مقاله ی شماره ی 3: بررسی آزمون های مخرب مکانیکی (متن انگلیسی)

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با سلام ، اگرچه می دونم که باید فارسی بنویسم، ولیکن تصمیم گرفتم مطالب و استانداردهایی را در احتیار دوستان قرار بدهم که متاسفانه فرصت ترجمه کردن آنها را ندارم.

THE SUCCESSFUL EMPLOYMENT OF METALS in engineering applications relies on the ability of the metal to meet design and service requirements and to be fabricated to the proper dimensions.The capability of a metal to meet these requirements is determined by the mechanical and physicalpropertiesofthe metal
Physical properties are those typically measured by methods not requiring the application of an external mechanical force (or load). Typical examples of physical properties are density, magneticproperties (e.g.permeability), thermal conductivity and thermal diffusivity, electrical properties (e.g.,resistivity), specific heat, and coefficient of thermal expansion. Mechanical properties, the primary focus of thisVolume, are described as the relationship between forces (or stresses) acting on a material and the resistance of the material to deformation (i.e., strains) and fracture. This deformation, however, may or may not be evident in the metal after
the applied load is removed. Different types of tests, which use an applied force, are employed to measure properties, such as elastic modulus, yield strength, elastic and plastic deformation (i.e., elongation), hardness,fatigue resistance, and fracture toughnes​

 

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آزمون کشش

آزمون کشش

THE TENSION TEST is one of the most commonly used tests for evaluating materials. In its simplest form, the
tension test is accomplished by gripping opposite ends of a test item within the load frame of a test machine. A
tensile force is applied by the machine, resulting in the gradual elongation and eventual fracture of the test item.
During this process, force-extension data, a quantitative measure of how the test item deforms under the applied
tensile force, usually are monitored and recorded. When properly conducted, the tension test provides forceextension
data that can quantify several important mechanical properties of a material. These mechanical
properties determined from tension tests include, but are not limited to, the following·
Elastic deformation properties, such as the modulus of elasticity (Young's modulus) and Poisson's ratio
Yield strength and ultimate tensile strength
Ductility properties, such as elongation and reduction in area
Strain-hardening characteristics
These material characteristics from tension tests are used for quality control in production, for ranking
performance of structural materials, for evaluation of newly developed alloys, and for dealing with the staticstrength
requirements of design.
The basic principle of the tension test is quite simple, but numerous variables affect results. General sources of
variation in mechanical-test results include several factors involving materials, namely, methodology, human
factors, equipment, and ambient conditions, as shown in the “fish-bone” diagram in Fig. 1. This article
discusses the methodology of the tension test and the effect of some of the variables on the tensile properties
determined. The following methodology and variables are discussed:
Shape of the item being tested
Method of gripping the item
Method of applying the force
Determination of strength properties other than the maximum force required to fracture the test item
Ductility properties to be determined
Speed of force application or speed of elongation (e.g., control of stress rate or strain rate)
Test temperature​

 

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استاندارد

استاندارد

استاندارد ASTM در خصوص آزمون کشش مواد فلزی E8 می باشد که اصطلاحاته اون به این شرحه :

Terminology
Definitions—The definitions of terms relating to tension​

testing appearing in Terminology E 6 shall be considered as

applying to the terms used in these test methods of tension

testing. Additional terms being defined are as follows:
3.1.1 discontinuous yielding—in a uniaxial test, a hesitation
or fluctuation of force observed at the onset of plastic deformation,
due to localized yielding. (The stress-strain curve need
not appear to be discontinuous.)
3.1.2 lower yield strength, LYS [FL−2]—in a uniaxial test,
the minimum stress recorded during discontinuous yielding,
ignoring transient effects.
3.1.3 upper yield strength, UYS [FL−2]— in a uniaxial test,
the first stress maximum (stress at first zero slope) associated
with discontinuous yielding at or near the onset of plastic
deformation.
3.1.4 yield point elongation, YPE— in a uniaxial test, the strain (expressed in percent) separating the stress-strain curve’s
first point of zero slope from the point of transition from
discontinuous yielding to uniform strain hardening. If the
transition occurs over a range of strain, the YPE end point is
the intersection between (a) a horizontal line drawn tangent to
the curve at the last zero slope and ( b) a line drawn tangent to
the strain hardening portion of the stress-strain curve at the
point of inflection. If there is no point at or near the onset of
yielding at which the slope reaches zero, the material has 0 %
YPE.
3.1.5 uniform elongation, Elu, [%]—the elongation determined
at the maximum force sustained by the test piece just
prior to necking or fracture, or both.​

3.1.Discussion—Uniform​

 

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نظر خواهی

نظر خواهی

نمی دونم چطور می شه مطالب رو کامل تر و به همراه تصاویر ونمودارها قرار داد؟ اگر این نحوه ارائه مطالب به درد بخوره ، بگید تا ادامه بدم؟

 

[k.m.r.c]

نمی دونم چطور می شه مطالب رو کامل تر و به همراه تصاویر ونمودارها قرار داد؟ اگر این نحوه ارائه مطالب به درد بخوره ، بگید تا ادامه بدم؟

با تشکر از شما دوست عزیز:
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با سپاس.....

 

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ادامه استاندارد E8

ادامه استاندارد E8

Significance and Use
Tension tests provide information on the strength and ductility of materials under uniaxial tensile stresses. This information may be useful in comparisons of materials, alloydevelopment, quality control, and design under certain circumstancesThe results of tension tests of specimens machined tostandardized dimensions from selected portions of a part ormaterial may not totally represent the strength and ductilityproperties of the entire end product or its in-service behavior indifferent environmentsThese test methods are considered satisfactory for acceptance testing of commercial shipments. The test methods have been used extensively in the trade fo thispurpose​

 

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Apparatus

Apparatus

دستگاه ها وماشین آلات آزمون کشش:​

5.1

Testing Machines—Machines used for tension testing

shall conform to the requirements of Practices E 4. The forces
used in determining tensile strength and yield strength shall be
within the verified force application range of the testing
machine as defined in Practices E 4.
5.2 Gripping Devices:
5.2.1 General—Various types of gripping devices may be
used to transmit the measured force applied by the testing
machine to the test specimens. To ensure axial tensile stress
within the gage length, the axis of the test specimen should
coincide with the center line of the heads of the testing
machine. Any departure from this requirement may introduce
bending stresses that are not included in the usual stress
computation (force divided by cross-sectional area).
N​

​

OTE 5—The effect of this eccentric force application may be illustrated

by calculating the bending moment and stress thus added. For a
standard 1⁄2-in. diameter specimen, the stress increase is 1.5 percentage
points for each 0.001 in. of eccentricity. This error increases to 2.24
percentage points/0.001 in. for a 0.350-in. diameter specimen and to 3.17
percentage points/0.001 in. for a 0.250-in. diameter specimen.
NOTE 6—Alignment methods are given in Practice E 1012.
5.2.2 ​

​

Wedge Grips—Testing machines usually are equipped

with wedge grips. These wedge grips generally furnish a
satisfactory means of gripping long specimens of ductile metal
and flat plate test specimens such as those shown in Fig. 1. If,
however, for any reason, one grip of a pair advances farther
than the other as the grips tighten, an undesirable bending
stress may be introduced. When liners are used behind the
wedges, they must be of the same thickness and their faces
must be flat and parallel. For best results, the wedges should be
supported over their entire lengths by the heads of the testing
machine. This requires that liners of several thicknesses be
available to cover the range of specimen thickness. For proper
gripping, it is desirable that the entire length of the serrated
face of each wedge be in contact with the specimen. Proper
alignment of wedge grips and liners is illustrated in Fig. 2. For
short specimens and for specimens of many materials it is
generally necessary to use machined test specimens and to use
a special means of gripping to ensure that the specimens, when
under load, shall be as nearly as possible in uniformly
distributed pure axial tension (see 5.2.3, 5.2.4, and 5.2.5).
5.2.3 Grips for Threaded and Shouldered Specimens and
Brittle Materials—A schematic diagram of a gripping device
for threaded-end specimens is shown in Fig. 3, while Fig. 4
shows a device for gripping specimens with shouldered ends.
Both of these gripping devices should be attached to the heads
of the testing machine through properly lubricated sphericalseated
bearings. The distance between spherical bearings
should be as great as feasible.
5.2.4 Grips for Sheet Materials—The self-adjusting grips
shown in Fig. 5 have proven satisfactory for testing sheet
materials that cannot be tested satisfactorily in the usual type of
wedge grips.
5.2.5 Grips for Wire—Grips of either the wedge or snubbing
types as shown in Fig. 5 and Fig. 6 or flat wedge grips may be
used.
5.3 Dimension-Measuring Devices—Micrometers and other
devices used for measuring linear dimensions shall be accurate
and precise to at least one half the smallest unit to which the
individual dimension is required to be measured.
5.4 Extensometers— Extensometers used in tension testing
shall conform to the requirements of Practice E 83 for the
classifications specified by the procedure section of this test
method. Extensometers shall be used and verified to include
the strains corresponding to the yield strength and elongation at
fracture (if determined).
5.4.1 Extensometers with gage lengths equal to or shorter
than the nominal gage length of the specimen (dimension
shown as “G-Gage Length” in the accompanying figures) may
be used to determine the yield behavior. For specimens without
a reduced section (for example, full cross sectional area
specimens of wire, rod, or bar), the extensometer gage length
for the determination of yield behavior shall not exceed 80 %
of the distance between grips. For measuring elongation at
fracture with an appropriate extensometer, the gage length of
the extensometer shall be equal to the nominal gage length​

required for the specimen being tested.

​

 

[mhami]

درخواست تحقیق تست مخرب قطعات

درخواست تحقیق تست مخرب قطعات

با سلام به تمامی اعضاء
من نیاز مبرم به یک تحقیق در مورد آزمونهای تست مخرب قطعات مکانیکی دارم خواهشمند است مرا راهنمایی نمائید

 

[reza_1364]

من یک مقاله دارم.برات میزارم

موفق باشی

 

[saeideh_77077]

سلام رضا. منم مطلب راجع به استاندارهای ASTM و DIN برای تست فشار می خوام. اگه داری.
راستی من یه تاپیک در همین مورد توی بخش مقالات نوشتم ولی نمی تونم پیدیش کنم.

 

[reza_1364]

سلام رضا. منم مطلب راجع به استاندارهای ASTM و DIN برای تست فشار می خوام. اگه داری.
راستی من یه تاپیک در همین مورد توی بخش مقالات نوشتم ولی نمی تونم پیدیش کنم.

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