A tensile tester is a machine used to determine a material’s strength and deformation behavior until break. Choosing the right tensile tester depends on the material you want to test and the standard you need to follow.
A tensile tester, also known as a pull tester or universal testing machine (UTM), is an electromechanical test system that applies a tensile (pull) force to a material to determine the tensile strength and deformation behavior until break.
A typical tensile testing machine consists of a load cell, crosshead, extensometer, specimen grips, electronics, and a drive system. It is controlled by testing software used to define machine and safety settings, and store test parameters defined by testing standards such as ASTM and ISO. The amount of force applied to the machine and the elongation of the specimen are recorded throughout the test. Measuring the force required to stretch or elongate a material to the point of permanent deformation or break helps designers and manufacturers predict how materials will perform when implemented for their intended purpose.
ZwickRoell tensile strength test machines, including the zwickiLine, ProLine, AllroundLine, and E-series machines, are specifically designed to meet customer requirements based on testing capacity, types of material, applications, and industry standards such as ASTM E8 for metals, ASTM D638 for plastics, ASTM D412 for elastomers, and many more. In addition to overall system safety and reliability, ZwickRoell designs and builds every tensile testing machine with a focus on providing:
- A high level of flexibility through ease of operation
- Simple adaptations to customer- and standard-specific requirements
- Future-proof expansion capabilities to grow with your needs
zwickiLine tensile testing machine for small test loads up to 5 kN
- Table-top installation and easy transport
- High-performance, flexible, and cost-effective
- Typical applications include tensile strength tests for production monitoring, goods inwards checks, quality assurance, and demonstration and teaching at a university or other academic institution
- LOAD CELL
The load cell converts tension force into an electrical signal that can be measured. ZwickRoell load cells ensure not only high product quality, but also seamless compatibility with all our machine components.
An extensometer is a device that measures the extension of a specimen, also known as strain measurement. Almost all tensile testing standards such as ASTM and ISO require strain measurement.
- SPECIMEN GRIPS
Specimen grips form the mechanical link between the specimen and the tensile testing machine. Their function is to transfer the movement of the crosshead to the specimen and transmit the test load generated in the specimen to the load cell.
- MOVING CROSSHEAD
The moving crosshead is essentially a cross beam that is controlled to move up or down. For a tensile test, the crosshead speed of the testing machine is directly related to the strain (elongation) rate in a test specimen.
The electronics control the moving parts of the tensile testing machine. The speed of the crosshead, and consequently the load rate, can be controlled by a microprocessor in the closed-loop servo controller (motor, feedback device, and controller).
Our testing software is an extremely user-friendly, wizard-guided, and Windows-based solution that allows users to set up the testing system, configure and run tests and view results.
- DRIVE SYSTEM
The drive system feeds electricity into the tensile testing machine’s motor at varying amounts and frequency, indirectly controlling the motor speed and torque.
All the components of a ZwickRoell tensile tester are designed to work together seamlessly.
For automated tensile tests, the testing machine is supplemented with a robotic testing system, which removes specimens from a magazine and inserts them in the specimen grips of the machine. A 2D code reader, cross-section measuring device or, depending on the test, a hardness tester or roughness measuring system can also be connected. Disposal of specimen remains is also handled by the automated tensile testing system.
The benefits provided by robotic systems apply to both large and small test series:
- Up until now, automated tensile testing has mainly been used by laboratories with high specimen volumes. Without the need for operator attendance, the fully automatic tensile testing system can be used for night shifts and over the weekend, with a consistent high level of efficiency, 24/7.
- Even for small test series starting with approximately 10 specimens, an automated tensile testing system proves worthwhile. With the use of a simple robotic testing system for tensile tests, qualified laboratory personnel are relieved of routine responsibilities and therefore available for more complex tasks.
The fully automatic tensile test eliminates subjective operator influences, such as hand temperature or skewed specimen gripping on the specimen and test assembly. This results in a high level of accuracy and reproducibility, and the quality of test results is significantly improved.
ZwickRoell is a global leader in materials testing and offers a deep level of expertise in automated tensile testing. We have delivered over 600 automated testing systems worldwide and continue to install approximately 40 systems every year. We take pride in our ability to match the right testing solution to each client’s unique business requirements, providing tailored solutions backed by long-term service and support partnerships.
If you are interested in learning more about the right robotic tensile testing solution for your test challenges, we encourage you to reach out to our team.
A tensile test, or tension test, is a test used to determine how a material reacts to an applied (pulling) force. Properties that are directly measured while performing a tensile test are ultimate tensile strength, maximum elongation, and reduction in area. From these measurements, the following properties can also be determined: modulus of elasticity (Young's modulus), deformation (Poisson's ratio), yield strength, and strain-hardening characteristics.
- Ultimate tensile strength - the maximum tensile stress a material can withstand before breaking
- Maximum elongation – the maximum strain a material can experience before failure
- Reduction in area – comparison between the original cross-sectional area of a specimen and the minimum cross-sectional area of the same specimen after complete fracture failure. It is used as an indicator to show to what extent a material will deform when subjected to a tensile load.
- Young’s modulus – essentially the stiffness of a material. That is, it indicates how easily a material will bend or stretch:
- Young’s modulus = Stress/Strain
- Stress = force/cross sectional area
- Strain = change in length/original length
- Poisson’s ratio – the ratio of change in the width to change in length in the direction of the stretching force.
- Yield strength – the maximum tensile stress an elastic material can undergo before permanent deformation occurs.
- Strain-hardening characteristics – strain hardening, also referred to as work hardening, occurs when a material is stretched beyond the yield point. Strain hardening increases the mechanical resistance and hardness but decreases ductility. Manufacturers can use this information to determine the material that meets their ductability requirements while maintaining the highest strength possible.
The data obtained during a tensile test can be plotted on a graph to produce a stress/strain curve.
This stress/strain curve shows a curve with a high level of strain hardening (1) and with a low level of strain hardening (2) after the yield point.
Manufactures in every industry from plastics and composites, to automotive, food and beverage and the highly regulated medical and pharmaceutical industry use tensile testing equipment to perform industry-standard tests to precisely measure the defining properties of their material, ensure standard-compliance, and ultimately be able to guarantee the quality and safety of their products.
- Plastic packaging − tensile force is applied to a plastic material specimen to help manufacturers determine the protective characteristics of the plastic when it is subjected to pulling forces like those that occur during shipping processes, for example.
- Concrete-reinforcing steel bars − tensile tests on metal specimens are used to determine various mechanical properties such as yield strength, ultimate tensile strength, elongation, and reduction of area to help manufacturers not only meet advertised quality and high-performance specifications but to comply with industry standards to ensure that products are safe for market release.
- Rubber compounds for use in tires – the elongation and tensile strength of tire rubber is tested for quality control purposes to avoid tire failures such as tread separation and blowouts.
After quality, reliability of test results, cost, and application, many other factors should be taken into consideration when choosing your machine:
- Flexibility – the ability to test a wide range of materials in a wide load range, the integration and easy change between accessories specifically designed for individual industry standards, types of material and applications, the option to operate the machine with or without a PC, and the mechanical modularity that allows for expansion and adaptation of your machine using many available test fixtures and specimen grips, all contribute to the overall flexibility of your testing machine.
- Safety – the safety of your tensile tester is imperative and extends from the implementation of physical safety features such as external safety doors, safety enclosures, safety interlocks and limit switches to software system monitoring and user management. ZwickRoell is dedicated to designing our testing systems with operator and machine safety at the forefront.
- Ease of use – the key is to choose a testing system that is both sophisticated by design and operability, while at the same time allowing operators to easily install test fixtures, set up test configurations, implement test programs, run tests, and interpret results.
- Adaptability – market developments and standard requirements are always evolving. When deciding on a tensile tester, you should make sure that your machine is able to adapt to these changes - from accessories and fixtures to the electronics and software programs.
- Software – testing software is intended to make the testing process easier for the operator and ensure uniform and standard-compliant test configurations. Our testing software is designed with the user and laboratory workflow in mind.
- Standards library – our testing software includes over 600 standard test programs, which allows you to select the right standard-compliant program for your application, simplifying test setup and configuration, and ultimately saving you time and effort and reducing the possibility of errors. For tests that go beyond the standard or for the ability to freely configure the test sequence of your machine, our software offers pre-prepared master test programs.
- Intelligent wizard – an intelligent wizard guides the user through the test configuration. Data is automatically checked for plausibility.
- Reports – whether they are simple or customized, our software allows you to define reports with virtually unlimited possibilities along with the option to save, export, and print.
- Automation - there is an increasing rate in the use of automation in materials testing, especially since even the smallest disruptions can alter measured values. ZwickRoell offers a wide range of possibilities for automation in materials testing. Testing systems range from efficient automation of small series tests using collaborating robots in the lab to fully automated testing laboratories that work around the clock.
- Aftermarket support – ZwickRoell provides individually tailored services and support throughout the entire lifecycle of our testing machine. We provide expert calibration services, preventive maintenance and inspection, training courses, machine relocation services, qualification services, a hotline and customer support and guaranteed spare parts availability for at least 10 years after a product has been discontinued.
- Company stability – ZwickRoell history dates back more than 160 years. We proudly stand on a solid foundation of 187 product and industry experts, 347 service employees, 80,000,000 tests performed by our machines annually.