Expert Details

Expert in Fatigue and Experimental Mechanics

Expert ID: 108154 California, USA

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Expert has spent the bulk of his career in developing improved methods for predicting the fatigue life of mechanical parts. He has helped dozens of companies in designing and evaluating products for adequate fatigue performance, covering the spectrum from construction equipment to medical devices. His experience in this area has been acknowledged by his selection to be co-editor of the widely used Fatigue Design Handbook of the Society of Automotive Engineers. Over the years, he has conducted numerous fatigue tests of materials, lab specimens, and actual components. His current research emphasizes effects on residual stresses on fatigue and multiaxial fatigue.

Expert has over two decades of experience in both analytical and experimental techniques for determining stresses and strains caused by loadings applied to components in service. He is very knowledgeable in methods of experimental stress analysis, ranging from strain gauges to holographic interferometry. He uses these methods on a daily basis in teaching, research, and consulting. He is also experienced in the calculation of stresses using theoretical solutions and utilizes finite element codes in his work.

Having knowledge of most of the methods of experimental stress analysis, Expert teaches a course on that topic. Much of his work, especially in recent years, has been devoted to developing new methods of experimental stress analysis, particularly those using optical methods such as holography and fiber optics. He keeps current in this area of knowledge through participation in the activities of the Society for Experimental Mechanics.

Expert has devoted a significant portion of his recent work to the development of a new method based on laser holography for the determination of residual stresses created in mechanical parts by manufacturing, fabrication, and assembly processes. He is also experienced in the use of conventional methods of residual stress measurement such as material removal, hole drilling, and X-ray diffraction. He has measured residual stresses in many different types of components, including carbon and graphite prosthetic heart valves, extruded aluminum precision mirror supports, and welded steel structures. One of Expert's specialties is determination of residual stresses by various experimental methods. Over the years, he has concentrated on the use of mechanical methods but is very familiar with other approaches such as X-ray and neutron diffraction. He is involved in a project to develop and implement a new approach for determining residual stresses using holographic interferometry. Over the years, he has gathered considerable information on the effects of residual stresses on fatigue performance.

Expert's PhD thesis utilized fracture mechanics to predict the remaining fatigue life of components in which cracks formed either by fatigue or were initially present as small manufacturing defects. He has continued to work actively in this area and has used fracture mechanics in applications ranging from the prediction of the static fatigue (stress corrosion cracking) life of optical fibers to prediction of the life of welded structures containing various types of weld defects. He is also experienced in performing fracture mechanics tests, including crack propagation tests.

For over 25 years, Expert has performed fatigue life evaluations for a wide variety of mechanical components, ranging from small parts in computer disk drives to welded structure in earthmoving equipment. These evaluations have included stress-based and strain-based approaches as well as the application of fracture mechanics to the prediction of fatigue crack growth. In addition to teaching a course on fatigue design and analysis, Expert is past co-editor of the SAE Fatigue Design Handbook and keeps abreast of the latest developments in this field. His current research interests concern effects of residual stresses on fatigue and development of improved life prediction methods to handle complex states of stress of the type often encountered in service.

Although fatigue of materials causes the vast majority of mechanical failures, other failure modes such as stress corrosion cracking, creep, fracture from overloads, surface failures such as pitting and spalling can also be the culprit. Expert is knowledgeable about these and other failure mechanisms, teaching a course covering these topics. He has also conducted a number of investigations to determine the cause of failures in mechanical devices ranging from computer disk drives to theater seats.

Expert teaches courses that cover the commonly used mechanical properties such as tensile strength, impact strength, hardness, and ductility properties. The courses emphasize how these properties can be employed in the design and structural integrity evaluations of products. He has either conducted or supervised numerous tests to determine mechanical properties and serves on committees of the American Society for Testing and Materials responsible for formulating test standards for the determination of mechanical properties.

Expert is knowledgeable of the material properties usually of interest in the design of mechanical components, such as yield and ultimate strengths and modulus of elasticity. In the course of his teaching and doing research and working for industrial clients, he has used material properties on virtually a daily basis for nearly three decades. He is also well acquainted with the type of tests that are typically performed to generate such properties, both through personal experience as well as participation in the activities of the American Society for Testing and Materials.

Expert is familiar with the stress analysis and long-term strength characteristics of optical fibers through work done cooperatively with a major manufacturer of fiber optic devices. He is involved in one research program to develop a new type of fiber optic strain sensor and another that is exploring the use of fiber optic sensors to monitor the development of residual stresses in a graphite-epoxy composite component.

Expert may consult nationally and internationally, and is also local to the following cities: San Jose, California - San Francisco, California - Sacramento, California - Oakland, California - Stockton, California - Fremont, California - Modesto, California - Salinas, California - Santa Rosa, California - Hayward, California

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Year Degree Subject Institution
Year: 1978 Degree: PhD Subject: Mechanical Engineering Institution: Stanford University
Year: 1970 Degree: MS Subject: Mechanical Engineering Institution: Stanford University
Year: 1968 Degree: BS Subject: Mechanical Engineering Institution: Stanford University

Work History

Years Employer Title Department Responsibilities
Years: 1978 to Present Employer: Undisclosed Title: Professor Department: Mechanical Engineering Responsibilities:
Years: 1968 to 1978 Employer: Title: Department: Responsibilities: Full-time employment and consulting experience in a wide variety of industrial projects-specializing primarily in testing and analysis.

Career Accomplishments

Associations / Societies
Expert is a member of two scientific honor societies.
Awards / Recognition
Expert won the Spergel Memorial Award for best paper on fiber optics technology at the 32nd International Wire and Cable Symposium. In 1994, he received the Hetenyi Award from the Society for Experimental Mechanics for the best research paper published in the journal Experimental Mechanics.
Publications and Patents Summary
Expert is past co-editor of the SAE Fatigue Design Handbook.

Fields of Expertise

durability, life-prediction methodology, mechanical fatigue, structural mechanics, structural-component life-prediction methodology, tensile strength, aerial lift, experimental stress analysis, strain gage, stress analysis, stress corrosion cracking, stress cracking, strain analysis, strain measurement, residual stress measurement, stress measurement, fracture mechanics, fracture stress, fatigue crack growth, metal failure, metal fatigue, materials failure analysis, solid mechanical property, impact resistance, material property, optical fiber failure, strain sensor, mechanical integrity, microelectronic equipment, fracture toughness, extension spring, high-strength carburizing, shear pin, assembly structural testing, stress-induced void, tensile testing, mechanical durability, void detection, metal fracturing, fatigue failure, stress intensity factor, tensile bar, solid property, MP35N superalloy, fatigue measurement, dynamic fatigue, plastic creep, thermal fatigue, metal weldment fatigue, tensile strength instrumentation, material fatigue testing, low-cycle fatigue, thermo-mechanical fatigue, Poisson ratio, construction equipment, bending moment, cyclic loading to investigate fatigue, in-service materials failure analysis, remaining life assessment, machine-element life-prediction methodology, metal plasticity modeling, metal deformation, metal tensile strength, specific modulus, copper mechanical property, plastic material property, forensic materials failure analysis, electronic equipment mechanical fatigue, force analysis, machine failure analysis, fracture mechanics software, mechanical engineering measurement, plant equipment life evaluation, medical device endurance testing, optical-material strain, machinery-related failure, machine design, American Society for Testing and Materials material code, mechanical stress, mechanical property testing, American Society for Testing and Materials, stress measurement standard, X-ray diffraction, mechanical strain, Rockwell hardness test, Knoop indentation test, mechanical test, metal welding, impact test, American Society of Mechanical Engineers code, thermoelasticity, ultimate tensile strength, torsion, structural code, statics, product safety, optical sensor, notch impact strength, nondestructive testing, metal mechanical property, materials standard, life testing, izod impact test, interferometry, holography, heart valve prosthesis, glass failure analysis, fiber optics, deformation analysis, creep, Charpy impact test, Brinell number

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