S21-1 PAT318, Section 21, March 2005 SECTION 21 MSC.FATIGUE SOFTWARE STRAIN GAUGE

S21-2 PAT318, Section 21, March 2005

S21-3 PAT318, Section 21, March 2005 A virtual test facility in the MSC.Fatigue environment

S21-4 PAT318, Section 21, March 2005 SOFTWARE STRAIN GAUGE n A Finite Element tool allowing the creation of Stress and Strain time histories at arbitrary locations on a Finite Element Model Surface n Uses: u Finite Element Model Results Verification u Comparison of Strain Values with Test Time Histories n Previous FEA techniques have only permitted comparison of single Stress or Strain values.

S21-5 PAT318, Section 21, March 2005 DESCRIPTION n A virtual strain gauge on a finite element model. This gauge can produce theoretical result time histories from multiple time varying applied loads n Time histories may be extracted at any point on the mesh surface n Results based on either standard or user defined strain gauge definitions. n The results from static, transient or quasi static finite element loading.

S21-6 PAT318, Section 21, March Strain (uE) Time (Secs) DISPLAY OF SIGNAL: SAETRN.DAC points. 9 pts/Secs Displayed: 4501 points. from pt 1 Full file data: Max = 999 at 0 Min = -495 at 1743 Mean = S.D. = 235 RMS = CORRELATION APPLICATIONS n Allows correlation between theoretical calculations with experimentally determined results. n Permits greater confidence in the finite element model of the real world structure. n Stress / Strain results may be subsequently analysed as: u Cycle Counts u PSD results u Damage / Life Values

S21-7 PAT318, Section 21, March 2005 time Hub Strain Real World StructureFEA Model Surface Software Strain Gauges time Hub Strain CORRELATION APPLICATIONS (Contd.)

S21-8 PAT318, Section 21, March 2005 WELDED STRUCTURE ANALYSIS n The Software Strain Gauge is also of benefit to the analyst performing MSC.Fatigue weld durability calculations in accordance with British Standard n When calculating fatigue life for welded structures the loading direction is of importance n The strain gauge allows extraction of time histories prior to Rainflow cycle counting in specific directions on an FEA structure

S21-9 PAT318, Section 21, March 2005 The Gauge tool allows access to strain time histories at the weld toe, providing important information for weld durability calculations. CLASS F WELD DETAIL (BS7608) Real World Structure FEA Model Software Strain Gauges WELDED STRUCTURE ANALYSIS (Contd.)

S21-10 PAT318, Section 21, March 2005 GAUGE DEFINITION n The gauges are defined as FEA groups, each containing between 1 to 3 elements. n Standard gauge definitions: u Uni-axial Gauges u T Gauges u Delta Gauges u Rectangular Gauges u Planar and stacked formulations. n User defined gauges may also be created u definitions stored in a gauge definition file.

S21-11 PAT318, Section 21, March 2005 IMPLEMENTATION n Gauge position: u Anywhere on the FEA model surface u Any orientation u Covering multiple finite elements. n Gauge results: u Averaged results from the underlying finite elements u Replicates the geometric averaging with actual instrumentation. u Transformed to the coordinate system and alignment of the software strain gauge. n Up to 200 simultaneous Software Strain Gauges

S21-12 PAT318, Section 21, March 2005 EXAMPLE PROBLEM: A SOFTWARE STRAIN GAGE Introduce software strain gage as a correlation tool on a mounting lug. Multiple loading inputs.

S21-13 PAT318, Section 21, March 2005 SOFTWARE STRAIN GAGE SETUP Define node to initially put gage on... and elements that define surface

S21-14 PAT318, Section 21, March 2005 LOADING INFO SETUP

S21-15 PAT318, Section 21, March 2005 PERFORM ANALYSIS n Define material and loading n Extract time histories from rosette n Perform rosette analysis and correlation

S21-16 PAT318, Section 21, March 2005 CORRELATION TECHNIQUES n Overlays and cross plots n Rosette analysis n Single location uniaxial life analyzer n Single location multiaxial life analyzer

S21-17 PAT318, Section 21, March 2005 EXERCISE n Perform Quickstart Guide Chapter 13 Exercise, A Software Strain Gauge n Be sure to ask for help if theres anything you dont understand

S21-18 PAT318, Section 21, March 2005