Din En Iso 16047

[Isabella Kells]

1X106 HeLa cells were intracellularly stained with 0.4 ug Anti-Human Histone H4 (16047-1-AP) and CoraLite488-Conjugated AffiniPure Goat Anti-Rabbit IgG(H+L) at dilution 1:1000 (red), or 0.4 ug Isotype Control. Cells were fixed and permeabilized with Transcription Factor Staining Buffer Kit (PF00011).

Chromatin was prepared from HEK-293 cells. The ChIP was performed with 10 g of cross-linked chromatin, 5 g of 16047-1-AP or Normal Rabbit IgG, and 60l of Protein A sepharose beads. The immunoprecipitated DNA was quantified by real time PCR. Primers are located in the first kb of the transcribed region.

Histone H4 is a 103 amino acid protein, which belongs to the histone H4 family. Histone H4 localizes in the nucleus and is a core component of nucleosome. Nucleosomes wrap and compact DNA into chromatin, limiting DNA accessibility to the cellular machineries which require DNA as a template. Histones thereby play a central role in transcription regulation, DNA repair, DNA replication and chromosomal stability. DNA accessibility is regulated via a complex set of post-translational modifications of histones, also called histone code, and nucleosome remodeling.

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ISO 16047:2005 specifies the conditions for carrying out torque/clamp force tests on threaded fasteners and related parts. It is applicable, basically, to bolts, screws, studs and nuts made of carbon steel and alloy steel, whose mechanical properties are specified in ISO 898-1, ISO 898-2 or ISO 898-6, having ISO metric threads with thread sizes M3 to M39. It is also applicable to the combination of other externally and internally threaded fasteners with a triangular ISO thread according to ISO 68. It is not applicable to set screws and similar threaded fasteners that are not under tensile stresses, nor to screws which form their own mating thread or threaded fasteners having additional self-locking features.

Amendments are issued when it is found that new material may need to be added to an existing standardization document. They may also include editorial or technical corrections to be applied to the existing document.

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Experts in fastener engineering know bolted joints can be troublesome. But given the lack of attention they frequently receive both during design and assembly, it is surprising they are not more troublesome than they are. I would argue the reason is, historically, many bolted joints have been over designed. However, as industries push for efficiency and lighter weight assemblies, bolted joints are asked to do more with less. Improving fastening efficiency requires increased confidence in the clamp load achieved with a given tightening strategy. Torque control is still the most commonly used tightening strategy, and while advances continue to be made in the accuracy and reliability of tooling, it is still only as good as the consistency in the relationship between torque and tension.

It can easily be forgotten that screws are one of the six simple machines (along with pulleys, levers and the like). The screw can take a small applied rotational force (torque), and multiply it into a large linear force (clamp load). However, only about 10% of the applied torque actually goes into creating clamp load, while the rest is consumed by friction. The numbers will vary based on joint components, but approximately 50% to 55% of torque is consumed by friction between bearing surfaces and 35% to 40% is consumed by friction between thread surfaces (and while losing 90% of your torque to friction may seem undesirable, keep in mind this is also the reason a nut stays tight and does not spin off immediately after you stop applying torque)! It then follows that controlling friction is the key to consistent clamp force at assembly. Zinc-aluminum flake coatings now come with a variety of formulations, lubricants and top coats to dial in torque-tension relationships, and topcoats have even improved the consistency of zinc electroplating. More and more OEMs are releasing fastener coating specifications now requiring specific torque-tension performance.

Now that the challenges with ISO 16047 are known, two ways its use can be improved are provided. First, the ISO fastener committee responsible for the document (TC 2 / SC 11), is aware of these challenges, and a project has been initiated to improve the standard. The intent is to remove as many of the options and variables as possible, so less experience or interpretation is required, and repeatability and reproducibility of results can be improved. Currently, Peak Innovations Engineering is participating in a study to determine if more tightly controlling the test washers and test nuts may reduce variability in results. However, the revision of ISO 16047 will be a multiple year process, with collaboration from industry experts from multiple countries. In the meantime, it is up to users of the standard to understand the limitations, further specify those requirements that the standard leaves open and use reputable sources for obtaining results.

In summary, the combination of advances in fastener assembly equipment and coatings can allow for increased confidence in clamp load achieved at assembly. This enables designs to use less or smaller fasteners by better utilizing their strength capacity. Benefits are reduced weight, improved assembly efficiency, and overall reduced costs. For all of this to be true, though, a sound understanding and control of fastener torque-tension performance, whether through coefficients of friction, K factors, or in-joint performance tests is required. While ISO 16047 serves as a guide for how to test for some of these parameters, it cannot stand alone without knowledge of its limitations and loopholes. Peak Innovations Engineering understands these limitations and can help assess what testing is best suited to improve your fastening performance.

Company Profile:

Peak Innovations Engineering has a highly technical team to design, test, validate, and enhance the bolted joints within your product application. Joint development and testing are all we do, so we do it better than other available options, both internal and external. Why consume your resources engineering and problem-solving areas that are secondary to your core responsibilities when we can take care of them quickly, definitively, and cost-effectively? www.pieng.com

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