James Henry Williams Jr. is a mechanical engineer, consultant, civic commentator, and teacher of engineering. He is currently Professor of Applied Mechanics in the Mechanical Engineering Department at the Massachusetts Institute of Technology (MIT). He is regarded as one of the world's leading experts in the mechanics, design, fabrication, and nondestructive evaluation (NDE) of nonmetallic fiber reinforced composite materials and structures. He is also Professor of Writing and Humanistic Studies at MIT.
Williams began his career in 1960 as an apprentice machinist at the Newport News Shipbuilding and Dry Dock Company. Within eight years he graduated from The Apprentice School, earned SB and SM engineering degrees from MIT, and returned to the Shipyard as a senior design engineer. Within another two years, he earned a PhD from the University of Cambridge, where he conducted theoretical elasticity and shell theory. He then chose to join the faculty at MIT, where he has spent the bulk of his career.
Williams was born in Newport News, Virginia, where he attended the segregated public schools. He was a rambunctious, "hell-raising" student who never took a textbook home. Still, Williams's brilliance was recognized by some of his teachers who permitted him to read whatever he chose while in school and devised especially difficult tests for him, independent of his classmates. Along with one or more of his teachers, he would also occasionally make up and grade the quizzes of his classmates. He went on to win statewide prizes in mathematics and science. He was also featured as a flutist in his high school band, and as an underclassman earned first chair in the all-state concert band. [1] [2]
In 1960, Williams was among the earliest African-Americans admitted to the selective Newport News Shipyard Apprentice School. It attracts an average of about 4500 applications per year for approximately 250 openings, with some of the applicants having earned bachelor's degrees. [3] [4] Williams is often regarded as the top academic student in the century-long history of the Apprentice School. In 1961 he won the Charles F. Bailey Bronze Medal (for the highest academic record by a first-year apprentice); in 1962, the Charles F. Bailey Silver Medal (highest academic record by a second-year apprentice); and, in 1963, the Charles F. Bailey Gold Medal (highest academic record by a third-year apprentice). Furthermore, in 1963 the Shipyard chose to award him a four-year full Homer L. Ferguson Scholarship to MIT. Throughout his years as a student at MIT, he consistently returned to the Shipyard during vacations and summers. [1] [2] [5]
In 1965, the Apprentice School awarded Williams the five-year diploma of Mechanical Designer. In 1967, he graduated from MIT with an SB in mechanical engineering, and after completing his SM in mechanical engineering in the winter of 1968, Williams returned to the Shipyard. During that period, he performed a range of mechanics calculations on the catapults, arrester cables, and power and propulsion systems of the nuclear-powered aircraft carrier USS Nimitz (CVN-68). During this same period, he held the title of Senior Design Engineer and was the only black among the hundreds of engineers at the Shipyard. In the fall of 1968, Williams entered the University of Cambridge (Trinity College) in England, earned the PhD in engineering, and returned to America to the mechanical engineering faculty of MIT in 1970. [6] [1] [7] [2]
Throughout his MIT career, Williams has been repeatedly acclaimed and honored with numerous awards. [8] [9] [7] [10] [11] [12] [13] [14] [15] [16] His teaching awards at MIT include:
Having served as the first Housemaster of MIT's undergraduate dormitory New West Campus Houses and having supervised more than 100 research theses, Williams is a highly regarded mentor of both undergraduate and graduate students. [9] [12] [17] [18] [19] [20] [21] [22] [23] [24] [25]
In the early 1970s, Williams sought to better understand the emerging carbon fiber reinforced polymeric composite materials, which were being touted as new materials to elevate the mechanical performance of structures. (Today, these materials are used in fighter and commercial aircraft, automobiles, ships, golf clubs, tennis racquets, and myriad other structures.) One of the major manufacturers of these new materials had observed that newly fabricated structures built from them had unacceptably high variabilities, resulting in structures of low reliability. Williams was retained as a consultant to determine why. [1] [26] In addition, Williams's efforts were recognized by both industry and the National Science Foundation and he was selected, through a university-industrial program, to spend the summer of 1974 at a major composites manufacturing facility. [27]
Williams soon realized that the unpredictability of the materials' properties was due to undetected flaws or damage within the materials as a consequence of either improper fabrication or handling, as well as the selection of the various constituents. When he examined the technical and research literature on the nondestructive testing (NDT) to find and characterize the flaws in those materials, he found very little. Moreover, the NDT results that he found generally related to metals, and most of them were qualitative. Then, in 1974, Williams founded the Composite Materials and Nondestructive Evaluation Laboratory in MIT's Mechanical Engineering Department. (He preferred the term "nondestructive evaluation" to the more common term of "nondestructive testing" to emphasize his interests in the broad structural behavior of materials even in the absence of macroscopic flaws.) [1] [26]
With his advanced facilities in applied mathematics and experienced insights in mechanical design, Williams sought—and his subsequent career is distinguished by—quantitative analyses and characterizations of composite materials' properties and residual life based on a combination of nondestructive measurements and theoretical mechanics. Such quantitative analyses and materials characterizations have elevated the field of nondestructive testing and increased the reliable use of composite materials and structures.
Williams has subsequently compiled an extensive list of research and consulting results—in several instances, groundbreaking "firsts"—in the design, fabrication, strength analysis, residual strength, fatigue life, and NDE of fiber reinforced composite materials and structures. As an industrial and governmental consultant and through his MIT Lab with his research students, he advanced the understanding of modern composite materials and structures, as well as the systems for experimentally testing them. [28] [29] [30] Among many achievements, he (1) conducted the theoretical stress analyses of isotropic and anisotropic shells subjected to symmetric and asymmetric loads; [31] [32] [33] [34] [35] (2) produced the first quantitative correlations for the solid-particle erosion of carbon fiber polymeric composites; [36] (3) conducted the stress analyses of adhesively bonded joints in composites; [37] [38] (4) analyzed the enhancement of composite properties by the introduction of thermoplastic microstructures; [39] [40] [41] [42] (5) conducted the elastic and plastic acoustic emission monitoring of materials and structures, including structural bridge steels; [43] [44] [45] [46] [47] [48] [49] (6) established the forefront of the quantitative thermographic analyses of composite materials and structures; [50] [51] [52] [53] [54] [55] (7) theoretically predicted and experimentally demonstrated the input-output signatures of ultrasonic transducers; [56] [57] (8) hypothesized and then produced the first ultrasonic wave–fatigue life correlations of as-fabricated composites; [58] [59] (9) hypothesized and then produced the first ultrasonic wave–residual strength correlations of impact-damaged composites; [60] (10) performed theoretical and applied ultrasonics of metals with and without macroscopic cracks, including a focus on structural bridge steels; [57] [61] [62] [63] [64] [65] (11) performed theoretical and applied ultrasonics of composites; [56] [66] [67] [68] [69] [70] [71] [72] [73] [74] [75] [76] [77] [78] [79] [80] (12) conducted theoretical and experimental dynamic fracture of composite materials and structures; [81] [82] [83] [84] [85] [86] [87] (13) performed theoretical analyses of wave propagation in anisotropic media as related to composite materials and structures; [88] [89] [90] [91] [92] [93] [94] [95] (14) developed statistical pattern recognition concepts for NDE; [96] [97] (15) devised strategies for the residual life prediction of composite aircraft structures; [98] [99] [100] and (16) developed acoustic emission and ultrasonic versus load correlations for synthetic braided mooring lines and composite tension legs for offshore deepwater platforms. [101] [102] [103] [104]
For the decade up to 2012, he and his research students have focused on the structural integrity damage assessment and repair of modern composites, with an emphasis on naval structures; and he continues to write sole-author documents on a range of technical topics, including several of the areas mentioned above, mechanical vibration and shock mitigation, and biomimetics. [6]
From the mid-1970s to the early 2000s, Williams also (1) conducted theoretical analyses on the earthquake isolation of buildings and structures by devising the highly unconventional concept of supporting them on sliding foundations; [105] [106] (2) developed wave-like analyses of the dynamics and control of large space structures for earth-orbiting structural systems; [107] [108] [109] [110] [111] [112] [113] and (3) performed numerous major governmental and industrial consultations, as briefly described below.
By the early 1980s, he had devised ultrasonic laboratory systems for monitoring the structural integrity of composite structures in high performance aircraft. [56] [114] He is known for having produced "the first theoretical models that predicted the acousto–ultrasonic waveforms as actually observed" in experiments and practice, as conducted at NASA Lewis and elsewhere. [57] Today, Williams is broadly recognized as one of the world's leading researchers in the mechanics and nondestructive testing of composite materials and structures: He was chosen by the editorial board of the American Society for Nondestructive Testing to be the first guest technical editor of its Special Focus issue on the NDT of Composites. [26]
Williams has also shown a sense of humor; 1) he led a group of students in building the world's largest yo-yo and tested it from the tallest building in Cambridge, Massachusetts; [27] [115] [116] (2) he has been called one of Boston's men of elegance and style; [13] [117] [118] [119] [120] and (3) he derived a mathematical proof of the counterintuitive number of rotations made by a non-slipping smaller cylinder rolling around a larger stationary cylinder, as presented in the popular "Ask Marilyn" column of the 72-year-old Parade Magazine, which is inserted into about 700 U.S. Sunday newspapers. [121] [122]
During his career, Williams has conducted dozens of industrial and governmental consultations including (1) papermaking calender rolls, for which "he is considered, by virtue of his extensive work in the field, to be the nation's leading expert on stresses in rotary paper dryers"; [33] [123] (2) the first automated system for installing recessed highway lane delineation reflectors; [124] (3) an earthquake analysis of the 500 KV bus system of the British Columbia (Canada) hydroelectric power generating station and the design of an isolation system to protect its electrical lines during seismic activity; [125] (4) the design of composite rocket motor casings; [126] (5) the residual-life prediction of composite aircraft structures; [127] (6) the stress analysis of a high-speed optical pulsing system; [128] (7) the stress analysis of pelvic implants and bone stints for the Orthopædic Unit of the Massachusetts General Hospital; [129] (8) the effect of ultrasonic irradiation on the enhancement of composite fabrication; [130] (9) the ultrasonic NDE delineation of strength and rupture modes in adhesively bonded joints; [11] [12] (10) the design of deepwater mooring composite systems for offshore oil platforms; [131] [132] [133] (11) an NDE regimen for the structural acceptance of composite automotive leaf springs; [134] among others.
In April 1991, Williams—at that time, the only native-born black American faculty member in the combined School of Engineering and School of Science at MIT—conducted a fasting sit-in each Wednesday throughout April. He was protesting the lack of black faculty and a lack of inspirational education for minority students. [135] [136] During his protest, he set up a temporary office in the corridor at the entrance of the offices of the MIT president and provost. He observed that some aspects of the black community have disproportionately suffered attendant with integration because, in the broadest sense, many talented blacks have left the black community (no matter where it exists)—they no longer live in or relate to it; "they have been encouraged to escape from their roots." The residual black community is less educated and financially poorer. He characterized this phenomenon as "neocolonialist." [137] [18] [25] [136] [138] [139] [140] [141] [142] [143] [144] [145] [146] [147]
On November 12, 2001, shortly after takeoff from John F. Kennedy International Airport, American Airlines Flight 587, an Airbus Industrie A300-600, crashed in Queens, New York, killing 251 passengers, a crew of 9, and 5 people on the ground.
At the request of several American Airlines pilots, Williams analyzed and then challenged the inspection requirements and the accident investigation conclusions of Airbus Industrie, the Federal Aviation Administration (FAA), and the National Transportation Safety Board (NTSB)—all of whom to varying degrees blamed the co-pilot of Flight 587 for the crash. The investigation and controversy concerning the crash focused on (1) the co-pilot's actions during takeoff, and (2) the aircraft's vertical stabilizer of the tail section, a complex structure of advanced composites. The vertical stabilizer on Flight 587 snapped off and landed in Jamaica Bay, away from the fuselage crash site.
According to Williams, Airbus adopted an inadequate inspection policy for its composite tail, the FAA approved Airbus's deficient inspection policy, and the NTSB mis-analyzed the cause of the airline disaster.
In so far as the vertical stabilizer was concerned, Airbus's nondestructive inspection policy was that damage that could not be seen with the unaided eye would not compromise its structural integrity. Such an inspection protocol greatly concerned Williams who characterized it as "a lamentably naive policy." [148] [149] Williams further stated and was frequently quoted in the print and broadcast media as describing Airbus's inspection policy as "analogous to assessing whether a woman has breast cancer by simply looking at her family portrait." [150] [151] [152] [148] [153] [154]
Through internet postings, [148] op-ed pieces, [153] industrial journal articles, [149] letters, [155] interviews in magazines and newspapers [150] [151] [156] [157] and TV appearances, [152] [158] [154] Williams challenged the preliminary remarks and the final report of the NTSB's accident investigation. Although there were several critics of the investigation, including varied pilots and pundits, Williams is widely regarded as the major engineering voice providing pushback against the conclusion that the air disaster was essentially the fault of the co-pilot.
Based largely on the steadfast criticism of Airbus and the NTSB by Williams, in a tour de force of engineering and civic commentary, he clearly influenced both the NTSB [159] and Airbus [160] to reverse their positions on the cause of the American Airlines 587 crash as well as the required inspection procedures, thus likely saving hundreds of lives of current and future commercial airline passengers. [150] [151] [157] [159]
Williams has written hundreds of technical publications in refereed journals, conference proceedings, and major reports to industrial and governmental agencies, dozens of non-technical op-ed and political commentaries, and two books. He is the author of the introductory textbook Wave Propagation and of the unconventional textbook Fundamentals of Applied Dynamics, which is a blend of history, dynamics and vibration.
Ultrasound is sound with frequencies greater than 20 kilohertz. This frequency is the approximate upper audible limit of human hearing in healthy young adults. The physical principles of acoustic waves apply to any frequency range, including ultrasound. Ultrasonic devices operate with frequencies from 20 kHz up to several gigahertz.
A composite material is a material which is produced from two or more constituent materials. These constituent materials have notably dissimilar chemical or physical properties and are merged to create a material with properties unlike the individual elements. Within the finished structure, the individual elements remain separate and distinct, distinguishing composites from mixtures and solid solutions. Composite materials with more than one distinct layer are called composite laminates.
Nondestructive testing (NDT) is any of a wide group of analysis techniques used in science and technology industry to evaluate the properties of a material, component or system without causing damage. The terms nondestructive examination (NDE), nondestructive inspection (NDI), and nondestructive evaluation (NDE) are also commonly used to describe this technology. Because NDT does not permanently alter the article being inspected, it is a highly valuable technique that can save both money and time in product evaluation, troubleshooting, and research. The six most frequently used NDT methods are eddy-current, magnetic-particle, liquid penetrant, radiographic, ultrasonic, and visual testing. NDT is commonly used in forensic engineering, mechanical engineering, petroleum engineering, electrical engineering, civil engineering, systems engineering, aeronautical engineering, medicine, and art. Innovations in the field of nondestructive testing have had a profound impact on medical imaging, including on echocardiography, medical ultrasonography, and digital radiography.
Delamination is a mode of failure where a material fractures into layers. A variety of materials, including laminate composites and concrete, can fail by delamination. Processing can create layers in materials, such as steel formed by rolling and plastics and metals from 3D printing which can fail from layer separation. Also, surface coatings, such as paints and films, can delaminate from the coated substrate.
Laser-ultrasonics uses lasers to generate and detect ultrasonic waves. It is a non-contact technique used to measure materials thickness, detect flaws and carry out materials characterization. The basic components of a laser-ultrasonic system are a generation laser, a detection laser and a detector.
Acoustic emission (AE) is the phenomenon of radiation of acoustic (elastic) waves in solids that occurs when a material undergoes irreversible changes in its internal structure, for example as a result of crack formation or plastic deformation due to aging, temperature gradients, or external mechanical forces.
Ultrasonic testing (UT) is a family of non-destructive testing techniques based on the propagation of ultrasonic waves in the object or material tested. In most common UT applications, very short ultrasonic pulse waves with centre frequencies ranging from 0.1-15 MHz and occasionally up to 50 MHz, are transmitted into materials to detect internal flaws or to characterize materials. A common example is ultrasonic thickness measurement, which tests the thickness of the test object, for example, to monitor pipework corrosion and erosion. Ultrasonic testing is extensively used to detect flaws in welds.
Micromechanics is the analysis of heterogeneous materials including of composite, and anisotropic and orthotropic materials on the level of the individual constituents that constitute them and their interactions.
Time-of-flight diffraction (TOFD) method of ultrasonic testing is a sensitive and accurate method for the nondestructive testing of welds for defects. TOFD originated from tip diffraction techniques which were first published by Silk and Liddington in 1975 which paved the way for TOFD. Later works on this technique are given in a number of sources which include Harumi et al. (1989), Avioli et al. (1991), and Bray and Stanley (1997).
This is an alphabetical list of articles pertaining specifically to Engineering Science and Mechanics (ESM). For a broad overview of engineering, please see Engineering. For biographies please see List of engineers and Mechanicians.
An electromagnetic acoustic transducer (EMAT) is a transducer for non-contact acoustic wave generation and reception in conducting materials. Its effect is based on electromagnetic mechanisms, which do not need direct coupling with the surface of the material. Due to this couplant-free feature, EMATs are particularly useful in harsh, i.e., hot, cold, clean, or dry environments. EMATs are suitable to generate all kinds of waves in metallic and/or magnetostrictive materials. Depending on the design and orientation of coils and magnets, shear horizontal (SH) bulk wave mode, surface wave, plate waves such as SH and Lamb waves, and all sorts of other bulk and guided-wave modes can be excited. After decades of research and development, EMAT has found its applications in many industries such as primary metal manufacturing and processing, automotive, railroad, pipeline, boiler and pressure vessel industries, in which they are typically used for nondestructive testing (NDT) of metallic structures.
Thermographic inspection refers to the nondestructive testing (NDT) of parts, materials or systems through the imaging of the temperature fields, gradients and/or patterns ("thermograms") at the object's surface. It is distinguished from medical thermography by the subjects being examined: thermographic inspection generally examines inanimate objects, while medical thermography generally examines living organisms. Generally, thermographic inspection is performed using an infrared sensor.
Carbon fiber-reinforced polymers, carbon-fibre-reinforced polymers, carbon-fiber-reinforced plastics, carbon-fiber reinforced-thermoplastic, also known as carbon fiber, carbon composite, or just carbon, are extremely strong and light fiber-reinforced plastics that contain carbon fibers. CFRPs can be expensive to produce, but are commonly used wherever high strength-to-weight ratio and stiffness (rigidity) are required, such as aerospace, superstructures of ships, automotive, civil engineering, sports equipment, and an increasing number of consumer and technical applications.
The wingbox of a fixed-wing aircraft is the primary load-carrying structure of the wing, which forms the structural centre of the wings and is also the attachment point for other wing components such as leading edge flaps, swing wings, trailing edge flaps and wing-tip devices. The wingbox continues beyond the visible wing roots and interfaces with the fuselage in the centre wingbox, which forms the structural core of an aircraft.
Jan Drewes Achenbach was a professor emeritus at Northwestern University. Achenbach was born in the northern region of the Netherlands, in Leeuwarden. He studied aeronautics at Delft University of Technology, which he finished with a M.Sc. degree in 1959. Thereafter, he went to the United States, Stanford University, where he received his Ph.D. degree in 1962. After working for a year as a preceptor at Columbia University, he was then appointed as assistant professor at Northwestern University.
Terahertz nondestructive evaluation pertains to devices, and techniques of analysis occurring in the terahertz domain of electromagnetic radiation. These devices and techniques evaluate the properties of a material, component or system without causing damage.
Microwave imaging is a science which has been evolved from older detecting/locating techniques in order to evaluate hidden or embedded objects in a structure using electromagnetic (EM) waves in microwave regime. Engineering and application oriented microwave imaging for non-destructive testing is called microwave testing, see below.
Carbon fiber testing is a set of various different tests that researchers use to characterize the properties of carbon fiber. The results for the testing are used to aid the manufacturer and developers decisions selecting and designing material composites, manufacturing processes and for ensured safety and integrity. Safety-critical carbon fiber components, such as structural parts in machines, vehicles, aircraft or architectural elements are subject to testing.
Welding of advanced thermoplastic composites is a beneficial method of joining these materials compared to mechanical fastening and adhesive bonding. Mechanical fastening requires intense labor, and creates stress concentrations, while adhesive bonding requires extensive surface preparation, and long curing cycles. Welding these materials is a cost-effective method of joining concerning preparation and execution, and these materials retain their properties upon cooling, so no post processing is necessary. These materials are widely used in the aerospace industry to reduce weight of a part while keeping strength.
Laszlo Adler is an American physicist and a Taine McDougal Professor Emeritus in the Department of Integrated Systems Engineering at the Ohio State University. He is known for his work in Ultrasonics, Acousto-optics, and Nondestructive Evaluation of Materials. He is a holocaust survivor and has been active in scientific research for over 60 years.
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