S TRESS A NALYSIS OF A H YDRAULIC A CTUATOR B ASED ON A CCUMULATOR R ESPONSE By John Connor Ernesto Gutierrez-Miravete, Thesis Adviser

I NTRODUCTION Pressure transients are the primary loads in hydraulic systems and can be due to several types of loading conditions which are not typically seen in normal operation This project builds upon Analysis of Accumulator Response to an External Force acting on a Hydraulic Actuator by Leonid Simkin The analysis determines if that accumulator is justified based on the reduction of space and weight the hydraulic actuator needs to be to meet the design criteria

D ESIGN C RITERIA Stresses were evaluated against established criteria in the American Society of Mechanical Engineers (ASME) Boiler Pressure Vessel Code (BPVC) 1.5 factor of safety on material yield strength 3.5 factor of safety on material ultimate strength Material Yield Strength, MPa Ultimate Strength, MPa Unit Weight, kN/m 3 Source 2011 T6 Aluminum Alloy [3] Material Yield Allowable Stress, MPa Ultimate Allowable Stress, MPa 2011 T6 Aluminum Alloy

T RADITIONAL A PPROACH – C YLINDER W ALL a b p1p1 p2p2

T RADITIONAL A PPROACH – C YLINDER E ND C AP b roro roro b t EC p2p2 p1p1

F INITE E LEMENT A NALYSIS Abaqus/Standard was used to create a static model using peak pressures Half of the actuator was modeled using symmetry boundary conditions Two Element types were evaluated Linear (C3D8I) Quadratic (C3D20) Internal and external pressures were applied to the model

R ESULTS - S TRESS Analysis Type Actuator Area Thickness (mm) Stress (MPa) Traditional Analysis Cylinder Body End Cap Abaqus Analysis Cylinder Body End Cap Analysis Type Actuator Area Thickness (mm) Stress (MPa) Traditional Analysis Cylinder Body End Cap Abaqus Analysis Cylinder Body End Cap Actuator Stresses without an Accumulator Actuator Stresses with an Accumulator

R ESULTS – A BAQUS S TRESS P LOTS Actuator Stresses without an Accumulator Traditional Approach Dimensions Abaqus Optimized Dimensions

R ESULTS – A BAQUS S TRESS P LOTS Actuator Stresses with an Accumulator Traditional Approach Dimensions Abaqus Optimized Dimensions

C OMPARISON BETWEEN DESIGNS The comparison is based off the Abaqus results Design Considerations No Accumulator With Accumulator Percent Difference Outer Diameter [m] % Actuator Weight [N] %

C ONCLUSION Traditional approach did not capture the peak stresses in the cylinder particularly around the end cap. Abaqus model generated high stresses requiring optimization of the actuators Accumulator addition into this system is not justified. Since the space envelope and weight of the actuator did not reduce to a point to justify the weight of the accumulator.