بازرسی جوش به روش UT و حد پذیرش

یک استاد دانشگاه درباره اقدام اخیر متروی تهران نوشت: برگزاری مسابقه نامه خودمونی به خدا از سوی مترو کار خوبی است اما بهتر است در کنار این اقدامات که مسجد محل هم می تواند انجام دهد، بخش اجتماعی مترو به کارهای اصلی خود بپردازد. ایجاد نارضایتی و ناراحتی هنر نیست.

بکارگیری اتباع خارجی بدون پروانه کار در مشاغل حوزه سلامت از قبیل مواد غذایی و بهداشت و درمان (رستوران، آشپزخانه، درمانگاه، داروخانه و ...) ممنوع است.

معاونت اجتماعی و پیشگیری از وقوع جرم دادگستری استان تهران 

شروط غیرقانونی در قرارداد کار چه هستند؟

شروط غیرقانونی در قرارداد کار، به توافقاتی گفته می‌شود که برخلاف قوانین آمره کار تنظیم شده‌اند و حتی در صورت رضایت کارگر، فاقد اعتبار قانونی هستند. یکی از مهم‌ترین نمونه‌های این شروط، تعیین ساعت کاری بیش از ۴۴ ساعت در هفته است که با قانون کار مغایرت دارد. همچنین گاهی کارفرما برای خود حق فسخ یک‌طرفه قرارداد را با تعیین مدت زمان مشخصی، مانند ۴۵ روز، قائل می‌شود که این شرط نیز برخلاف اصول قانونی روابط کار است.

از دیگر مصادیق شروط غیرقانونی می‌توان به تبعیض‌های جنسیتی در مزایای شغلی اشاره کرد؛ برای مثال، محروم کردن کارکنان زن از دریافت حق اولاد یا حق تأهل، امری غیرقانونی محسوب می‌شود. در برخی قراردادها نیز توافق می‌شود که مبلغ عیدی کمتر از میزان تعیین‌شده توسط قانون پرداخت شود یا دستمزد کارگر کمتر از حداقل دستمزد مصوب وزارت کار تعیین گردد که هر دو مورد باطل و فاقد اعتبار هستند.

Three types of seismic waves: 

(a) Rayleigh wave  ( Surface wave )

(b) compressional wave ( longitudinal wave )

(c) shear wave

Q30. During ultrasonic inspection (UT) on a 20 mm thick weld, an indication having length 2 mm observed, which is characterised as lack of fusion between the base metal and weld metal. As per the acceptance criteria in ASME Section VIII Division 1, this defect is: 

Not Acceptable

Acceptable

Acceptance depends upon the depth of flaw

None of above

(Explanation: According to ASME Section VIII Division 1, any indication characterized as a lack of fusion is unacceptable regardless of its size. Since the 2 mm long indication in the 20 mm thick weld has been characterized as lack of fusion, it would be unacceptable per ASME Section VIII Division 1 criteria, regardless of its size or depth

The angle at which 90° refraction of a longitudinalsound wave is reached is called the:

a. angle of incidence.

b. first critical angle.

c. angle of maximum reflection.

d. second critical angle.

When inspecting aluminum by the immersion method using water for a couplant, the following information is known: velocity of sound in water = 1.49 × 105 cm/s, velocity of longitudinal waves in aluminum = 6.32 × 105 cm/s, and angle of incidence = 5°. The angle of refraction for longitudinal waves isapproximately:

a. 22°

b. 18°

c. 26°

d. 16°

Sin5/x = 1.49 / 6.32

Beam divergence ( spread out ) is a function of the dimensions of the crystal and the wavelength of the beam transmitted through a medium, and it:

a. increases if the frequency or crystal diameter decreases.

b. decreases if the frequency or crystal diameterdecreases.

c. increases if the frequency increases and crystaldiameter decreases.

d. decreases if the frequency increases and crystaldiameter decreases.

The indication on the instrument display that represents the far boundary of the material being tested is called:

a. grass or hash.
b. the initial pause.
c. the main bang.
d. the back-surface reflection.

Moving a transducer over a test surface either manually or automatically is referred to as:

a. scanning.
b. attenuating.
c. angulating.
d. resonating.

A term  اصطلاحی که used in ultrasonics to express the rate at which sound waves pass through various substances is:

a. frequency.
b. velocity.
c. wavelength.
d. pulse length.

When the motion of the particles حرکت ذرات یک محیط  of a medium is transverse to the direction of propagation, the wave being transmitted is called a:

a. longitudinal wave.

b. shear wave.

c. surface wave.

d. lamb wave.

The boundary between  مرز بین two different materials دو ماده متفاوت  that are in contact with each other is called:

a. a rarefactor.
b. a refractor.
c. an interface.
d. a marker.

For discontinuity geometries other than flat, the echo amplitude دامنه اکو is usually from that observed _________ for a flat discontinuity, of similar orientation perpendicular to the sound beam.

a. identical

b. increased

c. decreased

d. elongated

To evaluate discontinuities that are oriented at anangle to the entry surface so that the sound beam strikes the plane of the discontinuity at right angles,the operator must:

a. change the frequency.

b. grind the surface.

c. angulate the transducer.

d. increase the gain.

In immersion testing, to remove the second water reflection from between the entry surface signal and the first back reflection, you should:

a.increase the repetition rate.

b.decrease the frequency.

c.decrease the sweep length.

d. increase the water path.

If a discontinuity is oriented at an angle other than90° to the sound beam, the results may be a:

a. loss of signal linearity.

b. loss or lack of signal reflected from thediscontinuity.

c. focusing of the sound beam.

d. loss of interference phenomena.

The change in direction of an ultrasonic beam whenit passes from one material to another material inwhich elasticity and density difer is called:

a.reflection 

b.rarefaction

c.angulation.

d.refraction.

In inspecting a 102 mm (4 in.) diameter threadedsteel cylinder for radial cracks extending from theroot of the threads, it would be preferable to transmit:

a.shear waves at an angle to the threads.

b.longitudinal waves from the end of the cylinder and perpendicular to the direction of the threadroots.

c. surface waves perpendicular to the thread roots.

d. shear waves around the circumference of the cylinder.

The distance from a given point on an ultrasonic wave to the next corresponding point is referred to as:

a. frequency.

b. wavelength.

c. velocity.

d. pulse length.

A testing technique in which the crystal or transducer is parallel to the test surface and ultrasonic waves enter the material being tested in a direction perpendicular to the test surface is:

a. straight beam testing.

b. angle beam testing.

c. surface wave testing.

d. lamb wave.

Which one of the following frequencies wouldprobably result in the greatest ultrasonic attenuationlosses?

a.1 MHz

b.2.25 MHz

c.10 MHz

d.25 MHz

"c" – Attenuation factor is attained by subtracting 1 inch (25mm) from the sound – path distance and multiplying the remainder by ⁰. The factor shall be rounded out to the nearest dB value.

Attenuation = (Sound path – 1 ) x 2

= ( 102.34/25.4(1") - 1" ) × 2 = 6 dB

- Indication Rating D

Indication dB ( A ) at 100% FSH ( Full Screen Height ) ( Max ) : 52 dB

Drop to 50% = 6 dB Drop ( افت ) 

D = A - B - C

A = 52 - 6 = 46

D = 46 - 48 - 6

D = - 8 dB

ASME B 31.1 – Power Piping – Ultrasonic Testing .

Welds that are shown by ultrasonic examination to have discontinuities that produce an indication greater than 20% of the reference level shall be investigated to the extent that ultrasonic examination personnel can determine their shape, identity, and location so that they may evaluate each discontinuity for acceptance in accordance with (B.1) and (B.2) below.

(B.1) Discontinuities evaluated as being cracks, lack of fusion,. or incomplete penetration are unacceptable regardless of length.

(B.2) Other discontinuities are unacceptable if the indication exceeds the reference level and their length exceeds the following:

(B.2.1) ¼” (6.0 mm) for t up to ¾” (19.0 mm).

(B.2.2) 1/3 t for t from ¾” (19.0 mm) to 2 ¼ “ (57.0 mm).

(B.2.3) ¾”. (19.0 mm) for t over 2¼” (57.0 mm)

Where t is the thickness of the weld being examined. If the weld joins two members having different thicknesses at the weld, t is the thinner of these two thicknesses

Or, HSD = T X Tan Ø

Similarly, FSD = 2T X Tan Ø

And, 1-1/2 Skip Distance = 3T X Tan Ø

Slag Inclusion 

LEG 2

T : 0.625 INCH

SOUND PATH (SA) : 1.736 INCH

DISTANCE FROM ZERO : 1.504

SA1+SA2=1.736

DEPTH : 0.382

POROSITY

SIZING