I. Core Structure and Functional Division

The basic structure of a tensile testing machine consists of four core components: the drive system, the force measurement system, the strain measurement system, and the control system. These components work together to complete the testing process:
The drive system: This is responsible for applying force (such as tension during stretching) to the specimen. It typically consists of a motor (servo motor, stepper motor, etc.) and a transmission mechanism (lead screw, guide rails). It can achieve various loading methods, such as uniform and variable speed.
The force measurement system: This uses a force sensor (such as a strain gauge) to convert mechanical force into an electrical signal, accurately measuring the force applied to the specimen.
The strain measurement system: This uses an extensometer (clamped to the specimen) or a displacement sensor to record the length change (such as elongation or compression) of the specimen during the loading process.
The control system: This consists of a computer and specialized software. It controls the speed and method of the drive system's loading, receives force and strain signals, processes the data, and generates a test report.
 

II. Detailed Workflow

Specimen Preparation and Clamping
According to testing standards (such as GB, ISO, and ASTM), the material is processed into a standard specimen (e.g., dumbbell-shaped for metal wire, long strips for plastic film). The specimen's ends are then secured in the upper and lower grips of the tensile testing machine. The grips should be selected based on the material's characteristics (e.g., wedge grips for metal, pneumatic grips for rubber, to prevent the specimen from slipping or breaking in the grips).
Parameter Setting
The control system sets parameters such as the test type (e.g., tension, compression, bending), loading speed (e.g., 5mm/min for plastic, 50mm/min for metal), and stop conditions (e.g., automatic shutdown upon specimen breakage).
Force Application and Signal Acquisition
The drive system moves the lower (or upper) grip, applying tension (for tensile testing) or compression (for compression testing) to the specimen.
The force sensor detects the force in real time, converting the mechanical force into a voltage signal (the strain gauge's resistance changes due to force deformation, which in turn changes the voltage), which is then transmitted to the control system. The deformation measurement system (such as an extensometer) simultaneously records the specimen's elongation (or contraction), which is also converted into an electrical signal and transmitted to the control system.
Data Processing and Result Output
The control system converts the force and deformation signals (e.g., force to N or kN, deformation to mm or percentage) and plots a "force-deformation curve" (or "stress-strain curve") in real time.
Key parameters are calculated based on the curve characteristics:
Tensile strength = maximum tensile force ÷ original specimen cross-sectional area;
Elongation = (post-fracture gauge length - original gauge length) ÷ original gauge length × 100%;
Yield strength: calculated from the force corresponding to the yield plateau in the stress-strain curve.
A test report containing the curve and parameters is generated, supporting data storage, printing, or export.
 

III. Key Technical Features

Precision Control: Accurate force and deformation measurements are ensured through high-precision sensors (error ≤ 0.5%), a servo drive system (speed control accuracy ≤ ±1%), and closed-loop feedback control. Versatility: By replacing fixtures and sensors, various tests such as tension, compression, bending, shear, and peel can be performed to accommodate different materials and standards.
Automation: Modern tensile testing machines are often equipped with computer software that supports automatic loading, automatic fracture detection, and automatic result calculation, reducing human error.

In short, the essence of a tensile testing machine is to convert the "mechanical behavior" of a material under stress into "quantifiable data," providing a scientific basis for material selection, quality control, and scientific research analysis. It is a core tool for testing the mechanical properties of materials.