GB/T 3098.18: Blind Rivets Mechanical Test Methods

Introduction to Shear and Tensile Testing

The GB/T 3098.18 standard specifies test methods for evaluating the mechanical properties of blind rivets, particularly core-pulling (draw-core) and drive (hit-core) types. These tests focus on shear and tensile strength, which are critical for ensuring the reliability of fasteners in various industrial applications such as aerospace, automotive, and construction. Shear testing assesses the rivet’s ability to withstand forces perpendicular to its axis, while tensile testing evaluates resistance to pulling forces along the axis. This standard ensures that blind rivets meet performance criteria under simulated real-world conditions, preventing failures in assembled structures.

Blind rivets are advantageous in scenarios where access is limited to one side of the workpiece. Core-pulling rivets involve a mandrel that is pulled to expand the rivet, while drive rivets are set by hammering. The standard outlines precise fixtures and procedures to minimize variables like deformation or misalignment, promoting accurate and reproducible results. Compliance with this standard is essential for manufacturers to certify product quality and for engineers to select appropriate fasteners. It references related standards like GB/T 3722 for testing machines, ensuring interoperability across testing protocols.

In practice, these tests help identify material weaknesses, such as insufficient hardness or dimensional inaccuracies, which could lead to premature failure. For instance, in high-vibration environments, superior shear strength is vital. The standard differentiates between routine and arbitration tests, where arbitration fixtures provide definitive results in disputes. This dual approach balances efficiency in production testing with precision in quality assurance. Overall, GB/T 3098.18 contributes to safer and more durable mechanical assemblies by standardizing evaluation methods, drawing from extensive industry experience in materials science and engineering.

Furthermore, the standard emphasizes the use of high-hardness steel for test plates and bushings to withstand test loads without influencing outcomes. It also addresses rivet installation per manufacturer recommendations, ensuring tests reflect actual usage. By incorporating detailed diagrams (though not reproduced here, referenced in the original), it aids in visualizing fixture setups. This comprehensive framework supports global harmonization of fastener standards, facilitating international trade and innovation in fastening technologies.

Test Principles

The fundamental principle of the tests in GB/T 3098.18 involves applying shear or tensile loads to blind rivet specimens fixed in specialized fixtures until failure occurs. For shear tests, the load is applied transversely to simulate cutting forces, while tensile tests apply axial loads to mimic pulling apart. This methodology allows for the determination of maximum load capacities, which are compared against specified minimum values to assess compliance.

In shear testing, the rivet is subjected to forces that attempt to slide the joined plates relative to each other, revealing the rivet’s resistance to such deformation. Tensile testing pulls the rivet along its length, testing the integrity of the head, body, and core. Both tests are conducted until damage, defined as fracture, deformation, or separation, providing data on ultimate strength. The standard ensures that loads are applied steadily to avoid dynamic effects that could skew results.

Key to these principles is the control of variables: fixtures must minimize plate deformation, and test machines must align loads precisely. This precision is crucial in industries where rivet failure could have catastrophic consequences, such as in aircraft fuselages. The principles align with broader mechanical testing standards, emphasizing repeatability and traceability. For blind rivets, specific considerations include the core type—breaking, non-breaking, or locking—which affects how loads are distributed during testing.

Practically, these tests inform design decisions, allowing engineers to calculate safety factors based on empirical data. They also support quality control in manufacturing, where batches are sampled and tested to ensure consistency. By adhering to these principles, the standard promotes advancements in rivet materials, such as high-strength alloys, enhancing overall performance in demanding applications.

Test Fixtures for Shear and Tensile Tests

The standard prescribes specific fixtures for shear and tensile tests, divided into routine and arbitration types. Routine fixtures are suitable for standard evaluations, while arbitration fixtures serve as definitive in disputes. For shear tests, routine fixtures (as in Figure 1) use steel plates with hardness ≥420 HV30, fixed to minimize deformation. Plates are discarded if holes become non-circular, worn, damaged, or exceed maximum diameters in Table 2.

Arbitration shear fixtures (Figure 3) employ bushings (Figure 2) made of quenched and tempered steel with ≥700 HV30 hardness, replaced for each test. These ensure automatic centering in the machine. Similarly, tensile routine fixtures (Figure 4) follow comparable material and discard criteria. Arbitration tensile fixtures (Figure 5) use the same bushing specifications, with options for spacers on longer rivets.

Fixtures incorporate surface roughness Ra=1.6 μm, deburred edges, and countersink angles matching rivet head nominals with tolerances -2° to 0°. Minimum circular area around specimens is D=25 mm. These designs prevent extraneous influences on test results, ensuring loads are purely shear or tensile. In engineering practice, proper fixture selection reduces variability, enhancing test reliability.

The distinction between routine and arbitration underscores the standard’s rigor, providing escalation paths for verification. Materials like high-hardness steel are chosen for their durability under repeated loads, reflecting industry best practices. This setup facilitates accurate measurement of rivet performance, critical for applications in structural engineering.

Thickness and Hole Diameter Specifications

Thickness specifications in Table 1 vary by rivet core type, ensuring plates or bushings adequately support the rivet during testing without premature failure. Hole diameters in Table 2 are tightly controlled to match nominal rivet sizes, preventing slippage or excessive play that could invalidate results. These dimensions are derived from empirical data and material properties to optimize test accuracy.

In application, adhering to these specs ensures consistent load distribution, crucial for valid comparisons across different rivet designs. Variations in thickness accommodate different head types, like protruding or countersunk, affecting stress concentrations. This precision supports advanced simulations in finite element analysis, where accurate inputs yield reliable predictions.

Rivet Forming and Assembly

Rivets are assembled by joining two identical thickness plates or bushings using the specimen, following manufacturer-recommended installation procedures with appropriate tools. Total assembly thickness must not exceed the rivet’s maximum specified riveting length, ensuring realistic simulation of service conditions.

This process replicates field installation, testing the rivet’s performance post-setting. Proper forming is vital to avoid defects like incomplete expansion, which could compromise strength. The standard’s emphasis on identical components minimizes asymmetry in load application.

In industry, this step integrates with quality systems, where assembly parameters are controlled to meet certifications. It also allows for evaluation of installation tools’ impact on final properties.

Test Procedures

Assemblies are mounted on compliant testing machines (GB/T 3722, GB/T 16491, or JB/T 9375), with fixtures ensuring automatic centering and linear load application along the shear plane or tensile axis. Loads are applied continuously at 7-13 mm/min until failure, recording maximum loads as the rivet’s capacity. Failure before minimum specified loads results in non-compliance.

These procedures standardize testing, enabling comparable results across labs. Speed control prevents rate-dependent effects, ensuring quasi-static conditions. Recording maximum loads provides quantitative data for specifications.

Practically, this facilitates batch acceptance testing and failure analysis.

Special Considerations for Short Rivets

For rivets with maximum riveting lengths shorter than twice the minimum thickness in Table 1, combined plate/bushing thickness equals the maximum length. Evaluation depends on whether plates withstand loads or fail prematurely.

1. If plates remain intact until rivet failure at or above minimum load, the rivet passes.
2. If rivet intact but plates fail at or above minimum, rivet passes without maximum load determination.
3. If plates fail below minimum with rivet intact, acceptance by agreement.
4. If rivet fails below minimum, it fails.

This accommodates design variations, ensuring fair assessment.

Sıkça Sorulan Sorular (SSS)

What distinguishes routine from arbitration fixtures in GB/T 3098.18?

Routine fixtures are for standard tests, while arbitration ones provide definitive results in disputes, using higher hardness materials and new bushings per test for precision.

How should test plates be discarded?

Discard if holes become non-circular, show wear, damage, or exceed Table 2 maximum diameters to maintain test integrity.

What load application speed is required?

7-13 mm/min continuously until failure, ensuring consistent, quasi-static testing conditions.

How are short rivets evaluated differently?

Use combined thickness equal to maximum riveting length; pass/fail based on whether plates or rivet fail first relative to minimum loads.

Why specify hardness for test materials?

Hardness ≥420 HV30 for plates and ≥700 HV30 for bushings prevents deformation, ensuring loads accurately reflect rivet properties.