STD-4000 is designed to perform compression tests on various steel or ceramic cross sections at very low speed in accordance with the relevant standards.

Upset Test (Cold Heading Test) is a method for evaluating the mechanical properties of materials, particularly for assessing wire performance within acceptance limits and its ability to withstand large and rapid plastic deformations without cracking or failing. In this test, a wire specimen of specified length and diameter is compressed between two parallel platens, which increases its diameter and decreases its length. The primary purpose is to verify that the wire can undergo significant deformation without defects. While tensile tests provide information on material strength and ductility (e.g., elongation), the upset test is specifically used to investigate compressive behavior and volume formability, which are critical for Cold Heading processes.

The tensile testing machine operates hydraulically and controls the load through an electro-hydraulic actuator (EHA). Displacement precision is enhanced by an AC servo motor and driver. Feedback from a non-contact displacement sensor mounted on the actuator enables highly precise testing at very low speeds (down to 0.01 mm/min).

Such performance is typically problematic and unattainable with conventional hydraulic systems. Unlike traditional setups, the EHA does not require continuous high-power operation, thereby reducing heat loss, power consumption, and mechanical wear – eliminating the need for an auxiliary oil cooling system. A further advantage, often highlighted by the operators, is the significantly reduced noise level compared to standard hydraulic system.

A pressure transducer is used to measure compressive force up to 400 t. The load frame is designed to allow easy mounting of various compression platens (unidirectional, incremental type).

Precise speed control is ensured by feedback from a high resolution (0.1 mm) non-contact electronic ruler, which stabilizes test speed across a wide actuator range. These capabilities allow operator to perform tests in accordance with ASTM A370, E8M, E9, E-209, C39M, C1609M, ISO6892-1/2, and ISO13314 standards.

High-resolution extensometers are available for precise strain measurement directly from the specimen rather than from the actuator. The system supports SANTAM’s STM Controller and JADOO Controller software. With these, the machine can record displacement through the extensometer attached to the specimen while simultaneously using the extensometer as feedback for closed-loop control under JADOO software, ensuring precise loading rate.

Upset Test Results Assessment

• After compression, the specimen is visually checked for cracks, breaks, or any surface or internal defects
• To pass the test, the wire specimen must show no visible cracks or breaks; the presence of any visible defect results in rejection
• The final shape of the wire is also critical – the deformation must be uniform and symmetric

If the Test Is Performed at High Speeds

• Material response may differ: some materials, especially at high strain rates, show brittle behavior. In such cases, a wire specimen that is accepted at lower speeds may crack at higher speeds and be mistakenly rejected
• Local heat generation: rapid plastic deformation can generate heat at localized points in the wire, temporarily affecting its mechanical properties.
• Inertia and non-uniform uniform force distribution: at very high speeds, inertia nay cause the comprehensive force to be unevenly distributed across the cross-section, leading to unreliable results

Recommended Speed (Direction)

• Standards generally do not specify an exact test speed (e.g., X mm/min) for Upset test. Instead, they emphasize on controlled and gradual load application
• The test speed should be low enough that plastic deformation occurs slowly and in a controlled manner, ensuring results accurately reflect the wire’s ductility. High-speed loading must be avoided, as it can lead to unreliable results or premature crack initiation. For this reason, the test is typically conducted under static and quasi-static conditions at relatively low speeds (e.g., few millimeters per minute).