More FEMAP and NX Nastran Projects
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A Summary of Additional FEMAP & NX Nastran Projects
Engineering Analysis of Armored Seat Pallets for HH-60G Apache Helicopters: The UH-60L SAR Martin-Baker seat pallet was modified to accommodate a 5 mm thick ballistic grade, hardened steel plate. The original all aluminum design was extensively redesigned to handle the 72 crash landing load cases as required by US Army for structural integrity. Prior engineering analysis work was followed as detailed in LSF00571 for the HH-60G Martin-Baker seat pallet installation stress analysis report. In the revised design, a lightweight aluminum pallet is attached via 18 bolts to a hardened steel plate. The aluminum component was meshed with 8-node bricks and the steel plate with plate elements. The seat structure was modeled using beam elements and was attached to the pallet via seat inserts that slide within rails that are cut into the aluminum pallet. The loading scenario consists of a 225 lb crewman that is subjected to various acceleration loads up to 20g in any one direction. The model was run in full contact model to capture the mechanical behavior between the seat inserts and pallet and the pallet against the armored plate. Results were interpreted under design safety factors that corrected the linear stress values for plastic damage based on MIL-HDBK-5H for 7075 aluminum alloy sheet plate. For example, the plastic bending ultimate allowable for 7075-T7351 plate is 131 ksi (e/D = 2.0) given a yield stress of 59 ksi. Design changes were made based on the stress results and an engineering report created for submittal to the client and review by the US Army. Results were accepted with no comment.
High-Temperature Ceramic Plasma Tube Analysis: An aluminum oxide (Al2O3) plasma tube is fabricated by brazing several arc cast Molybdenum focusing rings within the inner tube. Upon cooling to room temperature, the CTE differences between the alumina and moly components have the potential to create high tensile stresses in the ceramic component. Given the specialized geometry of the plasma tube, a detailed finite element analysis was performed. Results from this analysis were used to guide the design of new Mo internal components that drastically reduced the stress levels in the AL2O3 tube. A fracture mechanics study for brittle materials indicated at these reduced stress levels, the component would have no problem surviving installation handling and cycling thermal loading. The part is in production today.
LED Glass Panel Inspection Line: This project analyzed a large glass panel conveyor line having a length of approximately 80 meters. Inspection stations were spaced along the line where traveling cameras would be used to monitor the quality of the glass panel. These cameras would move in a non-stochastic manner but would nevertheless set up low and high-frequency vibrations in the line. These vibrations would then deteriorate the camera imaging process and cause other measurement challenges. Modal analysis was performed on key components of the line and major natural modes were shifted to limit camera induced vibration. A transient, modal-superposition analysis was also conducted to check the transmittance of the structure. It was then determined that by mass tuning of the structure, almost all of the camera induced vibration could be eliminated. The final structure was then build based on these analysis results. This line is now operating at several factories and is reported to be much quieter than its predecessors.
Large, Industrial U-Joint Stress Analysis: A 10" diameter U-Joint was analyzed to determine its limit load capacity. Full contact was enforced between the yoke, pin, internal block and drive pin sub-assemblies. Material selection studies were done to determine what would be the best mix of hardened, nitrided steels or a low-alloy tool steel (H1) or a flame carburized 8630. Results from the stress analysis were used to refine an existing design through the use of a bigger drive pin with a larger diameter internal tightening bolt. The whole assembly was pre-loaded and it was noted that bolt preload was an essential engineering variable that should be closely monitored. Fatigue and limit load analysis gave hard predictions between torque and life expectancy. Based on these numbers, the U-Joint was put into production and has operated without failure.
Wind Turbine Tower and Transmission Hub Structural Analysis: A small 5 KW wind turbine tower was analyzed for wind and seismic loading per UBC and ASCE 7-02. The tower was a conical steel tube built up in two sections. A complete rainflow counting fatigue analysis was performed on the tower per UBC specifications. Along with the tower analysis, the turbine power transmission shaft and blade attachment hub were analyzed for peak wind loading and steady-state fatigue damage. Results from the stress analysis work led to several design changes to improves its fatigue life.
National Institute of Science and Technology (NIST) Investigation of Respirator Fit and Function: This was an in-depth detailed project to study the fit and function of a fireman type respirator mask. LS-DYNA was used to perform the fit study of the mask against a simulated human head. The silicone material model was easy to obtain while that for human tissue required some investigation. The best material model fit for human skin was that of a soft rubber compound within an elastic membrane. A transient flow study within the nose cup of the respirator mask was conducted using CFdesign. Inhalation and expiration studies were conducted using standard respiratory breathing curves. Transient flow results indicated that the standard respirator mask creates some turbulence during inhalation that might cause breathing difficulty. Research papers are in process to elaborate upon these results with a shared co-authorship.
ASME Tube and Shell Heat Exchanger Vessel: Based on an initial design as developed by TEMA and ASME codes, a large pressure vessel was analyzed under ASME Section 8, Division 2 specifications with a complete seismic and buckling analysis. An interesting twist to this vessel analysis was that it was based on the client's existing vessel and was woefully under-designed for its intended application. Although one may take analysis work for granted, it is very easy to produce wrong numbers. Predictive Engineering takes great pride that it has never delivered bad results to a client and that in over 15 years of service, not one component analyzed by Predictive has failed due an analysis error.
Sliding and Contacting Auto Body Repair Clamps: General stress analysis work was done on a variety of small sliding clamps for the auto body repair industry. The models would often be composed of several small cast parts that would interact. The FE models would enforce contact between the adjacent parts and then loaded to the required rating. Once the design was optimized and approved for casting, initial samples of the cast part would be tested. The use of finite element modeling has allowed this one company to avoid all initial part failures and potential for downstream lawsuits.
Submarine Analysis Work via ABS and ASME Codes: Predictive engineering has certified two large, manned commercial submarines and a third experimental submarine destined for the Mariana Trench. We have extensive experience in ABS and ASME PVHO codes that allows us to guide the client toward the most optimized design for a manned submersible. Complete FE analysis can be done with a nonlinear buckling calculation to validate the submarine design. Our work has been strain gauged and validated under ABS surveyor requirements.
Transmission Shaft Stress Analysis: Stress analysis on several different types of transmission shafts have been done at Predictive Engineering. Complete transmission boxes have been simulated with interacting gear contact, shaft bearings and the total resultant load transfer to the supporting frame. Motor shaft work has also been done for a motorcycle engine, gear box, and other mechanical equipment.
Normal Modes Analysis of Scanning Electron Microscope Wafer Holder: Although the use of linear dynamics is common place in the world of precision equipment, the development of high accuracy, predictive FE models can be difficult. This work involved the creating of a very detailed FE model of a wafer holder having more than a 1,000,000 elements. Normal modes results were experimentally checked and found to be within 1%. Subsequent follow on designs were explicitly base on the FE work and have been put into production with no downstream vibration performance problems.
CTE Thermal-Stress Analysis of Composites: Fiber reinforced epoxy materials whether reinforced with graphite or Kevlar or glass are prone to developing high internal stresses due to CTE mismatches. The worst combination is that of laminates with Kevlar and graphite fibers. The mismatch between CTE's and the high-strength of the fibers can create high internal stresses in the laminate. Stress analysis work was done on an advanced CFRP composite that was coupled to sections containing blends of Kevlar and graphite layers. Results showed that the client could safely use the structure within the specified temperature range. This was done through the use of 2-D plate models and a complete 3-D analysis of individual layers. The Femap composite laminate modeler was instrumental in generating the FE model.
Electronic Connectors and Springs: The electronics industry enforces strict requirements on connector and contact spring performances. Although these devices are very simple mechanical elements, accurate analysis work is required to obtain useful fatigue results. Work has been performed for several major electronic device manufacturers in the design optimization of connector springs and clips, hook devices, and small mechanical parts. The majority of these parts were fabricated out of fully hardened Be-Cu or precipitation-hardened, martensitic stainless steel (SS 302).
ASME Pressure Vessel Analysis: Extensive experience has been earned in the analysis of dozens of simple to complex pressure vessels. Vessels have been certified under ASME Section VIII, Division 1 and 2 with every possible configuration of tube sheets, nozzle connections, partitions and operations. Work has also been executed under NQA-1 for extremely complex nuclear waste recycling vessels in seismic environments. Buckling analysis was done via ASCE and ASME requirements. In some cases, the buckling resistance of the vessel was certified by UG-2 exception using a non-linear approach to the structure. A complete rainflow counting fatigue analysis was also performed on all structural components, weld joints and piping structures.
Solar Panel Structural Design: Structural design was performed on a broad range of extruded aluminum sections to obtain an optimized design to support gale force wind loads (up to 50 lbf/ft^2). These panels are typically destined for residential and commercial roof tops. As part of the analysis, fatigue predictions were made on the aluminum components and fracture predictions for the glass cover sheet of the panel.
Power Spectral Density (PSD) Analysis, Separation Shock and Pyro Shock: A finite element model was constructed to simulated a broad range of military transport conditions (captive carry), launch (separation shock) and delivery (Pyro Shock) following MIL-STD-810e with reference to Method 514.4 and 516.4. The model was analyzed via PSD and Response Spectrum analysis modes. A fully non-linear transient model (LS-DYNA) was used for the separation shock analysis. Results from this work were used to validate the design of a critical piece of military armament.
Mechanical engineering analysis on a broad range of clamps and hooks used in the auto body repair industry. These clamps often involve multiple parts with contact behavior between highly stressed components. Stress analysis results are used to guide product development and optimize the tool design for weight and biometrics. Not only must the tool have a high strength to weight ratio, it must also fit comfortably in the hand of the user. All stress results are verified on production prototypes. Outstanding correlation between FEA results and tool load carrying capability has been demonstrated over seven years of product development. Modeling notes: FEA models are routinely created from complex sculpted Pro/E geometry files.
A plastic throttle pedal assembly structurally analyzed using the finite element analysis method. A free body diagram was developed to map the force transfer between the pedal arm and the body components. FEA was then performed on each separate part. By performing this analysis as a piece-part job, it was not necessary to implement a nonlinear contact algorithm allowing the analyses to run efficiently and quickly. Modeling notes: FEA models were imported from SDRC I-DEAS iges geometry.
Research program into the application of fracture mechanics toward the fatigue crack growth prediction of cast components. Leveraging experimental fatigue crack growth data provided by the company, fracture mechanics principles were applied in the analytical and FEA calculation of stress intensity factors (Kic). These stress intensity factors were then used to predict fatigue crack growth based on a modified Paris Law crack growth model in experimental castings. A three-dimensional (3-D) crack growth FEA model was also developed to extract full-field crack growth information. The final report showed good correlation between analytical and experimental life-cycle predictions.
Structural analysis to optimize the world's first 100% plastic house and foundation. Finite element analysis was performed on the roof, walls, and foundation structural components. Analysis challenges were found in accurately capturing the large deflection, stress-stiffening behavior of the roof structure and in developing an accurate foundation model. The foundation was particularly tricky due to the non-linear contact between the simulated floor joist and ground connections. Analysis results are being used to drive the design process toward more structurally optimized shapes utilizing less plastic while achieving higher strengths. Insights gained during this modeling effort show that extrusions will work as well as pultrusions for most continuous shapes.
Multi-component FEA model of a ultrasonic transducer head for a medical equipment start-up company. The model included the PZT ceramic transducer, foam backing, brass support structure and a polyethylene cap. Stress and deflection results were obtained based on pressure loading across the face of the transducer head. Based on material property data for the PZT ceramic, the transducer head was certified for manufacturing.
Modal frequency analysis performed on an optical thermal imaging pod used by major aircraft and helicopter manufacturers. The assembly included a mixture of aluminum castings, forgings, and electric sub-assemblies. The analysis model was then excited through a sinusoidal sweep under a prescribed acceleration loading. Harmonics were identified within the structure and compared to experimental shaker table results. Good correlation was shown between the FEA and shaker table results. The final report substantiated that the internal electrical components of the pod would be relatively unaffected by external harmonic excitation.
A broad range of analyses techniques used to virtually engineer stoker grates and their sub-assemblies for the world's largest manufacturer of these critical components within power generation furnace boilers. Stoker grates sit underneath almost every power generation boiler in the world. Their purpose is to support the fuel load (coal, wood chips, food processing waste, etc.), to provide a combustion air stream, and finally, to remove the burnt residue (ash). Vibrating the ash transport mechanism is the massive stoker bed via an oscillating drive. Structural issues arise due to vibration harmonics and temperature induced stresses. Direct transient finite element analysis was used to investigate piping stresses within the stoker grate. Models were built for the complete range of stoker grates using a complex medley of plates, beams, and spring elements. All of these models were subjected to direct transient, direct frequency and modal frequency dynamic analyses. Results from this work were used to optimize the stoker designs and to ensure extended service life. Additionally, thermally induced stresses in large castings were also investigated. Residual stresses arising from thermally induced plastic deformation were found to significantly affect the structural performance, and design changes were implemented in these castings.
Physics based kinematics model of impact hammer used to pulverize coal. Dynamic derived forces were then used to structurally optimize a wear-resistant impact hammer. The goal was to lower the stresses in the hammer allowing the use of a more abrasion-resistant cast iron. Design optimization through the use of finite element analysis facilitated the development of a novel impact hammer using an A-R cast iron that was hitherto unthinkable. A fracture mechanics assessment was also included as part of this investigation.
Forensic FEA work performed for a major supplier of after-market auto parts. A complete suspension module was idealized into a finite element model to allow the correct application of torsional boundary conditions to the sway bar component under investigation. Plate elements were used to model the rear sway arms while solid elements were used to allow the construction of a detailed model of the welded sway bar structure. The two FEA structures were connected together using rigid links and spring elements to simulate the coupling affects of bolts and rubber bushings. FEA results were used to validate new designs and to optimize the final design candidate. Field testing validated the modeling results and the part is now in production.
FEA services provided to the world's market leader in the manufacturing of large, complex, high-quality structural investment castings for the aerospace market. A very large complex investment casting model was analyzed for structural integrity. The wax pattern was modeled using 10-node tetrahedral elements with the investment shell modeled via a surface skin of shell elements. The assembly was then supported through risers and stiffeners attached to a steel platform. This complex assembly was then evaluated under multiple loading conditions. Stress results allowed greater confidence in the integrity of the final production casting.
FEA modeling and optimization work to develop the next generation of Stekel mill coiling drums. Stekel mills are gaining in popularity as a cost-effective alternative to multi-stand steel mills for the production of high-grade plate and sheet steels. A coiling drum is subjected to high stresses and high temperatures as it coils thick plate during the reversing Stekel mill operation. This project work was performed for a large industrial casting operation and it end user steel mill client. Several designs were virtually evaluated for high temperature deflection and strength characteristics. At the end of many design iterations, a new interior rib design was developed that provided 2x greater stiffness and lowered notch stresses at the slot opening. This coiling drum is now in service and performing as designed.
Aircraft landing gear slider. Finite element analysis was performed on a landing gear structure for a major aircraft landing gear manufacturer. Aerospace analysis work requires extreme attention to model construction, mesh quality, and analysis documentation procedure. The engineering idealization of the landing gear part was not trivial. To correctly account for contact behavior between the parts, gap elements were extensively used. With the employment of gap elements, the analysis procedure becomes nonlinear. Typically this is not a hindrance but due to the models large size (approximately 600,000 DOF) run time was a significant factor in the model‚s construction.
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