There
is an interesting but incomplete 2026 book by Alex Davies titled Kobuk the
Destroyer and other tales from the wild, unseen world of test engineering. (Kobuk
is a problem grizzly bear at the Grizzly & Wolf Discovery Center, who is an
expert at defeating products that should be bear-resistant). Google Books has a preview from this book. Alex begins describing it on page 5:
“Implementing
an idea hinges on, among other things, proving that whatever ends up in the
consumer’s hands will actually work, reliably and safely. That the thing will
hold its form and perform its function for years or decades. That when it
breaks, it won’t send razor-edged shards flying. That it will blunt the
consequences of the inevitable errors of the humans that use it, interact well
with its environment, and work in a way that its users expect and desire. Doing
all that requires the ability to foresee and forestall the novel modes of
failure that arrive with every innovation. That work falls most often not to
the inventor, but to the test engineer.
The
test engineer gets little attention in a world that lionizes inventors, and
that’s a shame – not just because their work involves chicken cannons,
flamethrowers, and mischievous grizzly bears, and not just because they rely on
the same ingenuity, foresight, and creativity that fits the inventor
stereotype. It’s a shame because they are the ultimate fixers, the people who
turn inventions into products by earning and rewarding the public’s trust.
This
book is about their work as it plays out in myriad times and places, with
manifold products and test regimes and industries. It’s about the people and
the machines and the laboratories and the standards and the cultural mores, the
measurement and mimicry of reality, the passing of judgment, and the occasional
shrug of the shoulders in the face of unending complexity. It’s about
approximating the inevitable and the near impossible: how pilots will mix up
instrument controls and how turbulence might snap plane wings. It’s about
avoiding not just the obvious disasters (the levee that crumbles) but the
equally catastrophic and stupefying ones (the tsunami that overtops the dam).
It’s about creating systems for doing that work – systems that, like the people
who make them, are fallible but can deliver success despite their
imperfections.
It's
about failure and failure and failure and fleeting interregnums of success.
It’s about how knowledge is formed, how rules are written and enforced, how
good things are made and bad things made good. It’s about accepting – whether
due to pain, disaster, or a honey-smeared bear snout – that our best efforts
are not always good enough. It’s about how we adapt to that fact by balancing
risk against reward, utility against safety, progress against hesitancy.
It's
about how we construct our world, because testing forms the backstory and
backbone of every thing in our lives.”
And
on page 15 he continues:
“THE
BEST PATH TO SUCH AN ENLIGHTENMENT IS NOT TO STUDY one product after another –
cars, planes, toys, and so on – but to break this work down by the kinds of
failure that test engineers regularly confront and plan for. We’ll look at six
different concepts, each of which encapsulates ways in which a product can boom
or bust.
The
first is limits, in which testing determines strength and durability –
like whether a bridge can withstand being hit by a container ship, or whether
your space bar will give out before your laptop does. The second is fool-proofing,
which is about preventing user error, from kids getting into medicine bottles
to lawn mowers lopping off toes. When failure does strike – when cars crash and
fires start – disintegration testing ensures that the product in
question minimizes the damage. Scale comes into play when the focus
shifts from one product to many, where ground beef is scanned for disease and
vaccines checked for impurities. Our penultimate chapter is about dynamics,
which considers how a product will impact the world around it, and vice versa.
This is where Formula I cars capture the wind and engineers redirect the
Mississippi River to buoy the sinking Louisiana coastline. Finally, we’ll close
with intention. This trickiest of all concepts asks not whether a
product functions as it’s designed to, but whether it produces the desired
result. As new technologies – artificial intelligence chief among them- push
everyone into a new frontier, we’ll see how our pioneering test engineers keep
up by combining old knowledge with new techniques.”
Chapter
titles and their starting pages are:
Introduction
– Bear Contact Time 1
Chapter
1 – Limits 17
Chapter
2 – Fool-Proofing 49
Chapter
3 – Disintegration 79
Chapter
4 – Scale 117
Chapter
5 – Dynamics 145
Chapter
6 – Intention 175
Conclusion
– The Total Test Environment 197
What
is missing from this book? Alex mentions some standards organizations –
Underwriters Laboratory (UL), the American National Standards Institute (ANSI),
the U. S. Consumer Product Safety Commission (CPSC), and very briefly the
Society of Automotive Engineers (now SAE International).
But
he does not mention either what was the American Society for Testing and
Materials (now ASTM International) or the International Standards Organization
(ISO). Standards produced by these organizations define a wide variety of
products. And typically, a product standard cross-references a constellation of
other standards.
If
you look for the strongest standard steel bolts or cap screws at stores like
Home Depot or Lowes, you will find them in a drawer labeled Grade 8. As shown
above, typically they will have a bronze color from zinc plating, and the head
will have six lines in a hexagonal pattern to identify them, along with a
manufacturer mark (in this case SJ). The standard for them is SAE J429:
Mechanical and Material Requirements for Externally Threaded Fasteners (most
recently dated 2014-05-06). You can read a pdf file of the 1999 version here. That
standard defines a very specific recipe for making Grade 8 fasteners – their composition,
processes and the resultant properties. The description summary says:
“This
SAE Standard covers the mechanical and material requirements for inch-series
steel bolts, screws, studs, screws for sems, and U-bolts in sizes to 1-1/2 in.
inclusive.
The
term ‘stud’ as referred to herein applies to a cylindrical rod of moderate
length threaded on either one or both ends or throughout its entire length. It
does not apply to headed, collared, or similar products which are more closely
characterized by requirements shown herein for bolts.
The
mechanical properties included in Table 1 were compiled
at an ambient temperature of approximately 20 °C (68 °F). These properties are
valid within a temperature range which depends upon the material grade used and
thermal and mechanical processing. Other properties such as fatigue behavior,
corrosion resistance, impact properties, etc., are beyond the scope of this
document and responsibility for ensuring the acceptability of the product for
applications where conditions warrant consideration of these other properties
shall be borne by the end user.”
J429
cross references the following six other SAE standards:
SAE J403: Chemical Compositions of SAE Carbon
Steels.
SAE
J404: Chemical Composition of SAE Alloy Steels.
SAE
J409: Product Analysis – Permissible Variations from Specified Chemical
Analysis of a Heat or Cast of Steel.
SAE
J123: Surface Discontinuities on Bolts, Screws, and Studs.
SAE
J417: Hardness Tests and Hardness Number Conversions.
SAE
J121: Decarburization in Hardened and Tempered Unified Threaded Fasteners.
J429
defines a very specific recipe for making Grade 8 bolts. The chemical
composition should allow heat treatment by quenching to produce a minimum of
ninety percent martensite (monitored via the as-quenched hardness). Then the
fasteners are tempered at a minimum of 800 oF. Threads are formed by
rolling.
Grade
8 has a minimum yield strength of 130,000 psi, and a minimum tensile strength
of 150,000 psi. Elongation is a minimum of 12%, and reduction in area is a
minimum of 35%. And the Rockwell hardness range is 33 HRC to 39 HRC. (39 HRC
converts to a maximum tensile strength of 177,000 psi).
The
next lower bolt grade (also quenched and tempered) is Grade 5, which is denoted
by a head with three lines in a triangular pattern. Grade 5 has a minimum yield
strength of 92,000 psi, and a minimum tensile strength of 120,000 psi.
Elongation is a minimum of 14%, and reduction in area is a minimum of 35%. Rockwell
hardness range is 25 HRC to 34 HRC. (34 HRC converts to a maximum tensile strength
of 152,000 psi).
Back
on November 4, 2017 I blogged about Ten years of experience, or one year’s
experience ten times? In that post I discussed SAE Standard J1401 – Road
Vehicle – Hydraulic Brake Hose Assembles for Use with Nonpetroleum-Base
Hydraulic Fluids. It included incorporating marker yarns (to identify the hose
manufacturer) along with the reinforcing braid. And using marker yarns was
spread to other types of hoses.
The
grizzly bear image came from Wikimedia Commons.
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