Fracture testing machines: automation

Fracture testing machines are used for the purpose of specimen mechanical properties evaluation.

The specimen is mounted on the testing machine for further tensile-compression testing that are performed till the destruction of the specimen.

Measured parameters

  • Ultimate tensile strength

    σu, calculated parameter

  • Relative elongation after fracture

    δ, calculated parameter

  • Yield stress point

    P0,2, graphical evaluation

  • Yield point

    σ0,2, calculated parameter

  • Relative reduction after fracture

    ψ, calculated parameter

  • Maximum value of the load for the specimen

    representation of the parameter

Operating principles

The digital sensors are used for the purpose of tests automation. The sensors measure the applied force value and the changes in linear dimensions of the specimen.

These parameters values are used for calculation of the estimated parameters that are further listed in the corresponding report.

Digital displacement sensor, consisting of primary transducer (e.g., strain-gauge sensor UU) and measuring module ZET 7110, is used for force value measurements. Digital displacement sensor, consisting of primary transducer (e.g., inductive transducer RL) and measuring module ZET 7111-L, is used for measuring of the tested specimen dimensions. The primary transducers are selected depending on the required measurement range.

Fracture testing machines_general layout

The primary transducers are mounted on the fracture testing machine directly and connected to the measuring modules, which are also installed in close vicinity.

The measuring modules transfer the parameters values to the PC for further processing with SCADA-project “Tensile tests of metals”.

In the course of tests process, there is displayed a graph of load and deformation parameters interdependence. Upon test process completion there is produced a report based on a particular template.

SCADA-project Fracture testing machines

Displacement and strain-gauge sensor readings along with the primary and final dimensions of the specimen (these parameters should be entered in the program by the operator) are used for the purpose of estimated parameters evaluation.

Prior to the beginning of tests performance, it is necessary to set initial dimensions of the specimen: cross-section diameter or lateral length (depending on the shape of the specimen). The specimen is placed into the testing machine and the test starts.

Yield point calculation

In the course of measurements performance the readings of displacement and strain-gauge sensors are used for building a graph Pl), where P stands for the applied  force, Δl – stands for averaging. From the data array there is selected a linear section, near which there is drawn a parallel line at the distance of 0,2lcalc. (20% of the gauge length). The crossing point of the straight line with the graph Pl) is used for the calculation of P0,2 and the yield point value.

yield point calculation example

Yield stress point calculation

Yield stress point is calculated by the formula:

σ0,2 (yield stress point)=P0,2 (yield stress point force)/F(initial cross-section of the specimen)

Ultimate tensile strength

In order to calculate σultimate tensile strength, the specimen is exposed to the fracture with gradually applied load up to its complete destruction. The maximum load value prior to the destruction of the specimen is the  Pmax – this value is considered to be the ultimate tensile strength.

The ultimate tensile strength is calculated by the formula:

σ (ultimate tensile strength)=Pmax/F0,

where σ – stands for the ultimate tensile strength value, P0,2 – the load value prior to the destruction of the specimen, F0 – the initial cross-section of the tested specimen.

Evaluation of relative elongation

Relative elongation of the tested specimen is calculated by the formula:

δ=100·(lfin-linitial)/linitial,

where δ – relative elongation, lfin – final estimated length, linitial – initial estimated length.

Evaluation of relative reduction

The relative reduction is calculated by the formula:

ψ=100·(FfinalFinitial)/Finitial,

where ψ – is the relative elongation, Finitial – initial cross-section of the specimen, Ffinal – final cross-section of the specimen.

SCADA project for fracture testing machines automation

Advantages

Full compliance
Automation
Instant data communication
Stable performance and reliability

System components and technical specifications

Fracture testing machines automation system normally includes the following components:

BASIC CONFIGURATION
Item Function Price
Strain gauge sensor TX25 conversion of strain into electrical signal from 830 USD
Displacement sensor RL600 conversion of displacement into electrical signal from 1 733 USD
ZET 7110 module for strain gauge signals conversion from 157 USD
ZET 7111-L module for displacement sensor signals conversion 202 USD
ZET 7176 interface converter for measurement data transfer to PC for further processing 134 USD
Software “Fracture testing” SCADA-project for automated tests performance 716 USD

Price of the system: from 3 773 USD

System basic configuration – technical specifications:

Parameter Value
Fracture force measurement range from 1 up to 10 tnf
Displacement measurement range from 0 up to 600 mm
Minimum permissible load < 1 % of the measurement range

Depending on a particular task, the technical specifications of the system can be changed by selecting transducers with optimal possible characteristics.

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