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ASTM D 790-2007(弯曲)

Designation:D790–07

Standard Test Methods for

Flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insulating Materials1

This standard is issued under the?xed designation D790;the number immediately following the designation indicates the year of original adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.A superscript epsilon(e)indicates an editorial change since the last revision or reapproval.

This standard has been approved for use by agencies of the Department of Defense.

1.Scope*

1.1These test methods cover the determination of?exural properties of unreinforced and reinforced plastics,including high-modulus composites and electrical insulating materials in the form of rectangular bars molded directly or cut from sheets, plates,or molded shapes.These test methods are generally applicable to both rigid and semirigid materials.However,?exural strength cannot be determined for those materials that do not break or that do not fail in the outer surface of the test specimen within the5.0%strain limit of these test methods. These test methods utilize a three-point loading system applied to a simply supported beam.A four-point loading system method can be found in Test Method D627

1.1.1Procedure A,designed principally for materials that break at comparatively small de?ections.

1.1.2Procedure B,designed particularly for those materials that undergo large de?ections during testing.

1.1.3Procedure A shall be used for measurement of?exural properties,particularly?exural modulus,unless the material speci?cation states otherwise.Procedure B may be used for measurement of?exural strength only.Tangent modulus data obtained by Procedure A tends to exhibit lower standard deviations than comparable data obtained by means of Proce-dure B.

1.2Comparative tests may be run in accordance with either procedure,provided that the procedure is found satisfactory for the material being tested.

1.3The values stated in SI units are to be regarded as the standard.The values provided in brackets are for information only.

1.4This standard does not purport to address all of the safety concerns,if any,associated with its use.It is the responsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.

N OTE1—These test methods are not technically equivalent to ISO178.

2.Referenced Documents

2.1ASTM Standards:2

D618Practice for Conditioning Plastics for Testing

D638Test Method for Tensile Properties of Plastics

D883Terminology Relating to Plastics

D4000Classi?cation System for Specifying Plastic Mate-rials

D4101Speci?cation for Polypropylene Injection and Ex-trusion Materials

D5947Test Methods for Physical Dimensions of Solid Plastics Specimens

D6272Test Method for Flexural Properties of Unrein-forced and Reinforced Plastics and Electrical Insulating Materials by Four-Point Bending

E4Practices for Force Veri?cation of Testing Machines E691Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method

2.2ISO Standard:3

ISO178Plastics—Determination of Flexural Properties of Rigid Plastics

3.Terminology

3.1De?nitions—De?nitions of terms applying to these test methods appear in Terminology D883and Annex A1of Test Method D638.

4.Summary of Test Method

4.1A bar of rectangular cross section rests on two supports and is loaded by means of a loading nose midway between the supports.A support span-to-depth ratio of16:1shall be used unless there is reason to suspect that a larger span-to-depth ratio may be required,as may be the case for certain laminated materials(see Section7and Note7for guidance).

1These test methods are under the jurisdiction of ASTM Committee D20on Plastics and are the direct responsibility of Subcommittee D20.10on Mechanical Properties.

Current edition approved Sept.1,2007.Published October2007.Originally approved https://www.wendangku.net/doc/076095793.html,st previous edition approved in2003as D790–03.

2For referenced ASTM standards,visit the ASTM website,https://www.wendangku.net/doc/076095793.html,,or contact ASTM Customer Service at service@https://www.wendangku.net/doc/076095793.html,.For Annual Book of ASTM Standards volume information,refer to the standard’s Document Summary page on the ASTM website.

3Available from American National Standards Institute(ANSI),25W.43rd St., 4th Floor,New York,NY10036,https://www.wendangku.net/doc/076095793.html,.

*A Summary of Changes section appears at the end of this standard. Copyright?ASTM International,100Barr Harbor Drive,PO Box C700,West Conshohocken,PA19428-2959,United States.

4.2The specimen is de?ected until rupture occurs in the outer surface of the test specimen or until a maximum strain (see 12.7)of

5.0%is reached,whichever occurs ?rst.

4.3Procedure A employs a strain rate of 0.01mm/mm/min [0.01in./in./min]and is the preferred procedure for this test method,while Procedure B employs a strain rate of 0.10mm/mm/min [0.10in./in./min].

5.Signi?cance and Use

5.1Flexural properties as determined by these test methods are especially useful for quality control and speci?cation purposes.

5.2Materials that do not fail by the maximum strain allowed under these test methods (3-point bend)may be more suited to a 4-point bend test.The basic difference between the two test methods is in the location of the maximum bending moment and maximum axial ?ber stresses.The maximum axial ?ber stresses occur on a line under the loading nose in 3-point bending and over the area between the loading noses in 4-point bending.

5.3Flexural properties may vary with specimen depth,temperature,atmospheric conditions,and the difference in rate of straining as speci?ed in Procedures A and B (see also Note 7).

5.4Before proceeding with these test methods,reference should be made to the ASTM speci?cation of the material being tested.Any test specimen preparation,conditioning,dimensions,or testing parameters,or combination thereof,covered in the ASTM material speci?cation shall take prece-dence over those mentioned in these test methods.Table 1in Classi?cation System D 4000lists the ASTM material speci-?cations that currently exist for plastics.

6.Apparatus

6.1Testing Machine —A properly calibrated testing ma-chine that can be operated at constant rates of crosshead motion over the range indicated,and in which the error in the load measuring system shall not exceed 61%of the maximum load expected to be measured.It shall be equipped with a de?ection measuring device.The stiffness of the testing machine shall be such that the total elastic deformation of the system does not exceed 1%of the total de?ection of the test specimen during

testing,or appropriate corrections shall be made.The load indicating mechanism shall be essentially free from inertial lag at the crosshead rate used.The accuracy of the testing machine shall be veri?ed in accordance with Practices E 4.

6.2Loading Noses and Supports —The loading nose and supports shall have cylindrical surfaces.The default radii of the loading nose and supports shall be 5.060.1mm [0.19760.004in.]unless otherwise speci?ed in an ASTM material speci?cation or as agreed upon between the interested parties.When the use of an ASTM material speci?cation,or an agreed upon modi?cation,results in a change to the radii of the loading nose and supports,the results shall be clearly identi?ed as being obtained from a modi?ed version of this test method and shall include the speci?cation (when available)from which the modi?cation was speci?ed,for example,Test Method D 790in accordance with Speci?cation D 4101.

6.2.1Other Radii for Loading Noses and Supports —When other than default loading noses and supports are used,in order to avoid excessive indentation,or failure due to stress concen-tration directly under the loading nose,they must comply with the following requirements:they shall have a minimum radius of 3.2mm [1?8in.]for all specimens.For specimens 3.2mm or greater in depth,the radius of the supports may be up to 1.6times the specimen depth.They shall be this large if signi?cant indentation or compressive failure occurs.The arc of the loading nose in contact with the specimen shall be sufficiently large to prevent contact of the specimen with the sides of the nose.The maximum radius of the loading nose shall be no more than four times the specimen depth.

6.3Micrometers —Suitable micrometers for measuring the width and thickness of the test specimen to an incremental discrimination of at least 0.025mm [0.001in.]should be used.All width and thickness measurements of rigid and semirigid plastics may be measured with a hand micrometer with ratchet.A suitable instrument for measuring the thickness of nonrigid test specimens shall have:a contact measuring pressure of 2562.5kPa [3.660.36psi],a movable circular contact foot 6.3560.025mm [0.25060.001in.]in diameter and a lower ?xed anvil large enough to extend beyond the contact foot in all directions and being parallel to the contact foot within 0.005mm [0.002in.]over the entire foot area.Flatness of foot and anvil shall conform to the portion of the Calibration section of Test Methods D 594

7.Test Specimens

7.1The specimens may be cut from sheets,plates,or molded shapes,or may be molded to the desired ?nished dimensions.The actual dimensions used in Section 4.2,Cal-culation,shall be measured in accordance with Test Methods D 5947.

N OTE 2—Any necessary polishing of specimens shall be done only in the lengthwise direction of the specimen.

7.2Sheet Materials (Except Laminated Thermosetting Ma-terials and Certain Materials Used for Electrical Insulation,Including Vulcanized Fiber and Glass Bonded Mica):

7.2.1Materials 1.6mm [1?16in.]or Greater in Thickness —For ?atwise tests,the depth of the specimen shall be the thickness of the material.For edgewise tests,the width of the

TABLE 1Flexural Strength

Material Mean,103psi

Values Expressed in Units of %

of 103psi V r A V R B r C R D ABS

9.99 1.59 6.05 4.4417.2DAP thermoset 14.3 6.58 6.5818.618.6Cast acrylic 16.3 1.6711.3 4.7332.0GR polyester

19.5 1.43 2.14 4.05 6.08GR polycarbonate 21.0 5.16 6.0514.617.1SMC

26.0

4.76

7.19

13.5

20.4

V r =within-laboratory coefficient of variation for the indicated material.It is obtained by ?rst pooling the within-laboratory standard deviations of the test results from all of the participating laboratories:Sr =[[(s 1)2+(s 2)2...+(s n )2]/n]1/2then V r =(S r divided by the overall average for the material)3100.B

V r =between-laboratory reproducibility,expressed as the coefficient of varia-tion:S R ={S r 2+S L 2}1/2where S L is the standard deviation of laboratory means.Then:V R =(S R divided by the overall average for the material)3100.C

r =within-laboratory critical interval between two test results =2.83V r .D

R =between-laboratory critical interval between two test results =2.83V R

specimen shall be the thickness of the sheet,and the depth shall not exceed the width(see Notes3and4).For all tests,the support span shall be16(tolerance61)times the depth of the beam.Specimen width shall not exceed one fourth of the support span for specimens greater than3.2mm[1?8in.]in depth.Specimens3.2mm or less in depth shall be12.7mm[1?2 in.]in width.The specimen shall be long enough to allow for overhanging on each end of at least10%of the support span, but in no case less than6.4mm[1?4in.]on each end.Overhang shall be sufficient to prevent the specimen from slipping through the supports.

N OTE3—Whenever possible,the original surface of the sheet shall be unaltered.However,where testing machine limitations make it impossible to follow the above criterion on the unaltered sheet,one or both surfaces shall be machined to provide the desired dimensions,and the location of the specimens with reference to the total depth shall be noted.The value obtained on specimens with machined surfaces may differ from those obtained on specimens with original surfaces.Consequently,any speci?-cations for?exural properties on thicker sheets must state whether the original surfaces are to be retained or not.When only one surface was machined,it must be stated whether the machined surface was on the tension or compression side of the beam.

N OTE4—Edgewise tests are not applicable for sheets that are so thin that specimens meeting these requirements cannot be cut.If specimen depth exceeds the width,buckling may occur.

7.2.2Materials Less than1.6mm[1?16in.]in Thickness—The specimen shall be50.8mm[2in.]long by12.7mm[1?2in.] wide,tested?atwise on a25.4-mm[1-in.]support span.

N OTE5—Use of the formulas for simple beams cited in these test methods for calculating results presumes that beam width is small in comparison with the support span.Therefore,the formulas do not apply rigorously to these dimensions.

N OTE6—Where machine sensitivity is such that specimens of these dimensions cannot be measured,wider specimens or shorter support spans,or both,may be used,provided the support span-to-depth ratio is at least14to1.All dimensions must be stated in the report(see also Note5).

7.3Laminated Thermosetting Materials and Sheet and Plate Materials Used for Electrical Insulation,Including Vulcanized Fiber and Glass-Bonded Mica—For paper-base and fabric-base grades over25.4mm[1in.]in nominal thickness,the specimens shall be machined on both surfaces to a depth of25.4mm.For glass-base and nylon-base grades, specimens over12.7mm[1?2in.]in nominal depth shall be machined on both surfaces to a depth of12.7mm.The support span-to-depth ratio shall be chosen such that failures occur in the outer?bers of the specimens,due only to the bending moment(see Note7).Therefore,a ratio larger than16:1may be necessary(32:1or40:1are recommended).When laminated materials exhibit low compressive strength perpendicular to the laminations,they shall be loaded with a large radius loading nose(up to four times the specimen depth to prevent premature damage to the outer?bers.

7.4Molding Materials(Thermoplastics and Thermosets)—The recommended specimen for molding materials is127by 12.7by3.2mm[5by1?2by1?8in.]tested?atwise on a support span,resulting in a support span-to-depth ratio of16(tolerance 61).Thicker specimens should be avoided if they exhibit signi?cant shrink marks or bubbles when molded.

7.5High-Strength Reinforced Composites,Including Highly Orthotropic Laminates—The span-to-depth ratio shall be cho-sen such that failure occurs in the outer?bers of the specimens and is due only to the bending moment(see Note7).A span-to-depth ratio larger than16:1may be necessary(32:1or 40:1are recommended).For some highly anisotropic compos-ites,shear deformation can signi?cantly in?uence modulus measurements,even at span-to-depth ratios as high as40:1. Hence,for these materials,an increase in the span-to-depth ratio to60:1is recommended to eliminate shear effects when modulus data are required,it should also be noted that the ?exural modulus of highly anisotropic laminates is a strong function of ply-stacking sequence and will not necessarily correlate with tensile modulus,which is not stacking-sequence dependent.

N OTE7—As a general rule,support span-to-depth ratios of16:1are satisfactory when the ratio of the tensile strength to shear strength is less than8to1,but the support span-to-depth ratio must be increased for composite laminates having relatively low shear strength in the plane of the laminate and relatively high tensile strength parallel to the support span.

8.Number of Test Specimens

8.1Test at least?ve specimens for each sample in the case of isotropic materials or molded specimens.

8.2For each sample of anisotropic material in sheet form, test at least?ve specimens for each of the following conditions. Recommended conditions are?atwise and edgewise tests on specimens cut in lengthwise and crosswise directions of the sheet.For the purposes of this test,“lengthwise”designates the principal axis of anisotropy and shall be interpreted to mean the direction of the sheet known to be stronger in?exure.“Cross-wise”indicates the sheet direction known to be the weaker in ?exure and shall be at90°to the lengthwise direction.

9.Conditioning

9.1Conditioning—Condition the test specimens at236 2°C[73.463.6°F]and5065%relative humidity for not less than40h prior to test in accordance with Procedure A of Practice D618unless otherwise speci?ed by contract or the relevant ASTM material speci?cation.Reference pre-test con-ditioning,to settle disagreements,shall apply tolerances of 61°C[1.8°F]and62%relative humidity.

9.2Test Conditions—Conduct the tests at2362°C[73.46 3.6°F]and5065%relative humidity unless otherwise speci?ed by contract or the relevant ASTM material speci?ca-tion.Reference testing conditions,to settle disagreements, shall apply tolerances of61°C[1.8°F]and62%relative humidity.

10.Procedure

10.1Procedure A:

10.1.1Use an untested specimen for each measurement. Measure the width and depth of the specimen to the nearest 0.03mm[0.001in.]at the center of the support span.For specimens less than2.54mm[0.100in.]in depth,measure the depth to the nearest0.003mm[0.0005in.].These measure-ments shall be made in accordance with Test Methods D5947.

10.1.2Determine the support span to be used as described in Section7and set the support span to within1%of the determined

value.

10.1.3For?exural?xtures that have continuously adjust-able spans,measure the span accurately to the nearest0.1mm [0.004in.]for spans less than63mm[2.5in.]and to the nearest 0.3mm[0.012in.]for spans greater than or equal to63mm [2.5in.].Use the actual measured span for all calculations.For ?exural?xtures that have?xed machined span positions,verify the span distance the same as for adjustable spans at each machined position.This distance becomes the span for that position and is used for calculations applicable to all subse-quent tests conducted at that position.See Annex A2for information on the determination of and setting of the span.

10.1.4Calculate the rate of crosshead motion as follows and set the machine for the rate of crosshead motion as calculated by Eq1:

R5ZL2/6d(1) where:

R=rate of crosshead motion,mm[in.]/min,

L=support span,mm[in.],

d=depth of beam,mm[in.],and

Z=rate of straining of the outer?ber,mm/mm/min[in./ in./min].Z shall be equal to0.01.

In no case shall the actual crosshead rate differ from that calculated using Eq1,by more than610%.

10.1.5Align the loading nose and supports so that the axes of the cylindrical surfaces are parallel and the loading nose is midway between the supports.The parallelism of the apparatus may be checked by means of a plate with parallel grooves into which the loading nose and supports will?t when properly aligned(see A2.3).Center the specimen on the supports,with the long axis of the specimen perpendicular to the loading nose and supports.

10.1.6Apply the load to the specimen at the speci?ed crosshead rate,and take simultaneous load-de?ection data. Measure de?ection either by a gage under the specimen in contact with it at the center of the support span,the gage being mounted stationary relative to the specimen supports,or by measurement of the motion of the loading nose relative to the supports.Load-de?ection curves may be plotted to determine the?exural strength,chord or secant modulus or the tangent modulus of elasticity,and the total work as measured by the area under the load-de?ection curve.Perform the necessary toe compensation(see Annex A1)to correct for seating and indentation of the specimen and de?ections in the machine.

10.1.7Terminate the test when the maximum strain in the outer surface of the test specimen has reached0.05mm/mm [in./in.]or at break if break occurs prior to reaching the maximum strain(Notes8and9).The de?ection at which this strain will occur may be calculated by letting r equal0.05 mm/mm[in./in.]in Eq2:

D5rL2/6d(2) where:

D=midspan de?ection,mm[in.],

r=strain,mm/mm[in./in.],

L=support span,mm[in.],and

d=depth of beam,mm[in.].

N OTE8—For some materials that do not yield or break within the5% strain limit when tested by Procedure A,the increased strain rate allowed by Procedure B(see10.2)may induce the specimen to yield or break,or both,within the required5%strain limit.

N OTE9—Beyond5%strain,this test method is not applicable.Some other mechanical property might be more relevant to characterize mate-rials that neither yield nor break by either Procedure A or Procedure B within the5%strain limit(for example,Test Method D638may be considered).

10.2Procedure B:

10.2.1Use an untested specimen for each measurement.

10.2.2Test conditions shall be identical to those described in10.1,except that the rate of straining of the outer surface of the test specimen shall be0.10mm/mm[in./in.]/min.

10.2.3If no break has occurred in the specimen by the time the maximum strain in the outer surface of the test specimen has reached0.05mm/mm[in./in.],discontinue the test(see Note9).

11.Retests

11.1Values for properties at rupture shall not be calculated for any specimen that breaks at some obvious,fortuitous?aw, unless such?aws constitute a variable being studied.Retests shall be made for any specimen on which values are not calculated.

12.Calculation

12.1Toe compensation shall be made in accordance with Annex A1unless it can be shown that the toe region of the curve is not due to the take-up of slack,seating of the specimen,or other artifact,but rather is an authentic material response.

12.2Flexural Stress(s f)—When a homogeneous elastic material is tested in?exure as a simple beam supported at two points and loaded at the midpoint,the maximum stress in the outer surface of the test specimen occurs at the midpoint.This stress may be calculated for any point on the load-de?ection curve by means of the following equation(see Notes10-12):

s f53PL/2bd2(3) where:

s=stress in the outer?bers at midpoint,MPa[psi],

P=load at a given point on the load-de?ection curve,N [lbf],

L=support span,mm[in.],

b=width of beam tested,mm[in.],and

d=depth of beam tested,mm[in.].

N OTE10—Eq3applies strictly to materials for which stress is linearly proportional to strain up to the point of rupture and for which the strains are small.Since this is not always the case,a slight error will be introduced if Eq3is used to calculate stress for materials that are not true Hookean materials.The equation is valid for obtaining comparison data and for speci?cation purposes,but only up to a maximum?ber strain

5%in the outer surface of the test specimen for specimens tested by the procedures described herein.

N OTE11—When testing highly orthotropic laminates,the maximum stress may not always occur in the outer surface of the test specimen.4 Laminated beam theory must be applied to determine the maximum tensile stress at failure.If Eq3is used to calculate stress,it will yield an apparent strength based on homogeneous beam theory.This apparent strength is highly dependent on the ply-stacking sequence of highly orthotropic laminates.

N OTE12—The preceding calculation is not valid if the specimen slips excessively between the supports.

12.3Flexural Stress for Beams Tested at Large Support Spans(s f)—If support span-to-depth ratios greater than16to 1are used such that de?ections in excess of10%of the support span occur,the stress in the outer surface of the specimen for a simple beam can be reasonably approximated with the following equation(see Note13):

s f5~3PL/2bd2!@116~D/L!224~d/L!~D/L!#(4) where:

s f,P,L,b,and d are the same as for Eq3,and

D=de?ection of the centerline of the specimen at the middle of the support span,mm[in.].

N OTE13—When large support span-to-depth ratios are used,signi?cant end forces are developed at the support noses which will affect the moment in a simple supported beam.Eq4includes additional terms that are an approximate correction factor for the in?uence of these end forces in large support span-to-depth ratio beams where relatively large de?ec-tions exist.

12.4Flexural Strength(s fM)—Maximum?exural stress sustained by the test specimen(see Note11)during a bending

test.It is calculated according to Eq3or Eq4.Some materials that do not break at strains of up to5%may give a load de?ection curve that shows a point at which the load does not increase with an increase in strain,that is,a yield point(Fig.1, Curve B),Y.The?exural strength may be calculated for these materials by letting P(in Eq3or Eq4)equal this point,Y.

12.5Flexural Offset Yield Strength—Offset yield strength is the stress at which the stress-strain curve deviates by a given strain(offset)from the tangent to the initial straight line portion of the stress-strain curve.The value of the offset must be given whenever this property is calculated.

N OTE14—This value may differ from?exural strength de?ned in12.4. Both methods of calculation are described in the annex to Test Method D638.

12.6Flexural Stress at Break(s fB)—Flexural stress at break of the test specimen during a bending test.It is calculated according to Eq3or Eq4.Some materials may give a load de?ection curve that shows a break point,B,without a yield point(Fig.1,Curve a)in which case s fB=s fM.Other materials may give a yield de?ection curve with both a yield and a break point,B(Fig.1,Curve b).The?exural stress at break may be calculated for these materials by letting P(in Eq 3or Eq4)equal this point,B.

12.7Stress at a Given Strain—The stress in the outer surface of a test specimen at a given strain may be calculated in accordance with Eq3or Eq4by letting P equal the load read from the load-de?ection curve at the de?ection corresponding to the desired strain(for highly orthotropic laminates,see Note

11).

12.8Flexural Strain,e f—Nominal fractional change in the length of an element of the outer surface of the test specimen at midspan,where the maximum strain occurs.It may be calculated for any de?ection using Eq5:

e f56Dd/L2(5) where:

e f=strain in the outer surface,mm/mm[in./in.],

D=maximum de?ection of the center of the beam,mm [in.],

L=support span,mm[in.],and

d=depth,mm[in.].

12.9Modulus of Elasticity:

12.9.1Tangent Modulus of Elasticity—The tangent modu-lus of elasticity,often called the“modulus of elasticity,”is the ratio,within the elastic limit,of stress to corresponding strain. It is calculated by drawing a tangent to the steepest initial straight-line portion of the load-de?ection curve and using Eq 6(for highly anisotropic composites,see Note15).

E B5L3m/4bd3(6)

4For a discussion of these effects,see Zweben,C.,Smith,W.S.,and Wardle,M. W.,“Test Methods for Fiber Tensile Strength,Composite Flexural Modulus and Properties of Fabric-Reinforced Laminates,“Composite Materials:Testing and Design(Fifth Conference),ASTM STP674,1979,pp.

228–262.

N OTE—Curve a:Specimen that breaks before yielding.

Curve b:Specimen that yields and then breaks before the5%strain limit.

Curve c:Specimen that neither yields nor breaks before the5%strain limit.

FIG.1Typical Curves of Flexural Stress(?

)Versus Flexural

Strain(e

)

where:E B =modulus of elasticity in bending,MPa [psi],L =support span,mm [in.],

b =width of beam tested,mm [in.],d =depth of beam tested,mm [in.],and

m =

slope of the tangent to the initial straight-line portion of the load-de?ection curve,N/mm [lbf/in.]of de?ec-tion.

N OTE 15—Shear de?ections can seriously reduce the apparent modulus

of highly anisotropic composites when they are tested at low span-to-depth ratios.4For this reason,a span-to-depth ratio of 60to 1is recommended for ?exural modulus determinations on these composites.Flexural strength should be determined on a separate set of replicate specimens at a lower span-to-depth ratio that induces tensile failure in the outer ?bers of the beam along its lower face.Since the ?exural modulus of highly anisotropic laminates is a critical function of ply-stacking sequence,it will not necessarily correlate with tensile modulus,which is not stacking-sequence dependent.

12.9.2Secant Modulus —The secant modulus is the ratio of stress to corresponding strain at any selected point on the stress-strain curve,that is,the slope of the straight line that joins the origin and a selected point on the actual stress-strain curve.It shall be expressed in megapascals [pounds per square inch].The selected point is chosen at a prespeci?ed stress or strain in accordance with the appropriate material speci?cation or by customer contract.It is calculated in accordance with Eq 6by letting m equal the slope of the secant to the load-de?ection curve.The chosen stress or strain point used for the determination of the secant shall be reported.

12.9.3Chord Modulus (E f )—The chord modulus may be calculated from two discrete points on the load de?ection curve.The selected points are to be chosen at two prespeci?ed stress or strain points in accordance with the appropriate material speci?cation or by customer contract.The chosen stress or strain points used for the determination of the chord modulus shall be reported.Calculate the chord modulus,E f using the following equation:

E f 5~s f 22s f 1!/~e f 22e f 1!

(7)

where:

s f 2and s f 1are the ?exural stresses,calculated from Eq 3or Eq 4and measured at the prede?ned points on the load

de?ection curve,and e f 2and

e f 1are the ?exural strain values,calculated from Eq 5and measured at the predetermined points on the load de?ection curve.

12.10Arithmetic Mean —For each series of tests,the arithmetic mean of all values obtained shall be calculated to three signi?cant ?gures and reported as the “average value”for the particular property in question.

12.11Standard Deviation —The standard deviation (esti-mated)shall be calculated as follows and be reported to two signi?cant ?gures:

s 5=~(X 22nX

ˉ2!/~n 21!(8)

where:

s =estimated standard deviation,X =value of single observation,n =number of observations,and

X ˉ=arithmetic mean of the set of observations.13.Report

13.1Report the following information:

13.1.1Complete identi?cation of the material tested,includ-ing type,source,manufacturer’s code number,form,principal dimensions,and previous history (for laminated materials,ply-stacking sequence shall be reported),

13.1.2Direction of cutting and loading specimens,when appropriate,

13.1.3Conditioning procedure,

13.1.4Depth and width of specimen,13.1.5Procedure used (A or B),13.1.6Support span length,

13.1.7Support span-to-depth ratio if different than 16:1,13.1.8Radius of supports and loading noses,if different than 5mm.When support and/or loading nose radii other than 5mm are used,the results shall be identi?ed as being generated by a modi?ed version of this test method and the referring speci?cation referenced as to the geometry used.13.1.9Rate of crosshead motion,

13.1.10Flexural strain at any given stress,average value and standard deviation,

13.1.11If a specimen is rejected,reason(s)for rejection,13.1.12Tangent,secant,or chord modulus in bending,average value,standard deviation,and the strain level(s)used if secant or chord modulus,

13.1.13Flexural strength (if desired),average value,and standard deviation,

13.1.14Stress at any given strain up to and including 5%(if desired),with strain used,average value,and standard devia-tion,

13.1.15Flexural stress at break (if desired),average value,and standard deviation,

13.1.16Type of behavior,whether yielding or rupture,or both,or other observations,occurring within the 5%strain limit,and

13.1.17Date of speci?c version of test used.

TABLE 2Flexural Modulus

Material Mean,103psi

Values Expressed in units of %

of 103psi V r A V R B r C R D ABS

338 4.797.6913.621.8DAP thermoset 485 2.897.188.1520.4Cast acrylic 81013.716.138.845.4GR polyester

816 3.49 4.209.9111.9GR polycarbonate 1790 5.52 5.5215.615.6SMC

1950

10.9

13.8

30.8

39.1

V r =within-laboratory coefficient of variation for the indicated material.It is obtained by ?rst pooling the within-laboratory standard deviations of the test results from all of the participating laboratories:Sr =[[(s 1)2+(s 2)2...+(s n )2]/n ]1/2then V r =(S r divided by the overall average for the material)3100.B

r =within-laboratory critical interval between two test results =2.83V r .D

R =between-laboratory critical interval between two test results =2.83V R

14.Precision and Bias 5

14.1Tables 1and 2are based on a round-robin test conducted in 1984,in accordance with Practice E 691,involv-ing six materials tested by six laboratories using Procedure A.For each material,all the specimens were prepared at one source.Each “test result”was the average of ?ve individual determinations.Each laboratory obtained two test results for each material.

N OTE 16—Caution:The following explanations of r and R (14.2-14.2.3)are intended only to present a meaningful way of considering the approximate precision of these test methods.The data given in Tables 2and 3should not be applied rigorously to the acceptance or rejection of materials,as those data are speci?c to the round robin and may not be representative of other lots,conditions,materials,or https://www.wendangku.net/doc/076095793.html,ers of these test methods should apply the principles outlined in Practice E 691to generate data speci?c to their laboratory and materials,or between speci?c laboratories.The principles of 14.2-14.2.3would then be valid for such data.

14.2Concept of “r”and “R”in Tables 1and 2—If S r and S R have been calculated from a large enough body of data,and

for test results that were averages from testing ?ve specimens for each test result,then:

14.2.1Repeatability —Two test results obtained within one laboratory shall be judged not equivalent if they differ by more than the r value for that material.r is the interval representing the critical difference between two test results for the same material,obtained by the same operator using the same equipment on the same day in the same laboratory.

14.2.2Reproducibility —Two test results obtained by dif-ferent laboratories shall be judged not equivalent if they differ by more than the R value for that material.R is the interval representing the critical difference between two test results for the same material,obtained by different operators using differ-ent equipment in different laboratories.

14.2.3The judgments in 14.2.1and 14.2.2will have an approximately 95%(0.95)probability of being correct.

14.3Bias —No statement may be made about the bias of these test methods,as there is no standard reference material or reference test method that is applicable.15.Keywords

15.1?exural properties;plastics;stiffness;strength

ANNEXES

(Mandatory Information)A1.TOE COMPENSATION

A1.1In a typical stress-strain curve (see Fig.A1.1)there is a toe region,AC,that does not represent a property of the material.It is an artifact caused by a takeup of slack and

alignment or seating of the specimen.In order to obtain correct values of such parameters as modulus,strain,and offset yield point,this artifact must be compensated for to give the corrected zero point on the strain or extension axis.

A1.2In the case of a material exhibiting a region of Hookean (linear)behavior (see Fig.A1.1),a continuation of the linear (CD)region of the curve is constructed through the zero-stress axis.This intersection (B)is the corrected zero-strain point from which all extensions or strains must be measured,including the yield offset (BE),if applicable.The elastic modulus can be determined by dividing the stress at any point along the Line CD (or its extension)by the strain at the same point (measured from Point B,de?ned as zero-strain).A1.3In the case of a material that does not exhibit any linear region (see Fig.A1.2),the same kind of toe correction of the zero-strain point can be made by constructing a tangent to the maximum slope at the in?ection Point H 8.This is extended to intersect the strain axis at Point B 8,the corrected zero-strain https://www.wendangku.net/doc/076095793.html,ing Point B 8as zero strain,the stress at any point (G 8)on the curve can be divided by the strain at that point to obtain a secant modulus (slope of Line B 8G 8).For those materials with no linear region,any attempt to use the tangent through the in?ection point as a basis for determination of an offset yield point may result in unacceptable error.

Supporting data are available from ASTM Headquarters.Request RR:D20–

1128.

N OTE —Some chart recorders plot the mirror image of this graph.

FIG.A1.1

Material with Hookean

Region

A2.MEASURING AND SETTING SPAN

A2.1For ?exural ?xtures that have adjustable spans,it is important that the span between the supports is maintained constant or the actual measured span is used in the calculation of stress,modulus,and strain,and the loading nose or noses are positioned and aligned properly with respect to the supports.Some simple steps as follows can improve the repeatability of your results when using these adjustable span ?xtures.A2.2Measurement of Span:

A2.2.1This technique is needed to ensure that the correct span,not an estimated span,is used in the calculation of results.

A2.2.2Scribe a permanent line or mark at the exact center of the support where the specimen makes complete contact.The type of mark depends on whether the supports are ?xed or rotatable (see Figs.A2.1and A2.2).

A2.2.3Using a vernier caliper with pointed tips that is readable to at least 0.1mm [0.004in.],measure the distance between the supports,and use this measurement of span in the calculations.

A2.3Setting the Span and Alignment of Loading Nose(s)—To ensure a consistent day-to-day setup of the span and ensure the alignment and proper positioning of the loading nose,simple jigs should be manufactured for each of the standard setups used.An example of a jig found to be useful is shown in Fig.A2.3

N OTE —Some chart recorders plot the mirror image of this graph.

FIG.A1.2Material with No Hookean

Region

FIG.A2.1Markings on Fixed Specimen

Supports

FIG.A2.2Markings on Rotatable Specimen

Supports

APPENDIX

(Nonmandatory Information)

X1.DEVELOPMENT OF A FLEXURAL MACHINE COMPLIANCE CORRECTION

X1.1Introduction

X1.1.1Universal Testing instrument drive systems always exhibit a certain level of compliance that is characterized by a variance between the reported crosshead displacement and the displacement actually imparted to the specimen.This variance is a function of load frame stiffness,drive system wind-up,load cell compliance and ?xture compliance.To accurately measure the ?exural modulus of a material,this compliance should be measured and empirically subtracted from test data.Flexural modulus results without the corrections are lower than if the correction is applied.The greater the stiffness of the material the more in?uence the system compliance has on results.X1.1.2It is not necessary to make the machine compliance correction when a de?ectometer/extensometer is used to mea-sure the actual de?ection occurring in the specimen as it is de?ected.

X1.2Terminology

X1.2.1Compliance —The displacement difference between test machine drive system displacement values and actual specimen displacement

X1.2.2Compliance Correction —An analytical method of modifying test instrument displacement values to eliminate the amount of that measurement attributed to test instrument compliance.

X1.3Apparatus

X1.3.1Universal Testing machine X1.3.2Load cell

X1.3.3Flexure ?xture including loading nose and specimen supports

X1.3.4Computer Software to make corrections to the dis-placements

X1.3.5Steel bar,with smoothed surfaces and a calculated ?exural stiffness of more than 100times greater than the test material.The length should be at least 13mm greater than the support span.The width shall match the width of the test specimen and the thickness shall be that required to achieve or exceed the target stiffness.

X1.4Safety Precautions

X1.4.1The universal testing machine should stop the ma-chine crosshead movement when the load reaches 90%of load cell capacity,to prevent damage to the load cell.

X1.4.2The compliance curve determination should be made at a speed no higher than 2mm/min.Because the load builds up rapidly since the steel bar does not de?ect,it is quite easy to exceed the load cell capacity.X1.5Procedure

N OTE X1.1—A new compliance correction curve should be established each time there is a change made to the setup of the test machine,such as,load cell changed or reinstallation of the ?exure ?xture on the machine.If the test machine is dedicated to ?exural testing,and there are no changes to the setup,it is not necessary to re-calculate the compliance curve.N OTE X1.2—On those machines with computer software that automati-cally make this compliance correction;refer to the software manual to determine how this correction should be made.

X1.5.1The procedure to determine compliance follows:X1.5.1.1Con?gure the test system to match the actual test con?guration.

X1.5.1.2Place the steel bar in the test ?xture,duplicating the position of a specimen during actual testing.

X1.5.1.3Set the crosshead speed to 2mm/min.or less and start the crosshead moving in the test direction recording crosshead displacement and the corresponding load

values.

FIG.A2.3Fixture Used to Set Loading Nose and Support Spacing and

Alignment

X1.5.1.4Increase load to a point exceeding the highest load expected during specimen testing.Stop the crosshead and return to the pre-test location.

X1.5.1.5The recorded load-de?ection curve,starting when the loading nose contacts the steel bar to the time that the highest load expected is de?ned as test system compliance. X1.5.2Procedure to apply compliance correction is as follows:

X1.5.2.1Run the?exural test method on the material at the crosshead required for the measurement.

X1.5.2.2It is preferable that computer software be used to make the displacement corrections,but if it is not available compliance corrections can be made manually in the following manner.Determine the range of displacement(D)on the load versus displacement curve for the material,over which the modulus is to be calculated.For Young’s Modulus that would steepest region of the curve below the proportional limit.For Secant and Chord Modulii that would be at speci?ed level of strain or speci?ed levels of strain,respectively.Draw two vertical lines up from the displacement axis for the two chosen displacements(D1,D2)to the load versus displacement curve for the material.In some cases one of these points maybe at zero displacement after the toe compensation correction is made.Draw two horizontal lines from these points on the load displacement curve to the Load(P)axis.Determine the loads (L1,L2).

X1.5.2.3Using the Compliance Correction load displace-ment curve for the steel bar,mark off L1and L2on the Load (P)axis.From these two points draw horizontal lines across till they contact the load versus displacement curve for the steel bar.From these two points on the load de?ection curve draw two vertical lines downwards to the displacement axis.These two points on the displacement axis determine the corrections (c1,c2)that need to be made to the displacements measure-ments for the test material.

X1.5.2.4Subtract the corrections(c1,c2)from the mea-sured displacements(D1,D2),so that a true measures of test specimen de?ection(D1-c1,D2-c2)are obtained.

X1.6Calculations

X1.6.1Calculation of Chord Modulus

X1.6.1.1Calculate the stresses(s f1,s f2)for load points L1 and L2from Fig.X1.1using the equation in12.23.

X1.6.1.2Calculate the strains(e f1,e f2)for displacements D1-c1and D2-c2from Fig.X1.3using the equation in12.8Eq. 5.

X1.6.1.3Calculate the?exural chord modulus in accor-dance with12.9.3Eq.7.

X1.6.2Calculation of Secant Modulus

X1.6.2.1Calculation of the Secant Modulus at any strain along the curve would be the same as conducting a chord modulus measurement,except that s f1=0,L1=0,and D1-c1 =0.

X1.6.3Calculation of Young’s Modulus

X1.6.3.1Determine the steepest slope“m”along the curve, below the proportional limit,using the selected loads L1and L2from Fig.X1.1and the displacements D1-c1and D2-c2 from Fig.X1.3.

X1.6.3.2Calculate the Young’s modulus in accordance with 12.9.1Eq.6

FIG.X1.1Example of Modulus Curve for a

Material FIG.X1.2Compliance Curve for Steel

Bar

SUMMARY OF CHANGES

Committee D20has identi?ed the location of selected changes to this standard since the last issue (D 790-03)that may impact the use of this standard.(September 1,2007)

(1)Revised 5.4,6.2,and 13.1.8.

(2)Deleted old Figure 1.

ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentioned in this https://www.wendangku.net/doc/076095793.html,ers of this standard are expressly advised that determination of the validity of any such patent rights,and the risk of infringement of such rights,are entirely their own responsibility.

This standard is subject to revision at any time by the responsible technical committee and must be reviewed every ?ve years and if not revised,either reapproved or withdrawn.Your comments are invited either for revision of this standard or for additional standards and should be addressed to ASTM International Headquarters.Your comments will receive careful consideration at a meeting of the responsible technical committee,which you may attend.If you feel that your comments have not received a fair hearing you should make your views known to the ASTM Committee on Standards,at the address shown below.

This standard is copyrighted by ASTM International,100Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959,United States.Individual reprints (single or multiple copies)of this standard may be obtained by contacting ASTM at the above address or at 610-832-9585(phone),610-832-9555(fax),or service@https://www.wendangku.net/doc/076095793.html, (e-mail);or through the ASTM website

(https://www.wendangku.net/doc/076095793.html,).

FIG.X1.3Example of the Material Curve Corrected for the

Compliance Corrected Displacement or

Strain

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8.如果有多个中断同时发生,系统将根据中断优先级响应优先级高的中断请求，若要调整中断事件的响应次序,可以利用 (1) 1.中断嵌套 1.中断响应 1.中断屏蔽 1.中断向量 9.以下有关强迫性中断事件的叙述中,哪一个是错误的 (1?) 1.输入输出中断来自通道或各种外部设备，用于反映通道或设备的工作情况 1.程序性中断，是正在运行程序有意识安排的而引起的中断 1.硬件故障中断是机器发生错误时产生的中断 1.时钟中断是硬件时钟到时等 10.下列中断中,哪一个不属于强迫性中断 (1) 1.设备出错 1.掉电 1.时间片到时 1.执行print语句 11.下列哪一个中断属于程序性中断 (1) 1.打印机结束工作 1.地址越界 1.时间片到时 1.掉电 12.在中断处理中,输入输出中断是指 (1) Ⅰ.设备出错Ⅱ.数据传输结束 1.只有Ⅰ 1.只有Ⅱ 1.Ⅰ和Ⅱ 1.都不是 14.计算机系统中设置的访管指令 (1) 1.只能在目录下执行 1.只能在管态下执行

不确定条件下的选择分析报告

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不肯定性(uncertainty)是指人们既不能确定某种经济行为一定会发生某种结果，又不能确定其发生的可能性大小。出现不肯定性的原因可能是人们行为本身就具有不确定性因素，或者是人们行为不完全独立，或者是人们缺乏必要的信息等等。风险(risk)是指人们虽然不能确定某种经济行为一定会发生某种结果，但能够确定其发生的可能性大小，或者说，经济行为产生某种结果的可能性大小是客观存在，由客观条件决定。比如人们可以根据已有的经验，确定出某种经济行为的各种可能结果，并且确定出每种结果发生的概率。这样一来，便可计算这种经济行为的期望值，并利用期望值进行分析。下面来看不确定性条件下选择的几个事例。例1. 抽彩(lottery) 设有两种奖品通过抽彩才能获得。第一种抽彩方式(即第一种彩票)是：获得奖品1的概率为p ，获得奖品2的概率为p -1。第二种抽彩方式(即第二种彩票)是：获得奖品1的概率为q ，获得奖品2的概率为q -1。抽彩人得到奖品1后，能获得1U 个单位的效用；获得奖品2后，能获得2U 个单位的效用。问抽彩人喜欢抽哪一种彩票？要回答这个问题，需要计算这两种彩票的预期效用（即效用的期望值）。用1EU 表示第一种彩票的预期效用，2EU 表示第二种彩票的预期效用。根据概率论的有关知识可知， 211)1(U p pU EU -+= ， 212)1(U q qU EU -+= 比较一下1EU 和2EU 的大小，如果21EU EU >，说明第一种彩票的效用期望值更大，因此抽彩人更喜欢第一种抽彩方式，选择第一种彩票。同理，当21EU EU <时，抽彩人会选择第二种彩票。当21EU EU =时，两种彩票的效用期望相同，因而对抽彩人来说无差异。这个例子同时也说明，一种彩票可以用抽彩的中奖概率分布来表示。比如说有一种彩票有n 个等级的奖励：1等奖，2等奖，…，1-n 等奖(末等奖)，n 等奖(无奖)。获得i 等奖的

操作系统选择题

操作系统的设计目标：方便性；有效性；可扩充性；开放性。方便性和有效性是操作系统的设计中最重要的两个目标。 1990年后开放性已成为新系统或软件能否被广泛应用的至关重要管的两个目标。操作系统的基本特征：并发性；共享性；虚拟性；异步性。并发性和共享性是多用户，多任务操作系统两个最基本的特征。并发性是多用户，多任务操作系统最重要的特征。在OS基本特征中，异步性是指进程是以人们不可预知的速度向前推进的。操作系统基本类型：批处理系统；分时系统；实时系统；在操作系统基本类型中，可靠性是实时系统最重要的特征。操作系统主要功能：处理机管理；存储器管理；设备管理；文件管理；用户接口；操作系统的用户接口：命令接口；程序接口；图形用户接口；在操作系统接口中，程序接口亦称为系统调用；目前比较流行的操作系统（实例）Windows;UNIX;Linux; UNIX系统最本质的特征（英文缩写）：OSI UNIX系统的内核结构可分为两大部分：进程控制子系统；文件子系统；进程三种基本状态：就绪状态；执行状态；阻塞状态；进程所请求的一次I/O完成后，将是进程状态从阻塞状态变为就绪状态。操作系统中处于执行状态的进程时间用完后进程状态将转变为就绪状态。操作系统处于执行状态的进程提出I/O请求后，进程状态将转变为阻塞状态；进程三种基本状态中，就绪状态是指进程已分配到除CPU以外所有必要资源。进程同步机制应遵循的准则：空闲让步；忙则等待；有限等待；让权等待；同步机制准则中，让权等待是指当进程不能自己进入自己的临界区时，应立即释放处理机；进程，文件，线程在系统中存在的唯一标志（英文缩写）：PCB;FCB;TCB; 在系统流利用数据结构（英文缩写）PCB描述进程的基本情况和活动过程；系统将被中断的CPU现场信息保护在该进程的数据结构（英文缩写）PCB中；在操作系统中，实现进程的同步的机制：信号量机制；管程机制； 1965年，荷兰学者Dijkstra提出的信号量机制是一种卓越有效的进程同步工具；产生进程死锁的必要条件：互斥条件；请求和保持条件；不剥夺条件；环路等待条件。在死锁的条件中，不剥夺条件是指进程已获得的资源只能在使用完时由自己释放。在死锁的条件中，互斥条件是指在一段时间内，某资源只能被一进程占用。资源的按序分配法是摒弃死锁条件中的环路等待条件来预防死锁的发生。现代操作系统产生死锁的条件中，互斥条件是不能被摒弃来预防死锁的发生。抢占式进程调度方式基于的主要原则：优先权原则；短进程优先原则；时间片原则。通常采用解除死锁的两种方法：剥夺资源；撤销进程；产生进程死锁的原因可归结为两点：竞争资源；进程间推进顺序非法； 1928年，Peter J.Denning指出程序执行时显现出：时间局限性，空间局限性虚拟存储器的理论依据：局部性原理在局部性原理中，产生时间局限性的典型原因是在程序中存在着大量的循环操作在局部性原理中，产生空间局限性的典型情况是程序的循序执行请求分页系统的主要硬件支持：请求页表机制，缺页中断机构，地址变换机构在请求分页系统的硬件支持中，当所要访问的页面不在内存时，由缺页中断机制

岩土钻掘工程学

岩土钻掘工程学总复习题（1）、名词解释： 1、磨锐式硬质合金钻头 2、自磨式硬质合金钻头 3、钻进规程 4、优质钻进规程 5、强力钻进规程 6、孕镶金刚石钻头的100%浓度 7、阀式正作用液动冲击器8、阀式反作用液动冲击器9、最优冲击间隔 10、钻孔轨迹11、顶角12、方位角 13、岩石的各向异性14、钻孔遇层角15、测斜 16、均角全距法17、钻孔弯曲18、冲击钻的悬距 19、圆孔了滤水管的孔隙率20、沉没比21、岩石的研磨性 22、回次钻速23、岩石的塑性24、硬质合金钻头的前角 25、金刚石浓度26、切削－剪切型碎岩27、阀式正作用液动冲击器 28、凿碎－剪切型碎岩29、钻孔测量环测定向法30、初级定向孔 31、钻孔空间弯曲32、岩矿心采取率33、机械钻速 34、技术钻速35、经济钻速36、循环钻速 37、切削－剪切型碎岩38、凿碎型碎岩39、凿碎－剪切型碎岩 40、钻孔测量环测定向法41、初级定向孔42．钻孔空间弯曲 43．岩矿心采取率44、岩石的硬度45、钻孔的方位角 46、均角全距法47、受控定向钻孔48、最优冲击间距 49、岩石破碎的三种方式50、金刚石浓度51、硬质合金钻头镶焊角 52、岩石的研磨性53、金刚石体积浓度54、钻孔的顶角 55、止水56、圆孔过滤器的孔隙率57、岩石的强度 58、钻孔遇层角59、单动双管钻具（2）、填空题 1、金刚石单动双管所用取芯方法是()，喷射式反循环钻具所用卡取岩心的方法是()。投卡料、卡簧卡取、爪簧取芯、干钻取芯、沉淀取芯、静压入取芯。 2、硬质合金钻头钻进4~5级以下岩石时以()为主、钻进6级以上岩石时应以()为主。大压力、高转速、大泵量。 3、钢粒钻头的硬度应()小于钢粒的硬度，用一次投砂法钻进时，水量应()。大于、小于、等于、保持均匀、逐渐增大、逐渐减小。 4、随着合金中钴含量的增加，硬度()，而抗弯强度()。

access 复习题判断选择填空操作题

1、Access字段名长度最多为____个字符。答案： 1：64 2、Access中，文本框分为3种类型：结合型、非结合型与____。答案： 1：计算型 3、OpenForm操作打开____。答案： 1：窗体 4、操作查询共有4种类型，分别是删除查询、生成表查询、____和更新查询. 答案： 1：追加查询 8、在Access中数据类型主要包括：自动编号、文本、备注、数字、货币、日期／时间、是／否、OLE对象、____和查阅向导等。答案： 1：超链接 9、纵栏式窗体将窗体中的一个显示记录按____分隔。答案： 1：列 10、Access2007中，对数据库表的记录进行排序时，数据类型为____、超级链接或OLE对象的字段不能排序答案： 1：备注型 11、链接是直接将____中的数据使用到Access的表、窗体、查询和报表中。一旦外部数据源发生变化，则所链接的表、查询、窗体和报表中的内容也相应改变。答案： 1：外部数据源 12、在创建报表的过程中，可以控制数据输出的内容、输出对象的显示或打印格式，还可以在报表制作的过程中，进行数据的____。答案： 1：统计计算 13、Access提供了两种字段数据类型保存文件或文本和数字组合的数据，这两种数据类型是文本型和____。答案： 1：备注型 14、操作查询是指仅在一个操作中更改多条____的查询。答案： 1：记录 16、创建分组统计查询时，总计项应选择____。答案： 1：Group By 17、纵栏式窗体每次显示____条记录。

18、SQL语言中提供了SELECT语句，用来进行数据库的____。答案： 1：查询 19、若要获得当前的日期及时间，可使用____函数。答案： 1：Now（） 20、Access数据库的类型是____。答案： 1：关系数据库 21、在设置查询的"准则"时，可以直接输入表达式，也可以使用表达式____来帮助创建表达式。答案： 1：生成器 22、在一个宏中运行另一个宏时，使用的宏操作命令是____。答案： 1：RunMacro 23、____是创建与设计数据访问页的一个可视化的集成接口，在该接口下可以修改数据访问页。答案： 1：设计视图 24、将活动窗口最小化的宏操作是____。答案： 1：Minimize 25、选择运算的结果关系同原关系具有____的结构框架，投影运算的结果关系同原关系通常具有工业－的结构框架。答案： 1：相同 26、数据库管理系统是位于____之间的软件系统。答案： 1：用户与操作系统 27、窗体有多个部分组成，每部分称做一个____。答案： 1：节 28、Access用参照完整性来确保表中记录之间____的有效性，并不会因意外而删除或更改相关数据。答案： 1：关系 29、多字段排序时，排序的优先级是____。答案： 1：从左到右 30、要确定"库存量"乘以"单价"的平均值是否大于等于Y5001且小于等于￥1000.可输入____ 答案： 1：AVG（库存量＊单价）BETWEEN 500 AND 1000

方案选择问题

知识点2：方案选择问题 9..甲乙两班到市场里去买苹果价格如下：甲班分两次共购买苹果70千克（第二次多于第一次）共付出189元，乙班则一次性购买70千克（1）乙班比甲班少付多少元？（2）甲班第一次，第二次分别购买苹果多少千克？ 10.一家游泳馆每年6-8月出售夏季会员证，每张会员证80元，只限本人使用，凭证购入场券每张1元，不凭证购入场券每张3元。（1）在这个游泳馆游泳多少次时，购会员证与不购证所付的钱数一样？（2）某人今年计划要游泳60次，购会员证与不购会员证哪些合算？ 11．某市移动通讯公司开设了两种通讯业务：“全球通”使用者先缴50?元月基础费，然后每通话1分钟，再付电话费0.2元；“神州行”不缴月基础费，每通话1?分钟需付话费0.4元（这里均指市内电话）．若一个月内通话x分钟，两种通话方式的费用分别为y1元和y2元．（1）写出y1，y2与x之间的关系式（即等式）．（2）一个月内通话多少分钟，两种通话方式的费用相同？（3）若某人预计一个月内使用话费120元，则应选择哪一种通话方式较合算？12.小明用的练习本可以到甲商店购买，也可以到乙商店购买，已知两商店的标价都是每本1元，甲商店的优惠条件是，购买10本以上，从第11本开始按标价的70%卖，乙商店的优惠条件是，从第一本开始按标价的80%卖。（1）小明要买20本时，到哪家商店省钱？（2）买多少本时到两个商店买都一样？（3）小明现在又31元钱，最多可以买多少本？ 13．某蔬菜公司的一种绿色蔬菜，若在市场上直接销售，每吨利润为1000元，?经粗加工后销售，每吨利润可达4500元，经精加工后销售，每吨利润涨至7500元，当地一家公司收购这种蔬菜140吨，该公司的加工生产能力是：如果对蔬菜进行精加工，每天可加工16吨，如果进行精加工，每天可加工6吨，?但两种加工方式不能同时进行，受季度等条件限制，公司必须在15天将这批蔬菜全部销售或加工完毕，为此公司研制了三种可行方案：方案一：将蔬菜全部进行粗加工．方案二：尽可能地对蔬菜进行精加工，没来得及进行加工的蔬菜，在市场上直接销售。方案三：将部分蔬菜进行精加工，其余蔬菜进行粗加工，并恰好15天完成。你认为哪种方案获利最多？为什么？应用题一、工资问题 1.（本题4+3分）自2008年爆发全球金融危机以来，部分企业受到了不同程度的影响，为落实“促民生、促经济”政策，盐城市某玻璃制品销售公司今年1月份调整了职工的月工资分配方案，调整后月工资由基本保障工资和计件奖励工资两部分组成（计件奖励工资=销售每件的奖励金额×销售的件数）．下表是甲、乙两位职工今年十一月份的工资情况信息：

色谱分离操作条件的选择

色谱分离操作条件的选择在气相色谱中，除了要选择合适的固定液之外，还要选择分离时的最佳条件，以提高柱效能，增大分离度，满足分离的需要。一、载气及其线速的选择根据van Deemter方程的数学简化式为 H = A + B / u + C u 可得到下图所示的H-u关系曲线。当u值较小时，分子扩散项B/u将成为影响色谱峰扩张的主要因素，此时，宜采用相对分子质量较大的载气（N2、Ar），以使组分在载气中有较小的扩散系数。当u较大时，传质项Cu将是主要控制因素。此时宜采用相对分子质量较小，具有较大扩散系数的载气（H2、He），以改善气相传质。各项因素对板高H的影响图中曲线的最低点，塔板高度最小，柱效最高，所以该点对应的流速即为最佳流速。最佳线速和最小板高可以通过H = A + B / u + C u进行微分后求得。上图的虚线是速率理论中各因素对板高的影响。比较各条虚线可知，当u值较小是，分子扩散项B/u将成为影响色谱峰扩张的主要因素，此时，宜采用相对分子质量较大的载气（N2、Ar），以使组分在载气中有较小的扩散系数。另一方面，当u较大时传质项Cu将是主要控制因素。此时宜采用相对分子质量较小，具有较大扩散系数的载气（H2、He），以改善气相传质。当然，还须考虑与所用的检测器相适应。二、柱温的选择柱温是一个重要的色谱操作参数，它直接影响分离效能和分析速度。柱温不能高于固定液的最高使用温度，否则会造成固定液大量挥发流失。某些固定液有最低操作温度。一般地说，操作温度至少必须高于固定液的熔点，以使其有效地发挥作用。降低柱温可使色谱柱的选择性增大，但升高柱温可以缩短分析时间，并且可以改善气相和液相的传质速率，有利于提高效能。所以，这两方面的情况均需考虑。

后悔理论：不确定条件下理性选择的替代理论

后悔理论：不确定条件下理性选择的替代理论格拉汉姆?鲁麦斯、罗伯特?萨戈登１1、卡尼曼和特沃斯基的证据　著　瓦奇译注当前不确定性条件下选择的经济分析，主要建立在几个基本公理之上，冯?诺伊曼和摩根斯坦（1947年），萨维奇（1954）等对这些公理的表述都不尽相同。这些公理被广泛认为代表不确定条件下理性行为的本质。然而，众所周知，很多人的行为方式系统违反这些公理。我们首先从卡尼曼和特沃斯基的论文《前景理论：风险条件下的决策分析》开始，这篇论文提供了这些行为的大量证据。卡尼曼和特沃斯基提出了一种他们称为前景理论的理论来解释他们的观察。我们在这里将提出一种比前景理论更简单的替代理论，并且我们相信它更具直觉吸引力。本文使用下列符号。第i 个前景记作X i 。具有概率p 1，…，p n （p 1+…+p n =1）的财富x 1，…，x n 的增加和减少，可以记作（x 1，p 1；…；x n ，p n ）。空结果被剔除，因此前景（x ，p ；0，1-p ）简记为（x ，p ）。复合前景，如以其他前景作为结果，可以表示为（X 1，p 1；…，X n ，p n ）。我们使用传统符号＞、≥和∽代表严格偏好关系、弱偏好和无差别。我们规定，对前景X i 和X k ，有X i ≥X k 或者X i ≤X k ；但是，我们通常不要求关系≥可传递。卡尼曼和特沃斯基的实验将假设的一对前景之间的选择提供给大学的教师和学生群体。表1列出了他们选择的结果，揭示了三种主要类型的对传统期望效用理论的违反： a)“确定性效应”或“公比效应”，例如，X 5＜X 6和X 9＞X 10的组合以及X 13＜X 14和X 15＞X 16的组合。也有“反向公比效应”，例如，X 7＞X 8和X 11＜X 12的组合。 b) 原始的“阿莱悖论”或“公共结果效应”，例如，X 1＜X 2和X 3＞X 4的组合。 c) 两阶段博弈中的“隔离效应”，例如，X 9＞X 10和X 17＜X 18的组合。 1

钻孔编录要点

钻孔编录要点 3.3.7 土的鉴定应在现场描述的基础上，结合室内试验的开土记录和试验结果综合确定。土的描述应符合下列规定： 1 碎石土应描述颗粒级配（均匀.不均匀）、颗粒形状、颗粒排列、母岩成分、风化程度、充填物的性质和充填程度、密实度（稍密.中密.密实）等； 2 砂土应描述颜色、矿物组成、颗粒级配、颗粒形状、粘粒含量、湿度（稍湿.湿.饱和）、密实度等。 3 粉土应描述颜色、包含物、湿度、密实度、摇震反应（取一块土放在手心用另一直手敲打这只手背看土中水分是否出来。强.弱）、光泽反应、干强度（强.弱）韧性（高.低）等； 4 粘性土应描述颜色、状态、包含物、光泽反应、摇震反应、干强度、韧性、土层结构等； 5 特殊性土除应描述上述相应土类规定的内容外，尚应描述其特殊成分和特殊性质；如对淤泥尚需描述嗅味，对填土尚需描述物质成分、堆积年代、密实度和厚度的均匀程度等； 6 对具有互层、夹层、夹薄层特征的土，尚应描述各层的厚度和层理特征。 3.3.4 粒径大于0.075mm 的颗粒质量不超过总质量的50%，且塑性指数等于或小于10 的土，应定名为粉土。 3.3.5 塑性指数大于10 的土应定名为粘性土。粘性土应根据塑性指数分为粉质粘土和粘土，塑性指数大于10，且小于或等于17 的土，应定名为粉质粘土；塑性指数大于17 的土应定名为粘土。注：塑性指数应由相应于76g 圆锥仪沉入土中深度为10mm 时测定的液限计算而符。 3.3.6 除按颗粒级配或塑性指数定名外，土的综合定名应符合下列规定： 1对特殊成因和年代的土类应结合其成因和年代特征定名； 2 对特殊性土，应结合颗粒级配或塑性指数定名； 3 对混合土，应冠以主要含有的土类定名； 4 对同一土层中相间呈韵律沉积，当薄层与厚层的厚度比大于1/3 时，宜定为―互层‖；厚度比为1/10～1/3 时，宜定为―夹层‖；夹层厚度比小于1/10 的土层，且多次出现时，宜定为―夹薄层‖。 5 当土层厚度大于0.5m 时，宜单独分层。 6.5.1 填土根据物质组成和堆填方式，可分为下列四类； 1 素填土:由碎石土、砂土、粉土和粘性土等一种或几种材料组成，不含杂物或含杂物很少； 2 杂填土：含有大量建筑垃圾、工业废料或生活垃圾等杂物； 3 冲填土：由水力冲填泥砂形成； 4 压实填土：按一定标准控制材料成分、密度、含水量、分层压实或夯实而成。（一）根据钻探班报表检查孔深和进尺。设钻具总长为L，机台高度为P，主动钻杆的机上余尺为c，则本回次孔深H2 H 2= L - P – c 本回次进尺L1为本回次孔深H1与上一回次孔深H2之差

钻孔工程设计-开孔-终孔

钻孔单项工程设计书一、钻孔单项工程设计的内容，应包括工程目的、位置（剖面号、钻孔与附近测桩或地物或相邻工程的距离）、钻孔设计座标、方位角与倾角、设计深度、钻孔构造及钻孔预期揭露的地质构造等；在设计中并应附有钻探地质技术要求如商定的顶角允许弯曲系数、验证深度和换层位置（特别是矿层）的允许误差、测定间隔、岩矿心采取率、简易水文观察、物、化探测井、封孔及其他要求；完成任务时间及理想柱状图（或理想层序表）。钻探单项工程设计书的格式见附表（1）。单项工程设计书上的孔口设计座标，在图纸上量出。二、单项工程设计书由地质人员提出，有关单位会签。其审批权限：凡设计的工程在地质总体设计或年度设计经大队以上的机关批准过的，其单项设计书由分队地质技术负责人、分队长批准即可生效，但孔口移动位置过大，不能保证设计目的者，及由机动工作量设计的钻孔，或未经大队以上机关批准的钻孔均由大队技术负责人及大队长批准。三、单项工程设计书，应在安装钻机以前提出。附表1 地质队分队矿区第号钻探单项工程设计书一、孔号：二、孔位：剖面号孔口设计座标：X；Y；Z 孔口与附近地物或相邻工程距离：三、设计目的：四、设计：井深米；开孔方位角：开孔倾角；要求终孔孔径：大于毫米。五、地质技术要求：

1、方位角、顶角每米测一次； 2、顶角允许弯曲系数每100米度； 3、岩心采取率要求大于 %；近矿围岩岩心采取率要求； 4、矿心采取率要求大于 %；回次大于 % 5、深度验证间距每米检查一次； 6、其它：六、水文地质要求：七、其它要求：八、理想岩石层序及钻进中应注意的地质情况：九、台月效率：十、要求竣工日期；不晚于年月日十一、备注：地质：物化探：水文地质：区段地质技术负责人：探矿：计划：年月日批准（审查）者：分队地质技术负责人：分队长：年月日批准者：大队地质技术负责人：大队长：年月日注：1、凡设计书中未具体安排的钻孔，或者属于机动工作量钻孔，需报大队审批； 2、本表一式四份：分队地质、机场、探矿及大队各一份