Electronic universal testing machine measures film tensile strength.

This article introduces the method of measuring the tensile strength of thin films using an electronic universal testing machine. During testing, the machine applies tensile force to the film sample, records the maximum tensile force and displacement through sensors, and then calculates the tensile strength using a formula. Key steps include preparing samples of standard dimensions, clamping them with appropriate fixtures, setting the correct tensile speed, and operating in a stable environment. Test results should be analyzed for average values and curve shapes to ensure data reliability. The entire process must strictly follow standards to guarantee measurement accuracy and provide a basis for material evaluation.

Introduction

In materials science and industrial quality control, the evaluation of the mechanical properties of thin-film materials is crucial. As a key indicator to measure the ability of thin films to resist tensile failure, the accurate determination of tensile strength relies on sophisticated testing equipment and standardized testing processes. With its high precision, wide range and good control performance, the electronic universal testing machine has become a common instrument for performing this test. This article will systematically describe the technical points, methods and related considerations of using electronic universal testing machines to determine the tensile strength of thin films.

Test Principle:

The electronic universal testing machine applies axial tensile load to the thin film specimen through a servo drive system, and uses high-precision sensors to simultaneously measure the load and displacement changes. Tensile strength (σ) is generally defined as the maximum tensile force (F) that a specimen is subjected to during tensile_max) and its initial cross-sectional area (A₀The basic calculation formula is as follows:

σ = F_max / A₀

The cross-sectional area is calculated by the product of the specimen width (b) and the average thickness (d). The load-displacement curve is recorded in real time during the testing process, which can then analyze the elastic modulus, elongation at break and other properties of the material.

Instruments and specimens

The test system is mainly composed of an electronic universal testing machine, a special film fixture and a thickness measuring device. The fixture should ensure that the specimen is well centered during the stretching process to avoid additional bending moments. Common specimens are dumbbell or long, and the specific size needs to be cut according to relevant material testing standards. The specimen should be prepared to ensure that the edges are smooth and there are no gaps, and the thickness measurement should take a multi-point average in the effective area of the specimen to improve the data reliability.

Critical equipment components	Main functional requirements
Testing machine host	Provides smooth displacement control and high-precision force measurement
Film fixtures	Firm clamping prevents slippage or local stress concentration
Thickness gauge	Resolution is typically in the micron range

Testing process

The standard testing process includes the following steps: First, the width and thickness of the specimen are accurately measured and recorded according to the standard. The specimen is then clamped symmetrically in the fixture to ensure that the stress axis coincides with the specimen centerline. Set test parameters such as tensile speed (usually selected based on material properties, e.g. 50 mm/min or 100 mm/min), initial gauge distance, and data sampling frequency. Start the test and the testing machine will stretch the specimen at a constant speed until it breaks. After the test, the system automatically calculates and outputs the results of tensile strength, elongation at break, etc. A sufficient number of specimens (usually no less than 5) should be tested for each set of materials to obtain statistically significant data.

Influencing factors

The accuracy of test results is influenced by various factors. The quality of specimen preparation, such as the integrity of the cut edges, directly affects the stress distribution. If the clamping force of the clamp is insufficient, it may lead to slippage, and if it is too large, it is easy to cause premature damage to the clamping part. Ambient temperature and humidity may have an impact on the properties of some polymer films, and it is recommended to test them in a standard laboratory environment. In addition, the selection of tensile speed needs to match the actual application conditions of the material or relevant standards, and too fast or too slow may cause the measured strength value to deviate from the real situation.

Main influencing factors	Control recommendations
Specimen size and preparation	Cut strictly according to standards, ensuring precise dimensions and flat edges
The fixture is centered and clamped	Carefully adjust the alignment and select the appropriate clamping surface and pressure
Test speed	Follow the specified speed range of the applicable standard
environmental conditions	Test and document real-world conditions in a controlled temperature and humidity environment

Analysis of results

Once the raw data is obtained, it needs to be analyzed effectively. In addition to calculating the average tensile strength versus standard deviation to assess the consistency of material properties, the load-displacement curve morphology should also be reviewed. The linear part of the curve can be used to estimate the modulus of elasticity, while the peak of the curve corresponds to the maximum load. If the results of the same group of specimens are largely discrete, it is necessary to check whether there are problems with the sample preparation, clamping method or the uniformity of the material itself. A complete test report should include specimen information, test conditions, raw data, calculation results, and necessary curve charts.

Summary

The use of an electronic universal testing machine to determine the tensile strength of thin films is a systematic technical work. From sample preparation, instrument calibration, parameter setting to result analysis, every step requires rigorous operation and adherence to applicable test standards. Through standardized testing, reliable material mechanical property data can be obtained, providing strong support for product development, quality control, and process improvement. Operators should continue to pay attention to relevant standard updates and testing technology developments to continuously improve the testing level.

References

1. Standard for general material tensile testing methods, involving the testing part of plastic and thin sheet materials.
2. Technical guide for the operation and calibration of the electronic universal testing machine.
3. Research on the mechanical properties of polymer thin film materials.