How to Use a Universal Testing Machine?

A universal testing machine (UTM) is a type of testing equipment widely used in fields such as material mechanics, mechanical manufacturing, and quality control. It can perform various mechanical tests on various materials, including tension, compression, bending, shear, and tear tests, to evaluate their mechanical and durability properties.

Electronic universal testing machines are electronically (or computer) controlled and come in two main types. One type uses a digital display, which simultaneously displays force, displacement, and deformation on a panel digital display window. These displays can be recorded at any time and printed out using a microprinter. Their key features include a wide range of force application rates, easy and accurate control, and ease of operation. The other type is fully computer-controlled, offering convenient and flexible operation. The machine can be controlled using a keyboard or mouse according to the display prompts, and data processing is automatic, with strong post-processing capabilities.

Working Principle 

Electronic universal testing machines use servo motors as their core power source and utilize precision control systems to accurately apply loads. The workflow can be divided into four key steps:

Power Transmission System: A servo motor drives a ball screw, converting the motor's rotational motion into linear motion of the crosshead. The ball screw's lead accuracy reaches 0.005mm, and when combined with a high-resolution encoder, it can achieve micron-level displacement control.

Load Measurement System: A strain gauge force sensor (such as an S-type or spoke-type sensor) is used. When the specimen is subjected to force, the strain gauge within the sensor deforms, which is converted into an electrical signal via a Wheatstone bridge circuit. Modern sensors have a range of 0.4%-100% FS and a nonlinear error of less than ±0.03%.

Deformation Monitoring System: In addition to crosshead displacement, a high-precision extensometer directly measures deformation within the specimen's gauge length, with a resolution of up to 0.1μm. This is particularly suitable for precision testing such as elastic modulus.

Closed-Loop Control System: Using a PID algorithm, the motor speed is adjusted in real time to achieve three closed-loop control modes: stress rate, strain rate, or displacement rate. For example, the GB/T 228.1-2021 standard requires that the strain rate for metal tensile testing be controlled within the range of 0.00025 to 0.0025/s.

Operational Procedures

Before using a universal testing machine, be fully prepared. First, inspect the machine's exterior for damage or deformation. Second, check that the power supply and hydraulic systems are functioning properly. Our company boasts comprehensive product innovation capabilities and a dedicated R&D and manufacturing system, ensuring the quality and stability of our universal testing machines.

Specimen Installation

Install the prepared specimen into the testing machine's fixture, ensuring a secure fit to prevent loosening during testing. China Machinery Testing's universal testing machines are equipped with advanced fixture systems that accommodate specimens of varying shapes and sizes, providing user convenience.

Parameter Setting

Set parameters such as test speed and force according to test requirements. China Machinery Testing's products incorporate numerous cutting-edge core technologies, including leading-edge measurement and sensing technology, ensuring accurate parameter settings.

Start the test After everything is ready, start the test machine to conduct the test. During the test, closely observe the test data and changes in the sample. The universal testing machine has real-time data monitoring and recording functions, which allows users to grasp the test situation at any time. Precautions The electronic universal material testing machine is a multi-parameter, multi-functional, high-precision, intelligent mechanical testing equipment. In order to prevent accidents, special attention should be paid to the following matters during use:

(1) Before starting the main machine, the displacement stroke limit protection device must be adjusted to ensure that the movable beam does not collide with the upper beam or workbench during the test.

(2) The unidirectional loading of the testing machine should not exceed 80% of the rated range of the load sensor, and the tensile and compressive loads of the bidirectional cyclic loading should not exceed 60% of the load sensor capacity.

(3) The length of the tensile clamp holding the sample shall not be less than 80% of the clamp length.

(4) The load and deformation measuring instrument should be preheated for 30 minutes before it can be turned on for the experiment.

(5) Before using a new sensor with an amplifier, the full range of each gear of the amplifier must be calibrated.

(6) When the testing machine is in stress (or strain) control, force shifting can be performed, but deformation shifting cannot be performed.

(7) When adjusting the various calibration parameters of the sensor, the operating procedures must be strictly followed, otherwise it is easy to cause an accident.

(8) If an abnormal situation occurs during the experiment, the "emergency stop" button should be pressed immediately, and then the cause should be found and the fault should be eliminated. After the system is normal, the experiment can be carried out according to the correct steps.

Application field

As an indispensable core testing equipment in the field of materials science and engineering, the universal testing machine has a wide range of applications and great importance, and has penetrated almost every corner of modern industry. It simulates the stress state of materials or components under different working conditions and performs various static mechanical performance tests such as tension, compression, bending, shearing, peeling, and tearing on them, thereby accurately obtaining key performance parameters such as strength, hardness, stiffness, ductility, toughness, and fatigue life of the material. This powerful testing capability makes it a "sharp eye" for quality control and product development.

Mechanical Manufacturing and Aerospace: In these two fields, where safety and reliability are paramount, even the slightest material defect can have catastrophic consequences. Universal testing machines are used to conduct rigorous mechanical property tests on key engine components (such as turbine blades and connecting rods), landing gear structures, fuselage skin materials, and high-strength bolts. They not only verify that materials meet design specifications but also simulate the durability of components under long-term alternating loads through fatigue testing, ensuring the safe flight of aircraft.

Automotive Manufacturing: Lightweighting and safety are two major themes in the contemporary automotive industry. Universal testing machines play a dual role here: first, they test the mechanical properties of lightweight materials such as high-strength steel, aluminum alloy, and carbon fiber to optimize vehicle body structures; second, they perform mandatory crash simulation tests (such as tension, compression, and tearing) on ​​safety components such as bumpers, seatbelts, airbags, and brake pads to ensure they can effectively protect occupants in the event of an accident. They are also used to verify the flame retardancy and durability of interior materials.

Electronics and Precision Manufacturing: In this field focused on miniaturization and high reliability, universal testing machines are shifting their focus to testing tiny precision components. They are used to test the bending strength of mobile phone screens, the solder joint strength of chip packaging contacts, the peel resistance of circuit boards, and the plug-in/out life of micro connectors. These tests ensure the stability and durability of consumer electronics and precision instruments in complex operating environments.

Building Materials and Civil Engineering: Just as a building rises from the ground, its safety begins with rigorous testing of building materials. Universal testing machines are widely used to test the tensile and yield strength of steel bars, the compressive strength of concrete, the adhesion of asphalt, the tear strength of waterproofing membranes, and the joint strength of geogrids. These test data provide direct support for building structural design, construction quality control, and engineering safety assessments, and are crucial to national economy and people's livelihoods.

Development Trends

Digitalization: Universal testing machines are evolving towards digitalization and automation. The use of digital sensors and computer software control systems digitizes and automates the testing process, improving efficiency and accuracy.

High Precision: With increasing testing demands, the accuracy of universal testing machines is increasing, from the typical ±1% to ±0.5%, ±0.2%, and even ±0.1%.

Multifunctionality: Universal testing machines are becoming increasingly multifunctional, capable of performing multiple tests simultaneously and evaluating the properties of various materials.

Networking: Universal testing machines are becoming increasingly networked, enabling remote monitoring, data sharing, and remote control, making remote testing more convenient.

Energy Saving and Environmental Protection: Universal testing machines are becoming more energy-efficient and environmentally friendly, employing energy-saving technologies and environmentally friendly materials to reduce energy consumption and environmental pollution.

FAQ

Q: Inaccurate Test Force

This may be caused by a sensor failure or inaccurate calibration. The solution is to check the sensor for proper function and replace it if any problems are found. Regularly calibrate the testing machine. China Machinery Testing has a professional after-sales team that can provide timely technical support and calibration services.

Q: Loose Fixtures

This may be caused by loose fixtures or wear caused by long-term use. The solution is to reinstall the fixture and ensure it is secure; replace the worn fixture. The fixtures of China Machine Testing are made of high-quality materials with good wear resistance and reliability.