Engineering topics

Jemian, Wartan A.

Publications and source records attributed to Jemian, Wartan A..

3 records

NASA NTRS1993

Weld fracture criteria for computer simulation

Due to the complexity of welding, not all of the important factors are always properly considered and controlled. An automatic system is required. This report outlines a simulation method and all the important considerations to do this. As in many situations where a defect or failure has occurrred, it is freqently necessary to trouble shoot the system and eventually identify those factors that were neglected. This is expensive and time consuming. Very frequently the causes are materials-related that might have been anticipated. Computer simulation can automatically consider all important variables. The major goal of this presentation is to identify the proper relationship to design, processing and materials variables to welding.

Jemian, Wartan A.↗

NASA NTRS1987

Linear Anomaly in Welded 2219-T87 Aluminum Alloy

Study of causes and significance of two types of linear anomalies sometimes appearing in radiographs of welds described in preliminary report. Manifested as light or dark linear features parallel to weld line in radiograph of weld. Contains diagrams and descriptions of phenomena occurring during welding process. Includes microdensitometer traces from x-radiographs of actual welds and from computer simulations based calculation of x-ray transmission through assumed weld structures. Concludes anomalies not unique to 2219-T87 aluminum alloy.

Jemian, Wartan A.↗

NASA NTRS1986

Weld radiograph enigmas

Weld radiograph enigmas are features observed on X-ray radiographs of welds. Some of these features resemble indications of weld defects, although their origin is different. Since they are not understood, they are a source of concern. There is a need to identify their causes and especially to measure their effect on weld mechanical properties. A method is proposed whereby the enigmas can be evaluated and rated, in relation to the full spectrum of weld radiograph indications. Thie method involves a signature and a magnitude that can be used as a quantitive parameter. The signature is generated as the diference between the microdensitometer trace across the radiograph and the computed film intensity derived from a thickness scan along the corresponding region of the sample. The magnitude is the measured difference in intensity between the peak and base line values of the signature. The procedure is demonstated by comparing traces across radiographs of a weld sample before and after the introduction of a hole and by a system based on a MacIntosh mouse used for surface profiling.

Jemian, Wartan A.↗