ISO 3800, DIN 969, MIL-STD-1312: Fatigue Test on Threaded Fasteners
The ISO 3800, DIN 969 and MIL-STD-1312 describe fatigue tests on threaded fasteners to determine high cycle fatigue.
As some of the most important fasteners, bolts, screws and studs are not only considered universally important in industry settings, but also for every day purposes. They are used in the construction of complex machinery and equipment, as well as vehicles and buildings. where they are usually subjected to cyclic loading.
The fatigue test on threaded fasteners is carried out with a constant mean load or a constant load ratio, until a specified number of cycles has been reached or until the specimen breaks. The collected test results can be displayed on an S-N curve.
Standards Test objective Video Running a test Testing machines Testing software Downloads
Standards for fatigue tests on threaded fasteners
The following standards are used for fatigue life testing of threaded connections:
- ISO 3800:Threaded fasteners; axial load fatigue testing; test methods and evaluation of results
The ISO 3800 standards specifies the requirements for the performance of axial load fatigue tests on threaded fasteners and provides recommendations for evaluation of the results. - DIN 969:Threaded fasteners - axial load fatigue testing - test methods and evaluation of results
The DIN 969 standard is almost identical to ISO 3800. However, DIN 969 does not include the combined test method (ISO 3800;1993 Chapter 7.4) described in ISO 3800. - MIL-STD-1312: Military Standard:Fastener Test Methods
The military standard MIL-STD-1312 establishes methods for testing fasteners to determine their physical and mechanical properties.
Objective of the fatigue test on fasteners to ISO 3800, DIN 969
The fatigue test is performed to evaluate the reliability and durability of threaded fasteners under real-life operating conditions. The test is used to verify if a threaded fastener is able to withstand a specified load for a specified duration, without any deterioration occurring from a strength perspective.
With this test, manufacturers can evaluate the quality of their threaded fasteners and, if necessary, make improvements to increase product reliability.
Performing a test to ISO 3800
The screw or threaded fastener is clamped in a fatigue testing machine. The screw is normally positioned so that the load is applied in the direction of its optimum strength direction.
The cyclic load is applied until the screw breaks or the specified number of cycles has been reached.
Specimen grips for testing threaded fasteners to DIN 969 & ISO 3800
ZwickRoell offers special specimen grips designed for fatigue tests on threaded fasteners under tensile and pulsating tensile load.
The lateral window openings on the specimen grip allow the screw to be inserted quickly and easily. The specimen is clamped by means of interchangeable reduction inserts selected according to the diameter of the screw. To make sure that the screws are properly fastened in the specimen grips, they are secured with a screw nut.
Testing machines for fatigue tests to ISO 3800, DIN 969
The vibrophore achieves very high frequencies with minimal energy consumption, which enables time- and cost-efficient durability testing on threaded fasteners. It is a full-fledged static and dynamic testing machine with a stiff four-column load frame and large test area that allows for testing of short and long screws and bolts. The installed load cell features an integrated accelerometer for mass compensation.
Fatigue data evaluation - the efficient evaluation of S-N curves according to ISO 3800
Fatigue Data Evaluation calculates S-N curves based on previously generated test results. This immediately provides the characteristic curve in the desired format. There is no need for you to create in-house Excel or Matlab calculation templates.
The test data generated with testXpert R is seamlessly transferred and integrated in the evaluation, and therefore does not have to be prepared separately. testXpert delivers the test data in the exact format required by the Fatigue Data Evaluation solution.
The test results on which the calculation of the S-N curve is based are visible to you in parallel to the curve and you can select them using the filter and selection functions.
