Knowledge

Validating and optimising your bolted joint design delivers safety and performance improvements, alongside streamlining costs. There is now a powerful new vibration test methodology using controlled shear force loading. It is significantly more advanced than traditional – and flawed – displacement amplitude-driven Junker Testing. This new approach enables you to test your bolted joint for resistance to rotational self-loosening under real-world conditions.

Testing underpins the fastener supply chain, from the fastener manufacturer’s basic fastener product performance and specification tests to the end-user Design Engineer’s bolted joint test rig and product testing. But testing in isolation has little value for fastener manufacturers, distributors and downstream original equipment manufacturers (OEMs). Design Engineers are increasingly integrating physical testing with software-based analysis to improve product safety and quality.

Vibrationmaster is engaged in commercializing a number of product lines based on their proprietary, patented technology, enabling the generation of vibration profiles with the specific advantage of continuously and independently controlling frequency and amplitude.

Abstract. Vibration can be desirable, such as when it is used to make music. More often, however, vibration is undesirable. It can introduce stress into mechanical systems and create fatigue that decreases service life. It can also loosen fasteners. This article discusses the root causes of the self-loosening of fasteners, then two practical examples illustrate the benefits and possible applications of vibration testing of fasteners, according to either standardised testing protocols or customised testing strategies simulating real-life conditions of the assembled parts. The requirements and protocols of the international standard ISO 16130, the USA national aerospace standard NASM 1312-7, the German national standard DIN 25201-4 B and its predecessor DIN 65151 are compared, with insights on their most suitable applications. Finally, the article describes a lean methodology to design a meaningful testing protocol.

Abstract. Are the Junker Test and standards based on it, DIN 65151, DIN 25201 and ISO 16130 fundamentally flawed for validating the integrity of bolted joints?

Did you know that the number of published scientific papers related to fastener self-loosening has grown 800% since 2013? Data from ResearchGate, ScienceDirect and others, all indicate the rotational self-loosening of fasteners is of increasing interest, and possibly concern, to an ever-growing number of researchers around the world. Read more about trends in scientific papers […]

What happens when fasteners become loose and how to prevent it? Fasteners self-loosening is the result of a combination of causes. Materials relaxation and embedding reduce the preload in bolted joints, in turn allowing vibration to initiate repeated transverse movement in the joint. Fasteners will come loose and fail, leading to equipment failures and dramatic […]

How can a team of mechanical engineers garantee the reliability and safety of bolted joints in new cars, planes or mobile phones, before they go into production? It is a well known fact that dynamic forces introduce stress and fatigue into mechanical systems and reduce their service life. Vibration can loosen fasteners, leading to dramatic […]

Locking threaded fasteners is essential to prevent bolted joints from becoming loose. Engineers designing new bolted joints, fasteners manufacturers and distributors rely on the fastener transverse vibration test to compare the relative performance of fastener locking solutions and design safer products. The Junker test procedures described in ISO 16130, DIN 65151 and DIN 25201-4 B […]

The Junker vibration test has become the standard for determining fasteners self-loosening behaviour under vibration. Testing procedures that reflect the real service conditions allow engineers to validate new bolted joints designs. If the purpose of testing is to certify fasteners to original equipment manufacturers (OEM) specifications or assess an insurance claim, ISO 16130, DIN 25201-4 […]