ENGINEERING SYSTEMS (Nottm) Ltd.
MECHANICAL STRENGH TESTING MACHINES
CK10 1 Tonne Desktop Testing Machine

1 Tonne Desktop Testing Machine (Ref: CK10)

The CK10 is a small, Bench top, vertical loading compression testing machine. It has been designed to enable the easy testing of brittle engineering materials. The built in acoustic sensor enables the crack detection in ceramic and coated materials.

Load capacity up to 10 kN (1000 kg), in units of kg, N or lb.

Resolution down to 10 gm with 100 kg Load Cell.

The CK10 is currently out of production. Re-design is necessary because some of the parts are no longer available.

Testing Facilities

CK10 Crack Detection

Crack Detection in a ceramic specimen

A hard ball is pressed onto the surface, with increasing load, until a ring crack occurs. This event is detected by the acoustic sensor. The size of the original surface crack is calculated and automatically displayed.

Micro-Crack detection in ceramic & brittle Materials

The CK10 can determine surface flaw sizes by Hertzian Indentation. A hard ball, mounted underneath the load cell, is pressed onto the surface to be tested, and the load is increased. The contact zone, between the ball and the specimen, increases in size with increasing load. A stress field is created and if this field intercepts a surface flaw above a certain size, the crack will extend abruptly around the contact zone to form a ring crack. This event is detected by the inbuilt acoustic sensor. The ring crack diameter can then be measured by the CK10's curtain microscope and when combined with the Ring Fracture Load and various materials constants, the CK10 works out, and outputs the original flaw size. CK10 3 or 4-point Bend Testing

3 & 4 Point bend test

3 Point bend testing using °8mm rollers for the lower contact points. A two point roller contact adapter provides the facility for 4 point bend testing. The acoustic emission sensor can be attached if required.

Determination of fracture toughness (KIC)

The above testing technique can be used to obtain a value for Fracture toughness. This traditionally 'difficult to measure parameter' can be determined without having to pre-crack the specimen. The only measurement required is the loads at which ring cracks form. A value for KIC can also be obtained from the following testing technique.

Edge toughness testing of brittle materials

The Edge Toughness (or resistance to chipping) of hard and brittle materials, such as cutting tool tips, can be determined by applying a point load (provided by a Rockwell indenter), to fracture or chipping, at a small distance from the edge of a specimen. The CK10 can be used to determine the Edge Toughness by dividing the loading distance from the edge by the chip fracture load. This technique can be used for research into the toughness (KIC) properties of the specimen material or for quality control during component production.

Proof testing

This can be carried out for both micro-crack detection and edge toughness. The specimen is loaded with loads which are below that which are expected to produce cracking or fracture.

Crack testing of coated surfaces

Surfaces which have been coated with hard materials can be tested for bonding by 3 or 4 point bend testing. The acoustic sensor is suitably positioned on the specimen or bending fixture so that the onset of cracking or debonding can be determined.

Basic hardness testing

If the CK10 is fitted with an optional 100 kg load cell, using the CK10's load and hold facility together with a Rockwell or Vickers indenter, a basic measure of hardness can be obtained. Using the CK10's microscope, the indentation size can be measured and the hardness can be calculated automatically by the machine.

Compression testing

Compression testing up to 10 kN can be carried out in the normal way, with the specimen placed onto the bottom table and the crosshead moving downwards to apply the load.

3 & 4 Point bend testing

The picture shows a specimen being tested in a roller contact 3 point bend rig. Very small, down to 8mm long, specimens can be tested using the °3mm roller contact adapter.

Other testing

Other test fixtures/rigs and extension pillars, can be designed and manufactured, on request, so that specialized testing can be carried out.

Acoustic sensor

The centre frequency is approx. 90kHz; for internal use this is filtered to remove the lower frequencies. The machine can be set to detect very low level signals in the above frequency range. An unfiltered amplified analogue output of the acoustic sensor signal is available at the rear BNC socket output.

Capacity

The standard load range is 0 to 10,000 Newton's (0 to 1000kg) and a peak hold facility is built in so that the maximum test load can be captured and held on the digital display. A choice of units i.e. N, kg or lb is available. For more sensitive readings, an optional 100kg load cell can be fitted. The test results can be output to any combination of: built in Printer, RS232 output, or analogue output of load.

Panel controls & outputs

The basic data and settings are displayed on a 40 column x 4 line LCD display. Positive action membrane switches, incorporated into the wipe clean front panel, control the action of the machine. A front flap conceals secondary controls which are occasionally used when setting up the machine. The rear panel provides the RS232, External Acoustic & Load Analogue output.

Guard

A guard assembly is supplied, this rotates about a pivot which is attached to the load frame base. For batch testing, closure of the guard can automatically start the testing sequence. If the guard is subsequently opened, the test will be aborted and the crosshead will return to its preset return position.

Machine design & construction

The CK10 has been designed in collaboration with Oxford University Department of Materials, and with the aid of DTI funding from a regional development grant.

The CK10 construction is modular. The mechanical loading frame and motor are combined and mounted onto the baseplate. For efficiency, a recirculating ball screw is used to drive the crosshead. The electronic design ensures that a minimum of interconnecting wiring is used.

The main cover is made of 16 gauge steel and incorporates the main control panel and the printer. The load cell is purpose designed and built. A sliding drawer mounted on the underside of the bottom cover contains the handbook and some of the essential tools for use with the CK10.

The integral printer is flush mounted on the side panel of the main casing and the paper roll and ribbon occupy a space within the body of the printer. The roll and ribbon can easily be changed via the printer's hinged door which opens to expose these items.

Overload and over travel protection is incorporated into the control electronics. When the Load Peak Hold is in operation, fracture is detected when the instantaneous load detected by the load cell falls to a set % of the maximum (peak held) load which has been reached during a particular test.

Because the control system is microcontroller driven by software stored in an EPROM, software upgrades and special purpose test requirements can easily be implemented by changing the EPROM.

Calibration

Before each machine leaves the factory, it is calibrated using a dead weight loading system. The machine can also be calibrated by using a proving ring. An electronic calibration switch is provided so that a daily calibration check can be made. Any of the previously mentioned units can be used for calibration.

Specification of the standard CK10 machine: