Steel Trim Research Articles

Mechanisms of die wear and wear-induced damage at the trimmed edge of high strength steel sheets

Die wear during trimming of advanced high strength steel (AHSS) sheets deteriorates the edge quality of trimmed sheets. In this work, the mechanisms of AISI D2 steel trim die wear and their effects on plastic deformation and fracture behaviour of the sheared edge of DP980 steel sheet were examined. A mechanical press equipped with D2 inserts was used to trim DP980 sheets with a clearance of 0.14 mm (10%). Abrasion and microchipping were identified as the wear mechanisms operating at the upper die, with microchipping becoming more dominant after 60,000 trimming cycles. The burr height and the length of the burnish zone of sheared DP980 sheets increased linearly with the chipped die edge percentage. The shear strains in the shear effected zone (SAZ) were estimated using martensite displacements as metallographic markers in the ferrite matrix as a function of the depth beneath the sheared edge. The depth of SAZ, and the plastic strains at a given depth within the SAZ increased with the number of trimming cycles. Correlation of the local stress and strain values generated in the SAZ showed that a saturation flow stress was reached near the sheared edge. The damage in SAZ occurred in the form of crack formation at the martensite/ferrite interfaces and fracture of martensite. Die wear reduced the tensile ductility of the DP980 sheets, and the fracture mode in tension changed from ductile with localized neck to more brittle sheared edge fracture initiating from surface cracks after 60,000 cycles.

Investigation of Adhesion Formation in New Stainless Steel Trim Spring Operated Pressure Relief Valves

Examination of proof test data for new (not previously installed) stainless steel (SS) trim spring operated pressure relief valves (SOPRV) reveals that adhesions form between the seat and disk in about 46% of all such SOPRV. The forces needed to overcome these adhesions can be sufficiently large to cause the SOPRV to fail its proof test (FPT) prior to installation. Furthermore, a significant percentage of SOPRV which are found to FPT are also found to “fail to open” (FTO) meaning they would not relief excess pressure in the event of an overpressure event. The cases where adhesions result in FTO or FPT appear to be confined to SOPRV with diameters less than or equal to 1 in. and set pressures less than 150 pounds per square inch gauge (psig) and the FTO are estimated to occur in 0.31% to 2.00% of this subpopulation of SS trim SOPRV. The reliability and safety implications of these finding for end users who do not perform pre-installation testing of SOPRV are discussed.

The Adhesion Failure Mode in Stainless Steel Trim Spring-Operated Pressure Relief Valves

This paper addresses dangerous failures of stainless steel (SS) trim spring-operated pressure relief valves (SOPRV) due to a particular failure mode (SS-to-SS adhesion), which is not currently being included in SOPRV failure rates. As a result, current methods for estimating or predicting failure rates for SS trim SOPRV significantly underestimate these failure rates and, consequently, overestimate the safety provided by the SOPRV as measured by its average probability of failure on demand (PFDavg) or its corresponding safety integrity level (SIL). The paper also illustrates the critical importance of root cause analysis (RCA) of dangerous SOPRV failures in understanding the impacts of various failure modes. Over 1300 proof test results for both new and used SS trim SOPRV from the Savannah River Site (SRS) were identified. RCA was used on the failed valves to classify those failed due to SS-to-SS adhesions. Statistical analysis of the data convincingly demonstrates adhesions, previously assumed to be only an in-storage failure phenomenon, are also an in-service failure mode, which needs to be included in SOPRV failure rates. The paper discusses the factors which potentially influence the adhesion failure mode, and suggests a possible approach to including this mode in failure rate predictions. An example illustrates how current failure rate models overestimate SS trim SOPRV safety by 1 or 2 orders of magnitude.

Very Decent of You

If you drive east on D117 you come up on a twisty road out of the scenic gorge where the town of Quillan is spread, and cross part of the Plateau du Sault to get to the little French town of Puivert. As you dip down the road to drive in, you notice a recreational lake, which was at one time a much larger body of water. If you come in from the west on the D road, you go through the market towns of Lavalenet and Foix before you arrive. You turn into the village and notice the aged stone row houses leaning over the narrow streets. An old church near the mairie just off the town square seems to be crumbling, some of its windows cracking as it falls back to an earlier time. There is a severe, cold looking war memorial near a bricked-up fountain, and a small caf? just up the hill beside an open atrium. You turn on to a road that swings toward the lake and drive through clusters of newer dwellings on the outskirts of town before you turn right into another row of stone houses at least several centuries old. These are in various states of order and disorder?but something catches your eye as you make a turn and drive down the narrow pavement. Propped against the bright blue door of one of the houses as you pass is a pair of binoculars leaning on the baseboard against the painted steel trim. If you know anything about optics, you quickly see that these are very good binoculars?Bushneil, made for the National Audubon Society, 8 x 42WA, a focus that brings distant objects up in marvelous clarity, 430 feet at 1100 yards with adjust able lenses in both eye pieces as well as the main focus wheel. There it is?this very good instrument without a case, just propped up on the base against the blue door. Perhaps fifty yards further down the pavement, past three or four more houses, the landscape opens to pastures and a stunning view of the Pyrenees foothills. You would like to reverse the car and go back to borrow those binoculars to take a look at this view, but you drive on a bit puzzled.

Movable Steel Trim Rods and the Orbit Dynamics of the Chalk River Superconducting Heavy Ion Cyclotron

Trim rods rather than trim coils have been chosen to isochronize the magnetic field. These provide good isochronism and the tolerances associated with the rods are acceptable. For low specific-energy high-mass ions, regions where ?r approaches unity have been studied in detail. The rods can readily remove unwanted error field components.