Design by Analysis: Historical Understanding

You can design simple things by mathematical physics you know, e.g. some Euler -Bernoulli theories can be enough to design a column under a table or some beams for cloth drying racks. Simple shapes, simple loads, simple material behavior, simple condition and simple interactions. Up to late 1950's (after World War II and Atomic bombings of Hiroshima and Nagasaki), engineers used and sometimes extended these rather simple mathematics to form mathematically closed solutions (analytical formulation) for common design problems like buildings, pressure vessels, airplane wing structure, combustion engines, etc. Trying to overcome the real challenges introduced by the needs for more sophisticated scenarios, they attempted several exact equations to design for complexities of loads, geometry, assemblies, interactions, conditions and material behaviors. When failed to abstractly justify the occurred events and accidents, they would flee to the reassuring world of scientific experiments to extract sufficient (empirical) data to enhance their formulations. Fracture mechanic is a good example of these (occasion driven) endeavors. As industries grew in production demand and politicians in economical concerns, it was found to be simply infeasible to conduct experimental campaigns for so many complex cases of designs and engineering. Sticking with what they had got so far, either conservatism or irresponsibility started to cover up for the new uncertainties. Uncertainties caused not only by mere lack of knowledge in physics and mechanical engineering, but also by witnessing several unpredictable failures like the ones shown below:

SS Schenectady Ship Fracture

Today easily predictable and preventable by sudden (brittle) fracture a damage mode considered under Design by Analysis

Tacoma Narrows Bridge Collapse

Today easily predictable and preventable by a simple modal analysis as part of Design by Analysis for vibrational loads.

These events became so common place that the whole society felt an alarming lack of competency in the engineering world that keep manifesting as rather stupid oversights. But the reality was that these failures were just unforeseen phenomena and events, rendering the design tools simply insufficient. At one point the fear of engineering failure became so tangible in public arena that it even manifested in movies of the time like No Highway in the Sky in 1951.

Therefore, in late 1950's some engineers with enough resources, capital and reputation started to fight against unpredictability of structures and machines in service and plausible accidents. As a consequence, at 1964 for pressure vessels in nuclear engineering, ASME introduced an approach toward design so powerful that never stopped growing in application since then and is still in use by experts to this day in all industries, Design by Analysis (DbA). Deviating from the previous Design by Rules or Design by Formulas where exact perfect mathematics or specific semi-empirical equations governed the whole design process analytically, DbA allowed numerical methods (instead of analytical) in approximating discrete and local quantities (instead of attempting exact mathematical solution for an entire continuum). DbA was backed by computational power in performing numerical iterations beyond human capacity in short time hence enabling designing for even the most complex scenarios of loads, geometry, assemblies, interactions, conditions and material behaviors. This was practically a bridge to bring in proven up to date and corrective academic knowledge into industrial practice to design more optimized systems in less time. Suddenly designing became dramatically easier and more reliable allowing saving time, money and number of employed engineers.

Analysis of a design scenario, as opposed to forcing rules and formulas of different and sometimes irrelevant origins into it, became the principle upon which engineers should have shown enough qualifications to be considered as design engineers. The term "Analysis" in this context means calculating the specific behavior of a mechanical system (that in its most basic form is a static structure) in response to a specific and clearly defined set of inputs using any type of mathematics to ensure functional and safety requirements. Tuned to address common short and long term metallic failure modes, the DbA encouraged stress analysis as the specific tool of conduct. Stress Analysis means calculation for determining an overview of the stress magnitude and distribution across the target body of the design. Finite Element Method (FEM) was therefore only a child of this open and inviting world. FEM thrived due to its special focus on stress and strain calculation as well as high compatibility to computer programming. Consequently, design by FEM started to devour all fields of engineering by its unparalleled predictive and diagnostic simulations, convincing senior engineers in its reliability over design by old formula for new designs and, elevating junior engineers in their ability for common practices of design engineering.

Design by Analysis using FEM surpassed all other design methods in engineering since it:

Is far more superior to human made design formulas both in terms of accuracy and range of application

Is easier to program than other numerical methods

Costs fractions of time and capitals spent on experimental campaigns

Is more versatile and inclusive than experimental tests

Unfortunately despite this important invention and advancement in computing power, technology and all rectifications made in engineering know-how to better the engineering design, lack of respect for life and integrity led many engineering products and reputation back to the dark ages.

Once they were at least humble enough confess it "... data on vessel quality provide evidence that part of the measured productivity increases were secured at the expense of quality" from https://www.journals.uchicago.edu/doi/10.1086/318605. But even such admissions are now rare as one can painfully learn from most of the Boeing's catastrophes after which whistles blowers keep dying some days before or after court appearances!

Therefore, as engineers (specially those practicing mechanical design), it is our historical responsibility to reclaim the rather lost reputation and ever more declining notion of quality by designing the best for the people. People include not only our planet mates or neighbors, who certainly judge us by the products we designed and made for them, but also ourselves and our loved ones.

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