At 13:46 Hawaii time on 28 April 1988, Aloha Airlines Flight 243 — a 19-year-old Boeing 737-297 climbing through 24,000 feet between Hilo and Honolulu — suffered an explosive decompression in which roughly 18 feet of the upper fuselage skin and structure peeled away in flight; chief flight attendant Clarabelle “C.B.” Lansing was swept overboard and never recovered, eight people were seriously injured, and the cause was not a bomb, a bird, or pilot error but fatigue cracking and crevice corrosion that had linked along a cold-bonded lap joint until the cabin tore open like a tin. The aircraft, registration N73711, had flown about 89,680 pressurization cycles — among the highest of any 737 in service — on Aloha’s short inter-island hops, and each cycle had loaded the joint that failed.
The fracture began at the longitudinal lap joint along stringer S-10L, on the upper row of rivets where the upper fuselage skin overlaps the lower. The joint had been assembled with a cold-bonded epoxy-scrim adhesive intended to share the pressurization load across the bonded area rather than through the rivets alone. When that bond disbonded — a known defect in early 737 production — salt-laden humid air entered the gap, crevice corrosion attacked the faying surfaces, and the entire hoop load funneled into the rivet holes. There, the countersunk “knife-edge” rivet design left a thin, sharp lip of metal at each hole, an ideal site for fatigue cracks to initiate. Cracks formed at many adjacent holes at once.
This was multiple-site damage: not one large crack growing slowly toward a detectable size, but dozens of small subcritical cracks, each individually below the inspection threshold, growing in parallel along the rivet row. When the ligaments between them failed, the cracks linked instantaneously into a single running fracture and a “flap” of fuselage unzipped. The National Transportation Safety Board, in report AAR-89/03, fixed the probable cause as the failure of Aloha’s maintenance program to detect the disbonding and fatigue damage at S-10L — a detection failure, not merely a structural one. The metal had behaved exactly as fracture mechanics predicted; the system meant to catch it had not. Inspections ran at night under poor lighting, crews were untrained to find disbonds, a Boeing service bulletin and an FAA Airworthiness Directive on the books had a scope too narrow to mandate the joint that failed, and a passenger had seen a crack while boarding and said nothing. Aloha 243 became the founding case of the aging-aircraft era in commercial aviation.
Between 1942 and 1946 the United States emergency shipbuilding program saw nearly 1,500 significant hull fractures across its all-welded merchant fleet, and on 24 November 1943 the worst-case form of that failure killed: the Liberty ship SS John P. Gaines broke clean in two and sank off the Aleutian Islands in the cold North Pacific, with the loss of 10 lives. The cause was not enemy action, not overloading alone, and not bad seamanship. It was brittle (cleavage) fracture of low-toughness steel that, below its ductile-to-brittle transition temperature, snapped without yielding — a crack that initiated at a stress raiser and ran the length of the hull through continuous welded plate that gave it nothing to stop against.
The Liberty ship and its tanker counterpart, the T2, were welded rather than riveted because welding was faster, used less steel, and could be done by an unskilled wartime workforce trained in weeks. That choice met the production target — 2,710 Liberty ships in under four years — but introduced a fracture mode the riveted hull did not have: a welded hull is metallurgically continuous, effectively one sheet of steel, so a crack that starts anywhere can propagate uninterrupted from gunwale to keel, where a riveted seam would have blunted and arrested it. The steel was the second half of the problem: rolled to a chemistry high in sulfur and carbon and low in manganese, it had poor notch toughness and a ductile-brittle transition temperature that, in winter North Atlantic and North Pacific water, the ship routinely operated below.
The U.S. Board of Investigation convened by the Secretary of the Navy in April 1943, whose third and final report issued on 15 July 1946, fixed the mechanism in service-wide terms: of 4,694 merchant ships welded during the emergency program, 970 sustained fractures, attributable to notches in steel that was notch-sensitive at low operating temperatures. The cracks favoured a specific detail — the square corner of a cargo hatch, often coinciding with a welded seam, where two stress concentrators stacked. From that notch, in cold water, a cleavage crack could initiate at a stress far below the steel’s nominal strength and run the full beam of the ship. The remedy was material and structural, not operational, and the work — with Constance Tipper’s Cambridge demonstration of the transition-temperature mechanism — grew into modern fracture mechanics. The case did not produce a trial; it produced a discipline.
At approximately 17:00 on 15 December 1967, in heavy Christmas rush-hour traffic, the Silver Bridge carrying US Route 35 across the Ohio River between Point Pleasant, West Virginia, and Kanauga, Ohio, collapsed in seconds and dropped 37 vehicles toward the water; 46 people died and 9 were injured. The cause was not flood, not overload, not a barge strike. It was a single 2.5 mm (0.1 in) crack in the head of one eyebar — link 330 at the north joint C13N — that had grown silently for 39 years by stress-corrosion cracking and corrosion fatigue until the bar fractured in a brittle cleavage, unzipping a chain that had no second load path to catch it.
The Silver Bridge was an eyebar-chain suspension bridge, in which the main cables were replaced by chains of flat, pin-connected steel links called eyebars. Each link in the Silver Bridge chain was made of only two eyebars side by side, joined to the next by a large pin through the forged eye at each end. The 1928 design — by the J. E. Greiner Company, built by the American Bridge Company — used a high-strength heat-treated steel run at unusually high working stresses to save weight and money, carrying a 700 ft main span and 2,235 ft of total deck on chains barely thicker than they had to be. The economy that made the bridge cheap also made it fragile: a two-bar link has no redundancy, and heat-treated steel run at high stress has little fracture toughness in reserve.
The fatal crack began at the rim of the pin hole in the head of eyebar 330, where fretting against the 11 in pin and water pooling in the joint set up a corrosive environment under sustained tension. Over four decades a crack roughly 2.5 mm deep grew by the joint action of stress-corrosion cracking and corrosion fatigue. On a near-freezing December evening, with the steel at its most brittle and the deck loaded with stalled holiday traffic, the crack reached critical size and the eyebar head cleaved. Its partner bar could not carry the doubled load; the link parted, the chain went slack, and the span fell. The National Transportation Safety Board — in its first major highway bridge investigation — fixed the cause unambiguously, and the failure rewrote how the United States inspects its bridges. No routine inspection of the era could have seen a 2.5 mm crack sealed at a pin-hole rim 100 ft above the river; the bridge was built so that finding it was the only thing that could have saved it.
At 15:16 on 19 July 1989, cruising near 37,000 feet over north-central Iowa, the tail-mounted No. 2 engine of United Airlines Flight 232 — a McDonnell Douglas DC-10-10 carrying 296 people from Denver to Chicago — disintegrated without warning; 44 minutes later the crippled airliner broke up on landing at Sioux Gateway Airport, killing 112 and leaving 184 alive. The cause was not bird strike, pilot error, or fire. It was a single high-cycle fatigue crack that had grown for years from a metallurgical defect buried in the bore of one titanium fan disk, until the disk burst and threw high-energy fragments through every hydraulic line on the aircraft at once.
The disk was the stage-1 fan rotor of a General Electric CF6-6D turbofan, a forged Ti-6Al-4V component roughly a metre across spinning at takeoff and climb power. Embedded in its bore, dating to the original titanium melt, was a “hard-alpha” inclusion — a brittle, low-ductility region where the casting had absorbed roughly 2.07 percent nitrogen by weight against a specified maximum near 0.02 percent. Sitting in the most highly stressed part of the disk, around a tiny cavity within it a fatigue crack initiated and crept outward, one spin-up and spin-down at a time, through some 17,000 flight cycles of revenue service.
Because the DC-10’s three independent hydraulic systems all routed lines through the tail in the arc swept by a bursting tail engine, the uncontained debris severed all three at once and drained every drop of fluid. The crew — captain Alfred Haynes, first officer William Records, second officer Dudley Dvorak, and off-duty check airman Dennis Fitch, who worked the wing throttles by hand — flew an aircraft with no working flight controls to a runway on differential thrust alone. The forensic verdict in NTSB report AAR-90/06 was unambiguous: a fatigue fracture from a hard-alpha inclusion, missed by six successive fluorescent-penetrant inspections, compounded by hydraulic architecture with no protection against a total loss. The survival of 184 of 296 was attributed almost entirely to the airmanship of a crew flying a configuration the manufacturer had never deemed survivable.
At roughly 11:00 p.m. on 16 January 1943, while moored at the fitting-out dock of the Kaiser Swan Island shipyard on the Willamette River at Portland, Oregon, the brand-new T2 tanker SS Schenectady cracked almost in two with a report heard a mile away; no one was killed and no one was hurt, because the ship lay in still water under no sea load, but the hull failed by brittle fracture of notch-sensitive steel in near-freezing weather — a crack that ran across the deck, down both sides, and nearly through the bottom in a fraction of a second. The vessel had been delivered only seventeen days earlier, on 31 December 1942, after sea trials without incident. There was no storm, no cargo overstress, no collision; the failure was internal to the steel and the welds, which is precisely why it became the textbook emblem of wartime hull fracture.
The Schenectady was an all-welded ship, one of thousands of emergency-program merchant vessels the United States built at unprecedented speed by replacing slow riveted construction with continuous welding. Welding made the hull a single monolithic body of steel with no riveted seams to interrupt a running crack — and that continuity is what doomed it: when a brittle crack started, nothing in its path stopped it. The night air had fallen to about minus 3 °C and the river to about 4 °C, and at that temperature the ship-plate steel of the day — high in sulphur, low in manganese, with a ductile-to-brittle transition temperature often well above freezing — had no toughness. It behaved like glass.
The crack initiated at a weld near a stress concentration, propagated through the cold, notch-sensitive plate, and split the hull just aft of the superstructure. The deck and sides parted; the ship jack-knifed on the bottom plating that alone remained intact, the midbody rising clear of the water while bow and stern sagged toward the river bottom. The U.S. Coast Guard attributed the failure to faulty welding; a Board of Investigation weighed “locked-in” residual stresses, the sharp temperature drop, and design discontinuities. Later metallurgical work — most influentially that of Constance Tipper at Cambridge — settled the mechanism: the steel itself went brittle in the cold, and the welds and notch-bearing details merely gave the crack a place to start. Of 4,694 welded merchant ships in the emergency program, about 970 sustained hull fractures and nineteen broke completely in two; the Schenectady survives as the cleanest demonstration because it failed with zero external load, isolating the material and the weld from every other variable.
At about 12:30 in the afternoon of 15 January 1919, on Commercial Street in Boston’s North End, a 50-foot-tall riveted steel tank holding roughly 2.3 million US gallons of molasses split apart and discharged its entire contents in a wave that killed 21 people and injured around 150. The cause was not fermentation pressure, not sabotage, and not an explosion. It was a brittle fracture of the tank’s thin, low-manganese steel shell, initiated at the over-stressed rivet holes beside a manhole at the base, propagating at the speed of sound through plates that were never thick enough and never inspected.
The tank belonged to United States Industrial Alcohol (USIA), through its subsidiary Purity Distilling, and had been thrown up in 1915 to store the molasses that fed wartime demand for industrial alcohol and munitions. It was 50 feet high and 90 feet in diameter and held about 13,000 short tons of liquid when full. The man who ordered and oversaw its construction, USIA treasurer Arthur Jell, had no architectural or engineering training. He did not commission stress calculations, did not have the steelwork checked by an engineer, and skipped the standard practice of filling the completed tank with water to test it under load — running only a few inches of water into the bottom rather than the full hydrostatic test that would have revealed the leaks before they revealed themselves.
The shell leaked from the day it was filled. Molasses wept from the seams so persistently that USIA painted the tank brown to disguise the runs, and neighborhood children collected the drips. At least one employee warned management that the structure was unsound; the company’s response was to re-caulk. The forensic verdict, settled across a three-year court audit at the time and confirmed by modern fracture-mechanics analysis decades later, was unambiguous: the wall plates were roughly half as thick as the load required, the steel was deficient in manganese and therefore brittle, and the failure began as cracks at the rivet holes where stress concentrated. On a January day the metal was well below its ductile-to-brittle transition temperature, and a structure already loaded near its limit failed without warning and without yielding.
The disaster ended in one of the longest civil proceedings in Massachusetts history. A court-appointed auditor found USIA liable after years of hearings, and the company paid out about $628,000 in settlements — on the order of $11 million in present money. The litigation also did what the absent engineer never had: it forced the lesson into law. Massachusetts and then jurisdictions across the country began requiring that major structures be designed, signed, and sealed by a licensed engineer or architect, the regulatory ancestor of the professional stamp.