服装导购必须知道的销售技巧(四)

1、DESIGN AND DEVELOPMENT OF AN ECONOMICAL TORSION TESTING MACHINEby Glenn Vallee, Ph.D., P.E.AndRobert ShortMechanical Engineering DepartmentWestern New England College聚划算 http:/ Objectives Design and build a torsion testing machine capable of performing the ASTM Torsion Test Machine must measure mate

2、rial properties to within 5% of published data Machine must be affordableTorsion Testing ApparatusExperimentally determines torsional shear properties of materialsA cylindrical test specimen is twisted until failureApplied torque and angle of twist are recordedASTM Standardized Test Method Used- Spe

3、cifies Test Procedure / Specimen GeometryDesign Constraints Machine must be capable of fracturing a steel test specimen Specimen diameter to be 3/8 inch to allow examination of fracture surfaces- ASTM therefore requires a specimen length of 6 inches to meet the min length/diameter ratio Torque and a

4、ngle of twist measuring devices to be easily accessible to studentsDesign Constraints Machine must produce measurements within 5% of published ASTM results Budget allocation of $500 Many Years of Service!Determination of Shear PropertiesJT Elementary Eq. (1)where = radius of the specimen cross secti

5、on J = polar moment of inertia of cross section Shear strain is calculated using Eq. (2) = /L where L = specimen length = angle of twistDetermination of Shear Properties Shear Modulus G is determined by finding the slope of the shear tress-strain diagram Shear modulus may also be calculated usingGJT

6、LEq. (3)Design Torque and Angle of Twist Requirements Equation (1) was used to estimate the torque required to yield a C1018 plane carbon steel test specimen in torsion 3000 in-lb would be required to fail C1018 material at constant rotational velocity Experiments were performed using aluminum to fi

7、nd required angle of twist (10 revolutions)Design LayoutDrive Train A DC motor with an integral gear reduction and speed controller was used A sprocket set having a 6:1 gear ratio developed required torqueFrame DesignBaseFrame / Motor Sub Assembly Two inch square steel channel was welded together to

8、 form the frameGage mounted on a 45 AngleTorque GageMeasurement of Torque A torque gauge was fitted to the fixed hubMeasurement of Torque (kpsi) (kpsi)2 = 1 = 2 Strain Gauge aligned with direction of Max Principle Stress45max12State of Pure ShearMeasurement of Angle of TwistPotentiometerWeightWheelS

9、procket A potentiometer was mounted to a wheel which contacted the rotating hub.Chuck Alignment A T-slide was used to prevent development of axial loads and to aid in alignmentTorque CalibrationFabricated Torque WrenchGage A weighted lever system was used to calibrate the torque gaugeTorque Calibrat

10、ion CurveComplete AssemblyPotentiometer LeadsMotor Speed ControlPower Switches / LEDsStrain Gauge LeadsPerformance Data Collection with Lab VIEW Testing of 1018 Cold Drawn Steel Shear modulus measured as 10.7 Mpsi, 3% lower than the published value Testing of 2014 Aluminum Shear modulus measured as

11、3.7 Mpsi, 5% lower than the published valueBudget AnalysisItem DescriptionManufacturerMfg. #VendorVendor #QuantityCost Ea. ($)Total Cost ($) DC MotorDayton4Z530Grainger4Z5311258258DC Speed ControlDart Controls125DV-C-KGrainger2M510177772 inch SprocketUS Tsubaki50B9FGrainger6L9271111112 inch Sprocket

12、Browning50Q60Grainger1L21319393Chain (10 feet)US Tsubaki50TW10Grainger2W09513434PotentiometerEITMW22B-10-2KNewark InOne83H756811010Drill ChuckJacobs30602McMaster3094A1721938Neon Lamp AssemblyRadio Shack2720712Radio Shack2720712144Neon Lamp AssemblyRadio Shack2720708Radio Shack2720708144Dual Binding

13、PostRadio Shack2740718Radio Shack2740718155 Final Cost ($)534Integration Into the ME Curriculum Torsion machine has been integrated in two ways- ASTM torsion experiment has been included in the junior laboratory sequence- design and use of the torsion machine is introduced in the sophomore Mechanics

14、 of Materials courseJunior Laboratory Experience Students examine the torque cell and calculate its limiting torsional strength Students create calibration curves for the torque cell and rotational potentiometer Steel and aluminum specimens are tested o failure and the results are compared to published dataMechanics of Materials Course Students examine the torque cell and calculate