Neometrix / Materials & Structural Test / Dynamic Actuator System / NMX-DAC-76

NMX-DAC-76 · ENGINEERED-TO-ORDER CLASS — SPECIFY · SIZE · FRAME · BUILD · TEST · PROVE

Dynamic Actuator System. Force is easy; speed is flow.

Name: Dynamic Actuator System
Brand: Neometrix
SKU: NMX-DAC-76

A dynamic actuator pushes and pulls a beam, a column or a joint, over and over and sometimes fast, to see how the structure behaves. The force it can give is set by the oil pressure and the size of its piston. How fast it can move is set by something else.

That something is flow. So the system has to deliver enough oil at the moment the actuator needs it, hold the other end of the actuator firmly, and control the motion in a closed loop.

Discuss a dynamic actuator system Capability note (PDF)

A single dynamic actuator on a self-reacting loading frame on a plain white studio background: a grey painted steel portal of two box columns, a thick crosshead and a base beam, a bright servo-hydraulic actuator with a polished rod, a load cell and a swivel head hung under the crosshead with a servo valve block and two black hoses on its side, and a pale grey concrete beam resting on two supports on the base beam below it, and no people

Fig · 01 — A dynamic actuator on a self-reacting frame: a portal of two columns, a crosshead and a base beam, the actuator hung under the crosshead and a concrete beam below it — illustrative render.

The force

pressure times pistonset by the supply and the area

The speed

the flow of oilvalve and accumulators decide it

The reaction

carried by a framestrong floor or self-reacting

The control

a closed loopforce or displacement

Status

engineered to orderno dynamic actuator system claimed

ISO 9001ISO 14001ISO 7500-1 reference standard

Overview

Why the whole job is the oil.

Because the actuator is only as fast as the oil that reaches it, and only as true as the frame that holds it.

A single servo-hydraulic dynamic actuator on a plain white studio background, lying on its side: a grey steel cylinder with a polished rod ending in a bright swivel head with a bright load cell, a bright aluminium servo valve block on top with two black hoses, a small bright accumulator beside it and a clevis end with a pin, and no people

Fig · 02 — A servo-hydraulic dynamic actuator: a steel cylinder with a polished rod, a load cell and a swivel head, and a servo valve block and an accumulator on the cylinder — illustrative render.

Force is easy; speed is flow.

What the system is for

It moves a structure, or a part of one, in a controlled way to see how it behaves: a beam, a column, a joint, a wall panel or a bearing. The actuator pushes and pulls, slowly or fast, under a controller that follows a force or a displacement. It suits a single actuator on a self-reacting frame, a multi-actuator rig on a strong floor, and a power unit and controller for actuators a laboratory already owns.

Why force is easy

The force an actuator gives is the oil pressure times the area of its piston. A larger piston turns the same supply pressure into a larger force. So force is a matter of choosing the piston.

Why speed is flow

The speed of the piston is the flow of oil into the cylinder divided by the area of the piston. A fast motion needs a high flow through the servo valve. A larger piston, which gives more force, needs more flow for the same speed.

Why the accumulators are there

The pump cannot answer the start of every motion in time, and in a cyclic test the average flow is far below the peak. An accumulator bank stores oil during the quiet part of the cycle and gives it back in the burst.

Why the reaction matters

Every force the actuator applies to the specimen is pushed back into whatever holds its other end. That is the reaction. The frame must carry the full force, and it must be stiff, because a frame that flexes is a source of error in what the test reports.

Strong floor or self-reacting frame

A strong floor and reaction wall carry the reaction into a foundation built for it. A self-reacting frame carries it inside its own steel and passes little to the floor, so it can stand where no strong floor exists.

Why a static calibration is not enough

A force measured at rest is not necessarily right at speed. The load cell and its amplifier are checked in motion as well as still, and the result goes into the record.

The method

Specify, size, frame, build, test, and prove.

Six steps in a fixed order. Sizing the valve and the accumulators for the speed and not only the piston for the force, and running the system at speed before any specimen, are the two a quick order skips.

1 · Specify

The specimens, the force, the stroke, the speed and the tests are stated by the customer.

2 · Size

The piston and the valve are sized together, and the valve and the accumulators are sized for the speed, not only for the force.

3 · Frame

The reaction frame is chosen and sized for the full force and for its stiffness, a strong floor or a self-reacting frame.

4 · Build

The actuator, the power unit, the controller and the frame are built as one installation.

5 · Test

The system is run at speed with a dummy specimen, the load cell is checked in motion, and the interlocks are tried, before any customer specimen is loaded.

6 · Prove

A record is kept for every test, with its commands, its readings and the checks, and handed over with the system.

Which reaction for which laboratory

Reaction	What it suits	What to watch
A strong floor and reaction wall	a laboratory that tests large structures and many different set-ups	it needs a foundation built for it and a grid of anchor points, and the wall must stay essentially rigid under load
A self-reacting frame	a laboratory without a strong floor, or one that needs to move the rig	the frame carries its own reaction, so its flexibility has to be kept small and its movement checked
An actuator on a frame the laboratory owns	a laboratory that already has a reaction frame	the existing frame must have the capacity for the force of the new actuator, which has to be checked before the order

The step people underrate is the speed. A system sized for force alone can push hard and still be too slow to run the test.

Work content

What the system contains, element by element.

Read it as a checklist: a system missing a row will move a specimen on paper and not at the speed the test needs.

A single hydraulic power unit on a plain white studio background: a low grey painted steel oil reservoir on a base frame carrying a grey electric motor and pump set, three tall slim bright stainless steel accumulators side by side beside it joined by a stainless manifold block, and two thick black hoses, and no people

Fig · 03 — A hydraulic power unit with an accumulator bank: a motor and pump set on an oil reservoir, and three tall accumulators joined by a manifold — illustrative render.

Element	What it does	What matters
Dynamic actuator	applies the force and the motion	a cylinder, a polished rod and a swivel head that take side load without binding, sized for the force and the stroke
Servo valve	controls the flow of oil	sized for the peak flow at the speed required, and mounted on the actuator so that the oil path is short
Load cell and displacement transducer	read the force and the motion	the feedback the controller works from, mounted so that they read the specimen and not the frame
Hydraulic power unit	supplies the oil	pumps, filtration and cooling sized for the average flow, with a clean and cool oil supply
Accumulator bank	stores oil for the peaks	sized for the peak flow, with manifolds and hoses sized to carry it to the valve
Closed-loop controller	follows the command	holds the force or the displacement to the command, with the loop tuned to the specimen and the frame
Reaction frame	carries the reaction	a strong floor and wall or a self-reacting frame, stiff as well as strong, with the movement of the frame itself checked
Fixtures and swivels	hold the specimen	swivel heads and fixtures that let the specimen move without binding or taking a side load
Safety guards and interlocks	protect people	limits on stroke and force, an emergency stop and guards round the specimen, because a specimen can fail suddenly under fast loading
Procedure	fixes the sequence	specify, size, frame, build, test and prove, the same for every system
Testing & documentation	prove the system first	run at speed with a dummy specimen, the load cell checked in motion, the interlocks tried, and a record the customer can inspect

The elements that decide whether the system is fast enough are the servo valve and the accumulator bank, and the one that decides whether it is true is the reaction frame. The first sets the speed, and the second sets how much of the motion goes into the specimen.

Full specification — expand

System	A servo-hydraulic dynamic actuator with a servo valve, a load cell and a displacement transducer; a hydraulic power unit with pumps, filtration, cooling and an accumulator bank; manifolds and hoses sized for the peak flow; a closed-loop controller for force and displacement; a reaction frame, either a strong floor and reaction wall or a self-reacting frame, with swivel heads and fixtures for the specimen; guards and safety interlocks; a written test plan; and calibration, testing and documentation before handover
The One Idea	Force is easy; speed is flow.
Why Force Is Easy	The force an actuator gives is the oil pressure times the area of its piston, so a larger piston turns the same supply pressure into a larger force, and force is a matter of choosing the piston
Why Speed Is Flow	The speed of the piston is the flow of oil into the cylinder divided by the area of the piston, so a fast motion needs a high flow through the servo valve, and a larger piston, which gives more force, needs more flow for the same speed
Why The Accumulators Are There	The pump cannot answer the start of every motion in time and in a cyclic test the average flow is far below the peak, so an accumulator bank stores oil during the quiet part of the cycle and gives it back in the burst
Why The Reaction Matters	Every force the actuator applies to the specimen is pushed back into whatever holds its other end, so the frame must carry the full force and must be stiff, because a frame that flexes is a source of error in what the test reports
Strong Floor Or Self-Reacting Frame	A strong floor and reaction wall carry the reaction into a foundation built for it, whereas a self-reacting frame carries it inside its own steel and passes little to the floor, so it can stand where no strong floor exists
Why A Static Calibration Is Not Enough	A force measured at rest is not necessarily right at speed, so the load cell and its amplifier are checked in motion as well as still, and the result goes into the record
Standards	ISO 7500-1 is the public standard for the verification of static uniaxial testing machines and their force-measuring systems, and it notes that static calibration values are not necessarily valid for dynamic testing. This page prints none of its classes, limits or tolerances, and no edition year: those come from the method the customer names and from the system. Approval of a system, or of a test result, rests with the customer and the authority they name; none is claimed here
Configurations	A single actuator on a self-reacting frame, a multi-actuator rig on a strong floor and reaction wall, and a power unit and controller for the actuators a laboratory already owns
Scope Boundary	This page is the dynamic actuator system. It is not a servo-hydraulic fatigue test system, which is a stiff frame for materials and components (see servo-hydraulic fatigue and structural test system), not a bridge expansion joint test facility, which tests one type of joint on its own foundation (see bridge expansion joint test facility) and not a jacking system, which lifts and holds a load (see hydraulic jacking system). A shake table and a drop test tower are different equipment again. No certification is claimed here
Status	Neometrix has quoted against successive dynamic actuator system requirements, and no delivered dynamic actuator system is claimed.

Configurations

One method, three ways to build the system.

The method, the sizing of the valve and the accumulators, and the record are shared. What changes is how many actuators there are and what holds them.

Single actuator, self-reacting frame

Portal, actuator and power unit

A portal frame, one actuator with its servo valve and load cell, and a power unit and controller, for beams, columns and joints in a laboratory without a strong floor.

Multi-actuator rig

Several actuators, one controller

Several actuators on a strong floor and reaction wall, run by one controller from a common command, for a whole frame or a wall.

Power unit and controller

For actuators already owned

A hydraulic power unit with an accumulator bank and a closed-loop controller for the actuators a laboratory already owns.

And the part that is not equipment at all, yet decides all three: the test plan. It fixes the commands, the speeds, the check of the load cell in motion, and what is recorded. It is written from the specimen and the question asked of it, not from the actuator.

Where it is used

Wherever a structure is moved to see what it does, and the motion has to be true.

The common thread is a specimen too large for a materials machine, and a result that other people will design with.

Structural engineering laboratories

Where beams, columns, joints and wall panels are loaded and cycled to find their strength and their stiffness.

Earthquake engineering research

Where cyclic and fast tests show how a structure behaves when the ground moves it back and forth.

Bridge bearing and joint testing

Where bearings and joints are moved under load, slowly and fast, before they are used.

Construction product testing

Where connections, anchors and building products are proved by a test that moves them as they would be moved.

Watch

See it in motion.

A short walkthrough video of the dynamic actuator system.

FAQ

Common questions.

Longer answers, for readers who want the reasoning.

Q · 01 What does a dynamic actuator system actually do?

It moves a structure, or a part of one, under control, and records what the structure does. The actuator pushes and pulls the specimen, a servo valve meters the oil, a load cell and a displacement transducer report back, and a controller compares them with the command and corrects the valve. The power unit supplies the oil and the frame carries the reaction. It does not shake the ground the way a shake table does, and it does not choose the test: that is the engineer's job.

Q · 02 Why is force easy and speed a matter of flow?

Because the force on the piston is the oil pressure times its area, and the supply gives a pressure to spare, so a bigger piston gives a bigger force. Speed is another matter. For the piston to move, oil has to flow in at one end and out at the other, and the flow is the speed times the area. A fast motion with a large piston needs a very large flow. The servo valve limits how much can pass, and the pump limits how much can be supplied for long.

Q · 03 Why does the system need accumulators?

Because the demand is not steady. In a cyclic test the actuator takes a burst of oil as it accelerates and then very little as it slows, so the average flow is far below the peak. A pump sized for the peak would be large and mostly idle. A pump sized for the average cannot answer the start of each motion in time. The accumulator bank bridges the two: it fills in the quiet part of the cycle and empties in the burst. It also steadies the supply pressure on which the controller relies.

Q · 04 Why does the reaction matter, and which frame is right?

Because the actuator pushes on the specimen and on whatever holds its other end with the same force. On a strong floor and wall, the reaction goes into a foundation designed for it. In a self-reacting frame, the steel carries it and little goes into the floor, so the rig can stand in a laboratory that has no strong floor. Either way the frame must have the capacity for the force and be stiff enough that its own movement does not disturb the result. If a laboratory already owns a frame, its capacity has to be checked against the new actuator before the order.

Q · 05 Is this the same as the servo-hydraulic fatigue system, the bridge joint facility or the jacking system?

No, and the differences are worth stating precisely. The servo-hydraulic fatigue and structural test system page covers a stiff frame for materials and components. The bridge expansion joint test facility page covers one type of joint on its own foundation. The hydraulic jacking system page covers cylinders that lift and hold a heavy load. This page is the dynamic actuator system. A shake table and a drop test tower are different equipment again. It does not replace any of them, and it does not claim what they claim a second time.

Q · 06 Has Neometrix built one of these?

We would rather answer this plainly than let a page imply otherwise. Neometrix has quoted against successive dynamic actuator system requirements, and no delivered dynamic actuator system is claimed. What stands behind the offer is adjacent: Neometrix engineers a servo-hydraulic fatigue and structural test system (see the servo-hydraulic fatigue and structural test system page), a bridge expansion joint test facility (see the bridge expansion joint test facility page) and a hydraulic jacking system (see the hydraulic jacking system page). The cylinders, servo valves, pumps, accumulators, transducers and controllers are catalogue items, bought in, not invented. What Neometrix engineers is the system around them: the sizing of the piston, valve and accumulators, the reaction frame, the manifolds, the control, the interlocks, the procedure and the test plan. So the honest position is that the system is engineered to order, the neighbouring disciplines are in the building, and the first system of this exact kind will be built around the customer's own specimens rather than taken off a shelf.

Q · 07 Which standard applies, and what can the system not do?

ISO 7500-1 is the public standard for the verification of static uniaxial testing machines and their force-measuring systems. It notes that values found by a static calibration are not necessarily valid for dynamic testing, which is why a dynamic system has its force measurement checked in motion as well as at rest. This page prints none of its classes, limits or tolerances, and no edition year: those come from the method the customer names and from the system. The system moves a specimen and keeps a record. It does not certify a structure: this page claims no certification or accreditation. No force, speed, flow, stroke or quantity figure is printed here, and approval for use rests with the customer and the authority they name; none is claimed here.

Q · 08 What do you need from us to quote?

Six things, and most of them describe your tests rather than the system. First, the specimens: their type and size, and what they are expected to do. Second, the force: the greatest load each actuator must apply, and how many actuators you need. Third, the stroke and the speed: the travel, and the fastest motion the test requires. Fourth, the tests: slow cyclic, fast, or both, and the range of frequency. Fifth, the frame: a strong floor and wall, a self-reacting frame, or the laboratory's own. Sixth, the record: what you want kept for each test. From that we come back with a system concept, a written test plan you can check, and a budgetary price.

The neighbouring hydraulic and test pages, and how they differ from this one.

Three neighbours: one tests materials, one tests a bridge joint, one lifts and holds.

↗ Testing materials

Servo-Hydraulic Fatigue & Structural Test System

A stiff frame and actuator for materials and components - a machine for coupons and parts, where this page is the actuator, its oil and its reaction frame for structures.

↗ A bridge joint

Bridge Expansion Joint Test Facility

One type of joint on its own foundation, moved and cycled under load - a facility for one product, where this page is the general-purpose actuator system.

↗ Lifting and holding

Hydraulic Jacking System

Cylinder jacks with a mechanical lock that lift a heavy structure and hold it - a slow lift, where this page moves a specimen fast and reverses it.

Browse all Neometrix product lines.

Get a quotation

Tell us the specimens, the force,
and how fast they must move.

The projects desk replies within two working days with a system concept, a written test plan you can check, and a budgetary quotation. Write to [email protected] or use the form.

Enquire — actuator system Capability sheet (PDF) +91 7777 876 876

ISO 9001 / 14001 ENGINEERED-TO-ORDER CLASS — DYNAMIC ACTUATOR SYSTEM SPECIFY · SIZE · FRAME · BUILD · TEST · PROVE — FORCE IS EASY; SPEED IS FLOW ENGINEERED IN NOIDA · INDIA