Tensile testing machine is a basic and widely used mechanical property testing equipment in the field of materials science and quality control. It provides key data support for product development, process optimization, and quality control by simulating the performance of materials under stress such as stretching, compression, and bending. This article will delve into the uses, working principles, classifications, selection points, and standard operating steps of tensile testing machines.
Uses:
The tensile testing machine has an extremely wide range of applications, covering almost all solid materials and some semi-finished products. Its main uses include the following aspects.
It is used to determine the mechanical properties of materials, such as tensile strength, yield strength, elongation at break, elastic modulus, Poisson's ratio and other core parameters of metals, plastics, rubber, textiles, composites, adhesives, leather, paper, and other materials.
It is used for process performance testing to evaluate the adaptability of materials under specific processing conditions, such as strength testing of welding joints, cupping tests of plates, repeated bending tests of wires, etc.
It is used for mechanical verification of components and finished products, and the actual force test of springs, fasteners, electronic component leads, medical sutures, packaging bag seals, etc. is carried out to verify whether they meet the design or use requirements.
It is used for adhesive and composite strength testing, evaluating the bond strength of adhesives or the interlayer bonding strength of composites through peeling such as T-peel or 90-degree peeling, as well as shearing.
It is used for quality control and failure analysis, and is regularly inspected during the production process to ensure the consistency of product mechanical properties. When a product breaks or fails, the cause of failure can be analyzed by reproducing the stressing process.
Principle
The principle of operation of the tensile testing machine is based on the basic laws of physics, the core of which is to precisely control the load applied to the specimen and to measure the resulting deformation of the specimen simultaneously. The whole process follows a specific logical closed loop.
The first is the clamping and driving link. The standardized specimen is installed between the upper and lower chucks of the testing machine through a special fixture. The drive system, usually a servo motor or hydraulic system, moves the beam at a uniform speed at a set speed, applying axial tensile force to the specimen.
The second is the force value perception link. The applied load is transferred to a force sensor that is connected in series with the specimen. The sensor converts mechanical deformations, such as changes in the resistance of strain gauges, into electrical signals, which provide real-time feedback on the magnitude of the current load.
Then there is the deformation measurement link. The elongation of the specimen is recorded by measuring the distance traveled by the beam by a displacement sensor, or by measuring the deformation within the gauge by means of a more accurate extensometer clamped directly on the specimen.
Finally, there is the data collection and control link. The control system collects force values and deformation data in real time, and draws the stress-strain curve or force displacement curve. By analyzing these curves, the software automatically calculates key characteristic values such as yield point, maximum force, and break point.
Common types
According to the different driving methods, structures and measurement accuracy, tensile testing machines can be mainly divided into the following types.
According to the driving mode, there are mainly electronic universal testing machines and hydraulic universal testing machines. The electronic universal testing machine is driven by a servo motor, which transforms the rotational motion into a linear motion of the beam through a ball screw. It is characterized by high accuracy, wide speed range, and no oil pollution, and is suitable for small and medium-sized force values that require high load and deformation control, such as plastics, films, fine metal wires, composite materials, etc. The hydraulic universal testing machine is driven by a hydraulic cylinder and the load is applied through the hydraulic control system. It is characterized by large load capacity and sturdy structure, and is mainly used in high-strength and large-load testing occasions such as metal materials, large components, and steel bar connectors.
According to the structural form, it includes single-column, double-column and horizontal. The single-column type has a compact structure and small footprint, and is usually used for light load testing with small loads such as less than 5kN, and is suitable for testing thin films, rubber, optical fibers, etc. The double-column type, also known as the portal type, has a stable structure and uniform force, and is a common form on the market, covering the test range from medium to large loads, providing better rigidity and neutrality. The horizontal type is mainly designed for extra-long specimens such as wire ropes, cables, textile filaments, or special tests such as peeling and friction, which is convenient for clamping long materials.
Selection skills
Choosing the right tensile testing machine is key to ensuring the validity of your test data and ROI. The following logical ideas should be followed when selecting.
First, clarify the test materials and standards. Determine the main test materials and the testing standards they follow, such as ISO, ASTM, GB, etc. The standard specifies the required test force range, speed accuracy, extensometer requirements, and fixture form.
Secondly, determine the load range. Estimate the maximum test force based on the strength of the material. It is recommended that the equipment range be within the common test force range, usually between 20% and 80% of the full scale, to ensure the best accuracy. A certain margin needs to be reserved, but it should not be too large, so as not to lack accuracy in small force value testing.
Next, focus on speed and precision. Depending on the requirements of the test standard, see if the beam speed adjustment range of the equipment meets the requirements, for example, rubber tests may require high speeds, while metal tests are relatively slow. At the same time, confirm the force accuracy level of the equipment, usually 0.5 or 1, and the displacement measurement accuracy.
Then pay attention to the matching of the fixture with the attachment. Fixtures are the key to the success or failure of the test. The corresponding fixture must be selected according to the shape of the specimen, such as sheet, rod, line, special-shaped, and material, such as fragile, high hardness, and softness, and whether it is necessary to be equipped with expansion accessories such as high-temperature furnace, high and low temperature chamber, extensometer, etc.
Finally, evaluate the software functional requirements. Evaluate whether the test software is user-friendly, whether the data management system is complete, whether it can export customized test reports, and whether it has complex calculation functions such as tearing, cyclic tensioning, relaxation, etc.