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ASTM E328 Stress Relaxation Test for materials and structures

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ASTM E328 Standard Test Methods for Stress Relaxation for Materials and Structures


ASTM E328 test method are testing for the stress relaxation of plastics has been withdrawn from this standard, and the responsibility has been transferred to Practice ASTM D2991. These test methods cover the determination of the time dependence of stress (stress relaxation) in materials and structures under conditions of approximately constant constraint, constant test environment, and negligible vibration. In the procedures, the material or structure is initially constrained by externally applied forces, and the change in the external force necessary to maintain this constraint is determined as a function of time.

The methods for conducting stress-relaxation tests on materials subjected to tension, compression, bending and torsion stresses are described in Parts A, B, C, and D, respectively. These test methods also include recommendations for the necessary testing equipment and for the analysis of the test data.


Stress relaxation of materials is an important characteristic when designing mechanical connectors, which must maintain permanent fastening. long-term failure of the connector may occur if stress relaxation is not considered. 

ASTM E328 Stress Relaxation Test for materials and structures


Load Application:

The ASTM E328 method involves preparing the specimen and applying a constant load to it using an universal testing machine. The decrease in stress within the specimens over time is monitored.


Measurement and Analysis:

The stress relaxation data is recorded as a function of time, strain, or temperature depending on the specific test objectives. The data is then analyzed to determine relaxation modulus, creep compliance, and relaxation time.


Safety and Best Practices in ASTM E328 Testing: 

Testing requires safe handling of materials and equipment especially in high-stress conditions use of PPE, maintenance of the test environment, and reqular maintenance. Proper documentation ensures compliance with industry regulations and traceability. 

Related Standard

ASTM A1061, A416 Multi-Wire Steel Prestressing Strand Tensile Elongation Test

ASTM A1061 tensile test for breaking elongation stress relaxation on steel wire deals with the standard types and grade requirements of seven-wire, uncoated steel strands for use in the construction of pre-tensioned and post-tensioned pre-stressed concrete. 

The two types of strand specified by the ASTM A1061 specification are low-relaxation and stress-relieved (normal relaxation). The base metal shall be made of carbon steel and shall undergo stranding and continuous thermal and mechanical treatment. Final product requirements of ASTM A1061 shall be furnished on reels or in reelless packs for packaging and marked with two strong tags for identification. The requirements specified in ASTM A1061 shall also be applicable for pre-stressed ground anchor construction.

ASTM A1064 Shear test for Steel Wire and Welded Wire Reinforcement, Plain and Deformed

ASTM A1064/A1064M : Standard Specification for Steel Wire and Welded Wire Reinforcement, Plain and Deformed, for Concrete


ASTM A1064 test standard covers steel wire and welded wire reinforcement produced from hot-rolled rod to be used for the reinforcement of concrete. The steel wire is cold-worked, drawn or rolled, plain (non-deformed, as-drawn or galvanized), or deformed. Welded wire reinforcement is made from plain or deformed wire, or a combination of plain and deformed wire. 


UnitedTest supply the testing machine and shear fixture to test the welded wire mesh, steel wire mesh, welded wire fabric such as used for concrete reinforcement. 

ISO 15630-3 Testing of Prestressing Steel Strands Relaxation, Fatigue, Tensile testing

ISO 15630-3 Steel for the reinforcement and prestressing of concrete — Test methods — Part 3: Prestressing steel

This standard specifies test methods applicable to prestressing steel (bar, wire or strand) for concrete.

ISO 15630-3, ASTM A416 and ASTM A1061 test standards offer guidelines for testing steel strands. Manufacturers of steel strands are required, through product standards, to test their products using both static and dynamic conditions.

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