Instron Tensile For Testing Damper Characteristics Engineering Essay

Automotive companies, constituents providers and motorsport squads typically capable dampers to set up based proving. This normally takes the signifier of running a pre-defined figure of rhythms at assorted different velocities for component lastingness ( service life ) proving. In world, proving is performed with a changeless amplitude supplanting across changing frequences ( Instron.co.uk, 2010 ) .

Dampers can be subjected to an drawn-out figure of rhythms ( 1 million for illustration ) at each velocity scope to see if a constituent or stuff fails to run into its required fatigue life ( choice confidence ) . Damper features are monitored throughout at regular intervals, and checked at the terminal of the trial to verify if the specimen is runing to plan.

Equally good as lastingness testing, rig-based damper testing is besides carried out to find muffling features. Either suiting either individual or multiple dampish set-ups ( Figure ) , some trial systems can run a short explosion of high-performing rhythms to mensurate muffling features, or run to the 1000000s of rhythms for lastingness testing ( Mts.com, Damper Test Systems, 2010 ) . Automotive companies will be peculiarly interested in how these features contribute to both sit comfort and handling.

Some systems used can make highly high speeds and forces for exactly mensurating the damping features used in public presentation testing ; as associated with motorsport. But high velocity action is non the exclusive preserve of dampish proving ; low speeds and forces are besides used to accurately mensurate the impact of seal clash and gas charge ( Mts.com, Damper Test Systems, 2010 ) .

Amongst other features, the consequence of hysteresis ( the inclination for otherwise elasticA stuffs to bounce with less force than required to deform them ) in the damper can be looked at. Attempts to ticket melody this consequence on bump and recoil with different shims can be investigated for illustration.

Other utilizations for rig-based damper testing may be to analyze NVH ( Noise, Vibration & A ; Harshness ) . What with the province of “ route furniture ” on the roads today, it is of import that there is no undue noise coming from the damper that may be cranky to the rider. Friction force testing is besides tested every bit good as inactive ( pneumatic ) or dynamic ( hydraulic ) specimen side lading. This can be done on a individual damper or on multi-specimen proving rigs like that shown in Figure.

Figure – 6 specimen dampers at the same time tested ( Mts.com, MTS Landmark Damper Test System, 2008 )

Some package can besides let place dependant gas force rating and temperature-dependent public presentation trials. Indeed a consideration while carry oning dampish lastingness proving in a closed environment is temperature control. Within a rig, the damper does non see the same chilling effects as it would when on the vehicle at velocity. Therefore air chilling fans or H2O jackets are used to command damper runing temperatures ; otherwise constituents may acquire excessively hot and fail.

In add-on path ( motorsport ) or route burden ( automotive ) informations can be inputted into the trial rig as will be explained subsequently. This is good as the public presentation or burden demands can be tailored for the specific undertaking ; before full-vehicle testing takes topographic point. This besides gives the chance for correlativity between path informations and trial rig informations to be compared ( Mts.com, Nissan Motor Case Study, 2008 ) .

Technology Reason

As with about all damper trials, it is peak force values ( in both bump and recoil ) at specific velocities that are required. This point can be thought of as the auto hitting a bump at high velocity ; correlating to a high ( peak ) force experienced. Typically, this value has to run into the given specification ( tolerance set ) in order to go through the standards set out for the trial. Standard force speed, and besides force supplanting, secret plans are normal end products. These are so used to cipher and analyze emphasis and strain on the constituent. The consequence that different bump/rebound and travel scenes have in respects to the force experienced on the portion, are besides investigated.

The consequences of this proving contribute significantly to FEA Validation. Although it can be dearly-won to set-up specific rigs for damper testing, physical testing is more sensitive than CAE entirely which can take to more effectual development determinations ; particularly at an early phase of vehicle development. In an automotive development universe, confirmation utilizing trial rigs contributes to more dependable paradigms built and more efficient proof activity.

This in bend contributes to important decreases in proving clip and money, by foregrounding anomalousnesss antecedently merely found in full vehicle proving on path. This therefore contributes to quality development ; intending higher quality autos for the client at a cheaper monetary value.

( Mts.com, Nissan Motor Case Study, 2008 ) .

For multi-national companies, trial rigs can assist besides correlative trial rig installations and attendant information measurings across different states. Repeatability, a important testing purpose, is besides improved when compared to track or route testing.

INSTRON 8501 Tensile Test Rig

The Instron 8501 servo hydraulic machine is used for proving dampers features within the Motorsport workshop. This machine can supply tensile and compressive tonss at changing rates. This can be used to obtain stress/strain curves in both tenseness and compaction, but more significantly in respects to damper testing, weariness informations when used with a cyclic wave form

( Princeton, n.d. ) ; 10Hz is the maximal frequence the machine can supply under cyclic burden. The trial rig can be seen in Figure along with the “ Buffer box ” digital accountant.

Bed home base

Hydraulic Ram

Safety Lock

Crossheading

Test Specimen ( Damper )

Aligned Columns

Load Cell

Digital Controller ( Buffer box )

Control Box

Manual Control Knobs

Figure – Instron 8501 tensile trial rig. Fast Track 8800 “ Buffer box ” besides seen right

As seen in Figure the machine consists of a bed home base, hydraulic random-access memory, crosshead and burden cell, two aligned columns and a safety lock. The random-access memory located on the bed home base ( at the underside ) is powered by a hydraulic actuator and servo-valve as shown in Figure. The servo-valve is controlled by the digital accountant shown in Figure. A 20L/min pump provides hydraulic fluid maintained at an optimum temperature by a water-cooled heat money changer ( UniversityofSheffield, 2009 ) . The hydraulic pump end product and the amplitude of the actuator gesture find the frequence response of the system. The actuator itself has a maximal velocity of 30cm/s with a entire shot of 150mm ( UniversityofSheffield, 2009 ) .

WIDTH=340

Figure – Servo valve runing gesture of hydraulic random-access memory ( Princeton, n.d. )

The crosshead can evidently be adjusted to an appropriate place for proving assorted specimen sizes and constellations. This placement can be carried out with the assistance of the hydraulic random-access memory by manner of utilizing the control box shown in Figure. The burden cell at the top of the rig is assembled to the crosshead and measures a reaction force rated to 100kN inactive burden or 50kN dynamic burden ( UniversityofSheffield, 2009 ) .

Figure – Control box used to command place of random-access memory

As with any trial, fixtures need to be made to mount the trial specimen between the random-access memory and burden cell. The repair is required to sleep together into a M30 all right LH yarn both top and bottom. Typical fixtures used for clamping dampers to the trial rig can be seen keeping the damper in Figure.

DIGITAL CONTROLLER

The Instron machine relies on a state-of-the-art digital servo hydraulic closed-loop accountant ; the Fast Track 8800. It is besides known as a “ Buffer box ” and can besides be seen in Figure. The Buffer box acts as an interface between the computing machine and trial rig and it contains switches and relays to command the servo-valve triping the random-access memory ( Figure ) .

Three types of motion can be controlled ; place control, burden control and strain control. Inactive and cyclic burden can be created by altering the wave form type ( sine, saw tooth or triangular, square, round ) . All experiment informations is displayed by the digital accountant and can be outputted to any external recording devices ( UniversityofSheffield, 2009 ) .

Software

Two types of package can be used with the Instron rig ;

BLUEHILL package is used for uni-directional testing as it merely measures informations in one manner. Therefore this is the preferable plan for simple stuff tensile and compaction testing

MAX32 is the package used for dampish testing as it can mensurate informations in both waies of rig propulsion doing it ideal for cyclic testing ; and hence dampish features

Restriction

Although the Instron machine is sufficient for low frequence cycling ( ideal for fatigue testing ) the rig does hold its restrictions. The valves within it are limited to minimum supplanting at high frequence for illustration. The rig provides typical values of 12mm amplitude moving ridges at 6Hz which is all right for fatigue testing ; the truth is besides really tightly controlled excessively.

However existent mechanical damper trial rig ergometers ( as seen in Figure ) can rhythm constituents at much higher frequences as the random-access memories are run utilizing a Piston and crankshaft ; and are hence non-hydraulic without any slow operating valves. This is much more utile for all-out dynamic damper testing.

However to decently carry on dynamic damper testing, this can be carried out in situ on a vehicle at the university within the four-post shaker rig following door.

Operation OF

The Instron rig within the motorsport workshop portions its usage of the fluid mechanicss system with the shaker rig. It besides portions the chilling system with the engine ergometer. Therefore neither the engine dyno nor the shaker rig can be used at the same clip as any damper testing.

The undermentioned operation guide assumes the fluid mechanicss powering the machine is switched on and operational ( electricity and H2O supplied ) , the digital accountant ( Buffer box ) and the computing machine are switched on and verified, and the MAX32 package opened. A weariness cycling trial is besides described utilizing a generic suspension damper already specified and installed into the rig utilizing the relevant ingredients.

Using the user interface set the random-access memory to its halfway place ( +/-50mm ) for cycling ( entire supplanting 100mm ) . The random-access memory so moves upwards to the damper. The random-access memory can besides be controlled manually utilizing the control box seen in Figure.

With the random-access memory moved upwards, the fixture can be tightened to the damper saddle horse. The damper by the way is moved to the center of its shot so as non to damage the lodging and a line on the damper is used for assisting run alonging up.

The crosshead is so set. It can be lowered manually utilizing the boss positioned on the forepart of the machine ( Figure ) or utilizing the control box ( Figure ) , so clamped in topographic point. Having adjusted the crosshead, each bolt should be torqued up to 800Nm.

The xanthous ring ( left Figure ) on the aligned column is the safety ring and should besides be clamped into place. It stops the crosshead from by chance dropping when torqued up to the right torsion of 40Nm. Care should be taken to guarantee the safety ring is unclamped before the crosshead is moved.

It is besides noted that the xanthous ring should sit at the top of the column beneath the crosshead in operation ; unlike that seen in Figure. The machine MUST NOT be run without the crosshead clamped or without the safety ring in place.

When the rig ( and fluid mechanicss ) have merely been turned on, the crosshead is sometimes hard to travel as the fluid is still cold and syrupy ; therefore it can take some aid ( drawing down on the crosshead ) to take down.

Using MAX32 computing machine package and specifically the “ Waveform Generator ” interface, the amplitude of input to the damper is so set within “ Control Parameter ” for weariness cycling. For this presentation 12.5mm was set as seen in Figure. In industry this is usually set to around an inch of wave amplitude.

Figure – Specifying the wave form type and rhythm conditions within Waveform Generator

Besides utilizing this interface, the type of moving ridge and frequence are defined as seen in Figure. This is sinusoidal typically but triangular ( sawtooth ) or round moving ridges can besides be specified.

Random Definition Wave ( Track Data )

A “ Random Definition ” moving ridge can stipulate measured path informations and use this to the dampish trial. This path information is derived from a additive potentiometer or LVDT mounted alongside the damper on the vehicle lapping the path.

In order for the natural path ( .csv ) information to be inputted into the Instron package, the file has to be turned into.rdf format. The potentiometer informations besides has to be scaled ( from a few millimeter ) to a fraction of the maximal supplanting utilizing Excel before it is inputted into the MAX32 package.

The rhythm count is so set ( Figure ) . The sample rate is besides set ; in this instance 0.5 kilohertz is selected. The informations decrease box can be toggled which specifies the rhythm interval read count ; every 5 for illustration as seen in Figure. This is utile for cut downing clip analyzing informations and besides diminishing the file size of the natural information ; therefore money in industry.

Figure – Different save parametric quantities that can be adjusted in readying for proving

The rig is now set-up and the trial can get down. Force and supplanting is plotted in existent clip on screen. At the terminal of the tally, a typical force supplanting graph is provided as seen in Figure. From this information speed curves can be calculated, and the trial repeated for a scope of frequences to obtain a scope of speeds.

Figure – Typical graphical end product of force against supplanting from a sinusoidal moving ridge input

The natural information ( forces and supplantings measured over clip ) are besides provided as a.csv file that can be opened and analysed in Excel.