• Production and quality control ofcomponents exposed to dynamicloading during their service life

Servo-hydraulic Testing Machines (STM) Standard versions1)

Model2) HC HB HA• Type/version table floor floor• Load frame nominal force [kN] 5 – 25 50 – 1000 50 - 500• Test stroke [mm] 100 100/250/400 100/250• Specimen length [mm] 100 – 700 100 – 1100 250 - 1500• Hydraulic power pack

* System pressure [bar] 210/280 210/280 210/280* Feed rate [l/min] 9 – 30 20 – 270 20 – 270

• Motor nominal power [kW] 5 – 20 11 – 160 11 – 160

1) Load frames available with higher rated actuators and different strokes on request2) Testing actuator mounted on upper crosshead of HC and HB frames, base-mounted on

HA frame

Fig. 1: Servo-hydraulic testing machineAmsler HC10

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4.3 testXpert® II – Intelli-gent and Reliable TestingSoftware

With testXpert®, Zwick has becomethe benchmark for intelligent andsophisticated materials testingsoftware used for the most in-depthresearch applications. By usingtestXpert® II customers reap thebenefits of more than 80 years’experience of materials testing andover 15,000 successful testXpert®

installations worldwide.

Some of the functions which haveproved particularly valuable in theaerospace industry are:

ZIMT Integrated MacroLanguageZIMT (Zwick Interpreter for MaterialsTesting) is a flexible programminglanguage which is integrated intotestXpert® II and which gives you ac-cess to all test data and many otherfunctions, making it easy to produceyour own calculations, displays andmacro functions. It provides acompletely open architecture forcustomers who need to create theirown testing sequences and calcu-late their own test results. The ZIMTeditor offers syntax highlighting andcontext sensitive help.

Sequence ProgrammingResearch in particular often calls fora freely programmable testingmachine. testXpert® II’s graphicsequence editor is a very powerfultool, allowing you to easily configuretest sequences using graphicalfunction blocks and based on aflowchart principle.

Statistical EvaluationsAll common statistical values areavailable for evaluation, with anintegrated option for displaying themas a histogram.

Comprehensive Import andExport InterfacesSpecimen data such as test specifi-cation, tolerance data, and otherimportant fields can be read from anexternal database and used todocument or control testXpert® IIfunctions. This reduces typographicalerrors and other time-related activi-ties to a minimum. All data fromtestXpert® can be exported veryeasily via standardized softwareinterfaces to all common windowsapplications. The testing machinecan also be linked to NI LabVIEW.Below is a selection of programmeswith which testXpert® II data can besynchronized:

• LabView• MS Excel, Access, Word• SAP• Oracle• ASCIIFig. 1: testXpert® II with synchronized video

Fig. 2: testXpert® II graphical sequence editor program

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4.4 Zwick testControlMeasurement and ControlElectronics

Measurement and control electronicsare an essential component of anytesting machine. Their design andfeatures determine which drive canbe operated, which measuring sys-tem connected and which functionscontrolled.

Zwick’s powerful testControl mea-surement and control electronicshave up to 10 digital or analog high-resolution inputs available for time-synchronous data acquisition. Anycommonly used analog or digitalsignal can be connected to thesestandard interfaces. All signals areprocessed in real time and trans-mitted to the PC in high resolution at500 Hz.

Many applications require additionalmeasurement signals as well as theusual channels such as force andelongation. testControl offers theflexibility demanded of measuringsystems in such applications,whether for applying additional straingages to a specimen or simulta-neously measuring temperature.

In addition to these direct interfacesto testControl, external measure-ment systems such as the HBMMGCplus can be linked.

This gives the further option ofquarter, half or full-bridge measure-ment of resistances, pressures,temperatures, accelerations, andsingle strain gages etc.

Control Cube

In collaboration with CaTs3

(Consultants in Automated Test andStructural-dynamic Simulation Sys-tems), Zwick provides easy-to-usesoftware, measurement and controlelectronics and data acquisition forsingle and multi-axis servo-hydraulictesting (up to 32 channels).

Fig. 1: Full integration of a HBM MGCplus in testXpert® IISmall picture: Digital I/O box, additional with two output channels

Fig. 2: Analog and digital signals can be connected to testXpert® and testControl

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4.5 Zwick Specimen Grips

Zwick’s comprehensive range ofspecimen grips of various designsand for differing test load ranges andtest temperatures covers a wide fieldof application. The specific applicationrange of a specimen grip is largelydetermined by its operating principleand maximum permitted test load;for tests in a temperature or climaticchamber the temperature range inwhich it can be used is also ofsignificance.

Load Transfer betweenSpecimen and Grips

With most specimens the test loadcan only be transmitted indirectly i.e.by friction. This means that the fric-tional force between the specimenends and the jaws of the specimengrips must always be greater thanthe test load. The gripping forces(perpendicular to the test load) re-quired for this are generated exter-nally (e.g. by pneumatic pressure) orderived mechanically from the testload (self-tightening specimen grips).

Gripping Force

Specimen grips with externallygenerated gripping force apply theset force level throughout the test.Especially with thick or soft speci-mens, however, specimen materialcan flow out of the grips under theinfluence of the test load, reducingthe specimen thickness. Withhydraulic and pneumatic specimengrips the gripping force remainsconstant, because the pressuregenerator supplies more pressurisedoil or compressed air. The grippingforce of screw grips decreases tosome extent depending on thestiffness and resilience of the grips.

Gripping Surfaces

The frictional force depends on boththe magnitude of the gripping forceand the coefficient of friction of thecontact surfaces. For this reasoninterchangeable jaws or jaw insertswith different gripping surfaces(shape, surface structure, materialetc.) are provided for many speci-men grips.

Grip Travel and Opening Width

Specimen grips with externalgripping force generation have longgrip travel and thus a large openingwidth, leaving a large free area forconvenient specimen insertion, evenfor thick specimens, and eliminatingthe need for interchangeable jawsfor different specimen thicknesses.

Fig. 1: Wedge-screw grips Fig. 3: Pneumatic grips

Fig. 2: Hydraulic grips

Fig. 4: High-temperature grips

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4.6 Zwick Extensometers

Measuring elongation and/or strainplaces extremely high demands on amodern testing system. For manyyears Zwick has been leading thefield in developing digital extensom-eters for a wide range of applications.

Today Zwick has the most compre-hensive range of analog and digitalextensometers, both contact andnon-contact. In 1998 Zwick haddeveloped and introduced the worldsfirst digital clip-on extensometer. In2004 the portfolio of extensometerswas extended with the optiXtensand multiXtens.

2007 saw the unveiling of laserXtens,offering high-resolution (down to0.15 µm), contact-free elongationmeasurement without the need toattach gage marks to the specimen.This system makes completely newapplications possible, such as thetesting of small specimens with gagelengths down to 1.5 mm. Thistechnology and heritage allowsZwick to provide the optimumextensometer for every application.

Fig. 1: videoXtens

Fig. 2: multiXtens Fig. 4: Selection process of extensometers

Fig. 3: laserXtens with round specimen

Contact Measurement Systems• multiXtens• Macro extensometer• Long-travel extensometer• Clip-on extensometer

Non-contact Measurement Systems• lightXtens• videoXtens• laserXtens• optiXtens

Extensometer Portfolio

Measuring Priciple,Properties

Functionality(auto / manual)

Environmentalconditions

Purchase,Running Costs,

Ease of Use

Specific Test Application

Comparsion and selection processcriteria (“must have” / “should have”)

Material(component)

Test Method,Standard

EnvironmentalInfluences

Budget

MaterialProperties

Specimen, TestSequence, Test Result

Temperature, Light,Noise

Purchasing,Running Costs

ExtensometerProperties

ExtensometerRequirements

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5 ZwickService

Worldwide Service

Customer satisfaction is a top priorityof the Zwick Roell Corporation. Withlocal service organizations in over 50countries, we help optimize the returnon your investment and to ensure thefunctionality of your testing machine.

We offer you a portfolio of serviceproducts ranging from consultancysupport, product demonstrations,pre-testing, contract testing, instal-lation, calibration and after-salessupport. You can view our completerange services on our website atwww.zwick.com or just contact yourlocal support office.

Specific Calibration for LoadFrame Alignment Accuracy

What is Nadcap?Nadcap program as a part of PRI(Performance Review Institute) wascreated in 1990 by the Society ofAutomotive Engineers and isheadquartered in Warrendale,Pennsylvania. Nadcap’s membershipof “prime contractors” convene tocoordinate industry-wide standardsfor special processes and products.Through the Performance ReviewInstitute, Nadcap providesindependent certification ofmanufacturing processes for theindustry. PRI’s mission is to “provideinternational, unbiased, independentmanufacturing process and productassessments and certificationservices for the purpose of addingvalue, reducing total cost, andfacilitating relationships betweenprimes and suppliers.”

Our Solution for NadcapConformity

In relation to materials testing ma-chines one of the main topics is thatof specimen alignment verification.

To comply with Nadcap requirementsit is necessary to measure and certifythe system alignment according toASTM E1012-05 (Verification of testframe and specimen alignmentunder tensile and compressive axialforce application). This is achieved byusing a special specimen fitted withstrain gages which is placed in thegrips / fixtures and subjected to load.During the verification process anymisalignment of the system must bemeasured and remain withinspecified limits.

The specimen strain gage signal isconditioned and processed using anelectronic signal conditioning systemwhich is connected to a PC soft-ware. In the event that the testingsystem does not meet the requiredspecification it may be necessary toadd a special mechanical alignmentdevice into the load string. Thistogether with the software simplifiesthe labour intensive task of adjustingthe alignment so that it is within thespecified limits.

Zwick’s offers alignment verificationas an option in its portfolio ofCustomer Support Services.

CalibrationZwick's calibration service is accred-ited by DKD1), UKAS2), COFRAC3)

and A2LA4) to DIN EN ISO/IEC 17025for on-site calibration of materialstesting machines. The referencemeasuring equipment used is regu-larly recalibrated. Depending on thecustomer's requirements, either aworks calibration (Zwick calibrationcertificate), ISO calibration (Zwickcertificate with documentationshowing measuring equipment super-vision to ISO9001) or DKD calibration(DKD certificate) is performed.

If necessary, the testing machinesand associated sensors will be ad-justed during calibration.

1) DKD: DeutscherKalibrier-Dienst

2) UKAS: United KingdomAccreditation Service

3) COFRAC: Comité Françaisd´Accréditation

4) A2LA: American Association forLaboratory Accredition

Applications Test Laboratoryand Contract TestingIn the last few years Zwick's appli-cations laboratory has becomecompetence-center of materalstesting withactive scientific exchange.

Overview of Applications:• Quasi-static testing (temeprature

range: -40 °C to +900 °C)• Determining impact strength• Hardness testing• Melt index testing• Component testing• Viscosity testing• Fatigue testing (temeprature

reange: -60 °C to +1200 °C)• Determining cyclic material

behavior (LCF)• Determining fracture mechanical

characteristic values

Fig. 1: Configuration for alignment verification

Zwick Asia Pte Ltd.25 International Business Park#04-17 German CentreSingapore 609916 · SingaporePhone ++65 6 899 5010Fax ++65 6 899 5014www.zwick.com.sginfo@zwick.com.sg

Zwick USA1620 Cobb International BoulevardSuite #1Kennesaw, GA 30152 · USAPhone ++1 770 420 6555Fax ++1 770 420 6333www.zwickusa.cominfo@zwickusa.com

Zwick Testing Machines Ltd.Southern AvenueLeominster, Herefordshire HR6 OQH Great BritainPhone ++44 1568-61 52 01Fax ++44 1568-61 26 26www.zwick.co.uksales.info@zwick.co.uk

Zwick France S.a.r.l.B.P. 45045F-95912 Roissy CDG Cedex FrancePhone ++33 1-48 63 21 40Fax ++33 1-48 63 84 31www.zwick.frinfo@zwick.fr

Zwick Ibérica Equipos de Ensayos S.L.Marcus Porcius, 1Pol. Les Guixeres, s/n Edificio BCIN08915 Badalona (Barcelona) - SpainPhone ++34 934 648 002 Fax ++34 934 648 048www.zwick.escomercial@zwick.es